Perfect surface crystallization and parasitic structures in nonstoichiometric glass-ceramics: Micro-/nanoscopic aspects

2013 ◽  
Vol 102 (19) ◽  
pp. 191903 ◽  
Author(s):  
Yoshihiro Takahashi ◽  
Yoshiki Yamazaki ◽  
Rie Ihara ◽  
Takumi Fujiwara
Keyword(s):  
Glass Ceramics ◽  
Surface Crystallization

Surface crystallization and phase evolution of BaO–SrO–TiO2–SiO2–Al2O3-based glass ceramics

2017 ◽  
Vol 130 (1) ◽  
pp. 221-228 ◽  
Author(s):  
M. Kosmal ◽  
M. Reben ◽  
P. Pichniarczyk ◽  
M. Ziąbka ◽  
S. J. Skrzypek
Keyword(s):  
Glass Ceramics ◽  
Phase Evolution ◽  
Surface Crystallization

Variation in Pockels constants of silicate glass-ceramics prepared by perfect surface crystallization

2018 ◽  
Vol 112 (2) ◽  
pp. 021904 ◽  
Author(s):  
Kazuya Takano ◽  
Yoshihiro Takahashi ◽  
Takamichi Miyazaki ◽  
Nobuaki Terakado ◽  
Takumi Fujiwara
Keyword(s):  
Silicate Glass ◽  
Glass Ceramics ◽  
Surface Crystallization

Surface Crystallization of ZnO-Al2O3-SiO2 Glass

2007 ◽  
Vol 280-283 ◽  
pp. 1655-1658
Author(s):  
Xiao Dong Li ◽  
Jie Mo Tian ◽  
Chen Wang ◽  
Li Min Dong
Keyword(s):  
Heat Treatment ◽  
Treatment Time ◽  
Glass Ceramics ◽  
Surface Crystallization ◽  
X Ray Diffraction ◽  
Crystalline Layer ◽  
Surface Conditions ◽  
X Ray ◽  
Treatment Processes ◽  
Electronic Microscope

ZnO-Al2O3-SiO2 glasses with different surface conditions were surface crystallized by different heat treatment process. Differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and scanning electronic microscope (SEM) were used to investigate the crystallization behavior of glasses, the crystalline components and microstructure of the as-got glass-ceramics. According to the DTA results, different heat treatment processes of surface crystallization on the glass were adopted. The SEM results show that surface conditions of glasses are important for the surface crystallization, and the thickness of surface crystalline layer increases with heat treatment time.

Competition Between Internal and Surface Crystallization in Glass-ceramics Developed for Actinides Immobilization

2003 ◽  
Vol 807 ◽  
Author(s):  
Pascal Loiseau ◽  
Daniel Caurant ◽  
Odile Majerus ◽  
Nöel Baffier ◽  
Catherine Fillet
Keyword(s):  
Crystalline Phase ◽  
Treatment Duration ◽  
Preparation Method ◽  
Glass Ceramics ◽  
Minor Actinides ◽  
Surface Crystallization ◽  
Waste Forms ◽  
Trivalent Actinides ◽  
Structure And Microstructure ◽  
Ceramic Matrices

ABSTRACTGlass-ceramic matrices containing zirconolite (nominally CaZrTi2O7) as the only crystalline phase in their bulk can be considered as good candidates for actinide-rich nuclear wastes (containing minor actinides or Pu) immobilization. In this study, three different methods are envisaged and compared to prepare such waste forms using neodymium as trivalent actinides surrogate. Independently on the preparation method, zirconolite is shown to be the only crystalline phase to nucleate in the bulk. However, crystallization of silicate phases (titanite CaTiSiO5 + anorthite CaAl2Si2O8) can occur from samples surface and can compete with zirconolite crystallization. The effect of the crystal growth thermal treatment duration (2–300 h) at high temperature (1050–1200°C) on glass-ceramics structure and microstructure is studied. In the oxides system studied here, it appears that zirconolite is not thermodynamically stable in comparison with titanite but, for kinetics reasons, such transformation will not occur during waste forms disposal.

scholarly journals Investigation DSC and XRD on the Crystallization Kinetics in the Phosphate Li2O−Li2WO4−TiO2−P2O5 Glassy Ionic System

2021 ◽  
Author(s):  
Hicham ES-SOUFI ◽  
L. Bih ◽  
Alan R. F. Lima ◽  
A. El Bouari ◽  
B. Manoun ◽  
...  
Keyword(s):  
Crystallization Process ◽  
Glass Ceramics ◽  
Chemical Durability ◽  
Surface Crystallization ◽  
Vibrational Modes ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray ◽  
Activation Energy Of Crystallization ◽  
Avrami Parameter

Abstract This work aims to investigate the prepared glasses within the 20Li2O−(50−x)Li2WO4−xTiO2−30P2O5 system, with 0≤x≤15 mol%. The bonds constituting the framework of these glasses were studied by Raman spectroscopy. The data analysis of the chemical durability showed that the dissolution rates depend on the composition of each glass. Thermal analysis by DSC technique was used to determine the activation energy of crystallization, it found in the glass of composition (x= 5) that Ec= 184.482 kJ/mol. The determinate Avrami parameter is around 1.7 which allows suggesting the mechanism is surface crystallization. The crystallization process of the prepared glasses is carried out by heating samples at 550°c for 4 hours and 12 hours. The crystallized phases are identified by XRD. The results of X−ray diffraction analysis confirm that TiO2 acts mainly as network forming units. The crystalline phases Li2WO4 (JCPDS# 01−072−0086) and (JCPDS# 01−087−0409) are formed during the crystallization process. The formation of these crystalline phases into the glasses depends on the time of heating at fixed crystallization temperature. FTIR spectra of the glass–ceramics show nearly the same IR vibrational modes as their parent glasses.

scholarly journals Structure and Properties of Piezoelectric Strontium Fresnoite Glass-Ceramics Belonging to the Sr–Ti–Si–Al–K–O System

Ceramics ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 86-97 ◽  
Author(s):  
Marie-Sophie Renoirt ◽  
Nathalie Maury ◽  
Florian Dupla ◽  
Maurice Gonon
Keyword(s):  
Glass Ceramic ◽  
Mirror Symmetry ◽  
Glass Ceramics ◽  
Preferential Orientation ◽  
Surface Crystallization ◽  
High Temperature Xrd ◽  
Crystallization Conditions ◽  
The Stability ◽  
Oriented Parallel

Crystallization of strontium fresnoite Sr2TiSi2O8 piezoelectric crystals in Sr–Ti–Si–K–Al–O parent glasses is investigated with the aim of showing the influence of composition and crystallization conditions on the microstructure and piezoelectric properties of the resulting glass-ceramic. All the investigated conditions lead to a surface crystallization mechanism that induces a preferential orientation of crystal growth in the glasses. Near the surface, all the glass-ceramics obtained exhibit (002) planes preferentially oriented parallel to their faces. Deeper in the specimens, this preferential orientation is either kept or tilted to (201) after a depth of about 300 µm. The measurement of the charge coefficient d33 of the glass-ceramic highlights that surface crystallization induces mirror symmetry in the polarization. It reaches 11 to 12 pC/N and is not significantly influenced by the preferential orientation (002) or (201). High temperature XRD shows the stability of the fresnoite phase in the glass-ceramics up to 1000 °C. Mechanical characterization of the glass-ceramics by impulse excitation technique (IET) highlights that the softening of the residual glass leads to a progressive decrease of Young’s modulus in the temperature range 600–800 °C. Damping associated to the viscoplastic transition become severe only over 800 °C.

scholarly journals Crystallization behaviour of Li2O·Nb2O5·SiO2 glass containing TiO2

2011 ◽  
Vol 5 (4) ◽  
pp. 223-227 ◽  
Author(s):  
Srdjan Matijasevic ◽  
Vladimir Zivanovic ◽  
Mihajlo Tosic ◽  
Snezana Grujic ◽  
Jovica Stojanovic ◽  
...  
Keyword(s):  
Phase Composition ◽  
Crystallization Behavior ◽  
Glass Ceramics ◽  
Primary Phase ◽  
Surface Crystallization ◽  
Complex Phase ◽  
Crystallite Sizes ◽  
Complex Phase Composition ◽  
Calculated Average

This paper deals with the crystallization of glass 30Li2O?15Nb2O5?50SiO2?5TiO2 (mol%). The crystallization behavior was studied under isothermal and non-isothermal conditions. XRD and SEM methods were employed for determination of phase composition and microstructure of crystallized glass. It was detected that this glass crystallizes by the surface crystallization mechanism. SEM micrographs of the crystallized samples revealed that the crystals grow in the form of dendrites. The glass-ceramics with complex phase composition was obtained. Three crystalline phases were detected where LiNbO3 has grown as primary phase and a secondary ones Li2Si2O5 and SiO2 appeared. The calculated average crystallite sizes are: 27 nm for LiNbO3 , 115 nm for Li2Si2O5 and 45 nm for SiO2 . From the experimental data an activation energy of crystals growth, calculated using the Kissinger relation, is Ea = 275 ?10 KJ / mol.

scholarly journals Mechanism and kinetics of glass-ceramics formation in the LiO2-SiO2-CaO-P2O5-CaF2 system

2009 ◽  
Vol 7 (2) ◽  
pp. 228-233 ◽  
Author(s):  
Martin Palou ◽  
Eva Kuzielová ◽  
Martin Vitkovič ◽  
Maha Noaman
Keyword(s):  
Thermal Analysis ◽  
Grain Size ◽  
Glass Ceramics ◽  
Surface Crystallization ◽  
Particle Sizes ◽  
Mechanism And Kinetics ◽  
Rate Of Heating ◽  
Kinetics Of ◽  
Calculated Activation

AbstractTwo glasses based on lithium disilicate (LS2), with and without fluorapatite (FA), were synthesised in the Li2O-SiO2-CaO-P2O5-CaF2 system with P2O5: CaO: CaF2 ratios corresponding to fluorapatite. Glass-ceramics have then been prepared by thermal treatment. The mechanism and kinetics of crystallization as functions of grain size and rate of heating were investigated using thermal analysis methods. The smaller particles crystallize preferentially by surface crystallization, which is replaced by volume crystallization at larger particle sizes. Inclusion of FA in the LS2 favours crystallization through the surface mechanism. The onset limit for volume crystallization replacing the surface mechanism is at about 0.3 mm for pure LS2 glass and 0.9 mm for glass containing FA. The calculated activation energies of the glasses (299 ± 1 kJ mol-1 for pure LS2 glass and 288 ± 7 kJ mol−1 for glass containing FA according to Kissinger, or 313 ± 1 kJ mol-1 for pure LS2 glass and 303 ± 8 kJ mol-1 for glass containing FA according to Ozawa) indicate that the tendency of the glasses to crystallize is supported by the FA presence. Bioactivity of all samples has been proved in vitro by the formation of new layers of apatite-like phases after soaking in SBF.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

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