Abstract
Ceramic foams were fabricated without using melting pots through the direct foaming of compacted powder mixtures of commercial quartz (SiO2) with fluxing agents (Na2CO3 and CaO) and a foaming agent (Na2SiO3·5H2O) at a relatively low temperature range (850−870 °C). The effects of the pressing pressure of the powders, the foaming time, foaming temperature, and mixture content were evaluated. The obtained cellular solid materials presented an acceptable volumetric expansion at a pressing pressure of 4 t. The materials only presented porosity at a minimum temperature of 850 °C and at a minimum time of 30 min. All the foamed samples showed an acceptable symmetric expansion and non-appreciable fissures. The study of the mixture content through the statistical software MODDE® shows that the porosity of the samples was principally affected by the Na2SiO3 content and the foaming temperature. The samples obtained at the optimum controlling factors proposed by this statistical software presented an apparent density, porosity, and mechanical strength of 1.09 ± 0.03 g/cm3, 56.01% ± 1.12%, and 3.90 ± 0.16 MPa, respectively. Glass and ceramics foams such as those obtained in this work become attractive as insulation materials in applications where high temperatures occur due to their higher melting points.
Highlights
Ceramic materials with the presence of porosity with any fraction, shape and size can be considered as cellular ceramics [1]
This study aims to research the feasibility of obtaining symmetric silica foams using compacted foams using compacted mixtures of these raw materials at low temperatures without using melting mixtures of these raw materials at low temperatures without using melting pots and evaluate the pots and evaluate the effect of the foaming temperature, pressing pressure, foaming time, and effect of the foaming temperature, pressing pressure, foaming time, and powder mix composition on powder mix composition on the characteristics of quartz foams obtained in the presence of sodium the characteristics of quartz foams obtained in the presence of sodium silicate as an environmentally silicate as an environmentally friendly foaming agent
The present study reveals that a direct foaming process of mixtures without melting pots of
Summary
Ceramic materials with the presence of porosity with any fraction, shape and size can be considered as cellular ceramics [1]. Studart et al have classified the most common processing routes to elaborate macroporous ceramics into three categories: direct foaming, replica, and sacrificial template methods [2]. The former is the most straightforward category for the preparation of cellular ceramics. Within this category, the sintering of powder mixtures that incorporate a foaming agent has been the most common processing route to make these porous ceramic materials, because the porosity and the pore structure can be controlled by adjusting the initial composition of the powder mixture [3,4]. The powder mixture is heated above its softening temperature, resulting in the sintering of a solid cellular ceramic because of the release of gas from the foaming agent
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