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The objective of this work was to study the influence of the addition of silver nanoparticles in the microstructure of mullite at two different temperatures of sintering (1500 and 1600 °C), in order to decrease the porosity and increase the density as well better the hardness and fracture toughness. The microstructural characteristics were studied by scanning electron microscopy, confocal scanning microscopy and X-ray diffraction. Mullite/Ag cermets with homogenous microstructure were and a fracture toughness of 2.42 MPа·m 1/2 .

The objective of this work was to study various aspects of liquid state diffusion bonding of cylindrical samples of Al2O3 and commercially pure niobium (99.7%) by brazing using a 25 µm thick 70Cu-30Zn (wt%) alloy as joining element. Initially, sintering of alumina powder was carried out in order to produce a 7 mm diameter samples at 1550°C by 120 minutes. Joining experiments were carried out on Al2O3/Cu-Zn/Nb/Cu-Zn/Al2O3 sandwich-like combinations at temperature of 920°C, 950°C and 980°C using different holding times under argon (Ar) atmosphere. The experimental results show a successful joining of alumina to niobium at 950°C and 980°C, however not at 920°C. Joining of Al2O3/Cu-Zn/Nb/Cu-Zn/Al2O3 occurred by the formation of a homogeneous diffusion zone with no interfacial cracking or porosity at the interface. Scanning electron microscopy (SEM) micrographs show the layer formed in the reaction zone. It was observed that the width of the reaction zone increases with bonding temperature and time. Electron probe microanalysis (EPMA) revealed that at any particular bonding temperature, Nb travel into the Cu-Zn joining element forming a circular precipitate phase near to the alumina ceramic.

Ni based braze filler metals containing B and Si elements, prepared either by rapid solidification or powder metallurgy have relatively low melting temperatures, which make them liable to join. This work presents the mechanical resistance of stainless steels 316L joints, bonded with an amorphous Metglas i MBF-15m foil at 1105 8C and 1170 8C joined for 5, 10, 15, 20 and 40 minutes, under a nitrogen atmosphere into an electric resistance furnace. Intermixed precipitate particles at the joining zone were formed and an improvement on the bonding samples for conditions of 1105 8C for 10 minutes were observed, since the number of unjoined islands were reduced and no interfase crack was detected. The average shear-tensile mechanical resistance of the joints ranged from about 54 MPa to 70 MPa, and from 47 MPa to 79 MPa, for samples joined at 1105 8C and 1170 8C, respectively.