Study On Densification Behavior Of Glass Powders

Both sintered glass ceramics and glazes involve the densification process of particle powder.For the former,since the shape of sintered glass is formed before or during sintering,this process can not only produce highly densified glass products,but also produce products with complex shape.Therefore,sintering method is widely used in laboratory and industry to prepare porous glass products.In this thesis,we take the particle powder of three different systems as the research object,respectively using melting method and sintering method to prepare sintered samples,by changing the sintering system and composition to explore the densification behavior of particle powder and its influence on its physical properties.The main results are as follows:（1）The sintering behavior of powder compacts of a boro-alumino-silicate glass was investigated under isothermal condition.In particular,the effect of sintering temperature,time and atmosphere on densification is systematically evaluated.Our sintering tests demonstrate that the densification can be significantly enhanced with increasing temperature,but relatively high translucency can be obtained in the temperature range in which there is a low crystallization tendency.In addition,a vacuum atmosphere is essential to sintering rate and ultimate density,thus leading to higher translucency than that in air atmosphere.Furthermore,the increase in densification accounts for the improvement of vickers hardness.These results are very relevant for the design of transparent glasses with powder sintering method.（2）The sintering mechanism of mineral glaze was studied by DSC-TG.At the same time,the influence of different heating rates on densification of glaze was investigated.DSC-TG curve showed that the weight loss of glaze during roasting was mainly caused by organic water release,oxidation of organic carbon and impurities into CO₂,and CO₂ gas released by thermal decomposition of feldspar and carbonate.Compared with K1 and K2,K3 is due to the introduction of borax to promote the formation of liquid in the low temperature stage,thus accelerating the melting of refractory minerals.Compared with the glaze quality of sample K1,K2 and K3,it was found that with the increase of heating rate,the surface defects and internal pores of the sample increased,resulting in the decrease of densification degree and hardness of the glaze.（3）K3 was selected as the basic mineral glaze and different Ca O/Mg O glass powder was used as additives to explore the influence of glass powder composition on the physical properties of natural mineral glaze and the interaction between glass powder and natural minerals.The results show that the porosity,densification and hardness of the glaze doped with glass powder decrease.,because the change of Mg O content affects the viscosity of melt.When mineral glaze is combined with Ca Mg24bulk glass,it is found that Na⁺and K⁺in mineral raw materials diffuse into bulk glass in accordance with Fick’s second law,which changes the coordination of Al³⁺,thus affecting the precipitation of glass crystals.With the increase of sintering temperature,the block glass partially melts,the network structure is loose,easy to ion diffusion.Therefore,the diffusion coefficients of Na⁺and K⁺obtained gradually increase.