Surface Review and Letters

Activated carbon fibers supported TiO₂ photocatalyst (TiO₂/ACF) in felt-form was successfully prepared with a dip-coating process using organic silicon modified acrylate copolymer as a binder followed by calcination at 500°C in a stream of Ar gas. The photocatalyst was characterized by SEM, XRD, XPS, FTIR, and BET surface area. Most of carbon fibers were coated with uniformly distributed TiO₂ clusters of nearly 100 nm. The loaded TiO₂ layer was particulate for the organic binder in the compact film was carbonized. According to XPS and FTIR analysis, amorphous silica in carbon grains was synthesized after carbonizing organic silicon groups, and the Ti–O–Si bond was formed between the interface of loaded TiO₂ and silica. Additionally, the space between adjacent carbon fibers still remained unfilled after TiO₂ coating, into which both UV light and polluted solutions could penetrate to form a three-dimensional environment for photocatalytic reactions. While loaded TiO₂ amount increased to 456 mg TiO₂/1 g ACF, the TiO₂/ACF catalyst showed its highest photocatalytic activity, and this activity only dropped about 10% after 12 successive runs, exhibiting its high fixing stability of coated TiO₂.

Advancing and receding contact angles below 5° have been obtained on PMMA surfaces with the implantation of argon and oxygen ions. The ion implantations were performed by means of the Immersion Plasma Ion Implantation (IPII) technique, a hybrid between ion beams and immersion plasmas. Characterization of treated PMMA surfaces by means of XPS and its combination with chemical derivatization (CD-XPS) have revealed the depletion of oxygen and the creation of dangling bonds, together with the formation of new chemical functions such as –OOH, –COOH and C=C. These observations provide a good explanation for the strong increase of the wetting properties of the PMMA surfaces.

Steel wires are implemented in numerous systems and undergo frequent faults due to tribological loading conditions. Therefore, this paper presents a study on the tribological performance of steel wire sliding against different counterfaces, namely, aluminum alloy, stainless steel, and mild steel using a block-on-ring tribo-tester. According to common mechanisms, the tests were performed under 5 N applied load and 0.15 m/s sliding velocity under dry contact condition. Additionally, scanning electron microscopy was used to examine the damaged features on the worn surfaces of the steel wire. Weight loss and friction coefficient results were presented versus sliding distances (0–1.6 km). In general, the results showed that friction coefficient did not reach the steady state due to the transformation of the wear mechanism from adhesive to abrasive mode. Nevertheless, the average of friction coefficient was found to be about 0.7 ± 0.1 for stainless steel and 0.2 ± 0.1 for mild steel. Weight loss gradually increased with the increase of sliding distance. The micrographs of worn surfaces revealed that the contact mechanism was transformed from adhesive to abrasive wear mode as implied by the scars and grooves on the wire surface.

Imidazoline surfactants belong to the category of cationic surfactants. Cationic surfactants are often quaternary nitrogen salts and are widely used both in nonaqueous systems and in applications such as textile softeners, dispersants, and emulsifiers. This study describes the surface-active properties of cationic imidazolinium surfactants synthesized from different fatty acids. Their laundry performance in combination with nonionic surfactants like detergency, foaming property, softening property, rewettability etc., is also emphasized.

A novel dual time-of-flight imaging analyzer has been developed for studies of gas phase reactions and the scattering or desorption of ions and molecules from surfaces. The analyzer is capable of experimentally selecting a two-dimensional slice of particles from a three-dimensional flux without the necessity for deconvolution of the resulting velocity images by the Abel transform. The analyzer operates through ionization of the scattered species and their subsequent flight through a field-free region. This initial flight allows a dispersion according to the species natural velocity distribution. The second time of flight deflects the ions through a right angle and through a flight tube allowing dispersion according to mass or charge before detection. The analyzer offers two modes of operation — the first of these produces a mass spectrum of the desorbing species, the second produces a two-dimensional velocity map of the desorbing species. Trial results using an effusive beam source and acetone as a test gas have demonstrated the operation of the analyzer. The operation of the analyzer has been simulated and optimized to reduce ion flight aberrations. A set of orthogonal two-dimensional polynomial functions have been derived to reduce residual aberrations across a broad range of operating conditions. An upper limit to the temporal resolution of the analyzer has been established and a set of working parameters for low distortion electron beam ionization have been presented.

Wide set of experimental results on binding energy of photoelectrons emitted from P 2p, P 2s, and O 1s core levels has been observed for inorganic phosphate crystals and the parameters were compared using energy differences Δ(O 1s - P 2p) and Δ (O 1s - P 2s) as most robust characteristics. Linear dependence of the binding energy difference on mean chemical bond length L(P–O) between phosphorus and oxygen atoms has been found. The functions are of the forms: Δ (O 1s - P 2p) (eV) = 375.54 + 0.146 · L(P–O) (pm) and Δ (O 1s - P 2s) (eV) = 320.77 + 0.129 · L(P–O) (pm). The dependencies are general for inorganic phosphates and may be used in quantitative component analysis of X-ray photoemission spectra of complex oxide compounds including functional groups with different coordination of P and O atoms.

Titanium nitride (TiN) widely used as hard coating material, was coated on tool steels, namely on high-speed steel (HSS) and D2 tool steel by physical vapor deposition method. The study concentrated on cathodic arc physical vapor deposition (CAPVD), a technique used for the deposition of hard coatings for tooling applications, and which has many advantages. The main drawback of this technique, however, is the formation of macrodroplets (MDs) during deposition, resulting in films with rougher morphology. Various standard characterization techniques and equipment, such as electron microscopy, atomic force microscopy, hardness testing machine, scratch tester, and pin-on-disc machine, were used to analyze and quantify the following properties and parameters: surface morphology, thickness, hardness, adhesion, and coefficient of friction (COF) of the deposited coatings. Surface morphology revealed that the MDs produced during the etching stage, protruded through the TiN film, resulting in film with deteriorated surface features. Both coating thickness and indentation loads influenced the hardness of the deposited coatings. The coatings deposited on HSS exhibit better adhesion compared to those on D2 tool steel. Standard deviation indicates that the coating deposited with thickness around 6.7 μm showed the most stable trend of COF versus sliding distance.

We have investigated the effects of substrate topography on the nucleation and growth behavior of 321 stainless steel (ss) films, introducing textured surfaces into mica substrates by the abrasion treatment. In this study, two groups of samples were prepared at three different sputtering time within 12 s using radio frequency (r.f.) magnetron sputtering and characterized by atomic force microscopy. Good nucleation uniformity has been obtained on the unabraded mica substrates due to the statistical distribution of nucleation sites. Especially, we have already observed an interesting unusual nucleation phenomenon, the island–rim structure on the abraded mica substrates after 4 s, where the island is fractal-like and the rim around the island was only occupied by few grains for nucleation. These ramified islands were located at the wide grooves introduced as predominate nucleation sites. The island–rim structure formed in initial nucleation process is closely associated with x, y velocity components of surface atoms and the distribution of active sites (related intimately to the surface free energy σ and strain energy ε) for nucleation. With the increasing of the sputtering time, voids and overlarge grains have been observed in the island–rim region after the sputtering time of 8 s and 12 s, respectively.

Copper indium diselenide (CuInSe₂) thin films were grown on indium–tin oxide (ITO)/soda-lime glass using a one-step cathodic electrodeposition process at potentials lower than -0.6 V vs SCE, and in the presence of a large excess of In³⁺. The source solution contained CuCl₂, InCl₃, and H₂SeO₃ complexed by citric acid. The concentration of InCl₃ in the electrochemical bath affected the structure, composition, stoichiometric ratio, and morphological properties of electrodeposited films. CuInSe₂ films with a chalcopyrite structure and quite good stoichiometry were directly electrodeposited from a solution of 20 mM InCl₃, 5 mM CuCl₂, and 8 mM H₂SeO₃. Annealing of these CuInSe₂ films in the temperature range from 300°C to 500°C improves their crystallinity and increases their grain size. Good chalcopyrite CuInSe₂ films with a (112) preferential orientation suitable for the production of efficient solar cells are obtained after annealing at 500°C. The formation mechanism of the ternary CuInSe₂ compound during the electrodeposition process was discussed.

Surface hardening of commercially pure titanium by using pulse on pulsed nanocrystalline plasma electrolytic carbonitriding has been studied in this investigation. Coating process has been performed on Triethanolamine-based electrolyte by cooling bath. Nanostructure of obtained compound layer was examined with figure analysis of SEM nanographs. The effects of process variables, i.e., Triethanolamine concentration, electrical conductivity of electrolyte, applied voltage, and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of nanocrystals. Finally the contribution percentage of effective factors of pulsed current was revealed and confirmation run show the validity of obtained results.

The corrosion behavior of the austenitic chromium–nickel steel in different concentrations (0.001, 0.002, 0.005, and 0.01 M) of dimethyl 2-(2–hydroxy phenyl amino)-3-(triphenyl phosphoranilidin) butane dioate (L–OH) in 0.5 M H₂SO₄ was investigated by potentiostatic polarization measurements. The effect of concentration and temperature on inhibition properties was determined. It was found that the presence of L–OH reduces markedly the corrosion rate of steel in the acid solution. The inhibition efficiency increases as the L–OH concentration is increased. Maximum inhibition efficiency (95%) was obtained for alloy in acid solution containing 0.01 M of L–OH. Thermodynamic parameters for adsorption of L–OH are calculated. It was found that the inhibitor is adsorbed on the steel surface and the experimental results are in agreement with Timken's isotherm. Negative values of the free energy of adsorption were obtained indicating the spontaneity of adsorption process. Scanning electron microscopy was done from the surface of exposed sample indicating uniform film on the surface of the alloy.

The performance of electroless (EL) Ni–B coated brass contacts under fretting conditions was evaluated. The contact resistance of EL Ni–B coated brass contact was measured as a function of fretting cycles. The surface profile and wear depth of the fretted zone were measured using laser scanning microscope. The study reveals that EL Ni–B coated contacts exhibit better performance under fretting conditions. However, at conditions which are prone for severe oxidation such as, low frequency (3 Hz) or high temperature (155°C), EL Ni–B coated contacts fail to exhibit a better stability. The quick removal of the oxide film by fretting motion, rapid oxidation of the fresh metallic particles and trapping of the oxidation products in the remaining coating, cause the contact resistance to increase to unacceptable levels at such conditions. The study concludes that EL Ni–B coating is not a suitable choice for connector contacts that could experience fretting under highly oxidizing conditions.

A set of AlN films were deposited by reactive direct current (DC) magnetron sputtering. Films were analyzed with X-ray diffraction and Auger Electron Spectroscopy (AES). There is a correlation between deposition parameters and crystal growth. Depending on the deposition parameters, films can present a hexagonal würzite (P6mm) or cubic zinc-blend (Fm3m) microstructure. Oxygen appears to induce on films a degree of amorphous growth and a distortion of the lattice parameters. For the film with cubic microstructure, AES transitions detected near the surface level at 56 eV and 66 eV were attributed to aluminum-oxide (Al_xO_y), AlN, and metallic Al.

Molecular aggregation and monolayer characteristics of non-amphiphilic p-terphenyl (TP) mixed with either polymethyl methacrylate (PMMA) or stearic acid (SA) at the air–water interface were investigated. The miscibility of the two components was evaluated by measuring and analyzing surface pressure versus area per molecule (π–A) isotherm. Both attractive and repulsive interactions between the sample (TP) and the matrix (PMMA or SA) were observed depending on the composition and microenvironment. TP and PMMA/SA were not completely miscible in the mixed monolayer. Aggregation and phase separation between sample TP and matrix molecule were revealed by UV–Vis absorption spectroscopic studies and confirmed by scanning electron micrograph of Langmuir–Blodgett films.

Aircrafts hold the outstanding mastery of the sky in modern wars, however the laser beam weapons can carry out laser attacking to aircrafts. The purpose of the present paper is to research on a new type laser protective material. Polycarbosilanes (PCS)/divinylbenzene mixtures containing ZrO₂ powders were brushed to the surface of the aluminum alloy plates and then cured at 150°C for 6 h. The PCS-coated plates were ablated by laser for 3 s. The phase identification of as-ablated powders was examined by X-ray diffraction. The results indicated that the as-ablated powders of cured PCS were composed of major phase β-SiC and smaller amounts of free carbon. The PCS composite coating played a certain role of laser ablation resistance. The effect of added ZrO₂ powders on the pyrolysis of PCS-coating under laser ablation is conspicuous.

TiO₂ film deposited on glass was irradiated in air with single-shot KrF excimer laser pulse. The surface roughened as the result of the laser ablation. It is further noted that single-pulse irradiation with fluence ranging from 400 to 1200 mJ/cm² gave rise to protrusion of the irradiated surface above the original surface, which is in contrast to usual expectation that irradiated surface is below the unirradiated surface. The surface protrusion is mainly attributed to the effect of surface tension. At the laser fluence of 1000 mJ/cm², cracks were formed in the irradiated area and severe film exfoliation was observed at the periphery of the irradiated area due to the release of internal stress. With higher laser fluence above 1000 mJ/cm², patches of film were observed to peel off within the irradiated areas. Hydrodynamic ablation is proposed to account for film exfoliation. The observed phenomenon is useful for further understanding how TiO₂ film reacts to strong UV laser irradiation.

Ti and C ions extracted from a metal vapor vacuum arc ion source (MEVVA) were implanted into H13 steel using a masking procedure to ensure reproducible conditions for testing and subsequent analysis. An optical interference microscope and pin-on-disc apparatus investigated the wear and friction characteristics of the steel. The Ti concentration depth profile from Rutherford backscattering spectroscopy was compared with that calculated by a TRIDYN code. It was observed by grazing-angle X-ray diffraction and transmission electron microscopy that carbide of Ti appeared in the doped region. The concentration depth profile and microstructure analysis can serve to illuminate the wear resistance improvement mechanisms of the Ti-implanted steel.

Effects of thermal expansion coefficient (CTE) mismatch on structure and electrical properties of TiO₂ film deposited on Si substrate by ion beam assistant electron beam evaporation have been investigated. Because of a high CTE mismatch between TiO₂ film and Si substrate, microcracks appeared in the TiO₂ film deposited directly on Si substrate after the as-deposited film was annealed at 600°C. In order to decrease the CTE mismatch, TiO₂ film was deposited on Si substrate which was covered by a ZrO₂ thin layer. As a result, crack–free TiO₂ film after annealed at the same temperature was obtained. Meanwhile, corresponding to the crack–free structure, the TiO₂ thin film has more stable dielectric properties and excellent I–V characteristics.

The polar phonon polariton modes in a wurtzite thin-film structure have been theoretically investigated in the present paper. It has been confirmed that there are two types of phonon polariton modes, i.e., the surface phonon polariton (SPP) modes and the confined phonon polariton (CPP) modes in wurtzite thin-film systems. The frequency ranges of the SPP and CPP modes have been discussed in detail. The dispersive equations for the two types of polarition modes are also deduced. Numerical calculations on a GaN thin-film structure reveal that, for a given free wavenumber k_t in x-direction, there are two branches of SPP modes in general. The width of the wurtizte thin film has important influence on the dispersive properties of the polariton modes, especially the width d is small. Our calculated result agrees well with the recent experimental observation in GaN thin-film system. Furthermore, we confirm that the SPP modes observed (at about the frequency of 700 cm^-1) is the low-frequency SPP modes. The CPP modes appear in two frequency ranges of [ω_zT,GaN,ω_tT,GaN] and [ω_zL,GaN,ω_tL,GaN]. There are infinite branches of CPP modes in each range. The low-frequency branch, in contrast to the high-frequency branch, is more dispersive. Moreover, the dispersion of lower-order CPP modes is more obvious than that of higher-order CPP ones. At last, the distribution properties of the electric field components E_x(z) for the SPP and CPP modes are discussed and analyzed. It is found that E_x(z) are either symmetrical, or antisymmetrical. The electric field components for SPP modes are mainly localized at the surfaces. The distribution properties of electric field components are quite analogous to the behaviors of bound electronic states in confined quantum systems. In terms of these features, the CPP modes in the GaN thin film structures are distinguished and labeled.

The radio frequency (RF) argon plasma induced surface modification of paper revealed novel surface characteristics and substantially changed surface topography. It was found that RF-argon glow discharge affects surface properties resulting in photo-degradation and chain-scission mechanism on paper network structure. High-power and extended treatment time caused increasing elemental carbon, while decreasing the oxygen concentration on paper surface. However, increased hydroxyls and the creation of new carbonyl functionalities were verified by trifluoroacetoanhydride and pentafluorophenylhydrazine in vapor-phase derivatization reactions.

In this paper, a kind of novel anatase TiO₂ nanoparticle with single-electron-trapped oxygen vacancies was prepared by hydrothermal treated nanotube titanic acid. The morphology, structure, and properties of the products were characterized by transmission electron microscope, X-ray diffraction, electron spin resonance, and photoluminescence. Photocatalytic decolorization of the Methylene Blue solution was carried out in the visible light region and showed a high photocatalytic activity.

Cadmium sulfide (CdS) nanocrystals are successfully fabricated on glass and silicon substrates at room temperature with low-frequency (460 kHz) inductively coupled plasma assisted magnetron sputtering technique. Both size and shape can be controlled by changing deposition parameters and substrates. Field-emission scanning electron microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction are adopted to measure the properties of CdS nanorods.