碱式硫酸镁多孔吸声材料的制备及性能研究

Preparation and performance of base magnesium sulfate porous sound absorbing materials

针对青海盐湖地区弃置堆积的水氯镁石难以规模化消纳问题,制备了碱式硫酸镁(BMS)水泥基多孔吸声材料,研究了原料硫酸镁、引气剂十四烷基甜菜碱(C_(14)BE)和矿物掺合料粉煤灰(FA)等对材料的微观孔结构和性能的影响。结果表明,硫酸镁和C 14 BE的浓度对溶液的起泡性能和泡沫稳定性影响显著,当二者浓度分别为2.4 mol/L(水灰比为1.1)和9.8 mmol/L时,所制得的BMS多孔材料的孔径大、开孔率高,抗压强度为2.0 MPa,降噪系数(NRC)可达0.70;FA掺杂使材料的孔壁增厚、力学性能提升,同时开孔率下降、吸声性能降低,但即使FA掺量增至40%,其NRC值仍然可达0.51。BMS多孔吸声材料的研制不仅为噪声控制领域提供了一种新型无机非金属材料,而且为盐湖镁资源的有效利用提供了一条新途径。

In the salt lake area of Qinghai,China,large-scale utilization of bischofite generated by decades of potassium exploitation has been a big issue.This paper reports a base magnesium sulfate(BMS)porous sound-absorbing material prepared using BMS cement as matrix material,tetradecyl betaine(C_(14)BE)as air-entraining agent,and fly ash(FA)as mineral admixture.The effects of the concentrations of magnesium sulfate and C_(14)BE,together with the dosage of FA on the pore structure,compressive strength and acoustic performance of BMS porous materials were investigated as well.The results reveal that the concentrations of magnesium sulfate and C_(14)BE have significant impacts on the foamability and foam stability of the solution.The foaming is inhibited by highly concentrated MgSO_(4)solution due to high viscosity and decrease in the solubility of C_(14)BE caused by a strong salting-out effect,whereas the foam stability is enhanced because of the remarkably increased surface tension and intermolecular force in the liquid film.The optimal concentrations of MgSO_(4)and C_(14)BE are determined as 2.4 mol/L and 9.8 mmol/L,respectively,under which the prepared materials are possessing of large pore size,high open porosity,excellent acoustic and mechanical performances.The noise reduction coefficient(NRC)and compressive strength of the porous BMS sound-absorbing material reach as high as 0.70 and 2.0 MPa with a density of 309 kg/m^(3).In addition,FA doping can lead to a decrease in open porosity and pore wall thickening in the porous materials,which is harmful to the sound absorption performance.Nevertheless,the NRC value of the BMS porous material reaches 0.51 with a FA dosage of 40%,which can still meet the requirement of sound-absorbing materials used at highway,railway,etc.The development of BMS porous sound-absorbing materials not only provides a new type of inorganic non-metallic materials for the field of noise control,but also provides a new way for the effective utilization of salt lake magnesium resources.