悬浮液等离子喷涂高效制备TiO2涂层及其光催化性能

目的 解决TiO2粉末催化剂在污水净化过程中易沉降和难回收问题,同时提高TiO2在可见光条件下降解有机污染物的速率。方法 采用悬浮液等离子喷涂(SPS)技术,以H2为辅助气体制备TiO2涂层,借助H2将高温等离子体焰流中熔融态TiO2中的Ti⁴⁺还原成Ti³⁺。通过场发射扫描电子显微镜、X射线衍射仪、X射线光电子能谱光谱仪、紫外-可见光谱仪等对TiO2粉末以及所制备涂层的结构形貌、物相组成、元素价态、光学特性进行分析。以亚甲基蓝为目标污染物,使用光化学反应仪测试粉末和涂层的光催化性能。结果 TiO2涂层表面呈现由熔融和半熔融颗粒组成的“喀斯特”微观形貌,表面粗糙度为2.94 µm,孔隙率为10.2%。TiO2粉末物相为纯锐钛矿,涂层物相由锐钛矿、金红石相及TiO2－x相组成。TiO2涂层中Ti³⁺的存在使其带间隙减小0.6 eV。在紫外光条件下,TiO2粉末的催化速率为0.003 48,而涂层的催化速率为0.003 45。在可见光条件下,粉末的催化速率与亚甲基蓝的光解速率相近,涂层的催化速率是0.003 07。结论 通过SPS技术成功制备了TiO2光催化涂层,其在可见光条件下的催化性能较粉末有显著提升。

High Efficiency Preparation TiO2 Coatings by Suspension Plasma Spraying and Photocatalytic Photocatalytic Performance

The purpose of the research was to ensure the original photocatalytic efficiency of TiO2 powder, solved the problems of easy sedimentation, difficult recovery and inconvenient use in flowing water area of powdered catalyst in the process of water treatment catalysis, then improved the absorption capacity of TiO2 to visible light through the preparation of coating. However, the dense TiO2 coating had small catalytic surface area, and then the photocatalytic effect would become worse. In addition, the TiO2 had a large band width (3.2 eV), which made it unable to use visible light for catalytic degradation of pollutants. In order to solve the above problems, TiO2 needed to be modified to reduce its band gap width and build a coating structure with large catalytic surface area and porosity. In this paper, the TiO2 powder was prepared into coatings by suspension plasma spraying (SPS) equipment, which was a combination of self-made suspension system and plasma spraying system (GTV CL, WI-091). A certain amount of TiO2 powder with an average particle size of 15nm was added into the deionized water to prepare TiO suspension with a solid content of about 12%. At the same time, the PAA dispersant was added to make the TiO2 powder better dispersed in deionized water. During the spraying process, the TiO2 suspension stably injected into the plasma through the self-made suspension system which integrated the functions of constant temperature, magnetic stirring and ultrasonic vibration. This self-made suspension feeding equipment system was a new type of multi-functional then ensured the uniformity and stability of TiO2 suspension. The injected TiO2 suspension interacted with the plasma flame flow (Ar-H2), the TiO2 coating was finally deposited on the surface of the aluminum matrix. The microstructure, phase composition and optical properties of TiO2 powder and TiO2 coating were analyzed by field emission scanning electron microscope, X-ray diffractometer, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy and other characterization equipment. With methylene blue as the target pollutant, the catalytic degradation performance of powder and coating under ultraviolet light and visible light was tested by photochemical reaction instrument, and the degradation results were fitted by the first-order kinetic equation. The results show that the TiO2 coating shows a "Karst Landform" morphology composed of molten and semi-molten particles, with the surface roughness of 2.94 µm and porosity of 10.2%. The morphology of the TiO2 coating will offer the large catalytic surface area. The TiO2 powder phase is pure anatase, the coating phase is composed of anatase, rutile phase and TiO2-x phase.The presence of Ti3+ in the TiO2 coating reduces the band gap by 0.6 eV, which enables TiO2 to better absorb visible light. As a result, under UV conditions, the catalytic rate of TiO2 powder is 0.003 48, while that of coating is 0.003 45. Under visible light, the catalytic rate of powder is similar to the photolysis rate of methylene blue, and the catalytic rate of coating is 0.00307. The TiO2 photocatalytic coating is successfully and efficiently prepared by SPS technology and the catalytic performance of TiO2 is significantly improved compared with powder under visible light.