H. Hadraba et al /Ceramics International 30(2004)853-863 500m Fig. 1. Microphotographs of alumina/zirconia layered composite LC HP/3Y. The fracture toughness of sintered deposits was measured First, a layered deposit with varied ZrO2 layer thickness by the indentation method(according to Japanese Industrial and constant Al2O3 layer thickness(70 um) was prepared Standard JIs R 1607) on a Vickers indentor at a loading ZrO2 layers of more than 60 um in thickness exhibited force of 98N cracks. These cracks were of large opening displacement Similar cracks were reported by Hillman et al. [9], who showed that such cracks had developed already in the 3. Results and discussion stage of drying and sintering due to the different green densities of individual layers. The following deposition 3.1. Electrophoretic deposition of layered composite were therefore performed such that the thickness of Al2O3 and ZrO2 layers in the produced layered composites were All depositions were conducted at a constant current of less than 50 um, which was the thickness of the layers in which the cracks did not appear. Layered composite mA, with the particles depositing on the anode as in the receding works [10, 11] prepared in this way was really free from these defects (Fg.1) ZrO, ALO bbzro AlyO 500m 3 um Fig. 2. Microstructure of alumina/zirconia interface in layered composite LC HP/3Y at(a)low and(b) high magnification.H. Hadraba et al. / Ceramics International 30 (2004) 853–863 855 Fig. 1. Microphotographs of alumina/zirconia layered composite LC HP/3Y. The fracture toughness of sintered deposits was measured by the indentation method (according to Japanese Industrial Standard JIS R 1607) on a Vickers indentor at a loading force of 98 N. 3. Results and discussion 3.1. Electrophoretic deposition of layered composite materials All depositions were conducted at a constant current of 5 mA, with the particles depositing on the anode as in the preceding works [10,11]. Fig. 2. Microstructure of alumina/zirconia interface in layered composite LC HP/3Y at (a) low and (b) high magnification. First, a layered deposit with varied ZrO2 layer thickness and constant Al2O3 layer thickness (70
m) was prepared. ZrO2 layers of more than 60
m in thickness exhibited cracks. These cracks were of large opening displacement. Similar cracks were reported by Hillman et al. [9], who showed that such cracks had developed already in the stage of drying and sintering due to the different green densities of individual layers. The following depositions were therefore performed such that the thickness of Al2O3 and ZrO2 layers in the produced layered composites were less than 50
m, which was the thickness of the layers in which the cracks did not appear. Layered composite prepared in this way was really free from these defects (Fig. 1)