Preparation And Properties Of High Sound Absorption Porous Ceramics By Dry Pressing

The porous sound absorption ceramics which possess excellent performance, such as high strength, high-temperature and corrosion resistance has a widely application prospect. Its application in the noise reduce and elimination is one of the main methods to control the increasingly serous noise pollution problems at present. In this thesis, the porous sound absorption ceramics were prepared by dry pressing using the silicon carbide as the pore-forming agent combining the silicon carbide and iron oxide to form.Firstly, the ceramic raw materials, clay, talcum and potash feldspar were used as raw materials. The effects of these components on the properties of apparent porosity, water absorption and sintered density of porous ceramics were investigated. The sample formulation with the highest apparent porosity and water absorption was chosen as the basic formulation, that was 55.00 wt.% ceramic raw materials, 15.00 wt.% clay,18.00 wt.% talcum and 12.00 wt.% potash feldspar. On the basis of this formulation, the effects of the raw material formula on the properties of samples were examined. In addition, the effects of the content of silicon carbide content, heating rate, holding time, milling time, sintering temperature and molding pressure on the apparent porosity, sintered density and microstructure of the samples were discussed in detail, respectively. Then, the processing parameters were optimized by the orthogonal experiments, and the optimized condition were the content of Si C 0.60 wt.%, heating rate 6℃/min, holding time 25 min, milling time 84 min, sintering temperature 1180℃, molding pressure 8MPa. The properties of the porous sound absorption ceramics prepared under the optimum condition were as follows: apparent porosity 65.20%, water absorption 101.50%, sintered density 0.65, moreover, the sound absorption coefficient of the sample reached the maximum value of 0.53 at 1600 Hz in a frequency range of 200-2000 Hz.On this basis, the iron oxide and silicon carbide were used as common pore-foaming agents to improve the sound absorption performance of the porous ceramics. The effects of the mass ratio of silicon carbide to iron oxide, heating rate, sintering temperature and molding pressure on the apparent porosity, sintered density and microstructure of the samples were investigated, respectively. The orthogonal experiment results indicated that the optimum conditions were the Si C/Fe2O3 1.6(mass ratio), heating rate 6℃/min, molding pressure 10 MPa, sintering temperature 1180 ℃. Porous sound absorption ceramic was prepared through the optimal solutions and it possessed the properties as follows: apparent porosity 77.20%, water absorption 212.00%, sintered density 0.37. In a frequency rage of 200-2000 Hz, the sound absorption coefficient reached the maximum value of 0.76 at 1000 Hz, which was approximately 0.23 higher than the sample only using the silicon carbide as forming agent. This result showed that the sound absorption property of the porous ceramics formed with the iron oxide and silicon carbide was significantly improved and reached a relatively high level.Finally, in order to further improve the sound absorption performance, the effects of thickness and air layer on the sound absorption coefficient of samples were investigated. The experimental results showed that as the thickness and air layer increased appropriately, the sound absorption performance of the sample in low frequency was improved, and the sound absorption peaks were shifted to the low frequency.In the thesis, the porous sound absorption ceramics which were prepared with the iron oxide and silicon carbide as the foaming agents through the dry pressing process possessed excellent sound absorption performance. The research which provided an important reference for the industrialized production of the sound absorption ceramics with high performance possessed important guiding value in both theory and practice.