Advances in Science and Technology Vol. 71

Abstract: The effect of surface modified Si-Al-C® fibre with carbon interface (SA/C fibre) addition on the densification of silicon carbide (SiC) composite was examined. An acid treatment (H2SO4 and HNO3) was carried out at 50°C for 3 h in order to add COO- group to the surface of SA/C fibre and to enhance the dispersibility of SA/C fibre in the SiC powder due to the mixing operation in the polar solvent. Commercially available ultrafine SiC powder (specific surface area: 47.5 m2∙g-1) was mixed with acid-treated SA/C fibre and sintering aid (4.8 mass% Al4C3 and 1.2 mass% B4C) in the presence of acetone. The relative density of the SiC composite with non-acid-treated SA/C fibre addition hot-pressed at 1800°C for 1 h in Ar atmosphere under a pressure of 62 MPa was 98.4%, whereas that of the SiC composite with acid-treated SA/C fibre addition increased to 98.7%. Furthermore, the fracture toughness increased from 5.6 MPa∙m1/2 to 7.0 MPa∙m1/2 for the acid-treated SA/C fibre addition.

Abstract: The effect of microfiber produced from recycled waste catalyst on microstructure and mechanical strength of cementitious complex binder was analysed. Complex binder reinforced with 1%, 3% and 5% fibers were exposed to 600, 800 and 1000°C for 3h. The influence of annealing temperature on morphology of fiber reinforced complex binder was analyzed applying SEM, XRD techniques. Experimental results showed that reinforcement with 1% of fiber had advantage on mechanical strength of complex binder up to 800°C. Meanwhile addition of 5% of fiber resulted in lowest values of strength and reduced bulk density of complex binder in all firing temperature range.

Abstract: The use of composite materials, mainly reinforced thermoplastic has increased on the polymer industry, mainly the polypropylene resins (PP) reinforced by glass fibers (GF). The ionizing radiation can promote alterations in the polymeric chains by scission and crosslinking reactions. The objective of this work is to study the effect of the ionizing radiation in the properties of the polypropylene long fiber glass reinforced thermoplastic. Pellets with 1,3 cm of length, contend 15wt% of the unidirectional long glass fiber were obtained by extrusion and, subsequently, the samples were molded by injection, irradiated and submitted to thermal and mechanical tests. The mechanical (tensile and impact) properties and thermal (HDT and Vicat softening temperature) of irradiated and non irradiated reinforced thermoplastic were determined. The doses of the irradiation of the samples were 30, 50 and 100 kGy in a source of 60Co. The results showed a reduction in the thermal and mechanical performances indicating a degradation of the polymeric matrix.