This paper focused on the characterization of the composites containing nickel aluminate spinel from Al₂O₃/NiO and Al₂O₃/Ni systems. The composites were prepared by die pressing of powders and subsequent sintering of green bodies in air atmosphere. Composites were characterized by XRD, SEM, EDS and DTA/TG/MS analyses. The physical properties of the composites were measured by Archimedes method. Quantitative description of the composites microstructure was made on the basis of SEM images using computer image analysis. The XRD studies and SEM observations of composites confirmed the presence of two phases Al₂O₃ and NiAl₂O₄ in the whole volume of samples from both systems. Spinel phase was evenly distributed throughout the volume of the material. Morphology of NiAl₂O₄ obtained from both systems was characterized by the presence of voids. The DTA/TG/MS measurements showed the characteristics of organic binder decomposition and type of gases released to the atmosphere during thermal treatment. Moreover, the DTA/TG analysis showed the temperature of spinel-phase formation for both systems. It was found that the spinel-phase NiAl₂O₄ formation retards the process of densification. Therefore, it can be concluded that densification of samples with spinel phase depends mainly on the volume of spinel phase in composite material and does not depend on the substrates used to prepare spinel phase. The values of the selected properties of Al₂O₃–Ni- and Al₂O₃–NiO-based materials confirmed that the physical properties depend on the type of substrates used in the fabrication of composites. The type of powder influences the open porosity of samples. For composites produced using NiO powder, open porosity is lower than for samples formed with nickel powder.

Alumina-nickel composite samples (with 0, 10 and 20 vol.% of Ni) are prepared via slip casting method. Nickel and aluminium oxide powders were used as precursors and diammonium hydrocitrate and citric acid were used as dispersants. The obtained materials were analysed by dilatometry, X-ray diffraction and SEM. The densities were measured by Archimedes method and the hardness and fracture toughness were determined by using Vickers hardness tester. Special attention was paid to the linear shrinkage and the effective coefficient of thermal expansion measurements. The shrinkage curves were obtained by dilatometry test in a heating mode. It was shown that the increased amount of Ni particles in Al2O3-Ni composite structure causes reduction of starting densification temperature, increasing temperature of maximum densification and decreasing total shrinkage of the sample during sintering.

The fabrication and the characterization of Al₂O₃/Ni composites with a gradient distribution of the Ni particles are reported. The composites have been obtained by centrifugal-slip casting and subsequent sintering and had the shape of a hollow cylinder. TG/DTA analysis was done for the nickel powder with the addition of the dispersant used in centrifugal-slip casting as well as for the composite green body. The measurements were performed in two atmospheres: argon and the mixture of argon and hydrogen (1:1). Additionally, coupling the thermobalance with the mass spectrometer allowed to determine type of gases released from the samples during thermal treatment. The morphology and chemical composition of the produced composites were analyzed using a scanning electron microscope equipped with an EDS detector. Interface between alumina and nickel was described. Moreover, the X-ray diffraction was made. The stereological analysis confirmed that the nickel particles are distributed in the composite in a gradient way.