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Capture Pumps
Published in Igor Bello, Vacuum and Ultravacuum, 2017
We may highlight again that inert gases, for example, argon can be pumped via burial and electric pumping pathways. In electric pumping, inert gas molecules are introduced below the surface of the titanium cathode as illustrated in Figure 15.21d. However, the titanium cathode is continuously eroded by the sputtering process. As a result, at some point of erosion, the captured molecules of the inert gas appear on the cathode surface. The continuous removal of the cathode material (Figure 15.21e) thus leads to releasing the inert gases back to vacuum in cycles. The process of the reappearing of inert gases in vacuum is called memory effect. The capturing of gases by burial process and electrical pumping represents small pumping effects. Inert argon is removed from vacuum by a titanium MIS pump with a pumping speed that is about 2% of that for air. Difficulties are also found in pumping of pure hydrogen. At relatively low temperature, hydrogen and titanium form titanium hydride, but at elevated temperature, hydrogen is desorbed. The pumping of pure hydrogen is also hindered by a very low sputtering rate of titanium by hydrogen ions due to the small masses and momenta that hydrogen ions transferred to the getter surfaces.
Sintering densification behaviors of Ti-1Al-8V-5Fe alloy based on TiH2 and TiH1.5 powders
Published in Materials and Manufacturing Processes, 2019
Yanan Zhang, Chunming Wang, Xing Guo, Yungui Chen
Some previous work has presented that the expensive vanadium powders replaced by the low-cost FeV80 master alloy powders, leading to the cost reduction of titanium alloys.[6] Additionally, researchers have found that the lower oxygen content and higher sintered density is realized easier by low-cost saturated titanium hydride (TiH2) powders[3,5,9–11], because of the escaped hydrogen atoms can remove fractional oxygen and clean the particle surface during the sintering process of TiH2.[12–14] Compared with saturated titanium hydride (TiH2), the unsaturated titanium hydride with low hydrogen content could be more economical and affordable because of the lower costs for hydrogenation, the smaller product deformation and high precision of the final product after the sintering process.[15] Additionally, our latest work also suggests that the unsaturated titanium hydride (TiH1.5) with low hydrogen content possesses superior compressibility.[16]