Surface Review and Letters

The microstructures, morphology features and the corrosion resistance of the different particle diameters of enamel coating were investigated in this paper. All enamel coating samples were immersed in 5wt.% NaCl solution. The effects of the diameter of micron-dimension enamel particles on the mild steel were discussed and the corrosion resistance of the different coatings were characterized by potentiodynamic polarization curves, scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM), the SECM was employed to identify the local reactivity and then estimate where pittings happen. In this paper, six kinds of diameter of enamel particles were sintered at 780${}^{\circ }$C on mild steel. The results indicated that the corrosion resistance of the enamel coating immersed in 5wt.% NaCl solution improved first and then declined with the decrease of particle size. Used by SEM and SECM, the result showed that as enamel particles become more small, the binding force becomes stronger. However, as the diameter of enamel particles decrease, the uniformity of the coating first improves and then decreases.

As the phenomenon of fatigue damage is a common failure mode of equipment, the reliability evaluation and life prediction have become a hot-spot. The precise prediction of fatigue life in the initiation stage has become necessary. The common prediction study for structural fatigue life takes less influence factors into consideration. The common prediction results of fatigue life cannot be quantitatively corrected by the influence factors at the same time. This paper presents a research on the prediction approach for structural fatigue life based on the multi-factor correction. The influence of some factors on the fatigue life was analyzed and the prediction approach for structural fatigue life based on multi-factor correction was raised. Then the fatigue life of axle housing was predicted by using the corrected approach, as the case study. Moreover, the result predicted by the local stress–strain approach and the experimental data were used to verify the accuracy of the corrected approach. It can be clearly demonstrated by the results that the corrected prediction approach can be used to achieve the precision fatigue life for engineering structures. Further, it is also a prediction approach endowed with engineering application prospects.

The Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique (PSAT). The cross-section micro structure, phase structure and microhardness of Ni modified layer were studied. The friction and wear behavior of the Ni modified layer and the Ti6Al4V substrate were analysed. The effects of displacement amplitude, frequency and fretting time on friction coefficient of the Ni modified layer were investigated. The results indicated that the wear rate was lower compared with that of the Ti6Al4V substrate. Friction coefficient of the Ni modified layer increased with the increase of frequency. But it was insensitive to the change of wear time and the displacement amplitude. The wear mechanism of the Ti6Al4V was adhesion and abrasion wear mechanism while the Ni modified layer showed slightly abrasion wear.

Sandwich stacked Ti/Cu/Si thin films were deposited on a single-side polished Si(111) substrate using DC magnetron sputtering system and annealed using a rapid thermal annealing (RTA) system. Complex dendritic patterns, whose branches are composed of Cu rods and triangular Cu microcrystals were obtained on Ti/Cu thin film annealed at 700${}^{\circ }$C. The shape of one triangular Cu microcrystal is a truncated equilateral triangular pyramid with a flat top. Triangular Cu microcrystals grow in the number when Ti/Cu thin films are annealed at 800${}^{\circ }$C. Experimental results show that anisotropy affects the growth of surface patterns and the top Ti capping layer works as a protection for the underlying Cu layer from oxidation.

A diamond-like carbon (DLC) coating was deposited on YT14 cemented carbide cutting tools using an MS (magnetron sputtering), and the surface–interface morphologies, phases, and bonding energy of the obtained coatings were investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The wear behaviors of DLC coatings were measured using high temperature wear tests. The results show that the $s{p}^2$ and $s{p}^3$ appear at 284.4, and 285.3eV, respectively, the DLC coating is composed of the crystal planes (111) and (220). The average COF of DLC coatings at 750, 800, and 850${}^{\circ }$C was 0.1956, 0.2082, and 0.4085, respectively, the wear depth increases with the wear temperatures increasing: At 750${}^{\circ }$C, the diamond planes (111) and (222) remained, while at 800 and 850${}^{\circ }$C, only the diamond plane (111) still remained, the diamond plane (220) was oxidized, resulting in wear capability decreasing. The wear mechanism was composed of abrasive wear, delamination, and oxidation wear.

The aim of this paper is to study the effect of erbium oxide (Er₂O₃) on porous silicon (PS) wafers used for photovoltaic application. An immersion of PS wafers in Er₂O₃ solution can be used to enhance light trapping and form an efficient surface by passivation process. PS was prepared by the stain-etching method and doped by Er species. In fact, the topography was investigated by the scanning electron microscope (SEM). In addition, the spectral behaviors of the reflectivity and the photoluminescence were discussed. The dependence of minority carrier lifetime was evaluated by means of the Quasi-Steady-State Photoconductance technique (QSSPC). Besides, an enhancement in lifetime was observed. A framework is provided for estimating an efficiency improvement in studied films which will help to guide the development of improved energy-efficient.

The preparation of ultrathin Ni layer onto the surface of glassy carbon electrode (GCE) by molecule anchoring method was studied in this paper in which two steps were involved: molecule anchoring (GCE-M) and ultrathin Ni layer adsorption (GCE-M-Ni). The result showed that by simply anchoring some molecules (purpald, bismuthiol I, DPTA, EDTA-2Na, ferrotitanium and thiourea) onto the surface of GCE, the adsorption of Ni layer would be improved relatively, thus improving the electrocatalytic ability of GCE toward sucrose, fructose and glucose. It was believed that the anchoring of these molecules helped the following adsorption of Ni layer. Good electrocatalytic characteristics for sugars oxidation of GCE-purpald-Ni were observed in this work with the immediate response, wide linear range from 0$\mu$M to 800$\mu$M and low detection limit down to 0.49$\mu$M for the sensing of total sugar (TS) concentration. The common interfering molecule such as ascorbic acid was proved of no interfering effect on the detection. Also, GCE-purpald-Ni was successfully applied to detect TS concentration in orange juice samples with high recovery rate of more than 85%. It is concluded that the molecule anchoring method can be used to the adsorption of ultrathin Ni layer onto the surface of GCE and works as one of the promising nonenzymatic sensings toward sugars.

We present theoretical models to study the localized electronic surface states in metallic structures. The materials under study have been chosen with different types of cubic meshes, fcc, sc and bcc. The calculation method used is closely related to the Linear Combination of Atomic Orbitals (LCAO) in the tight-binding method.

We consider three cases: each of the atoms is described by a single atomic orbital of $s$-, $p$- and $d$-type orbitals. In order to solve the rectangular secular equations of the systems under study, the phase field matching method is involved. In particular, we apply our approach to calculate the localized electronic surface states of some metals: (i) Chromium and Silver having, respectively, bcc and fcc structure and described as $1s$-type orbital. (ii) Nickel with sc crystallization and described by $1d$-type orbital. (iii) Palladium (Pd) given in fcc crystallization and described by $d$-type orbital. The obtained results illustrate spatial edge effects between the bulk modes and the localized electronic states of the metallic surfaces over the three orientations of high symmetry path. We observe many localized states above and below the bulk band range. In addition, the relaxation effect on the surface layer has been investigated to compute the localized electronic surface state in this case and illustrate the lift of the degeneracy compared to the first calculations based on an ordered surface. The spacing geometry caused by the relaxation on the surface has been determined by using the Molecular dynamic algorithm and Morse interatomic potential.

Plasma electrolytic oxidation (PEO) coatings were formed on aluminium alloy in additive Al₂O₃- and TiO₂-containing Na₂SiO₃-based electrolytes, respectively. The effect of these additives on morphology, composition and wearing properties of coatings was investigated. The morphology and composition of coatings were studied by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). Analysis of wearing properties of coatings were done by friction and wearing experiment. It was found that the use of additives greatly affects the surface morphology of coatings. It is shown that the content of $\alpha$-Al₂O₃ in coatings formed in Al₂O₃-containing electrolytes increased with the addition of Al₂O₃. However, the content of $\alpha$-Al₂O₃ in coatings formed in TiO₂-containing electrolytes first increased and then decreased. Among these coatings, the coating formed in silicate-based electrolytes system containing 7g/L Al₂O₃ showed the most superior wearing properties.

In this paper, we demonstrate theoretically an efficient way to improve the optical properties of the PIN silicon solar cell. We design an anti-reflecting coating (ARC) from one-dimensional ternary photonic crystals (PCs). Also, we design a back-reflector that composed of one-dimensional binary PC. By adding ARC layers, we have observed that the absorption is increased from 0.5 to 0.75. Moreover, by adding back reflector layers, we found that the absorption values rise to reach over 0.95 in the range of the photonic band gap (PBG) of the back reflector. Thus, using PCs in each ARC and back reflector has a significant enhancement of the absorption of the cell. Our design could have a distinct effect on the conversion efficiency of the cell. We use transfer matrix method to optimize the PBG of the back reflector. Finally, the numerical and simulated results of the cell are investigated by COMSOL Multiphysics that based on the finite element method (FEM).

In the present work, the effect of K₂O/Na₂O substitution on the bioactivity of Na₂O-CaO-P₂O₅-SiO₂ ceramics prepared by solid-state method was studied. Ceramics-based bioactive implants are economical; they require low processing temperature and are more bioactive when compared with glasses, glass ceramics and composites. K₂O is known to control proper function of cells and stimulate bone formation process. The hydroxyapatite layer developed on the surface of samples after soaking in stimulated body fluid solution was studied by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The results showed an increase in the bioactivity of the samples as Na₂O was partially replaced with K₂O. The addition of K₂O enhanced the apatite-forming ability of the ceramic samples and makes it suitable for filling defects and fracture in bones.

In this paper, octadecyltrichlorosilane (OTS) self-assembled multilayer (SAM) films are fabricated on Pyrex glass by dipping method. The hydrophobicity, constituent and surface morphology of OTS SAM at various dipping times in solutions of 1, 2 and 5mM concentrations are investigated. Characteristic absorption peaks around 2850 and 2920cm${}^{-1}$ are observed by FTIR and island-like structures on samples are detected by AFM. After 15min dipping time for solution of 5mM, water contact angle of the sample reaches the maximum value of 116.4${}^{\circ }$ with relatively low surface root mean square (Rms) roughness of 0.152nm. The critical surface tension (${\gamma }_c)$ of the analyzed sample is 18.2dyne/cm. The optimum dipping time in the solution of 5mM for a complete SAM film is about 30min. The study of the optimal conditions for the formation of integrated OTS SAM has significant scientific and practical values in modification of solid surfaces.

Tin Oxide has been explored for gas sensing and humidity sensing. In the present work, pure and copper-doped SnO₂ is synthesized by controlled spray pyrolysis technique. The films are homogeneous throughout. Rietveld analysis confirms the absence of other phases due to doping. The optical property is studied using UV-Visible spectroscopy which shows a change in the band gap with the introduction of the dopant. An elaborate impedance analysis is carried which showed the effect of doping. Cu-doped thin film showed a faster drop in the impedance when exposed to humidity. Significant change in the cole–cole plot is observed indicating better sensitivity with the doped sample in comparison to undoped. Higher humidity level from 80 to 92 RH is studied as it is important to detect the same in air conditioning systems, electronic devices, aviation systems and food processing systems. The equivalent circuit also reveals that the adsorption of water molecules on the surface of the thin films changes the impedance characteristics. Levenberg–Marquardt algorithm is employed for the theoretical calculations and identifying the equivalent circuit. The charge transfer in the doped sample is subjected to lesser grain resistance according to theoretical calculation and experimental results. A density functional approach is employed to study the band structure and explain the influence of Cu doping on pure SnO₂. The calculated result supports the use of Cu as a dopant for better humidity sensing device.

This work indicates the device properties of polycrystalline p-AgGaInTe₂ (AGIT) thin films deposited on bare and ITO-coated glass substrates with thermal evaporation technique. Device characteristics of n-CdS/p-AGIT heterostructure have been analyzed in terms of current–voltage ($I$–$V$) for different temperatures and capacitance–voltage ($C$–$V$) measurements for different frequencies, respectively. The series and shunt resistances were determined from the analysis of parasitic resistance for high forward and reverse bias voltages, respectively. The ideality factors were evaluated from $I$–$V$ variation at each sample temperature as lying in between 2.51 and 3.25. The barrier height was around 0.79eV at room temperature. For low bias region, the variation in the diode parameters due to the sample temperature exhibited the thermionic emission with $T_0$ anomaly, whereas space-charge-limited current analysis was also found to be pre-dominant carrier transport mechanism for this heterostructure. From $C$–$V$ measurements, the obtained built-in potential and series resistances were found to be in good agreement with $I$–$V$ results.

Semiconductors are the backbone of the optoelectronic industry. Direct band gap materials in the visible energy region are highly desirable for the efficient optoelectronic applications. In this work, we have probed the structural, electronic and optical properties of Mg-IV-V₂ (IV$=$Si, Ge, Sn and V$=$P, As) compounds by FP-LAPW calculations, based on density functional theory. Their crystal structure is chalcopyrite with space group of I-42d. The lattice constants of MgSiP₂, MgSiAs₂ and MgGeAs₂ are consistent with experimental results. These compounds show semiconductor behavior with direct band gap ranging from 1.3–2.15eV. Optical properties were also investigated. Optical properties include real and imaginary parts of dielectric constant, energy loss function, refraction and reflection. Direct band gap nature and good response in the visible region of these compounds predict their usefulness in optoelectronic devices.

Metal matrix composites are widely applied in the automotive and aircraft structural components. This work investigates the influence of mechanical and corrosion properties hybrid aluminium 2024 metal matrix composites having 5%, 10%, 15% and 20% of TiC and B₄C (equal amount) reinforcement compositions. The increase in volume fraction of B₄C and TiC particle in matrix alloy increases the hardness, yield strength, ultimate strength and decreases the ductility of the composite. SEM images show microstructure of the composites with particles having a different volume percentage of reinforcement. The uniform distribution of B₄C and TiC particles is most predominant in composite fabrication and the reinforcement particle additions have proved improved corrosion resistance in AA2024–B₄C–TiC MMCs.