Surface Review and Letters

Nowadays, the demand for needle-punched nonwoven fabrics has been increasing, especially in the areas of high-performance composites as reinforcement due to their potential of imparting high $z$-directional strength, easy resin absorption, light weight, and low cost. In this study, needle-punched nonwoven viscose fabric-reinforced epoxy composites are prepared by varying the area density of fabric mat (100gsm, 200gsm, 300gsm, and 400gsm) at constant fabric loading of 30wt.%. The effects of area density on mechanical and slurry abrasion behavior of composites are studied under controlled laboratory conditions. It is observed that the mechanical properties and abrasive wear resistance under steady-state condition has been improved with the increase in area density of fabric mat. Furthermore, experimental design through Taguchi’s L${}_{16}$ orthogonal array is applied to find out the optimal parametric combination for minimum wear rate. It is also observed through the analysis that silica sand size and sliding velocity are the most influential factors for wear rate.

In this study, the formation of porous Al₂O₃ on commercial 1050 aluminium alloy (AA1050) in 2M sulfuric acid (H₂SO₄) electrolyte was investigated. Anodization was performed at 12V and 15V specimens for a charge density of 757mC/cm² and 3231mC/cm². The resulting oxides were analyzed using scanning electron microscopy (SEM). According to analysis, a hexagonal oxide formation containing more than one nano pore was observed on the surface of the specimen. The structural properties of the porous oxide film were analyzed with electrochemical impedance spectroscopy (EIS) analysis and film-related features such as thickness of the porous and the barrier layer were obtained.

The authors provide insight into the problem of selective flotation of fluorite from quartz–fluorite ores. The flotation of fluorite mineral from ores by using acidized water glass as depressant has been studied for substitution of the commonly used depressant. It was found that the acidized water glass could achieve higher selectivity of fluorite minerals against gangue minerals in the fluorite flotation. The experimental results showed that YF collector has high selectivity in the flotation of fluoride for low-grade fluorite ores. The use of the YF collector also made it unnecessary to heat the pulp to a high temperature and achieved an acceptable reduction in the flotation temperature to $13^{\circ }$C. The YF collector should be used in neutral pH to separate fluorite from gangue and it could also improve fluorite recovery and flotation rate.

In this work, TiAlV thin films have been prepared on two different types of substrates: silicon and stainless steel (SS304) by two deposition methods: Pulsed Laser Deposition (PLD) and DC magnetron sputtering. Different techniques have been employed in order to characterize film properties such as: Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray (EDX), X-ray diffraction (XRD), microhardness and corrosion test. EDX analysis showed that the deposited films are slightly different from that of the target material Ti6Al4V alloy. The measured microhardness values are about 11.7GPa and 4.7GPa for films prepared by PLD and DC magnetron sputtering, respectively. Corrosion test indicated that the corrosion resistance of the two TiAlV films deposited on SS304 substrates in (0.9% NaCl) physiological normal saline medium was significantly improved compared with the SS304 substrates. These attractive results could permit applications of our films in the medical implants fabrication.

Energy restoration is the prime issue for the researcher and they have tried to develop advanced techniques and resources for renewable energy. The nanofluid is one of the resources for the restoration of energy which depends on the dynamic thermophysical properties of metal nanoparticles. The recent study is concerned with the thin film flow of carbon nanotubes (CNTs) water-based nanofluid for the improvement of heat transfer applications. The flow of two types of CNTs nanofluid was studied, comprising single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) over the surface of a thin stirring needle. The study has been carried out in the presence of a magnetic effect and viscous dissipation. The BVP 2.0 package has been used for the solution of the modeled problem. The effect of the physical constraints like Prandtl number, magnetic field and Eckert number vs the momentum and thermal boundary layers has been analyzed. The sum of the residual errors has been obtained up to the 20th order estimates to settle the strong convergence of the problem. The obtained results show that the thin film has a quick response to the increasing of heat transfer rate over the surface of a thin needle as compared to the thick boundary layers.

Critical point (CP) in a titration curve to quantify carboxylic, lactonic, and phenolic groups on multi-walled carbon nanotube (CNT) and Vulcan carbon (VC). Titration technique used was Boehm type and tipping point measurement from titration curve was done by second derivative method. The calculation functional groups on nanocarbons (NCs) presents lowest uncertainty previously published. An order of $\pm 10^{-4}$meq/g is the precision of the values obtained, one order of magnitude below reported. Both NCs display a high quantity of carboxylic groups created after being treated with regard to the other functional groups generated, mainly for functionalized Vulcan carbon VC-F.

The dynamic mechanical properties of Ti-6Al-4V alloy prepared by laser direct deposition (LDD) at different strain rates are of great significance for the application of LDD technology in the manufacture and repair of aero-engine parts. The quasi-static tensile test and dynamic compression test of Ti-6Al-4V alloy prepared by LDD (LDD-Ti-6Al-4V) were carried out under the quasi-static and high strain rate using INSTRON-5982 tensile test equipment and Split Hopkinson pressure bar (SHPB) equipment. The true stress–strain curve is obtained, which indicates that the LDD-Ti-6Al-4V has a strain rate strengthening effect. Moreover, the Johnson–Cook (J–C) constitutive model of LDD-Ti-6Al-4V was fitted based on experimental data, and the experimental process of SHPB was numerically simulated. The simulation results are basically the same as the experimental results, which proves the correctness of the J–C constitutive model of LDD-Ti-6Al-4V.

Push–pull tests of rolled magnesium alloy AZ31 were performed with a side-notch plate specimen to examine the crack growth behavior under negative mean stress conditions in conditions of high humidity. The effects of repetition of compression on crack growth were discussed. The geometry of the fracture surface and the changes in microstructure were related to the crack growth behavior. The crack growth rate varied even when the experimental conditions were the same. When the oxidized powder appeared from the cracked surface, the crack growth rate became lower. That was related to the changes in microstructure while the crack grew with local shear plastic deformation. The variation of crack closure point was related to the local shear plastic deformation.

Slurry erosion behaviors of HVOF WC-12Co and Cr₃C₂-25NiCr coatings as well as 16Cr5Ni martensitic stainless steel were investigated in the present paper. Erosion experiments were carried out using slurry with different rotational speeds, particle size and concentration to evaluate their influences on the coatings. It was found that the rotational speed had the most significant influence on WC-12Co coating, whereas the erosion particle size was a more dominant factor for the Cr₃C₂-25NiCr coating. Nevertheless, the effect of concentration was most important in the case of 16Cr5Ni steel. It is demonstrated that cermet composite coatings could effectively enhance the resistance of slurry erosion, and the WC-12Co coating exhibits a minimum erosion rate compared with the steel and Cr₃C₂-25NiCr coating. 16Cr5Ni steel and WC-12Co coating showed ductile and brittle mechanisms, respectively, whereas Cr₃C₂-25NiCr exhibited multiple mechanisms of ductile and brittle, dominantly ductile.

Crack identification in thick beams has improved increasing considerations from the scientific and building areas since the unpredicted structural failure may cause disastrous, catastrophic and life trouble. The goal of the present examination is to predict the unknown crack location and its depth in thick beams from the information of frequency data obtained from experimental examination. The effectiveness of the proposed strategy is approved by numerical simulations in view of experimental data for a cantilever beam, free-free beam and simply supported beam. With the improvements in delicate figuring, optimization strategies are acknowledged to be an extremely proficient instrument to offer an answer for crack identification issue. In the simulation modeling, the parameters, for example, shift; modal assurance criterion (MAC) and stiffness, are predicted by utilizing optimized deep learning neural network (ODNN) approach in view of crack location and size. To improve the weight in DLNN, the opposition-based ant lion (OAL) is used by minimizing the mean square error (MSE) rate. The result shows that the proposed model achieves the optimal performance compared with existing techniques.

The Casimir force between two rough surfaces grown through statistical growth models is studied, both theoretically and numerically. The models include the random deposition (RD), the random deposition with surface relaxation (RDSR), and the restricted solid-on-solid growth (RSOS). To calculate the Casimir force, the pairwise summation (PWS) method in $(2+1)$ dimensions is used. First, the force between two growing surfaces with RD equations, Edwards–Wilkinson, (EW) and Kardar–Parisi–Zhang (KPZ) equations is theoretically investigated. Then, using the Monte Carlo simulation, the rough surfaces with RD, RDSR, and RSOS models in $(2+1)$ dimensions are simulated in different growth times, and the Casimir force between each pair of rough surfaces in each time step is calculated. The results show that the force between the surfaces increases as the roughness increases.

Amorphous and crystalline Zn${}_{1-x}$Co_xS ($x=0.1$, 0.3, 0.5) thin films were grown on sapphire (Al₂O₃) substrates by pulsed laser deposition at substrate temperature of 25^∘C and 800^∘C, respectively. The X-ray diffraction results show that the crystalline film has a cubic zinc blende structure and the crystalline quality decreased with increasing Co-doping concentration. The X-ray diffraction and X-ray photoelectron spectroscopy spectra reveal that the samples reached an overdoping state at Co-doping concentration of $x=0.5$. The absorbance of films increases and the absorption edge shifts to longer wave length direction with increasing Co-doping concentration. The redshift of the band gap energy depends on the Co composition associating with the Urbach energy. Furthermore, the refractive index and dielectric constant increase with increasing Co-doping concentration. The dispersion parameters, such as dispersion energy ($E_d$), oscillator energy ($E_o$), static refractive index ($n_0$), static dielectric constant (${ϵ}_0$), interband transition strength moments ($M_{-1}$ and $M_{-3}$), oscillator strength $S_o$ and oscillator wavelength ${\lambda }_o$, have been analyzed by Wemple–DiDomenico single oscillator model. All these parameters were found to be dependent upon the Co-doping concentration in the Zn${}_{1-x}$Co_xS thin films.

This study is focused on the tribological properties of micro- and nano-crystalline diamond (MCD and NCD), non-hydrogenated and hydrogenated diamond-like carbon (DLC and DLC-H) and nitrogen-based (CrN, TiN and TiAlN) coatings sliding against the super alloy Inconel 718, in terms of the maximal and average coefficients of frictions (COFs), the worn morphologies and the specific wear rates, by the rotating ball-on-plate configuration under dry condition. The results show that the nitrogen-based films show comparable COFs and wear rates with the WC–Co substrates. The DLC and DLC-H show lower COFs compared with the nitrogen-based films. Furthermore, their wear resistance is limited due to their low thickness compared with MCD and NCD, which have the same elemental composition. The DLC-H coating exhibits much lower wear rate compared with the DLC coating, which may be derived from the passivation of dangling bonds by the linking of H to C atoms. The MCD and NCD films show the lowest average COFs and mild wear after tribotests, due to their high hardness and low adhesive strength between pure diamond and the super alloy.

Among all the tested films, the NCD film-based tribopair presents the lowest maximal and average COFs, tiny wear debris particles, mild wear of ball and plate without scratching grooves, indicating that the NCD film may be suitable to be deposited on cutting tools for super alloy machining.

In this work, ZnO nanorods (ZnO NRs) were successfully synthesized on FTO-glass via hydrothermal technique. Two steps were followed to grow ZnO NRs. In the first step, the seed layer of ZnO nanocrystals was deposited by using a drop cast method. The second step was represented by the hydrothermal growth of ZnO NRs on a pre-coated FTO- glass with the seed layer. The hydrothermal growth was conducted at 90^∘C for 2h. The resulted structure, morphology and optical properties of the produced layers were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) and UV-visible spectrophotometer, respectively. The analysis confirmed that the ZnO NRs grown by the hydrothermal method have a hexagonal crystal structure which was grown randomly on the FTO surface. The crystallite size was recorded 50nm and a slight microstrain (0.142%) was calculated. The bandgap was found to be in the range of 3.14–3.17eV. The ZnO NRs have a high density and large aspect ratio. A pH sensor with high sensitivity was fabricated using a two-electrode cell configuration. The ZnO NRs sensor showed the sensitivity of $-$59.03mV/pH, which is quite promising and close to the theoretical value ($-$59.12mV/pH).

We report here the development of MnO₂ nanostructure electrode for electrochemical energy storage application. MnO₂ nanoparticles synthesized by a facile and efficient precipitation approach have been investigated for supercapacitor application. The structures and morphologies of MnO₂ nanoparticles were systematically studied using X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The synthesized nanoparticles are observed spherical in shape with uniform size distribution. The electrochemical properties were studied in two-electrode configuration by cyclic voltammetry process. A specific capacitance of 52.8F/g has been obtained for MnO₂ nanoparticles at scan rate of 100mV/s. The electrode is able to deliver a power density of 0.66kW/kg and energy density of 1.8Wh/kg.