Surface Review and Letters

In this work, the surface properties of Mg–Al–Zn (AZ91D) alloy such as surface morphology, hardness and electrochemical corrosion were studied after copper ions (Cu${}^{+})$ irradiation at different energies (0.8, 1.5, 2.5 and 3.5MeV) while keeping the ion dose constant at $5\times 10^{14}$ ions/cm². The morphological features of irradiated samples showed defects composed of ejected material from the alloy surface that became more significant at 3.5MeV. The Vickers hardness was increased with increase of the Cu${}^{+}$ energy. The electrochemical testing of the samples was conducted in a Ringer Lactate solution. The potentiodynamic polarization results revealed anomalous changes in the corrosion rate of the Mg alloy with increase of the Cu${}^{+}$ energy. The corrosion rate was considerably decreased with increase of the Cu${}^{+}$ energy to 3.5MeV. These changes were associated with the surface defects and passive film formation on the alloy surface.

The development of new nanomaterials with controlled characteristics for nanophotonics is of great relevance. In this work, photonic crystals with reflectance at the wavelength of 690nm and the value of 28% were formed by porous-alumina-assisted-anodizing of system Al/Ta on Si wafer. By selecting improved anodizing modes of system Al/Nb on glass, the reflectance was increased to 42% at the wavelength of 340nm. This result shows the high promise of the proposed methods and in the future will significantly improve the result by trying two- or three-stage methods of porous-alumina-assisted-anodizing, nanoimprint stamps and optimization of the anodizing modes for any wavelengths.

Cenosphere fly ash particles are incorporated into AA6061 alloys with different concentrations ranging from 0wt.% to 10wt.% using a modified semi-solid metal processing technique. X-ray diffraction patterns were recorded to analyze the morphology of the aluminum-based metal matrix composites (AMCs). The major diffraction peaks of Al, SiO₂, Al₂O₃ and Fe₂O₃ are distinctly identified which revealed the presence of cenosphere particles and their integrity within the matrix is preserved. The high-resolution optical micrograph identifies the homogeneous distribution and uniform dispersion of the particles. Machinability of the prepared AMCs was investigated by electro discharge machining (EDM) using response surface methodology (RSM). Face-centered CCD of RSM was considered to design the number of experimental runs required. ANOVA was used to explore the influence of selected process parameters and their interactions on the performance characteristics of the systems by developing a second-order quadratic mathematical model for all the responses. Pulse on-time and pulse current were observed to be the most influencing independent variables of EDM system that affect the selected performance measures during spark erosion process. Finally, desirability function approach was employed to optimize the parameters. The optimal processing condition was identified as follows: pulse current: 6 A, pulse on-time: 1010$\mu$s, percentage of reinforcement: 2% and flushing pressure: 0.2 MPa. Very small percentages of deviation have been observed while comparing with the experimental results obtained for MRR (8.6%), TWR (10.3%) and SR (2.18%).

Machining quality depends on numerous factors such as speed, feed rate, quality of the materials, the cutting fluids used and so on. The quality of machining components can also be improved by using appropriate cutting fluids. In this study, the three different types of eco-friendly cutting fluids based on coconut oil with nano boric acid particles were synthesized with nanoadditives and characterized during the lathe-turning operation of mild steel. The obtained results were compared between the dry/plain turning (without the cutting fluid) and the turning with the cutting fluids like coconut oil and mineral oil with nanoparticles. In industries, a wide variety of cutting fluids are used; however, most of these cutting fluids are made up of synthetic materials which may affect the environment significantly. Hence, it is essential to develop eco-friendly cutting fluids for environmental sustainability. Here, the cutting fluids were characterized by the morphological study on nanoparticles (400nm) and the machined surface using scanning electron microscope (SEM), viscosity test, flash and fire point, surface roughness on machined part, tool tip-workpiece interface temperature, cutting force and flank wear measurement. The results showed that cutting fluids with 0.5% of boric acid had better performance.

Machining with minimum quantity lubrication (MQL) or minimum quantity cooling (MQC) as a subset of green machining is a process in which small volume fluid of high lubrication and cooling properties alongside high pressure air is used in the material removal process. The heat generated in the grinding process has a great impact upon the workpiece quality. Serving lubrication and heat transfer functions, cutting fluids have an essential role in reducing the temperature and thus improving the process of grinding. In this research, nanofluid made of graphene nanoparticles in water-based fluid as a cutting fluid of high heat transfer is utilized to investigate the effects of nozzle number and nozzle geometry of the MQC system on the cutting temperature and surface roughness of the workpiece. The effect of geometry and number of nozzles on grinding with MQC has not been studied so far. The study findings show that the nozzle outlet cross-section of rectangular, compared to circular, decreases the surface roughness and temperature by 30% and 36%, respectively. Moreover, compared to the single nozzle, the use of three nozzles results in a decrease of 19% and 31.7% in the surface roughness and temperature. Under the same machining conditions, the MQC method by 0.15wt.% nanofluid of graphene in water using a rectangular nozzle outlet of 1.2mm width makes surface roughness and temperature reduced by 67.2% and 48.3% compared to the dry condition, whereas decreased by 13.4% and 8.8% compared to the wet method, respectively.

Owing to the advancement in the field of materials, different range of grades have been developed. The machinability examination of these newer grades must be carried out for future applications. One such newer grade of magnesium with AZ31 is deemed for study during the drilling process. The independent parameters considered are spindle speed (SS), feed rate (FR) and drill bit diameter (DBD). The dependent parameters considered are burr height (BH), burr thickness (BT), drilling time (DT) and surface roughness (SR). Improving hole accuracy is essential for manufacturing superior products, which is discussed in this work. At the same time, the machining time has also to be minimized to increase the production rate. With these objectives, the experimental investigation is made. Further, an analytical model for predicting the responses is developed; later, optimization is carried out to obtain the desired responses through the desirability function approach. The multi-objective optimization suggests the SS of 1100rpm, the FR of 0.198mm/rev., and the DBD of 6mm for reducing the entire dependent is reckoned.

Today, manufacturing methods are classified into two groups as conventional and non- conventional manufacturing methods. While turning, milling, and drilling are among the conventional manufacturing methods, processes such as laser, plasma, electro erosion, ultrasonic machining and water jet machining are among non-conventional, namely modern manufacturing methods. The cutting tool does not used in modern manufacturing methods. This situation is an advantage. There are some uncertainties on the machining performance of abrasive types, apart from the superior properties of the method. In this study, the effect of different abrasive types on machining performance in abrasive water jet machining (AWJM) was investigated by using computer aided finite element analysis.

The density functional theory has been used to study the adsorption performance of polluting Cu${}^{2+}$ and Zn${}^{2+}$ ions on defective graphene. Compared to intrinsic graphene, the adsorption distance between defective graphene and Cu${}^{2+}$/Zn${}^{2+}$ decreases greatly, and the adsorption energy and charge transfer amount increases significantly. The calculation of charge density demonstrates that clear hybridization happens between defective graphene and Cu${}^{2+}$/Zn${}^{2+}$ ions, suggesting the formation of chemical adsorption. The frontier orbit analysis shows that defective graphene has greater electrical sensitivity after adsorbing Cu${}^{2+}$/Zn${}^{2+}$ ions. Therefore, defective graphene could be a potential material for the treatment of contaminating heavy metal ions.

In this study, an attempt has been taken to find out the appropriate optimal parameter setting that will provide the best quality product depending on experimental data during Electro Discharge Machining (EDM) of Titanium grade 6 alloy with the help of brass electrode and to compare the optimized results achieved from two optimization techniques. For this study, Face Centered Central Composite Design- (FCCCD) based Response Surface Methodology (RSM) coupled with Technique for order of preference by similarity to ideal solution (TOPSIS) and Grey Relational Analysis (GRA) has been applied to optimize the process parameters i.e. gap voltage ($V_g)$, peak current ($I_P)$, pulse on time ($T_{\mathrm{\text{on}}})$, and duty cycle ($\mathrm{\Gamma }$). Radial overcut (ROC), surface roughness ($R_a)$, material removal rate (MRR) and tool wear rate (TWR) are selected as output performance characteristics. To find out the significant process parameters, Analysis of variance (ANOVA) test has been performed at 95% confidence level. For validation of the study, confirmation experiments have been performed at optimal parameters setting which show the enhancement of Relative Closeness Coefficient ($S_{iw})$ up to 0.144082 using TOPSIS and Grey Relational Grade (GRG) up to 0.198014 using GRA, respectively.

Phytic acid (PA) and 3-aminopropyltrimethoxysilane (APTMS) were selected as organic additives and respectively doped into Na₂SiO₃-NaOH electrolyte to prepare ceramic coatings on AZ31B Mg alloys by Plasma Electrolytic Oxidation (PEO) method. The influences of two additives on corrosion resistance of the PEO coatings were compared. The microstructure, composition and corrosion resistance of the PEO coatings were examined by SEM, EDX, XPS, XRD, potentiodynamic polarization test and EIS measurement. The results indicated that each additive increased both the coating thickness and corrosion resistance. However, the PA-doped PEO coating achieves larger thickness but exhibits worse corrosion resistance than the APTMS-doped PEO coating due to larger pore size and looser microstructure.

This study aims at producing zinc (Zn)-rich epoxy ester (EE) paints for cold galvanizing of mild steel. Zn particles with a narrow particle size distribution of 1$\mu$m to 5$\mu$m were dispersed in EE resin by vacuum centrifuge mixer. The effect of Zn concentration in EE resin on cathodic protection ability of resulting paints was studied. Galvanic corrosion protection ability of the paints was studied in 3.5% (mass ratio) NaCl solution using electrochemical characterization techniques such as open circuit potential (OCP), Tafel analysis and electrochemical impedance spectroscopy (EIS). The results showed that cathodic protection ability depends on the loading of Zn particles in the EE and it is effective when the mass fraction of Zn was equal to or exceeded 90%. At this concentration, Zn particles developed interconnecting conducting networks as determined by scanning electron microscopy (SEM) which were responsible for the galvanic effect of the coating. The EE paints developed at mass ratio below 90% behaved as a conventional organic barrier coating and did not show any cathodic protection effect due to the lack of contact between Zn particles. The EE paint showed good resistance to abrasion and wear. The electrochemical behavior of Zn-rich EE paint (with cathodic protection ability) developed in this study was compared with commercial acrylic-based “cold galvanized paint” (Roval). EE-based “cold galvanized paints” were found to be more protective and long lasting compared to commercial “cold galvanized paints”.

The main objective of present work focuses to investigate the tribological behavior of Al 7075 hybrid metal matrix composite. Al 7075 metal matrix composites has many potential applications especially in automotive and aerospace industries, due to their light weight to strength ratio and high wear resistance. The composite is fabricated using two step stir casting process by varying 5% to 15% volume fractions of Silicon Carbide and Titanium Carbide. Optical microstructure showed reinforcement distribution into Al 7075 matrix. The wear and frictional properties of the hybrid metal matrix composites was studied by performing dry sliding wear test using a pin-on-disc wear tester. Tribological behaviors were examined by applying different normal loads of 10N, 20N, 30N with different sliding velocities (1m/s, 2m/s, 3m/s) at room temperature without lubrication. Wear rate and coefficient of friction for different normal load and sliding velocities were plotted and studied. The micro hardness value of AST15 was higher by 18.8% than the AST0 Composites. The wear rate prediction indicated the wear rate for AST15 as $2.1\times 10^{-3}$mm³/m as compared to AST0 which was $6.4\times 10^{-3}$mm³/m. The wear rate increases with the increase in load and sliding velocities. Scanning electron microscopy micrographs of the worn surface are used to predict the nature of the wear mechanism.

In the present paper, (ZnO)–(Co₃O₄) nanocomposite thin films have been prepared by using spray pyrolysis deposition on a glass substrate at 350^∘C. After that, the as-obtained films have been characterized and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the double beam UV-visible (UV-vis) spectrophotometer. Furthermore, the Bruggeman model is used to predict the evolution of the optical dielectric constant (real and imaginary parts: ${\epsilon }_r$ and ${\epsilon }_i)$ to compare them with those obtained from the experimental results. The XRD pattern reveals that the nanocomposite film has diffraction peaks 2$\theta =31.33^{\circ }$, 36.95^∘ corresponding respectively to the (220), (311) planes of cubic Co₃O₄ and another about of 2$\theta =36.26^{\circ }$ corresponding to the (101) plane of Wurtzite ZnO. Using the Debye Scherrer formula, the crystallite size of (ZnO)${}_{0.5}$–(Co₃O${}_4{)}_{0.5}$ nanocomposite is found about 32nm, while the obtained thickness of this nanocomposite is about 780nm using the DekTak Stylus profilometer. Besides, the morphology analysis shows that the nanocomposite sample is well covered without holes and/or cracks and it has uniform dense grains. The evaluation of the transmittance, reflectance, refraction index, extinction coefficient, real and imaginary parts of dielectric constant as function of wavelength illustrates that the optical response of nanocomposite thin film (ZnO)${}_{0.5}$–(Co₃O${}_4{)}_{0.5}$ depends on the influence of two mediums of pure materials ZnO and Co₃O₄ and their interaction. In addition, the direct band gap vs incident photon energy obtained from the Tauc plot equation shows that this nanocomposite has three values of band gap energy which are $E_{g1}=1.54$eV, $E_{g2}=2.2$eV (correspond to pure Co₃O₄ film) and $E_{g3}=3.47$eV (correspond to pure ZnO film). Besides, the application of the Bruggeman equation indicates that the influence of the values of volume concentration and optical dielectric constant of the ingredient nanomaterials (ZnO and Co₃O${}_4)$ is significant on the value of the effective dielectric constant of nanocomposite thin film. The specific result of this study is the similarity between the spectra obtained from the Bruggeman model and the measured one, which proves that the application of this model is useful for the prediction of the optical properties of the composite.

The development of NiTi-based shape memory alloys (SMAs) for some medical applications has been limited by releasing Ni element into the organic tissue. In this study, Ni${}_{47}$Ti${}_{50}$Sn₃-wire (at.%) SMA was produced using the arc-melting technique, and the alloy was subjected to non-isothermal processes. Some characteristics of the alloys, such as oxidation behavior, corrosivity, and in vitro study in simulated body fluid and physiological solution at body temperature, were investigated. The corrosion rate of the as-casted alloy was lower than the equiatomic-NiTi alloy found in the literature. The estimated ICP-MS results showed that the release of alloying constituents into the solutions is in accordance with the standards.

In this paper, the Plasma electrolytic oxidation (PEO) coatings were formed in K₂ZrF₆-containing electrolyte with the addition of glycerin on aluminum alloy. PEO coating increased the tribological and mechanical properties of the aluminum alloy. The effect of frequency on the properties of PEO coatings was studied. AFM observation showed that the micropores number increased with the increasing frequency. XRD results showed that the content of $\alpha$-Al₂O₃ ranged with the frequency increase. The coating formed in the electrolyte with the frequency of 800Hz was of the lowest friction coefficient and stablest curve. The glycerin is not only of ability to lower the defect of PEO coatings, but can also increase the wear resistance ability of the coatings.