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Yttria-stabilized zirconia (YSZ) thin nanocrystalline coatings at different substrate preheating temperatures were deposited via electron beam-physical vapour deposition (EB-PVD). Nanocrystalline ZrO 2 -Y 2 O 3 was deposited on the bond coat in order to compensate for the coefficient of thermal expansion (CTE), which can be functionalized as a thermal barrier coating (TBC). The aim of this study was to evaluate mechanical properties with respect to adhesion of zirconia nanocrystalline's top ceramic layer to the interfacial bond coat by utilizing micro and nano indentation tests. In the present paper, the structural studies were carried out using X-ray diffraction (XRD) analysis of coating content (8 mol% of Y 2 O 3 ). The tetragonal phase of stabilized zirconia was observed. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were employed to characterize the coatings' morphology and microstructure. The mechanical behavior of ZrO 2 -Y 2 O 3 thin films under point loading conditions was studied by nanoindentation using a Berkovich indenter with 130 nm tip radius. Therefore, adhesion of top coat to the interfacial underlying metallic bond coat known as MCrAlY (M = Ni, Co) was estimated according to the highest peak load tests; for a 120 mN peak load, the film manifested tolerable adhesion properties. Moreover, nanoindentation of ZrO 2 -Y 2 O 3 nanostructure deposited at 1050 ℃ substrate preheating temperature produced the highest hardness value of about 21.7 GPa. Vickers micro hardness was utilized with the aid of the Tabor equation in order to achieve deeper insight into the correlation between adhesion and deposition process parameters.

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This paper presents the results of experimental investigation on microstructure (size and morphology of eutectic Si), impact toughness and sliding wear properties of A356 Al-Si alloy and composites containing 10, 20 and 25 wt% of SiCp reinforcement produced by semisolid stirring technique. The results revealed that an increase in SiCp content leads to a reduction in the size of eutectic Si and also changes its morphology from plate-like to equiaxed. Furthermore, addition of 10 and 20 wt% silicon carbide reinforcement decreased the impact toughness by 6 and 18%, respectively. A356/25wt%SiCp composite registered the lowest impact toughness with reduction of 33% due to debonding and agglomeration of SiCp in the matrix. The sliding wear results showed that the wear resistance of the composites was significantly higher than that of the matrix alloy due to the increase in hardness as well as reduction in the size and also morphology transformation of eutectic silicon with increase in SiCp content. However, the existence of particle-porosity clustering with increasing the SiCp content to 25 wt% played a significant role in deteriorating the wear behavior of the composite.

In this study, natural deposits of Kankara kaolin clay were collected and investigated in order to determine physical, microstructural, thermal, and firing properties and assess clay’s suitability as starting material for various ceramic applications. Chemical analysis of the clay was performed using XRF. Mineralogical analysis and thermal analysis of the clay were conducted using XRD and thermogravimetric thermal analysis (TGA)/differential thermal analysis (DTA), respectively. In order to assess its ceramic behavior, the clay was fired at 900–1200 °C. Maturation characteristics of fired ceramics were assessed by measuring bulk density, apparent porosity, and shrinkage. It was found that main oxides in the clay are alumina, silica, and potassium oxide, while other oxides are present in trace quantities. Kaolinite, quartz, and illite are the phases found from the XRD results, while mullite ceramic phase formed at firing temperature above 1100 °C. Maturation tests showed that ceramic properties such as bulk density and shrinkage increase with temperature, while apparent porosity decreases with temperature. The results presented in this study prove that the clay is an appropriate material for producing traditional ceramics.

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