NANOSCIENCE AND NANOTECHNOLOGY IN CONSTRUCTION MATERIALS

Transcription

1 NANOSCIENCE AND NANOTECHNOLOGY IN CONSTRUCTION MATERIALS Antonio Porro (1) (1) Centre for Nanomaterials Applications in Construction, LABEIN-Tecnalia, Bilbao, Spain Abstract This opening paper gives an overview of the topics covered in the 2 nd International Symposium on Nanotechnology in Construction, which is centred on recent advances in Nanoscience and Nanotechnology with a focus on materials and their impact in the Construction Sector. Experts from funding agencies from both sides of the Atlantic Ocean and the Chair of the Scientific Committee will kick off with a revision of the current situation and future perspectives of Nanotechnology in Construction. The rest of the lectures by other leading international scientists will be grouped by subject, so that we will begin with those related to theoretical modelling of construction materials, then deal extensively with the characterisation and measurement of properties of construction materials, and finally we will hear about construction material and product development from several of the key players from different industrial and research centres. Keywords: Nanotechnology, Nanoscience, construction, materials. 1. INTRODUCTION Nanotechnology has the potential to revolutionise both industry and our way of life. Nanoscience, which deals with the need to understand nano-scale phenomena and to improve our ability to control the nanostructure of materials, provides the solid foundation of knowledge necessary for the expected nanotechnology-driven advances. It is known that material properties and performance can be improved by controlling nano-scale processes and structures. Therefore, this 2 nd Symposium on Nanotechnology in Construction aims to cover the topics currently under study in Nanoscience and Nanotechnology that will aid in the development of the next generation of construction materials. We are already starting to experience the changes brought about by the combination of science and technology with entrepreneurs and venture capitalists. These changes will be overshadowed in the next twenty years by an emerging even bigger set of changes based on a combination of information technology and Nanotechnology. This new and as yet

2 unappreciated wave of change will create a continuing series of new breakthroughs with new materials, goods and services that will continue to change how we build things. The new age created by these changes has been called by Newt Gingrich, the Age of Transitions [1]. Although Nanotechnology is a new term that is becoming progressively familiar to our Society, it was predicted in 1959 by Nobel laureate Richard Feynman in a paper presented at the California Institute of Technology entitled: There s plenty of room at the bottom: an invitation to enter a new field of physics [2]. Feynman stated that: when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have and of different things that we can do. The term Nanotechnology was later introduced by Norio Taniguchi, in his 1974 paper: On the basic concept of Nanotechnology [3]. Key advances in computation and in technical instrumentation were crucial to the advancement of research in this area, namely the development of powerful microscopes such as the Scanning Tunnelling Microscope (STM, 1981) and the Atomic Force Microscope (AFM, 1986), which have allowed us to see and manipulate atoms, molecules and nano-sized objects. The first Programme on Nanotechnology (at least the first one known by the author) was the U.K. National Initiative on Nanotechnology (NION), in the period At that time, the U.K. Government also developed the Link Nanotechnology Programme (LNP), in the period Later on, other initiatives and programmes were developed by other authorities and governments, which were either fully devoted to Nanotechnology-related research or at least included it. We will have the opportunity to hear about them in the first session of this Symposium. Up to now, we have been talking about Nanotechnology without offering a definition of the term itself. The reason is that there is not a common and universal definition for Nanotechnology, due to its unique possibilities and wide application fields. There is a common misconception that nanotechnology deals only with small objects (i.e. miniaturisation), whereas in fact nanostructures and phenomena at the nano-scale can affect all types of bulk materials [4]. Some of the possible definitions for Nanotechnology are: The capacity to create functional materials, devices and systems with novel functions and properties through the control of matter at the nano-scale. The exploitation of properties and phenomena developed at the nanometer scale. The mention to the scale, in the definition, was introduced to make clear that we are considering a scale in which matter shows a special behaviour due to both the quantum effects (prevailing up to 10 nm) as well as the high surface/interface effects. Two different strategies have been developed so far in this field. Firstly, the top-down approach, for manufacturing nano-scale structures by conventional miniaturisation techniques, which is mainly aimed at the manufacture of miniaturised devices. And secondly, the bottom-up approach, or molecular nanotechnology, starting from single atoms or molecules. This can be achieved by the slow physical manipulation of individual atoms oneat-a-time (e.g. using an AFM) or by the more sophisticated self-assembly of programmed components, such as occurs in biological systems. At the nano-scale, the difference between the scientific disciplines becomes blurred, and collaboration is required between scientists from different disciplines, such as chemistry, physics and materials engineering. The Centre for Nanomaterials Applications in Construction (NANOC), at LABEIN- Tecnalia, which has organised this interdisciplinary symposium, is a platform within LABEIN

3 aimed at developing key technological capacities that will allow the use of Nanotechnology as a tool to improve competitivity in the construction industry, particularly with regards to materials. Our main technological objective is to develop high performance materials for construction applications. Other more fundamental objectives of our research activities are to improve our knowledge of the basic structure of materials, and the connection between the nano/micro-scale and the resulting macroscopic properties, with an emphasis on multi-scale modelling of materials. Therefore this symposium is perfectly aligned with our own group s main objectives. The symposium also addresses other issues which also fit with our own scientific aims, which are to improve our understanding of the relations between structure, performance, processing and properties, by a combination of materials science and materials engineering, where multi-scale modelling is key to linking structure and performance. Nanotechnology is in the position to assist us in the development of materials (even hyperperformance materials) that will have increased durability with extended and improved performance. Specific nanostructures or nanoparticles could be used to confer a material with the desired multifunctional properties in terms of mechanical performance and / or thermal, electrical or magnetic conductivity / insulation. Hybrid organic-inorganic materials will be also be developed, which combine the specific properties of each component as well as resulting in new and superior properties. Active-adaptive materials able to give a specific answer according environmental changes or situations will also be seen in the future. This kind of material could have programmable characteristics, such as self-repairing capacity, or could be used as sensing elements in intelligent systems or components. In this 2 nd Symposium on Nanotechnology in Construction Materials, we are continuing the action initiated in the 1 st Symposium held in June 2003 and hosted by the University of Paisley (UK). Despite the relatively short period of time between both symposia, we will find that research on this matter has been developing very fast: Experts from funding agencies from both sides of the Atlantic Ocean and the Chair of the Scientific Committee will kick off with a revision of the current situation and future perspectives of Nanotechnology in Construction (Session 1). The rest of the lectures by other leading international scientists will be grouped by subject, so that we will begin with those related to theoretical modelling of construction materials (Session 2), then deal extensively with the characterisation and measurement of properties of construction materials (Session 3), and finally we will hear about construction material and product development (Session 4) from several of the key players from different industrial and research centres. 2. NANOTECHNOLOGY IN CONSTRUCTION, PRESENT AND FUTURE In Session 1, we will hear about the European Strategy for Nanotechnology [5] and the related European Action Plan for the period [6]. A mention will be made to several projects funded by the European Commission DG Research: E-CORE, NANOCONEX, TUNCONSTRUCT and I-STONE. The industry-led initiative European Construction Technology Platform, which includes a Focus Area on Materials, will be also mentioned as well as the inclusion of: Nanosciences, Nanotechnologies, Materials and New Production Technologies as Theme 4 on the European Commission Seventh Framework Programme [7]. In the United States, the National Nanotechnology Initiative (NNI) is a multi-agency coordinated approach to develop Nanotechnology [8] started formally in the year The

4 National Science Foundation (NSF) has been the lead funding agency in the US and a considerable part of its budget has been allocated to NNI. NSF supports fundamental research in all fields, including materials for construction and rehabilitation of infrastructure through its Civil and Mechanical Systems Division (CMS). The CMS [9] has been active in NSF s overall NNI activities and has made many awards for basic research in Nanotechnology. The NSF Division of Materials Research has awarded also a large number of nanomaterials research projects. We will have the opportunity to hear about the NSF-supported research in construction-related Nanotechnology. The first Session will be closed by the introduction of the Roadmap for Nanotechnology in Construction (RoNaC), which was developed as an aid for forecasting RTD directions and providing guidance to the construction industry, investors and national/international bodies supporting R&D programmes, about the diverse pathways towards current nanotechnology expectations. The RoNaC is based on the State-of-the-Art report [10] issued as part of the European 5 th FP Growth project NANOCONEX. 3. THEORETICAL MODELLING OF CONSTRUCTION MATERIALS FROM NANO TO MACROSCALE Through this session different aspects of theoretical modelling will be reported, attending a wide variety of materials (portland cements, fly ash activated cements, nanotubes, wood, etc), covering a wide range of scales (in fact from nano to macro), describing different phenomena (hydration process, growth mechanisms, drying, etc.), and employing a large set of computational methods (continuum models like FEM, phase field methods, or even ab-initio calculations). However, despite the diversity of topics, the whole session shares a common denominator: The search for minimal entities and concepts from which material s behaviour can be explained and predicted. We will see, for instance, that materials like bones, wood or cements offer more than a fortuitous resemblance, once the inherent ingredients are captured and identified. This is not surprising at all, since, in the end all materials are governed by the same physical and chemical rules. The relevant point for this Symposium is that these smallest parts from which materials can be modelled usually belong to the nano-scale. These are indeed the cases of the C-S-H gel, the most important hydration product in Portland cement systems, and the N-A-S-H gel, the main reaction product of type F fly ash activation. We will hear about work devoted to shed light on the origin of these cementitious nano-units and the origin of their cohesion, or on how the nanostructure of concrete can be related to the engineering properties like bulk drying shrinkage or elastic modulus. This nano-to-macro relationship is indeed the corner-stone of present technology. Our current challenge is, in fact, to provide smooth handshakes between existing computational methods and models, to cross over different scales and eventually lead to truly multi-scale descriptions. Only by this procedure, together with a close feedback with experimental data, will the technological revolution proclaimed by nanotechnology be accomplished. I would like to end by quoting the title of the lecture by Professor van Breugel, definitely affirming that there is no doubt that Multi-scale modelling is the vehicle for progress in fundamental and practice-oriented research.

5 4. CHARACTERISATION AND MEASUREMENT OF PROPERTIES OF CONSTRUCTION MATERIALS AT MICRO-TO-NANO SCALE Session 3 will focus on characterisation and measurement of properties of construction materials at micro-to-nano scale. Most of the contributions in this session deal with the measurement of properties and modification of the nanostructure of cement-based materials. Considerable progress over recent years is being achieved by the massive employment of nano-scale characterisation techniques to understand nano-scale processes in cementitious materials. Nuclear magnetic resonance, atomic force microscopy, micro- and nanoindentation and neutron scattering among others are becoming more and more routine techniques in the study of cement-based materials. We will see how they can be used to monitor the nano-scale time dependence of the chemical reactions involved in the curing of cement, how the nanostructure is affected by the addition of silica fume and how nanoparticle additions can control the Ca leaching of the C-S-H gel, how it is possible to measure the states of water, how the alkali dissolution of layered silicates can be monitored, or the evaluation of mechanical properties at the nano-level, and how to characterise the efficiency of polymer intercalation and the structure of C-S-H-polymer nanocomposites. Ultrasonic Force Microscopy and Focus-Ion-Beam (FIB) nanotomography will be presented as new characterisation techniques and their potential application for quantitative structural analysis and mapping of properties at the nanometre scale of construction materials. Some of the contributions in the second part of session 3 will also focus on other materials besides the typical construction material (i.e. Portland cement). These talks will address, among others, the study of the specific surface area and pore volume during hydration of fly ash belite cement paste by the BET-N 2 technique as well as the analysis of the importance of the nano-scale character for the superplastic behaviour in nanoceramics and the synthesis and characterisation (by NMR, FTIR ) of hybrid organic-inorganic materials using as starting materials both a geopolymer compound (obtained by reacting metakaolin in alkaline media) and an epoxy resin. Furthermore, besides the study of the nanostructure of the cementitious matrix, addition of relevant nanomaterials such as carbon nanotubes and nanoparticles and their characterisation will also be addressed as well as the application of Nano-Electro-Mechanical-Systems (NEMS) for concrete durability monitoring and quality control. To conclude the session, the importance of Nanotechnology in the production of new construction materials and the possibility and challenges for fabrication of nano-cement and nano-concrete will be explored. 5. NANOTECHNOLOGY FOR CONSTRUCTION MATERIAL AND PRODUCT DEVELOPMENT Lectures in Session 4 will cover recent studies on a wide range of construction materials (including concrete, admixtures, wood, coatings, insulation panels, etc.). The topics will range widely from nano-scale characterisation of the products, which have already been developed or are under development, to the implications of Nanotechnology for architecture. The recent advances presented in this session are likely to aid in the assessment of the potential impact of Nanoscience and Nanotechnology on the development of highperformance materials for the construction Sector.

6 REFERENCES [1] N. Gingrich, The age of Transitions. (2000). [2] R. Feynman, Engineering and Science, 23, 22 (1960). [3] N. Taniguchi, Proc. ICPE. Tokyo (1974). [4] Y. R. de Miguel, Chemistry & Industry, 8 (2004), [5] Towards a European Strategy for Nanotechnology and Nanosciences, COM (2004) 338. [6] Nanotechnologies: An Action Plan for Europe COM (2005) 243 [7] Towards FP7 (2005). [8] National Nanotechnology Initiative [9] NSF CMS Division [10] W. Zhu, P.J.M. Bartos and A. Porro, Application of Nanotechnology in Construction, Materials and Structures, 37, 273 (2004),