新型SiBNC陶瓷先驱体——聚硼硅氮烷的合成与表征

以甲基氢二氯硅烷、三氯化硼、六甲基二硅氮烷为起始原料, 采用共缩合的方法合成了一种新型的可溶可熔的SiBNC陶瓷先驱体--聚硼硅氮烷(PBSZ). 该法合成工艺简单, 且合成收率约为91% (w%). 采用元素分析、傅立叶红外光谱、核磁共振波谱、X射线光电子能谱、动态热机械分析、热重分析等对PBSZ的组成、结构和性能进行了表征. 结果表明, 先驱体的主要骨架为-Si-N-B-, 其中, B, N以硼氮六环形式存在, 而C则以Si-CH₃形式存在. 该先驱体熔点为69 ℃, 数均分子量为10802, 分子量分散系数为1.50. 此外, 所合成的先驱体具有优良的成型性, 在80 ℃的N₂气氛中可纺丝得到15～20 μm的有机纤维, 1000 ℃时相应陶瓷产率约为63% (w%).     

聚硼硅氮烷的合成及其流变性能研究

以二氯甲基硅烷、三氯化硼、六甲基二硅氮烷为起始原料,采用缩聚法合成了一种新型SiBNC陶瓷先驱体-聚硼硅氮烷(PBSZ)。通过调节原料二氯甲基硅烷的用量可获得不同软化点的先驱体。通过改进的毛细管流变仪,首次对熔融纺丝状态时聚硼硅氮烷(PBSZ)的流变特性展开了研究。结果表明：PBSZ熔融纺丝时,剪切速率在10～110s-1时,为切力变稀流体。非牛顿指数为0.83～0.90,粘流活化能约为142KJ/mol,表观粘度440～2460Pa·s,PBSZ对温度变化的敏感性较聚碳硅烷小,可纺温区较宽。PBSZ纺丝性能良好,纤维连续无断头长度﹥1600m,纤维直径﹤20μm。     

胺源对“一锅法”合成聚硼硅氮烷结构及性能的影响

以六甲基二硅氮烷(MM^N)、四甲基二乙烯基二硅氮烷(MM^NVi)和四甲基二硅氮烷(MM^NH) 3种不同结构的二硅氮烷为胺源,通过与氯硅烷和三氯化硼反应,制备出具有不同封端结构的聚硼硅氮烷.其中,以MM^N、MM^NVi为胺源可获得液态产物;以MM^NH为胺源时,因合成过程中发生活性基团间的过度交联导致产物凝胶.采用核磁共振波谱仪、红外光谱仪对液态前驱体聚合物及其热解产物的结构进行了表征.研究结果表明：通过“一锅法”制备的液态聚硼硅氮烷主链具有较多的支化和环状结构,随着封端结构中乙烯基含量的增加,所得前驱体的固化温度降低,固化反应活化能降低.与以MM^N为胺源和封端剂合成的聚硼硅氮烷相比,以MM^NVi为胺源所得前驱体固化前后陶瓷产率分别提高了14.9%及8.1%.并且,通过改变胺源的种类和比例可以调节热解产物的元素组成,合成的液态前驱体聚合物热解所得SiBCN陶瓷结晶温度高于1700℃.     

聚硼硅氮烷陶瓷前驱体分子结构设计和合成*

聚硼硅氮烷是制备高性能硅硼 碳氮（SiBCN）复相陶瓷的主要聚合物前驱体,在耐高温、抗氧化高性能陶瓷领域中具有重要的研究价值。本文分4个方面,即基于硼吖嗪的聚硼硅氮烷、侧基含有环硼氮烷或单硼烷的聚硼硅氮烷、基于多官能硼烷构筑的聚硅氮烷和含硼聚硅基碳化二亚胺,从聚硼硅氮烷分子结构设计、改性、合成及在多维尺寸材料中初步应用的角度综述了该领域国内外研究的新进展,指出了聚硼硅氮烷陶瓷前驱体设计合成研究发展中值得关注的新方向。     

聚硼硅氮烷的表征及其流变性能

以二氯甲基硅烷、三氯化硼、六甲基二硅氮烷为起始原料,采用缩聚法合成了新型SiBNC陶瓷前驱体--聚硼硅氮烷(PBSZ),其产率达90%. 通过调节二氯甲基硅烷的用量可获得不同软化点的前驱体. 采用改进的毛细管流变仪,首次对熔融纺丝状态时PBSZ的流变特性进行了研究. 结果表明,PBSZ熔融纺丝时,剪切速率在10～110 s~(-1)范围内时,为切力变稀流体,非牛顿指数为0.83～0.90,表观粘度为440～2 460 Pa·s,粘流活化能约为142 kJ/mol. PBSZ纺丝性能良好,纤维连续无断头长度＞1 600 m,纤维直径＜20 μm.     

聚硼硅氮烷前驱体的合成及性能研究

以三氯化硼和甲基氢二氯硅烷为原料,采用共氨解的方式合成了聚硼硅氮烷前驱体,并采用核磁共振波谱仪、傅里叶红外光谱仪、差式扫描量热仪、热重分析仪、光电子能谱、网络矢量分析仪等仪器对前驱体及其热解产物进行了表征。前驱体在1000 oC、氮气气氛下热解的陶瓷产率为71.1 %。在氨气气氛下热解可以有效降低热解产物中的碳含量,聚硼硅氮烷在900 oC氨气气氛下热解产物的碳含量低于1 %,并且该热解产物具有高的结晶温度、良好的抗氧化性能和介电性能,有望用于耐高温陶瓷基透波复合材料。     

新型氮化硼陶瓷纤维先驱体——含硅聚硼氮烷的合成与表征

以三氯化硼、六甲基二硅氮烷为起始原料, 采用一步法合成了一种新型含硅氮化硼陶瓷纤维先驱体——含硅聚硼氮烷. 该法合成工艺简单, 且合成收率约为87%(质量分数). 采用元素分析、傅立叶红外光谱、核磁共振波谱、热机械分析、动态流变分析等对含硅聚硼氮烷的组成、结构和性能进行了表征. 结果表明, N—B为含硅聚硼氮烷先驱体的骨架结构, 其中, B, N主要以硼氮六环形式存在, 而Si则以Si—CH₃, Si—N形式存在. 该先驱体软化点为110 ℃, 具有优良的成型性, 在190 ℃的N₂气氛中可纺丝得到20～25 μm的有机纤维.     

紫外光固化含硼氮六环的硅硼氮碳烷陶瓷单源先驱体的合成、表征及性能研究

以氯甲基三氯硅烷、三氯化硼和六甲基二硅氮烷为原料经过一步法合成出一种新型的端基为Si-Cl 基团的含硼氮六环的硼硅氮碳烷单体: B,B',B"-三[(三氯硅基)-亚甲基]环硼氮烷(TSMB), 用2-羟基丙烯酸乙酯和乙烯基乙二醇醚对TSMB 进行功能化改性, 得到可UV 固化的陶瓷单源先驱体a-TSMB 和e-TSMB; a-TSMB 和e-TSMB 经UV 固化、1400℃下裂解2 h 最后制备出陶瓷材料C1 和C2. 采用红外光谱(FT-IR)、核磁共振波谱(NMR)、等温差示光量热分析(DPC)、实时红外光谱(RT-IR)、热失重分析(TGA)、X 射线光电子能谱(XPS)和X 射线衍射法(XRD)分别对TSMB, e-TSMB 和a-TSMB 以及陶瓷C1 和C2 的结构、组成、UV 反应性、陶瓷产率和耐高温性能进行了研究. 结果表明: a-TSMB 和e-TSMB 两种陶瓷单源先驱体分子中含有硼氮六环结构, 分子末端为丙烯酸酯或乙烯基醚官能团, 与理论设计完全相符; a-TSMB 和e-TSMB 的光聚合反应在25 s 内分别完成82%和67%, 最终双键转化率可达到90.0%和74.0%, 其陶瓷产率在1300 ℃时为57.9%和48.5%; 陶瓷材料C1 和C2 中含有Si, B, C, N, O 五种元素, 且B 元素的含量达到4.4%和4.9%, 达到耐高温陶瓷对B 元素含量的要求, 在1400 ℃时陶瓷C1 和C2 均可保持非晶态具有优异的耐高温性能.     

超支化聚碳硅氮烷的合成与表征

聚碳硅氮烷是一种新型含硅有机金属聚合物,其主链由硅氮碳连接而成,侧链为有机基团;与其它含硅聚合物(聚硅氮烷、聚碳硅烷等)类似,聚碳硅氮烷适于用做力学性能极佳且耐高温氧化的氮化硅(Si3N4)和氮化硅/碳化硅(Si3N4/SiC)复相陶瓷的前驱体.[1]超支化聚合物具有溶解性好、粘度低     

三氯环硼氮烷和聚硼氮烷的合成与表征

以三氯化硼和氯化铵为原料,甲苯为溶剂,高产率(98%)地合成了具有硼和氮的六元环结构的三氯环硼氮烷(1);1分别与正丙胺(Ⅰ)和异丙胺(Ⅱ)反应制得正丙胺基环硼氮烷(1~Ⅰ)和异丙胺基环硼氮烷(1~Ⅱ);1~Ⅰ和1~Ⅱ经过脱胺和热聚合反应制得聚硼氮烷先驱体(2和3).用IR,NMR和XRD等对2和3的组成与结构进行了分析,探讨了聚硼氮烷的胺基取代基对聚硼氮烷聚合反应性及产物结构的影响.研究结果表明,3具有更强的热聚合特性.     

Chemical composition and porous structure of polymer-derived silicoboron carbonitride ceramics prepared via a monomer route

Polymer-derived silicoboron carbonitride (SiBCN) ceramics were facilely prepared using organosilicon monomers tris(dichloromethylsilylethyl)borane and bis(trimethylsilyl)carbodiimide as the starting materials. The polymer precursors were obtained either without adding styrene or by adding an appropriate amount of styrene into the mixture of the organosilicon monomers, followed by heat treatment and purifying. The chemical composition and pore structure of the polymer-derived SiBCN ceramics were studied. It was found that styrene diluted the monomers and hindered their chemical reaction from forming the polymeric network. The polymer precursor prepared with styrene was composed of boron-modified polysilylcarbodiimide as the matrix and dispersed polystyrene mainly of sizes 20–50 μm. Accordingly, a polymer-derived SiBCN ceramic with a three-dimensional continuous macroporous structure containing pores mainly of 20.9–58.1 μm with a total porosity of 74% was achieved. The B/N atomic ratio reached 0.58 with low oxygen content of 2.81 wt%, which satisfied the requirement for high-temperature application.     

New route to synthesize preceramic polymers for zirconium carbide

A preceramic polymer,polyzirconosaal(PZSA),was synthesized by the ligand-exchange reaction between polyzirconoxane (PZO) and salicyl alcohol(S A).The precursor was air-stable and exhibited excellent solubility and rheology.These properties are useful for the processing of C/C-ZrC composites via precursor infiltration and pyrolysis(PIP) process.The polymer to ceramic conversion was investigated by TG,XRD and TEM.Nanosized ZrC was formed by pyrolysis of this precursor at 1300℃in argon with ceramic yield of 57.8%.     

Genesis of nanostructured, magnetically tunable ceramics from the pyrolysis of cross-linked polyferrocenylsilane networks and formation of shaped macroscopic objects and micron scale patterns by micromolding inside silicon wafers

The ability to form molded or patterned metal-containing ceramics with tunable properties is desirable for many applications. In this paper we describe the evolution of a ceramic from a metal-containing polymer in which the variation of pyrolysis conditions facilitates control of ceramic structure and composition, influencing magnetic and mechanical properties. We have found that pyrolysis under nitrogen of a well-characterized cross-linked polyferrocenylsilane network derived from the ring-opening polymerization (ROP) of a spirocyclic [1]ferrocenophane precursor gives shaped macroscopic magnetic ceramics consisting of alpha-Fe nanoparticles embedded in a SiC/C/Si(3)N(4) matrix in greater than 90% yield up to 1000 degrees C. Variation of the pyrolysis temperature and time permitted control over the nucleation and growth of alpha-Fe particles, which ranged in size from around 15 to 700 A, and the crystallization of the surrounding matrix. The ceramics contained smaller alpha-Fe particles when prepared at temperatures lower than 900 degrees C and displayed superparamagnetic behavior, whereas the materials prepared at 1000 degrees C contained larger alpha-Fe particles and were ferromagnetic. This flexibility may be useful for particular materials applications. In addition, the composition of the ceramic was altered by changing the pyrolysis atmosphere to argon, which yielded ceramics that contain Fe(3)Si(5). The ceramics have been characterized by a combination of physical techniques, including powder X-ray diffraction, TEM, reflectance UV-vis/near-IR spectroscopy, elemental analysis, XPS, SQUID magnetometry, M?ssbauer spectroscopy, nanoindentation, and SEM. Micromolding of the spirocyclic [1]ferrocenophane precursor within soft lithographically patterned channels housed inside silicon wafers followed by thermal ROP and pyrolysis enabled the formation of predetermined micron scale designs of the magnetic ceramic.     

高硼含量的SiC陶瓷先驱体的合成和表征

采用经典硼氢化反应, 通过硼烷二级硫醚(BH₃·SMe₂)与二甲基二乙烯基硅烷(DVS)反应, 合成了聚硼碳硅烷(PBCS)陶瓷先驱体, PBCS在氮气中经高温裂解得到了高硼含量的SiC陶瓷.利用红外光谱、核磁共振波谱和热重分析对聚合物的结构和性能进行了表征; 利用元素分析、X射线衍射和扫描电子显微镜对聚合物的裂解产物进行了分析.结果表明, 聚合物的结构中含有B—C, Si—C和C—H键, 在1000℃氮气气氛中, 其陶瓷产率在50%以上.陶瓷产物在1100℃以无定形态存在, 硼含量高达6.46%, 在1300℃时出现明显结晶, 形成B₂O₃, C和β-SiC三相组成的多元复相陶瓷, 在1500℃以下陶瓷产物表面光滑, 结构致密.     

硅基聚合物前驱体转化陶瓷微观结构研究进展

聚合物前驱体转化法使得陶瓷材料的制备实现了可分子设计和可聚合物工艺加工,在陶瓷基复合材料、陶瓷纤维、功能涂层、特种胶粘剂等方面具有重要应用价值.不同于传统粉末烧结工艺,该方法涉及有机聚合物至无机陶瓷的转化过程,因此,聚合物前驱体的分子结构以及陶瓷化工艺对所制备陶瓷材料的微观结构和功能特性具有直接影响.本文综述了基于聚合...     

Copper‐Containing SiCN Precursor Ceramics (Cu@SiCN) as Selective Hydrocarbon Oxidation Catalysts Using Air as an Oxidant

A molecular approach to metal‐containing ceramics and their application as selective heterogeneous oxidation catalysts is presented. The aminopyridinato copper complex [Cu₂(Ap^TMS)₂] (Ap^TMSH=(4‐methylpyridin‐2‐yl)trimethylsilanylamine) reacts with poly(organosilazanes) via aminopyridine elimination, as shown for the commercially available ceramic precursor HTT 1800. The reaction was studied by ¹H and ¹³C NMR spectroscopy. The liberation of the free, protonated ligand Ap^TMSH is indicative of the copper polycarbosilazane binding. Crosslinking of the copper‐modified poly(organosilazane) and subsequent pyrolysis lead to the copper‐containing ceramics. The copper is reduced to copper metal during the pyrolysis step up to 1000 °C, as observed by solid‐state ⁶⁵Cu NMR spectroscopy, SEM images, and energy‐dispersive spectroscopy (EDS). Powder diffraction experiments verified the presence of crystalline copper. All Cu@SiCN ceramics show catalytic activity towards the oxidation of cycloalkanes using air as oxidant. The selectivity of the reaction increases with increasing copper content. The catalysts are recyclable. This study proves the feasibility of this molecular approach to metal‐containing SiCN precursor ceramics by using silylaminopyridinato complexes. Furthermore, the catalytic results confirm the applicability of this new class of metal‐containing ceramics as catalysts.     

Preparation of Activated Carbon Functional Ceramics From Coal Pitch

The influences of different impregnation temperatures,pre-oxidation,carbonization temperatures and activation conditions on the iodine value and carbon deviations was discussed.SEM,EDS,and BET techniques were used to investigate the microstructures and properties of materials.Results showed that activated carbon functional ceramic exhibited excellent comprehensive properties when porous ceramics adsorbed the coal pitch at 150 ℃ for 0.5 h,oxidized at 420 ℃ for 1.0 h,and carbonizated at 700 ℃ for 1.0 h and then activated by using KOH(20wt%) as agent at 800 ℃ for 1.0 h,as confirmed by the high iodine value(162.6 mg/g) and high specific surface area(83.5 m2/g).