ZrO2/Al2O3多孔陶瓷的制备与力学性能

采用凝胶-发泡法制备了ZrO2/Al2O3多孔陶瓷,研究了陶瓷浆料的流变性,固相含量对多孔陶瓷坯体显微结构与力学性能的影响,以及烧结助剂MgO含量与多孔陶瓷抗压强度及气孔率之间的关系.结果表明,在分散剂含量为0.4％(质量分数),球磨4 h,pH值为4的条件下,陶瓷浆料的黏度较低,有利于凝胶注模.固相含量增加,坯体气孔率下降.过高的固相含量使浆料流动困难,注模时引入空气导致坯体内形成较大的气孔甚至裂纹,使坯体抗压强度下降.由ZrO2引起的相变增韧及微裂纹增韧可有效改善多孔陶瓷的力学性能.随烧结助剂含量增加,多孔陶瓷气孔支撑体致密化程度增大,气孔率降低,抗压强度明显升高.多孔陶瓷的抗压强度最高达30 MPa.引入适量的ZrO2及烧结助剂,可制备气孔率适中、抗压强度高的多孔陶瓷.     

二氧化锆多孔纳米固体的制备与性质表征

利用溶剂热压方法,以ZrO2(5%Y2O3)纳米粉和几种不同的溶剂为原料,制备了一种新型的体块ZrO2多孔纳米固体,利用X射线衍射(XRD)、透射电子显微镜(TEM)、压汞仪和差热-热重(DTA-TGA)分析方法对样品进行了表征.进一步地,我们研究了溶剂的种类、温度和压力对ZrO2多孔纳米固体的孔容及孔径分布的影响,并对ZrO2多孔纳米固体的热稳定性进行了初步分析.测试结果表明制备的ZrO2多孔纳米固体的孔径分布范围很窄,孔容为0.1～0.2cc/g,比表面积为30～50m2/g,孔隙率为35%o～45%;另外,通过改变溶剂的种类、温度和压力可以在一定程度上调变多孔纳米固体的孔径、孔容及比表面积.     

Li2ZrO3包覆锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2的制备及其电化学性能

富锂锰基材料因其具有较高的充放电比容量而备受关注。针对其首次库仑效率低、循环和倍率性能差的问题,将具有三维Li^+通道的锂离子导体Li2ZrO3引入至富锂锰基正极材料Li[Li0.2Ni0.2Mn0.6]O2的表面对其进行包覆改性研究。通过XRD,TEM,SEM,EDS综合分析可知:Li2ZrO3成功包覆到样品表面。包覆层厚度为3 nm(包覆量1%,质量分数)时复合材料的电化学性能得到显著提升。0.1 C(1 C=200 mAh·g^-1)倍率下首次放电比容量可达271.5 mAh·g^-1,库仑效率为72.4%,降低了首次不可逆容量损失;0.5 C下循环100周次后放电比容量为191.5 mAh·g^-1,容量保持率为89.5%,5 C倍率放电比容量为75 mAh·g^-1,倍率性能提升。适当厚度的均匀Li2ZrO3包覆层可在样品表面形成核壳结构使样品更稳定,减少表面副反应,阻止生成较厚SEI膜,这得益于Li2ZrO3本身的高电导率、高电化学稳定性和较好的锂离子传导性。     

FeAl金属间化合物多孔材料的制备

以Fe、Al粉末为原料,用反应合成工艺制备FeAl金屑间化合物多孔材料,表征了孔结构.结果表明,在FeAl金属间化合物多孔材料的制备过程中烧结坯发生明显的体积膨胀;在1000℃以下,随着烧结温度的升高FeAl烧结坯的孔隙度和最大孔径增大;经1000℃烧结后FeAl多孔材料的孔隙度为35.3%,最大孔径为2.0 μm;造孔机理是Kirkendall效应造孔、反应造孔以及粉末颗粒间隙孔的演变.     

Preparation of tetragonal ZrO2-Gd2O3 powders

ZrO₂-Gd₂O₃ alloys containing 2,3,5 and 8 mol.% Gd₂O₃ have been prepared by mixed oxide (MO), hybrid sol-gel (SG), and co-precipitation (CP) routes. No tetragonal (t) phase is retained in the MO method, while 100% t phase is obtained in the calcined CP samples; the SG method leads to only partial stabilization of the t phase. Washing of the CP powders with propan-2-ol leads to unagglomerated powders with increased specific surface area (145 versus 89 m²g^–1) and sintered density (98% versus 79%). Cubic and t phase also appear on sintering the samples with >2 mol.% Gd₂O₃.     

Preparation of ZrO2 and ZrO2-Y2O3 coatings on silicon carbide fibers

The formation of ZrO₂ and ZrO₂-Y₂O₃ coatings from hydrous metal oxide sols on Nicalon NLM 202 silicon carbide fibers is investigated in detail. The results indicate that the microstructure of the oxide layer and the surface morphology of the coatings depend on the physicohemical properties of the sol. Kinetic studies of the oxidation of uncoated and coated fibers at different Y₂O₃ contents demonstrate that the oxidation rate of silicon carbide fibers decreases with increasing coating thickness. The effect of oxidation on the phase composition of Nicalon cloth samples coated with ZrO₂ and ZrO₂-Y₂O₃ is examined.     

Preparation and characterization of ZrO2 porous nanosolid and its composite fluorescent materials

ZrO₂ porous nanosolid has been successfully prepared by a novel hydrothermal hot-press (HHP) method, using ZrO₂ nanoparticles as the starting material. Furthermore, a kind of O, O-donating chelating regent, morin was assembled into the pores of ZrO₂ porous nanosolids, and a morin/ZrO₂ porous nanocomposite was obtained. Because of the interaction between morin molecules and the surface of ZrO₂ porous nanosolid, a blue-shift of the photoluminescence (PL) peak was observed in ZrO₂/morin nanocomposite by comparing with that of morin.     

多孔镍载体材料的制备

试验在常规粉末冶金方法基础上通过添加造孔剂的办法制备出高孔率(70%以上)、小孔径(最大冒泡孔径＜5 μ m)、高透过量,通孔率(通孔率可达97%以上)的多孔镍载体材料.主要进行了粉末粒度及形貌的分析选择研究,造孔剂的添加量与多孔镍载体性能关系的研究、烧结工艺对材料性能影响的研究.主要从孔率、最大冒泡孔径、透气系数、通孔率等方面着手,研究了造孔剂加入量及烧结工艺对该性能的影响,同时对不同条件下样品的性能进行了测试.     

Preparation and thermodynamic analysis of the porous ZrO2/(ZrO2 + Ni) functionally graded bolted joint

Ceramic–metal functionally graded materials (FGMs) have been extensively used in aerospace engineering where high strength and excellent heat insulation materials are desired. In this paper, the thermodynamic behavior of the Thermal Protection System (TPS) used bolted joints made up of porous ZrO₂/(ZrO₂ + Ni) FGMs is investigated by finite-element (FE) modeling. The bolted joint is subjected to reentry heating corresponding to the Access to Space Vehicle. Thermodynamic simulations are carried out to yield the transient response of the porous ZrO₂/(ZrO₂ + Ni) functionally graded bolted joint (FGBJ). The effects of the preload on the thermomechanical behavior and service reliability of the bolted joint are numerically analyzed in detail by ABAQUS codes. It is found that the preload relaxation of the bolted joint occurs at elevated temperature, and the preload has significant influence on service reliability of the bolted joint under transient thermomechanical circumstances. With the increase of the preload, stress concentration which occurs at the root of the first thread of the bolt increases rapidly and predominates in service reliability. Proper preload is thus defined to balance the service reliability and tightness of the bolted joint. Further studies show that the shape of the nut has a great effect on the stress concentration of the thread, the optimized nut is designed to reduce the stress concentration of the thread, and thus the reliability of the bolted joint is also improved.     

低温烧结法制备LZS系微晶玻璃及其性能

采用烧结法制备出LZS系微晶玻璃.使用DTA分析了玻璃的析晶过程,运用XRD、SEM等对晶相和晶粒大小进行了观察和分析,讨论了温度对烧结程度、主晶相、晶体微观形貌及热膨胀系数的影响.结果表明:当晶化温度低于725℃时,主晶相为硅酸锂锌,次晶相为Li2ZnSiO4并有少量石英;温度高于725℃时,主晶相转变为石英,次晶相为硅酸锂锌和Li2ZnSiO4,为长度在1.5μm左右的棒状晶体.在700～725℃之间烧结接近完成.最佳烧结温度为725℃.微晶玻璃热膨胀系数与烧结程度、晶相含量和主晶相的热膨胀系数有关.     

浸浆法制备生物多孔陶瓷

自然骨的主要无机成分是羟基磷灰石,由于纯羟基磷灰石对于人体组织有良好的生物相容性,被广泛使用为骨植入材料,为了得到孔径和孔隙率合适的羟基磷灰石框架,本文采用多孔聚氨脂泡沫浸浆法制备,实验表明,该方法可以有效的获得需要的羟基磷灰石框架。     

氧化锆流延基片的制备

研究了工艺参数对氧化锆流延片制备影响.结果表明,当流延体系9＜pH＜11.5,分散剂用量为1.5wt％,黏结剂含量为5wt％,球磨混合12h的ZnO2浆料稳定,素坯质量好.在1500℃经3h烧结,烧结样品显微结构致密,相对密度达98％.     

无团聚ZrO2-HfO2-Y2O3复合纳米粉体的制备

以分析纯ZrOCl2·8H2O、HfOCl2·8H2O和Y(NO3)3·6H2O为原料,采用反向滴定共沉淀-共沸蒸馏法成功地制备出无团聚的ZrO2-HfO2-Y2O3复合纳米粉体.借助XRD、TEM、BET等手段分析了制备工艺对粉体粒径和团聚状态的影响.研究表明,分散剂PEG的加入量及前驱体湿凝胶的处理方式对最终制备的ZrO2-HfO2-Y2O3复合粉体的晶粒度影响不大,但显著影响粉体的分散状态.分散剂加入量为1%(质量分数)并对湿凝胶共沸蒸馏处理条件下最终获得的粉体的分散性最好.前驱体沉淀经500℃焙烧1h后,生成了具有高氧离子电导率的立方晶型ZrO2基ZrO2-HfO2-Y2O3固溶体,粉体的平均粒径约为15nm.     

纳米Al2O3/ZrO2复合粉体的制备及表征

高性能的复合粉体是制备纳米复相陶瓷材料的关键.采用醇-水溶液加热法结合共沉淀过程制备纳米Al2O3/ZrO2复合粉体,研究了不同沉淀剂对粉体团聚的影响,利用透射电镜、X射线衍射、热重-差热分析、比表面积测定等技术对获得的纳米复合粉体进行了表征.结果表明:采用NH4HCO3作为沉淀剂可以得到几乎无团聚的碱式碳酸盐前驱物,该前驱物在煅烧过程中的物相变化显示四方相氧化锆(t-ZrO2)的形成温度大幅度地提高,同时在较低温度下生成了α-Al2O3,在1 100℃转变为t-ZrO2相和α-Al2O3相;粉体中两相颗粒分散良好、粒径一致、无硬团聚,其平均粒径为15～20 nm,比表面积为69.5 m2·g-1.     

Preparation and characterization of dispersed Rh2O3 on tetragonal ZrO2

Samples of well-dispersed hexagonal Rh₂O₃ on tetragonal ZrO₂ have been prepared by the code composition of the nitrates at 900°C. A comparison of the stability towards reduction of the bulk and dispersed Rh₂O₃ products demonstrates the influence of an interaction between the dispersed metal oxide and the support.     

亚微米Li2O-Al2O3-SiO2微晶玻璃制备

本文利用DTA、XRD和SEM对Li2O-Al2O3-SiO2(以下简称LAS)微晶玻璃核化晶化热处理制度及氟离子在该玻璃体系中的作用进行研究.通过分析得出:含氟LAS玻璃核化温度和晶化温度分别为620℃和710℃,比相同组份的不含氟Li2O-Al2O3-SiO2玻璃核化、晶化温度分别降低了40℃和160℃左右;引入氟离子明显降低LAS玻璃析晶温度,系统的活化能降低约54kJ/mol,当含氟LAS玻璃的核化时间为1h、晶化时间为4hrs,平均微晶颗粒尺寸在50nm左右.     

Preparation and microstructure of ZrO2-and LaGaO3-based high-porosity ceramics

We have studied the effects of the morphology and concentration of pore formers on the microstructure and gas permeability of porous zirconia-and lanthanum-gallate-based oxygen-ion-conducting ceramics. The results have been used to optimize the preparation conditions and composition of the ceramics. The resultant dense, fine-grained materials have porosities of up to }~56%.     

Preparation of Y2O3 stabilised ZrO2 ceramic nanopowders by surface doping

Abstract

Weakly agglomerated nanocrystalline Y₂O₃–ZrO₂ powder was prepared by dispersion Y₂O₃ on the surface of ZrO₂ nanopowder (7·3 nm) that was derived from gas phase synthesis. The utmost dispersion capacity of Y₂O₃ on the surface of ZrO₂ was determined to be 0·16 gY₂O₃ /gZrO₂ (or 8·7 mol.-%Y₂O₃–ZrO₂ ) which suggests that 3 mol.-%Y₂O₃ would be homogeneously dispersed on ZrO₂ and no phase segregation would occur during surface doping. The results show that the tetragonal phase content in surface doped ZrO₂ increased with grain growth or heating temperatures, unlike the undoped and the bulk doped ZrO₂ . The stabilisation of the tetragonal phase resulted from the incorporation of Y ³⁺ cations from the surface into the grains of ZrO₂ . This conclusion is supported by the X-ray photoelectron spectroscopy and X-ray diffraction evidence. Surface doped powders have a strong tendency to improve the anticoarsening ability and suppress grain growth, especially at higher doping levels and at lower heating temperatures.     

二氧化锆气凝胶制备和表征

以无机盐 硝酸氧锆为原料,采用醇 水加热 超临界干燥法制备了二氧化锆气凝胶。采用XRD、TEM和BET等手段对样品进行测试表征。研究结果表明:本方法可以制备具有高比表面、小粒径的二氧化锆气凝胶。气凝胶原粉的比表面最大,可达675.6m2/g。其晶相结构也不同于采用一般方法制备的ZrO2粉体。在焙烧温度低于700℃时,随着焙烧温度的升高,四方相的含量逐渐增大,到700℃时达到最大86%;经1000℃焙烧后尽管粒径>30nm,仍有约30%的ZrO2以四方相的形式存在。探讨了醇水加热法制备ZrO2气凝胶的成胶机理。