The influence of particle size on the kinetics of UO2 oxidation in aqueous powder suspensions

2006 ◽  
Vol 353 (1-2) ◽  
pp. 75-79 ◽  
Author(s):  
Olivia Roth ◽  
Tobias Bönnemark ◽  
Mats Jonsson
Keyword(s):  
Particle Size ◽  
Uo2 Oxidation ◽  
Kinetics Of

scholarly journals Reduction Mechanism of Fine Hematite Ore Particles in Suspension

2021 ◽  
Author(s):  
Zhiyuan Chen ◽  
Christiaan Zeilstra ◽  
Jan van der Stel ◽  
Jilt Sietsma ◽  
Yongxiang Yang
Keyword(s):  
Particle Size ◽  
Temperature Drop ◽  
Reduction Rate ◽  
Reduction Process ◽  
Reciprocal Relationship ◽  
Drop Tube ◽  
Surface Nucleation ◽  
Order Of Magnitude ◽  
Relationship Of ◽  
Kinetics Of

AbstractIn order to understand the pre-reduction behaviour of fine hematite particles in the HIsarna process, change of morphology, phase and crystallography during the reduction were investigated in the high temperature drop tube furnace. Polycrystalline magnetite shell formed within 200 ms during the reduction. The grain size of the magnetite is in the order of magnitude of 10 µm. Lath magnetite was observed in the partly reduced samples. The grain boundary of magnetite was reduced to molten FeO firstly, and then the particle turned to be a droplet. The Johnson-Mehl-Avrami-Kolmogorov model is proposed to describe the kinetics of the reduction process. Both bulk and surface nucleation occurred during the reduction, which leads to the effect of size on the reduction rate in the nucleation and growth process. As a result, the reduction rate constant of hematite particles increases with the increasing particle size until 85 µm. It then decreases with a reciprocal relationship of the particle size above 85 µm.

Particle size distribution model for kinetics of digesting alumina

2016 ◽  
pp. 59-64
Author(s):  
Li Bao ◽  
Ting-an Zhang ◽  
Weimin Long ◽  
Anh V. Nguyen ◽  
Guozhi Lv ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Distribution Model ◽  
Kinetics Of

scholarly journals Automated System for Kinetic Analysis of Particle Size Distributions for Pharmaceutically Relevant Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
John-Bruce D. Green ◽  
Phillip W. Carter ◽  
Yingqing Zhang ◽  
Dipa Patel ◽  
Priyanka Kotha ◽  
...  
Keyword(s):  
Particle Size ◽  
Clinical Importance ◽  
Automated System ◽  
Size Distributions ◽  
Mixing Conditions ◽  
Particle Size Distributions ◽  
Complex Formulation ◽  
Wide Range ◽  
Key Variables ◽  
Kinetics Of

Detailing the kinetics of particle formation for pharmaceutically relevant solutions is challenging, especially when considering the combination of formulations, containers, and timescales of clinical importance. This paper describes a method for using commercial software Automate with a stream-selector valve capable of sampling container solutions from within an environmental chamber. The tool was built to monitor changes in particle size distributions via instrumental particle counters but can be adapted to other solution-based sensors. The tool and methodology were demonstrated to be highly effective for measuring dynamic changes in emulsion globule distributions as a function of storage and mixing conditions important for parenteral nutrition. Higher levels of agitation induced the fastest growth of large globules (≥5 μm) while the gentler conditions actually showed a decrease in the number of these large globules. The same methodology recorded calcium phosphate precipitation kinetics as a function of [Ca2+] and pH. This automated system is readily adaptable to a wide range of pharmaceutically relevant systems where the particle size is expected to vary with time. This instrumentation can dramatically reduce the time and resources needed to probe complex formulation issues while providing new insights for monitoring the kinetics as a function of key variables.

scholarly journals Study on indium leaching from mechanically activated hard zinc residue

2011 ◽  
Vol 47 (1) ◽  
pp. 63-72 ◽  
Author(s):  
J.H. Yao ◽  
X.H. Li ◽  
Y.W. Li
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Planetary Mill ◽  
Leaching Rate ◽  
Obvious Effect ◽  
Diffusion Controlled ◽  
Leaching Reaction ◽  
Kinetics Of ◽  
Positive Effect ◽  
Solution Kinetics

In this study, changes in physicochemical properties and leachability of indium from mechanically activated hard zinc residue by planetary mill were investigated. The results showed that mechanical activation increased specific surface area, reaction activity of hard zinc residue, and decreased its particle size, which had a positive effect on indium extraction from hard zinc residue in hydrochloric acid solution. Kinetics of indium leaching from unmilled and activated hard zinc residue were also investigated, respectively. It was found that temperature had an obvious effect on indium leaching rate. Two different kinetic models corresponding to reactions which are diffusion controlled, [1-(1- x)1/3]2=kt and (1-2x/3)-(1-x)2/3=kt were used to describe the kinetics of indium leaching from unmilled sample and activated sample, respectively. Their activation energies were determined to be 17.89 kJ/mol (umilled) and 11.65 kJ/mol (activated) within the temperature range of 30?C to 90?C, which is characteristic for a diffusion controlled process. The values of activation energy demonstrated that the leaching reaction of indium became less sensitive to temperature after hard zinc residue mechanically activated by planetary mill.

Crystallization of nanosized titania particles prepared by the sol-gel process

1994 ◽  
Vol 9 (8) ◽  
pp. 2102-2108 ◽  
Author(s):  
E. Haro-Poniatowski ◽  
R. Rodríguez-Talavera ◽  
Heredia M. de la Cruz ◽  
O. Cano-Corona ◽  
R. Arroyo-Murillo
Keyword(s):  
Particle Size ◽  
Steady State ◽  
Light Scattering ◽  
Sol Gel ◽  
X Ray ◽  
Constant Size ◽  
Size Profile ◽  
Nanosized Titania ◽  
Sol Gel Process ◽  
Kinetics Of

Sols of titania were obtained by the sol-gel method and their size profile was followed by dynamical light scattering. In the early stages of the reaction an unstable behavior was detected. After this unstable regime the particle size reaches a steady state where the sols have a constant size while increasing in number. Once the sol concentration reaches its overlap value, the gelation regime takes place. For samples prepared in this way Raman spectra and x-ray diffractometry were used to characterize the kinetics of crystallization of the material.

Non-isothermal decomposition kinetics of nano-scale CaCO3 as a function of particle size variation

2021 ◽  
Vol 47 (1) ◽  
pp. 858-864
Author(s):  
Saibal Ray ◽  
Tapas Kumar Bhattacharya ◽  
Vivek Kumar Singh ◽  
Debabrata Deb ◽  
Shounak Ghosh ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Variation ◽  
Decomposition Kinetics ◽  
Isothermal Decomposition ◽  
Nano Scale ◽  
Kinetics Of

Analytical Light Microscopy: Examples of Practical Problemsolving and Efficiency in Pharmaceutical Quality Control and Formulation

1998 ◽  
Vol 4 (S2) ◽  
pp. 474-475
Author(s):  
D. A. Stoney ◽  
W. C. McCrone
Keyword(s):  
Particle Size ◽  
Quality Control ◽  
Light Microscopy ◽  
Raw Materials ◽  
Pharmaceutical Products ◽  
Macroscopic Description ◽  
Considerable Effort ◽  
Case Examples ◽  
Kinetics Of ◽  
Dissolution And Precipitation

Five applications of analytical light microscopy to problem-solving in the pharmaceutical industry are described and illustrated by case examples. Problems included are (1) the caking of pharmaceutical products, (2) chemical incompatibility, (3) nucleation and precipitation, (4) recognition of hydrates and polymorphs, and (5) identification and sourcing of contaminant particles.Considerable effort goes into the sizing of solid pharmaceutical raw materials and products. In many instances, particle size is used to help control the rate and uniformity of dissolution, which in turn affects the kinetics of drug delivery. Caking is a macroscopic description of the change in a sample from a finely-divided powder to a single solid molded aggregate. Caking obviously has a severe impact on handling and dissolution characteristics.Caking of a powder is almost always caused by moisture through the cyclical dissolution and precipitation on the surfaces of the particles. When exposed to sufficient vapor pressure, often through changes in humidity or temperature,

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