Transparent glass-ceramic is a new kind of functional material with homogenous and dense structure composed of fine crystal particles.Its preparation technique,species and properties were reviewed,and the development direction was discussed in the paper.

Transparent Glass-ceramics

Spectroscopic and photoluminescence characteristics of Sm3+ doped calcium aluminozincate phosphor for applications in w-LED

Spectroscopic studies of Dy3+ doped borate glasses for cool white light generation

The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–ceramic nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–ceramic nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–ceramic nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.

Thermal, Structural, and Enhanced Photoluminescence Properties of Eu3+-doped Transparent Willemite Glass–Ceramic Nanocomposites

Fabrication and enhanced photoluminescence properties of Sm3+-doped ZnO–Al2O3–B2O3–SiO2 glass derived willemite glass–ceramic nanocomposites

Oxidation resistance and water wettability of graphite flakes have been improved by a thin sol-gel film of magnesium aluminate spinel (MgAl 2 O 4 ) over its surface. The hydrosol has been synthesized by less expensive precursors and the spinel formation has been studied by scanning electron microscopy (SEM), supplemented with energy dispersive spectral analysis. After an easy-to-use mixing procedure, drying (110°C), and subsequent calcination (550°C), coated graphites were sieved to below 75 μm. The coating over the powder contained 1.5 wt% MgAl 2 O 4 , which enormously increased the oxidation resistance (performed at 600°, 900°, and 1200°C) and water wettability, as revealed by hydrophilic functional groups from infrared spectra. Defective, intermediate spinel structure of fine, lamellar Mg-doped γ-Al 2 O 3 has been considered to be significant for this improvement. An approximate (1:2) stoichiometry of (Mg:Al) in the coating composition was confirmed by an X-ray photoelectron spectroscopy test. Castables prepared by this graphite remarkably improved their bulk density and apparent porosity compared with those prepared by the as-received graphite. Casting water was reduced along with the amount of antioxidants. This also enhanced the resistance toward the basic slag by retaining the graphite in the refractory.

Spinel-Coated Graphite for Carbon Containing Refractory Castables

The performance of high alumina castables containing mullite and spinel coated graphites was investigated to explore their commercial application in carbon containing refractory composites. It was compared in terms of thermal shock resistance, refractoriness under load, static slag resistance test, pore size distribution, and physical properties, e.g., apparent porosity and cold crushing strength. The microstructures of these two castables, along with the other containing uncoated graphites, were also studied. Differential thermal analysis and X-ray diffraction patterns of heat-treated carbon-containing castable composites have also been noted. Castables containing mullite-coated graphite were found to be more resistant to repeated thermal shock cycles, whereas those containing spinel-coated graphites were more encouraging when slag resistance and overall physical properties are concerned.

Characteristics of Refractory Castables Containing Mullite and Spinel Coated Graphites

Role of different rare earth oxides on the reaction sintering of magnesium aluminate spinel

The Eu3+-doped novel precursor glass in the K2O-SiO2-SrO-Bi2O3-Ta2O5 system was prepared using the melt-quench technique. The transparent SrBi2Ta2O9 (SBT) glass-ceramic nanocomposites were derived from this glass using a controlled crystallization process. The formation of SBT crystal phase, size, and morphology with increase in heat-treatment time was examined using X-ray diffraction, field emission scanning electron microscopy, and fourier transform infrared transmission spectroscopy. Vicker's hardness study indicates marked improvement of hardness in the glass-ceramics compared to precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of D-5(0)-> F-7(j) (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 467 nm. These spectra reveal that the Eu3+ ions are gradually entering into the SBT nanocrystals present in the glass-ceramics. This study indicates that the incorporation of Eu3+ ions into SBT crystal lattice enhances the photoluminescence performance of the glass-ceramics by two-fold. It is believed that this work would generate significant impact in the exploration of SBT glass-ceramic nanocomposites.

Sunanda Mukhopadhyay

Papers

Fabrication and enhanced photoluminescence properties of Sm3+-doped ZnO–Al2O3–B2O3–SiO2 glass derived willemite glass–ceramic nanocomposites

Spinel-Coated Graphite for Carbon Containing Refractory Castables

Characteristics of Refractory Castables Containing Mullite and Spinel Coated Graphites

Role of different rare earth oxides on the reaction sintering of magnesium aluminate spinel

Synthesis and Properties of SrBi2Ta2O9‐Based Glass‐Ceramics Modified with Eu3+