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This paper presents the micro-shot peening of zirconia (ZrO)-advanced ceramics applicable for bio-medical, dental, automotive and aerospace sectors. A ZrO-advanced ceramic was micro-shot blasted with selected parameters as a first-step investigation focused on the topography, microstructure, surface hardness and the surface fracture toughness ( K) characteristics. A new technique of micro-blasting was conducted using a portable shot blaster. A white-light interferometer, scanning electron microscopy and Vickers indentation technique were employed for the analysis. This was followed by determining the K using an empirical equation. Surface roughness was improved by 34 % after micro-shot blasting treatment. No surface cracking was present which generally exists due to the brittle nature of the ceramic. The hardness, however, reduced by 5.6 % with a reduction in the Vickers crack length of 9 %. This improved the K by 3 % when comparing the micro-shot peened surface to the original, as-received surface. It is difficult to conclude if the ZrO-advanced ceramic has undergone plastic deformation and the movement of dislocations increased to strengthen the ZrO ceramic at this stage. However, based on the results, it can be predicted that a level of surface compression was induced beneath the micro-shot peened layer as indicated from the result of the surface topography and integrity. This would justify the hardness modification and the enhancement in K. [ABSTRACT FROM AUTHOR]

In this paper, the densification of a ceramic powder matrix that contained large macropores of the size much larger than the average grain size of the matrix was studied. The grain-boundary diffusion controlled sintering models of ceramic matrix contained large macropores were first established. A sintering potential associated with the macropores was also verified and introduced into the models. The experimental data were collected for the sintering of porous 8 mol% yttria-stabilized zirconia system with 20 vol% large pores. The predictions of the model were found in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The processing of yttria-stabilised zirconia (Y-ZrO2)-based ceramic nanocomposites by means of pulsed electric current sintering (PECS) is described. A nanometer-sized electrically conductive secondary TiCN phase was added to the insulating zirconia matrix in order to make the composite electrically conductive. The paper focuses on the importance of processing conditions and highlights the benefits of the PECS method as compared to more traditional hot pressing. The mechanical and microstructural properties of the ZrO2–TiCN composites have been determined, and the benefits of using an electrical current to densify these composites were explained in terms of the evolution of the electrical properties of the densifying powder compact. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells are currently constructed using a yttria stabilised zirconia electrolyte membrane. However, zirconia has a number of disadvantages associated with its use, such as the high operational temperatures required for it to exhibit acceptable levels of ionic conductivity. Alternative ceramics such as doped cerium oxide show promise as electrolytes capable of operating at reduced temperatures, but introduce additional problems such as electronic conduction and inferior mechanical properties. This paper describes the manufacture and characterisation of a number of prototype electrolytes consisting of a mixture of yttria stabilised zirconia and gadolinium doped ceria. Traditional ceramic processing techniques were used to produce the samples, which were then examined using dilatometry, impedance spectroscopy and X-ray diffraction. Results show a lowering of the ionic conductivity of zirconia with the addition of doped ceria. X-ray diffraction patterns obtained from the samples suggested that this effect could be attributed to the formation of a solid solution of ceria in zirconia. [ABSTRACT FROM AUTHOR]