Industry New Knowledge | "Journal of the European Ceramic Society" DIW Print Multistage Pore Structure Aluminum Borate Ceramics

Recently, Professor Jia Wenbao's team from the School of Materials Science and Technology of Nanjing University of Aeronautics and Astronautics published a research paper entitled Novel ceramic supports for catalyst with hierarchical pore structures fabricated via Journal European-direct Ceramic in "additive of the manufacturing writing Society". The direct ink writing technology combined with in-situ grown whiskers has promoted the development of 3D printing ceramic catalyst carrier-aluminum borate porous ceramics (ABPCs).

Original link:

　　https://www.sciencedirect.com/science/article/abs/pii/S0955221924002887

adventure of science and technology official website:

　　http://www.adventuretech.cn/

If it cannot be opened, please copy the URL to the browser.

research background

Porous ceramics have high porosity, stable chemical properties, large specific surface area, low bulk density, low thermal conductivity, high temperature resistance and corrosion resistance, and have many applications in metallurgy, biology, energy, environmental protection and other fields. The main preparation methods are foaming hole-making method, sol-gel method, additive manufacturing method and emulsion or foam template method. Among these methods, additive manufacturing is considered to be the ideal method for manufacturing porous ceramics with complex geometries.

graphic analysis

In this study, we used a combination of in-situ reaction and DIW to prepare aluminum borate whisker porous ceramics with high-order pore structure. The rheological properties of the slurry, especially the viscoelasticity, were optimized by adjusting the amount of dispersant, thickener, pH value and the amount of water added. Secondly, the influence of printing parameters and slurry rheology on the printed preform structure is studied by using the flow field model. The phase composition, microstructure, bulk density, apparent porosity and mechanical properties of ABPCs were discussed in detail. Then the specific surface area and pore size distribution of ABPCs were studied systematically. Importantly, the potential of ABPCs as high-performance catalyst supports was demonstrated.

In direct ink writing technology, the characteristics of the ink are very important, and the uniform distribution of the ink has a great influence on the quality and accuracy of the printed sample. Figure 1 shows the effect of the amount of dispersant (FS20) on the viscosity of the ink. Comparing the slurry with FS20 and the ink without FS20, it is obvious that the viscosity of the former is obviously reduced. With the addition of FS20 increasing from 0.1wt% to 0.4wt%, the viscosity of the ink first decreases and then increases, and reaches the lowest viscosity when the addition of FS20 is 0.2wt%. This is because an appropriate amount of FS20 can be adsorbed on the surface of the powder particles to enhance the electrostatic interaction and spatial repulsion between the particles in the ink. This promotes dispersion and reduces viscosity. However, an excessive amount of FS20 results in the formation of brush-like structures between the functional groups of FS20 in the ink, resulting in an increase in viscosity.

Fig.1 Effect of dispersant (FS20) dosage on ink viscosity

Figure 2 shows the apparent morphology of ABPCs filaments after sintering at different temperatures. It can be seen from the figure that there are a large number of whiskers on the surface, which can be considered as aluminum borate whiskers. With the increase of sintering temperature, the grain size of aluminum borate gradually increases, indicating that the higher sintering temperature promotes the growth of aluminum borate grains. In addition, when the sintering temperature increases from 1000 ℃ to 1100 ℃, the length of the aluminum borate whisker also increases, and the morphology of the whisker is needle-like. When the sintering temperature is further increased, the aluminum borate whisker grows up evenly, forming a larger columnar crystal, and the aspect ratio of the whisker decreases with the increase of the sintering temperature.

Fig.2 SEM images of ABPCs filaments after sintering at different temperatures

Figure 3 shows the pore size distribution of ABPCs filaments after sintering at different temperatures. It was observed that all ABPCs samples, sintered at different temperatures, exhibited a hierarchical pore structure. The median pore diameter (volume) of ABPCs filaments increases with increasing sintering temperature. When the sintering temperature is 1000 ℃ or 1100 ℃, it is mainly composed of sub-micron pores, and above 1200 ℃, it is mainly composed of micron pores. With the increase of sintering temperature, the proportion of sub-micron pores gradually decreases, while the proportion of micron pores gradually increases.

Fig.3 Pore size distribution of ABPCs sintered at different temperatures

research conclusion

In this study, a new method of preparing a new type of catalyst ceramic carrier by in-situ growth of whiskers with aluminum borate as the carrier was explored. The DIW 3D printing process allows for the creation of large pores, while the in-situ whiskers facilitate the formation of submicron or micron-sized pores on the extruded filaments.