Study On The Mechanical Properties And Diffusion Mechanism Of Porcelain Tiles Enhanced By Ion Exchange

With the gradual increase in the production and market demand of building ceramics in China,the development of thin building ceramics is irresistible.Thinning of building ceramic tiles is of great significance for the ceramic industry to achieve the goal of energy saving,low carbon and green development.However,with the decrease of building ceramic thickness,the crushing rates of green body and finished products increase significantly,which cannot meet the actual requirements of large-scale production and building scene application.Therefore,in this paper,ion exchange technology was used to enhance the strength of thin ceramic tiles by’squeezing effect’produced by ion exchange with large radius and small radius.The key factors affecting the strength of building tiles were mainly studied,and the diffusion mechanism of ion exchange was discussed.The main results were as follows:（1）Taking the tiles as the research object,the industrial KNO₃molten salt containing KOH additive was used to strengthen the tile by ion exchange.The changes of mechanical properties and microstructure of the tiles after exchange were analyzed.The effects of temperature,time and additive KOH content on the enhancement effect were explored,and the diffusion coefficient was calculated in combination with Boltzmann-Matano model.The results showed that the change of tiles strength was obviously affected by ion exchange temperature,time and additive content.When the temperature was 450℃,the exchange time reached 5 h and the additive KOH content was 0.3 mol%,the strength of building tile reached the maximum value of 86.53 MPa,50.3%higher than that before exchange.Under this condition,the surface K⁺ion concentration and diffusion depth both reached the maximum value,and the diffusion coefficient increased to 1.8×10^-15m~2/s.（2）Adding additive Cs₂CO₃in industrial KNO₃molten salt to explore the effect of additive on the strength of tiles and the optimal process parameters.It was found that when Cs₂CO₃was not added to the molten salt,the optimum temperature and time of exchange are 630℃and 5 h respectively,and the maximum strength value was 86.25MPa.Under these conditions,the strength of tiles reached the maximum（90.65 MPa）when exchanged in industrial KNO₃molten salt containing 6 wt%Cs₂CO₃.Compared with the strength of tiles exchanged in molten salt without Cs₂CO₃additive,it was increased by 4.4 MPa.At this time,the concentration sum of K⁺and Cs⁺ions on the surface was the highest,and the surface compressive stress was the largest.When 0.7mol%KOH was added into the above molten salt system,the maximum strength reached98.13 MPa,an increase of 8.3%.（3）Taking the sintered ston of a company as the research object,the effects of raw material composition,temperature,time and types and contents of molten salt additives on ion exchange enhancement effect were explored.The mechanical properties of the sintered stone after exchange with tiles were analyzed and compared.The results showed that the strength of the sintered stone increased first and then decreased with the increase of temperature and time.The optimum temperature and time of exchange in industrial KNO₃molten salt were 400°C and 5 h,respectively.The strength reached the maximum value of 86.35 MPa and the increase rate was 65.35%.When the addition of KOH additive was 0.3 mol%,the time to reach maxium strength was shortened from 5 h to 3 h,which was more conducive to reducing energy consumption compared with the exchange temperature and time of tiles.The flexural strengths of tile and sintered stone enhanced by ion exchange process increased by 26.9%and 32.7%respectively,and the thickness decreased by 16.28%and 15.21%respectively.