G. M. Belokurov

Photosensitive material based on PETN mixtures with aluminum nanoparticles

A study was made of the explosion probability and the pressure of explosive decomposition products of PETN samples of density 1.73 g/cm3 with different contents of Al nanoparticles under pulsed laser irradiation (1060 nm; 20 ns). It was experimentally found that the maximum sensitivity and maximum pressure of explosion products are obtained when the mass concentration of nanoparticles is 0.1%. In this case, the mixture sensitivity increases by factor of ≈100 with respect to the samples containing no nanoparticles. The observed effect is due to radiation absorption directly by nanoparticles with the formation of “hot spots,” which initiates an exothermic reaction in the main substance. It is shown that the addition of 0.1% Al decreases the impact sensitivity with respect to the samples without additives. This makes it possible to consider this mixture as a promising material for optical detonators.

Determining the optical properties of light-diffusing systems using a photometric sphere

A facility based on a photometric sphere has been developed for determining the optical properties of metal nanoparticles in transparent matrices. A method for processing experimental data of light scattering spectroscopy and determining the efficiencies of light absorption and scattering is proposed based on a solution to the inverse problem of the theory of radiative transport in a scattering layer with the use of an analytical solution to the radiative transport equation by the spherical harmonics method. The proposed method has been tested on pentaerythritol tetranitrate−aluminum composites. The influence of parameter variation is analyzed, and a conclusion is drawn that the efficiencies of light absorption and scattering by nanoparticles can be correctly determined.

Studies of the contribution of light scattering and absorption by inclusions of aluminum nanoparticlese in PETN

A method of an integrating sphere is used to study the optical characteristics of PETN containing 0.1% of aluminum inclusions with a particle size of ≈100 nm, depending on the concentration of inclusions and sample thickness. The study is carried out by using a stationary light source with a wavelength of 643 nm and a pulsed neodymium laser with a pulse duration of 14 ns. The extinction coefficients are calculated. It is concluded from the experimental results that light is absorbed by particles with the formation of “hot spots,” while an increase in the path of photons in the matrix due to scattering at inclusions and an increase in the possibility of light absorption by the PETN matrix are secondary phenomena.

Role of shock waves in initiating the detonation of pentaerythritol tetranitrate by a pulsed electron beam

The results of measurements of the velocity of shock waves generated in pressed pentaerythritol tetranitrate samples by a pulsed electron beam (0.25 MeV, 15 J/cm2, and 20 ns) and of the velocity of expansion of the explosion products into vacuum are presented. It was demonstrated that, during the interaction of the electron beam with pentaerythritol tetranitrate, it experiences decomposition accompanied by a pressure rise high enough to produce a shock-wave initiation of the sample.

Effect of the initial temperature on the threshold of laser initiation of pentaerythritol tetranitrate seeded with aluminum nanoparticles

The effect of temperature on the threshold of explosive decomposition of pentaerythritol tetranitrate samples with a density of ρ = 1.73 g/cm3 containing 0.1 wt % 100- to 120-nm aluminum particles under the action of laser pulses (λ = 1.06 μm, τ = 20 ns) is examined. A model capable of describing the experimental results is proposed, according to which the explosive decomposition of the samples is associated with the absorption of laser radiation by structural defects of pentaerythritol tetranitrate and aluminum nanoparticles. It is demonstrated that, at 300 K, explosion initiation is largely determined by the heating of aluminum nanoparticles with the formation of chemical decomposition kernels nearby.

Spectrokinetic characteristics of light emission at the early stages of the laser-initiated explosive decomposition of PETN-based composites containing metal nanoparticle inclusions

Spectrokinetic characteristics of light emission from PETN-based composites containing metal (aluminum, nickel, or iron) nanoparticle inclusions are reported. These characteristics have been measured online using a spectrophotochronograph during the action of a laser pulse (1064 nm, 14 ns). As the PETNbased composites are laser-irradiated, the chemical reaction causing the explosive decomposition of the sample begins during the action of the laser pulse. The observed light emission in the 350–750 nm spectral range can be classified as chemiluminescence.

Spectral-kinetic characteristics of luminescence of pentaerythritol tetranitrate with inclusions of iron nanoparticles upon explosion induced by laser pulses

Spectral-kinetic characteristics of luminescence of tetranitropentaeritrite with inclusions of iron nanoparticles upon an explosion induced by laser pulses are measured with high temporal resolution. It is shown that the luminescence occurring during exposure to the laser pulse is a result of initiating a chemical reaction in tetranitropentaeritrite and is chemiluminescence. The glow is presumably associated with the excited nitrogen dioxide, NO2, which is formed by the rupture of O–NO2 bond in the tetranitropentaeritrite molecule.

Optoacoustic Effects in Pentaerythritol Tetranitrate with Ultrafine Aluminum-Particle Inclusions under Pulsed-Laser Action

Results of studying optoacoustic characteristics of pentaerythritol tetranitrate (PETN) specimens with inclusions of ultrafine aluminum particles (100 nm) are presented. Regularities of the increase of extinction coefficient kef and signal amplitude U on a piezodetector by increasing laser-pulse fluence H have been established. Estimates have been made, and it has been concluded that, during a laser pulse, heating of aluminum inclusions and a shell surrounding it occurs up to a gasification temperature and appear craters on a specimen’s surface appear at H > 0.1 J/cm2.

Specific features of explosive decomposition of pentaerythritol tetranitrate exposed to an electron beam with an explosive emission cathode

A comparative examination of the critical energy density of explosive decomposition of pentaerythritol tetranitrate exposed either to an electron beam of a GIN-600 accelerator (240 keV, 20 ns) with an explosive emission cathode or to this beam combined with metal low-temperature diode plasma has been performed. It has been demonstrated that the contribution of plasma to the development of explosive decomposition is appreciable at explosion probabilities P ≤ 0.2. At higher energy densities and explosion probabilities P ≥ 0.5, the contribution of plasma to the overall beam energy density did not exceed 10%.

Spectrokinetic characteristics of light emission from pentaerythritol tetranitrate single crystals detonating under the action of a high-current electron beam

The spectrokinetic characteristics of light emission from pentaerythritol tetranitrate exposed to an electron beam pulse (0.25 MeV, 20 ns, 15 J/cm2) are measured in real time. It is shown that, during the impact of an electron beam, cathodoluminescence from the sample is observed. Light emission from PETN explosion occurs on the microsecond time scale. Spectral pyrometry measurements processed in the Wien coordinates yielded a sample explosion temperature of T ≈ 3000 K.