Crystallization Kinetics Of Glass Research Articles

Effect of BaO on the crystallization kinetics of glasses along the Diopside–Ca-Tschermak join

We report on the effect of BaO on the crystallization kinetics of glasses in the diopside (CaMgSi2O6)–Ca-Tschermak (CaAl2SiO6) system. Partial substitution (i.e. 5%, 10% and 20%) of Ba2+ for Ca2+ was attempted in composition CaMg0.8Al0.4Si1.8O6, in three different glasses while partial substitution of B3+ for Al3+ was made in the fourth glass. Structural investigations on the glasses have been made by density measurements, molar volume and Infra-red spectroscopy (FTIR). Non-isothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all the four glasses. The Avrami parameter for the glass powders is ∼2, indicating the existence of intermediate mechanism of crystallization. Crystallization sequence in the glasses has been followed by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and FTIR. Augite crystallized out being the dominant phase in all the glass–ceramics, while different polymorphs of BaAl2Si2O8 were present as secondary or minor phases.

Study of Crystallization Kinetics in Glasses along the Diopside-Ca-Tschermak Join

We report on the thermal stability and crystallization kinetics of the glasses in the diopside (CaMgSi2O6)–Ca-Tschermak (CaAl2SiO6) system. Four glasses with compositions corresponding to different diopside/Ca-Tschermak ratio were studied. Structural investigations on the glasses have been made by employing Infrared spectroscopy (FTIR). Activation energies for structural relaxation and viscous flow have been calculated using the data obtained from differential thermal analysis. The existence of glass-in-glass phase separation was observed in all the glasses. Kinetic fragility of the glasses along with other thermal parameters have also been calculated. Nonisothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all the four glasses. The Avrami parameter for the glass powders is ∼2, indicating the existence of intermediate mechanism of crystallization. Crystallization sequence in the glasses has been followed by X-ray diffraction analysis, scanning electron microscopy, and FTIR.

The influence of Ta2O5 additions on the thermal properties and crystallization kinetics of a lithium zinc silicate glass

The lithium zinc silicate glass exhibits two crystallization exotherms corresponding to the formation of Li2ZnSiO4 and silica phases, respectively. The silica phases include tridymite and cristobalite. The influence of Ta2O5 additions on the thermal properties and non-isothermal crystallization kinetics of this glass, including nucleation rate maxima and activation energies for crystallization, has been determined by differential scanning calorimetry and X-ray diffraction. It has been found that Ta2O5 affects the crystallization behavior markedly, inhibiting the crystallization of high thermal expansion silica phases at lower concentrations, whilst at higher concentrations also suppressing crystallization of the Li2ZnSiO4 phase. At the higher concentrations, these phases are replaced by small amounts of LiTaO3 and LiTaSiO5.

Crystallization study of Na-Gd phosphate glass using non-isothermal DTA

Na-Gd phosphate glasses doped with Ce3+ are intensively studied due to their high intensity radioluminescence. Crystallization kinetics of glass with nominal composition of NaGd(PO3)4 was investigated using non-isothermal DTA at heating rates between 10 and 115 K min−1 and evaluated by the Kissinger and Ozawa peak methods. The activation energy for crystallization was determined for heating rates lower than 72 Kmin−1 as 789.91 and 802.77 kJ mol−1 by using the Kissinger and Ozawa methods, respectively. Formation of nuclei, their dimensions and movement of the crystallization front were observed using isothermal optical thermomicroscopy.

Nucleation and Crystallization of Glass-Ceramics from Coal Fly Ash

The nucleation and crystallization kinetics of glass obtained by melting coal fly ash with additives at 1550°C have been investigated. The optimum heat treatment schedule for the glass was nucleation at 825°C for 60min before crystallization at 962°C for 4h. The activation energy for crystallization of the glass-ceramics, obtained by the DDTA result, was 280.03 kJ/mol, lower than that of glass-ceramics obtained from pure reagents. The low activation energy is caused by impurities in fly ash, serving as nucleation agent. The results of XRD and SEM show that glass-ceramics developed nano-sized spherical wollastonite.

The crystallization of an aluminosilicate glass in the K 2O–Al 2O 3–SiO 2 system

The aims of the study were to explore the nucleation and crystallization kinetics of an aluminosilicate glass in K2O-Al2O3-SiO2 system and to characterize it. A starting glass composition of wt%; 64.2% SiO2, 16.1% Al2O3, 10.9% K2O, 4.3% Na2O, 1.7% CaO, 0.5% LiO and 0.4% TiO2 was heated in an electric furnace and later quenched to produce glasses. The glass powders were heat treated using differing heat treatment schedules and quenched. Dta, Xrd, Eds and Sem analyses were used to characterize and explore the crystallization kinetics of the glasses. Phase separation of the glasses was identified and characterized in the glasses. Tetragonal leucite, cubic leucite and sanadine glass-ceramics were produced. Fine leucite crystals (1 microm2) were crystallized with minimal matrix microcracking. Amorphous phase separation appeared to be an important precursor to nucleation and crystal growth in the alkali aluminosilicate glasses explored. It was possible to control the crystallization of tetragonal leucite and sanidine phases by selected heat treatment of glass powders and monoliths, resulting in the production of fine grained tetragonal leucite glass-ceramics.

Crystallization kinetics and phase transformation of xLi 2S–(1− x)Sb 2S 3, x=0–0.17 glass

Thermal analysis methods are widely used to study crystallization kinetics in glasses. The non-isothermal crystallization kinetics of xLi 2S–(1− x)Sb 2S 3, x=0–0.17 were investigated using differential scanning calorimetry (DSC). The activation energies, E a, for crystal growth have been determined for glass samples with particle size of <75 μm. The phases at which the glasses crystallized after the thermal process have been identified by powder X-ray diffraction (XRD) analysis.

Crystallization kinetics of glasses in the Te-Cl system

This paper reports on the results of investigations into the crystallization kinetics of glasses in the Te–Cl system. The critical heating rate for glasses in the composition range from 0.33Te · 0.67Cl to 0.63Te · 0.37Cl is determined by the volumetric technique. It is found that the Te3Cl2 glass is characterized by the lowest critical heating rate.

Nucleation and crystallization kinetics of glass derived from incinerator fly ash waste

Nucleation and crystallization kinetics concerning the conversion of a glass made from municipal solid waste (MSW) incinerator fly ash to glass-ceramics have been investigated. The maximum nucleation rate was found near 720 °C. Activation energies of crystallization were 468–293 kJ/mol and decreased with increasing powder particle size. Avrami exponents for crystallization were 1.5–2.0 which indicates that surface crystallization dominates the overall crystallization. Maximum crystallization can be achieved in a temperature range of 870–980 °C and this temperature increased as the particle size of the specimen increased.

An assessment of isothermal crystallization kinetics in glass by mathematical modeling

A mathematical model is presented to assess the devitrification kinetics of glasses under isothermal conditions. The model takes into account all the experimentally observable aspects of nucleation and growth behavior. A particle size distribution function is defined from the nucleation and growth parameters, and used to calculate the transformed volume fraction, the number of crystals and their mean and maximum radii according to the isothermal heat treatment time. The model was validated with a barium disilicate glass that crystallizes uniformly and rapidly into spherical particles; the nucleation and growth curves were therefore determined for BaSi 2O 5 crystals. The simulated and experimental results are compared and discussed. The model closely approximates the actual results, and can describe the devitrification kinetics of any glass matrix for which the nucleation and growth mechanisms have been defined.

Evaluation of crystallization kinetics of glasses by non-isothermal analysis

Based on Johnson-Mehl-Avrami transition equation, this paper proposes a new non-isothermal method for evaluating the crystallization kinetics of glasses. An equation relating the kinetic parameters of the crystallization activation energy, E, and the frequency factor, v, to the inflection-point temperature, Tf, and the heating rate, β, of differential thermal analysis (DTA) experiment is established. The inflection-point temperature, Tf, can be easily determined from the derivative differential thermal analysis (DDTA) curves. The validity of the proposed method is ascertained by applying it to Li2O·2SiO2 glass. The acquired values of the crystallization kinetic parameters by this method are excellent agreement with the isothermal analysis results. In contrast, the traditional non-isothermal methods give much higher values.

Glass‐Forming Ability and Crystallization Tendency Evaluated by the DTA Method in the Na2O–B2O3–Al2O3 System

In order to evaluate the crystallization tendency of glasses, the ratio of the crystallization temperature to the liquidus temperature (Tc/TL) was obtained by DTA measurement for the Na2O–B2O3 and Na2O–B2O3–Al2O3 systems. The critical cooling rate for glass formation (Q*) was also measured. The measurements were performed in the composition range of (100 −x)Na2O–(x)B2O3, (x= 25–35 and 60–100 mol%), and (100 −y)0.5Na2O·0.5B2O3−(y)Al2O3, (y= 6–34 mol%). The relationship between Tc/TL and Q* was discussed. A linear relationship between Tc/TL and log Q* for these systems was found. Furthermore, the relationship between Tc/TL and Q* was verified by computer simulation based on the crystallization kinetics of glass or supercooled liquid.

Relation between low temperature viscosity and crystallization kinetics of glasses

Low temperature viscosity ranging from 10 7 to 10 11 poises in BaO-La 2O 3-B 2O 3 glasses were measured by a penetrometer. There is a close relation between low temperature viscosity and crystallization kinetics of glasses. Glasses with flat viscosity temperature curves are more resistant to crystallization than glasses with steep viscosity temperature curves in low temperature range. A new method to predict crystallization tendency of glasses with low temperature viscosity properties is proposed in this paper.

Investigation on the crystallization kinetics of glasses from the GeSeIn system

The crystallization kinetics of glasses from the GeSeIn system is investigated using differential thermal techniques under non-isothermal conditions. The energy of nucleation and growth of the crystal phase is determined and a comparative estimation of the crystallization ability of the glasses is given. The composition of the crystallized phases is identified by X-ray analysis. It is established that the first to crystallize are GeSe and GeSe 2, followed by In 2Se 3 and Se. This agrees with the state diagram of the ternary system GeSeIn. The morphology of the crystals obtained is determined by electron microscopy.

Kinetics of phase transformations in amorphous materials by DSC. Part I

New analytical methods are introduced for the determination of kinetic parameters of crystallization of an amorphous alloy from DSC transformation exotherms. Isothermal and heating rate methods, as well as a method for separation of two superimposed crystallization reactions are discussed. The basic operating principles and accuracy of the two currently most popular DSC instruments (the DuPont 1090 (E.I. Dupont de Nemours Inc., Wilmington, DE, U.S.A.) and the Perkin Elmer DSC7 (Perkm Elmer Corporation, Norwalk, CT, U.S.A.)) in the context of glass crystallization kinetics are critically evaluated and compared.

A remark on the applicability of DTA and the reliability of non-isothermal determination for the crystallization kinetics of glasses

The most decisive phenomena arising either from specific DTA measurements (heat inertia, temperature deviation, self-heating) or from non-isothermal kinetic treatment (overlapping models, characteristics determinations) are discussed.

Raman scattering study of glass crystallization kinetics

Laser induced glass-crystalline transition is studied by light scattering. Three significant effects are observed depending on the incident laser energy density: (i) Spectral band narrowing indicating cluster enlargement constitutes a precursor effect, (ii) an intensity increase effect indicates a rapid rise of the density of clusters attaining microcrystalline size and (iii) a dynamical reversal effect indicative of glass-crystalline instability. Cluster volume and crystallization appear as separate but related threshold phenomena.

Study on crystallization kinetics in glass by differential thermal analysis

Study on crystallization kinetics in glass by differential thermal analysis

Thermal analysis of non-isothermal crystallization kinetics in glass forming liquids

A brief review is given of previously suggested methods for analysis of experimental data of non-isothermal crystallization kinetics based on the Johnson-Mehl-Avrami transformation rate equation. Conditions for applicability are outlined and an estimate of error is made. A method of non-isothermal analysis is presented which facilitates rapid data evaluation over large temperature ranges and which justifies the previous applications in the literature of Kissinger's method to the analysis of crystallizations kinetics. An extension of these methods is made to the case of growth rates which obey a Vogel-Further temperature relation.