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.

中文翻译：

---

冷冻铸造多孔 Al2O3/MgO 陶瓷作为潜在的声学吸声材料

在声学工程和建筑中，广泛使用称为吸声器的材料。目前此类材料有多种选择，并且更多的材料正在研究中。这项研究针对通过冷冻铸造工艺生产的多孔陶瓷进行，以提出具有独特性能（例如耐恶劣环境）的新解决方案。冷冻铸造方法允许通过悬浮液的低温冷冻来控制地为不同类别的材料创建开放连接的多孔结构。材料样品是使用Al2O3（氧化铝）/MgO（氧化镁）材料并使用莰烯作为溶剂生产的。使用三种不同浓度的两种固体成分（重量为 60/40、72/28 和 90/10）制备样品。每个样品浓度实现不同的形态相组成和多孔结构。因此，我们在本文中探讨了这些浓度参数如何干扰声吸收。此外，使用与吸声和微观结构相关的数值和实验方法对样品进行了表征。 60/40 和 90/10 样本在 2000-3000 Hz 频率范围内的吸声系数值高达 0.7。微观结构特征显示孔隙率沿其厚度逐渐变化，影响其吸声性能。我们的研究结果强调了表征多孔陶瓷的复杂性，并强调了了解影响吸声的一些材料成分因素的重要性。因此，这项研究为多孔陶瓷冻铸材料的复杂性质及其声学特性提供了宝贵的见解，为该领域的持续探索做出了重大贡献。