Zonal Melting Research Articles

Raman spectra and phase composition of MnGeO3 crystals

MnGeO3 single‐crystal samples have been synthesized by optical zonal melting and spontaneous crystallization. X‐ray crystal analysis showed the first sample to be a two‐phase one with phase ratio as follows: 17% – monoclinic C2/c, and 83% – orthorhombic Pbca; the phase ratio of the second sample was unknown. Raman spectra have been produced for these samples. Lattice dynamics has been simulated and polarization dependencies of lines' intensities have been analyzed to interpret experimental Raman spectra and to attribute lines to the spectra of monoclinic and orthorhombic phases. Copyright © 2015 John Wiley & Sons, Ltd.

Energy-saving continuous fractionation and deep purification of organic materials by zonal melting

Energy-saving continuous fractionation and deep purification of organic material by zonal melting is considered. This approach permits the combination of various purification methods: fractionation by directional and/or counterflow solidification; and deep purification by single-zone or multizone melting. Simplified (for engineering use) and more detailed mathematical descriptions of the solidification of a binary melt with a stable phase boundary are considered. The rates of crystal nucleation and growth in binary melts are taken into account, as well as the influence of mass transfer on the heat transfer, the thermal diffusion, and the need for considerable temperature gradients. The mathematical descriptions employ effective distribution coefficients of the components that take account of the change in boundary-layer thickness on solidification (melting). The discrepancy between practical experience and the calculation results is no more than 10%, with 95% probability. An industrial system for continuous deep purification by zonal melting is proposed. It is based on a roller crystallization unit. A general mathematical description of the solidification of a binary melt is formulated and provides the basis for a simplified mathematical description and an algorithm for its solution in engineering calculations.

Television pyrometry improvement

The article analyzes the problem of television pyrometry improvement by determination of the range of linearity of the television system luminous-signal characteristics. The contemporary scientific literature practically does not have any materials on the relevant research methods or their results. It places special emphasis on the importance of the problems, laid down in this article.If we consider characteristics, that determine accuracy of the temperature measurement in methods of the television bispectral pyrometry, the main characteristics shall be equivalent wavelength, effective to the noise difference of color temperatures and luminoussignal characteristic. Clearly, accuracy of the temperature measurement is affected by a dark signal range of the specific device. First of all, in such a case it is necessary to make experimental studies of performance of the facilities, which are used today or evaluated from the perspective of their use in the bispectral television pyrometry. We have accumulated a considerable amount of experimental materials in course of the experiments. They concern formation of signals both in the television information-measuring system parameters of zonal melting, and in the television equipment of another destination, particularly, in the television pyrometers that can be used for control over the temperature conditions for pipe rolling technologies, in the television devices for food product quality control, environmental monitoring, in the television microscopy etc.

Noncontact IR Meter of Local Temperature

The general arrangement, principle of operation, and basic technical characteristics of pyroelectric noncontact local-temperature meter with nonmechanical (electronic) modulation of infrared radiation operating in the range 300-800°C are described. The device is intended for measuring the temperature of solid bodies inside vacuum assemblies. The meter can be used in the systems used to control and adjusting various technological processes (laser and electric welding, plasma and zonal melting) and also for diagnosing the temperature of the almost in accessible objects (furnaces, engines, high-voltage equipment, etc.).

Special features of electron-beam boronizing of steels

Electron-beam treatment is a promising method of surface treatment. It can be used in traditional technological operations, i.e., melting, welding, soldering, facing, quenching, and annealing, and in new processes, i.e., polymerization, local change of magnetic properties, recrystallization of the surface layer, zonal melting, etc. Chemical heat treatment of a metal surface with a daubing applied by means of a powerful electron beam is an interesting technique. By varying the composition of the daubing we can change the properties of the metal surface (wear resistance, corrosion strength, high-temperature strength, etc.). Electron-beam heating has some advantages over laser treatment, namely, (1) a high coefficient of the absorption of electron beam by the metal, which makes it possible to treat the surface effectively without absorbing coatings, (2) simplicity of organization of rapid scanning of the treated surface by the electron beam, (3) high efficiency of the electron gun (up to 70–80%), (4) the possibility of creating quite compact technological electron-beam units with a power of tens and hundreds of kilowatts, (5) treatment in vacuum. In this connection interest in works in this field has grown. The present paper concerns results of a study of the structure and properties of boronized layers deposited on carbon steels by the method of electron-beam treatment under vacuum and by the traditional method for comparison.

1234. Obtaining ultraclean vacuum conditions in an equipment for zonal melting of metals: B G Lazarev et al,Dokl AN SSSR, 215 (4), 1974, 839–841 ( in Russian)

1234. Obtaining ultraclean vacuum conditions in an equipment for zonal melting of metals: B G Lazarev et al,Dokl AN SSSR, 215 (4), 1974, 839–841 ( in Russian)

On influence of some secondary effects on the processes of electron zonal melting of refractory metals: O S Kobyakov and E E Petushkov,Growth of Single Cryst of Refrac and Rare Metals, Coll, Nauka Moscow 1973, 76–79 ( in Russian).

On influence of some secondary effects on the processes of electron zonal melting of refractory metals: O S Kobyakov and E E Petushkov,Growth of Single Cryst of Refrac and Rare Metals, Coll, Nauka Moscow 1973, 76–79 ( in Russian).

On stability of conditions of electron zonal melting of refractory metals: E E Petushkov et al,Growth of Single Cryst of Refrac and Rare Metals, Coll, Nauka Moscow 1973, 62–65 ( in Russian).

On stability of conditions of electron zonal melting of refractory metals: E E Petushkov et al,Growth of Single Cryst of Refrac and Rare Metals, Coll, Nauka Moscow 1973, 62–65 ( in Russian).

1077. Dislocations in molybdenum single crystals preprared by zonal melting: B S Predtechenskiy and L S Starostina,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 213–217 ( in Russian)

1077. Dislocations in molybdenum single crystals preprared by zonal melting: B S Predtechenskiy and L S Starostina,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 213–217 ( in Russian)

1073. Thermal conditions and refining of metals at electron crucibleless zonal melting: V V Shishkov et al,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 128–132 ( in Russian)

1073. Thermal conditions and refining of metals at electron crucibleless zonal melting: V V Shishkov et al,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 128–132 ( in Russian)

1078. Investigation of structure and defects of molydbenum single crystals grown by electron-beam zonal melting: V A Krakhmalev and G A Kleyn,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 217–224, ( in Russian)

1078. Investigation of structure and defects of molydbenum single crystals grown by electron-beam zonal melting: V A Krakhmalev and G A Kleyn,Growth and Defects of Metallic Crystals, Coll, Nauk Dumka Kiev 1972, 217–224, ( in Russian)

The structure of the mid-oceanic rift zone of the Indian ocean and its place in the world rift system

We report results obtained from detailed geological—geophysical surveys of representative parts of the rift zone and other associated tectonic zones of the Indian Ocean. Detailed bathymétrie maps and seismic profiles and the analysis of all geophysical data are presented. The petrography, petrochemistry and physical properties were investigated for some specimens of magmatic rocks from the rift zone. The rift zone and the Mid-Oceanic Ridge of the Indian Ocean are zones of active development of the earth's crust under the intensive influence of the upper mantle. The earth's crust in the rift zone is a mosaic of normal crustal blocks and upper mantle material squeezed out upwards. The first were formed by zonal melting processes with the division of pyrolite into peridotites and gabbro-basalts. The second are residual peridotites squeezed out upwards in a crystalline state and subjected to varying degrees of serpentinization. The serpentinization occurs at a depth of 10–15 km and arises because of the degassing of the mantle. From the amount of titania and silica, the degree of differentiation of the mantle under the Indian Ocean is less than under the continents.

Zonal melting as mechanism in evolution of the Earth's crust

The paper treats the problem of upward movement of a molten zone in the Earth's crust. Due to the melting temperature gradient of 3°C/sm, such a zone is in an unstable state: melting occurs at the upper boundary, where crystallization takes place at the base. During this process, the net thickness of the molten zone decreases, since additional heat is required to raise the temperature of the overlying rock to the melting point. The process continues until the thickness of the molten zone is reduced to zero or until it reaches a level above which open fractures exist. Based on thermodynamic considerations, estimates are given for the rate of upward movement and thinning: lifting the upper boundary of the molten zone from a depth of 100 km to 20 km requires a reduction in thickness by about 60 km or 30 km, in the continental or oceanic crust, respectively. The lifting time is estimated as 10–100 m. y. --H. Jahns.

ORIGIN OF THE SPHERES OF THE EARTH

The heat generated by U, Th, and K4O was great enough only to cause thorough differentiation of terrestrial substance into spheres. During Archean time there was universal and vigorous rise of granitic magmas which replaced basalt blocks of folded continental provinces. Granitic magmas extruded on oceanic bottoms were partly dissolved in the water. Radioactive heat caused zonal melting and degassing of readily fusible and volatile fractions of the mantle. The process of smelting and degassing or readily fusible and volatile fractions resulted in granitization when it occurred directly beneath sedimentary and other rocks: in submarine processes the low fusing phase is disintegrated, with part of it, especially the gases, dissolved. In subaerial processes, the low fusing phase loses its volatiles into the atmosphere. The most volatile fraction led to formation of hydrosphere and atmosphere. During the entire evolution of the Earth, a discrete and mighty radial process of smelting and degassing has been goin...