Dense mullite was produced through the reaction and sintering of an attrition‐milled mixture of kyanite (Al2O3·SiO2) and aluminum metal. Kyanite and aluminum were attrition‐milled then slowly heated at 1°3C/min to 1100°3C in air, and rapidly heated to 1600°3C and held for 1 h. During heating, the aluminum metal is oxidized first in the solid state and then as a liquid. The attrition‐milled kyanite decomposes yielding mullite and rejecting silica, which then reacts with the alumina formed from oxidation of the aluminum. Expansion from the aluminum oxidation and kyanite decomposition partially compensates for the normal sintering shrinkage. A dense, fine‐grain‐size mullite results.
This work analyzes the mechanical behavior of new composite materials with polymeric matrix, made from recycled polyethylene terephthalate (r-PET), reinforced with 10, 20, 30 and 40 wt% Zn metal particles, processed under isothermal sintering at constant temperature (256°C) and time (15 min) conditions. The r-PET/Zn composite material samples were obtained by a powder traditional technique, namely, ball-milling, uniaxial dye-pressing to obtain pre-forms followed by isothermal sintering. The observations through optical microscopy of the overall morphologies that resulted after sintering the samples studied, were compared against the r-PET-control sample without reinforcement, processed under the same conditions. From the results, it was found that the metal particles were distributed uniformly in the matrix; further, increasing amounts of metal particles tended to improve the mechanical behavior resulting in a stronger material, as was the case of the two materials with higher metal contents (30 and 40 wt% Zn).
The synthesis of alumina (Al 2 O 3 )-composites having different amount of very fine titanium and titanium carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; the first step consisted of the pressureless-sintering of Al 2 O 3 -titanium powders which were thoroughly mixed under high energy ball-milling and through the second step it was induced the formation of titanium carbide during different times at 500 °C by the cementation packing process. SEM and EDS analysis of the microstructures obtained in both sintered and cemented bodies were performed in order to know the effect of the activated carbon used as cementing agent on the titanium for each studied composite. It was observed that a titanium carbide layer growth from the surface into the bulk and reaches different depth as the titanium content in the composites increases. On the other hand, the use of ductile titanium notably enhanced density level and fracture toughness of the composites.
The effect of different titanium additions (0.5, 1, 2, 3 and 10 vol. %), milling intensity (4 and 8 h) and sintered temperature (1500 and 1600 °C) on microstructure and fracture toughness of Al2O3-based composites was analyzed in this study. After high energy milling of a titanium and Al2O3mixtures, powder mixture presents fine distribution and good homogenization between ceramic and metal. After milling powders during 8 h they were obtained very fine particles with 200 nm average sizes. Microstructures of the sintered bodies were analyzed with a scanning electron microscopy, where it was observed that the microstructure presents the formation of a small and fine metallic net inside the ceramic matrix. From fracture toughness measurements realized by the fracture indentation method, it had that when titanium content in the composite increases, fracture toughness is enhanced until 83% with respect to the fracture toughness of pure Al2O3. This behavior is due to the formation of metallic bridges by titanium in the Al2O3matrix.
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