水热法制备球形二氧化锆粉体的研究

以氯氧锫为前躯体通过水热法制备出了粒径在5μm左右,粒度分布均匀的球形二氧化锆粉体.研究结果表明水热温度、水热时间以及醇水比例对产物的微观结构均有影响.140℃水热处理24h获得产物为无定型态的氢氧化锆粉体,而200℃水热处理24h可获得单斜和四方混相的二氧化锆粉体.随水热时间的延长,产物相结构经历了由无定型氢氧化锆向单斜与四方混相的二氧化锆转变,相转变机制则经历了由均匀饱和析出机制到溶解沉淀为主、原位结晶为辅机制再到原位结晶为主、溶解沉淀为辅机制的变化过程.     

Y2O3对YSZ粉体物相组成和显微结构的影响

以不同氧化钇含量的电熔钇稳定氧化锆微粉为主要原料,于20 MPa下干压成型,并将其在1650℃下进行无压烧结.研究氧化钇含量对氧化锆微粉物相组成及微观结构的影响.结果表明:Y2 O3含量为7wt％时,试样主要由四方相和少量的单斜相组成,此时YSZ试样的体积密度最大,显气孔率最低,致密度最高.同时Y2 O3含量的增加,促进了氧化锆粉体的烧结,并使其发生了由单斜相向四方相和立方相的转化.     

低压条件下纳米氧化锆的水热结晶合成

本文采用水热结晶法研究了在较低压力下纳米氧化锆粉体的制备和性质。制备出了结晶完整、分散性良好、粒度约为十几纳米的超细氧化锆粉体。用XRD、TEM等测试方法对晶相组成、晶粒粒度、晶貌特征等与水热结晶温度及保温时间的关系进行了研究。并对单斜相氧化锆和四方相氧化锆的晶粒形成过程进行了讨论。     

低压条件下纳米氧化锆的水热结晶合成

本文采用水热结晶法研究了在较低压力下纳米氧化锆粉体的制备的性质。制备出了结晶完整、分散性良好、粒度约为十几纳米的超细氧化锆粉体。淫ＸＲＤ、ＴＥＭ等测试方法对晶相组成、晶貌特征等与水热结晶温度及保温时间的关系进行了研究。并对单斜相氧化锆和四方相氧化锆的晶粒形成过程进行了讨论。     

ZrO2增韧陶瓷的研究进展

综述了ZrO2陶瓷及添加氧化物稳定剂对四方相氧化锆的稳定性影响，以及ZrO2陶瓷材料的种类，增韧机理及其主要应用领域，并展望了氧化锆增韧陶瓷的研究发展趋势。     

ZrO2-C质耐火材料中碳对氧化锆的稳定作用

分别以粒度均<0.045 mm的氧化钙部分稳定氧化锆、氧化镁部分稳定氧化锆和氧化钇部分稳定氧化锆为原料,酚醛树脂作为结合剂和碳源,按部分稳定氧化锆与酚醛树脂质量比为9 1配料,研究了在埋焦炭条件下于1 600℃渗碳处理后3种部分稳定氧化锆的相组成变化,以及保护渣对渗碳处理后氧化锆稳定性的影响。结果表明:1)高温下树脂碳对氧化锆存在渗碳过程,并对氧化锆有稳定作用,促进了部分稳定氧化锆中单斜相向四方相的转化;但也发现渗碳过程对部分稳定氧化锆中的氧化钙和氧化镁稳定剂存在还原作用并引起其挥发。2)由于渗碳处理过程中部分氧化钙和氧化镁稳定剂被还原挥发,高温下空气气氛中部分稳定氧化锆随着氧化锆晶格中碳的氧化而迅速失稳;而在埋炭条件下部分稳定氧化锆晶格中碳的存在减缓了部分稳定氧化锆的失稳过程。     

高分散氧化锆纳米晶体的合成与表征

用阳离子表面活性剂十六烷基三甲基溴化胺（C19H42BrN）进行自组装,在水热条件下合成了高分散、近似球形、均匀粒径的氧化锆纳米晶体。用热重-差示扫描、Fourier变换红外光谱、X射线衍射、透射电镜、可见-紫外光谱以及N2吸附-脱附等方法对样品进行了表征分析。研究表明：阳离子表面活性剂对形成氧化锆纳米晶体具有明显的导向作用,500℃煅烧的样品其晶粒尺寸约为15nm,分散性能良好,以四方相为主。     

氧化锆陶瓷微珠浆料的制备

笔者以3YSZ(3mol%的氧化钇稳定的氧化锆)为原料,制备氧化锆陶瓷微珠浆料,研究了pH值、分散剂含量、引发剂含量及加入方式、水浴温度、搅拌转速等因素对浆料性能的影响,使用数码显微镜对陶瓷微珠球形度、粒径等进行表征。研究结果表明:浆料固相含量为62.5%,分散剂含量为1.5%、m(AM)∶m(APS)=1∶0.2,浆料pH值为10,反应温度55～65℃,搅拌转速200 r/min时可得到致密度高、球形度好、粒径在100～300μm的氧化锆陶瓷微珠生坯。     

Y—TZP陶瓷的蠕变活化能

本文研究了一种氧化钇稳定四方氧化锆多晶体陶瓷的高温蠕变活有以及应变速率、晶粒大小和致密度等因素对其蠕变活化能的影响，讨论了材料的形变机理。     

醇对低温水热合成四方相钛酸钡的影响

以Ba(OH)2·8H2O和Ti(OC4H9)4为原料,氨水为矿化剂,以不同醇/水混合溶剂作为分散介质,在180℃下反应120 h,水热合成四方相钛酸钡粉体,研究不同醇对粉体的影响,并通过XRD、TEM、IR及激光纳米粒度分析对粉体进行了表征.结果表明以一元醇为溶剂有利于合成四方相钛酸钡,其中又以乙醇为最优,以乙醇/水为溶剂合成的四方相钛酸钡粉体的c/a最大可达1.0090,且粉体纯度高,粒径分布狭窄,晶粒形貌发育完整,呈现球形和四方形.     

Comparison of the Osteogenic Potential of Titanium and Modified Zirconia-Based Bioceramics

Zirconia is now favored over titanium for use in dental implant materials because of its superior aesthetic qualities. However, zirconia is susceptible to degradation at lower temperatures. In order to address this issue, we have developed modified zirconia implants that contain tantalum oxide or niobium oxide. Cells attached as efficiently to the zirconia implants as to titanium-based materials, irrespective of surface roughness. Cell proliferation on the polished surface was higher than that on the rough surfaces, but the converse was true for the osteogenic response. Cells on yttrium oxide (Y₂O₃)/tantalum oxide (Ta₂O₅)- and yttrium oxide (Y₂O₃)/niobium oxide (Nb₂O₅)-containing tetragonal zirconia polycrystals (TZP) discs ((Y, Ta)-TZP and (Y, Nb)-TZP, respectively) had a similar proliferative potential as those grown on anodized titanium. The osteogenic potential of MC3T3-E1 pre-osteoblast cells on (Y, Ta)-TZP and (Y, Nb)-TZP was similar to that of cells grown on rough-surface titanium. These data demonstrate that improved zirconia implants, which are resistant to temperature-induced degradation, retain the desirable clinical properties of structural stability and support of an osteogenic response.     

Preparation of Yttria-Stabilized Zirconia Microtube by Electrochemical Vapor Deposition

A microtube of yttria-stabilized zirconia of ca. 100 μm diameter was prepared. An yttria-stabilized zironia film was formed over a surface-oxidized nickel wire with a diameter of 10 μm by electrochemical vapor deposition using zirconium tetrachloride and yttrium trichloride as metal sources, and nickel oxide as an oxygen source for the reaction. The YSZ-coated wire was then immersed in aqueous 11.5 mol.L^-1 hydrochloric acid to dissolve the nickel and nickel oxide, and a microtube of 80 mol? yttria-stabilized zirconia with a cubic crystal structure was obtained. The surface of the microtube was rough, but was pinhole-free, from SEM observation. The thickness of the zirconia layer was about 3 μm.     

Impulse Laser Effect on Graphitized Surface of Y–TZP-Ceramics

Refractories and Industrial Ceramics - The role of a graphite layer on the surface of ceramics based on tetragonal zirconia, partially stabilized by yttrium oxide (Y–TZP-ceramics) under the...     

Electric insulating material for thermoelectrodes working in vacuum

Conclusions Yttrium oxide possesses better properties than alumina, zirconia, and magnesia, which means it can be recommended as an electric insulating material for high temperature thermocouples or as a construction material for high-temperature insulations, for instance, as a material for making sectors for protecting the inductor in vacuum electric furnace.In order to save material the yttrium oxide can be recommended for use only in the hottest zone with contact on the coolest side with the refractory components made from alumina, zirconium dioxide, and magnesia at temperatures up to 1700°C.The yttrium oxide can be successfully used as a stabilizing additive for zirconium dioxide in making heat-resistant components or vacuum-tight protective sheaths. This additive reduces the rate of volatilization of the solid solution of zirconia-yttria in vacuum at temperatures above 2000°C.Translated from Ogneupory, No. 5, pp. 50–53, May, 1970.     

Mechanical behaviour of yttria- and ferric oxide-doped zirconia at different temperatures

The variation of strengh, deformability, fracture toughness and other characteristics of partially stabilized zirconia ceramics (Y–Fe–PSZ) doped with 3% yttrium and 3% ferric oxide over a temperature range from −140 to 1400°C were investigated. Fracture toughness (K_1c) values obtained by the methods such as SENB, SEPB, IS and IF were compared. Lower temperatures resulted in an increase in fracture toughness by approximately 29%. Using the Vickers indents as stress concentrators for the IS tests we derived the relationship between K_1c values and mean values of radial crack length described by a second-degree polynomial. The data for zirconia (Y–PSZ and Mg–PSZ) and silicon-nitride ceramics, as well as the fractographic data, were used to analyse the results. It was established that the addition of ferric oxide exerted a positive effect on the strengh and fracture toughness of zirconia ceramics.     

Deposition Via Dip Coating Technique of Dense Yttrium Stabilized Zirconia Layers

A deposition of yttrium stabilized zirconia layer for its use as an electrolyte in solid oxide fuel cell was performed using dip coating technique. Two commercially available surfactant systems were evaluated; nonionic surfactant which stabilizes only by steric repulsion and anionic surfactant which provides both steric and electrostatic repulsion. Dip coating process was optimized to two step deposition process. Uniform 10–15 μm thick yttria stabilized zirconia (YSZ) electrolyte layer is obtained after the final sintering step at 1400°C. Impedance spectroscopy measurements showed that selected phosphate ester based surfactant has negligible effect on the performance of the YSZ material as electrolyte.     

A review on the hydrothermal ageing behaviour of Y-TZP ceramics

The state of understanding on the devastating effects of hydrothermal ageing on the properties of yttria-tetragonal zirconia polycrystal (Y-TZP) when exposed to humid environment are reviewed. The prime factors governing the ageing-induced tetragonal to monoclinic phase transformation include the tetragonal grain size, sintering techniques particularly two-step sintering, microwave sintering and electric field assisted sintering, and yttria content are discussed. In addition, the beneficial effects of sintering additives or dopants in promoting sintering as well as suppressing the ageing-induced monoclinic formation are also deliberated. Selective dopants and co-dopants such as copper oxide, alumina, iron oxide and magnesium oxide were found to be beneficial in suppressing hydrothermal ageing in zirconia. Other important boundary conditions to be considered when evaluating the ageing behaviour of Y-TZP includes the ageing environment i.e. temperature, medium and applied pressure which were discovered to have an impact on the rate of phase transformation. Furthermore, the effects of ageing-induced monoclinic formation on the surface topography and mechanical properties of Y-TZP are reviewed. This review indicated that the ageing of Y-TZP can be rather intricate as there are many combinatory factors that needs to be tailored in order to develop an ageing-resistant zirconia without compromising on the transformation toughening effect and other properties.     

Composition and structure of fused microspheres of stabilized zirconia

Conclusions Monocrystalline and polycrystalline microspheres up to 250 in diameter were produced from stabilized ZrO₂ by subjecting granules of a mixture of commercial zirconia and yttrium oxide powders to a high-temperature treatment in a high-frequency discharge.In the process, the powders are purified of admixtures (Si, Fe, Ca, and Mg), the prescribed ratio of zirconia and yttrium oxide remaining unaffected.The microhardness of the microspheres was 1140–1290 kg/mm² which corresponds to that of monocrystals of similar composition.The production of a granulated fractionated material in the form of microspheres by a treatment in a high-frequency discharge makes it possible to dispense with operations like fine grinding, briquetting, and firing and crushing the briquets in the production of high-density granular fillers.Translated from Ogneupory, No. 2, pp. 49–52, February, 1976.     

Ball milling assisted preparation of nano La–Y/ZrO2 powder ternary oxide system: Influence of doping amounts

Zirconia powder with good dispersion, fine particle size, and stability is used as high-quality raw material in many fields, such as ceramic materials and refractories. In this paper, the influence of lanthanum oxide (La₂O₃) and yttrium oxide (Y₂O₃) co-doped zirconia (ZrO₂) on its phase transformation behavior, phase stability, and microstructure were investigated. The ball milling method is applied to fabricate different amounts of La₂O₃-doped yttrium oxide stabilized zirconia oxide. Then, the powder obtained from ball milling was roasted using the microwave sintering method. The samples were characterized using XRD, FT-IR, Raman, SEM and BET to determine the optimal conditions for La₂O₃–Y₂O₃ co-doped ZrO₂ powder. The results showed that replacing part of Y₂O₃ with La₂O₃ increases zirconia powder's tetragonal and cubic phase, enhancing the fracture strength of the subsequent synthesized materials. At the same time, the stability of zirconia stabilized with La₂O₃ doping is significantly improved compared to that of Y₂O₃ alone. According to all analysis methods, when the doping amount is 2.8Y0.2La, the powder's phase composition, stability, particle size distribution, and dispersion degree are the best compared with other doping amounts in our study. The obtained powder has a smaller specific surface area, a lower surface energy, a smaller porosity, and a higher density. The samples under this condition can be better used in subsequent materials. The enhancement of various properties of zirconia can significantly prolong the service life of materials in practical applications.     

Effect of hydrothermal aging on dental multilayered zirconia for monolithic restorations: An in vitro study

The aim of this in vitro study was to investigate the changes in mechanical, optical, and surface properties of multilayered zirconia during hydrothermal aging.One conventional block (Katana Zirconia HT) and three multilayered blocks (Katana Zirconia ML, STML, and UTML) of monolithic zirconia were examined. Bar-shaped specimens were autoclaved at 134°C and 0.2MPa for 0, 5, and 10 h. The Young's modulus, three-point flexural strength, and nanoindentation hardness were measured to evaluate the mechanical properties. The surface roughness, phase distribution, surface microstructure, and elemental composition were measured to analyze the surface properties. The contrast ratio and total transmittance were measured via spectrophotometry to evaluate the optical properties. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent and paired sample t-tests (α = .05).The monoclinic phase increased gradually after hydrothermal aging. The yttrium and zirconium concentrations decreased, and the oxygen concentration and the surface roughness increased in all specimens (P<.05) after the aging process. All specimens showed significant grain push-out and microcracks. The total transmittance increased, and the contrast ratio and Young's modulus decreased in all specimens (P<.05) after the aging process. The nanoindentation hardness and three-point flexural strength exhibited a decreasing tendency after the aging process. However, there were no statistical differences (P>.05) between the materials. Significant interactions between material grades and hydrothermal aging were found for all the properties studied (P<.001).Microstructural alterations and significant phase transformations were detected on the surface of the multilayered zirconia after hydrothermal aging. The hydrothermal aging led to increased surface roughness, opaqueness, and elasticity of multilayered zirconia. The optical, mechanical, and surface properties of multilayered zirconia were influenced by the grade of the material after hydrothermal aging. Careful consideration of the grade of materials is necessary for the appropriate selection of multilayered zirconia ceramics for monolithic restorations.