Low-quality fuel problems with advanced engine materials

Demands for high efficiency and power in the future will bring the use of advanced materials including ceramics, composites and augmented metals in engines and other technologies. In many cases, these materials may be subject to corrosion by high temperature gases and molten salt deposits resulting from contaminants (eg sodium, sulphur and vanadium) in the fuel or environment. This paper gives a short overview of the state of knowledge that exists today concerning ceramics and metals corrosion by fuel contaminants, and of possible new avenues for research and materials development.     

锆基大块非晶合金及其晶化合金在0.5mol/L H2SO4中的腐蚀行为研究

根据合金的DSC曲线制定了Zr60Al15Ni25、Zr52.5Al10Ni10Cu15Be12.5和Zr65Al10Ni10Cu15等锆基大块非晶合金的等温退火工艺,获得了与非晶态合金具有相同成分的晶化合金。通过研究非晶态合金和晶化合金在0.5mol/L H2SO4中的极化曲线,结合扫描电镜(SEM)和能量散射X射线谱(EDS)分析,发现,在0.5mol/LH2SO4中非晶态合金和晶化合金都具有非常优异的耐腐蚀性能,但非晶合金的耐腐蚀性能要比晶化合金稍好。这主要是因为晶态合金的结构中不存在晶界、位错等缺陷,同时非晶态合金中的组元具有很高的活性,使合金更快地进入钝态。     

Fatigue Behaviors of a Ni-free ZrCuFeAIAg Bulk Metallic Glass in Simulated Body Fluid

Fatigue behaviors of a biocompatible Ni-free Zr60.14Cu22.31Fe4.85Al9.7Ag3 Zr-based bulk metallic glass （BMG） have been studied under three-point-bending test in a simulated body fluid （SBF） at 37 ℃ and compared with those in air at room temperature （RT）. The BMG shows a high fatigue limit of approximately 366 MPa in SBF, which was slightly lower than that in air （400 MPa）. The fatigue cracks tended to initiate from the defects such as cast-pores, inclusions and corners of the samples and propagate in a similar path in SBF and in air. Three distinct regions, i.e. a crack-initiation region, a stable crack-growth region and an unstable fast-fracture region were clearly observed on the fatigue-fractured surface. Although pitting occurred at the defects where crack initiated, it does not affect significantly the fatigue life of the BMG, because the lifetime in the present BMG is mainly determined by crack propagation. The high corrosion-fatigue limit of the studied BMG results from its excellent corrosion resistance in SBF and intrinsically good toughness.     

Corrosion performances in simulated body fluids and cytotoxicity evaluation of Fe-based bulk metallic glasses

The aim of this work is to investigate the corrosion resistance and biocompatibility of three kinds of Fe based bulk metallic glasses (BMGs), Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ (BMG1), (Fe₄₄Cr₅Co₅Mo₁₃Mn₁₁C₁₆B₆)₉₈Y₂ (BMG2), and Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Er₂ (BMG3) by electrochemical measurements and indirect contact cytotoxicity assays, respectively. In comparison with 316 L SS biomedical steel, Fe based BMGs show better corrosion resistance in both simulated body fluids (Hank's solution and artificial saliva). The OCP curves show that the passive film on the Fe based BMG surfaces is quite stable, like 316 L SS. The corrosion current densities obtained from the anodic polarization curves from the lowest to highest are as follows: BMG3 < BMG1 < BMG2 < 316 L SS. The EIS analysis indicates that the Fe Based BMGs have larger polarization resistance value than that of 316 L SS except for BMG2 in artificial saliva. The pitting corrosion potentials of Fe based BMGs are much higher than that of the 316 L SS, resulting in very few ions releasing into the electrolytes while a significant amount of Ni and Fe ions release was found for 316 L SS under the same condition. The indirect cytotoxicity results suggest that all three Fe based BMG extracts have no cytotoxicity to L929 and NIH3T3 cells. All these results demonstrate that Fe based BMGs will open up a new path for the biomedical applications, especially in dental implantology.     

蒸金设备、工艺改进分析

本文主要介绍了两种不同的结构和蒸发源的蒸金镀膜的方法以他们在现代半导体工业中的应用及带来的经济效果。     

燃煤磁流体熔渣对氧化物材料腐蚀的试验研究

用一定碱度的粒化煤渣以高温短时间的埋浸法对材料进行了４次腐蚀试验，最高温度及力应的保温时间分别为１５００℃４ｈ、１５５０℃３０ｈ、１６５０℃３０ｈ、１６５０℃５ｈ和１７００℃５ｈ。试验结果表明：致密的高氧化铝瓷和高氧化锆瓷的耐渣腐蚀性比其它材料的好，用等静压成型、高温烧成的透明氧化铝瓷的耐渣性又是其中最好的。     

Synthesis and properties of bulk metallic glasses in the ternary Ni–Nb–Zr alloy system

Bulk metallic glasses (BMGs) with high thermal stability, good mechanical properties and high corrosion resistance were synthesized in the Ni–Nb–Zr system. A large bulk glass-forming region with 60 < Ni < 64, 28 < Nb < 38 and 0 < Zr < 9 (in at.%) was found. The critical size for the glass formation is 3 mm. These investigated Ni-based BMGs process high glass transition temperature of about 880–900 K and high on-set crystallization temperature of 915–932 K as well as high compressive fracture strength of approximate 3.0–3.2 GPa along with some compressive plasticity of about 2%. Electrochemical measurements indicate they also exhibit high corrosion resistance, i.e., large passive region above 1.5 V (vs. saturated calomel reference electrode, SCE). The influence of the Zr content on the glass-forming ability (GFA) and corrosion behaviors was carefully studied, indicating that some Zr addition improves the GFA and corrosion resistance.     

Ni42Cr6Fe封接合金氧化膜和氧化物晶须的结构

用ＴＥＭ、Ｘ－Ｒａｙ、ＳＥＭ等技术研究了Ｎｉ４２Ｃｒ６Ｆｅ玻封合金在高温湿Ｈ２中形成的氧化膜及氧化物晶须的结构。结果表明：氧化膜主要由Ｃｒ２Ｏ３和（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４两组相成，氧化膜底层是以Ｃｒ２Ｏ３为主的组织，氧化膜表层是以（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４为主的组织；Ｓｉ在氧化膜与合金界面分布，Ａｌ则在内氧化层中形成内氧化物质点；氧化膜表面生长的氧化物晶须的杆部为（Ｆｅ，Ｍｎ）Ｃｒ２Ｏ４单晶，头部为     

Characterization of surface layers formed under natural environmental conditions on medieval glass from Siponto (Southern Italy)

In this paper a low-vacuum scanning electron microscope (SEM) coupled with an energy-dispersive X-ray spectrometer (EDX) was used to investigate the alteration processes that occur on silica–soda–lime glass exposed to soil materials and dated from XI to second half of XIII sec. The chemical data were collected for altered glass gel and fresh glass. In order to study the influence of chemical composition on weathering process, 16 glasses have been selected on the basis of the chemical characterization and on the basis of the different corrosion processes present on the fragments. Six selected samples had been produced with the use of natron as fluxer and 10 samples with the use of plant ash as fluxer. The analysed pieces come from Siponto excavations (Foggia, Italy) and they include feet and rims of chalices, fragments of lamps and of globular bottles.     

Current developments of nanoscale insight into corrosion protection by passive oxide films

Oxide passive films are a key for the durability of metals and alloys components as well as a central issue in corrosion science and engineering. Herein, we discuss current developments of the nanometer and sub-nanometer scale knowledge of the barrier properties and adsorption properties of passive oxide films brought by recent model experimental and theoretical investigations. The discussed aspects include (i) the chromium enrichment and its homogeneity at the nanoscale in passive films formed on Cr-bearing alloys such as stainless steel, (ii) the corrosion properties of grain boundaries in early intergranular corrosion before penetration and propagation in the grain boundary network, and (iii) the interaction of organic inhibitor molecules with incompletely passivated metallic surfaces. In all three cases, key issues are highlighted and future developments that we consider as most relevant are identified.     

Surface modification of Ca60Mg15Zn25 bulk metallic glass for slowing down its biodegradation rate in water solution

Three kinds of new barrier films were introduced on the surface of Ca₆₀Mg₁₅Zn₂₅ bulk metallic glasses (BMGs) in order to slow down its biodegradation/corrosion rate, including fluoroalkylsilane (FAS) coating, pure Fe film and (Fe + FAS) bilayer. The changes of surface morphology were characterized by scanning electron microscopy (SEM). Contact angle meter was applied to test the surface wettability at ambient temperature. The corrosion rate was investigated by immersion test in deionized water. It was found that various micro-nanoscale hierarchical structures could be constructed after different surface treatments. By suitable surface modification strategy, Ca₆₀Mg₁₅Zn₂₅ BMG showed increased water contact angle even up to 133.6°. The immersion experiment results showed that Fe film and FAS thin film coatings with hydrophobic and insulative characteristics are beneficial to provide effective anti-corrosive protection to Ca₆₀Mg₁₅Zn₂₅ BMG, with the sequence: Fe coating > (Fe + FAS) treated > FAS treated.     

Effect of PWVA/Sb2O3 complex inhibitor on the corrosion behavior of carbon steel in 55%LiBr solution

The inhibition performance of PWVA/Sb₂O₃ complex inhibitor on carbon steel was studied in 55%LiBr + 0.07 mol L⁻¹ LiOH solution. Results indicated that the complex inhibitor decreased both anodic and cathodic polarization current density and widened the passive potential region of carbon steel in test solution and can be classified as mixed inhibitor. The complex inhibitor exhibited excellent inhibition performance on carbon steel when the concentrations of PWVA and Sb₂O₃ were 300 and 200 mg L⁻¹, respectively. With the solution temperature increasing from 145 to 240 °C, the corrosion rates of carbon steel increased from 4.71 to 120.66 μm y⁻¹. In solution containing the complex inhibitor, the relationship between relative coverage ratio of inhibitor on carbon steel surface and inhibition efficiency at 145 °C was obtained as the equation μ = 0.94η, it was a direct proportion. This result proved that the complex inhibitor inhibited the corrosion of carbon steel by geometric blocking effect. When solution temperature was 160 °C, the adsorption Gibbs free energy of PWVA and Sb₂O₃ on carbon steel were −49.59 and −44.29 kJ mol⁻¹, respectively. It indicated that the adsorption processes of PWVA and Sb₂O₃ on carbon steel surface were spontaneous processes. As a strong oxidant, PWVA facilitated the compact passive film comprising of FeO, Fe₂O₃ and Fe₃O₄ forming on the surface and itself was reduced to heteropoly blue. Sb₂O₃ adsorbed on carbon steel surface formed an adsorption film. PWVA and Sb₂O₃ behaved synergistic effect. The corrosion resistance performance of carbon steel in 55%LiBr + 0.07 mol L⁻¹ LiOH solution was improved by PWVA/Sb₂O₃ complex inhibitor.     

船用继动器壳体材料的腐蚀性能分析

用电化学测试手段分别测定了 2 0钢、2Cr1 3、QAl9 2、QAl 1 0 3 1 .5和QAl1 0 4 4等 5种材料在NaCl溶液中的腐蚀电位及与QAl9 2偶接时的电偶腐蚀电流的变化 ,并对测试后各试样的腐蚀状态进行了观察。结果表明 ,铝青铜材料的抗腐蚀性比钢好。其中QAl 1 0 4 4的腐蚀电位最为偏正 ,但它与QAl9 2配副会对QAl 9 2产生较大的阳极电偶腐蚀 ;QAl9 2和QAl 1 0 3 1 .5材料与QAl 9 2配副均有较好的耐电偶腐蚀性能。研究结果对继动器壳体材料的选择具有指导意义     

真空感应熔炼CuCr25合金氧含量的影响因素

研究了坩埚材料、真空度和合金元素Al对真空感应熔炼CuCr2 5合金氧含量的影响。结果表明 :使用碱性氧化物MgO坩埚制得的CuCr2 5合金的氧含量非常高 ,达到千分之几 ,同时可以引起Cr的偏析。而使用中性氧化物Al2 O3 坩埚后可以完全避免这些问题 ,合金的组织和性能大大改善 ,氧含量降低到 70 0× 10 -6左右 ,如果在此基础上添加适量的脱氧剂Al,则可以制备出性能优异的CuCr2 5触头材料 ,其性能完全达到常规CuCr5 0触头材料的水平。