Influence Of Heating Conditions On Crystallization Performance And Specific Enthalpy Of E-glass

In this works,the specific thermal capacity,specific enthalpy and crystallization heat of E-glass form room temperature to 1350℃with different treatment were studied.3T enthalpy graph of glass was put forward on the basis of 3T graph of glass crystal theory.The treatment condition was mainly in temperature and time,which changed from 900℃to 1200℃and 1 to 10 hours respectively.The crystal phase,crystal percent,micro morphology were characterized by X-Ray Diffraction(XRD) and scanning electron microscopy(SEM).Relative calibration coefficient of heat flux DSC was brought forward to calculate the specific thermal capacity of mental oxide and glasses.Relative calibration coefficient of Heat flux DSC was a novel way to calibrate specific thermal capability of mental oxide and glasses,mainly process was described as follow.1.Demarcated the DTA equipment with standard mental oxide2.Find the relationship between calibration coefficient of different mental oxide thermal capability and mental atomic weight of oxide3.Calculated the relative calibration coefficient of Heat flux DSC and relative calibration coefficient of complex oxide4.Measure the thermal capability of mental oxide,complex oxide and compound5.The standard deviation of oxide thermal capability was between 0.014 and 0.040.E- Glass with five different compositions was investigated on the basis of specific thermal capability measurement,and the results indicated:To Sample 1 glass,between 950 to 1000℃CaAl₂Si₂O₈ crystal was appeared.At 1000℃for 3h crystal was appeared firstly and the enthalpy was 1540J/g for sample appeared crystal. The enthalpy difference between critical crystal and quenched sample was 306J/g.Crystal percent increased with prolonging treated time,and the crystal energy turned to a certain data. The relation between heat crystal and crystal percent was y=-590.5-2856exp(-x/0.0489).The energy for crystal formed was quite huge at begin,when 1%crystal appeared about 2918J/g energy was needed for 1g sample.About 600J energy was needed for 1g sample when 25% crystal appeared.The relation between heat crystal and heat treated time at 950 and 1000℃was:ΔH₉₅₀=-18.1-23.7t-1.39t²;ΔH₁₀₀₀=-15.0-20.54t;The relation is alike for specific enthalpy and treated time,the fiting was:H₉₅₀=1824-111.1t-6.78t²;H₁₀₀₀=1739.3-50.09t.To Sample 2 glass,glass devitrification temperature was 1000℃.As prolong the treated time,the thermal of phase transfer was linear decreased,relations were H=2041.5-58.8t andΔH=-1.06-7.21×t(t was treated time).The crystal appeared after 12 hours treatment,at the beginning the enthalpy changes was due to the phase separation of glass,the crystal was CaAl₂Si₂O₈ and the percent and enthalpy were 8.6%and 1339J/g,which was 589J/g lower than quenched sample.To Sample 3glass,between 900 to 1200℃Mg₂Al₄Si₅O₁₈ crystal was appeared.For a big range of crystal temperature,the heat of crystallization was hard to compute accurately.The critical point for crystal first appeared was that sample heat treated at 900℃for 3h,and its enthalpy was 1857J/g,which was 8.6J/g less compared with quenched sample.Energy for crystal was little and it's easy to obtain crystal for sample 3.Crystallization percentage had a linear relation with heat treated time at a 1000℃heat treatments,X=0.318+4.98t,where X was crystallization percentage;t was heat treated time.The crystallization percentage would be more than 50%after 10h heat treated at 1000℃.To Sample 4 glass,glass devitrification temperature was 950℃.Critical point for crystal CaSiO₃ first appeared was that sample heat treated at 950℃for 3h,and its enthalpy was 1481.3J/g,which was 177.7J/g less,compared with quenched sample.Glass Enthalpy had a linear relation with heat treated time at 950℃heat treatments,H=1495-7.5t,where H was Glass Enthalpy;t was heat treated time.To Sample 5 glass,glass devitrification temperature was 930℃.At 950℃for 3h crystal MgSiO₃ was appeared firstly and sample enthalpy was1460.8J/g,which was 121.2J/g less compared with quenched sample.Glass Enthaipy had a linear relation with heat treated time at 950℃heat treatments,H=1505-10.8t,where H was Glass Enthalpy;t was heat treated time.From room temperature to 1350℃,the enthalpy decreased as treated time and temperature increased.With relative calibration coefficient method of DSC,the TTT energy graph was put forward,which could calculate the specific enthalpy of glass crystallization,and the changes of glass internal energy with different temperature and time treatment.Base on the change of specific enthalpy,the condition of devitrification could be judged.For 1-5# samples,difference between critical point for crystal first appeared and quenched sample was 306J/g,589J/g,8.6J/g,177.7J/g and 121.2J/g respectively.So the tendency for crystal occurred was 3,5,4,1 and 2.