Introduction

Tribology (from the Greek word spibm ''tribo'' meaning ''to rub'') is defined by the Oxford dictionary as ''the branch of science and technology concerned with interacting surfaces in relative motion and with associated matters (as friction,

M. Nosonovsky

College of Engineering and Applied Science, University of Wisconsin, Milwaukee, WI 53201, USA

Nanoprobe Laboratory for Bio- and Nanotechnology and Biomimetics (NLB2), The Ohio State University, 201 W. 19th Avenue, Columbus, OH 43210-1142, USA e-mail: [email protected]

M. Nosonovsky and B. Bhushan (eds.), Green Tribology,

Green Energy and Technology, DOI: 10.1007/978-3-642-23681-5_1,

© Springer-Verlag Berlin Heidelberg 2012

wear, lubrication, and the design of bearings—Oxford English Dictionary)''. The word ''tribophysics'' was used already in the 1940s by David Tabor and Philip Bowden for the name of their laboratory in Melbourne University, Australia [36]. The term ''tribology'' was officially introduced in 1966 by Prof. H. Peter Jost, then the chairman of a working group of lubrication engineers, in his published report for the U.K. Department of Education and Science. It was reported that huge sums of money had been lost in the UK annually due to the consequences of friction, wear, and corrosion. Therefore, it was strongly recommended to unite multidis-ciplinary scientific and engineering efforts in these areas, so that they could benefit from one another. As a result, several centers for tribology were created in many countries. Since then the term has diffused into the international engineering field; various tribological organizations and societies have been established, such as the Society of Tribologists and Lubrication Engineers (STLE), and many specialists now claim to be tribologists.

Typical tribological studies cover friction, wear, lubrication, and adhesion and involve the efforts of mechanical engineers, material scientists, chemists, and physicists [9, 11, 12]. Since the emergence of the word tribology almost 50 years ago, many new areas of tribological studies have developed which are at the interface of various scientific disciplines, and various aspects of interacting surfaces in relative motion have been the focus of tribology. These areas include, for example, nanotribology, biotribology, the tribology of magnetic storage devices and micro/nanoelectromechanical systems (MEMS/NEMS), and adhesive contact [8-12, 15-17]. The research in these areas is driven mostly by the advent of new technologies and new experimental techniques for surface characterization.

Few researchers have reported the need for ecological or ''green'' tribology. Bartz [5] stated that, ''Savings of resources of energy and reducing the impact on the environment are the most important aspects of ecotribology. In the course of relevant practices savings of basic resources and materials, optimum design, optimum operation, reduced energy consumption and the protection of the environment have to be covered... Using environmentally acceptable lubricants is the key factor for this.'' He suggested a diagram which he called ''ECO-Balance-Sheet-Tree'' which summarized all of these aspects. Sasaki [67] has emphasized the need for ecological tribology, which he considered a response to the world economic and financial crisis of 2008 as well as the global worming crisis as reflected by the ''Kyoto Protocol.'' The new concept of ''green tribology'' has been defined as ''the science and technology of the tribological aspects of ecological balance and of environmental and biological impacts.'' Jost [38] elaborated on the need for green tribology and has mentioned that the influence of economic, market, and financial triumphalisms have retarded tribology and could retard 'green tribology' from being accepted as a not-unimportant factor in its field. Therefore, by highlighting the economic benefits of tribology, tribology societies, groups and committees are likely to have a far greater impact on the makers of policies and the providers of funding than by only preaching the scientific logic... Tribology societies should highlight to the utmost the economic advantage of tribology. It is the language financial oriented policy makers and markets, as well as governments, understand.

These earlier mentions by researchers called scientists to pay attention to green tribology; however, they did not define the field in a rigorous scientific or academic manner. The first scientific volume on green tribology emerged in 2010, when Philosophical Transaction of the Royal Society A, the oldest (published since 1666) and one of the most prestigious research journals in the world, decided to devote a theme issue to ''green tribology,'' edited by M. Nosonovsky and B. Bhushan. In that volume, the editors defined green tribology in quite a broad way, so that it encompassed biomimetic tribology (which follows the ways of living nature to solve engineering problems, eco-friendly lubrication, and clean and sustainable energy applications [58]. The presumption was that the combination of these areas under the umbrella of green tribology could enhance them all and help to benefit from one another by establishing new links.

Ten chapters were published in the theme issue. Nosonovsky and Bhushan [58] suggested twelve principles and three areas of green tribology. Several chapters were devoted to biomimetic surfaces. Bormashenko [22] reviewed wetting transitions on biomimetic superhydrophobic surfaces, while Bhushan and Nosonovsky [20] discussed various wetting regimes with emphasis on the lotus effect and rose petal effect regimes. Shark-skin effect surfaces were discussed by Dean and Bhushan [27], whereas antifouling biomimetic surfaces were investigated by Salta et al. [66]. Nosonovsky [49] discussed the principles of friction-induced self-organization. In the application area, Kotzalas and Doll [42] reviewed the tribological aspects of wind power turbines, whereas Wood et al. [75] discussed tribological constraints of marine renewable energy systems. Lovell et al. [46] discussed the effect of boric acid additives on the performance of green lubricants, and Li et al. [44] studied green waxes, adhesives, and lubricants.

Several workshops, conference sections, and symposia took place after that, which confirmed the volume's inclusive approach, as well as the interest in green tribology in general. Green tribology topics have been covered at a number of conferences [50, 51, 59].

The specific field of green or environment-friendly tribology emphasizes the aspects of interacting surfaces in relative motion, which are of importance for energy or environmental sustainability or which have impact upon today's environment. This includes tribological technology that mimics living nature (biomi-metic surfaces) and thus is expected to be environment friendly, the control of friction and wear that is of importance for energy conservation and conversion, environmental aspects of lubrication and surface modification techniques, and tribological aspects of green applications, such as wind-power turbines, tidal turbines, or solar panels (Fig. 1.1). It is clear that a number of tribological problems could be put under the umbrella of ''green tribology'' and are of mutual benefit to one another.

Fig. 1.1 The paradigm of green tribology: renewable energy (represented by a wind turbine), biomimetic surfaces (represented by the gecko foot), and biodegradable lubrication (represented by natural vegetable oil)
Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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