scholarly journals INFLUENCE OF SIZE AND PRESSURE ON THE TEMPERATURE DEPENDENCIES OF THERMODYNAMIC PROPERTIES OF PLATINUM

2021 ◽  
pp. 465-474
Author(s):  
Сергей Петрович Крамынин
Keyword(s):  
Heat Capacity ◽  
Thermal Expansion ◽  
Elastic Modulus ◽  
Equation Of State ◽  
Surface Energy ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Interatomic Interaction ◽  
Isobaric Heat Capacity ◽  
Temperature Dependences

Основываясь на параметрах парного потенциала межатомного взаимодействия Ми-Леннард-Джонса для Pt, и используя RP-модель нанокристалла, изучены температурные, барические и размерные зависимости следующих свойств: модуля упругости, коэффициента теплового расширения, изобарной теплоемкости и поверхностной энергии. Расчет уравнения состояния Pt показал хорошее согласие с экспериментом. Уравнение состояния было рассчитано вдоль пяти изотерм: T = 300, 1300, 1500, 1700, 1900 К. Впервые с единых позиций выполнены расчеты температурных зависимостей указанных свойств Pt в диапазоне от 0 K до 1500 K вдоль изобар 0 и 50 ГПа. Расчеты указанных зависимостей проведены как для макро-, так и для нанокристалла кубической формы из 306 атомов. Показано, что при изобарно-изотермическом уменьшении размера нанокристалла Pt происходит уменьшение значений модуля упругости и поверхностной энергии, а значения коэффициента теплового расширения и изобарной теплоемкости увеличиваются на исследуемом интервале температур. Based on the parameters of the pair interatomic interaction potential of the Mie-Lennard-Jones for Pt, and using the RP-model of the nanocrystal, the temperature, pressure and size dependencies of the following properties are studied: elastic modulus, thermal expansion coefficient, isobaric heat capacity, and surface energy. The calculation of the equation of state showed good agreement with experiment. The equation of state was calculated along five isotherms: T = 300, 1300,1500, 1700, 1900 K. For the first time, calculations of the temperature dependences of the above properties of Pt in the range from 0 to 1500 K along 0 and 50 GPa isobars were performed from a unified standpoint. Calculations of these dependencies were carried out for both macro- and cubic nanocrystals of 306 atoms. It is shown that with an isobaric-isothermal decrease in the nanocrystal size, the values of the elastic modulus and surface energy decrease, while the values of the thermal expansion coefficient and isobaric heat capacity increase over the investigated temperature range.

scholarly journals THE SIZE DEPENDENCIES OF PROPERTIES OF MO-W ALLOY OF EQUIATOMIC COMPOSITION

2020 ◽  
pp. 128-135
Author(s):  
Сергей Петрович Крамынин
Keyword(s):  
Heat Capacity ◽  
Thermal Expansion ◽  
Surface Energy ◽  
Expansion Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
Interatomic Interaction ◽  
Isobaric Heat Capacity ◽  
Substitution Alloy ◽  
Capacity Surface ◽  
Thermal Volume Expansion

Основываясь на параметрах парного потенциала межатомного взаимодействия Ми-Леннард-Джонса для Mo и W были рассчитаны параметры потенциала для сплава замещения Mo - W эквиатомного состава. Получены размерные зависимости для уравнения состояния, модуля упругости, коэффициента теплового расширения, изобарной теплоемкости, поверхностной энергии и производной поверхностной энергии по температуре. Также получены температурные зависимости коэффициента теплового расширения изобарной теплоемкости для макро- и нанокристаллов сплава Mo - W. Было показано, что температурная зависимость коэффициента теплового объемного расширения для нанокристалла лежит выше, чем зависимость для макрокристалла, также обнаружено, что с уменьшением размера уменьшается модуль упругости, коэффициент теплового объемного расширения возрастает, а удельная поверхностная энергия нанокристалла сплава Mo - W уменьшается. Based on the parameters of the Mie-Lennard-Jones pair-wised potential of the interatomic interaction for Mo and W , the potential parameters for an equiatomic Mo - W substitution alloy were calculated. Size dependences for the equation of state, modulus of elasticity, coefficient of thermal expansion, isobaric heat capacity, surface energy and surface energy temperature derivative were obtained. Temperature dependencies of coefficient of thermal expansion and isobaric heat capacity for macro- and nano-crystals of Mo - W alloy were also obtained. It was shown that the temperature dependence of the thermal expansion coefficient for a nanocrystal is higher than that for a macrocrystal. It was also found that with a decrease in size, the elastic modulus decreases, the thermal volume expansion coefficient increases, and the specific surface energy of the alloy nanocrystal Mo - W decreases.

scholarly journals Thermal Properties of Stabilized Zirconia at Low Temperatures

1985 ◽  
Vol 38 (4) ◽  
pp. 617 ◽  
Author(s):  
JG Collins ◽  
SJ Collocott ◽  
GK White
Keyword(s):  
Heat Capacity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Low Temperatures ◽  
Linear Thermal Expansion Coefficient ◽  
Linear Thermal Expansion ◽  
Stabilized Zirconia ◽  
Elastic Data

The linear thermal expansion coefficient a from 2 to 100 K and heat capacity per gram cp from 0�3 to 30 K are reported for fully-stabilized zirconia containing a nominal 16 wt.% (9 mol.%) of yttria. The heat capacity below 7 K has been analysed into a linear (tunnelling?) term, a Schottky term centred at 1�2 K, a Debye term (e~ = 540 K), and a small T5 contribution. The expansion coefficient is roughly proportional to T from 5 to 20 K and gives a limiting lattice Griineisen parameter 'Yo ::::: 5, which agrees with that calculated from elastic data.

Heat Transfer Characteristics of Nitrogen in Supercritical Region Using Redlich-Kwong Equation of State

2019 ◽  
Vol 17 (10) ◽  
Author(s):  
Hussain Basha ◽  
G. Janardhana Reddy ◽  
N. S. Venkata Narayanan
Keyword(s):  
Heat Transfer ◽  
Thermal Expansion ◽  
Equation Of State ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Physical Parameters ◽  
Heat Transfer Characteristics ◽  
Reduced Pressure ◽  
Supercritical Region ◽  
Transfer Characteristics

Abstract The present paper studies through numerical methods, the thermodynamic heat transfer characteristics of free convection flow of supercritical nitrogen over a vertical cylinder. In the present analysis, the values of volumetric thermal expansion coefficient ($\beta$) are evaluated based on Redlich-Kwong equation of state (RK-EOS) and Van der Waals equation of state (VW-EOS). The calculated analytical thermal expansion coefficient values using RK-EOS are very close to NIST data values in comparison with VW-EOS. A set of coupled nonlinear partial differential equations (PDEs) governing the supercritical fluid (SCF) flow are derived, converted into non-dimensional form with the help of suitable dimensionless quantities and solved using Crank-Nicolson implicit finite difference method. The simulations are carried out for nitrogen in the supercritical region. The obtained numerical data is expressed in terms of graphs and tables for various values of physical parameters. The increasing value of reduced temperature decreases the average Nusselt number and skin-friction coefficient, whereas amplifying value of reduced pressure enhance the heat transfer rate and wall shear stress in the SCF region. Present results are compared with the previous results and the two are found to be in good agreement, i. e. the numerically generated results found to be in agreement with existing results.

Determination of the Equation of State of Polyisobutylene

1969 ◽  
Vol 42 (5) ◽  
pp. 1409-1411
Author(s):  
B. E. Eichinger ◽  
P. J. Flory
Keyword(s):  
Thermal Expansion ◽  
Equation Of State ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Pressure Coefficient ◽  
Experimental Results ◽  
Characteristic Parameters ◽  
Thermal Pressure

Abstract The density, thermal expansion coefficient, and thermal pressure coefficient for polyisobutylene of mol wt 40,000 have been accurately determined from 0 to 150°. Results are compared with the reduced equation of state employed in the theory of solutions. The characteristic parameters v*, T*, and p* required for the treatment of polyisobutylene solutions are obtained from the experimental results.

scholarly journals Колебательные и тепловые свойства оксианионных кристаллов

2018 ◽  
Vol 60 (3) ◽  
pp. 565
Author(s):  
Д.В. Корабельников
Keyword(s):  
Heat Capacity ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Density Functional ◽  
Functional Theory ◽  
Atomic Orbitals ◽  
Thermodynamic Potentials ◽  
Intramolecular Vibrations ◽  
Ir And Raman

AbstractThe vibrational and thermal properties of dolomite and alkali chlorates and perchlorates were studied in the gradient approximation of density functional theory using the method of a linear combination of atomic orbitals (LCAO). Long-wave vibration frequencies, IR and Raman spectra, and mode Gruneisen parameters were calculated. Equation-of-state parameters, thermodynamic potentials, entropy, heat capacity, and thermal expansion coefficient were also determined. The thermal expansion coefficient of dolomite was established to be much lower than for chlorates and perchlorates. The temperature dependence of the heat capacity at T > 200 K was shown to be generally governed by intramolecular vibrations.

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