Jingjing Liu

Optimal design on the high-temperature mechanical properties of porous alumina ceramics based on fractal dimension analysis

Fractal theory and regression analysis were employed for the first time to investigate the effect of pore size and pore distribution on high-temperature mechanical properties of porous alumina ceramics (PAC). In the present work, PAC with the comparable porosity, different pore sizes and pore distributions were prepared using carbon black as the pore-forming agent. Particular emphasis in this study was placed on the establishment of correlation between the thermal shock resistance and pore properties. The relationship between fractal dimension (Df) andthermal shock resistance parameter (Rst) in specimens presented the negative power function, indicating that low Df could benefit the improvement of thermal shock resistance in specimens. The results showed that the increase of pore size and pore sphericity leads to a reduced Df, the enhanced hot modulus of rupture (HMOR) and. The decrease of proportion of micro-pores below 2 μm, the increase of mean pore size and pore sphericity could result in the decrease of Df, and then improve Rst and HMOR of specimens. Based on the correlation between Rst and pore characteristics, PAC with improved thermal shock resistance could be achieved when their pore structure meets the above features.

Synthesis of low-cost porous ceramic microspheres from waste gangue for dye adsorption

Low-cost porous ceramic microspheres from waste gangue were prepared by simple spray drying and subsequent calcination. Effects of calcination temperature on phase and microstructure evolution, specific surface area, pore structure, and dye adsorption mechanism of the microspheres were investigated systematically. Results showed that the microspheres were spherical, with some mesopores both on the surface and inside the spheres. The phase kept kaolinite after calcined at 800 and 900°C and transformed into mullite at 1000°C. The microspheres calcined at 800°C showed larger adsorption capacity and removal efficiency than those calcined at higher temperatures. Methylene blue (MB) and basic fuchsin (BF) removal efficiency reached 100% and 99.9% with the microsphere dosage of 20 g/L, respectively, which was comparable to that of other low-cost waste adsorbents used to remove dyes in the literature. Adsorption kinetics data followed the pseudo-second-order kinetic model, and the isotherm data fit the Langmuir isotherm model. The adsorption process was attributed to multiple adsorption mechanisms including physical adsorption, hydrogen bonding, and electrostatic interactions between dyes and gangue microspheres. The low-cost porous microspheres with excellent cyclic regeneration properties are promising absorbent for dyes in wastewater filtration and adsorption treatment.

Effects of Calcination Temperature on the Microstructure and Adsorption Properties of Attapulgite Microspheres

The attapulgite microspheres were produced by spray drying method and calcination process subsequently. The effects of calcination temperature on the microstructure and adsorption properties of methylene blue(MB) were investigated systematically. Results show that the median diameter of the microspheres increases after calcination. The adsorption capacity and removal efficiency of MB reaches the maximum values(96.62mg/g and 96.6%) after calcined at 600°C and decreases with the temperature increasing. The adsorption process can be described better by the pseudo-second-order kinetic model and fit the the Langmuir equation. The attapulgite microsphere shows good adsorption properties, which may be used as potential applications in various dyeing wastewater fields.

Design and formulation of polyurethane foam used for porous alumina ceramics

The present work studied a simple direct foaming method for preparation of porous alumina ceramics by expansion of a ceramic suspension based on polyurethane (PU) foam system. The effects of polyurethane formulas including catalyst composition, blowing agent content, NCO index and solid content on the samples properties were investigated. The results showed that the homogeneity, porosity and mechanical properties are various for different formulas. The dried green bodies showed diametrical compressive strength in the range of 0.39–1.25xa0MPa and were amenable to machining operations such as milling, drilling and lathing. Meanwhile, PU formulas play an important role in the microstructures and mechanical properties of green bodies and sintered ceramic foams. Pyrolytic removal of polyurethane skeleton followed by sintering at 1550xa0°C produced alumina bodies with open cell porosity 54–75% and diametrical compressive strength 1.39–28.47xa0MPa. Microstructure showed both large (200–300 μm) and small (50–100 μm) pores all with various sizes of windows. Based on the optimization of polyurethane formulation, the porous alumina foam with porosity of 64% and compressive strength of 25.26xa0MPa was prepared. This polyurethane foam system is easily available and low-cost, which could be widely applied in preparation of other porous ceramics, such as ZrO2, SiO2, etc.