Surface Review and Letters

Capacitive deionization (CDI) is a recently developed electrosorption technology for deionization using porous electrodes. The electrode materials play an important role in the efficiency. This paper highlights the current research status of carbon-based materials as the electrode and the adsorption models in the CDI. It includes the types and performances of carbon-based materials and the main influencing factors of the desalination characteristics. Also, operating parameters such as charging voltage, flow rate, concentration of feed solution, treating time and temperature are summarized.

Surface energies of strained Cu surfaces were studied systematically using first-principles methods. Results showed that the strain-stabilization of Cu surface was anisotropic and strongly related to the strain distribution. This strain-induced approach could be used as an effective way to engineer the surface energies of metals.

Si-doped diamond films with various Si concentrations are deposited on WC-Co substrates using HFCVD method, with the mixture of acetone, tetraethoxysilane (TEOS) and hydrogen as the reactant source. A variety of characterizations, including FE-SEM, AFM, Raman, XRD, surface profilometer and Rockwell indentation, are conducted to systematically investigate the influence of Si incorporation on diamond films. As the Si/C ratio from 0% to 5%, the grain size of as-deposited films decreases from 4 μm to about 50 nm, and the surface roughness reduces from Ra ~ 290 nm to Ra ~ 180 nm. Besides, the intensity ratio of I(111)/I(220) varies from 0.57 to 0, indicating the 〈110〉 preferred orientation of the nanocrystalline structure in the 5% doped diamond films. The silicon doping is beneficial for the formation of non-diamond carbide phases in the films, according to the Raman spectra. Moreover, the film adhesion is also improved with the increase of Si/C ratio.

The morphology, composition and mechanism of the non-NBT phase in the Sr-doped NBT [SNBT, (Na_0.5Bi_0.5)_1-xSr_xTiO₃] thin films by chemical method were investigated using XRD, SEM, crystallization analysis and thermodynamics analysis. The results showed that the non-NBT phase is the porphyroblastic grains in the matrix and looks like a plate-shaped polyhedron. The mechanism of the non-NBT phase formation is that the Sr²⁺ and Na⁺ combined with to form initial simple titanate, such as SrTiO₃, Na₂TiO₃, or NBT phase decomposed because of the volatilization of Bi under a higher annealing temperature or longer annealing duration, and then transform into the secondary simple titanates (Sr²⁺,2Na⁺)TiO₃ or (Sr,Na)_xTi_yO_z. Moreover, the NBT phase disappeared for the SNBT films annealing at temperatures higher than 600°C and for 15 min.

The inhibition effect of synthesized N′-(phenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, N′-(4-methylphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides, and N′-(4-methoxyphenylmethylidene)-2-(2-methyl-1H-benzimidazol-1-yl)acetohydrazides on the corrosion behaviour of N80 steel in 15% hydrochloric acid solution was investigated using weight loss, potentiostatic polarization and electrochemical impedance spectroscopy methods. The inhibition efficiency increased as the concentration of the inhibitors was increased. The effect of temperature on corrosion inhibition was investigated by weight loss method and thermodynamic parameters were calculated. Potentiodynamic polarization measurements show that all the three studied inhibitors act as mixed inhibitor. The adsorption of inhibitors on N80 steel surface obeys Langmuir adsorption isotherm. The structure of inhibitors was optimized using semiemperical AM1 method. Theoretical parameters such as the highest occupied molecular orbital (E_HOMO), lowest unoccupied molecular orbital (E_LUMO) energy levels, energy gap (ΔE = E_LUMO - E_HOMO), dipole moment (μ), global hardness (γ), softness (σ), binding energy, molecular surface area and the fraction of electrons transferred (ΔN) were calculated and the adsorption mechanism was discussed. Scanning electron microscopy was used to characterize the surface marphology of the N80 steel.

In this work, we report the formation of In₆Se₇ thin films by laser irradiation of In/Se layered structure. Indium layer was deposited on glass substrates by thermal evaporation on which selenium thin film was grown by chemical bath deposition from an aqueous solution containing 10 ml of sodium selenosulphate (0.1 M), 1.0 ml acetic acid (25%) and 70 ml distilled water during 5 min. The In/Se coated glass substrates were irradiated using a 532 nm continuous laser for 3–5 min. Structure, morphology, optical and electrical properties of the irradiated thin films were analyzed using various techniques. X-ray diffraction analysis showed that the irradiated thin films were In₆Se₇ of monoclinic structure. X-ray photoelectron spectroscopic study on the laser irradiated samples provided uniform relative composition of In and Se in the thin films formed after laser irradiation. The morphology, optical and electrical properties of the irradiated samples were investigated. The optical band gap of the In₆Se₇ thin films was 2.2 eV and also, the thin films were photoconductive.

Nitrogen doped TiO_2-x films have been prepared by using N-ion implantation method. X-ray diffraction patterns of the N-doped TiO_2-x films could be indexed with rutile TiO₂ and Ti₇O₁₃ in structure. XPS measurements revealed a 2.73 atm.% concentration of N atoms in the N-doped films and two N 1 s photoelectron binding energies at 396.3 and 399.9 eV originating from N-doped TiO₂ and N-doped Ti₇O₁₃, respectively. The photocatalytic properties of the N-doped films under visible light have been investigated by degradation of methylene blue solution.

La₂O₃ doped Ni-based coatings have been prepared by electrospark deposition technique. The effect of La₂O₃ on the microstructure, hardness and wear behavior of the as-prepared Ni-based coatings is investigated by using X-ray diffractometer, scanning electron microscope, wear tribometer and Vickers hardness tester. Results indicates that the microstructure, hardness and wear resistance of La₂O₃ doped Ni-based coatings are effectively improved as compared to the undoped one, and the coating with the addition of 2.5 wt.% La₂O₃ shows the optimal improvement effects. The addition of La₂O₃ can reduce the defects, refine grains and increase hardness of the coating, which can inhibit the nucleation and propagation of cracking, consequently resist cutting and fracture during the wear process. Moreover, the addition of La₂O₃ leads to changes in abrasion mechanism of the coatings, and the reasons resulting in different abrasion mechanisms are discussed.

CrCuN films were deposited under different substrate temperatures by direct current (DC) magnetron sputtering. The structure and wear resistance of the films were then studied. The substrate temperature has almost no effect on the film composition, phase constitution and preferred orientation. The CrCuN films have 3 at.% Cu and consist of CrN phases with CrN(200) preferential growth independent of the substrate temperature. But a strong effect of the substrate temperature on the wear behavior is noticed. The film prepared under the substrate temperature of 100°C has the best wear performance. Its friction coefficient and wear rate are 0.1 and 6.6 × 10^-6 mm³/Nm, respectively.

Potentiostatic two step anodizing of titanium utilized for preparation of self organized titania nanotubes arrays with diameter of 150 nm. Then the new alginate method has been applied for incorporation of NiO into the nanotubes. The prepared hybrid materials have been characterized by various methods including field emission scanning electron microscopy, X-ray diffractometry and cyclic voltammetry analyses. The X-ray diffraction patterns of samples were also studied by Rietveld's method. Results showed that the prepared electrode containing anatase, rutile and NiO phases with fraction of 70, 8, and 22%, respectively. It was found that by application of the new method, porous NiO uniformly coated on nanotubes surface and great enhancement of specific capacitance from 0.14 to 3.8 mF cm^-2 could be obtained. The prepared nanocomposites are promising materials for supercapacitance application and also for solar energy harvesting systems.

In this paper, we discuss the formation of ceramic coatings by a combined processing of low-temperature pack aluminizing and oxidation treatment on the surface of X80 pipeline steel substrates in order to improve the corrosion resistance ability of X80 pipeline steel. First, Fe-Al coating consisting of FeAl₃ and Fe₂Al₅ was prepared by a low-temperature pack aluminizing at 803 K which was fulfilled by adding zinc in the pack powder. Pre-treatment of X80 pipeline steel was carried out through surface mechanical attrition treatment (SMAT). Further oxidation treatment of as-aluminized sample was carried out in the CVD reactor at 833 K under oxygen containing atmosphere. After 1 h duration in these conditions, ceramic coating consisting of α-Al₂O₃ was formed by in situ oxidation reaction of Fe-Al coating. Those coatings have been characterized by different techniques including X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscope (EDS), respectively. Ceramic coating shows a dense and uniform microstructure, and exhibits good coherences with X80 pipeline steel substrates. By electrochemical corrosion test, the self-corrosion current density of X80 pipeline steel with as-obtained ceramics coating in 3.5% NaCl solution shows an obvious decrease. The formation of α-Al₂O₃ ceramic coating is considered as the main reason for the corrosion resistance improvement of X80 pipeline steel.

Superhydrophobic cotton fabrics are prepared using silica and titania hybrid sol and hexadecyltrimethoxysilane. The surface morphology of cotton fabrics is characterized by scanning electron microscopy. The water contact angles on the as-prepared superhydrophobic cotton fabrics is 159° when the volume ratio between sodium silicate solution and titania sol is 1:3, and the corresponding cotton fabrics can keep the contact angle of 152° after 10 cycles of home machine washing. Meanwhile the treated cotton fabrics can also keep superhydrophobicity after 60 min of UV light irradiation. These results indicate that the cotton fabrics treated with silica and titania hybrid sol and modified with hexadecyltrimethoxysilane show excellent superhydrophobic stability under washing and UV light irradiation. This paper provides the new notion and beneficial reference for the application of the superhydrophobic cotton fabrics in the future.

Molybdenum thin films were sputter deposited under different conditions of DC power and chamber pressure. The structure and topography of the films were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the films are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The films produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for films produced at high pressure.

In order to improve the wear resistance of the cable bolt and increase its life-time during operation, plasma nitriding was employed to obtain a protective nitriding layer on its surface. The microstructure, phase constitution, microhardness and wear resistance of the nitriding layer were investigated. It was shown that continuous and dense nitriding layers were formed on the surface of the samples. The microhardness of the nitrided sample was enhanced by the formation of nitriding layer, which mainly consisted of Fe₄N and Fe₃N. The mass losses of the nitrided samples were much smaller and the wear rates were almost hundred times lesser than that of the substrate. Plasma nitriding treatment can effectively enhance the wear resistance of cable bolt.