Bridgman growth of germanium crystals in a rotating magnetic field

Volz, M. P.; Walker, John S.; Schweizer, Markus; Cobb, S. D.; Szofran, F. R.

doi:10.1016/j.jcrysgro.2005.05.031

Cited by 25 publications

(19 citation statements)

References 18 publications

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“…The parameter g describes the axial efficiency of F Lh and depends on the aspect ratio, R = 2R 0 /H 0 , e.g., g = 0.62 for R = 1 but g = 0.312 for R = 2 (see reference 27). Equation [9] is a good predicter of the angular velocities not only of laminar flows [28] but also of turbulent flows driven by an RMF. [29] In this way, we could use X ce to estimate Re m and N. Using the values of magnetic induction B 0 and the corresponding values of Ta and X ce (which are given in Table I), the magnetic Reynolds number and the interaction parameter for the maximum magnetic Taylor number (B 0 = 3.3 mT), were approximately Re m % 0.33 9 10 À2 and N % 3.8 9 10 À3 , respectively.…”

Section: B Rotating Magnetic Fieldmentioning

confidence: 98%

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Contactless Mixing of Liquid Metals

Nikrityuk

Eckert

Grundmann

2009

Metall Mater Trans B

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This work is devoted to the numerical study of mixing two miscible liquid metals, e.g., Sn and Pb, that are driven either separately by a rotating magnetic field (RMF), by a traveling magnetic field (TMF), or by a combination of both fields from the state of rest. The geometry studied is an enclosed cylindrical cavity with an aspect ratio equal to unity (the diameter of the cylinder is equal to its height, 2R 0 = H 0 ). The initial condition is a cylinder with the lower half filled with a melt that has two times the molecular viscosity of the liquid in the upper part of the cavity. Based on the mixture model of the two-fluid flow and the axisymmetric Navier-Stokes equations, the transient transport of momentum as well as the species for rotary and axial stirring is modeled. The numerical simulations were performed under microgravity conditions for Ekman numbers between 10 À3 and 10 À4 for the RMF-driven flow and for Reynolds numbers between 100 and 400 for TMF-driven flow that corresponded to both laminar and weak turbulent flows. The simulations analysis showed that for RMF, the rapid increase in the mixing rate occurs because of randomly appearing Taylor-Go¨rtler vortices that move up and down along the side wall of the cylinder and that dissipate in the Bo¨dewadt layers. The TMF stirring with forcing parameters that produced laminar flow offers a better mixing performance than the RMF stirring at the same magnetic field intensity. However, with an increase in magnetic forcing, the RMF and TMF lead to comparable mixing times for the same value of magnetic field induction. Additionally, we discuss different mixing scenarios that include the use of time-modulated RMF and TMF. Numerical simulations showed that the discontinuous superposition of RMF and TMF-defined as the sequential switching on and off of both fields with a well-defined period-enhances the mixing in comparison with the non-superimposed case.

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Section: B Rotating Magnetic Fieldmentioning

confidence: 98%

“…RMF and TMF fields are used widely for experimental studies of the influence a liquid phase motion has on heat and mass transfer during crystal growth [2,[8][9][10]11] and solidification of metal alloys. [3,4,12] In such experiments, it is necessary that all alloy components are distributed homogeneously in the melt.…”

Section: Introductionmentioning

confidence: 99%

Contactless Mixing of Liquid Metals

Nikrityuk

Eckert

Grundmann

2009

Metall Mater Trans B

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“…The structural and electrical properties of the crystals depend on the melt flow which can be influenced by external magnetic fields. By applying a non-steady magnetic field, the flow can be tailored to improve the quality of the crystals and the yield of the growth process [3][4][5]. The induced melt flow, however, tends to be time-dependent.…”

Section: Introductionmentioning

confidence: 99%

Vertical gradient freeze growth with external magnetic fields

Lantzsch

Grants

Pätzold

et al. 2008

Journal of Crystal Growth

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“…Stationary magnetic fields are used to improve the quality of crystals by suppressing convection (natural and/or Marangoni) and controlling the directional solidification and segregation of species [1][2][3][4][5][6][7][8][9][10][11][12][13]. Rotating magnetic fields, on the other hand, have been used to obtain better mixing in the melt, better control for the heat and mass transport characteristics of the system and also for the shape of the growth interface [14][15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%