Effect of calcium source particle size on properties of low thermal conductivity anorthite ceramics
To prepare high-performance low thermal conductivity porous anorthite refractory materials,anor-thite ceramics were prepared by the high temperature solid-phase reaction at 1 100,1 200,1 300,and 1 400 ℃ holding for 3 h,respectively,using quartz sand fine powder as the silicon source,Al(OH)3 as the aluminum source,and limestone fine powder(1 110.3 nm of average particle size)and nano calcium car-bonate of four particle sizes(653.1,564.4,362.2,and 313.5 nm of average particle size)as the calcium sources.The effects of the heat treatment temperature and calcium source on the properties of the anorthite ceramics were studied.The results indicate that different types of calcium sources(limestone and nano calcium carbonate)have little effect on the phase composition of the synthesized samples,but nano calci-um carbonate can significantly reduce the formation temperature of anorthite.As the nano calcium carbon-ate average particle size decreases from 653.1 nm to 313.5 nm,the anorthite ceramics transform from granular to lamellar and plate columnar;the apparent porosity of the samples is around 18％and the bulk density is around 1.40 g·cm-3,both of which are not significantly affected;the cold compressive strength of the samples increases from 15.3 MPa to 19.3 MPa,and the thermal conductivity decreases from 1.893 W·m-1·K-1 to 1.633 W·m-1·K-1.Nano calcium carbonate can reduce the thermal conductivity of an-orthite ceramics,providing a technical approach for preparing low thermal conductivity ceramics.
nano calcium carbonatehigh temperature solid-phase methodanorthitelow thermal conductivity
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