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Wear Behavior of P/M High Nb Containing γ-TiAl Alloy in Different Environments
Jingwen Qiu,Zhengfan Fu,Bin Liu,Yong Liu,Jianhui Yan,Di Pan,Weidong Zhang 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6
The wear behavior of Ti–45Al–7Nb–0.3W (at%) alloy prepared by powder metallurgy (P/M) has been investigated using pinon-disk wear tests at the room temperature. The dry sliding wear tests were performed against on a zirconia disk in differentenvironments, viz, argon, hydrogen in nitrogen mixture, air and oxygen. The worn surfaces of Ti–45Al–7Nb–0.3W pins andwear debris were examined by scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscopy. It was found that the high Nb containing Ti–45Al–7Nb–0.3W alloy didn’t exhibit better wear resistance in the presence ofoxygen than commercial γ-TiAl (Ti–47Al–2Nb–2Cr–0.2W) alloy. The oxidation on the worn surface and spalling of oxidescaused by the mechanical force during sliding were the main reason for the high wear losses in the air and oxygen. Thezirconia disk underwent a phase transformation caused by the high contact temperature and stress during the sliding tests. The abrasive particles produced in the wear tests largely consisted of the zirconia particles in different environments, exceptin the pure oxygen. The hard zirconia debris was embedded into the friction layer on the worn surfaces of TiAl pins, whichprovided protection against wear to some extent. The main wear mechanisms of Ti–45Al–7Nb–0.3W alloy were abrasivewear of two-body and three-body, some delamination and plastic deformation.
Preparation of Functionalized Magnetic Silica Nanospheres for the Cellulase Immobilization
Wenjuan Zhang,Jianhui Qiu,Limin Zang,Eiichi Sakai,Huixia Feng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.1
Cellulase was immobilized on functionalized magnetic silica nanospheres using glutaraldehyde as a cross-linking agent. The morphologies, structures and magnetic properties of this immobilized cellulase were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and vibrating sample magnetometry. The properties of immobilized cellulase were investigated, including the amount of immobilized cellulase and its relative activity, stability and reusability. The results indicated that immobilized cellulase exhibited better resistance to high temperature and pH inactivation in comparison to free cellulase. Moreover, immobilized cellulase with and without cross-linking agent were investigated and the former had greater amount of immobilized cellulase and better operational stability. The amount of immobilized cellulase with the cross-linking agent was 92 mg/g support. Furthermore, the activity of the immobilized cellulase was still 85.5% of the initial activity after 10 continuous uses, demonstrating the potential of this immobilized cellulase for large-scale biofuel production.
Chaomin Yin,Chen Li,Kun Ma,Xiuzhi Fan,Fen Yao,Defang Shi,Wenjing Wu,Jianhui Qiu,Guoyuan Hu,Hong Gao 한국식품과학회 2023 Food Science and Biotechnology Vol.32 No.7
In this study, the influence of γ-irradiation with different dose (0, 4, 8, and 16 kGy) on chemical composition, physicochemical features and bioactivities of polysaccharides extracted from Lentinula edodes (LEP) were investigated. The carbohydrate content (from 59.47 to 70.96%), the solubility, the ⋅OH and DPPH scavenging ability of LEP increased with the increased γ-irradiation dose, while the protein content, the weight-average and number-average molecular weight of LEP were significantly decreased with the increased γ-irradiation dose. Moreover, γ-irradiation treatment caused LEP color changes and surface topography destroyed. γ-Irradiated LEP showed higher hypoglycemic activities in vitro than that of non-irradiated LEP. Moreover, γ-irradiated LEP had better proliferation promoting effects on Lactobacillus rhamnosus and L. plantarum. These results showed that γ-irradiation treatment changes the physicochemical features of LEP, thus affects its antioxidant, hypoglycemic and prebiotic properties, which suggests that γ-irradiated LEP has potential application in the pharmaceutical industries and functional foods.