Activation Energy For Crystal Growth Research Articles

Influence of CeO2 addition on crystal growth behavior of CeO2–Y2O3–ZrO2 solid solution

Nanopowders with cubic fluorite-type structure as well as uniform distribution in particle size were synthesized by hydrothermal method in the ternary oxide zirconia–yttria–ceria system with ceria content of 0–25mol%. X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimeter (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), specific surface area (SBET) and high resolution transmission electron microscopy (HRTEM) were applied to characterize the structure, thermal decomposition, morphological characteristic and crystal growth of the produced powders. Qualitative analyses indicate that the as-synthesized nanoparticles are single-phase crystallites with an average particle size of 4–9nm. The specific surface area, lattice parameter and microstrain are closely related to Ce4+ concentration. Moreover, activation energy of crystal growth is significantly dependent on the dopant (CeO2) concentration. It firstly increased and then decreased with increasing dopant concentration, and the maximum value was observed at the dopant concentration of 5mol%.

Recycling solar panel waste glass sintered as glass‐ceramics

AbstractThe mass of waste solar panels in Taiwan is 1000 tons per year. The recycling of waste glass from solar panels, therefore, is an important issue. Solar panel waste glass is a potentially valuable source of major oxides, including SiO2 and Na2O. This investigation evaluated the feasibility of converting solar panel waste glass into new glass‐ceramic materials using DTA and XRD. The crystallized phases were cordierite, anorthite, parawollastonite, and pyroxene. As the material was heated to 600°C and then to 850°C, the hardness and degree of crystallization of the glass‐ceramic samples slowly increased. Experimental results demonstrate that the degree of crystallization of the glass‐ceramic samples increased with hardness. The activation energy of crystal growth was 22.42 kJ mol−1. Density, hardness, and flexural strength were strongly correlated with each other and increased with the degree of crystallization of all sintered samples. The solar panel waste glass that was fired at 850°C had a dense and homogeneous well‐sintered microstructure and contained large glass‐like zones. The nuclei grew slowly to form crystallites when the samples were heated. This indicates that solar panel waste glass is indeed suitable for the glass‐ ceramic materials. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

Evolution of cell resistance, threshold voltage and crystallization temperature during cycling of line-cell phase-change random access memory

Doped SbTe phase change (PRAM) line cells produced by e-beam lithography were cycled 100 million times. During cell cycling the evolution of many cell properties were monitored, in particular the crystalline and amorphous resistance, amorphous resistance drift exponent, time-dependent threshold voltage, threshold voltage as a function of RESET pulse height, crystallization temperature, and activation energy of crystal growth. The power of the present approach is that all these properties were measured simultaneously during the life of single cells. The evolution of the cell properties can be summarized by (i) an initialization phase characterized by settle-in effect of the material surrounding the programmable region, (ii) a usable life phase where initially the cell properties remain fairly constant until after ∼5 × 105 cycles decomposition of the programmed region caused degradation of the cell properties, and (iii) finally an end of life phase where the cell is stuck in the SET state after typically 108 cycles. Although generally the threshold voltage is directly related to the amorphous resistance it was found that during cycling this relation is not constant but evolved as well. Instead, the crystallization temperature could be linked to the threshold voltage throughout the complete life cycle of the cell which could lead to new insights to the nature of the threshold event.

Utilization of DTA in the Determination of a Crystallization Mechanism in Transparent Glass-Ceramics with a Nanocrystalline Structure

Non-isothermal differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to study the nucleation and crystallization behavior of mica glass-ceramics with LiF as nucleating agent. The models enabled establishing the kinetic parameters for crystal growth of individual phases. The activation energies for crystal growth were found to be in the range of 161–301 KJ/mol, 416–424 KJ/mol, and 583–1011 KJ/mol for base glasses, samples with substitution of Li2O for K2O and samples with addition of LiF, respectively. Formation of transparent glass-ceramics from studied glass-samples has been investigated. Transparency is assumed to occur in the samples with nanocrystalline structure.

The crystallization kinetics of Sb2S3 in (GeS2)0.4(Sb2S3)0.6 glass

AbstractThe crystallization kinetics of antimony trisulphide in (GeS2)0.4(Sb2S3)0.6 glass has been studied by thermomechanical analyzer and microscopy. The linear crystal growth kinetics of Sb2S3 has been observed in the temperature range 293 °C ≤ T ≤ 327.5 °C. The activation energy determined of TMA method (E = 240 ± 5 kJ·mol‐1) is relatively close to the activation energy of crystal growth (EG = 274 ± 7 kJ·mol‐1) from optical microscopy measurements. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of the organic additions on crystal growth behavior of ZrO 2 nanocrystals prepared via sol–gel process

ZrO 2 powders were synthesized via sol–gel process using zirconium oxychloride octahydrate as the raw material. The effects of addition of glacial acetic acid and N,N-dimethylformamide (DMF) on crystal growth and chemical bond of powders were discussed. The structural evolution, phase transformation and morphological characteristic of powders were investigated by differential scanning calorimetric analysis (DSC), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After adding the acetic acid and DMF, the crystallite size of ZrO 2 decreased from about 26.48 to 13.94 nm when calcination at 600 °C for 40 min, and the activation energy for crystal growth reduced approximately from 7.76 ± 0.62 to 2.74 ± 0.28 kJ/mol in the initial stage, while abruptly increased to 26.48 ± 1.09 kJ/mol in the later stage. The specific surface area decreased from 26.73 to 0.51 m 2/g. Meanwhile, the metastable tetragonal phase could be stabilized in ZrO 2 nanocrystals at 600 °C for 40 min.

Influence of Surrounding Dielectrics on the Data Retention Time of Doped Sb2Te Phase Change Material

The crystallization properties of as-deposited and laser written amorphous marks of doped Sb2Te phase change material are found to be only dependent on the top dielectric layer. A ZnS:SiO2 top dielectric layer yields a higher crystallization temperature and a larger crystal growth activation energy as compared to a SiO2 top dielectric layer, leading to superior data retention times at ambient temperatures. The observed correlation between the larger crystallization temperatures and larger crystal growth activation energies indicates that the viscosity of the phase change material in the amorphous state is dependent on the interfacial energy between the phase change material and the top dielectric layer.

The effect of K2O on the crystallization of niobium germanate glasses

The effect of K2O content on the crystallization of niobium germanate glasses with 22.7- 24.27 wt% of GeO2 and 54.59-57.48 wt% of Nb2O5 was examined. The glasses crystallize by primary crystallization and the formed crystalline phases were K6Nb6Ge4O26, K3.8Nb5Ge3O20.4 and KNbO3. Increasing the K2O content caused a decrease in the GeO2 content of the primary phases. The effect of the K2O content on the kinetics of primary crystallization was analyzed. It was demonstrated that an increase of the K2O content decreased the activation energy of crystal growth at first of the crystallization peaks (Ec1). At second crystallization peaks the activation energies of crystal growth increased (Ec2).

Mesoporous and nanocrystalline sol–gel derived NiTiO 3 at the low temperature: Controlling the structure, size and surface area by Ni:Ti molar ratio

Nanocrystalline nickel titanate (NiTiO 3) thin films and powders with mesoporous structure were produced at the low temperature of 500 °C by a straightforward particulate sol–gel route. The sols were prepared in various Ni:Ti molar ratios. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the powders contained mixtures of the NiTiO 3 and NiO phases, as well as the anatase-TiO 2 and the rutile-TiO 2 depending on the annealing temperature and Ni:Ti molar ratio. Moreover, it was found that Ni:Ti molar ratio influences the preferable orientation growth of the nickel titanate, being on (202) planes for the nickel dominant powders (Ni:Ti ≥ 75:25) and on (104) planes for the rest of the powders (Ni:Ti: ≤ 50:50). The average crystallite size of the powders annealed at 500 °C was in the range 1.5–2.4 nm and a gradual increase occurred up to 8 nm by heat treatment at 800 °C. The activation energy of crystal growth decreased with an increase of Ni:Ti molar ratio, calculated in the range 24.93–37.17 kJ/mol. Field emission scanning electron microscope analysis revealed that the deposited thin films had mesoporous and nanocrystalline structure with the average grain size of 20–35 nm. Moreover, atomic force microscope images presented that the thin films had a hill-valley like morphology with roughness mean square in the range 41–57 nm. Based on Brunauer–Emmett–Taylor analysis, the synthesized powders showed mesoporous structure containing pores with needle and plate like shapes. The mesoporous structure of the powders was stable at high annealing temperatures and one of the highest surface areas (i.e., 156 m 2/g) reported in the literature was obtained for the powder containing Ni:Ti = 50:50 at 500 °C.

Phase structure and crystallization of the bulk glassy FeCoZrWB alloys

AbstractIn the present work, the high‐energy X‐ray diffraction (XRD) measurements performed using monochromatic synchrotron radiation of 112 keV (λ=0.110696 Å), were utilized to compare a phase constitution of melt‐spun ribbon and suction‐cast rods of Fe61Co10+xZr5W4–xB20 alloys (where x = 0, 2, 3 at.%). For bulk amorphous samples of the investigated alloys DSC studies allowed to determine the activation energies of crystal growth and differences in crystallization kinetics at constant heating rates. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface Devitrification and the Growth of Cristobalite in Borofloat® (Borosilicate 8330) Glass

Borofloat® (borosilicate 8330) glass is an important type of inorganic glass, both scientifically and commercially. During prolonged heat treatment of this glass above its glass transition temperature of 525°C, heterogeneous nucleation, and growth of cristobalite crystals occur. The kinetics and morphology of this crystal growth have been studied for heat treatment temperatures at and above 660°C. The activation energy for crystal growth is estimated to be 185±10 kJ/mol. This is attributed to the diffusion of boron, rather than sodium, being the rate‐limiting step within the borosilicate framework. Contact with the atmosphere is shown to initiate the nucleation of cristobalite crystals, while deposition of a thin silicon nitride surface coating on the glass helps to prevent this nucleation.

Synthesis and characterisation of nanostructured neodymium titanium oxides by sol–gel process: Controlling the phase composition, crystal structure and grain size

Nanocrystalline neodymium titanium oxide thin films and powders with different phase compositions with mesoporous structure were produced by a straightforward particulate sol–gel route. The sols were prepared in various Nd:Ti molar ratios and they showed a narrow particle size distribution in the range 20–26 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of Nd 4Ti 9O 24, Nd 2Ti 4O 11, Nd 3Ti 4O 12 for titanium dominant powders (Nd:Ti ≤ 45:60), mixtures of Nd 2TiO 5 and Nd 2O 3 for neodymium dominant powders (Nd:Ti ≥ 75:25) and pure Nd 3Ti 4O 12 phase for equal molar ratio of Nd:Ti, depending on the annealing temperature and Nd:Ti molar ratio. Moreover, it was found that Nd:Ti molar ratio influences the preferable orientation growth of the neodymium titanium oxide compounds. Transmission electron microscope (TEM) images confirmed that the average crystallite size of the powders annealed at 400 °C was in the range 1.0–2.8 nm and a gradual increase was occurred up to 6.7 nm by heat treatment at 1000 °C. The activation energy of crystal growth reduced with a decrease of Nd:Ti molar ratio, calculated in the range 6.90–18.12 kJ mol −1. Low activation energies indicating that the grain size will not change much with increase in temperature. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had uniform, mesoporous and nanocrystalline structure. Moreover, atomic force microscope (AFM) images presented that the thin films had a columnar like morphology with average grain size in the range 17–30 nm at 600 °C and 47–60 nm at 800 °C, depending upon the Nd:Ti molar ratio. Based on Brunauer–Emmett–Taylor (BET) analysis, the synthesized powders showed mesoporous structure containing pores with sphere like shapes. The surface area of the powders was enhanced by increasing Nd:Ti molar ratio and reached as high as 110 m 2 g −1 for the powder containing Nd:Ti = 75:25 (molar ratio) at 400 °C. In addition, the mesoporous structure of the powders was stable at high annealing temperatures up to 900 °C.

The utilization of rare earth tailing for the production of glass–ceramics

Abstract A new glass–ceramic was synthesized by adding rare earth tailing in traditional glass. The glass transition temperature, glass crystallization temperature, activation energy of crystal growth and the microstructures of the glass–ceramics were investigated by DSC, XRD and SEM. The results show that the crystallization peak of the glass–ceramics becomes sharper and shifts to lower temperature with increasing tailing content. Additionally, the addition of the tailing leads to a clear decrease of the size of precipitated crystals, and the crystal sizes of the sample containing 50% tailing are in a range of 30–70 nm. The activation energy of the crystal growth of the glass–ceramics declines with rising tailing percent. And the activation energies of the samples with tailing percents of 30, 50 and 70 wt.% are 310, 439 and 376 kJ mol−1, respectively. The Avrami constants of these samples were calculated as 2.3, 3.2 and 3.3, which indicate two-dimensional growth and bulk crystallization. The major crystalline phases were identified as anorthite and diopside.

In vitro bioactivity and crystallization behavior of bioactive glass in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2

AbstractIn this study, bioactivity of glass in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2 was investigated. For this purpose, a glass sample was prepared by the traditional melting method. Crystallization behavior of bioactive glass was also investigated using differential thermal analyses. The Avrami constant of bioactive glass sample calculated according to the Ozawa equation was 3.72 ± 0.4, which indicates bulk crystallization. Using the Matusita-Sakka and the Kissinger equations, activation energy of crystal growth was determined as (394 ± 17) kJ mol−1 and (373 ± 12) kJ mol−1, respectively. These results indicate that the crystallization activation energy data of bioactive glass obtained in this study are accurate and reliable. Bioactivity of the resultant glass sample was analyzed by immersion in simulated body fluid. Scanning electron microscopy, thin film X-ray diffraction, ultraviolet spectroscopy and inductively coupled plasma techniques were used to monitor changes in the glass surface and the simulated body fluid composition. The results revealed that a hydroxyapatite layer was formed on the glass surface after 21 days of immersion in SBF. Formation of the hydroxyapatite layer confirmed the bioactivity of the glass in the system SiO2-CaO-Al2O3-P2O5-Na2O-MgO-CaF2. In addition, physical and mechanical properties of the sample were measured to determine changes in the properties with the immersion time. The results show that bioactive glass maintained its strength during the immersion in a simulated body fluid solution.

Low temperature nanostructured zinc titanate by an aqueous particulate sol–gel route: Optimisation of heat treatment condition based on Zn:Ti molar ratio

Nanocrystalline zinc titanate (ZnTiO 3) thin films and powders with purity of 94% were produced at the low sintering temperature of 500 °C and the short sintering time of 1 h by a straightforward aqueous particulate sol–gel route. The effect of Zn:Ti molar ratio was studied on the crystallisation behaviour of zinc titanates. The prepared sols showed a narrow particle size distribution in the range 17–19 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of the rhombohedral-ZnTiO 3, cubic-ZnO, cubic-Zn 2TiO 4 phases, as well as the anatase-TiO 2 and the rutile-TiO 2 depending on the sintering temperature and Zn:Ti molar ratio. Moreover, it was found that Zn:Ti molar ratio and sintering temperature influence the preferable orientation growth of the zinc titanate, being on (2 1 1) planes for molar ratios of Zn:Ti = 25:75 and 50:50 and on ( 1 1 ¯ 0 ) planes for molar ratio of Zn:Ti = 75:25 at sintering temperature of 600 °C. Transmission electron microscope (TEM) images showed that the average crystallite size of the powders annealed at 400 °C was around 2 nm and a gradual increase occurred up to 8 nm by heat treatment at 1000 °C. The activation energy for crystal growth of nanocrystalline ZnTiO 3 calculated in the range 07.86–14.79 kJ/mol. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had mesoporous and nanocrystalline structure with the average grain size of 19–23 nm at 600 °C and 34–39 nm at 800 °C depending upon the Zn:Ti molar ratio.

Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35–80 °C. The activation energy for growth of CeO2 nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO2 particles in narrow size range. CeO2 nanocrystals precipitated at 35 °C were further annealed at temperatures in the range 300–700 °C. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.

Crystallization Kinetics of Ammonium Perchlorate in an Agitated Vessel

Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60ºC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found to be equal to 5.8 kJ/ mole. Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed) . The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.

CRYSTALLIZATION KINETICS OF AMMONIUM PERCHLORATE IN AN AGITATED VESSEL

31 Overall crystal growth kinetics for ammonium perchlorate in laboratory scale batch agitated vessel crystallizer have been determined from batch experiments performed in an integral mode. The effects of temperature between 30-60oC, seed size 0.07, 0.120 and 0.275 mm and stirrer speed 160, 340, and 480 rpm, on the kinetics of crystal growth were investigated. Two different methods, viz. polynomial fitting and initial derivative were used to predict the kinetics expression. In general both methods gave comparable results for growth kinetics estimation. The order of growth process is not more than two. The activation energy for crystal growth of ammonium perchlorate was determined and found to be equal to 5.8 kJ/ mole. Finally, the influence of the affecting parameters on the crystal growth rate gives general expression that had an obvious dependence of the growth rate on each variables of concern (temperature, seed size, and stirrer speed) . The general overall growth rate expression had shown that super saturation is the most significant variable. While the positive dependence of the stirrer speed demonstrates the importance of the diffusional step in the growth rate model. Moreover, the positive dependence of the seed size demonstrate the importance of the surface integration step in the growth rate model. All the studied variables tend to suggest that the growth rate characteristics of ammonium perchlorate from aqueous solution commenced in a batch crystallizer are diffusion kinetic controlled process.

Non-isothermal crystallization of K2O·TiO2·3GeO2 glass

The crystallization of K2O·TiO2·3GeO2 glass under non-isothermal condition was studied. In powdered glass with particle sizes less than 0.15 mm, surface crystallization was dominant and an activation energy of crystal growth of Ea,s=327±50 kJ mol−1 was calculated. In the size range 0.15 to 0.45 mm, both surface and volume crystallization occurred. For particle sizes >0.45 mm, volume crystallization dominated with spherulitic morphology of the crystals growth and Ea,v=359±64 kJ mol−1 was calculated.

Crystal Growth Rates in Doped SbxTe Fast-Growth Phase-Change Films Studied with Transmission Electron Microscopy

ABSTRACTIsothermal crystallization of doped SbxTe fast-growth phase-change films was investigated using transmission electron microscopy with in situ heating. SbxTe films with four different values for the Sb/Te ratio, x=3.0, 3.3, 3.6 and 4.2, were analyzed and the films were sandwiched between two types of dielectric layers. One dielectric layer type is based on 80at.%ZnS-20at.%SiO2, the other on (Ge,Cr)N. The crystal growth rates reduce if the phase-change films are sandwiched between amorphous dielectric layers. The reduction is very pronounced at the lowest measured temperatures (150 °C), becomes smaller at higher temperatures and probably disappears at around 200 °C. The crystal growth rates increase with increasing Sb/Te ratio, but the activation energy for crystal growth is not significantly affected by the Sb/Te ratio. Finally a systematic study of the effect of the electron beam of the TEM on the crystal growth rates is performed showing accelerated growth rates. The present work shows that particularly at relative low temperatures, just above the glass-transition temperature, the growth rates as limited by the atomic mobilities are sensitive to various (boundary) conditions, e.g. capping layers and irradiation.