In recent years there is a high interest in the freeze-casting process because it is a simple, economical, and environmentally friendly method for obtaining highly porous materials. Most of the materials obtained by this technique have directional pore structure and anisotropic properties. However, a wide range of pore size and morphology can be obtained by the control of processing parameters, such as solvent type, solids concentration, particle size, freezing rate, and types of additives. The varied morphologies permit the application of freeze-casted materials in various technological applications. However, despite the high amount of studies about freeze-casting of ceramic materials in the last years, review articles addressing the influence of processing parameters on the pore characteristics of obtained ceramics are still scanty. Therefore, this review addresses the influence of freeze-casting process parameters on the pore characteristics of the ceramic materials.

No abstract

No abstract

The Friction Stir Welding (FSW) process is a quite recent joining method whose particular characteristics yield to materials modifications not yet fully understood. This paper aims to present the research results of a study focused on the modifications induced in an aluminium alloy AA5083 – H111, when processed by FSW to build components for structural applications. The welded samples were firstly analysed by optical microscopy in order to define the different joined zones and to identify defects. Further tests included the measurement of the Vickers microhardness, grain and particle distribution and chemical analysis of the constituents, particularly of the intermetallic second phase particles, by Auger spectroscopy. Special attention has been given to the characterisation of several microstructural “non-homogeneities” like a laminated structure called onion ring and an identified anomaly (in the form of a line), whose presence was evaluated in order to determine its effects on the final joint properties. The results have shown important new details about the relationship between the microstructure and the final joint structural properties, contributing to improve the knowledge about the materials behaviour increasing the potential of utilization of the FSW process.

Alumina is a polymorphic bioceramic that has been extensively investigated for application in bone regeneration. Dense α-alumina has been considered a suitable biomaterial for dental and orthopedic implants due to its superior mechanical properties. However, its use is limited due to its high inertia in a biological environment. Recent investigations have focused on its distinct phases and surface characteristics through the control of morphology, physical properties, and chemical composition to enhance bioactivity. This article presents a brief review of the developments in porous α-alumina and amorphous-γ-alumina transition. Most studies have shown that composites and alumina coated with bioactive materials, high surface area, and hydroxylated surface can significantly improve biological properties. Cellular responses such as fixation, growth, and proliferation, as well as biomineralization, are the main studies to validate improvements in bioactive properties.