氮化硅陶瓷的微波烧结

利用ＴＥ１０３单模腔微波烧结系统对添加６％（Ｙ２Ｏ３＋Ａｌ２Ｏ３）的α、β－ＳｉＮ４粉的微波加热特征进行了研究。通过选择合理的保温材料和烧结工艺，获得了较高密度、结构均的氮化硅烧结体。实验发现，对于粉末为α－Ｓｉ３Ｎ４的试样，在相变发生的温度内，相变的发生比较密化进程更早而且发生在一个相对更低的温度，研究结果也表明，在微波烧结中相变促进致密化进程。在较短的内警备交高的密度和较好的力学性质，氮化硅的     

细晶钛酸钡陶瓷的烧结方法

本文用两步法、两段法、高压成型常压烧结、高压烧结和掺杂烧结等特殊方法烧结得到了细晶钛酸钡陶瓷,它们的烧结温度低于常规烧结的温度.用扫描电子显微镜观测了陶瓷的显微结构.结果表明:用这些特殊方法烧结得到的陶瓷的晶粒尺寸远小于常规法烧结得到的钛酸钡陶瓷的尺寸.此外,对它们的烧结机理进行了简单的解释.     

易熔粘土陶瓷烧结材料

研究了由三种含伊利石易熔粘土和两种添加剂－－霞石正长岩和合成假硅灰石配制的两种致密陶瓷坯料的烧结过程。结果表明，采用几种矿物和粒度组成不同的同型粘土可以扩大烧结范围。     

陶瓷烧结新技术—微波烧结

本文综述了微波烧结陶瓷材料这一新技术在国内外的研究，应用和进展，并介绍和指出了微波烧结的原理，特点及其未来展望。     

复相α—β—sialon陶瓷的微波反应烧结

微波烧地因具有极快的加热和烧结速度及内在性和体积性加热等特征使制品有潜力均匀地烧结，并获得较高的密度和均匀的微观结构通过适当的保温方式，名义组成为α：β＝２０：８０的复相α－β－ｓｉａｌｏｎ陶瓷在２．４５ＧＨｚ单模腔微波烧结系统于１６５０℃保温１０ｍｉｎ能完全反应，烧结致密，获得较高的密度和较小的晶粒尺寸及好的力学性能。     

低温烧结的刚玉陶瓷

当前,不含熔剂的材料,其烧结温度高达1700～1800℃;而含有熔剂的,其烧结温度则为1600～1650℃。这是俄罗斯工业生产的刚玉陶瓷材料所表现出的明显的技术缺陷。上述缺陷主要表现为热处理设备易快速磨损、耐火制品和能源消耗较高、周围环境遭受热污染。除此之外,高温烧结会导致制品强烈再结晶、形成内气孔和降低强度。因此,开发烧结温度低的、又具有高的物理机械性能和使用性能的材料是十分迫切的。     

氧化铝陶瓷及其烧结

氧化铝陶瓷具有良好的性能，故应用广泛。本文介绍了氧化铝变体、氧化铝陶瓷的性质和用途。论述了氧化铝陶瓷烧结动力学并分析了影响烧结的主要因素。     

高压烧结纳米钛酸钡陶瓷的结构和铁电性

在压力为6GPa和温度为1000℃的条件下烧结得到了钛酸钡(BaTiO3)陶瓷,其晶体的平均尺寸约为30nm,相对密度大于96%.在-190～200℃,用Raman光谱确定晶体的结构,用介电转变峰表征晶体的铁电性.结果表明:随温度升高,在30nm BaTiO3陶瓷中,发生从三方相→正交相→四方相→三方相的连续相变;在室温,晶体的正交相和四方相共存.当频率为1kHz时,在120℃附近有1个宽的介电转变峰,介电常数为1920.铁电性分析表明:高压烧结得到的BaTiO3陶瓷的铁电性消失的临界尺寸小于30nm.     

KSZP陶瓷的烧结和力学性能

研究了ＫＺｒ２Ｐ３（ＫＺＰ）－ＳｒＺｒ４Ｐ６Ｏ２４（ＳＺＰ）系统陶瓷（ＫＳＺＰ）的显微结构和力学性能，添加ＭｇＯ作为烧结助剂，使材料力学性能得到显著的改善，抗弯强度达到１２３ＭＰａ，断裂韧性为２．１ＭＰａ．ｍ＾１／２弹性模量达１１０ＧＰａ，Ｖｉｃｋｅｒｓ硬度为４．５ＧＰａ。     

粘土陶瓷的微波快速烧结

通过对添加不同金属或半导体粉末的粘土陶瓷的微波煤结研究，在实验上突破了一种简易并快速同波烧结低损耗的材料的方法，在大量实验数据的支持下，得出各种添加剂促进坯体吸收微波的顺序为：ＳｉＣ〉Ｆｅ〉Ｓｉ〉Ａｌ。同时通过对烧结后粘土陶瓷的力学性能和显微结构分析发现各添加剂对材料力学性能的促进顺序为：ＳｉＣ〉Ａｌ〉Ｆｅ〉Ｓｉ。     

埋粉烧结对BaTiO3陶瓷性能的影响

将自制的水热法BaTiO3粉体干压成形后,分别进行无埋料烧结、Al2O3粉体做埋料烧结和母体BaTiO3粉体做埋料烧结,对烧结后陶瓷体的致密度、显微结构及介电性能进行了分析.结果表明:埋粉烧结对BaTiO3陶瓷体的性能产生显著影响;BaTiO3粉体做埋料时得到的瓷体密度高、晶粒小、电性能优良.     

Colossal Permittivity in Microwave‐Sintered Barium Titanate and Effect of Annealing on Dielectric Properties

Colossal permittivity (ε′ = 301,484 at room temperature and 1 kHz) of barium titanate was induced in ceramics synthesized using the microwave sintering method. Three different sintering processes (conventional, spark plasma, and microwave) were performed to better understand colossal permittivity in sintered barium titanate. The dielectric permittivity measurements revealed that the appearance of colossal permittivity has strong dependence on the sintering temperature and atmosphere, and less on the grain size of the sintered ceramics. However, the as‐sintered barium titanate samples produced by microwave sintering show high dielectric loss (tanδ > 1) consistent with oxygen reduction during the microwave sintering process and consequent accumulation of oxygen vacancies and associated charge carriers at the grain boundary. Since the highly conductive state of as‐sintered ceramics precludes their use in dielectric applications, thermal annealing at different conditions was performed to recover insulating characteristics. Microwave‐sintered barium titanate with post annealing process (950°C for 12 h in air) showed low dielectric loss (tanδ = 0.045) at room temperature and 1 kHz, while still showing a much higher permittivity (ε′ = 36,055) than conventionally sintered barium titanate (ε′ = 3500).     

两步烧结法制备纳米氧化钇稳定的四方氧化锆陶瓷

采用共沉淀法制备纳米氧化钇稳定的四方氧化锆（yttria stabilized tetragonal zirconia,3Y-TZP）粉体。利用X射线衍射、N2吸附–脱附等温线,透射电子显微镜对3Y-TZP粉体的物理性能和化学性能进行表征。研究了纳米3Y-TZP粉体的烧结曲线,分析了3Y-TZP素坯在烧结过程中的致密化行为和显微结构,探讨了两步烧结工艺对3Y-TZP纳米陶瓷微观结构的影响。结果表明：采用共沉淀法,在600℃煅烧2h后,可获得晶粒尺寸为13nm、晶型发育良好、团聚较少的纳米3Y-TZP粉体;采用两步烧结法,将素坯升温至1200℃保温1min后,再降温到1050℃保温35h,可获得相对密度大于98%,晶粒尺寸约为100nm的3Y-TZP陶瓷。两步烧结法通过控制煅烧温度和保温时间,利用晶界扩散及其迁移动力学之间的差异,使晶粒生长受到抑制,样品烧结致密化得以维持,实现在晶粒无显著生长前提下完成致密化。     

Comparison between microwave and conventional sintering on the properties and microstructural evolution of tetragonal zirconia

In this research, the comparison between microwave sintering and conventional sintering on the mechanical properties and microstructural evolution of 3?mol% yttria-stabilised zirconia were studied. Green bodies were compacted and sintered at various temperatures ranging from 1200?°C to 1500?°C. The results showed that microwave assisted sintering was beneficial in enhancing the densification and mechanical properties of zirconia, particularly when sintered at 1200?°C. It was revealed that as the sintering temperature was increased to 1400?°C and beyond, the grain size and mechanical properties for both microwave- and conventional-sintered ceramics were comparable thus suggesting that the sintering temperature where densification mechanism was activated, grain size was strongly influenced by the sintering temperature and not the sintering mode.     

Effect of hot-pressing sintering on thermal and electrical properties of AlN ceramics with impedance spectroscopy and dielectric relaxations analysis

The effects of hot-pressing sintering on the phase composition, microstructure, thermal and electrical properties of AlN ceramics with CeO₂–CeF₃ additives were studied. During hot-pressing sintering, high pressure reduced the grain boundary phase CeAlO₃ and decreased the concentration of oxygen in AlN ceramics. The hot-pressing sintered AlN samples had a much higher thermal conductivity of 191.9 W/m·K than pressureless sintered ones because of the great reduction of grain boundary phases and oxygen impurities in AlN ceramic. As the carbon content in hot-pressing sintered sample was very high, carbon contamination led to the decrease in electrical resistivity and changes in polarization mechanisms for AlN ceramics. The relaxation peak in the dielectric temperature spectrum with an activation energy of 0.64 eV for hot-pressing sintered samples was caused by electrons from free carbon at low temperature. Overall, hot-pressing sintering can effectively increase the thermal conductivity and change the electrical properties of AlN ceramics.     

正温度系数电阻陶瓷复阻抗频谱的计算机模拟

通过建立数学模型,编制了具有不同数量等效电阻-电容(resistor capacitor,RC)电路结构单元的正温度系数电阻(positive temperature coefficient resistance,PTCR)陶瓷的复阻抗频谱的计算机程序.对在还原气氛下烧结后再氧化的高施主掺杂BaTiO3陶瓷的阻抗虚部和电模量虚部随测试频率变化的曲线进行了拟合,结果表明:还原性的Ba1-xLa3 xTi4 1-xTi3 xO3再氧化后形成Ba1-xLa3 Ti4 1-x/4(V""Ti)x/4,在晶界处可能形成了两个具有PTCR效应的RC结构单元.     

功能陶瓷材料及其应用研究进展

介绍铁电、压电等功能陶瓷及其片式元件应用研究的若干新进展.基于过渡液相烧结机制的高性能压电陶瓷材料具有低烧结温度、高压电常数和低介质损耗等诸多优点.低烧多层压电变压器(MPT)以其低驱动电压、小体积、高升压比、薄型片式化等优点在液晶显示背光电源等方面获得应用.多层压电变压器及其背光电源具有高功率密度、高转换效率、薄型化和低成本等特点.基于缺陷化学原理和无晶粒长大的致密化烧结动力学,制备了亚微米/纳米晶钛酸钡基陶瓷及其薄层化贱金属内电极MLCC.研制了低烧铁氧体材料及其片式电感器.介绍了压电陶瓷超声微马达的结构与特性.     

Sintering behaviour and properties of manganese-doped alumina

The effect of manganese (0.1, 0.5 and 1.0?wt%) on the sintering and mechanical properties of alumina was studied. Sintering was carried out by the conventional heating method in a box furnace and in a hybrid multimode microwave furnace. XRD analysis revealed the precipitation of a spinel second phase (MnAl₂O₄) in manganese-doped samples as a result of manganese limited solubility in the corundum lattice. The addition of 0.1?wt% manganese was most beneficial in enhancing the densification of alumina (97.5% relative density when compared to 94.2% for the undoped sample), hindered grain growth, and improved the hardness of the ceramic when sintered at 1500?°C. The study also revealed that microwave sintering was effective in suppressing grain growth of alumina. In addition, the hardness was dependent on the sintered bulk density and that grain coarsening ensued as the density of the sintered alumina exceeded 95% of theoretical.     

掺杂La2O3对刚玉基复相陶瓷的烧结和力学性能的影响

刚玉基复相陶瓷材料具有高硬度、高强度及耐磨性等优异的力学性能,是结构陶瓷领域研究的热点之一,具有广阔的应用前景.以α-Al2O3、SiC和ZrO2为原料,掺杂少量稀土氧化物La2O3,采用无压埋烧工艺,制备了稀土掺杂刚玉基复相陶瓷.通过XRD、SEM等手段研究La2O3添加量对复相陶瓷微观结构和性能的影响.结果表明:掺杂La2O3可将复相陶瓷的烧结温度降低至1540℃,经1540℃烧结的掺杂复相陶瓷强度和硬度分别为183 MPa和18.46 GPa.La2O3位于晶界处抑制晶粒长大,促进晶粒细化,利于样品的致密化,同时其晶界强化作用有利于复相陶瓷强度的提高.