Improvement of corrosion resistance of AZ91D magnesium alloy by gadolinium addition

Based on the previous investigation on beneficial introduction of holmium into magnesium alloy, the effect of gadolinium, an adjacent rare earth element, on corrosion resistance was examined. The corrosion behavior of two Mg-9Al-Gd alloys （Mg-9Al-0.45Gd and Mg-9Al-l.43Gd） was evaluated and compared with that of Mg-9Al alloy without Gd by means of specimen mass loss and hydrogen evolution in 3.5% NaCl solution saturated with Mg（OH）2. The Gd-containing alloys exhibit enhanced corrosion resistance with respect to the plain Mg-9Al alloy. The microstructures of Mg-9Al alloy and Mg-9Al-0.45 Gd alloy were observed by electron probe microanalysis （EPMA） and energy dispersion spectroscopy （EDS）. The alloys with Gd addition show a microstructure characterized by a phase solid solution, surrounded by minor amount of β phase and more grain-like Gd-containing phase. To illustrate the involved mechanism their polarization curves were recorded. The electrochemical investigations reveal that Gd addition shifts the corrosion potential of the alloy towards active, as Gd containing phase is more active and hence less cathodic. As a result, the micro-galvanic corrosion is suppressed. Moreover corrosion product films formed on the Gd containing alloys are more compact and provide a better protective effectiveness than that on the alloy without Gd against corrosion. Repassivation measurements in mixture solution of 0.21 mol/L K2CrO4＋0.6 mol/L NaCI also verify the beneficial role of Gd addition. Based on the present preliminary analysis, both the deposited Gd-containing phases and corrosion product films are believed to be responsible for the improved corrosion behaviour due to Gd addition.     

镁合金化学转化膜

综述了镁合金化学转化膜技术的现状，主要涉及化学转化处理工艺及在多种不同处理液中所得到的转化膜的特性，最后还展望了今后镁合金化学转化膜的发展趋势。     

低团聚掺锑氧化锡纳米微粉的制备

以SnCl4?5H2O和SbCl3乙醇溶液为原料,用阴离子树脂交换除氯水解法制得无Cl–的掺锑氢氧化锡胶体沉淀。并用乙酸异戊酯作脱水剂。结果表明,用乙酸异戊酯共沸蒸馏干燥法能有效防止粉体的硬团聚,得到了比表面积为284.43m2/g掺锑氢氧化锡微粉。热处理后得到了低硬团聚、电阻率为0.405?·cm的掺锑氧化锡纳米晶体。     

环境湿度对聚酰胺力学性能的影响及其微观机理探讨

从环境湿度角度对聚酰胺(PA)的力学性能进行了研究。选用PA66进行一系列的有关湿度试验。通过不同湿度环境下与时间相关的力学性能试验,研究了环境湿度对PA66力学性能的影响。发现,在老化初期PA66的力学性能下降,但随着时间的延长,力学性能有所回升,有的甚至略微超过原始性能。同时,也探讨了引起PA性能变化的微观机理。     

聚氨酯弹性灌封料的研制

通过合成聚氨酯弹性灌封料,研究了异氰酸酯种类、多元醇、NCO/OH摩尔比以及阻燃剂的种类对灌封料性能的影响。结果表明,以蓖麻油为A组分多元醇,PAPI、液化MD I混合异氰酸酯为B组分,选用IPPP为阻燃剂,两组分NCO/OH摩尔比为0.9~1.2混合时,得到的产品固化后硬度适中,性能良好。     

Fe／HCl体系中缓蚀剂吸脱附诱导的电流／电位振荡

研究了HCl介质中活性电位区有机缓蚀剂在Fe电极表面吸脱附诱导产生的电化学振荡现象，及缓蚀剂浓度、电极电位和溶液搅拌等因素对振荡行为的影响。结果表明，在HCl介质中Fe电极的活性电位区同样得到了规整的电流振荡波，但相同条件下的振荡行为要弱于H2SO4介质中，随缓蚀剂浓度升高，振荡波的周期变长，振荡 减弱；由阴极到阳极，电流振荡波形不同，周期也有所增长，搅拌对电流振荡无明显影响，同时报道了该缓蚀体系中恒电流电位振荡的新现象。     

POSITRON LIFETIME STUDIES ON SYSTEMS OF PALLADIUM FILLED GALVANOSTATICALLY WITH HYDROGEN OR DEUTERIUM

The positron lifetime spectroscopy was used to investigate the electron structures of crystal lattice and its defects in palladium samples filled galvanostatically with hydrogen and deuterium, respectively. The results have indicated that the positron lifetime were all the same between hydrogen and deuterium filled samples in which the positron lifetime τ(?) increased about 10%, corresponding to the volume expansibility after the formation of hydrides PdH or PdD phases during electrolyzing commom water or heavy water with Pd cathode; and Will not change with time in 3 weeks after stopping electrolysis; but could be recovered to 116±1ps, the value in polycrystalline pure palladium, after annealing at high temperature.     

铜镍合金表面膜对其电化学行为的影响

<正> 一、引言 铜及铜基合金在含氯离子介质中,表面可形成一层氧化膜,许多研究工作者对此进行了大量的研究。Kruger考察了蒸馏水中铜表面膜的生长动力学。Blundy指出Cu-Ni合金表面膜的主要组份为Cu_2O,合金元素Ni、Fe不影响Cu_2O膜的结构。膜中也发现有少量的Cu_2(OH)_3Cl,有时发生偏聚,形成岛状沉积。关于膜的厚度,文献中报导不一,一般为几千埃。 目前多数人认为,铜及铜合金在含氯离子介质中的耐蚀性是由于表面生成的这一层氧化膜,但对这层膜影响金属腐蚀的具体机制研究得较少,多数文献只讨论了极化组抗Rp的变化。本文作者用电化学方法,结合表面分析结果,对铜镍合金B-30(以下简称B-30)生成表面膜过程中及生成表面膜后的电化学反应机制进行了讨论;对电化学极化过程,和浸泡过程中所形成的表面膜的性能进行了比较,对其差异进行了初步探讨。     

铜镍合金B-30在氯化钠介质中的电化学行为

用电化学方法研究了铜镍合金B-30在氯化钠介质中的阳极和阴极过程。B-30的阳极过程受产(?)扩散控制,表面形成膜阻滞阳极过程;阴极过程是氧的还原,在腐蚀电位φ_c附近是活化控制。按此机理推导了求腐蚀电流Ic的动力学公式,并用计算机解析,求出了部份动力学参数。