铝熔体中添加NH4Al(SO4)2制备Al/Al2O3复合材料

向铝熔体中添加脱水的硫酸铝铵,于900℃下发生分解反应,反应分解的Al2O3原位生成颗粒增强铝基复合材料。SEM观察表明,Al2O3颗粒在铝基体中细小弥散分布,形成球形的、不团聚的增强体颗粒。与基材相比,Al/Al2O3复合材料的耐磨损性能明显提高,耐磨性是基材的4倍,且由硫酸铝铵原位生成的复合材料耐磨性优于添加氧化铝形成的复合材料。拉伸实验结果显示,复合材料的抗拉强度没有明显变化,且塑性有所降低。     

Controlling limiting length of tunnels on Al foil electroetched in HCl-H2SO4 solution

The limiting length of tunnels, llim, of Al foil electro-etched in HCl-H2SO4 solution and the corresponding anodic polarization curves in the same solution were measured. It is found that there is a dependence of llim on the potential difference, △φ, between the pitting potential, φpit, and the corrosion potential, φcorr, of Al foil, when the temperature and H2SO4 concentration of HCl-H2SO4 electrolyte are changed. The dynamic equation on the tunnel growing and the linear equation between llim and △φ were deduced by analyzing the relationship among the over-potential on Al foil surface, the transport over-potential in tunnel solution and the over-potential at tunnel tip during the electro-etching. The results show that the growing velocity of tunnels decreases with their extending in length and the changing trend of llim can be judged by measuring △φ, which supplies a convenient access to explore new kinds of etchants.     

Ti3Al基合金表面两种Cr1-xAlxN(x=0.18,0.47)涂层的热腐蚀性能

利用磁控反应溅射的方法在Ti3Al基合金表面制备了两种不同铝含量的Cr0.82Al0.18N与Cr0.53Al0.47N涂层,测试了这两种涂层在800℃(NR2SO4+25 mass%K2SO4)熔融盐膜百的热腐蚀动力学,并采用X射线衍射仪和带能谱的扫描电镜分析腐蚀产物相组成以及微观结构.结果表明,两种涂层均可降低Ti3Al基合金的热腐蚀速率;涂层热腐蚀产物主要为具有保护性的Cr2O3和θ-Al2O3混合氧化膜,θ-Al2O3的含量随着涂层中Al含量上升递增;和θAl2O3相比,Cr2O3在熔融硫酸盐中的稳定性更好,Cr0.82Al0.18N涂层抗热腐蚀性能优于Cr0.53Al0.47N涂层.     

Effects of SO2 and SO3 on the Na2SO4 induced corrosion of nickel

The effects of SO₂ and SO₃ in the environment on the hot corrosion behavior of Ni in the temperature range 750–950°C has been studied. Below the melting point of Na₂SO₄ (884°C), rapid corrosion takes place by formation of a Na₂SO₄-NiSO₄ melt, which can penetrate the porous oxide scale and give rise to sulfide information by coming in contact with the metal. The distribution of the sulfides depends on the SO₂ level in the ambient gas. Continued corrosion occurs by a sulfidation-oxidation mechanism. At temperatures above the melting point of Na₂SO₄, accelerated degradation occurs via dissolution of the surface scale, followed by reprecipitation of the oxide in a nonprotective form.Deceased     

Initial atmospheric corrosion of zinc in presence of Na2SO4 and （NH4）2S04

Initial atmospheric corrosion of zinc in the presence of Na₂SO₄ and (NH₄)₂SO₄ was investigated via quartz crystal microbalance(QCM) in laboratory at relative humidity(RH) of 80% and 25 °C. The results show that both Na₂SO₄ and (NH₄)₂SO₄ can accelerate the initial atmospheric corrosion of zinc. The combined effect of Na₂SO₄ and (NH₄)₂SO₄ on the corrosion of zinc is greater than that caused by (NH₄)₂SO₄ and less than that caused by Na₂SO₄. Fourier transform infrared spectroscopy(FTIR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM) were used to characterize the corrosion products of zinc. (NH₄)₂Zn(SO₄)₂, Zn₄SO₄(OH)₆·5H₂O and ZnO present on zinc surface in the presence of (NH₄)₂SO₄ while Zn₄SO₄(OH)₆·5H₂O and ZnO are the dominant corrosion products on Na₂SO₄-treated zinc surface. Probable mechanisms are presented to explain the experimental results.     

A study of the Ag(s)/Ag2SO4(l) high temperature reference electrode

Ag(s)/Ag₂SO₄(l) reference electrodes for use in hot corrosion research were fabricated and their properties were studied at 927°C (1200°K). The McDanel^TM MV 30 mullite tube was used as sheath of the reference electrode and concentrations of the tested electrolytes were varied from 0.1 to 10 m/o Ag₂SO₄ (l) + Na₂SO₄ (l). 10 m/o Ag₂SO₄ was always used as electrolyte in the reference electrode. The working electrodes with less than 2 m/o Ag₂SO₄ showed marked potential drift as the Ag₂SO₄ concentration was lowered, showing poor potential stability. However, the initial values of cell voltages obeyed Nernstian behavior for all range of Ag₂SO₄ concentrations in the working electrodes, which showed that Ag(s)/Ag₂SO₄(l) electrodes behaved reversibly. Galvanostatic polarization was performed on a pair of 10 m/o Ag₂SO₄ reference electrodes to test the reversibility. The polarizability was 3.5 mV/10 μA with no hysteresis loop on the polarization curve, showing that the reversibility was satisfactory. The potential of gold electrode in molten Na₂SO₄ was measured under pure oxygen atmosphere with 10 m/o Ag₂SO₄ electrode as a reference potential. The results showed that the potential of gold electrode could be explained by the 2 Na + SO₃ + 1/2 O₂ → Na₂SO₄ cell reaction.     

Initial atmospheric corrosion of zinc in presence of Na_2SO_4 and (NH_4)_2SO_4

1 Introduction In view of the widespread use of zinc, as metallic sheet or zinc coatings, it was desirable to study its corrosion behaviour in the wide variety of atmospheres. The atmospheric corrosion of zinc has been studied in field exposures as well …     

添加剂对铝酸钠溶液晶种分解产生Al(OH)3和Al2O3的影响

研究了疏水性添加剂脂肪酸类阴离子表面活性剂与21-碳烷不同配比对铝酸钠溶液分解产生氢氧化铝和氧化铝的粒度、强度及分解率的影响,考察了产物Al(OH)3和Al2O3的强度和粒度之间的关系,探讨了添加剂影响铝酸钠溶液晶种分解的相关机理.结果表明:脂肪酸质量分数在32%～49%,添加剂加入量为150×10g/L时,有利于提高分解率,但对提高Al(OH)3和Al2O3的强度和粒度不利;脂肪酸质量分数在15%～22.5%时,Al(OH)3和Al2O3在强度和粒度方面呈相一致的对应关系,添加剂可促进Al(OH)3的附聚,提高Al(OH)3和Al2O3的粒度和强度,但对提高分解率作用不大;Al(OH)3的粒度过大时,会引起其强度降低,导致Al0O3粒度下降;加入添加剂后,可形成球状的Al(OH)3晶体,有利于形成粒度大、强度高的氧化铝.     

Pt和PtBi在H2SO4-CH3OH中的氧还原性能

采用氩弧熔炼后热处理方法制备了PtBi金属间化合物材料.采用循环伏安和旋转圆盘电极手段进行电化学性能测试.通过在0.5 mol/L H2SO4 0.25 mol/L CH3OH溶液中对氧还原的起始电位和电流密度大小比较发现,与光滑铂电极相比,PtBi金属间化合物具有良好的氧还原催化性能和抗甲醇中毒性能.从结构方面分析了PtBi具有抗甲醇中毒性能的原因,认为是PtBi中大的Pt-Pt间距不利于甲醇的吸附解离.X射线光电子能谱(XPS)结果表明,PtBi材料中Pt的d电子空穴增加,可能是导致PtBi电极表面氧还原电流增大的原因.     

钛(TA2)及钛合金(TC4)表面等离子渗Nb研究

采用双层辉光离子渗金属技术进行钛（TA2）及钛合金（TC4）的等离子渗Nb表面改性研究。分析了合金化条件对渗层Nb含量及厚度的影响，在此基础上得到优化的典型工艺条件。研究发现，在1000℃进行合金化时，放电气压对渗层表面Nb含量有显著的影响，在本试验选取的气压范围（20～80Pa）之内，气压为65Pa时可以得到最佳质量的渗层。对此典型条件下渗层的组织形貌及成分分布特征进行了观察与分析，测试了渗层的显微硬度并用划痕法评价了渗层结合强度。结果表明，渗层表面Nb含量可达70％左右，向内逐渐降低，呈梯度分布特征。渗层与基体结合良好，硬度显著提高。     

Dissolution theory of gold in alkaline thiourea solution(Ⅲ) ——Thermodynamics on dissolution of gold in alkaline thiourea solution containing Na _2SO_3

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｅｃｈａｎｉｓｍａｎｄｃｈｅｍｉｃａｌｐｒｏｃｅｓｓｆｏｒｄｉｓｓｏｌｖｉｎｇｇｏｌｄｉｎａｃｉｄｉｃｔｈｉｏｕｒｅａｓｏｌｕｔｉｏｎｗｅｒｅｓｔｕｄｉｅｄｂｙｍａｎｙｒｅｓｅａｒｃｈｅｒｓ［１～５］，ｗｈｏｇｅｎｅｒａｌｌｙｔｈｏｕｇｈｔｔｈａｔｔｈｉｏｕｒｅａａｓａｓｔｒｏｎｇｌｉｇａｎｄｃｏｍｐｌｅｘｅｓｓｅｌｅｃｔｉｖｅｌｙｗｉｔｈｇｏｌｄｉｏｎｔｏｆｏｒｍｓｔａｂｌｅｃｏｍｐｌｅｘｉｏｎＡｕ［ＣＳ（ＮＨ２）２］＋２，ａｎｄｓｏｍｅｏｘｉｄａｎｔｓ…     

Corrosion behavior of Ti(C,N)-Ni/Cr cermets in H2SO4 solution

The effects of partial substitution of Ni with Cr on the microstructure and corrosion resistance of Ti(C,N)-based cermets in H₂SO₄ solution were investigated in this paper. The results showed that partial substitution of Ni with Cr had a minor effect on the microstructure, whereas the hardness of the Ti(C,N)-based cermets could be improved for dissolution of Cr in Ni binder. The corrosion behavior of Ti(C,N)-based cermets with different Cr content in 0.2 mol/L H₂SO₄ solution was also studied via potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and corrosion test. The tested Ti(C,N)-Ni/Cr cermets had three typical passive regions. The current of the first passive region was reduced and the passive range was enlarged with the increase of Cr content in binder attributed to the synergistic effect of Ti-based and Cr-based passive layers. But the remaining passive regions were pseudopassive regions. The EIS results also demonstrated that the impendence of the reaction rose with the increase of Cr content in binder. Moreover, the corrosion resistance of cermets in H₂SO₄ solution was improved remarkably by Cr dissolving in the binder, which gave rise to the enhanced passivation ability.     

Effect of magnetism on the solution energy of 3p (Al, Si) and 4p (Ga, Ge) elements in iron

The method based on the density-functional theory has been used to study the solubility of 3p (Al, Si) and 4p (Ga, Ge) elements in ferromagnetic and paramagnetic states of bcc iron. To simulate the paramagnetic state, two different approaches have been employed, which were implemented using the SIESTA and LSGF packages. It has been established that the solution energy of all these impurities decreases upon the transition into the paramagnetic state. The solution energies obtained by averaging over the ensemble of unpolarized magnetic configurations agree well with the values obtained in the coherentpotential approximation. At the same time, the allowance for the magnetic polarization in the vicinity of an impurity leads to a decrease in the solution energy, which is most clearly pronounced at temperatures close to T _C. The temperature dependence of the solution energies of the impurities in the paramagnetic state is discussed.     

Coarsening of γ (Ni–Al solid solution) precipitates in a γ′ (Ni3Al) matrix

The coarsening behavior of Ni–Al solid–solution precipitates in an Ni₃Al matrix was investigated in alloys containing 22.0–22.8 at.% Al aged at 650–800 °C for times exceeding 1800 h. The rate constant for coarsening increases with equilibrium volume fraction as predicted by the MLSW theory. The activation energy for coarsening, 314.1 ± 16.6 kJ mol⁻¹, agrees very well with results from conventional diffusion experiments. The particle size distributions are not in very good agreement with the predictions of any theory; possible reasons are discussed. The particles become more spherical with decreasing elastic self-energy. The results are consistent with the premise that a strong volume fraction effect is observed so long as diffusion in the matrix phase, and not through the precipitate–matrix interface, controls the kinetics.     

制取活性锌粉的Zn(Ⅱ)-NH3*H2O-(NH4)2SO4体系电解法

研究了在Zn(Ⅱ ) NH3 ·H2 O (NH4 ) 2 SO4 体系中电解制取活性锌粉新工艺。结果表明 :在常温下 ,电流效率高达 88.19%,每吨产品能耗为 32 5 4.37kW·h ,其产品质量符合GB6 890 86标准 ;活性锌粉杂质含量低 ,锌含量≥ 98.78%,有效锌含量≥ 96 %,锌的总回收率为 97.97%。该法与以金属锌为原料的蒸馏法、雾化法相比较 ,成本大幅度降低。     

(Al3Zr+Al2O3)p/A356复合材料液态模锻的研究

采用熔体反应法———液态模锻成形工艺,制取了Al3Zr与Al2O3颗粒共同增强的铝基复合材料。结果表明:通过该工艺成型的复合材料组织致密,无气孔、缩孔等铸造缺陷;相对于金属模成形的复合材料,其抗拉强度提高了127%,耐磨性及伸长率也都有较大地提高,力学性能较好。     

铝箔表面化学镀锌对其在HCl-H 2 SO 4体系中电蚀性能的影响

将高压铝电解电容器用电子铝箔在含Zn2＋的5.0%NaOH溶液中实施化学镀锌处理,然后在HCl＋H2SO4电解液中进行直流电解扩面腐蚀得到腐蚀箔;采用极化曲线研究化学镀锌处理对扩面腐蚀时铝箔点蚀电流、点蚀电位的影响,利用电化学交流阻抗（EIS）研究化学镀锌处理对铝箔电解腐蚀时电化学特征的影响;使用扫描电镜（SEM）观察化学镀锌处理对腐蚀箔表面和横截面形貌的影响;测试100 V形成电压下腐蚀箔的比电容。结果表明：铝箔表面化学镀锌形成的Zn-Al微电偶有助于电蚀时降低点蚀电极反应的阻力,提高点蚀电流密度,增加铝箔表面蚀孔密度和蚀孔分布的均匀性;随着碱液中Zn2＋浓度的提高,腐蚀箔的比电容逐渐增加。     

Growth of anodic oxide films on AC2A alloy in sulphuric acid solution

Growth behaviour of anodic oxide films on AC2A Al cast alloy was investigated in sulphuric acid solution using SEM, optical microscope (OM) and confocal scanning laser microscope (CSLM) and energy dispersive spectroscopy (EDS). The AC2A alloy contains three different types of second-phase particles: Al–Cu, Al–Cu–Fe–Si and Al–Si particles. The growth of anodic oxide films was critically retarded by the presence of non-reactive particles of Al–Si, while little effect was observed by the presence of active particles of Al–Cu and Al–Cu–Fe–Si. The most severe retardation effect on the growth of anodic films on AC2A alloy resulted from agglomerated Al–Si particles.     

Study on Electrodeposition of Gadolinium in (p-CH3C6H4SO3)3Gd-DMF Solution

1 ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒａｒｅｅａｒｔｈ ｃｏｂａｌｔａｌｌｏｙｓｈａｖｅｔｈｅｐｏｔｅｎｔｉａｌｆｏｒｍａｋｉｎｇｔｈｅｍａｇｎｅｔｉｃａｎｄｍａｇ ｎｅｔｏ ｏｐｔｉｃａｌｍａｔｅｒｉａｌｓ .Ｓｏｆａｒ ,ｔｈｅｒａｒｅｅａｒｔｈ ｃｏｂａｌｔａｌｌｏｙｆｉｌｍｓａｒｅｓｕｂｓｔａｎｔｉａｌｌｙｐｒｏｄｕｃｅｄｂｙｓｐｕｔｔｅｒｉｎｇｏｒｖａｃｕｕｍｐｌａｔｉｎｇ .Ｉｆｓｕｃｈｆｉｌｍｓａｒｅｐｒｅｐａｒｅｄｂｙｅｌｅｃｔｒｏｄｅｐｏｓｉ ｔｉｏｎｉｎｓｔｅａｄ ,ｐｒｏｄｕｃｔｉｏｎｅｆ…