碳化硅薄膜陶瓷致梯度化贯通孔新方法及成孔机理

Due to the weak gradient and connectivity of through pores in ceramics fabricated by common processes, a new method is conceived for preparing SiC film ceramic with a desire porosity gradient and hole-through structure for capturing PM2.5 particles. The polarity water molecular and charged particles in ceramic suspension will rearrange orderly to strengthen connection drived by the outside electric field coupling with freezing to generate through pores in ceramic body. Then the hydrolytic condensation products of siloxane diffuse in graded way along the above pores to modify the ceramics. The ceramics with gradient and through pores will be formed through interaction of SiC particles with the hydrolytic condensation products of siloxane by means of calcination. With the relationship between the structure, composition characters, which is based on the processing conditions causing pores, the mechanisms will be revealed how the through pores in ceramic suspension are formed moved by outside electric field combining with freezing, how the hydrolytic condensation products graded sedimentate along these through pores, and what the effect of calcination condition of ceramic on the gradient pores are. The relationship between porous structure and separation and mechanical performance will be revealed using the results of filtration efficiency and mechanic strength of ceramic samples with different structures. The mechanisms about formation of gradient porous structure are great worthy for preparing SiC film ceramic with a gradient and through pores structure in science and theory.

针对梯度孔陶瓷材料常规制备方法存在孔梯度性及贯通性较差等问题，提出一种能捕获PM2.5颗粒的碳化硅薄膜陶瓷致梯度化贯通孔新方法。该方法以外电场驱动陶瓷浆料中极性水分子梯度冷冻冰晶致孔趋向性及荷电陶瓷颗粒趋向排列，强化陶瓷胚体孔道贯通性；以硅氧烷水解缩合产物在陶瓷胚体中梯度化扩散，实现对陶瓷胚体孔道的梯度性修饰。以焙烧实现碳化硅颗粒与硅氧烷水解产物交联，最终获得梯度化贯通孔陶瓷材料。通过调节影响致孔条件，获得具有不同组成及结构特征样，通过两者间的科学关联性，揭示电场驱动下陶瓷浆料冷冻干燥贯通孔形成规律、硅氧烷水解缩合产物在陶瓷胚体贯通孔中的梯度沉积机制、陶瓷胚体烧结因素对梯度化贯通孔的影响机制。通过对不同结构特征样的过滤效能及力学性能评价，揭示孔结构特征与分离性能及力学性能本质关联性。攻克多级孔结构材料形成机制，为构建多尺度梯度化贯通薄膜陶瓷材料及其制备新方法提供科学依据和重要的理论价值。

多孔SiC陶瓷薄膜可实现从纳米尺度筛选到可见尺度粒子分离，控制均匀梯度孔要比均一孔更为复杂。因此，寻求梯度孔薄膜陶瓷材料制备仍是一个具有一定挑战性的课题。.本项目提出垮纳米－微米－毫米多尺度梯度化多孔材料概念，以冷冻干燥法制备了层状结构多孔陶瓷胚体，以液压预水解硅氧烷醇水浸渍陶瓷胚体，借助溶剂自然挥发携带硅氧烷水解产物沿陶瓷胚体孔道表面迁移，结合表面富集层硅氧烷水解缩合产物的反向迁移，实现硅氧烷水解产物在陶瓷胚体孔的梯度性沉积；在焙烧中使陶瓷胶粒及硅氧烷水解产物的烧结交联，最终获得梯度化孔陶瓷材料。借助SEM，BET，XPS等各种手段，研究了硅氧烷水解缩合产物在碳化硅表面吸附规律，以及微观结构对所制材料分离性能及力学性能的影响规律等，揭示了梯度孔结构形成机制，突破了梯度多孔陶瓷制备技术，研制出梯度多孔SiC陶瓷材料，将快速提升我国高温除尘材料的研发技术，对节能和环保形成强有力的支撑，并为其它材质梯度多孔陶瓷材料制备提供理论及技术支持。.本项目以氧化石墨烯为原料、聚乙烯醇为交联剂，通过水热法自组装和冷冻干燥法制备三维结构多孔石墨烯，利用比表面积分析仪（BET）、X射线衍射仪（XRD）红外光谱仪（FTIR）和扫描电子显微镜（SEM）对三维多孔石墨烯的比表面积、微观形貌及结构表征分析，考察不同因素对三维多孔石墨烯吸附亚甲基蓝(MB)的影响，并探讨其吸附过程的动力学和热力学。结果表明三维多孔石墨烯具有微孔、介孔和大孔共存的孔隙结构，比表面积达141.686m2/g；三维结构多孔石墨烯吸附能力高，吸附容量最高为13.66mg/g，MB去除率最大为91.1%；三维多孔石墨烯对MB溶液的吸附过程是吸热的，符合准一阶动力学模型和langmuir等温线模型。.本项目创新性的采用水热自组装法和冷冻干燥法成功地合成了具有三维相互贯通的多孔孔道结构，解决了石墨烯易团聚的难题，加快了传质速率，提高了吸附效率，提供了一种新的三维结构多孔材料的合成技术。