Nonisothermal reaction kinetics and preparation of ferroelectric strontium bismuth niobate with a layered perovskite structure

2004 ◽  
Vol 19 (10) ◽  
pp. 2956-2963 ◽  
Author(s):  
Chung-Hsin Lu ◽  
Wei-Tse Hsu ◽  
Jiun-Ting Lee
Keyword(s):  
Reaction Kinetics ◽  
Formation Mechanism ◽  
Integral Method ◽  
Correlation Coefficients ◽  
Differential Method ◽  
Layered Perovskite ◽  
Heating Rates ◽  
Integral Methods ◽  
Diffusion Controlled ◽  
Layered Perovskite Structure

Ferroelectric layered perovskite SrBi2Nb2O9 has been successfully prepared through a new process using BiNbO4 as a precursor. The SrBi2Nb2O9 formation mechanism was investigated using a nonisothermal analysis method at constant heating rates. The weight loss recorded in thermal analysis under different heating rates was analogized to the reaction conversion. A combination of the differential and integral methods was introduced to solve the reaction mechanisms. Analysis using the differential method revealed that two kinds of diffusion-controlled models have higher linear correlation coefficients than other models. Based on the integral method principle, a new integral equation combining the Arrhenius equation and the Lobatto approximation was derived in this study. The established equation significantly simplified the conventional calculation process and improved the accuracy for predicting the reaction models. Analysis using the integral method corroborated that the SrBi2Nb2O9 formation mechanism is governed by Jander's diffusion controlled model, and the activation energy was calculated to be 192.1 kJ/mol. The proposed methods and the derived equations can be further applied to other solid-state-reaction systems to elucidate their reaction kinetics and estimate the related kinetic parameters.

Calculation of the three-dimensional turbulent boundary layer in the vessel’s bow and midship area by the integral method

2021 ◽  
Author(s):  
T.G. Artyushina
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Mathematical Models ◽  
Integral Method ◽  
Three Dimensional ◽  
Physical Modelling ◽  
Limited Range ◽  
Differential Method ◽  
Friction Resistance ◽  
Integral Methods

The quality of technical solutions applied in ship design and construction is substantially determined by the validity of viscous flow parameters, especially in the vicinity of thrusters. The influence of shapes on velocity, pressure and turbulence distribution can be assessed by physical experimentation. Along with undeniable advantages, physical modelling has a number of disadvantages: high labour input and cost, limited range of parameters variation (e.g. Reynolds numbers), difficulty in separating the influence of individual factors. Therefore, the development of mathematical models and numerical calculation schemes based on them is extremely relevant. Calculation of friction resistance and calculation of the velocity field in the vicinity of a vessel comes down to the calculation of its boundary layer and trace parameters. Current mathematical models with a planar representation, i.e. working with projections rather than real curves, do not give an accurate description. This has led to the need for a mathematical model that can address all of the required characteristics of a three-dimensional turbulent boundary layer. Both differential and integral methods are used to calculate three-dimensional boundary layers. The model is capable of calculating the characteristics of the spatial boundary layer in the stern and the viscous wake, in the bow and in the middle of the vessel. The model is quite versatile: it has been successfully used both for computing the boundary layer characteristics in the bow and midship area by the integral method based on the thick boundary layer concept, and for computing the turbulent flow in the stern and viscous wake by the differential method based on the partial parabolic concept using the k-ε turbulence model. In this paper we will elaborate on the integral method calculation.

Reaction kinetics and formation mechanism of magnesium ferrites

2005 ◽  
Vol 425 (1-2) ◽  
pp. 131-136 ◽  
Author(s):  
Jong-Gyu Paik ◽  
Man-Jong Lee ◽  
Sang-Hoon Hyun
Keyword(s):  
Reaction Kinetics ◽  
Formation Mechanism

Electrical Characterization and Microstructures of Y2O3-Doped Bi4Ti3O12 Thin Films

2013 ◽  
Vol 591 ◽  
pp. 208-211
Author(s):  
Min Chen ◽  
J. Liu ◽  
X.A. Mei
Keyword(s):  
Thin Films ◽  
Electrical Characterization ◽  
Rf Magnetron Sputtering ◽  
Layered Perovskite ◽  
Random Orientation ◽  
Large Shift ◽  
Si Substrates ◽  
Layered Perovskite Structure ◽  
Lower Temperature ◽  
Curie Temperature Tc

Y2O3-doped bismuth titanate (Bi4-xYxTi3O12: BYT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Y-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Y doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BYT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Path Integral Methods for the Probabilistic Analysis of Nonlinear Systems Under a White-Noise Process

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Mario Di Paola ◽  
Gioacchino Alotta
Keyword(s):  
Path Integral ◽  
Path Integration ◽  
Integral Method ◽  
Degrees Of Freedom ◽  
Kolmogorov Equation ◽  
Integral Methods ◽  
Alternative Approach ◽  
Path Integration Method ◽  
Path Integral Method ◽  
Barrier Problems

Abstract In this paper, the widely known path integral method, derived from the application of the Chapman–Kolmogorov equation, is described in details and discussed with reference to the main results available in literature in several decades of contributions. The most simple application of the method is related to the solution of Fokker–Planck type equations. In this paper, the solution in the presence of normal, α-stable, and Poissonian white noises is first discussed. Then, application to barrier problems, such as first passage problems and vibroimpact problems is described. Further, the extension of the path integral method to problems involving multi-degrees-of-freedom systems is analyzed. Lastly, an alternative approach to the path integration method, that is the Wiener Path integration (WPI), also based on the Chapman–Komogorov equation, is discussed. The main advantages and the drawbacks in using these two methods are deeply analyzed and the main results available in literature are highlighted.

Defect Structure and Oxide-ion Conduction in (La, Sr)2NiO4+δ with Layered Perovskite Structure

2020 ◽  
Vol 49 (9) ◽  
pp. 1071-1074
Author(s):  
Naoto Kitamura ◽  
Kakeru Ishizaki ◽  
Naoya Ishida ◽  
Yasushi Idemoto
Keyword(s):  
Defect Structure ◽  
Perovskite Structure ◽  
Layered Perovskite ◽  
Ion Conduction ◽  
Layered Perovskite Structure ◽  
Oxide Ion Conduction ◽  
Oxide Ion

Modulation spectroscopy. Kinetics for the self-reactions of some α-aminoalkyl radicals in solution

1982 ◽  
Vol 60 (3) ◽  
pp. 274-278 ◽  
Author(s):  
Paul R. Marriott ◽  
Arlindo L. Castelhano ◽  
David Griller
Keyword(s):  
Absorption Spectrum ◽  
Reaction Kinetics ◽  
Unpaired Electron ◽  
Rate Constants ◽  
Lone Pair ◽  
The Self ◽  
Modulation Spectroscopy ◽  
Alkyl Radicals ◽  
Diffusion Controlled ◽  
Kinetics Of

The optical spectra and reaction kinetics of some a-aminoalkyl radicals, RĊHN(CH2R)2; R≡H, Me, Ph, were measured in solution using the technique of modulation spectroscopy. These radicals undergo diffusion controlled self-reaction with rate constants [Formula: see text]. When R≡Ph, the absorption spectrum has a well defined maximum at 346 nm; ε = 3390 M−1 cm−1, while the spectra when R≡H or Me were less intense [Formula: see text] and tailed into the visible. These spectra are substantially red-shifted when compared with those of simple alkyl radicals, an effect which is thought to be due to the interaction between the unpaired electron and the lone pair of electrons on nitrogen.

Kinetic Calculations for the Calcination Reaction of Limestone Modified by Alkaline Industrial Wastes

2011 ◽  
Vol 356-360 ◽  
pp. 1175-1179 ◽  
Author(s):  
Hong Tao Liu ◽  
Kui Hua Han ◽  
Sheng Li Niu ◽  
Chun Mei Lu
Keyword(s):  
Calcium Content ◽  
Isoconversional Method ◽  
Differential Method ◽  
Point Of View ◽  
Industrial Wastes ◽  
Heating Rates ◽  
Metal Impurities ◽  
Carbide Slag ◽  
High Calcium ◽  
Kinetic Calculations

The enhancement of alkaline industrial wastes on the desulfurization performance and utilization of limestone has already been found. In order to explore the reason of this phenomenon from the kinetic point of view, two typical alkaline wastes, carbide slag with a high calcium content and Bayer process red mud with more metal impurities, were adopted to research. Kinetic behavior of calcination reaction was calculated using the isoconversional method of Kissinger-Akahira-Sunose method (a differential method) and Flynn-Wall-Ozawa method (an integral method) at four different heating rates: 10, 20, 40 and 80 K•min-1. Values calculated by these two methods are very close, and the calculated result shows that calcination rate constant of modified limestone is obviously greater than that of original limestone, under the same calcination temperature, which means that alkaline wastes are advantageous to the thermal decomposition of limestone.

Large Remanent Polarization of Pm2O3-Doped Bi4Ti3O12 Films

2013 ◽  
Vol 591 ◽  
pp. 104-107
Author(s):  
Min Chen ◽  
X.A. Mei ◽  
C.Q. Huang
Keyword(s):  
Remanent Polarization ◽  
Hysteresis Loops ◽  
Differential Resistance ◽  
Rf Magnetron Sputtering ◽  
Layered Perovskite ◽  
Random Orientation ◽  
Si Substrates ◽  
Current Voltage ◽  
Layered Perovskite Structure ◽  
Current Voltage Characteristics

Pm-doped bismuth titanate (Pm4-xLaxTi3O12: BPT) and pure Bi4Ti3O12(BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. For the samples with x=0.25, 1.0, and 1.25, the current-voltage characteristics exhibited negative differential resistance behaviors and their P-V hysteresis loops were characterized by large leakage current, whereas for the samples with x=0.5 and 0.75, the current-voltage characteristics showed simple ohmic behaviors and their P-V hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BPT Fims with x=0.75 were above 40μC/cm2 and 60KV/cm , respectively.

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