Available online at www.sciencedirect.com Journal of the European Ceramic Society 33 (2013) 1403–1411 Modeling of the beryllia ceramics formation process Uzak Zhapbasbayev a,∗ , Gaukhar Ramazanova a , Zamira Sattinova b , Ainash Shabdirova a a Kazakh-British Technical University, 050000, Tole bi Street, 59, Almaty, Kazakhstan b L.N. Gumilyev Eurasian National University, 010000, Munaitpasov Street, 5, Astana, Kazakhstan Received 10 August 2012; received in revised form 4 January 2013; accepted 7 January 2013 Available online 12 February 2013 Abstract Simulation results of the formation process of the ceramic fabrications by a hot molding method are presented. Mathematical model describes motion and heat exchange of the liquid thermoplastic slurry of beryllia including the aggregate state change. Velocity and temperature fields during the formation process in the bushings with flat and circular cavities are obtained. Heat flow distribution at the wall of the form-building cavity is demonstrated. The increase of the slurry density during the transition from the liquid state into the viscous–plastic and solid–plastic states is defined. Comparison of the calculated data versus experimental data is presented. © 2013 Elsevier Ltd. All rights reserved. Keywords: Thermoplastic slurry; Formation process; Solidification; Viscous–plastic state; Solid–plastic state 1. Introduction The method of hot molding 1,2 includes motion and heat exchange of the slurry in the liquid state, as a solid–liquid mixture and as a solid–plastic mixture. At stages of filling the form-building cavity and holding under pressure, it is very important to ensure a most structure destruction for obtain- ing the homogeneous slurry. 2 It is achieved by ultrasonic (US) exposure. 2–5 Minimal friction upon walls of the form-building cavity and maximal plasticity must be reached during the solid- ification process, to avoid the destruction of the newly formed structure of the molding. Hydrodynamics of thermoplastic slurry during molding relates to the class of the physical processes of flow and defor- mation. Slurry flow maintains its configuration after leaving the feeder. It was found during experiments, that for consid- ered molding velocities, the flow of the thermoplastic slurry in the casting mould is laminar. 2 The slurry arrives in the mold at the temperature of 75 ◦ C and cools down up to 45 ◦ C, at which the molding can be extracted from the mold without buckling. 2 ∗ Corresponding author. Tel.: +7 727 266 83 11; fax: +7 727 272 33 68. E-mail addresses: u.zhapasbayev@kbtu.kz, uzak.zh@mail.ru, gaukhar iz ram@mail.ru (U. Zhapbasbayev), gaukhar iz ram@mail.ru (G. Ramazanova), ainash06@gmail.com (Z. Sattinova), sattinova zamira@mail.ru (A. Shabdirova). Development and realization of the hot molding method mainly have an empirical nature, 2–4 and carrying out of the detailed analysis of the motion and heat exchange will allow to more soundly study the ceramics formation process. Below, the modeling of the ceramics formation process of beryllia by hot molding method is presented. 2. Rheological model of the thermoplastic slurry Thermoplastic slurry (high-viscous suspension) is a two- phase dispersed system, where solid mineral phase is beryllia powder (Table 1), and liquid phase is an organic binder. 2,5,6 Organic binder consists of 3 components: paraffin, beeswax and oleic acid in the ratio of 0.82:0.15:0.03. Beryllia powder has granulometric composition by fractions (Table 1). Mass fraction ω = m bin /(m ber +m bin ) of organic binder normalized to unity is changed in the range of 0.095–0.117, where m bin is the mass of binder and m ber is the mass of beryllia powder. Molding properties of the slurry are satisfactory for this com- position of the BeO powder (Table 1), if binder mass content is varied from ω = 0.095 to ω = 0.117. The required amount of binder rises with increasing amount of finer fractions in the BeO powder, which worsens molding characteristics of the slurry. An increase of the amount of coarser fractions in the BeO powder causes a coloring of ceramic, which is sign of presence of micro pores and fractures. 0955-2219/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2013.01.010