scholarly journals Explanation of the cluster structures melting mechanism and their influence on the molten state’s physical and chemical nature

2021 ◽  
Vol 316 (1) ◽  
pp. 62-68
Author(s):  
G. S. Shaikhova ◽  
Keyword(s):  
Temperature Dependence ◽  
Melting Temperature ◽  
Chemical Nature ◽  
Bethe Lattice ◽  
Molten State ◽  
Melt Temperature ◽  
Metal Melts ◽  
Cluster Fragmentation ◽  
Melting Mechanism ◽  
Physical And Chemical

There are results of the melts of semimetals and semiconductors of various structural groups research in the article. On the example of simplified regular Bethe lattice one can model destruction and aggregation of structures in clusters and on it’s basis to substantiate the metal melts properties in the form of nanolayers. The variety of compressibility polytherms forms in electronic melts requires typing, since their analysis makes it possible to explain the mechanism of the aggregation and dissolution processes of extended objects in melts. The article contains formulas that allow explaining the mechanism of the dissolution of cluster structures and their influence on the physicochemical nature of the molten state. There is considered the process of cluster fragmentation. Larger fragments of clusters are formed in the process of crushing, and this fact leads to the compressibility that decreases more rapidly, only after passing through the extremum it begins to increase due to the thermal loosening. The study of the function's compressibility for an extremum in the compressibility's temperature dependence also indicates the changing process of the clusters decomposition mechanisms in melts with an increase in temperature and vice versa to aggregation with a decrease in the melt temperature to the melting temperature.

scholarly journals How Atoms of Polycrystalline Nb 20.6 Mo 21.7 Ta 15.6 W 21.1 V 21.0 refractory High-Entropy Alloys Rearrange during the Melting Process

2021 ◽  
Author(s):  
Shin-Pon Ju ◽  
Chen-Chun Li
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
Single Crystal ◽  
Melting Temperature ◽  
Md Simulation ◽  
Melting Process ◽  
Structural Rearrangement ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Melting Mechanism

Abstract The melting mechanism of single crystal and polycrystalline Nb 20.6 Mo 21.7 Ta 15.6 W 21.1 V 21.0 RHEAs was investigated by the molecular dynamics (MD) simulation using the 2NN MEAM potential. For the single crystal RHEA, the density profile displays an abrupt drop from 11.25 to 11.00 g/cm 3 at temperatures from 2910 to 2940 K, indicating all atoms begin significant local structural rearrangement. For polycrystalline RHEAs, a two-stage melting process is found. In the first melting stage, the melting of the grain boundary (GB) regions firstly occurs at the pre-melting temperature, which is relatively lower than the corresponding system-melting point. At the pre-melting temperature, most GB atoms have enough kinetic energies to leave their equilibrium positions, and then gradually induce the rearrangement of grain atoms close to GB. In the second melting stage at the melting point, most grain atoms have enough kinetic energies to rearrange, resulting in the chemical short-ranged order (CSRO) changes of all pairs.

scholarly journals Real Nano “Light Vaccine” Will Benefit to COVID-19 Pandemic Control

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Jianshe Yang
Keyword(s):  
Near Infrared ◽  
Chemical Nature ◽  
Strong Acid ◽  
Alveolar Type ◽  
Type Ii ◽  
Nir Light ◽  
Physical Absorption ◽  
Acid And Base ◽  
And Control ◽  
Physical And Chemical

AbstractThis highlight presents a recent technique of “Light Vaccine” for COVID-19 pandemic control. Though this technique has the germicidal advantage to SARS-CoV-2, its shortcomings will limit the wide and in-depth application. We make a perspective of real nano light vaccine, which will play an important role in the prevention and control of COVID-19. Briefly, This flow chart described the MWCNT was fabricated with strong acid and base conditional mixture in order to achieve the p-WCNT (chemical process); then modified with RNA layse and receptor binding domain (RBD) by covalent conjugation and physical absorption to get f-WCNT (functionalization); thereafter, f-WCNT was used in the multi-cell culture system interacting with SARS-CoV-2 to identify the special affinity of f-WCNT to ACE2 labeled alveolar type II cells and the inhibition capacity to SARS-CoV-2. This design, is different from the so called “light vaccine”, has the real function to against SARS-CoV-2 by local cellular temperature-rising through photothermal conversion under the near infrared (NIR) light irradiation, according to the physical and chemical nature of carbon nanotubes, and initiates the immune response consequently.

The Pressure of CO2 Crystal Melting Temperature Dependence

2014 ◽  
Vol 887-888 ◽  
pp. 935-938
Author(s):  
Shuai Zhang ◽  
Lei Chen ◽  
Zhi Shuai Wu ◽  
Shang Wu Hou
Keyword(s):  
Phase Transition ◽  
Temperature Dependence ◽  
Melting Temperature ◽  
Order Phase Transition ◽  
Melting Curve ◽  
Clapeyron Equation ◽  
First Order ◽  
First Order Phase Transition ◽  
Crystal Melting ◽  
First Order Phase

This paper is based on the CO2crystal as an example, through the two reasonable simplification ΔH(T,P) ΔH(T) and ΔV(T,P) ΔV(P) into the Clapeyron equation to calculate the melting curve. Because the Clapeyron equation can describe all the first-order phase transition, accordingly it is determining the material T-P diagram provides a new way.

Study on the Melting Mechanism of Maleic Anhydride

2020 ◽  
Vol 10 (1) ◽  
pp. 65-78
Author(s):  
Bratati Das ◽  
Ashis Bhattacharjee
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Maleic Anhydride ◽  
Temperature Dependence ◽  
Growth Models ◽  
Melting Process ◽  
Nucleation And Growth ◽  
Crystalline Solid ◽  
Scanning Calorimetry ◽  
Melting Mechanism

Background: Melting of a pure crystalline material is generally treated thermodynamically which disregards the dynamic aspects of the melting process. According to the kinetic phenomenon, any process should be characterized by activation energy and preexponential factor where these kinetic parameters are derivable from the temperature dependence of the process rate. Study on such dependence in case of melting of a pure crystalline solid gives rise to a challenge as such melting occurs at a particular temperature only. The temperature region of melting of pure crystalline solid cannot be extended beyond this temperature making it difficult to explore the temperature dependence of the melting rate and consequently the derivation of the related kinetic parameters. Objective: The present study aims to explore the mechanism of the melting process of maleic anhydride in the framework of phase transition models. Taking this process as just another first-order phase transition, occurring through the formation of nuclei of new phase and their growth, particular focus is on the nucleation and growth models. Methods: Non-isothermal thermogravimetry, as well as differential scanning calorimetry studies, has been performed. Using isoconversional kinetic analysis, temperature dependence of the activation energy of melting has been obtained. Nucleation and growth models have been utilized to obtain the theoretical temperature dependencies for the activation energy of melting and these dependencies are then compared with the experimentally estimated ones. Conclusion: The thermogravimetry study indicates that melting is followed by concomitant evaporation, whereas the differential scanning calorimetry study shows that the two processes appear in two different temperature regions, and these differences observed may be due to the applied experimental conditions. From the statistical analysis, the growth model seems more suitable than the nucleation model for the interpretation of the melting mechanism of the maleic anhydride crystals.

Density and Surface Tension of Fe-Cu Melts

2020 ◽  
Vol 992 ◽  
pp. 545-550
Author(s):  
Vladimir V. Vyukhin ◽  
O.A. Chikova ◽  
Ksenya Yu. Shmakova
Keyword(s):  
Surface Tension ◽  
Temperature Dependence ◽  
Cast Steel ◽  
Liquid Alloys ◽  
Humid Atmosphere ◽  
Damping Characteristics ◽  
Metal Melts ◽  
Cu Alloys ◽  
Two Phases ◽  
Large Machine

Fe-Cu alloys are used as structural materials for manufacture of large machine parts subjected to shock loads. Fe-Cu alloys have a higher corrosion resistance in a humid atmosphere and in salt solutions than cast steel. Fe-Cu alloys have high enough damping characteristics. Upon cooling the Fe-Cu melts is stratified into two phases before crystallization which in field of gravity are separated by density. It is possible to suppress delamination and obtain a material with structure of a “frozen emulsion” by heating melt to the temperature T* determined for each composition by a specific way. In this paper, we studied surface tension of liquid alloys of Fe-1wt.% Cu, Fe-20wt.% Cu, and Fe-30wt.%Cu in order to determine the temperature T*. For the melt of Fe-20wt.% Cu value T*=1670°C is highest. It is confirmed by results of measuring temperature dependence of surface tension. Temperature dependence of the surface tension Fe-Cu melts is characterized by a positive value of the temperature coefficient of surface tension dσ/dT which is abnormal for metal melts. Experimental data on the density, the surface tension of Fe-Cu liquid alloys have of independent metrological importance for practical foundry.

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