Natural fibers are low-cost fibers with low density and high specific properties. These fibers are biodegradable and non-abrasive. The natural fiber composites offer unique properties comparable to those of conventional synthetic fiber composites. However, development of these composites is often hampered by weak compatibility between fibers and polymer matrix and poor thermal resistance, which often reduce their performance. This paper reports thermal properties and flammability of cotton/vinyl ester composites containing some flame retardant materials such as ammonium molybdate, aluminum trihydroxide, antimony trioxide and Chlorez tested by thermogravimetric analysis and flame retardancy. Addition of flame retardants to cotton/vinyl ester composites reduced burning rate and produced a self-extinguishing flame in some flame-resistant systems. In addition, alkali treatment of cotton fibers using 15% NaOH solution was conducted to improve compatibility of cotton fibers and vinyl ester resin. Tensile test indicated that the treated cotton fibers improved the interfacial bonding and enhanced elongation-at-break of the composites.
The hot pressing process of monolithic Al 2 O 3 and Al 2 O 3 -SiC composites with 0-25 wt% of submicrometer silicon carbide was done in this paper. The presence of SiC particles prohibited the grain growth of the Al 2 O 3 matrix during sintering at the temperatures of 1450°C and 1550°C for 1 h and under the pressure of 30 MPa in vacuum. The effect of SiC reinforcement on the mechanical properties of composite specimens like fracture toughness, flexural strength, and hardness was discussed.The results showed that the maximum values of fracture toughness (5.9 ± 0.5 MPa. m 1/2 ) and hardness (20.8 ± 0.4 GPa) were obtained for the Al 2 O 3 -5 wt% SiC composite specimens. The significant improvement in fracture toughness of composite specimens in comparison with the monolithic alumina (3.1 ± 0.4 MPa.m 1/2 ) could be attributed to crack deflection as one of the toughening mechanisms with regard to the presence of SiC particles. In addition, the flexural strength was improved by increasing SiC value up to 25 wt% and reached 395 ± 1.4 MPa. The scanning electron microscopy (SEM) observations verified that the increasing of flexural strength was related to the fine-grained microstructure. K E Y W O R D S alumina, ceramic composites, densification, hot pressing, mechanical properties, microstructure, silicon carbide How to cite this article: Akbari E, Ghassemi Kakroudi M, Shahedifar V, Ghiasi H. The influence of different SiC amounts on the microstructure, densification, and mechanical properties of hot-pressed Al 2 O 3 -SiC composites. Int J Appl Ceram Technol. 2020;17:491-500. https ://doi.
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