| With the rapid development of industry and urbanization, noise pollution has become increasingly serious, which not only affects people’s normal work, study and life, but also endangers human body health. In order to reduce the noise pollution, it is very important to develop new building sound-absorbing materials. According to the principles of safety, decoration and lower cost, sound-absorbing materials with porous structure were prepared with tile polished waste as a raw material, which was beneficial to the recycling utilization of resources, environmental protection, and promoting the sustainable development of ceramic industry.Firstly, according to the single factor experiment, the contents of the polished tile waste and ordinary cement were confirmed to be 25-35 wt% and 5-15 wt%, respectively. The orthogonal experiment of L9(34) was carried out, choosing the polished brick waste, cement, cooling speed as factors, choosing the average sound absorption performance and intensity as the evaluation index. The best recipe was selected:porcelain stoneware tile powder 75 wt%, polished tile waste 25 wt%, additionally, ordinary cement 10 wt%, the best cooling time 30 min. The result shows that the influence of cooling rate on the comprehensive performance and the average sound absorption coefficient of the sound absorbing material was the most obvious, and the effect of cooling rate on the intensity of the sound absorbing material is not significant. The more amount of cement, the better the foaming and sound-absorbing effect. However, the strength of the prepared material was poor. The faster the cooling rate, the better the average sound absorption performance. The cooling rate has smaller influence on strength of the prepared material.The cause of the foaming of the propous material was studied according to experimental and theoretical analysis. The result ruled out the foaming possibility of organic matter and ordinary cement, which confirmed that SiC in polishing ceramic tile waste is main origin of the foaming during sintering. Silicon carbide in the polishing waste is easily oxidized under high temperature and alkaline molten salt conditions, causing the corrosion or broken of the protective layer on the silicon carbide and the rapidly oxygen diffusion through the protective layer. These lead to a substantial increase in the chemical reaction of SiC with oxygen to generate a large amount of CO2 and CO gas. The product gas is not timely discharged outward to remain in the liquid, resulting in the closed pore generation. The effect of the polishing brick waste on sintering properties was analyzed by dynamics calculation. Mullite crystallization activation energy reduced to 530 from 780 kJ/mol with the increase of polishing brick waste. The lower the crystallization activation energy, the easier the mullite formation. With the increase of polishing brick waste, Avrami constant reduces to 1.12 from 1.82, which means that mullite crystallization growth dimension decreases. The small growth dimension is advantageous to the formation of needle-like mullite crisscross network, which has a certain enhancement effect on the microstructure of the prepared material.The molten liquid phase was formed with the addition of cement fired at 1200℃ which accelerated the oxygen diffusion velocity and promoted the foaming. The connected pores structure was obtained. Through thermodynamic calculation and analysis, the result shows that the formation trend of calcium feldspar is more abvious than that of mullite with the increase of CaO content, in the case of high SiO2 content. XRD analysis results also show that calcium feldspar and quartz are the main crystal phase when CaO content is 5%. At the same time, the comprehensive performance of the sample is better, when the ordinary cement addition amount was 10%. In addition, the hydration of cement has no effect on the foaming performance of the porcelain tile.The influence of pore structure and porosity on the sound absorption performance and intensity was studied. The forming process of porous ceramics is also discussed. These results show that SiC was oxidized under high temperature, producing a large number of high-temperature and suitable viscosity melt phase because of the addition of cement, which promoted the foaming reaction, made the hole connected under the faster cooling rate. The connected hole structure was formed. The material absorption coefficient is related to the pore structure. The higher the porosity, the better the sound absorption performance. The smaller the pore size, the better the sound absorption performance. Meanwhile, the nonlinear mapping relation of the input-output model of the material system was established by using waste content, cement content, cooling rate, porosity and density as input variables. Training of the sample data and prediction of testing samples were carried out using the self-designed neural network. And the satisfactory forecasting results are obtained. The obtained optimum formula is consistent with the orthogonal experiment. The properties and relative parameters of sound-absorbing materials made by the optimized formula were obtained:the average absorption coefficient 0.255 between 160 Hz and 2000 Hz, bending strength 3.93 MPa, true porosity 64.45%, apparent porosity 42.05% and bulk density 0.89 g/cm3.The influence factor of absorption spectrum characteristics of porous ceramic sound-absorbing material was studied by analyzing material thickness, bulk density and the behind cavity. With the increase of the thickness, bulk density and the behind cavity of the material, the first resonance frequency moved in low frequency direction. The low frequency sound absorption performance of materials increased. Sound wave propagation in a standing wave tube was simulated by using CFD software Fluent. It describes a standing wave tube model analysis method by CFD. Furtherly, the model was verified by comparison with the experimental test results from the overall frequency, defferent cavity depths and different thickness. The model can be assisted to study the sound absorption properties of porous ceramic sound absorbing material. |
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