掺杂La2O3对金属陶瓷惰性阳极性能的影响

采用Fe-Ni合金为基体,增强相用AlO,掺杂少量的LaO制备一种金属陶瓷惰性阳极试样,分析了烧结温度对试样2323结构的影响,研究了掺杂LaO对试样的体积密度、气孔率、导电率、高温氧化性能,腐蚀速率的影响。23     

La2O3对TZM合金烧结坯组织与性能的影响

采用粉末冶金法制备TZM-La合金板坯,以Mo粉、TiH2、ZrH2、稀土氧化物La2O3和石墨粉为原料,钢模压制和1 900℃高温烧结。用扫描电镜和能谱分析研究第二相粒子对TZM-La板坯组织性能的影响。结果表明,添加La2O3后,板坯晶粒明显细化,致密度提高,韧性得到显著改善。     

Al2O3La2O3Y2O3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al₂O₃La₂O₃Y₂O₃/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al₂O₃/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y₂O₃、La₂O₃稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al₂O₃La₂O₃Y₂O₃/Cu材料的抗熔焊性和抗烧损性优于Al₂O₃/Cu材料的性能.在直流阻性负载条件下Al₂O₃La₂O₃Y₂O₃/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.      

固体酸La2O3-Ga2O3/硅胶的研制及其催化合成丙酸异丁酯

采用自制固体酸La2O3-Ga2O3/硅胶为催化剂催化丙酸与异丁醇进行酯化反应合成了丙酸异丁酯,并采用IR分析对催化剂进行了表征。催化剂的制备条件为La2O3∶Ga2O3∶硅胶=5∶20∶75(质量比),500℃焙烧2 h。考察了催化剂用量、醇酸物质的量比、反应时间、带水剂种类和催化剂的重复使用性等因素对酯化率的影响。结果表明,适宜的反应条件为0.20 mol丙酸,催化剂用量1.00 g、醇酸物质的量比1.8,反应时间90 min,酯化率可达98.2%。     

镧改性固体催化剂SnO2-WO3/La2O3的制备及其催化性能

500℃焙烧3 h条件下制备了摩尔比nSn∶nW=2∶1,含3.0%(质量分数,下同)La2O3的镧改性固体催化剂SnO2-WO3/La2O3,采用IR分析对其进行了表征。通过改变催化剂用量、30%H2O2用量、反应时间及催化剂重复使用性等因素,系统考察了该稀土改性双金属氧化物催化氧化环己酮合成己二酸的催化性能。实验结果表明,己二酸的适宜合成条件为:100 mmol环己酮,1.25 g催化剂SnO2-WO3/La2O3,50 mL 30%H2O2,回流反应7 h,目的产物己二酸收率达77.7%。SnO2-WO3/La2O3连续使用6次己二酸收率仍可接近40%。     

氧化铈刻蚀金刚石表面形貌表征

为研究氧化铈刻蚀对于金刚石表面形貌的影响,将金刚石单晶与氧化铈粉末以质量比1:5的比例混合,并在N₂气氛下对金刚石进行刻蚀处理。通过对刻蚀后金刚石的表面形貌、表面刻蚀深度、物相组成的表征与分析探究氧化铈粉末刻蚀对于金刚石表面形貌的影响。利用铜基结合剂金刚石试样的抗弯强度评估刻蚀对于金刚石与结合剂之间把持力的影响。结果表明:氧化铈能成功对金刚石单晶表面进行选择性刻蚀。随着温度的升高,金刚石各个晶面的刻蚀深度加深;在相同条件下,氧化铈对金刚石（100）面的刻蚀程度大于金刚石（111）面。当刻蚀温度为900 ℃时,金刚石（111）面刻蚀深度为753.23 nm,（100）面刻蚀深度为1.60 μm。在N₂气氛下,900 ℃氧化铈刻蚀后的金刚石单颗粒抗压强度低于未加氧化铈刻蚀剂刻蚀的金刚石抗压强度,但是高于在空气气氛下未加氧化铈刻蚀剂刻蚀的金刚石以及在空气中直接氧化铈刻蚀的金刚石抗压强度。与未处理金刚石相比,氧化铈刻蚀后的铜基结合剂金刚石试样的抗弯强度有较大提升。     

温度对La2O3-SiO2-CaO-Al2O3-MgO系高温熔体结构的影响

稀土玻璃陶瓷铸造过程中的连续降温会使熔体的微观结构发生变化。通过对不同温度(1 550～1 100℃)的淬冷样品进行Raman、XRD和SEM-EDS分析,研究了温度对La₂O₃-SiO₂-CaO-Al₂O₃-MgO系高温熔体结构的影响。研究结果表明：温度较高时淬冷样品呈非晶态,温度较低时淬冷样品呈晶态。对非晶态淬冷样品的Raman谱线进行解谱后发现,随着温度的降低,各硅氧/铝氧四面体基本结构单元Raman峰位向高频方向偏移,且低频(200～800 cm^-1)结构单元峰位偏移幅度大,高频(800～1 200 cm^-1)结构单元峰位偏移幅度小;La₂O₃能够抑制各结构单元峰位向高频方向偏移。XRD和SEM-EDS结果表明：添加La₂O₃后La₂O₃-SiO₂-CaO-Al_2<...     

La2O3掺杂纳米W粉致密化行为与性能

采用溶液燃烧合成法制备了La₂O₃掺杂纳米钨（W）粉,分析了La₂O₃掺杂纳米W粉的致密化行为及La₂O₃对纳米W粉致密化行为的影响,研究了烧结后合金的显微组织形貌、导热性能及显微硬度。结果表明,La₂O₃会显著抑制纳米W粉的致密化速度,纯W粉在1350 ℃烧结后的相对密度可达到96.2%,而La₂O₃掺杂纳米W粉在1500 ℃烧结后的相对密度仅为95.0%。在1500 ℃烧结后的La₂O₃掺杂W合金的晶粒尺寸为0.57 μm,比纯W粉烧结合金的晶粒尺寸小一个数量级,因此其导热性能也较纯W粉烧结合金有所降低,但是显微硬度得到显著提升。     

保温时间对锰氧化物刻蚀金刚石单晶的影响

研究了在不同保温时间下MnO₂对金刚石单晶的表面刻蚀, 通过扫描电子显微镜和拉曼光谱对刻蚀后金刚石单晶不同晶面的表面形貌和刻蚀机理的进行了表征与分析, 并对腐蚀过程中金刚石表现出来的各向异性进行了探讨。结果表明: 当金刚石和MnO₂质量比为1:5时, 金刚石单晶的刻蚀程度随着保温时间的延长而增大; 在相同保温时间下, {111}晶面比{100}晶面刻蚀严重; 金刚石表面腐蚀后的形貌与对应晶面的碳原子排列有关, {100}面倾向于形成四边形的刻蚀坑, 而{111}面则会形成轮廓为三角形的腐蚀坑, 且金刚石单颗粒的抗压强度随刻蚀时间的延长而下降; 刻蚀机理为MnO₂与金刚石表面C原子发生反应, 导致金刚石表面发生刻蚀。     

掺杂ZrO2对Laβ-Al2O3固体电解质的性能影响

研究了掺杂不同量的ZrO₂对Laβ-Al₂O₃固体电解质的电导和抗热震性能的影响。结果表明ZrO₂的加入导致电导率下降,抗热震性能提高。为此,以加入质量分数10%ZrO₂为宜。     

La2O3对ZrO2-Y2O3-Ta2O5陶瓷材料结构及性能的影响

采用固相合成法在氧化钇部分稳定氧化锆(YSZ)陶瓷材料的基础上引入氧化物Ta2O5以及稀土氧化物La2O3取代部分Y2O3,获得一种新型的La2O3-ZrO2-Y2O3-Ta2O5陶瓷材料。分别利用X射线衍射仪、扫描电子显微镜和STA-449C热膨胀仪对材料的物相组成、微观结构及热膨胀性能进行表征。结果表明,陶瓷材料的主晶相仍为四方相,晶粒尺寸减小,在RT～1200℃温度范围内热膨胀系数有所减小。     

Effect of La2O3 on electrical friction and wear properties of Cu-graphite composites

Sliding friction and wear experiments using Cu-La2O3-graphite composites against Cu-5 wt.%Ag alloy ring were conducted at a constant sliding speed of 10 m/s, a current density of 10 A/cm2 and a load of 2.5 N/cm2. These composites with different La2O3 and graphite contents were fabricated by hot-pressing. Physical and mechanical properties of the composites were examined. Morphologies of the worn surface of composites were observed using optical microscopy. X-ray photoelectron spectroscopy spectra were used to study compositions of the lubricating film. The results showed that with the increasing addition of La2O3, hardness, flexural strength and electrical resistivity increased, but the relative density dropped. The friction coefficient increased with the increasing addition of La2O3. Composite containing 3 vol.% of La2O3 and 37 vol.% of graphite showed the best wear resistance. The main wear mechanisms of composites were abrasive wear, oxidative wear and adhesive wear.     

Y2O3和La2O3对金属陶瓷内衬显微硬度和耐蚀性的影响

研究了钇、镧等添加物对金属陶瓷内衬显微硬度和耐蚀性的影响.结果表明加入Y2O3、La2O3和SiO2可使陶瓷层的孔隙度降低,一定程度上使耐蚀性增加.La2O3对提高陶瓷层性能的效果比Y2O3要好.     

Preparation of La（OH）3 and La2O3 with Rod Morphology by Simple Hydration of La2O3

Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of the hexagonal phase of La（OH）3, indicating that the hydration process is very rapid. The as-prepared La（OH）3 is almost entirely with a needle- or rod-like shape with a width of 2 - 3 μm and a length of 5 - 8 μm. The mechanism of the formation of La（OH）3 with rod-like morphology was preliminarily presented. It is easier to expand the simple hydration process on a large scale than the hydrothermal process.     

La2O3-Mo阴极材料中La2O3稳定性研究

本文采用高温光电子能谱方法对La2O3-Mo阴极及碳化La2O3-Mo阴极材料表面La2O3的化学稳定性进行了研究。实验结果表明,La2O6并不具备文献报道的极好的化学稳定性。材料中的La2O3在高温、真空条件下,其部分晶格氧发生分离。La2O3可以被Mo2C还原成单质La。单质La的结合能高于La2O3的结合能。实验证实单质La3d5／2的结合能为835．96eV,并首次给出La3d3／2的结合能实验数值为852．23eV。     

Effect of La2O3 on Microstructure and Transmittance of Transparent Alumina Ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.     

La2O3对含B2O3无氟连铸保护渣物理性能的影响

针对含B2O3无氟保护渣抑制晶体析出的问题,研究了当保护渣碱度(CaO/SiO2)等于0.9,成分为wCaO27％～36.47％、wSiO230％ ～ 40.5％、wAl2O34％、wMgO5％、wNa2O0.8％、wLi2O％、wB2O34％时,wLa2O3从0增加到20％对无氟结晶器保护渣结晶性能及渣膜传热的影响.试验表明La2O3能够提高保护渣的渣膜厚度,提高其结晶率和结晶温度,降低熔渣的熔化温度,从而有效提高控制结晶器传热的能力.     

Fe2O3添加剂对锆酸钙陶瓷烧结性能的影响

以分析纯Ca(OH)₂和m-ZrO₂为原料, 按物质的量1:1进行配料, 添加不同质量分数Fe₂O₃粉末作为添加剂, 经充分混合后压制成?20 mm×20 mm圆柱试样, 再经1600℃保温3 h煅烧制备得到锆酸钙陶瓷试样(CaZrO₃)。利用显气孔体密测定仪、X射线衍射仪及扫描电子显微镜分析Fe₂O₃粉末添加剂对CaZrO₃陶瓷材料烧结性能、物相组成及微观结构的影响。结果表明:当没有添加Fe₂O₃粉末时, 试样烧结前后线变化率为12.72%, 体积密度为3.92g·cm-3, 显气孔率为14.9%, CaZrO₃晶粒尺寸为4.22μm; 当加入质量分数0.75%Fe₂O₃粉末时, 试样烧结前后线变化率为17.20%, 体积密度为4.68 g·cm-3, 显气孔率为6.8%, CaZrO₃晶粒尺寸为5.21μm。     

High Temperature Chemical Reaction of La2O3 in H3BO3 -C System

The high temperature chemical reaction process of La2O3 in H3BO3-C system was studied by means of XRD and TG-DTA.The results showed that dehydration reaction of H3BO3 occurred in the temperature range of 82～390 ℃;La2O3 and B2O3 reacted to form LaB3O6,LaBO3,and B4C in the temperature range of 836～1400℃;at 1450 ℃,B4C and LaBO3 further reacted to form LaB4,and partial LaB4 and B reacted to form LaB6;at 1500 ℃,LaB4 and B reacting into LaB6 was the main reaction,and the content of LaB6 increased with prolonging time.