Papers by Keyword: Silicon Carbide Whisker

Abstract: Shape memory polymers (SMPs) are polymer materials that can fix the temporary shape and then recover to their original permanent shape by external stimulation, i.e. applied heat. In this research, shape memory polymer composites (SMPCs) from benzoxazine (BA-a)-epoxy binary systems reinforced with adamantine silicon carbide whisker (SiC_w) are investigated. The SiC_w contents are controlled to be in range of 0 to 15% by weight. All specimens were fabricated by compression molding technique. The results revealed that the shape memory polymer composites showed higher glassy state storage modulus with increasing amount of the whisker suggesting substantial reinforcement effect of the whisker used. The glass transition temperature (T_g) was also improved from 102°C of the based polymer to the value about 122°C with the addition of about 15% by weight of the silicon carbide whisker. Finally, shape recovery stress systematically increased from the value about 1.5MPa of the unfilled polymer matrix to the value about 3.2MPa with an addition of 15% by weight of the silicon carbide whisker. The positive effect on thermal stability from SiC_w addition is expected from the modification and will be reported in this work.

Abstract: The dispersion stability of silicon carbide whisker (SiCw) which is by-product of SiC was researched using distilled water as dispersing medium, polyethylene imine (PEI), tetramethylammonium hydroxide (TMAH), poly(meth)acrylamide (PMAM) as the dispersants. The sedimentation and optical microscope technology are used to observe whisker dispersion ，FTIR and ZETA electric potential are used to explore its dispersion mechanism . The results show that the order of dispersion capacity of the dispersant was PEI> TMAH> PMAM.When 1.25vol% PEI was used as dispersant, SiCw can be dispersed homogeneously at pH=9 and 10, in the meanwhile, if TMAH was used, the added amount would be 0.75vol% in which the pH is in range of 11-12.

Abstract: Chemical vapor deposition (CVD) is an effective method of preparing silicon carbide whiskers or films and chemical vapor infiltration (CVI) can be successfully used as the preparation of SiC composites. In this paper, silicon carbides whiskers were firstly deposited on substrates of RB-SiC by CVD process and then silicon carbide composites were prepared by chemical vapor infiltration in the SiC whiskers in an upright chemical vapor deposition furnace of Φ150mm×450mm with methyltrichloride silicane (MTS) as precursor gas, H2 as carrier gas and Ar as dilute gas. The morphologies of the SiC whiskers grown on RB-SiC substrate and SiC composites infiltrated in SiC whiskers were determined by scanning electron microscope (SEM), and the crystalline phase of the final deposits were confirmed with X-ray diffractometry (XRD) As a result, the curly defects of whiskers decrease with the addition of dilute gas. And by chemical vapor infiltration in SiC whiskers the, SiC composites were successfully prepared. Finally the deposits were determined as β-SiC.

Abstract: Silica-sol and activated carbon were used to prepare SiC whiskers by microwave heating. The effect of packing density of raw material powders on the morphologies of SiC whiskers has been investigated. It was argued that by decreasing the packing density of raw material powders, the growing space of the SiC whiskers increases and the morphologies of the whiskers changes from flexural to straight along with the increase in length. When the packing density was lower than 0.26 g/cm³, straight and dispersal SiC whiskers with high slenderness ratio could be obtained.

Abstract: Effect of whisker orientation on mechanical properties of hydroxyapatite-SiCw composite bioceramics was studied in this paper. Experiment results show that the mechanical properties of the material are the best when the tensile stress acted on the composite material is parallel with the hot pressing plane or the shearing stress is normal to the hot pressing plane, and they are the worst when the tensile stress acted on the composite material is normal to the hot pressing plane or the shearing stress is parallel with the hot pressing plane. This will offer great guidance for practical applications of the hydroxyapatite-SiCw composite bioceramics.

Abstract: Theory calculation result indicates that the maximal critical content of SiCw in hydroxyapatite-SiCw composite bioceramics is 23.7%. Hydroxyapatite-SiCw composite micropowder was synthesized using in-situ composite method, and hydroxyapatite-SiCw composite bioceramics with different content of SiCw were produced by hot pressing sintering method. The microstructures of the materials were analyzed by SEM, and the mechanical properties were tested. The results show that the mechanical properties of composite material are the best when the whisker content is 20~23.7%.