Multi-factor Analysis Of Firing Temperature Measurement By Thermal Expansion Method And Its Application To Guangxi Ancient Ceramics

The determination of original firing temperature is a crucial link in the research of ancient ceramic by scientific and technological analysis,at present there are many technological means to determinate the firing temperature of the ancient ceramic,among them,because the thermal expansion technique has the characteristics of experimental operation and analysis process is simple and the results are reliable and direct,so it is widely recognized by the archaeometry scholars.However,the temperature measurement operation of this method varies from person to person,and the results have obvious human error.Moreover,the theoretical research of this method can be continuously deepened on the basis of a large number of simulation experiments.In view of the above problems,the development process of sintering theory is discussed in this paper,and various factors that influence the sintering of ceramics are discussed;the physical and chemical changes of the main components of ceramic materials,such as quartz?SiO₂?,kaolinite?2SiO₂·Al₂O₃·2H₂O?,feldspar?KAlSi₃O₈,NaAlSi₃O₈,CaAl₂Si₂O₈,etc.?at high temperature were analyzed and discussed;the changes of phase composition and microstructure of clay at different sintering temperatures are studied by XRD and SEM;verifies the factors that influence the temperature measurement results of thermal expansion,through a large number of simulation experiments to established the reasonable application standard of the method at considering the sintering degree,material type,heating rate of the test,selection of judgment curve and initial point determination;the feasibility and reliability of the thermal expansion method for the determination of the original firing temperature of low temperature ceramics are studied.In addition,the firing temperature of ancient ceramics that collected from Guizhou kiln,Yanguan kiln,Jiangwali kiln,Zhonghe kiln,Chenggaun kiln,Lingdong kiln,Xishan kiln in Guangxi province has been researched by the thermal expansion method.Through research,got the following main conclusions:?1?The heating rate,degree of sintering and the selection of the judging curve will exert a great influence on the temperature measurement results.?2?Samples of different material types and different sintering degrees have their most suitable heating rate and judgment method for themselves to determine the measured value.The optimal temperature heating rate of the ancient ceramics with low alumina clay is 5k/min,and the judging curve should be determined according to the degree of sintering.The optimal temperature heating rate of the fine white porcelain with high kaolin content is 7.5k/min,and the judging curve should be choice the thermal expansion curve.?3?The correction formula can greatly improve the temperature measurement accuracy of the tested samples that temperature measurement result under 1080?and above 1250?,and the temperature measurement error can be controlled within 17?.?4?Thermal expansion curve and the first derivative curve appear abrupt after 1200?,the temperature measurement result is not the starting point for the net contraction occurs?peak temperature?,and should be the starting point of the curve on the abrupt expansion began??5?In determination of the firing temperature of low temperature pottery,the multiple reheating method can be very good to determine the temperature of the simulated sample that original firing temperature range 460?to 630?,but to those samples that original firing temperature range 660?to 860?,the method can not be well determined and needs further discussion.?6?In the celadon kiln system the Tang Dynasty Guizhou kiln and the southern Song Dynasty Yanguan kiln ceramics's firing temperature is generally not high,ranging from 1100¹180?and from 1100¹170?respectively.It is indicated that the high temperature technology of these two kilns has been in a stable state for a long time.The most ceramic samples in Jiangwali kiln the firing temperature about 1200?,firing temperature is higher,but the ceramic samples in Yuan Dynasty Shanggaizhou kiln the firing temperature ranging from 1248.5¹284.6?,it's average firing temperature is more than 80 degrees Celsius higher than the ceramic samples in Song Dynasty Jiangwali kiln,the kiln located at same place with Shanggaizhou kiln.It shows that the high temperature technology of the Quanzhou celadon kiln has been greatly improved from song dynasty to yuan dynasty.?7?In blue white porcelain kiln system the vast majority of Xishan kiln porcelain sample firing temperature over 1300?,the highest of 1455.5??This is the highest firing temperature ever seen in Chinese ancient ceramics?.It's average firing temperature is1323.2?,138?higher than the average firing temperature?1185.3??of Zhonghe kiln porcelain,90?higher than the average firing temperature?1233.0??of Chengguan kiln porcelain,76?higher than the average firing temperature?1247.6??of Lingdong kiln porcelain.It shows that,in terms of the high temperature technology of the kiln,the firing technology of xishan kiln reached a high level.