Design of porous aluminum oxide ceramics using magnetic field-assisted freeze-casting
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Design of porous aluminum oxide ceramics using magnetic field-assisted freeze-casting Said Bakkar1, Jihyung Lee1, Nicholas Ku2, Diana Berman1, Samir M. Aouadi1, Raymond E. Brennan2,a), Marcus L. Young1,b) 1
Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203, USA CIV USARMY CCDC ARL, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005-5425, USA a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] 2
Received: 8 May 2020; accepted: 16 July 2020
Magnetic field-assisted freeze-casting of porous alumina structures is reported. Different freeze-casting parameters were investigated and include the composition of the original slurry (Fe3O4 and PVA content) and the control of temperature during the free casting process. The optimum content of the additives in the slurry were 3 and 6 wt% for PVA and Fe3O4, respectively. These conditions provided the most unidirectional porous structures throughout the length of the sample. The sintering temperature was maintained at 1500 °C for 3 h. The application of a vertical magnetic field (parallel to ice growth direction) with using a cooling rate mode technique was found to enhance the homogeneity of the porous structure across the sample. The current study suggests that magnetic field-assisted freeze-casting is a viable method to create highly anisotropic porous ceramic structures.
Introduction Porous ceramic structures are of great interest due to their unique set of physical and chemical properties, including low density, low thermal conductivity, structural stability, and corrosion resistance [1, 2, 3, 4, 5, 6]. The ability to design porous ceramics with a wide range of porosities enables their use in various applications, that include liquid or gas filtration systems, thermal barrier coatings, lightweight components [7, 8], biomedical implants [9, 10], fuel cells, and batteries [11, 12]. Existing methods which enable the controlled production of porous ceramic structures include replica, sacrificial template, direct foaming, 3D-printing, sol–gel casting, and freeze-casting methods [13, 14]. Each of these methods exhibits various advantages and disadvantages that were discussed in reference [15]. In the current study, we explore the magnetic field-assisted freeze-casting method on ceramic materials since the magnetic field assists in the freeze-casting-based design of porous ceramic preforms with highly uniform and aligned pores, thus enabling the production of a low-cost, safe, and robust design of porous ceramic structures, which can later be infiltrated with molten metal to create metal matrix composites [9, 16].
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The freeze-casting method involves using aqueous or organic-based slurries composed of a solid phase powder and a liquid carrier that are directionally frozen [16]. The freezecasting method usually consists of four main steps: (i) preparing the colloidal ceramic slurry, (ii) freezing the slurry, (iii) r
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