冷凝器换热管失效分析

采用宏观检查,化学分析和金相检验等方法对冷凝器换热管报废原因进行了分析,结果表明,由于不锈钢焊接管在含有氯离子的冷却水中形成钝化－活化微电池,致使不锈钢焊接管腐蚀而报废,采取改换材料为18－8型无缝奥氏体不锈钢管和改良冷却水等措施,取得良好效果。     

Inductively coupled plasma — plasma enhanced chemical vapor deposition silicon nitride for passivation of InP based high electron mobility transistors (HEMTs)

Silicon nitride thin films have been deposited on InP-based structures at both room and high temperatures in an RF-inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) equipment. Metal insulating semiconductor (MIS) diodes have been widely investigated using either SiH₄+NH₃ or SiH₄+N₂ gas phase. I–V measurements conducted on these diodes reveal high resistivity and breakdown electric field even at low deposition temperature (50°C). Double channel (DC) High electron mobility transistors (HEMTs) have been passivated by SiN_x films deposited at room temperature using SiH₄+NH₃ precursors. Passivated devices exhibit a very low drift over a 45 h period of stress under high gate-drain electric field.     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅲ.不同pH值H2S溶液中碳钢的腐蚀电化学行为

利用极化曲线和阻抗技术 ,对低碳钢在不同pH值H2 S溶液中的腐蚀电化学行为进行了研究。结果表明 ,在溶液pH值较低时 ,腐蚀电极主要受阳极酸性溶解过程控制 ,表面无硫化物沉积 ,其阻抗谱除高频容抗弧外 ,低频有一感抗弧存在 ;随pH的升高 ,腐蚀电位明显负移 ,电流密度减小 ,表面出现硫化物的不连续沉积 ,腐蚀因溶液pH值的增加和硫化物的沉积而减小 ,电极过程主要受硫化物的生长所控制 ;在pH值为 6.2时 ,由于HS 的阴极去极化 ,腐蚀电流增加 ;当pH大于 7后 ,电极表面因氧化膜的生成而呈现钝化特征 ,极化电阻显著增加。基于溶液中HS 同OH 的竞争吸附 ,提出可能的腐蚀历程 ,据此可解释有关实验事实。     

热镀锌钢板钝化工艺对耐蚀性的影响

为提高热镀锌钢板的耐蚀性,对热镀锌钢板铬酸盐钝化工艺进行了研究.采用盐雾试验、钝化膜的微观形貌等手段分析了钝化液浓度及钝化工艺参数(钝化液温度、烘干时间、烘干温度等)对热镀锌钢板铬酸盐钝化膜耐蚀性的影响.结果表明,采用试验确定的钝化工艺处理得到的钝化膜耐蚀性明显提高,对实际生产具有较好的指导意义.     

Effect of platinum group metal addition on microstructure and corrosion behaviour of Ti–47·5 at-%Al

Plain and alloyed titanium aluminides of composition Ti–47·5 at-%Al were prepared with the addition of 1·0 at-% platinum group metals (PGMs). The as cast alloys were subjected to potentiodynamic scans in 5, 15 and 25 wt-%HCl solutions at room temperature, and the PGM containing alloys were assessed for their abilities to spontaneously passivate by cathodic modification. Plain titanium aluminide had a duplex microstructure consisting of lamellar (α₂ and γ alternating lamellae) and γ-TiAl phase grains. The introduction of 1·0 at-%PGMs (platinum, palladium and iridium) led to the formation of a new phase, developing more in the γ-TiAl phase grains and a general improvement of corrosion resistance by increasing the corrosion potential to nobler values. Platinum group metal additions to plain TiAl resulted in the corrosion potentials falling in the passive region of plain TiAl, indicating spontaneous passivation of PGM alloyed TiAl in 5 and 15 wt-%HCl solutions. In 25 wt-%HCl solution, the addition of PGMs shifted the cathodic process in the transpassive or active region of plain TiAl, resulting in either case in the dissolution of the alloy due to the absence of an extended passivation region. The cathodic modification of PGM alloyed TiAl occurred as a result of PGM accumulation on the surface of the TiAl alloys, which simultaneously improved the hydrogen evolution efficiency and inhibited anodic dissolution.     

The partial state-of-charge cycle performance of lead-acid batteries

Negative plate lugs of flooded lead-acid battery were corroded during partial state-of-charge (PSoC) pattern cycle life tests simulated from stop and go vehicle driving.     

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

Susceptibilities to stress corrosion cracking(SCC) of X80 pipeline steel in relatively concentrated carbonate/bicarbonate solutions with different chloride ion concentrations or p H value at a passive potential of-200 m V vs SCE were investigated by slow strain rate tensile test.In order to explore the SCC mechanism and the evaluation criterion for the SCC susceptibility of the steel in passive state,electrochemical measurements were taken.Potentiodynamic polarization curves were obtained at different potential sweep rates,and electrochemical impedance spectroscopy measurements were taken after fast polarization to the passive potential.The effects of chloride ion and p H on SCC behaviors of X80 steel at the passive potential were also discussed.The results showed that the SCC mechanism of X80 pipeline steel was greatly influenced by the passive film formed in these solutions.The SCC behaviors followed the film suppressed anodic dissolution mechanism in these circumstances,because the filming process accounted for a considerable proportion of the overall electrode process.The criteria for evaluating the SCC susceptibility of the steel at passive potential were proposed and validated.Decreasing in the concentration of chloride ion or increasing in p H value resulted in the reduction in SCC susceptibility.The existence of chloride ion greatly lowered the passivation tendency and the film stability,while its concentration determined the dissolution rate of the steel matrix.Higher p H value was responsible for the stable and tenacious passive films and the high repassivation capability.It was also inclined to lower the anodic dissolution rate at crack tips by retarding the cathodic oxygen reduction.     

表面钝化纳米铝粉的制备及氧化机理分析

采用高频感应线圈加热,以蒸发-冷凝法制备了纳米铝粉,用空气进行钝化处理,得到有钝化层保护的纳米铝粉.使用透射电镜、场发射扫描电镜、X射线衍射、差热分析DTA等测试手段,研究了表面钝化处理对纳米铝粉抗氧化性能的影响.结果表明:经过表面钝化处理的纳米铝粉粒径范围为15～60nm,纳米铝粉表面包覆了3～5nm厚的氧化铝膜,形成明显的核/壳结构,具有较好的抗氧化性能,这对于纳米铝粉的存储、活性保护机理的探讨有一定的意义.     

Characterization of Aluminum Powders: II. Aluminum Nanopowders Passivated by Non‐Inert Coatings

Results of DTA‐TG investigation and chemical analysis of electro‐exploded aluminum nanopowders, passivated and/or coated with the non‐inert reagents: nitrocellulose (NC), oleic acid (C₁₇H₃₃COOH) and stearic acid (C₁₇H₃₅COOH), which were suspended in kerosene and ethanol, amorphous boron, nickel, fluoropolymer, ethanol and air (for comparison), are discussed. Surface protection of aluminum nanopowders by coatings of different origin results in significant advantages in the energetic properties of the powders. Aluminum nanopowders with a protecting surface show increased stability to oxidation in nitrogen, air and in water during storage period. On the basis of the experimental results, a diagram of the formation and stabilization of the coatings is proposed. The kinetics of the interaction of aluminum nanopowders with nitrogen, air and water is discussed. Recommendations concerning the efficiency of non‐inert reagent passivation are proposed on the basis of comprehensive analysis of the experimental data.     

Significantly improved high k dielectric performance:Rare earth oxide as a passivation layer laminated with TiO2 film

In order to achieve a super gate dielectric performance,rare earth oxides featuring for large band gap,good thermodynamic stability and relatively high k value were selected to be laminated with TiO₂ film to prepare bilayer dielectric films.As an example,the microstructure,morphology,band gap structure and electrical performance of TiO₂-Y₂O₃ bilayer films were systematically investigated.Results show that stacking sequence of TiO₂ and Y_...