Chemical nanocoating

It is possible to alter the intrinsic properties of materials by chemical nanocoating, which cannot be achieved by conventional methods. Generally the core-shell nanostructures are divided into two categories (1) lanthanides doped in the core (2) lanthanides doped in the shell. The former are synthesized in order to improve the quantum efficiency of lanthanide ions or design bio-labels, while the latter are meant for the study of surface modifications on the lanthanide luminescence or the synthesis of lanthanide-doped hollow nanospheres. 

Nanocoatings on textiles to create textile surface with innovative functional properties and without adversely affecting the fabric feel via using various techniques such as nanosol, polymer dispersions, and chemical vapor deposition [12,41,60,65, 69-71]. 

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... 

The rationale behind nanocoating is simple it is well documented that materials are believed to possess different properties at a nanoscale (particularly l-l(X)mn) [8]. This offers the opportunity for exploration of novel applications. For instance, common properties such as melting point, fluorescence, electrical conductivity, magnetic permeability, and chemical reactivity alter with particle size. 

Another problem limiting the application of nanociystalline materials is prep>aration of nanocrystalline alloys. Currently, the bulk metallic nanomaterials can only be prepared at the laboratory scale, usually by compacting prepared nanocrystalline powders. However, consolidation of the nanopowders into bulk materials needs high temperature and pressure which may considerably coarsen the structure. Because of this difficulty, surface nanocoating has been considered a potential industry application. Nanocrystalline costing are often prepared by chemical vapour deposition (CVD), physical vapour deposition (PVD), electrochemical deposition, electro-spark deposition, and laser and electron beam surface treatment. 

Gehrke et al. [ 131 ] recently used a dip-coating process to deposit photocatalytic TiO nanoparticles (P25, Evonik) on a metallic filter material (micro-sieve). The fouling repellent and photocatalytic nanocoatings degraded the water impurities close to the micro-sieve surface before a dense cake layer was formed. This kind of surface activation is, however, restricted to chemically robust materials, excluding polymeric membranes that would be degraded by the induced oxidation process [125]. 

Polypropylene (PP) is, besides polyesters, one of the most widely used polymers for producing synthetic fibres, especially for technical applications. PP fibres are mostly used in different technical fields due to their excellent mechanical properties, high chemical stability and processability. However, because of low surface energy, lack of reactive sites and sensitivity to photo- or thermal oxidation the polymer properties are insufficient for some applications. Therefore, several techniques for fibre modification have been reported, e.g. plasma treatment, chemical modification and nanomodification, i.e. production of nanocoated and nanofilled materials. 

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