CERAMICS INTERNATIONAL SEVIER Ceramics International 30(2004)853-863 www.elsevier.com/locate/ceramint Electrophoretic deposition of alumina and zirconia II. Two-component systems Hynek Hadraba*, Karel Maca, Jaroslav Cihlar Received 30 May 2003: received in revised form 17 August 2003; accepted 25 September 2003 Abstract The similar electrophoretic mobility of Al2O and ZrOz in the isopropanol suspensions containing monochloroacetic acid enabled a controlled preparation of layered and particle composites Al2O3/ZrO2 as well as functionally gradient materials with gradual composition transition from Al2O3 to ZrO2. In view of the negative charge of Al2 O3 and Zro particles in the isopropanol suspensions used, all the prepared types of composite were deposited on the anode and thus they were not affected by possible solvent electrolysis, which contributed to their defect-free and low-porosity structure. Phenomena related to the deposition kinetics of these composites as well as some properties of as-sintered composites are described in the paper. o2003 Elsevier Ltd and Techna Group s r l. All rights reserved eywords: B Composites, D. Al2O3; D ZrO2; Electrophoretic deposition 1. Introduction could not find in the available literature any experimental work on electrophoretic deposition of Al2O3/ZrO2 particle Depending on the geometry of the reinforcement phas composites. Only Wang et al. [3 described the preparation composite materials can be subdivided into particle, fiber of a particle composite based on Al2O3/Zro2, which was and layered composites[1]. The technique of electrophoretic formed when a deposit of Al/ZrO2 particles was sintered in deposition appears to be of much promise in the preparation oxygen atmosphere of particle and layered composites Layered composite materials are produced by alternating In electrophoretic deposition of particle composites it electrophoretic depositions of suspensions of different com- is necessary that all the simultaneously deposited phases position. The preparation of Al2O3/ZrO2 layered composite should have identical charge polarity and electrophoretic via alternating electrophoretic deposition from aqueous [4, 51 mobility in order to obtain a homogeneous deposit [2]. To but more often from ethanol [6-8] suspension of Al2O3 and obtain maximum density and homogeneity of the chem- Z O2 particles was reported in the literature. The preparation ical composition of deposit it is also important that the of ceramic layered composites made up of thin layers poses deposited phases be thoroughly dispersed in the suspension problems from the viewpoint of the appearance of stresses retical possibility of electrophoretic deposition of particle on the interface of two different materials. These stresses and not coagulated. Deliso et al. [2] predicted the theo- appear in the process of deposit drying and sintering due te composite based on Al2O3 and ZrO2 as early as 1988 different deposit green densities, and also due to different B hen they found that Al2O and ZrOz particles in aqueous thermal expansion of materials while the sintered composite lized by ammonium polyacrylate. Although in the literature of the dng sit These stresses may lead to the defor mation One of the ways of avoiding the problems related to the Al2O3/ZrO composites and also on particle composites harp transition between two layers is to introduce weak of other than Al203/ZrO2 composition, the present authors interfaces between them, another way is to prepare function ally gradient responding author. Fax: +420-541 143202 in this paper understood as heterogeneous multi-component ail address: hadraba a umi. fme. vutbr cz(H. Hadraba) materials with composition gradient. The consequence of a 0272-8842/$30.00 0 2003 Elsevier Ltd and Techna Group S r l. All rights reserved doi:10.1016/ ceramist2003.09.020Ceramics International 30 (2004) 853–863 Electrophoretic deposition of alumina and zirconia II. Two-component systems Hynek Hadraba∗, Karel Maca, Jaroslav Cihlar Department of Ceramics, Brno University of Technology, Brno 616 69, Czech Republic Received 30 May 2003; received in revised form 17 August 2003; accepted 25 September 2003 Available online 20 March 2004 Abstract The similar electrophoretic mobility of Al2O3 and ZrO2 in the isopropanol suspensions containing monochloroacetic acid enabled a controlled preparation of layered and particle composites Al2O3/ZrO2 as well as functionally gradient materials with gradual composition transition from Al2O3 to ZrO2. In view of the negative charge of Al2O3 and ZrO2 particles in the isopropanol suspensions used, all the prepared types of composite were deposited on the anode and thus they were not affected by possible solvent electrolysis, which contributed to their defect-free and low-porosity structure. Phenomena related to the deposition kinetics of these composites as well as some properties of as-sintered composites are described in the paper. © 2003 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: B. Composites; D. Al2O3; D. ZrO2; Electrophoretic deposition 1. Introduction Depending on the geometry of the reinforcement phase, composite materials can be subdivided into particle, fiber and layered composites [1]. The technique of electrophoretic deposition appears to be of much promise in the preparation of particle and layered composites. In electrophoretic deposition of particle composites it is necessary that all the simultaneously deposited phases should have identical charge polarity and electrophoretic mobility in order to obtain a homogeneous deposit [2]. To obtain maximum density and homogeneity of the chem￾ical composition of deposit it is also important that the deposited phases be thoroughly dispersed in the suspension and not coagulated. Deliso et al. [2] predicted the theo￾retical possibility of electrophoretic deposition of particle composite based on Al2O3 and ZrO2 as early as 1988, when they found that Al2O3 and ZrO2 particles in aqueous medium had the same electrophoretic mobility if stabi￾lized by ammonium polyacrylate. Although in the literature much data is given on electrophoretic preparation of layered Al2O3/ZrO2 composites and also on particle composites of other than Al2O3/ZrO2 composition, the present authors ∗ Corresponding author. Fax: +420-541143202. E-mail address: hadraba@umi.fme.vutbr.cz (H. Hadraba). could not find in the available literature any experimental work on electrophoretic deposition of Al2O3/ZrO2 particle composites. Only Wang et al. [3] described the preparation of a particle composite based on Al2O3/ZrO2, which was formed when a deposit of Al/ZrO2 particles was sintered in oxygen atmosphere. Layered composite materials are produced by alternating electrophoretic depositions of suspensions of different com￾position. The preparation of Al2O3/ZrO2 layered composite via alternating electrophoretic deposition from aqueous [4,5] but more often from ethanol [6–8] suspension of Al2O3 and ZrO2 particles was reported in the literature. The preparation of ceramic layered composites made up of thin layers poses problems from the viewpoint of the appearance of stresses on the interface of two different materials. These stresses appear in the process of deposit drying and sintering due to different deposit green densities, and also due to different thermal expansion of materials while the sintered composite is cooling [9]. These stresses may lead to the deformation of the deposit [5] or even to the appearance of cracks [9]. One of the ways of avoiding the problems related to the sharp transition between two layers is to introduce weak interfaces between them, another way is to prepare function￾ally gradient materials (FGM in the following), which are in this paper understood as heterogeneous multi-component materials with composition gradient. The consequence of a 0272-8842/$30.00 © 2003 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2003.09.020