Improving The Strength Of Domestic Ceramics By Surface Treatments

In recent years,with the rapid development of China's industrialization process,China's daily-use ceramic industry is growing up,and its output has been ranked the first in the world for many years.However,China's daily-use ceramic products mainly meet the needs of the mid-to-low-end market,and have a low market position and a small market share in the high-end daily-use ceramics market.With the continuous improvement of living standard and the change of consumption concept,people have put forward an urgent demand for high-end daily-use ceramic products,such as glaze effect,mechanical properties,etc.,but there are still many problems in high-end daily-use ceramic products,such as poor thermal stability,low bonding strength between body and glaze,weak mechanized washing resistance,insufficient recycling performance and etc.Based on the basic theory of fracture of ceramic materials,this work takes ordinary daily-use ceramic body as the research object,uses three surface treatment methods of ceramic coating,ion exchange and polishing to strengthen it,studies the influence of different surface treatment methods on the strengthening effect of the body and discusses the relevant strengthening mechanism.Firstly,the ceramic coating was used to reinforce the ceramic body,and the phase composition,microstructure,thermal properties and optical properties of the samples were studied.The effects of sintering temperature,the ratio of thermal expansion coefficient,the ratio of cross-sectional area and the particle size of coating powder on the strength of the coating-enhanced daily-use ceramic body were investigated.The results show that the phases of the ceramic coating are cordierite,magnesium aluminum spinel and spodumene.ZnO can reduce the crystallization temperature of cordierite in the ceramic coating,while spodumene can effectively reduce the thermal expansion coefficient of the ceramic coating.When the sintering temperature is 1300?,?s/?c=1.32,SS/Sc=25.83,and the average particle size of surface area is D=2.228 ?m,the maximum flexural strength is 128.6±2.4 MPa,which increases by 90.8%compared with that of the blank sample(67.4±2.1 MPa).At the same time,the microhardness is also slightly improved.The final ceramic coating reinforced green body has better reflectivity(65%),lightness(L=85)and thermal shock resistance(220?20? thermal cycle five times without cracking).Secondly,the ceramic body was strengthened by ion exchange method,that is,the ceramic body was placed in KNO3 molten salt and treated for a period of time at a certain temperature.The influence of temperature and time on the reinforce effect of ion-exchange was studied.The results show that the ion exchange temperature and time have optimized values.When the treatment temperature is 550? and the holding time is 5h,the exchange efficiency of K+and Na+ is the highest,and the ion exchange layer is the most stable.The highest flexural strength is 122.5±2.9 MPa,which is 81.7%higher than that of the blank sample(67.4±2.1 MPa).At the same time,the microhardness of the sample is also improved to 708.4 kg·mm-2 by ion exchange,15.8%higher than that of the blank sample(611.8 kg·mm-2).Finally,the surface of the ceramic body was polished with abrasive paper(800 mesh,1000 mesh,1500 mesh,2000 mesh,3000 mesh).The relationship between the bending strength and the surface roughness of the body after polishing with abrasive paper,as well as the influence of the polishing process parameters on the polishing effect and the strength improvement of the body were studied.The results show that the maximum flexural strength is 97.4±1.8 MPa,which is 44.5%higher than that of the blank sample(67.4±2.1 MPa),when 800 mesh abrasive paper is used for rough polishing,pressure is applied for fixing,and polishing is continued for 20 min under 2000 mesh abrasive paper,and the polishing rate is 100 r/min.Comparing the three different surface treatment processes,the results show that the ceramic coating has the best reinforcement effect on blank body,followed by ion exchange and polishing treatment.The ion exchange method is not suitable for wide application in the actual production of daily-use ceramics because it involves the molten salt treatment process.The cost of polishing is the lowest,but the effect is not good.The preparation process of ceramic coating is simple and the reinforcement is the best,which can be applied in the practical production of daily-use ceramics.