Surface modification of carbon nanofibers with SiC by heating different SiO vapor sources in argon atmosphere

Abstract

In order to improve interfacial bonding strength between carbon nanofibers (CNFs) and SiC matrix in CNFs/SiC composites and to disperse CNFs uniformly in the matrix, SiC coating on surface of CNFs was performed in argon atmosphere in the temperature range of 1400 to 1800°C using SiO 2 , SiO, and mixture of Si and SiO 2 powders (Si/SiO 2 powder) as silicon sources, and the modification and dispersibility of the treated CNFs were investigated. ¢-SiC particles were deposited on the surface of the CNFs in all the specimens at 16001800°C. So more SiC was formed by heating CNFs with SiO powder at 1600°C. However, the formed SiC was oxidized at higher temperature, practically, at 1800°C. This oxidation was advanced more by using SiO 2 and Si/ SiO 2 powders as silicon sources and very fine carbon fibers were observed on the surface of CNFs. The dispersibilities of CNFs heated with Si/SiO 2 and SiO powders were superior to those of as-received CNFs, CNFs treated with NaClO 3 solution and CNFs heated with SiO 2 powder, which resulted from the advanced oxidation of CNFs and the silanol group (SiOH) on surface of formed SiC.

Pressureless sintering of SiC-coated carbon nanofiber/SiC composites and their properties

“…Their XRD patterns are shown in the previous paper. 5) SiC deposited on the CNFs using SiO 2 were less than that deposited on the CNFs using other silicon sources, particularly the SiC deposited on the CNFs using SiO 2 at 1400°C were very little. Nevertheless, the SiC-coated CNFs prepared using SiO 2 at 1400, 1600 and 1800°C were used in this study because the CNFs had a fewer defects.…”

“…The dispersibility of CNFs became higher in the water of pH = 10 with an increase in amount of SiC coating on CNFs. 5) So the dispersibility of the SiCcoated CNFs, particularly the 1800-coated CNFs, were superior to that of the non-coated CNFs. Therefore, the 1800-coated CNFs could be dispersed more uniformly in SiC matrix and so the SiC matrix was densified more uniformly and the grain growth of SiC also progressed more uniformly at lower temperatures of 20502100°C, as shown in Figs.…”

“…Nevertheless, the SiC-coated CNFs prepared using SiO 2 at 1400, 1600 and 1800°C were used in this study because the CNFs had a fewer defects. The CNFs coated with more SiC had more defects, 5) and so the strength of such CNFs should be weaker. 10) The SiC-coated CNFs prepared using SiO 2 at 1400, 1600 and 1800°C are shown as 1400-coated CNFs, 1600-coated CNFs and 1800-coated CNFs, respectively, in this paper.…”

“…The SiC deposited on the CNFs increased with an increase in the preparing temperature of the coating, as mentioned in the previous paper. 5) As non-coated CNFs, the CNFs oxidized in NaClO 3 solution 4), 5) were used in this study. The surface of the oxidized CNFs became hydrophilic, and so they had better dispersibility than the pristine CNFs.…”

“…In our previous study, 5) the SiC coating on CNFs was performed at 14001800°C in argon atmosphere using SiO 2 , SiO and mixture of Si and SiO 2 powders (Si/SiO 2 powder) as silicon sources, and the modification and dispersibility of the treated CNFs were investigated. So we found that ¢-SiC particles were deposited on the CNFs in all the specimens at 16001800°C, and the dispersibilities of the SiC-coated CNFs were superior to those of as-received CNFs and oxidized CNFs.…”