O—Y型SiC纤维制备及吸波性能研究

为了进一步提高异形SiC纤维的吸波性能，以阻抗匹配理论为指导，设计了O—Y型（喷丝板上由外往里，分别排布了圆形和三叶形两种喷丝孔），通过熔融纺丝、不熔化和烧成，制备了O—Y型同板多形SiC纤维，并对纤维的介电和吸波性能进行了研究。研究表明，在X波段，O—Y型SiC纤维的tanδ0.3～1.3，具有较好的频响效应；O-Y型SiC纤维中三叶形纤维异形度的变化，会引起介电参数的较大变化，异形度在0．9左右时，其tan8最高；O-Y型SiC纤维吸波性能优于纯三叶形SiC纤维和同质量比的圆形和三叶形混杂SiC纤维。     

以聚碳硅烷为先驱体制备ZrB2-SiC-C超高温陶瓷

通过在1800℃和20MPa条件下热压烧结ZrB2和聚碳硅烷（PCS）裂解粉制得ZrB2-SiC-C复合材料。样品中从PCS裂解得到的SiC体积分数从0％开始按5％递增到30％。通过XRD、SEM、维氏压痕测试等手段表征了样品的相组成、微观结构和力学性能。研究表明可得到15％和20％SiC含量的致密均匀样品，其具有好的韧性，但由于C的存在，硬度相对较低。     

碳纳米管-聚碳硅烷陶瓷先驱体的制备研究

通过化学修饰得到一种改性的碳纳米管,可均匀分散于聚碳硅烷中形成一种碳纳米管掺混的陶瓷先驱体CNT-PCS,实验表明,该CNT_PCS熔体的流动指数大于1,粘流活化能为195．4kJ／mol。该新型先驱体可用于制备高性能碳纳米管增强碳化硅陶瓷材料,也可进行熔融纺丝,以制备碳纳米管增强的碳化硅纤维。     

聚碳硅烷树脂性能及应用研究

合成了聚碳硅烷树脂,以该树脂为原料制备了SiC纤维。用电镜、红外光谱、X射线衍射、差热分析、热失重等方法对SiC纤维进行了研究,并对以聚碳硅烷树脂作为浸渍物质涂覆石墨进行了初步研究。     

Suppression of Active Oxidation of Polycarbosilane-Derived Silicon Carbide Fibers by Preoxidation at High Oxygen Pressure

Three types of polycarbosilane-derived SiC fibers (Nicalon, Hi-Nicalon, and Hi-Nicalon S) with different SiO₂ film thicknesses ( b ) were subjected to exposure tests at 1773 K in an argon-oxygen gas mixture with an oxygen partial pressure of 1 Pa. The suppression effect of a SiO₂ coating on active oxidation was examined through TG, XRD analysis, SEM observation, and tensile tests. All the as-received fibers were oxidized in the active-oxidation regime. The mass gain and the SiO₂ film development showed a suppression of active oxidation at b values of ≧0.070 μm for Nicalon, ≧0.013 μm for Hi-Nicalon, and ≧0.010 μm for Hi-Nicalon S fibers. Considerable strength was retained in the SiO₂-coated fibers. For Hi-Nicalon fibers, the retained strength was 71%–90% of the strength in the as-received state (2.14–2.69 GPa).     

掺混纳米微粉的聚碳硅烷熔融纺丝工艺研究

运用功率超声将纳米Ｎｉ粉均匀分散到聚碳硅烷（ＰＣＳ）中，通过熔融纺丝制备出了直径约１５～３５μｍ的有机纤维。研究了超声过程对纳米微粉分散状态的影响及掺混型ＰＣＳ熔融纺丝的工艺条件。     

Influence of Temperature on the Properties of Polycarbosilane

A polycarbosilane precursor of SiC fiber was synthesized at high temperature under high pressure from liquid polysilane (LPS), which was obtained by thermal decomposition of poly(dimethylsilane). The effect of reaction temperature on the Si–H bond content, degree of linearity, Si–Si bond content, molecular weight, molecular weight distribution, elemental composition, softening point, and yield of the polycarbosilane (PCS) was studied spectroscopically (FTIR, UV, ¹H-NMR, and ²⁹Si-NMR) and by gel permeation chromatography (GPC). The results showed that the molecular weight, yield and softening point of the PCS increased, the molecular weight distribution broadened, and the Si–Si bond content and degree of linearity decreased when the reaction temperature increased. The Si–H bond content increased when the thermolysis reaction temperature was less than 450°C and decreased when the temperature was over 460°C. Increasing of the reaction temperature affected the composition with a general decrease in the amount of carbon, hydrogen and oxygen in the product. A middle molecular weight region of PCS in the GPC appears when the reaction temperature approaches 450°C; and, the as-synthesized PCS was stable with low Si–Si bond content. Synthetically, the conversion process is initially the formation of PCS by thermal decomposition of LPS, which is followed by an increase in molecular weight via condensation of PCS molecules.     

聚碳硅烷纤维在环己烯气氛中的不熔化处理

将聚碳硅烷(PCS)纤维在环己烯气氛中进行化学气相交联不熔化处理,其氧含量比空气不熔化处理大大降低,组成和结构也发生了变化,气体副产物中存在环己烷和小分子硅烷.在环己烯气氛中,随着温度的升高,PCS分子的Si-H键的反应程度逐渐提高,纤维的凝胶含量逐渐增大.环己烯受热引发PCS分子中的Si-H和Si-CH3键断裂生成Si自由基和Si-CH2自由基,促进PCS分子间形成Si-CH2-Si交联结构;同时,环己烷作为侧基引入到PCS分子结构中,使纤维的碳含量随之增高.随着反应温度的升高,部分环己烷侧基和少量小分子硅烷会从PCS分子主链脱出.     

用有机硅聚合物制造陶瓷材料

介绍了国内外用有机硅聚合物制造陶瓷纤维及陶瓷基复合材料方面的进展。