聚乙烯类/石蜡木塑相变储能材料的制备与性能

以聚乙烯类基质作为支撑材料,石蜡作为相变剂,研究和制备了聚乙烯类/石蜡木塑相变储能材料。研究表明,当石蜡的添加量为25%时,HDPE、LDPE和LLDPE三种基质的石蜡木塑相变储能材料的拉伸强度分别下降了53.18%、60.48%、66.81%,弯曲强度分别下降了67.68%、62.24%、69.07%,力学性质下降均超过50%。性能测试得出HDPE的综合性能较好,在石蜡的添加量为20%时,HDPE、LDPE和LLDPE的相变温度分别为56.27℃、57.87℃、56.62℃,相变焓分别为125.85J/g、100.30J/g、124.65J/g。通过氯仿提取石蜡,研究聚乙烯类基质的包裹性能,结果表明不同的基质都解决了石蜡的渗漏问题。     

Thermodynamic Properties of Gases from Speed-of-Sound Measurements

A procedure for deriving thermodynamic properties of gases from speed of sound is presented. It is based on numerical integration of ordinary differential equations (ODEs) (rather than partial differential equations—PDEs) connecting speed of sound with other thermodynamic properties in the T-p domain. The procedure enables more powerful methods of higher-order approximation to ODEs to be used (e.g., Runge-Kutta) and requires only Dirichlet initial conditions. It was tested on gaseous argon in the temperature range from 250 to 450 K and in the pressure range from 0.2 to 12 MPa, and also on gaseous methane in the temperature range from 275 to 375 K and in the pressure range from 0.4 to 10 MPa. The density and isobaric heat capacity of argon were derived with absolute average deviations of 0.007% and 0.03%, respectively. The density and isobaric heat capacity of methane were derived with absolute average deviations of 0.006% and 0.09%, respectively.     

Estimation of Thermodynamic Properties from Binary Phase Diagram

The general relationship between binary phase diagrams and the thermodynamic properties was system-atically derived without any assumption.A procedure was presented to estimate the thermodynamic proper-ties from the binary phase diagrams.     

Ideal Gas Thermodynamic Properties of Propyl tert-Butyl Ethers from Density Functional Theory Results Combined with Experimental Data

Ideal gas thermodynamic properties, S°(T), C _p°(, T), H°(T)–H°(0), _f H°(T), and _f G°(T), are obtained on the basis of density functional B3LYP/6-31G(d,p) and B3LYP/6-311 + G(3df,2p) calculations for two propyl tert-butyl ethers. All torsional motions about C–C and C–O bonds were treated as hindered internal rotations using the independent-rotor model. An empirical approximation was assumed to account for the effect of the coupling of rotor potentials. The correction for rotor–rotor coupling was found by fitting to entropy values determined from calorimetric measurements. Enthalpies of formation were calculated using isodesmic reactions.     

Thermodynamic Properties of Sutherland Fluids from an Analytical Perturbation Theory

Analytical expressions are obtained for the thermodynamic properties of fluids with potentials consisting of a spherical hard core plus an attractive tail of the form 1/r (Sutherland fluids). To this end, use is made of the Barker–Henderson perturbation theory together with an analytical expression for the first coordination shell of the radial distribution function of the reference hard-sphere fluid. This expression was derived previously on the basis of the analytical solution of the Percus–Yevick integral equation theory. The results are compared with available simulation data for a wide range of densities, temperatures, and values of the potential parameter . The overall agreement is good, and the accuracy is similar to that obtained using more accurate solutions for the radial distribution function of the hard-sphere fluid leading to nonanalytical expressions for the thermodynamic properties of the fluid considered.     

DIPPR Project 882: Transport Properties and Related Thermodynamic Data for Binary Mixtures

DIPPR Project 882 was organized to develop a computerized databank of selected and evaluated physical, thermodynamic, and transport properties for mixtures of primarily organic compounds. The properties include: liquid viscosities, liquid thermal conductivities, mutual diffusion coefficients, excess volumes and densities, surface tensions, critical temperatures, critical pressures and densities, and solubilities of sparingly soluble organic compounds. The collection is not complete. It is estimated that the complete collection covers about 90% of the mixture classes, contains about 85% of the binary systems published, references about 80% of the data sources, and is a repository for about 85% of all the data published (these estimates exclude density and solubility where the coverage was not intended to be comprehensive). Exhaustive literature searches were made. The data from the original literature were assessed and differences from the pure component values derived from the DIPPR Project 801 and other reliable evaluated data sources for pure compounds were noted. In cases where the differences were excessive, the data sets were rejected. The total collection consists of about 2140 mixture/property pairs covering 361 mixture classes. The results of the project are distributed as five books in the series Transport Properties and Related Thermodynamic Data of Binary Mixtures published by the American Institute of Chemical Engineers and in electronic form as the DIPMIX Database on Transport Properties and Related Thermodynamic Data for Binary Mixtures distributed by the Thermodynamics Research Center.     

Thermodynamic Properties of MgSc and AlSc from First-Principles Phonon Calculations

The thermodynamic properties of intermetallic compounds MgSc and AlSc with CsCl-type B2 structure have been studied by performing density functional theory and density functional perturbation theory within the quasi-harmonic approximation in comparison with NiAl. The linear thermal expansion of the lattice, coefficients of thermal expansion, isothermal bulk modulus, phonon dispersions, phonon density of states, and specific heat capacities at constant volume and constant pressure have been obtained. Comparisons have been made with available experimental data and the results of previous calculations, and good agreement has been obtained. Our results show that the thermal expansion of MgSc is larger than that of AlSc.     

Thermodynamic Properties of Sulfur Hexafluoride

We present new vapor phase speed-of-sound data u(P, T), new Burnett density–pressure–temperature data (P, T), and a few vapor pressure measurements for sulfur hexafluoride (SF₆). The speed-of-sound data spanned the temperature range 230 KT460 K and reached maximum pressures that were the lesser of 1.5 MPa or 80% of the vapor pressure of SF₆. The Burnett (P, T) data were obtained on isochores spanning the density range 137 mol·m^–34380 mol·m^–3 and the temperature range 283 KT393 K. (The corresponding pressure range is 0.3 MPaP9.0 MPa.) The u(P, T) data below 1.5 MPa were correlated using a model hard-core, Lennard–Jones intermolecular potential for the second and third virial coefficients and a polynomial for the perfect gas heat capacity. The resulting equation of state has very high accuracy at low densities; it is useful for calibrating mass flow controllers and may be extrapolated to 1000 K. The new u(P, T) data and the new (P, T) data were simultaneously correlated with a virial equation of state containing four terms with the temperature dependences of model square-well potentials. This correlation extends nearly to the critical density and may help resolve contradictions among data sets from the literature.     

Thermodynamic Properties of He@C60

Contributions to thermodynamic properties of the endohedral He@C₆₀, resulting from motion of He inside the cage, are calculated. The contribution to C_v shows a maximum at low temperatures. The maxima for ³He@C₆₀ and ⁴He@C₆₀ are at about 41 K and 30 K, respectively.     

Thermodynamic Properties of He@C60

Abstract

Contributions to thermodynamic properties of the endohedral He@C₆₀, resulting from motion of He inside the cage, are calculated. The contribution to C _v shows a maximum at low temperatures. The maxima for ³He@C₆₀ and ⁴He@C₆₀ are at about 41 K and 30 K, respectively.     

Thermodynamic Properties of Metal-Carbon Melts

The partial and total enthalpies of mixing of Si-C and Ni-C liquid alloys at 2000 K are determined by isoperibol calorimetry. The mixing enthalpies in these systems are found to be small and negative, in agreement with earlier results. The thermochemical properties of dilute Al-C solutions are studied at 1773 K for the first time. The mixing enthalpies of metal-carbon melts are estimated from the standard enthalpies of formation of metal carbides. The calculated mixing enthalpies of liquid metal-carbon alloys agree with experimental data.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 682–686.Original Russian Text Copyright © 2005 by Kudin, Makara.     

Thermodynamic Properties of 1,1,1,2,3,3,3-Heptafluoropropane

A vapor pressure equation has been developed for 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) based on previous measurements from 202 to 375K, from which the boiling point of HFC-227ea was determined. Based on the previous pressure–volume–temperature (PVT) measurements in the gaseous phase for HFC-227ea, virial coefficients, saturated vapor densities, and the enthalpy of vaporization for HFC-227ea were also determined. The vapor pressure equation and the virial equation of state for HFC-227ea were compared with the available data. Based on the previous measurements of speed of sound in the gaseous phase for HFC-227ea, the ideal-gas heat capacity at constant pressure and the second acoustic virial coefficient of HFC-227ea were calculated. A correlation of the second virial coefficient for HFC-227ea was obtained by a semiempirical method using the square-well potential for the intermolecular force and was compared with results based on PVT measurements. A van der Waals-type surface tension correlation for HFC-227ea was proposed, based on our previous experimental data by the differential capillary rise method from 243 to 340K.     

Thermodynamic Properties of Lanthanum Chlorides

The enthalpies of atomization of LaCl, LaCl₂, and LaCl₃ are determined by measuring the vapor pressure over liquid and solid LaCl₃ and assessing the equilibrium constants of the gas-phase reactions BaCl + La = Ba + LaCl and 2BaCl + La = 2Ba + LaCl₂, using the appearance potentials of ions and the ionization potentials of the lanthanum chlorides: _at H ⁰(LaCl, 298 K) = 502.4 ± 0.5 kJ/mol, _at H ⁰(LaCl₂, 298 K) = 999.2 ± 0.8 kJ/mol, and _at H ⁰(LaCl₃, 298 K) = 1524.6 ± 2.0 kJ/mol. In addition, the enthalpies of formation of gaseous lanthanum chlorides are determined using new data on the thermodynamic functions of condensed LaCl₃ and gaseous LaCl, LaCl₂, and LaCl₃: _f H ⁰(LaCl, g, 298 K) = 48.9 ± 1.0 kJ/mol, _f H ⁰(LaCl₂, g, 298 K) = –326.6 ± 1.2 kJ/mol, and _f H ⁰(LaCl₃, g, 298 K) = –730.7 ± 2.0 kJ/mol. The ionization and appearance potentials of ions resulting from electron impact ionization of LaCl₃ are determined.     

Calculation of Thermodynamic Properties from Phase Diagram of the Pb-Zn System

The formulas for obtaining the interaction parameters of the liquid solution were first deduced from the immiscible phase diagram of binary system. Then. the relationships between activity coefficients and interaction parameters of the binary system were also deduced. Finally, thermodynamic properties of the Pb-Zn system were calculated by using these formulas.     

Experimental Evaluation of Properties of Cross-Linked Polyethylene

This article describes several aspects of the production of cross-linked polyethylene. Advantages and disadvantages of chemical, or electron beam irradiation, cross-linking processes are discussed. The material under test is thermoshrinking low density polyethylene, produced at the Megarad s.r.l. (Cassino, Italy) firm. It is mostly used as blanket insulation for low and medium electrical voltage cables and as anticorrosion protection for gas pipes. The performance of end products is verified through destructive tests. In particular, we evaluated the gel fraction, the modulus of elasticity at 150°C and the elongation percent on commercial pipes and on specimens manufactured by varying certain parameters, such as the irradiation dose.     

Physical and Photographic Properties of Polyethylene Oxides

In the presence of gelatin no adsorption of the unsubstituted polyethylene oxides {PEO) on silver or silver bromide could be detected and it must be assumed that the concentration of PEO in the adsorbed gelatin layer is the same as in the bulk emulsion. It is supposed that the adsorbed gelatin layer is made more hydrophilic by PEO. This results in: (a) an accelerated fixation of a silver bromo-iodide emulsion in a concentrated sodium sulphite solution. Especially the solution of the iodide-rich parts of the grain surface is increased probably due to a stronger hydration of the silver ions. The iodide-rich phase is important in development on account of locally formed latent image. This explains, why developers in which solution physical development plays the prominent part, are strongly activated by PEO especially in the case of iodide-containing silver bromide emulsions ; (b) a decrease of the adsorption of hydrophilic developing agents. This applies to the di-anion of hydroquinone and explains the PEO-inhibition of alkaline hydroquinone development.     

Thermodynamic Properties of HFC-236ea

The density of gaseous and liquid 1,1,1,2,3,3-hexafluoropropane (HFC-236ea) and the speed of sound in liquid HFC-236ea have been studied by a γ-attenuation technique, an ultrasonic interferometer, and an isochoric piezometer method over the temperature range of 263–423 K at pressures up to 4.05 MPa. The purity of the samples used throughout the measurements is 99.68 mol%. The pressures of the saturated vapor were measured over the same temperature range. The experimental uncertainties of the temperature, pressure, density, and speed-of-sound measurements were estimated to be within ±20 mK, ±1.5 kPa, ±(0.05–0.30)%, and ±(0.05–0.10)%, respectively.     

Thermodynamic Properties of Matrine in Ethanol

In this paper, the enthalpies of dissolution of matrine in ethanol (EtOH) were measured using a RD496-2000 Calvet microcalorimeter at 309.65 K under atmospheric pressure. The differential enthalpy (Δ_dif H _m) and molar enthalpy (Δ_sol H _m) of dissolution of matrine in ethanol were determined. And the relationship between heat and the amount of solute was also established. Based on the thermodynamic and kinetic knowledge, the corresponding kinetic equation that described the dissolution process was determined to be \fracdadt=2.36×10^-4(1-a)^1.09{\frac{{\rm d}\alpha}{{\rm d}t}=2.36\times 10^{-4}(1-\alpha )^{1.09}} . Moreover, the half-life, t _1/2 = 48.89 min, Δ_sol H _m = −12.40 kJ · mol⁻¹, Δ_sol S _m = −354.7 J · mol⁻¹ · K⁻¹, and Δ _sol G _m =  97.43  kJ · mol⁻¹ of the dissolution process were also obtained. The results show that this work not only provides a simple method for the determination of the half-life for a drug but also offers a theoretical reference for the clinical application of matrine.