The effect of the temperature dependence of the heat conductivity on the physical laws of the bulk synthesis of a composite

2021 ◽  
pp. 33-39
Author(s):  
N.V. Bukrina ◽  
Keyword(s):  
Temperature Dependence ◽  
Heat Conductivity ◽  
Chemical Compounds ◽  
Heat Conductivity Coefficient ◽  
Temperature Dependent ◽  
High Temperature Synthesis ◽  
Formal Kinetic ◽  
Cylindrical Mold ◽  
Comparison Of The Results ◽  
Physical Laws

Two-dimensional model of high-temperature synthesis of chemical compounds and alloys in a dynamic thermal explosion mode when a powder compact is heated in a steel cylindrical mold by an induction heat source are proposed. The complex of chemical reactions is described by a total reaction with effective formal kinetic parameters. The kinetic law takes into account strong retardation of the reaction by the layer of the synthesized product that prevents the interaction of the reagents. The model makes it possible to investigate the macroscopic physical laws of the synthesis of a composite with a change in the heating rate and reactor dimensions. It is made a comparison of the results obtained for a constant heat conductivity coefficient and a temperature-dependent heat conductivity coefficient. It is revealed that taking into account the temperature dependence of the heat conductivity coefficient can lead to a numerical change in the ignition delay time and to a qualitatively different temperature distribution in the reactor bulk.

Unusual (zig-zag) temperature dependence of the rate constant for irreversible thermoinactivation of hydrophilized enzymes

1990 ◽  
Vol 55 (5) ◽  
pp. 1366-1371 ◽  
Author(s):  
Virginius Šikšnis ◽  
Vadim V. Mozhaev ◽  
Nina Galkantaite ◽  
Nikolai S. Melik-Nubarov ◽  
Genadii Denis ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Effective Activation Energy ◽  
Conformational Transition ◽  
Glyoxylic Acid ◽  
Kinetic Scheme ◽  
Covalent Modification ◽  
Effective Activation ◽  
Temperature Dependent ◽  
Stable Conformation ◽  
Formal Kinetic

Hydrophilized preparations of α-chymotrypsin and trypsin obtained by covalent modification of the enzymes with anhydrides of aromatic carboxylic acids (trimellitic, pyromellitic and mellitic) or with glyoxylic acid display an unusual temperature dependence of the rate constants of irreversible thermoinactivation: the linear plots (with positive and negative values of an effective activation energy) alternate in a zig-zag manner. A formal kinetic scheme describing this behaviour is suggested, involving the temperature-dependent conformational transition of modified α-chymotrypsin into a more stable conformation.

19F Nuclear Quadrupole Coupling in some Halomethanes

1986 ◽  
Vol 41 (1-2) ◽  
pp. 171-174 ◽  
Author(s):  
M. Frank ◽  
F. Gubitz ◽  
W. Ittner ◽  
W. Kreische ◽  
A. Labahn ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Simple Model ◽  
Temperature Dependence ◽  
Coupling Constants ◽  
Temperature Dependent ◽  
Distribution Method ◽  
Quadrupole Coupling ◽  
Time Differential ◽  
Nuclear Quadrupole

The 19F quadrupole coupling constants in CF4, CHF3, CClF3 and CHClF2 are reported. The measurements were carried out temperature dependent using the time differential perturbed angular distribution method (TDPAD). The temperature dependence can be satisfactorily described in the framework of the Bayer-Kushida theory. A simple model is used to explain the appearance of H-F and Cl-F coupling constants in CHF3/CHClF2 and CClF3, respectively.

Electronic Properties of Bismuth Nanowires

2001 ◽  
Vol 679 ◽  
Author(s):  
Stephen B. Cronin ◽  
Yu-Ming Lin ◽  
Oded Rabin ◽  
Marcie R. Black ◽  
Gene Dresselhaus ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Band Structure ◽  
Temperature Dependence ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Temperature Dependent ◽  
Si Substrates ◽  
Bismuth Nanowires ◽  
Bi Nanowire ◽  
Anodic Alumina Templates

ABSTRACTThe pressure filling of anodic alumina templates with molten bismuth has been used to synthesize single crystalline bismuth nanowires with diameters ranging from 7 to 200nm and lengths of 50μm. The nanowires are separated by dissolving the template, and electrodes are affixed to single Bi nanowires on Si substrates. A focused ion beam (FIB) technique is used first to sputter off the oxide from the nanowires with a Ga ion beam and then to deposit Pt without breaking vacuum. The resistivity of a 200nm diameter Bi nanowire is found to be only slightly greater than the bulk value, while preliminary measurements indicate that the resistivity of a 100nm diameter nanowire is significantly larger than bulk. The temperature dependence of the resistivity of a 100nm nanowire is modeled by considering the temperature dependent band parameters and the quantized band structure of the nanowires. This theoretical model is consistent with the experimental results.

3D-[Pr(Im)3(ImH)]@ImH: Ein dreidimensionales Netzwerk mit vollständiger Stickstoffkoordination aus einer Imidazolschmelze / 3D-[Pr(Im)3(ImH)]@ImH: A Three-Dimensional Network with Complete Nitrogen Coordination Obtained from an Imidazole Melt

2006 ◽  
Vol 61 (7) ◽  
pp. 792-798 ◽  
Author(s):  
Klaus Müller-Buschbaum
Keyword(s):  
Crystal Engineering ◽  
Material Science ◽  
Three Dimensional ◽  
Temperature Dependent ◽  
Temperature Synthesis ◽  
3 Dimensional ◽  
High Temperature Synthesis ◽  
Dimensional Network ◽  
Bright Green ◽  
Gas Molecules

The reaction of a melt of unsubstituted imidazole with praseodymium metal yields bright green crystals of 3D-[Pr(Im)3(ImH)]@ImH. Imidazolate ligands coordinate η1 via both N atoms their 1,3 positioning within the heterocycle being responsible for the connection of praseodymium atoms. A 3-dimensional network is formed with imidazole molecules from the melt intercalated in the crystal structure. The imidazole molecules can be released and temperature dependent reversibly be exchanged with gas molecules including argon. Thus the solvent free high temperature synthesis of rare earth elements with amine melts can also be utilized for “crystal engineering” and the synthesis of compounds with material science aspects. Furthermore 3D-[Pr(Im)3(ImH)]@ImH is the first unsubstituted imidazolate of the lanthanides.

On Free Vibrations at Temperature-Dependent Material Properties and Transient Temperature Fields

1972 ◽  
Vol 39 (3) ◽  
pp. 723-726 ◽  
Author(s):  
U. Olsson
Keyword(s):  
Temperature Dependence ◽  
Analytical Solutions ◽  
Material Properties ◽  
Free Vibrations ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Material Damping ◽  
Temperature Dependent ◽  
Temperature Variations ◽  
Damping Parameter

The influence of the temperature-dependence of the material properties on the free vibrations of transiently heated structures is investigated. Analytical solutions are given for linear, exponential, and harmonic temperature variations when the material damping parameter, Poisson’s ratio, and Young’s modulus depend on the temperature.

Temperature dependent electronic band structure of wurtzite GaAs nanowires

Nanoscale ◽  
2018 ◽  
Vol 10 (3) ◽  
pp. 1481-1486 ◽  
Author(s):  
Neimantas Vainorius ◽  
Simon Kubitza ◽  
Sebastian Lehmann ◽  
Lars Samuelson ◽  
Kimberly A. Dick ◽  
...  
Keyword(s):  
Band Structure ◽  
Temperature Dependence ◽  
Electronic Band Structure ◽  
Temperature Dependent ◽  
Electronic Band ◽  
Gaas Nanowires

Temperature dependence of the indicated transitions in wurtzite GaAs.

On the time delay of the photoplastic effect

1986 ◽  
Vol 1 (1) ◽  
pp. 3-6 ◽  
Author(s):  
Joseph Pellegrino ◽  
J. M. Galligan
Keyword(s):  
Time Delay ◽  
Temperature Dependence ◽  
Cadmium Telluride ◽  
Deformation Temperature ◽  
Mercury Cadmium Telluride ◽  
Charge Carriers ◽  
Temperature Dependent ◽  
Simple Analysis ◽  
Photoplastic Effect

Photoplasticity in mercury cadmium telluride, Hg1-x Cdx Te with x = 0.3, has been studied as a function of light frequency and deformation temperature. We show that there is an easily measurable time delay accompanying irradiation of the crystal and the change in stress. This time delay is temperature dependent, suggesting a diffusion of charge carriers, introduced by the light, to the interior of the crystal. A simple analysis is given of the observed temperature dependence that is consistent with the experiments.

THE INFLUENCE OF THE VALUE OF THE THERMAL FLUX SUPPLIED TO THE WALL ON THE SPATIAL DISTRIBUTION OF THE HEAT CONDUCTIVITY COEFFICIENT OF SUPERCRITICAL WATER IN THE CHANNELS

2017 ◽  
Author(s):  
Nataliia Fialko ◽  
◽  
Viktor Prokopov ◽  
Julii Sherenkovskiy ◽  
Sergey Aleshko ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Computer Modeling ◽  
Supercritical Water ◽  
Heat Conductivity ◽  
Thermal Flux ◽  
Heat Conductivity Coefficient ◽  
Tube System

The paper presents the results of computer modeling for research the regularities of the influence of the value of the thermal flux supplied to the tube system on the structure of the distribution of the heat conductivity of supercritical water in the channels.

Temperature Dependence of Photoresponse in p-Type GaAs/AlGaAs Multiple Quantum Wells: Theory and Experiment

1999 ◽  
Vol 607 ◽  
Author(s):  
F. Szmulowicz ◽  
A. Shen ◽  
H. C. Liu ◽  
G. J. Brown ◽  
Z. R. Wasilewski ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Temperature Dependence ◽  
Bound States ◽  
Light Hole ◽  
Multiple Quantum ◽  
Temperature Dependent ◽  
Long Wavelength ◽  
Hole Level ◽  
Polarization Characteristics ◽  
P Type

AbstractThis paper describes a study of the photoresponse of long-wavelength (LWIR) and mid-infrared (MWIR) p-type GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) as a function of temperature and QWIP parameters. Using an 8x8 envelope-function model (EFA), we designed and calculated the optical absorption of several bound-to-continuum (BC) structures, with the optimum designs corresponding to the second light hole level (LH2) coincident with the top of the well. For the temperature-dependent study, one non-optimized LWIR and one optimized MWIR samples were grown by MBE and their photoresponse and absorption characteristics measured to test the theory. The theory shows that the placement of the LH2 resonance at the top of the well for the optimized sample and the presence of light-hole-like quasi-bound states within the heavy-hole continuum for the nonoptimized sample account for their markedly different thermal and polarization characteristics. In particular, the theory predicts that, for the LWIR sample, the LH-like quasi-bound states should lead to an increased Ppolarized photoresponse as a function of temperature. Our temperature dependent photoresponse measurements corroborate most of the theoretical findings with respect to the long-wavelength threshold, shape, and polarization and temperature dependence of the spectra.

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