Structure and Properties of Highly Porous Alumina-Based Ceramic Materials after Heating by Concentrated Solar Radiation

Vladimir G Babashov,Yurii V Stolyankov,Sultan Kh Suleimanov,Evgeny A Shein,Mikhail I Daskovskii

doi:10.3390/ceramics5010003

Abstract

Three ceramic fibrous materials of the Al2O3-SiO2 system with different densities have been treated using concentrated solar radiation. The experiment was performed using technological capabilities of the Big Solar Furnace in the 2 modes: the first mode includes heating up to 1400–1600 °C, holding for 1.5–2 h; the second mode (the fusion mode) includes heating up to 1750–1900 °C until the sample destruction, which is accompanied by fusion. Upon completion of the experiment, the phase composition, microstructure, and compressive strength of the materials were studied. It was shown that the investigated materials retained their fibrous structure under prolonged treatment in the first mode up to temperatures of 1600 °C. The phase composition of the ceramic materials changes during the experiment, and with a decrease in the density, the modification is more pronounced. Treatment of all three materials under study in the fusion mode resulted in the formation of the eutectic component in the form of spherulites. The compressive strength of the materials was found to be slightly reduced after exposure to concentrated solar radiation.

Highlights

The development of high-temperature heat-insulating materials based on oxide fibers is the actual worldwide line of inquiry
According to [1], the structure of the material based on the Al2 O3 -SiO2 system contains solid non-fibrous inclusions, which have a negative effect on the material properties during long-term operation at high temperatures, especially under cyclic loading
Composition diffraction pattern taken from the surface of the initial materials is represented by high-intensity diffraction pattern taken from the surface of the initialreflections materialsfrom (i.e., before exmullite (3Al2O3·2SiO2; PDF #79-1455) and low-intensity reflections from delta-aluminum posure to concentrated solar radiation) is represented by high-intensity reflections from oxide (δ-Al2O3; PDF #79-1455) (Figure 4)

Summary

Introduction

The development of high-temperature heat-insulating materials based on oxide fibers is the actual worldwide line of inquiry. The application of refractory oxide fibers as precursors of heat-insulating materials are favored due to their exceptional oxidation resistance at temperatures above 1200 ◦ C, chemical inertness with respect to most substances, and low density. Ceramic refractory materials based on the Al2 O3 -SiO2 system are widely used as heat-insulating materials. Referring to [2], mullite fiber-reinforced Al2 O3 -SiO2 aerogel composite obtained using hybrid sol-gel process has excellent heat-insulating characteristics, high-temperature stability, and high mechanical properties. Mullite fiber increases the material strength, while the unique porous structure ensures good heat-insulation properties. The heat resistance of the Al2 O3 aerogel-SiO2 fiber composite [3,4] is ensured by the formation of a crystal structure based on the γ-Al2 O3 and δ-Al2 O3 phases. According to [5], Al2 O3 -SiO2 ceramics can be produced by combination of silica-sol infiltration and Selective

Methods

Results

Conclusion