纳米Y2O3对高Nb-TiAl合金高温蠕变性能的影响

在不同温度、不同应力条件下对高Nb-TiAl合金进行蠕变测试,结合扫描电子显微镜(SEM)、透射电子显微镜(TEM)等分析手段探究纳米Y₂O₃对Ti-45Al-6Nb-2.5V合金高温蠕变性能的影响。铸态高Nb-TiAl合金组织为α₂/γ层片结构,纳米Y₂O₃的添加可显著细化合金组织并改善合金的高温拉伸性能。蠕变结果分析得出,添加0.15at.%纳米Y₂O₃会显著改善Ti-45Al-6Nb-2.5V合金的抗蠕变性能,在800℃/300MPa条件下,合金稳态蠕变速率由2.389×10^_-7s^_-1降至1.500×10^_-7s^_-1;在850℃/250MPa条件下,合金的蠕变寿命由14.10h延长至61.50h。添加纳米Y₂O₃提高合金蠕变抗力的机制是Y₂O₃与基体具有较高的结合强度,可以有效阻碍位错运动,减弱孔洞萌生的倾向。经分析,两种合金在800℃/300MPa下的蠕变行为主要受位错攀移与孪晶控制,蠕变损伤断裂机理为孔洞萌生与裂纹扩展。     

La2O3含量对搅拌摩擦加工制备Ni /Al复合材料组织和性能的影响

采用搅拌摩擦加工方法在Al基体中添加不同La₂O₃含量的混合粉末(Ni+La₂O₃),制备 (Ni+La₂O₃)/Al复合材料。采用SEM、EDS、 EPMA及XRD对复合区微观结构及相组成进行分析,采用室温拉伸试验对 (Ni+La₂O₃)/Al复合材料力学性能进行了测试。结果表明,随着La₂O₃含量的增加,(Ni+La₂O₃)/Al复合材料的组织和性能先变好后变差。当La₂O₃添加量达到5%时,复合材料中Al₃Ni增强颗粒分布均匀、颗粒数量最多,块状的Ni粉团聚减少,其抗拉强度达到最大值215MPa,相比Ni/Al复合材料(抗拉强度176MPa),其抗拉强度提高了22%;当La₂O₃的添加量为7%时,复合材料中Al₃Ni增强颗粒含量减少,块状Ni粉团聚重新出现,抗拉强度下降至201MPa。     

钽表面铜掺杂Ta2O5纳米棒的制备及抗菌性能研究

本实验采用两步水热法在钽基体表面制备出掺杂Cu_²⁺的Ta₂O₅纳米棒薄膜。采用XRD、SEM、XPS等方法分析了材料的物相和表面微观结构。用ICP检测了样品在生理盐水中离子析出浓度,最后通过平板计数法检验了不同含量铜掺杂Ta₂O₅薄膜的抗菌能力。结果表明,通过两步水热处理,在钽表面生成了简单斜方晶体结构的Ta₂O₅纳米棒阵列,Cu_²⁺的掺杂不会对纳米棒薄膜的微观形貌和物相造成显著影响。随时间的增加,掺铜薄膜的铜离子析出速率逐渐趋于平缓。平板计数法表明,Cu_²⁺ 的掺杂量达到2.68At%时,铜掺杂Ta₂O₅纳米棒薄膜的抗菌性能最好,抗菌率达99.2%。     

La2O3掺杂AgSnO2电接触材料的制备及性能研究

以Ag、Sn、La₂O₃粉为原料,采用机械合金法制备复合粉体。结合氧化法与粉末冶金工艺,对复合粉体进行氧化、压制、烧结。采用扫描电镜(SEM)和能谱仪、硬度计、金相显微镜、金属电导率测量仪等对复合粉体氧化前后的形貌以及电接触材料烧结前后的性能进行表征。结果表明：烧结后,电接触材料硬度较于烧结前明显下降。同时电接触材料随Sn含量增大,电阻率升高,密度反而下降。在一定的La₂O₃(0wt.%、0.75wt.%、1.5wt.%、2.25wt.%、3wt.%)含量范围内,La₂O₃掺杂量越高,密度越低。同时电接触材料经烧结后,随La₂O₃含量增加,其电阻率先降后升,在La₂O₃含量为0.75wt.%时,电接触材料的电阻率最低。     

Al2O3包覆LiNi0.03Co0.05Mn1.92O4正极材料的制备及其电化学性能

以Al(NO3)3?9H2O为包覆原料,通过燃烧法制备得到LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料。通过X射线衍射(XRD),场发射扫描电子显微镜(FESEM)和透射电镜(TEM)等表征手段对材料的结构和形貌进行分析,并通过恒电流充放电、循环伏安(CV)、交流阻抗(EIS)等测试分析材料的电化学性能。结果表明,Al2O3包覆没有改变LiNi0.03Co0.05Mn1.92O4的尖晶石型结构,包覆层厚度约10.6nm。LiNi0.03Co0.05Mn1.92O4@Al2O3正极材料电化学性能得到了明显改善,1 C和10 C倍率下初始放电比容量分别为119.9 mAh?g-1和106.3 mAh?g-1,充放电循环500次后容量保持率分别为88.4%和78.2%,而未包覆的LiNi0.03Co0.05Mn1.92O4在1 C和10 C倍率下初始放电比容量分别为121.2 mAh?g-1和104.0 mAh?g-1,500次循环后容量保持率分别为84.1%和67.6%。LiNi0.03Co0.05Mn1.92O4@Al2O3活化能为32.92 kJ?mol-1,而未包覆材料的活化能为36.24 kJ?mol-1,包覆有效降低了材料Li+扩散所需克服的能垒,提高了材料的电化学性能。     

Dry Sliding Wear Behaviour of Al2O3-Cr2O3 Coatings with Different Contents of Cr2O3EI北大核心CSCD

Cr₂O₃对 Al₂O₃-Cr₂O₃复合涂层与高硬度陶瓷接触时的摩擦磨损行为及磨损机制的影响尚未揭示。采用大气等离子喷涂的方法制备 Cr₂O₃含量不同的 Al₂O₃-Cr₂O₃复合涂层以研究 Cr₂O₃的影响机制。试验结果表明：Cr₂O₃明显减少了涂层的微观孔隙;复合涂层中 α-Al₂O₃ / γ-Al₂O₃的相对含量比明显高于 Al₂O₃ 层中的 37%;Al₂O₃-40%Cr₂O₃涂层的硬度与 Al₂O₃涂层相比提高了 48%,断裂韧性是 Al₂O₃涂层的 2 倍多;当载荷为 5 N、10 N 和 15 N 时,Al₂O₃-40%Cr₂O₃复合涂层的摩擦因数最低,磨损率依次降低 60%、85% 和 79%。但是当载荷为 20 N 时,Al₂O₃-20%Cr₂O₃复合涂层的摩擦因数最低,磨损率降低了 50%。微观脆性断裂是涂层的主要磨损机制。复合涂层耐滑动磨损性能与 Cr₂O₃含量及磨损条件是密切相关的。微观结构、硬度、断裂韧性、导热系数等是影响 Al₂O₃-Cr₂O₃ 复合涂层耐磨损性能的重要因素。研究结果可为高耐磨性 Al₂O₃基涂层的设计和应用提供指导。     

Pd/ZrO2-Al2O3催化剂中载体制备对CH4转化活性的影响

为推动ZrO2-Al2O3在天然气汽车尾气净化催化剂中的实际应用,并阐明其制备条件对负载催化剂转化活性的影响机制,文章以ZrO2-Al2O3复合氧化物为载体,采用等体积浸渍法制备了Pd/ZrO2-Al2O3催化剂,并在连续流动固定床反应器上研究了ZrO2-Al2O3复合氧化物的制备对催化剂低温CH4氧化活性的影响。结果表明：制备方法中,相比于浸渍法和胶溶法,沉淀法更能提高催化剂活性;锆源、铝源优选中,以Zr(NO3)4为锆源、拟薄水铝石为铝源时能获得较高的催化活性;组分配比中,以w (ZrO2): w (Al2O3)=10:90的催化活性最高。XRD、低温N2吸附、CO脉冲吸附的结构表征表明,ZrO2-Al2O3复合氧化物的大的比表面积、孔容、孔径是促进贵金属Pd分散,提升催化剂低温CH4转化活性的关键因素。     

La2O3掺杂氧化铝气凝胶的制备与耐温性能研究

以仲丁醇铝为前驱体,采用溶胶-凝胶法结合丙酮-苯胺原位生成水技术,通过乙醇超临界干燥,制备出不同含量(1.5 mol%~12 mol%)La₂O₃掺杂的氧化铝气凝胶。采用电子扫描电镜(SEM)、透射电子显微镜(TEM)、X线衍射仪(XRD)、N₂吸附分析仪等仪器表征了La₂O₃掺杂对氧化铝气凝胶的微结构和耐温性能的影响。结果表明：La₂O₃的引入使氧化铝气凝胶的形貌由球状颗粒向大的片状结构转变。适量的La₂O₃掺杂能提高氧化铝气凝胶的比表面积,9 mol% La₂O₃掺杂的氧化铝气凝胶比表面积最大。通过La₂O₃掺杂,能够抑制氧化铝晶粒在高温下的生长和α-Al₂O₃的相变,提高氧化铝气凝胶的耐温性能。1200℃热处理后,La₂O₃掺杂的氧化铝气凝胶仍维持在θ-Al₂O₃,比表面积为86.5 m₂/g,高于未掺杂的氧化铝气凝胶(46 m₂/g)。     

原位氧化工艺制备Ag-92SnO2In2O3电接触材料研究

以Ag-65SnIn-8熔炼雾化粉体为原料,采用原位氧化工艺制备了Ag-60SnO₂In₂O₃中间体粉体,与雾化纯银粉配比成Ag-92SnO₂In₂O₃材料,通过混粉-等静压-烧结-热压-挤压技术制备Ag-92SnO₂In₂O₃带材,再通过固相复合工艺制备所需要的Ag-92SnO₂In₂O₃/Cu/Fe电接点材料。相对比常规氧化工艺制备的Ag-60SnO₂In₂O₃中间体粉体制备的Ag-92SnO₂In₂O₃/Cu/Fe电接点材料,原位氧化工艺制备的Ag-92SnO₂In₂O₃/Cu/Fe电接点材料电阻率可达2.1μΩ.cm以下,硬度可达85~110HV;产品应用于380V,65A,功率因数0.7的电动机负载电路的热保护器中,电器寿命满足5000次分断要求,替代AgCdO/Cu/Fe电接点材料,实现环保,无镉化切换。     

La2O3对MGH956合金TIG焊焊缝组织和性能的影响

为了研究La₂O₃对焊缝组织和性能的影响,分别以未填加、填加2%和4%La₂O₃的填充材料对MGH956合金进行TIG焊接,应用光学显微镜、扫描电镜和透射电镜对焊缝的微观组织和拉伸断口进行观察,同时测试焊缝的抗拉强度.结果表明,适当提高La₂O₃含量,可以使焊缝晶粒得到细化,填加2%La₂O₃的焊缝晶粒最细小均匀,焊缝中的颗粒相增多且分布均匀,强化机制是由细晶强化和Orowan强化共同作用,但当La₂O₃加入量达到4%时,发现颗粒相有团聚现象,强化主要由位错塞积引起.填加2%La₂O₃的焊缝抗拉强度最大,为628 MPa,拉伸断口为韧-脆混合断裂.     

Preparation and properties of sintered molybdenum doped with La2O3/MoSi2

Sintered Mo with the addition of La₂O₃/MoSi₂ was prepared via the process of solid–solid doping + powder metallurgy. X-ray diffraction experiment, hardness test, three-point bending test and high-temperature tensile test were carried out to characterize the samples. The XRD pattern of a typical sample shows that the sintered Mo was mainly composed of Mo, La₂O₃ and Mo₅Si₃. Mo₅Si₃ was probably formed through the reaction between MoSi₂ and the Mo matrix. Densities and fracture toughnesses of both doped Mo and pure Mo were measured and contrasted. Sintered Mo with the addition of 0.2 wt% La₂O₃/MoSi₂ has the highest toughness, while more addition of La₂O₃/MoSi₂ has smaller effect on improving toughness or even embrittles Mo. The results of three-point bending test and high-temperature tensile test show that the bending strength and high-temperature tensile strength of doped Mo are both higher than those of pure Mo. The formation of Mo₅Si₃ improves the high-temperature strength. The La₂O₃/Mo₅Si₃ dispersed in the Mo matrix refined the grains, and thus strengthened the Mo matrix by dispersion strengthening and grain refinement.     

纳米级和微米级稀土氧化物掺杂W-La2O3-Y2O3-ZrO2 阴极尖端的组织和性能

使用粉末冶金法将纳米级(70–80 nm)和微米级(500–600 nm)稀土氧化物(La₂O₃,Y₂O₃)与钨粉混合,随后通过冷等静压、中频感应烧结、旋锻、拉拔等一系列工艺制备了W-1.5La₂O₃-0.1Y₂O₃-0.1ZrO₂(质量分数,%)材料。对含有纳米和微米尺寸稀土氧化物的阴极样品使用相同的焊接电流,分别进行了0.5、1、2 h的氩弧焊。结果表明,具有纳米级稀土氧化物的样品在焊接过程中表现出更高的工作稳定性,烧损同比降低了近85.4%。此外,随着工作时间的延长,阴极尖端不同区域的稀土氧化物聚集度显著增加。结合COMSOL Multiphysics温度模拟发现,第二相的扩散活化能降低了近34%。这是因为更为细小的第二相有效地控制了钨基体组织的演变,保留了大量晶界作为通道,促进了活性物质在电子发射过程中的扩散。     

Preparation, microstructure and properties of molybdenum alloys reinforced by in-situ Al2O3 particles

The conventional molybdenum alloys, lacking of hard particles enhancing wear property, have relative poor wear resistance though they are widely used in wear parts. To resolve the above question, Mo alloys reinforced by in-situ Al₂O₃ particles are developed using powder metallurgy method. The in-situ α-Al₂O₃ particles in molybdenum matrix are obtained by the decomposition of aluminum nitrate after liquid-solid incorporation of MoO₂ and Al(NO₃)₃ aqueous solution. The α-Al₂O₃ particles well bonded with molybdenum distribute evenly in matrix of Mo alloys, which refine grains of alloys and increase hardness of alloys. The absolute density of alloy increases firstly and then decreases with the increase of Al₂O₃ content, while the relative density rises continuously. The friction coefficient of alloy, fluctuating around 0.5, is slightly influenced by Al₂O₃. However, the wear resistance of alloy obviously affected by the Al₂O₃ particles rises remarkably with the increasing of Al₂O₃ content. The Al₂O₃ particles can efficiently resist micro-cutting to protect molybdenum matrix, and therefore enhances the wear resistance of Mo alloy.     

Thermal conductivity and thermal cycle life of La2O3 and HfO2 doped ZrO2-Y2O3 coatings produced by EB-PVD

The effects of La₂O₃ and HfO₂ addition on thermal conductivity and thermal cycle life of EB-PVD YSZ coatings were investigated. La₂O₃ and HfO₂ were selected as additives, because they significantly suppress the sintering of YSZ. The developed coating showed low thermal conductivity as well as high resistance to sintering. Burner rig tests confirmed that the developed coating have a superior thermal insulating effect and have a longer life than that of a coating with conventional composition.     

BN/Al2O3 复合粉末及其聚合物基复合材料的制备与导热性能

采用固-液相共混法制备了多种BN/Al₂O₃复合粉末,通过冻融法和表面修饰法对BN进行了改性处理,改变表面修饰剂类型和摩尔比得到了前驱体和烧结态BN/Al₂O₃复合粉末,并利用机械混合法制备了聚合物基BN/Al₂O₃复合材料,并测试分析了其导热性能。结果表明,经冻融处理的BN分散性和界面相容性明显优于未经冻融处理的BN。多巴胺对BN的改性效果优于聚乙二醇。采用多巴胺作为表面修饰剂且BN与Al(NO₃)₃的摩尔比为1:1时,能够得到纳米Al₂O₃均匀包覆的微米BN粉末,即BN/Al₂O₃微纳复合粉末,其聚合物基复合材料的导热系数可达0.62 W·m^-1·K^-1,是纯聚合物导热系数的3倍,是采用纯微米BN粉末制备的聚合物基复合材料导热系数的1.5倍。在BN表面附着的Al₂O₃可以形成层状热传导通道,能够有效提高聚合物基BN/Al₂O₃复合材料的热导率。     

Mechanical properties of La2O3 doped diamond-like carbon films

Twelve La₂O₃ doped diamond-like carbon (DLC) nanofilms were deposited using unbalanced dual-magnetron sputtering. AFM, XRD, Raman spectroscopy, AES, XPS, TEM, contact surface profiler and nanoindenter were employed to investigate the structure and tribological properties of deposited films. The results show that the La₂O₃ doped DLC films are amorphous. La₂O₃ doping obviously decreases internal stress, and effectively increases the elastic modulus. This results from the dissolving and dissolution of La₂O₃ within the amorphous DLC matrix. Furthermore, the friction coefficient of the doped DLC films decreases, and adhesion strength increases. These are attributed to the lubrication function of La₂O₃ and the formation of transition layer at interface, respectively.     

Y2O3对原位自生TiC增强Ni基涂层组织和性能影响

采用氩弧熔覆的方法,以Ni60A自熔性合金粉末为粘结相,添加Ti粉、C粉和不同含量的稀土氧化物Y₂O₃,在16Mn钢基体上制备出TiC陶瓷颗粒增强金属基熔覆涂层. 运用XRD, SEM等手段对复合涂层的显微组织进行表征和分析,并对熔覆涂层的硬度及耐磨性进行了测试. 结果表明,适量添加Y₂O₃可以使涂层组织中枝晶的方向性减弱、同时细化涂层组织,使涂层组织更加均匀,涂层的硬度和耐磨性有显著提高. 添加2% Y₂O₃熔覆涂层的组织为最细,涂层具有较高的显微硬度和良好的耐磨性能.     

Microstructure and characterization of La2O3 and CeO2 doped diamond-like carbon nanofilms

Seven kinds of hydrogen-free La₂O₃ and CeO₂ doped DLC films with thickness of 220-280 nm were deposited on Si (100) substrates by unbalanced magnetron sputtering. Nanoparticles with diameter of 20-30 nm are formed on the surface of films. The surface roughness Ra of films is in the range of 1.5-2.0 nm. C, La, Ce and O elements distribute uniformly along the depth direction, and C, La, and Ce elements diffuse into the Si substrate at the interface. X-ray photoelectron spectroscopy confirms that the La₂O₃ and CeO₂ form within the DLC amorphous films, and Raman spectra indicate the obvious amorphous characteristics of DLC films. High-resolution transmission electron microscopy shows the nanocrystallines structure with diameter of 2-3 nm of 16% La₂O₃ and 10% CeO₂ doped DLC films, and Fourier transformation spectroscopy also exhibits the obvious crystalline characteristics. In this work, the microstructure of two kinds of rare earth oxides doped DLC composite films is measured and analyzed.     

In-situ TiB2 and Al2O3 formation by DC plasma spraying

In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al-12Si, B₂O₃ and TiO₂ powder was deposited onto an aluminum substrate using atmospheric plasma spraying (APS). It has been observed that, during the coating process, TiB₂ and Al₂O₃ are in-situ formed through the reaction between starting powders and finely dispersed in hypereutectic Al-Si matrix alloy. Also, obtained results demonstrate that in-situ reaction intensity strongly depends on spray conditions.