2205双相不锈钢沉积氯化钠之高温腐蚀

本文研究表面沉积2 mg/cm2氯化钠的2205双相不锈钢(2205 DSS)在500 vppm NaC(l g)流动气氛加热炉内550~850℃下之高温腐蚀.结果显示,2205 DSS之高温腐蚀动力学遵守)物线定律,腐蚀反应速率随温度的上升而加速.高温腐蚀后生成的腐蚀皮膜结构由外而内依次为Fe2O3、Fe3O4、Cr2O3及FeCr2O4,不同温度下腐蚀生成的皮膜结构并无明显相异,唯850℃之试片于氧化皮膜脱落后,从其表层较容易检测到S iO2及N iO.在双相结构腐蚀顺序实验中,对表面沉积2 mg/cm2氯化钠的试片,其腐蚀顺序与α、γ相无关,为全面性的腐蚀.但于500 vppm NaC l(g)的流动气氛下,虽无法分辨α、γ相的腐蚀顺序,但可发现γ相较α相有较快速腐蚀的现象.     

煤催化气化工艺中碱金属腐蚀刚玉质耐火材料的实验研究

针对煤催化气化反应器设计中遇到的材料问题,采用碳酸钾及催化气化工况富含碱金属气化灰渣为实验原料,进行了碱金属腐蚀刚玉质耐火材料的实验研究。着重考察了有氧空气气氛和无氧还原性气氛、反应温度、反应时间、碱金属存在形态对腐蚀行为的影响,并结合SEM-EDX、XRD、核磁Al谱等表征手段,研究了反应前后碱金属和刚玉质耐火材料的成分、物相及结构变化。结果表明,碱金属对耐火材料腐蚀行为受反应的温度、气氛、时间及碱金属存在形态等因素影响较大。分析表明,有氧空气气氛下腐蚀尤为严重的原因是,原料中存在的钾与刚玉耐火材料发生化学反应生成新的钾的铝酸盐物相,且其含量随温度升高、反应时间延长而增加。     

基于差示扫描量热技术的生物质热解两步连续反应模型研究

采用差示扫描量热分析仪对我国的一种生物质试样在空气气氛中进行了实验, 发现试样从常温到923 K高温的低速升温过程中, 经历了两步明显的放热过程. 对放热机理的分析表明, 第一步主要是由半纤维素和纤维素的有氧热解过程控制, 第二步放热过程则受木质素热解和炭的氧化反应的共同作用. 采用等转化率方法和优化计算方法, 对热解过程的动力学模型进行了研究, 结果表明, 两步连续反应机理可用于描述生物质在空气气氛中热解的放热动力学.     

高温氟化盐对熔盐堆用材料的腐蚀行为研究进展

氟化物熔盐在熔盐堆(MSR)中可用作为核燃料载体和冷却剂,其独特热物理化学性质能极大提高MSR的传热效率。但MSR高温和强腐蚀条件对材料的选择使用要求非常苛刻,特别是氟化物熔盐在高温下对结构材料的腐蚀直接关系到MSR的安全运行和使用寿命,成为制约MSR应用发展的关键。本文综述了LiF-NaF-KF(Flinak)和LiF-BeF2(Flibe)熔盐与金属合金材料、碳材料及陶瓷材料腐蚀行为方面的研究进展,对材料在不同条件下腐蚀行为的机理进行了分析。研究发现,应用于MSR的高镍基合金及石墨材料存在着高温腐蚀性及机械性能差等弱点。未来新型高镍基合金、C/C复合材料及新型陶瓷材料(SiC及其复合材料、其他陶瓷材料)有望在氟化物熔盐体系中获得应用,并最终解决MSR用材料的困惑,实现MSR快速工业化发展。     

Na 掺杂对硅酸锂吸收CO2性能的影响

通过高温固相反应法, 在添加不同比例Na2CO3的条件下, 合成出一系列可在高温500～750 ℃之间直接吸收CO2的硅酸锂材料. 利用扫描电子显微镜、X射线粉末衍射仪分别观察和评价了合成材料的表面形貌与结构特征, 用热重分析仪测量了硅酸锂材料的CO2吸收性能. 实验结果表明, 通过适量Na元素的掺杂, 能够提高硅酸锂材料吸收CO2的性能, 当Na2CO3的添加量x=0.02时, 合成的硅酸锂材料在CO2气氛下, 于700 ℃恒温保持约15 min即可达到吸收平衡, 材料的吸收量为(46±0.6)%(w), 与未经掺杂的材料相比, 吸收容量有所提高. 此外, 气氛中CO2的浓度对材料吸收CO2的速率有较大影响.     

用于预测高温高浓度溴化锂溶液中碳钢腐蚀行为的BP神经网络(英文)

本文建立了预测碳钢在LiBr溶液中腐蚀速率的神经网络模型.该模型拟合了碱度,温度,LiBr和Na2MoO4浓度变化对碳钢全面腐蚀速率的影响,可用于准确预测不同温度下,在含有不同缓蚀剂的LiBr溶液中的碳钢腐蚀速率,其预测值和实验值完全吻合,为研究溴冷机中金属材料的腐蚀和现场监测提供了新的思路和方法.     

负载于刻蚀镍泡沫上钯纳米粒子作为乙醇氧化高性能电催化剂

发展具有高催化活性和高稳定性的非Pt阳极催化剂目前仍面临着巨大的挑战. 除了设计催化剂以外,设计合适的载体对提高电催化剂性能也具有重要意义. 在这篇论文中,作者报导了一种以混合酸(HNO₃+H₂SO₄+H₃PO₄+CH₃COOH) 腐蚀的镍泡沫负载Pd纳米粒子作为高性能电催化剂用于碱性条件下乙醇氧化. 因具有开放孔结构、快速电解质渗透能力及快速的电荷传输性能,这些镍泡沫负载的Pd纳米粒子显示了很好的电催化活性和循环稳定性,显示了该材料在乙醇阳极氧化具有较好的应用前景.     

锆合金初始氧化行为的原位近常压XPS研究

锆基合金由于具有低的热中子吸收截面、良好的耐腐蚀性能和力学性能等优点,通常被用于水冷核反应堆中的核燃料包壳和其他结构材料。通过在合金中添加适量的Nb元素可以有效地降低锆合金的氧化速率和吸氢分数,从而改善锆合金的耐腐蚀性能。尽管对锆合金的耐腐蚀性能得到了广泛的认识,但关于其在接近真实氧化腐蚀条件下的原位研究一直是具有挑战性的课题。本工作中利用近常压X射线光电子能谱(NAP-XPS)原位研究了1.3 × 10^-8 - 1.3 × 10^-1 mbar (1 mbar = 100 Pa)连续分压下室温到623 K温度时两种锆基合金表面在水,氧中的初始氧化腐蚀行为。结果表明,未添加Nb和添加1%Nb的锆合金表面在初始氧化过程中锆元素都会由金属态向多种氧化态过渡。水蒸气环境下两种合金的氧化速率都要低于氧气环境。室温下无论水蒸气还是氧气环境两种合金的氧化速率都要比623 K高温情况下的慢。在623 K的氧气气氛下,未添加Nb的锆合金相较于添加1%Nb的锆合金更容易被氧化,Nb的添加一定程度上会降低氧物种的吸附能力。在室温下和623 K低水蒸气压力下,1%Nb锆合金氧化速率更快,Nb促进OH^-在表面生成。而在623 K高水蒸气压力下,未添加Nb的锆合金有更易于被氧化的倾向,Nb在高温下向表面扩散并抑制OH^-键的断裂,但两种样品表面短时间内都无法被完全氧化。     

氢键构筑的新颖微孔配位聚合物[Co_2(Hisor)_2·(4,4′-bpy)_2(H_2O)_2]·4,4′-bpy的合成与结构

近年来 ,微孔配位聚合物的研究越来越引起人们的重视 .与传统的微孔材料硅酸盐、硅铝酸盐、磷铝酸盐等相比 ,微孔配位聚合物具有独特的优势 :一方面 ,可以将金属离子所特有的磁学、光学、电学和氧化 -还原等特性引入所设计合成的配位聚合物中 ;另一方面 ,有机配体的多样性、可修饰性和与各种金属离子的不同组合 ,为设计合成尺寸可控、形状可控和性质可控的各种配位聚合物提供了可能 .因此 ,微孔配位聚合物在分子磁性、分子识别、信息储存、分离、催化和非线性光学等方面有着广泛的应用前景 .于是 ,设计和合成微孔配位聚合物成为当前具有挑战…     

锌铝层状双金属氢氧化物焙烧物对钢筋的缓蚀作用研究

在空气气氛下合成了锌铝层状双金属氢氧化物(Zn-Al LDHs)和焙烧物(Zn-Al CLDHs),扫描电镜结果表明,所制得的双金属氢氧化物具有明显的层状结构. 文中研究了Zn-Al CLDHs 对钢筋的腐蚀保护效果,Zn-Al CLDHs固体在NaCl 溶液中浸泡处理3 h 后,钢筋的腐蚀速率显著降低. 实验证明,Zn-Al CLDHs 在结构重组过程中可吸收溶液中的Cl^-,同时释放出OH^-,改善腐蚀环境,有效抑制钢筋的腐蚀.     

Application of scanning SIMS techniques for the evaluation of the oxidation behavior of high-purity molybdenum

Refractory metals are primarily characterized by a high melting point combined with a rather poor corrosion resistance under oxidizing atmosphere and therefore are mainly used in high temperature processes under reducing atmosphere or in vacuum. Exposure to an atmosphere of high humidity can lead to oxidation of the material even at room temperature. Different methods of surface pre-treatment have been applied to investigate their influence on the oxidation behavior of high-purity molybdenum. Within the scope of this work molybdenum foils and molybdenum discs consisting of the same base material were investigated. Since lateral surface structure as well as the in-depth distribution of contaminants are expected to play an important role in the oxidation process, both the in-depth distribution of the constituents within the oxide layer and the lateral distribution at the surface level of the oxide have been analyzed. Scanning SIMS has been engaged to analyze the uppermost structures of the oxide layer. In order to achieve maximum detection power and to gain the in-depth information, stigmatic SIMS has been applied to investigate the in-depth distribution of the interesting specimen constituents.     

High-temperature corrosive damage to superalloys during operation of blades of gas-turbine engines and power plants

The role of liquid nickel-sulfide eutectic in the mechanism of corrosive damage is determined by investigations of products of high-temperature oxidation and corrosion of superalloys with the use of scanning-electron microscopy and X-ray spectroscopic and X-ray structural analyses. It is found that the sulfide corrosion rate is controlled by the process of the dilution of the high-temperature nickel alloy within the liquid nickel-sulfide eutectic, diffusion of alloying constituents of the alloy in the liquid phase, and their subsequent oxidation.     

Relationships among Preparative Technique,Phase Composition and Bending Strength of Bauxite Porcelain

1 INTRODUCTION Bauxite porcelain is a novel “K2O–Al2O3–SiO2” system ceramic by using sintered bauxite, clay and potash feldspar and albite as the main raw materials with the Al2O3’s content of 50%～60(massfraction). Compared to the traditional“K2O–Al2O3–SiO2” feldspar porcelain by using quartz, bolus alb and potash feldspar and albite as the main raw materials, the bauxite porcelain possesses such advantages as high mechanical strength, excellent electrical insula- tion prop…     

High temperature corrosion of valve steels in atmosphere containing water vapor

The kinetics and mechanism of high temperature corrosion of two valve materials (X33CrNiMn23-8 and X50CrMnNiNbN21-9 steels) in water-vapor-containing atmosphere have been studied as a function of temperature (973–1,273 K) and gas composition, being the mixture of nitrogen, oxygen, and water vapor. In all experiments this atmosphere contained 50 vol.% of water vapor and the concentration of oxygen was changed from 0.001 to 50 vol.%. The oxidation kinetics have been studied thermogravimetrically in microthermogravimetric equipment, enabling the registration of weight changes of the oxidizing samples as a function of time with the accuracy of the order of 10⁻⁶ g. It has been found that the corrosion process of both steels is rather complex and can not be described by one kinetic rate law. X33CrNiMn23-8 steel, containing higher chromium concentration, shows better corrosion resistance than the X50CrMnNiNbN21-9 steel, but both these materials undergo more rapid corrosion in water vapor than in oxygen atmospheres. This phenomenon results from non-protective, heterogeneous scales, formed in water vapor, as compared to protective Cr₂O₃ scales, developing in oxygen atmosphere. It may be then concluded that the presence of water vapor in corrosive atmosphere plays a definitely negative role in corrosion processes.     

Determination of the Concentration of Petroleum Products and Oils in Films at the Surface of Water Using a Solid-Electrolyte Analyzer

A method was proposed for estimating the total amount of organic substance at the air–water interface. The method combines sampling by the transfer of an organic film to the probe surface with the coulometric determination of the amount of oxygen consumed for the high-temperature oxidation of the sample in a solid-electrolyte analyzer. The effect of the composition of the film and the material of the probe on the transfer of model oil films under the conditions of fast withdrawal of the probe from water was studied. It was demonstrated that organic substance can be accumulated at the surface of the probe on multiple withdrawal.     

Stability of lithium hydride in argon and air

The oxidation behaviors of LiH under a high purity argon atmosphere, an argon atmosphere with some O2 and H2O impurities, and ambient air at both room and high temperatures, are investigated using a variety of analytical instruments including X-ray diffractometry, thermogravimetry, mass spectrometry, scanning electron microscopy, and specific surface area analysis. The oxidation behaviors of the ball-milled LiH under different atmospheres are also studied and compared with those without ball milling. It is shown that no oxidation of LiH occurs under a high-purity argon atmosphere. However, oxidation of LiH takes place when the argon atmosphere contains some H2O and O2 impurities. At temperatures higher than approximately 55 degrees C, oxidation of LiH proceeds via the reaction of LiH + 1/4 O2 = 1/2 Li2O + 1/2 H2, whereas at room temperature oxidation of LiH is likely caused by the simultaneous reactions of LiH + H2O = LiOH + H2 and LiH + 1/2 O2 = LiOH. The oxidation behavior of LiH in ambient air with a 27% relative humidity can be well described by the Johnson-Mehl-Avrami equation. Furthermore, the ball-milled LiH oxidizes faster than the unmilled one, which is due to the finer particle size and larger surface area of the ball-milled powder.     

高温比热容测试常见问题及误差分析

介绍了同步热分析仪(STA449F3)测试高温比热容过程中的常见问题及误差分析.采用差示扫描量热三步法测试高温比热容.试验结果表明,提高仪器的稳定性和升温速率可减小比热测试值与理论值之间的误差.此外,将常规一段升温测试分割成若干个窄温区间,提高了高温比热容测试的准确性.     

合成气气氛下褐煤与生物质共液化残渣的燃烧特性

利用热重研究了不同液化条件(溶剂、温度、气氛、水分)下褐煤与生物质共液化所得残渣的燃烧特性。通过比较共液化残渣燃烧的三个特征温度,着火点、燃烧峰温和燃尽温度,对比分析了液化条件对残渣燃烧特性的影响及其原因,同时研究了残渣燃烧的动力学。结果表明,四氢萘为溶剂所得残渣的燃烧特性好于甲苯为溶剂的;360℃下所得液化残渣燃烧反应性好于420℃下的;合成气气氛下所得液化残渣燃烧反应性好于氢气气氛下的;液化过程加入水后,所得残渣的燃烧反应性降低。不同液化条件下所得残渣的加氢程度和收率不同,使残渣具有不同的H/C原子比、比表面积和灰分,从而对残渣的燃烧特性产生影响。残渣的燃烧特性符合三段二级反应,大部分残渣三段活化能遵循"高-低-高"的变化规律。     

CaSO4在CO气氛下的平行竞争反应实验与模型研究

采用热重等温实验研究了不同CO体积分数下CaSO4的分解反应,利用红外光谱仪分析反应析出的气体成分,通过亚甲基蓝分光光度法测定固体残留物中CaS的质量分数。在CO气氛下,CaSO4分解反应为平行竞争反应,反应生成了CaO和CaS。在0.5％CO体积分数下,CaSO4分解最终产物以CaO为主。在2%和4％CO体积分数下,反应初期分解产物以CaO为主,后期分解产物以CaS为主。分解反应最终产物中CaS质量分数随CO体积分数增加而升高,随温度升高而降低。推导出平行竞争反应模型,可以很好的描述CaSO4的平行竞争反应。     

原煤低温氧化预脱硫的实验研究

采用三种高硫煤，在固定床反应器中考察了原煤在空气、空气水蒸气和空气氮气气氛下低温氧化预脱硫过程的影响因素，包括煤种（总硫含量、形态硫分布和挥发分含量）和化学反应条件（温度、停留时间）。脱硫前后的样品中硫及硫形态、热值、工业分析和元素分析依据国际进行测定。实验结果表明硫及碳质的氧化在开始阶段以不同的速率析出，随后反应中差别减小；黄铁矿硫可得到高的脱除率；水蒸气适当比例的加入可以增加黄铁矿的脱除，同时降低碳的转化和热量的损失；而氮气的加入在降低碳和热量的损失外，降低了硫的脱除。