Search

Porous ceramics are demanded in a wide range of high‐temperature, biological and energy‐related applications, but may show conflicting properties or suffer from poor mechanical properties. Introducing pores at different length scales has been shown to be a promising design strategy to combine antagonistic performance parameters and reach high porosity without severely compromising strength. Herein, a cost‐effective and simple process to create strong, highly porous ceramics via direct ink writing of suspensions of hollow microspheres into cellular architectures with pores at three hierarchical levels is reported. X‐ray diffraction, rheological measurements, scanning electron microscopy, and mechanical tests are conducted to thoroughly study the processing steps and morphology of the printed hierarchical porous ceramics. The presence of pores at multiple length scales increases significantly the mechanical strength of the porous structure, providing a useful platform for the manufacturing of lightweight ceramics from inexpensive and widely available feedstock materials. [ABSTRACT FROM AUTHOR]

Herein, the advantage of single-shell hollow microspheres on forming pores has been exploited to acquire porous ceramics with homogeneous microstructure, while the hollow microspheres also acted as reaction source. Dispersant reaction method has been applied to realize the perfect combination between microspheres and Si3N4 particles, which could be attributed to the repulsion between particles is weakened, particles agglomerate together and holding microspheres among them tightly. Owing to the normal distribution of hollow spheres and their single-shell structure, porous Si2N2O-Si3N4 ceramics with uniform pore distribution have been fabricated. The results show that the addition of silica hollow spheres contributes to the decrease in dielectric constant, since their porosity could be increased effectively and Si2N2O phase exhibiting low dielectric constant is generated. High-performance porous Si3N4 ceramics with porosity of 45.7% have been prepared through employing fly ash hollow microspheres, which possess flexural strength of 108.76 ± 6.25 MPa, fracture toughness of 1.78 ± 0.09 MPa m1/2 and dielectric constant of 3.53. This strategy is proved to be a convenient, eco-friendly and effective method to synthesize ideal candidates for radomes. [ABSTRACT FROM AUTHOR]

A novel kind of nanowire sponges, namely Si3N4 nanowire‐weaving microspheres, synthesized from a simple, convenient, high‐efficient approach are proposed here. As the reverse template, three‐dimensional foam skeleton structure with uniform pores and ultrathin pore walls is constructed via the effective particle‐stabilized foam method, where the silica sol and carbon black are chosen as the raw materials, providing the sufficient space for the growth of nanowires during the carbothermal reduction reaction process. The formation mechanism of this novel sponge is studied via multiple characterization methods. Si3N4 nanowires formed microspheres possess uniform and curving morphology due to the stable environment for growing via vapor–solid mechanism, leading to the relatively high specific surface area of 86.77 m2/g. Owing to in‐situ oxidation process, micro‐spherical SiO2 nanowire sponges with similar morphology are synthesized, which present diameter in range of 20‐40 nm and specific surface area of 50.47 m2/g. This work provides insights for the design of high‐performance nanowire sponges with promising applications in the filtration, thermal insulators, and catalyst supports fields. [ABSTRACT FROM AUTHOR]

In this paper, attapulgite microspheres were prepared by spray drying method and calcination subsequently. The effects of calcining temperature, microsphere dosage, contact time and concentration of dye on the adsorption properties of malachite green were investigated systematically. Results show that the fibrous and fold microstructure could be seen on the surface of the porous microspheres, and was mainly composed of palygorskite. The adsorption capacity of malachite green for microspheres increased firstly (500-700 °C) and then declined (800-1 000 °C ) with the calcination temperature increasing. The adsorption capacity and removal efficiency of malachite green for microspheres treated after 600 °C was 95.45 rng/g and 95.5%, respectively. The ad- sorption capacity of malachite green increased with the amount of microspheres and original concentration of the dye increasing, and the adsorption process could be described by the pseudo-second-order kinetic model. [ABSTRACT FROM AUTHOR]

In this work, gangue/palygorskite composite microspheres were fabricated through spray drying process and activated by calcination treatment. Its microstructure and adsorption capacity for the removal of dye (MB) were also studied, systematically. Results showed that kaolinite, α‐quartz and palygorskite were the major phases in microspheres after proper calcination (lower than 900°C). BET‐specific surface area of the microspheres reached the maximum value of 62.23 m2/g at 700°C, and then decreased with further increasing the heating temperature. In general, composite microspheres showed the largest adsorption capacity of MB after heat‐treated at 700°C. The qmax of MB onto microspheres was 29.9‐51.9 mg/g. The adsorption process of MB onto microspheres was well described by both the pseudo‐second‐order kinetic and Langmuir isotherm model. The composite microspheres also had extraordinary recyclability. This novel microsphere could be employed as a candidate for novel absorbent and filter medium in the practical application for dye treatment in industrial applications. [ABSTRACT FROM AUTHOR]