Study Of Preparation Technology And Electro Thermal Property Of TiO₂ Composite Coating

Compared with typical oil, water or steam heater roller, ceramic heater roller could provide precise temperature uniformity, easy temperature control, handling safety and low energy consumption to reduce the maintenance cost and downtime. Ceramic heater roller also has the comparative property to induction heater roller. The generalization of ceramic heater roller in the whole industry would probably increase productivity, decrease cost and save energy. In America, there are few companies such as American Roller Company researching ceramic heater roller. There are almost no studies in our country.In this paper, ceramic heating system was designed and ceramic heater rollers with TiO2 as heating layer and Al2O3 as insulating layer were produced by atmospheric plasma spraying system. H2 flow, spraying current coating thickness and heat treatment temperature were adjusted to research the influencing factors on the electrical conductivity of TiO2 coatings. Optical microscope, XRD, XPS and two-point probe method were applied to analyzing microstructure, phase composition, surface chemical state of TiO2 coatings. The result showed that: H2 flow is the main factor influencing the electrical conductivity of TiO2 coatings. The conduction mechanism of TiO2 coatings was evaluated comprehensively. Electrifying heating method was also used to research the electrifying heating property and failure pattern of the TiO2 ceramic heater roller.The main results in the paper are as follows:(1) Ceramic coating system was designed. Ceramic heater roller produced by 9M atmospheric plasma spraying system. in laboratory with utmost heating temperature approaching 400℃could be electrified persistently at low temperature 150℃. Guidance to the navel, high efficient, energy saving ceramic heater roller was supplied.(2) Effects of H2 flow, spraying current coating thickness and heat treatment temperature on the electrical conductivity of TiO2 coating were systematically studied. Conclusion was made that H2 flow was the main factor influencing the electrical conductivity of TiO2 coating. The electrical conductivity of TiO2 coatings increases with the increasing of H2 flow and spraying current and decreases with the increasing of coating thickness. Spray current makes sense in a certain range and the electrical conductivity reaches maximum at 500A under test condition. The influencing factors are all within a certain range. High temperature heat treatment can significantly reduce the electrical conductivity of the coatings.(3) Analyze was made that exponential relationship exists between the resistivity of APS TiO2 coating and temperature. The n type semiconducting property of TiO2 war attributed to point defect which formed deoxidation TiO2-X during spraying. Formation of F-color center leads coating to be dark blue.(4) Through heating at low temperature 150℃, powers of ceramic heater rollers with different H2 flow at scheduled temperatures under 150℃were obtained. The heating continuity, wave character and repeatability tests were made to testify the stability of APS TiO2 coating at low temperature. Failure phenomena were analyzed to prove the failure types and failure mechanism.