Study On The Preparation Of Honeycomb Ceramics With Micro-sized Pores And Its Application

Honeycomb ceramics, with unidirectional aligned pores and superior performance ofhigh surface area, high permeability, low density and high thermal insulation have beenwidely applied in different kinds of fields such as mechanics, metallurgy, chemicalengineering, electronics as well as advanced field of aerospace and so on. Commercialhoneycomb ceramics are traditionally produced by extrusion molding process, have beenwidely used for a host of catalyst supports in automobile exhaust treatment. However, theapplication of honeycomb ceramic with hundred micron-sized pores in photocatalyst supportsis rarely reported.In this paper, Al2O3and Si3N4honeycomb ceramics with micron-sized pores wereprepared by alginate gelling method which considered to be eco-friendly、low cost andsimplicity of processing. We had systematically and comprehensively studied the effects ofvarious experimental parameters on the gel reaction, including the solid loading of slurry、thecompositon and content of NaAlg、the concentration of Ca2+and reaction temperatures. Thephase composition and microstructure of sintered samples were characterized by XRD andSEM respectively. Honeycomb ceramics with controllable pores and porosity were preparedby adjusting the experimental parameters. We realized its use as photocatalyst supports indecomposing an aqueous methyl blue solution under UV light for the first time.According to the experimental results, both the Al2O3-NaAlg slurry and Si3N4-NaAlgslurry(whose solid loading≤30wt%) are performing shear thinning properties; It is foundthat the types and contents of NaAlg have a great important influence to the microstructure ofhoneycomb ceramics; while the raction temperature control the spreading movement of Ca2+ions, the higer was the temperature, the more intensively astatic spreading of the ions, as aresult, leading to the unidirectional capillaries distorted. By varying the initial solid loading (10-30wt%) of Al2O3slurries, the porosity of alumina ceramics ranged from60to79.5%with controlled pore size (180~315μm). By varying the initial solid loading (5-20wt%) ofSi3N4slurries, we preared the honeycomb ceramics with pore size of50~200μm and porosityof50.36~64.27%, whose channels similar “honeycomb-like” microstructure, the“honeycomb-like” microstucture was formed by a large number of rod-like β-Si3N4grainsoverlapped each other. The length of the rod-like grains can be controlled by adjusting thesintering temperature, the largest aspect ratio of β-Si3N4can reach20. This self-organizationprocess can provide a new idea for preparing porous Si3N4ceramics.TiO2coatings prepared by sol-gel method demonstrated excellent adhesion to thesubstrates. When the solid loading of supports reached15wt%, the TiO2coatings showed thehighest photocatalytic efficiency of79.52%. Besides, TiO2films possessed nearly the samephotocatalytic activity as titania/water suspension. Thus, the honeycomb ceramic prepared byself-organization process holds promise for use as photocatalyst supports in water purificationwithout recycling process of powders.