Abstract
ABSTRACT The main objective of this work was to evaluate the effects of rice husk ash and wollastonite microfibers incorporation, added per clay partial substituition, on physical and thermal properties of refractory ceramic composites. The raw materials characterization occurred with respect to their chemical composition (XRF), phase composition (XRD) and granulometry by laser. The composites were avaluated by physical properties - apparent porosity, bulk density, water absorption, linear retraction after sinterization and mass variation - and thermal properties - thermal conductivity and thermal shock. The rice husk ash used in the present work proved to have potential as a ceramic precursor in the development of refractories. The clay substitution per ash and the microfiber different percentages resulted in an increase in water absorption and apparent porosity and a reduction in the linear retraction. The increase in porosity suggests that the mullitization was insufficient. Regarding the thermal performance, the thermal conductivity was inversely proportional to the porosity and the microfiber percentage. In addition, the higher the thermal-shock temperature gradient the lower was the number of cycles resisted by the composites.
Highlights
The majority of emerging countries, like Brazil, has agrobusiness as one of the economy main pillars
The main objective of this work was to evaluate the effects of rice husk ash and wollastonite microfibers incorporation, added per clay partial substituition, on physical and thermal properties of refractory ceramic composites
The composites were avaluated by physical properties - apparent porosity, bulk density, water absorption, linear retraction after sinterization and mass variation - and thermal properties - thermal conductivity and thermal shock
Summary
The majority of emerging countries, like Brazil, has agrobusiness as one of the economy main pillars. The RHA in its amorphous form it is already known as an alternative source of silica since assumes pozzolanic properties [7, 8]; it is resistant to chemical corrosion, temperature variations and presents low thermal conductivity, high melting point, low bulk density and high porosity These characteristics make it an excellent co-product to be introduced in several spheres of industry such as electronics, cement and ceramics [3, 9, 10]. In the specific case of ceramics composed of silica and alumina, wollastonite diffuses rapidly with these materials at low temperatures, reducing thermal expansion and minimizing fractures and shrinkage [12] In this context, the presente study aimed to develop low-cost and sustainable refractory ceramic composites by analyzing the effects of RHA and wollastonite incorportantion on its physicial and thermal properties
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