A study on the anodic protection of Titanium evaporators in Al2(SO4)3 solution

The feasibility of the anodic protection of titanium evaporators in Al₂(SO₄)₃ solution was studied by the measurement of polarization curves, weight loss, solubility of passive film and AC impedance. The protection parameters and efficiency were determined. In addition, the practical technology of anodic protection was studied by screening reference electrodes and auxiliary cathodes. Throwing power was also measured. Four rows of tube-type evaporators of titanium have been anodically protected in situ. Field tests lasting more than one year show satisfactory results.     

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.     

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 …     

含高温孕育剂W4双相不锈钢焊条的研究

为进一步提高双相不锈钢焊条的抗裂性能,研制了一种含高温孕育剂W4的双相不锈钢焊条,并对其铸钢堆焊焊缝组织,抗裂性等进行了试验分析,结果表明该焊条焊缝组织性能良好。     

Corrosion in SO2 of pure and preoxidized copper at high temperature

A kinetics and morphological study of the reaction of pure SO₂ with copper over the temperature range 500–950°C showed that only Cu₂S formed despite the fact that thermodynamic ally its formation is not expected. Alternatively, the formation of Cu₂O, expected from the Cu-O-S diagram did not occur during sulfidation; however, its evaporation was observed in an atmosphere of pure SO₂ at high temperature. Thus copper differs from others metals such as nickel or cobalt by its low reactivity with SO₂ compared to the oxidation reaction; therefore, it was possible to follow the beginning of sulfidation.     

The effect of K2SO4 additive in Na2SO4 deposits on low temperature hot corrosion of iron-aluminum alloys

To understand the effect of K₂SO₄ additive in an Na₂SO₄ deposit on low temperature hot corrosion, the corrosion behavior of Fe-Al alloys induced by Na₂SO₄+K₂SO₄ was compared to that by Na₂SO₄ alone, and sulfation of Fe₂O₃ in the presence of either Na₂SO₄ or Na₂SO₄+K₂SO₄ was studied. It was found that K₂SO₄ additive promoted the low temperature hot corrosion, but did not change the corrosion-mechanism. Experimental results refuted the prior suggestions that the accelerated hot corrosion resulted either from the formation of K₃Fe(SO₄)₃ or from the stimulation of sulfation of Fe₃O₃. The earlier formation of the eutectic melt caused the accelerated hot corrosion, or in other words, the K₂SO₄ additive shortened the induction stage of hot corrosion.     

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     

锐钛矿型TiO_2(101)面与Ag相互作用的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法对锐钛矿型TiO_2(101)面上两种键桥形式吸附Ag原子的吸附能、电子布居、单位键长及电子结构等参数进行计算,研究Ag/锐钛矿型TiO_2复合材料中的Ag与TiO_2的相互作用。研究发现,锐钛矿型TiO_2(101)吸附Ag原子时,将是O-Ag之间的电子转换;并且,Ag原子更容易与锐钛矿型TiO_2(101)面的键桥Ti上的O原子发生反应生成相应的化合物。     

铜在Na2SO4溶液中的腐蚀及MBO的缓蚀作用

用石英晶体微天平（ＱＣＭ）和电化学方法研究了铜在０．５ｍｏｌ／Ｌ Ｎａ２ＳＯ４溶液中的腐蚀行为,在该介质中,铜表面形成由多种硫酸盐构成的不具保护性的腐蚀产物膜,铜表现为线性增重,当加入１ｍｍｏｌ／Ｌ２－巯基苯并恶唑（ＭＢＯ）时,腐蚀过程被大大抑制,含ＭＢＯ的Ｎａ２Ｓｏ４溶液中形成的缓蚀膜具有较好的稳定性。     

Thermodynamics of the Na2SO4-K2SO4-CoSO4 system and their relevance to low-temperature hot corrosion

Thermodynamic calculations and experiments were performed to determine the SO₃ partial pressures and temperatures at which K₂SO₄-CoSO₄ binary mixed liquid phases form on CoO and Co₃O₄ in the presence of K₂SO₄. The calculations and experiments are in excellent agreement. Similar calculations were also made of the compositions at the liquidus surface and the associated SO₃ partial pressures for the K₂SO₄-Na₂SO₄-CoSO₄ ternary system. These calculations show that the presence of K₂SO₄ substantially reduces the SO₃ partial pressures required to stabilize a liquid salt phase on the surface of oxidized cobalt alloys at 600–800°C. Consequently, at these temperatures the hot corrosion in coal-fired systems, where K levels are high, is expected to be worse than in oil-fired systems, where K levels are low. This prediction was confirmed by experiments in a pressurized fluidized bed coal combustor and in an atmospheric pressure burner rig.     

Electrochemical polymerization of aniline on aluminum electrode from an oxalic acid and H2SO4 solutions

In this study, the polymerization of aniline on Al and Pt electrode was examined by cyclic voltammetry There had been reversible reaction on Al electrode. But on the other hand there had been irreversible reaction on Pt electrode. The addition of aniline into the solution led the decrease of current values. The current decreased by adsorption of anodic products on polymer surface. The fact that the anodic peak potential shifted to positive value shows that polyaniline (PANI) catalyzed the formation of polymer. This case shows that the aniline shifted the electrode potential to positive side by the adsorption on the surface. When Al electrode covered with polymer (in 50 mV s⁻¹ potential scanning rate after 20 cycles) was immersed into 1 N HCl solution, the inorganic layer decomposed on the metal surface. This led to decrease the polarization resistance of the metal. SEM microphotographs and EDX fingerprints also confirmed these results.     

304不锈钢在NaCl-(NH4)2SO4-NH4Cl溶液中的腐蚀行为

用电化学极化曲线和交流阻抗方法，研究了对304不锈钢（304SS）在3％NaCl和NaCl-（NH4）2SO4-NH4Cl混合溶液中的腐蚀行为．结果表明，在混合溶液中浸泡750h后，304SS仍然保持良好的钝化状态，其平均腐蚀电流密度为0．056mA／cm^2．根据交流阻抗研究结果，不锈钢在3％NaCl溶液中，主要表现出裸金属表面的点蚀和形成一定程度的钝化膜的特征，在2．0g／LNaCl、0．67g／L（NH4）2sSO4、2．3g／LNH4Cl混合溶液中，不锈钢表面形成稳定致密的钝化膜的典型特征．此钝化膜的电阻远小于腐蚀反应极化电阻．即使在形成良好的钝化膜的情况下，不锈钢所表现出的优良的抗腐蚀性能主要是由于金属表面活性点的钝化，而非钝化膜对离子导电或者对反应物／产物的扩散过程的阻隔作用．     

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.     

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。     

Ce（SO4）2对化学镀镍液及镀层性能的影响

采用电化学方法研究了Ce（SO4）2对化学镀镍液及镀层性能的影响。结果表明：Ce（SO4）2的添加总体上提高了化学镀镍层的耐腐蚀性能和沉积速率,当加入量为2mg·L^-1时,镀层具有最高的沉积速率;当加入量为5mg·L-1时,镀层具有最好的耐蚀性能;Ce（SO4）2能够在电极表面吸附,对次亚磷酸根氧化的促进作用表现在提高了其氧化电流密度,并通过影响化学镀镍的阳极反应来影响化学镀镍层的沉积速率;Ce（SO4）2的加入增大了化学镀镍反应的活化能,提高镀液的稳定性。     

Modulated Phases in the Ba2SiO4-Ca2SiO4 System of A2BX4, K2SO4-related Structures

Abstract

The A₂BX₄ family of K₂SO₄-related structures have long been of interest to crystal chemists, largely due to the numerous different polymorphs and complicated sequences of phase transitions they sometimes exhibit as a function of temperature. For most such A₂BX₄ compounds, there are essentially only two distinct structure types or parent structures — a high-temperature, ?hexagonal‘ form isomorphous to α-K₂SO₄ and a lower-temperature, orthorhombic form isomorphous to β-K₂SO₄. In addition to these two prototype structures, however, there often exist weakly distorted, or modulated, variants. In the case of the Ba_2-xCa_xSiO₄ system, five such modulated variants have been found via an electron diffraction study and characterized. The characteristic satellite extinction conditions associated with the weak satellite reflections have been used to determine displacement eigenvectors and atomic displacement patterns associated with each of the observed modulation wave-vectors. The widespread occurrence of modulated phases within the A₂BX₄ family of K₂SO₄-related structures suggests an almost chronic instability to displacive modulation.     

First-principles study of the bonding characteristics of TiAl(111)/Al2O3(0001) interface

First principles calculations were carried out for α-Al₂O₃(0001) surface and γ-TiAl(111)/α-Al₂O₃(0001) interface to study the adhesion properties of the interface and to clarify the mechanisms that govern the adhesion of TiAl and its oxidation product Al₂O₃. Two type interface models, the TiAl(111) with Al- and O-terminated α-Al₂O₃(0001) surfaces denoted as T(A₁)-type and T(O_T)-type interface, respectively, were considered. The Universal Binding Energy Relation (UBER) was used to determine the separation between TiAl and Al₂O₃ and the work of adhesion of the γ-TiAl(111)/α-Al₂O₃(0001) interface. Optimization was then performed for all interfaces considered here using the separation obtained with UBER. The lowest work of adhesion is −1.05 J/m² for the T(A₁)-type interface and is −4.04 J/m² for the T(O_T)-type interface. There exists competition between O–Ti and O–Al (on the TiAl side) interactions; however O–Al bond is stronger than O–Ti bond because the main body of the Al valences is involved in the hybriding with O p electrons, while only part of the Ti d valence is involved in the O–Ti bonding. Thus the O–Al interaction dominates the adhesion between TiAl(111) and Al₂O₃(0001) surfaces, and it can be inferred that an Al-rich TiAl surface will favor the adhesion between TiAl/Al₂O₃.