The evolvement of oxygen from polyaluminocarbosilane(PACS) to Si-Al-C-(O) fibers and its effect on properties were investigated by element analysis, solid-state 27Al nuclear magnetic resonance(NMR), Fourier transform ...The evolvement of oxygen from polyaluminocarbosilane(PACS) to Si-Al-C-(O) fibers and its effect on properties were investigated by element analysis, solid-state 27Al nuclear magnetic resonance(NMR), Fourier transform infrared spectroscopy(FT-IR), thermo-gravimetric analyses(TGA), scanning electron microscope(SEM) and X-ray diffraction(XRD). Element analysis of PACS precursor polymer gives an empirical formula of SiC2.1H11.1O0.12Al0.024. 27Al NMR spectra mass gain shows that the oxygen of cured PACS fibers comes from aluminum aletylacetanate (Al(AcAc)3) and the curing process. Oxygen content can be regarded as a constant mass during the pyrolysis process. During the sintering process of Si-Al-C-O fibers into Si-Al-C fibers, oxygen and carbon decreases with the release of a small amount of CO and/or SiO. Oxygen has a positive effect on the ceramic yield while has a negative effect on the crystallization of Si-Al-C-O fibers. It has great influence on mechanical properties of Si-Al-C-O and excellent tensile strength is usually obtained at the oxygen content of 8%-10%. The Si-Al-C-(O) fibers have excellent thermal stability and creep resistance.展开更多
Using polymer-derived technology, continuous high-temperature resistant Si-Al-C fibers were prepared by one step method, which included melt-spinning of polya-luminocarbosilane (PACS), curing of continuous PACS fibers...Using polymer-derived technology, continuous high-temperature resistant Si-Al-C fibers were prepared by one step method, which included melt-spinning of polya-luminocarbosilane (PACS), curing of continuous PACS fibers, and sintering of the cured products. The results show that the average diameter and tensile strength of continuous Si-Al-C fibers are 11 to 12 μm and 1.8 to 2.0 GPa, respectively. The chemical formula of Si-Al-C fibers is SiC1.01O0.0400Al0.024, which is nearly stoichometric. The fibers are mainly composed of β-SiC crystalline, small amount of α-SiC, and amorphous SiC. Continuous Si-Al-C fibers exhibit excellent thermal stability. When the fibers were exposed in argon for 1 h, the tensile strength did not decrease until 1500℃. After heat treatment at 1800℃ in argon for 1 h, the fibers maintained about 80% of the initial strength. It was higher than that of Nicalon and Hi-Nicalon fibers.展开更多
采用不同Al含量的聚铝碳硅烷（PACS）为先驱体,通过不同的PACS纤维不熔化方法调节O引入量,制备了具有不同Al和O含量的连续Si Al CO纤维。研究了Si Al CO纤维经高温处理转变为Si（Al）C纤维过程中,Al、O含量对Si CxOy相分解、β-Si C结...采用不同Al含量的聚铝碳硅烷（PACS）为先驱体,通过不同的PACS纤维不熔化方法调节O引入量,制备了具有不同Al和O含量的连续Si Al CO纤维。研究了Si Al CO纤维经高温处理转变为Si（Al）C纤维过程中,Al、O含量对Si CxOy相分解、β-Si C结晶生长和微观形貌的影响。结果表明：纤维中Si CxOy相的分解温度区间为1300～1700℃,与Al、O含量基本无关;提高Al含量可减少纤维在高温下表面形成粗大Si C结晶颗粒和相互连通的气孔,并且对1700℃以上β-Si C结晶生长的抑制作用增强,有利于烧结致密化;利用纤维中O元素,以放出CO或CO2方式脱除富余C,但O含量过高导致气体逸出时产生较大孔洞,不利于烧结致密化。当Al和O含量分别约为0.6wt%和9wt%时,Si Al CO纤维经高温处理后能得到具有较大β-Si C晶粒尺寸的致密化Si（Al）C纤维。展开更多
基金Project(59972042) supported by the National Natural Science Foundation of China
文摘The evolvement of oxygen from polyaluminocarbosilane(PACS) to Si-Al-C-(O) fibers and its effect on properties were investigated by element analysis, solid-state 27Al nuclear magnetic resonance(NMR), Fourier transform infrared spectroscopy(FT-IR), thermo-gravimetric analyses(TGA), scanning electron microscope(SEM) and X-ray diffraction(XRD). Element analysis of PACS precursor polymer gives an empirical formula of SiC2.1H11.1O0.12Al0.024. 27Al NMR spectra mass gain shows that the oxygen of cured PACS fibers comes from aluminum aletylacetanate (Al(AcAc)3) and the curing process. Oxygen content can be regarded as a constant mass during the pyrolysis process. During the sintering process of Si-Al-C-O fibers into Si-Al-C fibers, oxygen and carbon decreases with the release of a small amount of CO and/or SiO. Oxygen has a positive effect on the ceramic yield while has a negative effect on the crystallization of Si-Al-C-O fibers. It has great influence on mechanical properties of Si-Al-C-O and excellent tensile strength is usually obtained at the oxygen content of 8%-10%. The Si-Al-C-(O) fibers have excellent thermal stability and creep resistance.
基金the National Natural Science Foundation of China (Grant No. 59972042)
文摘Using polymer-derived technology, continuous high-temperature resistant Si-Al-C fibers were prepared by one step method, which included melt-spinning of polya-luminocarbosilane (PACS), curing of continuous PACS fibers, and sintering of the cured products. The results show that the average diameter and tensile strength of continuous Si-Al-C fibers are 11 to 12 μm and 1.8 to 2.0 GPa, respectively. The chemical formula of Si-Al-C fibers is SiC1.01O0.0400Al0.024, which is nearly stoichometric. The fibers are mainly composed of β-SiC crystalline, small amount of α-SiC, and amorphous SiC. Continuous Si-Al-C fibers exhibit excellent thermal stability. When the fibers were exposed in argon for 1 h, the tensile strength did not decrease until 1500℃. After heat treatment at 1800℃ in argon for 1 h, the fibers maintained about 80% of the initial strength. It was higher than that of Nicalon and Hi-Nicalon fibers.
文摘采用不同Al含量的聚铝碳硅烷（PACS）为先驱体,通过不同的PACS纤维不熔化方法调节O引入量,制备了具有不同Al和O含量的连续Si Al CO纤维。研究了Si Al CO纤维经高温处理转变为Si（Al）C纤维过程中,Al、O含量对Si CxOy相分解、β-Si C结晶生长和微观形貌的影响。结果表明：纤维中Si CxOy相的分解温度区间为1300～1700℃,与Al、O含量基本无关;提高Al含量可减少纤维在高温下表面形成粗大Si C结晶颗粒和相互连通的气孔,并且对1700℃以上β-Si C结晶生长的抑制作用增强,有利于烧结致密化;利用纤维中O元素,以放出CO或CO2方式脱除富余C,但O含量过高导致气体逸出时产生较大孔洞,不利于烧结致密化。当Al和O含量分别约为0.6wt%和9wt%时,Si Al CO纤维经高温处理后能得到具有较大β-Si C晶粒尺寸的致密化Si（Al）C纤维。
