Estudo de compostos cerâmicos para utilização em coatings de alta emissividade
Abstract
The constant search for means to reduce the energetic consumption
motivates the use of high emissivity ceramic coatings in many high temperature
applications. Its use aims to increase heat transfer efficiency by radiation from
substrates on which coatings are applied, reducing the emission of gases that
contribute to global warming by saving energy in heating processes. They are
composed by refractory components and high emissivity materials such as
cerium oxide, chromium (III) oxide, boron carbide and others with scarce
availability or low commercial viability. The objective of this study is to improve
knowledge in the compounds of high melting point that have high emissivity,
seeking alternatives to more abundant and greater efficiency in their use in
ceramic coatings compositions. For this purpose were evaluated different
ceramic compounds in the composition of these high emissivity coatings. To
verify the heat transfer efficiency was analyzed the coated surfaces and its
temperature maintenance in substrates with and without application of coating,
by an indirect method of measuring the emissivity. This method basically
consists in compare the emissivity from the different coated surfaces with
various coating compositions made from viable emissivity agents, using infrared
temperature measurement. Also its microstructure and the chemical analysis
were evaluated. The use of iron chromite achieved a promising result elevating
the surface emissivity about 8% in relation to a coating composition without any
emissive agent.