Ceramic membranes play an important role in high temperature gas-solid filtration. However, the thermal stability of the ceramic support at high temperatures has always been a problem. In this study, porous fused silica ceramic supports were fabricated with hexagonal boron nitride as a sintering aid. The results shown that hexagonal boron nitride could inhibit the crystallization of fused silica ceramic particles at high temperature and act as a sintering addictive to reduce firing temperature. The obtained supports have an average pore size of 72 µm, an open porosity of 42%, a bending strength of 16.5 MPa, a Weibull modulus of 8.67 and a gas permeability of 4.23 × 10 5 m 3 /(m 2 h bar). The bending strength of the support remained 16 MPa after 30 cold-hot cycles, exhibiting high thermal shock resistance . After corrosion in 20 vol% H 2 SO 4 solution for 8 h, the weight and the bending strength of the support were diminished by 0.6% and 24.32%, respectively. So, the ceramic support showed good acid corrosion resistance .
Jianbing Song,Kaixin Song,Jinsheng Wei,Huixin Lin,Junming Xu,Jun Wu,Weitao Su
Apatite structure of CaLa 4 Si 3 O 13 ceramics was prepared by the conventional solid-state reaction route. The Rietveld refinement of powder X-ray diffraction (XRD) and analysis of scanning electron microscope images demonstrated that CaLa 4 Si 3 O 13 belonged to a hexagonal structure with space group of P 6 3 / m (No. 176) and grew in a shape of hexagonal prism. The effects of crystallinity, porosity, grain morphology, grain size distribution, and oxygen vacancy on the microwave dielectric properties were investigated in detail as a function of sintering temperature . The existence of Oxygen vacancies and the stretching and bending modes of SiO 4 tetrahedral units were discussed by Raman spectra. Excellent microwave dielectric properties were obtained with ε r = 14.5, Q × f = 31,100 GHz (at 9.05 GHz), τ f = −22 ppm/°C, indicating possible potential applications for microwave substrate applications.
Ya-Ru Wu,Jun-Hong He,Li-Jin Cheng,Jia-Min Wu,Yu-Sheng Shi
Porous Si 3 N 4 ceramics are widely used in the aerospace field due to its lightweight, high-strength, and high wave transmission. Traditional manufacturing methods are difficult to fabricate complex structural and functional ceramic parts. In this paper, selective laser sintering (SLS) technology was applied to prepare porous Si 3 N 4 ceramics using AlN as an inorganic binder. And the effects of AlN content on the properties of the obtained ceramic samples were explored. As the AlN content increased, nano-Al 2 O 3 and nano-SiO 2 formed the eutectic liquid phase, enhancing the sintering densification and phase transformation of Si 3 N 4 poly-hollow microspheres (PHMs). The island-like partial densification structures in Si 3 N 4 green bodies increased. During the high-temperature sintering, the eutectic liquid phase partially transformed into the mullite phase or reacted with AlN and Si 3 N 4 to form the Sialon phase. With the increase of AlN content, the fracture mode of Si 3 N 4 ceramics changed from fracturing along PHMs to fracturing across PHMs. The bonding depth between PHMs increased and the connection between the grains was tighter, so the Si 3 N 4 ceramics became denser. With the increase of AlN addition, the total porosity of the porous Si 3 N 4 ceramics tended to decrease and the flexural strength gradually increased. When AlN content was 20 wt%, the total porosity and the flexural strength were 33.6% and 23.9 MPa, respectively. The addition of AlN inorganic binder was carried out to develop a novel way to prepare high-performance porous Si 3 N 4 ceramics by SLS.
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