Abstract
The polymer-derived SiC fibers are mainly used as reinforcing materials for ceramic matrix composites (CMCs) because of their excellent mechanical properties at high temperature. However, decomposition reactions such as release of SiO and CO gases and the formation of pores proceed above 1400 °C because of impurities introduced during the curing process. In this study, polycrystalline SiC fibers were fabricated by applying iodine-curing method and using controlled pyrolysis conditions to investigate crystallization and densification behavior. Oxygen and iodine impurities in amorphous SiC fibers were reduced without pores by diffusion and release to the fiber surface depending on the pyrolysis time. In addition, the reduction of the impurity content had a positive effect on the densification and crystallization of polymer-derived SiC fibers without a sintering aid above the sintering temperature. Consequently, dense Si-Al-C-O polycrystalline fibers containing β-SiC crystal grains of 50~100 nm were easily fabricated through the blending method and controlled pyrolysis conditions.
Highlights
Silicon carbide (SiC) fiber with excellent oxidation resistance, high tensile strength, elastic modulus at high temperature is mainly used as a reinforcing material for ceramic matrix composites (CMCs) [1,2,3]
SiC fibers are generally manufactured by the processes of meltspinning, curing, and pyrolysis using polycarbosilane (PCS) as a ceramic precursor [4,5]
The curing methods essential for conversion from polymer fiber to ceramic fiber are classified into oxidation curing method [8,9,10], electron beam (EB) curing method [11,12,13], and chemical vapor curing (CVC) method [14,15,16], respectively
Summary
Silicon carbide (SiC) fiber with excellent oxidation resistance, high tensile strength, elastic modulus at high temperature is mainly used as a reinforcing material for ceramic matrix composites (CMCs) [1,2,3]. SiC fibers are generally manufactured by the processes of meltspinning, curing, and pyrolysis using polycarbosilane (PCS) as a ceramic precursor [4,5]. The polymer-derived SiC fibers can be largely divided into amorphous SiC fibers and polycrystalline SiC fibers depending on the oxidation resistance temperature, and various manufacturing methods have been studied to fabricate high-performance polycrystalline SiC fibers [6,7]. Oxygen as a cross-linker reduces the heat resistance of SiC fibers and causes problems in fabricating dense and polycrystalline SiC fibers. The EB curing method was developed to manufacture high-heat resistant SiC fibers through the curing process without oxygen. The EB-cured PCS fibers are relatively converted into polycrystalline SiC fibers above 1500 ◦ C through the formation of radical bonds such as Si-Si and Si-C under a strong electron beam. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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