Calculation of transport properties and intermolecular potential energy function of the binary mixtures of H2 with Ne,Ar, Kr and Xe by a semi-empirical inversion method

The present paper contains inspection of the improved corresponding states principle for transport properties of hydrogen and the binary mixtures of hydrogen with Ne, Ar, Kr and Xe. The set of corresponding states parameters has been defined by a complex numerical analysis of a carefully selected body of experimental data. The obtained correlations for the reduced orientation-averaged diffusion and viscosity collision integrals are restricted to low densities in a temperature range from T = ?/k to the onset of ionization. These equations have been inverted directly to give the isotropic and effective intermolecular potential energy curve for binary mixtures of H₂ with Ne, Ar, Kr and Xe corresponding to the viscosity collision integrals. The results are then used to obtain the best Morse-Spline-Van der Waals (MSV) potential parameters. Our inverted potential energies have been compared with experimental intermolecular potentials that were obtained by molecular beam scattering and infrared spectroscopic measurements. In this research, the Chapman–Enskog and Wang Chang-Uhlenbeck-de Boer (WCUB) version of kinetic theory have been used in conjunction with our inverted potential energies to reproduce viscosity, diffusion, thermal conductivity and thermal diffusion factor of binary mixtures of H₂ with Ne, Ar, Kr and Xe in a wide temperature range for equimolar composition. As the deviation plots illustrate, our obtained intermolecular potential energies (on the basis of the algorithm presented in the inversion process) represent the low-density transport properties of binary mixtures of H₂ with Ne, Ar, Kr and Xe within their expected experimental uncertainties. Close agreement between the predicted values and the literature results of transport properties demonstrates the predictive power of the inversion scheme.     

Temperature dependence of viscosity and density of viscous liquids determined from thermal noise spectra of uncalibrated atomic force microscope cantilevers

We demonstrate that the thermal response of uncalibrated atomic force microscope cantilevers can be used to extract the density and the viscosity of viscous liquids with good accuracy. Temperature dependent thermal noise spectra were measured in water/poly(ethylene glycol) mixtures. Empirical parameters characteristic of the resonance behavior of the system were extracted from data recorded for one of the solutions at room temperature. These parameters were then employed to determine both viscosity and density values of the solutions simultaneously at different temperatures. In addition, activation energies for viscous flow were determined from the viscosity values obtained. The method presented is both fast and reliable and has the potential to be applied in connection with microfluidic systems, making macroscopic amounts of liquid and separate measurements with a viscometer and a densimeter redundant.     

Experimental and modeling study of the oxidation of benzene

This paper describes an experimental and modeling study of the oxidation of benzene. The low‐temperature oxidation was studied in a continuous flow stirred tank reactor with carbon‐containing products analyzed by gas chromatography. The following experimental conditions were used: 923 K, 1 atm, fuel equivalence ratios from 1.9 to 3.6, concentrations of benzene from 4 to 4.5%, and residence times ranging from 1 to 10 s corresponding to benzene conversion yields from 6 to 45%. The ignition delays of benzene–oxygen–argon mixtures with fuel equivalence ratios from 1 to 3 were measured behind shock waves. Reflected shock waves permitted to obtain temperatures from 1230 to 1970 K and pressures from 6.5 to 9.5 atm. A detailed mechanism has been proposed and allows us to reproduce satisfactorily our experimental results, as well as some data of the literature obtained in other conditions, such as in a plug flow reactor or in a laminar premixed flame. The main reaction paths have been determined for the four series of measurements by sensitivity and flux analyses. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 503–524, 2003     

The mixing properties of hexafluorobenzene with carbon tetrachloride and with perfluoromethylcyclohexane

Excess thermodynamic functions (free energies, enthalpies and entropies of mixing) have been obtained from measurements of vapour pressures, together with excess volumes of mixing, for mixtures of hexafluorobenzene with carbon tetrachloride and with perfluoromethyl-cyclohexane (tetradecafluoromethylcyclohexane). Deviations from thermodynamic ideality are large, although the systems are completely miscible. Critical temperatures of the mixtures are also reported. A correlation between the data, anticipated from a simple model for mixtures of asymmetric molecules, does not obtain.     

A comparison of two single-pulse shock-tube techniques: The thermal decomposition of ethyl chloride and n-propyl chloride

This investigation presents a detailed examination of the relative reliability of the comparative and absolute rate methods as they are applied to kinetic studies in the single-pulse shock tube. For this purpose two previously studied reactions, the thermal elimination of HCl from ethyl chloride and n-propyl chloride, were selected and mixtures of these compounds were shock heated to temperatures in the range of 960°-1100°K. The experimental results were analyzed by both methods and the rate constants obtained from these analyses are compared with those of previous studies. The advantages and shortcomings of both methods are noted and it is concluded that reliable kinetic data can be obtained by the absolute rate (isolation technique) method with careful examination of the gas-dynamic flow conditions and taking cognizance of the incident shock deceleration. The limitations of the comparative rate technique encountered in the present study were similar to those detailed in previous investigations.     

Advanced kinetic tools for the evaluation of decomposition reactions

Summary An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMR_ad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures).     

Kinetic Studies of the Thermal Decomposition of KDNBF, a Primer for Explosives

KDNBF (potassium 4,6-dinitrobenzofuroxan) has been used as a primer explosive in igniters and detonators for many years. Considerable information about the sensitivity of KDNBF to various stimuli, such as impact, friction, shock and electrostatic charge, is known. However, the thermal sensitivity of KDNBF has been relatively unexplored. Hence, there is very little information available concerning the fundamental thermal properties of KDNBF. Therefore, as part of an extensive thermal hazard assessment, DSC, TG, accelerating rate calorimetry (ARC) and heat flux calorimetry (HFC) measurements have been undertaken on KDNBF. The results demonstrate that KDNBF decomposes via a multi-step exothermic process directly from the solid state. The decomposition process does not appear to depend on the nature of the atmosphere, except in the final stage of the TG decomposition in air, where remaining carbonaceous material is converted to CO₂. The first stage of the decomposition is sufficiently rapid that ignition occurs if too large a sample is used. Dynamic and isothermal methods were used to obtain the kinetic parameters and a range of activation energies were obtained, depending on the experimental conditions. The kinetic results have been analyzed in terms of various solid state decomposition models. This revised version was published online in August 2006 with corrections to the Cover Date.     

Experimental and modeling study of the oxidation of 1‐butyne and 2‐butyne

Ignition delays were measured behind shock waves in the cases of hydrocarbon–oxygen–argon mixtures containing 1‐butyne or 2‐butyne (1 or 2% of hydrocarbons for equivalence ratios from 0.5 to 2). Reflected shock waves permitted to obtain temperatures from 1100 to 1600 K and pressures from 6.3 to 9.1 atm. A detailed mechanism of the reactions of 1‐butyne and 2‐butyne has been explained in the line of the mechanism developed previously for the reaction of C₃–C₄ unsaturated hydrocarbons (propyne, allene, 1,3‐butadiene) [Int J chem Kin 1999, 31, 361]. It is based on the most recent kinetic data values published in the literature and is consistent with thermochemistry. This mechanism has been validated by comparing the results of our simulations to the experimental results obtained for ignition delays in our shock tube and to measurements of species obtained during thermal decomposition [Int J Chem Kin 1995, 27, 321; J Phys Chem 1993, 97, 10977]. The main reaction pathways have been derived from flow‐rate and sensitivity analyses. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 172–183, 2002; DOI 10.1002/kin.10035     

Tomography and elemental analysis using neutrons in transmission

Expressions for the calculation of minimum detectable mass and length fractions of elements, compounds and mixtures in a sample using neutron attenuation coefficients are derived, based on previous work done with photon attenuation coefficients. These expression allow quantitative information about elemental concentration to be extracted from neutron transmission measurements and neutron transmission tomography. Calculations are carried out for the detectable mass fraction of hydrogen in a number of sample matrices of industrial interest and of elements in a water matrix highlighting the differences with photon attenuation measurements. Results are presented for three neutron energies, cold (0.001 eV), thermal (0.025 eV) and fast (14 MeV).     

Thermodynamics of mixed electrolyte solutions. VIII. An isopiestic study of the ternary system KCl−MgCl2−H2O at 25°C

The osmotic coefficients of aqueous solutions of mixtures of potassium and magnesium chlorides were derived from isopiestic measurements at 25°C. The isopiestic data were treated by the methods of both Scatchard and Friedman, and the results obtained agree very well over the ionic strength range of 1–5. Interaction coefficients were obtained from both formalisms. Excess free energies of mixing were calculated and compared with those of similar systems.     

Thermal decomposition of some metal sulphates

The thermal decomposition temperatures of some metal sulphates (iron, copper, cobalt, nickel, zinc and lead sulphates) have been investigated by TG and DTA. The mechanism of decomposition of these sulphates is discussed, making use of additional information obtained from isothermal studies and X-ray diffraction measurements. The activation energies of these reactions were calculated and found to increase, with almost the same increments, in the order Zn<Fe<Co<Ni<Cu.     

Synthesis,characterization and thermal decomposition of copper(II), nickel(II) and cobalt(II) complexes of 3-amino-5-methylpyrazole Schiff-bases

Copper, nickel and cobalt complexes of Schiff-bases, obtained by condensation of 3-ammo-5-methylpyrazole with salicylaldehyde; 2,3-dilhydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, and 2-hydroxynaphthaldehyde, were synthesized and characterized. Analytical data and electrical conductivity measurements indicate the formation of 1:1 and 1:2 complexes. Magnetic moments and spectral properties support O_h, T_d, penta-coordinate and square planar structures for the complexes. T.g.a., d.t.g., d.t.a. and d.s.c. studies on the formed complexes show three and four decomposition steps. Complexes obtained by direct reaction between the metal salt and the corresponding Schiff-base have magnetic moments, stereochemistry and thermal properties which are different from their analogues obtained by template synthesis. Activation energies E_a and enthalpies ΔH, associated with thermal decomposition of the complexes, were also calculated. Some of the complexes have been tested for antimicrobial activity.     

Excess Gibbs energies of mixing in the system H2O−NaCl−Na2SO4−MgSO4 at 298.15°K

Isoptestic results are reported for aqueous mixtures of Na₂SO₄ with solutions of NaCl+MgSO₄ at constant mole ratio of NaCl:MgSO₄. The Gibbs energies of mixing obtained from these measurements are combined with earlier results on the same system to derive diagrams giving Gibbs energies of mixing in the quaternary system at constant ionic strengths of 1 and 6. The osmotic coefficients of the mixture are compared with those predicted from the theory of Reilly and Wood.     

The thermal stability of copolymers of allyl alcohol with acrylonitrile and methyl methacrylate

Homopolymerization of allyl alcohol (AA) initiated by gamma rays and copolymerization of AA with methyl methacrylate (MMA) and acrylonitrile (AN) were investigated. The thermal stabilities of the homopolymers and copolymers were determined and their degradation activation energies calculated. The copolymers, P(AA/AN), obtained from AA + AN monomers were more stable thermally than those copolymers, P(AA/MMA), formed from AA + MMA monomer mixtures.     

Zur Kinetik der chloridkatalysierten thermischen Zersetzung von Ammoniumnitrat

On the Kinetics of Chloride Catalyzed Thermal Decomposition of Ammonium Nitrate The activation energies and frequency factors of thermal decomposition reactions of ammonium nitrate and mixtures of ammonium nitrate and chloride have been determined by volumetric measurement of the gaseous decomposition products evolved on linear hcating. The rate constants obtained from these values show that thermal stability and initial decomposition temperature of ammonium nitrate are considerably reduced by addition of small amounts of chloride.     

The measurement of rates of initiation in the thermal polymerization of styrene

The thermal initiation of the polymerization of styrene has been studied at temperatures from 60–140°C using DPPH as a free radical scavenger. Rates of free radical formation, measured by the decrease in absorbance at 525 nm, are about seven times greater than those obtained from inhibition period measurements. The difference is probably due to the much greater reactivity of trinitrobenzene derivatives towards diradicals from styrene than towards styryl monoradicals. This view is supported by the different behaviour of the AIBN initiated polymerization of styrene in the presence of DPPH. The thermal initiation process has a low efficiency of initiation and the activation energy is 121 kJ/mole. The results strongly support the diradical mechanism for the thermal initiation of styrene polymerization.     

Thermodynamics of aqueous mixtures of nonelectrolytes. I. Excess volumes of water-n-alcohol mixtures at several temperatures

Excess volumes of binary mixtures of water with methanol, ethanol and 1-propanol were obtained from density measurements at 5 degree intervals from 15 to 35°C over the entire composition range. Excess thermal expansion coefficients, partial molar excess volumes, and expansibilities at 25°C were derived from the results. The significance of these values is discussed in relation to hypothesized structural changes in the mixtures.     

Kinetic analysis of thermal degradation of recycled polycarbonate/acrylonitrile-butadiene-styrene mixtures from waste electric and electronic equipment

The study of properties in waste polymeric materials is important for a further recycling and eventual reuse. The determination of thermal properties of PC-ABS mixtures obtained from waste electric and electronic equipment (WEEE) by using thermogravimetric analysis (TGA) has been carried out in this work. Kinetic parameters, such as apparent activation energies, have been calculated by using the autocatalytic model, which has shown a good correlation with experimental data. A good agreement between calculated and experimental results was observed for PC-based mixtures. This is an indication that the addition of a high amount of ABS permits the creation of a network formed by elastomeric domains which leads to a general increase in heterogeneity of the mixture.     

Mineral-carbon sorbents based on post-decarbonization lime and mixture of hydrocarbons

Summary An attempt was made to obtain mineral-carbon sorbents from waste products of petrochemical industry: lime from the decarbonization of river water to be used in technology and hydrocarbon wastes obtained in the treatment of industrial waste waters. The sorbents were prepared by thermal decomposition of mixtures of the mineral and carbon components. In order to optimize the preparation conditions, physicochemical studies were performed of both the mineral matrix and the mineral-carbon sorbents. Adsorption measurements involving nitrogen, water, and benzene as adsorbates were used for determining the parameters of porous structure of the obtained materials and their hydrophilic-hydrophobic properties. The properties influencing the sorptive properties of the organic compounds present in the petrochemical wastes were pointed out.     

Aqueous solutions containing amino acids and peptides. Part 22 - free energetic and enthalpic virial coefficients at 25°C for some interactions of isofunctional amides

The excess free energies of aqueous solutions containing N-acetyl-L-prolinamide, N-acetyl-N-methyl-L-alaninamide and binary mixtures of these have been determined at 25°C from isopiestic measurements. The corresponding excess enthalpies for the last two systems have been obtained from enthalpy of dilution measurements. The results derived have been considered using the Savage-Wood group additivity principle, and it is shown that this works remarkably well although deviations are observed which are probably significant.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.