Nanomaterial corrosion resistance

While these techniques are widely used, they do not provide sufficient purity. Liquid phase purification is not an environmentally friendly process and requires corrosion-resistant equipment, as well as costly waste disposal processes. Alternative dry chemistry approaches, such as catalyst-assisted oxidation or ozone-eiuiched air oxidation, also require the use of aggressive substances or supplementary catalysts, which result in an additional contamination. Moreover, in many previous studies trial and error rather than insight and theory approaches have been applied. As a result, a lack of understanding and limited process control often lead to extensive sample losses of up to 90%. Because oxidation in air would be a controllable and enviromnentaUy friendly process, selective purification of carbon nanomaterials, such as CNT and ND, in air is very attractive. In contrast to current purification techniques, air oxidation does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of carbon nanomaterials. 

In general, vapor deposition methods refer to any process in which materials in a vapor state are condensed on a surface to form a solid-phase. These processes are normally used to form coatings to alter the mechanical, electrical, thermal, optical, corrosion resistance and wear resistance properties of various substrates. Recently, vapor deposition methods have been widely explored to fabricate various nanomaterials such as NS-T102. Vapor deposition processes usually take place in a vacuum chamber. If no chemical reaction occurs, this process is called physical vapor deposition (PVD) otherwise, it is called chemical vapor deposition (CVD). In CVD processes, thermal energy heats the gases in the coating chamber and drives the deposition reaction. 

Nano-clay incorporated polymer coatings are important for modifying properties of surfaces. Nano-clay incorporated thermoset polymer nanocoatings exhibit superior properties such as super-hydrophobicity, improved wettability, excellent resistance to chemicals, corrosion resistance, improved weather resistance, better abrasion resistance, improved barrier properties and resistance to impact, scratches, etc. [116]. The parameters such as dipping time, temperature, nature of surfactant, and purity of nanomaterials decides the coating thickness. Clay-epoxy coating... 

Recently, the research on exploring the use of carbon nanomaterials as metal-free catalysts has been one of the major subjects for the fuel cell research. Owing to their wide availability, environmental acceptability, corrosion resistance, and unique surface and bulk properties, carbon nanomaterials are ideal candidates for metal-free ORR catalysts. In this context, we have demonstrated that vertically aligned nitrogen-doped carbon nanotube (VA-NCNTs) array exhibited three times higher ORR electrocatalytic activity and better long-term operation durability... 

In order to understand the effect of nanocrystallization in detail, the passive film on an Ni-based alloy has been studied. X-ray photoelectron spectroscopy (XPS) results indicated that the composition of the passive film was significantly different between the NC coating and the corresponding traditional coarse ciystalline alloy. The passive film on the conventional alloy consisted of Cr, Ti and Ni oxides, whereas only Cr and Ti oxides were present in the passive film on the NC coating. There were distinctly different qnantities of the elements present in the two passive films. As shown in Table 4.more Cr exists in the passive film on the NC coating. The resnlts testified that nanociystallization improved the enrichment of passive elements in the passive film, which may be one of the main reasons for the high corrosion resistance of nanomaterials. 

Abstract Electrodeposition is a weU-known conventional surface modification method to improve the surface characteristics, decorative and functional, of a wide variety of materials. Now, electrodeposition is emerging as an accepted versatile technique for the preparation of nanomaterials. Work done in this direction is discussed in this chapter. The basics of electrodeposition are introduced, then the electrodeposition of nanomaterials using special techniques for reducing grain size. Methods such as pulse and pulse reverse current deposition, template-assisted deposition and use of additives and grain refiners are explained with suitable examples. Deposition of nanostructured metals, alloys, metal matrix composites, multilayers and biocompatible materials reported in the literature are discussed. Finally, there is a discussion of the improved corrosion resistance of electrodeposited nanostructured materials, quoting results reported in Uterature. 

Key words electrodeposition, nanomaterials, pulse and pulse reverse electrodeposition, template-assisted deposition, additives and grain refiners, nanostuctured metals and alloys, nanocomposites, multilayers, biocompatible materials, corrosion resistance of electrodeposited nanostuctured materials. 

Electrodeposition is a versatile technique for the production of nanostructured materials with lower capital investment, higher production rates and few shape and size limitations. Electrodeposited nanomaterials such as nanostractured metals, alloys and metal matrix composites have proven successful in providing superior corrosion resistance of substrate materials compared with the corresponding microstmctured materials. 

Abstract Nanomaterials such as polyelectrolytes, layered clays, sol-gel encapsulants and surface-modified nanoparticles can function as carriers of corrosion inhibitors. Carried in this way, the inhibitors can be released on demand, triggered by change in pH, ion exchange and change in oxidation state. This chapter gives an outline of such carriers with an emphasis on the surface-modified nanoparticle/nanostructure ofboehmites. Subsequently, the chapter provides a detailed account of self-assembled nanofihns on various surfaces such as nickel oxide, copper oxide and iron oxide and their effect on corrosion resistance. 

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