Yakov Fironov

The features of laser drilling of composite highly porous ceramics, consisting of aluminosilicates, glass and a small additive of polystyrene (EPS), are studied both experimentally and theoretically/ It is found that the formation of a liquid phase can contribute to the strengthening of ceramics. A number of factors determining the dynamics of hole formation is proposed. These include not only the previously known processes of heating, melting, ablation, and ejection for metals and dense… Показать еще

The features of laser drilling of composite highly porous ceramics, consisting of aluminosilicates, glass and a small additive of polystyrene (EPS), are studied both experimentally and theoretically/ It is found that the formation of a liquid phase can contribute to the strengthening of ceramics. A number of factors determining the dynamics of hole formation is proposed. These include not only the previously known processes of heating, melting, ablation, and ejection for metals and dense ceramics, but also a number of others: boiling of the component of the mixture with the lowest temperature of thermal decomposition and its departure from the affected zone; melt less volatile component; sealing the ceramics adjacent to the walls; glass transition of the liquid phase upon cooling after irradiation. These effects depend on the density of the composite as well as on the viscosity of the liquefied material. Свернуть

The features of laser drilling of highly porous composite ceramics consisting of aluminosilicate, glass, and a small addition of polystyrene (EPS) were studied experimentally. It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors determining the dynamics of hole formation is proposed. These include not only heating, melting, ablation, and ejection, previously known for metals and dense ceramics, but also a number of others:… Показать еще

The features of laser drilling of highly porous composite ceramics consisting of aluminosilicate, glass, and a small addition of polystyrene (EPS) were studied experimentally. It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors determining the dynamics of hole formation is proposed. These include not only heating, melting, ablation, and ejection, previously known for metals and dense ceramics, but also a number of others: boiling-up of the mixture component with the lowest temperature of thermal decomposition and its departure from the affected zone; melt of less volatile components; compaction of ceramic adjoining the walls; glass transition of the liquid phase on cooling after irradiation. These effects depend on the density of the composite as well as on the viscosity of the liquefied material. Свернуть

In this work, we experimentally study the features of laser drilling of composite highly porous ceramics consisting of aluminosilicates, glass and a small addition of polystyrene (EPS). It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors that determine the dynamics of hole formation is proposed. These include not only the processes of heating, melting, ablation, and ejection, well known previously for metals and dense ceramics… Показать еще

In this work, we experimentally study the features of laser drilling of composite highly porous ceramics consisting of aluminosilicates, glass and a small addition of polystyrene (EPS). It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors that determine the dynamics of hole formation is proposed. These include not only the processes of heating, melting, ablation, and ejection, well known previously for metals and dense ceramics, but also a number of other specific processes: (a) boiling of the component of the mixture with the lowest temperature of thermal decomposition and its escape from the affected zone; (b) a melt of less volatile components; (c) sealing the ceramics adjacent to the walls due to the mechanical sealing effect of ablative pressure; (c) glass transition of the liquid phase upon cooling after the end of irradiation. Свернуть

The features of laser boring of composite highly porous ceramics consisting of aluminosilicates, glass and a small additive of polystyrene (EPS) are studied experimentally. It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors determining the dynamics of hole formation is proposed. These include not only the previously known processes of heating, melting, ablation, and ejection for metals and dense ceramics, but also a number of… Показать еще

The features of laser boring of composite highly porous ceramics consisting of aluminosilicates, glass and a small additive of polystyrene (EPS) are studied experimentally. It was found that the formation of a liquid phase can contribute to the strengthening of ceramics. A list of factors determining the dynamics of hole formation is proposed. These include not only the previously known processes of heating, melting, ablation, and ejection for metals and dense ceramics, but also a number of others: boiling of the component of the mixture with the lowest temperature of thermal decomposition and its departure from the affected zone; melt less volatile component; sealing the ceramics adjacent to the walls; glass transition of the liquid phase upon cooling after irradiation. These effects depend on the density of the composite as well as on the viscosity of the liquefied material. Свернуть

The effect of the pulsed laser irradiation in air on Cr23C6 ceramic with Cr3C2 and Cr7C3 additives
has been studied. It is established that the main process occurring in the zone of laser radiation is the melting of the ceramic surface of chromium carbide and the formation of a crater. This process is accompanied by the ejection of melt droplets from the crater zone and the dissociation of chromium carbides. As a result, the crater area is enriched in such ablation products as Cr, C, CO, and… Показать еще

The effect of the pulsed laser irradiation in air on Cr23C6 ceramic with Cr3C2 and Cr7C3 additives
has been studied. It is established that the main process occurring in the zone of laser radiation is the melting of the ceramic surface of chromium carbide and the formation of a crater. This process is accompanied by the ejection of melt droplets from the crater zone and the dissociation of chromium carbides. As a result, the crater area is enriched in such ablation products as Cr, C, CO, and CO2. Reduction of hydrogen in the crater zone and neighboring areas leads to slowing down of the rate of oxidation processes, and the presence of ablation products such as Cr and C atoms promotes the process of synthesis of oxycarbides CrxCyOz (x ≈ 0.3–0.8, y ≈ 0.03–0.3, z ≈ 0.61–0.26) in the gas phase. Emission of the newly formed products of ablation from the crater and their distribution to the neighboring areas is accompanied by coagulation of nanoparticles into clusters. Depending on the length of flight of nanoclusters through different temperature zones and temperature of the deposition surface, oxycarbides with different morphology are formed: from islets (like fractal clusters) to film ones. The deposited ablation products are characterized by the signs of particle size “separation.” This makes it possible to create films of a given type and purpose. The passage of particles of different sizes through a gaseous medium containing oxygen is accompanied by the oxidation of oxycarbides to Cr2O3. Свернуть

Refractory non-oxygen compounds such as carbides, nitrides, and borides are extensively useful in design and production of new materials due to their high melting point, hardness, electric conductivity, etc., which are determined by the corresponding chemical bonds. The synthesis of composite ceramics based on these compounds extends considerably area of application of this type of materials.

The purpose of this paper is to study:
1) phase transformations that occur in the zone of… Показать еще

Refractory non-oxygen compounds such as carbides, nitrides, and borides are extensively useful in design and production of new materials due to their high melting point, hardness, electric conductivity, etc., which are determined by the corresponding chemical bonds. The synthesis of composite ceramics based on these compounds extends considerably area of application of this type of materials.

The purpose of this paper is to study:
1) phase transformations that occur in the zone of local high-power stationary laser heating of TiN - TiB2 ceramics in the air, and
2) morphology and composition of films formed from the ablation products.

The aim 1) is of interest from the standpoint of degradation of composite ceramics at high temperatures under the conditions of the formation of a narrow crater, which is difficult for the atmosphere oxygen to enter. The aim 2) is of interest as a new LCVD method of coating a complex composition by sprayed ceramics.
Свернуть

In the work, the process of local laser heating of TiN–TiB2 ceramics in air is considered. It has been established that the development of high-temperature processes in the irradiation zone (T ≥ 2000 °C) is accompanied by the decomposition of TiN and TiB2 into TiNx, TiB, Ti, and B and by the formation of vaporous ablation products, which are oxidized to TiO2 and B2O3 depending on the length of the flight path. As a result of the deposition of these oxides with different TiO2/B2O3 ratio on the… Показать еще

In the work, the process of local laser heating of TiN–TiB2 ceramics in air is considered. It has been established that the development of high-temperature processes in the irradiation zone (T ≥ 2000 °C) is accompanied by the decomposition of TiN and TiB2 into TiNx, TiB, Ti, and B and by the formation of vaporous ablation products, which are oxidized to TiO2 and B2O3 depending on the length of the flight path. As a result of the deposition of these oxides with different TiO2/B2O3 ratio on the substrate, TixByOz composite films form. Depending on the type and temperature of particles deposited on the substrate, it is possible to obtain films in the form of a continuous vitreous layer, mixture of vitreous islands and spherical particles, and chains of spherical particles of different diameter. Свернуть

The process of high-temperature heating of TiB2 armor ceramics in air in a continuous and pulsed mode of laser irradiation has been studied by the X-ray diffraction and SEM methods. It has been established that, in the irradiation zone, the temperature increases up to 3000 °C and over, resulting in the decomposition of TiB2 and appearance of ablation products, which, in passage of air, oxidize and form dense films (in the pulsed mode) or “reticulated” films (in the CW mode) consisting of boron… Показать еще

The process of high-temperature heating of TiB2 armor ceramics in air in a continuous and pulsed mode of laser irradiation has been studied by the X-ray diffraction and SEM methods. It has been established that, in the irradiation zone, the temperature increases up to 3000 °C and over, resulting in the decomposition of TiB2 and appearance of ablation products, which, in passage of air, oxidize and form dense films (in the pulsed mode) or “reticulated” films (in the CW mode) consisting of boron and titanium oxides. The mechanism of laser-induced breakdown of TiB2 ceramics is similar to the mechanism of ballistic destruction. Свернуть

The paper presents the physicochemical corrosion process of composite TiN - TiB2 ceramics in
the mode of pulsed laser irradiation in the atmosphere. It has been established that as a result of the
development of high-temperature oxidation TiN and TiB2 processes and partial dissociation of these
compounds the crater on the surface is formed. Oxidation processes lead to the formation of TiNx, TiB, TiO2, B2O3 and N2, whereas dissociation yields in Ti, B and N2, correspondingly. The gas… Показать еще

The paper presents the physicochemical corrosion process of composite TiN - TiB2 ceramics in
the mode of pulsed laser irradiation in the atmosphere. It has been established that as a result of the
development of high-temperature oxidation TiN and TiB2 processes and partial dissociation of these
compounds the crater on the surface is formed. Oxidation processes lead to the formation of TiNx, TiB, TiO2, B2O3 and N2, whereas dissociation yields in Ti, B and N2, correspondingly. The gas and vapor products (B2O3 and N2) and part of the TiO2 melt in the form of droplets are removed away from the crater. Such compounds as TiNx, TiB and TiO2 are enriched the surface of the crater walls. Свернуть

The effect of laser radiation on ceramics Cr23C6 with additives of Cr3C2 and Cr7C3 was studied. It is established that the main process occurring in the laser zone radiation, is the melting of the ceramic surface of chromium carbide and the formation of crater. This process is accompanied by the ejection of melt droplets from the crater zone and the dissociation of chromium carbide. Deposition products are characterized by signs of “separation” in particle size, which will allow to create… Показать еще

The effect of laser radiation on ceramics Cr23C6 with additives of Cr3C2 and Cr7C3 was studied. It is established that the main process occurring in the laser zone radiation, is the melting of the ceramic surface of chromium carbide and the formation of crater. This process is accompanied by the ejection of melt droplets from the crater zone and the dissociation of chromium carbide. Deposition products are characterized by signs of “separation” in particle size, which will allow to create coatings of a certain type. Span of particles of various sizes through a gaseous medium containing oxygen, is accompanied by the oxidation of oxycarbides to Cr2O3. Свернуть

In the work, a laser treatment of Cr23C6 ceramics in air is considered. It has been established that, as a result of high-temperature laser heating, the melting of Cr23C6, formation of a crater, ejection of melt drops, and dissociation of chromium carbide (Cr23C6 → Сr + C) inside the crater occur. The enrichment of the gaseous atmosphere of the crater in atomic carbon leads to the formation of a СO/CO2 atmosphere, retardation of oxidation processes and, as a result, the synthesis of chromium… Показать еще

In the work, a laser treatment of Cr23C6 ceramics in air is considered. It has been established that, as a result of high-temperature laser heating, the melting of Cr23C6, formation of a crater, ejection of melt drops, and dissociation of chromium carbide (Cr23C6 → Сr + C) inside the crater occur. The enrichment of the gaseous atmosphere of the crater in atomic carbon leads to the formation of a СO/CO2 atmosphere, retardation of oxidation processes and, as a result, the synthesis of chromium oxycarbides CrxCyOz, where x ~ (0.3–0.8), y ~ (0.03–0.3), and z ~ (0.61–0.26) in the vapor–gas phase. As the laser cloud expands, the processes of formation, coagulation and coalescence of ultra nanoparticle/clusters, and then crystallization of large formations occur. Due to the presence of particles with different sizes in the gaseous atmosphere, precipitation products show signs of “separation”: finer particles precipitate at a larger distance from the crater than coarser particles. This makes possible to obtain CrxCyOz coatings of different morphology, namely, island-, film-, and mixed-type coatings. Свернуть

Nowadays photonic crystals (nonlinear materials with periodic dielectric structure) are used widely in a great number of industries, from polarizers and beam splitters to lasers (in this paper, nonlinear photonic crystals will be considered).

We obtain a set of nonlinear equations for pulses propagating in the forward and reverse directions using the method of connected waves. This analysis includes temporal and transverse structures, as well as losses and periodic nonlinear effects.

In this Wiki page I described a cryptographic primitive that is used to transfer the secret bit of information from several Alice's agents to several agents of Bob, which after a certain time, picked up by Alice, opens for reading.

When preparing this material, articles were mainly used from Physical Review Letters.