电流密度对铝合金微弧氧化陶瓷膜性能的影响

主要研究了电流密度对铝合金表面微弧氧化膜组织和性能的影响,使用扫描电子显微镜、激光共聚焦电子显微镜和X-射线衍射仪对不同电流密度下制备的微弧氧化膜的表面形貌和相组成进行了分析,同时测定了其表面显微硬度。结果表明,铝合金表面微弧氧化膜主要由α-Al2O3和γ-Al2O3组成,而且Ja高对陶瓷膜中α-Al2O3相的影响较γ-Al2O3大,Jκ/Ja对膜中γ-Al2O3相的影响较大,对微观结构有较大影响。高Ja制备的陶瓷膜主要组成相为α-Al2O3,低Ja为γ-Al2O3相,并确定了当Ja为6A/dm2,Jκ/Ja为0.8时陶瓷膜硬度最大可达1540HV。     

医用镍钛合金表面微弧氧化膜层的显微结构及耐蚀性

采用由NaAlO2和NaH2PO2组成的电解液,以微弧氧化技术在医用镍钛合金表面制备Al2O3陶瓷膜层,以减少合金表面Ni含量,并进一步提高其耐腐蚀性能,使其具有良好的生物相容性.随微弧氧化过程中处理时间的延长,试样表面的游动火花由白色逐渐向橙色转变,火花数减少但尺寸增大.所得陶瓷膜层由γ-Al2O3晶相组成,随着处理...     

预制膜层对铝合金微弧氧化陶瓷层性能的影响

在硅酸钠电解液体系中,利用微弧氧化技术,对无预制膜层和含化学氧化膜或稀土转化膜的6061铝合金表面进行陶瓷化处理,研究了预制膜层处理对陶瓷膜层性能的影响。结果表明,预制膜层处理能够降低起弧电压,有利于膜层增厚和硬度提高。无预制膜的铝合金微弧氧化膜层表面呈现凹凸不平的多孔状结构,经预制膜层处理后,其表面粗糙度变小。微弧氧化后,铝合金表面膜层主要由α-Al2O3和γ-Al2O3晶体相组成,而含预制膜层试样中,硬度较大的α-Al2O3相的相对含量较高。与无预制膜层及含化学氧化膜的试样相比,稀土转化膜试样的膜层厚度和硬度最大,粗糙度最小,表面较大较深的孔洞缺陷减少。     

NaAlO2-K2ZrF6体系铝合金微弧氧化膜层组织及性能研究

在NaAlO2-K2ZrF6组成的电解液体系中,利用微弧氧化的方法在LY12铝合金的表面制备陶瓷膜.结果表明,膜层由α-Al2O3、γ-Al2O3和分布于膜外层的c-ZrO2组成,沿膜层截面由内向外α-Al2O3减少,γ-Al2O3和c-ZrO2增加.8 g/L NaAlO2-1 g/L K2ZrF6体系与NaAlO2体系的膜层比较,具有更大的硬度和更好的耐磨性及耐腐蚀性能:最大硬度提高了25.69％,磨损率下降了64.29％,摩擦系数略有下降,腐蚀电流密度降低了96.34％.     

15SiCp/2024铝基复合材料表面微弧氧化膜的摩擦学特性

利用微弧氧化方法在15SiCp/2024铝基复合材料表面制备了一层较厚的陶瓷膜.分析了膜层的成分、结构和硬度分布.通过SRV球盘摩擦磨损实验研究了陶瓷膜的摩擦学行为,分析了磨痕的形貌特征.结果表明:微弧氧化膜由疏松的外层和致密的内层组成.致密层主要包括莫来石、a-Al2O3和γ-Al2O3相.膜层的最大显微硬度超过20GPa.抛光复合材料后的陶瓷膜致密层与ZrO2球对磨的干摩擦系数约为0.36;其磨损率只有基体的1/50.微弧氧化表面处理较大地提高了铝基复合材料的耐磨性.     

Analysis on film formation mechanism of scanning micro-arc oxidation on aluminum ahoy surface

以硅酸盐体系为电解液,利用扫描式微弧氧化(SMAO)方法在铝合金2024的表面成功制备出“蛇形”和“HIT”图案的陶瓷膜层.对扫描式和传统微弧氧化工艺进行了对比,采用扫描电镜和X射线衍射研究了SMAO陶瓷膜的结构和相组成.结果表明,与传统微弧氧化放电过程不同,扫描式微弧氧化在沿阴极前进的方向上依次分布着钝化区、阳极氧化区和微弧氧化区,没有观察到弧光放电.经过一次扫描生成的陶瓷膜厚度约为17μm,膜层只有疏松层,且其中的α-Al2O3含量高于γ-Al2O3.对扫描式微弧氧化放电机理的分析表明,电场在阳极表面的梯度变化可能是同一时间内存在不同放电区域的原因,高达2 400 A/dm2的电流密度使扫描式微弧氧化具有高的成膜效率,同时也导致了疏松层内含有大量的α-Al2O3.     

阴极电流密度对微弧氧化ZrO2陶瓷膜及耐蚀性的影响

在氟锆酸钾电解液体系中,采用微弧氧化的方法在LY12铝合金表面原位生长ZrO2的陶瓷膜层,研究阴极电流密度对陶瓷膜层组成及耐腐蚀性的影响.结果表明陶瓷膜层主要由m-ZrO2,t-ZrO2组成,且以t-ZrO2为主晶相.随着阴极电流密度的增加,膜层内的KZr2(PO4)3逐渐减少,膜层的厚度增大,膜层表面的放电孔洞尺寸变小,致密性有所提高;陶瓷膜层腐蚀电流密度减小,点蚀电位正移,耐蚀性提高.但继续增加阴极电流密度,膜层厚度和致密性有所下降,腐蚀电流密度增大,点蚀电位负移,耐蚀性下降.     

铝合金微弧氧化热力学机理及影响因素的分析

微弧氧化是一种新型的表面处理技术,能够在有色金属表面生成陶瓷膜.从微弧氧化的热力学机理出发,通过动力学和热力学能量平衡分析了α-Al2O4、γ-Al2O3转化,分析微弧氧化中相的转变同电流密度、氧化时间之间的关系.     

硼酸对铝合金微弧氧化膜耐蚀性的影响

研究了硼酸质量浓度对6060铝合金表面微弧氧化膜组织和性能的影响。对在不同硼酸质量浓度下生成的铝合金微弧氧化膜的表面形貌及相组成进行了分析;并通过腐蚀试验评价其耐腐蚀性能。结果表明:微弧氧化膜主要由α-Al2O3和γ-Al2O3相组成,当硼酸质量浓度为1g/L时,膜层的表面粗糙度最低;当硼酸质量浓度为1.5g/L时,膜层耐蚀性能最佳。     

铝合金微弧熔凝Al2O3形核及转变热力学分析

微弧氧化是在铝合金表面原位制备陶瓷膜层的一项新技术.针对陶瓷膜层在形成过程中的两次相变,分析计算Al2O3液相中的形核过程以及γ-Al2O3向α-Al2O3转变过程Gibbs自由能的变化,分析相变驱动力与温度及过冷度的关系.研究结果表明:约在1200K左右过冷度时,可从液相Al2O3直接析出γ-Al2O3晶核,γ-Al2O3形核Gibbs自由能的变化符合T模型,α-Al2O3的形核行为可采用D-R模型计算,α-Al2O3和γ-Al2O3的均质形核率具有相同的数量级;微弧放电区域的热影响作用可造成γ-Al2O3向α-Al2O3的转变,温度为1500K时转变驱动力比1100K时增大了约12.3%.     

Effect of hydrocarbon species on no oxidation over diesel oxidation catalysts

The effect of propylene concentration on NO oxidation as a function of temperature and position over a model Pt-Pd/Al₂O₃ diesel oxidation catalyst was investigated. Propylene had an apparent inhibition effect on NO oxidation. This apparent inhibition is a result of NO₂, as the NO oxidation product, acting as an oxidant in the reaction with propylene. This was verified with experiments that included NO₂, and a resulting significant temperature decrease in the onset of NO₂ reduction when propylene was present. Furthermore, increasing amounts of propylene further decreased the NO₂ reduction temperature. Similar results were observed with m-xylene and dodecane addition as well. The results also demonstrate that NO₂ was consumed preferentially relative to O₂ during hydrocarbon oxidation. With low inlet levels of O₂, the addition of NO₂ apparently inhibited propylene oxidation after the onset of NO₂ reduction. This subsequent inhibition was due to the NO formed, demonstrating that propylene results in reduced NO₂ outlet levels while NO inhibits propylene oxidation.     

分子氧化及光电催化氧化对石油Pickering乳液的破乳研究进展

石油开采、集输、加工过程中会面临复杂的工况条件,原油中的天然表面活性剂与人工添加乳化剂以及纳微米固体颗粒共同形成石油Pickering乳液,使得油水体系呈稳定的水包油（O/W）、油包水（W/O）或多重乳化状态。油水乳状液作为注水采油的主要产物,其高效破乳是石油工业链条中的普遍需求。目前对于石油Pickering的破乳仍然借鉴普通油水乳液的方法,而对于成因复杂的油水乳状液,以去除成膜乳化剂为目标的氧化破乳法比传统破乳法的效果更佳。为此,本文基于高效的氧化破乳机制,介绍了石油Pickering乳液的特点及危害,与非氧化反应类型的传统化学破乳法进行对比,综述了分子氧化、光催化氧化、电化学氧化三类技术对于不同来源及特征的油水乳状液的破乳进展。通过对每种方法的机理过程、应用实例、优缺点等方面详细分析,总结了分子氧化、光催化氧化、电化学氧化在石油Pickering乳液破乳中的局限性,并对今后如何实现石油Pickering乳液精准破乳提出展望。     

High-pressure effects on lipid oxidation

Rendered pork fat (0.44 water activity, A_w) was subjected to high-pressure treatment of 800 MPa for 20 min at 19°C prior to storage at 4, 25, and 50°C. In all cases, high pressure-treated samples oxidized more rapidly (had a shorter induction period) as shown by the peroxide value (PV), 2-thiobarbituric acid value, and ultraviolet absorbance. The effect was less marked at lower pressures. In contrast, at all water activities outside the range of 0.40–0.55, the PV of the high pressure-treated pork fat was lower than control samples stored similarly, and the PV of rancid fat decreased slightly on pressure treatment at 19°C, but not at higher temperatures. This effect may explain the observed inhibition of oxidation at most water activities. At 0.40–0.55 A_w, other factors, such as the liberation of transition metals, may override the destruction of peroxides.     

光、微波、热催化氧化效果的比较

在微波催化和热催化比较中,采用相同的加热功率,处理100mL质量浓度为1g/L的甲基橙,试验条件为1g催化剂,1mL质量分数为30%的H2O2,0.07gFeSO4·7H2O,加热18min,微波催化对甲基橙的COD去除率达到90.1%,而热催化对甲基橙的COD去除率只有73.5%,微波催化明显优于热催化。在微波催化和光催化比较中,在相似的实验条件下,微波催化对低浓度甲基橙加热3min,色度去除率达到近100%,而用光催化要30min才能使去除率达到100%,微波催化明显优于光催化。经过Fe-C预处理,再经过微波催化,染料、炼焦、炼油、餐饮废水处理后主要污染物指标COD达到国家二级排放标准。     

Partial oxidation reactions on phosphate-based catalysts

In this work emphasis has been placed on phosphate-based catalysts used for partial oxidation reactions, such as vanadyl pyrophosphate, iron phosphates and hydrogen/hydroxy-phosphates, zirconium hydrogen phosphates as layered compounds used to stabilise/entrap Cr and V oxyhydroxy-macrocations. It is shown that, in partial oxidation reactions, the catalyst surface behave in a rather dynamic and labile way, reconstructing under activation and/or catalytic reaction conditions and adapting itself to the stereochemistry of the reactants. The active sites are shown to have a molecular size, to be isolated and to present several catalytic functions, as hydrocarbon activation, H atom abstraction, lattice oxygen incorporation and electron transfer through the solid material to allow the redox process to occur. The metal cations are the active species and the role of the phosphate tetrahedra is not only to bind the MO₆ octahedra together to constitute a dense or layered compound but also to bring some specific redox and acid–base properties. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fast methanol oxidation on polycrystalline Pt

Fast cyclic voltammetry and a combined chronoamperometry/cyclic voltammetry pulse-sweep technique are used to study methanol oxidation on platinum in sulphuric acid. Measurement of suppression of hydrogen desorption charges simultaneously with charges for stripping of the CO poison allows for accurate baseline correction of the CO stripping peaks. Saturation coverages of CO formed from methanol, formic acid and dissolved CO are not all the same and differ in their potential dependence. Only dissociative adsorption of methanol to give adsorbed CO and subsequent oxidation of CO to CO₂ occurs during continuous cycling, but in the pulse-sweep method evidence was found for the existence of a parallel pathway occurring independently of adsorbed CO production, provided there is some surface not covered by CO or oxide.     

Deactivation on vehicle-aged diesel oxidation catalysts

Topics in Catalysis - This paper studies oxidation catalytic converters that were vehicle-aged in a diesel automobile. The deposition of several atoms (S, P, C, Si, Ca, Zn and Fe) was detected by...     

提高褐猛矿氧化率的试验研究

在褐猛矿矿石中加入不同的添加物进行焙烧试验,结果表明;在矿石中单独加入萤石或方解石混合焙烧,都有利于褐猛矿的氧化,且用量越多越好。但从环保和成本上计算,使用方解石比萤石环境污染小,价格低廉、易得,经济而实惠。