纳米Y2O3对Ni-WC合金喷焊层组织和耐磨性的影响

通过在含35%WC的Ni基自熔合金粉末中添加微量的纳米Y2O3,研究纳米Y2O3对合金喷焊层组织、硬度和耐磨性影响规律及其作用机制.实验结果表明,添加适量的纳米Y2O3可细化合金喷焊层组织,提高合金喷焊层硬度和耐磨性,改善合金喷焊层和基体的结合状态,并且经一定温度的后续热处理,可进一步提高合金喷焊层硬度和耐磨性.     

La2O3对高碳钢堆焊金属组织与耐磨性的影响

研制了不同La2O3加入量的高碳钢堆焊用药芯焊丝,并制作了相应的堆焊试样。采用金相显微镜对其显微组织进行了观察,X射线衍射仪对其相组成进行了分析,洛氏硬度计和砂带式摩擦磨损试验机对其宏观硬度和耐磨性进行了检测,场发射扫描电子显微镜对其磨损表面进行了观察。结果表明:堆焊金属的组织主要由黑色针状马氏体、白色网状高合金马氏体及残余奥氏体组成。随着La2O3加入量的增加,高合金马氏体含量增加,堆焊金属的硬度和耐磨性也增加,当La2O3加入量为3.44%(质量分数)时,二者均达到最大值。堆焊金属中加入La2O3使初生奥氏体晶粒细化,提高了其基体组织的强硬性,与作为耐磨相的高合金马氏体共同作用,使堆焊金属的耐磨性提高。     

氧化铈对M80S20喷涂层和喷焊层显微组织及耐磨性的影响

通过光学金相和扫描电镜观察、X射线能谱和X射线衍射分析及干滑动磨擦磨损试验,探讨了稀土氧化物(CeO_2)对M_(80)S_(20)合金喷涂层和喷焊层的显微组织及耐磨性的影响。试验结果表明,加入8％CeO_2可以明显改善喷涂层和喷焊层的显微组织,提高显微硬度和耐磨性。     

Cu-Al合金添加稀土元素内氧化研究

研究了Cu-Al合金中添加稀土元素La的内氧化热力学。热力学计算结果表明:合金内氧化在热力学上是可行的,内氧化过程中La2O3较容易生成,且溶质Al,La合金元素较基体Cu更容易被氧化生成氧化物,并且La元素较Al元素更易氧化。由此说明,La的加入促进了合金内氧化过程的进行。铜基复合材料的导电率、硬度和密度均随着内氧化温度升高而增大。当内氧化温度超过900℃后,材料的性能变化趋于平缓。     

稀土元素对提高镍基喷焊合金层耐磨性的效果

通过在喷焊合金粉末中添加稀土合金及其化合物的方法，研究稀土对镍基喷焊合金层性能的影响，探讨了稀土在镍基喷焊合金中应用的可能性，试验结果表明稀土能够明显提高喷焊合金层的耐磨性，细化喷焊合金层组织，改善喷焊合金层和基体的结合状态。     

MC尼龙-纳米La2O3复合材料的制备及性能研究

用原位分散聚合法制备了一系列MC尼龙／纳米La2O3复合材料，研究了纳米La2O3用量对复合材料力学性能的影响，用SEM观察了La2O3粒子在MC尼龙基体中的分散情况，用XRD对复合材料的晶体结构进行了表征。SEM观察结果表明，当纳米La2O3用量小于1％时，纳米La2O3均匀分散于MC尼龙基体中，团聚情况很少，当纳米La2O3用量大于1％时，纳米La2O3开始团聚；XRD研究结果表明，纳米La2O3没有改变MC尼龙的结晶形态；力学性能的研究结果表明，随着纳米La2O3用量的增加，复合材料的拉伸强度、断裂伸长率、缺口冲击强度、弯曲强度和弯曲模量都呈先升后降的趋势，当纳米La2O3用量为0．5％时，复合材料的拉伸强度和断裂伸长率达到最大值，分别比MC尼龙提高17．9％和52．1％，当纳米La2O3的用量为1．0％时，复合材料的缺口冲击强度、弯曲强度和弯曲模量达到最大值，分别比MC尼龙基体提高36，6％．12．7％和16．3％。     

La0.8Sr0.2Mn（Fe）O3-δ作为SOFC合金连接体系保护涂层的作用效果

工作温度在800℃以下的固体氧化物燃料电池可采用铁素体不锈钢SUS430（含Cr16％-17％（质量分数））作为连接体材料，然而不锈钢在高温下极易发生氧化形成Cr2O3和Fe3O4等尖晶石相化合物，从而大大地降低了电池的性能。本研究的主要目的是通过空气等离子喷涂（APS）La0.8Sr0.2Mn（Fe）O3-δ（LSM20）和La0.8Sr0.2Mn（Fe）O3-δ（LSF20）保护性涂层来降低合金的氧化生长速率，尤其是减少Cr2O3相的生长。采用XRD和SEM／EDX表征了氧化层的相组成和微观结构特征。在800℃空气中进行了热震实验，经50次循环，LSM20和LSF20涂层合金十分稳定，而SUS430合金氧化层表现出明显地剥落和失重现象。LSF20涂层具有明显的氧化增重速率慢，氧化后界面电阻低，能有效地抑制Cr向合金表面扩散等优点，在800℃空气中氧化1000h后，LSF20涂层合金的界面电阻比LSM20涂层合金的降低了23倍。     

Mo-La_2O_3阴极碳化层组织结构研究

采用高分辨透射/扫描电镜,X射线衍射和俄歇探针等分析手段对实用型的FU-6051电子管的碳化Mo-La2O3阴极显微组织结构进行了观察分析。碳化Mo-La2O3阴极碳化层为疏松多孔的Mo2C块状组织,其中有许多垂直于丝轴方向的晶界与孔洞串,相互贯通直至阴极表面。碳化层与芯部基体钼结合良好,两者间无明显的过渡层。活性物质La2O3在阴极的碳化层和基体中分布均匀,但在阴极表面有相当程度的富集。La2O3在碳化层中以两种方式存在:在晶界、孔洞中以微米级的颗粒富集,在Mo2C晶体内部弥散分布纳米级La2O3粒子。     

钒,铬对快速凝固Al-Ti-Fe合金的组织结构与显微硬度的影响

利用X射线衍射(XRD)和透射电镜(TEM)研究了V, CrAl-Ti-Fe合金组织及显微硬度的影响. 结果表明 Al-Ti-Fe-(V,Cr)合金急冷态组织均为过饱和Al基固溶体; 300 ℃×10 h处理后, Al-2.5Ti-2.5Fe-2.5Cr合金析出Al3Ti和Al13Cr2相; 400 ℃×10 h处理后, Al-Ti-Fe-(V,Cr)合金均析出Al13Fe4相.随退火温度的升高, 快速凝固Al-2.5Ti-2.5Fe-2.5V合金的显微硬度略有下降, 快速凝固Al-2.5Ti-2.5Fe-2.5Cr合金的显微硬度略有上升,表明V, Cr元素的加入有利于快凝Al-2.5Ti-2.5Fe合金显微硬度的增加.     

稀土对ZA-27合金高温性能的影响

研究了ｃＣｅ≥４５％（ｗｔ）的混合稀土对ＺＡ－２７合金显微组织及高温机械性能的影响。结果表明，在锌铝合金中，稀土元素可与Ａｌ、Ｚｎ、Ｃｕ等形成多种复杂成分化合物，其硬度高，热硬性好，分散于晶界或枝晶间，细化了组织，且有效地阻碍了高温时基体的变形和晶界移动。添加适量的稀土，可使ＺＡ－２７合金在１５０℃时的抗拉强度提高３０％，硬度提高２５％，延伸率虽有所下降，但冲击韧性却得以改善。同时发现，室温强度变化不大，唯塑性、韧性略有下降。     

Mechanical and electrochemical properties of platinum coating by double glow plasma on titanium alloy substrate

In this paper, a platinum coating was deposited on titanium alloy substrate by a double glow plasma. Phase and microstructure of platinum coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The microhardness of the coating was estimated by nanoindentation instrument. The adhesive force between the coating and the substrate was performed with scratch tester. The electrochemical behavior of the platinum coating in 3.5 wt % sodium chloride solution was investigated by potentiodynamic polarization. The results indicated that an adherent platinum coating could be successfully obtained on titanium alloy substrates. Compared with the titanium alloy substrate, the platinum coating had a relative low corrosion current density and high corrosion potential. It indicated that the platinum coating had a better corrosion resistance than the titanium alloy substrate.     

La2O3对Ni/γ-Al2O3甲烷化催化剂的助催化作用

我国将稀土作为助剂引入镍基甲烷化催化剂,大大提高了催化剂的活性和热稳定性,并已投入工业应用［1－3］．稀土对不同镍催化剂反应性能及其作用机理的研究已有一些报导［3－7］．谢有畅等观察到镍负载在经单层La2O3改性的γ－Al2O3表面,其晶粒要比没有La2O3时小得多．Rotgerink等认为添加La后反应速率的增加不只是由于几何效应,而是La对甲烷化本身有促进作用,单位镍表面的活性是随La含量不同而改变的,活性增加的同时表观活化能也增加［5］．作为助剂的La2O3在氢还原和反应过程中的变化及其作用的研究和讨论较少,目前一般认为添…     

Effect of Y2O3 on microstructural characteristics and wear resistance of cobalt‐based composite coatings produced on TA15 titanium alloy surface by laser cladding

The effects of Y₂O₃ on the microstructure, phase composition of the coatings, microhardness and wear resistance of cobalt‐based composite coatings prepared by laser cladding were investigated. The TA15 titanium alloy was selected as substrate which the cobalt‐based composite powder with different content of Y₂O₃ was cladded on. The microstructure of the coatings was observed by scanning electron microscope (SEM) and metallurgical microscope. The phase structure of the coatings was determined by X‐ray diffraction (XRD), and the microhardness and wear resistance of the coatings were measured by hardness tester and wear testing machine. The results show that the rare earth oxide Y₂O₃ can refine and purify the microstructure of the coatings, reduce the porosities and cracks and improve compactness of the coatings. Moreover the addition of Y₂O₃ improves the microhardness of the coatings and reduces the friction coefficient, thus improving the wear property of the coatings. And the wear resistance of the coating with Y₂O₃ has improved about 50 times; the highest value of microhardness in the coating is HV1181.1. And 0.8 wt% content of Y₂O₃ in the coating is the best choice for improving the microhardness and wear resistance of the coating. It is feasible to improve the microstructure and tribological properties of laser cladding coatings by adding of Y₂O₃. Copyright © 2014 John Wiley & Sons, Ltd.     

Zn-La合金制备及其电化学性能研究

采用固相扩散法合成Zn＿La合金,并研究La对锌电极化学性能的影响.实验表明:La的适量添加能抑制锌电极的枝晶及腐蚀等问题,从而明显改善锌电极的循环性能,其中以0.5at.%La的添加量为最佳.在100mA/g电流密度下,循环80周期后,其放电容量仍达520mAh/g,XPS测试表明,La主要以La2O3/La(OH)3的形式附着在锌电极表面上.正是由于La2O3/La(OH)3的存在,显著改善了锌电极的循环充放电寿命.     

熔盐法制备Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体及其介电性能研究

以CaCO3,CuO,TiO2,La2O3为反应物,NaCl,KCl为熔盐,通过熔盐法分别在700、750、800、850℃条件下合成Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体。利用XRD和SEM分别对陶瓷粉体的物相结构和微观形貌进行了分析,并对其介电性能进行了测试。实验结果表明,随着合成温度的升高,陶瓷粉体的钙钛矿相含量逐渐增大,与传统固相法相比,熔盐法制备的粉体无团聚现象,耗时少。Ca0.9La0.2/3Cu3Ti4O12粉体制备的陶瓷在1 000℃烧结、测试频率在100 Hz~10 kHz时,获得优良的介电性能:介电常数大大超过104,介电损耗在0.1~0.47之间。     

析氯钛基RuO_2－Co_3O_4－TiO_2（60）涂层的研究

用稳定极化、Ｘ射线衍射、透射电镜和扫描电镜的方法研究了钛基ＲｕＯ_２－Ｃｏ_３Ｏ_４－ＴｉＯ_２（６０）涂层的析氯活性、导电性、使用寿命、微观结构和表面形貌。并对其活性表面积进行了评价。详细讨论了涂层成份、微观结构和表面形貌对涂层析氯活性和活性表面积的影响。发现在０～１０ｍ／ｏＣｏ_３Ｏ_４和６０ｍ／ｏＴｉＯ_２成份范围内ＲｕＯ_２、Ｃｏ_３Ｏ_４和ＴｉＯ_２可形成单一金红石型固溶体,且有优异的析氯活性、电导率和使用寿命。以此研究为基础可改进氯碱工业广泛使用的传统ＲｕＯ_２－ＴｉＯ_２阳极,降低阳极涂层中贵金属含量,提高阳极的电化学性能．     

Photocatalytic,phosphorus-doped,anatase oxide layers applicable to titanium implant alloys

Titanium alloys provide excellent corrosion resistance and favorable mechanical properties well suited for a variety of biomaterial applications. The native oxide surface on titanium alloys has been shown to be less than ideal and surface modification is often needed. Previously, an optimized anodization process was shown to form a porous phosphorus-enhanced anatase oxide layer on commercially pure Ti grade 4. The anodized layer was shown to improve osseointegration and to reduce bacteria attachment when photocatalytically activated with UVA preillumination. The primary objective of the present study was to create a similar phosphorus-enhanced anatase oxide layer on series of titanium alloys including commercially pure Ti grade 4, Ti-6Al-7Nb, Ti-6Al-4V ELI, alpha + beta Ti-15Mo, beta Ti-15Mo, and Ti-35Nb-7Zr-5Ta. Phosphorus-enhanced anatase oxide layers were formed on each titanium substrate. Anatase formation was shown to generally increase with oxide thickness, except on substrate alloys containing niobium. Phosphorus uptake was shown to be dependent on the titanium alloy chemistry or microstructure. Anodized layers formed on beta-structured titanium alloys revealed the lowest phosphorus uptake and the most nanosized surface porosity. A methylene blue degradation assay showed anodized layers on commercially pure Ti and both Ti-15Mo alloys to exhibit the highest levels of photocatalytic activity. Given the range of mechanical properties available with the commercially pure Ti and Ti-15Mo alloys, the results of this study indicate the benefits of phosphorus-enhanced anatase oxide coatings may be applicable to a wide variety of biomaterial applications.     

Formation and Mechanical Properties of CoNiCuFeCr High-Entropy Alloys Coatings Prepared by Plasma Transferred Arc Cladding Process

Plasma transferred arc cladding process was used to fabricate CoNiCuFeCr multi-element alloys coatings. The experimental results show that the coating forms a face-centered-cubic solid solution phase. The microstructure of the coating is mainly composed of dendrite and discontinuous interdendritic segregation. The average hardness of the coating reaches 194.8 HV₁₀₀. The nano-indentation testing indicates that the micro-hardness and elastic modulus of the coating are 3.64 GPa and 211 GPa, respectively. The CoNiCuFeCr high-entropy alloy coating has excellent wear and corrosion resistance. The wear resistance of the coating is about 1.7 times higher than that of Q235 steel substrate under the same wet sand rubber wheel abrasion testing conditions. In 1N hydrochloric acid solution, the coating presents lower i _corr values in polarization curves and higher fitted R _f values in EIS plots than that of as-cast 304 stainless steel.     

锶掺杂对氧化镧催化甲烷氧化偶联反应的影响

甲烷氧化偶联反应(OCM)是天然气直接转化利用的重要途径之一.该反应通过甲烷和氧气在催化剂作用下一步将甲烷直接转化为乙烯等具有高附加值的产品,避免了涉及高能耗过程的合成气间接路径,不仅有可能减少中间副产物的生成,还有可能大大提升整个过程的能源利用效率.因此,研究OCM反应具有十分重要的实际意义.目前氧化镧基催化剂具有良好的催化活性、产物选择性和热稳定性,但在OCM反应中产品收率仍未能达到工业应用的要求,因而近几十年来高效OCM催化剂的研发一直是研究热点.实验发现,锶掺杂氧化镧催化剂具有更为优异的催化性能,主要表现在具有比纯氧化镧催化剂更高的催化活性和产物选择性,但对于锶掺杂的影响机制仍然缺乏系统的理论研究.目前普遍认为,甲烷活化是OCM反应的第一步,也是决速步,这主要是由于C?H键活化需要越过很高的能垒,因此往往需要很高的温度.本文主要采用团簇模型,通过密度泛函理论计算来研究OCM反应中锶掺杂对氧化镧催化剂上甲烷活化性能的影响及其作用原理.本文构建了八种锶掺杂的氧化镧团簇作为该催化剂模型,可分为没有自由基性质的团簇(LaSrO2(OH),La2SrO4,La3SrO5(OH),La5SrO8(OH))和具有自由基性质的团簇(LaSrO3,La2SrO4(OH),La3SrO6,La5SrO9).我们计算了甲烷在这些锶掺杂氧化镧团簇上Sr?O和La?O酸碱对位点以及氧自由基活性位点上的活化机制,以研究锶掺杂对OCM反应活性的影响,并与我们前期计算的纯氧化镧团簇上甲烷活化性能进行了对比.通过计算甲烷在不同锶掺杂氧化镧团簇上的物理和化学吸附能、活化能垒以及甲基自由基的脱附能,发现锶掺杂氧化镧团簇上的甲烷活化在热力学和动力学上都要比纯氧化镧团簇上更为有利.对于具有相同金属原子数目的团簇,甲烷在La?O上活化的能垒大小为:化学计量比的La?Sr?O团簇<非化学计量比的La?Sr?O团簇<化学计量比的La?O团簇;而甲烷在Sr?O上活化的能垒大小依次是:化学计量比的La?Sr?O团簇<非化学计量比的La?Sr?O团簇.给定一个锶掺杂氧化镧团簇,甲烷在不同活化位点上的活化能垒大小通常是:O·<相似文献