scholarly journals Effects of M2+ (M = Ca, Sr, and Ba) Addition on Crystallization and Microstructure of SiO2-MgO-Al2O3-B2O3-K2O-F Glass

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Mrinmoy Garai ◽  
Nibedita Sasmal ◽  
Basudeb Karmakar
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Glass Ceramics ◽  
Single Step ◽  
Microstructural Properties ◽  
Melt Quenching ◽  
Base Glass ◽  
Sealing Material ◽  
Wide Range ◽  
Ceramic Microstructure

In understanding the effect of K+ substitution by M2+ (M = Ca, Sr, and Ba) on crystallization and microstructural properties of boroaluminosilicate glass system, the SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glasses were prepared by single-step melt-quenching at 1500°C. Density of base glass (2.64 g·cm−3) is found to be decreased in presence of CaO and SrO. Tg is increased by 5–10°C and Td decreased by 13–20°C on addition of M2+. The variation of Tg, Td and decrease of thermal expansion (CTE) from 7.55 to 6.67–6.97 (×10−6/K, at 50–500°C) in substituting K+ by M2+ are attributed to the higher field-strength of Ca2+, Sr2+, and Ba2+. Opaque mica glass-ceramics were derived from the transparent boroaluminosilicate glasses by controlled heat treatment at 1050°C (duration = 4 h); and the predominant crystalline phase was identified as fluorophlogopite (KMg3AlSi3O10F2) by XRD and FTIR study. Glass-ceramic microstructure reveals that the platelike mica flake crystals predominate in presence of K2O and CaO but restructured to smaller droplet like spherical shaped mica on addition of SrO and BaO. Wide range of CTE values (9.54–13.38 × 10−6/K at 50–800°C) are obtained for such glass-ceramics. Having higher CTE value after crystallization, the CaO containing SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glass can be useful as SOFC sealing material.

Microstructure and Crystallization of MAS Glass-Ceramics Containing Alkali Oxides

2010 ◽  
Vol 177 ◽  
pp. 437-440
Author(s):  
Zhuo Hao Xiao ◽  
Jian Er Zhou ◽  
Yong Qing Wang
Keyword(s):  
Heat Treatment ◽  
Glass Ceramics ◽  
Melt Quenching ◽  
Base Glass ◽  
Sio2 Glass ◽  
Sio2 System ◽  
Treatment Conditions ◽  
Strength Tests ◽  
Alkali Oxides ◽  
Regular Network

MgO-Al2O3-SiO2 glass-ceramics containing 4.0w% alkali oxides were prepared by conven- tional melt quenching technique. The effects of heat treatment conditions on crystal types, microstructure and break strength of the glass-ceramics were studied by DSC, XRD, SEM and break strength tests. The main crystallization phases of this glass system are β-quartz (Li2-2xMgxAl2Si3O10) and β-Spodumene, no cordierite phase found. The glass-ceramics possessed a regular network-shaped microstructure feature formed by pyroxene crystals. With the increase of temperature, the β-Quartz around pyroxene crystals converted into β-spodumene and the regular network-shaped microstructure feature getting weaker and disappeared. The average break strength of the glass-ceramics containing no cordierite crystals based on MgO2-Al2O3-SiO2 system is about 150MPa, which is much high than the base glass.

Zn2+- Controlled Crystallization and Microstructure in K-Li-Mg-B-Si-Al-F Glass

MRS Advances ◽  
2018 ◽  
Vol 3 (60) ◽  
pp. 3525-3533 ◽  
Author(s):  
Mrinmoy Garai ◽  
Anoop K. Maurya ◽  
Shibayan Roy
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Ceramic ◽  
Vickers Microhardness ◽  
Glass Ceramics ◽  
Network Modifier ◽  
Base Glass ◽  
Controlled Crystallization

Abstract Text:The crystallization of (9-X) K2O-1Li2O-12MgO-10B2O3-40SiO2-16Al2O3-12MgF2-X PbO/BaO/ZnO (X =0/5) composition (wt.%) were studied by means of dilatometry, DSC, XRD, SEM and microhardness analysis. Density of base K-Li-Mg-B-Si-Al-F glass (2.59 g.cm–3) is found to be increased on addition of the network modifier oxides PbO, BaO and ZnO content. Addition of Pb2+, Ba2+ and Zn2+ furthermore increased the glass transition temperature (Tg.). A characteristic exothermic hump is found to be appeared in DSC thermograph at the temperature range 800-950°C; and that is ascribed to the formation of crystalline phase fluorophlogopite mica, KMg3(AlSi3O10)F2. Opaque glass-ceramics were prepared from K-Li-Mg-B-Si-Al-F glasses (with and without containing PbO, BaO and ZnO content) by controlled heat-treatment at 1000°C. Interlocked type microstructure combined of flake like fluorophlogopite mica crystals is obtained in ZnO-containing K-Li-Mg-B-Si-Al-F glass-ceramic; and such microstructural pattern is ascribed to cause large thermal-expansion (>11.5×10-6/K, 50-800°C).Vickers Microhardness of base glass-ceramic (5.12 GPa) is increased when contains ZnO (5.26 GPa). ZnO-containing boroaluminosilicate glass-ceramic is, hence, considered with potential interest as they can exhibit the microcrack resistivity in high temperature recycling operation (like SOFC).

scholarly journals Impact of Morphology and Microstructure on the Mechanical Properties of Ge-As-Pb-Se Glass Ceramics

2020 ◽  
Vol 10 (8) ◽  
pp. 2836 ◽  
Author(s):  
Rashi Sharma ◽  
Rebecca Welch ◽  
Myungkoo Kang ◽  
Claudia Goncalves ◽  
Cesar Blanco ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Vickers Hardness ◽  
Glass Ceramic ◽  
Volume Fraction ◽  
Glass Ceramics ◽  
Post Heat Treatment ◽  
Base Glass ◽  
Parent Glass ◽  
Crystal Phases

The impact of base glass morphology and post heat-treatment protocol on the mechanical properties (Vickers hardness and Young’s modulus) of a multi-component glass-ceramic was examined. Two parent chalcogenide glasses with identical composition but varying morphology (homogeneous and phase separated) were evaluated for their mechanical properties following identical thermal processing to induce crystallization. The nucleation and growth rates of the starting materials were compared for the two glasses, and the resulting crystal phases and phase fractions formed through heat treatment were quantified and related to measured mechanical properties of the glass ceramics. The presence of a Pb-rich amorphous phase with a higher crystal formation tendency in the phase-separated parent glass significantly impacted the volume fraction of the crystal phases formed after heat-treatment. Pb-rich cubic crystal phases were found to be dominant in the resulting glass ceramic, yielding a minor enhancement of the material’s mechanical properties. This was found to be less than a more moderate enhancement of mechanical properties due to the formation of the dominant needle-like As2Se3 crystallites resulting from heat treatment of the homogeneous, commercially melted parent glass. The greater enhancement of both Vickers hardness and modulus in this glass ceramic attributable to the high-volume fraction of anisotropic As2Se3 crystallites in the post heat-treated commercial melt highlights the important role base glass morphology can play on post heat-treatment microstructure.

Influence of Heat Treatment Conditions on Crystallization and Thermal Expansion of Las Glass-Ceramics

2010 ◽  
Vol 168-170 ◽  
pp. 1712-1716
Author(s):  
Zhuo Hao Xiao ◽  
Ming Hua Luo
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Matrix Glass ◽  
Treatment Conditions ◽  
The Matrix ◽  
Crystal Phases ◽  
Quenching Method

The LAS glass containing P2O5has been prepared by conventional molten quenching method. The influence of heat treatment conditions on crystallization behavior, including phase transformation and microstructure, and thermal expansion coefficient (TEC) of Li2O–Al2O3–SiO2(LAS) glass-ceramics were investigated. DSC, XRD, SEM and TEC were used to detect the microstructure and properties of glass-ceramics under the different heat-treatment conditions. The results show the virgilite crystalline separated firstly from the matrix glass when heat treatment temperature was 850 °C. As the heat treatment temperature increased from 850 °C to 1050 °C, virgilite and β-spodumene were identified as main crystal phases. The TEC of glass-ceramics ranges from 0.5×10-6 °C-1to 2.8×10-6 °C-1, which is much lower than that of matrix glass.

Study on Properties of Leucite for Dental Porcelain Compositions

2011 ◽  
Vol 66-68 ◽  
pp. 1522-1527
Author(s):  
Li Na Sui ◽  
Li Yan Yu ◽  
Li Feng Dong
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Powder Diffraction ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Clinical Applications ◽  
High Concentration ◽  
Melt Quenching ◽  
Dental Porcelain ◽  
X Ray

Leucite crystal was prepared using SiO2-Al2O3-K2CO3-Na2CO3as raw materials and adopting melt quenching and appropriate heat treatment temperatures. The crystal was characterized and analyzed by X-ray powder diffraction, the coefficient of thermal expansion, and biocompatibility. The results showed that appropriate Na2O could advance the growth of leucite, but high concentration facilitates the formation of KAlSiO4crystal. The coefficient of thermal expansion was 24.52×10-6/°C at 600 °C, and thereby the coefficient could be adjusted by adding appropriate amount of leucite. The biocompatibility of leucite was almost the same as the Songfeng powder for clinical applications.

Li2O-Al2O3-SiO2 Glass-Ceramics Used As Anodic Bonding Materials

2008 ◽  
Vol 368-372 ◽  
pp. 1436-1438 ◽  
Author(s):  
Hong Li ◽  
Yun Du ◽  
Jin Shu Cheng ◽  
Tian He Wang
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Glass Ceramics ◽  
Treatment Method ◽  
Substrate Material ◽  
Anodic Bonding ◽  
Treatment Schedule ◽  
Crystal Phases ◽  
Step Heat Treatment

The glass-ceramics, whose coefficient of thermal expansion approximately matched to that of silicon, were studied to replace conventional heat-resistant glass as substrate material for anodic bonding. The basic glasses of the Li2O-Al2O3-SiO2 system with TiO2 and ZrO2 as nucleation agents were prepared by melting technology, and the temperatures of nucleation and crystallization were determined. The glass-ceramics were obtained by two-step heat-treatment method. The oriented crystallization of glasses in gradient temperature field was studied. The crystal phases and microstructures of glass- ceramics were analyzed. Effect of heat-treatment schedule on the coefficient of thermal expansion was discussed. The results showed that the most of the main crystal phases of the samples were β-spodumene. The coefficient of thermal expansion of sample was about 32.5×10-7/°C, which was approach to that of silicon.

Crystallization and Thermal Expansion of MgO-Al2O3-SiO2-TiO2 Glass-Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 1635-1638
Author(s):  
Hua Shao ◽  
Kai Ming Liang ◽  
Feng Zhou ◽  
Fei Peng
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Phase Separation ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Treatment Condition ◽  
Glass Ceramics ◽  
Heat Treatment Condition ◽  
Crystallization Sequence ◽  
The Relationship

Crystallization sequence of MgO-Al2O3-SiO2-TiO2 system glass was investigated by means of DTA, XRD, SEM and EDS. The relationship between crystalline phases, heat treatment methods and thermal expansion coefficient (α) were well discussed. The results have shown that: The glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phases. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss and α-cordierite made their appearance successively. The thermal expansion coefficient as a function of the heat treatment condition was studied.

BaO-Al2O3-SiO2-B2O3 Glass-Ceramic SOFCs Sealant: Effect of ZnO Additive

2017 ◽  
Vol 751 ◽  
pp. 455-460 ◽  
Author(s):  
Nattapol Laorodphan ◽  
Jiratchaya Ayawanna
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Solid Oxide Fuel Cells ◽  
Glass Ceramic ◽  
Coefficient Of Thermal Expansion ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
X Ray ◽  
Barium Aluminosilicate ◽  
Xrd Patterns

The crystallization of planar solid oxide fuel cells (SOFCs) sealant glasses in the systems BaO-Al2O3-SiO2-B2O3 (BaBS) and BaO-Al2O3-SiO2-B2O3-ZnO (BaBS-Zn) was investigated via both X-ray diffractometer and scanning electron microscopy with energy dispersive spectroscopy. The effect of nucleation heat-treatment of the BaBS glass at different temperature for 5 hours, i.e. 550 and 590 °C, on the crystallization behavior was also studied. Thermal expansion profiles of the glasses indicate that both glasses have a low sealing temperature. XRD patterns of all BaBS glass-ceramics, devitrified at 800 °C for 30 hours, show that Ba2Si3O8, BaAl2Si2O8, Ba3B2O6 and some unknown crystalline phases were found. It was also found that crystalline size of unknown barium aluminosilicate with low silicon content depends on the nucleation heat-treatment temperature. For the ZnO-containing glass, ZnO reduces the coefficient of thermal expansion value of glass and causes the devitrification of large needle-like barium zinc silicate phases. The crack at the YSZ/BaBS-Zn glass-ceramic interface was also observed. Two barium silicate phases, which are BaZnSiO4 and BaZn2Si2O7 were devitrified in ZnO-containing glass-ceramic.

scholarly journals Nano-Crystallization of Ln-Fluoride Crystals in Glass-Ceramics via Inducing of Yb3+ for Efficient Near-Infrared Upconversion Luminescence of Tm3+

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1033
Author(s):  
Jianfeng Li ◽  
Yi Long ◽  
Qichao Zhao ◽  
Shupei Zheng ◽  
Zaijin Fang ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Near Infrared ◽  
Upconversion Luminescence ◽  
Glass Ceramics ◽  
Upconversion Emission ◽  
Ceramic Composites ◽  
Wide Range ◽  
Transmission Window ◽  
Optical Applications ◽  
Upconversion Emissions

Transparent glass-ceramic composites embedded with Ln-fluoride nanocrystals are prepared in this work to enhance the upconversion luminescence of Tm3+. The crystalline phases, microstructures, and photoluminescence properties of samples are carefully investigated. KYb3F10 nanocrystals are proved to controllably precipitate in the glass-ceramics via the inducing of Yb3+ when the doping concentration varies from 0.5 to 1.5 mol%. Pure near-infrared upconversion emissions are observed and the emission intensities are enhanced in the glass-ceramics as compared to in the precursor glass due to the incorporation of Tm3+ into the KYb3F10 crystal structures via substitutions for Yb3+. Furthermore, KYb2F7 crystals are also nano-crystallized in the glass-ceramics when the Yb3+ concentration exceeds 2.0 mol%. The upconversion emission intensity of Tm3+ is further enhanced by seven times as Tm3+ enters the lattice sites of pure KYb2F7 nanocrystals. The designed glass ceramics provide efficient gain materials for optical applications in the biological transmission window. Moreover, the controllable nano-crystallization strategy induced by Yb3+ opens a new way for engineering a wide range of functional nanomaterials with effective incorporation of Ln3+ ions into fluoride crystal structures.

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