Rheological Properties And Curing Regularity Of Al₂O₃-SiO₂ Foam Slurry

The foaming method has been attracted extensive attention due to its simple process,controllable structural and environmental protection.However,this method was not widespread use because of a quite long period for the solidification and drying is required.As suspension,the rheological behavior of foam slurry reflected the evolution of its structure and performance.Therefore,research about the rheological property of foam slurry and the effect of gelling agent on it,analyzed the relationship between rheological property and curing characteristic was significant to the use of foaming method.Meantime,the microwave drying was selective,controllable,high-efficiency,could be used to solve the problems of long drying cycle,uncontrollable drying cycle and green bodies damage easily exist in the hot-wind drying process.So the drying process of wet green bodies was study and providing theoretical foundation for the extensive use of microwave drying of porous lightweight materials.Hence,in this work,the gel-casting combined with foaming method was used to prepare Al₂O₃-SiO₂ porous materials.Organic hydrogel,such as diacetate glyceride?TAG?,silica sol?SS?,hydroxypropyl cellulose?HPC?,polyvinyl alcohol?PVA?and polyimide?PI?,was selected as gelling agent replace the traditional gel system.The internal relation of rheological behavior and solidification period was analyzed by studying the influence of the variety of gelling agent and the amount of foam on them.The drying process of wet green bodies was studied systematically by microwave drying.The feasibility of microwave drying and the influence of microwave export power and mount of foam on drying efficiency were explored at the same time.In order to analyze the effect of novel curing and drying method on structure and property of materials,the Al₂O₃-SiO₂ porous materials were prepared by the optimized foaming-gelcasting technology and the microstructure and physical properties of production were measured.Specific studies and results as follows:?1?TAG,SS,HPC,PVA and PI were selected as gelling agent of gel-casting process.Their effect on viscosity,thixotropy,viscoelasticity and curing time of Al₂O₃-SiO₂ foam slurry were tested to analyze the influence of variety of gelling agent on rheological property and its relationship with curing time.The results shown that,viscosity,strong modulus increased,linear viscoelastic range enlarge,thixotropy weaken and curing time decreased.When the amount of foam was 1200 m L/kg,TAG?2 wt.%?,SS?1 wt.%?,and PVA?0.5 wt.%?as gelling agent collectively,a 3D network structure with density and stability was form,the slurry has excellently rheological behavior for solidification,and the curing time was 7 h,shorter 23 h than the traditional curing process.?2?TAG?2 wt.%?,SS?1 wt.%?,and PVA?0.5 wt.%?apply to Al₂O₃-SiO₂ foam slurry as gelling agent.The viscosity,thixotropy,viscoelasticity and curing time of slurry were tested to analyze the influence of mount of foam on rheological property and its relationship with curing time.The results shown that the initial viscosity and storage modulus of slurry increased due to the density of network structure increased.But the linear viscoelastic range decreased and thixotropy subdued with the decreased of the content of foam.The curing time reduced from 7 h to 4 h when the amount of foam was decreased from 1200 m L/kg to 600 mL/kg compared with the curing time of slurry contain?3?The microwave drying combined with hot-wind drying was employed to the drying process of wet green bodies.Effect of microwave output power and the amount of foam on drying efficiency were studied,the drying kinetics of green bodies was also analyzed.The results indicated that the drying time decreased with the increased of microwave output power and the amount of foam.The microwave drying process conform to the Page equation and the final kinetic equation was MR = exp {-?1.50321-1.7377 × 0.63124 P?· t [0.30691 P /?P-0.297?]},and it could predict the degree of drying at any moment during the whole drying process of green bodies?4?Optimized foaming-gelcasting method was used to prepare the Al₂O₃-SiO₂ porous lightweight materials and TAG?2 wt.%?,SS?1 wt.%?and PVA?0.5 wt.%?as gelling agent.The influence of novel preparation process on microstructure and mechanical properties of materials were studied.The results shown that the drying time was increased with the increased of the amount of foam and the drying time of novel drying process was shorter 24³6 h than the traditional process.The pores of materials were smooth and distribution homogeneous.The minimum bulk density was 0.528 g·cm-3 by adjusted the amount of foam from 600 m L/kg to 1200 m L/kg.The flexural strength?1.83 MPa?and compressive strength?14.86 MPa?were all higher than the materials prepared by traditional method which flexural strength and compressive strength were 1.82 MPa and 9.95 MPa respectively.