Spraying Technology For Key Parts Of A New Photocatalytic Air Purification Device Based On Liquid Material Plasma Spraying

Since the industrial era,there has been a sharp increase in carcinogenic pollutants in the air,among which volatile organic compounds（VOC_S）can poison the central nervous system,liver,kidneys and other organs of the human body.In the past few years,relevant researchers have proposed using air purification devices to remove VOCS from the air.In air purification devices,photocatalytic filters are key components that play a major role in the removal of VOC_S.The photocatalytic coating on their surface plays a decisive role,that is,using sunlight or artificial light can degrade VOC_S into non-toxic products（CO₂,H₂O,etc.）.The coating material on the surface of the filter is mainly titanium dioxide（TiO₂）based catalyst,but TiO₂ catalyst cannot use visible light for photocatalysis and needs to be modified to improve its visible light response ability.In this study,TiO₂ coatings with visible light catalytic properties were prepared by high performance liquid plasma spraying technology.On the one hand,due to the thin coating,the substrate temperature has a great impact on the phase composition and microstructure of the coating during the plasma spraying process,thus affecting the photocatalytic and mechanical properties of the coating.Therefore,this article controls the substrate temperature during the spraying process and explores the relationship between the substrate temperature and photocatalytic and mechanical properties.On the other hand,TiO₂ based photocatalytic coatings have hydrophilicity,which can easily adhere to dust and scale,leading to reduced catalytic performance and even catalytic failure of the coatings.Therefore,this article uses the hydrophobic material perfluoroalkoxyvinyl ether copolymer（PFA）to dope and modify the TiO₂ coating,and prepares the PFA/TiO₂ hydrophobic self-cleaning photocatalytic coating to improve its hydrophobic self-cleaning function.SEM,EDS,XRD,XPS and other detection methods were used to characterize the microstructure,phase composition,and elemental valence of the coating.The evolution trend of the mechanical,hydrophobic,and photocatalytic properties of the coating was explained by analyzing and discussing the coating bonding strength,surface static contact angle,and degradation rate of methylene blue（MB）reagent.The main research content and results are as follows:（1）TiO₂ photocatalytic coating was prepared by liquid material plasma spraying technology.Coating thickness is within 15μAt around m,under visible light conditions,the catalytic rate of TiO₂ coating on MB is 0.00307,while the catalytic rate of the original TiO₂ powder is 0.During the spraying process,high spraying temperature accompanied by reducing H₂ reduces TiO₂,thereby achieving Ti³⁺self doping modification,greatly reducing band gap,and enabling the catalyst to have catalytic ability under visible light.（2）TiO₂ coatings were prepared at different substrate temperatures（250℃,180℃,110℃）.As the substrate temperature decreases,the photocatalytic performance of the coating gradually improves,and the MB degradation rate under visible light increases from69%to 80%.However,the mechanical properties of the coating showed a downward trend,with a decrease in coating bonding strength of 12.28 MPa and a decrease in the critical normal load value of 1.77 N during scratch testing.（3）Preparation of PFA/TiO₂ hydrophobic photocatalytic coatings doped with TiO₂ with different mass fractions of PFA（0%,5%,15%,25%）.The contact angle of pure TiO₂ coating is 28.2°,and the hydrophobic angle of doped PFA coating is greater than 90°,exhibiting hydrophobic properties.The contact angle gradually increases with the increase of PFA doping ratio,with a maximum contact angle of 134°.Under UV/visible light conditions,the photodegradation activity of PFA doped coatings is higher than that of pure TiO₂coatings.The catalytic activity of the coating under visible light increases with the increase of PFA doping amount,with a degradation rate of up to 95%for MB.