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     

烧结技术与氮化硅陶瓷显微结构研究

以文以编号为ＳＰＮ氮化硅与编号为Ｍ２０，Ｍ５０的Ｓｉａｌｏｎ材料为例在无压烧结，气烧结和热等静压烧结等工艺条件下进行烧结，测试了材料性能，用ＳＥＭ，ＥＭ和Ｘ衍射等分析手段观察材料的显微结构和相组成，及其对材料性能的影响进行了讨论。     

氮化硅陶瓷烧的烧结

氮化硅陶瓷广泛用作高温结构材料,是很有前途的陶瓷材料之一。本文研究了氮化硅硅瓷烧结动力学,分析了影响氮化硅陶瓷烧结的因素,为氮化硅陶瓷结提供了依据。     

陶瓷材料微波烧结工艺与机理研究现状

微波烧结作为一种新型材料烧结技术,在陶瓷材料制备领域受到越来越多的关注.与传统烧结技术相比,微波烧结具有快速高效、节能环保以及改善材料微观结构,提高材料性能的优点.本文介绍了传统烧结和微波烧结的特点,对比了传统烧结和微波烧结陶瓷材料的烧结工艺和力学性能;列举了运用微波烧结法制备的典型结构陶瓷的烧结工艺及其力学性能;全面综述了陶瓷材料微波烧结机理;最后提出了微波烧结在未来发展中亟待解决的问题.     

微波烧结在陶瓷材料中的应用

微波烧结作为一种陶瓷材料烧结的新方法,近年来得到飞速发展。本文介绍了微波烧结的原理,阐述了微波烧结在陶瓷 材料中的应用,并分析了微波烧结存在的问题及其解决途径。     

陶瓷材料的微波连续化烧结系统研究

陶瓷材料烧结通常需要整体在窑炉内烧结,以保证材料性能.本文利用微波烧结的特性,研究了混合场的模型,设计了微波连续化烧结系统,并在该系统上成功地实现了Φ40×2400mm的陶瓷辊棒的微波连续化烧结.结果表明,微波烧结陶瓷辊棒的抗热震性能及抗弯强度均有较大幅度提高.本研究对微波烧结的实用化具有较大的推动作用.     

无压烧结氮化硅陶瓷的研究

本文选用MgO-Al2O3作为复合添加剂，采用无压烧结，设计Si3N4-MgO-Al2O3系烧结体、Si3N4-SiC-MgO-Al2O3系烧结体，研究各种配方在不同忝型压力不同烧结条件下烧结体的性能，测定室温抗折强度、体积密度、体积变化和气孔率，通过X射线衍射分析鉴定烧结体的物相结构，从而确定了最佳工工艺范围。     

烧结温度对氮化硅陶瓷球显微结构和力学性能的影响

以α-Si3N4粉为原料,纳米级Y2O3和Al2O3为烧结助剂,采用气压烧结工艺制备氮化硅陶瓷球,研究了烧结温度对陶瓷球显微结构及力学性能的影响.结果表明,随着烧结温度的升高,陶瓷球的维氏硬度和压碎强度先提高后降低,断裂韧性不断提高.烧结温度为1780℃的陶瓷球综合力学性能最佳,其相对密度达到了99％,维氏硬度、断裂韧...     

Pulsed Electric Current Sintering of Silicon Nitride

Pulsed electric current sintering (PECS) has been used to densify α-Si₃N₄ powder doped with oxide additives of Y₂O₃ and Al₂O₃. A full density (>99%) was achieved with virtually no transformation to β-phase, resulting in a microstructure with fine equiaxed grains. With further holding at the sintering temperature, the α-to-β phase transformation took place, concurrent with an exaggerated grain growth of a limited number of elongated β-grains in a fine-grained matrix, leading to a distinct bimodal grain size distribution. The average grain size was found to obey a cubic growth law, indicating that the growth is diffusion-controlled. In contrast, the densification by hot pressing was accompanied by a significant degree of the phase transformation, and the subsequent grain growth gave a broad normal size distribution. The apparent activation energy for the phase transformation was as high as 1000 kJ/mol for PECS, almost twice the value for hot pressing (∼500 kJ/mol), thereby causing the retention of α-phase during the densification by PECS.     

氮化硅陶瓷材料的热力学分析

运用热力学方法分析了氮化硅陶瓷在制备和使用过程中涉及的物理化学过程,包括Si3N4烧结、Si3N4在真空中的挥发、Si3N4的稳定性、Si3N4与金属固体的作用4个方面,结合实际论述了反应发生、发展的条件、反应的优先性、生成化合物的稳定性及热力学方法的适用性.     

低温放电等离子烧结法制备氮化硅陶瓷

分别以MgO-Al2O3或MgO-AlPO4作为烧结助剂,采用放电等离子体低温快速烧结方法制备了主相为α相的Si3N4陶瓷材料.采用X射线衍射和扫描电子显微镜分析了样品的物相组成和显微结构;研究了烧结助剂及其含量、烧结温度对陶瓷样品的相对密度与力学性能的影响.结果表明:当采用4%质量分数,下同)MgO-4%Al2O3烧...     

Densification and Sintering Kinetics in Sintered Silicon Nitride

The sintering sequence of Y₂O₃-Al₂O₃-doped Si₃N₄ was investigated with respect to the relationship between densification, α→β transformation, and microstructural development. Quenching studies were performed to reveal these interactions during a complete sintering cycle. Isothermal studies were conducted to examine the sintering kinetics and compared to Kingery's liquid-phase sintering model. The bulk density increased to ≥90% of theoretical density with only minor transformation taking place. Major transformation occurred in a late sintering stage and was accompanied by the development of elongated grains. The kinetic order of the densification process, taking into account an appropriate correction, was larger than any of the rate exponents predicted by the Kingery model, indicating that other single or mixed mechanisms were active.     

多孔氮化硅陶瓷透波材料研究进展

多孔氮化硅陶瓷透波材料具有优异的机械性能、耐热性能及介电性能,成为透波材料科学研究领域中的热点之一。本文介绍了多孔氮化硅陶瓷的主要制备技术,并对国内外多孔氮化硅陶瓷透波材料的应用研究进展进行了综述。     

Si3N4／Si3N4陶瓷连接的研究进展

本文综述了Ｓｉ３Ｎ４／Ｓｉ３Ｎ４陶瓷连接的研究现状，论述不同连接工艺对接头强度的影响。     

低温无压烧结氮化硅陶瓷的相变及致密化研究

采用氧化铝（Al2 O3）和氧化钇（Y2 O3）为烧结助剂,利用无压烧结工艺在低温下制备氮化硅陶瓷材料。利用XRD和SEM等着重研究了无压烧结氮化硅陶瓷低温阶段时的物相组成及其致密化。结果表明：当添加剂含量为10％,烧结温度高于1430℃时,α→β相转变较快;当烧结温度达到1510℃时,α相全部转变为β相。     

Push-Pull Fatigue of Sintered Silicon Nitride Ceramics at Elevated Temperatures

The fatigue tests under push-pull completely reversed loading and pulsating loading were performed for silicon nitride ceramics at elevated temperatures. Then the effects of stress wave form, stress rate, and cyclic understressing on fatigue strength, and cyclic straining behavior, were examined. The cycle-number-based fatigue life is found to be shorter under trapezoidal stress wave loading than under triangular stress wave loading, and to become shorter with increasing hold time under the trapezoidal stress wave loading. Meanwhile, the equivalent time-based life curve, which is estimated from the concept of slow crack growth, almost agrees with the static fatigue life curve in the short and intermediate life regions, showing the small cyclic stress effect and the dominant stress-imposing period effect on cyclic fatigue life. The fatigue strength increased in stepwise stress amplitude increasing test, where stress amplitude is increased stepwise every given number of stress cycles, at 1100° and 1200°C. Occurrence of cyclic strengthening was proved through a gradual decrease in strain amplitude during a pulsating loading test at 1200°C in this material, corresponding to the above cyclic understressing effect on fatigue strength.