Sialon复相陶瓷刀具材料的研制

本文在相关研究与组份设计的基础上，研制成β－Ｓｉ３Ｎ４／α－Ｓｉａｌｏｎ与α‘－β’－Ｓｉａｌｏｎ两种复相陶瓷，对这两种材料进行了力学与热学等性能以及力学性能与显微结构关系研究。并以国产原料与德国ＳｔａｒｃｋＬＣ－１２原料，采用ＧＰＳ与ＨＰ烧成工艺制成刀片，作了金属切削加工对比试验。     

用于燃煤磁流体发电通道的Sialon绝缘材料的研究

本文研究了Sialon陶瓷的组成和工艺条件;制备了用作燃煤磁流体发电通道绝缘材料的Sialon试样;测定了Sialon陶瓷的电绝缘性、抗热震性、抗溶渣腐蚀性、电场强度、导热性和热膨胀系数等项性能。结果表明,Sialon陶瓷有良好的抗热震性、抗熔渣腐蚀性、电绝缘性、电场强度和其它物理—力学性能。Sialon陶瓷的良好性能已在静态试验和动态试验(累计试验时间分别多为85、202和85小时)中得到证实。动态试验先后于1988、1989和1990年在中国科学院电工研究所进行。静态腐蚀和动态试验结果分析表明,钾和熔渣中其它有害物质并扩散到材料内部而只聚集在试样表面。熔渣和试样之间的反应很微弱,在壁面温度很低时这种作用甚至可以忽略。电弧和熔渣粒子冲刷也会造成试样损伤。研究结果表明,Sialon陶瓷是一种很有希望的燃煤磁流体发电通道绝缘材料。     

Reaction Sintering of β-sialon／Al2O3／SiO2 Mixtures in Flowing Nitrogen at High Temperatures

β-sialon/alumina/silica mixtures were sintered in flowing nitrogen at 1500℃ and 1600℃ respectively.The sintering properties and morphology of samples were investigated by SEM, EDS and XRD. Results show that sintered properties of the samples are influenced by soaking temperatures and compositions. Bulk densities of samples are increased with the increase of the soaking temperature, whereas the apparent porosities are decreased. Mass loss of the sintered samples at 1500℃ is lower than that at 1600℃, but all the mass loss remains approximately constant with the increase of sialon content. From the point of thermodynamic analysis,Complex chemical reactions take place in samples during sintering process and the volatile of SiO (g) is responsible for the mass loss of samples. Compared to cross section microstructure of β-sialon/Al2O3/SiO2 mixtures sintered in coke powder bed consisting of the dense center with well-developed column of sialon phase, the transitional part with needle like grain nitrogen-containing phase and the loose part with short granular Al2 O3 phase, those of mixtures sintered in flowing nitrogen is of well-developed sialon in dense center and slightly loose part with sialon debris.     

Structure and properties of plasma-sprayed sialon coatings

a’-Sialon(Si₆_zAl_zO_zN_8-z, where z = 1,2,3, or 4) was plasma sprayed in air, and the structure and properties of the coating were evaluated. Coatings of the Sialon could be produced when z = 3 or 4, whereas coatings were hardly formed for Sialon with z = 1 and 2. The relative density and the Vickers hardness of the Sialon coatings (z = 3 and 4) increased with an increase in plasma power. Elemental analysis and X-ray diffractometry revealed that Sialon partially decomposed during thermal spraying. Nitrogen gas addition to the secondary plasma gas was effective in suppressing this decomposition.     

铁精粉还原炉用Si3N4（Sialon）/SiC材料在H2O—H2—N2气氛中热力学计算分析

根据热力学原理对Si—C—N—H—O五元系统进行了平衡状态下的相稳定性计算,绘制了在1 073 K和1 223 K下的SiC、Si₃N₄、Si₂N₂O和SiO₂4个稳定相的稳定性与N₂分压和H₂O分压的关系图,即优势区域图,分析了其凝聚相的稳定区域。同时结合SEM显微结构分析氢气还原炉中Si₃N₄/SiC和Sialon/SiC制品抗H₂O—H₂—N₂气氛的侵蚀性能。     

Textured silicon nitride: processing and anisotropic properties

Abstract

Textured silicon nitride (Si₃N₄) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si₃N₄, with emphasis on the anisotropic and abnormal grain growth of β-Si₃N₄, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for β-Si₃N₄ seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike β-Si₃N₄ single crystals are presented. Various anisotropic properties of textured Si₃ N₄ and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si₃N₄ with a unique microstructure composed of oriented elongated β-Si₃N₄ and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured α-Sialon is also reviewed, because the presence of elongated α-Sialon grains allows the production of textured α-Sialon using the same methods as those used for textured β-Si₃N₄ and β-Sialon.     

Al2O3-Si系原材料在氮气气氛下的高温物理化学变化过程

以电熔刚玉和单质硅为原料压制成试样，分别在氮气气氛、1400—1600℃高温反应烧结，获得五个不同温度点合成的试样，采用XRD分析技术研究试样的物相演变过程，从而对Al2O3-Si原料在氮气气氛下反应过程中的物相变化和反应过程进行了研究。结果表明：在氮气气氛条件下，经高温反应，新产生的主要物相是β—Sialon和Si3N4。同时，新生成物相β—Sialon（Si6-ZAlZOZN8-Z，0〈Z〈4．2）中的Z值与温度和原料配比密切相关。     

Sialon陶瓷与40Cr钢连接中缓冲层的作用

本文研究了Sialon陶瓷与40Cr钢活性钎焊连接中缓冲层的作用.结果发现:缓冲层材料本身可能影响活性钎料与陶瓷的界面连接强度,对Ag_(57) Cu_(38) Ti_5活性钎料,Cu和Ta是较好的缓冲层材料,而对 Kovar,Ni-15 Cr-15Co则较差;用软性缓冲层如 Cu来松弛应比用硬性缓冲层如Mo来避免应力更加重要;软性缓冲层有一个合适的厚度范围,其h/L≈0.02—0.1;采用软/硬复合缓冲层可以有效的提高接头强度。最后作者提出了设计梯度材料作为专用缓冲层材料的设想。     

粗真空条件下锡基钎料与Sialon陶瓷的润湿和连接

采用座滴法和四点弯曲方法研究了粗真空条件下锡基钎料在Ｓｉａｌｏｎ陶瓷上的润湿性和连接强度．在１Ｐａ，１１７３Ｋ，２０ｍｉｎ的实验条件下，锡基钎料的静态润湿角小于２０°．加入Ｚｎ，Ｐｂ后，钎料钎焊Ｓｉａｌｏｎ／Ｓｉａｌｏｎ陶瓷时的接头连接强度有明显提高，Ｓｎ－５Ｃｕ－５Ｔｉ，Ｓｎ－５Ｃｕ－５Ｔｉ－２０Ｚｎ，Ｓｎ－５Ｃｕ－５Ｔｉ－１０Ｐｂ的平均接头连接强度分别为９０．８，１５３．４，１６９．１ＭＰａ；最高接头连接强度分别为１１９．８，２００，２１６．７ＭＰａ．在粗真空条件下锡基钎料可以实现陶瓷的良好连接，且接头残余应力较小．本文首次观察到锡基钎料中挥发性组元Ｚｎ对粗真空条件下润湿前驱膜有明显的影响．对临界润湿温度、粗真空条件下第三组元的作用及这种活性钎料的潜在应用价值进行了讨论．