Application of the Master Sintering Curve Theory to Non-Isothermal Sintering of BaTiO3 Ceramics

2005 ◽  
Vol 494 ◽  
pp. 417-422 ◽  
Author(s):  
Maria V. Nikolić ◽  
Vera P. Pavlović ◽  
Vladimir B. Pavlović ◽  
Nebojsa Labus ◽  
B.D. Stojanović
Keyword(s):  
Activation Energy ◽  
Barium Titanate ◽  
Heating Rate ◽  
High Purity ◽  
Master Curve ◽  
Sintering Behavior ◽  
Densification Behavior ◽  
Sintering Process ◽  
Heating Rates ◽  
Temperature Time

In this paper a practical approach to the analysis of sintering of BaTiO3 using the Master Sintering Curve concept has been presented. Non-isothermal sintering of high-purity non-doped BaTiO3 ceramics was monitored using a sensitive dilatometer at three different heating rates (10, 20 and 30 oC/min) up to 1380oC. Densification of BaTiO3 during sintering was analyzed using the Master Curve Sintering Theory. A MSC was defined characterizing the sintering behavior of barium-titanate regardless of the heating rate. Construction of the MSC enabled estimation of the process activation energy. Using defined MSC, densification behavior of BaTiO3 ceramics during sintering can be predicted for arbitrary temperature-time excursions and these predictions can be used in controlling and planning the sintering process of this material.

Application of Master Sintering Curve Theory to Predict and Control the Sintering of Nanocrystalline TiO2 Ceramic

2008 ◽  
Vol 368-372 ◽  
pp. 1588-1590
Author(s):  
Da Li ◽  
Shaou Chen ◽  
Wei Quan Shao ◽  
Xiao Hui Ge ◽  
Yong Cheng Zhang ◽  
...  
Keyword(s):  
Sintering Behavior ◽  
Heating Rates ◽  
Temperature Function ◽  
Rutile Tio2 ◽  
Densification Curve ◽  
Final Density ◽  
Thermal Histories ◽  
Constant Heating ◽  
And Control ◽  
Temperature Time

Master sintering curve (MSC), in which the sintered density is a unique function of the integral of a temperature function over time, is insensitive to the heating path. In this paper, the densification of rutile TiO2 was continuously recorded at heating rates of 2 °C/min and 5 °C/min, respectively, by dilatometer. The MSC for rutile TiO2 was constructed for pressureless sintering using constant heating rate date based on the combined-stage sintering model. The construction and application of the MSC were described in detail for different thermal histories. The MSC can be used to predict and control the densification, final density, and microstructure evolution during the whole sintering. The final density can be predicted for an arbitrary temperature–time path. A good consistence exists between the predicted and experimental densification curve, confirming that it is possible to accurately predict and control the sintering behavior of TiO2 from the initial to final stage of sintering using MSC.

scholarly journals Comparative study of the reaction kinetics of three residual biomasses

BioResources ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. 2891-2905
Author(s):  
Arnaldo Martinez ◽  
Lourdes Meriño ◽  
Alberto Albis ◽  
Jorge Ortega
Keyword(s):  
Activation Energy ◽  
Heating Rate ◽  
Lignin Content ◽  
Cellulose Degradation ◽  
Calorific Value ◽  
Degradation Process ◽  
Proximate Analysis ◽  
Cellulose Content ◽  
Heating Rates ◽  
Biomass Residues

Kinetic analysis for the combustion of three agro-industrial biomass residues (coconut husk, corn husk, and rice husk) was carried out in order to provide information for the generation of energy from them. The analysis was performed using the results of the data obtained by thermogravimetric analysis (TGA) at three heating rates (10, 20, and 30 K/min). The biomass residues were characterized in terms of proximate analysis, elemental analysis, calorific value, lignin content, α-cellulose content, hemicellulose content, and holocellulose content. The biomass fuels were thermally degraded in an oxidative atmosphere. The results showed that the biomass thermal degradation process is comprised of the combustion of hemicellulose, cellulose, and lignin. The kinetic parameters of the distributed activation energy model indicated that the activation energy distribution for the pseudocomponents follows lignin, cellulose, and hemicellulose in descending order. The activation energy values for each set of reactions are similar between the heating rates, which suggests that it is independent of the heating rate between 10 K/min and 30 K/min. For all the biomass samples, the increased heating rate resulted in the overlap of the hemicellulose and cellulose degradation events.

Sintering Behavior and Mechanism of Pure BaTiO3 Ceramic Prepared by High-Gravity Reactive Precipitation

2006 ◽  
Vol 11-12 ◽  
pp. 27-30
Author(s):  
Xiao Hui Wang ◽  
Xiao Lin Liu ◽  
Jian Feng Chen
Keyword(s):  
Particle Size ◽  
Barium Titanate ◽  
Viscous Flow ◽  
Heating Rate ◽  
Sintering Behavior ◽  
High Gravity ◽  
Constant Heating Rate ◽  
Mean Particle Size ◽  
The Mean ◽  
Constant Heating

Sintering behavior and mechanism of barium titanate powders prepared by high-gravity reactive precipitation (HGRP) process has been investigated by a dilatometer. The mean particle size of barium titanate powders prepared by HGRP was about 80 nm. Pure BaTiO3 pellets were sintered at a constant heating rate of 2.0 K/min and the temperature of shrinkage-onset for pellet was 1060°C. The maximal shrinkage was 165um and the maximum of shrinkage rate was 8.0 x 10-3 / min at 1170°C. The sintering mechanism for the initial stages of sintering was determined by isothermal dilatometric measurements and was found to be viscous flow.

Kinetics Study on Non-Isothermal Crystallization of Amorphous Alloy Mg65Cu15Ag10Y10

2011 ◽  
Vol 413 ◽  
pp. 432-438
Author(s):  
Xiao Jun Wang ◽  
Tian Dong Xia ◽  
Xue Ding Chen
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Heating Rate ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Continuous Heating ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Local Activation ◽  
Local Activation Energy

The crystallization kinetics of amorphous alloy Mg65Cu15Ag10Y10has been studied by differential scanning calorimetry in the mode of continuous heating annealing. It is found that both DSC curves and activation energy show a strong dependence on the heating rate. The activation energy for crystallization are determined as 186.1 and 184.4 KJ mol−1for the heating rates β=5-20 Kmin−1, and 107.5 and 110.0 KJmol−1for the heating rates β=20-80Kmin−1, when using the Kissinger equation and the Ozawa equation, respectively. Local activation energy at any volume fraction crystallized was obtained by the general Ozawa's isoconversional method. The average value of local activation energy for heating rates ranging from 5 to 20Kmin−1is 180.9 KJ mol−1and for heating rates ranging between 20 and 80Kmin−1is 110.2 KJ mol−1. Using the Suriñach curve fitting procedure, the kinetics mode was specified. The JMA kinetics is manifested as a rule in the early stages of the crystallization. The JMA exponent,n, initially being larger than 4 and continuously decreases to about 2 along with the development of crystallization. The NGG-like mode dominates in the advanced stages of the transformation. These two modes are mutually independent. The proportion between the JMA-like and the NGG-like modes is related to the heating rate.

scholarly journals A Modified Model for Kinetic Analysis of Petroleum Coke

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Iman Eslami Afrooz ◽  
Dennis Ling Chuan Ching
Keyword(s):  
Activation Energy ◽  
Distribution Function ◽  
Normal Distribution ◽  
Heating Rate ◽  
Reaction Model ◽  
Normal Distribution Function ◽  
Gravimetric Analysis ◽  
Heating Rates ◽  
Shrinking Core ◽  
Volume Reaction

In this study, a nonisothermal kinetics analysis of petcoke was performed at heating rates of 10, 15, and 20°C/min using thermal gravimetric analysis (TGA). The behaviour of petcoke at different gasification stages (dewatering, volatilization, char burning, and burnout) was studied. The effect of heating rate on the activation energy of petcoke gasification was also investigated. The activation energy of petcoke was estimated using different kinetic models that include volume reaction model (VRM), shrinking core model (SCM), random pore model (RPM), Coats and Redfern model (CRM), and normal distribution function (NDF). The NDF model was modified in this study. It was found that the experimental data were best fitted with the modified normal distribution function (MNDF) and SCM. The results also showed that activation energy decreases as heating rate increases, leading to reduction in gasification completion time.

Decomposition Kinetics of Switchgrass: Estimating Activation Energy

2014 ◽  
Vol 881-883 ◽  
pp. 726-733
Author(s):  
Gui Ying Xu ◽  
Jiang Bo Wang ◽  
Ling Ping Guo ◽  
Guo Gang Sun
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Apparent Activation Energy ◽  
High Purity ◽  
Isoconversional Methods ◽  
Decomposition Kinetics ◽  
Heating Rates ◽  
Model Free ◽  
Chemical Utilization ◽  
Kinetics Of

TG analysis was used to investigate the thermal decomposition of switchgrass, which is a potential gasification feedstock. 10 mg switchgrass sample with the particles between 0.45 and 0.70 mm was linearly heated to 873 K at heating rates of 10, 20, 30 K/min, respectively, under high-purity nitrogen. The Kissinger method and three isoconversional methods including Friedman, Flynn-wall-Ozawa, Vyazovkin and Lenikeocink methods were used to estimate the apparent activation energy of switchgrass. With the three isoconversional methods, it can be concluded that the activation energy increases with increasing conversion. The four model free methods reveal activation energies in the range of 70-460 kJ/mol. These activation energy values provide the basic data for the thermo-chemical utilization of the switchgrass.

Optimization of heating schedules in pyrolytic binder removal from ceramic moldings

2000 ◽  
Vol 15 (2) ◽  
pp. 449-457 ◽  
Author(s):  
J. H. Song ◽  
J. R. G. Evans ◽  
M. J. Edirisinghe ◽  
E. H. Twizell
Keyword(s):  
Heating Rate ◽  
Degradation Products ◽  
Ambient Pressure ◽  
Extended Model ◽  
Heating Rates ◽  
Binder Removal ◽  
Time Profiles ◽  
Removal Time ◽  
Allowable Rate ◽  
Temperature Time

A model that finds the maximum permissible heating rate for pyrolysis of ceramic moldings is extended to produce multi-segment temperature–time profiles to minimize the binder removal time. The degradation of the polymer and the diffusion of degradation products in solution to the free surface in a cylinder containing 50 vol% alumina and polyalphamethylstyrene is considered. The theory has previously been validated experimentally for fixed heating rates for cylindrical and flat plate geometries and for overpressure debinding. The extended model, presented here, calculates the vapor pressure of monomer over solution and modifies the heating rate to keep this just below ambient pressure. In this way, the temperature follows the maximum allowable rate at each stage to prevent boiling and hence the incidence of defects.

Study on the Pyrolysis Characteristics and Mechanism of KCl-Pretreated Sunflower Stalk

2013 ◽  
Vol 448-453 ◽  
pp. 1665-1674
Author(s):  
Dong Yu Chen ◽  
Qing Yu Liu ◽  
Yan Qing Hu
Keyword(s):  
Activation Energy ◽  
Heating Rate ◽  
Three Dimensional ◽  
Kinetic Mechanism ◽  
Metal Salts ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Energy Value ◽  
Pyrolysis Characteristics ◽  
Mechanism Model

To study the influence of KCl pretreating on the pyrolysis kinetics of sunflower stalk, the pyrolysis of sunflower stalk pretreated by different concentration KCl solutions were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The Ozawa and Kissinger methods were employed to calculate the activation energy and the Šatava method was used to obtain the kinetic mechanism model. The results showed that the pyrolysis process of the sunflower stalk pretreated by 3% and 10% KCl solution can be separated into four stages (water loss, depolymerization and vitrification, thermal decomposition, and carbonization). With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the higher temperature direction, and the maximum pyrolysis rate and its corresponding temperature increase too. Adding a small amount of metal salts is conducive to the formation of volatile, and a certain amount of metal salts can improve the charcoal yield. More KCl additive makes the lower activation energy value, and the obtained activation energy value increases with the heating rate increasing. By means of the Šatava method, the kinetic mechanism model for the pyrolysis of KCl-pretreated sunflower stalk is Zhuralev-Lesakin-Tempelman equation, which is three-dimensional diffusion.

Sintering Behavior of NbC-Reinforced Steel

2005 ◽  
Vol 498-499 ◽  
pp. 192-197
Author(s):  
Domingos S. Paulo ◽  
Antonio Eduardo Martinelli ◽  
Clodomiro Alves Jr. ◽  
Jorge H. Echude-Silva ◽  
Michelle P. Távora ◽  
...  
Keyword(s):  
Heating Rate ◽  
Plasma Reactor ◽  
Liquid Phase Sintering ◽  
Sintering Behavior ◽  
Heating Rates ◽  
Heating Source ◽  
Sintering Additive ◽  
Dispersed Particles ◽  
Plasma Sintering ◽  
Reinforced Steel

Powdered steel reinforced by NbC dispersed particles was sintered both in resistive furnace at 1180°C or in plasma reactor at 850°C (reference temperature) using heating rates that ranged from 10 to 100°C/min. Fe3P was used as liquid phase sintering additive. The microstructure of the resulting materials was visualized by scanning electronic microscopy. Distinctive microstructural features were observed as a function of the heating source and heating rate. Plasma sintering at rates ~ 30°C/min revealed different microstructural features comparing edge and sample bulk. Homogeneous mixtures of Fe and NbC could be sintered in resistive furnace and plasma reactor using relatively low heating rates. Plasma sintering at 800°C for 1 h (heating rate of 10°C/min) resulted in relative densities of ~ 91% of the theoretical density of the composite. Sintering in resistive furnace for 1150°C resulted in relative densities ~ 94%.

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