Optimizing mechanical and electrical properties of 3YTZP/MWNT ceramic nanocomposites


Recent technological advances in industries and the general society require composite materials processing of not only remarkable mechanical properties, but also exceptional functionalities. To this note, carbon nanotubes have become a material of great interest due to their dazzling properties. As a result, this has motivated many researchers to focus on ceramic composites containing carbon nanotubes with the aim of improving the matrix’s properties. Carbon nanotubes possess some unwelcoming properties such as chemical inertness and entanglement due to van der Waal forces, which inhibit their full exploitation. Consequently, the search for an enhancer of the carbon nanotube benefits that does not damage the nanotubes has intensified. Previously published work has highlighted on various acid treatment techniques that have been proposed. Colloidal method has emerged as the most auspicious. Unfortunately, colloidal technique incorporating carbon nanotubes acid treatment and aqueous solution pH control is yet to be fully exploited for the processing of zirconia/carbon nanotubes composites.

Inst. Ciencia de Materiales de Sevilla (ICMS, CSIC-Universidad de Sevilla) researchers in Spain: Dr. Rosalía Poyato, Dr. Gutiérrez Mora, Professor A. Munoz, Professor Ana Morales Rodríguez and Professor Ángela Gallardo López conducted a study whose main objective was to differentiate the benefits/disadvantages of the various colloidal processing routines employed in terms of optimizing multiwall carbon nanotubes distribution through the ceramic matrix. Their research approach entailed modifying the acid treatment to be applied to the nanotubes and also the use of an acid/basic pH during composite powder mixing. Their work is published in the research journal, Ceramics International.

The research techniques employed entailed preparation of zirconia polycrystals composites with 2.5% by volume of multiwall carbon nanotubes by spark plasma sintering of powders prepared using different colloidal processing routines. The processing routines employed involved subjecting the multiwall carbon nanotubes to two different acid treatments and ulterior composite powder mixing in aqueous solution with either basic or acid pH. Finally, the researchers analyzed the effects of each routine on the composites hardness, microstructure, electrical conductivity and fracture behavior.

The authors observed that no multiwall carbon nanotubes damage during processing was detected by Raman spectroscopy. In addition, carbon nanotubes bundles were found in all the composites forming different patterns depending on the processing route. Moreover, the researchers noted that similar values of hardness were obtained for all the composites. The carbon nanotubes bundles were seen to act as fracture short paths. Furthermore, a similar anisotropic behavior was observed for the electrical conductivity.

Rosalía Poyato and colleagues study has elucidated on the effect of acid-treatment and colloidal-processing conditions on the room temperature mechanical and electrical properties of tetragonal zirconia polycrystals/multiwall carbon nanotubes ceramic nanocomposites. It has been seen that the studied nanocomposites show a rather homogeneous microstructure with most of the multiwall carbon nanotubes well dispersed at the zirconia grain boundaries. In addition, the remarkable electrical anisotropy observed in all the composites points to a preferential orientation of the carbon nanotubes bundles in the direction perpendicular to the Spark Plasma Sintering loading axis. Altogether, the results here direct that the best processing routine for obtaining highly conductive tetragonal zirconia polycrystals/multiwall carbon nanotubes composites with homogeneous microstructure is the one which combines multiwall carbon nanotubes stirring during the acid treatment and further powder processing by charge stabilization.


About the author

Dr. Gutiérrez Mora career began in 1998 in the group of Mechanical Properties of Solids at the University of Seville where he completed his Ph.D. entitled “Mechanical behavior at high temperatures of YSZ nanocrystals”. After receiving his Ph.D. he worked at Argonne National Laboratory (Illinois, USA) in the Energy Technology as a postdoctoral fellow from 2000 to 2002. In 2003, he returned to the group of Mechanical Properties of Solids of the University of Seville after obtaining a Ramón y Cajal fellowship. Since 2008, he is a Tenured Professor in the Department of Condensed Matter Physics at the University of Seville.

He is author or co-author of over 40 papers in international journals. His current line of research consists on the study of the mechanical properties at room temperature and the tribological behavior of monolithic and composite ceramic materials.

About the author

Dr. Rosalía Poyato completed her B.Sc. in Physics at the University of Seville (Spain) and received her PhD in Applied Physics at the Autónoma University of Madrid (Spain). After obtaining her PhD, she developed her research at the University of Connecticut and Ohio State University (USA), as a postdoctoral research Fulbright fellow.  At this moment, she is a Tenured Researcher at the Materials Science Institute of Seville (mixed Institute of the Spanish National Research Council and the University of Seville) and her current research interests include processing and characterization of ceramic composites including carbon nanostructures (carbon nanotubes and graphene).

She has co-authored over 50 papers in international journals. Dr. Poyato is now co-leader of a research project funded by the Spanish National Science Foundation and the European Feder Funding: Processing and microstructural, mechanical and electrical characterization of ceramic-graphene composites.

About the author

Ángela Gallardo López had her Bachelor in Physics in 1994, at the University of Seville, with a special mention for best academic results in her area. She performed a Ph.D in the same University “Order and disorder of point defects and its influence on the mechanical properties of Y2O3-ZrO2”, in the area of Materials Science (1999) and a postdoctoral stage in the UFRJ (Rio de Janeiro, Brasil, 2000).

Tenured professor at the University of Seville from 2009. For the last ten years, she has been involved in the processing, microstructural, mechanical, electrical and tribological characterization of advanced ceramic composites with carbon nanotubes and most recently with graphene-based nanostructures. At present, she is the leader of a research project on graphene/ceramic composites financed by the Spanish MINECO and European FEDER fundings.

About the author

Ana Morales Rodríguez is a tenured professor at Condensed Matter Physics Department of the University of Seville (Spain). After receiving her Ph.D. in Materials Science in 2004 (high–temperature mechanical properties of zirconia/nickel composites for use as solid oxide fuel cells), she joined the University of Seville as assistant professor. From 2005 to 2007 she developed her postdoctoral activity in research stays at the National Institute of Applied Sciences (University of Lyon) in France. Her postdoctoral research focused on fatigue behaviour of fibre–reinforced CMCs.

She currently works on ceramics and ceramic composites reinforced with carbon nanostructures, in aspects from processing to microstructural and mechanical characterization (mainly plasticity and fracture). She has participated in 8 research projects and she has authored or co-authored around 30 scientific papers in peer–reviewed materials science journals.

About the author

Professor A. Munoz hold a PhD in Physical Sciences from the University of Seville (Spain) in 1988 and Professor of Physics of Condensed Matter at this University. He has participated in 21 research projects at national level, being the principal investigator in three of them and has directed two doctoral theses. His research activity has been focused on the field of Materials Science, more specifically in the study of the structural and functional properties of amorphous solids, crystalline solids and advanced ceramic materials, monolithic and compounds of ceramic matrix and reinforcing elements. As result of this activity, he has participated in the publication of a hundred works, most of them in international journals of recognized prestige in the field of Materials Science.

He has also participated in the organization of several national and international conferences in this field. At the same time, he has worked as teacher for the last 30 years in the Condensed Matter Physics Department of the University of Seville (Spain), teaching different subjects and occupying different teaching positions.


R. Poyato, A. Morales-Rodríguez, F. Gutiérrez-Mora, A. Muñoz, Á. Gallardo-López. Effect of acid-treatment and colloidal-processing conditions on the room temperature mechanical and electrical properties of 3YTZP/MWNT ceramic nanocomposites. Ceramics International, volume 43 (2017) pages 16560–16568


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