活性填料铝在聚碳硅烷裂解陶瓷中的应用

研究了活性填料铝（Ａｌ）在聚碳奎烷（ＰＣＳ）先驱体裂解陶瓷中的应用。研究表明：活性填料Ａｌ能有效降低陶瓷素坯的气孔率及其在裂解过程中的收缩率;素坯在裂解后线收缩率为０;Ａｌ可与Ｎ２气氛反应生成氮化物,可明显提高ＰＣＳ的陶瓷产率,此外,它还能有效地提高烧成体的强度,当φ（Ａｌ）：φ（ＰＣＳ）＝６０％时,烧成体的三点弯曲强度达２１２ＭＰａ。     

活性填料对聚碳硅烷裂解陶瓷性能的影响

研究了裂解温度对活性填料Al-聚碳硅烷裂解陶瓷的线收缩率、陶瓷产率、力学性能等的影响，研究表明，随着裂解温度升高，材料的线收缩率，陶瓷烧成体的密度、陶瓷产率、力学性能和微观结构均随温度升高而发生变化，活性填料Al在先驱体裂解过程中熔融并反应生成AlN，从而提高了体系的陶瓷产率，反应产生体积膨胀效应，抑制了坯体在裂解中的线收缩率，所形成的微观结构有利于提高材料的力学性能，当裂解温度为10000℃时，体系的陶瓷产率约为115%，体系的线收缩为-0.97%，材料的三点弯曲强度约为212MPa，而不含活性填料体系的陶瓷产率，烧结收缩率和三点弯曲强度分别为65%，1.49%和64MPa。     

化学络合法在溶胶—凝胶过程中的应用

在利用溶胶－凝胶技术制备先进玻璃及陶瓷时，经常碰到诸如这样一些问题：金属醇盐先驱体在醇中的溶解度小；反应活性大，易生成沉淀；而且一些醇盐很难直接买到。化学络合物方法可以克服这些缺点。本文阐述了添加络合剂的络合方法在溶胶－凝胶上的应用，包括如下几个方面：（１）改变一些醇盐的溶解度，使之溶解在醇溶剂中；（２）控制先驱体的反应活性；（３）变非醇盐先驱体为醇盐先驱体；（４）合成有机－无机复合材料；（５）通     

化学络合法在溶胶－凝胶过程中的应用

在利用溶胶－凝胶技术制备先进玻璃及陶瓷时，经常碰到诸如这样一些问题：金属醇盐先驱体在醇中的溶解度小；反应活性大，易生成沉淀；而且一些醇盐很难直接买到。化学络合物方法可以克服这些缺点。本文阐述了添加络合剂的络合方法在溶胶－凝胶上的应用，包括如下几个方面：（１）改变一些醇盐的溶解度，使之溶解在醇溶剂中；（２）控制先驱体的反应活性；（３）变非醇盐先驱体为醇盐光驱体；（４）合成有机－无机复合材料；（５）通过络合剂的作用合成一些易潮解的凝胶；最后讨论了络合物凝胶的分子设计等问题。     

关于橡胶补强的新进展

分别阐述了溶胶-凝胶工艺原位生成的填料和碳纳米管等材料对强性体的补强作用,并与粘土填料的补强效果进行了对比。     

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.     

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.     

纤维用含硼SiC陶瓷先驱体的研究进展

综述了硅硼碳(SiBC)先驱体、硅硼碳氧(SiBCO)先驱体和硅硼碳氮(SiBCN)先驱体等纤维用含硼碳化硅(SiC)陶瓷先驱体的合成方法,分析了不同陶瓷先驱体的组成、结构和性能,比较了几种合成含硼SiC先驱体方法的优缺点,提出了纤维用含硼SiC陶瓷先驱体的合成新思路。     

Si-Al-C-N陶瓷先驱体研究进展

Si-Al-C-N陶瓷具有较好的耐高温、抗氧化以及抗蠕变等性能。综述了近年来Si-Al-C-N陶瓷先驱体及其裂解陶瓷的研究进展,介绍了合成Si-Al-C-N先驱体的3种主要方法及相应先驱体及其裂解陶瓷的性能,并对今后的研究方向做出了展望。     

复相铁氧体空心球的制备

用丙烯酸、氨水作缓冲络合剂,以氨水作沉淀剂,合成了复相铁氧体空心球的先驱体,利用IR对先驱体反应机理进行了探讨;通过喷雾干燥、火焰喷烧方法制备了复相铁氧体空心微球.并利用SEM、XRD对试样进行了结构分析和表征,研究了预热处理先驱体及回火对空心球组成和形貌的影响.     

聚合物制备工程陶瓷的研究概况

随着聚碳硅烷、聚硅氮烷、聚硅氧烷以及聚硅硼烷等先进前驱体材料的开发,由含硅陶瓷预制体聚合物制备的工程陶瓷在Si-O-C-N-B体系中占有重要的地位。耐高温的SiC和SiN陶瓷纤维增强陶瓷基复合材料(CMC)已在航空、航天结构中获得应用,而耐中、低温的新型涂层、单向带,泡沫和复杂形状的构件在未来将在能源、环境、运输和通讯领域占有重要的地位。综述了陶瓷预制体聚合物的合成、聚合物制备陶瓷的性能、聚合物制备陶瓷的方法以及影响聚合物热解的主要因素。     

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。     

Polymer derived ceramics with β-eucryptite fillers: A novel processing route to negative and near zero expansion materials

A polymer derived ceramic with near-zero or negative thermal expansion was manufactured from a powder mixture consisting of β-eucryptite fillers having a negative thermal expansion, and a polymethylsilsesquioxane preceramic polymer. The composite starting material was manufactured by ball-milling and warm-pressing and pyrolysis in inert atmosphere. The thermal expansion behavior of the composite material was controlled via the filler volume fraction and via the pyrolysis temperature. An influence of the filler material on the pyrolysis process was found.     

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.     

Fabrication of ceramic particles from preceramic polymers using stop flow lithography

Stop flow lithography (SFL) combines aspects of microfluidic and photolithography to continuously fabricate particles with uniform planar shapes as dictated by a mask. In this work we aim to expand the palette of materials suitable for SFL processing by investigating the use of UV-crosslinkable preceramic polymers to make ceramic particles. A commercially available methacrylated-polysiloxane was used as the preceramic polymer and was mixed with 2.5 wt% Irgacure 651 photoinitiator. A simple SFL system was assembled to continuously fabricate UV-crosslinked preceramic polymer particles in the shape of hexagons, triangles, and gears with diameters ranging from 100 to 200 μm and thicknesses of 74 μm +/- 4 μm. Particles were harvested from the excess preceramic solution, cleaned and then pyrolyzed at 1000 °C to transform them into silicon oxycarbide ceramic particles. Particle shape was maintained during pyrolysis despite a ～80 % linear shrinkage due to the removal of acryl and methyl side groups, as confirmed via FTIR. After pyrolysis the outer diameters of the SiOC particles ranged from 20 to 40 μm with thicknesses of 10 μm–12 μm. Pyrolyzed particles were successfully recovered and dispersed in water. This work demonstrates a robust path for the fabrication of ceramic particles with specific shapes from preceramic polymers via SFL.     

Multiple metals doped polymer-derived SiOC ceramics for 3D printing

Multiple metals doped polymer-derived SiOC ceramics with octet truss structure were prepared by employing a photosensitive methyl-silsesquioxane as preceramic polymer through sol-gel method and Digital Light Processing 3D printing. The physical and chemical properties of the preceramic polymers and printed octet truss structure SiOC ceramics were investigated. Results show that the organosilicon preceramic polymers have outstanding photocuring properties and could transform into amorphous SiOC ceramics at 800–1200?°C. It is illustrated that the excellent mechanical properties of SiOC ceramics with octet truss structure (after 3D printing and pyrolysis) are attributed to the metal elements pinning in the amorphous matrix on the atomic level. Doping other metal elements such as Fe, Ni, Co, Pt, etc, is thought to bring promising properties for the lattice structure SiOC ceramics and potentially further expand its applications in the future.     

Additive manufacturing of silicon carbide by selective laser sintering of PA12 powders and polymer infiltration and pyrolysis

In this work, we propose a novel hybrid additive manufacturing technique, which combines selective laser sintering (SLS) of polyamide powders and subsequent preceramic polymer infiltration and pyrolysis to manufacture Silicon Carbide components for complex architectures. By controlling the porosity of the sintered polymeric preform we are able to control the shrinkage upon the first infiltration and pyrolysis. This enabled the manufacturing of smaller features than those achievable with other manufacturing techniques. The mechanical strength of the resulting ceramic increased with the number of reinfiltration cycles up to 24 MPa, inversely the residual porosity decreased to 10 vol%. The microstructure showed two distinct phases of SiOC and SiC. The first was attributed to the interaction between the porous polyamide and the ceramic precursor during the first infiltration. SiC derived from the pyrolysis of the preceramic precursor alone.     

先驱体转化法制备多孔陶瓷的研究现状

多孔陶瓷作为重要的陶瓷材料,广泛应用于冶金、化工等众多领域,其制备工艺的改进一直是研究重点。先驱体转化法是20世纪末提出的制备多孔陶瓷新型工艺,利用陶瓷先驱体高温裂解产生气体的特性,可将其作为粘结剂、骨料、发泡剂制备多孔陶瓷,具有成型工艺简单,烧成温度低等特点,拥有广泛的应用前景。本文主要从以上几个方面简要介绍先驱体转化法制备多孔陶瓷的工艺、结构和性能的研究现状。     

Chemical modification of preceramic polymers: Their reactions with transition metal complexes and transition metal powders

Conclusions This research has demonstrated that a variety of chemistries can be carried out with preceramic polymers that in general are characterized by the presence of an abundance of reactive functional groups. Such chemistries can serve to upgrade a given preceramic polymer by catalytic or stoichiometric processes; they can be used to from new and useful hybrid polymers from the original preceramic polymer, as shown in the present work and also in some of our previously published work; they can, by their pyrolysis in the presence of metal powders, act as chemical reagents that deliver the elements of interest for reaction with the metal to give useful ceramics. Thus the preparation of a preceramic polymer is not the end of the chemistry in the monomer-to-polymer-to-ceramic conversion, but rather it presents many possibilities for further chemistry.     

Optimized preceramic polymer for 3D structured ceramics via fused deposition modeling

3D structured ceramics stemmed from preceramic polymers via additive manufacturing have attracted much attention recently. However, these polymers with high ceramic yield are so brittle that extrusion-based additive manufacturing techniques are hardly able to be utilized for assembling 3D structures. Herein, we developed a strategy to prepare feedstocks for these manufacturing techniques, i.e., utilizing a small amount of thermal-plastic polymer to optimize the preceramic polymer while good compatibility is required between the two polymers to ensure a homogeneous mixture. Polycarbosilane and polypropylene were selected as the representative materials. Polypropylene occupied a small proportion (≤5wt.%) and significantly improved the formability of the precursor. Three-dimensional SiC were obtained via fused deposition modeling combined with crosslinking and pyrolysis. The SiC ceramic filaments showed a mean tensile strength of 471 MPa. The strategy is also applicable to a large field of ceramic systems with corresponding precursor, such as sialon ceramic and multicomponent Si-based ceramics.