Avaliação da Utilização do Pó da Casca de Arroz e Hidróxido de Alumínio na Produção de Materiais Cerâmicos a Base de Argila Enriquecida com Alumina

Abstract

Rice is one of the most produced and consumed grains in the world, being part of the culture and economy of many countries. Among these countries, Brazil is considered a major producer of rice, especially in the southern region of the country. Rice cultivation generates large quantities of slowly degrading residues, which have been incorporated into the development of new materials. Rice husk is one of the significant residues generated by the industry and has been the focus of several research studies in the last decade due to its high silica content. Silica is a compound extensively used in various industries, including metallurgy, chemistry, aerospace, and construction. The utilization of a residue rich in this mineral is an interesting and viable strategy to add value to a byproduct of a process that would otherwise be discarded. The ceramic industry is one of the major consumers of silica in its products, particularly in the manufacturing of refractory and insulating ceramic materials. Considering this scenario, the present research aimed to evaluate the physical, chemical, mechanical, and thermomechanical properties of ceramic materials composed of clay enriched with aluminum oxide, rice husk powder, and aluminum hydroxide. The composition of the ceramic samples consisted of partial replacement of clay with rice husk ash powder, at a mass percentage of 5%, and the addition of aluminum hydroxide at a predetermined weight based on XRF data analysis. The samples were pressed at 35.0 MPa and heat treated at 1000°C for 1 and 3 hours. Mechanical properties were investigated through compression strength and three-point flexural strength tests. Thermomechanical performance was evaluated through thermal shock resistance test. Physical properties were assessed through linear shrinkage, mass variation, apparent porosity, water absorption, and bulk density tests. The results related to physical properties demonstrate that the specimens with clay replacement by rice husk powder (ACA formulation) and clay replacement by rice husk powder and aluminum hydroxide (ACAH formulation) caused an increase in mass variation, decrease in linear shrinkage, increase in porosity, and water absorption for these samples compared to clay formulation without replacement (A formulation). The replacement of materials in the matrix resulted in a decrease in compression strength and an increase in flexural strength. There was an improvement in the performance of the samples that resisted more cycles of thermal shock in the compositions with clay replacement. The chemical composition of the samples showed phases of the Al-Si system, primary mullite, as well as corundum, aluminum oxide, and aluminum silicate. The production of ceramic material with rice husk powder and aluminum hydroxide replacement has the potential to exhibit characteristics similar to insulating refractories. Keywords: ceramic composites. silico-aluminous ceramics. rice husk powder.