Preparation And Properties Of Sound-absorbing Ceramics Based On Low-grade Non-metallic Minerals

The usage of porous sound-absorbing materials is an effective means in noise control engineering.Porous sound-absorbing ceramics are widely used as their advantages of high temperature resistance,high strength,acid and alkali corrosion resistance,etc.Tuff,which is produced when mines perlite or bentonite,has been rarely used.Especially,magmatic soil is generally discarded as solid waste.As magmatic soil and tuff are silicate mineral materials,they can also be used as raw materials for ceramics,glass,cement,etc.This work explored the preparation of porous ceramics with high sound absorption ability,developed simple and reliable procedure using low grade nonmetallic ore as the raw materials.In this study,the porous sound-absorbing ceramics were prepared by the combination of the foaming method and the template method.The magma soil and tuff as the main raw materials,and the silicon carbide,the silicon carbide,carbon powders and borax were used as the foaming agent,pore-forming agent and flux,respectively.The main contents of this paper are as below(1-6).(1)The feasibility of preparation process was investigated,Fixed magmatic soil:tuff=2:1,and over 160 mesh sieve,borax dosage was 2.5 wt.%.The effects of sintering temperature,straw,silicon carbide,and sample thickness on sound absorption properties were explored.Results showed that the porous sound-absorbing ceramics had been successfully prepared by this procedure.The influence of open cell by two kinds of pore-forming agents,namely straw and carbon powers,were screened.The latter one showed better open cell,but some samples featured some crack.(2)To eliminate the crack,adding sintering additives,i.e.,glass powder,bentonite and alumina or adjusting cooling rate to improve the toughness of ceramics in the system of carbon powder as template.Results showed that the both additives could solve the crack effectively and choose the latter to cut costs.(3)On the basis of the above experiment,single factor method was employed to study the effects of raw material ratio,sintering temperatures,heating rate,water dosage,forming pressure,foaming agent contents(FAC),pore-forming agent contents(PAC),and borax contents on the sound absorption properties.(4)Basing on the single factor experiment results,orthogonal experiment method was selected to further optimize the process parameters.The interaction of foaming agent,pore-forming agent and flux agent were investigated,respectively.Visual analysis was used to analyses date.Results showed that the foaming agent and pore-forming agent were the significant factors for the effects of the properties of samples.(5)The influence of sound absorption properties with mechanism by structural agent,apparent porosity(H),pore size(D),and thickness,were stated.Moreover,Delany-Bazley and Voronina were chosen to simulate the sound absorption coefficients(α).(6)The H,D,compression strength,sound absorption properties,phase compositions,and morphology of sound-absorbing ceramics were measured.Results showed that the combined foaming method with template method,eliminated the defects of poor sound absorption properties that prepared by one of the methods,could prepared porous ceramics with excellent sound absorption properties.Comparing with a single foaming method or a template method,the new method could elevate the sound absorption coefficient(α)and H by 258%and 728%,respectively.The optimum sound absorption properties of the ceramics,i.e.α=0.71,the noise reduction coefficient(NRC)=0.50,and H=52.53%,were obtained at mass ratio of magmatic soil to tuff=3:1,sintering temperature=1175 ~oC,heating rate=15 ~oC/min,water dosage=13 wt.%,forming pressure=15 MPa,borax contents=2.8 wt.%,FAC=1.8 wt.%and PAC=4 wt.%,respectively.In this study,sound-absorbing ceramics were prepared by the new procedure combined foaming method and template method,and with low grade non-metal ore as the raw materials.The products not only possessed excellent sound absorption properties,but also could provide a new way for the development and utilization of magmatic soil and tuff.