耐辐射高铅玻璃熔制挥发物分析及控制

Analysis and Control of Volatile Matter in Radiation Resistant High Lead Glass Melting

用于制备耐辐射光纤面板的高铅(铅当量≥0.3)玻璃材料须具备较高的折射率、较好的X射线吸收性能、较高的可见光透过率以及良好的热稳定性和化学稳定性。但由于其高铅含量对熔制坩埚及耐火材料腐蚀性极高,且熔制过程中挥发量较高,玻璃组分不易稳定控制,目前仅国外少数企业能够高质量稳定生产。研究了玻璃熔制过程中影响挥发物的3个主要因素,有效控制挥发物的挥发率由2.00%降至0.51%左右,确定了最佳熔制温度以及通气压强,并在此条件下分别采用2种方式向玻璃中引入铅,通过能谱仪和光电子能谱仪对该高铅玻璃在熔制过程中的挥发物进行了研究,确定了其挥发物成分以铅氧化物为主,其中铅的价态以四价为主,二价为辅。

Introduction Radiation resistant optical fiber panel is a kind of optical fiber material device with special functions.As a core component of X-ray radiology,this fiber material is widely used in digital X-ray imaging,pet medical treatment,security inspection,industrial nondestructive testing and food safety testing.The industry entry threshold for radiation resistant fiber optic panels is relatively high.The existing market of high lead glass materials for radiation-resistant optical fiber panel is basically monopolized.To ensure high visible light transmittance,good thermal stability,and chemical stability of glass materials used in radiation resistant fiber optic panels,a higher content of PbO is introduced into the glass composition to further improve its refractive index and X-ray absorption performance In this paper,the main factors (i.e.,temperature,atmospheric pressure and raw material) affecting the volatilization of PbO in the melt of high-lead glass for radiation-resistant optical fiber panels were analyzed.Materials and method A yellow lead was selected as a raw material to introduce lead into the glass,and the experiments were carried out at different melting temperatures.The melting temperature was optimized based on the experimental results.The atmosphere pressure of crucible kiln changed to further control the volatilization of radiation-resistant glass in the melting process.Under the optimal process conditions,a more effective way to control volatiles was explored via changing the lead oxide introduction method.Also,the volatiles of the glass melt with different raw material introduction methods were determined by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS),and the main components and contents of the volatiles were analyzed.Results and discussion In the mixed materials with the same lead oxide content,the glass in the melting process of volatile amount decreases,and the volatility rate decreases from 2.00% at 1530℃ to 1.53% at 1500℃ as the melting temperature decreases.In addition,when the melting temperature decreases<1500℃,hard-melt substances in the glass sample appear possibly due to the enrichment of CaO,LaO and PbO.At 1500℃,the volatilizing amount of glass decreases with the increase of atmospheric pressure in crucible,and the volatilizing rate decreases from 1.53% at 0 MPa to 0.80% at 0.4 MPa.When the pressure of the gas further increases,it leads to massive stripes on the surface of the glass liquid,affecting the quality of the product.At the same lead oxide content in the mixing material,melting temperature and ventilation pressure,lead oxide is introduced into the glass by two approaches,i.e.,lead is introduced into the glass with yellow lead as a raw material,and lead is introduced into the glass with red lead as a raw material.Based on the results of composition test and analysis of the glass material obtained by melting,the glass in the melting process of volatile amount decreases,and the volatility rate decreases from 0.80% to 0.51%when red lead is used to introduce lead into the glass.From the EDS spectra of volatile sample,lead oxide volatilizes in glass material during melting process.As yellow lead is used as a raw material to the glass introduction,the percentage of lead atoms in the volatiles is 35.44%.As red lead is used as a raw material,the percentage of lead atoms in the volatiles is 22.21%.The XPS spectra of volatile samples with two different lead introduction methods show that element lead is the main valence state,the valence state is auxiliary.Conclusions The influences of melting temperature,ventilation pressure and raw material introduction mode on the volatiles in the glass melting process were investigated.At the melting temperature of 1500℃,the ventilation pressure of 0.4 MPa,and red lead as a raw material to introduce lead into the glass,the volatile amount of volatiles in the glass melting process was effectively controlled,and the volatility of lead oxide was reduced from 2.00% to 0.51%.At the melting temperature of 1500℃and ventilation pressure of 0.4 MPa,red lead or yellow lead as a raw material to introduce lead,the valence state of Pb element in the glass melting volatiles was mainly tetravalent,and the divalent was auxiliary.The content ratio of tetravalent lead and divalent lead was 4.79 and 4.94,respectively.