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.

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.

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.

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).

Effect of Heat Treatment Conditions on Properties of Lead‐Free Bi2GeO5 Ferroelectric Glass Ceramics

2009 ◽  
Author(s):  
P. Kantha ◽  
K. Pengpat ◽  
G. Rujijanagul ◽  
T. Tunkasiri ◽  
S. Eitssayeam ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Glass Ceramics ◽  
Lead Free ◽  
Treatment Conditions

Effect of Heat Treatment Conditions on Microstructure and Infrared Transmission Property of Germanate Oxyfluoride Glass-Ceramics

2010 ◽  
Vol 663-665 ◽  
pp. 1285-1288
Author(s):  
Zhuo Hao Xiao ◽  
Sheng Long Wang
Keyword(s):  
Heat Treatment ◽  
Crystal Size ◽  
Structural Characteristics ◽  
Glass Ceramics ◽  
Infrared Transmission ◽  
Oxyfluoride Glass ◽  
Treatment Conditions ◽  
Ir Transmission ◽  
Temperature Ranges ◽  
Good Transparency

Germanate oxyfluoride glass in CaF2/BaF2-AlF3-SiO2-GeO2 was prepared by melt quenching technique and subsequently converted to glass-ceramics with microstructures comprised nano-crystallites in a residual glass matrix by two-step heat treatments process. DSC, XRD, SEM and IR transmission investigations were used to determine structural characteristics and optical property of the prepared germanate oxyfluoride glass-ceramics. The influences of heat treatment conditions on crystallization behaviors and infrared transmission were discussed. The results show that crystal phase in the glass-ceramics is only Ge2Al6O13 and the crystal size is about 20nm-80nm when treated temperature ranges from 900 oC to 960oC. Good transparency is exhibited in visible light band to midinfrared band (5.0um) when treated temperature is low than 940 oC.

Microstructure and Crystallization Behavior of Glasses in the ZrO2-ZnO-Al2O3-SiO2 System

2007 ◽  
Vol 336-338 ◽  
pp. 1590-1592
Author(s):  
Xiao Dong Li ◽  
Jie Mo Tian ◽  
Chen Wang ◽  
Li Min Dong ◽  
Qing Feng Zan
Keyword(s):  
Heat Treatment ◽  
Crystallization Behavior ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Sio2 Glass ◽  
X Ray ◽  
Grain Sizes ◽  
Zro2 Phase ◽  
Crystal Phases ◽  
Electronic Microscope

Crystallization behavior of ZrO2-ZnO-Al2O3-SiO2 glass has been studied by differential thermal analysis, X-ray diffraction analysis and scanning electronic microscope. ZrO2 doped in the glass induces the phase separation effectively. The crystal phases obtained are gahnite (ZnAl2O4) and a small amount of ZrO2 phase. SEM photographs show that the crystal phases distribute uniformly in the glass ceramics and the grain sizes of glass ceramics after different heat treatment are less than 60nm.

Development of Machinable Glass-Ceramic without Nucleating Agents

2015 ◽  
Vol 830-831 ◽  
pp. 436-439
Author(s):  
C. Venkateswaran ◽  
Amarnath Padala ◽  
H. Sreemoolanadhan ◽  
M.R. Ajith ◽  
Mariamma Mathew ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Heat Treatment Condition ◽  
Aluminum Silicate ◽  
Nucleating Agents ◽  
Treatment Conditions ◽  
Magnesium Aluminum Silicate ◽  
Optimum Heat ◽  
Alumino Silicate

Mica containing glass-ceramic is prepared by crystallizing magnesium alumino silicate glass between 600°C and 1100°C without the use of any additives or nucleating agents. Effects of ceramization heat treatment conditions on phase constitution and microstructures are analyzed using XRD and HRSEM respectively. Developed glass-ceramics have been analyzed for its microhardness and machinability. Optimum heat treatment condition for achieving uniformly distributed fluorophlogopite phase essential for machinability, and at the same time, magnesium aluminum silicate phase for increasing the hardness, is presented.

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.

Melted Synthetic Zirconolite-Based Matrices: Effect of Cooling Rate and Heat Treatment on Ceramic Microstructure and Chemical Durability

2000 ◽  
Vol 663 ◽  
Author(s):  
T. Advocat ◽  
P.J. McGlinn ◽  
C Fillet ◽  
G. Leturcq ◽  
S. Schuller ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Glass Ceramics ◽  
Chemical Durability ◽  
Aluminosilicate Glass ◽  
Residual Glass ◽  
Slow Cooling ◽  
Oxide Mixture ◽  
Advanced Degrees ◽  
Treatment Conditions ◽  
Key Factor

ABSTRACTThe heat treatment conditions are a key factor in fabricating zirconolite ceramics and glass-ceramics following high-temperature melting. An oxide mixture melted at 1450°C and subsequently heat-treated at 1200°C yielded a glass-ceramic containing crystallized zirconolite–2M. The silica-enriched residual glass represented about 60-70 vol% of the total; the actinide surrogates (Nd, Ce)were equally distributed between the residual glass and the zirconolite crystals. Zirconolite ceramics obtained after melting an oxide mixture at 1600–1700°C consisted of zirconolite, perovskite and rutile. Rapid cooling rates (> 100°#x00B0;··min-1) were obtained by pouring the melt into ingot molds; the resulting zirconolite ceramics were characterized by crystals of zirconolite-2M ranging from 1 to no more than 20 μm. Slow cooling (< 25°C#x00B0;··min-1 produced ceramics with crystals several hundred micrometers long. Despite the microstructural differences, the chemical durability of the zirconolite ceramics was identical. The initial alteration rates r0 were about two orders of magnitude lower than those measured for the residual aluminosilicate glass of the zirconolite glass-ceramics. Moreover, during long-term leach tests at high S/V ratios to obtain advanced degrees of reaction progress, the alteration rates of all the materials diminished by over 3 to 4 orders of magnitude below r0.

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