The method of determination combustion rate of powdered porous silicon with limited space is presented. The values of the combustion rates of porous silicon are close to the values of the rates of explosives.

With a decrease in the thickness of the walls separating the space of pores in porous semiconductors, the potential energy of interaction between an electron and a donor (or a hole and an acceptor) can become greater than the kinetic energy of a free charge carrier. As a consequence, such interlayers lose their conductivity and transit into the dielectric state (Mott phase transition). With regard to the conditions of electrochemical pore formation, this means that as the pore channels approach each other during anodic etching to a distance at which the current flow through the wall that separates them stops, the potential of its surface ceases to be determined by the external electric bias and the electrochemical process, that leads to a further decrease in the thickness of such a wall, stops. Expressions are obtained for the limiting thickness of the walls of pores formed in degenerate semiconductors of n- and p-type conductivity. In contrast to the well-known model that relates the loss of conductivity by pore walls to the combination of space charge layers, the proposed model allows a consistent explanation for the experimental data for both n- and p-type silicon with doping levels above 10 18 cm -3 . Keywords: thickness limitation, pore formation, silicon, donor, acceptor.

The paper investigates the influence of gas dynamic cold spraying followed by laser processing of stainless steel samples on their dynamic (spallation) strength under the impact load at a 105 s–1 strain rate. The impact velocity effect on the microstructure and dynamic strength is studied herein. It is shown that the dynamic strength of steel samples after laser processing remains unchanged compared to unprocessed samples. Amorphization and melting are observed in the spallation region of the processed samples. Intense mechanical twinning develops inside austenite grains after the load application, and a largest number of twins is observed in unprocessed samples.

The results of dynamic testing of alumina samples with different graphene content are presented. The tests were carried out using a split Hopkinson rod according to the “Brazilian test” method at an impact speed of 10 m/s. The optimal value of the graphene content was obtained. The strength characteristics of the alumina nanocomposite with graphene reach a maximum at this value.

Laser and electron-beam initiation of the combustion process of energy-saturated composite films were studied. Composites were produced from porous silicon, a fluorine-containing polymer, and graphene. It is shown that the impact of a high-current electron beam of nanosecond duration does not lead to the excitation of the combustion process. Moreover, the process of film combustion during laser initiation is accompanied in some cases by the appearance of a zone of secondary flame and white smoke.

The paper presents the results of a study on the effectiveness of few-layer graphene synthesized under SHS conditions from lignin as a modifying additive in creating composite pyrotechnic complexes based on porous silicon and calcium perchlorate. It was found that the addition of few-layer graphene (20–30 wt. %) could significantly increase the probability of the ignition of pyrotechnic compositions by laser diode (infrared) radiation (wavelength of 976 nm and power of 15 MW/m2) compared to the initial pyrotechnic compositions. Using few-layer graphene also leads to a sharp increase in sensitivity to infrared laser radiation and the initiation of explosive transformations in retrofitted pyrotechnic compositions compared to the initial pyrotechnic compositions. Due to the high productivity and low cost of the technique for synthesizing few-layer graphene, the use of composite pyrotechnic compositions modified with few-layer graphene is profitable in the actual industry. A phenomenological model of the formation mechanism of 2D graphene structures under the conditions of the SHS process is proposed.

Исследовано влияние скважности импульсного тока на деформационное поведение, микроструктуру и характер разрушения алюминиевой бронзы БрАЖНМц 9-4-4-1 при растяжении. Проведены испытания на растяжение, изучена структура бронзы. Установлено, что величина скважности тока оказывает заметное влияние на характер кривых напряжение – деформация и механические свойства бронзы, а при минимальной скважности в бронзе возможно образование микротрещин, вызывающих ускоренное разрушение.

The review describes examples of increasing the susceptibility of photosensitive energy-saturated metal complexes to the effects of coherent laser radiation when nanocarbon materials are introduced into samples. Possible mechanisms of the synergistic effect of the influence of nanocarbon additives on the ignition thresholds of the complexes are proposed

Carbonization of a biopolymer (lignin) in self-propagating high-temperature synthesis (SHS) led to the production of 2D graphene structures. With the help of modern analytical methods (Raman spectroscopy, X-ray diffraction) and electron microscopy, the resulting product was confirmed to have a few-layer 2D graphene structure. The predicted photovoltaic properties of the resulting few-layer graphene were implemented for laser ignition of a model pyrotechnic composition based on porous silicon. A phenomenological model of the formation mechanism of 2D graphene structures under the conditions of the SHS process is proposed.

With a decrease in the thickness of the walls separating the space of pores in porous semiconductors, the potential energy of interaction between an electron and a donor (or a hole and an acceptor) can become greater than the kinetic energy of a free charge carrier. As a consequence, such interlayers lose their conductivity and transit into the dielectric state (Mott phase transition). With regard to the conditions of electrochemical pore formation, this means that as the pore channels approach each other during anodic etching to a distance at which the current flow through the wall that separates them stops, the potential of its surface ceases to be determined by the external electric bias and the electrochemical process, that leads to a further decrease in the thickness of such a wall, stops. Expressions are obtained for the limiting thickness of the walls of pores formed in degenerate semiconductors of n- and p-type conductivity. In contrast to the well-known model that relates the loss of conductivity by pore walls to the combination of space charge layers, the proposed model allows a consistent explanation for the experimental data for both n- and p-type silicon with doping levels above 10^18 cm^-3.

The article presents the results of studies on laser ignition of films of pyrotechnic compositions based on porous silicon, fluorine-containing polymer and graphene. The effect of graphene additives on the ignition process and the process of film combustion was analyzed. It was shown that in a number of cases the process of film combustion is accompanied by the appearance of a secondary flame zone and smoke formation.

The effect of pulse current ratio on deformation behavior, microstructure and nature of fracture of aluminum bronze BrAZhNMts 9-4-4-1 under tension is studied. Tensile tests are performed and the structure of the bronze is determined. It is shown that pulse current ratio noticeably influences the behavior of the stress-strain curves and bronze mechanical properties. With a minimum pulse ratio within bronze microcrack formation is possible causing accelerated failure.

Experimental data for the destruction of an aluminum sheath covering a press-fitted PMMA cylinder are reported. A copper conductor to be exploded is inserted into the cylinder along its axis, and a voltage is applied to the conductor from a capacitor charged to 20–22 kV. An explosion-induced pressure is transferred by a blast shock wave to PMMA and then to the metallic sheath. As a result, the PMMA cylinder breaks down and the aluminum sheath ruptures. The amplitude of the explosion-induced pressure, which is transferred to the PMMA cylinder and then from the cylinder to the sheath, has been estimated by measuring radial pressures, and sheath rupture stresses have been determined. The microstructure of the ruptured aluminum sheath has been examined using a Tescan scanning electron microscope and a Discovery optical stereomicroscope.

The theoretical analysis and direct experiments with samples based on n- and p-type porous silicon demonstrate that porous silicon becomes a piezoelectric because of the reduction of the symmetry of the crystal lattice. It is shown that both n and p types of porous silicon have piezoelectric properties. The piezoelectric properties of n-type porous silicon are 2.5 times weaker than the piezoelectric properties of p-type porous silicon at the same porosity because pores in p-type silicon become wider and smoother with an increase in the distance from the surface, whereas pores in n-type porous silicon become narrower and more sinuous.

The protection of various objects experiencing shock loads from the impact of irregularly shaped impactors with impact velocities over 1.5-2.0 km/s is of considerable interest and is relevant. Computer modeling of the processes of high-speed interaction of impactors with various objects in order to create optimal designs requires deep knowledge of the physical and mechanical properties and processes occurring in the thickness of at least the material of the barrier (object). However, the existing technical measuring instruments make it possible to register only the kinematic parameters of the deformation and destruction of the barrier and impactor, while the development of internal processes remains inaccessible for visualization. In addition, the physical processes of high-speed deformation and destruction occurring in obstacles are highly dependent on the many contact boundaries that are inherent in irregularly shaped strikers, and in computer modeling and experimental studies, strikers, as a rule, have the correct geometric shape (cylinder, sphere). As a result, there is a significant loss of calculation accuracy. The article is devoted to the analysis of the behavior of various FCC metals - aluminum alloys, stainless steel, and aluminum bronze under impact loading by irregularly shaped projectiles with velocities of 1.5-2.0 km/s. Transformations of the deformed state of materials are revealed and it is shown that they depend little on the initial structure.

Dynamic tensile strength and ductility were studied within the range of strain rates from 0.6 to 1.2 × 103 s−1 by applying the split Hopkinson bar method on aluminum bronze samples the surface of which was processed by laser hardening and laser alloying. A number of effects are found: laser surface treatment of the samples significantly reduces the plastic properties of the material and increases the conditional yield stress, the tensile strength values of processed and unprocessed samples are close to each other, oscillations of the yield stress are observed, which can be interpreted as a "yield tooth" phenomenon. Deformation mechanisms explaining these effects were proposed based on the structural heterogeneity of the hardened surface layer and the sample as a whole.

The results of dynamic testing of aluminum oxide samples with different graphene content are presented. The tests were carried out using a split Hopkinson rod according to the "Brazilian test" method at an impact speed of 10 m/s. The optimal value of the graphene content was obtained. The strength characteristics of the aluminum oxide nanocomposite with graphene reach a maximum at this value.

Laser and electron-beam initiation of the combustion process of energy-saturated composite films were studied. Composites were produced from porous silicon, a fluorine-containing polymer, and graphene. It is shown that the impact of a high-current electron beam of nanosecond duration does not lead to the excitation of the combustion process. Moreover, the process of film combustion during laser initiation is accompanied in some cases by the appearance of a zone of secondary flame and white smoke.

The results of experimental studies of the dynamic characteristics of tinless bronze of the BrAZhNMts 9-4-4-1 brand of two types (in cold-rolled and annealed states) at different strain rates are presented. An experimental determination of the dynamic characteristics of bronze was carried out using a modification of the Kolsky method for dynamic tension using a split Hopkinson pressure bar. Tests were carried out with different strain rates up to rupture of the samples. It has been found that for both states, an increase in the strain rate leads to a significant change in the mechanical characteristics. The material after annealing showed a decrease in strength properties compared to the initial state by 20–22%. Compared to the static standard characteristics, the dynamic reduction in area has increased for both types of metal condition, and the dynamic reduction in area in the annealed state is 18–25% higher than the reduction in the cold-rolled state, i.e. in the annealed state, bronze is more ductile, which fits into the traditional theory of heat treatment. After dynamic testing, the fractured specimens were cut along the central tensile axis along the diameter so that the analytical sections (surfaces of the specimens that are ground, polished and chemically etched to reveal the structure or defectiveness of the specimens) were perpendicular to the fractures. The microstructural analysis of the destroyed samples and multifractal parametrization of their structures were carried out. On the basis of multifractal analysis in terms of the latent ordering parameter, it was found that the annealed state is less resistant to structural phase transition than the cold-rolled state. In annealed samples, a larger number of excited local regions appear, in which the hydrodynamic nature of the flow is possible and, as a result, such samples are more plastic.