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•Microhotplate catalytic sensors based on anodic alumina supports are prepared.•Methane detection sensitivity reaches 15 mV/vol. % CH4.•Operando X-ray diffraction and thermogravimetry ...studies are performed.•Hysteresis in sensitivity correlates with Pd oxides content in the Pd-Pt catalyst.
Catalytic pellistor-type sensors are widely used for the analytical detection of flammable/explosive gases. Further improvement of the characteristics of the sensors can be achieved by the development of miniature sensing elements based on planar microhotplates, which allows one to decrease the power consumption substantially. Here we demonstrate the microhotplate catalytic sensors based on anodic aluminium oxide supports for methane detection. The sensor response approaches the value of 15 mV/vol. % CH4 at the optimal supply voltage. A wide hysteresis in sensor response is observed during the cycling of the supply voltage. This phenomenon is studied under operando conditions using X-ray diffraction and thermogravimetry. The obtained results have a significant impact on the development of optimal working regimes, and the production of planar catalytic sensors on porous supports.
A technological complex was developed in order to remove clay minerals, iron oxide, and fractions heavier than 2.9 tons/m
3
from glass quartz sands. The basis of the scheme of the apparatus chain of ...the complex consists of a trammel screen with a new design, jigs, and concentration tables with electromagnetic inductors. It was shown under laboratory conditions that sand in the highest demand — VS-030-V grade — was obtained from sands containing (by weight): 97.32% SiO
2
, 0.92% Al
2
O
3
, 0.43% Fe
2
O
3
, 0.11% TiO
2
, and 0.04% Cr
2
O
3
. A distinguishing feature of the technological scheme of gravity separation of sands is the counterflow motion of the initial feed and the heavy fraction.
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.
Water wetting films on a quartz surface were found to become unstable with increasing temperature. This is believed to be associated with the temperature dependence of the structure of the water in ...the layer at the wall. Aparameter characterizing the strength of the structural forces is calculated from measurements of the contact angle. The sign inversion of the parameter is associated with the forces of hydrophobic attraction predominating over the forces of hydrophilic repulsion in a definite temperature interval. The results of deferrization of glass quartz sands by flotation during thermal action on water wetting films are presented.
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 paper studies synthetic osteoplastic powder biocomposite, which is bioactive and extremely relevant for bone defect recovery in dentistry and maxillo-facial surgery. Biocomposite fabrication ...strategy is based on an original sol-gel (template) synthesis of the porous wollastonite containing 30 wt.% of hydroxyapatite. The way to tailor porosity in the material has been proposed involving siloxane-acrylate latex and carbon fibers as pore-forming templates. Phase formation in the composition structure has been investigated by the means of TG/DTA/DSC and XRD. SEM, low temperature nitrogen sorption, and mercury porosimetry has been used to characterize biocomposite's morphology and microstructure. “In vitro” and "In vivo" biocompatibility tests have been carried out. Histological analysis and multislice CT reveal the ability of the biocomposite to integrate into the area of the under-jaw defect (alveolar socket) of the test animal. Blood count assay shows no direct toxic influence of such implants on a living organism.
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•Highly bioactive osteoplastic CaSiO3(wollastonite)/HAp powder is prepared.•Original sol-gel (template) strategy enabling to tailor microstructure is shown.•Different kinds of templating agents were used to design porous architecture.•Blood tests showed no toxic impact of the biocomposite on living organism.•“In vivo” studies demonstrated complete implant's integration into under-jaw defect.
The authors present the gravity concentration-and-flotation technology for joint processing of gold ore and placer gold mining waste ensuring high gold recovery. The research is carried out using ...samples of ore from a primary gold deposit under mining and from waste of gold placer mining in the Yano- Kolyma gold province in the Russian Federation. The feature of the technology is the use of bullion gold in the gold flotation circuit. Bullion gold is recovered from gold placer mining waste by gravity concentration. The ore and waste processing by gravity concentration and flotation is based on the jet flow of feed material and rough concentrate. The second flotation stream circuit uses the technology of aerosol column flotation. The efficiency of investment to joint processing of gold ore and placer gold mine waste is evaluated.
According to modern theories, the parameters of neutral mesons such as their mass and width are closely connected with the medium in which the mesons are present. Experimental data on the study of ...mesons in a nuclear medium are in demand for development of theoretical models describing processes in the field of nonperturbative quantum chromodynamics (QCD). Masses and widths of neutral mesons produced in meson-nucleus interactions on various nuclei are measured in the Hyperon-M experiment at the U70 accelerator. The paper describes a method for precision measurement of the parameters of neutral mesons, presents the results on measurement of the mass and width of the
meson and preliminary results on the measurement of the mass and width of the
meson. The measurements indicate the absence of dependence of the quantities under study on the nuclear environment.
The article is dedicated to the development and investigation of conditions for obtaining the aggregate stable colloid solutions of magnetite - magnetic fluids. The developed method differs from the ...known ones and involves new ways of producing and stabilizing magnetic nanoparticles with a narrow particle size distribution.
Studies at the Nuclotron in JINR indicate the presence of a previously unknown resonance-like structure in the two-photon mass spectrum in the region of 300–400 MeV/
c
2
, observed in nucleus–nucleus ...interactions. The goal of this work is to search for such structures in the two-photon mass spectrum in meson–nuclear interactions at a momentum of 7 GeV/
c
at the Hyperon-M experiment of the U-70 accelerator complex. An upper limit has been established on the ratio of the cross section for the formation of unknown resonance structures to the cross section for the production of
-meson
at the 95% confidence level.
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