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Full-Text Articles in Engineering
Cadmium Sulfide-Buffered Pv Systems: Assessing The Environmental, Health, And Economic Impacts, Maqsood Ali Mughal, Rajesh Sharma
Cadmium Sulfide-Buffered Pv Systems: Assessing The Environmental, Health, And Economic Impacts, Maqsood Ali Mughal, Rajesh Sharma
Journal of the Arkansas Academy of Science
As the world’s population continues to grow, global energy crises are expected to rise in the future, thus accelerating the demand for renewable energy technology, particularly solar photovoltaics. The energy sector will face an increasingly complex array of interlocking challenges - technological, environmental, health, economic, and regulatory. In this paper, we study CdS, a widely used buffer material in thin film photovoltaics, to assess and monetize environmental, health, and socio-economic externalities associated with the use of the material. Currently, CdS has a significant advantage over other alternate buffer materials in terms of efficiency and low-cost production of large-area processing of …
Restrained Shrinkage Of Fly Ash Based Geopolymer Concrete And Analysis Of Long Term Shrinkage Prediction Models, Md R. Islam, Mahbub K. Ahmed, Hosney Ara Begum, Erez N. Allouche
Restrained Shrinkage Of Fly Ash Based Geopolymer Concrete And Analysis Of Long Term Shrinkage Prediction Models, Md R. Islam, Mahbub K. Ahmed, Hosney Ara Begum, Erez N. Allouche
Journal of the Arkansas Academy of Science
The research presented in this manuscript describes the procedure to quantify the restrained shrinkage of geopolymer concrete (GPC) using ring specimen. Massive concrete structures are susceptible to shrinkage and thermal cracking. This cracking can increase the concrete permeability and decrease the strength and design life. This test is comprised of evaluating geopolymer concrete of six different mix designs including different activator solution to fly ash ratio and subjected to both restrained and free shrinkage. Test results obtained from this experimental setup was plotted along with the available empirical equation to observe the shrinkage strain of GPC and a model was …
Growth Rate Calculations For Epitaxially Grown Thin Films, D. Bullock
Growth Rate Calculations For Epitaxially Grown Thin Films, D. Bullock
Journal of the Arkansas Academy of Science
No abstract provided.
Stability And Optimization Of Photoconductivity In Thermally Vacuum Evaporated Indium (Iii) Sulfide Thin Films, Gustavo Rehder, Robert Engelken, Randy Stidham, Richard Tanner, Lee Ketchum, Anil Baral
Stability And Optimization Of Photoconductivity In Thermally Vacuum Evaporated Indium (Iii) Sulfide Thin Films, Gustavo Rehder, Robert Engelken, Randy Stidham, Richard Tanner, Lee Ketchum, Anil Baral
Journal of the Arkansas Academy of Science
Long term stability of photosensitivity versus time in indium (III) sulfide thin films thermally vacuum evaporated onto photocell-patterned printed circuit boards varies sensitively with several factors including contact metal type, contact metal diffusion and electromigration into the semiconductor, doping, and encapsulation method. Because of the significant photoconductivity and relative low toxicity and environmental impact of this compound semiconductor, it is important to better characterize these dependences toward commercial applications. We will report on measurements of photoconductivity vs. time as functions of such factors and evolving methods to stabilize this photoconductivity.
Thin Film Deposition Of Silicon For Solar Cell Applications, Sailesh Kumar, Roger M. Hawk
Thin Film Deposition Of Silicon For Solar Cell Applications, Sailesh Kumar, Roger M. Hawk
Journal of the Arkansas Academy of Science
Thin films of silicon have been formed using a patented electrostatic deposition method which utilizes charged particle motion in an electric field. After deposition, the films are heat treated for varying times and temperatures in a programmable furnace maintained under a purified argon atmosphere. X-ray diffraction (XRD) confirmed that these films were polycrystalline in nature. These films were found to have grain sizes of about 50 microns. Solar cells were fabricated using these large grained polycrystalline silicon films by sputtering pure gold as both front and back contacts. The cells have shown efficiencies of 1.8%. This paper reports on the …
Preparation Of Powder Precursors And Evaporation Of Photoconductive Indium Sulfide Films, Chris Barber, Robert Engelken, Brandon Kemp, Wasim Aleem, Imran Khan, Chris Edrington, Michael Buck, Clayton Workman, Anup Thapa, Tom Jakobs
Preparation Of Powder Precursors And Evaporation Of Photoconductive Indium Sulfide Films, Chris Barber, Robert Engelken, Brandon Kemp, Wasim Aleem, Imran Khan, Chris Edrington, Michael Buck, Clayton Workman, Anup Thapa, Tom Jakobs
Journal of the Arkansas Academy of Science
We have demonstrated significant photoconductance in indium sulfide thin films prepared by thermal vacuum evaporation ofIn2$3 powders synthesized in-house by chemical precipitation ofInCl3 or In(CH3COO)3, and (NH4)2S or Na2S. The Delta G lambda/Gdark values have been as high as 0.1 in the initial unoptimized films. Excess sulfur (via a mixture of polysulfide and sulfide ions in the synthesis bath) appears to be important in achieving reproducible and large photoconductivities. In2S3 is particularly attractive as a lower toxicity alternative to CdS in optoelectronic applications such as photovoltaic and photoconductive cells.
Diagnostics Of Cdte Electrodeposition By Rest Potential Voltammetry, Brandon Kemp, Robert Engelken, Arif Raza, Arees Siddiqui, Omer Mustafa
Diagnostics Of Cdte Electrodeposition By Rest Potential Voltammetry, Brandon Kemp, Robert Engelken, Arif Raza, Arees Siddiqui, Omer Mustafa
Journal of the Arkansas Academy of Science
Due to the extreme sensitivity of the partial elemental currents (i.e.,iCd, iTe) and, hence, stoichiometry to deposition voltage, temperature, mass transport, and ambient light intensity during electrodeposition of semiconductor films, it is important to implement in-situ methods for monitoring the stoichiometry and related semiconductor efficacy of the growing film. We report investigation of open circuit rest potential (Eoc) voltammetry as one such method during electrodeposition of CdTe from aprotic electrolytes such as ethylene glycol. Plots of transient open circuit potential versus sweep voltage exhibit distinct transition and plateau structures corresponding to Te, CdTe, and Cd phases and correlating with the …
Molten Salt Electrolytes For Electrodeposition Of Cdte Films, Arif Raza, Robert Engelken, Brandon Kemp, Arees Siddiqui, Omer Mustafa
Molten Salt Electrolytes For Electrodeposition Of Cdte Films, Arif Raza, Robert Engelken, Brandon Kemp, Arees Siddiqui, Omer Mustafa
Journal of the Arkansas Academy of Science
We report preliminary investigation of several molten salt electrolytes containing CdCl2 and TeCl4 for the electrodeposition of CdTe films at temperatures well above (>250 °C) those used with aqueous and organic electrolytes. These high temperatures have potential todramatically increase the crystallite size (Poole, Engelken, et al., 1994), as is important for optoelectronic device applications of CdTe, a leading II-VIsemiconductor. This paper willsurvey the results obtained withelectrolytes such as B2O,/HBO2 (m.p. - 230'C), NaCH3COO (m.p. » 324°C), ZnCl2 (m.p. - 283*C), and LiCl/KCl (m.p. * 350 °C), with an emphasis on the latter two. Key material to be presented includes …
Solid State Nmr Of Hydrogen In Thin Film Synthetic Diamond, G. Burnside, Roger M. Hawk, Richard A. Komoroski, W. D. Brown
Solid State Nmr Of Hydrogen In Thin Film Synthetic Diamond, G. Burnside, Roger M. Hawk, Richard A. Komoroski, W. D. Brown
Journal of the Arkansas Academy of Science
Thin film synthetic diamond promises to be the next semiconductor material, if the manufacturing processes which produce it can be controlled. Solid state nuclear magnetic resonance (NMR) using magic angle spinning (MAS) is used to measure the content of hydrogen in diamond which controls the resistivity of the diamond thin films. Spectral results are presented for proton NMR of thin film synthetic diamond. Experimental calibration techniques using BaF2 as the hydrogen standard will be discussed, as well as acquisition times, pulsing sequences, spinning rates, and rotor composition.
Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu
Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu
Journal of the Arkansas Academy of Science
The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides.
Tetraethylene Gycol-Based Electrolytes For High Temperature Electrodeposition Of Compound Semiconductors, Chris Poole, Robert Engelken, Brandon Kemp, Jason Brannen
Tetraethylene Gycol-Based Electrolytes For High Temperature Electrodeposition Of Compound Semiconductors, Chris Poole, Robert Engelken, Brandon Kemp, Jason Brannen
Journal of the Arkansas Academy of Science
We report an investigation of tetraethylene glycol (TEG) solutions of chloride salts (CdCl2 ,TeCl4 ,and HgCl2 ) for electrodeposition of films of CdTe and Hg1.xCdxTe, leading II-VI semiconductors. The high boiling point (314°C), below-room temperature (T) (-6°C) melting point, adequate metal chloride solubilities, and low toxicity of TEG make it a good candidate for electrodeposition at T > 200°C. Such temperatures tend to activate growth of larger crystallites than with aqueous electrolytes at T< 100 °C, as are advantageous in optoelectronic applications. Initial results do, indeed, indicate a dramatic increase in crystallinity with deposition temperature, especially for the CdTe films which are nearly amorphous when grown at room temperature. Hg1.xCdxTe films (x< 0.5) are marginally polycrystalline when grown at room temperature but also improve in crystallinity at higher growth temperatures. There appears to be a strong decrease in film adherence and uniformity as growth temperature increases for both materials probably because the greatly increased carrier concentrations at higher temperatures increase film conductivity which, in turn, supports easy electroplating of protruding loose dendritic and/or columnar crystallites, instead of the monolayer-by monolayer growth of lower conductivity material as occurs at lower temperatures, especially in the higher bandgap/lower conductivity CdTe. The same increase in film conductivity with temperature is responsible for the decrease in the relative photosensitivity of both the CdTe and Hg1.x CdxTe with temperature. At all temperatures, the inferior adherence, uniformity, and photosensitivity as well as the superior crystallinity of Hg1.xCd xTe over that of the CdTe are also explained by its lower bandgap and higher conductivity. On balance, however, the initial results prove the utility of high temperature TEG electrolytes for electrodepositing CdTe and Hg1.xCdxTe films with much better crystallinity than for those grown at lower temperatures, notably in aqueous baths.
Evaluation Of Photodiode Arrays For Use In Rocket Plume Monitoring And Diagnostics, Dallas Snider, M. Keith Hudson, Robert B. Shanks, Reagan Cole
Evaluation Of Photodiode Arrays For Use In Rocket Plume Monitoring And Diagnostics, Dallas Snider, M. Keith Hudson, Robert B. Shanks, Reagan Cole
Journal of the Arkansas Academy of Science
The spectroscopic analysis of plume emissions is a non-intrusive method which has been used to check for fatigue and possible damage throughout the pumps and other mechanisms in a rocket motor or engine. These components are made of various alloys. Knowing the composition of the alloys and for which parts they are used, one can potentially determine from the emissions in the plume which component is failing. Currently, Optical Multichannel Analyzer systems are being used which utilize charge coupled devices, cost tens of thousands of dollars, are somewhat delicate, and usually require cooling. We have developed two rugged instruments using …
Application Of Stable Operating Criterion To Grating Tuned Strong External Feedback Semiconductor Lasers, Haiyin Sun, Malay K. Mazumder
Application Of Stable Operating Criterion To Grating Tuned Strong External Feedback Semiconductor Lasers, Haiyin Sun, Malay K. Mazumder
Journal of the Arkansas Academy of Science
Stability analysis is done by applying criterion dnQ((o)/cfco>0 for grating tuned strong external feedback semiconductor lasers. The resulting stable and unstable operating ranges agree well with experiment results.
Techniques For Efficiency Calibration Of Photon Detectors For X-Rays And Low Energy Gamma Rays, Rahul Mehta
Techniques For Efficiency Calibration Of Photon Detectors For X-Rays And Low Energy Gamma Rays, Rahul Mehta
Journal of the Arkansas Academy of Science
No abstract provided.
Measurement Of The Coefficient Of Thermal Expansion Of Superconducting Thin Films Using Powder X-Ray Diffraction, Biju Chandran, R. Calvin Goforth, S. Nasrazadani
Measurement Of The Coefficient Of Thermal Expansion Of Superconducting Thin Films Using Powder X-Ray Diffraction, Biju Chandran, R. Calvin Goforth, S. Nasrazadani
Journal of the Arkansas Academy of Science
The High Density Electronics Center (HiDEC) at the University of Arkansas, Fayetteville is developing the technology for High Temperature Superconductor Multi-Chip Modules (HTSC-MCM's). As part of this work, we are looking at the mechanical properties of HTSC materials. An important mechanical property which influences the mechanical integrity of the hybrid MCMis the coefficient of thermal expansion (CTE) of the HTSC films. As a first step in developing a procedure for the determination of the CTE of HTSC materials, the lattice parameters and the CTE of an alpha-alumina substrate have been determined by powder x-ray diffraction technique. An extension of this …
Semi-Conducting Properties Of Gray Tin As A Laboratory Introduction To Solid State Physics, Glenn F. Powers, Gene E. Louallen, Robert M. Rickett
Semi-Conducting Properties Of Gray Tin As A Laboratory Introduction To Solid State Physics, Glenn F. Powers, Gene E. Louallen, Robert M. Rickett
Journal of the Arkansas Academy of Science
No abstract provided.
Plastic Mounting Technique For Herbaria, Albert Robinson Jr.
Plastic Mounting Technique For Herbaria, Albert Robinson Jr.
Journal of the Arkansas Academy of Science
No abstract provided.