Oxidation kinetics of large nickel particles

1999 ◽  
Vol 14 (7) ◽  
pp. 3051-3058 ◽  
Author(s):  
Richard Karmhag ◽  
Gunnar A. Niklasson ◽  
Mats Nygren
Keyword(s):  
Boundary Diffusion ◽  
Metal Particles ◽  
Particle Sizes ◽  
Median Particle Size ◽  
Polycrystalline Nickel ◽  
Thermally Activated ◽  
Nickel Particles ◽  
Median Diameter ◽  
Median Particle ◽  
Kinetics Of

Oxidation of polycrystalline nickel particles with an approximate median diameter of 158 μm has been studied by thermogravimetric measurements in the temperature range 773–1473 K. The oxidation was found to be thermally activated with an apparent activation energy of about 1.9 eV at temperatures below 1073 K and 1.2 eV at higher temperatures. Our data showed the qualitative features expected for oxidation of spherical metal particles. The kinetics was compared with a homogenous field coupled-currents theory for oxidation of spherical metal particles. Calculations using a median particle size or a distribution of particle sizes could only give a satisfactory fit to part of the experimental data. Possible explanations for the deviations in terms of space charge, grain boundary diffusion, grain growth, and sintering are discussed in this paper. Scanning electron microscopy studies of the particles after oxidation showed that a large difference exists in the surface structure and the degree of sintering between the particles oxidized at low and high temperatures.

Influence of Powder Particle Size of Slurries on Mechanical Properties of Porous Hydroxyapatite Ceramics

2005 ◽  
Vol 284-286 ◽  
pp. 365-368 ◽  
Author(s):  
Yin Zhang ◽  
Yoshiyuki Yokogawa ◽  
Tetsuya Kameyama
Keyword(s):  
Particle Size ◽  
Flexural Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Particle Sizes ◽  
Wet Milling ◽  
Median Particle Size ◽  
Powder Characteristics ◽  
Median Particle

The effect of different particle sizes on the flexural strength and microstructure of three different types of hydroxyapatite (HAp) powders was studied. The powder characteristics of laboratory synthesized HAp powder (Lab1 and Lab2) were obtained through a wet milling method, and the median particle size and the specific surface area of powders are different with the dryness period. The median particle sizes of Lab1 and Lab2 are 0.34 µm and 0.74 µm, and the specific surface areas of Lab1 and Lab2 are 38.01 m2/g and 19.77 m2/g. The commercial HAp had median particle size of 1.13 µm and specific surface area of 11.62m2/g. The different powder characteristics affected the slip characteristics, and the flexural strength and microstructure of the sintered porous HAp bodies are also different. The optimum value for the minimum viscosity in these present HAp slip with respect to its solid loading and the optimum amount of the deflocculant were investigated. The flexural strengths of the porous HAp ceramics prepared by heating at 1200°C for 3 hrs in air were 17.59 MPa for Lab1 with a porosity of 60.48％, 10.51 MPa for Lab2 with a porosity of 57.75％, and 3.92 MPa for commercial HAp with a porosity of 79.37％.

scholarly journals Numerical Simulation of Melting Kinetics of Metal Particles during Tapping with Argon-Bottom Stirring

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 901
Author(s):  
Kinnor Chattopadhyay ◽  
Rodolfo Morales-Davila ◽  
Alfonso Nájera-Bastida ◽  
Jafeth Rodríguez-Ávila ◽  
Carlos Rodrigo Muñiz-Valdés
Keyword(s):  
Room Temperature ◽  
Melting Furnace ◽  
Melting Process ◽  
Melting Rate ◽  
Metal Particles ◽  
Melting Kinetics ◽  
Nickel Particles ◽  
Filling Time ◽  
The Impact ◽  
Kinetics Of

Molten steel is alloyed during tapping from the melting furnace to the argon-bottom stirred ladle. The metallic additions thrown to the ladle during the ladle filling time are at room temperature. The melting rates or kinetics of sinking-metals, like nickel, are simulated through a multiphase Euler–Lagrangian mathematical model during this operation. The melting rate of a metallic particle depends on its trajectory within regions of the melt with high or low turbulence levels, delaying or speeding up their melting process. At low steel levels in the ladle, the melting rates are higher on the opposite side of the plume zone induced by the bottom gas stirring. This effect is due to its deviation after the impact of the impinging jet on the ladle bottom. The higher melting kinetics are located on both sides at high steel levels due to the more extensive recirculation flows formed in taller baths. Making the additions above the eye of the argon plume spout increases the melting rate of nickel particles. The increase of the superheat makes the heat flux more significant from the melt to the particle, increasing its melting rate. At higher superheats, the melting kinetics become less dependent on the fluid dynamics of the melt.

scholarly journals Studies on the effect of coal particle size on biodepyritization of high sulfur coal in batch bioreactor

2015 ◽  
Vol 17 (1) ◽  
pp. 97-102 ◽  
Author(s):  
Sradhanjali Singh ◽  
Haragobinda Srichandan ◽  
Ashish Pathak ◽  
Chandra Sekhar Gahan ◽  
Sujeong Lee ◽  
...  
Keyword(s):  
Particle Size ◽  
Large Scale ◽  
Xrd Analysis ◽  
Batch Reactors ◽  
Particle Sizes ◽  
Median Particle Size ◽  
Batch Bioreactor ◽  
Moderate Thermophiles ◽  
Median Particle ◽  
Loss Of Mass

Abstract The moderate thermophilic mix culture bacteria were used to depyritize the Illinois coal of varying particle sizes (-100 μm, 100-200 μm, +200 μm). Mineral libration analysis showed the presence of pyrite along with other minerals in coal. Microbial depyritization of coal was carried out in stirred tank batch reactors in presence of an iron-free 9K medium. The results indicate that microbial depyritization of coal using moderate thermophiles is an efficient process. Moreover, particle size of coal is an important parameter which affects the efficiency of microbial depyritization process. At the end of the experiment, a maximum of 75% pyrite and 66% of pyritic sulphur were removed from the median particle size. The XRD analysis showed the absence of pyrite mineral in the treated coal sample. A good mass balance was also obtained with net loss of mass ranging from 5-9% showing the feasibility of the process for large scale applications.

A High Resolution Study of Alumina Supported Iridium Catalysts

1980 ◽  
Vol 38 ◽  
pp. 202-203
Author(s):  
C. Stoeckert ◽  
B. Etherton ◽  
M. Beer ◽  
J. Gryder
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Metal Particles ◽  
Optical Transfer Function ◽  
Particle Sizes ◽  
Iridium Catalysts ◽  
Transmission Electron ◽  
Optical Transfer ◽  
Conventional Transmission Electron Microscope ◽  
Resolution Study

The interpretation of the activity of catalysts requires information about the sizes of the metal particles, since this has implications for the number of surface atoms available for reaction. To determine the particle dimensions we used a high resolution STEM1. Such an instrument with its simple optical transfer function is far more suitable than a conventional transmission electron microscope for the establishment of particle sizes. We report here our study on the size and number distribution of Ir particles supported on Al2O3 and also examine simple geometric models for the shape of Ir particles.

scholarly journals Adsorption of malic acid at the hydroxyapatite/aqueous NaCl solution interface

2021 ◽  
Author(s):  
Władysław Janusz ◽  
Ewa Skwarek
Keyword(s):  
Zeta Potential ◽  
Malic Acid ◽  
Particle Sizes ◽  
Nacl Solution ◽  
X Ray Diffraction ◽  
Radioisotope Method ◽  
X Ray ◽  
Solution Interface ◽  
Adsorption Desorption ◽  
Kinetics Of

AbstractThe aim of the study was the basic incidence on the phenomenon of adsorption that occurs at the hydroxyapatite/malic acid interface, leading to a change in the surface properties of hydroxyapatite, Analytical methods used in the research: X-ray diffraction (XRD) as well as by the, adsorption–desorption of nitrogen (ASAP), potentiometric titration. The specific adsorption of malic acid ions at the hydroxyapatite interface was investigated by means of the radioisotope method. The zeta potential of hydroxyapatite dispersions was determined by electrophoresis with Zetasizer Nano ZS90 by Malvern. The particle sizes of hydroxyapatite samples were analyzed using Masteriszer 2000 Malvern. Studies on the kinetics of malic acid on hydroxyapatite from a solution with an initial concentration of 1 mmol/dm3 have shown that the adsorption process is initially fast, followed by a slow adsorption step. An increase in the pH of the solution causes a decrease in the malic acid adsorption as a result of competition with hydroxyl ions. The presence of adsorbed malic acid was confirmed by the FTIR measurements. The effect of malic acid adsorption on the zeta potential and particle size distribution of hydroxyapatite in the NaCl solution was investigated.

scholarly journals A Gentle Sedimentation Process for Size-Selecting Porous Silicon Microparticles to Be Used for Drug Delivery Via Fine Gauge Needle Administration

Silicon ◽  
2020 ◽  
Author(s):  
Elida Nekovic ◽  
Catherine J. Storey ◽  
Andre Kaplan ◽  
Wolfgang Theis ◽  
Leigh T. Canham
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Porous Silicon ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Agglomeration ◽  
Gas Generation ◽  
Intravitreal Drug Delivery ◽  
Median Diameter ◽  
Experimental Values

AbstractBiodegradable porous silicon (pSi) particles are under development for drug delivery applications. The optimum particle size very much depends on medical use, and microparticles can outperform nanoparticles in specific instances. Here we demonstrate the ability of sedimentation to size-select ultrasmall (1–10 μm) nanoporous microparticles in common solvents. Size tunability is quantified for 1–24 h of sedimentation. Experimental values of settling times in ethanol and water are compared to those calculated using Stokes’ Law. Differences can arise due to particle agglomeration, internal gas generation and incomplete wetting. Air-dried and supercritically-dried pSi powders are shown to have, for example, their median diameter d (0.5) particle sizes reduced from 13 to 1 μm and from 20 to 3 μm, using sedimentation times of 6 and 2 h respectively. Such filtered microparticles also have much narrower size distributions and are hence suitable for administration in 27 gauge microneedles, commonly used in intravitreal drug delivery.

scholarly journals Kinetics of thermally activated processes in cordierite-based ceramics

2018 ◽  
Vol 138 (5) ◽  
pp. 2989-2998 ◽  
Author(s):  
Nina Obradović ◽  
Vladimir Blagojević ◽  
Suzana Filipović ◽  
Nataša Đorđević ◽  
Darko Kosanović ◽  
...  
Keyword(s):  
Thermally Activated ◽  
Activated Processes ◽  
Kinetics Of

Thermally activated demagnetization in elongated oxide-coated metal particles

2004 ◽  
Vol 272-276 ◽  
pp. 1528-1529 ◽  
Author(s):  
J.M González ◽  
F.J Palomares ◽  
A Hernando-Mañeru ◽  
M.P Morales ◽  
C.J Serna ◽  
...  
Keyword(s):  
Metal Particles ◽  
Thermally Activated ◽  
Coated Metal

Obtaining and research of pharmaceutical properties of antiemetics in a form of powder for inhalation

2021 ◽  
Author(s):  
Igor M. Ivanov ◽  
Tatiana B. Pechurina ◽  
Nikolai G. Vengerovich ◽  
Mikhail A. Yudin ◽  
Aleksandr S. Nikiforov ◽  
...  
Keyword(s):  
Particle Size ◽  
Dosage Form ◽  
Production Method ◽  
Particle Fraction ◽  
Median Particle Size ◽  
Antiemetic Drugs ◽  
Median Particle ◽  
Pharmaceutical Properties ◽  
Mass Median ◽  
Respirable Particle

Samples of antiemetic drugs (ondansetronum, palonosetronum, metoclopramidum) in the form of powder for inhalation have been developed by the method of spray drying. The granulometric composition, hygroscopicity and aerodynamic distribution of aerosol particles of the drugs have been investigated. The dosage form of the powder for inhalation of antiemetics (ondansetronum and palonosetronum) in terms of its particle size distribution, hygroscopicity and content of the agent corresponds to those for inhalation using dry powder inhalers. In the study of the phase-dispersed composition of aerosol, ondansetronum and palonosetronum in the dosage form of powder for inhalation as part of the HandiHaler inhaler (at a flow rate of 60 l / min) showed high rates of the released dose up to 72-76%, respirable particle fraction (up to 5 m) up to 54 -56% and a mass median particle size of about 3 microns. Obtaining the inhaled form of metoclopramide requires optimization of the production method for receiving the product with acceptable pharmaceutical properties.

Sign in / Sign up

Export Citation Format

Share Document