Kazakhstan customer order 3*40GP insulating mullite bricks.
Microstructure of mullite lightweight insulation bricks affected by clay content
Figure 1 is a comparison of secondary electron electron microscope photos of mullite lightweight insulation bricks with different clay contents after hydrofluoric acid treatment. The clay contents are 20wt.%, 30wt.%, and 40wt.%. It can be seen from Figure (a) that the acicular and columnar mullites are assembled into plate-shaped or massive aggregates, and the surface of the aggregates is distributed with acicular mullites perpendicular to the surface. This is because the crystals of kyanite The morphology is a columnar, plate-like or strip-like aggregate. Kyanite decomposes at high temperature to form mullite, and the crystallization direction of mullite is perpendicular to the crystal plane of the original kyanite, and finally forms a tight network cross structure. It is the existence of this cross network structure that greatly improves the mechanical properties of mullite materials. It can also be seen from Figure (a) that at the same temperature, the decomposition and transformation of small kyanite particles (such as area A) tends to be more complete than that of large kyanite particles (such as area B), indicating that blue The particle size of spar has an impact on its mullitization, and the smaller particle size is conducive to mullitization, which is consistent with the research findings of Song Jifang and Li Junwen.
As the clay content increases, the content of kyanite gradually decreases. From the comparison of Figure 1 (a), (b) and (c), it can be seen that the proportion of well-defined plate-shaped mullite aggregates is decreasing, a kind of The elongated, relatively loose mullite (such as region C) is replacing the short, thick, relatively compact mullite produced by the decomposition of kyanite and mullite, and the low-melting phase is significantly increased. Combined with the true density in Figure 1, it can be seen that the forms of mullite generated by the decomposition of kyanite and clay are not the same. The mullite generated by kyanite decomposition and mullite is relatively compact, and the mullite grains generated by the clay reaction relatively loose. As the clay content increases, the kyanite content gradually decreases, so there are more and more loose mullite aggregates, so the true density of mullite lightweight insulation bricks with greater clay content is smaller. .