In the past, CCl2F2 had been widely used in the dry etching process of the GaAs-based materials, However, it causes ozone depletion and is detrimental to the environment. In order to prevent further ozone depletion, it is necessary to search for some substitutedl gases. In this study, chloric gases, like BCl3 and SiCl4, were used to provide an alternative way for the reactive ion etch of GaAs and AlGaAs. To provide high etching selectivity between GaAs and AlGaAs, a fluorine containing gas SF6 is added, to increase the etch rate of GaAs than that of AlGaAs, which is due to the formation of non-volatile solid AlF3. In this study the etching characteristics of the BCl3/SF6, SiCl4/SF6 were studied and high etching selectivity between AlGaAs/GaAs is achieved.

A conceptual design of chemical heat pump system with reactive ceramics incorporated has been proposed and exemplified by several chemical reactions on activated metal oxides. It functions at temperatures of waste heat. The system involves the following endothermic reactions; (1) activation of metal oxide ceramics to activated ceramics using an oxygen-free inert gas, (2) H2O decomposition by the activated ceramics to form H2 gas at 300°C, (3) formation of CH4 from H2 and CO2 at 200–300°C, (4) CO2 decomposition to gaseous CO on activated oxide ceramics at 600–700°C. The working materials are typically magnetite, metal-bearing ferrites, transition metal-modified magnetite and other metal oxides. These basic reactions have been demonstrated to occur at temperatures of waste heat. The chemical heat pump will be effectively operated by incorporating their oxide membrane into the system. These findings have facilitated us to exploit a new field of research work. The above integrated chemical system may help the mitigation of CO2 in the global scale.

Increasing use of High Temperature Superconducting Ceramics (HTSC) in various applications and the cost of the new superconducting powder dictated the need for evaluating the potential of reusing the old HTSC material (yittrium-barium-copper oxide (YBCO); YBa2Cu3O7-x) with minimum reprocessing. This study examined various methods to reprocess two years old sintered and melt bulk YBCO ceramics. YBCO components were ground and processed with and without adding various amount of silver powder, organic binders and new YBCO powder. The reprocessed YBCO powder was also characterized at every step of processing using X-ray diffraction (XRD) and Differential Thermal Analysis (DTA) to identify impurities.

The old YBCO components were first crushed and then ground using automatic grinder and a jet-mill. The ground powder was then mixed with additives and/or binders and compacted uniaxially to 45 ksi. The range of sintereing temperatures from 905 °C to 980 °C were selected based on the past history of sintering/melting temperatures. The reground powder was found to have impurity phases due to its exposure to carbon dioxide and humidity in the atmosphere. Addition of Ag powder resulted in higher relative densities at lower sintering temperatures. The need for re-calcination of used powders was also considered to improve the performance of reprocessed powders. The sintering temperature was selected based on achieving 85% relative density. The results show that the reprocessed powders have to be sintered at higher temperatures than their previous history. The sintered and melt-textured YBCO made from reprocessed powder had similar or better superconducting properties compared to the new powder.

Surfactants increase the accessibility of adsorbed hydrocarbons and mobilize immiscible petroleum hydrocarbons for treatment. Biosurfactants have the advantage of biodegradability and non-toxicity over their synthetic counterparts, and can be produced from renewable sources. In this study the production of biosurfactant from molasses was investigated in continuously stirred batch reactors. The effects of substrate concentration, yeast extract and peptone on biomass accumulation and biosurfactant production were investigated. Biosurfactant production was quantified by surface tension reduction and critical micelle dilution (CMD). Biosurfactant production was directly correlated with biomass production, and was improved with the addition of yeast extract. Centrifugation of the whole broth reduced surface tension. The performance of the biosurfactant produced from molasses under non-aseptic condition is comparable to other published results.

XANES (X-ray Absorption Near Edge Spectroscopy) has been employed to evaluate the efficacy of a process designed to encapsulate and reduce TcO4- in cement matrices, thereby immobilizing Tc. The oxidation state of Se following bioremediation of Se by bacteria has also been determined by XANES. The XANES measurements were performed at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS) at the respective K edges of Tc (21.0 keV) and Se (12.7 keV). Comparison of the XANES spectra of Tc in untreated cement to Tc in slag treated cement and to the chemical shifts of reference materials, shows that the oxidation state of Tc is the same in both cements. Thus, the addition of a reducing agent to the cement formulation does not significantly reduce the TcO4-. The common soil bacterium, Bacillus subtilis, is known to incorporate Se on or within the cell wall when exposed to a Se(IV) solution. The Se XANES spectra of B. subtilis, as well as bacillus isolated from selenium rich soil, show that the organisms reduce selenite to the red allotrope of elemental Se.

Surface contaminations are removed by laser irradiation with pulse output and short wavelength from various substrate such as magnetic head slide, glass and metals. Laser cleaning is a new dry process to remove surface organic contaminations without using ultrasonic cleaning in organic solvents. This provides a new dry process to clean different substrate surfaces and can take the place of conventional wet cleaning processes such as ultrasonic cleaning with CFC and other organic solvents. The mechanisms of laser cleaning may include laser photodecomposition, laser ablation and surface vibration due to the impact of laser pulse. It is found that short wavelength and short pulse duration are necessary for effective cleaning. It is also found that an appropriate energy density is critical to achieve effective cleaning without causing surface oxidation and secondary contamination.

CuO/Al2O3 sorbents based on three aluminas of different pore structure and surface area around 125 m2/g were prepared. Two of the aluminas exhibited bimodal pore size distribution, while the third had narrow unimodal distribution. The effect of copper loading on the physical characteristics of the aluminas (pore size distribution and surface area) was examined using mercury porosimetry and gas adsorption. The reactivity of the sorbents towards SO2 was investigated by carrying out thermogravimetric experiments using simulated flue gas.