Selenic acid electrolyte provides porous anodic aluminium oxide (AAO) films with low porosity and high optical transparency. Here, the high-temperature behaviour of AAO obtained in a selenic acid ...electrolyte is reported for the first time. The crystallization of as-prepared amorphous AAO at about 800 °C is accompanied by the elimination of electrolyte impurities, an increase in pore diameter from 15 to 21 nm, and an increase in specific surface area to 55 m2·g−1 due to the mesopore formation inside the cell walls. The second crystallization stage at about 1150 °C results in the formation of coarse-grained corundum (α-Al2O3) films with a mean grain size of about 11 μm. Each of the grains consists of regularly arranged 27-nm-diameter pores, which are stable up to 1300 °C. AAO physicochemical properties depend on the annealing temperature. In particular, chemical stability is up to three orders of magnitude higher after two-step crystallization. Optical properties and thermal expansion of selenic-acid-made porous AAO films with different phase composition are quantified. The crystallization of as-prepared AAO to low-temperature Al2O3 polymorphs has a minor influence on optical transmittance and effective refractive index of AAO, whereas the coarse-grained structure of corundum causes an order of magnitude decrease in average transmittance in the visible region. The coefficient of thermal expansion increases by 25% to 8.5 × 10−6 K−1 for α-Al2O3 porous films compared to as-prepared AAO.
Display omitted
•Annealing behaviour of anodic alumina prepared in selenic acid electrolyte is studied.•Specific surface area reaches 55 m2·g−1 at 803 °C due to formation of mesopores.•Coarse-grain α-Al2O3 films with pores of 30 nm in diameter are stable up to 1300 °C.•Coefficient of thermal expansion of annealed anodic alumina is 8.5 × 10−6 K−1.•Drastic increase in the chemical stability of anodic alumina is observed after annealing.
This paper is dedicated to a study of conductivity and current-voltage characteristics (IV curve) of lithium niobate (LN, LiNbO3) single crystals. The studied crystals have been turned to a single ...domain state. We have researched nominally pure congruent (CLN) and strongly doped LiNbO3:Mg and LiNbO3:Zn crystals at Т = 300–450 K. Magnitude, activation energy and type of conductivity have been established in CLN, LiNbO3:Mg and LiNbO3:Zn in the temperature range Т = 300–450 K. Coercive field in LiNbO3:Mg and LiNbO3:Zn crystals is much lower than in CLN. However, we have determined that nonlinearity of IV curve exists in CLN crystals and is absent from LiNbO3:Mg and LiNbO3:Zn crystals at temperatures up to 450 K and external electric field strength up to 12 kV/mm. The paper suggests possible explanation for the observed effects.
•Lithium niobate (LN) crystals conductivity and I-V curves are studied at 300–450 K.•Electrical properties of CLN pure, Mg and Zn doped LN single crystals are compared.•Conductivity types were determined in CLN, Mg and Zn doped LN at 300–450 K.•CLN has nonlinear I-V curve, LN:Mg and LN:Zn crystals have linear I-V curves at 400 and 450 K.
The research is aimed at solving the problem associated with the complexity of using fibres from wood waste as a raw material for a rapidly developing additive technology. The ability to adapt ...wood-fibre composite material to additive technologies will provide the industry with an annual growth of more than 20% with a new type of inexpensive biodegradable material. To solve the problem, an analysis of literature sources describing 3D printing methods and composite materials used in additive technologies was carried out. A combination of two methods of extrusion printing with a polymer filament and a paste-like composition containing wood-fibre waste is proposed. The prototypes were produced using a two-extruder 3D printer. The morphological characteristics of the fibrous composite material made of pine wood were previously studied using a particle analyser and scanning electron microscopy. The strength of samples made from different types of multicomponent polymers with different content of fibrous composite material from wood waste was also studied. Recommendations on the use of a polymer composition containing pine wood fibres for 3D printing in the manufacture of decorative products of complex shape for furniture are given.
—
The long-term stability of counters consisting of extruded-scintillator strips and wavelength-shifting fibers was studied. The aging study was carried out for scintillators and wavelength-shifting ...fibers before starting the mass production of counters. Aging at a higher rate and higher temperatures was used in the study, which was then continued as an interesting R&D work. The decrease in the light yield was at a level of 3% per year during an initial 5–6 years. The aging then proceeds slower and nearly ceases after a 26% decrease over 20 years. The study of preliminarily aged samples was repeated after a 2.5-year pause; it showed that the aging rate for these scintillators was less than 0.5% per year at 20°C. The results obtained over 4.5 years by direct measurements and by using a faster-aging technology were in good agreement.
The work was devoted to import-substitution of foreign material based on polymer-modified plaster that is used in additive technologies, namely in Binder Jetting technology. Wood-based fibrous ...material was proposed for use. For this, granulometric analysis of particles obtained from crushing in a mill was performed. Fibrous materials based on beech, oak, larch, alder, and pine were prepared under identical crushing conditions. Pine particles had dimensions most like those of the imported polymer. Scanning electron microscopy of the various types of fibrous materials found that pine and larch particles deviated most from a round shape. Therefore, they would have a low bulk density, which would require more binder for 3D-printing. The fibrous material had a more complicated and developed shape that provided better binding of particles to each other, in contrast to smooth particles of polymer-modified gypsum. This could have a positive effect on the strength of items prepared using Binder Jetting technology.
Using the results of studying the electrical conductivity in the temperature range ~295–460 K and the IR absorption spectra of a series of LiNbO
3
:Mg crystals, it is shown that an increase in the Mg ...content leads to sharp decrease in the H
+
ion mobility during their displacement along the polar direction. This effect is observed most clearly in LiNbO
3
:Mg crystals with high (superthreshold) impurity content.
The paper deals with the effectiveness of the drug "L-lysine monohydrochloride feed". Animals of the experimental group additionally included in the main diet of 2.5% L-lysine monohydrochloride feed ...by weight of concentrates. The inclusion of the studied additive in the diets of young pigs contributes to an increase in the average daily gain of 14.1%, reducing the cost of feed by 11.73% compared with the control group. As a result of the research it was found that due to the use of the drug L-lysine monohydrochloride feed, an additional 3.38 kg gain per head or 253.5 rubles was obtained. During the study on laying hens aged 25 to 33 weeks, egg production was studied, which by the end of the experiment was: 93.7% in the control group, 95.2% in the experimental, which is 1.5% more. In addition, there is a tendency to increase egg weight by 1 g or 1.8%, yolk weight and its specific weight in the egg by 2 g or 13.3%, respectively, as well as thickening of the shell by 3 microns or 8.1%, and a decrease in shell content by 1%.
Studies on growing young pigs for rearing and fattening using a mixture of enzyme preparations were carried out on animals aged 2 to 7 months in the dynamics of their growth and development. The ...animals receiving compound feed used in the economy served as control. The compound feed of the first experimental group was enriched with a mixture of additional enzyme preparations amylosubtilin G3x and cellolux-F, and the second experimental group - a mixture of amylosubtilin G3x and protosubtilin G3x. The use of a mixture of amylosubtilin G3x and cellolux-F increases the average daily growth by 13.6 %, reduces feed costs by 11.8 % compared to the control group's pigs, a mixture of amylosubtilin G3x and protosubtilin G3x - an average daily increase of 8.7 %, a decrease in feed costs by 7.9 % compared to the control group's pigs. The highest content of muscle tissue in the half-carcasses was observed in animals in the first experimental group (58.5 %) and in the second experimental group (58.17 %), which is higher in the control group by 0.93 and 0.6, respectively. The results of research in the technology of pork production reveal new possibilities of using a mixture of enzyme preparations.
The mechanical properties of composite material prepared by impregnation of oxyfluorinated nonwoven needlepunch cloth with a dispersion of polyurethane are studied. The volume did not change during ...curing of the adhesive oxyfluorinated fibrous filler. The optimal duration of the oxyfluorination of the cloth, use of which could produce a composite material with significantly increased stretching resistance with a relatively low degree of impregnation, was established. The oxyfluorinated filler had practically no effect on the strength of the composite material with a reduced relative elongation at break.
The variations of electrical conductivity and the primary pyroelectric coefficient with temperature for lithium niobate (LiNbO
3
) crystals grown from melt containing K
2
O flux are studied in the ...range of 292–450 K. These crystals are found to exhibit considerable anisotropy of electrical conductivity, and the proton conductivity is dominant in the studied temperature range.
PDF