Vacuum wetting and contact interaction of some of the metallic melts with indium and tin oxides

Due to the unique combination of electric and optical properties such semiconductor oxides as tin and indium oxides are very perspective multifunctional materials for variety of microelectronic devices production. Experimental studies of these materials allow to define, for example energetic characteristics of the devices created and also to improve existing technologies of films formation, joining of electrocontacts to tin and indium oxides based materials by way of brazing which require additional wetting studies. It should be noted that data on wetting of mentioned oxides by metals are practically absent in literature. Thus a detailed study of the interfacial interaction, adhesion and wetting of ceramic SnO2 and In2O3 materials with some pure metal melts in vacuum was performed by the sessile drop method using foto- and video- fixing including concentration, temporal and temperature dependences of contact angles. It was found that most of the pure metals studied don't wet SnO2 ceramics. However rather intense chemical interaction took place in vacuum at high temperatures in contact of some metals (Sn, Ge, In) with surface of SnO2. It was also shown the effect of the experiment temperature and hold-up time on the values of contact angles. Wetting angles for powdery pressed specimens of In2O3 in the temperature range studied don't change noticeably and vary in a narrow range. For example, for Ga wetting angles vary from about 138 to 128 deg and for Sn  125119 deg, Wetting of SnO2 surface with AgCu melt with different copper content was shown to be insufficient to use it as a brazing alloy, yet this system can be used as a basis for creating a brazing composition. Keywords: indium oxide, tin dioxide, semiconductor, wetting, contact interaction, metal melt.

Relationship between Kinematic Viscosity and Cluster Size in Multicomponent Metal Melts

We analyzed the temperature dependences of the kinematic viscosity and density of Fe73.5Cu1M3Si13.5B9 melts, where M = Nb, Mo, V, and Cr, in the temperature range from 1450 to 1950 K using the transition state theory. It is shown that the activation energy of viscous flow is proportional to the particle size on a natural logarithmic scale. The lowest viscosity and the highest free volume has the Nb melt. In melts with Mo, V, and Cr, the structural units of viscous flow upon heating and cooling are clusters about 0.6 nm in size. In a melt with Nb, at the initial stage of heating, the vibrations of individual atoms prevail, the movement of which creates viscosity. After heating the Nb melt above the critical temperature of 1770 K, the viscous flow is associated with clusters about 1 nm in size. At the cooling stage, the cluster structure of the Nb melt is retained up to a temperature of 1450 K.

Solar noble gases in an iron meteorite indicate terrestrial mantle signatures derive from Earth’s core

Noble gases are important tracers of planetary accretion and acquisition of volatiles to planetary atmospheres and interiors. Earth’s mantle hosts solar-type helium and neon for which 20Ne/22Ne ratios advocate either incorporation of solar wind irradiated solids or solar nebula gas dissolution into an early magma ocean. However, the exact source location of primordial signatures remains unclear. Here we use high-resolution stepwise heating gas extraction experiments to analyse interior samples of the iron meteorite Washington County and find that they contain striking excesses of solar helium and neon. We infer that the Washington County protolith was irradiated by solar wind and that implanted noble gases were partitioned into segregating metal melts. The corollary that solar signatures are able to enter the cores of differentiated planetesimals and protoplanets validates hypotheses that Earth’s core may have incorporated solar noble gases and may be contributing to the solar signatures observed in Earth’s mantle.

Formation of Diffusion Coatings Based on Nickel and Chromium in the Medium of Fusible Liquid Metal Solutions on Austenitic Steels

The technology of diffusion saturation of austenitic steels by chromium and nickel in the medium of low-melting liquid metal melts is shown. The saturation temperature was up to 1050°C, and the duration was up to 8 hours. It was found that it is the most effective to apply coatings according to the technological scheme: pre-carburization-diffusion metallization – final carburization. It was found that the coating consists of 4 layers. The surface layer has a thickness of up to 5 mkm and a microtuberance of up to 19500 MPa. The second layer, up to 12 mkm thick, has a microhardness of up to 7500 MPa. The third, up to 50 mkm thick, has a microhardness of 2300 MPa. In the fourth layer, up to 150 mkm thick, the microhardness gradually decreases from 2300 MPa to the microhardness of the base. At the same time, the total thickness of the coatings is up to 200 mkm.

Explanation of the cluster structures melting mechanism and their influence on the molten state’s physical and chemical nature

There are results of the melts of semimetals and semiconductors of various structural groups research in the article. On the example of simplified regular Bethe lattice one can model destruction and aggregation of structures in clusters and on it’s basis to substantiate the metal melts properties in the form of nanolayers. The variety of compressibility polytherms forms in electronic melts requires typing, since their analysis makes it possible to explain the mechanism of the aggregation and dissolution processes of extended objects in melts. The article contains formulas that allow explaining the mechanism of the dissolution of cluster structures and their influence on the physicochemical nature of the molten state. There is considered the process of cluster fragmentation. Larger fragments of clusters are formed in the process of crushing, and this fact leads to the compressibility that decreases more rapidly, only after passing through the extremum it begins to increase due to the thermal loosening. The study of the function's compressibility for an extremum in the compressibility's temperature dependence also indicates the changing process of the clusters decomposition mechanisms in melts with an increase in temperature and vice versa to aggregation with a decrease in the melt temperature to the melting temperature.

Inert gas absorption and pore formation in nickel-based hot-melt alloys

An integrated approach to the generalization and analysis of scientific and technical literature in the direction of improving the technological processes of spraying metal melts used a comprehensive approach The processing and analysis of experimental data for the determination of argon at different stages of heat-resistant alloy production were performed. Micro structural analysis of nickel-based heat-resistant alloys obtained by gas and centrifugal spraying was performed. A significant increase in the mass fraction of argon in the melt is shown when held in a furnace before gas or centrifugal spraying, the absence of capture of inert gas by sprayed liquid particles during centrifugal spraying is shown, unlike the process of gas spraying, it is shown. The results of the study indicate the absence of "dissolution" of Ar or a mixture of Ar-He in the liquid or solid state at argon levels up to 1 • 10-4% of the mass. It is established that centrifugal spraying of metal melts allows obtaining compact powders with small particle size distribution at relatively low energy consumption. It is also noted that argon is captured by the metal only in the process of moving on the disk, and not due to the weak dynamic gas interaction directly on the melt droplets. Hence, its amount in the metal increases after the argon’s injection into the furnace chamber and at the subsequent centrifugal spraying does not change, in comparison with gas spraying. A technological possibility has been found to significantly reduce the amount of gas pores and the mass fraction of inert gas in nickel-based heat-resistant alloys. Nickel-based heat-resistant alloys obtained by the method of gas and centrifugal spraying make it possible to improve the quality of products for the aviation industry, their reliability when operating in extreme conditions. Keywords: gas spraying, centrifugal spraying, heat-resistant alloy, argon, helium, pore formation.

Enhancing the durability of cutting carbide tools by controlling the state and properties of its surface layers using complex chemical and thermal treatment

A current way of increasing cutting efficiency in the turning operation is applying functional coatings based on carbides, nitrides, carbonitrides, etc. on the cutting tool surface. Most technologies for applying functional coatings are supposed to use technically sophisticated, expensive equipment. In addition, the coatings have a sharp change in properties at the coating-coated material boundary. The technology of diffusion saturation from the medium of low-melting liquid metal melts lacks these disadvantages. The aim of the work was to study the effect of the formation of a coating based on titanium carbide on the surface of a cutting tool made of hard TiC-WC-Co and WC-Co alloys on its wear resistance and the quality of the product surface after turning. The research methods included field tests, micro-x-ray spectral analysis, optical microscopy, and microdurametric tests. The paper presents the results of research of turning of materials of various cutting group using a carbide tool with a functional diffusion coating obtained due to saturation in the melt containing Pb, Bi, Li, Ti. The resulting coatings had a thickness of 3-6 microns, and contributed to an increase in tool life up to 7.4 times compared to the tools with PVD coating and tools without coatings as well as a decrease of the roughness parameter Ra of the treated surface up to 2 times.