Microstructural development and mechanical performance of mullite-alumina and hibonite-alumina ceramics with controlled addition of a glass phase

Abstract

Robust mechanical properties of refractory ceramics are critical to their performance in industrial applications. To investigate the effects of glass on the sinterability and mechanical properties of refractory ceramics, a controlled amount of glassy phase (10 wt. %) was added to mullite (Al6Si2O13)-alumina (Al2O3) and hibonite (CaAl12O19)alumina composites. Two liquid compositions within the Al2O3-SiO2-CaO system were chosen to produce a glass at 1600 ºC that exists in equilibrium with a mullite-alumina composite and a hibonite-alumina composite. We performed a comparative study of the mechanical properties (hardness, flexural strength, and creep resistance) of mullitealumina and hibonite-alumina composites with and without glassy phases. The observed microstructures clearly affected the mechanical properties. The strong interface created 2 between the three phases in each subsystem and the reduced amount of residual porosity in the composites with an added glassy phase may explain the increase in strength, hardness, and creep resistance of the composites. However, better mechanical properties and finer grain sizes of mullite make the mullite-alumina (-glass) system a better candidate for refractory applications that require improved mechanical properties.

Influence of Firing Temperature on the Physical, Thermal and Microstructural Properties of Kankara Kaolin Clay: A Preliminary Investigation

“…This result indicates that the kaoline phase transformed into mullite [18]. Since the presence of mullite phase increases thermal shock and creep resistance of fired clay [19], mullite materials have potential applications as ceramic substrates and refractories under high temperatures.…”

Effects of flake-shape and content of nano-mullite on mechanical properties and fracture process of corundum composite ceramics

“…In order to achieve a low sintering temperature, a high content of 25% mullite is necessary, where the optimal sintering temperature is reduced to1550° C. Accordingly, the flexural strength and fracture toughness are 263.7 MPa and 5.0 MPa•m 1/2 , respectively. Comparatively, the mechanical performances are higher than those reported in the open literature [29][30][31]36]. Figure 13 shows the effects of mullite content and sintering temperature on critical crack size and work of fracture.…”

“…The mechanical properties of alumina ceramics are dependent on various factors, such as particle size of raw materials [28][29][30][31], sintering method [-32-35] and grain size of the final ceramics [35][36][37][38]. Hu et al studied the relationship between sample grain size and fracture toughness from mechanics point of view [39,40].…”

Effect of the addition of glasses as sintering aids on microstructure and properties of nanoalumina

“…Alumina compounds with secondary oxides phases are often manufactured to improve some properties, such as corrosion and oxidation resistance, hardness and mechanical stability. Particularly, the formation of a glassy phase during sintering at high temperatures may aid the densification of alumina ceramics [5].…”