Crystallization of Lithium Disilicate Glass Using Microwave Processing

Abstract

The crystallization of lithium disilicate (LS2) glass using a variable frequency microwave (VFM) processing technique was investigated. Lithium disilicate glass samples were prepared from commercial frit using a conventional glass melting and casting technique. A two‐stage heat‐treatment regime was used to crystallize the glass samples. The nucleation and crystallization temperatures were determined by the thermal analysis of the prepared LS2 glass. The LS2 glass samples were nucleated by conventional heating, followed by the crystallization step using two different techniques: conventional and microwave crystallization. Characterization of the prepared glass‐ceramic samples by both techniques was conducted using X‐ray diffraction, Fourier transform infrared reflectance spectroscopy, Raman spectroscopy, and scanning electron microscopy. Variable frequency microwave processing was successfully used to crystallize LS2 glass. Enhanced kinetics and slightly different crystallization mechanisms were observed in the VFM crystallization process as compared with the conventional one.

Structural and Microwave Properties of Silica Xerogel Glass-Ceramic Sintered by Sub-millimeter Wave Heating using a Gyrotron

“…The -OH functional group and lots of dangling bonds on the surface as well as loose Si-O network of silica xerogel blocked by crystallization are responsible for an increased transparency of the silica xerogel [35] and, consequently, for a decreasing of the reflection loss. Such observation is consistent with the results of the previous studies, which have found that crystalline lithium disilicate has a much lower dielectric loss than the amorphous glass state, and that its reflection loss is reduced substantially during the crystallization process [36]. Furthermore, the loss tangent of quartz silica (crystalline form) at microwave frequencies was much lower (2 orders of magnitude) than vitreous silica (amorphous form) [37].…”

Investigation of silica from rice husk ash wastes as an alternative material for microwave absorbers

“…At 1200 °C, the XRD pattern for the sintered silica xerogel shows a presence of a characteristic peak of cristobalite indicating the beginning of a crystallization phase. A lot of dangling bonds on the surface as well as loose Si-O network of silica xerogel blocked by crystallization are responsible for an increased transparency of the silica xerogel and, consequently, for a decreasing of the reflection loss [14][15]. Such an observation is consistent with the results of the previous studies, which have found that crystalline lithium disilicate has a much lower dielectric loss than the amorphous glass state, and that its reflection loss is reduced substantially during the crystallization process [15].…”

“…mullite structure, appear. Mullite derived from crystalline cristobalite dissolution remains in the liquid phase and, therefore, increases Si-O-Si bonds [12,14]. This results in a decrease in the reflection loss.…”

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