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Plastic Deformation Mechanism of the Ti6Al4V Micro-gear Formed Under an Electrical Field
Bo Zeng,Xiangzhong Yan,Zhiqiang Xie,Jian Liu,Jie Wang,Kunlan Huang,Yi Yang 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1
Despite the fact that titanium alloy micro-gear has superior performance and can withstand special conditions, it is difficult to machine due to its poor plasticity and high strength. We proposed an eco-friendly, efficient, and sustainable electric field assisted micro-plastic forming technology (micro-EFAPFT) for forming titanium alloy microparts. Ti-6Al-4 V alloy bars were extruded into micro-gears using an electrothermal coupling field and Joule heating in a graphite mold. The micro-gear has high precision, good surface quality, and a simple process. The whole process takes only 380 s. The findings demonstrate that the best gear forming degree, fewer microstructure defects, and hardness reaching 330.1 HV—4.4% higher than that of the raw material—occur when the pressure holding period is 120 s. During the plastic deformation process, phase transformation and recrystallization occur, increasing the fraction of α phase from 96.6–99.68% and increasing the grain orientation difference. The tooth tip has finer grains but longer dislocation lines. In conclusion, the electric field accelerates dislocation motion, reduces dislocation density, and increases material plasticity, allowing the Ti6Al4V micro-gear to be formed in a single step. The experimental results validate the feasibility of this technology for producing titanium alloy micro-gear and can be used to guide the production of different materials and shapes of microparts.
Hongkai Guo,Hu Xu,Chengwen Zhao,Xiangzhong Hao,Ziyuan Yang,Weijun Xu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-
Achieving high catalytic performance with the lowest cost possible cathode material is critical for electrocatalyticsynthesis of H2O2 by oxygen reduction reaction. In this work, we describe a method ofpreparing highly active yet stable graphite felt electrocatalysts containing ultrahigh-loading oxygen contentby using organic acid anodic modification. The results show that modified graphite felt surface wasmore hydrophilic and introduced a large amount of defect sites and oxygen-containing groups. Moreover,the influence of mass oxalic/citric acid ratio and oxidation time of graphite felt cathode were investigated. As a result, H2O2 electrogeneration was 1.6 times as much as that of virgin graphite felt counterpart at themass oxalic/citric acid ratio of 2:1 oxidation for 40 min. However, overoxidation also impaired the electricalproduction of H2O2 due to decarboxylation. Finally, the effect of cathode potential and reaction pHon graphite felt cathode was optimized. As for the modified graphite felt, the maximum accumulationrate of H2O2 reached 4.5 mg h1 cm2 at the conditions of 0.85 V (SCE), 0.4 L min1 O2 flow rate andpH = 3. In addition, it kept a stable performance for electrochemical generation of H2O2 during 8 cycles.
Genetic Reprogramming after Somatic Cell cloning
Tian, X.Cindy,Xu, Jie,Xue, Fei,Kubota, Chikara,Du, Fuliang,Yang, Xiangzhong 한국수정란이식학회 2002 한국수정란이식학회 학술대회 Vol.2002 No.1
Cloning by nuclear transfer in mammals using somatic cells has enormous potential applications. However, somatic cloning has been inefficient in all species in which NT is successful. High abortion and fetal death rates have been observed. These developmental defects have been attributed to incomplete nuclear reprogramming by the somatic cloning process. In this review, we will discuss studies conducted in our labs to understand the nuclear reprogramming process.