异质元素改性聚硅氧烷衍生SiOC陶瓷研究进展

有机聚合物衍生陶瓷(PDCs)技术是陶瓷材料的主流制备技术之一。作为制备高性价比陶瓷材料的理想原料,聚硅氧烷(PSO)衍生SiOC陶瓷得到很好的发展。通过异质元素改性可进一步提高SiOC陶瓷的热稳定性和拓展功能特性,成为近年来的研究热点。本文在介绍SiOC陶瓷微观结构的基础上,分别从提高热稳定性和拓展功能特性的角度,综述了异质元素改性PSO衍生SiOC陶瓷的研究现状。结合原子局部化学环境的演化行为来揭示异质元素的作用机制以及加强改性SiOC陶瓷的应用研究是后续研究需要重点关注的问题。     

低温分相法制备高比表面积微/介孔SiOC陶瓷（英文）

以含氢聚硅氧烷(PHMS)、四甲基四乙烯基环四硅氧烷(Dvi4)和铂络合物为原料,采用热交联合成交联体,通过水蒸汽辅助热解促进前驱体低温分相及后续HF对SiOC陶瓷侵蚀基础上,获得高比表面积微/介孔SiOC陶瓷。采用XRD、FT-IR、SEM和BET等测试技术对试样的物相组成、化学键、微观结构、比表面积和孔径分布等进行了表征。实验结果表明,水蒸气能够促进前驱体低温分相,使SiOC陶瓷中生成Si-O-Si键、SiO_2纳米畴和SiO_2纳米晶,这些可以作为造孔剂而被HF侵蚀,从而提高了SiOC陶瓷的比表面积。在热解温度1300℃条件下,微/介孔SiOC陶瓷具有最大比表面积1845.5 m2/g,孔径分布2.0～10 nm。     

低温分相法制备高比表面积微/介孔SiOC陶瓷

以含氢聚硅氧烷(PHMS)、四甲基四乙烯基环四硅氧烷(D₄ ^vi)和铂络合物为原料, 采用热交联合成交联体, 通过水蒸汽辅助热解促进前驱体低温分相及后续HF对SiOC陶瓷侵蚀基础上, 获得高比表面积微/介孔SiOC陶瓷。采用XRD、FT-IR、SEM和BET等测试技术对试样的物相组成、化学键、微观结构、比表面积和孔径分布等进行了表征。实验结果表明, 水蒸气能够促进前驱体低温分相, 使SiOC陶瓷中生成Si-O-Si键、SiO₂纳米畴和SiO₂纳米晶, 这些可以作为造孔剂而被HF侵蚀, 从而提高了SiOC陶瓷的比表面积。在热解温度1300℃条件下, 微/介孔SiOC陶瓷具有最大比表面积1845.5 m²/g, 孔径分布2.0~10 nm。     

激光裂解含二茂铁的聚硅氧烷制备SiOC(Fe)陶瓷涂层研究

激光裂解聚合物先驱体在金属表面制备性能优异的陶瓷涂层,解决了金属本身存在的耐磨防腐蚀性能不足的问题,已成为一种行之有效的方法。采用激光裂解含二茂铁的聚硅氧烷制备了SiOC(Fe)陶瓷涂层,采用电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱(XPS),分析了激光裂解含二茂铁的聚硅氧烷生成物的组成与结构,并初步研究了其裂解机理。结果表明:在激光作用下,含二茂铁的聚硅氧烷在激光裂解过程中会发生非平衡态的自由基化学反应,生成的陶瓷涂层主要由晶态的SiC、Fe_3C,非晶态的SiO_2、Fe_2O_3、Fe_3O_4以及C单质、C_6H_(18)OSi_2等物质组成,由二茂铁激光裂解生成的Fe_2O_3、Fe_3O_4、Fe_3C相对制备的陶瓷涂层孔隙具有填补作用。二茂铁质量分数越大,陶瓷涂层表面越平整致密,孔隙越少。     

聚硅氧烷转化制备硅氧碳多孔陶瓷的研究进展

硅氧碳多孔陶瓷耐高温,密度低,比强度高,比表面积大,热导率低,介电性能优良,应用前景广阔。聚合物前驱体转化法已成为颇具前景的陶瓷材料制取手段。文章在简要介绍聚硅氧烷的基础上,从聚硅氧烷热解前、热解过程中以及热解后不同阶段形成特定的孔结构出发,重点阐述了通过聚硅氧烷热解制备硅氧碳多孔陶瓷的工艺研究现状,并提出了亟待解决的问题。     

先驱体法聚硅氧烷制备SiCf/Si-O-C复合材料的性能研究

以聚硅氧烷为先驱体,采用先驱体转化法制备SiCf/Si-O-C复合材料.研究了吸收剂含量不同对复合材料的弯曲强度、密度、热膨胀系数的影响,同时测试了材料对雷达波的反射率,结果表明低频带区有良好的吸波性能.对材料微观结构进行了分析讨论,发现界面结构与致密度是SiCf/Si-O-C复合材料具有高性能的主要原因.     

制备工艺对SiCf/Si-O-C复合材料弯曲强度的影响

以聚硅氧烷为先驱体，采用先驱体转化法制备SiCf／Si-O-C复合材料。研究制备工艺参数模压压力、裂解时升温制度、裂解温度、保温时间对材料的力学性能的影响。通过对复合材料微观结构的分析研究，发现界面结构与致密度是影响SiCf／Si-O-C复合材料性能的主要因素。     

陶瓷/石墨烯块体复合材料的研究进展

石墨烯是2004年首次成功制备的新型二维碳纳米材料。由于其独特的二维结构和优异的性能, 近年来已成为国内外材料领域的研究热点。本文结合本课题组的相关工作, 综述了石墨烯应用于陶瓷块体复合材料的新近研究成果,包括碳纳米管、SiOC、Al₂O₃以及Si₃N₄等为基体的石墨烯块体复合材料,重点介绍了陶瓷/石墨烯块体复合材料的制备方法、增韧机制以及优异的物化性能, 并探讨了陶瓷/石墨烯块体复合材料的研究发展方向和应用前景。     

硅基陶瓷前驱体用于耐高温连接材料研究进展

硅基陶瓷前驱体聚合物具有与一般高分子聚合物相似的加工工艺特性,并可在高温下转化为陶瓷材料,在航空航天等领域有着广泛的应用。与传统的机械连接、焊接等连接技术相比,硅基陶瓷前驱体应用于耐高温连接材料具有工艺简单、应力分布均匀、连接温度低等优势。陶瓷前驱体用于连接材料可分为两种情况：经固化及高温热解处理后再使用的连接材料称为耐高温连接剂;固化后不经热解而直接使用的连接材料称为耐高温胶粘剂。本文对包括聚碳硅烷、聚硅氮烷和聚硅氧烷在内的硅基陶瓷前驱体用作耐高温连接剂和耐高温胶粘剂的研究进展分别进行了概括总结,并对其优缺点进行了分析,最后指出了硅基陶瓷前驱体用于耐高温连接材料研究仍存在的问题和今后的发展方向。     

先驱体转化法制备连续纤维增韧陶瓷基复合材料的研究

综述了先驱体转化法制备连续纤维增韧陶瓷基复合材料在先驱体、填料、浸渍裂解工艺、热处理工艺以及微观结构(界面层、气孔)等方面的研究状况.先驱体主要有聚碳硅烷、聚硅氮烷、聚硅氧烷等,填料包括活性填料和惰性填料两种,温度、压力、时间等因素对浸渍裂解过程的影响很大,界面结合的强度关系到复合材料的性能,所以制备复合材料时,各方面的因素都得不断摸索,确定最佳的制备方案.最后,提出了目前该方法存在的问题以及未来的研究方向.     

Effects of exterior gas pressure on the structure and properties of highly porous SiOC ceramics derived from silicone resin

Silicon oxycarbide porous ceramics were obtained through pyrolysis of a silicone resin filled with SiOC powders via a simple self-blowing process. The effects of exterior gas pressure on the porosity, compressive strength and microstructure of the porous ceramics were investigated. The porosity (total and open) generally decreased with increasing exterior gas pressure. It was possible to control the total and open porosity of porous ceramics within a range of 58.3-69.8% and 43.9-58.4% respectively, by adjusting the exterior gas pressure while keeping the silicone resin content at 70 vol.%. The compressive strength increased with increasing the exterior gas pressure, and the average compressive strength of the porous ceramics was in the range of 3.9-14.9 MPa. Micrographs indicated that with the exterior gas pressure increasing, the final pore structure of porous ceramics became more and more regular and equirotal.     

透明陶瓷——无机材料研究与发展重要方向之一

透明陶瓷是在纳米材料科学与技术和先进陶瓷制备科学发展的基础上,集结构与功能一体化于一身的重要材料,它将为国民经济各个领域的发展和国防工业中高科技项目的发展提供关键材料.同时陶瓷从传统不透明→半透明→接近完全透明涉及到大量基础科学问题,尤其是材料的微结构（包括气孔、晶界、晶粒尺寸、形貌等等）对光物理的影响还不十分清楚,因此作为无机材料研究与发展的重要方向之一,需要化学、物理、材料、激光等各个学科领域的共同努力.本文着重介绍透明陶瓷的研究进展.     

Thermal-Conductivity Studies of Macro-porous Polymer-Derived SiOC Ceramics

A three-dimensional reticular macro-porous SiOC ceramics structure, made of spherical agglomerates, has been thermally characterized using a freestanding sensor-based $3\omega $ method. The effective thermal conductivity of the macro-porous SiOC ceramics, including the effects of voids, is found to be $0.041\,\hbox { W}\cdot \hbox { m}^{-1}\cdot \hbox { K}^{-1}$ to $0.078\,\hbox { W}\cdot \hbox { m}^{-1}\cdot \hbox { K}^{-1}$ at room temperature, comparable with that of alumina aerogel or carbon aerogel. These results suggest that SiOC ceramics hold great promise as a thermal insulation material for use at high temperatures. The measured results further reveal that the effective thermal conductivity is limited by the low solid-phase volume fraction for the SiOC series processed at the same conditions. For SiOC ceramics processed under different pyrolysis temperatures, the contact condition between neighboring particles in the SiOC networks is another key factor influencing the effective thermal conductivity.     

Processing of polysiloxane-derived porous ceramics: a review

Abstract

Because of the unique combination of their attractive properties, porous ceramics are considered as candidate materials for several engineering applications. The production of porous ceramics from polysiloxane precursors offers advantages in terms of simple processing methodology, low processing cost, and easy control over porosity and other properties of the resultant ceramics. Therefore, considerable research has been conducted to produce various Si(O)C-based ceramics from polysiloxane precursors by employing different processing strategies. The complete potential of these materials can only be achieved when properties are tailored for a specific application, whereas the control over these properties is highly dependent on the processing route. This review deals with processing strategies of polysiloxane-derived porous ceramics. The essential features of processing strategies—replica, sacrificial template, direct foaming and reaction techniques—are explained and the available literature reports are thoroughly reviewed with particular regard to the critical issues that affect pore characteristics. A short note on the cross-linking methods of polysiloxanes is also provided. The potential of each processing strategy on porosity and strength of the resultant SiC or SiOC ceramics is outlined.     

The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane-Derived Silicon Oxycarbide

A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer-derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single-domain NP for ceramic materials.     

碳化硼抗弹陶瓷的制备方法及应用

碳化硼陶瓷具有高硬度、高熔点和低密度的特点,是优异的结构陶瓷,在民用、宇航和军事等领域都得到了重要应用。本文中综述了碳化硼结构陶瓷的优异性能和制备新方法,重点介绍了自蔓延高温合成法(SHS),碳管炉、电弧炉碳热还原法,激光化学气相反应法,溶胶-凝胶碳热还原法等合成碳化硼粉末的主要方法以及碳化硼成型和烧结的常用方法,简述了碳化硼抗弹陶瓷材料的发展应用和研究现状。     

低温环境下结构陶瓷的相变、断裂机理与性能的研究进展

低温技术的不断发展使其应用于越来越多的领域中, 例如航空航天、超导、核聚变等。在一些低温工程领域中, 结构陶瓷有着其他材料不可替代的应用前景。本文综述了低温极端环境下几种典型结构陶瓷材料的国内外研究现状与进展, 包括氧化锆基结构陶瓷在低温下的相变机理与性能、氧化铝陶瓷的低温性能以及氮化硅、碳化硅等非氧化物陶瓷在低温下的基础力学性能及断裂机理。     

Macroporous SiOC Ceramics with Dense Struts by Positive Sponge Replication Technique

Highly porous SiOC ceramics (≥90% open porosity) containing dense struts have been prepared following positive sponge replication technique using silsesquioxane based preceramic polymer. The morphological features including cell size, cell window size, and strut size of the macroporous SiOC ceramics have been analyzed using electron microscopy. Subtle variation in the crosslinking condition of the preceramic polymer infiltrated polyurethane template enables the formation of hollow as well as dense struts, which has a profound influence on compressive strength of the macroporous bodies. Synchrotron radiation micro computed tomography is used to construct the three dimensional images of the macroporous ceramics that indicate isotropy of the pores and excellent interconnectivity.