Properties And Bonding Mechanism Of Unfired High Alumina Brick Combined By Rectorite

The unfired high alumina brick was a kind of refractories which was undesired to be fired at high temperature.It had the advantages of simple manufacturing processs,low energy consumption,and low environmental pollution,which met the development requirements of energy conservation and environmental protection.At present,phosphate was widely used as the binder of unfired high alumina brick,but the problems of polytropic crystal,hygroscopic property and environmental pollution limited its development.In this paper,the unfired high alumina bricks were prepared with rectorite and white mud as a binder,respectively.The present works were mainly focused on the following aspects.Firstly,the clay slurry of rectorite and white mud were respectively prepared with ball milling,including wet grinding and dry grinding.And then the clay slurry was respectively used as a binder to prepare the unfired high alumina brick.The properties of the clay slurry and the unfired high alumina brick were analyzed to explore the clay's bonding mechanism.Finally,silica sol was introduced to further improve the bonding strength,and the bonding mechanism of clay-silica sol was put forward subsequently.The main conclusions are as follows:(1)After ball milling of wet grinding and dry grinding,rectorite slurry possessed good stability,high viscosity and surface potential,but decreasing particle size.And the interlayer structure of rectorite damaged with increased curl,crossed,irregular micron flakes.Similarly,the viscosity and surface potential of the white mud were increased,and the particle size was refined after the wet grinding.While the performance of white mud was limited after dry grinding,and the particle size was increased due to the aggregation.Besides,the number of nano flakes increased with shape of false hexagon after wet grinding and dry grinding.(2)Ball milling could significantly improved the cold compressive strength(CCS)of the unfired alumina brick which was combined by rectorite,reaching 31MPa(with dry grinding)and 35 MPa(with wet grinding).The CCS of brick combined by white mud was still low even after ball milling.Due to the excellent rheological behavior,surface electrical behavior,microstructure and morphology of rectorite,it was well combined with alumina particles,thus making better bonding strength in the unfired high alumina brick.While,white mud and bauxite particles were not tightly combined together,thus making worse bonding performance.The introduction of kyanite improved the poor performance of refractoriness under load of samples combined by rectorite,which increased to 1484 ? with linear expansion of 0.9 %.(3)The wet grinding of rectorite with silica sol further improved the CCS of the brick,which reached 40 MPa(after drying at 110 ?)and 116 MPa(after heat treatment at 750 ?),but done little to the brick combined by white mud with silica sol.After wet grinding rectorite with silica sol,the bonding strength increased because the improvement of adhesivity and micron flakes cladding between rectorite,silica sol and alumina particles.Although the addition of silica sol increases the liquid content of the sample at high temperature,the increased viscosity of the liquid phase made for the promotion of refractoriness under load to some extent.Similarly,the introduction of kyanite improved the poor performance of refractoriness under load of the brick combined by rectorite,which increased from 1331 ? to 1507 ?.