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The rupture of the left ventricle free wall is one of the most dangerous complications of myocardial infarction. Due to the widespread availability of echocardiography method, the detection of this fatal complication and the number of lives saved after surgery grew. The survival of patients depends on early diagnosis, stabilization of the patient’s condition, promptness and tactics of surgical intervention. We report a case of successful closure of a rupture of the left ventricle free wall on the 15th day after myocardial infarction.

To simulate a quantum system with continuous degrees of freedom on a quantum computer based on quantum digits, it is necessary to reduce continuous observables (primarily coordinates and momenta) to discrete observables. We consider this problem based on expanding quantum observables in series in powers of two and three analogous to the binary and ternary representations of real numbers. The coefficients of the series ("digits") are, therefore, Hermitian operators. We investigate the corresponding quantum mechanical operators and the relations between them and show that the binary and ternary expansions of quantum observables automatically leads to renormalization of some divergent integrals and series (giving them finite values)., Comment: 22 pages, 8 figures

To simulate a quantum system with continuous degrees of freedom on a quantum computer based on qubits, it is necessary to reduce continuous observables (primarily coordinates and momenta) to binary observables. We consider this problem based on expanding quantum observables in series in powers of two, analogous to the binary representation of real numbers. The coefficients of the series (“digits”) are therefore orthogonal projectors. We investigate the corresponding quantum mechanical operators and the relations between them and show that the binary expansion of quantum observables automatically leads to renormalization of some divergent integrals and series (giving them finite values).

Europium doped yttrium oxide nanophosphors (Y 2 O 3 doped with 5% Eu 3+ ), which consists of spherical single-phase monoclinic particles with an average size of 17 nm, was prepared by laser synthesis. While the monoclinic material has a low efficiency of only 19% of a μm-sized commercial Y 2 O 3 :Eu product, the cubic phase after calcination at 900 °C achieves 68% despite the remaining hydroxo-groups at the surface and still small crystallite size (56 nm). An ethanolammonium salt of citric acid (Dolapix CE64) was used as a dispersant in water suspension. To estimate the stability of the dispersed phase, the electrokinetic potential and agglomerate sizes were measured as a function of pH. With this dispersant, a 30 wt% nanopowder water suspension, showing a Newtonian viscosity of about 6 mPa × s, was obtained. Maximum content of the nanopowder of about 60 wt% can be accomplished in the slurry, still fluid enough to be used to cast a highly uniform and dense ceramic green body to sinter nanostructured Y 2 O 3 :Eu 3+ phosphors ceramics.

Theoretically and with the help of numerical simulation the coagulation rate of nanoparticle suspensions is analyzed. Analytical expressions are proposed that describes the rate of stationary coagulation of the nanoparticles suspended in a solvent (dna/dt, where na is the particle concentration) and the characteristic coagulation time θ=−na/(dna/dt). In the contrast to traditionally used equations, the proposed expressions allow one to describe with high accuracy the rate of stationary coagulation of not only low concentrated suspensions, where the volume content of nanoparticles is ρ≪1 %, but also rather highly concentrated ones, at ρ∼1 % and more (ρ=nava where va is a particle volume), which are relevant for most of the industrial applications. Analytical expressions are written for both three-dimensional geometry, which is relevant for real colloids, and two-dimensional geometry, which is useful to compare results of the analytical solution and numerical simulation. Computer experiments are performed in the framework of the two-dimensional method of stochastic dynamics. Satisfactory agreement of the obtained analytical expressions with the results of numerical calculations is demonstrated. The dependences of the coagulation time on the height of the interparticle energy barrier and on the suspension concentration are analyzed. It is shown that, in contrast to the obtained theoretical expressions, the traditionally used formulas overestimate the characteristic coagulation time for highly concentrated suspensions by more than an order of magnitude., Materials science, Nanotechnology, Colloids, Concentrated, Suspension, Coagulation, Stochastic dynamics

Transparent yttrium aluminum garnet (Y 3(1+ x ) Al 5 O 12 ) ceramics with different deviations from stoichiometry were fabricated by solid-state reactive sintering of commercial powders. The influence of non-stoichiometry on phase composition, microstructure, grain growth kinetics and optical transparency of the ceramics were studied. It was found that for Al 2 O 3 -excess samples, the transmittance and the average grain size decreased sharply due to the Al 2 O 3 secondary phase. For the stoichiometric sample sintered at 1760 °C for 10 h, the highest transmittances of 83.1% at 1064 nm and 80.2% at 400 nm were obtained. For Y 2 O 3 -excess samples, when the excessive content was smaller than 0.7 mol%, the transmittance decreased slightly and the average grain size increased. However, when the deviation was larger than 0.7 mol% the transmittance and the average grain size decreased due to the secondary phases.

Well-dispersed yttria nanopowders were synthesized by a precipitation method from yttrium nitrate solution using ammonium hydrogen carbonate as a precipitant. Needle-like precursor Y 2 (CO 3 ) 3 ·2.79 H 2 O undergoes fragmentation and decomposition into isolated quasi-spherical Y 2 O 3 particles upon calcination in air. Highly transparent YAG ceramics were fabricated from the as-synthesized Y 2 O 3 powder and the commercial α-Al 2 O 3 powder by vacuum sintering. Phase transformation, morphology evolution, and sinterability of Y 2 O 3 powders, microstructure and optical properties of YAG ceramics were investigated in detail. The densification, grain growth, linear shrinkage and phase transformation of the as-sintered ceramics were also explored. The activation energy for grain growth in the ceramic sample is 881 kJ/mol. With optimized preparation conditions, YAG ceramics with the average grain size of about 20 μm were fabricated by sintering at 1780 °C for 20 h, whose in-line transmittance reached 83.7% and 80.3% at the wavelength of 1064 nm and 400 nm, respectively.

Transparent polycrystalline YAG ceramics were fabricated by solid-state reactive sintering of a mixture of commercial α-Al2O3 and Y2O3 powders with tetraethoxysilane (TEOS) and MgO as sintering aids. Pressed samples were sintered from 1500 °C to 1750 °C in vacuum. Phase transformation, densification, microstructure evolution, grain growth kinetics and optical transparency of YAG ceramics were examined. Fully dense YAG transparent ceramic with average grain size about 17 μm was obtained by vacuum sintering at 1730 °C for 10 h and the in-line transmittance of the sample was 80.9% at 1064 nm wavelength. The maximal transmission 82.8% was demonstrated for the sample sintered at 1730 °C for 20 h, whose average grain size was about 22 μm. These pure YAG ceramics can be used for optical windows applications.

Undoped and Nd- or Yb-doped laser-grade yttrium aluminum garnet and (Y,La)2O3 ceramics with a transmittance above 80% in the 1-μm lasing region have been prepared by solid-state reactions using nonagglomerated Y2O3 and Al2O3 nanopowders. The Y2O3 nanopowders were prepared via laser evaporation, chemical precipitation from urea solutions, and grinding of commercially available Y2O3 in a purposedesigned laboratory-scale attritor at stirrer rotation rates of up to 1500 rpm. The YAG ceramics were prepared using commercially available Al2O3. After grinding, all of the powders had a particle size on the order of a hundred nanometers. Green compacts produced from the nanopowders were sintered in a vacuum furnace between 1615 and 1750°C to give highly transparent ceramic samples.

Polycrystalline Nd:YAG ceramics were fabricated by the solid-state reaction and vacuum sintering method using Y2O3, α-Al2O3 and Nd2O3 as starting powders. These powders were mixed in ethanol doped with MgO and TEOS and ball milled for different time periods. The samples were sintered from 1500 °C to 1760 °C for 0.5–20 h. Effects of ball milling time on the particle size of powder mixtures as well as ceramics densification process, microstructure evolution and optical transparency of the as-prepared Nd:YAG ceramics were mainly investigated. It was demonstrated that coarse powders can be ground into fine particles. Porosities of Nd:YAG ceramics sintered at 1600 °C and 1760 °C decrease with the increase of ball milling time up to 12 h and are kept almost unchanged with further increasing the time. Contamination of the powders with impurities, which may not be observed in microstructures, when the ball milling time is overlong, and the very few residual micro-pores, will cause an infinitesimal decrease in transmittance. The grain growth kinetics of Nd:YAG ceramics fabricated from the optimal ball milling process was also studied in this paper. The highest in-line transmittance of 83% at 1064 nm was obtained by sintering the sample at 1760 °C/3 h from the powder mixtures ball milled for 12 h.

We consider quantum mechanics for which the system time is one of generalized coordinates. The generalized Hamiltonian has an unbounded spectrum, which allows us to introduce a Hermitian time operator. In the proposed formulation of quantum mechanics, a system time and observer’s time are introduced. The Schrodinger equation in the system time either does not hold or holds only approximately. The wave function is assumed to be square integrable with respect to all coordinates, including the system time. In some limit, this formalism reproduces standard quantum mechanics and the corresponding measurement theory.

The physicochemical properties of Y2O3 and Al2O3 nanopowders produced by the laser synthesis were studied. Carbonate and nitro groups along with bound water are formed on the surface of the Y2O3 nanopowders, whereas only nitro groups are formed in the case of Al2O3. After calcination of the nanopowders at temperatures higher than 750 °C in air followed by cooling to room temperature, the nanopowders repeatedly sorb H2O and CO2. The influence of commercial dispersant Dolapix CE64 on the stabilization of aqueous dispersions of the Y2O3 and Al2O3 nanopowders was studied. The obtained results can be used in colloidal methods of compacting optical ceramics.

To prepare ytterbium doped lanthania yttria nanopowder a method of laser evaporation of mixed oxides was used. After calcinations of the powder at 1200 °C a pure single-phase solid solution Yb 3+ :(La x Y 1− x ) 2 O 3 was formed in the nanoparticles. Influence of lanthanum oxide as an isovalent additive on the yttria structure was investigated. The lanthanium ions were proved to be a good aid to sinter yttria ceramics doped with Yb 3+ at moderate temperatures about 1650 °C. The ceramics with relative density higher than 99.99% and grain size about 40 μm were fabricated. Full transmittance of 1.8 mm thick Yb 0.11 La 0.23 Y 1.66 O 3 ceramics reached 82.5% at 800 nm. This material could be a good gain medium for ytterbium high power pulse lasers.

Weakly agglomerated nanoparticles of (Ho 1-x La x ) 2 O 3 solid solutions were synthesized with the help of a self-propagating high-temperature synthesis (SHS). The nanopowders were studied by a simultaneous thermal analysis (TG-DSC), X-ray diffraction (XRD), BET and FT-IR spectroscopy methods. Changes of the particles morphology after annealing at different temperatures and ball milling were investigated by a scanning electron microscopy (SEM) and a dynamic light scattering (DLS) method. It was found that annealing at a temperature of 900 °C in air and ball milling of the SHS nanopowders allow obtaining rounded shape particles with a mean diameter of about 20 nm and C-type cubic crystal structure. Up to 10 mol.% of the lanthana was shown to dissolve in the holmium oxide nanoparticles. © 2019 Russian Science Foundation: 18-13-00355 This work was supported by the Russian Science Foundation (research project No. 18-13-00355 ).

To produce highly transparent Yb-doped yttrium lanthanum oxide (Yb3+:(LaxY1–x)2O3) ceramics two original technologies were used: laser synthesis of nanopowder and pulsed magnetic compacting. Sintering of the compacts in vacuum 3×10–4 Pa at 1600–1700 °C during 13 hours led to transparent ceramics fabrication. The ceramics with relative density higher than 99.99% and grain size about 40 µm were fabricated. Full transmittance of 1.8 mm thick Yb0,11La0,23Y1,66O3 ceramics reaches 82.5%@800 nm. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Methods for synthesis of nanosized precursors for the preparation of yttrium-aluminum garnet from organic-inorganic derivatives of yttrium and aluminum have been developed. It has been shown that most of the methods for carrying out the process result in the formation of precursors with high specific surface area. The precursor obtained using nanosized powder of aluminum oxide and yttrium acetylacetonate is the least agglomerated. The data obtained can be used when preparing optical ceramic from yttrium-aluminum garnet.

Symmetric fully liquid-crystalline triblock copolymers of various structures containing optically active mesogenic groups are for the first time synthesized via pseudoliving radical reversible addition-fragmentation chain-transfer polymerization. Their phase behavior and physicochemical and optical properties are studied. It is shown that, depending on composition, at low temperatures block copolymers can form at temperatures phase-separated structures caused by microsegregation of blocks of different chemical natures and that, with an increase in temperature, these structures can mix to form a cholesteric mesophase characterized by a helical supramolecular structure. A model illustrating the molecular packing of block copolymers with a phase-separated lamellar structure is advanced. The effect of the molecular structure of the block copolymers on their optical properties is discussed.

A fiber ytterbium laser is used to obtain weakly aggregated nanopowders for yttria-stabilized zirconia solid electrolytes, ZnO and ZnS phosphors, and YAG- and Y2O3-based optical ceramics. The characteristics of the nanopowders are reported. The productivity and energy consumptions of the process with the use of fiber and CO2 lasers are compared. The influence of the buffer gas pressure in the evaporation chamber on the specific surface area of the nanopowder and particle size distribution is studied. The elemental composition of nanoparticles is found to change relative to the composition of the target when yttrium aluminum garnet is evaporated. In the pulsed mode of operation, the energy needed for nanopowder production is minimal when the radiation pulse is about 100 μs long.

Precision X-ray diffraction at synchrotron radiation was used to reveal the separation of perovskite-like oxides SrCo0.8-xFe0.2NbxO3-z (x = 0.2 and 0.3) into two phases of a similar structure identical to initial perovskite structure, but having different unit cell parameters and supposedly different oxygen deficiency. The structural transformation is accompanied by oxygen outlet from the structure. The study of oxygen atoms intercalation from air into the oxygen-deficient structure showed that the structural changes are reversible: heating to 400°C in air restores the initial state of samples.

Results of tribological testing of stable colloidal dispersions of detonation nanodiamond (DND) in combination with other lubricant additives in mineral oil, greases as well as in polyalphaolefin (PAO) oil are reported. The synergistic effect of combining DND with polytetrafluoroethylene (PTFE), copper nanoparticles or a commercial additive Vanlube (non-phosphor containing anti-wear additive) is reported. Testing of the formulations using ring-on-ring, shaft/bushing and four ball test techniques was performed. The test results reveal more than 80-90% decrease of friction coefficient, about 50% decrease of a diameter of wear spot as well as several times increase of extreme pressure failure load for certain formulations. A strong synergistic effect when using a combination of DND/PTFE additives was observed by a sharp decrease of friction coefficient. It was also demonstrated that the use of smaller DND aggregate size (10nm versus 120nm) resulted in better lubricating performance of PAO-based oil formulation.

Strontium cobaltite doped with Fe and Nb, SrCo0.6Fe0.2Nb0.2O3−z, with perovskite-like structure, being one of the promising materials for oxygen permeable membrane implementation, has been investigated via in situ high temperature X-ray powder diffraction on Bruker D8 Advance instrument and high-resolution powder diffraction at synchrotron radiation beamline. The oxygen outlet from the lattice has been found to stay in correlation with the structural rearrangement forming two phases with different oxygen deficiency. The activation energy of phase splitting process has been estimated to be Eactivation ≈ 0.63 ± 0.06 eV.

The phase stability of SrCo0.8Fe0.2O3−d perovskite doped with niobium was studied by in situ high-temperature X-ray diffraction in the temperature range of 30–1000 °C and oxygen partial pressure 0.2–10−5 atm. The stability of the cubic perovskite structure in a wide range of oxygen partial pressures is the main advantage of SrCo0.8−xFe0.2NbxO3−d (x = 0.1–0.3) system in comparison with SrCo0.8Fe0.2O3−d. It is suggested that equilibrium of the thermal expansion with changes of the oxygen non-stoichiometry leading to the same lattice parameters in the oxidizing and reducing environments at the catalytic temperatures is a necessary requirement for stable operation of perovskite as an oxygen-conducting membrane. In the case of SrCo0.8−xFe0.2NbxO3−d perovskite this condition is met at x = 0.2. This makes the SrCo0.6Fe0.2Nb0.2O3−d composition promising for application as oxygen-conducting membrane.

Oxide nanopowders Y 2 O 3 , Nd 3+ :Y 2 O 3 , Nd 3+ :Y 2 O 3 + Sc 2 O 3 , Al 2 O 3 , Nd 3+ :Y 2 O 3 + Al 2 O 3 , ZrO 2 were prepared with the help of pulse-repetitive CO 2 laser evaporation and subsequent vapor condensation in the flow of buffer gas. The mean size of the nanoparticles was about 10 nm. All these nanoparticles were found to be in metastable state at room temperature. Structure of the nanoparticles, the results of X-ray, thermogravimetry and differential scanning calorimetry (TG–DSC) analysis, as well as reasons of metastable lattice formation are discussed.

Perovskite SrCo0.6Fe0.2Nb0.2O3-z attracts attention as a promising material with high oxygen conductivity. The sample was investigated by means of high-temperature X-ray powder diffraction and thermogravimetry. Phase transition was detected near 400 °C and accompanied with significant mass loss. The phase transition affects oxygen mobility, important for the synthesis of oxygen permeable membranes. The unit cell parameters are proved to change with temperature after two effects (1) reversible conventional thermal expansion and (2) irreversible contraction-expansion due to the changes in the oxygen content. In situ high-temperature X-ray diffraction experiments allowed us to separate the contributions and to measure them as a function of temperature.

About new technology of production of transparent ceramics including laser synthesis of nanopowders, their magnetic pulsed compaction and vacuum sintering is reported. The results of investigations of the synthesized samples of transparent ceramics made from neodymium-activated yttrium oxide are presented. It has been shown that in a 1.1 mm thickness sample with optical loss coefficient α1.07μm = 0.03 cm−1 laser generation at λg ∼ 1.08 μm with a slope efficiency of 15% at laser diode pumping at a wavelength of 807 nm has been obtained.

The results of investigations of mechanical, optical and laser characteristics of ceramics made from neodymium-activated yttrium oxide are presented. The ceramics were fabricated with the use of a new technology including Laser synthesis of nanopowders and their magnetic pulsed compaction (LSN&MPC). The fracture toughness (K 1C = 0.9-1.4 MPa m 1/2 ) and microhardness (H v = 11.8 GPa) of the ceramics have been determined. It has been found that ceramic samples sintered in the temperature range from 1550 to 2050 °C have (1-150) vol. ppm porosity and optical loss coefficient in the range from 0.03 to 2.1 cm -1 . It has been shown that pore content in this range did not influence on the optical loss coefficient. Laser generation at λ g ≈ 1.079 μm with a slope efficiency of 15% under laser diode pumping has been obtained in 1.1 mm thickness sample with α 1.07 μm = 0.03 cm -1 .

Pulsed cathodoluminescence of Nd3+: Y2O3 nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd3+: Y2O3 cubic phase is located at λ1 ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd3+ arise in the spectrum at λ2 ≈ 750 nm and λ3 ≈ 720 nm. The emission spectrum of all Nd3+: Y2O3 materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd3+: Y2O3 materials is mainly determined by local absorption (self-absorption) of neodymium ions.

The polarization reversal process under pulsed laser irradiation without application of electric field was investigated in single crystalline congruent and MgO doped lithium niobate LiNbO 3 . The nano-domain structures obtained in different experimental conditions were statistically analyzed and characterized in terms of domain growth anisotropy.

We studied mechanical, optical, and lasing parameters of neodymium-doped yttrium oxide ceramics synthesised by using a new technology involving the laser synthesis of nanopowders and their magnetic pulsed compaction. The fracture toughness of ceramics to cracks and its microhardness were measured to be KIC = 0.9—1.4 MPa m1/2 and Hν = 11.8 GPa, respectively. Ceramic samples sintered in the temperature range from 1550 to 2050°C have the porosity (1—150)×10-4% and the optical loss coefficient α1.07 = 0.03—2.1 cm-1 at a wavelength of 1.07 μm. It is shown that such porosity does not affect the optical loss coefficient of light. Lasing at ≈1.079 μm with a slope efficiency of 15% was obtained in a 1.1-mm-thick sample pumped by laser diodes.

The possibility of synthesizing technological Nd 3+ Y 2 O 3 and Y 2 O 3 optically transparent ceramics is studied. This technology is different from the conventional approaches, because the compacting was performed using the uniaxial static compression with ultrasonic treatment of the compacted nanopowder. It was found that the relative compact density in the case of compaction of weakly agglomerated powders with an average parti- cle size of about 10 nm varies in the range from 0.48 to 0.58 depending on pressure (240-720 MPa), and it weakly depends on the ultrasonic treatment. At the same time, using ultrasound for nanopowder compaction allowed enhancement of the optical properties of ceramics and indeed race in its radiation attenuation factor at the wavelength of 1.06 µ m from 8.26 to 2.53 cm -1 . The radiation attenuation is related to the scattering centers observed in the samples: pores and inclusions with a content of about ~10 -2 and 10 -3 vol %, respectively, as well as the compaction defects that play a predominant role in the process. It is pointed out that the developed approach is promising for manufacturing large-volume, optically transparent ceramics.

In this paper the fabrication of dense, optically transparent ceramics by compaction and sintering of nanosized Y 2 O 3 powders, doped by different Nd 2 O 3 content (1.0 and 3.3 mol%) is investigated. The sintering temperature was decreased substantially, and there were no extra additives inserted into basic oxide due to high nanosystem activity. The as synthesized powder was transformed from monoclinic to cubic modification by the preliminary calcination in air at 800 °C in order to avoid cracking during sintering. This phase transformation of the starting powder, annealing of the compacts in air (1200 °C) and sintering in vacuum for 1 h at 1700 °C allowed to fabricate optically transparent ceramics with well-formed boundaries, average crystalline size of 30–40 μm and vanishingly small porosity with pore size less than 0.5 μm.

YSZ, YSZ + Al 2 O 3 , Ce 0.78 Gd 0.22 O 2-δ , and 5NdY 2 O 3 nanopowders are obtained using target evaporation with a repetitively pulsed CO 2 laser and subsequent vapor condensation in the flow of a carrier gas. The design of the laser complex for producing the nanopowder and the block diagram and the characteristics of the repetitively pulsed CO 2 laser pumped by a combined discharge are presented. The size distribution of the nanoparticles is studied and the x-ray data are reported. It is demonstrated that a nanopowder output rate of 15-75 g/h linearly increases with the mean laser power. Under equal conditions, the size distribution of the particles is weakly affected by the type of the target material. The results obtained are interpreted.

The dynamics and the spectral kinetic characteristics of the plume emerging in the vicinity of graphite targets, pressed pellets consisting of zirconium oxide powder stabilized with yttrium (YSZ) and yttrium-aluminum oxides with neodymium (YAO:Nd), and single-crystal YAG:Cr are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a wavelength of 10.6 μm, a peak power of up to 9 kW, a pulse energy of 1.69 J, and a pulse duration of 330 μs at a level of 0.1. The plume propagates normally to the target surface at an angle of 45° relative to the laser radiation. The spectral kinetic characteristics of the plume luminescence are discretely measured along the entire length. It is demonstrated that the plumes of all targets (except for the single-crystal YAG:Cr) represent the flows of a weakly nonequilibrium gas plasma with a temperature of 10 kK (graphite) and 3.1–4.7 kK (YSZ and YAO:Nd pressed pellets). The plume size is determined by the peak power of the laser pulse. The luminescence of the two-atom radicals (C2 in graphite; ZrO and YO in YSZ; and YO, AlO, and NdO in YAO:Nd) dominates in all of the plumes. A single radical (YO) and the spectral lines of atoms and atomic ions are observed in the YAG:Cr plume. A relatively high temperature of the graphite plume is maintained owing to the energy of the exothermic reaction involving the association of carbon atoms and the energy of the vibrationally excited molecules resulting from this reaction.

Spectral and kinetic properties of a plume formed in the vicinity of a graphite and a pressed yttrium-stabilised zirconium oxide (YSZ) powder targets irradiated in air by a 10.6-μm pulsed CO2 laser with a peak power of 1.5–9 kW at room temperature are studied. The plume propagated at right angles to the target surface and at an angle of 45° to the laser radiation. The spectral and kinetic characteristics of its luminescence were measured discretely along the entire length of the plume. It is shown that the YSZ plume as well as the graphite plume is a flux of nonequilibrium gaseous plasma at a temperature of about 4.7–3.1 kK, in which a luminescence of YO and ZrO radicals is excited.

Spectral and kinetic characteristics of a plume formed in the vicinity of a graphite target exposed to radiation from a pulsed CO2 laser at 10.6 μm with a peak power of 9 kW (pulse energy 1.69 J, pulse duration 330 μs at the 0.1 level) in air are studied at room temperature. It is shown that the plume propagating at a right angle to the target surface and at an angle of 45° to the laser radiation is a nonequilibrium gas plasma flow at a temperature of the order of 10 kK; its shape and size are determined by the shape and power of the laser pulse. Emission of C+ ions and C2 molecules is excited in the plume. The temperature and emission are sustained by the energy of the exothermic reaction of association of carbon atoms and the vibrationally excited molecules formed in it.

The characteristics (phase composition, grain shape, grain size distribution, and specific surface area) of Ce0.78Gd0.22O2-δ nanopowders produced by exposing the target to pulsed CO2 laser radiation are reported. Reasons for a threefold increase in the output of the experimental powder-preparation unit (up to 60 g/h) with the characteristic grain size (≈10 nm) remaining unchanged are discussed.

Experimental data on the nonlinear dynamics of a plasma torch generated by a laser pulse of large width acting upon a graphite target are presented and discussed. The mushroom shape of the luminous region and the duration of emission observed in experiment are explained by the development of the Richtmyer-Meshkov instability at the carbon plasma-air interface and by the formation of nanoparticles in the plasma expanding into the buffer gas.

The design and characteristics of a setup for producing metal oxide nanopowders with an output of up to 20 g/h are discussed. The grain mean size in the powders is 15 nm, and the radiation power consumption is 30—40 (W h)/g. Y2O3-stabilized ZrO2 (YSZ) and Al2O3 + YSZ nanopowders are prepared by target evaporation with a pulse-periodic CO2 laser, followed by vapor condensation in an air stream. The mean power, peak power, and efficiency of the pulse-periodic CO2 laser, excited by a combined discharge, are, respectively, 1 kW, 10 kW, and ≈10%. Data for the powder specific surface, grain shape, and grain size distribution, as well as results of X-ray phase and structure analysis, are reported.

The results of investigations aimed at the development of a repetitively pulsed CO2 laser with an active medium volume of 1000 cm3 pumped by a combined discharge are generalised. It is shown that, at pump pulse durations of 200–500 μs the optimal characteristics are achieved at active-medium pressures of 60–100 Torr. In this case, the laser efficiency at the initial stage of its operation can reach 22% and; if the energy dissipated in the region of the cathode potential drop is neglected, the efficiency is 28%. After emission of 3×105 pulses, the laser efficiency falls to 12%. It has been found that adding CO with a relative concentration [CO]/[CO2] ~0.75 increases the input and output power by almost 50%. The lasing efficiency is then 10%—12%, and the service life of the laser is by more than 106 pulses with a power decrease of no more than 10%. Adding hydrogen up to a concentration [H2]/[CO2] ~10 leads to an increase in the energy supplied to the gas due to a decrease in the rate of ionisation processes. However, the optimal ratio is [H2]/[CO2] ~ 1, at which the output power increases by 15%. In a long-term operating mode, the laser power is 1 kW at a peak power of 10 kW and an efficiency of 12%.

A combined method of excitation of a gaseous medium is used in an investigation of the energy characteristics of a non-self-sustaining discharge as functions of the capacitance of the capacitor bank, the number of pulses per burst, and the burst repetition rate for different time intervals between the pulses in a burst and different flow velocities of the gas. It is shown for infrared lasers that under optimal pumping conditions the average discharge power can reach 8.5 W/cm3 for a pulse power of 25 W/cm3.

The results of investigations of mechanical, optical and laser characteristics of ceramics made from neodymiumactivated yttrium oxide are presented. The ceramics was fabricated with the use of a new technology including L aser s ynthesis of n anopowders and their m agnetic p ulsed c ompaction (LSN&MPC). The fracture toughness Κ IC = 0,9 - 1,4 MPa•m 1/2 ) and microhardness (H V = 11,8 GPa) of the ceramics have been determined. It has been found that ceramic samples sintered in the temperature range from 1550 to 2050°C have (1 - 150) vol. ppm porosity and optical loss coefficient α 1,07 μm = 0,03 - 2,1 cm -1 . It has been shown that pore content in this range did not influence on the optical loss coefficient. Laser generation at λ g ≈ 1,08 μm with a slope efficiency of 15 % at laser diode pumping has been obtained in 1.1 mm thickness sample with α 1,07 μm = 0,03 cm -1 .

General properties of intersecting extremal p-brane solutions of gravity coupled with dilatons and several different d-form fields in arbitrary space-time dimensions are considered. It is show that heuristically expected properties of the intersecting p-branes follow from the explicit formulae for solutions. In particular, harmonic superposition and S-duality hold for all p-brane solutions. Generalized T-duality takes place under additional restrictions on the initial theory parameters .

The dynamics and the spectral kinetic characteristics of the plume emerging in the vicinity of graphite targets, pressed pellets consisting of zirconium oxide powder stabilized with yttrium (YSZ) and of garnet stock with neodymium (YAG:Nd) are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a wavelength of 10.6mm, a peak power of up to 9 kW, a pulse energy of up to 1.69 J, and a pulse duration of 330ms at a level of 0.1. The plume propagates normally to the target surface at an angle of 45° relative to the laser radiation. The spectral kinetic characteristics of the plume luminescence are discretely measured along the entire length. It is demonstrated that the plumes of all targets represent the "ows of a weakly nonequilibrium gas plasma with a temperature of 10 kK (graphite) and 3.1...4.7 kK (YSZ and YAG:Nd pressed pellets). The plume size is determined by the peak power of the laser pulse. The luminescence of the two-atom radicals (C2 in graphite; ZrO and YO in YSZ; and YO, AlO, and NdO in YAO:Nd) dominates in all of the plumes. A relatively high temperature of the graphite plume is maintained owing to the energy of the exothermic reaction involving the association of carbon atoms and the energy of the vibrationally excited molecules resulting from this reaction. The dynamics of plasma plume was studied by luminescence imaging and shadowgraphy.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This report deals with the production and characteristics of Y2O3 -stabilized ZrO2 (YSZ), A12O3+YSZ, GDC, Nd:Y2O3 and Nd:YAG nanopowders prepared by evaporation of the materials with the help of a pulse-repetitive CO2 laser. The design of a setup for the nanopowders production, scheme and characteristics of the original CO2 laser excited by a pulse-periodic combined discharge are reported. For YSZ; Al2O3+YSZ, Nd:Y2O3, Nd:YAG the output rate was 15-25 g/h, for GDC ~ 50-75 g/hour, the energy consumption 30-40 (W*h)/g and 8-15 (W*h)/g, respectively. Data for the nanopowders specific surface, size distribution, the results of X-ray phase and structure analysis, as well as the results of luminescence analysis are discussed. The analysis of the obtained results showed that two main factors that determine the output rate of the nanopowders synthesis are the type of material evaporated and the mean laser radiation power. The mean size of the nanoparticles doesn't depend on the type of material.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

YSZ, YSZ + Al2O3, Ce0.78 Gd0.22O2−δ, and 5NdY2O3 nanopowders are obtained using target evaporation with a repetitively pulsed CO2 laser and subsequent vapor condensation in the flow of a carrier gas. The design of the laser complex for producing the nanopowder and the block diagram and the characteristics of the repetitively pulsed CO2 laser pumped by a combined discharge are presented. The size distribution of the nanoparticles is studied and the x-ray data are reported. It is demonstrated that a nanopowder output rate of 15–75 g/h linearly increases with the mean laser power. Under equal conditions, the size distribution of the particles is weakly affected by the type of the target material. The results obtained are interpreted.

No Abstract Available.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The paper reports about a new pulse-repetitive high-efficient technological CO2-laser and its applications. An original method of active medium excitation was used for laser pumping. Efficiency of the laser constructed on the basis of this method reached 12%, average radiation power 600 W, pulse power ~ 10 kW. The laser was used for YSZ powders production by successive evaporation and crystallization in the gas stream. The output rate was 15-20g/h, specific surface of the powder was up to 70m2/g. Evaporation of materials by CO2 laser was also used for ZrO2 and Al2O3 thin films deposition on stainless steel plates. The average thickness of the film was ~500nm, the deposition rate was ~10nm on the area ~1cm2 per pulse. The deposited films have high adhesion properties.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Our paper reports about YSZ powders production by successive evaporation and crystallization in the gas stream. In the laser applied the original method of active medium excitation was used. Efficiency of the laser constructed on the basis of this method reached 22% and specific power output /spl sim/1 W/cm/sup 3/. Pulsed regime is proved to be more efficient for active medium excitation and target evaporation then continuous one. Targets made from coarse YSZ powder with a Y/sub 2/O/sub 3/ content of 10.15 mol.% were evaporated and crystallized in a stream of cleaned air. Cubic-structure YSZ particles were obtained which had a shape close to spherical. Particle size distribution was close to a lognormal distribution with dg=10 nm and /spl sigma/=1.75. Specific surface of the powder was up to 70 m/sup 2//g, while the Y/sub 2/O/sub 3/ content reduced to 9.8 mol.%.

The development of high-efficiency and scaleable CO/sub 2/ lasers is important both for technology, and for high-scale lasers development. As a rule, the pumping and consequently radiation are realized continuously, when all pumped through discharge gap media is excited. As a result, good energetic parameters and minimum ratio between pumping through the discharge gap gas volume and output energy are reached. In the pulsed regime the main part of the gas pumped between pulses appears to be not excited. However, pulsed radiation treats a target more effectively. That is why methods which can provide high specific energy, scalability, and high laser efficiency, are developed. The paper investigates energetic characteristics and efficiency of a combined discharge pumped CO/sub 2/ laser, which does not contain current reducing elements in the excitation electrical circuit. The new pulsed-repetitive laser pumping regime is realized. The possibility of obtaining high efficiency (22% or 28% without cathode fall) is shown. The output power density is /spl sim/1 W/cm/sup 3/. It is proved that combined discharge energetic characteristics are no worse than ones of e-beam controlled discharge and significantly better then ones in other discharges.