Study On The Preparation And Properties Of Alumina Ceramics Prepared By Pre-gelling Starch Consolidation

The bioceramic is a kind of promising functional ceramic can be used as a biological or specific physiological function.The traditional preparation of ceramic has many defects which hindered the development of the complex shape of functional ceramics.This experiment aims to study an in-situ colloidal forming technology,and prepare dense alumina ceramics with precision size and complex shape.The preparation of pre-gelling starch consolidation was developed on the basis of in-situ solidification.The pre-gelling starch consolidation can effectively solve the defects caused by the traditional.The high purity nano-alumina??-Al₂O₃?particles was the object we studied,starch was used as binder and curing agent,magnesium oxide,zirconium oxide and yttrium oxide as sintering agent,citric acid ammonium as dispersing agent?1%?,polyvinyl alcohol?PVA?as the body enhancer,and using NaOH to adjust pH value.The starch suspension was heated 10¹5min in 80?and the pH was adjusted to 10after cooling.Then we should add mixture in suspension and homogenization,injection mould.In addition,the consolidation will occur after heated 1.5h in 83?.Finally,demolding,drying and sintering.The flexural strength was measured by three point bending,SEM was used to observe the material microstructure and grain boundary.EDS and XRD was used to analysis phase of the material and the grain boundary,observing the morphological changes of starch granules and the cell growth by fluorescence microscopy.This paper studied the properties of three kinds of starch.The original size of corn starch particles was similar with cassava,and the maximum size starch granules was potato starch.The initial gelatinization temperature of corn starch was the highest,and the volume expansion of corn starch was obvious at 80?,while the cassava starch and potato were at 60?.During the pre-gelation process,the starch particles absorb water and swell,and the granular structure became loose,which ensured that the starch granules can be completely gelatinized during the solidification forming process.The flexural strength of greenbody fabricated by corn starch,cassava starch and potato starch was 3.99MPa,2.73MPa,4.476MPa,respectively.In addition,the highest strength of the alumina ceramic was 200 MPa prepared by corn starch.It was obvious that the corn starch was the most suitable starch.The obvious volumetric constriction of greenbody will occur at 1450?,while grain growth occurred at1550?.During the process,the corn starch content of 0.5%was the optimal concentration to achieve highest mechanical strength of the prepared high purity nano-alumina ceramics,with the size of grains was 1.5-2.5?m,measured flexural strength of 341MPa,and a relative density of 96.01%when sintered in 1600?keeping 2.5h.The sintered temperature can be reduced when Mg²⁺and Zr⁴⁺can activate the lattice and increase the driving force of sintering.It was important that t-ZrO?Y₂O₃?and MgAl₂O₄ hindered the growth of grains and helped to achieve grain refinement when they existed in the grain boundaries.Finally,it can be concluded that the cytotoxicity grade of the material is 0 or 1,which has good biocompatibility and cannot affect the cell morphology and growth.