Ali Shanaghi

Effect of duty cycle on residual stress and tribology behaviour of TiCx nanostructure coating deposited by PACVD method

Abstract In this paper, nanostructured TiCx was coated onto H11 hot working steel by pulsed dc plasma assisted chemical vapour deposition method, and various duty cycles were carried out in order to observe the influence of this parameter on residual stress and tribology behaviours. The duty cycles were 33, 40 and 50% at 510°C operating temperature. Therefore, wear behaviour, hardness and chemical analyses of TiCx nanostructure coating were characterised, and it was found that the residual stresses in the coating were compressive, which were −1·1516, −0·1323 and −0·1752 MPa at three different duty cycles, i.e. 33, 40 and 50% respectively. According to the results, the coating that was applied at 40% exhibited superior wear resistance and possessed the lowest friction coefficient of ∼0·06 in a pin-on-disc test against WC–Co.

EFFECT OF INHIBITOR AGENTS ADDITION ON CORROSION RESISTANCE PERFORMANCE OF TITANIA SOL–GEL COATINGS APPLIED ON 304 STAINLESS STEEL

Hybrid organic–inorganic coatings are deposited on 304 stainless steel substrates by the sol–gel technique to improve the corrosion resistance. A titania-based nanostructured hybrid sol–gel coating is impregnated with three different microencapsulated healing agents (inhibitors) including cerium, Benzotriazole (BTA), and 8-Hydroxyquinoline (8H). Field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS) are performed to investigate the barrier performance properties. The optimum conditions to achieve corrosion protective coatings for 304 stainless steel were determined. The Nyquist plots demonstrate that the activation time of the coating containing 8H as an organic healing agent shows improved behavior when compared to other coatings including cerium and BTA. Cerium as an inorganic healing agent is second and BTA is third and minimum. An increase in the impedance parameters such as resistance and capacitance as a function of immersion time is achieved in a 3.5wt.% NaCl solution by using healing agents such as BTA. Actually, over the course of immersion, the barrier performance behavior of the coatings changes and reduction of the impedance observed from the coatings containing Ce and 8H discloses deterioration of the protection system after immersion for 96h of immersion in the 3.5% NaCl solution. However, after 96h of immersion time, the concentration of chloride ions is high and causes increase in defects, micro cracks, hole on the surface of hybrid titania nanostructured coating containing Ce and 8H by destruction of coating, and also hybrid titania nanostructured coating containing BTA; BTA is released from coating to improve the resistance of passive film, which is created on the surface.

Stable multilayer TiO2–SiO2 coatings for antireflection applications

In this paper, multilayer TiO2–SiO2 containing polydimethylsiloxane (PDMS) coatings were produced by using sol-gel method. To further investigate, the effect of triton as a non-ionic surfactant on PDMS modified single and multilayer silica and titania coatings was studied. The results showed stability of optical triton containing coatings disappears with time due to this material improve the wetting properties of PDMS sols and helps to instability by water absorption. But without triton, antireflective multilayer coatings with high transmittance 98% and excellent durability were obtained by using PDMS as additive material. This coating can be used as well as in solar applications.

An experimental investigation of corrosion resistance of mild steel by sol-gel process using TiO2 nanostructure coating and prediction of optimal parameters

A TiO2 nanostructure coating has shown to significantly improve the thermal and electrical properties of steel plates and increase their resistance to oxidation, corrosion, and wear, especially in high temperature applications. In this research, the corrosion resistance properties of a mild steel substrate by applying TiO2 nanostructure coating using the sol-gel method were investigated. The quality of the coating, however, is notably affected by such process parameters as the dip-coating rate, drying time, heat-treatment rate, and the number of coating layers. Moreover, this article presents an integrated approach to the optimal parameter setting for the above process. Using experimental data from a coating process by the sol-gel method, an artificial neural network is trained to map the vector of process parameters onto a measure of corrosion resistance. An evolutionary search algorithm is then employed to find the optimum set(s) of process parameters. The efficiency of the proposed approach is demonstrated using a case study involving a 316L stainless steel substrate.

Effects of Duty Cycle on Texture Orientation and Composition of TiCx Nanostructured coatings

Nanostructured titanium carbide (TiCx) coatings are deposited on steel substrates by plasma chemical vapor deposition using three different duty cycles of 33, 40, and 50% and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The relationship between the texture orientation/elemental concentration and duty cycle can be divided into two regimes, carbide (TiCx) state and oxycarbide (TiCxOy) state. The coatings crystallize into a TiC NaCl-type crystal structure (FCC) in the carbide and oxycarbide states and a smaller “x” in the TiCx coatings causes the transformation of the preferred orientation of (200) in the carbide state to (111) in the oxycarbide state. A poorly crystallized anatase phase is also observed from the coatings deposited using duty cycles of 40 and 50% and this anatase phase is detected from the oxycarbide state.

Improving of Corrosion Behavior of Al 7075 by Applied Titania–Benzotriazole Nanostructured Coating with Sol Gel Method

Nowadays, self-healing coatings display high abrasion resistance and bond strength. Application of these coatings are reckoned the most common and the most economic method for restoration and protection against corrosion by which metal structures durability is enhanced. The major role of a self-healing hybrid coating in corrosion inhibition is to supply materials for controlling types of corrosion. In this paper, titania–Benzotriazole nanostructured coating has been applied to substrate Al 7075 by using the sol–gel process and immersion method. The bonds existing in the hybrid coating, structure and morphology and coating corrosion behavior have been studied using Fourier transform infrared spectroscopy (FTIR), GIXRD, atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and impedance electrochemical test, respectively. The obtained results are indicative of generating a homogeneous, uniform, crack-free titania–Benzotriazole nanostructured coating associated with excellent optimization of corrosion resistance at 2.8% Benzotriazole.

Influence of TEOS concentration and Triton additive on the nanostructure silica sol-gel anti-reflective coatings

Nanostructured silica antireflective coatings were fabricated on glasses by sol-gel technique. Various silica sols [varying in composition: tetraethyl orthosilicate (TEOS) concentration and Triton additive] were synthesised by the acidic catalysed process and then subsequently coated on substrates. The coatings prepared in this work were characterised using UV-visible spectroscopy, Fourier-transformed infrared spectrophotometer and filed emission scanning electron microscopy. Results indicated that the dense silica films permit a considerable reduction of these light reflections compared with uncoated glasses in all the cases studied, but the degree of reduction is different depending on the composition of the precursor solution. It was found that the transmittance increased from 0.915 for the bare slide up to 0.96 for the best made sample corresponding to the Triton-doped silica. The addition of Triton x-100 to the silica sols improved the optical property of thin films due to existence of nanoporous in the coatings. The SiO2 concentration is an effective parameter to prepare the antireflective films. Decrease in SiO2 precursor cause to decrease in gelation time and, therefore; the suitable SiO2 particles and pores are well formed.

A novel route to prepare hydrophobic and durable antireflective hybrid silica coating by sol-gel method

The application of antireflective coatings to the glass covers of solar thermal collectors, allows increasing the efficiency of the whole system. The work presented here describes the room temperature synthesis of highly transparent and hydrophobic silica coatings using tetraethylorthosilicate (TEOS) as a precursor and polydimethylsiloxane (PDMS) as a hydrophobic modifying agent via a simple dip coating technique. Then, the films were characterized by measuring contact angle and optical transparency, Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) measurements. A new two-step method by double layer of acidic and basic sols was employed. Results showed the maximum transmittance of the antireflective solar glass with double layer coating is about 95.02% at 565 nm wavelength, which is about 4% higher than the substrate glass. The durability of the materials used in solar systems is a key point since they should keep their initial properties during the operational lifetime. In this work, the stability of the optical properties of the films after one year at room temperature in an environment has been achieved, thanks to the application of a hydrophobic treatment and two step-catalyzed sols to the coating. The addition of PDMS to the silica sols improved the hydrophobicity of the coating, and prevented to some extent the coating from cracking which occurred in a pure inorganic thick antireflective coating. It was observed that the obtained silica films become hydrophobic with the introduction of the hydrophobic organic group and static water contact angle (97°) was obtained for the silica film prepared with double layer of acidic/basic coating.

Effect of Catalyst Type on Structural, Morphological, and Optical Properties of SiO2 Thin Film Applied by Sol-Gel Method

The application of antireflective coatings to the glass covers of solar thermal collectors, allows increasing the efficiency of the whole system. Among the methods for applying nanostructure coatings, sol-gel method was selected in this study. Via this method, an antireflective silica coating deposited on glass and the solar transmittance was investigated. The precursor solutions were made by mixing tetraethylorthosilicate (TEOS), ethanol, water and alkali (NH3) or acid (HNO3) catalyst in the molar ratio of 1:3.5:0.35:0.005. In addition, the role of two types of catalysts was examined. UV-visible spectroscopy, Fourier-transformed infrared spectrophotometer, Scanning electron and Optical microscopy were used for the characterization of silica thin films. Results showed that nanoporous silica layers cause to considerable reduction of these light reflections compared with uncoated glasses. It was found that the amount of reduction as well as the adhesive properties is depending on the type of catalyst. Results revealed that not only solar transmittance of acidic-catalyzed coatings is higher than of alkali-catalyzed coatings, but also acidic-catalyzed coatings possess adhesive-resistance higher than alkali-catalyzed coatings. However, at high pH condition, the condensation rate is very fast, and the growth tends to form spherically expanding clusters cause to increasing porosity. The dense and strong binding acidic-catalyzed films have a good antireflective property; because of that, the nanoporousity appears on the surface.

EFFECT OF OPERATING TEMPERATURE ON STRUCTURE PROPERTIES OF TICX NANOPARTICLE COATING APPLIED BY PACVD

Titanium carbide (TiC) is a widely used hard coating to improve the wear resistance and lifetime of tools because of its outstanding properties such as high melting point, high hardness, corrosion ...