【摘要】：采用陶瓷先驅體轉化法制備碳化硅(SiC)陶瓷纖維具有拉伸強度高、模量高、纖維直徑小等優(yōu)點,廣泛應用于航天、航空、以及其它耐高溫應用領域。但是通過該方法制備出的Si C陶瓷在耐高溫性能上的表現(xiàn)通常很難達到使用預期。主要是因為SiC陶瓷中存在的富余C和富余O對其高溫結晶會產生不利影響,無定形結構Si—C—O會分解為SiO、CO和C,其中SiO和C會進一步發(fā)生反應生成新的β-SiC相,新生成SiC相會在已結晶的β-SiC晶界處結晶長大,從而撐破晶界,導致材料的熱穩(wěn)定性低于理論值。本論文的主要研究內容有:1)使用低溫等離子體處理技術,改性聚碳硅烷的反應活性,采用紅外光譜(FT-IR)對反應產物進行結構表征,并通過熱重分析(TGA)對改性產物進行陶瓷產率分析;2)引入具有抑晶作用的異種元素B、Al,改善SiC先驅體聚碳硅烷(PCS)的高溫熱穩(wěn)定性,以頻那醇硼烷(PIN-BH)為硼源,以乙酰丙酮鋁(Al(AcAc)3)為鋁源,在N2氣氛下,以二甲苯為溶劑,分別與PCS進行縮合反應,合成了化學性質穩(wěn)定的含B、Al聚碳硅烷(B-PCS、Al-PCS),將PCS、PIN-BH以及PCS、Al(AcAc)3在不同工藝條件下進行回流反應,研究并確定其最佳改性工藝;3)著重研究B改性PCS,為除去反應物PIN-BH,對B-PCS進行300℃熱處理,并在Ar氣氛下燒結成為SiC陶瓷,通過FT-IR和核磁共振氫譜(1H-NMR)表征了B-PCS分子結構中的含B基團,通過凝膠滲透色譜(GPC)表征了B-PCS的交聯(lián)行為以及分子量及其分布,通過X射線衍射儀(XRD)表征了B-PCS陶瓷產物的抑晶行為。研究結果表明,1)低溫等離子處理使PCS中Si—H鍵的含量增加;2)B改性PCS的最佳工藝為:PIN-BH投料配比10%wt,反應時間5h,反應溫度110℃,陶瓷產率為相較于PCS從78.7%上升至90.1%,數(shù)均分子量(?)從4818上升至5123,分子量分布變寬;3)B-PCS分子側鏈中存在含B基團;B-PCS在1400℃的燒結產物存在無定形SiC結構,而PCS燒結產物中并不存在,說明B元素起到了對SiC的高溫抑晶作用。
[Abstract]:Sic (SiC) ceramic fibers prepared by ceramic precursor transformation have many advantages such as high tensile strength, high modulus and small fiber diameter. They are widely used in aerospace, aviation and other high temperature resistance applications. However, the performance of Si C ceramics prepared by this method in high temperature resistance is difficult to meet the expectations of use. The main reason is that the existence of surplus C and O in SiC ceramics will have a negative effect on the crystallization at high temperature. The amorphous Si-C-O will be decomposed into SiO,CO and C, in which SiO and C will react further to form a new 尾-SiC phase. The newly formed SiC phase will grow up at the crystalline 尾-SiC grain boundary, thus breaking through the grain boundary, resulting in the thermal stability of the material being lower than the theoretical value. The main contents of this thesis are as follows: 1) the reaction activity of polycarbosilane modified by low temperature plasma treatment was studied. The structure of the product was characterized by infrared spectroscopy (FT-IR). The ceramic yield of the modified product was analyzed by thermogravimetric analysis (TGA). 2) introducing the dissimilar element Bnl with inhibitory effect to improve the high temperature thermal stability of SiC precursor polycarbosilane (PCS), using PIN-BH as boron source and acetylacetone aluminum (Al (AcAc) 3 as aluminum source. In N _ 2 atmosphere, PCS,PIN-BH and PCS,Al (AcAc) _ 3 were refluxed under different conditions by condensation reaction with PCS in N _ 2 atmosphere. The optimum modification process was studied and determined. 3) the heat treatment of B-PCS by B modified PCS, to remove the reactant PIN-BH, was carried out at 300 鈩，

本文編號：2289387