Thermal insulation materials based on spherical corundum

Abstract

For the lining of thermal equipment with a hydrogen-containing medium and a working temperature up to 1800~ corundum refractories, which are characterized by the optimum combination of physicochemical and thermomechanical properties, responsible for the technical and economic desirability of their use, are most promising.The life of corundum refractories at 1800~ in reducing media is determined by their purity and the thermal insulation properties primarily by the structure.To obtain corundum thermal insulation parts with more than 99 wt.% A1203 a mixture of G-00 and GK (85-95% a-A1203)aluminas and foam ~olystyrene was used [i]. After firing the parts had an apparent density of 1.05-i.08 g/cm , a compressive strength of 7.5-20 N/mm 2, and an additional volumetric shrinkage at 1750~ of less than 1%. However, the significant volumetric shrinkage of the parts in firing makes it difficult to produce large parts of complex configurationby this method.For the purpose of obtaining shrinkage-free thermal insulation corundum parts with not less than 99 wt.% A1203 it is desirable to use a porous filler of aluminum oxide distinguished by a constant volume in heating to 1800~C. Hollow corundum granules (spherical corundum) produced by inflation of molten corundum meet these requirements [2].

The Influence of Alumina Bubbles on the Properties of Lightweight Corundum–Spinel Refractory

“…It was well-known that alumina bubbles were widely used in thermal insulation materials due to their low thermal conductivity [23][24][25]. On account of its spherical shape and hollow structure, Li et al [26,27] studied alumina bubble addition on the properties of mullite castables.…”

Effect of Composite Binder on the Property of Lightweight Bubble Alumina Ceramics

“…It is well known that lightweight bubble alumina ceramics are excellent heat‐insulating materials with low density, high strength, and refractoriness under load 1–4 . Compared with the dense refractory, 5,6 the main advantages of bubble alumina ceramics are summarized as follows: low density, light weight, good thermal shock resistance, and high heat‐insulating and low thermal capacity.…”

“…It is well known that lightweight bubble alumina ceramics are excellent heat-insulating materials with low density, high strength, and refractoriness under load. [1][2][3][4] Compared with the dense refractory, 5,6 the main advantages of bubble alumina ceramics are summarized as follows: low density, light weight, good thermal shock resistance, and high heat-insulating and low thermal capacity. While compared with other common heat-insulating refractory materials, 7,8 the bubble alumina ceramics have higher compressive resistance, higher softening temperature under load, and lower permanent linear shrinkage.…”