掺杂不同质量分数Y_2O_3、MgO对Al_2O_3陶瓷显微结构及介电性能的影响

利用放电等离子烧结技术制备了不同质量分数Y_2O_3单独掺杂及不同质量分数Y_2O_3、MgO共同掺杂的Al_2O_3陶瓷,研究了烧结助剂掺杂质量分数对Al_2O_3陶瓷显微结构及介电性能的影响。结果表明,孔隙率是影响Al_2O_3陶瓷介电性能的主要因素;单独掺杂质量分数为0.25% Y_2O_3时,Al_2O_3陶瓷得到最优的介电性能,介电常数(ε_r)为9.5±0.2,介质损耗(tanδ)稳定在10~(-3)数量级以内;同时掺杂Y_2O_3和MgO能进一步改善其介电性能,当两者质量分数均为0.25%时,得到最优值,介电常数(ε_r)为10.3±0.2,介质损耗(tanδ)稳定在8×10~(-4)以下。     

Effect of Rare Earths on Mechanical Properties and Microstructures of Si3N4-based Ceramics

Si3N4-hased ceramics exhibit excellentproperties such as high strength, high corro..sion resistance, high fire resisting property andhigh thermal shock resistance. However, up tonow, the application of St3N4-based ceramicsis still limited by their poor ductility, lowtoughness and stability. Adding fiber or whisher into ceramic matrix is a useful tougheningmethod, but fiber and whisker are costly and itis difficult to homogenize them in ceramic matrix. Furthermore, ceramic powders can not fill…     

添加ZrO2对Si3N4复合陶瓷材料力学性能的影响

通过无压烧结制备了ZrO2-Si3N4复合陶瓷材料,并以排水法、SEM和DDL100型万能拉伸机进行表征。研究了ZrO2含量对Si3N4陶瓷的致密度、显微结构和力学性能的影响。结果表明,随着ZrO2含量的增加,Si3N4陶瓷致密度增加;抗弯强度和断裂韧性先增大后减小,当ZrO2含量达到10%时,Si3N4的抗弯强度和断裂韧性同时达到最大值,分别为362MPa和7.0MPa.m1/2。ZrO2增韧Si3N4陶瓷的机制为应力诱导相变。     

Effect of Y2O3 and Dy2O3 on Microstructure and Mechanical Behaviors of Aluminum Nitride Ceramics

The effects of two types of additives, Y2O3 and Dy2O3, on the sintering and mechanical behaviors of AlN ceramics were investigated. The experimental results show that the sintering temperature can be decreased and the mechanical behavior can be improved by adding rare earth in AlN ceramics. The strength of AlN ceramics with Y2O3 and Dy2O3 are 326 and 320 MPa, respectively, which are 97.6% and 93.9% higher than the un-doped AlN ceramics. The fracture behavior on the fracture surfaces of rare earth oxide AlN ceramics was found to be a mixed mode of transgranular fracture and intergranular fracture. As a result, it is concluded that the improvement of bending strength of AlN ceramics with Y2O3 and Dy2O3 addition are mainly achieved by strengthening the grain boundary.     

稀土Y、Ce对钼合金力学性能的影响

实验以MoO2和Ce(NO3)3.6H2O、Y(NO3)3.6H2O为原料,通过固-液掺杂、还原、烧结、拉伸制备钼合金丝。通过XRD、扫描电镜以及力学性能试验,研究了稀土元素Y、Ce在粉末及钼合金中的存在形式以及对钼合金力学性能的影响。结果表明:Y、Ce元素分别以CeO2和Y2O3形式存在于钼粉中,Y对钼粉颗粒长大的抑制效果高于Ce;钼合金中,稀土Y和Ce作用不同,Y抑制晶粒的长大,延迟烧结;而Ce促进烧结,使烧结完全致密化;钼合金丝中,CeO2质点以纤维状存在,有利于提高钼丝的塑性,而Y2O3质点以球状颗粒存在,钼合金丝的室温和高温抗拉强度较高。Y、Ce的共同作用,MYCe合金丝综合力学性能好。     

稀土氧化物复合ZrO2陶瓷的制备及应用研究进展

稀土氧化物可作为稳定剂、烧结助剂、掺杂改性剂加入到ZrO₂陶瓷材料中,能极大地提高和改善陶瓷材料的强度、韧性,降低其烧结温度,减少生产成本.文中简要综述了稀土氧化物ZrO₂陶瓷材料的制备及应用研究状况,包括Y₂O₃复合ZrO₂陶瓷粉体、富铈稀土氧化物复合ZrO₂陶瓷粉末、Nd₂O₃复合ZrO₂陶瓷材料、Pr₂O₃\Pr₆O₁₁复合ZrO₂陶瓷、La₂O₃复合ZrO₂陶瓷、Yb₂O₃复合ZrO₂陶瓷、Sm₂O₃复合ZrO₂陶瓷材料及氧化锆中掺杂多种稀土氧化物陶瓷粉体的制备和应用,分析讨论了一些需要解决的问题,并展望了稀土复合ZrO₂陶瓷制备技术及未来研究发展趋势.      

Effect of Y2O3 and Sm2O3 on Sintering and Mechanical Behaviors of Alumina Ceramics

The effects of Y2O3 and Sm2O3 doping on the sintering temperature, microstructure and mechanical behaviors of Al2O3 ceramics were investigated. The experimental results show that the sintering temperature can be decreased and the mechanical behavior can be improved by adding rare earth in alumina ceramics. The relative density of rare-earthdoped alumina ceramics reaches 98.8% after sintering at 1600 ℃ for 2 h, and its bending strength and fracture toughness reach 439 MPa and 5.28 MPa·m1/2,respectively.Introduction of Y2O3 and Sm2O3 in Al2O3 can restrain the growth of grains, refine the size of grains, and thus form a fine-grained structure. The fracture characteristic is the mixed modes of intergranular and transgranular fracture.     

Dielectric Properties of CeO2 -Doped Ba( Zr, Ti)O3 Ceramics

The influence of additive amount of CeO2 on the properties of Ba(Ti, Zr)O3 (BTZ) capacitor ceramics prepared using conventional solid-state reaction method was investigated. The dielectric constant(ε) increases to a maximum when w( CeO2 ) is about 1.0% and then decreases again at higher doping concentration of CeO2. The dielectric constant gets a maximum while w ( CeO2 ) is about 1. 0%, and the dielectric loss is minimum while w ( CeO2 ) is0.5 %. CeO2 can decrease the curie temperature, widen the εr-T peak and decrease the absolute value of dielectric constant temperature coefficient. The influence mechanism of CeO2 additive on the properties of the BTZ ceramics was discussed. The results show that CeO2 additive influences the properties of BTZ ceramics by means of forming defect solid solution , shifting curie temperature peak effect, segregating in crystal boundary , and impeding grain growth.     

Preparation of transparent Y2O3 ceramic by slip casting and vacuum sintering

In the present work transparent Y2O3 ceramics were made by slip casting and vacuum sintering of nanopowders with sodium poly-acrylic acid(PAA-Na) as dispersant.The rheological properties of Y2O3 nanopowder slurry were investigated using different amounts of dis-persant and solid contents.The microstructures and transmittance of the sintered ceramics were also studied by means of scanning electron microscopy(SEM) and ultra-violet visible spectrometry.The results showed that rheological behaviors of the Y2O3 nanopowder slurry were effectively promoted by sodium polyacrylic acid.Highly dispersive and stable slurries were obtained as the dispersant was added over 1.0 dwb% under the fixed conditions of pH 11 and 45 wt.% solid content.All the slip cast green bodies were sintered into highly dense ceramics after sintering at 1700 oC for 5 h in vacuum,wherein the sample added with 1.1% sodium polyacrylic acid exhibited the highest relative den-sity of 99.36% and transmission of 30% at 800 nm wavelength.     

Effects of rare earth oxides on dielectric properties of Y2Ti2O7 series ceramics

A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on the microstructure and dielectric properties of Y2Ti2O7 ceramics were investigated. The experimental results showed that the rare earth ions were considered to dissolve in Y-sites of the pyrochlore structure, different rare earth oxides and concentration had different influences on Y2Ti2O7 cerami...     

Effects of Doping CeO2, Er2O3 on Properties of TiO2-SiO2 Ceramics for Catalyst Supporter of deNOx

Effects of doping CeO2 and Er2O3 on the mechanical strength, thermal expansion coefficient, sintering temperature of TiO2-SiO2 ceramics were investigated. The experimental results and the microscopic analysis of SEM, XRD, TG-DSC, FT-IR and TEM show that adding CeO2 and Er2O3 into TiO2-SiO2 ceramics can prohibit the growth of its crystal grains, make their size uniform and form them into a dense structure, which finally enhance its mechanical behaviors, and the lower thermal expansion coefficient that leads to an excellent property of thermal shock resistance. After the reforming TiO2-SiO2 ceramics doped by CeO2 was sintered at 1380 ℃, the bending strength reached to 83 MPa, and the thermal expansion coefficient was 9.8×10-6/℃ within the temperature range of 25～800 ℃, which provides a promising basis of making equipped honeycomb catalyst of deNOx.     

混合稀土增强Al2O3基泡沫陶瓷制备研究

以氧化铝、高岭土等为主料,富CeO2混合稀土为改性剂,制备具有较好流变性的水基陶瓷浆料,采用有机泡沫浸渍法制备挂浆均匀的预制体,经干燥烧结得到孔隙均匀、强度高的Al2O3基泡沫陶瓷（CF）。文章研究了含稀土陶瓷浆料的粘度变化规律,确定了最佳烧结制度,并研究了稀土加入量对CF力学性能的影响。实验发现,混合稀土加入量达到3％时,可使CF常温抗压强度提高约70％。     

Preparation and Performance of Al2 TiO5 -TiO2 -SiO2 Honeycomb Ceramics by Doping Rare Earth

A preferable honeycomb ceramics of Al2TiO5-TiO2-SiO2 doped by CeO2 and Er2O3 with high performance was prepared by means of extrusion molding and the effects of CeO2 and Er2O3 on the mechanical strength, thermal stability, and sintering temperature of ATS ceramics were mainly investigated. The experimental results and the microscopic analysis by scanning electron microscope, X-ray powder diffxaction, and TG-DSC showed that adding CeO2 and Er2O3 into ATS could prohibit the growth of their crystal grains and make their size uniform, which finally decrease its sintering temperature, and also enhance its mechanical performance as well as thermal stability. After the reforming, ATS doped by 0.5% CeO2 ＋0.5% Er2O3 was sintered at 1250 ℃, its bending strength reached to 177A MPa and thermal expansion coefficient was 3.8 ~ 10^-6/℃ at 25 - 1000℃, which provided a promising basis of making monolithic honeycomb catalyst of deNOx.     

Bonding of Silicon Nitride Ceramic Composite with RE_2O_3Al_2O_3SiO_2 Glass Solders

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CeO2-Co3O4 Catalysts for CO Oxidation

CeO2-Co3O4 catalysts for low-temperature CO oxidation were prepared by a co-precipitation method. In combination with the characterization methods of N2 adsorption/desorption, XRD, temperature-programmed reduction （TPR）, and FT-IR, the influence of the cerium content on the catalytic performance of CeO2-Co3O4 was investigated. The results indicate that the prepared CeO2-Co3O4 catalysts exhibit a better activity than that of pure CeO2 or pure Co3O4. The catalyst with the Ce/Co atomic ratio 1 ： 16 exhibits the best activity, which converts 77% of CO at room temperature and completely oxidizes CO at 45 ℃.     

正交法研究添加Y2O3对Ti-6Al-4V合金组织与性能的影响

采用正交实验方法,应用放电等离子烧结(SPS)技术制备出Y2O3含量分别为0.2%、0.6%、0.8%的Ti-6Al-4V合金,探究烧结温度、烧结压力、Y2O3含量和保压时间对Ti-6Al-4V合金显微组织、烧结密度和力学性能的影响,优化烧结工艺。结果表明,烧结温度对烧结密度的影响最大,接下来依次为烧结压力、Y2O3含量、保压时间;烧结温度对力学性能的影响最大,接下来依次为Y2O3含量、烧结压力、保压时间。当烧结温度1200℃、烧结压力50 MPa、保压时间5 min、Y2O3含量0.6%,烧结样的密度和压缩强度高,分别达到4.4138 g/cm3、1881.4 MPa,相比未添加Y2O3的Ti-6Al-4V合金,其压缩强度提高15.7%。     

Effect of the Fourth Element on Bonding of Silicon Nitride Ceramics with Y_2O_3-Al_2O_3-SiO_2 Glass Solders

Ｂｏｎｄｉｎｇｏｆｓｉｌｉｃｏｎｎｉｔｒｉｄｅｃｅｒａｍｉｃｓｗｉｔｈｏｘｉｄｅｇｌａｓｓｓｏｌｄｅｒｈａｓｂｅｅｎａｃｈｉｅｖｅｄｖｅｒｙｇｒｅａｔｓｕｃｃｅｓｓ[1～ 11] .Ｏｗｉｎｇｔｏｔｈｅｌｏｗｅｒｓｏｆｔｅｎｉｎｇｔｅｍｐｅｒａｔｕｒｅｏｆｒｅｓｉｄｕａｌｇｌａｓｓｉｎｊｏｉｎｔ ,ｔｈｅｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｅｎｇｔｈｏｆｊｏｉｎｔｈａｓｂｅｅｎｄｅｔｅｒｉｏ ｒａｔｅｄ .Ｉｎｏｒｄｅｒｔｏｉｍｐｒｏｖｅｔｈｅｊｏｉｎｔｓｔｒｅｎｇｔｈａｔｅｌｅｖａｔｅｄｔｅｍｐｅｒａｔｕ…     

稀土氧化物粒子对钼合金粉末冶金过程及力学性能的影响

试验研究了掺杂La2O3、Y2O3、CeO2稀土氧化物颗粒对钼合金的粉末物性、烧结进程、制品的烧结致密度及压力加工丝材的室温力学性能的影响规律。试验结果表明,掺杂稀土氧化物粒子细化了钼粉的粒度,降低了松装密度和粒度分布范围,同时导致粉末团聚现象增多;稀土氧化物粒子延迟了钼合金的烧结进程,降低了烧结制品的致密度,同时细化了烧结体晶粒尺寸。稀土氧化物粒子以弥散强化和细晶强化的形式,提高了钼合金丝的室温强度。CeO2显著提高了钼合金丝的室温韧性,La2O3、Y2O3则降低了钼合金丝的室温韧性。     

Physicochemical Processes of Fabricating Ceramic Materials Based on Nanopowders of Zirconium,Yttrium, Cerium,and Aluminum Oxides

When studying nanoceramics, it is necessary to constantly keep in mind the closest interrelation of their fabrication method, structure, and properties. Nanoceramic materials are used in various branches of technology as structural and functional materials. Nanoceramics are also widely used in medicine. They are harmless, stable, and have great affinity to living organisms. ZrO2-based nanoceramics have a lower elastic modulus than other oxide materials. The specificity of their application lies in their high rupture strength, thermal shock resistance, and chemical stability at high temperatures. However, it is necessary to solve the problem of increasing the fracture toughness of ZrO2-based ceramic materials. The complex alloying of ZrO2 with yttrium and cerium oxides and the use of the Al2O3 additive leads to an increase in the fracture toughness and lowering of the negative effect of materials in the biological medium. In this work, the physicochemical properties of ceramic powders and materials of the ZrO2–2Y2O3–4CeO2–Al2O3 system synthesized by the chemical deposition of inorganic precursors when applying the sol-gel technology are considered based on scientific data and experimental studies. Alloying pure zirconium oxide by stabilizing Y2O3 and CeO2 oxides and thermal hardening of Al2O3 ensure the conservation of the tetragonal structure at room temperature, which makes it possible to retard and control the crack resistance of the material under the load. Investigations into the influence of the sintering temperature and aluminum oxide content on the microstructure and grain size, as well as physicomechanical properties of ceramic materials of compositions ZrO2–2Y2O3–4CeO2 + 1 wt % Al2O3 and ZrO2–2Y2O3–4CeO2 + 3 wt % Al2O3, are carried out.     

Effects of Rare-Earth La2O3 Addition on Microstructures and Electrical Properties of SrTiO3 Varistor-Capacitor Dual Functional Ceramics

Generally, metal oxide varistors used for the pro tection of electrical circuits are based on ZnO andTiO2[1,2]. ZnO varistor, which is widely used due toits high non linearity coefficient, is composed of ZnOceramics with minor oxide additive…