scholarly journals The Concurrent Sintering-Crystallization Behavior of Fluoride-Containing Wollastonite Glass-Ceramics

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 681
Author(s):  
Chuanhui Li ◽  
Peng Li ◽  
Jianliang Zhang ◽  
Fengjuan Pei ◽  
Xingchen Gong ◽  
...  
Keyword(s):  
Precipitation Amount ◽  
Glass Ceramics ◽  
Temperature Characteristic ◽  
Thermal Analyzer ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Liquid Sintering ◽  
Sintering Method ◽  
Maximum Content ◽  
Slag Melting

The fabrication of well densified wollastonite with smooth appearance by direct sintering method is still a challenge due to the competitive behaviors between sintering and crystallization. In this study, the coarser glass frits with a size of 1–4 mm are subjected to heat treatment at different temperatures. An attempt of integrating differential thermal analyzer with a slag melting temperature characteristic tester was exploited to monitor the heat and geometry changes during the heating. The results showed that the addition of CaF2 can significantly promote the crystallization of wollastonite at 940 °C, while hindering the sintering ability. At higher temperature, the increase of CaF2 acts as flux and favors the formation of eutectics, leading to a decline in the precipitation amount of wollastonite. The predominated liquid sintering brought fast shrinkage. It was found out that high content of CaF2 narrows the dense sintering temperature range and results in uneven surfaces. In order to obtain wollastonite glass-ceramics with smooth appearance, the maximum content of CaF2 in sintering glass-ceramics should be limited to 2 wt.%.

Synthesis of Cordierite Powders by Low Temperature Combustion Method

2008 ◽  
Vol 368-372 ◽  
pp. 192-194 ◽  
Author(s):  
Ying He ◽  
He Ping Zhou ◽  
Han Feng Wang
Keyword(s):  
Low Temperature ◽  
Glass Ceramics ◽  
Combustion Method ◽  
Dissipation Factor ◽  
Sintering Behavior ◽  
Low Temperature Combustion ◽  
Low Dielectric ◽  
Different Temperatures ◽  
Temperature Combustion ◽  
Higher Temperature

The cordierite powders have been synthesized by low temperature combustion technique using urea as fuel, nitrates as oxidizer and silicic acid as silica source. The sintering behavior and crystallization process were investigated. The results showed that the powders could be sintered at a temperature lower than 1000 °C. The μ-cordierite crystallized from glass at first, and then transformed into α-cordierite at higher temperature. The obtained cordierite based glass ceramics at different temperatures have low dielectric constant (4.16 ~ 5.02 at 1 MHz) and low dielectric dissipation factor (≈ 0.003 at 1 MHz) as well as low temperature sintering behavior, which is compatible for electronic packaging.

Anderson-Stuart Model to Analyze AC and DC Conductivity of Lithium Zinc-Silicate Glass / Glass-Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 919-924
Author(s):  
M.S. Jogad ◽  
V.K. Shrikhande ◽  
A.H. Dyama ◽  
L.A. Udachan ◽  
Govind P. Kothiyal
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Low Frequency ◽  
Frequency Region ◽  
Dc Conductivity ◽  
Frequency Range ◽  
High Frequency Region ◽  
Dc Conductivities ◽  
Conductivity Variation ◽  
Different Temperatures

AC and DC conductivities have been measured by using the real (e¢) and imaginary (e¢¢) parts of the dielectric constant data of glass and glass-ceramics (GC) at different temperatures in the rage 297-642K and in the frequency range 100 Hz to 10 MHz. Using Anderson –Stuart model, we have calculated the activation energy, which is observed to be lower than that of the DC conductivity. The analysis for glass/glass-ceramics indicates that the conductivity variation with frequency exhibits an initial linear region followed by nonlinear region with a maximum in the high-frequency region. The observed frequency dependence of ionic conductivity has been analyzed within the extended Anderson–Stuart model considering both the electrostatic and elastic strain terms. In glass/glassceramic the calculations based on the Anderson-Stuart model agree with the experimental observations in the low frequency region but at higher frequencies there is departure from measured data.

scholarly journals Effect of calcination temperature and calcination time on the kaolinite/tio2 composite for photocatalytic reduction of CO2

2012 ◽  
Vol 58 (4) ◽  
pp. 10-22 ◽  
Author(s):  
Martin Reli ◽  
Kamila Kočí ◽  
Vlastimil Matějka ◽  
Pavel Kovář ◽  
Lucie Obalová
Keyword(s):  
Crystallite Size ◽  
Physical Adsorption ◽  
Photocatalytic Reduction ◽  
Thermal Hydrolysis ◽  
Calcination Time ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Titanyl Sulphate ◽  
Reduction Of Co2 ◽  
Hydrolysis Of

Abstract The kaolinite/TiO2 composite (60 wt% of TiO2) was prepared by thermal hydrolysis of a raw kaolin suspension in titanyl sulphate and calcined at different temperatures (600, 650 and 700°C) and for different times (1, 2 and 3 h). The obtained samples were characterized by XRPD, N2 physical adsorption and SEM, and tested for photocatalytic reduction of CO2. The different calcination conditions did not influence TiO2 phase composition, only slightly changed the specific surface area, and significantly affected crystallite size of kaolinite/TiO2 composite. A higher temperature and longer duration of calcination lead to higher crystallinity of the powder. The photocatalytic results showed that the crystallite size determined the efficiency of kaolinite/TiO2 photocatalysts.

Phase equilibria in NaAlSiO4–KAlSiO4–SiO2–H2O at 100 MPa pressure: equilibrium leucite composition and the enigma of primary analcime in blairmorites revisited

2014 ◽  
Vol 78 (1) ◽  
pp. 171-202 ◽  
Author(s):  
C. M. B. Henderson ◽  
D. L. Hamilton ◽  
J. P. Waters
Keyword(s):  
Mineral Assemblage ◽  
Volcanic Rocks ◽  
Stoichiometric Composition ◽  
Pressure Equilibrium ◽  
Upward Transport ◽  
Higher Temperature ◽  
Invariant Points ◽  
Water Saturated ◽  
Low K ◽  
Maximum Content

AbstractExperiments in the system NaAlSiO4(Ne)−KAlSiO4(Ks)−SiO2(Qz)−H2O at 100 MPa show that the maximum content of NaAlSi2O6 in leucite is ∼4 wt.% and that analcime is close to the stoichiometric composition (NaAlSi2O6.H2O). Analcime forms metastably on quenching the higher-temperature experiments; it is secondary after leucite in experiments quenched from 780°C, while from 850°C it forms by alteration of leucite, and by devitrification of water-saturated glass. Both processes involve reaction with Na-rich aqueous fluids. Stable analcime forms at 500°C, well below the solidus, and cannot form as phenocrysts in shallow volcanic systems. New data for natural analcime macrocrysts in blairmorites are presented for the Crowsnest volcanics, Alberta, Canada. Other researchers have suggested that primary analcime occurs as yellow-brown, glassy, analcime phenocrysts. Our microprobe analyses show that such primary analcime is close to stoichiometric, with very low K2O (<0.1 wt.%), minor Fe2O3 (0.5−0.8 wt.%) and CaO (∼0.5 wt.%). An extrapolation of published experimental data for Ne−Ks−Qz at >500 MPa PH2O, where Anl + melt coexist, suggests that at >800 MPa two invariant points are present: (1) a reaction point involving Kf + Ab + Anl + melt + vapour; and (2) a eutectic with Kf + Anl + Ne + melt + vapour. We suggest that the nepheline-free equilibrium mineral assemblage for Crowsnest samples is controlled by reaction point (1). In contrast, blairmorites from Lupata Gorge, Mozambique, form at eutectic (2), consistent with the presence of nepheline phenocrysts. Our conclusions, based on high- vs. low-pressure experiments, confirm the suggestion made by other authors, that Crowsnest volcanic rocks must have been erupted explosively to preserve glassy analcime phenocrysts during very rapid, upward transport from deep in the crust (H2O pressures ≫500 MPa). Only rare examples survived the deuteric and hydrothermal alteration that occurred during and after eruption.

Temperature Characteristic of Green Upconversion Luminescence in Er3+/Yb3+Codoped Oxyfluoride Borosilicate Glass Ceramics

2015 ◽  
Vol 36 (9) ◽  
pp. 1001-1005
Author(s):  
林杨杨 Lin Yang-yang ◽  
陈铠炀 Chen Kai-yang ◽  
唐霞艳 Tang Xia-yan ◽  
赵士龙 Zhao Shi-long ◽  
徐时清 Xu Shi-qing
Keyword(s):  
Borosilicate Glass ◽  
Upconversion Luminescence ◽  
Glass Ceramics ◽  
Temperature Characteristic

scholarly journals Synthesis of Fe3O4 and Fe2O3 nanoparticles using hybrid electrochemical-thermal method

2020 ◽  
Vol 55 (3) ◽  
pp. 221-228
Author(s):  
HA Simol ◽  
R Sultana ◽  
M Y A Mollah ◽  
MS Miran
Keyword(s):  
Iron Oxide ◽  
Total Pore Volume ◽  
Thermal Method ◽  
Prepared Compound ◽  
Xrd Pattern ◽  
Spectral Techniques ◽  
Different Temperatures ◽  
Ft Ir ◽  
Higher Temperature ◽  
Lower Temperature

Nanocrystalline Fe3O4 and Fe2O3 particles were successfully synthesized by an innovative hybrid electrochemical-thermal method. The as-prepared compound was calcined for an hour from 100 to 600oC temperatures. The crystallinity, morphology and chemical state of the synthesized powders were characterized by XRD, TG-DTA, SEM/EDS, FT-IR, and UV–Vis spectral techniques after calcinations. The Brunauer–Emmett–Teller (BET) plots confirmed that iron oxide nanoparticles (NPs) calcined at 400oC has a surface area of 18.28 m2 g-1 with a total pore volume of 0.2064 cc g-1. From XRD pattern it is revealed that the precursor calcined at lower temperature (100-400oC) correspond to Fe3O4,while the ones calcined at higher temperature follow Fe2O3 pattern. The morphology of iron oxide NPs calcined at different temperatures were studied with scanning electron microscope (SEM) and exhibits spherical shaped geometries with average diameters of 80-150nm. Bangladesh J. Sci. Ind. Res.55(3), 221-228, 2020

scholarly journals Hydrothermal Carbonization Brewer’s Spent Grains with the Focus on Improving the Degradation of the Feedstock

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3226 ◽  
Author(s):  
Pablo Arauzo ◽  
Maciej Olszewski ◽  
Andrea Kruse
Keyword(s):  
Water Content ◽  
Liquid Product ◽  
Reaction Times ◽  
Hydrothermal Carbonization ◽  
Heating Value ◽  
High Heating Value ◽  
Acid Addition ◽  
Spent Grains ◽  
Different Temperatures ◽  
Higher Temperature

Hydrochar is a very interesting product from agricultural and food production residues. Unfortunately, severe conditions for complete conversion of lignocellulosic biomass is necessary, especially compared to the conversion of sugar compounds. The goal of this work is to improve the conversion of internal carbohydrates by application of a two-steps process, by acid addition and slightly higher water content. A set of experiments at different temperatures (180, 200, and 220 °C), reaction times (2 and 4 h), and moisture contents (80% and 90%) was performed to characterize the solid (high heating value (HHV), elemental) and liquid product phase. Afterwards, acid addition for a catalyzed hydrolysis reaction during hydrothermal carbonization (HTC) and a two-steps reaction (180 and 220 °C) were tested. As expected, a higher temperature leads to higher C content of the hydrochar and a higher fixed carbon (FC) content. The same effect was found with the addition of acids at lower temperatures. In the two-steps reaction, a primary hydrolysis step increases the conversion of internal carbohydrates. Higher water content has no significant effect, except for increasing the solubility of ash components.

scholarly journals Analysis of a Lab-Scale Heat Transformation Demonstrator Based on a Gas–Solid Reaction

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2234 ◽  
Author(s):  
Jana Stengler ◽  
Julius Weiss ◽  
Marc Linder
Keyword(s):  
Experimental Studies ◽  
Hydration Reaction ◽  
Solid Reaction ◽  
Discharge Performance ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Solid Bulk ◽  
Heat Transformation ◽  
Modelling Approach ◽  
Gas Solid Reaction

Heat transformation based on reversible chemical reactions has gained significant interest due to the high achievable output temperatures. This specific type of chemical heat pump uses a reversible gas–solid reaction, with the back and forward reactions taking place at different temperatures: by running the exothermic discharge reaction at a higher temperature than the endothermic charge reaction, the released heat is thermally upgraded. In this work, we report on the experimental investigation of the hydration reaction of strontium bromide (SrBr2) with regard to its use for heat transformation in the temperature range from 180 °C to 250 °C on a 1 kg scale. The reaction temperature is set by adjusting the pressure of the gaseous reactant. In previous experimental studies, we found the macroscopic and microscopic properties of the solid bulk phase to be subject to considerable changes due to the chemical reaction-. In order to better understand how this affects the thermal discharge performance of a thermochemical reactor, we combine our experimental work with a modelling approach. From the results of the presented studies, we derive design rules and operating parameters for a thermochemical storage module based on SrBr2.

Effect of Annealing on Microstructure of Hydroxyapatite Coatings and their Behaviours in Simulated Body Fluid

2014 ◽  
Vol 922 ◽  
pp. 657-662 ◽  
Author(s):  
Sharidah Azuar Abdul Azis ◽  
John Kennedy ◽  
Peng Cao
Keyword(s):  
Heat Treatment ◽  
Simulated Body Fluid ◽  
Body Fluid ◽  
Ion Beam ◽  
Apatite Formation ◽  
Ion Beam Sputtering ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Xrd Patterns ◽  
Post Deposition

In this study, hydroxyapatite (HA) coatings on Ti6Al4V substrate were deposited using an ion beam sputtering technique. Owing to its medical applications, the crystalline phases present in the HA must be controlled. This study investigated the effect of post-deposition heat treatment at different temperatures and evaluated the microstructure of the HA coatings and their behaviours in simulated body fluid (SBF). The post-deposition treatment of the as-deposited samples was carried out in an air-circulated furnace at a temperature between 3000C and 6000C. The XRD patterns reveal that the minimum temperature to transform the HA coating from amorphous to crystalline phase is 4000C. A higher temperature at 6000C leads to a growth of the crystalline HA phases. Fourier transform infrared spectroscopy (FTIR) measurements show the existence of hydroxyl and PO-bonds in all coatings and the amounts varied with temperature. Atomic Force Microscopy (AFM) study suggests that the nanostructured crystalline HA starts to grow at 4000C and becomes more obvious at a higher temperature of 6000C. The simulated body fluid (SBF) test reveals that better apatite formation with post deposition heat treatment at 6000C would potentially enhance the formation of new bone (osseointegration).

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