Freeze-cast porous Al2O3/MgO ceramics as potential acoustic sound absorption

Abstract

In acoustic engineering and architecture, materials called acoustic absorbers are widely used. There are currently numerous options for such materials, and many more are being researched. This study is conducted on porous ceramics produced via the freeze-casting process to propose new solutions with unique properties, like resistance to harsh environments. The freeze-casting method allows for the controlled creation of open-connected porous structures for different class materials through the cryogenic freezing of the suspension. The material samples are produced with Al2O3 (alumina)/MgO (magnesium oxide) material using camphene as solvent. The specimen samples are prepared using three different concentrations of the two solid components (60/40, 72/28, and 90/10 in weight). Each sample concentration achieves different morphology phase compositions and porous structures. Hence, we explore in the paper how those concentration parameters could interfere with acoustic absorption. Further, the samples were characterised using numerical and experimental methods related to sound absorption and microstructure. The 60/40 and 90/10 samples achieve sound absorption coefficient values upwards of 0.7 around the 2000-3000 Hz frequency range. The microstructure characteristics show the porosity gradually changing along its thickness, interfering with their sound absorption properties. Our findings highlight the complexities of characterising porous ceramics and emphasise the significance of understanding some material composition factors affecting sound absorption. Hence, this study provides valuable insights into the intricate nature of porous ceramic freeze-cast materials and their acoustic properties, substantially contributing to the ongoing exploration in this domain.