CAJ | 학술논문

氧含量是SiAlCO纤维在1700℃以上烧结致密化,并得到近化学计量比元素组成的关键因素,而氧元素主要来源于前驱体聚铝碳硅烷( PACS)纤维的不熔化过程.本文采用一种新的不熔化方法,以预氧化-热交联的方式对PACS纤维进行不熔化处理,实现了热解后所得SiAlCO纤维中氧含量在10%~13%(质量分数)范围内可调节.为保证PACS纤维在热交联过程中不熔融,其最低预氧化条件为190℃下保温4 h,对应氧引入量为7.87%,预氧化纤维在惰性气氛下450℃保温2 h,可实现不熔化.通过凝胶液相色谱( GPC)、红外光谱( IR)及热重-质谱联用( TG-MS)等方法研究预氧化和热交联过程,结果表明,预氧化过程主要是Si—H氧化生成Si—OH,部分Si—OH相互缩聚,在分子间形成Si—O—Si,使PACS数均分子量提高.热交联分为2个阶段,300℃以下主要是残留的Si—OH之间形成Si—O—Si交联结构；300~450℃主要发生Si—H与Si—CH3之间脱H2的缩聚反应,形成Si—CH2—Si交联结构.
양함량시SiAlCO섬유재1700℃이상소결치밀화,병득도근화학계량비원소조성적관건인소,이양원소주요래원우전구체취려탄규완( PACS)섬유적불용화과정.본문채용일충신적불용화방법,이예양화-열교련적방식대PACS섬유진행불용화처리,실현료열해후소득SiAlCO섬유중양함량재10%~13%(질량분수)범위내가조절.위보증PACS섬유재열교련과정중불용융,기최저예양화조건위190℃하보온4 h,대응양인입량위7.87%,예양화섬유재타성기분하450℃보온2 h,가실현불용화.통과응효액상색보( GPC)、홍외광보( IR)급열중-질보련용( TG-MS)등방법연구예양화화열교련과정,결과표명,예양화과정주요시Si—H양화생성Si—OH,부분Si—OH상호축취,재분자간형성Si—O—Si,사PACS수균분자량제고.열교련분위2개계단,300℃이하주요시잔류적Si—OH지간형성Si—O—Si교련결구；300~450℃주요발생Si—H여Si—CH3지간탈H2적축취반응,형성Si—CH2—Si교련결구.
The oxygen content of the SiAlCO fibers was a key for the transformation from SiAlCO fibers to dense stoichiometric SiC fibers after sintering at >1700 ℃, which was mainly introduced during curing process. The novel preoxidation-thermal curing method was applied to the conversion of polyaluminocarbosi-lane( PACS) fibers and the oxygen content of the SiAlCO fibers as-pyrolyzed was adjustable in 10%—13%( mass fraction) . A minimal degree of preoxidation of the PACS green fibers, which performed at 190 ℃ for 4 h leading to 7. 87%(mass fraction) oxygen pick-up, is necessary for their further thermal-curing. Then, the preoxidation fibers formed crosslinking structure after thermal-curing at 450 ℃ under N2 flow. The curing process was investigated by gel permeation chromatography(GPC), infrared spectrum(IR) and thermogravi-metric analysis-mass spectra(TG-MS). The results show that the Si—OH bonds are formed after the Si—H bonds in the structure of PACS fibers reacting with oxygen molecular during preoxidation. Additionally, partial Si—OH bonds could react with each other continuously to form Si—O—Si structure, resulting in molecular in-crease. During the thermal-curing process, the residue of Si—OH further react with each other at lower than 300 ℃. The formation of Si—CH2—Si structure resulted from the reaction between Si—H bond and Si—CH3 bond happened in the range of 300—450 ℃.