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Materials Science and Engineering

Air Force Institute of Technology

2017

Articles 1 - 8 of 8

Full-Text Articles in Engineering

Use Of A Novel Infrared Wavelength-Tunable Laser Mueller-Matrix Polarimetric Scatterometer To Measure Nanostructured Optical Materials, Jason C. Vap, Stephen E. Nauyoks, Michael R. Benson, Michael A. Marciniak Oct 2017

Use Of A Novel Infrared Wavelength-Tunable Laser Mueller-Matrix Polarimetric Scatterometer To Measure Nanostructured Optical Materials, Jason C. Vap, Stephen E. Nauyoks, Michael R. Benson, Michael A. Marciniak

Faculty Publications

Nanostructured optical materials, for example, metamaterials, have unique spectral, directional, and polarimetric properties. Samples designed and fabricated for infrared (IR) wavelengths have been characterized using broadband instruments to measure specular polarimetric transmittance or reflectance as in ellipsometry or integrated hemisphere transmittance or reflectance. We have developed a wavelength-tunable IR Mueller-matrix (Mm) polarimetric scatterometer which uses tunable external-cavity quantum-cascade lasers (EC-QCLs) to tune onto and off of the narrowband spectral resonances of nanostructured optical materials and performed full polarimeteric and directional evaluation to more fully characterize their behavior. Using a series of EC-QCLs, the instrument is tunable over 4.37-6.54 μm wavelengths …

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Modeling Micro-Porous Surfaces For Secondary Electron Emission Control To Suppress Multipactor, James M. Sattler, Ronald Coutu Jr., Robert A. Lake, Tod V. Laurvick, Tyson C. Back, Steven. B. Fairchild Aug 2017

Modeling Micro-Porous Surfaces For Secondary Electron Emission Control To Suppress Multipactor, James M. Sattler, Ronald Coutu Jr., Robert A. Lake, Tod V. Laurvick, Tyson C. Back, Steven. B. Fairchild

Faculty Publications

This work seeks to understand how the topography of a surface can be engineered to control secondary electron emission (SEE) for multipactor suppression. Two unique, semi-empirical models for the secondary electron yield (SEY) of a micro-porous surface are derived and compared. The first model is based on a two-dimensional (2D) pore geometry. The second model is based on a three-dimensional (3D) pore geometry. The SEY of both models is shown to depend on two categories of surface parameters: chemistry and topography. An important parameter in these models is the probability of electron emissions to escape the surface pores. This probability …

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On-Chip, High-Sensitivity Temperature Sensors Based On Dye-Doped Solid-State Polymer Microring Lasers, Lei Wan, Hengky Chandrahalim, Cong Chen, Qiushu Chen, Ting Mei, Yuji Oki, Naoya Nishimura, Lingjie Jay Guo, Xudong Fan Aug 2017

On-Chip, High-Sensitivity Temperature Sensors Based On Dye-Doped Solid-State Polymer Microring Lasers, Lei Wan, Hengky Chandrahalim, Cong Chen, Qiushu Chen, Ting Mei, Yuji Oki, Naoya Nishimura, Lingjie Jay Guo, Xudong Fan

Faculty Publications

We developed a chip-scale temperature sensor with a high sensitivity of 228.6 pm/°C based on a rhodamine 6G (R6G)-doped SU-8 whispering-gallery mode microring laser. The optical mode was largely distributed in a polymer core layer with a 30 μm height that provided detection sensitivity, and the chemically robust fused-silica microring resonator host platform guaranteed its versatility for investigating different functional polymer materials with different refractive indices. As a proof of concept, a dye-doped hyperbranched polymer (TZ-001) microring laser-based temperature sensor was simultaneously developed on the same host wafer and characterized using a free-space optics measurement setup. Compared to TZ-001, the …

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Electron Paramagnetic Resonance Study Of Neutral Mg Acceptors In Β-Ga2O3 Crystals, Brant E. Kananen, Larry E. Halliburton, Elizabeth M. Scherrer, K. T. Stevens, G. K. Foundos, K. B. Chang, Nancy C. Giles Aug 2017

Electron Paramagnetic Resonance Study Of Neutral Mg Acceptors In Β-Ga2O3 Crystals, Brant E. Kananen, Larry E. Halliburton, Elizabeth M. Scherrer, K. T. Stevens, G. K. Foundos, K. B. Chang, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR) is used to directly observe and characterize neutral Mg acceptors (Mg0Ga) in a β-Ga2O3 crystal. These acceptors, best considered as small polarons, are produced when the Mg-doped crystal is irradiated at or near 77 K with x rays. During the irradiation, neutral acceptors are formed when holes are trapped at singly ionized Mg acceptors (Mg−Ga). Unintentionally present Fe3+ (3d5) and Cr3+ (3d3) transition-metal ions serve as the corresponding electron traps. The hole is localized in a nonbonding p orbital on a threefold-coordinated oxygen ion …

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Analysis Of Additively Manufactured Lattice Structures Using Finite Element Methods, Christopher A. Box Mar 2017

Analysis Of Additively Manufactured Lattice Structures Using Finite Element Methods, Christopher A. Box

Theses and Dissertations

Additive Manufacturing (AM) processes are well known for their ability to fabricate parts with complex geometries. Lattice structures leverage this ability to create parts with high strength-to-weight ratio and other desirable structural qualities. This research presents a parameterized modeling tool using common Finite Element Analysis (FEA) and scripting software with which aggregated lattice structures can be analyzed, given different geometric properties and loading conditions. A full factorial Design of Experiments is run to explore the effects of various parameters on the strength of lattice structures. Experimental compressive strength results from three FDM-produced PLA lattices are discussed and compared to predictions …

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Transient Nonlinear Optical Properties Of Thin Film Titanium Nitride, Sarahkatie Thomas Mar 2017

Transient Nonlinear Optical Properties Of Thin Film Titanium Nitride, Sarahkatie Thomas

Theses and Dissertations

nitride (TiN) and scandium nitride (ScN), using the beam deflection characterization technique. The thin films were made at the Air Force Research Lab by controllably unbalanced magnetron sputtering. Transition metal nitrides, specifically TiN, are used widely in industry because of their unique properties, including extreme hardness and high damage threshold. The properties of thin film transition metal nitrites are dependent on the chemical structure of the thin film, which can be heavily influenced by substrate and deposition method. This durability and tunability is an asset in applications such as sensor protection and all optical computing. Two substrates, sapphire (Al2 …

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Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 900°C In Air And In Silicic Acid-Saturated Steam, Ronald K. Mitchell Mar 2017

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 900°C In Air And In Silicic Acid-Saturated Steam, Ronald K. Mitchell

Theses and Dissertations

Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for demanding aerospace applications such as aircraft engine hot-section components. In these applications the composites will be subjected to cyclic and sustained loadings at elevated temperature in aggressive combustion environments. Current aircraft engines employ Nickel-based superalloys in applications such turbine blades, where the metallic alloys must perform at or near their operating temperature limits in highly corrosive environments. The SiC/SiC composites, which offer low density, high strength and fracture toughness at elevated temperatures could potentially replace Nickel-based superalloy in aircraft engine applications. However, before the SiC/SiC composites can be safely used …

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Defect-Related Optical Absorption Bands In Cdsip2 Crystals, Elizabeth M. Scherrer, Brant T. Kananen, Eric M. Golden, F. Kenneth Hopkins, Kevin T. Zawilski, Peter G. Schunemann, Larry E. Halliburton, Nancy C. Giles Mar 2017

Defect-Related Optical Absorption Bands In Cdsip2 Crystals, Elizabeth M. Scherrer, Brant T. Kananen, Eric M. Golden, F. Kenneth Hopkins, Kevin T. Zawilski, Peter G. Schunemann, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

When used as optical parametric oscillators, CdSiP2 crystals generate tunable output in the mid-infrared. Their performance, however, is often limited by unwanted optical absorption bands that overlap the pump wavelengths. A broad defect-related optical absorption band peaking near 800 nm, with a shoulder near 1 µm, can be photoinduced at room temperature in many CdSiP2 crystals. This absorption band is efficiently produced with 633 nm laser light and decays with a lifetime of ∼0.5 s after removal of the excitation light. The 800 nm band is accompanied by a less intense absorption band peaking near 1.90 µm. Data …

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