Structure of detonation waves in nitromethane and a nitromethane/methanol mixture

The results of experimental studies of the structure of the reaction zone for steady-state detonation of nitromethane and its mixtures with methanol. For pure nitromethane, the characteristic reaction time and detonation parameters were determined. For a nitromethane/methanol mixture, a dependence of the detonation parameters of the mixtures on methanol concentration is presented. It is shown that in pure nitromethane and with small additions of methanol, the detonation front is stable, or the size of the inhomogeneities of the front is less than 1 m. At a methanol concentration of 10% or higher, instability of the front is observed.     

Sensitivity of nitromethane for low velocity detonation

Recently the occurrence of a low velocity detonation (LVD) in nitromethane has been demonstrated. In the present study this phenomenon has been further investigated by mapping the shock loading regime in which a stable LVD can develop. A confinement geometry has been chosen that earlier appeared to be able to sustain the LVD. A calibrated shock donor system has been used, so that loading shock strengths were known. The critical shock strengths for the occurrence of both high and low velocity detonation could thus be determined. Including LVDs, nitromethane appears to have a sensitivity comparable to that of relatively sensitive high explosives. The results also indicate that the geometries of some standard shock sensitivity tests are not fully adequate to detect an LVD in nitromethane.     

Solvatation des ions par le nitromethane

The direct potentiometric determination of the normal potentials of Cu/Cu⁺, Cu⁺/Cu²⁺, Ag/Ag⁺, Hg/Hg²⁺₂ couples in nitromethane and the comparison of these values with the normal potentials in aqueous solution makes possible the calculation of solvation coefficients γ_(t)(Mⁿ⁺) of the corresponding cations; the Strehlow hypothesis (γ(Fc) = γ(Fc⁺)) has been used. An indirect method using the determination of the solubility constants of alkaline chlorides and alkaline earth chlorides leads to the normal potentials of alkaline and Mg²⁺ cations and thus to the γ_(t) values of these ions.The measures of the AgX^-₂ stability constants and of the AgX solubility constants lead to the γ_(t) values of X^? and AgX^?₂ anions (X^? = Cl^?, Br^?, I^?, Scn^?, CH₃CO^?₂, CN^?, BrO^?₃, (C₆H₅)₄B^?). A comparison of γ_(t)(H⁺) and γ_(t)(Ag⁺) for 20 solvents is given.     

Physicomechanical properties of acetate fibres modified with nitromethane vapors

The physicomechanical characteristics of acetate fibres were investigated in different stages of their spontaneous elongation in nitromethane vapors. It was shown that acetate fibres are strengthened and the coefficients of variation for the breaking strength and elongation at break decrease at the beginning of treatment with vapors of a specific solvent. A hypothesis was advanced concerning the possible mechanism of the reaction of the polymer with the solvent vapors in which it forms a mesophase.Translated from Khimicheskie Volokna, No. 1, pp. 50–53, January–February, 1995.     

Detonation sensitivity of liquid nitromethane doped with methyl nitrite

It has been suggested, by other workers, that the isomerization of normal nitromethane (NM CH₃NO₂) to methyl nitrite (CH₃ONO) is an important first step in the chemical kinetics of liquid NM detonation. We examine this idea by studying the effect of direct methyl nitrite addition on NM's detonation sensitivity. Failure diameter is used as the measure of sensitivity. A comparison is made between the effect of methyl nitrite addition and that of a known sensitizer of NM i.e., the NM aci ion (CH₂NO₂⁻). Methyl nitrite is found to be an ineffective sensitizer relative to NM's aci ion.     

Effect of diethylenetriamine on the structure of detonation waves in nitromethane

This paper presents the results of experimental studies of the reaction zone structure in steady-state detonation of nitromethane sensitized by diethylenetriamine (DETA). The concentration of DETA was varied within 0.0125–15%. It is shown that small additions of DETA lead to a qualitative change in the flow pattern in the reaction zone. After the shock, the mass flow rate continues to increase for about 10 ns, reaches a maximum, and only then decreases. The amplitude of the chemical spike decreases by an order of magnitude. These features are explained by the decomposition of nitromethane sensitized by DETA in front of the shock wave, which is due to a sharp increase in the initial reaction rate.     

Detonation characteristics of diluted liquid explosives: Mixtures of nitromethane with methanol

Detonation in mixtures of nitromethane with methanol as an inert (nonexplosive) diluent is studied. Ignition experiments with mixtures in steel tubes of various diameters provided information on the effect of the degree of dilution on detonability. Mass velocity profiles with a chemical spike characteristic of detonation waves were recorded at the unsteady detonation front in all mixtures studied. This made it possible to distinguish the Chapman-Jouguet state and obtain a fairly complete set of detonation parameters. The dependence of the pressure in the detonation products on the methanol concentration is determined, which is required, in particular, to find the true (absolute) limit of detonation propagation for the concentration of diluted liquid explosives using the method proposed and validated by A. N. Dremin. Some results were found to be inconsistent with one-dimensional detonation theory.     

Stabilization of unstable detonation waves in mixtures of nitromethane with inert diluents

Mass velocity profiles of detonation waves in mixtures of nitromethane with acetone and methanol with added diethylenetriamine sensitizer were measured using a VISAR laser interferometer. It was found that even small, about 1%, concentrations of acetone and methanol, inert diluents, led to instability of the one-dimensional detonation front in nitromethane. The results of the experiment show that the use of the sensitizer is an effective method of flow stabilization and if the concentration of the inert diluent does not exceed 10%, the detonation front becomes stable with the addition of 1% diethylenetriamine. At a higher diluent concentration, the sensitizer does not suppress the instability but decreases the oscillation amplitude by several times. The addition of diethylenetriamine to the mixture has been found to increase the detonation velocity.     

硝基甲烷在离子液体BMImP6中的电化学行为

以铂微盘电极为工作电极,采用循环伏安等测试方法研究了硝基甲烷在离子液体1-正丁基-3-甲基咪唑六氟磷酸盐(BMImPF₆) 中的电化学行为,讨论了温度、扫描速度以及底物浓度等因素对其电化学行为的影响。结果表明,硝基甲烷在离子液体BMImPF₆中的还原反应是受扩散控制的不可逆过程。估算了不同温度下硝基甲烷在离子液体BMImPF₆中的扩散系数及其与温度的Arrhenius关系,其扩散活化能 E _a为22.28 kJ·mol^-1。     

Detonation properties of diluted liquid explosives: A mixture of nitromethane with nitrobenzene

A set of data characterizing the detonation process in mixtures of nitromethane with nitrobenzene is determined with the use of an electromagnetic method. The dependence of the pressure of detonation products on nitrobenzene concentration is established. Information on the effect of dilution ratio of nitromethane by nitrobenzene on detonability was obtained in experiments on mixture explosion. The results are compared with the results of previous similar studies of mixtures of nitromethane and methanol.     

On the validity of the thermal explosion model in shock wave initiated nitromethane

By means of Perot Fabry Velocimetry (PFV) we recorded material velocities generated by an intense shock wave (P > 70 kbar) in pure nitromethane. Our experiments show that nitromethane does not behave according to the Campbell-Travis model for detonation in liquid explosives. We do not find any evidence for a so-called superdetonation, which would start behind and overtake the pressure shock wave. Our recordings of material velocities show a behavior of the liquid explosive very similar to that of solid polycrystalline explosives and are compatible with the heterogeneous decomposition scheme.     

Role of chloronium complex in the electrochemical chlorination of c-hexene in nitromethane

The anodic chlorination of c-hexene in NM solution having 150 ppm water content involves three charge-transfer reactions. The effect of potential on change in product distribution is more effective at the beginning of electrolysis. A mechanism for the process is suggested.     

The influence of nitromethane adsorption on the oxidation of formic acid at platinum electrodes

Co-adsorption of nitromethane at Pt electrodes, and its influence on HCOOH electrocatalytic oxidation were investigated by cyclic voltammetry and potentiostatic quasi-steady state polarization curves. Potentiodynamic I/E curves in the presence of nitromethane show a considerable current increase in the low potential region (0.2–0.5 V). This effect is maintained under quasi-steady state conditions.Electrosorption studies performed with nitromethane indicated that partially reduced species are adsorbed on the electrode surface. These species could be responsible for the observed promoting effect.The results obtained with nitromethane addition are compared with acetonitrile and dimethylsulfoixide. Competition for adsorption sites and modifications of surface adsorption energy produced by additive adsorption, account for their specific influence on the HCOOH oxidation rate.     

The electrochemical bromination of c-hexene on a Pt electrode in nitromethane solution

In this process a complex intermediate forms between the olefin and Br₂ evolved and it transforms to dibromo-c-hexane. At higher potential values the electrochemical oxidation of this complex results bromo-c-hexanol, the formation of which is hindered by oxide layer on the electrode surface.