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Industrial Applications
Published in Vlado Valković, Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
Mitchell et al. (2005) have studied the formation of optically active, metal silicides using ion implantation and oxidation. While Si-based ICs dominate the microelectronics marketplace, they cannot be fabricated with optical functionality since Si is indirect. Alternative materials have been used in such applications but the ability to integrate' optically active material directly onto a silicon substrate to co-opt the advances in Si technology and processing capabilities is the better solution. Many of the transition metals form silicides that are direct band gap semiconductors and, as such, may be integrated with Si to achieve the desired optical properties. Ion implantation of the transition metal into Si was used to form the desired silicide phase by reaction of the metal with the Si substrate. Depending upon the fluence the resulting implanted layer can consist of a two-phase region in which the silicide phase forms as isolated precipitates randomly oriented within a heavily dislocated Si matrix. Rutherford backscattering/ion channeling spectrometry was used to monitor this process as a function of temperature and time. A unique method for orienting the silicide precipitates to align them crystallographically with the Si substrate and eliminate the ion-induced dislocations that form during the initial implant is discussed. This method involves oxidation of the implanted region to segregate the silicide phase at the oxide interface.
Screening Smokes: Applications, Toxicology, Clinical Considerations, and Medical Management *
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Lawrence A. Bickford, Harry Salem
Chemistry and generation. This smoke, sometimes referred to as HC smoke or Zn/HCE smoke, is produced by burning a mixture of equal parts of hexachloroethane (HCE, a chlorine donor) and zinc oxide with approximately 6% granular aluminum. The mixture is usually ignited by a pyrotechnic starter mixture, resulting in a self-perpetuating exothermic reaction and the generation of a dense white smoke containing ZnCl2, zinc oxychlorides, carbon dioxide, carbon monoxide, hydrogen chloride, tetrachloroethylene, and traces of phosgene (RAMC, 2002). ZnCl2 leaves the reaction zone as a hot vapor, and on cooling below the condensation point, it nucleates to form an aerosol that is hygroscopic. Hydrated ZnCl2 particles then scatter light and obscure vision. In view of the affinity of ZnCl2 for water, the aerosol probably consists of the hydrated forms of ZnCl2 under most atmospheric conditions (Katz et al., 1980). Some formulations may contain a small amount of (ca. 10%) calcium silicide and liberate silicon on combustion (Cullumbine, 1957). Increasing the proportion of calcium silicide raises the reaction temperature and the burning rate (Jarvis and Wart, 1971). Results from a study of Zn/HCE smoke characteristics during a military exercise gave MMAD measurements of the particles in the range 0.4–2.8 μm and thus, respirable (Young et al., 1989). In extensive field studies, DeVaull et al. (1989) found MMADs ranging from 0.77 to 1.05 μm (geometric standard deviation [gsd] 1.78–2.35). Simulated combat training during a military operation indicated that trainees were exposed to ZnCl2 in concentrations ranging from 0.02 to 0.98 mg m−3 during a 225 min period (Young, 1992). Zn/HCE smoke may be generated by grenades, candles, smoke pots, cartridges, and air-delivered bombs (RAMC, 2002). Zn/HCE smoke has also been used in fire-fighting exercises (ATSDR, 1994).
Influence of lubricating conditions on the two-body wear behavior and hardness of titanium alloys for biomedical applications
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
In this study, cp-Ti, Ti-Si-Zr, and Ti-Al-V alloys for potential use in medical applications were analyzed with structural analysis and hardness measurements using in vitro chewing test experiments. Ti-Si-Zr alloys have a different microstructure and mechanical behavior depending on the Si ratio. Ti-2.5Si-5Zr contained the αǁ phase, while the Ti-5Si-5Zr contained α| and silicide phase structures. Furthermore, as the content of Si in the alloy increases, the hardness of the titanium alloy decreases. The emergence of orthorhombic martensite in quenched water the Ti-2.3Si-7.5Zr alloy was previously described by Bega et al. (2006) assumes that the orthorhombic α-phase is an intermediate between the BCC and HCP cages – indicating that in our quenched alloys with higher silicon content, phase stability is shifted from α| towards β region with formation of an α ferrite intermediate (Bega et al. 2006; Tkachenko et al. 2014). In this study, the cast hypo-eutectic Ti-5Si-5Zr alloy exhibited two-phase structures of primary titanium dendrites and coarse silicide eutectic type (Ti, Zr)- 5Si typical for this class of materials (Zhu and Flower 1991).