悬浮液等离子喷涂高效制备TiO_(2)涂层及其光催化性能

High Efficiency Preparation TiO_(2) Coatings by Suspension Plasma Spraying and Photocatalytic Photocatalytic Performance

目的 解决TiO_(2)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TiO_(2)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TiO_(2)涂层,借助H2将高温等离子体焰流中熔融态TiO_(2)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TiO_(2)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TiO_(2)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2.94μm,孔隙率为10.2%。TiO_(2)粉末物相为纯锐钛矿,涂层物相由锐钛矿、金红石相及TiO_(2)-x相组成。TiO_(2)涂层中Ti3+的存在使其带间隙减小0.6eV。在紫外光条件下,TiO_(2)粉末的催化速率为0.00348,而涂层的催化速率为0.00345。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0.00307。结论通过SPS技术成功制备了TiO_(2)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。

The purpose of the research was to ensure the original photocatalytic efficiency of TiO_(2) 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 TiO_(2) to visible light through the preparation of coating.However,the dense TiO_(2) coating had small catalytic surface area,and then the photocatalytic effect would become worse.In addition,the TiO_(2) 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,TiO_(2) 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 TiO_(2) 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 TiO_(2) 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 TiO_(2) powder better dispersed in deionized water.During the spraying process,the TiO_(2) 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 TiO_(2) suspension.The injected TiO_(2) suspension interacted with the plasma flame flow(Ar-H2),the TiO_(2) coating was finally deposited on the surface of the aluminum matrix.The microstructure,phase composition and optical properties of TiO_(2) powder and TiO_(2) 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 TiO_(2) coating shows a"Karst Landform"morphology composed of molten and semi-molten particles,with the surface roughness of 2.94µm and porosity of 10.2%.The morphology of the TiO_(2) coating will offer the large catalytic surface area.The TiO_(2) powder phase is pure anatase,the coating phase is composed of anatase,rutile phase and TiO_(2)-x phase.The presence of Ti3+in the TiO_(2) coating reduces the band gap by 0.6 eV,which enables TiO_(2) to better absorb visible light.As a result,under UV conditions,the catalytic rate of TiO_(2) powder is 0.00348,while that of coating is 0.00345.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 TiO_(2) photocatalytic coating is successfully and efficiently prepared by SPS technology and the catalytic performance of TiO_(2) is significantly improved compared with powder under visible light.