| As40Se60 chalcogenide glass is a widely used infrared material with spectral transmission range ranging from 1.0 to 12 μm.Its properties and preparation technology have become the research focus of infrared materials.The relationship between viscosity and temperature is an important basis for glass production and processing.As a new type of non-oxide glass,the research on the viscosity-temperature characteristics of As40Se60 chalcogenide glass is of great significance for recognizing the physical properties of materials,regulating the production process,and realizing the commercial application of As40Se60 chalcogenide glass.In this paper,As40Se60 chalcogenide glass was prepared by melting quenching.The viscosity from solid to liquid was tested,and the measured viscosity temperature data was fitted.The viscosity-temperature equation and kinetic strength index of As40Se60 chalcogenide glass were obtained.The corresponding temperatures were calculated according to the viscosity-temperature equation and the characteristic viscosity points,and the accuracy of the corresponding temperatures was studied and demonstrated,and then the key technological parameters such as annealing,forming and melting of As40Se60 chalcogenide glass were optimized and determined.The results are as follows:(1)The viscosity of As40Se60 chalcogenide glass from liquid to solid was measured by fiber elongation method,plate rotation method and cylinder rotation method.The fragility m is 39.According to Raman spectrum,the viscosity change of As40Se60 chalcogenide glass has important relation with the distance between[-Se-As-Se-]chain structure and van der Waals force.(2)The fitting results confirmed that the VFT equation was the most accurate in fitting the measured viscosity-temperature point,thus obtaining the equation of the viscosity change with temperature of As40Se60 chalcogenide glass:(?)Where:T-thermodynamic temperature(K),η-viscosity(Pa s).Combining the corresponding viscosity value of viscosity,the As40Se60 strain point T=423 K(η=1014.5 Pa·s),annealing point T=433 K(η=1013.0 Pa·s),glass transition point T=443 K(η=1012.0 Pa·s),expansion softening point T=451 K(η=1011.5 Pa·s),Littleton softening point T=511 K(η=106.6 Pa·s),flow point T=551 K(η=105.0 Pa·s),working point T=573 K(η=104.0 Pa·s),melting point T=643 K(η=102.0 Pa·s)and other important features of viscosity calibration point.(3)Based on the temperature corresponding to the characteristic viscosity point,the optimal temperatures for melting,molding and annealing of As40Se60 chalcogenide glass were determined through comparative experiments:Near by melting point and temperature on As40Se60 chalcogenide glass in high temperature homogenization and low temperature quenching cold,according to the infrared transmission properties of the samples and optical defects,combined with the As-Se binary phase diagram,prove that homogenization temperature higher than the melting point of T=643 K(η=102.0 Pa s),glass raw materials begin to dissolve and homogenization,the higher the temperature,raw material between the diffusion coefficient,the greater the glass melting system efficiency,and infrared transmission performance,the better.When the quenching viscosity is less than 100.0 Pa·s,the glass will form a large number of uneven stripes due to turbulence.Therefore,the homogenization temperature of As40Se60 chalcogenide glass should be higher than 673 K(η=102.0 Pa·s),and the quenching temperature should be controlled near 754 K(η=100.0 Pa·s).Simulation results show that the working point T=573 K(η=104.0 Pa·s)is the reasonable molding temperature of As40Se60 chalcogenide glass.The temperature and the near point is used to mold the As40Se60 chalcogenide glass.The results showed that the As40Se60 chalcogenide glass had a strong tendency of crystal evolution when T=593 K(η=103.4 Pa·s),and could not be molded.After the viscosity was higher than 104.0 Pa·s,a large number of cracks appeared in the pressed sample due to excessive viscosity.According to the viscosity temperature characteristics and crystal evolution of As40Se60 chalcogenide glass,the reasonable temperature range of mold forming is T=573～593 K(η=103.4～104.0 Pa.s).The temperature corresponding to strain point,annealing point and expansion softening point was used to anneal As40Se60 chalcogenide glass.The results show that the strain point T=423 K(η=1014.5 Pa·s)is the lower annealing temperature of As40Se60 chalcogenide glass,below which the glass is in the elastic state,the particles inside the glass cannot move and the stress cannot be relaxed.The glass removes most of the stress better at the annealing point T=433 K(η=1013.0 Pa·s),and the particles inside the glass get enough energy to dissipate the stress under the action of thermal motion.As the annealing temperature continues to rise,the stress of the glass decreases,but the reduction is very small.As the annealing temperature continues to rise,the stress of the glass decreases,but the reduction is very small.When the temperature rises to the dilatation-softening point T=451 K(η=1011.5 Pa·s),the glass deforms.The reasonable annealing temperature range of As40Se60 chalcogenide glass is T=433～451 K(η=1011.5～1013.0 Pa·s). |
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