Nano-plates

Refs. [i] BudevskiE, Staikov G, Lorenz WJ(1996) Electrochemical phase formation and growth. An introduction to initial stages of metal deposition. VCH, Weinheim, pp 4-6 [ii] Watanabe T (2004) Nano-plating. Microstructure control theory of plated film and data base of plated film microstructure. Elsevier, Amsterdam, pp 97-106... 

CNT has already been exploited in NEMS as the basis for a rotary element for a magnetically actnated nano-plate [96] and additional NEMS devices relying on both the novel mechanical and electrical properties of CNTs wiU continne to be developed in the years to come. Composite materials containing CNTs, especially inorganic material/CNT blends, have been demonstrated to have enhanced mechanical and tribological properties, unattainable with current metallurgical techniques [97]. These electroless and electrodeposited composites wiU provide a new class of materials available for MEMS and NEMS devices. 

Nano-Plating Microstructure Control Theory of Plated Film and Data Base of Plated Film Microstructure (Elsevier, London, 2004). 

Numerous metal and alloy coatings can be prepared by electrodeposition and are suitable for nano-plating technologies, including Ag, Au, Cd, Co, Cr, Cu, Fe, Ni, Pt, Sn, Zn, and most alloys of the listed metals [7], Either a fairly inert counter electrode, such as a Pt mesh, a carbon rod, or a plate of the metal to be plated are used. In the latter case, the zero valent metal of the anode is oxidized and dissolved at the same rate as metal ions are reduced a the working electrode. In this manner, the cations concentration of the electrolyte bath is continuously replenished. In industrial applications usually a galvanostatic is favored over a potentiostatic deposition technique. 

As with advanced polymer composite, a nanocomposite is formed from the combination of two or more materials however, one of the materials has nanoscale (< 100 nm) dimensions. Nanoparticles can be classified into three categories depending on the number of their nanoscale dimensions (i) nano-spheres (ii) nano-fibres and (iii) nano-plates, having three, two and one nanoscale dimension, respectively, Thostenson et al. (2005). Paul and Robeson (2008) have given a comprehensive review of nanoparticles. Only nano-fibres and nano-plates will be mentioned in this chapter, as these are relevant to possible structures concerned with sustainable energy. 

Advantages of incorporating nano-plates into FRP composites... 

Whilst there have been some components manufactured using CNT and nano-plates in development, the nanoparticle markets have been constrained by three main issues, namely ... 

Tran, N.H., Wilson, M.A. Milev, A.S., Dennis, G.R., Kannangara, G.S.K. and Lamb, R.N. (2006), Dispersion of silicate nano-plates within poly(acrylic acid) and their interfacial interactions . Science and Technology of Advanced Materials, Vol. 7, No. 8, pp. 786-791. 

Nano-plates are generally naturally occurring layered materials such as layered silicates (montmorillonite plates, a type of clay) which is dispersed within polymers for nanocomposite formation (Hackman and Hollaway, 2006 Tran et al. (2006) initially man-made materials such as silicate acids were used (Wang et al., 1996). The objective in a nanocomposite produced from plate-like fillers is to disperse the latter in a polymer to take advantage of... 

The principal exploitable properties that nano-plates can bring to a polymer composite are shape related, with the main ones being ... 

Low levels of nano-plates have a big effect on these properties in thermoplastic composites, and this was the first area to arouse interest [16]. Typical results are presented in Table 10.1 and show how much benefit can be achieved at very low loadings, and when conditions favour exfoliation, dispersion and strong interaction with the polymer. 

However, the real test is how the nano-plates compare with other reinforcing fillers like talc, mica and glass fibre. Currently there is much controversy over the ability of nanoplates to provide real benefits in properties such as stiffness, compared to conventional reinforcing fillers, especially glass fibres. Present results are very mixed and complicated... 

From the rule of mixtures predictions, nano-plates should not give higher modulus and tensile strength than is obtainable from the same volume fraction of thicker plates and fibres of the same modulus, strength and aspect ratio. 

These are important properties, and usually decrease as the stiffness is increased. One of the great expectations for nano-plates in thermoplastics was that they would give products with better toughness for a given stiffness. 

Unfortnnately, this is not an area that is readily treated by theoretical analysis, and present experimental results are mixed. Many factors contribute to toughness, including particle size and shape, polymer degradation and crystallinity and interface properties. Some of the cnrrent problems with nano-plates in this area probably stem from formulation issues and from the present sub-optimum nature of surface treatments and a clearer picture should emerge as these are eliminated. 

Because of their high aspect ratios, nano-plates have the potential to give very good results at low volume fractions, accompanied by good clarity and low density. However, as with other properties, their absolute performance is restricted by the volnme fractions... 

Platy nano-particles, such as nano-clays and micas, have some potentially useful flame retardant effects, and are currently receiving a lot of attention for this application. This topic has recently been reviewed [34, 35]. The other forms of nano-particle do not seem to have the same effectiveness. This subject, which was briefly treated in Chapter 6, is discussed in more detail here, but the earlier chapter should be referred to for details of fire retardant tests, especially the cone calorimeter which is widely used in studies involving nano-plate fillers. 

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