High-temperature corrosion of nickel in SO2

The reaction of nickel with SO₂ has been studied in the temperature range 650–1100°C at SO₂ pressures from 10 to 760 Torr. Reaction kinetics have been studied by thermogravimetry; the reacted specimens have been characterized by means of metallography, scanning electron microscopy, and electron microprobe analysis. The reaction involves oxidation and sulfidation except at sufficiently high temperatures and low pressures of SO₂ (e.g., 1000°C and 10 Torr SO₂) where only formation of NiO takes place. Approximately linear reaction kinetics are observed between 650 and 900°C. Reaction mechanisms are discussed, and the relative importance of oxide formation and sulfidation is interpreted in terms of the thermodynamics of the Ni-O-S system.     

The reaction of preoxidized nickel in SO2 at high temperatures

The reaction between preoxidized nickel and SO₂ was studied at 800–1000° C. The experimental methods consisted of thermogravimetry, metallography, scanning electron microscopy, and electron microprobe analysis. Sulfur accumulates in the surface layer of the metal during the SO₂ exposure. It is concluded that this is due to transport of SO₂ through the oxide scale. This leads in turn to formation of a Ni-S liquid solution which eventually ruptures the scale and causes an accelerated, breakaway reaction behavior. The induction period for the accelerated reaction increases with increased preoxidation and furthermore is influenced greatly by the microstructure of the oxide scale.     

High-temperature corrosion of manganese in pure SO2

The corrosion of manganese in 1 atm of pure SO₂ has been studied from 700 to 900°C. The reaction shows two approximately parabolic stages, the first being faster; the reaction products are MnO and MnS. In the early moments of the reaction a fine mixture of oxide and sulfide is formed directly at the scale surface, which is not in equilibrium with the gas phase due to rate control by the surface reaction. This process ends quickly due to the lowering of the Mn activity at the scale surface, and then an outer region of MnO surmounting a dispersion of coarse MnS particles in the oxide develops. The rate control shifts to solid-state diffusion, and the scale surface equilibrates with the gas. The sulfide is produced in this stage in the interior of the scale as a consequence of sulfur penetration by two mechanisms whose relative importance is discussed. The reaction produces a protective scale, and the rate is close to that for oxidation of Mn in 1 atm O₂ at the same temperature.     

Separation and recovery of Cu and As from copper electrolyte through electrowinning and SO2 reduction

Cu and As were separated and recovered from copper electrolyte by multiple stage electrowinning, reduction with SO₂ and evaporative crystallization. Experimental results showed that when the current density was 200 A/m², the electrolyte temperature was 55 °C, the electrolyte circulation rate was about 10 mL/min and the final Cu concentration was higher than 25.88 g/L, the pure copper cathode was recovered. By adjusting the current density to 100 A/m² and the electrolyte temperature to 65 °C, the removal rate of As was 18.25% when the Cu concentration decreased from 24.69 g/L to 0.42 g/L. After As(V) in Cu-depleted electrolyte was fully reduced to As(III) by SO₂, the resultant solution was subjected to evaporative crystallization, then As₂O₃ was produced, and the recovery rate of As was 59.76%. The cathodic polarization curves demonstrated that both Cu²⁺ concentration and As(V) affect the limiting current of Cu²⁺ deposition.     

Corrosion of nickel with small alloy additions of Si,Fe, and Mn in SO2+O2/SO3 at 700°C

The corrosion of nickel with alloy additions of Si, Fe, and/or Mn up to 4 wt% has been studied in SO ₂+O₂/SO₃ at 700°C. All alloy additions greatly improve the corrosion resistance of nickel in oxygen-rich atmospheres (O₂ with about 4% SO₂); the best improvements are achieved with Si, Fe+Si, and Fe+Mn+Si additions. High-purity nickel corrodes rapidly under these conditions; the scale then consists of NiO+Ni₃S₂, and the sulfide forms a three-dimensional network along the grain boundaries of the NiO grains and serves as the diffusion path for rapid outward migration of nickel. From studies of the microstructure and distribution of the alloying elements in the protective scales, it is proposed that the alloying additions exert their beneficial effects by accumulating/segregating at the grain boundaries of NiO (e.g., as silicates) and thereby influence the wetting characteristics and disrupt the sulfide network.     

组织和温度对Cu表面氧化速率的影响

利用扫描电镜、X射线衍射仪和氧化称重实验对铜表面氧化速率进行研究,分析了不同组织、晶粒和温度对铜氧化性能的影响。结果表明：铜的组织结构是影响其氧化性能的主要因素,非密排的（100）晶面上界面能高、晶面原子堆垛相对疏松和原子尺度上粗糙,且氧化膜生长连续,氧化速率高于密排的（111）晶面;温度升高,铜表面的内能增大,铜原子较易成为活化原子与氧气发生反应,同时增大了铜原子在氧化膜中的扩散速率,加速了铜的氧化;铜试样经过等径角挤压（ECAP）后,（111）晶面铜表面的面积增大,氧化速率降低,晶界不是影响铜氧化速率的主要因素,能量较小的晶面原子所占的面积增大,铜的氧化速率减小。     

Corrosion of iron in sulfur dioxide at 0.1 MPa

The reaction of iron with sulfur dioxide at 0.1 MPa and 1073 K was studied. The composition and morphology of the scales, transport phenomena occurring in the growing scales, and kinetics of the process were investigated. Scanning electron microscopy and various techniques of X-ray analysis were used. The transport phenomena were studied by marker and by radiotracer techniques. The scales were composed of sulfide and oxides and grew by the outward diffusion of metal. It was concluded that the process initially took place through the reaction of iron with sulfur dioxide molecules. During the next stage of the process the reaction with sulfur dioxide molecules as well as with oxygen molecules is possible.     

Corrosion of some pure metals in basaltic lava and simulated magmatic gas at 1150°C

The extraction of thermal energy from subterranean magma can be achieved by the use of a suitable heat exchanger extending into the molten rock. Although the engineering feasibility of this scheme has not been proven, engineering data, including materials compatibility information, will be required ultimately. The work summarized in this paper was designed to provide an understanding of the reaction mechanisms and modes of degradation of various metals so that the best generic types of alloys can be selected for structural components and instrumentation. Fifteen pure metals were studied. These included base metals such as iron, nickel, and cobalt; some precious metals: platinum, rhodium, and palladium (possible thermocouple or lead-wire materials); refractory metals: tungsten, molybdenum, tantalum, niobium, vanadium, and rhenium; plus other high melting metals such as titanium and zirconium. Samples were exposed to basaltic lava at 1150°C for periods of 24 and 96 hr. A cover gas was used to produce oxygen and sulfur fugacities corresponding to those of the gases dissolved in basaltic melts. The corrosion behavior can be classified into five categories: (A) no attack (Pt and Re); (B) slight oxidation (Cr and Mo); (C) heavy oxidation (W, Ta, Nb); (D) sulfidation (Fe, Ni, Co, Pd, Rh); and (E) reaction with lava constituents (V, Ti, Zr). Group (A) metals were inert for all practical purposes. Group (B) metals formed thin adherent oxides initially, under which sulfides eventually formed in the substrate. Attack was minimal. Group (C) metals exhibited extensive oxide formation and virtually no sulfidation. Some reaction between the base-metal oxides and those in the lava took place. Group (D) metals all formed liquid sulfides which penetrated the substrate grain boundaries. All of these metals except cobalt were completely degraded. Cobalt was only partially penetrated by the liquid sulfide formed. Group (E) metals formed silicates, oxides, mixed oxides, and dissolved oxygen in the metal which completely embrittled the metal substrate. A small amount of sulfidation occurred, but sulfidation played virtually no role in the corrosion of these metals. Extensive analyses of the reaction products by scanning electron microscopy, X-ray energy dispersive analysis, electron microprobe analysis, and metallography are presented for each metal. The products formed are discussed with reference to thermodynamic stability diagrams, and the reaction path concept is used to explain some of the corrosion product morphologies.This work supported by the United States Department of Energy under Contract AT(29-1)-789.on leave at Sandia Laboratories, Albuquerque, New Mexico.     

High-temperature corrosion of pure chromium in SO2 (700–1000°C)

The corrosion of chromium under 1 atm of pure SO₂ has been studied over the range 700–1000°C at 100°C intervals. The reaction rate is higher than in pure oxygen and the scale does not contain sulfides, but only a small concentration of sulfur, in contrast with the behavior of other transition metals, even though the thermodynamic conditions are similar. Possible causes for this peculiar behavior are examined and discussed with reference to the results of the corrosion of chromium in pure oxygen.     

Studies on the mechanism of high temperature corrosion of cobalt in SO2 atmospheres with the use of18O and35S isotopes

The composition and morphology of scales formed on cobalt in sulfur dioxide atmospheres (1.013 × 10⁵ Pa) at 850 and 900°C and transport phenomena occurring in the growing scales have been investigated. The transport phenomena have been studied by the marker method and with the use of SO₂ labeled with the oxygen isotope¹⁸O and sulfur isotope³⁵S. The scales were composed of sulfide and oxide mixtures and grew due to the outward diffusion of cobalt and inward transport of SO₂ molecules through the discontinuities in the scale. These molecules, as well as the oxidant originating from the dissociation of the outer scale layer, take part in the formation of the inner scale layer.     

Transport of reactants during scale formation on copper in SO2+O2 atmosphere at 973 and 1073 K

The reaction between copper and a mixture of SO₂+O₂ was studied at 973 and 1073 K. The experimental methods included optical microscopy, X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray analysis, and radiotracer. It is concluded that the inward transport of oxidants through the scale as well as oxygen and sulfur dioxide liberation in the reactions taking place at phase boundaries suggest that secondary processes occur inside the oxide-sulphate layer. Therefore, Cu₂O and CuOCuSO₄ appear inside this layer. In the metal-consumption zone, a Cu₂O layer forms, which contains small amounts of a sulfide phase near the metal-scale interface.     

Sulfidation behavior of a ferritic commercial alloy in different sulfidizing environments at high temperature

The sulfidizing behavior of Fe–22Cr–4Al–0.15Zr (wt.%) was studied in two atmospheres: S₂ vapor over the range 4.4–25.4 Pa and H₂–H₂S mixtures corresponding to aP _{S 2} range 0.2–1.297 Pa in the temperature range 973–1373 K. It was found that the constitution of the gaseous phase is of great importance on the corrosion kinetics and the morphology of the corrosion products. Furthermore, a stratification phenomenon during scale growth was observed during the initial sulfidation stage in H₂–H₂S mixtures containing a sufficiently high H₂S partial pressure. This behavior was not observed during tests in puresulfur vapor.     

Deformation behavior of dispersion-strengthened copper at high temperature

1. Introduction Dispersion-strengthened copper (DSC) is a promising material developed recently. Considerable attention has been focused on it because of its excel- lent high-temperature properties. The metallic mate- rial, which is strengthened by solution strengthening, deformation strengthening, and ageing strengthening, is always low at high temperature, and the strength- ening factor contradicts with the electrical conduc- tivity of the material to a certain extent [1-2]. But DSC has g…     

High-temperature oxidation of Fe-16.7% Mn-2.1% Ni-6.6% Si alloy in SO2

The oxidation of an austenitic Fe-16.7% Mn-2.1% Ni-6.6% Si (by weight) alloy in SO₂ in the temperature range 600–900°C is described. The corrosion products formed on this alloy in this environment below 800°C consist only of oxides, rather than a mixture of oxides and sulfides as is observed for unalloyed Fe or Mn. The kinetics of oxidation of the alloy in SO₂ in this temperature range are similar to those in O₂. It is proposed that these characteristics result from the presence of a thin silicate layer near the scale-metal interface that alters the gradient of oxygen potential within the scale.     

高温长时退火后纯铜丝的组织与性能

将ø8 mm退火态T2纯铜棒材,通过工业拉丝机进行多道次冷拉拔变形,最终得到ø3.5 mm的拉拔态试样,对其进行了600 ℃保温不同时间的退火试验,并通过组织形貌的观察、力学和电学性能的测试,研究了退火后纯铜试样组织与性能的关系。结果表明:拉拔态纯铜组织经退火后形成新的再结晶晶粒,并伴有退火孪晶比例的增加。随着退火时间的增长,再结晶晶粒不断长大,抗拉强度和断后伸长率小幅波动。退火态试样的平均抗拉强度为拉拔态的67.3%,平均断后伸长率是拉拔态试样的8倍,平均导电率比拉拔态提高约3.3%,且随着退火时间的增加导电性得到逐步提高。     

The corrosion of pure niobium in oxidizing,sulfidizing, and oxidizing-sulfidizing gas mixtures at 600–800°C

The corrosion of pure niobium has been studied at 600–800°C in various environments as part of a study of the corrosion resistance of its alloys with iron, cobalt, and nickel to atmospheres of low-oxygen and/or high-sulfur activities. The results have shown that not only the sulfidation but also the corrosion in mixed atmospheres and particularly the oxidation under low oxygen pressures of pure niobium are quite slow, with kinetics rather similar in the three types of gas mixtures used. The good corrosion resistance of niobium to attack by oxygen under low pressures is quite interesting because this element is corroded very rapidly by oxygen under high oxygen pressures, due to the formation of the nonprotective highest oxide Nb₂O₅ as a main corrosion product.     

铜电解液净化中铜砷的分离与回收(英文)

经二氧化硫还原、蒸发结晶,使铜电解液中铜、砷、锑和铋得到有效去除。结晶产物经过溶解、氧化、中和、沉淀、过滤和蒸发结晶,得到三氧化二砷和硫酸铜。当采用SO2将铜电解液中As(Ⅴ)充分还原为As(Ⅲ),并加热蒸发浓缩铜电解液中硫酸浓度至645g/L时,铜电解液中铜、砷、锑和铋的去除率分别为87.1 %,83.9 %,21.0 %和84.7%。在温度30℃,将65g结晶产物溶于200mL自来水时,砷的去除率为92.81%。将所得滤液在如下条件下净化:n(Fe):n(As)为1.2,双氧水为理论用量的19倍,氧化温度为45℃,氧化时间为40min,终点pH为3.7,净化后蒸发浓缩结晶,所得硫酸铜溶液中硫酸铜含量达到98.8%。     

加热温度对超纯铁素体含铜不锈钢热脆敏感性的影响

在Gleeble 3500热模拟机上对21Cr-1.4Cu超纯铁素体不锈钢铜进行高温拉伸试验,研究加热温度对试验钢铜脆敏感性的影响。采用扫描电子显微镜、激光共聚焦显微镜和能谱分析等方法对显微组织和化学成分进行了对比分析。结果表明：1300 ℃加热时,试验钢由于过烧产生了高温脆性。1150 ℃加热时,铜脆敏感性最高,产生铜裂。1200~1250 ℃加热时,铜脆敏感性较低,发生塑性变形。研究发现,加热温度为1150 ℃时,形成的氧化物开始呈液态,冷却后形成包裹状或共晶结构的硅酸盐细颗粒。这些脆性物质使晶界强度降低,结合松脆最后导致严重铜裂。