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.

scholarly journals Structural Features and Synthesis of CeO2-Doped Boroaluminosilicate Oxyfluoride Transparent Glass Ceramics

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Zhenlin Wang ◽  
Laifei Cheng
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Glass Ceramics ◽  
Structural Features ◽  
Temperature Decrease ◽  
Silicate Network ◽  
Network Modifier ◽  
Transparent Glass ◽  
Pass Through

This study investigated the effects of CeO2on structure and synthesis of boroaluminosilicate transparent glass ceramics containing CaF2nanocrystals prepared through isothermal crystallization of the melt-quenched glasses with composition 54SiO2–10B2O3–13Al2O3–14Na2O–3ZnO–2Li2O–4CaF2doped with 0–1.2 mol% CeO2. CeO2in polyvalent states acting as network modifier leads to disruption of the silicate network and the conversion of [BO3] to [BO4] generating the nonlinear variations in crystallization, and thermodynamic and optical features. Glass transition temperature and the crystallization temperature decrease firstly and then increase with the increase of CeO2content. Correspondingly, the size of CaF2nanoscale crystals and the absorption coefficient of the glass ceramics are found to pass through a maximum and then decrease with increasing CeO2addition. Increasing CeO2concentration and elevating treating temperature lead to red-shift of absorption edge and transparency deterioration of glass ceramics.

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 Crystallization and thermo-mechanical properties of Li2O-ZnO-CaO-SiO2 glass-ceramics with In2O3 and Fe2O3 additives

2015 ◽  
Vol 9 (4) ◽  
pp. 215-223 ◽  
Author(s):  
Saad Salman ◽  
Samia Salama ◽  
Ebrahim Mahdy
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Expansion Coefficient ◽  
Vickers Microhardness ◽  
Glass Ceramics ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Prepared Glass ◽  
Melting Technique ◽  
Controlled Crystallization

Li2O-ZnO-CaO-SiO2 based glasses were prepared by the conventional melting technique and subsequently converted to glass-ceramics by controlled crystallization. The nucleation and crystallization temperatures were determined by differential thermal analysis (DTA). The effects of adding In2O3 and Fe2O3 addition on the crystallization behaviour and thermo-mechanical properties of the prepared glass-ceramics were investigated. A study on the microstructure, close to the internal phases of the resulting glass-ceramics, was followed by using scanning electron microscope (SEM). The dilatometric thermal expansion and Vickers? microhardness of the crystalline products were also evaluated. The crystalline phases that can be found in the resulting glass-ceramics, identified by X-ray diffraction (XRD) analysis, are ?-quartz-[SiO2], lithium zinc silicate-[Li2ZnSiO4], lithium disilicate-[Li2Si2O5], wollastonite-[CaSiO3], wollastonite containing iron, ferrobustamite-[(Ca0.79Fe0.21)SiO3], and lithium indium silicate of pyroxene type-[LiInSi2O6]. Average thermal expansion coefficient (in the temperature range 25-700?C) decreased from 191?10-7 1/?C to 115?10-7 1/?C and the Vickers? microhardness increased from 3.56 to 5.44GPa with the increase of In2O3 and Fe2O3 contents in the glass-ceramics. The changes in the obtained expansion coefficient and microhardness were due to the formation of different phases which in turn influenced the rigidity/bonding and microstructure in the resultant glass-ceramics.

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.

Oxynitride Glasses and Glass Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
Stuart Hampshire
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
Glass Ceramic ◽  
Glass Ceramics ◽  
Heat Treatments ◽  
Oxynitride Glass

Silicon nitride based ceramics contain oxynitride glass phases at the grain boundaries which can impair subsequent high temperature properties. Investigations of bulk glasses in various M-Si-Al-O-N systems have been carried out and it has been shown that up to 15 atomic % N can be incorporated into these oxynitride glasses. Studies have revealed that nitrogen increases the viscosity, hardness and glass transition temperature of the glasses. Heat treatments of the glasses to form crystalline phases have been reported but further improvements are possible if glass-ceramic processes using two-stage heat treatments are introduced. The development of oxynitride glasses and the effects of nitrogen on properties are reviewed and the optimisation of glass-ceramic heat-treatments are reported.

Proposal for a material with negative thermal expansion

2016 ◽  
Vol 30 (32) ◽  
pp. 1650238
Author(s):  
Mikrajuddin Abdullah
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
Transition Temperature ◽  
Metal Organic Framework ◽  
Negative Thermal Expansion ◽  
Lennard Jones ◽  
Model Predictions ◽  
Metal Organic ◽  
Organic Framework

I propose a model of a material that exhibits negative thermal expansion (NTE) properties and criteria for the occurrence of linear and volumetric NTE. I derived the criteria for an arbitrary force between rigid units in the material. These criteria are also discussed specifically for the Lennard–Jones (6–12) potential and in more detail for metal–organic framework (MOF) materials comprising rigid units connected by organic linkers. Qualitatively, the model predictions can explain some observed results. Surprisingly, the model can produce equations for the transition temperature from NTE to positive thermal expansion (PTE), [Formula: see text] K, which is exactly the same as the temperature at which the glass transition begins to occur in most polymers, i.e., [Formula: see text] K.

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 Core/Clad Phosphate Glass Fibres Containing Iron and/or Titanium

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Ifty Ahmed ◽  
S. S. Shaharuddin ◽  
N. Sharmin ◽  
D. Furniss ◽  
C. Rudd
Keyword(s):  
Thermal Expansion ◽  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Tensile Modulus ◽  
Average Diameter ◽  
Phosphate Glasses ◽  
Dissolution Medium ◽  
The Core ◽  
Controllable Degradation

AbstractPhosphate glasses are novel amorphous biomaterials due to their fully resorbable characteristics, with controllable degradation profiles. In this study, phosphate glasses containing titanium and/or iron were identified to exhibit sufficiently matched thermal properties (glass transition temperature, thermal expansion coefficient and viscosity) which enabled successful co-extrusion of glass billets to form a core/clad preform. The cladding composition for the core/clad preforms were also reversed. Fe clad and Ti clad fibres were successfully drawn with an average diameter of between 30~50 μm. The average cladding annular thickness was estimated to be less than 2 μm. Annealed core/clad fibres were degraded in PBS for a period of 27 days. The strength of the Fe clad fibres appeared to increase from 303 ± 73 MPa to 386 ± 45 MPa after nearly 2 weeks in the dissolution medium (phosphate buffered solution) before decreasing by day 27. The strength of the Ti clad fibres revealed an increase from 236 ± 53 MPa to 295 ± 61 MPa when compared at week 3. The tensile modulus measured for both core/clad fibres ranged between 51 GPa to 60 GPa. During the dissolution study, Fe clad fibres showed a peeling mechanism compared to the Ti clad fibres.

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