Formation of nano-crystalline quartz crystals from ZnO/MgO/Al2O3/TiO2/ZrO2/SiO2 glasses

Characterization of mineral wools obtained from ornamental rock wastes

“…The main phases present in the mixtures at 800°C were silicates, a similar result was also found by Hunger et al (2010). Quartz was identified as the main phase in the mixtures to produce glass wool (M-GW 81.8% and MG-GW 40.51%), and the anorthite was detected as a main component in the mixtures to produce rock wools (M-RW 28.93% and MG-RW 39.32%).…”

The crystallization of MgO–Al2O3–SiO2–ZrO2glass-ceramics with and without the addition of Y2O3– a combined STEM/XANES study

“…[1][2][3][4][5][6][7] Since the MAS system tends to surface nucleation, [8][9][10][11] the addition of nucleating agents such as TiO 2 , 1,12-14 ZrO 2 2-7, 14-16 or both 17,18 is necessary to achieve bulk crystallization. If the glass contains high enough concentrations of these nucleation agents, during thermal treatment at temperatures slightly above T g , crystallization in these glasses is initiated by the formation of TiO 2 , ZrO 2 or ZrTiO 4 precipitations.…”

“…If the glass contains high enough concentrations of these nucleation agents, during thermal treatment at temperatures slightly above T g , crystallization in these glasses is initiated by the formation of TiO 2 , ZrO 2 or ZrTiO 4 precipitations. 4,16,18 Depending on the chemical composition, a further thermal treatment at higher temperatures may lead to the crystallization of quartz solid solutions. [1][2][3][4][5][6][7] These quartz solid solutions (also denoted as µ-cordierite or "stuffed quartz") typically contain MgO and Al 2 O 3 in concentrations of 8 to 10 mol%, thus stabilizing the hexagonal, high-temperature β-quartz phase during cooling to room temperature, which, if not stabilized, would otherwise transform into the trigonal, low-temperature α-quartz phase.…”

“…1 temperatures in the range from 520 to 580 °C, 1 which is accompanied by a decrease in volume of around 0.7 %. 18 The large thermal expansion coefficients (CTE) of the low quartz solid solution (α 20-300°C = 13.2 10 -6 K -1 ) and spinel (α 20-800°C = 8 10 -6 K - 1 19 ) as well as the strong volume decrease during the phase transition of the quartz solid solution are responsible for high stresses in the glassceramics, resulting in excellent mechanical properties thereof. 1,18 Glass-ceramics containing high quartz solid solutions usually exhibit strengths of around 100 MPa, 3,5,7 while in those containing low quartz solid solutions and spinel, strengths of up to 475 MPa are observed.…”

“…18 The large thermal expansion coefficients (CTE) of the low quartz solid solution (α 20-300°C = 13.2 10 -6 K -1 ) and spinel (α 20-800°C = 8 10 -6 K - 1 19 ) as well as the strong volume decrease during the phase transition of the quartz solid solution are responsible for high stresses in the glassceramics, resulting in excellent mechanical properties thereof. 1,18 Glass-ceramics containing high quartz solid solutions usually exhibit strengths of around 100 MPa, 3,5,7 while in those containing low quartz solid solutions and spinel, strengths of up to 475 MPa are observed. 3 The specific temperature and duration required for the formation of 'transferable" quartz solid solution is strongly affected by the chemical compositions, including the concentrations of nucleating agents and other additives.…”