Depassivation of some metals by sliding friction

Nickel, TA6V4 alloy and 316L stainless steel were passivated in aerated sulphuric acid solution (0.5 M), and submitted to sliding friction against a loaded alumina ball. The effects of sliding speed and normal applied load on tribological behaviour of the passivating films were analyzed. Friction coefficients were measured and the metal wear rates were deduced from 3D profilometry recordings on the wear tracks. Current variations were also measured during friction tests and the results are discussed in terms of depassivation-repassivation kinetics induced by the passivating film breakdown. The effects of sliding speed and applied load on the depassivation kinetics and thus current enhancement due to friction were particularly studied. The Passivating film formed on nickel surface shows the best resistance to friction and wear, whereas TA6V4 alloy shows the worst behaviour. The Passivating film on this alloy wears easily leading to a high material consumption. 316L stainless steel situates between the two other materials.     

孔隙对NiTi形状记忆合金中B2-R相变影响的相场模拟

建立了适用于含孔隙NiTi合金中B2-R相变的相场模型,并用该相场模型研究了多孔NiTi合金中B2-R转变的微观组织演化过程以及孔隙率和孔尺寸对R相变体生长动力学行为的影响.多孔NiTi合金中R相变体以相互协调的方式形成"带状"的三维结构和"鱼骨"状的二维组织,变体之间形成的孪晶面包括{101}B2和{001}B2 2...     

3种锆合金的高温氧化行为

对Zr-A和Zr-B锆合金在700-1200℃的O_2中进行了等温氧化实验,观察了合金的氧化动力学行为和基体微观结构演变,并与低Sn的Zr-4合金作了对比.结果表明,700—1200℃氧化时,3种锆合金的动力学曲线基本服从抛物线规律,Zr-B合金在700℃氧化1200 s后速率出现转折;800℃时Zr-A和Zr-B合金的氧化速率出现转折;1000℃时3种合金动力学曲线由抛物线变为近似直线;1100℃以上氧化时,动力学曲线呈抛物线规律,未出现转折.在1100℃以上氧化时,合金成分对3种合金的高温氧化性能影响甚微.依据氧化增重数据得到了3种合金在700—1200℃氧化反应的抛物线速率常数K_p的表达式.     

Electrochemical hydrogen storage properties of non-stoichiometric La0.7Mg0.3−xCaxNi2.8Co0.5 (x = 0-0.10) electrode alloys

The microstructure and electrochemical hydrogen storage characteristics of La_0.7Mg_0.3−xCa_xNi_2.8Co_0.5 (x = 0, 0.05 and 0.10) alloys prepared by arc-melting and subsequent powder sintering method are investigated. The electrochemical measurement results show that the cycle stability after 100 charge/discharge cycles first increases from 46.4% (x = 0) to 54.3% (x = 0.05), then decreases to 43.2% (x = 0.10), and the high rate dischargeability increases from 64.5% (x = 0) to 68.5% (x = 0.10) at the discharge current density of 1200 mA/g. The electrochemical impedance spectroscopy analysis indicates that the electrochemical kinetics of the alloy electrodes is improved by increasing Ca. The entire results exhibit that a suitable content of Ca (x = 0.05) can improve the overall electrochemical hydrogen storage characteristics of the alloys.     

Kinetics of forward extraction of Ti(Ⅳ) from H2SO4 medium by P507 in kerosene using the single drop technique

The kinetics of forward extraction of Ti(Ⅳ) from H2SO4 medium by P507 in kerosene has been investigated using the single drop technique.10-5.07[TiO2+][H+]-1[NaHA2](o). Analysis of the rate expression reveals that the rate determining step is(TiO)2+(i)+ (HA2)-(i)(←→)spectively. The experimental negative △S± values indicate that the reaction step occurs via SN2 mechanism.     

一种曼尼希碱在酸性介质中对碳钢缓蚀行为的研究

采用动电位扫描极化曲线和交流阻抗法,研究了自制曼尼希碱缓蚀剂ZD-1在5%H2SO,溶液中对Q235钢的缓蚀作用及缓蚀机理,并计算得出相应的热力学数据.研究表明:ZD-1是一种缓蚀效果显著、以阴极控制为主的混合型缓蚀剂,它在Q235钢表面发生了化学吸附,吸附过程为放热过程,吸附行为服从El-Awadv动力学模型.     

变压吸附氯乙烯精馏尾气工艺改进

介绍了变压吸附氯乙烯精馏尾气的工艺改进情况,改进后的工艺采用分路回收方法,实现了氯乙烯、乙炔和氢气的分别回收,该工艺运行平稳,可降低转化系统负荷,且氯乙烯和乙炔均达到了零排放,具有一定的经济效益和环境效益。     

变压吸附法回收氯乙烯精馏尾气

对氯乙烯精馏尾气变压吸附装置运行后出现的问题进行了分析,并采取相应的措施进行了改进。     

催化剂表面酸度的快速测定法

以吡啶为吸附剂,采用差动变压器代替原来的测高仪来测量重量变化,实现了化学吸附量的自动记录,并与石英弹簧重量吸附-红外光谱法测定的结果比较,结果表明:两种方法测得结果的相关性很好,差动变压器重量吸附法灵敏度更高.这种装置还可以推广到其它重量吸附仪上,并且比国外电子天平重量吸附成本低,便于推广.     

The kinetics of enzyme catalyzed synthesis of sterol ester

The production of sterol ester by transesterification of β‐sitosterol with fish oil (TAG) catalyzed by Thermomyces lanuginosus immobilized lipase enzyme with varied reaction parameters such as temperature, substrate molar ratio, concentration of enzyme to deduce the enzyme kinetics for the reaction was investigated. For this transesterification reaction, the kinetic model was derived by using Ping Pong Bi Bi Mechanism. The K_m value from the first plot containing fish oil as substrate was 1.31 ± 0.05, while K_m from the second plot containing β‐sitosterol as substrate was 1.01 ± 0.04; identical V_max (0.213 ± 0.06) values were obtained by keeping one of the substrate concentration constant and varying the other. Practical applications : Deduction of reaction kinetics is an important criterion to ascertain the viability of any chemical process. Enzymatic processes need special attention to set model reaction parameters which could help in optimization or design of the actual process. In the present study we have derived the enzyme kinetics for the production sterol ester, an important nutraceutical, and calculated its K_m and V_max values along with the Arhenius activation energy to establish the viability of the reaction.