Density and Young modulus of Al2/O3-Ni composites obtained via slip casting method

Magdalena Gizowska, Mikołaj Szafran, Łukasz Wasilewski, Katarzyna Konopka

Quarterly No. 4, 2009 pages 390-395

DOI:

keywords: ceramic slurry, ceramic-metal composites, Al2O3-Ni

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abstract In the article preliminary results concerning fabrication technology and properties of Al2O3-Ni composite obtained by slip casting method are presented. Beside the mixture of ceramic (α-Al2O3 powder of average particle diameter 0.4 μm and density of 3.926 g/cm3) and metallic (nickel powder of average particle diameter 2.13 m and density of 8.9 g/cm3) powders slurry included binder (poly(vinyl alcohol) introduced into slurry as water-based solution), solvent (distilled water; liquid medium within particles were dispersed) and a composition of deflocculants (citric acid and diammonium citrate). The pH value of slurry was controlled so that double layer of ceramic and metallic powders were of different charge and heteroflocculation takes place (there is an electrostatic attraction of particles of different charge). This effect can guarantee homogeneous distribution in Al2O3-Ni composites obtained via slip casting method. Good powder consolidation is crucial in ceramic and ceramic matrix composites fabrication rout. Preliminarily consolidated powder or powder mixture is subsequently consolidated in sintering process. Influence of deagglomeration of slurry and sintering procedure on powder consolidation and Young modulus was investigated. Subjecting slurries based on alumina and nickel powder mixture to ultrasound deagglomeration process contributed to higher green density and reduced linear sintering shrinkage, whereas it didn’t destroy nickel agglomerates. Observations carried out by means of scanning electron microscope proved that composite show closed porosity. Large pores are placed by nickel agglomerates (melt during sintering process). Young modulus parameter was measured for Al2O3-Ni composite (that exhibited the highest density) and Al2O3 material (fabricated in the same conditions) which are as follows: 370 GPa for composite and 390 GPa for ceramic material. Materials show minor difference in Young modulus parameter value.