scholarly journals Sublimation Kinetic Studies of theZr(tmhd)4Complex

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
T. S. Arul Jeevan ◽  
K. S. Nagaraja
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Heating Rate ◽  
Reaction Mechanisms ◽  
Kinetic Studies ◽  
Nitrogen Atmosphere ◽  
Dynamic Measurements ◽  
Pure Nitrogen ◽  
Value Analysis ◽  
Pure Nitrogen Atmosphere

The thermal behaviour of tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium(IV), [Zr(tmhd)4] was investigated by nonisothermal and isothermal thermogravimetric methods in a high pure nitrogen atmosphere. The influence of the heating rate in dynamic measurements (6, 8, 10, and 12°C/min) on activation energy was also studied. The nonisothermal sublimation activation energy values determined following the procedures of Arrhenius, Coats and Redfern, Kissinger, and Flynn-Wall yielded76±5,92±2,81±8, and72±7 kJ/mol, respectively, and the isothermal sublimation activation energy was found to be87±4 kJ/mol over the temperature range of 411–462 K. Different reaction mechanisms were used to compare with this value. Analysis of the experimental results suggested that the actual reaction mechanism was anRndeceleration type.

Substrates Effect on the Phase Transition of GaN Thin Films by Sputter Deposition

2019 ◽  
Vol 971 ◽  
pp. 79-84
Author(s):  
Chun Guang Zhang
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Nitrogen Atmosphere ◽  
Sputter Deposition ◽  
X Ray Diffraction ◽  
Pure Nitrogen ◽  
X Ray ◽  
Zinc Blende ◽  
Planar Magnetron ◽  
Pure Nitrogen Atmosphere

As a promising third generation semiconductor material, gallium nitride (GaN) has become a research hotspot in optoelectronic field nowadays. In this paper, GaN thin films were grown by radio frequency (RF) planar magnetron sputtering of a powder GaN target in a pure nitrogen atmosphere at (0.2 – 2.0) Pa, (10 - 100) W onto various substrates such as GaAs (100), Si (100), Si (111), Al2O3(0001) and glass without any buffer layer. A clear phase transition from the metastable cubic zinc-blende (c - ZB) to the stable hexagonal wurtzite (h - WZ) dependence on substrates has been found in the GaN thin films. And the phase transition of GaN films were studied by X-ray diffraction (XRD), photoluminescence (PL) and Raman spectroscopy.

scholarly journals Titan’s past and future: 3D modeling of a pure nitrogen atmosphere and geological implications

Icarus ◽  
2014 ◽  
Vol 241 ◽  
pp. 269-279 ◽  
Author(s):  
Benjamin Charnay ◽  
François Forget ◽  
Gabriel Tobie ◽  
Christophe Sotin ◽  
Robin Wordsworth
Keyword(s):  
3D Modeling ◽  
Nitrogen Atmosphere ◽  
Pure Nitrogen ◽  
Geological Implications ◽  
Pure Nitrogen Atmosphere

scholarly journals Ab-Initio Computational Study : The Activation Energy Changes and Steric Effects In Peptide Synthesis Of Ac-AA-NH2 and Ac-AP-NH2

Molekul ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. 137
Author(s):  
Indah Pratiwi ◽  
Bambang Cahyono ◽  
Parsaoran Siahaan
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Ab Initio ◽  
Peptide Synthesis ◽  
Reaction Mechanisms ◽  
Steric Effect ◽  
Computational Study ◽  
Computational Method ◽  
Side Chain ◽  
Concerted Reaction

Ab-Initio computational method can be used for simulating reaction mechanisms, such as concerted reaction mechanism on peptide synthesis. The concerted reaction is one of many possible pathways on how peptide can be synthesized. The purpose of this study are probing the concerted reaction mechanism and comparing the steric effect to the reaction, given by different side-chain of alanine (A) and proline (P). Two dipeptides formed from alanine and proline were computed at HF-SCF/6-31G** theory level: Ac-AA-NH2 and Ac-AP-NH2. The res.lts show the activation energy of Ac-AA-NH2  and Ac-AP-NH2 forming via concerted pathway are 167.541 kJ/mol and 161.044 kJ/mol, respectively. The steric difference in side-chain affects the dihedral angle of the structure, and also gives difference to the entropy value of reaction.

Kinetic Study of PVC Pyrolysis in Air by Thermogravimetric Analysis Using the Friedman Method

2012 ◽  
Vol 427 ◽  
pp. 64-69 ◽  
Author(s):  
Bin Han ◽  
Yu Long Wu ◽  
Wei Feng ◽  
Zhen Chen ◽  
Ming De Yang
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Heating Rate ◽  
Inert Atmosphere ◽  
Nitrogen Atmosphere ◽  
Pyrolysis Process ◽  
Pyrolysis Mechanism ◽  
Second Stage ◽  
Friedman Method

The thermal degradation of PVC in air ambience was investigated by the thermogravimetric analysis (TGA). The experiments were carried out at different heating rate of 5, 10, 20 and 40°C/min, respectively. The activation energy was calculated by the Friedman method. The pyrolysis mechanism of PVC in air was discussed and compared with that in Nitrogen atmosphere. The pyrolysis process of PVC in air could be divided into two main stages: 200 °C ~ 380 °C and 400 °C ~ 600 °C, which obtained by TGA at the heating rate of 5°C/min. The second stage could be further subdivided into two parts by 465 °C. It can be concluded that the oxygen in air affected the second stage more obviously than that of the first one, in comparison with inert atmosphere. The activation energy of the second stage was still larger than the first stage.

CaMg2N2 – ein gemischtes Erdalkalimetallnitrid mit anti-La2O3-Struktur / CaMg2N2 – a Mixed Alkaline-Earth Metal Nitride with anti-La2O3 Structure

1995 ◽  
Vol 50 (4) ◽  
pp. 619-622 ◽  
Author(s):  
Verena Schultz-Coulon ◽  
Wolfgang Schnick
Keyword(s):  
Alkaline Earth ◽  
Earth Metal ◽  
Nitrogen Atmosphere ◽  
Molar Ratio ◽  
Alkaline Earth Metal ◽  
Tetrahedral Coordination ◽  
Acid Base ◽  
Pure Nitrogen ◽  
Metal Nitride ◽  
Pure Nitrogen Atmosphere

CaMg2N2 (trigonal, P3̄ m 1 (Nr. 164); a = 354.046(1), c = 609.079(2) pm; Z = 1) is isotypic to the anti-La2O3 structure with octahedral and tetrahedral coordination for Ca2+ and Mg2+ ions, respectively. The compound has been prepared by the reaction o f the binary nitrides Ca3N2 and Mg3N2 (molar ratio 1:2) in a tungsten crucible under a pure nitrogen atmosphere at 1050 °C. The formation of the solid CaMg2N2 may be interpreted in analogy to reactions o f related oxides as an acid-base reaction between the binary nitrides with different coordination tendencies of Ca2+ and Mg2+ ions. An analysis of the binary aristotype anti-La2O3 indicates that this structure is predisposed for building ternary phases.

scholarly journals Thermal Spectroscopy and Kinetic Studies of PEO/PVDF Loaded by Carbon Nanotubes

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Laila Hussein Gaabour
Keyword(s):  
Activation Energy ◽  
Carbon Nanotubes ◽  
Thermal Stability ◽  
Heating Rate ◽  
Polyvinylidene Fluoride ◽  
Kinetic Studies ◽  
Multiwalled Carbon ◽  
Polymeric Matrices ◽  
Swcnts And Mwcnts ◽  
Thermal Stability Of

Nanocomposites of polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) without and with low content of single and multiwalled carbon nanotubes (SWCNTs-MWCNTs) were prepared and studied by thermogravimetric analysis (TGA) using different heating rate. TGA results indicate that the thermal stability of neat PEO/PVDF blend was improved with both heating rate and incorporation of carbon nanotubes (CNTs). The degradation temperature for neat blend was lower than those of the nanocomposites after adding both SWCNTs and MWCNTs. As increase of heating rate, the onset of decomposition is irregularly moved to higher temperatures. This indicates that the thermal stability of the polymeric matrices has been improved after addition of CNTs. The residual weight of the samples left increased steadily with adding of both SWCNTs and MWCNTs. Kinetic thermodynamic parameters such as activation energy, enthalpy, entropy, and Gibbs free energy are evaluated from TGA data using Coats-Redfern model. The values of all parameters irregularly decrease with increasing of heating rate due to increasing of heating rate temperature, the random scission of macromolecule chain in the polymeric matrices predominates and the activation energy has a lower value.

Mode Transition and Related Discharge Phenomena of a Tube Plasma Source Operating in Low-Pressure Pure Nitrogen Atmosphere

2015 ◽  
Vol 43 (2) ◽  
pp. 544-551 ◽  
Author(s):  
Chunyu Miao ◽  
Dequan Shi ◽  
Chunyu Ma ◽  
Chunsheng Ren ◽  
Wenqi Lu ◽  
...  
Keyword(s):  
Plasma Source ◽  
Low Pressure ◽  
Nitrogen Atmosphere ◽  
Mode Transition ◽  
Pure Nitrogen ◽  
Pure Nitrogen Atmosphere

Ligand-Enabled γ-C(sp3)–H Olefination of Free Carboxylic Acids

2020 ◽  
Author(s):  
Kiron Kumar Ghosh ◽  
Alexander Uttry ◽  
Francesca Ghiringhelli ◽  
Arup Mondal ◽  
Manuel van Gemmeren
Keyword(s):  
Reaction Mechanism ◽  
Carboxylic Acids ◽  
Michael Addition ◽  
Kinetic Studies ◽  
Wide Range ◽  
Palladium Catalyzed

We report the ligand enabled C(sp3)–H activation/olefination of free carboxylic acids in the γ-position. Through an intramolecular Michael-addition, δ-lactones are obtained as products. Two distinct ligand classes are identified that enable the challenging palladium-catalyzed activation of free carboxylic acids in the γ-position. The developed protocol features a wide range of acid substrates and olefin reaction partners and is shown to be applicable on a preparatively useful scale. Insights into the underlying reaction mechanism obtained through kinetic studies are reported.<br>

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