The bonding strength of powder coatings in gas-flame spraying with the hydrogen–oxygen flame

Magnetic quenching of the emission intensities of HPO and SnH in hydrogen—oxygen flames

THE hydroperoxyl radical has been postulated as an intermediate in numerous oxidation reaction mechanisms. In particular, mechanisms involving it are capable of giving detailed explanations of the explosion limits and reaction-rates in hydrogen–oxygen systems in static reaction vessels1,2. In discussing hydrogen-oxygen and hydrogen–air flames, however, reactions of HO2 are usually omitted, on the assumption that most of the flame reaction occurs at too high a temperature for the HO2 forming reaction (2) to compete with the chain-branching reaction (1). We have recently obtained evidence, arising from a detailed investigation of a slow-burning hydrogen–oxygen–nitrogen flame and from calculations involving two faster (higher temperature) flames, that this assumption may be invalid in many cases.

The STM images acquired in the constant current mode were found to resolve individual close-packed gold atoms on Au(111) and iodine atoms on Pt(111). Measurements were made in air on the facets formed on single crystal spheres. Single crystals were prepared by melting pure metal wires with a hydrogen–oxygen flame.

The external magnetic field effect on the emission intensity of the Na D line in hydrogen—oxygen flames

A flame metal combustion method for production of nanoparticles

Rotational Raman scattering from premixed and diffusion flames

The problem of increasing the adhesive strength of plasma powder coatings by introducing a metal bundle from a new composite powder of domestic production into them has been solved. Synthesis of composite powder material is carried out by the method of cladding matrix ceramic particles with a metal component. The results of studies of a new powder material of the composition (ZrO2+8%Y2O3) with a granular composition of 40/80 microns obtained by chemical cladding of zirconium dioxide particles with a nickel shell (30 wt.%), as well as the coating formed from it. The regularities of the formation of an experimental coating from this powder material with a spherical particle shape have been studied using electron microscopy and X-ray diffraction analysis. It is established that a coating with a two-phase composition (T-ZrO2+Ni) is formed during high-energy plasma spraying. In cross-section, the coating is a composite structure consisting of zirconium dioxide grains with nickel interlayers. The coating is characterized by an average hardness of HV(medium) ~ 7,6 GPa and a surface roughness of Ra(medium) ~ 6,12 microns. When micro-indenting, the coating does not show fragility. The scratch test method was used as the main method for studying the strength properties of the coating. During sclerometry, a predominantly cohesive mechanism of coating destruction was established. The destruction occurs by a cohesive mechanism with a violation of the bonds in a thin surface layer and is accompanied by chipping of the microfragments of the coating. The critical load of the beginning of the formation of microcracks (Rs) ~ 10 N and the beginning of the formation of chevron microcracks (Rt) ~ 45 N were determined. The high adhesive strength of the adhesion of the investigated coating to the substrate is shown, since during the tests there is no detachment from the substrate up to the maximum load (200 N). The developed ceramic coating is promising for protection against mechanical and erosive wear of critical parts of power engineering working at elevated temperatures.

Purpose of research .The purpose of this work is to study the influence of the granulometric composition of electrospark cobalt-chromium poweders on the physico-mechanical properties of additive products. Methods. Wastes of cobalt-chromium alloy“CELLIT was chosen for this research.Butyl alcohol was chosen as a working fluid. To obtain cobalt-chromium powder materials by electrospark dispersion, a unit for ESD of conductive materials was used. The dispersed material was charged into a desiccator filled with butyl alcohol used as a working fluid for dispersion. Butyl alcohol C 4 H 9 OH belongs to monatomic alcohols. It is a colorless slightly viscous liquid with a peculiar smell of fusel oil,miscible with organic solvents.Butanol is used as a solvent in the paints and coatings industry, in the manufacture of resins and plasticizers, and in many other industries. To obtain experimental samples of additive products, the unit for lamination of powder materials by plasma was used. The authors studied the granulometric composition of the obtained powders by the method of ultrasonic dispersion in a liquid. The research methodology is FR 1.27.2009.06762 Technique of particle size measurements in suspensions, emulsions and aerosols in nanometer and colloidal ranges with the use of dynamic light scattering effect. Results. Experiments proved that the conditions of production and dispersion of powders determine their behavior during sintering.With the increase ofthe dispersion of the powder, sintering process accelerates and proceeds more actively, and the mechanical properties of the resulting products improve.Intensification of powder sintering is facilitated by oxides contained in large quantities in fine powders and reduced when heated during their sintering. The sponge metal surface, formed after the disappearance of the oxide, is more active than the surface, which is initially free from the oxide film.With the increase of dispersion and specific surface area of the powder, its penetration increases, the porosity decreases, and the microhardness increases. The presence of powder particles of different fractions increases the density of its shrinkage by filling cavities and micropores at the joints of large particles, which further leads to the decrease of the roughness of sintered products and the increase of the ultimate compressive and bending strength. Conclusion. The conducted research reveals the relationship between the technology of electrospark cobalt-chromium powders production and physico-mechanical properties (porosity, microhardness, ultimate compressive strength, ultimate bendingl strength, roughness of the surface layer, etc.) of the experimental samples, and also allows controlling the process of the formation of structure and properties of products obtained by additive technologies.

Chemical alloying and characterization of nanocrystalline bismuth telluride

1. Granulated Cr and Cr + 30% Ni powders can be obtained by milling strip rolled from mixtures of fine Cr and Cr + 30% Ni powders with 5% paraffin wax. 2. Granulated Cr and Cr + 30% Ni powders exhibit good consolidation characteristics, and their moldability is sufficient for the production of filter parts. 3. Shrinkage during the sintering of compacts from granulated powders is practically independent of the starting intergranular porosity and is governed by the magnitude of shrinkage of the porous granulated particles (with the exception of Cr + 30% Ni powders with a granule size of −0.3 + 0.15 mm, whose shrinkage increases with increasing intergranular porosity). 4. After the sintering of compacts from granulated Cr powders, the granules have a substantial residual porosity, while Cr + 30% Ni powder granules become practically nonporous after sintering. 5. During the sintering of granulated Cr and Cr + 30% Ni powders, the starting intergranular porosity of compacts is retained (in spite of the high shrinkage of Cr + 30% Ni compacts), i. e., no significant intergranular shrinkage takes place. 6. The temperature required for effective sintering is 1523–1573° K for porous compacts from granulated Cr powders and 1373° K for compacts from granulated Cr + 30% Ni powder. 7. Granulation markedly increases the permeability of porous materials obtained from fine Cr and Cr + 30% Ni powders compared with the permeability of specimens produced from the fine powders.

Advanced chemical vapor deposition (CVD) system has been developed for rapid formation of the superconducting oxide tape on long metal substrates. In this system, mixed fine powder of source materials were slowly fed to a vaporizer with carrier gas by a fine powder feeder, and the source gas from the vaporizer were continuously introduced to the reactor with oxygen gas.

As was shown in the section on the knowledge gap, SLS technology has great potential for use in MID production, in combination with plating within the LDS process chain. At the same time, the technological maturity of the SLS process in the LDS process chain has not yet been developed beyond the laboratory stage. The challenges that have been reported in the literature must still be overcome. Thus, they will be studied and examined within this chapter, with the goal of developing a working solution. The first approach cited above, of utilizing an LDS additive in the SLS process, was associated with inconsistencies in process stability. Nevertheless, the investigation incorporated a DSC analysis that indicated the possibility of a process window. In the second approach, a fine metal powder was used by Amend et al. in a manner analogue to ADDIMID technology, and it was possible to process the powder by using SLS. However, there was a drawback: the high level of unwanted metallization. In this dissertation, the instability of the process that uses the LDS additive is investigated in order to understand how that additive affects the process. Instead of the LDS additive, copper powder can be used as an additive, and its use is expected to result in a stable process. Section 3.1 contains these investigations based on DSC analyses. Since the actual mechanism of activation is not yet fully understood, the most recent theories are presented, and possible alternatives are discussed in section 3.2. A material model is developed in section 3.3 to describe the compound containing polymeric material and metal powder. It can be used to estimate the compound density, the particle distribution and reasonable concentration of metal powder in the compound that is optimized to enable the activation, but avoid unwanted metallization. In addition, it is a useful tool for converting knowledge of the theoretical composition into hands-on mixing ratios. Finally, the model serves as an aid understanding of the activation mechanism. Nevertheless, there are still two contradictory theories, and it is not possible to validate the one or the other by using the model. Thus, an experiment that determines the actual activation mechanism is described in section 3.4.

The rapid emergence of cold spray technology provides numerous applications that require spraying fine (<10 microns) powders, providing more uniform deposition, improved measurement of deposition efficiency and quick turn around time. The performance of high-pressure commercial powder feeders, currently available, lacks one or more of these desired performance characteristics. Further, researchers are interested in spraying many powders of different materials or particle size distributions where the powder feeder can be quickly and easily cleaned without replacing expensive consumables. The Ktech laboratory powder feeder has been designed to operate under a wide variety of carrier gas pressures (0 – 500 psig). This laboratory feeder delivers a continuous flow of powder, has a variable canister volume and is quick and easy to clean. This unique design facilitates short run research applications or higher volume extended run time dispensing. The feeder is designed to operate in either a locally or remotely through a PC based Ethernet connection. The laboratory powder feeder represents an excellent tool for high-pressure cold spray or low-pressure thermal spray processes requiring the delivery of fine powders.

Hydrogen-oxygen flame acceleration in narrow open ended channels

Background. The deficiency of essential nutrients in the human body is the root cause of reduced efficiency, general resistance of the body to various diseases. That is an urgent problem in the context of the spread of coronavirus infection. In this regard, the search for opportunities to meet the needs of the population in food products that contain biologically active substances (BAS) through the use of high-value and at the same time available plant raw materials is extremely important. Marigolds attract special attention among such raw materials. The aim of the work is to study the chemical composition and evaluate the consumer properties of Tagetes L. varieties, zoned in the Kiev region, to prove the possibility of increasing the biological value of pasta by adding to their recipe powder from marigold inflorescences. Materials and methods. The object of research is pasta of B group (noodles). Inflorescences of marigolds of different varieties gathered during the flowering period in July-September 2019–2020 in the territory of Vasylkiv and Obukhiv districts of Kyiv region, Ukraine were used as enriching plant raw materials. The quality of finished pasta was assessed by organoleptic and physicochemical indexes (moisture content and titratable acidity). The content of mineral elements in the fine powder of marigold inflorescences was determined on the EXHERT-3L device, the quantitative composition and BAS identification – by spectrophotometric analysis on the device Specord-200 Analytic Jena UV-vis. The integrated quality index of pasta products was calculated taking into account the importance factors of individual indexes. Results. Comparing the obtained results, we can state that all the studied varieties – Gold Kopfen, Orange Flame, Hawaii, Equinox are characterized by high biological value, regardless of the area of collection. As a result of calculated and experimental studies it was determined that the addition of 7 % of the supplement does not provide the required supply of vitamins and minerals. Replacing the flour in the recipe by 20 % significantly improves the mineral composition, but deteriorates the taste and aromatic properties of pasta. The most optimal and rational amount of added additive is 15 %, as it improves the organoleptic properties of pasta and enriches their BAS. Conclusion. The usage of non-traditional vegetable raw materials, in particular powder from marigold inflorescences, which is rich in biologically active substances, allows not only to expand the range, improve the quality of finished products, but also increase the biological value of the product. The optimal amount of additive –powder from marigold inflorescences, was defined. It is 15 % by weight of flour in the production of noodles. This concentration allows not only to improve the organoleptic properties, but also to increase the content of biologically active substances – vitamins, micro- and macronutrients. The usage of non-traditional natural raw materials (powder from marigold inflorescences) allows to abandon artificial colorsand give the finished pasta a pleasant colorand aroma.