Kinetics of the transformation process of PbSO4 to PbO2 in a lead anodic film

1995 ◽  
Vol 390 (1-2) ◽  
pp. 29-33 ◽  
Author(s):  
Jia-Rong Wang ◽  
Guo-Lin Wei
Keyword(s):  
Transformation Process ◽  
Anodic Film ◽  
Kinetics Of

Kinetic model for calcium sulfate α-hemihydrate produced hydrothermally from gypsum formed by flue gas desulfurization

2015 ◽  
Vol 48 (3) ◽  
pp. 827-835 ◽  
Author(s):  
Mingliang Tang ◽  
Xuerun Li ◽  
Yusheng Shen ◽  
Xiaodong Shen
Keyword(s):  
Flue Gas ◽  
Calcium Sulfate ◽  
High Performance ◽  
Transformation Process ◽  
Flue Gas Desulfurization ◽  
Synthesis Process ◽  
Stable Phase ◽  
Hydrothermal Conditions ◽  
Simple Method ◽  
Kinetics Of

Modeling of the kinetics of the synthesis process for calcium sulfate α-hemihydrate from gypsum formed by flue gas desulfurization (FGD) is important to produce high-performance products with minimal costs and production cycles under hydrothermal conditions. In this study, a model was established by horizontally translating the obtained crystal size distribution (CSD) to the CSD of the stable phase during the transformation process. A simple method was used to obtain the nucleation and growth rates. A nonlinear optimization algorithm method was employed to determine the kinetic parameters. The model can be successfully used to analyze the transformation kinetics of FGD gypsum to α-hemihydrate in an isothermal batch crystallizer. The results showed that the transformation temperature and stirring speed exhibit a significant influence on the crystal growth and nucleation rates of α-hemihydrate, thus altering the transformation time and CSD of the final products. The characteristics obtained by the proposed model can potentially be used in the production of α-hemihydrate.

scholarly journals Effect of Two-Step Austempering Process on Transformation Kinetics of Nanostructured Bainitic Steel

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 166 ◽  
Author(s):  
Chunhe Chu ◽  
Yuman Qin ◽  
Xuemei Li ◽  
Zhinan Yang ◽  
Fucheng Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Energy Barrier ◽  
Bainitic Ferrite ◽  
Transformation Process ◽  
Transformation Rate ◽  
Bainitic Steel ◽  
Transformation Kinetics ◽  
Activation Energy Barrier ◽  
Quenching Process ◽  
Kinetics Of

The two-step austempering process has been reported to be an effective method to accelerate the bainitic transformation process by introducing martensite (Q-M-B). However, in this study, it was found that the Q-M-B process reduced the incubation time, but the transformation duration remained nearly unchanged. The notably reduced activation energy barrier for nucleation of bainitic ferrite on the preformed martensite should be responsible for the reduced duration time of the Q-M-B process. A process that both of the two steps were above, Ms (Q-B-B), has been demonstrated to increase transformation rate and improve the amount of bainitic ferrite, which probably results from the additional hysteresis free energy provided by the first quenching process.

Mathematical research of the phase transformation kinetics of alloyed steel

2019 ◽  
Vol 85 (12) ◽  
pp. 25-32
Author(s):  
A. S. Kurkin
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Phase Transformations ◽  
Diffusion Processes ◽  
Kinetic Equations ◽  
Transformation Process ◽  
Avrami Equation ◽  
Published Data ◽  
Transformation Rate ◽  
Kinetics Of

Regulation of the process parameters allows obtaining the desired properties of the metal. Computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. Methods of mathematical modeling are used to study the main diffusion and diffusion-free processes of transformations in alloyed steels during heating and cooling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov – Avrami and Austin – Rickett equations which describe in different ways the time dependence of the diffusion transformation rate and attained degree of transformation has been carried out. It is shown that the Austin – Rickett equation is equivalent to the Kolmogorov – Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov – Avrami equation in modeling the kinetics of ferrite-pearlite and bainite transformations and validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon – Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and disadvantages of the Koistinen – Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the transformation degree, similar to the Kolmogorov – Avrami and Austin – Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the equations is developed, providing the minimum standard deviation of the constructed dependence from the initial experimental data. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development for some steels is revealed. The advantage of using equations of the Austin – Rickett type when constructing models from a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in modeling diffusion processes of austenite decomposition to description of the processes of formation and decomposition of martensite in alloyed steels.

Monitoring the intracellular transformation process of surface-cleavable PLGA particles containing disulfide bonds by fluorescence resonance energy transfer

2015 ◽  
Vol 3 (45) ◽  
pp. 8865-8873 ◽  
Author(s):  
Dahai Yu ◽  
Guangyang Zou ◽  
Xiaojing Cui ◽  
Zhengwei Mao ◽  
Irina Estrela-Lopis ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Fluorescence Resonance Energy Transfer ◽  
Disulfide Bonds ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Transformation Process ◽  
Fluorescence Resonance ◽  
Kinetics Of ◽  
Surface Cleavage ◽  
In Cells

The FRET technique was used to quantify the surface cleavage kinetics of PLGA particles containing disulfide bonds in cells.

Phase-Transformation Kinetics of TiO2 in TiO2/(O′+β′)-Sialon Multi-Phase Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 2318-2321
Author(s):  
Jian Yang ◽  
Xiang Xin Xue ◽  
Li Mei Pan ◽  
Mei Wang ◽  
Tai Qiu
Keyword(s):  
Phase Transformation ◽  
Kinetic Model ◽  
Raw Materials ◽  
Transformation Process ◽  
Transformation Kinetic ◽  
Order Kinetic ◽  
Weight Percentage ◽  
Tio2 Anatase ◽  
Additive Content ◽  
Kinetics Of

TiO2/(O′+β′)-Sialon multiphase ceramics with different phase composition of TiO2 were prepared by pressureless sintering under high-purity N2 atmosphere with (O′+β′)-Sialon powder and nano TiO2 (anatase) powder as raw materials, Yb2O3 or Tb2O3 as additive. For each sample, the weight percentage of anatase in TiO2 was calculated from XRD data and the kinetics of anatase-rutile transformation was investigated, wherein the emphasis was placed on the influence of Yb2O3 and Tb2O3. The results indicate that the added Tb2O3 and Yb2O3 serve the significant function of inhibition and promotion on the phase transformation, and the effects are enhanced and attenuated with increasing additive content, respectively. For the sample without additive, the transformation process follows apparent first-order kinetic model. The addition of Yb2O3 or Tb2O3 results in completely different transformation kinetic law. For the samples with Yb2O3 added, the transformation is an apparent second-order reaction, whereas a unique kinetic model, CA=kt1/2+C, is valid for the samples containing Tb2O3. In the two cases, the effect of the additive content on the transformation can be perfectly reflected by the apparent rate constant.

Phase Transformation Kinetics of TiSi2

1993 ◽  
Vol 311 ◽  
Author(s):  
R.R. Mann ◽  
L.L. Clevenger ◽  
Q.Q. Hong
Keyword(s):  
Phase Transformation ◽  
Effective Activation Energy ◽  
Single Crystal Silicon ◽  
Transformation Process ◽  
Silicon Substrates ◽  
Effective Activation ◽  
Transformation Kinetics ◽  
Crystal Silicon ◽  
Face Centered ◽  
Kinetics Of

ABSTRACTThe microstructure and kinetics of the polymorphic C49 to C54-TiSi2 phase transformation have been studied using samples prepared as in self-aligned silicide applications. For C49-TiSi2 thin films formed at temperatures of 600°C and 625°C on (100) single-crystal silicon substrates, the effective activation energy was 5.6 ± 0.3 and 5.7 ± 0.08 eV, respectively, for this phase transformation carried out in the temperature range of 600°C to 700°C. The transformation process was observed to occur by nucleation and growth of the orthorhombic face-centered (C54) phase from the as-formed orthorhombic base-centered (C49) phase.

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