Wang Chao, Rong Yedong, Zhang Boran, Yang Jinlong
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
Langmuir. 2022 Jan 25;38(3):1141-1150. doi: 10.1021/acs.langmuir.1c02791. Epub 2022 Jan 11.
Porous ceramics are good candidates for thermal-insulating materials. Glass is a low-cost material that possesses low intrinsic thermal conductivity of less than 10 W·m·K. However, the mechanical strength of a homogeneous glass material is fairly low. We, in this work, have fabricated AlO-hollow glass sphere (HGS) foam ceramics with a facile particle-stabilized foaming method. The obtained foam ceramic presents a hierarchical microstructure that is rare to be seen elsewhere using this foaming technique. The foaming system contains two types of particles having opposite charges, and the particle-stabilized foaming mechanism is hence discussed. The optimal sample possesses a porosity above 94% with a thermal conductivity as low as 0.0244 W/m·K, which reaches the level of superinsulating materials. The compressive strengths of the foam ceramics range from 0.07 to 0.83 MPa. The effective medium theory model is used to calculate the thermal conductivities as reference. The deviation of the theoretical values from the experimental ones are derived from the effect of the hierarchical microstructure of the foams. The results of this work may deepen one's understanding and pave new ways for the particle-stabilized foaming technique. The unique microstructure of the ceramic may also shed some light on fabricating superior thermal-insulating ceramic materials.
多孔陶瓷是隔热材料的理想选择。玻璃是一种低成本材料，其固有热导率较低，小于10W·m·K。然而，均质玻璃材料的机械强度相当低。在这项工作中，我们采用一种简便的颗粒稳定发泡法制备了AlO空心玻璃微珠（HGS）泡沫陶瓷。所获得的泡沫陶瓷呈现出一种分级微观结构，使用这种发泡技术在其他地方很少见到。发泡体系包含两种带相反电荷的颗粒，因此讨论了颗粒稳定发泡机理。最佳样品的孔隙率高于94%，热导率低至0.0244W/m·K，达到了超级隔热材料的水平。泡沫陶瓷的抗压强度范围为0.07至0.83MPa。使用有效介质理论模型计算热导率作为参考。理论值与实验值的偏差源于泡沫分级微观结构的影响。这项工作的结果可能会加深人们的理解，并为颗粒稳定发泡技术开辟新的途径。陶瓷独特的微观结构也可能为制造优质隔热陶瓷材料提供一些启示。
