Presentation Title: Aqueous Processing of Lead-free Functional Materials for a Better World
Prof. José Ferreira presented this talk in the webinar on Materials Science, Engineering and Technology organized by Vebleo
Author: José M. F. Ferreira1, Susana M. Olhero1, Ajay Kaushal1, Budhendra Singh2, Igor Bdikin2, Tim Button3
Affiliation:
1Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
2TEMA-NRD, Aveiro Institute of Nanotechnology (AIN), University of Aveiro, 3810-193 Aveiro, Portugal
3School of Metallurgy and Materials, University of Birmingham, Birmingham, UK
Biography
Assoc. Prof. José Ferreira is Associate Professor with Habilitation at the Department of Materials and Ceramic Engineering, CICECO – Aveiro Institute of Materials, University of Aveiro.
Assoc. Prof. José Ferreira is the leader of the Advanced Processing Group. Assoc. Prof. José Ferreira ‘s main research interests include the development and colloidal processing of advanced ceramic and glass materials for various structural and functional materials applications (Microelectromechanical Systems, optical and energy related materials, and materials for applications in biomedicine, especially in dentistry, orthopedics and tissue engineering.
Throughout his scientific career, Assoc. Prof. José Ferreira has supervised 40 Master and 24 PhD students, registered 16 patents, published 6 book Chapters and more than 570 articles in SCI journals, including 2 Feature Articles.
Assoc. Prof. José Ferreira also published 25 articles in referred journals and 92 papers in conference proceedings. He has delivered more than 80 Invited Lectures, including Key Note and Plenary Lectures in international conferences.
Assoc. Prof. José Ferreira is recipient of several awards, including the ‘Stimulus to Excellence – 2005 award’ from the Portuguese Foundation for Science and Technology (FCT); the ‘Chinese Ceramic Society – 2005’ award; the Membership of the World Academy of Ceramics (www.waceramics.org) since July 2013; and the title of Fellow of the European Ceramic Society (ECerS), June 24th, 2015, Toledo, Spain.
Abstract
Functional materials possess unique properties such as high piezoelectric, electro-mechanical coupling and high dielectric permittivity that enable their use in piezo generators, sensors, piezo actuators, and transducers. Lead zirconate titanate (PZT) is the most widely used piezoelectric ceramic worldwide because of its greater sensitivity in comparison to barium titanate (BT) or barium-strontium titanate solid solutions (BST).
However, the fabrication and use of lead-bearing components put serious environmental threats, justifying the search for alternative materials. On the other hand, bulk ceramics and thick films for multilayer ceramic capacitors are usually prepared by dispersing the piezoelectric powders in organic solvents, which also rise grave safety, environmental and economic concerns, rising the interest in using water as dispersion medium.
However, the starting powders of ferroelectric materials tend to undergo hydrolysis and non-stoichiometric dissolution reactions in contact with water. Such reactions strongly mitigated the success of several previous wet processing attempts of these kinds of materials in aqueous media.
Further, shaping micro components of complex 3D geometry and high aspect ratio with high dimensional accuracy at the micrometre scale range usually requires the use of high-tech micromachining tools. Moreover, the production of patterned components and engineering systems at micro- and nano-scales is very challenging and beyond the capability of current micromachining tools.
This presentation discloses an integrated multipurpose research aiming at overcoming the most stringent technological limitations above referred, while shedding light on responsible physico-chemical phenomena. The overall approach involves: (i) preventing the hydrolysis and non-stoichiometric dissolution reactions of the starting water sensitive powders of BT, BST, and lead-free BZT-BCT ceramics; (ii) the preparation of long-term stability and high concentrated suspensions; (iii) the development of a novel direct consolidation technique based on aqueous solutions of epoxy resin and its polymerization upon adding a polyamine-based hardener.
This Epoxy Gel Casting (EGC) method enables obtaining high aspect ratio components with green strength high enough for overcoming the shear stresses upon unmoulding. Besides these key findings, the results also enable to conclude about:
(i) the need of a suitable powders’ surface treatment to prevent hydrolysis; (ii), the anions of the polyelectrolyte dispersants act as monodentate and/or bidentate chelates towards alkaline hearth cations, thus enhancing the dissolution reactions in the presence of dispersant; (iii) EGC is an interesting cost effective technique for fabricating micro-components with complex shapes and varied sizes; (iv) homogeneous powders for dry pressing can be prepared by freeze granulation of the stable suspensions.
Graphical Abstract
This talk was delivered in the webinar organized by Vebleo