G. E. Val’yano

Investigation of the characteristics of a colloidal solution and its solid phase obtained through ablation of zinc in water by high-power radiation from a copper vapor laser

Experimental data are presented on the study of a colloidal solution created through zinc ablation in water by means of high-power radiation from a copper vapor laser. Absorption spectrum analysis is performed in the optical range of λ = 200–600 nm. The structural composition and morphology of the solid phase isolated from the colloid are determined by means of X-ray diffractometry, and atomic-force and scanning electron microscopy. It is demonstrated that ZnO, as well as zinc, nanoparticles, which oxidize to ZnO under colloid ageing, are present in the colloid composition after target irradiation. The ZnO end product has a complex structure, which is based on hexagonal crystals 40 × 80 nm in size on average.

Investigation of the high-temperature properties of zirconium nitride by impulse current heating method

The zirconium nitride specimens were obtained as a thin (2.5 μm) layer deposited on the insulating K-8 glass substrates by the magnetron sputtering technique. The impulse current heating permitted reaching the nitride melting region in 5 μs. The current, the voltage, and the radiation at the wavelength of 856 nm were registered. The energy input (the enthalpy), E, the heat capacity, Cp, the resistivity, ρ (referred to the initial specimen dimensions), and the temperature, T, were calculated. The results on the resistivity, the specific heat, and the melting temperature (2700 K) of the zirconium nitride under a high content of nitrogen (about 49 at %) and oxygen (about 11 at %) in the specimen were obtained. The limit temperature in the investigation was as high as 3400 K.

Formation of hollow micro- and nanostructures of zirconia by laser ablation of metal in liquid

Nanosized zirconia particles were generated by the laser ablation of metal in water and aqueous solutions of sodium dodecyl sulfate (SDS); the structure and morphology of the material were studied by X-ray diffractometry, Raman scattering spectroscopy, and scanning electron microscopy. The cubic, tetragonal, and monoclinic phases of zirconia and an organic-inorganic nanocomposite of Zr-SDS are found in the ablation product upon exposure of zirconium to powerful nanosecond laser pulses with a high repetition rate. Morphologically, the synthesized dioxide is present mainly in the amorphous state. Depending on the experimental conditions, the crystallized part of the dioxide consists of aggregates of rounded dense particles and hollow formations, whole or partially collapsed, close to spherical in shape. It is assumed that vapor-gas bubbles generated during ablation serve as templates for hollow micro- and nanoscale structures.

A ceramic based on partially stabilized zirconia: Synthesis, structure, and properties under dynamic load

A ceramic based on zirconia partially stabilized by yttrium oxide has been prepared. The main properties of the prepared ceramic have been characterized: density, ultimate strength under twisting, microhardness, elasticity coefficients, etc. The microstructure and phase composition of the ceramic and its phase transformations under mechanical action have been studied. The properties of the ceramics under dynamic load have been studied, and the values of the dynamic elastic limit and splitting strength have been obtained. The results have been compared with the literature data.

The features of the synthesis of ZnO nanostructures by laser ablation of zinc in water-surfactant solutions

The data of experimental investigation of optical properties of colloidal solution, its composition and morphology of the dispersed phase, resulting from laser ablation of zinc in aqueous solutions of surfactants—sodium dodecyl sulfate (SDS) and dioctil sodium sulfosuccinate (AOT) are presented. It is shown that an optical absorption spectra of the colloids, X-ray spectra and AFM (atomic force microscopy) images solid phase of colloids can trace the dynamics of synthesis ZnO nanostructures from zinc nanoclusters in the size of nanometers to fractal aggregates (FA) up to hundreds of nanometers. Determinants of this process are the average power and duration of irradiation, the frequency of the laser pulses, the colloid aging time, the type and concentration of surfactant in the solution. At the selecting of appropriate regimes of the process, along with zinc oxide other nanoproducts-hydrozincite and organic-inorganic layered composite [(β)-Zn(OH)2 + SDS] are obtained.

Phase transitions of partially stabilized zirconia under stepwise shock-wave loading

High-density partially yttria-stabilized zirconia ceramics were manufactured. The primary properties of the manufactured ceramics, such as crack resistance, ultimate bending strength, hardness, elastic moduli, etc., were characterized. The microstructure of the ceramics and the phase transitions under mechanical (including shock-wave) and thermal actions were studied.

Ceramics based on partly stabilized zirconium dioxide: technology, structure, properties, and behavior under dynamic action

Technology is described for manufacturing dense ceramic from very fine powder based on zirconium dioxide partly stabilized with yttrium oxide. Some engineering properties of the manufactured ceramic are defined. Its microstructure and phase composition are studied. Ceramic properties with impact-wave loading are studied, and values of dynamic elastic limit and spalling strength are obtained.

Investigation of the Formation of a Fine-Crystalline Alumina Coating on the Surface of a Blank Aluminum Powder Coating Test Panel as a Result of its Filtration Combustion

Formation of a fine-crystalline α-Al2O3 coating on the surface of an aluminum blank powder coating test panel by filtration combustion (FC) in air was investigated. Finely ground sodium silicate glass (1 vol.%) introduced into the composition of the blank aluminum panels was used as the activating agent of the filtration combustion. It was found that a fine-crystalline aluminum oxide coating with a thickness of 30 – 50 μm with crystals ranging 0.1 – 2.0 μm in size forms over the entire surface of the sample upon completion of the filtration combustion. The properties of the produced samples were as follows: density 2.3 g/cm2, open porosity 15%, ultimate bending stress 120 MPa, fracture toughness 3.6 MPa·m1/2, Brinell hardness 32.

Structure and Physicomechanical Properties of Porous Ceramic Based on Al2O3 Prepared Using a Filtration Combustion Method

Atechnological approach is proposed making it possible to prepare highly porous ceramic based on Al2O3 using a method of filtration combustion (FC). The method is based on an exothermic oxidation reaction (in an FC regime) of aluminum powder PAP-2 particles mixed with spherulites of commercial alumina (type 1 material) or kaolin fibers (type 2 material). Depending on the volume faction of PAP-2 open porosity for sintered type 1 material is from 38 to 50%, and ultimate strength in bending is from 10 to 50 MPa. Good material thermal shock resistance, evaluated from the relative loss of crack resistance after thermal cycling by a regime of heating to 850°C and cooling in an air stream (18°C), comprises 12 – 15% and is unchanged after five successive thermal cycles. Material of type 2 is an ultra-lightweight heat insulator with density of 0.25 – 0.50 g/cm3. The bearing strength is 0.10 – 0.15 MPa, and thermal conductivity in the range 20 to 1000°C is 0.06 – 0.17 W/(m·K).

Damage of an Ultrasonic-Waveguide Surface during Cavitation Accompanied by Sonoluminescence

The surface of a titanium (VT1-0) waveguide, which exhibits the sonoluminescence effect, is analyzed. The effect of sonoluminescence on the waveguide induces the formation of a series of cavities on its surface. Temperatures at the waveguide surface have been estimated, which makes it possible to assess the processes occurring upon sonoluminescence. If the effect observed is a high-temperature phenomenon, traces of metal melting are expected to be found on the waveguide surface. Analysis of the titanium waveguide shows that the observed surface destruction is due to mechanical impact and the absence of visible melting traces is likely to indicate that high temperatures are not reached.