Methodologies of Application of Sol-Gel Based Solution onto Substrate: A Review

Just as the diverse as the various substrates that can be coated is the choice of several coating methods by which the coating can be applied to these pretreated surfaces. They include the manual methods, where great skills and experience is needed, on the other hand there are automated and robotics coating control methods where coating can be applied with more precise manner. Sol-gel process is one of the promising bottom up nano-coating technologies to develop thin film over various metallic substrates. The property and characteristic of the resulting film is strongly influenced by the various parameters and reaction conditions of the sol-gel process and of course on the deposition techniques. In this review, we have thrown some lights on different coating application processes covering theoretical principle, advantages, disadvantages, and special various parameters controlling the final film quality

Boiling Study of Nanofluid on Graphene Coated Substrate

A comparative study is done to understand the effect of variation in surface energy of substrates on boiling and dry-out characteristics of nanofluid. Droplet of TiO2 nanofluid on glass substrate shows strong pinning along the droplet perimeter. As the droplet evaporates, boundary of nanofluid droplet recedes slowly towards the center leaving a ring-shaped stain of concentrated nanoparticles. Surface energy of glass substrate is modified by graphene coating, confirmed by increase in contact angle. While boiling of nanofluid on graphene coated glass substrate shows an almost uniform dry-out pattern. Reduced wettability of nanofluid droplet on graphene coated glass substrate is responsible for this behavior

Graphene oxide and functionalized multi walled carbon nanotubes as epoxy curing agents: a novel synthetic approach to nanocomposites containing active nanostructured fillers

A novel synthetic approach is developed wherein graphene oxide and oxidized multiwalled carbon nanotubes are used as curing agents to induce cross-linking of an epoxy resin, thereby yielding a nanostructured epoxy composite with excellent dispersion of the carbon nanomaterials. This method allows for incorporation of up to 50 wt% of carbon nanomaterials within the polymeric matrix. The combination of covalent bonding and π–π interactions ensure excellent dispersibility of the nanomaterials within the polymeric matrix. These nanocomposites offer an alternative to the hazardous high-temperature fluorination and amine curing reactions that are usually required to formulate epoxy composite systems. Structural, mechanical, and morphological characterization of the composite material confirms the distribution, integrity, and potential to resist corrosion on a steel surface while also indicating the excellent adhesion and flexibility of the nanocomposite coatings

Nanostructured Magnesium Composite Coatings for Corrosion Protection of Low-Alloy Steels

Corrosion of base metals represents a tremendous problem that has spurred a global search for cost-effective and environmentally friendly alternatives to current corrosion-inhibiting technologies. In this work, we report a novel sustainable hybrid Mg/poly­(ether imide) (PEI) nanocomposite coating that provides corrosion protection to low-alloy steels at relatively low coating thicknesses and with reduced weight as compared to conventional metallic coatings. The coatings are constituted using Mg nanoplatelets dispersed within a polyamic acid matrix that is subsequently imidized on the steel substrate to form PEI. The coatings function through a combination of sacrificial cathodic protection (afforded by the preferential oxidation of the Mg nanoplatelets), anodic passivation through precipitation of corrosion products, and the inhibitive action of the PEI polymeric matrix. The use of nanostructured Mg allows for reduced coating thicknesses and a smoother surface finish, whereas the PEI matrix provides excellent adhesion to the metal surface. Based on potentiodynamic testing and prolonged exposure to saline environments, the novel coating materials significantly outperform galvanized Zn and Zn-rich primer coatings of comparable thickness

Anodized Steel Electrodes for Supercapacitors

Steel was anodized in 10 M NaOH to enhance its surface texture and internal surface area for application as an electrode in supercapacitors. A mechanism was proposed for the anodization process. Field-emission gun scanning electron microscopy (FEGSEM) studies of anodized steel revealed that it contains a highly porous sponge like structure ideal for supercapacitor electrodes. X-ray photoelectron spectroscopy (XPS) measurements showed that the surface of the anodized steel was Fe₂O₃, whereas X-ray diffraction (XRD) measurements indicated that the bulk remained as metallic Fe. The supercapacitor performance of the anodized steel was tested in 1 M NaOH and a capacitance of 18 mF cm^–2 was obtained. Cyclic voltammetry measurements showed that there was a large psueudocapacitive contribution which was due to oxidation of Fe to Fe­(OH)₂ and then further oxidation to FeOOH, and the respective reduction of these species back to metallic Fe. These redox processes were found to be remarkably reversible as the electrode showed no loss in capacitance after 10000 cycles. The results demonstrate that anodization of steel is a suitable method to produce high-surface-area electrodes for supercapacitors with excellent cycling lifetime

Effective Piezoelectric Response of Substrate-Integrated ZnO Nanowire Array Devices on Galvanized Steel

Harvesting waste energy through electromechanical coupling in practical devices requires combining device design with the development of synthetic strategies for large-area controlled fabrication of active piezoelectric materials. Here, we show a facile route to the large-area fabrication of ZnO nanostructured arrays using commodity galvanized steel as the Zn precursor as well as the substrate. The ZnO nanowires are further integrated within a device construct and the effective piezoelectric response is deduced based on a novel experimental approach involving induction of stress in the nanowires through pressure wave propagation along with phase-selective lock-in detection of the induced current. The robust methodology for measurement of the effective piezoelectric coefficient developed here allows for interrogation of piezoelectric functionality for the entire substrate under bending-type deformation of the ZnO nanowires