U.S. Air Force Research Lab Summer Faculty Fellowship Program

U.S. Air Force Research Lab Summer Faculty Fellowship Program

U.S. Air Force Research Lab Summer Faculty Fellowship Program

AFRL/RX (Wright-Patterson Air Force Base, Ohio )

SF.25.21.B10064: Cold spray physics-based hydrodynamic modeling and simulation

Gonzales, Manny - 937-255-9835

Cold spray is a promising additive repair technique whereby metallic powder is accelerated through a nozzle and supersonically impinges onto a substrate. The impact process generates shock waves and solid-state bonding (sometimes liquid-phase bonding) of the substrate and particles through extreme deformations, hydrodynamic instabilities and flow, and solid-state mechanisms such as dynamic recrystallization. Aerospace alloys such as Al 6061 may be repaired by the cold spray process. However, the complexity of the physical process also generates defects and incomplete bonding due wave reverberation and interparticle spallation. Cold spray is often modeled as a single particle event, but the neighborhood relationships and interactions with other particles determines the evolution of the microstructure. The proposed research opportunity seeks to develop a physics-based cold spray hydrodynamic model which captures the flow characteristics, particle neighborhood relationships and defect characteristics of the cold spray process. The process model will be connected to in-situ data from the actual cold spray machine and use the information to probe the mechanisms of defect generation and bonding in a number of aerospace alloys of interest. Applicants must be U.S. Citizens and flexible to work at Wright-Patterson AFB.

SF.25.21.B10063: Structure/Property/Performance Linkages for advanced reactive materials in extreme dynamic environments

Gonzales, Manny - 937-255-9835

Advanced, intermetallic-forming reactive materials present a viable option to enhance weapons effects by integrating into a conventional warhead and coupling their response with the ordnance. These materials have heterogeneous microstructures, are often multiphase, and couple a thermochemical response with a mechanochemical phenomena driven by shock compression of the material. Often, the meso and micro-scale features of the material control the dynamic performance and the interplay and coupling physics between the shock waves coming from the ordnance and the reactive material define the figures of merit for this material class. Different processing strategies can help control the material microstructure and can help achieve desirable mechanical properties, but often at the expense of thermochemical properties. The purpose of the research is to establish a framework for developing the structure/property/performance linkages for a number of multiphase reactive material mixtures (e.g. Ni+Al, Ti+B, Ti+Si, etc) via numerical simulation (hydrocode modeling, continuum-based simulation) of candidate meso and microstructures, informing characterization studies (via SEM/EBSD/EDS and micro-CT), and providing input to deformation and net-shape processing trials to optimize the microstructure and identify structure/property linkages. Digital microstructural quantification techniques such as n-point correlation statistics and principal component analysis along with physics-based hydrocode simulation will be conducted and an analytical framework to assess the shock compression response of candidate microstructures will be developed in this effort. Applicants must be U.S. Citizens and there is flexibility for on-site vs. remote participation.

SF.25.21.B10059: PFAS remediation using photocatalysis

Rao, Rahul - 937-255-9123

Per- and Poly-fluoroalkyl substances (PFAS), the so-called "forever" chemicals are dangerous contaminants that persist in the environment. This problem is particularly relevant to the Air Force, where these chemicals contaminate the soil and water surrounding air fields. Thus, there is an increasing need to develop state-of-the-art methods to detect and remove PFAS from the environment. In this research, we will use photocatalysis to irradiate (UV as well as visible light) and cleave the PFAS molecules into their atomic constituents. This will involve the synthesis of novel UV photocatalyst nanomaterials such as gallium oxide, indium oxide or titania nanoparticles and nanowires as well as plasmonic nanoparticles under visible light irradiation, and their integration into membranes through functionalization. Characterization will be done by optical spectroscopy (FT-IR, Raman, and photoluminescence), NMR and mass spectrometry. This research will aid ongoing efforts for PFAS remediation in the Soft Matter Materials branch at AFRL.

SF.25.21.B10058: Integrated Photonic Materials

Bedford, Robert - 937-713-5521

As an enabling platform, integrated photonics has become critical to low-cost, high-performance classical- and quantum-sensing systems for DOD applications. The field of integrated photonics has greatly accelerated in recent years thanks in large part to the developed maturity of linear and nonlinear materials and improvements to the reproducibility of manufacturing processes. In order to extend this capability to next-generation requirements, exploration of new materials and structures are essential. Natural systems such as nonlinear oxides (e.g. lithium niobate, barium titanate), and metamaterials based on interface structures such as asymmetric quantum-wells, superlattices, and digital alloys are all approaches to achieve performance that far-surpasses existing capabilities. Ability to efficiently integrate these to more mature integrated photonic platforms (e.g. silicon photonics) in a hybrid approach is of extreme interest. Moreover, structures which can be designed to enhance nonlinear signals through dispersion engineering (e.g. exceptional points) to improve capabilities beyond natural materials is valuable. Areas of interest are materials and processes that can enhance sensing and information systems and evaluate them for advancement of application potential. We explore potential material candidates using standard integrated photonics modeling software, realize materials through thin-film growth (MBE, PLD, sputtering), and test materials and structures through linear and nonlinear spectroscopy with a variety of integrated photonic RF testing across relevant bands of interest.

SF.25.21.B10046: Synthesis and advanced characterization of single crystal functional materials

Susner, Michael - 815-258-5078

The Air Force Crystal Growth Center (AFCGC) at the Photonic Materials Branch of the Materials and Manufacturing Directorate at AFRL is looking for Summer faculty who will want to utilize our state of the art materials growth and characterization center for research into the fundamental structure-property relationships of functional single crystalline materials. Our main foci of research are nonlinear optical materials, ferroelectrics, and magnetic materials for eventual sensing/device applications.

Our facility has close to 40 furnaces for Czochralski, Bridgman, flux, and vapor transport growths as well as two PPMS systems and one MPMS-2 for thermal, electrical, and magnetic characterization of these materials. We also have temperature-dependent XRD and Raman capabilities as well as high pressure apparatus for characterization

SF.25.21.B10038: In situ characterization of nanostructured polymeric and biological materials

Drummy, Lawrence - 937-255-9160

Polymeric and biologically based materials are of current interest for a wide array of technologically relevant applications including flex hybrid electronics, foldable deployable structures, and responsive materials. Additionally, the interface between these materials and devices is relevant to applications in sensors, catalysis, and anti-fouling surfaces. This research opportunity is aimed at developing new methods for 3D characterization of structure and dynamics across length scales and time scales. Development of experimental techniques, as well as data analytics tools for analyzing and reconstructing complex microscopy data are of significant interest. Advanced microscopy and scattering techniques including Electron Microscopy, Optical Characterization Techniques, In-Situ Microscopy, Electron Tomography and others will be critical to solving the materials challenges described.

SF.25.21.B10014: Printable Soft Elastomers for Soft Robotic Applications

Sowards, Laura - 937-255-9894

Objectives: Utilize novel formulations of photopolymerizable soft elastomers to add functionality, such as the ability to be self-healing. Create new soft robot designs and 3D print with vat photopolymerization methods. Use experimental methods, modeling, and simulation to predict and characterize the properties and performance of these new materials and structures.

Description: The growing field of soft robotics uses highly compliant materials for their construction. They have increased flexibility and adaptability when compared to rigid robots and are often designed in ways that mimic the movements of living organisms. Photopolymerizable soft elastomers are useful materials for creating soft robots as they are 3D printable. This allows the ability to create and print a complex 3D design utilizing vat photopolymerization methods within a single day, thus rapid design iteration. The material properties of the soft elastomer are an important area of study. The soft elastomer formulation can be tailored to have additional properties, such as self-healing capabilities, which adds functionality and the ability to make repairs and “heal” the material using simple techniques. Coupon specimens of the soft elastomer material will be mechanically tested (tension, compression, pure shear, etc.) and resulting data fit with constitutive models to predict performance and guide formulation and processing changes. Commercial finite-element analysis tools will be used to engineer (design, optimize, and control) new robotic designs. This research supports the ultimate goal of creating 3D printed soft robots with specialized functionalities attributable to their designed morphology and/or embedded devices to achieve the desired feedback and response.

Research Classification/Restrictions: The research project is unclassified, open to US citizen students only.

SF.25.21.B10013: Multiscale Multifidelity Framework for Assessing the Performance of Polymer Matrix Composites

Flores, Mark - 937-255-2302

Multiscale is becoming more widely adopted by the community when assessing the performance of Polymer Matrix Composite materials. However, phenomenological equations that exist at the microscale begin to break down. Experimental evidence is required to test the efficacy of micromechanical models to validate a multiscale approach. Although advancements have been made in understanding the performance of composite material with various levels of fidelity, much still needs to be done with respect to fracture behavior. The overall objective of this program is to begin developing a micro and mesoscale experimental framework 1) to assess failure initiation and propagation of microstructures: 2) link mechanical behavior to mesostructures and 3) develop analytical/numerical methods for assessing the performance of composite materials. The program seeks to investigate complex failure behavisssor in situ SEM experimentation and X-ray nCT analysis

SF.25.21.B10011: Microbiomes and Metabolic Modeling

Varaljay, Vanessa - 937-255-9157

Microorganisms, including bacteria and fungi, can inhabit DAF aircraft and fuel tank materials. These microorganisms can survive on and even thrive on the coatings and biofuels causing biocorrosion. The AF has isolated and identified the many microorganisms comprising the microbiomes of these environments. Employing experimental assays, multi-omics tools, such as genomics (DNA), transcriptomics (RNA), or proteomics (protein), as well as metabolic and network modeling will elucidate complex microorganism-materials interactions. The use of multi-omics tools results in large amounts of data which need to be analyzed using sophisticated computational tools and software on high performance computing clusters. This research opportunity will focus on integrating experimental data, bioinformatics, and modeling of DAF microorganisms to determine the interplay of microbial activities and environmental factors in biocorrosion.

The research project is unclassified, open to US citizens only.

SF.25.21.B10010: Investigating the latent space of machine learning models of microstructure

Shah, Megna - 937-255-5420

Generative adversarial networks, among other deep learning methods, have shown impressive results creating "deep fakes", fake images that cannot be distinguished from real ones. This work has been applied to microstructures, with equally impressive results. These approaches involve constructing images from a latent space representation, found in the training process, which encodes realistic images in a low-dimensional compact, differentiable space. Deep fakes are interpolations in this space and are statistically equivalent to those in the training set, but are not in the training set, itself. A natural question then is, what has actually been encoded into the latent space? Are the dimensions of the latent space meaningful to a materials scientist, and how can one navigate the latent space? Recent work in representations of faces indicates that there are natural, interpretable dimensions such as hair color, face pose, or nose length. We hypothesize that the latent space in a microstructure context, based on a properly trained model, could provide a roadmap of attainable, non-equilibrium microstructures, with linkages to processing and properties. If our hypothesis is correct, this opens the possibility of control over microstructure by exploiting the latent space, including finding discontinuities in the latent space, determining whether it is simply connected or would contain 'holes' that would be inaccessible by conventional processing methods, validating simulation methods in terms of the true variability of their outputs, quantifying uncertainty, and detecting rare events. In principle, this would be material agnostic, but the initial primary interest would be structural metallic systems.

SF.25.21.B10009: Composite Performance Research

Przybyla, Craig - 937-252-5323

Performance prognosis and characterization of advanced polymer matrix composites and ceramic matrix composites requires an understanding of the material structure and response mechanisms at multiple scales. Here we seek to characterize the enviro-mechanical response and develop appropriate models to provide accurate prognostics tools for behavior and life prediction. Of particular interest are new tools for the automated characterization of the response at the scales most important to the primary damage mechanisms. Additionally, we are seeking more accurate models sensitive to the complex enviro-mechanical environments expected in both air and space systems. For ceramic matrix composites, these environments can be quite extreme, which add significant complexity for both the experimental characterization and modeling approaches. As such we encourage novel proposals that support innovated experimental, theoretical and/or computational approaches that support these areas of research. US Citizenship required.

SF.25.21.B10008: Durability and damage tolerance of additively manufactured aerospace metal alloys

Krug, Matthew - 937-255-1387

Establishing predictability of structural performance for additively manufactured (AM) metals is a major requirement for broadening the suite of AM applications of to include durability critical (DC) components. The US Air Force would benefit from technology, tool and methodology development to improve the predictability of AM metal fatigue performance. Such efforts could include advancements related to: non-destructive inspection, probabilistic crack growth calculations, quantification of crack-defect or crack-microstructure interactions, part geometry considerations, variable load missions, integration of AM-process data (e.g. in-situ monitoring), etc. Project proposals that integrate multiple of these or other relevant items to advance the state of the art for metal AM toward DC components will be most likely to be selected. Applicants must be US persons, and on-site presence at Wright Patterson AFB is preferred.

SF.25.21.B10007: Materials for controlling the propagation of mechanical waves

Juhl, Abigail - 937-656-9213

This topic addresses control of acoustic and elastic wave propagation using both active and passive phononic crystals (PnC) and resonant metamaterials (RMM), which are typically architected materials composed of periodic unit cells. The performance of these materials depends not only on the constitutive materials used for their composition but also the structural configuration of their unit cell, requiring competency in both material science and structural dynamics. One goal of this research is the development of material systems (e.g. electromechanical, magnetorheological, thermoelastic, etc.) that can be processed via additive manufacturing to create tunable PnC/RMM capable of changing their dynamic behavior in response to external stimuli. Another goal is the development of techniques to aid in the design of the unit cell architecture to enable novel effects (e.g. optimization, numerical modeling, analytical relationships, etc.). The overarching objective of this research area is to solve practical Air Force problems using PnC/RMM phenomena like negative effective properties, non-reciprocity, non-linearity and interface effects (e.g. boundary conditions, lattice defects, topological edge modes). Common Air Force applications include aeroacoustics, vibration reduction, noise reduction, and impact resistance. Applicants must be a US Citizen.

SF.25.21.B10006: Advancing human-machine teaming for agile automation

Hardin, James - 937-656-8634

Bridging the gap between human objectives and machine behaviors is key to agile automation for DAF-relevant high-mix low-volume manufacturing and automated research. On the human side, this topic consists of interfaces, such as AR and VR, that enable more complete digitization, communication, and standardization of the objectives of a particular task. On the machine side, this topic involves abstraction of fundamental machine behaviors into flexible archetypes such as “affix screw” or “assemble engine”. Both of these elements produce massive amounts of data that needs to be organized. stored, and processed. Ultimately, these two sides must overlap to generate an adaptable communication pipeline between human and machine. Furthermore, there must be some sort of standardization to facilitate translation to new people and machines. Research topics of interest cover novel approaches to the challenges listed above.

SF.25.21.B10005: Developing Trustworthy Human-Machine Teams for Manufacturing

Gillman, Andrew - 937-656-4398

With the goal of “Teaching Tools to Be Teammates”, we are exploring how to make a variety of robotic manufacturing systems more agile and autonomous while actively collaborating with human subject level experts in order to achieve functional agility and overcome large deviations from the planned objective. Recent advances in machine learning and artificial intelligence have shown promise in providing this agility, and we are exploring how to employ these algorithms while augmenting classic control theory, optimization, and physics-based modeling to enable more autonomy in manufacturing. For these autonomous technologies to become pervasive in industrial manufacturing environments, humans will need to develop the appropriate level of trust in their capabilities, which become increasingly more critical in more collaborative operations. Research topics exploring trust calibration, trust dynamics, and/or explainable AI for human-robot interactions with interest in applications to manufacturing ecosystems are encouraged.

SF.25.21.B10004: Phonon-Engineering of Solid-State Systems

Dass, Chandriker - 512-786-5952

The control, generation, and manipulation of light within solid-state materials has been an active area of research for many decades, leading to a plethora of photonics-based technologies over wide frequency bands of the electromagnetic spectrum. This same level of control does not exist for phonons, however, which play a dominant role in the optical and thermal properties of many materials. We are soliciting proposals on the topic of phonon-engineering of solid-state systems with application potential for quantum technologies, thermal management, and energy harvesting.

SF.25.21.B10003: Nondestructive Materials State Awareness methods for Additive Manufacturing

Cherry, Matt - 937-255-9171

This topic addresses the discovery, development and maturation of nondestructive evaluation methods for quantifying the material state of as-printed additively manufactured (AM) parts. Additively manufactured materials can have drastically varying residual stress and local microstructural variability with changing processing conditions, which can significantly impact part performance. In order to improve quality assurance/quality control, new nondestructive assessment methods for quantifying the microstructure and properties of as-printed AM materials will be investigated. These methods can include, but are not limited to, resonance testing, bulk wave ultrasound, nonlinear ultrasound, and low-frequency electromagnetic techniques. Algorithms that rely on physics-based models to simulate the response from the NDE sensors and performing inversion for the relevant material properties may be explored. Lastly, multi-modal techniques are also of interest that enhance the interpretation of material state data for AM parts.

SF.25.21.B10002: Processing and Performance of Ceramic-Metal Hybrid Systems for Functional Ceramic and Carbon Matrix Composites

Apostolov, Zlatomir - 937.255.9030

Ever since their inception, carbon and ceramic matrix composites have been designed with purely structural considerations in mind. While both the processing and performance of these material classes have noticeably improved, the demands placed on hypersonic platforms have also evolved in both intensity and scope, with some being outside the structural domain. This has necessitated a shift in the perception that functional materials are only feasible or needed in the lower-temperature regimen, and has directed attention to the synergistic combination of ceramic-metal or carbon-metal hybrid systems, utilizing refractory metals as engineered substructures within structural composites. Our focus is on elucidating the processing-structure-property relationships in such systems, where the metallic substructure of single- or multi-phase composition is dispositioned throughout the volume of the composite, and is deposited with comparable feature size via conventional (i.e. pre-assembled shapes) or additive manufacturing methods in the early stages of the composite manufacturing process. Areas of interest include, but are not limited to, metal-ceramic compatibility at high temperatures, evolution of electromagnetic properties of metallic network with increased environmental loads, and the exploration of the metal-unique properties for manipulating the thermal or electro-magnetic state of the composite.

US Citizenship required.

SF.25.21.B10001: Advanced Processing and Performance of Ultra-High Temperature Ceramics in Composite, Monolithic, and Protective Coating Systems

Apostolov, Zlatomir - 937.255.9030

The constant desire for enhanced flight performance at hypersonic speeds has pushed the current generation of structural materials to the limits of their capabilities, as components in either propulsion or aeroshell designs. Carbon and conventional ceramic composites (both oxide and non-oxide) are not adequate for the areas on these platforms experiencing the highest environmental loads, and require protection or replacement by ultrahigh-temperature ceramic (UHTC) materials. Our focus is on elucidating the processing-structure-property relationships as manifested in UHTC-based composites, monoliths, or protective coatings for refractory substrates. Specific compositions of interest include the carbides and borides of groups IV and V transition metals, with some emphasis on hafnium, tantalum, and zirconium. Processing methodologies span the range of preceramic precursors, reactive melt-infiltration, vapor-phase deposition, solid-state sintering and directed-energy assisted techniques. In achieving more capable architectures, these are utilized in either conventional composite and monolith processing, or a more advanced additive manufacturing framework. Both process and performance models are of interest to elucidate the factors driving the processing efficiency and oxidation behavior. The deposition and performance of graded architectures in multi-phase coatings systems with various constituent layer properties are of particular importance.

US Citizenship required.

SF.25.21.B0003: Design of Mechanically Adaptive Materials and Responsive Architectures

Buskohl, Philip - (937) 255-9152

Mechanically adaptive materials respond to environmental cues by converting external stimuli into motion via an internal material algorithm defined by composition and structure. Such programmable polymers include shape memory polymers (thermal stimulus), self-oscillating gels (chemical), sulfonylated polyimides (humidity) and liquid crystal elastomer networks (thermal/photo). The resultant motion, shape change or mechanical property remodeling offers unique opportunities for remote sensing, energy harvesting, robotics, and human performance technologies. Their impact can be further expanded through the design and patterning of composite adaptive materials, which contain active and inactive material domains. In addition to amplifying behavior through structural design, such as maximizing deflection through a cantilever, bi-stable plate or torsional spring geometry, arrangements of mechanically active and inactive units within a monolith can lead to communication, sensing, locomotion, or logic behaviors. The aims of this work include the development of computational design tools, novel fabrication methodology and experimental characterization of adaptive materials with programmable properties. Material sets that exhibit nonlinear elastic behavior and coupling between global topology and local material property control are of broad interest for this effort.

SF.25.21.B0002: Metal Additive Manufacturing Processing Science

Schwalbach, Edwin - 937-255-9840

Rapid thermal excursions and repeated cycling across solid-liquid and solid-solid phase transformations are common in metal additive manufacturing processes, the details of which are often tightly coupled to component geometry. The consequences of these unique processing attributes for microstructure evolution and material performance remain poorly understood and are typically viewed as a hindrance rather than for their potential benefits. Ongoing efforts seek to understand the implications of these details and ultimately design and test novel processing pathways that can spatially manipulate microstructural features such as grain size and morphology, crystallographic texture, chemical/phase inhomogeneities, defect content, and residual stresses. Essential to this is the development of methods for rapidly assessing and optimizing processing pathways to include fast-acting/surrogate process models, integration of novel microstructural prediction capabilities, and strategies to reduce problem complexity and dimensionality.

SF.25.20.B0013: In operando Characterization of Polymer Matrix Composites

Koerner, Hilmar - (937) 255-9324

Current manufacturing processes of polymer matrix composites are time intensive and require special tools. Our research centers on high-temperature polymer thermosets and the understanding of processing conditions that enable robust, advanced part manufacturing processes, such as 3D Printing or resin transfer molding. Specifically, our goal is to develop and confirm advanced capabilities for relating the fundamental principles that govern processes to the evolution of micro/nanostructure, cure chemistry, filler alignment, and their effects on resulting mechanical performance. This includes probing the polymer/filler interaction using advanced characterization methods and the study of in operando structure and morphology evolution. Techniques include X-ray/Neutron scattering (including Synchrotron radiation experiments), electron microscopy, atomic force microscopy, and rheology.

SF.25.20.B0012: Atomistic Scale Materials Hybridization for Multifunctionality

Roy, Ajit - 937-255-9034

Materials hybridization (hetero-material configuration) all the way to atomistic scale offers unprecedented opportunities for optimizing materials functionality (electronic, thermal, chemical, and mechanical) at reduced material consumption and potentially reduced materials qualification costs. Multi-material heterogeneity through efficient design of materials interface morphology, processing protocol for precise placement of atoms/molecules via appropriate processing routes are desired. Our emphasis is in integrating scale-appropriate (atomic, meso, continuum) materials modeling with processing science towards developing scalable materials processing approaches and understanding the fundamentals of materials response influencing device performance. Interest is in employing innovative materials modeling, (DFT, MD, tight binding DFT, meso-scale, continuum mechanics) to facilitate developing scalable nano-processing and manufacturing approaches, such as, printing, laser or e-beam processing. Creative material metrology in conjunction of the materials modeling is also of interest.

SF.25.20.B0011: Responsive Liquid Electronics

Tabor, Christopher - (937) 255-9184

Abstract: Low melting point metal alloys with majority constituents such as gallium and bismuth have recently provided unprecedented intrinsic properties for flexible, stretchable, and reconfigurable electronics. Two flavors of these materials have emerged in our group; (1) bulk fluids that are pneumatically controlled within microchannels and embedded fluidic tubing to physically rewire and “reprogram” the hardware components of electronics and RF devices, and (2) colloidal embodiments whereby the liquid metal colloids are suspended in a solvent and exhibit melting point suppression, high surface area, and can be used as inks for additive manufacturing. The novel intrinsic property of these liquid metals that enables these application areas is the formation of an oxide skin on the liquid alloy, which provides a self-encasing viscoelastic shell. This shell can be controlled in thickness and composition leading to a range of new tunable responsive attributes that we are exploring in our lab.

SF.25.20.B0008: Flexible 2D materials for electronics and sensing

Glavin, Nicholas - 9372556977

Flexible and stretchable devices based on two-dimensional (2D) materials are known to exhibit a rare combination of high electronic, sensing, and optoelectronic performance with the ability to accommodate large amounts of strain. This unique coupling is enabled by the broad optical absorption in graphene and other 2D material systems, quantum confinement of energy carriers in the 2D plane resulting in ultrafast transport dynamics, the van der Waals bonding between the layers, and the enhanced electromechanical properties that arise due to the extreme thinness of the material. We are interested in incorporation of 2D materials on polymeric substrates through direct synthesis, laser manipulation, and transfer processes to utilize the exceptional properties of these materials for future electronics and sensors. Materials of interest include elemental 2D structure including graphene, silicene, and phosphorene, as well as transition metal dichalcogenides, hexagonal boron nitride, and emerging van der Waals materials and heterostructures. By developing effective strategies to crystalize, dope, and functionalize these materials in a controlled manner, the development of robust, strainable, and high performing flexible electronics and sensors can be realized for future Air Force applications.

SF.25.20.B0006: Topological Insulator – Magnetic Heterostructures

Neal, Adam - 937-255-9136

Topological insulators, first observed experimentally in 2008, and whose theoretical development in the 1970’s and 1980’s was the subject of the 2016 Nobel Prize in Physics, are unique materials which are insulating in the bulk, but have intrinsic metallic topological states on their surface. These topological surface states result from the very large spin-orbit coupling in topological insulators, and they are intrinsic to the material, existing at any surface regardless of its orientation relative to the underlying crystal structure. Due to the large spin-orbit coupling, topological insulators have been used to generate spin-polarized currents and spin-torques in magnetic materials to which they are closely coupled. The goal of this project is to evaluate the spin-torque properties of topological insulators coupled to magnetic materials via electrical, magnetic, and/or optical characterization techniques in order to develop topological insulator – ferromagnet structures for non-volatile memory, neuromorphic/probabilistic computing, and/or radio frequency applications. Candidates should characterize topological insulator materials coupled to magnetic materials or perform relevant theoretical analysis/simulation relevant to the development of these materials and structures for device applications.

SF.25.20.B0004: Developing Next-Generation Multi-Functional Composites for Aerospace Applications using Multi-scale Modeling and Machine Learning Approaches

Varshney, Vikas - 937-255-2568

There is an ever-changing, constant need for designing novel composite materials for aerospace applications that offer a broader gamut of multi-functionality (sensing, electrical and thermal properties, desired interfaces characteristics, adhesion, energy storage/harvesting, low density, etc.) and structural stability (mechanical behavior, stiffness or compliance, fracture toughness, high temperature stability, minimal physical aging, etc.) with an eventual goal of minimizing costs and maximizing operational performance and efficiency. Experimentally, this design space is often explored via building upon previous reported literature towards synthesizing and characterizing state-of-the-art composite materials for various applications. This opportunity seeks motivated summer faculty fellows and their students to employ well-formalized atomistic modeling (quantum chemistry, molecular dynamics) and coarse-grain methods as well as to develop new modeling methods and data analytics/machine learning/artificial intelligence frameworks to investigate and understand structure-property-performance relationships in multi-functional polymeric matrix composites (PMCs) and ceramic matrix composites (CMCs) for next-generation multi-functional composites geared towards aerospace applications. The summer faculty fellows will work along with a number of AFRL (Air Force Research Laboratory) scientists and engineers towards solving complex problems related to PMCs and CMCs design, processing and structural performance. Specific topics could include (but not limited to) a) utilizing of the shelf AI/ML methods as well as develop physics-informed AI/ML methods for PMCs materials design and discovery as well as structural performance prediction in PMCs and CMCs; & b) complement experimental efforts with multiscale modeling approaches towards better appreciation of molecular origins of structure-property-performance relationships in PMCs and CMCs

SF.25.20.B0003: Advanced Processing of Ceramic and Ceramic Matrix Composite Structures

Rueschhoff, Lisa - 937-255-9060

New and/or advanced materials and processing techniques are required to enable the development of next generation Air Force propulsion and hypersonic components. Our focus is on fundamental structure-property-processing relationships for ceramics and ceramic matrix composites (CMCs) across all constituents and length scales. Materials of interest include ceramics and CMCs with high- and ultra-high temperature ceramic (UHTC) components that can withstand the harsh environments encountered in AF components. These materials include, but are not limited to: oxide and non-oxide based CMCs, structural ceramics with RF transparency, and fiber-reinforced UHTCs. Advancements in regards to fundamental understanding of the inherent material properties, novel processing routes, and relevant environmental characterization are desired. Additive manufacturing (AM) methods such as direct ink writing, fused deposition modeling, and stereolithography are all tools of interest for creating more complex-shaped ceramic and composites with tailorable microstructures. Additionally, exploration of process modeling and/or in-situ monitoring is beneficial in providing enhanced understanding of traditional and AM-based ceramic and CMC processing.

SF.25.20.B0002: Development of Inorganic and Hybrid Polymers and Composites for High Temperature Resins and Coatings

Monzel, William (Jacob) - 937-255-9004

In this research we seek to develop coatings and composites for use at high temperatures in oxidizing environments. The use of state-of the art organic resins are limited by oxidation at higher temperatures. In this temperature regime, metal components are traditionally used. However, the use of suitable polymeric composites would result in significant weight savings. Inorganic and hybrid (organic-inorganic) polymers may provide a viable route for lightweight, thermo-oxidatively stable materials with processing similar to traditional polymer composites. Specifically this work is concerned with carbosilane and aluminum phosphate polymers, and highly networked Alumino/Siloxo (-O-Al- and -O-Si-) systems. Example resin systems of interest include phosphate geopolymers and similar siloxane materials, including MQ/MT siloxanes and polyhedral oligomeric silsesquioxane (POSS) systems. To improve mechanical properties, hybridization with high performance organic resins may also be investigated. US citizenship required.

SF.25.19.B0016: Nonlinear Optical Materials Engineering

Jones, John - 937-255-9106

Research Program Abstract/Content. Also, specify any security/citizenship constraints/requirements needed in order to participate in the Research Program/Topic Abstract: Employ resonant and effective media approaches in composite systems to develop and engineer structured nonlinear optical materials with nanoscale layered dimensions. The goal is a comprehensive effort using: 1) growth of materials using physical vapor deposition (PVD), 2) characterization in situ during growth of materials, 3) ex situ characterization using surface analysis techniques such as XPS, XRD, XRR, TEM, SEM, AFM, etc. and 4) optical response quantification with optical characterization techniques such as pump-probe, and second harmonic generation (SHG). Content: Applications involving nonlinear optical materials include for example the need of wavelength conversion for quantum information systems and can be explored, along with other material properties, by developing thin films of multilayer, or multilayer composite films. For example, nanolaminates, or materials deposited sequentially having thicknesses on the order of tens of nanometers, can be generated in-house using physical vapor deposition techniques of laser ablation and magnetron sputtering with in situ ellipsometry. Films could be individually centrosymmetric materials and superlattice like structures designed in such a manner as to realize a second-order nonlinear optical response by breaking inversion symmetry, resulting in nonlinear effects such as SHG. In Situ ellipsometry is used in conjunction with pulsed laser deposition (PLD) and magnetron sputtering (MS) for precision growth of the nanolaminates. In situ sensing techniques include an Andor ICCD with focus lens, a fiber coupled spectrometer with ICCD, and spectrometer with PMT for TOF measurements of PLD. SEM/TEM/XPS/EDS/POLARIZABILITY can be used for materials thin film characterization, and other properties such as optical characterization can be accomplished using nonlinear optical characterization techniques including second harmonic generation (SHG).

SF.25.19.B0015: Enabling Tailorable Material Properties with Synthetic Methods

Baldwin, Luke - 937-255-1503

The ability to synthetically tailor the molecular structure and chemical architecture of functional materials provides an opportunity to meet many Air Force application needs. Agile synthetic platforms are desirable for research tasks related to organic sensors, adhesives, and stimuli-responsive materials. Furthermore, incorporation of these systems into flexible devices remains vital to their long term success on the battlefield. Research efforts will leverage AFRL expertise and capabilities in materials science, chemistry, engineering, and biochemistry to target human performance monitoring, wearable devices, and responsive structures. Specific areas of interest include polymer synthesis, sequence specific materials, adaptable materials and organic material synthesis. Furthermore, there remains interest in incorporating machine learning methods into synthesis and material properties studies, as well as using continuous flow chemistry to synthesize materials and macromolecules.

SF.25.19.B0013: Atmospheric Plasma CVD for Electronics Applications

Ferguson, John - 937-255-9029

Research interests include atmospheric plasma enhanced chemical vapor deposition of materials for electronic applications, new materials for thermal management and approaches to improve electronics package thermal conductivity, thermal transport at interfaces, high thermal conductive substrates and die attach materials. Additional interests include development of new and novel characterization techniques for thermal transport as well as new characterization techniques at the nano-scale and meso- scale for thermal and electrical properties.

SF.25.19.B0012: Two-dimensional materials and their heterostructures for advanced electronics applications

Kennedy, William - 937-255-9987

Our group develops new materials and processes for advanced electronics and computing architectures using a combination of top-down and bottom-up approaches. We leverage the emergent properties of two dimensional materials to enable fundamentally new capabilities in sensing, RF communications, and computing. Materials of interest include 2D transition metal dichalcogenides (TMDs), transition metal carbides/nitrides (MXenes), transition metal borides (MBenes), and thin film hybrid organic-inorganic perovskites (HOIPs). We routinely use an extensive suite of characterization tools to understand the processing-structure-property relationships in these materials. These include CW spectroscopy (UV-Vis, FTIR, Raman), modulation spectroscopy (electroabsorption), surface probe microscopy (AFM, AFM-IR, microwave AFM), electron microscopy (SEM, TEM, EELS), and X-Ray scattering (XRD, GISAXS, GIWAXS). We invite faculty fellows whose research interests will leverage these experimental resources to solve critical challenges central to the development of DAF-relevant technologies.

References
• Scalable synthesis of 2D van der Waals superlattices (https://arxiv.org/abs/2111.02864)
• Reversibly Tailoring Optical Constants of Monolayer Transition Metal Dichalcogenide MoS2 Films: Impact of Dopant-Induced Screening from Chemical Adsorbates and Mild Film Degradation (https://pubs.acs.org/doi/abs/10.1021/acsphotonics.1c00183)
• Laser writing of electronic circuitry in thin film molybdenum disulfide: A transformative manufacturing approach (https://www.sciencedirect.com/science/article/pii/S1369702120303394)
• Halogen Etch of Ti3AlC2 MAX Phase for MXene Fabrication (https://pubs.acs.org/doi/abs/10.1021/acsnano.0c08630)
Direct detection of circular polarized light in helical 1D perovskite-based photodiode (https://www.science.org/doi/10.1126/sciadv.abd3274)

SF.25.19.B0011: Studies of Ultra-Wide Bandgap Materials for Power Electronics and RF Power Electronics Applications

Neal, Adam - 937-255-9136

The recent maturity of solid state devices based on Gallium Nitride and Silicon Carbide has increased the maximum operating power of solid state power electronics and radio frequency (RF) power electronics devices, enabling higher output powers and reduced size and weight for systems based on these devices. With the success of these materials, there is a natural motivation to search for next generation ultra-wide bandgap materials to further enhance the performance of solid state power electronics and RF power electronics. Ultra-wide bandgap materials are those with a bandgap higher than Gallium Nitride (GaN) and Silicon Carbide (SiC), whose bandgaps are 3.4eV and 3.3eV respectively. Gallium Oxide (Ga2O3), with its bandgap of 4.5 eV, and Aluminum Gallium Nitride (AlGaN), with bandgaps as high as 6.2 eV for binary AlN, are examples of candidate materials which could further improve power electronics and RF power electronics device performance due to their larger bandgaps and resulting larger critical breakdown electric fields. In order to realize practical technologies based on these materials, an understanding of their material properties and those of their heterostructures, including transport, doping, defects, dielectric interface, metal-semiconductor interface, and ohmic contacts, is essential. In addition, understanding how material growth affects these properties is also critical. Candidates should grow and/or characterize ultra-wide bandgap materials in order to evaluate and/or improve properties of interest to enable future electronics technologies based on ultra-wide bandgap materials.

SF.25.19.B0009: Organic and Inorganic Polymer Hybrids for High Temperature Composite Resins, Adhesives and Coatings

Pruyn, Timothy - (937)255-1142

Our research team focuses on developing new high-performance lightweight structural materials. This includes increasing the service temperature of lightweight, processable, relatively low cost, polymer-based composite materials. Specifically, our focus is developing organic and inorganic systems that meet these processing, thermal, and mechanical needs while allowing for the possibilities of additional functionality. This includes the exploration of chemistries that incorporate organic and inorganic molecules and the design of new high temperature polymers and hybrids. Our research and ongoing projects encompasses synthesis, processing, and characterization of molecular inorganic/organic hybrids, inorganic and organometallic polymers, pre-ceramic polymers, high temperature adhesives, fiber sizings and interface coatings. We are also interested in modeling of these high temperature molecules and polymers to help drive polymer architecture design. Characterization techniques include chemical structure analysis, scattering, microscopy, spectroscopy, and thermal analysis.

SF.25.19.B0007: Nondestructive Evaluation, Characterization, Analytics

Uchic, Michael - 937-255-0594

This topic addresses fundamental technical challenges toward reliable nondestructive quantitative materials and damage characterization, regardless of scale. The intended application of this technology is towards improved nondestructive evaluation (NDE) capabilities that are integral to the sustainment and structural integrity of USAF airframes and engines and to the qualification of new materials with tailored properties. This includes but is not limited to technologies such as electromagnetic radiation across all frequency ranges, mechanical waves (e.g., ultrasound), and thermal diffusion-based methods. Current research focuses on the following activities:
• Development and utilization of forward models for quantitative prediction and optimization of NDE methods, which, have clear potential to account for the complexity of aerospace components.
• Development and utilization inverse methods to quantify the material state from NDE data, which, have clear potential to account for the complexity of aerospace components
• Analytics and statistical methods for data discovery from NDE data
• Implementation of uncertainty quantification of NDE models and experimental methods
• Correlative analysis of NDE data with ‘ground truth’ 3D data
• Creation of new NDE methods, and miniaturization of existing methods
• Integration of robotics (including swarm approaches), spatial registration sensors, machine vision, augmented and virtual reality, autonomous control systems, and other advanced technology with NDE methods
• Capability validation of in-situ damage detection sensors (Structural Health Monitoring (SHM)) via probability of detection methods


This topic is restricted to citizens of the United States.

SF.25.19.B0006: Nondestructive Evaluation for Additive Composite Materials

Wertz, John - 614-824-8280

Additive composite materials may one day revolutionize the design of USAF airframes. However, nondestructive evaluation (NDE) methods for characterizing manufacturing defects and damage remain in their infancy. Novel NDE methods to address this challenge are critical to implementation of these materials within USAF aircraft. Methods may include, but are not limited to, new or improved sensor designs that reveal greater detail than current state-of-the-art techniques like ultrasound, eddy current, or thermography; new models or analytical methods for defect or damage inversion; and/or the development of structural health monitoring (SHM) or self-sensing capabilities to provide real-time feedback on the material state.

SF.25.19.B0005: 4-D Analysis of Metallic Microstructures

Payton, Eric - 937-255-9882

The size, shape, and spatial distributions of phases and defects in a material comprise its microstructure. During thermomechanical processing, microstructures evolve in ways that affect the useful life and properties of structural metallic materials. Fast and accurate prediction of microstructures and their temporal evolution is needed for optimization of the processing routes used for producing aerospace components out of new alloys. Taking into account the micromechanisms activated by complex deformation processing phenomena (which may concurrently include grain boundary sliding, dynamic recrystallization, and precipitation of secondary phases) requires the development of new techniques for measuring microstructure morphology, topology, and statistics; for generation of representative synthetic microstructures; for running mesoscale simulations of microstructure evolution under realistic processing conditions; and for improving our understanding of the effects of deformation processing on microstructures through emerging characterization techniques. Proposals are sought that (1) have significant potential for simultaneously advancing both computational and experimental capabilities in-house at AFRL; (2) present pathways for incorporation of understanding of micromechanistic phenomena of microstructure evolution into fast-acting multi-scale models suitable for coupling with finite element simulations of thermomechanical processes; and (3) address novel alloy systems with significant potential for aerospace applications.

SF.25.19.B0004: Modeling, Synthesis, and Characterization of Point Defects for Quantum Technology

Bissell, Luke - 937 255 9130

Quantum technologies demand unique materials properties which depend on the specific application. For example, quantum information processing benefits from single photon sources that work at room temperature, with short excited state lifetimes. Quantum metrological applications rely on factors such as ground state electronic spins with long coherence times, optical spin-polarization effects, and electronic fine structures that are dependent on strain and electric / magnetic field interactions.
Single photon sources have been identified in systems such as diamond, silicon carbide, hexagonal boron nitride, and gallium nitride. We search for color centers that may have material properties that are more favorable than known systems for high rep-rate single photon sources, quantum sensing, and metrology. The rapid identification of such color centers and prediction of their photophysical properties would impact the existing quantum technology industry.
We theoretically model defect sites of interest with respect to physical parameters key to quantum technological applications. We use supercell and cluster approaches. Factors of interest include: absorption energy, emission wavelength, excited state lifetime, and the dependence of these quantities on electric, magnetic, and strain fields. We are also looking at ways to apply machine learning to identify new candidate defect centers.
We study novel ways to efficiently incorporate defects into diamond during synthesis, such as using rational design of defect molecules, and e-beam chemistry . Finally, we characterize the suitability of the synthesized defects for quantum technology applications using confocal microscopy, single-photon counting, magneto-optical spectroscopy, and electron microscopy.

SF.25.19.B0003: Structural Ceramics for Aerospace Applications

Cinibulk, Michael - 937 255 9339

The Ceramic Materials & Processes Research Team`s core focus areas center on research in the development of advanced fiber-reinforced ceramic-matrix composites (CMCs) and their constituents and in understanding how service environments degrade performance at the constituent level. Fundamental scientific issues remain to be addressed to enable the development of a full range of high-performance ceramics and ceramic-matrix composites for Air Force air and space applications. Current research focuses on investigating higher temperature nonoxide fiber and matrix constituents for enhanced durability, development of oxide fiber coatings and interface control, developing fabrication processes specifically for nonoxide composites, investigating the stability of constituents in aggressive environments, and understanding key environmental effects on constituent-level behavior that affects life in relevant service environments. Intended service environments for these composites include turbine and scramjet engines, as well as hot structures and thermal protection systems for hypersonic vehicles.

SF.25.19.B0002: Novel Ceramic Nanostructures, Preceramic Polymer Chemistry, Additive Manufacturing, and Composites for Extreme Environments

Dickerson, Matthew - 937-255-9147

Our research is focused on developing synthesis and advanced processing strategies that yield high-temperature materials with well-controlled and novel nanostructures. By exploiting nanoscale design, structural hierarchy, synthesis, and processing we strive to improve the performance of ceramic materials and composites for applications in extreme environments or multifunctional roles. Summer faculty fellows will work with the multidisciplinary AFRL team to pursue revolutionary concepts in high-temperature material design and synthesis. Our research group focuses on materials synthesis, nanomaterials, advanced manufacturing, and biomimetic materials. Advanced concepts in high-temperature composites are also of interest.

Materials currently being studied include inorganic nanomaterials, hybrid nanomaterials, preceramic polymers, dendrimer polymers, refractory ceramics, non-oxide ceramics, organometallic polymers, semiorganic polymers, hyperbranched polymers, block co-polymers, 2D materials, nanotubes, C/C, and ceramic nanocomposites.

https://scholar.google.com/citations?user=cqQDl34AAAAJ&hl=en

This opportunity is open to US citizens only.

SF.25.18.B0007: High Temperature Oxidation and Environmental Resistance in Refractory Complex Concentrated Alloys

Butler, Todd - (937) 255-5420

Refractory complex concentrated alloys (RCCAs) are an emerging class of alloy that have the potential to push the temperature capability of current metallic solutions. While these alloys have been shown to have higher specific strength than nickel-based superalloys at elevated temperatures, they have been limited by environmental attack. Recent work has highlighted compositions that have shown increased oxidation resistance in comparison to conventional refractory alloys, which is promoted by the sluggish oxidation of complex oxides. While this work has identified some beneficial prototype oxide structures much more fundamental work is required to deliver inherent oxidation resistance for a structural RCCA alloy. We are interested in foundational work focused on inherent oxidation of these complex systems including: understanding of oxidation thermodynamics and kinetics, identification of protective oxide products and predictive oxidation models. We are also interested in exploring the use of coatings and surface treatments to increase oxidation resistance while minimally effecting the bulk composition.

SF.25.18.B0005: Magnetoelectric Materials for Frequency Tunable Microwave Electronics

Page, Michael - (937) 255-4671

The objectives of this research are to investigate different magnetoelectric materials and phenomena with an eye towards elucidating novel materials physics that can be used for frequency agile microwave electronics. Description: Ferromagnetic resonance (FMR) in ferro/ferromagnetic materials is a promising physical phenomena for frequency tunable microwave electronics as is indicated by the widespread use of FMR in Yttrium Iron Garnet (YIG) based frequency agile oscillators and filters. Investigating novel frequency agile driving mechanisms and approaches holds the key to paving the way towards next generation microwave electronics. Thus, we are interested in studies involves investigations into novel materials, processes and physical phenomena associated with the dynamics of magnetic materials including ferromagnetic resonance and spin waves at microwave frequencies and the ability to induce/tune such high frequency oscillations without the use of external electromagnets. Towards this aim promising topics of study include, but not limited to voltage tunable FMR, novel current FMR tuning mechanisms, anti-ferromagnetic resonance, exchange bias or dipolar bias as a means to shift, fix, or adjust FMR frequencies, acoustic-driven FMR, and/or material studies associated with composite multiferroics.

SF.25.18.B0004: Laser Processing of Soft Materials and Devices

Glavin, Nicholas - (937) 255-6977

The use of lasers to directly crystallize, functionalize, pattern and induce local surface reactions in soft materials represents an exciting processing development for future flexible devices. With this technique, materials can be processed on soft, flexible substrates by restricting the absorption of the light to the active material only and also allow sub-micron photon-matter interactions and patterning. Particular materials of interest include 2D materials, organic electronic materials, nanoparticles, and other nanomaterials for flexible sensors, transistors, and photonic devices. In-situ process diagnostics will look into kinetics of phase transformation, microstructure, and morphology of the nanomaterials undergoing laser processing. Post processing characterization will include x-ray characterization, atomic force microscopy, Raman and photoluminescence, as well as electrical testing in both the DC and RF domains. This research program will address the Air Force manufacturing and processing needs for next generation flexible electronics for man/machine communication and conformal ISR.

SF.25.18.B0002: Ultra-wide bandgap (UWBG) Materials for Electronics and Optoelectronics

Mou, Shin - (937) 255-9779

The objective is to study the fundamental properties of ultra-wide bandgap (UWBG) semiconductor materials (bandgap larger than 4 eV, e.g., AlN, Ga2O3, diamond, cubic boron nitride) including electronic transport measurement, defect information, photoluminescence, capacitance spectroscopy, etc. It will also involve the fabrication of the test structures for these measurements. UWBG semiconductors have the intrinsic advantages of large breakdown voltages for high power handling, emitting deep ultra-violet light, and providing stable single photon emission at room temperature due to their large bandgaps. Fundamental studies need to be pursued to understand the basic properties of these materials due to the early stage of research and development we are at. Therefore, in this topic, we look into various ways to characterize the UWBG materials to gain important knowledge on their bandstructures, electronic transport properties, defect information, interface properties, and optical emission. The characterization techniques include but are not limited to Hall-effect measurements, voltage-current measurements, capacitance spectroscopy, photoluminescence, and optical absorption. Sample preparation and test structure fabrication will also be involved to produce the test samples. The goal of this project is to generate critical and novel knowledge to evaluate UWBG materials for the interests of AF and DoD.

SF.25.17.B0001: Advanced Materials for Switching Memory Devices

Ganguli, Sabyasachi - 9372551139

An overarching theme for this research is materials development to enable more precise control over the memristor switching properties, electrical testing results from device pairs that exhibit multi-terminal latching, and efforts towards integration of multiple devices to emulate neuron functions such as programmable spiking behavior. The ultimate goal of this research program is the realization of a memristor-based, fully non-digital, neuron equivalent that can function as a unit cell in a cellular neural network. Dense crossbar arrays of non-volatile memory (NVM) devices represent one possible path for implementing massively-parallel and highly energy-efficient neuromorphic computing systems. Different types of NVM devices – including phase change memory, conductive-bridging RAM, filamentary and non-filamentary RRAM, and other NVMs –for use within a neuromorphic computing application would be investigated in this research.
Specific research would look into synthesis by Atomic Layer Deposition and Pulsed Laser Deposition, device processing (photolithography), and device performance characterization of these NVM materials. Material characterization methods like SEM and TEM (material microstructure and morphology), spectroscopic ellipsometry, x-ray diffraction, atomic force microscopy, photoluminescence, temperature-dependent Hall-effect/sheet-resistivity, temperature-dependent current-voltage, deep level transient spectroscopy, transmission line, TDTR (Time Domain Thermo Reflectance) can be applicable to establish structure property relationships. Applicants with backgrounds in various semiconductors and their electrical and thermal characterization techniques, and in simple device processing techniques are desirable. This research program will address to Air Force needs for the next generation extreme environment survivable high power RF electronics.

SF.25.16.B0002: Damage Tolerant Multifunctional Polymer Composites

Nepal, Dhriti - (937) 255-3232

Efficient materials design and development of tools for their damage prediction are crucial for multifunctional composites. Biomimetic design has opened up avenues for achieving extraordinary combinations of toughness and strength, similar to natural composites, although natural composites still surpass these properties. Key challenges include lack of understanding of the failure mechanisms in such composites and the influence of size, shape, and orientation of the nanofiller on toughening. There are still open questions about chemical structure and morphology around the interphase region and its influence on the mechanics. Overcoming these challenges requires careful design and a multidisciplinary approach combining synthesis, processing, characterization (across scales), and multiscale modeling. We are interested in understanding the failure mode from the nano- to higher scales, and the underlying processing structure-property relationship. Key interests include the biomimetic design of hierarchical structures; elucidating the fundamental principles of the underlying fracture mechanism based on chemistry and shape/size/distribution of the nanofillers; investigating corresponding electrical and optical properties; and establishing techniques to predict failure using molecular and mesoscale mechanics modeling. Techniques include bulk and surface spectroscopy, high-resolution X-ray micro-computed tomography, nanoscale chemical/physical/mechanical mapping, atomic force microscopy, electron microscopy, in-situ testing, and multiscale modeling.
Keywords:
Biomimetic; Nanocomposite; Nanoscale imaging; Polymer; Mechanical properties; Spectroscopy; Fracture mechanics; Electro-optical properties; Multiscale modeling;

SF.25.16.B0001: Surface and Interface Control of Gallium Alloys for Integrated Stretchable Electronics

Tabor, Christopher - (937) 255-9184

Abstract: Gallium liquid metal alloys (GaLMAs) are room temperature fluidic conductors that can be confined to microchannels to explore flexible and stretchable electronics as well as reconfigurable agile RF electronics. The major hurdles to implementing these GaLMA materials are two-fold, controlling (1) the spontaneously forming oxide skin on the liquid alloy and (2) the reactive nature of the liquid alloy with nearly every metallic electrode material. To overcome these limitations, controlling the surface chemistry of the liquid alloys in critical and identifying electronic materials that functionally interface well with the GaLMA without reacting with them are critical issues to address. Exploring these relationships through modeling, fabrication, characterization, and processing developments is an area where extensive research is being conducted. Novel additive manufacturing techniques such as aerosol jet and inkjet among others can contribute to proper control over the surface and interface chemistry of the GaLMA materials.

SF.25.14.B8922: Computer Simulations for Design of Improved Aerospace Materials

Berry, Rajiv - 937-255-2467

Research relates to current and prospective interests in design of improved materials for aerospace applications. Methodologies include electronic structure theory, chemical kinetics modeling, and molecular dynamics (including coarse-grained MD). Properties of interest include computation of transport properties (diffusion, electrochemical characteristics) and physical properties (glass transition, fragility, and density), elucidation of reaction pathways, prediction of interfacial phenomenon, and calculation of mechanical properties. More recently, emphasis has shifted to the simulation of bio-inspired materials as a function of pH, ionic strength and peptide/nucleotide sequence and structure. Projects of interest are described below:

(1) Classical and coarse-grained molecular dynamics are being conducted to simulate the assembly and function of biopolymers. Knowledge gained from these studies will be used to produce both biological and bio-inspired materials with tailored mechanical properties for a variety of Air Force applications, including structural components, sensors and templates for materials processing.

(2) Molecular dynamics simulations are being employed to investigate the biocompatibility of candidate polymer hydrogels as injectable biosensors. Candidates are modelled to predict their mechanical and transport properties as well as their ability to degrade in a biological environment. The principal outcomes will be guidance to development scientists and engineers in terms of hydrogel match to skin compliance, clearer identification of the factors which most affect small-species diffusion, and comparative degradation rates among the candidates.

(3) Atomistic simulations are being used to explore functional applications of biological macromolecules. Implementation of cutting-edge codes and libraries (such as AlphaFold2, code released on 15 July 2021) on DoD-HPC supercomputers are enabling rapid and accurate determination of protein structure and function starting from the protein sequence. Such techniques are being incorporated in automated workflows in singularity containers. They offer opportunities for developing protocols to rapidly respond to challenges in chemistry and biology which impact US DOD and in particular aerospace interests such as biosequestration of valuable metals and biodegradation of environmental pollutants.

Keywords: Quantum mechanics (DFT); Classical molecular dynamics (all-atom and coarse-grained); Development of hybrid QM-MD techniques; Mechanical properties of polymer composites, assembly and structure-function relationships of bio-inspired materials; Biosequestration; Biodegradation

US citizenship required.

SF.25.14.B1101: Investigating Additive Manufacturing Polymer Matrix Composite Performance

Flores, Mark - 937-255-2302

Additive manufactured (AM) polymer matrix composites (PMCs) game-changing disrupting technological trends are clear and are becomings more widely adopted in the design of an aircraft. However, in order for this material to come into fruition in the design of an aircraft sub-system, the material must be evaluated in accordance to the Aircraft Structural Integrity Program (ASIP) MIL-STD-1530. The Durability and Damage Tolerance (DADT) requirements must take into account stability, producibility, supportability, predictability of structural performance, characterization of mechanical and physical properties. The framework is quite evident and clear on the amount of engineering that is needed to satisfy the certification of the material while providing a substantial pathway to advance AM technologies further. However, according to the AFLCMC/EZ Structures Bulletin, among the most difficult challenges for AM processes is the ability to establish an “accurate prediction of structural performance” specific to DADT. Machine learning has allowed researchers to design materials via the additive manufacturing process. Topology optimization has proven to be a creative outlet during the design phase, but primarily focuses on static boundary conditions and stiffness. Although, a variety of complex geometries with varying material stiffness could be generated, the lack of DADT focused requirements ultimately precludes the ability to address feasibility studies for structural parts during the early stages of its development. AFRL seeks to further the community’s knowledge on the performance of additively manufactured composites and has identified these key challenges in addressing AM composites.
· Materials Characterization (i.e. Effects of Defects, Effects of Processing, size scales )
· Limited understanding of acceptable ranges of variation
· Limited understanding of key failure mechanisms and material anomalies
· Development of capable NDI methods

SF.25.13.B7103: Nucleation and Growth of Carbon Nanotubes

Maruyama, B - (937) 255-0042

Carbon nanotubes have been studied extensively beginning in the early 1990's. Their unparalleled properties make them attractive for application in composites, electronic devices, sensors, etc. However, production of nanotubes remains inefficient and expensive, and the as-produced purity is typically less than desired. Improvements in production yield, catalyst efficiency, purity and type selectivity will enhance the viability of these materials. A fundamental understanding of the mechanisms by which nanotubes nucleate and grow is pursued in order to achieve such improvements by in-situ characterization of nucleation and growth.

We are exploring rational design of catalysts for CVD synthesis of carbon nanotubes. We modify the catalyst and catalyst support and observe the resultant changes in nanotube growth. We have also developed an Autonomous Rapid Experimentation System (ARES) to increase our ability to explore this complex parameter space. We work collaboratively with different disciplines including materials science, chemistry, physics, robotics, operations research and artificial intelligence/machine learning.

SF.25.13.B1009: Intelligent Manufacturing

Berrigan, John - (937) 203-0873

The smart factory of the future is a flexible system can adapt to and learn from new conditions in real or near-real time, and autonomously run entire production processes. This topic seeks to teach manufacturing tools to become teammates through investigation of novel approaches to machine vision, data fusion, and human-machine trust models in the context of materials processing or manufacturing. Manufacturing processes of interest include, direct ink write additive manufacturing, spray processes, and robotic assembly.

SF.25.09.B0153: Modeling Structural Alloys for Aerospace Applications

Woodward, C.F - (937) 255-9816

This research focuses on developing and applying modeling and simulation methods to explore broad aspects of metal alloy development. Target materials include, but are not limited to, high temperature structural materials such as Ni-based superalloys, refractory metal intermetallics and Ti-Al alloys. Current areas of interest include modeling plasticity at the atomic and micron scales using electronic structure, atomistic and dislocation dynamics methods. Research in this area includes size scale, chemical, ordering, solution, and precipitate effects. Also, free energy models, based on first principles methods, are used to predict phase stability and the nature and evolution of defects in these materials. This includes properties of both the liquid and solid phases and the microstructural evolution of complex metal alloys. Significant computational resources are available through the High Performance Computing Modernization Office to perform large scale calculations, analysis and visualization. Research is closely integrated with the group's 3-d characterization and micro-scale plasticity experimental techniques and the AFRL/RX characterization facility.

SF.25.09.B0146: Metals Probabilistic Performance

Turner, Todd - (937) 255-5460

The research focus is to develop a comprehensive understanding of relevant damage initiation and accumulation mechanisms and failure of aerospace structural metallic alloys and develop next-generation validated damage evolution and probabilistic fatigue life prediction methodologies necessary for forecasting durability and reliability during service. Specific topics of interest include: (1) microstructure-sensitive probabilistic fatigue and damage tolerance models, with emphasis on life-limiting properties, (2) initiation, microstructure-scale (small) crack growth and continuum-scale (long) crack growth under service loading conditions such as fatigue, dwell-fatigue and thermal-mechanical fatigue loading, (3) 3-dimensional crack growth and advanced fracture mechanics, including microstructure-scale (small) crack growth and continuum-scale (long) crack growth, (4) high fidelity microstructure-sensitive constitutive models for use in 3-dimensional simulation of damage accumulation in actual microstructures, (5) advanced micro- and macro-mechanics experimentation including microstructure-scale deformation mapping, multi-scale (microscale, milliscale and conventional) specimen testing under uniaxial and multi-axial loading conditions, and (6) influence of surface treatments such as peening (e.g. shot peening, laser shock peening etc.) and stress concentration sites such as holes on fatigue life and damage tolerance. Models emphasizing mechanism-based approaches for reduction in uncertainty, Bayesian methods and independent validation of predictive capabilities are of interest to us. We are seeking Integrated Computational Materials Science and Engineering (ICMSE) based multi-scale approaches and models that can be used to probabilistically predict location specific properties in geometrically complex components with nominally uniform or gradient microstructures / chemistries. Specific materials of interest include, but not limited to, Titanium alloys, Nickel-base superalloys, additively manufactured metals, and functionally graded and joined metals. Specialized high temperature testing capabilities, material characterization facilities and significant computational resources are available for multi-scale experiments and computations.

US Citizens only.

SF.25.07.B5509: Theory and Computation for the Design of Functional Materials

Pachter, Ruth - 937-255-9689

We are exploring development of materials for applications in photonics and electronics that include, but are not limited to, materials with improved optical responses, materials for quantum technologies, materials having novel electronic sensing modalities, or materials for neuromorphic computing. To enhance the capability for "real materials" design and atomic-scale control, our research focuses on developing and applying fundamental theoretical and computational materials science approaches, including multiscale modeling. The application of machine learning methods to accelerate materials discovery and development, and algorithm developments for computational modeling on quantum processors, are also of interest. The goal is to explain measured properties and predict key observables that determine materials behavior, which are verified experimentally, also in a device setting. Examples comprise optical excitations in finite and extended material systems, including nonlinear optical processes in low-dimensional materials; electron transfer and transport phenomena; interfacial interactions; and biological processes. Access to high performance computing facilities is available.

USA citizenship is required.

SF.25.07.B5471: Development and Characterization of Photorefractive Materials

Evans, Dean - (937) 656-9059

Photorefractive materials are being studied for applications in all-optical devices where the transfer of energy from one beam to another (beam coupling) occurs through a photorefractive grating. In inorganic photorefractives, contra-directional two-beam coupling is achieved when two counter-propagating beams interfere and form a reflection grating. The use of this geometry for studying the photorefractive properties of a material has the advantage of simplicity because only one incident beam is used, while the second beam is generated by the Fresnel refection inside the material. We have also investigated photorefractive transmission gratings in hybridized organic-inorganic photorefractive materials, as well as light scattering effects in hybridized organic-inorganic photovoltaic liquid crystal cells. Ferroelectric nanoparticles have been incorporated in the hybridized organic-inorganic photorefractive materials to enhance the optical gain.
We are interested in developing and understanding the physics of bulk and hybridized materials that exhibit the photorefractive effect in the visible, near-infrared, and infrared spectral regions. Because the photovoltaic effect can strongly influence the formation of gratings in some materials, we are also interested in the electrical properties of photorefractive materials. Inorganic crystals, liquid crystals, and ferroelectric nanoparticles are being explored.
References
Carns JL, et al: Optics Letters 31: 993 (2006).
Cook G, et al: Optics Express 16: 4015, 2008
Basun SA, et al: Physical Review B, 84: 024105, 2011
Evans DR, et al: Physical Review B, 84: 174111, 2011
Basun SA, et al: Physical Review B 93: 094102, 2016.
Shcherbin K, et al: Optics Express 6: 3670, 2016.
Keywords:
Nonlinear optics; Photovoltaic effect; Hybridized-organic-inorganic-photorefractive materials; Liquid crystal light valves; Photorefractive effect; Contra-directional two-beam coupling

SF.25.07.B5456: Surface Phenomena in the Formation of Epitaxial Plasmonic Quantum Structures

Eyink, Kurt - (937) 255-5710

This research focuses on the production and modeling of epitaxial plasmonic structures in conjunction with quantum III-V semiconductor structures obtained during the molecular beam epitaxial growth. In this research we are currently focusing on two different approaches ones uses semi-metallic ErAsSb layers and nanoparticles in close proximity to epitaxial quantum structures and study the interaction between plasmonic fields formed around the metallic species and the quantum structures which can alter their emission and absorption characteristics. The other is aimed at forming hyperbolic metamaterials through AlGaSb/InAsSb or SLS structures to form a hyperbolic stack whose properties are tuned through doping or optical pumping. In this work, we employ both in situ sensors (such as spectroscopic ellipsometry, desorption mass spectrometry, and reflection high energy diffraction) and ex situ characterization (such as variable angle spectroscopic ellipsometry, AFM, STM, x-ray reflectivity and in-plane x-ray diffraction). An intermediate goal is to correlate the growth conditions with the response seen in a hyperbolic metamaterial. We are also applying various electrical, magnetic, and optical fields to these structures to dynamically change these structures. These layers are being formed to enhance detector, emitter, and other electronic and optical structures relevant to DOD applications.

SF.25.07.B4282: Infrared Optical Material Development

Guha, S - (937) 255-6636 x3022

Strong third order nonlinear optical performance is demonstrated by many materials in the infrared (IR), including narrow and mid-bandgap semiconductors in the bulk form, as well as thin-film coatings of various oxides. Our overall goal is to understand and optimize the nonlinear optical properties of these materials through theoretical and experimental studies involving IR laser beams in different wavelength and pulse duration regimes. Currently, the IR materials project includes the development of materials, versatile characterization of materials properties, and detailed understanding of materials properties through modeling. The materials being developed include novel semiconductor alloys in crystalline or glassy forms and thermochromic oxide thin films. A variety of laser systems are used to characterize the materials at cryogenic and ambient temperatures. The modeling effort includes semiconductor material modeling, as well as laser beam propagation modeling with the eventual goal of combining the two efforts to obtain complete information about the laser-material interaction. Laser beam propagation modeling presents challenges for fast optical systems-especially when aberration of lenses have to be taken into account-and for propagation through multiple linear and nonlinear optical elements. Development of infrared sources through nonlinear optical frequency conversion is also an ongoing activity.

SF.25.07.B4280: Characterization of nano-optical plasmonic systems

Urbas, A.M - (937) 830-3534

Controlling light at the sub-wavelength scale has the potential to dramatically redefine how optical devices and technologies work in addition to opening up numerous applications where control of optical interactions is useful, from low cost and compact optical sensors to future applications in quantum information and sensing. In order to investigate metamaterial, nano-optical, and plasmonic effects, we conduct a program focused on fabrication and characterization of photonic structures and devices. Areas of emphasis include novel materials for structured optical materials systems, incorporating active materials into plasmonics and nano-optical elemetns, and the design and fabrication of metasurface and metamaterial based devices with these systems. For example, two dimensional materials, nitrides and highly doped oxides show significant potential in plasmonics. These can provide unique routes to active plasmonics and nonlinear systems. As well, the exploration of materials which can expand the operating range of plasmonic systems and increase their resilience may open up new applications, not possible with noble metal plasmonic systems. Plasmonic systems with gain have the potential to become novel light sources, such as single and coherent photon sources, in addition to providing low loss optical routing. Finally, we explore the use of metasurface devices for imaging, spectroscopy, and integrated photonics. We probe these complex and integrated systems through combinations of linear and nonlinear spectroscopy with near field and time domain techniques. Through these studies, we advance the understanding of nano-optical systems and effects while advancing application potential.

SF.25.07.B3757: Dynamic Optical Materials using Soft Matter Motifs

Godman, Nicholas - 937-255-9824

We study the structure/property relationships of a variety of materials systems, which are broadly applicable to linear and nonlinear optical materials. Emphasis is placed on utilizing the electro-optical properties of liquid crystals for a wide variety of applications, including the development of switchable diffractive optical elements using controlled phase separation of polymer/liquid crystal composites. We are examining the fundamental polymer and liquid crystal physics, which govern the morphology and subsequent electro-optical behavior of this unique class of composites. Our interests include understanding the complex balance between phase separation, diffusion, and polymerization kinetics, and how these change as a function of the starting materials and conditions. Other liquid crystal interests include new twisted liquid crystal motifs, cholesteric and cholesteric polymer films, and novel combinations of liquid crystal and polymer structures. Current interests include photo and electro-optic mixtures of cholesteric liquid crystal/polymer mixtures, polymer photochemistry, physics of polymer structures grown from surfaces, anisotropic polymerization methodologies, polymerization strategies/designs within structured media, and novel photonic thin films fabricated using plasma enhanced chemical vapor deposition techniques.

SF.25.07.B0141: Fabrication of Materials for Nonlinear Optics Applications

Grusenmeyer, Tod - (937) 255-9212

We are investigating the synthesis and characterization of materials for nonlinear optics applications. The systems we are studying include chromophores, nanoparticle-chromophore hybrids, quantum dots, two-dimensional materials, perovskites and photonic polymer systems. We investigate the fabrication and properties of polymer composites, molecular glasses, multilayers, metalens systems and optical structures containing these materials. We also perform investigation of excited state behavior, including flash photolysis, ultrafast transient absorption spectroscopy and emission spectroscopy. Researchers with experience in chemical synthesis, polymer engineering and optical design are encouraged to apply.

SF.25.06.B5511: Modeling of Time-Dependent Behaviors in Composite Materials

Hall, Rick - 937-255-9097

Needs exist to characterize the time-dependent, thermomechanical behaviors of composite materials and their constituents under the multi-faceted influences of e.g. high temperatures, intrusion of fluids, damage, and loss and modification of material properties due to reactive and manufacturing processes. Constitutive models are under development which are thermodynamically consistent and eventually suitable for finite element structural modeling. Desired solution schemes may require stability-enhancing, multiscale enrichment delivering accuracy exceeding that obtained through standard relationships between interpolants and nodal degrees of freedom. Reduced/surrogate computational models based on the previously-described physics-based models are also of interest for application to Process-Structure-Property frameworks suitable for machine learning and probabilistic assessments of data features.

SF.25.06.B5510: Durability and Damage Tolerance of Polymer Matrix Composites

Flores, Mark - 937-255-2302

Research focus is on the development of process-modeling and material behavior tools for structural polymer matrix composites to support the development of an Integrated Computational Materials Engineering approach for material design. The overall objective is the development of fundamental processing-structure-property relationships for composites through integration of analytical, numerical and experimental tools. Emphasis is placed on models that describe the fundamental behavior of the material including: (1) failure initiation and propagation that including micro and global buckling for compression loading of composites; (2) spectrum loading fatigue crack initiation and growth in composites; (3) linking processing and mechanical performance models for aerospace grade structural composites; and (4) development of analytical/numerical and testing methods for characterizing and modeling the environmental degradation of polymer matrix composites. Interest includes continuously reinforced composites manufactured from uni-directional layers as well as textile fiber morphologies (weaves and braids). Excellent facilities are available including polymer composite processing lab, thermal analysis lab, x-ray tomography, electro-optics lab and mechanical testing lab.

SF.25.06.B5508: Hetero-structured Nano Materials and Devices

Roy, Ajit - 937-255-9034

he innovative utilization of materials heterogeneity through efficient design of materials interface morphology, especially at the atomistic and nano scale, offers new opportunities in tailoring properties (electronic, thermal, chemical and mechanical) of materials and influencing device performance. The emphasis is in understanding the role of hetero-material interface physics at the atomic scale to tailoring properties and linking that to continuum – geared towards efficient materials design for quantum devices, memoristors, energy, and sensors. Employing meso scale modeling approaches (such as tight binding DFT, MD, etc.) is of interest for quantitative interpretation of experimental data, along with the integration of atomistic and meso scale is of interest for tailored materials design of multiple constituents, vacancy, point defects, and its nanostructured interface design.

SF.25.06.B4279: Towards Bottom Up Meta Materials: Hetero-Assemblies of Functional Nano-Structured Hybrids and Polymers

Vaia, R - (937) 255-9209

The ability to engineer the performance of a material system is directly related to the precision of the techniques available to prescribe the structure and arrangement of its constituents (i.e. its architecture). Many emerging technologies require organic-inorganic compositions (30-60%) and architectural refinement that challenge traditional blending concepts, as well as demanding throughput and acreage that challenge emerging high-energy lithography and deposition technologies. Demands for such films and bulk materials range from high performance dielectrics, human performance sensors, and energy storage, to plasmonics, optical metamaterials, nonlinear-optical devices, and compliant conductors.
Efforts focus on establishing the principles underlying processing-structure-property relationships through a multi-disciplinary team that combines synthesis, processing, simulation, physics and concept demonstration. The goal is to understand the factors limiting structural perfection, and thereby establish predictability between the design of the organic-inorganic building block and the properties of its resultant assembly and device. Principle interests include inorganic nanoparticle synthesis, interface modification with a focus on the biotic-abiotic, self- and directed assembly, plasmonics, electro-optical performance, mechanical adaptivity, autonomic response and process compatibility with print-to-device technologies. Techniques include polymer physics, scattering (optical, x-ray, and neutron including synchrotron radiation experiments for real-time characterization), electron microscopy, atomic force microscopy, standard linear and nonlinear optical characterization, bulk and surface spectroscopy, modeling, processing, and synthesis.

AFRL-Materials and Manufacturing

Mr. Groff, Mark
AFRL/RX
2977 P Street, Bldg. 653, Room 416
Wright Patterson Air Force Base, Ohio 45433
Telephone:
Email: mark.groff.1@us.af.mil