Fundamental Research On Preparation Of High-temperature Floamed Ceramics

The high-temperature floamed ceramic is a kind of excellent new-type wall materials withthermal insulation and fireproof function, but its foaming process is difficult to control. So it’sdifficult to realize the industrialization production of high-temperature floamed ceramics. Theeffect of material formula and process parameters on the pore structure and bulk density ofhigh-temperature floamed ceramics were examined in this work, in order to get the basicpreparation technology of high-temperature floamed ceramics, which is expected to providebasic guidance for the preparation technology.SiC and Fe2O3were selected as a part of raw materials in this work, and the effect of theircontent on pore structure and bulk density was studied. Besides the forming and growingprocess of pore were observed by SEM images, and the effect of sintering process on theperformance of floamed ceramics was also studied, such as sintering temperature, heating rate,holding time. The results show that SiC realizes its foaming function by self oxidationreaction, and its oxygen source is mainly oxygen in the air and oxygen atoms in the melt. Itsfoaming process is intense and high efficiency, and is controlled by sintering temperature andcontent of fluxing material and foaming agent. Fe2O3realizes its foaming function byreversible decomposition reaction, and its foaming process is controlled by Fe2O3content andsintering temperature. In addition, SiC is severely oxidized at880℃and obvious porestructure appears at1100℃，and heating and preservation process will promote the growthand penetrating of pore. Fe2O3is severely decomposed at860℃and obvious pore structureappears at1100～1120℃, and heating and preservation process does not significantly affectits pore structure. SiC can greatly decrease sintered density of floamed ceramics even whenits addition is less than1%, but its foaming process is not easy to control so that pore is easyto link up. Fe2O3cannot greatly reduce sintered density and its appropriate amount is2%, butit foaming well so that most of pores are closed and its size distribution is even.In addition, the effect of addition of feldspar mineral and alkaline earth silicate mineralson the pore structure and bulk density were studied in chapter4, and the effect of sintering process on properties of melt was also researched such as sintering temperature, heating rate,holding time. The results show that the viscosity and surface tension of melts influence porestructure and sintered density of floamed ceramic greatly. The melt viscosity of potassiumfeldspar is higher than albite, so feldspar minerals in law material formula should be based onpotassium feldspar; alkaline earth silicate minerals can greatly reduce the melt viscosity andsintering temperature has great influence on the its function, so its content should be less than4%.It is believed that this work can provide guidance for the preparation of floamed ceramicswith good pore structure and low bulk density.