Surface Review and Letters

Sb₂O₃- and CeO₂-doped ZnO thin films were prepared by RF magnetron sputtering technique. The influence of Sb₂O₃ and CeO₂ on the structure and ultraviolet (UV) absorption properties was studied by X-ray diffraction and UV–Vis spectrophotometry. Results show that multiple doping of films had a prominent effect on the development of crystal grains and the UV absorption property. Ce and Sb exist in many forms in the ZnO film. The multiple-doped films also show enhanced UVA absorption, and the UV absorption peak widens and the absorption intensity increases. Sb plays a dominant role on the structure and UV absorption of ZnO thin films, which are enhanced by Ce.

Diamond films have been deposited on the interior hole surface of cobalt-cemented tungsten carbide (WC–Co) drawing dies from acetone, trimethyl borate (C₃H₉BO₃), tetraethoxysilane (C₈H${}_{20}$O₄Si, TEOS) and hydrogen mixture by hot-filament chemical vapor deposition (HFCVD) method. The structures and quality of as-deposited diamond films are characterized with field-emission scanning electron microscopy (FESEM) and Raman spectroscopy. The abrasion ratio and the adhesive strength of as-deposited diamond films are evaluated by copper wire drawing tests and ultrasonic lapping tests, respectively. The results suggest that diamond films with small grain size and high growth rate can be obtained due to the mutual effects of boron and silicon impurities in the gas phases. The results of ultrasonic lapping tests show that diamond films doped with boron and/or silicon can bear the severe erosion of the large diamond powder. Diamond films peeling off within the reduction zone of the drawing dies cannot be observed after testing of 2h. The abrasion ratio of boron and silicon-added diamond films is five times that of diamond films without any addition. Adding boron and/or silicon in the diamond films is proved to be an efficient way to obtain high-adhesive-strength and high-abrasion-resistance diamond-coated drawing dies.

An Al–Cr composite alloyed layer composed of an Al enriched layer, a Cr enriched layer and a transition layer from the surface to the bulk along the cross-section was deposited on a 45# steel substrate by composite technology, where Cr was deposited using double glow plasma surface metallurgy (DGPSM), and Al was then implanted by ion implantation (IIP) to achieve higher micro-hardness and excellent abrasive resistance. The composite alloyed layer is approximately 5$\mu$m, and as metallurgical adherence to the substrate. The phases are Al₈Cr₅, Fe₂AlCr, Cr${}_{23}$C₆, Cr (Al) and Fe (Cr, Al) solid solution. The wear resistance tests were performed under various rotational speed (i.e. 280, 560 and 840r/min) with silicon nitride balls as the counterface material at ambient temperature. The Al–Cr composite alloyed layer exhibits excellent wear resistance when the speed is 280r/min with a friction coefficient as low as 0.3, which is attributed to Al₈Cr₅ in the Al implanted layer that withstands abrasive wear. Better wear resistance (friction coefficient: 0.254) at 560r/min is resulted from the formation of a high micro-hardness zone, and an oxidation layer with lubrication capacity. In addition, the composite alloyed layer suffers severe oxidative wear and adhesive wear at 840r/min due to the increment of the frictional heating. When compared to the 45# steel substrate, the enhanced wear resistance of the Al–Cr composite alloyed layer demonstrates the viable method developed in this work.

The NiO/YSZ anode materials of SOFCs with Bi₂O₃ as sintering aids were successfully prepared by dry-pressing process. The effects of Bi₂O₃ content on the sintering properties of NiO/YSZ anode materials were studied, including the effects on the density, open porosity, weight loss, phase composition, microstructure, mechanical strength and electrical conductivity. In particular, the weight loss, relative density and bending strength of the sintered NiO/YSZ ceramics increased with the increase of Bi₂O₃ content while the open porosity decreased gradually. The density of the NiO–YSZ ceramics with 6wt.% Bi₂O₃ sintered at 1250${}^{\circ }$C could reach that of the ceramics without Bi₂O₃ sintered at 1400${}^{\circ }$C. For Bi₂O₃ concentration higher than 6wt.%, phase transformation of zirconia from monoclinic to cubic structure occurs, causing volume change and microcracks in the anode materials. Therefore, the optimum adding amount of Bi₂O₃ is 6wt.%, which can reduce the sintering temperature to 1250${}^{\circ }$C. The ceramics with 6wt.% Bi₂O₃ have relatively high bending strength and low sintering temperature. This is of great significance for improving the performance of the anode and cutting the cost.

In this paper, superhydrophobic surfaces are developed on polycrystalline copper using a combination of mechanical and chemical treatments by shot peening, dislocation etching and stearic acid treatment. The key point in this combined approach is the fabrication of a dislocation forest by shot peening. These sites were dissolved by etching, and hierarchical structures were fabricated. When these etched surfaces are treated by stearic acid, which has low surface energy, they become superhydrophobic with contact angle more than 150${}^{\circ }$. Because of the superior properties and low costs involved with this method, it is expected to be widely used in the industry to fabricate superhydrophobic surfaces.

Novel bismuth nanoparticle-modified mesoporous carbon (MPC) was successfully prepared on a glassy carbon electrode (Bi@MPC/GCE) for the adsorptive stripping voltammetric determination of nickel by complexing with dimethylglyoxime (DMG). The presence of MPC obviously improved the properties of Bi particles like the electron transfer ability, particle size and hydrophicility, important parameters to achieve preferable analytical performances of Bi@MPC/GCE toward Ni(II). The best electrochemical behaviors of Bi@MPC/GCE was obtained for the stripping determination of Ni(II), compared with electrodes individually modified with Bi and MPC. The synergic effect between metallic Bi and ordered MPC (forming a 3D array like Bi microelectrodes) made major contribution to such improved electrochemical properties of Bi@MPC/GCE for Ni(II) sensing. The good linear analytical curve was achieved in a Ni(II) concentration range from 0.1$\mu$M to 5.0$\mu$M with a correlation coefficient of 0.9995. The detection limit and sensitivity were calculated to be 1.2nM ($S∕N=3$) and 1410$\mu$AmM${}^{-1}$cm${}^{-2}$, respectively. The new method was successfully applied to Ni(II) determination in soybean samples with recoveries higher than 99% and proved to be a simple, efficient alternative for Ni(II) monitoring in real samples.

Materials composed of single or a few pure/modified graphitic layers can be easily synthesized using chemical methods. In the present work, nanocomposites of reduced graphene oxide (RGO) with zinc oxide (ZnO) have been prepared via in situ reduction of graphite oxide (GO). X-ray diffraction spectra (XRD) confirmed the coexistence of RGO and ZnO crystal planes. The XRD results were complimented by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. Incorporation of ZnO phase into the graphitic layers has been identified with the help of scanning electron microscopy (SEM). Incorporation of ZnO into graphitic layers has enhanced the thermal and optical characteristics of RGO but turned out with the reduced electrical conductivity. These nanocomposites illustrated fascinating antimicrobial activities against human pathogens E. coli and S. aureus.

This work explores the structural, surface and optical properties of NiO films grown on Si, GaAs, PET and glass substrates. The NiO films were deposited on these substrates under same conditions by using radiofrequency (RF) magnetron sputtering of NiO target at 100${}^{\circ }$C. The structural study by X-ray diffraction (XRD) showed the existence of (200) and (220) oriented NiO peaks on all the substrates. The preferred orientation of NiO films on Si, GaAs and glass was along (200) plane whereas the film grown on PET was observed to be oriented along (220) plane. The crystallite size of NiO on GaAs was the largest among the other substrates. The RMS surface roughness on PET was higher as compared to the other substrates. The band gap of NiO films grown on glass and PET was estimated from UV–Vis transmittance spectroscopy whereas the UV–Vis reflection spectroscopy was carried out to find out the band gap of NiO grown on GaAs and Si substrates. The band gap of NiO on PET was higher than its band gap obtained on other substrates. The results obtained on properties of NiO films on different substrates were correlated with each other.

Glassy carbon electrodes (GCE) were modified by carboxylated graphene oxide/lanthanum with various concentrations of hexadecyl trimethyl ammonium bromide (CTAB), and the treated electrodes, called CTAB/GO-COOLa/GCE, were prepared for the detection of uric acid (UA) and dopamine (DA) by using the differential pulse voltammetry (DPV) and the cyclic voltammetry (CV). The results show that the modified electrode’s electrocatalytic activity could be affected by several factors in the examination, they are the pH value of the system, the main content of CTAB, various concentrations and rates of scan. With a combination of carboxylated graphene oxide/lanthanum and CTAB, the resulted CTAB/GO-COOLa/GCE sensors showed preeminent selectivity and obvious catalytic property toward the electro-oxidation of UA and DA. In optimized conditions, the response of the CTAB/GO-COOLa/GCE electrode for DA was linear in the region of 0.03–500.0$\mu$M with detection limits of 0.036$\mu$M $\mathrm{\text{(S/N}}=3)$. Two linear response ranges for the determination UA were obtained from ranges of 1 to 200$\mu$M and 200 to 1300$\mu$M with a detection limit of 0.42$\mu$M $\mathrm{\text{(S/N}}=3)$. Moreover, the refined electrode was used in the inspection of DA and UA in real samples of serum and urine successfully, displaying its potential application of real samples involved in electroanalysis.

This paper addresses the squeezed flow of third grade fluid between two parallel disks. Heat transfer in present flow is characterized by Cattaneo–Christov theory. Thermal relaxation time effects on the boundary layer is examined. Suitable transformations are invoked for a system of ordinary differential equations. Convergent series solutions are thus obtained using homotopic approach. Influences of different parameters on the velocity and temperature profile are discussed.

This work aimed to study the feasibility of using iron-contaminated graphite as an adsorbent for As(V) removal from water. The adsorbent was prepared by grinding graphite concentrate with steel ball. The study was performed through the measurements of adsorption capacity, BET surface area and XPS analysis. The experimental results showed that the iron-contaminated graphite exhibited significantly high adsorption capacity of As(V). The higher the iron contaminated on the graphite surface, the higher the adsorption capacity of As(V) on the material obtained. It was suggested that the ion-contaminated graphite was a good adsorbent for As(V) removal.

In this work, the oblique angle dependence of Seebeck coefficient ($S$) on the Zn polycrystalline thin film was demonstrated. The electrical conductivity and Seebeck coefficient are investigated in the temperature range between 25${}^{\circ }$C and 100${}^{\circ }$C. We observed a notable increase of $S$ and a decrease in electrical conductivity, and the power factor ($S^2\sigma$) increased more than two times at $\theta =80^{\circ }$. Obliquely deposited metallic films have shown great potential to achieve much higher thermoelectric figure of merits than their normal counterparts. Here, the thermoelectric properties of Zn Polycrystalline crystalline thin film have been investigated. The thickness and deposition angle dependence of its related thermoelectric parameters have been studied.

ZnO:Mg nanocomposite formation by two-step laser ablation in deionized water is analyzed. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis were employed to obtain infrared spectra, crystalline structures, optical absorption spectra, morphology and spatial composition of the prepared nanocomposite. The FTIR result shows that bonds at $\sim$480cm${}^{-1}$ and 900cm${}^{-1}$ correspond to Zn–O and Mg–O stretching modes. The XRD pattern observed the hexagonal wurtzite of ZnMgO phase at $2\theta =34.31^{\circ }$ and 34.76${}^{\circ }$. SEM image shows a flower-like hierarchical structure with a full array about 2$\mu$m. The absorption spectra demonstrate that a band gap of nanocomposite increases as the Mg content increases.

This paper investigates the impact of heat input and post-weld aging behavior at different temperatures on the laser paper welded maraging steel grade 250. Three different levels of heat inputs were chosen and CO₂ laser welding was performed. Aging was done at six different temperatures: 360${}^{\circ }$C, 400${}^{\circ }$C, 440${}^{\circ }$C, 480${}^{\circ }$C, 520${}^{\circ }$C and 560${}^{\circ }$C. The macrostructure and microstructure of the fusion zone were obtained using optical microscope. The microhardness test was performed on the weld zone. Tensile tests and impact tests were carried out for the weld samples and different age-treated weld samples. Fracture surfaces were investigated by scanning electron microscopy (SEM). Microhardness values of the fusion zone increased with increasing aging temperature, while the base metal microhardness value decreased. Tensile properties increased with aging temperature up to 480${}^{\circ }$C and reduced for 520${}^{\circ }$C and 560${}^{\circ }$C. This was mainly due to the formation of reverted austenite beyond 500${}^{\circ }$C. XRD analysis confirmed the formation of reverted austenite.

RF magnetron-sputtered CrCuN coatings with ultra-low Cu content (0.53–2.1 at.%) were deposited using Cr${}_{97}$Cu₃ target (at.%) by changing the substrate negative bias from 0V to $-$200V. The CrNiN coatings with different nickel contents (0, 2.92 and 8.79 at.%) were sputtered by different-component Cr–Ni alloy targets (Cr, Cr${}_{95}$Ni₅ and Cr${}_{80}$Ni${}_{20}$, in at.%). The effect of bias and alloying element content on coating toughness was investigated by nanoindentation. The results show that all the coatings have unsatisfied toughness because of $H$/$E^{*}<0.1$. With increasing bias, the toughness of CrN and CrCuN coatings improves basically due to grain refinement caused by high bias effect. Under the same bias, although CrCuN coatings have finer grains, their toughness is still lower than that of CrN coatings because of inadequate copper coverage degree as a result of ultra-low copper content. On the contrary, once there is an appropriate alloying element content of 2.92 at.% Ni, the toughness of CrNiN coatings increases with the nickel content due to relatively higher Ni coverage degree.

Pure nanocrystalline SnO₂ films were grown on a clean glass substrate by using sol–gel dip coating and chemical bath deposition (CBD) techniques for gas sensor applications. The films were annealed in air at 300${}^{\circ }$C, 400${}^{\circ }$C, and 500${}^{\circ }$C for 60min. The deposited films with a thickness of approximately 300 $\pm$ 20 nm were analyzed through X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. Results revealed that the films produced by dip coating exhibited a tetragonal rutile structure and those produced by CBD showed a tetragonal rutile and orthorhombic structure. The crystalline sizes of the films produced by dip coating annealed at 300${}^{\circ }$C, 400${}^{\circ }$C, and 500${}^{\circ }$C were 8, 14, and 22.34 nm and those for CBD films at these temperatures were 10, 15, and 22 nm, respectively. AFM and SEM results indicated that the average grain size increased as annealing temperature increased. The transmittance and absorbance spectra were then recorded at wavelengths ranging from 300nm to 1000nm. The films produced by both the methods yielded high transmission at visible regions. The optical band gap energy of dip-coated films also increased as annealing temperature increased. In particular, their optical band gap energies were 3.5, 3.75, and 3.87eV at 300${}^{\circ }$C, 400${}^{\circ }$C, and 500${}^{\circ }$C, respectively. By comparison, the energy band gap of CBD-prepared films decreased as annealing temperature increased, and their corresponding band gaps were 3.95, 3.85, and 3.8eV at the specified annealing temperatures. The films were further investigated in terms of their sensing abilities for carbon monoxide (CO) gas at 50 ppm by measuring their sensitivity to this gas at different times and temperatures. Our results demonstrated that dip-coated and CBD-prepared films were highly sensitive to CO at 200${}^{\circ }$C and 250${}^{\circ }$C, respectively.

The corrosion inhibition effect of synthesized 1,3-benzothiazole at very low concentrations on 410 martensitic stainless steel in 3MH₂SO₄ solution was studied through potentiodynamic polarization and weight loss measurements. The observation showed that the organic compound performed effectively with average inhibition efficiencies of 94% and 98% at the concentrations studied from both electrochemical methods due to the inhibition action of protonated inhibitor molecules in the acid solution. The amine and aromatics functional groups of the molecules active in the corrosion inhibition reaction were exposed from Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopic analysis. Thermodynamic calculations showed cationic adsorption to be chemisorption adsorption, obeying the Langmuir adsorption isotherm. Images from optical microscopy showed an improved morphology in comparison to images from corroded stainless steel. Severe surface deterioration and macro-pits were observed in the uninhibited samples.

The study of soil colloids is essential because the stability of soil colloidal particles are important processes of interest to researchers in environmental fields. The strong nonclassical polarization of the adsorbed cations (Na${}^{+}$ and K${}^{+})$ decreased the electric field and the electrostatic repulsion between adjacent colloidal particles. The decrease of the absolute values of surface potential was greater for K${}^{+}$ than for Na${}^{+}$. The lower the concentration of Na${}^{+}$ and K${}^{+}$ in soil colloids, the greater the electrostatic repulsion between adjacent colloidal particles. The net pressure and the electrostatic repulsion was greater for Na${}^{+}$ than for K${}^{+}$ at the same ion concentration. For K${}^{+}$ and Na${}^{+}$ concentrations higher than 50mmol L${}^{-1}$ or 100 mmol L${}^{-1}$, there was a net negative (or attractive) pressure between two adjacent soil particles. The increasing total average aggregation (TAA) rate of soil colloids with increasing Na${}^{+}$ and K${}^{+}$ concentrations exhibited two stages: the growth rates of TAA increased rapidly at first and then increased slowly and eventually almost negligibly. The critical coagulation concentrations of soil colloids in Na${}^{+}$ and K${}^{+}$ were 91.6mmol L${}^{-1}$ and 47.8mmol L${}^{-1}$, respectively, and these were similar to the concentrations at the net negative pressure.