三层结构的氧化锆陶瓷整体烧结研究

对三层结构的ZrO2陶瓷的整体烧结行为进行了较深入的研究,提出了提高三层结构的ZrO2陶瓷整体烧结的措施。研究结果表明:对于三层结构的ZrO2陶瓷,通过采取波浪型界面结构,改进表面层配方,降低升温速率等手段能获得整体烧结性能良好,抗弯强度达到682MPa,硬度15.56GPa的力学性能优良的复合陶瓷材料。     

氧化锆层状复合陶瓷成型和烧结特性

由不同成型方法,单面或双面加压,制备了氧化锆层状复合陶瓷,研究了制备方法和工艺参数,如：加压压力、时间,对生坯密度的影响.探讨了生坯密度与烧结收缩之间的相关性.研究结果表明：选取成型压力在250 MPa左右,双向加压方式,可以获得沿x,y,z轴方向收缩较一致的层状陶瓷制品.引入评价不同方向的烧结收缩变化参数k（=a/b,a和b分别为沿x,y和z方向的烧结收缩率）,kxy,kz,当kxy=kz=1时,表示烧结过程基本完成,坯体中颗粒已达到致密化状态;当kxy-1/kz^2=0或接近于0时,表示沿x,y轴和z轴方向的烧结收缩基本无差别,是一种最佳的层状陶瓷烧结状态.     

常压烧结莫来石／氧化锆／碳化硅复相陶瓷的研究

本文对莫来石／氧化锆／碳化硅复相陶瓷进行了Ｎ２气氛中常压烧结的研究。实验结果表明：ＳｉＣ粒子添加量≤２０ｖｏｌ％，材料均可致密烧结并可获得均匀的微观结构。ＳｉＣ粒子的加入使材料人力学性能较莫来石／氧化锆陶瓷有明显的提高，并在ＳｉＣ含量为１０ｖｏｌ％时达到峰值，室温强度和断裂韧性分别为６０１ＭＰａ和５．８ＭＰａ＾Ｃ２，接近热压材料。     

先进陶瓷材料快速烧结技术发展现状及趋势

快速烧结技术在节省时间和能源方面的巨大优势使其成为一直以来的研究热点.近几十年来,快速烧结技术(如火花等离子烧结、闪电烧结、选区激光烧结、感应烧结、微波烧结和传统烧结装置中的快速烧结等)的发展,使陶瓷材料的快速烧结成为可能.本文综述了近20年来先进陶瓷领域中的快速烧结技术和烧结机理,并对火花等离子烧结中直流脉冲电流和机...     

Development of ZrO2‐MgO nanocomposite powders by the modified sol‐gel method

The ZrO₂‐MgO nanocomposites were synthesized using a new sol‐gel method with sucrose and tartaric acid as a gel agent. The samples were characterized by thermal analysis (TG/DTA), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray mapping (EDX mapping), and Ultraviolet‐visible spectroscopy (UV‐vis). The results showed that the cubic phase of ZrO₂‐MgO was formed in the presence of both gel agents. The average particle size of the samples synthesized with sucrose was lower (30 nm) than that of tartaric acid (50 nm). Finally, the formation mechanism and the optical properties of zirconia‐magnesia have been discussed.     

CaO-B2O3-SiO2系微晶玻璃的低温烧结机理

研究了CaO-B2O3-SiO2系微晶玻璃的烧结过程、析晶机制、微观结构以及介电性能等。该材料能够在850℃的低温烧结，烧结体具有良好的介电性能（er=4.975,tgδ≤0.001,1GHz)。微观结构主要为75％－80％体积百分比的晶相（晶粒尺寸为50－100nm)，少量的残余玻璃相和气孔；主要晶相为CB（CaO.B2O3),C6S4(6CaO.4SiO2)和CS（CaO.SiO2)。该材料适用于高频电子元器件等领域。     

纳米陶瓷的特性和烧结

本文介绍了纳米陶瓷新颖的性能和特殊的烧结方法,阐述了这些特殊烧结方法的烧结机理。同时也对纳米复相陶瓷的性能和制备方法进行了介绍,并对纳米陶瓷今后的研究进行了展望。     

Sintering of Zirconia Nanopowder by Microwave-Laser Hybrid Process

A new hybrid sintering process has been developed by replacing all but one laser by microwaves in the existing simultaneous multiple laser process (SIMPLE). Microwave energy has been used to preheat the material before laser radiation, and the synergism between microwave and laser energies could effectively heat the material to temperatures of 1700°C and beyond in just a few minutes. Using this process, rapid sintering of 3Y–ZrO₂ (3Y–TZP) pellets has been achieved in a few minutes. Microstructural investigations reveal that the microwave–laser hybrid sintered pellets of 3Y–ZrO₂ have nanograins averaging about 20 nm. The microwave–laser hybrid sintering process can clearly be a new approach for fabrication of nanoceramics and nanocomposites.     

Fully coupled electromagnetic‐thermal‐mechanical comparative simulation of direct vs hybrid microwave sintering of 3Y‐ZrO2

Direct and hybrid microwave sintering of 3Y‐ZrO₂ are comparatively studied at frequency of 2.45 GHz. Using the continuum theory of sintering, a fully coupled electromagnetic‐thermal‐mechanical (EMTM) finite element simulation is carried out to predict powder samples deformation during their microwave processing. Direct and hybrid heating configurations are computationally tested using advanced heat transfer simulation tools including the surface to surface thermal radiation boundary conditions and a numeric proportional‐integral‐derivative regulation (PID). The developed modeling framework shows a good agreement of the calculation results with the known experimental data on the microwave sintering of 3Y‐ZrO₂ in terms of the densification kinetics. It is shown that the direct heating configuration renders highly hot spot effects resulting in nonhomogenous densification causing processed specimen's final shape distortions. Compared with the direct heating, the hybrid heating configuration provides a reduction of the thermal inhomogeneity along with a densification homogenization. As a result of the hybrid heating, the total densification of the specimen is attained without specimen distortions. It is also shown that the reduction of the sample size has a stabilization effect on the temperature and relative density spatial distributions.     

Microstructure and mechanical properties of Al2O3/ZrO2 composites by two-step sintering

Composites of Al₂O₃/ZrO₂ (containing 25, 50, and 75 vol% ZrO₂) were prepared by mixing Al₂O₃ and ZrO₂ suspensions. The microstructural control via two-step sintering (TSS) was the main objective of this work. For this purpose, different sintering curves were constructed, aiming to achieve the best temperature combination for the sintering steps that provides higher density and finer microstructure. The results were compared with single-step sintering (SSS). Furthermore, microhardness and fracture toughness were measured for the best TSS specimens under each composition. The results showed that the high densities were obtained, and the reduction of grain size was greater than 40% for two-step sintered specimens, compared to SSS ones. Consequently, microhardness values increased. However, fracture toughness values remained unchanged.     

Microstructure evaluation of 3YSZ sintered by Two-Step Flash Sintering

Flash Sintering (FS) is an energy-efficient sintering technique, which allows a considerable reduction in processing time and temperature. However, a recurring problem of flash sintered samples is the microstructural heterogeneity, which occurs mostly on samples with a high surface-to-volume ratio (e.g., cylindrical samples). Thus, aiming to obtain homogeneous microstructures and smaller grain sizes, this work evaluated the application of Two-Step Flash Sintering (TSFS) in 3YSZ and compared them with samples sintered by FS. The TSFS experiments consisted of applying a first step of current density with greater magnitude (100 mA mm^-2 and 200 mA mm^-2) followed by the second step with smaller magnitude (50 mA mm^-2 and 75 mA mm^-2). In the FS experiments, a single step of current density was used (100 mA mm^-2 and 200 mA mm^-2). The Results showed that TSFS significantly reduced the microstructural heterogeneity compared to FS, promoting smaller and more homogeneous grain sizes in different regions of the samples.     

烧结细晶氧化铝陶瓷的新方法

致密的氧化铝陶瓷可用三种方法烧结得到。从SEM照片可看出：样品比较致密,样品的相对密度大于93％．用两步法和两段法烧结得到的氧化铝陶瓷的晶粒尺寸小于400nm,用常规方法烧结得到的氧化铝陶瓷的晶粒尺寸约为650nm。而且,用两步法和两段法烧结时烧结温度低于常规烧结。实验结果表明：两步法和两段法烧结能得到细晶的氧化铝陶瓷。     

Fine-grained transparent MgAl2O4 spinel obtained by spark plasma sintering of commercially available nanopowders

A high transmittance/small grain size combination for pure spinel ceramics from commercially available nanopowders without sintering aids can be obtained by SPS sintering. By using a low heating rate ≤10 °C/min and a sintering temperature ≤1300 °C, a transparent polycrystalline MgAl₂O₄ spinel was fabricated by SPS with an in-line transmission of 74% and 84% for 550 nm (visible) and 2000 nm (NIR) wavelengths respectively. A small average grain size of about 250 nm was obtained and the pores located at the multiple grain junctions have a mean size of about 20 nm. The high in-line transmission is linked not only to the low residual porosity but particularly to the very small size of pores.     

TZP陶瓷中立方相氧化锆的X射线定量相分析

采用X射线衍射方法研究了四方相氧化锆多晶 (TZP)陶瓷中的物相 ,提出了应用氧化锆双谱线峰强度比I( 2 0 0 ) /I( 0 0 2 ) 计算TZP陶瓷中少量立方相氧化锆 (c-ZrO2 )含量的X射线定量相分析方法 .此外 ,推导建立了TZP材料中c -ZrO2 和t -ZrO2 的X射线定量相分析的计算公式xc=Ic ,t ( 2 0 0 ) -KtIt( 0 0 2 )Ic ,t ( 2 0 0 ) +( f +fKt-Kt)It ( 0 0 2 )× 10 0 %xt=( 1+Kt) fIt( 0 0 2 )Ic ,t( 2 0 0 ) +( f+fKt-Kt)It( 0 0 2     

浸入式水口渣线ZrO2-C材料的侵蚀机制

通过观察损毁样品的侵蚀和渗透情况,研究浇铸TRIP钢时保护渣对ZrO2-C渣线材料的侵蚀机制。ZrO2及其稳定剂CaO的侵蚀溶解是渣线材料侵蚀的决定因素。氧化是石墨损毁的主要方式,石墨在钢水里的溶解对其损毁不起重要作用。ZrO2溶解量和石墨氧化量的比值随着热面到钢水垂直距离的减少而减少。然而,与其他炼钢用碳结合耐火材料不同,在本研究的特殊情况下,石墨被保护渣浸润,它仍然充当耐火成分,但仅部分作为抗渣渗透剂。渣渗透后,ZrO2开始被侵蚀,降低了抗渣侵蚀性,然而渣中成分的气相传输可能导致CaO在未渗透区域脱溶。     

醇-水溶液加热法制备纳米ZrO2粉体的烧结行为

对醇－水溶液加热法所制得的粉体的烧结行为进行了研究。结果表明,经过４５０℃,５ｈ煅烧,醇－水溶液加热法所制得的粉体的硬团本比较小,因而烧结性能比较好;在１１５０℃,２ｈ的条件下烧结,获得相对密度达９８．５％的烧结体。     

Sintering Behavior of Nanocrystalline Zirconia Doped with Alumina Prepared by Chemical Vapor Synthesis

Powders of nanocrystalline zirconia doped with 3–30 mol% alumina have been synthesized using chemical vapor synthesis (CVS). Dense or mesoporous ceramics of small and narrowly distributed grain and pore sizes in the nanometer range are obtained via pressureless vacuum sintering. The microstructural development of the doped samples is strongly dependent on the alumina content. Sintering of zirconia samples with 3 and 5 mol% alumina at temperatures of 1000°C for 1 h results in fully dense, transparent ceramics with grain sizes of 40–45 nm and homogeneous microstructures.     

少量掺杂Al2O3、SiO2的Mg-PSZ陶瓷材料的液相烧结

通过在Mg-PSZ陶瓷材料中少量掺杂Al2O3或SiO2,可使材料在较低温度(≤1550℃)下实现液相烧结,使材料的烧结温度大幅度降低.随Al2O3、SiO2掺杂量摩尔分数在1%～4%范围内增加,材料中m-ZrO2相组成增加,相应的烧结密度降低.所形成的镁铝尖晶石相多分布于ZrO2晶粒间,而形成的镁橄榄石相多镶嵌于ZrO2晶粒内.     

Highly-stable,nondegradable M2A-reinforced YSZ ceramic composites prepared by SPS

Magnesia-rich spinel (M₂A)-reinforced yttria-stabilized zirconia (YSZ) ceramic composites have been fabricated by SPS using m-ZrO₂, Y₂O₃, and waste-derived M₂A powders. The results showed that m-ZrO₂ in M₂A-free YSZ0 specimen is partially stabilized upon temperature rising into tetragonal phase whereas YSZ10-50 composites containing 10-50 wt% M₂A demonstrated variant behavior where their m-ZrO₂ is stabilized into a cubic form. YSZ10-50 composites SPSed at 1400°C for 30 minutes revealed greater than 99% relative density, 10-13 GPa Vickers hardness, 3.5-5 MPa m^0.5 fracture toughness and less than 0.5% apparent porosity. Aging hydration test for five hours soaking at 134°C and water vapor pressure of 2 bar, resulted in a conversion of ~2.8% of t-ZrO₂ to m-ZrO₂ for M₂A-free YSZ0 composite but it does not affect the YSZ10-50 composites. The outcomes indicate that M₂A has significantly improved both the densification and stabilization behavior of m-ZrO₂ through facilitating the diffusion of Y³⁺, Mg²⁺, and Al³⁺ ions inside zirconia lattice structure. In this regard, this study opens the door wide for producing fully stabilized c-ZrO₂ ceramics that could be potentially utilized as industrial ceramics for a broad scope of structural applications of high temperature, high-stress and corrosive environmental conditions.