Aluminizing process of titanium in aluminum melts A7 and AK12 was investigated. The influence of aluminizing regime on the structure and chemical composition of the coating on the titanium alloy ...VT1-0 was established.
The heat resistance of titanium with coatings based on titanium aluminides deposited by liquid-phase aluminizing followed by a high-temperature hold is studied. The effect of the duration of the hold ...of titanium specimens in an aluminum melt and of the duration of the high-temperature exposure of the aluminized specimens on the chemical and phase composition, structure and heat resistance of the coatings is determined.
Foam aluminum is a promising material with a unique combination of mechanical and operational properties: low specific gravity, low thermal conductivity, the ability to absorb acoustic and ...electromagnetic oscillations, and the ability to deform under constant load. At present, the most used methods for producing aluminum foam are methods based on mixing a gas or blowing agent (porophore) into the aluminum melt and forming a porous structure during the aluminum melt solidification. An alternative to this technology is the formation of a porous structure through the use of soluble granules, which are pre-filled in the mold, and then, after the granules are impregnated with aluminum melt and the casting is solidified, they are leached. Studies of porous aluminum formation processes carried out by impregnation of a mold with soluble granules with an aluminum melt confirmed that the melt cooling rate depends on the thermal casting conditions (the mold temperature with granules and the poured alloy temperature), as well as on the size of water-soluble granules, their thermophysical properties and their packing density in the mold. Calculation and experimental studies have shown that the melt cooling rate in a mold with water-soluble granules is 1.8–10 times higher than when casting off solid aluminum castings. Porous aluminum structure metallographic studies have shown that the grain size is 2–4 times smaller than that of solid castings.
The process of argon arc welding of nickel onto titanium with a nonconsumable electrode with feeding of the nickel filler wire into the liquid metal pool is investigated. The influence of the welding ...modes on the geometrical parameters of the bead and on the susceptibility of the forming surface layer to crack formation is described. The effect of the welding modes on the chemical and phase compositions of the formed surface layer of titanium nickelide is determined. The chemical and phase compositions of the welded-on layer are shown to affect its hardness and wear resistance.
•FTIR spectra of Methylene Blue cation (MB+) were analyzed in their free form (gas-phase), hydrated crystal form and in solution.•The complications, emerging during the interpretation are due to the ...high activity of this molecule to the intermolecular interactions.•FTIR spectra of aqueous solution and hydrate show manifestation of dimerization and H-aggregation.•Intermolecular hydrogen bonds and π–π interaction of MB+ aromatic rings were observed during self-association.•The analysis of FTIR spectra indicates the identical nature of emerging intermolecular interactions for H-aggregates and hydrates.
Fourier-transform infrared (FTIR) spectra of cationic dye methylene blue (MB) were analyzed in its free form (gas-phase), hydrated crystalline state, and dried MB solution. A good agreement of experimental FTIR spectra with the results of theoretical calculations of MB vibration modes was observed. The calculations were performed by means of the density functional theory (DFT/B3LYP/6–31+G(d)), using Gaussian-03 software package. Vibrational bands of the N+(CH3)2 (1640–1650cm−1) and C-S-C (625-615, 1095cm−1) functional groups are characteristic of the presence of MB monomers in the studied samples. The participation of the N+(CH3)2 functional group in the formation of one bridging H-bond with OH groups of the solvent has been confirmed. The decrease in intensity of these bands with the increase of the fraction of dimers and H-aggregates of MB was observed. It was concluded that the configuration and primary localization of the charge in the heterocycle of ionic form MB+ are changed in the case of formation of dimers and H-aggregates. For samples with a dominant fraction of dimers and H-aggregates, the occurrence of intermolecular H-bonds of the type Nhet…Н-O⋯S+het was found. The occurrence of peaks at 1339–1356, 1481–1491, and 885cm−1 was observed. It was concluded that there is formation of dimers and H-aggregates due to interaction of sulfur and nitrogen atoms with OH groups of water molecules. Moreover, the manifestation of π-π stacking interactions of aromatic rings of the heterocycle of ionic form MB+ during self-association was determined on the basis of data on the behavior of the peaks of heterocyclic of СН (3050–3015cm−1), СС, СN (1600–1595cm−1), СС, and СN (1564–1546cm−1) vibrations.
The heat resistances of titanium, nickel, and carbon steel with aluminum-based coatings produced by liquid-phase aluminizing with diffusion annealing at 850 and 950°C are studied and compared. The ...influence of the holding time of aluminized titanium, nickel, and carbon steel specimens at 950°C on the changes in their weight and oxidation rate is revealed.
Magnesium foam is a promising material in industry and medicine due to its low density, high damping properties, ability to absorb acoustic and electromagnetic vibrations, and biocompatibility with ...the human body. The methods developed for producing products from porous magnesium by filtering the liquid melt through soluble granules ensure the production of porous magnesium with a pore size of at least 4 mm. To reduce the pore size by increasing the fluidity and fillability of the granular filling during the production of porous magnesium, vibration treatment of the melt during pouring has been proposed. The conducted studies have shown that vibration treatment allows increasing the fluidity of the Mg90 magnesium melt. In addition, a refinement of the magnesium structure and an increase in hardness are observed. Vibration treatment during the pouring and forming of porous magnesium contributes to an increase in the depth of impregnation of the granular filling and creates conditions for producing products from porous magnesium with a pore size of up to 2 mm, a density of 0.55–0.75 g/cm
3
, and a porosity of 57–68%.
Some discrete distributions such as Bernoulli, binomial, geometric, negative binomial, Poisson, Polya–Aeppli, and others play an important role in applied problems of probability theory and ...mathematical statistics. We propose a variant of a multivariate distribution whose components have a given univariate discrete distribution. In fact we consider some very general variant of the so-called reduction method. We find the explicit form of the mass function and generating function of such distribution and study their properties. We prove that our construction is unique in natural exponential families of distributions. Our results are the generalization and unification of many results of other authors.
Liquid-phase technology for fabricating composite materials with a magnesium matrix and titanium reinforcement is proposed. Possibilities of improving adhesive bonding between composite components ...under casting conditions with preliminary deposition of an aluminum layer on titanium reinforcement and process activation with chloride-fluoride fluxes are considered. Cohesive strength between magnesium and titanium within composites is determined. Tensile tests of composite material specimens are performed and metallographic and x-ray spectrum analyses are conducted. The most effective activating flux compositions are proposed after analyzing composite material structure. Mechanical property tests for composites prove the efficiency of reinforcing a magnesium matrix with titanium.
Foam aluminium is a promising material with a unique combination of mechanical and operational properties: low specific gravity, low coefficient of thermal conductivity, ability to absorb acoustic ...and electromagnetic oscillations, the ability to deform under constant load. To increase the mechanical properties of foams, it has been proposed to use layered composite structures as foam aluminium-titanium, which can be successfully prepared by mould filling with molten aluminium with installed titanium sheets, between which is a layer of water-soluble granules. Increasing the adhesion strength between foam aluminium and titanium is ensured by aluminium alloying with nickel. The process investigation of aluminium wetting and spreading doped with nickel on titanium under the conditions of formation of foam aluminium-titanium composites is carried out. The influence of flux composition, melt temperature and degree of doping on the spreading area of aluminium on titanium, the wetting strength and adhesion strength of aluminium and titanium are established.
