scholarly journals Kinetics of stepwise nitrogen adsorption by size-selected iron cluster cations: Evidence for size-dependent nitrogen phobia

2021 ◽  
Author(s):  
Annika Straßner ◽  
Matthias P. Klein ◽  
Daniela V. Fries ◽  
Christopher Wiehn ◽  
Maximilian E. Huber ◽  
...  
Keyword(s):  
Nitrogen Adsorption ◽  
Iron Cluster ◽  
Size Dependent ◽  
Kinetics Of

Kinetics of synthesizing process for obtaining iron nanopowder by chemical-metallurgical method under isothermal conditions

2021 ◽  
pp. 72-77
Author(s):  
Tien Hiep Nguyen ◽  
◽  
Van Minh Nguyen ◽  
Keyword(s):  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Reduction Process ◽  
Nitrogen Adsorption ◽  
Specific Rate ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

In this work the kinetics of synthesizing process of metallic iron nanopowder by hydrogen reduction from α-FeOOH hydroxide under isothermal conditions were studied. α-FeOOH nanopowder was prepared in advance by chemical deposition from aqueous solutions of iron nitrate Fe(NO3)3 (10 wt. %) and alkali NaOH (10 wt. %) at room temperature, pH = 11, under the condition of continuous stirring. The hydrogen reduction process of α-FeOOH nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 390 to 470 °C. The study of the crystal structure and composition of the powders was performed by X-ray phase analysis. The specific surface area S of the samples was measured using BET method by low-temperature nitrogen adsorption. The average particle size D of powders was determined via the measured S value. The size characteristics and morphology of the particles were investigated by transmission and scanning electron microscopes. The calculation of the kinetic parameters of the hydrogen reduction process of α-FeOOH under isothermal conditions was carried out by the Gray-Weddington model and Arrhenius equation. It is shown that the rate constant of reduction at 470 °C is approximately 2.2 times higher than in the case at 390 °C. The effective activation energy of synthesizing process of iron nanopowder by hydrogen reduction from α-FeOOH was ~38 kJ/mol, which indicates a mixed reaction mode. In this case, the kinetics overall process is limited by both the kinetics of the chemical reaction and the kinetics of diffusion, respectively, an expedient way to accelerate the process by increasing the temperature or eliminate the diffusion layer of the reduction product by intensive mixing. It is show that Fe nanoparticles obtained by hydrogen reduction of its hydroxide at 410 °C, corresponding to the maximum specific rate of the reduction process, are mainly irregular in shape, evenly distributed, the size of which ranges from several dozens to 100 nm with an average value of 75 nm.

Size dependent absorption kinetics of sedimenting nanoparticles

2013 ◽  
Author(s):  
Manoranjan Ghosh ◽  
Karabi Ghosh ◽  
Seema Shinde ◽  
S. C. Gadkari
Keyword(s):  
Absorption Kinetics ◽  
Size Dependent ◽  
Dependent Absorption ◽  
Kinetics Of

Size-dependent thermal decomposition and kinetics of ultrafine alkali metal styphnates

RSC Advances ◽  
2014 ◽  
Vol 4 (74) ◽  
pp. 39463-39471 ◽  
Author(s):  
Rui Liu ◽  
Wenyuan Zhao ◽  
Tonglai Zhang ◽  
Li Yang ◽  
Zunning Zhou ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Alkali Metal ◽  
Decomposition Temperature ◽  
Size Dependent ◽  
Kinetics Of

The styphnate of smaller size possesses lower decomposition temperature and higher reactivity.

scholarly journals Continuous Nucleation and Size Dependent Growth Kinetics of Indium Phosphide Nanocrystals

2020 ◽  
Vol 32 (10) ◽  
pp. 4358-4368 ◽  
Author(s):  
Brandon M. McMurtry ◽  
Kevin Qian ◽  
Joseph K. Teglasi ◽  
Anindya K. Swarnakar ◽  
Jonathan De Roo ◽  
...  
Keyword(s):  
Indium Phosphide ◽  
Growth Kinetics ◽  
Size Dependent ◽  
Dependent Growth ◽  
Kinetics Of ◽  
Continuous Nucleation

scholarly journals Kinetic study of CO2 reaction with CaO by a modified random pore model

2016 ◽  
Vol 18 (1) ◽  
pp. 93-98 ◽  
Author(s):  
S.M.M. Nouri ◽  
H. Ale Ebrahim
Keyword(s):  
Mercury Porosimetry ◽  
Nitrogen Adsorption ◽  
Intrinsic Rate ◽  
Product Layer ◽  
Carbonation Reaction ◽  
Pore Model ◽  
Partial Pressures ◽  
Pore Size Distributions ◽  
Kinetics Of ◽  
Random Pore Model

Abstract In this work, a modified random pore model was developed to study the kinetics of the carbonation reaction of CaO. Pore size distributions of the CaO pellets were measured by nitrogen adsorption and mercury porosimetry methods. The experiments were carried out in a thermogravimeter at different isothermal temperatures and CO2 partial pressures. A fractional concentration dependency function showed the best accuracy for predicting the intrinsic rate of reaction. The activation energy was determined as 11 kcal/mole between 550–700°C. The effect of product layer formation was also taken into account by using the variable product layer diffusivity. Also, the model was successfully predicted the natural lime carbonation reaction data extracted from the literature.

XPS AND XPD ANALYSIS OF NITROGEN ADSORPTION ON THE Ti(0001) SURFACE

1997 ◽  
Vol 04 (06) ◽  
pp. 1309-1314 ◽  
Author(s):  
D. P. FRICKEL ◽  
M. V. KUZNETSOV ◽  
E. V. SHALAEVA
Keyword(s):  
Photoelectron Spectroscopy ◽  
Titanium Surface ◽  
Nitrogen Adsorption ◽  
Text Structure ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
The Third ◽  
Adsorption Temperature ◽  
Nearest Neighborhood ◽  
Kinetics Of

X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD) were used to examine the kinetics of nitrogen adsorption on the Ti(0001) surface at temperatures from 220 to 570 K and adsorption exposures from 0 to 1000 L. At the adsorption temperature T=300 K two chemically nonequivalent states of nitrogen were found: NI (1×1 lattice) localized in octapores between the first and second titanium monolayers and NII (presumably [Formula: see text] structure) on the titanium surface. The third nitrogen state, N0 , which is also localized on the surface but has unoccupied octapores in the nearest neighborhood, is observed with a decrease in the adsorption temperature to 220 K. A model of nitrogen interaction with the Ti(0001) surface in vacuum was proposed proceeding from the temperature dependence of the kinetic adsorption curves.

Size-dependent tissue kinetics of PEG-coated gold nanoparticles

2010 ◽  
Vol 245 (1) ◽  
pp. 116-123 ◽  
Author(s):  
Wan-Seob Cho ◽  
Minjung Cho ◽  
Jinyoung Jeong ◽  
Mina Choi ◽  
Beom Seok Han ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Size Dependent ◽  
Kinetics Of ◽  
Tissue Kinetics

Oxidation Anisotropy and Size-Dependent Reaction Kinetics of Zinc Nanocrystals

2009 ◽  
Vol 113 (33) ◽  
pp. 14644-14650 ◽  
Author(s):  
Xiaofei Ma ◽  
Michael R. Zachariah
Keyword(s):  
Reaction Kinetics ◽  
Size Dependent ◽  
Kinetics Of

scholarly journals Size-Dependent Kinetics of Hydriding and Dehydriding of Pd Nanoparticles

2010 ◽  
Vol 104 (13) ◽  
Author(s):  
Christoph Langhammer ◽  
Vladimir P. Zhdanov ◽  
Igor Zorić ◽  
Bengt Kasemo
Keyword(s):  
Pd Nanoparticles ◽  
Size Dependent ◽  
Kinetics Of

scholarly journals The Modeling of Nitrogen Mass Transport in CoCr Alloys

2016 ◽  
Vol 36 (331) ◽  
pp. 19-26
Author(s):  
Akvilė Petraitienė
Keyword(s):  
Diffusion Coefficient ◽  
Plasma Nitriding ◽  
Nitrogen Concentration ◽  
Nitrogen Adsorption ◽  
Nitrogen Diffusion ◽  
Depth Profiles ◽  
Swelling Rate ◽  
Cocr Alloy ◽  
Kinetics Of ◽  
Good Agreement

Abstract The kinetics of plasma nitriding of CoCr alloy below temperatures of nitrides formation and mechanisms of nitrogen penetration are analyzed by proposed kinetic modeling in this article. Proposed nitrogen diffusion model is based on the trapping – detrapping (TD) model and developed taking into account the effect of the concentration dependent diffusivity of nitrogen, nitrogen adsorption on the surface of alloy and surface swelling process. The model indicates the influence of chromium atoms to nitrogen atoms diffusivity. The model consists of time and depth dependent diffusion, which is described by a partial differential equation, and it is solved by using Crank – Nicolson finite difference method. By fitting of experimental nitrogen depth profiles, it is shown that nitrogen diffusion coefficient varies with nitrogen concentration according to Einstein-Smoluchowski relation. Nitrogen depth profiles in plasma nitrided medical grade CoCr alloy (ISO 5831 – 12) at T = 400 °C for 1, 4 and 20 hours calculated on the basis of this model are in good agreement with experimental nitrogen profiles. Furthermore, the swelling process is showed and analyzed, derived the dependency of swelling rate on nitriding duration – the swelling rate is inversely proportional to the square root of nitriding duration. The obtained diffusion coefficient value and the swelling process rates satisfy the experimental data form Ref. The derived model explains physical processes during plasma nitriding and allows obtaining nitrogen depth profiles for any requisite nitriding duration.

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