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The article presents experimental results of research concerning the action of weak electric and magnetic fields on physicochemical transformations in samples of hard coal with a previously destabilized microstructure. The actions of electric and magnetic fields are fundamentally different by many parameters. It has been shown that after treatment with a weak electric field, coal posted an electret potential with an anomalously continuous charge relaxation. Compared to untreated coal samples, the rate of methane emission from methane-saturated samples is maximum for long-flame coal and decreases as it approaches anthracite. The electric field stimulates the grinding of microparticles, a decrease in the maximum gas outlet temperature, a decrease in the enthalpy value in the formation of a new phase, and an increase in the chemical activity of treated coal samples. Fundamentally different results were obtained with magnetic stimulation of coals. In X-ray diffractograms of coal powders after magnetic treatment, the values of the maxima of the main peaks are the largest in comparison with the original samples and those treated with an electric field, which is consistent with an increase in the size of microparticles in a magnetic field. There is an increase in the heat of combustion and a decrease (by 5 times) in the loss of coal mass during heating. [ABSTRACT FROM AUTHOR]

The properties of azido-acetylenic derivatives of s-triazine containing various combinations of propynyloxy, propynylamino, N-methyl-propynylamino, and azido groups have been studied, and their enthalpy of formation in the condensed phase, density, and impact and friction sensitivities have been determined. Based on these data, the energy parameters of detonation, combustion, and adiabatic transformation for individual compounds and their compositions with the binder SKI-3 isoprene rubber have been calculated. The results of the integrated experimental and theoretical studies suggest a high heat of combustion of the investigated individual compounds and compositions based on them. [ABSTRACT FROM AUTHOR]

Accurate evaluation of combustion enthalpy is of high scientific and industrial importance. Although ab-initio computation of the heat of reactions is one of the promising and well-established approaches in computational chemistry, reliable and precise computation of heat of combustion reactions by ab-initio methods is surprisingly scarce in the literature. A handful of works carried out for this purpose report significant inconsistencies between the computed and experimentally determined combustion enthalpies and suggest empirical corrections to improve the accuracy of the ab-initio predicted data. The main aim of the present study is to investigate the reasons behind those reported inconsistencies and propose guidelines for a high-accuracy estimation of heat of reactions via ab-initio computations. We show comparably accurate prediction of combustion enthalpy of 40 organic molecules based on a DSD-PBEP86 double-hybrid density functional theory approach and CCSD(T)-F12 coupled-cluster computations, with mean unsigned errors with respect to experimental data being below 0.5% for both methods. [ABSTRACT FROM AUTHOR]

The heat of combustion and the enthalpy of formation of 7,7′-bis(terfurazan[3,4-b:3,4′-d:3″,4″-f]azepine (I) and 1,1′-dioxide-7,7′-bis(terfurazan[3,4-b:3,4′-d:3″,4″-f] azepine (II), were experimentally determined. Product I was studied by X-ray diffraction analysis, and its crystallographic characteristics were determined. The efficiency of using compounds I and II as components of solid composite propellants was analyzed, and the type of compositions in which they are more effective than HMX was determined. [ABSTRACT FROM AUTHOR]

The standard enthalpy of formation of 1,4-diethynylbenzene experimentally to be 500.6 ± 6.7 kJ/mol. Calculations show that 1,4-diethynylbenzene has a relatively high adiabatic combustion temperature (about 1970 K at a pressure of 5 atm) and very high heat of combustion in oxygen (42 MJ/kg); therefore, 1,4-diethynylbenzene can be used as the basis to develop an effective dispersing agent of solid fuel that provides an adiabatic combustion temperature of up to 2500 K at a heat of combustion far exceeding the values provided by HMX and the other azides of N-heterocycles previously proposed for this purpose. [ABSTRACT FROM AUTHOR]

Thermal decomposition of disubstituted salts of high-energy 5,5'-azotetrazole (sodium, ammonium, hydrazine, guanidine, aminoguanidine, and triaminoguanidine salts) under isothermal and nonisothermal conditions in solid and liquid phases is studied. The relationship between the basicity and the thermal stability of the 5,5'-azotetrazole salt is demonstrated. The boundary of possible existence of 5,5'-azotetrazole salts in terms of the basicity index pKa is determined. Gaseous and condensed products of decomposition are analyzed, and a mechanism of thermal decomposition of 5,5'-azotetrazole is proposed. The enthalpies of formation of some 5,5'-azotetrazole salts are determined, and the most reliable values are chosen on the basis of the analysis of the data obtained in the present study and those available in publications. [ABSTRACT FROM AUTHOR]

The heat of combustion and the standard enthalpy of formation of 3,4-bis(4-azidofurazan-3-yl)furoxan (DAzFF) and 4-azido-4″-nitro-3,3′:4′,′3′-terfurazan (AzNTF) were experimentally determined. Thermodynamic analysis was performed to investigate the efficiency of these compounds as potential components of metal-free solid composite propellants based on an active binder with the possibility of introducing an additional small amount of oxidizer with a high oxygen content, e.g., ammonium perchlorate. [ABSTRACT FROM AUTHOR]

We have investigated under laboratory conditions the effect of the combustion site modeled by a steppe combustible on wood specimens of different profiles (flat and cylindrical specimens) with the use of IR diagnostics. Experiments were carried out with the use of a JADE J5330SB infrared imager in the spectral range of 2.64-3.25 μm. The temperature profiles on the surface of wood specimens of different forms (flat and cylindrical specimens) have been obtained and the heat-stressed parts under the action of the model combustion site imitating a low-intensity low forest fire have been determined. [ABSTRACT FROM AUTHOR]

Results of experimental studies on pyrolysis of brown coals of the Lelchitsy deposit, which were conducted on Laboratory setups in stationary and moving layers for producing high-caloric energy carriers, are presented. The yield of the pyrolysis products is determined; the chemical composition of solid, liquid, and gaseous products of thermochemical treatment is considered. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the thermochemistry of heteroatomic compounds. The study describes a proposed approach called enthalpy of combustion of organic compounds. It also claims that the aforementioned approach is effective in finding out the heat of combustion of heteroatomic organic compounds and biorganic compounds.

The progression of chemical reactions is determined by both thermodynamics and kinetics factors. Micropyretic/combustion reaction is a cascade of many chain chemical reactions and thermodynamics and kinetics of the ignition reaction are expected to greatly affect the overall reaction outcome. Furthermore, the stability of the sequential reaction and its progression are correspondingly changed once micropyretic parameters are changed. Improper ignition of micropyretic reaction provides either excessive or insufficient external energy, thus causes over-heating or extinguishing of the combustion front during propagation and therefore the heterogeneous structures. To achieve the homogeneous micropyretic reaction, it is thought possible to control ignition energy. A numerical study on the correlation of thermodynamics and kinetics factors of ignition on the stable Ni + Al reaction and the required ignition energy is reported in this study. The influences of activation energy ( E), enthalpy of the micropyretic reaction ( Q), pre-exponential factor ( K o), thermal conductivity ( K), heat capacity ( C p ), and thermal activity of the reactants and product, on the temperature/heat loss at the ignition spot and the length of pre-heating zone are respectively studied. It is found that the activation energy and heat capacity have the most significant effects on the ignition energy. The required ignition energy is increased by 44.0% and 23.9%, respectively, when the activation energy and the heat capacity are both increased by 40.0% [ABSTRACT FROM AUTHOR]

The response function of the burning rate of a solid propellant to periodically varying pressure is found with allowance for the cross-flow (erosion) effect in the linear approximation of the phenomenological theory of nonsteady combustion. Numerical results are obtained for the simplest propellant model with the minimum number of parameters. An elementary acoustic perturbation (planar monochromatic traveling acoustic wave) is considered. The role of steady-state and nonsteady cross-flow components at low and high values of the erosion ratio is elucidated. [ABSTRACT FROM AUTHOR]

Combustion of a fuel oil droplet on a hot oblique surface, whose temperature varies between 350 and 700° C, has been studied experimentally. The influence of the heat conductivity of the wall and its roughness, as well as of the droplet-surface contact angle on the fuel combustion time has been determined. The data on the change in the droplet mass in the process of combustion are presented and chromatographic analysis of the fuel has been performed [ABSTRACT FROM AUTHOR]

Examines the combustion of a disk compacted from a mixture of solid reactants. Combustion front propagated from the central region of the sample toward the periphery; Coefficient of heat transfer from the sample boundary into the environment; Evidence that the temperature behind the front are substantially lower than the combustion temperature.