Biological Template Preparation Of Porous SiC And CeO₂ Ceramics

Bio-template method is a simple approach for synthesis of hierarchical micro/nonporous oxide materials with biological natural structurce,In this dissertation,We employed bio-template method to prepare Hierarchical micro/nanoporons Ceria materials with biogenic morph-structures through facile reaction conditions with the assistance of leaves,maize straw,straw,which were chosen as the bio-template based on their natural abundance and low-cost.The novel hierarchical porous ceria materials were synthesized via the effective double-replications of the real microporons structure of biological cell membrane and the virtual cellular nanoporons with cerium source.Based on this research,the reaction processes and synthetic mechanisms of biological cerium oxid materials prapared by various templates and the effect of ceria material structures were investigated,The mian research resultsare as follows.In this paper, We use maize straw and straw as biological templates, NaF as cosolvent,Fe powder as catalyst, The sintering temperature is 1250-1450 ℃, After high temperature boronization silicon reaction, maize straw and straw multilevel pore structure were duplicated. Then remove the residual carbon in high temperature stove at 750 ℃. Using X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM) analysis of phase composition and microstructure of Si C ceramics,using BET test aperture of Si C ceramics. The results show that the SiC ceramics can Duplicate the biological hole structure of maize straw profect, SiCw generated in 1250 ℃and 1350 ℃, SiC particle generated at 1450 ℃. The best process conditions 1450 ℃ to generate multiple porous SiC crystals form, insulation 2h, catalyst content is 6%, under the technological conditions of the pore size distribution of porous silicon carbide ceramics is evener, the products less impurities. Under the effect of catalyst and cosolvent, forming a communion in the surface of carbon template, the temperature of the formation of SiC can effectively decrease, porous silicon carbide reaction generated mainly by LS mechanism.Using maize straw and plant leaves as biological templates, put the biological templates in cerium nitrate solution impregnation,Solution concentration is 0.01 mol/L,0.02 mol/L and 0.03 mol/L. Finally, CeO2 generated under the sintering. Analysis to study the morphology of porous ceria,phase composition, sintering temperature and the influence of the porous ceria precursor concentration by TGA and DSC, XRD, SEM,The results show that the precursor concentration in 0.02 mol/L, sintering temperature is550 ℃,CeO2 is our ideal porous ceria, under the condition, the porous cerium oxide has uniform pore size distribution.Research suggests that the formation of porous ceriumoxide has four steps, a cerium nitrate is dissolved releasing Ce3+, to replace the hydroxyl and carboxyl in biological templates H+ form Ce-O; Secondly, the thermal decomposition of OH- combined with Ce-O generated O–Ce-(OH) 3; Three is on the biological templates self-assembly CeO2; Lastly, At 550 ℃ remove the template,then biofilm formation cerium oxide crystals.