共查询到20条相似文献,搜索用时 46 毫秒
1.
M. Pandey S. Jha R. Kumar S. Mishra R. R. Jha 《Journal of Thermal Analysis and Calorimetry》2012,107(1):135-140
The burning rate of AN–HTPB-based propellant catalysed with chromium salt has been studied using conventional strand burner
under the various pressure range, i.e. from atmospheric pressure to 6.897 MPa and verified with Piobert law, i.e. r = aP
n
. At atmospheric pressure, the burning rate AN–HTPB propellant was being accelerated with the chromium-based catalysts used.
In case of lead chromate-catalysed system, burning rate was observed 2.655 times higher than burning rate (r = 0.200 mm s−1) of virgin AN–HTPB propellant sample. However, the Copper chromate-catalysed propellant burned with slower rate (r = 0.160 mm s−1) than the virgin AN–HTPB propellant sample. The burning rate of all catalysed propellant samples are found to be the pressure
sensitive and accelerated higher with rise of pressure. The highest burning rate (r = 2.422 mm s−1) was recorded with ammonium dichromate and lowest (r = 1.40 mm s−1) with lead chromate-catalysed propellant sample with the rise of pressure up to 6.897 MPa at different pressures. A linear
relationship was observed between the burning rate and pressure rise which followed the Piobert law, i.e. r = aP
n
. The pressure index (n) values of AN–HTPB-based samples were calculated higher when catalysed with ammonium dichromate, Copper Chromate, Cr2O3, Potassium dichromate (n = 0.525, 0.555, 0.429, and 0.408 respectively) and lower (n = 0.226) with lead chromate compared to virgin sample (n = 0.405). Higher value indicates the positive effect on accelerating the burning rate with catalyst at higher pressure ranges. 相似文献
2.
M. M. Goncharenko V. V. Lobanov P. E. Strizhak 《Theoretical and Experimental Chemistry》2005,41(5):290-294
The potential energy profile of the Pt⋯CO and Pt2⋯CO systems was calculated within the formalism of density functional theory. It was shown that bonding in these systems is
only achieved after a triplet-singlet transition, which is unusual for the interaction of a CO molecule with the surface of
a platinum crystal.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 278–282, September–October, 2005. 相似文献
3.
Uduzei F. Edgal 《Journal of mathematical chemistry》2007,42(4):1101-1134
We develop general expressions for partial nearest neighbor probability density functions (PNNPDF’s) for equilibrium multi-component
systems, valid for arbitrary partial densities, temperatures, and interaction potentials; thus providing an alternative means
of describing structure at the microscopic (atomic scale) level for multi-component material systems. This paper thus complements
an earlier paper (U.F. Edgal and D.L. Huber, J. Phys. Chem. B 108, 13777–13788 2004) in the analytical investigation of the classical statistical thermodynamics of multi-component systems.
The connection between PNNPDF’s and the commonly employed partial m-body distribution functions is detailed. Results for PNNPDF’s
and partial m-body distribution functions applicable for the poisson-distributed multi-component system and the low density
binary mixture of hard spheres are provided. The statistical geometry of the systems is further studied through a brief investigation
of particle clustering. A major hallmark of the above investigation involves the several multiple integrals and multiple sums
encountered, that were quite formidable to perform, even in the absence of particle interactions. 相似文献
4.
The stability of hydrogen-bonded complexes, DMF–H
n
CCl4−n
(n = 1–3), has been investigated by several theoretical methods including the MP2 level of ab initio theory at various basis
sets from 6-31+G* to 6-311++G**. Two stable configurations (respectively a and b) were obtained for each complex with no imaginary frequencies. The minimum energy structure of these complexes has also been
analyzed by means of the atoms in molecule theory at MP2/6-311++G** level. It is found that C–H···O hydrogen bonding exists
in these systems and that the intensity of HB interaction gradually increases with successive chlorination. Computed results
indicate that these complexes automatically assemble into different stable configurations. For the complexes under consideration,
their stabilities can be mainly ascribed to the intermolecular HB interaction. The present work is helpful to clearly understand
the interaction mechanism of these complexes in theory. 相似文献
5.
We report on a quantum-chemical study of the electronic and optical properties of a series of β, β′-edge-fused zinc porphyrin
with different aromatic rings, in order to design efficient sensitizers for dye-sensitized solar cells (DSSCs). Our calculations
found that the replacement of quinoxaline moiety in ZnQMA (having high power conversion efficiency η of 6.3%) with other aromatic rings decreases the HOMO–LUMO energy gap mainly due to destabilization of the HOMO level. For
all of the investigated compounds, the reorganization energies of electron and hole are in the same order of magnitude as
and similar to those of ZnQMA. The absorption spectra in both Soret and Q bands for most of the considered molecules exhibit red shifts to some extent
with respect to that of ZnQMA. In the simulated dye-sensitized TiO2 systems, the bidentate adsorption mode of porphyrin derivatives is computed to be energetically favored compared to the monodentate
one, which well confirms the experimental results observed by X-ray photoelectron spectroscopy. The slightly shorter Ti–O
bond lengths calculated for D–TiO2 systems point toward a stronger interaction of the dye with the titania surface compared to ZnQMA–TiO2 systems. Our calculation indicates that the designed molecule D is promising to challenge the current photoelectric conversion efficiency record 6.3% of ZnQMA. 相似文献
6.
Jian-Hua Yi Feng-Qi Zhao Ying-Hui Ren Bo-Zhou Wang Cheng Zhou Xiao-Ning Ren Si-Yu Xu Hai-Xia Hao Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1029-1036
The high-pressure thermal properties and their correlation with burning rates of the composite modified double base (CMDB)
propellants containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz), a substitute of hexogen (RDX),
were investigated using the high-pressure differential scanning calorimetry (PDSC). The results show that there is a main
exothermal decomposition process with the heating of each propellant. High pressure can restrain the volatilization of NG,
accelerate the main decomposition reaction, and make the reaction occur easily. High pressure can change the main decomposition
reaction mechanism function and kinetics, and the control process obeys the rule of Avrami–Erofeev equation at high pressure
and chemical reaction at normal pressure. However, the mechanism function can not be changed by the ballistic modifier. The
correlation between PDSC characteristic values and burning rates was carried out and found that u and
( p \Updelta H\textd / \Updelta T ) 1 / 2 \left( {p \, \Updelta H_{\text{d}} { / }\Updelta T} \right)^{ 1 / 2} keep a good linear relation, k
u
keeps a similar changing trend with u, and it can be used to study the effect of the ballistic modifier or the other component on the burning rates. 相似文献
7.
Z. Fengqi G. Hongxu L. Yang H. Rongzu C. Pei G. Sheng-li Y. Xu-wu S. Qizhen 《Journal of Thermal Analysis and Calorimetry》2006,85(3):791-794
The constant-volume combustion energies of
the lead salts of 2-hydroxy-3,5-dinitropyridine (2HDNPPb) and 4-hydroxy-3,5-dinitropyridine
(4HDNPPb), ΔU
c
(2HDNPPb(s) and 4HDNPP(s)),
were determined as –4441.92±2.43 and –4515.74±1.92
kJ mol–1 , respectively, at 298.15 K. Their
standard enthalpies of combustion, Δc
m
H θ(2HDNPPb(s) and 4HDNPPb(s), 298.15 K), and standard enthalpies of formation,
Δr
m H θ(2HDNPPb(s) and 4HDNPPb(s),
298.15 K) were as –4425.81±2.43, –4499.63±1.92 kJ
mol–1 and –870.43±2.76, –796.65±2.32
kJ mol–1 , respectively. As two combustion
catalysts, 2HDNPPb and 4HDNPPb can enhance the burning rate and reduce the
pressure exponent of RDX–CMDB propellant. 相似文献
8.
Fei Yu Guochun Yang Shuixing Wu Yun Geng Zhongmin Su 《Theoretical chemistry accounts》2011,129(1):45-51
Due to the different molecular stacking conformations, two kinds of intermolecular interactions, arene–arene π-stacking interaction
and Cu–Cu interaction coexist in the polymorphs of [C6F5Cu]2(4,4′-bipy) crystals, 3-α and 3-β. However, the relative magnitude of the two kinds of intermolecular interactions in 3-α and 3-β is different. With the help of first-principle band structure calculations, the relationship between the charge transport abilities and
the intermolecular interactions in the two polymorphs was investigated for the first time. The analysis of band structures
and Г point wave functions of the band-edge state in the valence band of crystal 3-α shows that the Cu–Cu interaction so-called cuprophilic interaction determines the hole transport ability, although this interaction
is weaker than that in crystal 2 of C6F5Cu(py) discussed in our previous work, which is a promising hole transport material. For polymorph crystal 3-β, the wave functions of LUMO are mainly localized on the bipyridine (bpy) groups, which are result from the arene–arene π-stacking
interaction between the bpy groups. Such a π–π stacking interaction dominates the electron transport ability in the conduction
band of 3-β and makes the electron main carrier for transporting. The results are also supported by the analysis of effective masses
and density of states (DOS). Thus, the charge transport properties are dominated by different intermolecular interactions
due to the different molecule stacking in the two polymorphs. 相似文献
9.
The adsorption of 1,3,5-trinitro-s-triazine (RDX) and triacetone triperoxide (TATP) on representative fragments of metal organic framework (IRMOF-1) was studied at the B3LYP/6-31G(d) level of theory. For examined adsorbates several possible adsorption positions toward the IRMOF-1 fragments were found. The adsorption strength of the adsorbate on IRMOF-1 is largely affected by the geometry of the active site of IRMOF-1 which controls the orientation of the target molecule with respect to the IRMOF-1 fragment. The calculations show that the adsorption on these fragments occurs due to the formation of hydrogen bonds between the molecular C–H groups and the oxygen atoms of IRMOF-1. The RDX and TATP molecules are the most strongly adsorbed on the linker fragment of IRMOF-1. This type of adsorption results in the polarization of RDX and TATP on the IRMOF-1 fragments. The interaction energy of two most stable RDX-, and TATP-IRMOF-1 adsorption systems are ?9.8 and ?12.8 kcal/mol, respectively. It can be concluded that the 1,4-benzenedicarboxylate site of IRMOF-1 shows the stronger molecular adsorption of RDX and TATP than the site containing [Zn4O(CO2)6] and also it is characterized by higher reactivity than the other considered sites. The binding of studied explosive molecules to IRMOF-1 consists of interplay between attractive interactions between the target molecule and MOF as well as the shielding by the IRMOF-1 fragment induced by the molecular adsorption. The relative importance of these effects depends on the chemical nature, the size, and the shape of the molecule and MOF. Small-size molecules require smaller space for the adsorption and also they are less shielded by the sizeable adsorbent. So they interact better when adsorbed on larger IRMOF-1 fragment. On the other side, larger molecules show higher adsorption strength with small fragments of IRMOF-1. 相似文献
10.
To study the importance of charge–charge and cation-π interactions for the binding of positively charged amine ligands to
their receptors, the energies of interaction between [(CH3)4–N]+, [(CH3)3–NH]+, and [(CH3)4–NH3]+ and acetate, as a model of Asp and Glu, and with benzene, as a model of aromatic side chains, were obtained at the MP2/aug-cc-pVDZ
level of theory. The free energies of solvation in water were also calculated for the different amines. It was found that,
although primary amines form stronger charge–charge interactions with acetate than tertiary or quaternary amines, the difference
is not large enough to compensate their higher solvation energy. Quaternary amines show the weakest interaction with acetate.
However, their alkyl groups can interact with various aromatic groups, enhancing ligand binding to the receptor. The analysis
was completed with MD calculations on amine binding to the G protein-coupled receptors β2AR and CCR5. The calculations on the model systems were found to be in good agreement with the simulations of the ligand-receptor
complexes.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
11.
The chemical stability of a propellant and its influence on the ballistic properties during aging is a subject of interest.
The effect of aging on ballistic properties, viz., ignition delay, burning rate, and heat of combustion for an aluminised
ammonium perchlorate–hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant during accelerated aging were investigated.
Samples of composite propellants were aged at 60 and 70 °C at relative humidity of 50% in a climatic chamber. The propellant
samples were tested with pressurized nitrogen gas environment for ignition delay measurement. Test results indicate that aging
does not have any appreciable effect on ignition delay. The change in ignition delay time is less than 3% within the scatter
of the data. Experiment results indicate that burn rate do affect with pressure but aging does not have much effect on burn
rate. It was also observed that the burning rate at low pressures did not undergo significant changes during the aging period.
The most significant of all the ballistic properties of this propellant is the burning rate exponent which increased by about
10% during the aging period. 相似文献
12.
The Flory–Huggins interaction parameter, χ
23, characterizing the interaction between solvents in a mixed stationary phase has been calculated using inverse gas chromatography
(IGC). The χ
23 parameters for four mixed solvent systems formed by mixing a non-polar branched alkane, 19, 24-dioctadecyldotetracontane
(C78), with four different polar solvents are analysed as a function of temperature. Two of the polar solvents are formed
by replacing one of the –CH3 groups of C78 by –OH (POH) group and –CN (PCN) group and the other two polar solvents are formed by replacing all the four
–CH3 groups of C78 by four –CF3 (TTF) groups and four –OCH3 (TMO) groups. The five solvents have similar structures and nearly the same molar volume and in mixtures, they form regular
solutions. For the mixture, C78 + POH, χ
23 was calculated at two compositions and for the remaining three mixtures χ
23 was calculated at equimolar composition. Eight solute probes representing all possible chemical structures and polarity were
used under conditions approaching infinite dilution. The effects of temperature, concentration of the mixed solvent and probe
solute on χ
23 are presented and discussed. The probe-independent χ
23 values were also calculated by linear regression analysis using the retention data of all the solute probes. In all the mixed
solvents considered here the χ
23 values are probe-dependent and decrease with increase of temperature. 相似文献
13.
Ab initio study of the cooperativity between NH···N and NH···C hydrogen bonds in H3N–HNC–HNC complex
Baoan Gong Bo Jing Qingzhong Li Zhenbo Liu Wenzuo Li Jianbo Cheng Qingchuan Zheng Jiazhong Sun 《Theoretical chemistry accounts》2010,127(4):303-309
Ab initio calculations at the MP2/aug-cc-pVTZ level have been performed to study the cooperativity of hydrogen bonds in homoclusters
(HNC–HNC–HNC and HNC–HNC–HNC–HNC) and heteroclusters (H3N–HNC–HNC and H3N–HNC–HNC–HNC). The cooperative energies in the HNC–HNC–HNC and H3N–HNC–HNC trimers are –2.05 and –2.56 kcal/mol, respectively. The result shows that the cooperativity in the heterotrimer
is larger than that in the homotrimer. A similar result also happens in the tetramers. The energy decomposition scheme indicates
that orbital interaction is a major contribution to the cooperative energy of N···HN hydrogen bond, whereas the electrostatic
and orbital interactions to that of C···HN hydrogen bond. The effect of HNC chain length on the strength of N···HN hydrogen
bond has also been considered at the MP2/aug-cc-pVDZ level. It is indicated that the interaction energy of N···HN hydrogen
bond trends to be a fixed value when the HNC number tends to be infinite, and the strength of N···HN hydrogen bond is regulated
mainly through the electrostatic and polarization interactions although the charge transfer interaction also has an effect
on it. 相似文献
14.
Vibrational spectroscopy standoff detection of explosives 总被引:1,自引:0,他引:1
Leonardo C. Pacheco-Londoño William Ortiz-Rivera Oliva M. Primera-Pedrozo Samuel P. Hernández-Rivera 《Analytical and bioanalytical chemistry》2009,395(2):323-335
Standoff infrared and Raman spectroscopy (SIRS and SRS) detection systems were designed from commercial instrumentation and
successfully tested in remote detection of high explosives (HE). The SIRS system was configured by coupling a Fourier-transform
infrared interferometer to a gold mirror and detector. The SRS instrument was built by fiber coupling a spectrograph to a
reflective telescope. HE samples were detected on stainless steel surfaces as thin films (2–30 μg/cm2) for SIRS experiments and as particles (3–85 mg) for SRS measurements. Nitroaromatic HEs: TNT, DNT, RDX, C4, and Semtex-H
and TATP cyclic peroxide homemade explosive were used as targets. For the SIRS experiments, samples were placed at increasing
distances and an infrared beam was reflected from the stainless steel surfaces coated with the target chemicals at an angle
of ∼180° from surface normal. Stainless steel plates containing TNT and RDX were first characterized for coverage distribution
and surface concentration by reflection–absorption infrared spectroscopy. Targets were then placed at the standoff distance
and SIRS spectra were collected in active reflectance mode. Limits of detection (LOD) were determined for all distances measured
for the target HE. LOD values of 18 and 20 μg/cm2 were obtained for TNT and RDX, respectively, for the SIR longest standoff distance measured. For SRS experiments, as low
as 3 mg of TNT and RDX were detected at 7 m source–target distance employing 488 and 514.5 nm excitation wavelengths. The
first detection and quantification study of the important formulation C4 is reported. Detection limits as function of laser
powers and acquisition times and at a standoff distance of 7 m were obtained. 相似文献
15.
The monomer/dimer equilibrium has been studied for a series of alkyl and aryl substituted and functionalized iminochlorophosphane
species of the type R–N=P–Cl. In agreement with experiment, theoretical data always favor the dimer when the group R is small,
while bulky groups such as Mes* destabilize the dimer by a considerable steric repulsion. This effect is superimposed by electronic
effects. Para-substitution in the aryl systems either favors the monomer (energy gain ca. 15–30 kJ/mol) when a π-electron donating group such as p-NMe2 is used or favors the dimer when a π-electron withdrawing group such as p-NO2 is used (energy gain ca. 1–13 kJ/mol). 相似文献
16.
B. L. Korsounskii V. V. Nedel'ko N. V. Chukanov T. S. Larikova F. Volk 《Russian Chemical Bulletin》2000,49(5):812-818
Thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW) in the solid state and in solution was studied by thermogravimetry,
manometry, optical microscopy, and IR spectroscopy. The kinetics of the reaction in the solid state is described by the first-order
equation of autocatalysis. The rate constants and activation parameters of HNIW thermal decomposition in the solid state and
solution were determined. The content of N2 amounts to approximately half of the gaseous products of HNIW thermolysis. The thermolysis of HNIW and its burning are accompanied
by the formation of a condensed residue. During these processes, five of six nitro groups of the HNIW molecule are removed,
and one NO2 group remains in the residue, which contains amino groups and no C−H bonds.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 815–821, May, 2000. 相似文献
17.
A. S. Maslakova E. L. Krasnykh S. V. Levanova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(2):163-168
Saturated vapor pressures and enthalpies of evaporation of trisubstituted esters of glycerol and carboxylic acids C1–C5 with normal and branched structure were determined by the transpiration method in the temperature range of 300–371 K. Dependences
of enthalpies of evaporation on the number of carbon atoms in a molecule and on the retention indices are established. Prognostic
possibilities of existing calculation schemes are analyzed for compounds with three carboxyl groups in a molecule. 相似文献
18.
Gian Luigi Bendazzoli 《Theoretical chemistry accounts》2007,118(1):135-142
We present and discuss a variational single-product approximation to the van der Waals dispersion interaction leading to a
simple formula for C
6 that seems capable to give more than 99% of the ‘exact’ value. The formula is derived from Hylleraas’ variational principle
in the tensor product space of the interacting molecules and therefore enjoys bounding properties. The formula has been tested
by computing the C
6 dispersion constants of H–H, and, at Full CI level, of the following systems: He–He, He–Li, Li–Li, LiH–LiH, HF–HF. Connections
with the London formula are discussed.
Contribution to the Fernando Bernardi Memorial Issue. 相似文献
19.
Ying-Hui Shao Xiao-Ning Ren Zi-Ru Liu 《Journal of Thermal Analysis and Calorimetry》2010,101(3):1135-1141
The eutectic binary phase diagrams of volatilizable energetic material 1,3,3-trinitroazetidine (TNAZ) with 1,3,5-trinitro-1,3,5-triazacyclohexane
(RDX) and 1-methyl-2,4-dinitroimidazole (MDNI) have been investigated by high pressure differential scanning calorimeter (PDSC),
respectively. The liquefying and melting processes of TNAZ/RDX and TNAZ/MDNI volatilizable systems have been studied. On the
basis of the data of apparent fusion heat and liquefying temperature, the phase diagrams of apparent fusion heat (H) with composition (X) and liquefying temperature (T) with composition (X) were constructed, respectively. The results showed that the gasification or volatilization of easy volatile energetic materials
could be efficiently restrained by high pressure atmosphere, and the perfect and ideal phase diagrams can be constructed.
The eutectic temperatures for TNAZ/RDX and TNAZ/MDNI are measured to be 95.5 and 82.3 °C, respectively. The eutectic compositions
of mole ratios for the two systems are obtained to be 93.55/6.45 (T–X method), 93.79/6.21 (H–X method) and 62.25/37.75 (T–X method), 63.29/33.71 (H–X method), respectively. 相似文献
20.
The interaction of the adenosine triphosphate (ATP) molecule (the ATP subsystem) with the magnesium complex [Mg(H2O)6]2+ (the Mg subsystem) in the singlet (S) and triplet (T) states in an aqueous medium mimicked by 78 water molecules was studied
by the molecular dynamics (density functional theory) method MD DFT:B3LYP with the 6–31G** basis set at T = 310 K. Potential energy surfaces for the S (lowest-lying) and T (highest-lying) states are significantly separated in space.
The Mg complex moves along these surfaces to approach either oxygen atoms of the γ-β phosphate groups (O1–O2) (S PES) or oxygen
atoms of β-α phosphate groups (O2–O3) (T PES). Chelation of the γ-β β-α and phosphates yields, respectively, a stable low-energy
complex ([Mg(H2O)4-(O1–O2)ATP]2−) and a metastable high-energy complex ([Mg(H2O)2-(O2–O3)ATP]2−), which differ in the number of water molecules surrounding the Mg atom. Crossing of two triplet PESs is accompanied by the
formation of an unstable state characterized by redistribution of spins between the Mg and ATP subsystems. This state, sensitive
to interaction with the 25Mg nuclear spin, induces an unpaired electron spin, which initiates the ATP cleavage by the ion-radical mechanism, yielding
a reactive radical ion of adenosine monophosphate (•AMP−), which was earlier found experimentally by the of chemically induced dynamic nuclear polarization (CIDNP) method. Biological
aspects of the results obtained are discussed.
Original Russian Text ? A.A. Tulub, V.E. Stefanov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7,
pp. 1188–1195. 相似文献