碳化硅泡沫陶瓷的制备工艺研究进展

本文概述了碳化硅泡沫陶瓷的主要应用领域,着重介绍了近年来碳化硅泡沫陶瓷的制备工艺,并评述了其优缺点,最后针对目前的不足提出了碳化硅泡沫陶瓷未来的发展方向.     

泡沫陶瓷材料的研究进展

介绍了泡沫陶瓷的特性、制造工艺，并列举了泡沫陶瓷在几个方面的主要应用。指出了当前陶瓷材料的研究热点和今后发展需要解决的问题。     

泡沫陶瓷材料的研究进展

介绍了泡沫陶瓷的特性、制造工艺，并列举了泡沫陶瓷在几个方面的主要应用。指出了当前陶瓷材料的研究热点和今后发展需要解决的问题。     

碳化硅陶瓷材料的制备工艺和应用研究进展

碳化硅陶瓷材料由于具有轻质高强、导热性能好、膨胀系数低、硬度高、抗氧化等优异的性能,被广泛用作高温结构部件。本文围绕碳化硅材料在光学反射镜材料的应用,对碳化硅材料的制备工艺和应用方面的进展作简要综述。     

泡沫陶瓷材料制备方法及应用的研究进展

分析了泡沫陶瓷广泛的应用前景，总结了泡沫陶瓷的分类方法和特点，详细介绍了其生产制备的工艺方法和典型应用，最后提出了我国泡沫陶瓷工业的发展需要注意的问题。     

碳化硅致密陶瓷材料研究进展

碳化硅材料以其优异的性能得到了越来越广泛的应用,通过简要介绍碳化硅致密陶瓷的制备方法及其性能和总结近年来国内外的研究进展,来展望碳化硅致密陶瓷材料的研究发展趋势。     

金属过滤器用高性能碳化硅泡沫陶瓷的制备

介绍了一种适用于大规模工业化生产高强度金属过滤用碳化硅泡沫陶瓷的方法。采用商用SiC粉体和聚氨酯泡沫通过2次挂浆工艺可以制备出最大平均抗弯强度达到2．87 MPa,平均孔径在3 mm左右,同时具备优良的抗热震性能和高达1700℃耐火度的碳化硅泡沫陶瓷。探讨了浆料的牯度、流变性能对挂浆性能的影响及第2次挂浆对强度的增强机理,说明1次浆料的触变性能和适当固相含量的2次浆料是高强度泡沫陶瓷制备的关键,而2次挂浆工艺对强度提高的主要贡献来源于第2次浆料对1次挂浆烧结后留下空洞的有效弥补。     

泡沫陶瓷材料的制备及多功能性

泡沫陶瓷是一种重要的多孔材料,由众多的气孔在空间通过各种方式排列而成,因其特殊的结构具有多功能性。根据国内外最新文献,本文综述了泡沫陶瓷材料的制备方法,介绍了泡沫陶瓷优异的过滤与分离性、吸声性、隔热性等多种功能性。     

泡沫陶瓷的研究进展

本文介绍了泡沫陶瓷的特性和制造工艺，并列举了泡沫陶瓷在的主要应用领域，指出了当前陶瓷材料的研究热点和今后要解决的问题。     

Innovation in ceramic foam filters manufacturing process

Ceramic filters have singular properties such as high permeability and specific surface area associated to low density. Some examples of their use can be found in liquid metal deep filtration, water treatment, air purification, and others. These particular properties are dependent on the filters' manufacturing process. One of the most used techniques to produce filters is the replication method, which provides a tridimensional network of struts and interconnected pores. However, a common issue of all ceramic filters produced by this technique is their low mechanical strength due to the hollow struts and microcracking generated during the thermal decomposition of the sponge. Intending to address this limitation and produce filters with higher mechanical strength, this paper analyzed a modified process route for manufacturing filters. Samples of preheated Al₂O₃ filters were vacuum infiltrated with ceramic suspensions (Al₂O₃ and SiO₂) of different solids concentrations (15-40 wt%), particle size distribution (nano to micrometric size) at distinct processing times (1-5 minutes). The data analysis indicated that the best balance among mechanical strength, mass, and strut thickness was achieved by infiltration with SiO₂ colloidal suspension (40 wt%) per 1 minute. SEM analysis confirmed that the struts were filled and microcracks were sealed with colloidal particles.     

Synthesis of a foam ceramic based on ceramic tile polishing waste using SiC as foaming agent

Due to the large amount of ceramic tile polishing waste generated in China, the recycling of this waste residue becomes important. Herein a foam ceramic was successfully produced by using ceramic tile polishing waste as main raw material. In this research, SiC was added as the foam agent, and the foaming mechanism was also investigated. The results showed that the best dosage of SiC was 1%. Furthermore, in order to obtain a foam ceramic with better structure, the sodium phosphate was added in raw materials as foam stabilizer. The influence of this addition on the microstructure and properties of foam ceramic was investigated. It was found that the optimum additive amount of sodium phosphate is 2–3%.     

Processing,properties and microstructure of SiC foam derived from epoxy-modified polycarbosilane

SiC foams having controlled porosity were fabricated using epoxy modified polycarbosilane (EMPCS). The EMPCS was synthesized by refluxing adequate amount of epoxy and polycarbosilane (PCS) in THF solution at 150 °C. The EMPCS having epoxy content of 0%, 10% and 20% by weight were termed as PCS, 10EMPCS and 20EMPCS respectively. Thermal foaming of the EMPCS was carried out at 1000 °C under inert atmosphere followed by ceramization at 1200, 1400 and 1600 °C under vacuum. The cell size of the ceramized SiC foam was found to be varying between 100 and 700 µm. The ceramized SiC foams were characterized for their density, porosity and compressive strength. Total porosity was found to be 81.8 ± 3.9, 87 ± 4.1 and 90.6 ± 4.6% for the PCS, 10EMPCS and 20EMPCS based SiC foams while their bulk densities were found to be 0.6 ± 0.03, 0.4 ± 0.02 and 0.3 ± 0.01 g/cc respectively. Compressive strength was found to be the highest for the SiC foams ceramized at 1600 °C for all the types of EMPCS. The compressive strength of the 10EMPCS is found to be 2.2 ± 0.2 MPa, 2.5 ± 0.2 MPa and 3.8 ± 0.3 MPa for the foams pyrolyzed at 1200 °C, 1400 °C and 1600 °C respectively while the strength was 1.9 ± 0.1 MPa, 2.1 ± 0.2 MPa and 2.9 ± 0.2 MPa for the 20EMPCS based SiC. The 20EMPCS based SiC foam of thickness 10 mm was exposed to oxy-acetylene flame for 120 s, back face temperature was found to be around 300 °C. Microstructure and phase analysis was carried out to understand the effect of epoxy content and ceramization temperature on physical, mechanical and thermal properties of different types of the SiC foams.     

Polymer-derived SiC ceramic aerogels with in-situ growth of SiC nanowires

Herein, the SiC ceramic aerogels with in-situ growth of SiC nanowires (SiC_w/SiC CAs) have been synthesized by polymer‐derived ceramics (PDCs) method. The morphology, microstructure, and phase composition of the as-prepared samples were systematically investigated through SEM, XRD, TEM, Raman spectrum, FT-IR spectrum, and XPS spectrum techniques. The results showed that the as-obtained SiC_w has a diameter of about 80 nm and a length of 1–3.5 μm. In addition, the formation mechanism and evolution process of growth SiC_w were systematically studied using a VLS growth mechanisms. The way in this work could be expanded to synthesize other Si-based porous ceramic aerogel nanostructed with nanowires.     

Effect of adding of SiC particulate on the microstructure and shear strength of SiC ceramic joint brazed with Si-24Ti alloy

In order to refine the grain size of TiSi₂ silicide and reduce the formation of micro-defects in the joint, and thereby increasing the joint strength of SiC ceramic brazed with Si-24Ti (wt.%), a small amount of SiC particulates were added in the brazing alloy. The microstructure and mechanical strength of SiC joints was investigated by using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectrometer, and shear strength test. The results indicated that SiC particulates enhanced the nucleation and grain refinement of the TiSi₂ and Si phase. The adding of appropriate content of SiC (<1 wt.%) could effectively refine the size of TiSi₂ phase and increase the fraction of Si-TiSi₂ eutectic zone. However, excess addition of 1.5 wt.% SiC caused the coarsening of TiSi₂ phase due to the clustering of added fine SiC particulates. With the increasing of SiC particulate content, the shear strength of the joints increased at first and then decreased. The maximum shear strength of 106.3 MPa of SiC joint was obtained for the joint brazed with 1 wt.% SiC addition, which was ~19% higher than that of the joint brazed without SiC particulates.     

SiC_f/Ti复合材料在航空发动机中的应用进展

综述了碳化硅纤维增强钛基(SiCf/Ti)复合材料国外的研究和应用现状,以及SiCf/Ti复合材料制备技术的研发进展,分析了这类先进复合材料优越的力学性能。综述分析表明,SiCf/Ti复合材料具有较高的比强度和比刚度、高的抗疲劳和抗蠕变特性,在未来航空发动机上有广阔的应用前景。同时指出,由于目前SiCf/Ti复合材料制备成本昂贵,其应用进展受到严重制约,建议对该材料大力开展系统性应用研究。     

聚合物稳泡剂耐温性研究进展

在油气井开发过程中,虽然对稳泡剂的稳泡效果认识较早,但很少对其耐温性能进行对比研究,随着油气资源找寻方向由浅层油藏逐渐转变为高温油藏、裂缝型以及低渗油藏,聚合物稳泡剂的耐温性能成为重要研究课题。该文对稳泡剂的3个主要施工领域:泡沫压裂液稳泡剂、泡沫驱油稳泡剂、泡沫洗井液稳泡剂的耐温性进行对比分析,阐述了其在油田应用中的优势与不足,针对国内外聚合物稳泡剂耐温性差、稳泡效果不明显、合成过程复杂等问题,提出改进合成工艺、纳米复配、功能性单体自组装等建议,来达到提高聚合物耐温性与稳定性的目的。     

Joining of SiC ceramic by using the liquid polyvinylphenylsiloxane

ABSTRACT

The joining of SiC ceramic using the liquid polyvinylphenylsiloxane at the high temperature was investigated. The characteristic evolution of polyvinylphenylsiloxane during heating process, shear strength and microstructure of joint were especially discussed. The results show that active groups Si-OH and CH=CH₂ of polyvinylphenylsiloxane through cross-linking at low temperature (200°C) form the macromolecular structure, crosslinked polyvinylphenylsiloxane possess the higher ceramic yield and structure stability at high temperature. Shear strength of SiC joints increase with the joining temperature from 1000 to 1200°C, and then decrease when the joining temperature reaches to 1350°C. Combination with microstructure of fine grains of SiO₂ and SiC dispersion in the Si–O–C ceramic of the join layer and new phase SiC formation on the joint interface through the gas–solid reactions, the shear strength of joint achieves the maximum at 1200°C. The defects of joint increase with temperature higher than 1200°C, and the shear strength of joint begin to decrease.     

Study on crosslinking of polymers and joining mechanism of SiC ceramic

ABSTRACT

Based on crosslinking of polymers with different vinyl contents at low temperature and pyrolysis of the polymer at high temperature, joining temperature and impregnation cycles of an SiC joint were discussed. Polyvinylphenylsiloxane as the polymer with active groups of Si–OH and CH=CH₂ by crosslinking enhances ceramic yield and thermal stability. The microstructure of the polymer changes from amorphous ceramic into grains of SiO₂ and SiC, grains can dispersion strengthening enhances strength of joint layer. Shear strength of SiC joints reaches the maximum at 1200°C. A relatively good interface between the SiC substrate and pyrolysis product of the polymer is formed, but there exist loose cracks or voids in the joint layer which affect the shear strength of the joint. The shear strength of the SiC joint reaches 69.2?MPa through seven times of vacuum impregnation/pyrolysis enhancement. According to the microstructure and properties of the SiC joint, the pyrolysis mechanism of the joining layer as part of the joint by using polyvinylphenylsiloxane is explained.