CeraMat

Graded structures obtained by coupling different WC grades, also containing cubic carbides type (Ta, Nb)C with Co as binder, were produced by vacuum sintering. Different batches of cylindrical samples were compacted by coupling two different grades and were sintered at 1450°C under vacuum. The hardness properties as well as the shrinkage due to sintering process are function of the employed grades and show gradual change between the single values of each of the coupled grades.

The paper is focused on the processing of aluminum alloy chips using powder metallurgy. Chips obtained from recycled AlSi5Cu2 alloy were ball milled with the addition of silicon carbide powder with an average size of 2um. Mechanical alloying process was employed to obtain homogeneous composite powder. The effect of processing time (0 - 40h) on the homogeneity of the system was evaluated, as well as a detailed study of the microstructure of AlSi5Cu2 aluminum chips and SiC particles during MA was carried out.

The present work investigates the possibility of using powder metallurgy processing for producing a metal matrix composite. Materials were prepared from AlSi5Cu2 chips with reinforcement of 10, 15, 20 wt. % silicon carbide. Aluminum alloy chips were milled with SiC powder in a high-energy ball mill by 40 hours. Mechanical alloying process lead to obtain an uniform distribution of hard SiC particles in the metallic matrix and refine the grain size. The consolidation of composite powders was performed by vacuum hot pressing at 450°C, under pressure of 600 MPa by 10 min.

The Laser Granulometer is an efficient instrument for detecting the reactivity of cement clinkers components in contact with water. Results are satisfactorily comparable with those obtained by means of different analysis techniques. Further applications are suggested.

The use of infrared spectroscopy has shown that even the order involving a few unit cells can affect the crystalline solid reactivity. In the case of monocalcium aluminate hydration in the presence of a calcareous filler, it was possible to observe that an increase of carbonate lattice disorder caused a decrease of induction time and an increase of hydration rate of CA* * Cement Chemists' Notations: A = Al2O3; C = CaO; C = CO2; H = H2O - CaCO3 mixture and a change of developed phases mutual ratios.