Prediction for crystal growth rates in borides under supercooled temperature conditions

Abstract

Two-types of phase-field (PF) calculations were developed to predict the crystallization of borides. The first calculation used an empirical PF mobility [L exp = A(k B T¦T/6³ 2 3 ©) B ], which was determined from experimental crystal growth rates (v exp ). The calculation results for various binary borides such as Liand PbO-2B 2 O 3 , agreed well with the experimental v exp below their melting points. Furthermore, the A and B values of the L exp for the borides depended on diffusivity and cation molar mass, including that it is important for cation transfers during crystallization. The second calculation solved the PF equation using versatile PF mobility (L¤ ³ rD/¬ 2 ), in which an interfacial process (r) was included. The calculation results agreed well with the first calculation results and the experimental v exp , except for Li 2 O-2B 2 O 3 . In Li 2 O-2B 2 O 3 , the interfacial process strongly affected the crystal growth rates because of the strong nonlinear phenomenon. For diffusive ceramics such as Li 2 O-2B 2 O 3 , we should use the empirical L exp . However, the versatile PF equation, which includes the interfacial process (L¤) can predict the v exp of many borides.

Phase-field simulation of vapor pressure for micropore formation in pseudo-binary system, B₂O₃–UO₂

“…25)-27) In addition, the experimental v of some borides showed more than 10 ¹6 m/s. 27) The v of B 2 O 3 -UO 2 was relatively small in borides because uranium dioxide is a very heavy molecule. Therefore, we concluded there would be no contradictions in the solidification growth rates of UO 2 which were obtained by the PF simulation.…”