Research On The Glass Transition Temperatures Of Metal Melt

There are three characteristic temperatures for describing the glass transition behavior of melt:the actual glass transition temperature Tg, the kinetics ideal glass transition temperature To (VFT temperature), the thermodynamics ideal glass transition temperature Tk (Kauzmann temperature). Only when the precise data and their related laws is known, we can accurately predict the formation ability of metal amorphous and the correctly design the composion of amorphous material. The kinetic fragility index (m), which can be determined in terms of the glass transition temperature (Tg) of glasses at different heating rates, is another parameter to predict the kinetic fragility of glass. The fragility of liquids have been widely used to study the dynamic behavior of sorts of metallic glasses, studying the fragility of liquids can help people to recognize the nature of glassy state deeply. The Ge-Se-Sb and Ge-Se chalcogenide glasses and crystals prepared with melt quenching method. By using DSC, XRD, IR, the properties of kinetics and thermodynamics of Ge-Se-Sb chalcogenide glasses and the kinetics properties of Ge-Se chalcogenide glasses are studied in this thesis. The research results are as follows:(1)The infrared transmittance of Ge-Se-Sb chalcogenide glass is about 60% while the infrared transmittance of Ge-Se chalcogenide glasses is about 43%.(2)The glass transition temperature Tg of Ge-Se-Sb chalcogenide glass increases with the heating rate. Tg is also sensitive to the composition too. Tg firstly increases and then decreases with increasing the germanium content. When the content of Ge is 25%, Tg reaches the maximum. As the result of crosslinked network structure and overall mean bond energy in the chalcogenide glass. On the other hand, it reveals remarkably kinetic effect as the Tg increases with the heating rate increases. At same heating rate, the value of Tg of Ge3oSe7o glass is higher than that of the Ge25Se75 glass, the reason is overall mean bond energy, too.(3)The kinetics ideal glass transition temperature T0 of GexSe90-xSb10 (x=20,23,25,30) glasses firstly increases and then decreases with increasing the germanium content. The T0 of ss is also higher than that of the Ge25Se75 glass.(4)The value of TK of GexSe90-xSb10 (x=20,23,25,30) glasses was 376.89 K,401.68 K,418.77 K and 473.41 K, respectively, while Tk increases linearly with the increase of germanium content((20≤x≤30)).(5)The fragility index (m) is estimated to be 20.7-23.2, Tg/Tk was estimated to be 1.183-1.352, suggesting that the GexSe90-xSb10 glasses should be considered as a strong liquid. The fragility index were 26.3 and 21.9, suggesting that the GexSe100-x (x=25,30) glasses should be considered as a strong liquid.The value of Trg (=Tg/Tm) is larger than 2/3, indicating that the nucleation and grain growth of the crystalline phase can be suppressed and thus the amorphous phase can be formed.