The Distribution Constant in Hydrothermal Quartz Growth

Laudise, R.A.; Kolb, E.D.; Lias, N.C.; Grudenski, E. E.

doi:10.1007/978-1-4615-7113-1_51

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…When calculating the equilibrium distribution coefficient k 0 in the case of low impurity concentrations it is convenient to use the theoretical methods of calculations based on the thermodynamic constants of the equation of ideal solutions. According to this concept it be can use a special case of the Schroeder -Le Chatelier equation for refractory metals [8]:…”

Section: Zone Recrystallization Methodsmentioning

confidence: 99%

Zone Recrystallization of Zirconium and Hafnium

Kozhevnikov

Pylypenko

Kozhevnikova

2021

EEJP

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The work studied the possibility of obtaining of the high-purity samples of zirconium and hafnium by the method of zone recrystallization of round rods with electron-beam heating in a vacuum of 1∙10-4 Pa. Some meltings were carried out in a constant electric field with the variability of its connection. It is shown that the simultaneous passage of several refining processes (evaporation of highly volatile metallic impurities, zone recrystallization with directional displacement of impurities to the end of the sample, electrotransport) made it possible to efficient refining of zirconium both from metallic impurities and from interstitial impurities. The best degree of purification was achieved when zone melting carrying out in an electric field directed opposite to the zone movement. In this case, the displacement of interstitial impurity ions coincided with the direction of movement of the liquid zone. Samples of zirconium with a purity of 99.89 wt. % were obtained (the concentration of aluminum was reduced by 5, iron - 11, copper - 45, chromium - 75, silicon - 10, titanium - 2.5, oxygen - 3.3, nitrogen - 3, carbon - 2 times). The hafnium samples refined by the zone recrystallization method were characterized by a purity of 99.85 wt. %. The concentrations of both all metal impurities and interstitial impurities were significantly reduced (concentration in wt% oxygen was 0.011, carbon - 0.0018, nitrogen - 5∙10-5). A study of gas evolution from samples of iodide hafnium and refined hafnium was carried out. It was found that the maximum gas release peak fell on the temperature range of 500 ... 550 °C. The use of an integrated approach, including high-temperature heating, stages of zone melting at different rates, and thermal cycling in the range of the polymorphic transformation temperature, made it possible to obtain single-crystal hafnium samples. According to X-ray diffraction data, the parameters of the hafnium crystal lattice were determined: а = (0.31950 ± 5·10-5) nm and с = (0.50542 ± 5·10-5) nm (at 298 K), which corresponds to the density ρ = 13.263 g/cm3 and axial ratio с/a = 1.5819.

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Section: Zone Recrystallization Methodsmentioning

confidence: 99%

Zone Recrystallization of Zirconium and Hafnium

Kozhevnikov

Pylypenko

Kozhevnikova

2021

EEJP

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“…For this reason, a new industry has increased -single crystal growing. Single crystals of metals and semiconductors are produced by growing from a melt mainly in three ways: vertical directed crystallization (VDC) -the Bridgman method [1]; pulling from a melt onto a seed -the Czochralski method [2,3] and crucibleless melting -the Pfann method [4].…”

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confidence: 99%

Production Of High-Purity Cadmium Single Crystals By Vertical Directed Crystallization Method

Shcherban

Ковтун

Солопихин

et al. 2020

EEJP

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The process of producing high-purity Cd crystals by the vertical directed crystallization (VDC) from a melt according to the Bridgman method is investigated. Single crystals with the preferred growth direction and were produced. The angles of deviation of the growth direction relative to the axis of the samples are α = 27.2° and α = 0.5°. The crystal perfection, microstructure and microhardness of the grown crystals are determined. As shown by x-ray diffraction analysis, in this VDC variant of high-purity cadmium, a perfect single-crystal structure is not reached. In the start section there are separate grains with different orientations, the amount of which decreases in the end section of the single crystal. This results in the formation of a more perfect single-crystal structure with a preferred orientation, which occupies the entire cross section of the crystal. The microhardness of the upper and lower sections of single crystals was determined. The more contaminated end sections of the crystals have lower microhardness than the initial parts. The impurity composition of the start and end sections of single crystals produced from cadmium of various grades purity was studied. The efficiency of impurity elements redistribution along single crystals is the same for different grades of cadmium. The developed VDC process can be used for growing single crystals of low-melting metals, such as Zn, Pb, Te, In, Bi, Sn, etc.

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The Distribution Constant in Hydrothermal Quartz Growth

Cited by 2 publications

References 5 publications

Zone Recrystallization of Zirconium and Hafnium

Zone Recrystallization of Zirconium and Hafnium

Production Of High-Purity Cadmium Single Crystals By Vertical Directed Crystallization Method

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