Study On The Dry Forming Firing Technology And Colouration Mechanism Of Nixing Pottery

Qinzhou Nixing pottery is one of the four Chinese famous potterys and along with the booming development of National Economy and culture,Nixing pottery industry is obtain to be protected,inherited and developed,but the traditional pottery of Nixing cannot not meet the needs of the Nixing pottery industry development.To shorten Nixing pottery production cycle and improvev production efficiency,using the dry forming method of preparation to shorten molding time,which is significant to shorten production cycle.Therefore,the test about firing technology of Nixing pottery products which using dry forming method of preparation,was studied in this paper.The influence of the conditionfactors such as furnish components,forming pressure,sintering temperature,heating rate,holding time,sintering atmosphere to the sintering property of Nixing pottery was researched.The results showed that,in the same experimental condition,the products which with larger proportion white mud,had bigger contractibility rate,smaller water absorption,lager volume density and higher flexural strength relatively.The sintering temperature of the products with white/red of 6/4,were 1140 0C to 1170℃ in the oxidation atmosphere,and 1080 0C to 1100 0C in the reducing atmosphere.In this experimental condition,40 MPa was the forming pressure critical point in which the volume density and flexural strength of products were reached to maximum in the dry forming process,12℃·min-1 was the heating rate critical point in which the volume density and flexural strength of products were dropped suddenly in the sintering process,4 h was the holding time critical point in which the volume density and flexural strength of products were had stabilized.So in the actual production process,the products with higher intensity property can be produced when the forming pressure close to critical pressure point,the temperature rate less than critical rate point,and the holding time close to the critical tine point.In the range of 100℃ to 1180℃ of the products with being added calcium carbonate,the line contraction rate of the products which with being added calcium carbonate 10%,decreased 0.5%relatively,the volume density decreased 0.1 g·cm-3 relatively,the water absorption increased over 2.0%relatively,the flexural strength low 0.2 MPa to 2.0 MPa relatively.The sintering temperature of the products with being added manganous carbonate,was lesser than 1090℃,and the basic decomposition of manganous carbonate had completed at 1050℃ to 1060℃,and the more calcium carbonate being added,the lager volume density and flexural strength relatively.In this paper,XRD and SEM technology were applied to analyze the phase components and the microstructure of the Nixing pottery products.The results showed that,an accidental coloring can be showed when the Nixing pottery products being fired in the reducing atmosphere,it was due to the ferrous silicate can be generated since 1060℃in that condiction,which led to illumination effect.In the range of sintering temperature of Nixing pottery,a dynamic equilibrium betweet ferrous ion and ferric iron was being in crystal,and the body is green or blue-green when the equilibrium is to move to ferrous ion,on the contrary is yellow.The dynamic equilibrium is to move to ferrous ion when the brick sintered in the reducing atmosphere,or with appropriate addition of calcium carbonate and manganous carbonate,but to ferric iron as calcium carbonate excess.