Papers by Keyword: Foam Ceramics

Abstract: Studies of the influence of vibration impact on the strength of foam-ceramic raw material, produced on the basis of chemically modified natural silicites, are presented. The natural oscillation frequencies of mineral particles are established, taking into account their size, density and ultimate shear stress of raw suspensions. It is shown that the coincidence of the natural and forced oscillations of the particles leads to an increase in the thixotropic effect. Using the technology of a controlled «sol-gel» transition in the structure of raw material, swelling under the influence of vibration load, samples of the material were obtained with a higher-quality macrostructure without the use of binders. Indicators of compressive strength and average density of raw and ceramics are given.

Abstract: Explosion suppression and isolation apparatus act as the last barrier to minimize casualties and property loss. Regrettably, the present techniques, such as water tubs and dust barriers, cannot effectively suppress multiple and continuous explosions. Being a porous medium, foam ceramics are characterized with large porosity and strong resistance against high temperature and shocks. Theoretical analysis and experimental study suggest that, due to numerous collisions with the walls in foam ceramics, the free radicals –generated in the chemical reactions of gas combustion and responsible for flame propagation, can be significantly destroyed, the reactive heat release be restrained, thus making the chemical reactions non-self-sustained. As a result, flame propagation is quenched. Furthermore, foam ceramics can markedly attenuate shock waves. Thus, if properly designed and arranged in the roadways, the material is expected to become a new-generation gas explosion suppression and isolation method in coal mines.

Abstract: Using corundum, quartz, kaoline, etc, as base components and CeO2-rich mixed rare earth as modifier, foam ceramics were fabricated adopting the organic foam impregnation process. The mixed rare earth addition had much improving effects on the matrix mechanical properties owing to much glass phase and acerate mullite growing. While 3wt% was considered to be the optimal addition, in this case, homogeneous and compact ceramic microstructure with maximal glass condensation and minimal porosity formed, with the matrix compressive strength and the flexural strength at room temperature reached 0.87MPa and 0.66MPa respectively, which were 52.6% and 73.7% higher than the original samples respectively. As the mixed rare earth addition exceeded further, the compressive strength increased slowly and the flexural strength descended gradually. XRD and SEM were used to structure strengthening mechanism analysis.

Abstract: Al2O3-TiO-TiO2 multiphase foam ceramic was prepared with Al powders and TiO2 powders by combustion synthesis, Direct observation and metallographic microscope indicated that the pore diameter is 100~6000μm, and Archimedean method showed that the porosity is 35~50%. The influencing factors of the pore diameter and porosity and, the effects of adding SiO2 on compression strength of the Al2O3- TiO-TiO2 multiphase foam ceramic were discussed. It was shown that the addition of proper high temperature foaming agent can increase porosity and adding SiO2 can decrease porosity. The Al2O3-TiO-TiO2 multiphase foam ceramic has good mechanical properties and high-temperature resistance.

Abstract: The SiOC foam ceramics were prepared using polyurethane sponge and polysiloxane as raw materials. The effects of the pyrolysis temperature, the concentration of polysiloxane solutions, and the content of SiC nano-powder on compression strength of the SiOC foam ceramics have been investigated respectively. The optimum compression strength of SiOC foam ceramics is obtained at the pyrolysis temperature of 1250°C and the concentration of solution PSO of 0.8 g/ml. Adding SiC nano-powder into PSO can effectively increase compression strength of samples, and the maximum compression strength, 20.8 MPa, is obtained when the content of SiC nano-powder is 5 wt%. Microstructural study reveals that the foam ceramics have an open, uniform and interconnected porous structure with high porosity of 80%.