Surface Engineering By Israa Faisal University of Al-Qadisiyah College of Engineering Materials Engineering Department

Advanced Surface Coatings The past decade has seen a rapid development in the range of techniques which are available to modify the surfaces of engineering components. This in tum has led to the emergence of the new field of surface engineering­ the design of a composite system (coating plus substrate) that produces a performance which cannot be achieved by either the coating or substrate alone. With this expansion comes the problem of deciding on the correct surfacing technology for a given application. Clearly, to take full advantage of the benefits which surface engineering offers, there is a need to explain, in a structured way, the basic features and interrelationships of the most recently developed coatings and treatments.

Nanocompsite coating have shown increasing interest in recent years in many strategic industries such as automotive, aerospace, petroleum, and electronics. Nanocomposite coatings are engineered to provide attractive and cost-effective functional surface coatings with superior properties for anticorrosion, antimicrobial, antifogging, and adhesive applications. The unique characteristics of nanocomposite coatings include enhanced mechanical strength, weight reduction, improved barrier properties, and increased heat, wear, and scratch resistance for lifelong performance. Compared to the traditional anticorrosive composite coatings ,the superior performance of their nanocomposite counterparts is mostly attributed to the improved morphology with nanoscale phase-separated domains.

The simplest approach for the preparation of anticorrosive nanocomposite coatings is through the direct mixing of inorganic nanoparticle additives with the organic coating matrix. However, the recent advanced nanotechnologies are based on designing and functionalization of nanoparticles prior to their incorporation into the nanocomposite coatings to enable them to provide effective and continuous corrosion protection functionality. These include self-healing nanocomposite coatings, stimuli-responsive layer-by-layer nanocomposite coatings, organic-inorganic hybrid nanocomposite coatings, electroactive nanocomposite coatings based on electrically conductive polymers, and various carbon nanostructures.

Classification of nanocomposite coatings A nanocomposite coating is a material composed of at least two immiscible phases, separated from one another by interface region. the material must contain the nanometer scale in at least one dimension in which the major component is called matrix in which fillers are dispersed . the classification of nanocomposite coatings is based on various methods dealing with Type of nanostructured fillers or (ii) type of matrix where filler nanostructures are dispersed. Type of Nanostructured Fillers. there are 3 main groups of nanocomposite coating as follows : (i) 0 D nanocomposite coatings: the filler are nanoparticles (3 dimensions in nanometer scale). (ii)1D nanocomposite coatings: the filler are nanotubes or whiskers (2 dimensions in nanometer scale (iii) 2D nanocomposite coatings: the filler are nanolayers.(1 dimension in nanometer scale).

Type of Matrix. Tow types of matrix which are organic and inorganic matrix can be found. thus, there are 4 main groups of nanocomposite coating as follows (matrix/ nanofiller): (i) Organic/inorganic nanocomposite coatings (O/I nanocomposite coatings) (ii) Organic/organic nanocomposite coatings (O/O nanocomposite coatings) (iii) Inorganic/organic nanocomposite coatings (I/O nanocomposite coatings) (iv) Inorganic/inorganic nanocomposite coatings (I/I nanocomposite coatings)

Materials 1. Materials for Matrix For organic matrix, called polymer-based nanocomposite, the most used polymers for preparation of nanocomposite coating can be listed as follows: epoxy], polyurethane, polyethylene glycol (PEG), polyvinylidene fluoride (PVDF) ,polystyrene], rubber-modified polybenzoxazine (PBZ) [, polyamide ,and UV-curable polymers . For inorganic matrix, such as metal matrix or alloy matrix, these nanocomposite coatings could be prepared by various methods, including chemical vapor deposition (CVD), powder metallurgy, physical vapor deposition (PVD) thermal plasma spray], sol-gel Metal matrix composite coatings that dispersed a second phase have attracted extensive attention owing to unique properties such as oxidation and corrosion resistance ,wear resistance ,and magnetic properties .

2. Materials for Nanofillers For inorganic nanofillers, the types of nanoparticles are carbides , nitrites ,borides ,oxides ,metallic particles. For organic nanoparticles (organic nanofiller), the most used nanoparticles were PTFE, PEO, PANi ,or nanocellulose and cellulose nanocrystal