Engineering Commons^™

Experimental Investigation Of The Thermochemical Reduction Of Arsenite And Sulfate: Low Temperature Hydrothermal Copper, Nickel, And Cobalt Arsenide And Sulfide Ore Formation, Nicholas Allin

Graduate Theses & Non-Theses

Experiments were conducted to determine the relative rates of reduction of aqueous sulfate and aqueous arsenite (As(OH)₃,aq) using foils of copper, nickel, or cobalt as the reductant, at temperatures of 150ºC to 300ºC. At the highest temperature of 300°C, very limited sulfate reduction was observed with cobalt foil, but sulfate was reduced to sulfide by copper foil (precipitation of Cu₂S (chalcocite)) and partly reduced by nickel foil (precipitation of NiS₂ (vaesite) + NiSO₄·xH₂O). In the 300ºC arsenite reduction experiments, Cu₃As (domeykite), Ni₅As₂, or CoAs (langisite) …

Virtual Substrate Synthesis For Low-Cost High Efficiency Iii-V, Sean J. Babcock

Electrical & Computer Engineering Theses & Dissertations

The use of the low-cost thin-film vapor-liquid-solid (TF-VLS) method in the manufacturing of III-V solar cell substrates has the potential to provide a lightweight, flexible, and cheaper alternative to traditional III-V substrates typical of state-of-the- art power generation technology. The TF-VLS process has been shown to produce high optoelectronic quality polycrystalline InP on lightweight flexible metal foils. In this work, this novel method is applied to the growth of binary and ternary III-V materials which include: InP, InAs, and InGaP on Mo foils and/or sputtered Mo on Si wafers.

As a result of InP trials, powder XRD measurements have identified …

Synthesis And Characterization Of Transition Metal Arsenide Nanocrystals And The Metastability And Magneto-Structural Phase Transition Behavior Of Mnas Nanocrystals, Yanhua Zhang

Wayne State University Dissertations

This dissertation study focuses on (1) probing the magneto-structural phase transformation in nanoscale MnAs; (2) evaluation of the size-dependent phase stability of type-B MnAs (prepared by rapid injection); and (3) developing a general synthetic method for transition metal arsenide nanoparticles.

Discrete MnAs nanoparticles that adopt different structures at room temperature (type-A, α-structure and type-B, β-structure) have been prepared by the solution-phase arrested precipitation method. Atomic pair distribution and Rietveld refinement were employed on synchrotron data to explore the structural transitions of the bulk and nanoparticle samples, and these results were compared to AC magnetic susceptibility measurements of the samples. The …

The Importance Of Scattering, Surface Potential, And Vanguard Counter-Potential In Terahertz Emission From Gallium Arsenide, D L. Cortie, R A. Lewis

Faculty of Engineering - Papers (Archive)

It is well established that under excitation by short (<1 ps), above-band-gap optical pulses, semiconductor surfaces may emit terahertz-frequency electromagnetic radiation via photocarrier diffusion (the dominant mechanism in InAs) or photocarrier drift (dominant in GaAs). Our three-dimensional ensemble Monte Carlo simulations allow multiple physical parameters to vary over wide ranges and provide unique direct insight into the factors controlling terahertz emission. We find for GaAs (in contrast to InAs), scattering and the surface potential are key factors. We further delineate in GaAs (as in InAs) the role of a vanguard counter-potential. The effects of varying dielectric constant, band-gap, and effective mass are similar in both emitter types