| Summary: | 碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 95 === (1-x)Li2O-xNa2O-Al2O3-4SiO2 glasses were obtained through the substitution of Na2O for Li2O at the constant mole of Al2O3 and SiO2. Differential thermal analysis (DTA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) analysis were utilized to study the characterization, structure and crystallization behavior of (1-x)Li2O-xNa2O-Al2O3-4SiO2 glasses.
The coefficient of thermal expansion and density of these as-quenched glasses increase from 6.5410-6 to 10.110-6 K-1 and 2.378 to 2.533 g‧cm-3 when the Na2O content increases from 0 to 0.4 mol, respectively. The electrical resistivity has a maximum value at Na2O．(Li2O+Na2O)-1=0.4. The FT-IR spectra show that the symmetric stretching mode of the SiO44- tetrahedra (1035-1054cm-1) and AlO45- octahedra (713-763cm-1) exhibiting that the network structure is built by SiO45- tetrahedra and AlO45-.
The nucleation of (1-x)Li2O-xNa2O-Al2O3-4SiO2 glasses are studied by differential thermal analysis. Based on the shift of the differential thermal analysis crystallization-peak temperature and calculating the number of nuclei by SEM analysis, for evaluating the influence of temperature and time of heat-treatments on nucleation, is described. It is found a maximum value(2.475×108 number．m-2)at 1033 K for 90 minutes expect the C2. The maximum value of the C2 is slightly decreased from 1033 K to 1018 K. With increased Na2O content, the effect of temperature and time in (1-x)Li2O-xNa2O-Al2O3- 4SiO2 glasses is not apparent.
The non-isothermal kinetic of crystallization of (1-x)Li2O-xNa2O-Al2O3-4SiO2 glasses decreases from 444 to 284 kJ‧mol-1 when the Na2O content increased from 0 to 0.4 mol. Moreover, the activation energy increased from 284 to 446 kJ‧mol-1 when the Na2O content increased from 0.4 to 0.6 mol. The crystallization parameters m and n approached 2, indicating that the surface nucleation and two-dimensional growth were dominant in (1-x)Li2O-xNa2O- Al2O3-4SiO2 glasses. On the other hand, the isothermal kinetic of crystallization of β-spodumene from the (1-x)Li2O-xNa2O- Al2O3-4SiO2 glasses was investigated using quantitative X-ray diffraction (XRD) method. The activation energy of crystallization decreases from 359.16 to 317.80 kJ‧mol-1 when the Na2O content increases from 0 to 0.4 mol and increases from 317.80 to 376.88 kJ‧mol-1 when the Na2O content increases from 0.4 to 0.6 mol. The growth morphology parameter is approximately 2, which reflects the plate-like morphology of the β-spodumene crystals formation. By the Debye-Scherrer equation, the crystallite size of the β-spodumene increased from 49.7 nm to 59.1 nm. With the Na2O content decreasing, the increase scope of the crystallite size reduces from 9.40 nm to 4.15 nm and the activation energy for the growth of the β-spodumene increases from 4.639 to 5.030 kJ．mol-1 with Na2O content increased. However, the β-spodumene in the (1-x)Li2O-xNa2O-Al2O3- 4SiO2 glasses growth more difficultly.
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