先驱体转化法制备泡沫陶瓷的发展现状

泡沫陶瓷由于具有一系列优异的性能,使得其应用范围越来越广泛,其制备方法也在不断地发展.先驱体转化法制备泡沫陶瓷是20世纪末才出现的一种新型工艺.它具有制备温度低、陶瓷组成和结构町设计、容易成型复杂构件等优点,成为目前泡沫陶瓷制备方法中的一个研究热点.根据泡沫陶瓷制备过程中成孔原理的不同,先驱体转化法制备泡沫陶瓷大致町以分为三类:(1)直接发泡法;(2)有机泡沫浸渍法;(3)添加造孔剂法.本文详细地介绍了由这三类先驱体转化法制备泡沫陶瓷的研究现状,并分析了其优缺点以及亟待解决的问题.     

碳化硅陶瓷先驱体聚甲基硅烷的研究进展

介绍了聚甲基硅烷的主要合成方法和性能,特别是其反应活性和高温热裂解性能.综述了聚甲基硅烷及其改性先驱体应用于制备碳化硅纤维、碳化硅基复合材料、多孔陶瓷材料等领域的研究进展.聚甲基硅烷作为碳化辞陶瓷先驱体,其制备简单、热解产物接近碳化硅的化学计量比,具有广阔的应用前景.未来该领域的研究重点是聚甲基硅烷的规模化合成,低成本改性聚甲基硅烷先驱体研究,聚甲基硅烷系列复合先驱体的制备等.     

生物形态多孔陶瓷的研究进展

生物形态多孔陶瓷可被用于分离膜、触媒催化载体、过滤器件和微反应器等工业领域.自然界的生物材料具有完美独特的结构形态,以其为模板经遗态转化工艺制备生物形态的多孔陶瓷,受到研究者的广泛关注.本文分别从生物模板的选材、多孔陶瓷制备工艺、反应机理和应用等4个方面,归纳和分析了近年来生物模板法制备多孔陶瓷材料的研究进展,提出了生物模板法制备多孔陶瓷工艺过程中存在的一些问题,并对该领域今后的研究和发展提出了一些建议.     

陶瓷先驱体催化裂解研究进展

有机聚合物衍生陶瓷技术具有聚合物分子可设计性强、成型容易和制备温度低等优点,已经成为陶瓷及其复合材料的主要制备技术之一。裂解是陶瓷先驱体实现从有机到无机转化的关键步骤,对目标陶瓷的组成、结构和性能有着决定性的影响。在陶瓷先驱体中添加过渡金属进行催化裂解,可以改变其裂解行为,进而调控和拓展裂解产物的结构和性能。本文从不同过渡金属对陶瓷先驱体的催化裂解作用入手,总结了陶瓷先驱体催化裂解的研究现状,探讨了催化机理,并就后续深化研究与应用提出了发展建议。     

氮化硼陶瓷先驱体研究进展

本文综述了多种氮化硼陶瓷先驱体的合成路径、合成机理、分子结构特点、物理化学特性,以及其陶瓷化过程和陶瓷产物特性.综述了当前各类先驱体的优点和存在的主要问题,展望了氮化硼先驱体今后的发展方向.并介绍了它们在先驱体转化法制备氮化硼纤维、涂层以及复合材料等方面的应用情况.     

先驱体转化法制备连续纤维增韧陶瓷基复合材料的研究进展

介绍了先驱体转化法制备连续纤维增强陶瓷基复合材料的研究现状,简要综述了聚碳硅烷、聚硅氮烷、聚硅氧烷3种先驱体的研究现状以及增强纤维的种类。分析了陶瓷基复合材料的应用现状和今后的研究方向。     

发泡工艺制备多孔陶瓷研究进展

闭孔型多孔陶瓷是一类重要的耐温隔热材料,由于其具有很好的化学稳定性、较低的热传导等优良特性,被广泛应用于众多领域。发泡工艺是制备闭孔型多孔陶瓷的主要方法,本文综述了发泡工艺制备多孔陶瓷的孔形成机理、发泡剂的类型及其近年来在多孔陶瓷制备领域的研究进展。     

多孔陶瓷的制备方法及研究现状

近年来,多孔陶瓷材料在保温、气体过滤、催化载体、分离膜、窑具、骨和牙齿的生物医学替代品,以及传感器材料等领域应用越来越广泛。针对多孔陶瓷制备工艺和性能的研究呈现快速发展的趋势,并取得了大量的研究成果。本文以多孔陶瓷的制备工艺为主线,综述了部分烧结法、牺牲模板法、复制模板法、直接发泡法和3D打印法等5种主要多孔陶瓷制备方法的发展现状与研究成果。同时也探讨了各种方法的优缺点以及未来的发展方向,为多孔陶瓷的进一步发展提供了指导和参考。     

氧化物多孔陶瓷制备工艺的研究进展

氧化铝,氧化锆等氧化物多孔陶瓷具有低密度、高比表面积、高抗压强度、低热导率和耐腐蚀等优异的物理化学性能,应用越来越广泛.本文介绍了氧化物多孔陶瓷几种较为常见的制备方法,重点综述了冷冻注模工艺和凝胶注模工艺两种制备氧化物多孔陶瓷的研究现状.最后总结了目前在制备氧化物多孔陶瓷上存在的困难,并对其发展方向提出了合理的展望.     

专利信息

正一种高开孔率多孔碳化硅陶瓷材料的制备方法本发明公开了一种高开孔率多孔碳化硅陶瓷材料的制备方法,通过将具有耐高温、抗氧化的碳化硅短纤维与碳化硅陶瓷先驱体粘结剂混合,制成水浆料,真空抽滤成型得到湿坯,随后加热干燥并固化陶瓷先驱体,最后在惰性气氛下裂解,得到碳化硅陶瓷粘结碳化硅纤维的多孔碳化硅材料。本发明制备的多孔碳化硅材料具有开孔率高、比表面高、透气性好、机械强度高,抗热冲击、耐腐蚀     

Recent developments in gelcasting of ceramics

Gelcasting is a well-established colloidal processing method with a short forming time, high yields, high green capacity and low-cost machining, and has been used to prepare high-quality and complex-shaped dense/porous ceramic parts. In this article, we reviewed recent developments in gelcasting technology for ceramic preparation. For environmental pollution reduction during ceramic preparation by gelcasting, the development of low-toxic and nontoxic gelcasting systems is discussed. The occurrence and control of inner stress and surface-exfoliation in ceramic green bodies prepared by gelcasting are analyzed, and then some methods to control and eliminate the inner stress and surface-exfoliation in ceramic gelcast green bodies, especially for colloidal injection molding of ceramics (CIMC) are proposed. Finally, the applications of gelcasting for the fabrication of porous ceramics and complex-shaped ceramics (e.g., microbeads, rutile capacitor, thin-wall rutile tube, refractory nozzle) are summarized.     

Processing and 3D printing of SiCN polymer-derived ceramics

Preceramic polymer resins are attractive for the 3D printing of net-shaped ceramic components. Recently various processes have been demonstrated for 3D printing of polymer-derived ceramics (PDCs). Ultimately in these processes, the process outcomes strongly depend on the process parameters. In particular, for PDCs the ceramic density, and ceramic yield are affected by the catalyst concentration and cross-linking duration. Here, we use thermal analysis and FTIR to quantify the interrelation of the process parameters on the process outcome for polysilazanes and demonstrate 3D printing of PDC components based on the best-identified process parameters. The results of this work can be used as guidelines for future additive manufacturing of PDCs.     

Fabrication of dense SiSiC ceramics by a hybrid additive manufacturing process

In this work, we report the fabrication of Silicon infiltrated Silicon Carbide (SiSiC) components by a hybrid additive manufacturing process. Selective laser sintering of polyamide powders was used to 3D print a polymeric preform with controlled relative density, which allows manufacturing geometrically complex parts with small features. Preceramic polymer infiltration with a silicon carbide precursor followed by pyrolysis (PIP) was used to convert the preform into an amorphous SiC ceramic, and five PIP cycles were performed to increase the relative density of the part. The final densification was achieved via liquid silicon infiltration (LSI) at 1500°C, obtaining a SiSiC ceramic component without change of size and shape distortion. The crystallization of the previously generated SiC phase, with associated volume change, allowed to fully infiltrate the part leading to an almost fully dense material consisting of β-SiC and Si in the volume fraction of 45% and 55% respectively. The advantage of this approach is the possibility of manufacturing SiSiC ceramics directly from the preceramic precursor, without the need of adding ceramic powder to the infiltrating solution. This can be seen as an alternative AM approach to Binder jetting and direct ink writing for the production of templates to be further processed by silicon infiltration.     

Poly(methylsilane)—A High Ceramic Yield Precursor to Silicon Carbide

Preceramic polymers offer exceptional potential for low-temperature processing of both oxide and non-oxide ceramics. In addition, shapes such as fibers, films, and membranes that are not commonly available using standard processing techniques are readity available using preceramic polymers. In non-oxide ceramics, the ceramic products generally available from preceramics do not exhibit all of the typical properties associated with the same materials produced by standard, high-temperature processing approaches. In part, this appears to be because there are very few preceramic polymers that lead to high-purity, single-phase materials. Poly(methylsilane), (–[MeHSi] _x –), produced from MeSiH₃, can be used to produce relatively pure, bulk SiC at temperatures below 1000°C. The transformation process from polymer to ceramic is followed by ²⁹Si NMR and diffuse reflectance IR. The polymer first undergoes a major rearrangement from poly(silane) to poly(carbosilane) at 400°C. Above 400°C, the resulting poly(carbosilane) decomposes to a hydrogenated form of SiC as shown by spectroscopic analysis of the 600°C material. Further heating, to 1000°C for 1 h, provides very narrow ²⁹Si peaks indicative of β-SiC mixed with small amounts of α-SiC polytypes. Chemical analysis, when coupled with the ²⁹Si and XRD results, suggests that poly(methylsilane) produces resonably pure, nanocrystalline SiC at temperatures much lower than previously observed for other SiC preceramic polymers.     

Investigation of Strut Crack Formation in Open Cell Alumina Ceramics

An investigation was made into the source of strut cracking during the fabrication process of open cell ceramics that are produced by coating a polymeric foam. Several sources for the stress that produces these cracks were considered, viz., differential drying, thermal expansion mismatch between the polymer and the green ceramic coating, and the gas pressure produced by pyrolysis of the organic skeleton. Thermogravimetric analysis of the polymeric foam was used to estimate the gas evolution rate associated with the pyrolysis process, but this was found to be very low compared to the pressures required to cause strut damage. SEM observations on samples taken by interrupting the fabrication procedure showed the cracks were not produced during drying but rather at a temperature near the melting/decomposition point of the polymer and prior to pyrolysis. It was then deduced that the differential thermal expansion between the polymer and the ceramic coating was the source of the stress. The strut cracking is observed to occur primarily in the region of the highly curved strut edges of the polymer foam, at which the ceramic coating is often rather thin. Techniques to change the processing procedure to overcome the strut cracking are discussed.     

环氧树脂含量对激光选区烧结制备多孔煤系高岭土陶瓷性能的影响

目前,我国对煤系高岭土资源的整体深加工技术水平较低,导致了资源浪费和环境污染。本文分别以煅烧煤系高岭土和环氧树脂为原料和粘结剂,利用激光选区烧结工艺制备多孔煤系高岭土陶瓷,研究了环氧树脂含量对多孔煤系高岭土陶瓷性能的影响。研究表明,制备的多孔煤系高岭土陶瓷主要物相为莫来石和方石英,其孔隙分布均匀。随着环氧树脂质量分数从10%增大到25%,多孔煤系高岭土陶瓷素坯的抗弯强度由0.17 MPa增大到0.32 MPa,多孔煤系高岭土陶瓷的抗弯强度由2.81 MPa减小到0.82 MPa,其气孔率由50.37%增大到59.69%。以煤系高岭土为原料,采用激光选区烧结工艺制备多孔陶瓷对煤系高岭土资源的开发利用具有较为重要的意义。     

先驱体裂解制备陶瓷材料中存在的问题及解决方案

阐述了先驱体转化法的优劣性,并针对存在的问题提出了解决方案,着重阐述了添加活性填料的作用,介绍了活性填料的选择原则及活性填料控制先驱体裂解制备陶瓷材料应用特征,并就国内外的研究进展和未来发展方向进行了综述。     

Processing route dramatically influencing the nanostructure of carbon-rich SiCN and SiBCN polymer-derived ceramics. Part I: Low temperature thermal transformation

In this study, the significant effect of the processing route on the nanostructure evaluation of carbon-rich SiCN and SiBCN polymer-derived ceramics is reported. For the first time, bulk carbon-rich SiCN and SiBCN ceramics are successfully produced by warm pressing of polyphenylvinylsilylcarbodiimide and polyborophenylsilylcarbodiimide. The bulk samples were compared with their analogous powder samples with respect to the developed nanostructure. Representative temperatures of 1100 and 1400 °C were chosen in order to investigate the effect of processing route used on the crystallization behavior of those samples. As the solid-state structure of polymer-derived ceramics (PDCs) is highly sensitive to the molecular structure of the precursor, the variation of processing route and pyrolysis temperature during the polymer to ceramic transformation and decomposition enables to alter the nanostructure of PDCs. It was found that the bulk carbon-rich SiCN and SiBCN ceramics show an improved thermal stability against crystallization as compared to their powder analogues.     

Fabrication of Porous SiC Ceramics with Special Morphologies by Sacrificing Template Method

Sacrificial template technique is widely used in producing porous materials with controlled morphologies and tailored properties. In this paper, unique templates such as filters, carbon nanotube, carbon fiber and silica were used to make porous SiC ceramic with special morphologies. Template derived porous ceramic plates, SiC nano-net, fiber-inverse and bead-inverse porous SiC ceramic were successfully prepared from the preceramic precursor, polymethylsilane (PMS). The synthesis procedures were involved with the infiltration of the templates with appropriate concentration of the preceramic polymer, their curing, pyrolysis and subsequent template removal. The synthesized porous SiC was characterized by SEM, TEM, XRD and BET methods.