富/乏油下滚子修形对圆柱滚子轴承剪切应力的影响

以NJ2205圆柱滚子轴承为分析对象，通过Ansys软件对滚子进行建模，分析富油和乏油工况下滚子与滚道之间出现的“边缘效应”问题，对比分析未修形、全凸修形和对数修形下滚子与滚道剪切应力分布情况。结果表明，在径向载荷为11.45 kN、转速为4 000 r/min、富油工况下，沿滚子母线方向的剪切应力小于乏油，无修形方式时剪切应力最大，对数修形方式时剪切应力最小；在富油工况和乏油工况下，全凸修形时的剪切应力相比于未修形时分别减小了17.02%和10.58%；对数修形时的剪切应力相比于未修形时分别减小了32.95%和17%。因此，NJ2205圆柱滚子轴承的滚子采用对数修形曲线能有效地降低剪切应力

Core-Shell Structured Ru@PtRu Nanoflower Electrocatalysts toward Alkaline Hydrogen Evolution Reaction

本文通过分步还原Ru、Pt前驱体,制备了以Ru为核、PtRu合金为壳的[email protected]纳米花电催化剂,其平均直径为16.5±4.0 nm. 利用高分辨电子显微镜、电感耦合等离子体原子发射光谱和X射线光电子能谱等表征了这种电催化剂的结构和组成. 在1 mol·L -1 KOH水溶液中,核壳结构[email protected]/C纳米花氢析出反应的过电位为22 mV（@10 mA·cm -2）,耐久性测试后过电位增加至30 mV（@10 mA·cm -2）,明显优于商业Pt/C电催化剂（初始值：60 mV@10 mA·cm -2,耐久性测试后：85 mV@10mA·cm -2）. 显著提高的电化学活性可能源于核壳结构[email protected]纳米花的电子效应和几何效应,耐久性的改善可能源于核壳结构[email protected]纳米花结构的稳定性.Water electrolysis for hydrogen production is beneficial for solving the problem of energy crisis and environmental issues. It is necessary to study highly active and cost-effective catalysts toward hydrogen evolution reaction (HER) to reduce the consumption of noble metals. Herein, we report the synthesis of core-shell structured [email protected] nanoflowers electrocatalyst by stepwise reduction of Ru and Pt precursors in the mixture of oleylamine and benzyl alcohol at 160 oC. The average diameter of the resultant [email protected] was 16.5±4.0 nm with a bulk atomic ratio between Pt and Ru of 0.24:1 and a surface ratio of 3.3:1 between Pt and Ru. Therefore, we speculate the formation of core-shell structure with Ru as the core and PtRu alloy as the shell. The performance of the electrocatalyst toward alkaline HER was tested in 1.0 mol·L -1 KOH aqueous solution. The [email protected] exhibited pronounced alkaline HER activity with a small overpotential of 22 mV at 10 mA·cm -2, a low Tafel slope of 43 mV·dec -1, and a high mass activity of 5.68 A·mg -1Pt+Ru at an overpotential of 100 mV, all largely surpassing commercial Pt/C (60 mV, 101 mV·dec -1, 1.53 A·mg -1Pt). The attained [email protected] also held outstanding long-term cycling stability. After 10,000 potential cycles from 0.1 to -0.1 V (vs. RHE), the overpotential increased to 30 mV at 10 mA·cm -2, while increased to 85 mV for Pt/C. The significantly improved electrochemical activity may be derived from the electronic and geometric effects of the electrocatalyst. The improvement of durability may be due to the stability of the flower-like dendritic morphology.国家重点研发计划课题No(2019YFB1504501);大连理工大学重点专项No(DUT19ZD208);大连理工大学重点专项No(DUT20ZD208);中央引导地方专项No(2020JH6/10500021);辽宁省重点研发计划项目No(2020JH2/10100025);大连市重点学科重大项目资助No(2020JJ25CY003)通讯作者:宋玉江E-mail:[email protected]:SONGYu-jiangE-mail:[email protected]大连理工大学化工学院精细化工国家重点实验室,辽宁 大连 116024State Key Laboratory of Fine Chemicals, School of Chemical Engineering,Dalian University of Technology, Dalian 116024, Liaoning, Chin