Papers by Author: Zeng Yong Chu

Abstract: In this paper, effect of heat treatment on the SSA of Si-C-O fibers was investigated and morphologies of the treated fibers were studied using SEM. The results revealed that weight loss was proportional to the treatment time at 1573K and the specific surface area (SSA) increased sharply when the weight loss reached above 6wt%. A rough and porous ceramic fiber with SSA of 23.76m2/g could be obtained at the weight loss of 9.1wt%, as a result of the treatment at 1573K for 32h.

Abstract: Hollow nanostructures have important applications in the field of gas adsorption, separation and storage due to their large specific surface areas. Silicon carbide nanotubes (SiCNTs) are one kind of such materials. In this paper, SiCNTs were synthesized from multiwalled carbon nanotubes (MWCNTs) via chemical vapor reaction (CVR) and purification. The SiCNTs were characterized by XRD, SEM and TEM. The results revealed that C-SiC nanotubes were obtained after CVR and most carbon were removed after purification with some traces retained inside SiCNTs. Hydrogen storage capacities measurements indicated that SiCNTs are superior to MWCNTs.

Abstract: In the preparation of polymer-derived SiC fibers, nanochannels are believed to be formed in the early pyrolysis stages due to loss of large volumes of pyrolysis gases. In this paper, small angle X-ray scattering (SAXS) was applied to the characterization and calculation of nanochannels in partiallypyrolyzed SiC fibers. The SAXS measurements showed that nanochannels with a radius of 1.0-20 nm were formed for fibers heat-treated at 973K and 1173K. But their distributions were not continuous and at lower part of the distribution, a peak value was observed at about 1.2nm. This means if the nanochannels are finely controlled, the partially-pyrolyzed SiC fibers have great potential application in the fields of hydrogen storage, gas separation, and so on.

Abstract: Microflaws were detected on the cross-section of polymer-derived silicon carbide fibers and their formation mechanism was studied by varying the curing degree and the firing rate. The results show that microflaws decrease in size with increase of the curing degree due to an increased ceramic residue. The results also show that microflaws decrease in size with decrease of the firing rate. No microflaws are detectable when the firing rate is as low as 10K/h. This indicates that the microflaws are the main channels of evolution gases and the pressure of these gases leads to their formation and propagation. So a high curing degree and a low firing rate are both preferred in the preparation of dense silicon carbide fibers.