炭辅助的固态粒子烧结工艺制备多孔TiO2/不锈钢膜

提出了一种炭辅助的固态粒子烧结工艺, 可在大孔烧结金属载体表面直接制得无过渡层的多孔陶瓷膜。以纳米TiO₂为成膜粒子, 以大孔不锈钢滤管为载体, 以聚乙烯醇(PVA)为粘结剂, 采用浸渍提拉法在载体表面涂覆。考察了不同烧结气氛(氮气和空气)对陶瓷膜制备的影响。通过扫描电子显微镜、X射线衍射、热重分析和孔径测试对材料进行表征。实验发现, 试样在空气中烧结后膜层发生严重剥落, 而在氮气中烧结后膜层完整。这是由于PVA在氮气中高温碳化生成炭, 所形成的TiO₂和炭的混合结构削弱了因载体表面状况差和陶瓷—金属间热膨胀系数不匹配而引起的陶瓷层烧结应力。待陶瓷颗粒烧结后, 涂层中的炭经空气热处理脱除。所制备的多孔TiO₂/不锈钢膜的膜层厚度约10 μm, 平均孔径为0.21 μm, 室温下氮气通量为1.72 m³/(m²·h·kPa)。

Preparation of Porous TiO2/Stainless-steel Membranes by Carbon Assisted Solid-state Particle Sintering

Porous ceramic membranes on macroporous metal support without any intermediate layer were prepared by a solid-state particle sintering assisted with carbon. Nano-scale TiO₂ particle and macroporous stainless-steel tube were employed as membrane material and support, respectively. For surface coating, polyvinyl alcohol (PVA) was used as adhesive agent, and dip-coating procedure was performed. Effect of different sintering atmosphere (i.e., nitrogen and air) during the preparation of porous ceramic membrane was investigated. For characterization, scanning electron microscopy, X-ray diffraction, thermogravimetry and porometry analyses were conducted, respectively. It was found that serious peeling of the ceramic membrane was occurred when the coated sample was heat-treated in air, but an integrated membrane was achieved when the sintering atmosphere was replaced with nitrogen. Owing to the existence of carbon generated by the carbonization of PVA in nitrogen at high temperature, the mixed structure of TiO₂ and carbon can help to weaken the membrane sintering stress which is caused by poor quality of the support surface and by mismatch of the thermal-expansion-coefficients of ceramic and metal. After the sintering of TiO₂ particle, the generated carbon can be removed by heat-treatment in air, resulting in a porous TiO₂/stainless-steel membrane. The membrane thickness and mean pore size are 10 μm and 0.21μm, respectively, and the corresponding nitrogen flux is 1.72 m³/(m²·h·kPa) at room temperature.