An empirical method for predicting detonation pressure of CHNOFCl explosives

This paper describes a new method for prediction of the Chapman-Jouguet detonation pressures of CHNOFCl explosives using the heat of detonation, Q_det, the number of moles of gaseous products of detonation per gram of explosive, α, and the average molecular weight of gaseous products, M. The equation has the form: P_CJ=15.88α(MQ_det)^1/2ρ₀²−11.17, where P_CJ is the Chapman-Jouguet detonation pressure and ρ₀ the loading density. Calculated P_CJ by this procedure show good result with respect to measured detonation pressure for any pure or mixture of ideal and some of less ideal CHNOFCl explosives at ρ₀>0.8 g/cm³.     

Application of heat conduction calorimetry to high explosives

This paper describes some thermal analysis experiments conducted on high explosive samples. These employ differential scanning calorimetry to monitor thermal effects at elevated temperatures (around 200 °C) and heat conduction calorimetry to record thermal effects at much lower temperatures (below 100 °C).The work shows that, due to the generally high thermal stability of many high explosive compositions, heat generation rates are very low, if detectable at all, at normal storage temperatures, even when using a very sensitive instrument. The sensitivity and reproducibility of this technique has been investigated in detail by Wilker et al. [S. Wilker, U. Ticmanis, G. Pantel, Detailed investigation of sensitivity and reproducibility of heat flow calorimetry, in: Proceedings of the 11th Symposium on Chemical Problems Connected with the Stability of Explosives, Sweden, 1998] and shown to be capable of recording heat generation rates of less than a microwatt. This allows continuous measurement of decomposition processes in nitrate ester based propellants at temperatures as low as 40 °C. However, the measurement of very low levels of heat generation is difficult, time consuming and therefore expensive. If the assumption is made that the life limiting process is invariably the slow decomposition of the energetic component, this will frequently lead to very long service lifetime predictions.A number of possible complications are identified. Firstly, due to its low detection threshold, a heat conduction calorimeter may detect other reactions which will not lead to failure, but which may still dominate the heat flow signal. Secondly, the true failure process may generate little energy and be overlooked. In view of these considerations, at present it seems unwise to rely on heat conduction microcalorimetry as the only tool for the assessment of the life of high explosive energetic systems.Based on examples of life terminating processes in high explosives during storage and use, it is clear that decomposition of the energetic material is not invariably the cause of system failure. It is also by no means the only reaction that may take place in, and be observed by, a heat conduction calorimeter.     

Studies of thermokinetics in an adiabatic calorimeter

An adiabatic calorimeter in which automation of the control of the adiabatic condition and the thermogram recording is achieved in a simple way has been designed for studies of both thermochemistry and thermokinetics. A new method for specific heat measurements has been proposed and specific heats ofn-heptane were measured to test the reliability of this calorimeter.     

Theoretical studies on heats of formation,detonation properties,and bond dissociation energies of monofurazan derivatives

The heats of formation (HOFs) for a series of monofurazan derivatives were calculated by using density functional theory. It is found that the ? CN or ? N₃ group plays a very important role in increasing the HOF values of the furazan derivatives. The detonation velocities and detonation pressures of the furazan derivatives are evaluated at two different levels. The results show that the ? NF₂ group is very helpful for enhancing the detonation performance for the furazan derivatives, but the case is quite the contrary for the ? CH₃ group. An analysis of the bond dissociation energies and bond orders for the weakest bonds indicate that the substitutions of ? CN group are favorable and enhances the thermal stability of the furazan derivatives, but the ? NO₂ groups produce opposite effects. These results provide basic information for the molecular design of novel high‐energy density materials. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Quantum chemical studies on the structure and detonation properties of the fused polynitrodiazoles: New high energy density molecules

In this study, we explore the possibility that fused polynitrodiazoles act as high energy density materials. Density functional theory calculations at the B3LYP/aug‐cc‐pVDZ level were performed to predict the structure, energy of explosion (≈1.68 kcal g^?1), density (≈1.98 g cm^?3), detonation velocity (≈9.50 km s^?1), and detonation pressure (≈41.50 GPa) of model molecules. The predicted properties have been found to be promising compared with 3,4,5‐trinitro‐1H‐pyrazole, 1,3,5‐trinitro‐1,3,5‐triazinane, and octahydro‐1,3,5,7‐tetranitro‐l,3,5,7‐tetraazocane. The nature of azoles of the molecule presumably determines the geometry, stability, sensitivity, density, and detonation performance. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Substituent effects on heats of formation, group interactions, and detonation properties of polyazidocubanes

We have calculated the heats of formation (HOFs) for a series of polyazidocubanes by using the density functional theory (DFT), Hartree-Fock, and MP2 methods with 6-31G* basis set as well as semiempirical methods. The cubane skeleton was chosen for a reference compound, that is, the cubane skeleton was not broken in the process of designing isodesmic reactions. There exists group additivity for the HOF with respect to the azido group. The semiempirical AM1 method also produced reliable results for the HOFs of the title compounds, but the semiempirical MINDO3 did not. The relationship between HOFs and molecular structures was discussed. It was found that the HOF increases 330-360 kJ/mol for each additional number of the azido group being added to the cubane skeleton. The distance between azido groups slightly influences the values of HOFs. The interacting energies of neighbor azido groups in polyazidocubanes are in the range of 2.3 approximately 6.6 kJ/mol, which are so small and less related to the substituent numbers. The average interaction energy between nearest neighbor --N3 groups in the most stable conformer of octaazidocubane is 2.29 kJ/mol at the B3LYP/6-31G* level. The relative stability related to the number of azido groups of the title compounds was assessed based on the calculated HOFs, the energy gaps between the frontier orbitals, and the bond orders of the C--N3 and C--C bonds. The predicted detonation velocity of hepta- and octa-derivatives is over 9 km/s, and the detonation pressure of them is ca. 40 GPa or over.     

Heat capacity and transition phenomena of structure I and II trimethylene oxide clathrate hydrates

Heat capacities of structure I and II trimethylene oxide (TMO) clathrate hydrates doped with small amount of potassium hydroxide (x=1.8×10^–4 to water) were measured by an adiabatic calorimeter in the temperature range 11–300 K. In the str. I hydrate (TMO·7.67H₂O), a glass transition and a higher order phase transition were observed at 60 K and 107.9 K, respectively. The glass transition was considered to be due to the freezing of the reorientation of the host water molecules, which occurred around 85 K in the pure sample and was lowered owing to the acceleration effect of KOH. The relaxation time of the water reorientation and its distribution were estimated and compared with those of other clathrate hydrates. The phase transition was due to the orientational ordering of the guest TMO molecules accommodated in the cages formed by water molecules. The transition was of the higher order and the transition entropy was 1.88 J·K^–1(TMO-mol)^–1, which indicated that at least 75% of orientational disorder was remaining in the low temperature phase. In the str. II hydrates (TMO·17H₂O), only one first-order phase transition appeared at 34.5 K. This transition was considered to be related to the orientational ordering of the water molecules as in the case of the KOH-doped acetone and tetrahydrofuran (THF) hydrates. The transition entropy was 2.36 JK^–1(H₂O-mol)^–1, which is similar to those observed in the acetone and THF hydrates. The relations of the transition temperature and entropy to the guest properties (size and dipole moment) were discussed.Contribution No 57 from the Microcalorimetry Research CenterThe authors would like to express their sincere thanks to the Nissan Science Foundation for their financial support.     

Determination of heats of the thermal gas-phase formation of intermediates with overlapping spectra

The previously proposed procedure for the determination of heats of thermal gas-phase reversible reactions using kinetic spectroscopy was extended for the case of the formation of two intermediate species with overlapping UV spectra. The model problem was solved, and the error of the method was estimated. Applicability of the method was shown for the reversible formation of trimethylenemethane (TMM) and but-1-ene-2,4-diyl from methylene-cyclopropane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 1998.     

新型高能炸药热分解研究进展

炸药的热分解对其安定性和库存可靠性等研究是很重要的。本文总结了国内外有关TNAZ(1,3,3-三硝基氮杂环丁烷)、NTO(3-硝基-1,2,4-三唑-5-酮)、LLM-105(1-氧-2,6-二氨基-3,5-二硝基吡嗪)、FOX-7(1,1-二氨基-2,2-二硝基乙烯)等几种新型高能炸药的热分解研究。分别从理论上、实验上阐述了它们的热分解研究现状,指出了以前研究中存在的问题,预测了钝感高能炸药热分解的发展前景。参考文献32篇。     

Theoretical studies on high energetic density nitramine explosives containing pyridine

The insensitive property of explosives containing pyridine is combined with the high energy of nitramine explosives,and the concept of new nitramine explosives containing pyridine is proposed,into which nitramine group with N N bonds is introduced as much as possible.Based on molecular structures of nitramine compounds containing pyridine,density functional theory(DFT) calculation method was applied to study designed molecules at B3LYP/6-31+G(d) level.The geometric and electronic structures,density,heats of formation(HOF),detonation performance and bond dissociation energies(BDE) were investigated and comparable to 1,3,5-trinitro-1,3,5-triazinane(RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).The simulation results reveal that molecules B and D perform similarly to traditionally used RDX.Molecule E outperform RDX,with performance that approach that of HMX and may be considered as potential candidate of high energy density compound(HEDC).These results provide basic information for molecular design of novel high energetic density compounds.     

Heat capacity measurement of ZrOx and (Zr1−yNby)Ox from 325 TO 905 K

Heat capacities of zirconium-oxygen alloys, ZrO_x (x=0.17, 0.20, 0.28 and 0.31), and those of niobium doped alloys, (Zr_1–yNb_y)O_x (x=0.17 and 0.28, y=0.005 and 0.01), were measured from 325 to 905 K by an adiabatic scanning calorimeter. Two kinds of heat capacity anomalies were observed for all samples. The anomaly at higher temperatures was assigned to be due to an order-disorder rearrangement of oxygen atoms. Another anomaly at lower temperatures was due to a non-equilibrium phenomenon. The entropy change due to the order-disorder transition for Zr-O solid solution at higher temperature obtained from this experiment was compared with the theoretical value. The transition temperature, transition enthalpy and entropy changes due to the order-disorder transition decreased with increasing niobium contents, indicating that arrangement of oxygen atoms in lower temperature phase may be partially disordered by the interaction between niobium and oxygen atoms.

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Zusammenfassung Mittels eines adiabatischen Scanning-Kalorimeters wurden im Temperaturbereich 325–905 K die Wärmekapazitäten von Zirkonium-Sauerstoff Legierungen ZrO, (mit x=0.17, 0.20, 0.28 und 0.31) und von mit Niob versetzten Legierungen (Zr_1–yNb_y)O_x gemessen. Für alle Proben konnten zwei Arten von Wärmekapazitätsanomalien beobachtet werden. Die Anomalie bei höherer Temperatur wird einer Ordnung-Unordnung-Umwandlung von Sauerstoffatomen zugeschrieben. Eine andere Anomalie bei niedrigerer Temperatur steht mit einer Nicht-Gleichgewichtserscheinung in Zusammenhang. Die Entropieänderung der Ordnung-Unordnung-Umwandlung für einen Zr-O Mischkristall aus diesem Experiment wurde mit dem theoretischen Wert verglichen. Umwandlungstemperatur, Umwandlungsenthalpie- und Entropieänderungen der Ordnung-Unordnung-Umwandlung nehmen mit steigendem Niobgehalt ab, was zeigt, daß die Anordnung der Sauerstoffatome in Phasen mit niedrigerer Temperatur partiell durch die Wechselwirkungen zwischen Niob- und Sauerstoffatomen gestört werden kann.

     

VLW equation of state of detonation products

Based on the virial theory, we proposed VLW equation of state of detonation products (VLW EOS). Its basic theory and applications were described. The distinct features of the VLW EOS were First, the detonation performance of the new high energy density materials could be predicted more reliably. Second, it had extensive application. The detonation parameters of both the condensed high energy density materials and the gaseous fuel air explosives could be calculated. Moreover, combustion performance of propellants could also be precisely calculated. The calculation results were satisfactory. Supported by the National Natural Science Foundation of China (Grant No. 1860382), and the Science Foundation of China Academy of Engineering Physics (Grant Nos. 920513, 9401009 & 960577)     

A new calorimeter for simultaneous measurement of isotherms and heats of adsorption

A new calorimeter designed for simultaneous measurements of heats and isotherms of gas adsorption and desorption systems is presented. It consists of a volumetric/manometric gas adsorption instrument, the adsorption vessel of which is placed within a second vessel filled with inert gas. This gas acts as a sensor, as not only its temperature but also its pressure is increased if heat is released from the adsorption vessel via the sensor gas to its thermostated surroundings. Indeed, the time integral of the sensor gas pressure signal turned out to be strongly related to the total heat released from the adsorption vessel.A basic theoretical equation of the measurement procedure is given. Results of numerous calibration measurements are presented. The question of what type and amount of sensor gas should be used to achieve high sensitivity of the instrument is discussed.Two examples of measurements of heats of adsorption and adsorption isotherms are given, namely adsorption of N₂ on alumina oxide (CRM-BAM-PM-104) at 77 K and CO₂ on zeolite Na13X and wessalite DAY both at 298 K.     

Effects of the type of calorimeter and the use of plasticizers and hydrophobizers on the measured hydration heat development of FGD gypsum

Thermal phenomena at the hydration of calcium sulphate hemihydrate (CaSO₄·0.5H₂O) are investigated in the paper. Time development of hydration heat of β-calcium sulphate hemihydrate prepared from flue gas desulphurization (FGD) gypsum is determined using two different types of calorimeter, namely the differential calorimeter DIK 04 and the isothermal heat flow calorimeter KC 01, and the differences in measured data analyzed. Then, the effects of plasticizers and hydrophobizers on the hydration process of analyzed gypsum mixtures are studied.     

Thermodynamic Investigation of the Azeotropic Mixture Composed of Water and Benzene

The molar heat capacity of the azeotropic mixture composed of water and benzene was measured by an adiabatic calorimeter in the temperature range from 80 to 320 K. The phase transitions took place in the temperature range from 265.409 to 275.165 K and 275.165 to 279.399 K. The phase transition temperatures were determined to be 272.945 and 278.339 K, which were corresponding to the solid-liquid phase transitions of water and benzene, respectively. The thermodynamic functions and the excess thermodynamic functions of the mixture relative to standard temperature 298.15 K were derived from the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to temperature.     

Determination of cell asymmetry in temperature-modulated DSC

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.On leave from Toray Industries, Inc., Otsu, Shiga 520, JapanOn leave from Toray Research Center, Inc., Otsu, Shiga 520, JapanThis work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U. S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC0S-96OR22464. Support for instrumentation came from TA Instruments, Inc. and Mettler-Toledo, Research support was also given by ICI Painls, and Toray Industries, Inc.     

Free and bound water influence on Spirulina platensis survival

The heat effects arising at heating of Spirulina platensis cell culture containing different quantity of water (from 98.2 to 10.5 mass% H₂O) have been studied. The hydration of Sp. pl. cells determined by the method of microcalorimetry at 25°C (Δn) was equal to 0.32±0.02 g H₂O/g of dry biomass. The heat (–Q) evolved by cells in the temperature range 5–52°C decreased exponentially at decrease of mass% H₂O and reached zero value at 30.5±3.0 mass% H₂O. The total heat of cell denaturation did not change in the range 98.2–40.5 mass% H₂O and it sharply dropped at lower values of water.     

Heat Capacity Measurement of Boron Nitride-filled Polybenzoxazine: The composite structure-insensitive property

Specific heat capacity of boron nitride-filled polybenzoxazine has been investigated by using temperature-modulated differential scanning calorimetry, TMDSC, to study that it is a composite structure-insensitive property, i.e. independent of the degree of filler network formation. Many aspects of boron nitride filler such as particle size, particle surface area, particle shape, and filler loading are investigated. At the same filler loading, we observe insignificant change in composite specific heat capacity due to the effect of particle size, particle surface area, and particle shape. Filler loading is found to be the only aspect of filler that can change the specific heat capacity of this filled system. A linear relationship between the composite heat capacities and filler loading is observed and can be predicted by the rule of mixture with an error within ±1%. Within the temperature range betwen 0 and 80°C, the temperature dependent heat capacity of this composite can simply be expressed in the form of a linear equation: C _p=A+BT.This revised version was published online in November 2005 with corrections to the Cover Date.     

Calorimetric study of the immersion heats of lead(II) and chromium(VI) from aqueous solutions of Colombian coffee husk

Summary This work shows the result of the study of the Pb(II) and Cr(VI) ions adsorption by means of a Calvet type calorimeter of heat conduction that can operate at 150şC. The calorimeter was electrically calibrated to establish its sensitivity and reproducibility, obtaining K=12.95±0.05 W V^-1 and chemically it was examined with tris-(hydroxymethyl)-aminomethane (THAM)-HCl system, obtaining ΔH= -30.91±0.03 kJ mol^-1. The activated carbon sample obtained from coffee husk and the calorimetric results obtained were related to other techniques used to perform this type of studies.     

Theoretical investigation on density,detonation properties,and pyrolysis mechanism of nitro derivatives of benzene and aminobenzenes

Nitro derivatives of benzene and aminobenzenes are optimized at the DFT‐B3LYP/6‐31G* level. The heat of formation (ΔH_f) and crystal theoretical density (ρ) are estimated to evaluate the detonation properties using the modified Kamlet–Jacobs equations. Thermal stability and the pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies (BDE) at the unrestricted B3LYP/6‐31G* level. The kinetic parameter and the static electronic structural parameters can be used to predict the stability and the relative magnitude of the impact sensitivity of homologues. According to the quantitative standard of the energy and the stability as an HEDC, the title compounds having more than four nitro groups satisfy this requirement. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009