Rodrigo Moreno Prof. Rodrigo Moreno obtained the PhD degree in Chemistry by Universidad Autónoma de Madrid in 1988. He has developed all his scientific activity in the Institute of Ceramics & Glass (CSIC, Spain), where he become Tenured Scientist in 1990, Research Scientist in 1999, and Research Professor in 2004. He is the leader of the Synthesis and Colloidal Processing Group at ICV from 2005. His main interest lies on the synthesis of ceramic powders, the colloidal stability and rheology of ceramic suspensions, and the manufacture of structural and functional materials by colloidal processing techniques. He is co-author of more than 240 ISI journal articles, 9 patents, several book chapters, and one book. He has been member of the organization committees of more than 40 national and international conferences and has pronounced more than 50 invited lectures. Prof. Moreno is member of the Spanish Ceramic Society, the Spanish Society of Materials, and the American Ceramic Society, and is one of the editors of the Journal of the European Ceramic Society.

 

Colloidal processing of nanocomposites of SiC reinforced with carbon nanotubes with different characteristics for wear applications

Rodrigo Moreno

Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas, 28049 Madrid, España

Resumo
Although SiC materials obtained by liquid phase sintering have excellent properties for wear applications some strategies to enhance the wear resistance have been explored such as the reduction of sintering aids content, the hardening of intergranular phase, the refinement of particle size or the elongation of grains, etc. Another approach that is receiving increased attention is the use of carbon nanodispersoids, which act as self-lubricating-phase thus improving the resistance to wear. However, a major problem in the manufacture of ceramic based composites containing carbon-based structures is the difficulty to attain a good dispersion of the carbon second phase, especially for low-cost, simple aqueous processing routes. The objective of this work was to develop a facile, reliable processing route to produce carbon nanotubes (CNTs) reinforced SiC through a colloidal processing approach. Aqueous suspensions were studied in terms of colloidal stability by zeta potential measurements and rheological behavior, considering the effect of a number of parameters in the rheology, such as the solids loading, the pH and deflocculants content, the sonication time, and the effect of the characteristics of the CNTs. A set of CNTs with different length, thickness and surface functionalization, were used. The nano-SiC aqueous suspensions exhibited a complex rheological behavior with very large thixotropic cycles that indicate strong coagulation at high shear rate. It has been shown that, regardless of their specific characteristics, the incorporation of CNTs prevent the coagulation of these nanoceramic suspensions, whence it is inferred that aqueous colloidal processing is well-suited for the environmentally friendly preparation of CNT-reinforced ceramic matrix nanocomposites. Once selected the best dispersing conditions the suspensions were freeze dried and the resulting powders were sintered by non-conventional spark plasma sintering. The sliding wear behavior of the sintered composites was studied and the results are correlated with the microstructural features and the processing parameters to provide some relevant implications for the microstructural design of advanced triboceramics.


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