Preparation And Application Of Magnetic Metal Coating On Ceramic Substrates

The electromagnetic technology has greatly improved our life quality,such as the induction cooker,which provides us with an efficient approach to use energy.Therefore,the electromagnetic heating technology is more efficient and safer than traditional heating technology.Traditional heating methods have a lot of energy transfer processes,while the electromagnetic heating technology can directly heat the vessels using electromagnetic induction technology.Thus,the heating efficiency was improved because the energy,does not need to be transferred in the medium.So electromagnetic heating has a great advantage of controllability than other heating methods,which can realize a great diversity and versatility of heating process.As for small household rice cooker appliance field,all the rice cooker inner by electromagnetic heating was metal inner,such as iron and 430 stainless steel.However,for some non-magnetic materials,such as ceramics and glass without magnetocaloric function,they are not suitable to use electromagnetic heating system,and they can only be heated by hot disc or infrared heating with low heating efficiency and hard controllability of cooking temperature.But ceramics and glass are generally recognized as a healthy and environmentally friendly material in rice cooker field,Therefore,it has a important significance to study how to let the non-magnetic materials such as ceramics and glass have the electromagnetic heating function through thermal spraying technology,and it can improve people's dietary safety,reduce the intake of metal extracts,and provide a strong guarantee for people's healthy diet.The experiments results show that a functional coating can be prepared on the surface of non-magnetic materials using thermal spraying technology.The coating as magnetic materials can make the non-magnetic materials have the thermomagnetic effect,calling this coating as thermomagnetic coating.Using arc thermal spraying method,a magnetic metal coating can be prepared on the outside surface of daily heat-resistant ceramic pot,and then a protective layer was sprayed on the outer surface of metal coating.In this work we tested the bonding strength between metal coating and ceramics,the electrical parameter of metal layer,the bonding performance between protective layer and metal coating.Finally,we evaluated the comprehensive performance of product in practical application.The experiments results show that:1.The arc spraying process can be used to prepare an aluminum metal layer as a transition layer on the surface of heat-resistant ceramics,and then we spray a magnetic conductive metal(iron,430 stainless steel)on the surface of aluminum metal layer.The metal layer was firmly bonded with the daily heat-resistant ceramic pot,and after three thermal shocks experiment from hot source to cold end between 450 degree and 20 degree,the heat-resistant ceramic pot with composite coating has not split or damaged.Furthermore,the power can reach 1500 W when it works.2.The protective silicone resin or ceramic coating layer on the surface of metal layer have excellent performance even after 96 hours salt corrosion test.In the dry-burning condition,the silica resin protective layer is easy to change color and ageing,while the ceramic coating protective layer is hard to change color,because the ceramic coating have a good perform at high temperature,better than the silica resin protective layer.3.The cooker with a ceramic pot can still work normally after 2000 times cooking test(equivalent 5years service life).Results show that the metal layer on the surface of ceramic pot did not fall off,the color not changing,the rice sweet and good smell after thousands of cooking cycles.It is worth noting that the metal layer transfers the electromagnetic function to heat-resistant ceramic pot,and have a long service life.Based on the above analysis and study,the best process is as below: first spraying an aluminum layer on the surface of ceramic pot through arc thermal spraying,then spraying an iron layer on the surface of aluminum layer,finally spraying a protective coating on the iron layer.All the testing results show that thermomagnetic coating technology is an effective way to solve the heating problem of non-magnetic materials such as ceramics,and also can achieves the goal of energy saving and high efficiency.