Surface free energies of electroless Ni–P based composite coatings

Surface free energy of a solid surface gives a direct measure of intermolecular interactions at interfaces and has a strong influence on adsorption and adhesion behaviour. However few data are available for the surface free energies of electroless Ni–P based composition coatings. In this paper, the electroless Ni–P, Ni–P-surfactant, Ni–Cu–P, Ni–P–PTFE and Ni–Cu–P–PTFE composite coatings were prepared under various coating conditions. The chemical compositions, surface morphology and thickness of the coatings were measured using an energy dispersive X-ray microanalysis (EDX), a scanning electron microscope (SEM) and a digital micrometer respectively. The contact angles of water, diiodomethane and ethylene glycol on the coatings were measured automatically using dataphysics OCA-20 contact angle analyser. The surface free energy of the coatings and their components (e.g. dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the incorporation of surfactant or PTFE particles into Ni–P matrixes has a significant influence on the surface free energy of the coatings, while the incorporation of copper into Ni–P matrixes has no significant influence on the surface free energy of the coatings.     

Alloy formation at the Ni–Al interface for nickel films deposited on Al(110) surfaces

Alloy formation at the Ni–Al interface for thin nickel films deposited on Al(110) surfaces has been studied using high-energy ion scattering/channeling (HEIS) and X-ray photoelectron spectroscopy (XPS). For nickel atoms deposited at room temperature on Al(110), a large amount of nickel–aluminum intermixing occurs at the interface. For the first two monolayers (ML) of deposited nickel, an NiAl-like compound is formed. The intermixing continues with a different rate, forming an Ni₃Al-like compound for nickel coverages from 2 to 8 ML, at which point a nickel metal film begins to grow on the surface. Nickel atoms deposited at 250°C on the Al(110) surface exhibit no surface compound formation, but diffuse up to 400 Å into the aluminum substrate. Interatomic potentials based on the embedded-atom method (EAM) are used in a Monte Carlo approach to simulate the evolution of the Ni–Al(110) interface as a function of the nickel coverage. The calculated ion-scattering yields and X-ray photoelectron intensities from nickel and aluminum atoms in these simulated interfaces are in good quantitative agreement with the experimental results. The simulations show a high-density Ni–Al alloy forming at the Al(110) surface which apparently inhibits outward diffusion of aluminum, leading to the more nickel-rich alloy and finally nickel film growth. The ion-scattering simulations show an unusually large amount of backscattering occurring below the Ni–Al(110) interface, apparently associated with defocusing of the incident ion beam.     

ArF-excimer-laser annealing of 3C–SiC films—diode characteristics and numerical simulation

We fabricated Schottky barrier diodes using 3C–SiC films deposited on Si(1 1 1) by lamp-assisted thermal chemical vapor deposition and annealed with an ArF excimer laser. Improvement in both the reverse current and the ideality factor was obtained with 1–3 pulses with energy densities of 1.4–1.6 J/cm² per pulse. We solved a heat equation numerically assuming a transient liquid phase of SiC. The calculated threshold energy density for melting the surface was 0.9 J/cm². The thermal effects of Si substrate on SiC film were also discussed. The experimental optimum condition was consistent the numerical simulation.     

Water and oil wettability of hybrid organic–inorganic titanate–silicate thin films deposited via a sol–gel route

Hybrid organic–inorganic titanate–silicate thin films were deposited on silicium wafer via a sol–gel route. Hybrid sols were formulated by mixing an inorganic titanium alkoxide solution with solutions of hybrid organic–inorganic silicon alkoxides partially substituted with non-hydrolysable alkyl chains. Three organo-silicate precursors were used to introduce methyl, octyl, or hexadecyl chains in the oxide network. Physico-chemical and morphological properties of derived hybrid films have been studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry, and atomic force microscopy. Contact angle measurements have also been performed to assess the water and mineral oil wettability of hybrid films. Wettability properties of these films are discussed with respect to physico-chemical and morphological features. It is shown that increasing the fraction and length of alkyl chains in the oxide network conjointly increases water and oil contact angles measured on such hybrid films.     

Sol–gel based anti-reflection coatings on wedged laser rods using a spin coater

Anti-reflection (AR) sol–gel coatings are deposited on wedge glass optics for high-power lasers using spin coating technique. Characterization of these coatings on BK-7 glass substrates is carried out in terms of thickness profile across the surface, thickness variation w.r.t. wedge angle, and its effect on AR coating reflectivity, at different wedge angles from 1° to 7°. Results of the study are used to deposit AR coatings on inclined end faces of Nd:phosphate glass laser rods.     

Structural and electrochemical characterization of Ni nanostructure films on steels with brush plating and sputter deposition

Layers of nickel were coated on low carbon steel substrates applying both brush plating and DC magnetron sputtering techniques. X-ray diffraction analysis showed a preferential orientation along (1 1 1) for both sputter deposited and brush plated Ni nanostructure coatings. The sputtered Ni film showed better crystallinity as observed from XRD compared to brush plated Ni film on steel on account of the favorable conditions for grain growth in sputtering. SEM analysis indicated that the coatings are very regular without pores, with columnar structure for the sputter deposited Ni coatings. AFM was also applied for surface topography examination. Microhardness value was found to be higher for sputtered Ni film. Corrosion performance of these nanostructured Ni coatings were evaluated using electrochemical techniques and observed that the corrosion resistance of brush plated Ni film sample was significantly higher than that of the sputtered Ni film.     

Sol–gel preparation and characterisation of dense proton conducting Sr3CaZr0.5Ta1.5O8.75 thin films

Dense proton conducting Sr₃CaZr_0.5Ta_1.5O_8.75 films (1.25 μm, with grain size in the 200–400 nm range) were deposited, using the sol–gel method, on Al₂O₃–8%Y₂O₃-stabilised ZrO₂ plates. The obtained gels were characterised by differential and thermogravimetric thermal analysis (DTA–TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of a study of the structural and electrical properties of Sr₃CaZr_0.5Ta_1.5O_8.75 films deposited on the mentioned substrates are presented herein. The structural data for the gels and films were compared with those obtained for the same material prepared by solid state synthesis. Electrical properties of the sandwich-type structure were investigated by AC impedance conductivity measurements at different temperatures, in both dry and wet 5% H₂/Ar atmospheres. A careful analysis of the impedance spectra for this complex structure was performed, using a model with a series of five electrical circuits, having resistance and capacitance coupled in parallel. The specific responses observed in the impedance spectra were assigned to the corresponding substrate and layer contributions. A significant improvement, by an order of magnitude, in the electrode response was observed in the presence of the interleaving Sr₃CaZr_0.5Ta_1.5O_8.75 proton conducting layer, between the electrode and electrolyte. This enhancement is lost at temperatures above that at which the Sr₃CaZr_0.5Ta_1.5O_8.75 dehydrates and its protonic conductivity diminishes. Considering the structural and electrical characterisation results, these Sr₃CaZr_0.5Ta_1.5O_8.75 sol–gel derived films have a potential use for proton conducting electrolyte or intermediate layer in fuel cells.     

Tuning the phase transition of ZnO thin films through lithography: an integrated bottom‐up and top‐down processing

An innovative approach towards the physico‐chemical tailoring of zinc oxide thin films is reported. The films have been deposited by liquid phase using the sol–gel method and then exposed to hard X‐rays, provided by a synchrotron storage ring, for lithography. The use of surfactant and chelating agents in the sol allows easy‐to‐pattern films made by an organic–inorganic matrix to be deposited. The exposure to hard X‐rays strongly affects the nucleation and growth of crystalline ZnO, triggering the formation of two intermediate phases before obtaining a wurtzite‐like structure. At the same time, X‐ray lithography allows for a fast patterning of the coatings enabling microfabrication for sensing and arrays technology.     

Growth, structural and optical properties of CdxZn1−xS thin films deposited using spray pyrolysis technique

Cd_xZn_(1−x)S (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) thin films were deposited by the chemical spray pyrolysis technique using a less used combination of chemicals. Depositions were done at 573 K on cleaned glass substrates. The composition, surface morphology and structural properties of deposited films were studied using EDAX, SEM and X-ray diffraction technique. XRD studies reveal that all the films are crystalline with hexagonal (wurtzite) structure and inclusion of Cd into the structure of ZnS improved the crystallinity of the films. The value of lattice constant ‘a’ and ‘c’ have been observed to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm, respectively. The band gap of the thin films varied from 3.32 to 2.41 eV as composition varied from x = 0.0–1.0. It was observed that presence of small amount of cadmium results in marked changes in the optical band gap of ZnS.     

The mechanism of PEO process on Al–Si alloys with the bulk primary silicon

This study focuses on mechanism of ceramic coating on Al–Si alloys with bulk primary Si using plasma electrolytic oxidation (PEO) technology. Al–Si alloys with 27–32%Si in weight were used as substrates. The morphologies, composition and microstructure of PEO coatings were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray system (EDX). Results showed that the PEO process had four different stages. The effect of bulk Si is greatly on the morphology and composition of coatings at first three stages. Anodic oxide films formed on Al and Si phases, respectively. When the voltage exceeded 40 V, glow appeared and concentrated on the localized zone of interface of Al and Si phase. Al–Si–O compounds formed and covered on the dendrite Si phase surface, and the coating on bulk Si, which was silicon oxide, was rougher than that on other phase. If the treatment time was long enough, the coatings with uniform surface morphologies and elements distribution will be obtained but the microstructure of inner layer is looser due to the bulk Si.     

Effect of hydrazine and hydroxylaminophosphate on chrome plating from trivalent electrolytes

The influence of hydrazine and hydroxylaminophosphate on solution chemistry and quality of chromium coatings deposited from Cr(III) formate-urea baths has been studied by FT-IR, XPS and AFM. The results have shown that hydrazine and hydroxylaminophosphate differently affect Cr plating. The morphology of Cr deposits obtained in the formate-urea electrolytes is a typical nodular structure with a less nodular and smoother fine-grained structure of Cr obtained in the presence of hydroxylaminophosphate. Hydrazine, in contrast, worsened the quality and lowered the hardness of the deposits. The current efficiency of chromium increases in the presence of both hydrazine and hydroxylaminophosphate. This may be related with the ability of these ligands to reduce the CrH content in the growing Cr deposit. The data obtained suggest that hydroxylaminophosphate improves the stability of the active [Cr(carbamide)_n(H₂O)_6−n]³ complexes providing good quality of the deposits and prolonged working lifetime in the formate-urea bath.     

Aluminium oxide thin films prepared by plasma-enhanced chemical vapour deposition

Thin films of aluminium oxide have been deposited on glass, quartz, Si(100), steel, nickel, and aluminium by plasma-enhanced chemical vapour deposition (PECVD) using aluminium acetylacetonate (Al(acac)₃) as precursor. The deposits are hard (up to 2370 HK) and show good adherence to the substrates. The influence of various experimental parameters on deposition rate, film composition and hardness has been studied. The bias turned out to be the most effective parameter.On leave from Beijing Solar Energy Research Institute, Beijing, P.R. China     

Electrodeposition of nanostructured Ni(1−x)Mnx alloys films from chloride bath

NiMn alloys were electrodeposited from chloride bath with various Mn content up to 10 at.%. The effect of bath composition and current density on Mn content of electrodeposited thin films was explored. A maximum of 9.8 at.% Mn content in deposited films was obtained at optimized current density of 40 mA/cm² and MnCl₂/NiCl₂ concentration ratio of 2.5 in the bath. The morphology and crystal structure of deposits were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The constituents in the films were determined by energy dispersive X-ray spectroscopy (EDS). It was revealed that the structure of NiMn coatings had an average grain size of about 17 nm. It was found that the deposits exhibited FCC structure with prefer orientation of <111>. The soft magnetic properties of electrodeposited films were measured by vibrating sample magnetometer (VSM). It was observed that the magnetic parameters such as coercivity and saturation magnetization were decreased with increasing of Mn in the deposits.     

Deposition of refractory coatings by LCVD

TiC layers have been successfully deposited locally on tool steel specimens and real small industrial tools in order to improve their mechanical and corrosion properties. TiC films have been produced by the pyrolytic laser chemical vapour deposition technique, using a low power RF-modulated CO₂ laser and a gas mixture of TiCl₄/CCl₄/H₂/H/Ar. The surface temperature was monitored by a microcomputer-based feedback loop system that was specially developed and integrated to control the laser. SEM, EDX, XRD and TEM analysis showed that close stoichiometric TiC (fcc structure, lattice constant a=4.2Å) was deposited in the films with nanocrystalline structure. The microhardness of the coatings was in the range 2500–3200HK. Furthermore, an ArF excimer laser was used to enhance the deposition rate.     

Optical characteristics of nickel and boron carbonitride films in Si(100)/Ni/BC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> structures

The optical characteristics of nickel films deposited on Si(100) substrates by vacuum thermal evaporation have been studied. The thickness and optical constants of the films are determined using monochromatic zero ellipsometry, while the inverse problems are solved within the three-layer optical model of the samples. It is shown that thermal annealing leads to a change in the optical constants of nickel films in the heating-temperature range of 500–900°C. Boron carbonitride layers deposited on silicon substrates with a nickel sublayer are analyzed within multilayer optical models, which make it possible to determine the refractive index and absorption coefficient distributions along the thickness of the synthesized Si(100)/Ni/BC _x N _y structure.     

Laser surface alloying of an electroless Ni–P coating with Al-356 substrate

Laser surface alloying of an electroless plating Ni–P coatings on an Al-356 aluminium alloy was carried out using a 1-kW pulsed Nd:YAG laser. The microstructure, chemical composition and phase identification of the alloyed layer were determined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD), respectively. It was shown that laser surface treatment produced a relatively smooth, crack-free and hard surface layer. The hardness of the surface significantly increased due to the formation of the uniformly distributed fine Ni–Al intermetallic phases. The corrosion behaviour of the surface alloyed specimens in 3.5% NaCl solution at 23 °C was also determined by electrochemical techniques. The laser-alloyed surface showed an improved corrosion and pitting potential compared to the substrate as well as the plated Ni–P coating.     

Raman spectroscopy of the PTCDA–inorganic semiconductor interface: evidence for charge transfer

In the present work, we investigate the vibrational properties of a PTCDA molecule with an additional positive or negative charge using density functional theory. With respect to the calculated vibrational frequencies of the neutral molecule, some modes in particular in the region 1200–1800 cm⁻¹ show large shifts. These calculations are compared with resonant Raman spectra of sub-monolayer PTCDA films on passivated semiconductor surfaces, both before and after annealing the deposited films at elevated temperatures (350 °C). Independent of the sample treatment, the sub-monolayer Raman spectra correspond quite well to reference spectra obtained for thicker films, and we find no evidence for the strong shifts predicted in the calculations for the charged species. From the small changes in the mode frequencies it can be concluded that any charge transfer present involves significantly less than one elementary charge.     

Physical and electrochemical characterizations of Ni-SiO2 nanocomposite coatings

Advances in materials performance often require the development of composite system. In the present investigation, SiO₂-reinforced nickel composite coatings were deposited on a mild steel substrate using direct current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of the Ni and Ni-SiO₂ nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of SiO₂ particles in the Ni nanocomposite coating on the microhardness and corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon oxide particles were obtained. The preferred growth process of the nickel matrix in crystallographic directions <111>, <200> and <220> is strongly influenced by SiO₂ nanoparticles. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~23 nm for electrodeposited nickel and ~21 nm for Ni-SiO₂ nanocomposite coatings. The crystallite structure was fcc for electrodeposited nickel and Ni-SiO₂ nanocomposite coatings. The incorporation of SiO₂ particles into the Ni matrices was found to improve corrosion resistance of pure Ni coatings. The corrosion potential (E _corr) in the case of Ni-SiO₂ nanocomposite coatings had shown a negative shift, confirming the cathodic protective nature of the coating. The Ni-SiO₂ composite coatings have exhibited significantly improved microhardness (615 HV) compared to pure nickel coatings (265 HV)     

Polymerization of Langmuir–Blodgett films of diacetylenes

Monolayer and multilayer assemblies of Langmuir–Blodgett films of 10–12 pentacosadyinoic acid (12–8 diacetylene) were deposited on flat gold substrates. Micrometre-size features were patterned by polymerization of the films by using standard electron beam lithography. Polymerized areas on a monolayer and bilayer, as well as multilayer films, were examined by scanning electron microscopy, atomic force microscopy and resonant Raman spectroscopy. It was established that polymerized areas on a monolayer and bilayer LB film adhere onto the gold substrate after development. The exposure curve, sensitivity, contrast and resolution of the polymer have been determined by using atomic force microscopy and correlated with the deposition conditions and molecular parameters. Stresses induced in the organic film during polymerization lead to an in-plane buckling of the micrometre-size polymer structure. A simple self-consistent theory was developed to predict critical strain and critical length of buckling. The observed effect of buckling of polymers might open an avenue for a wide range of important practical applications in the area of nanomechanical engineering.     

微波ECR磁控溅射制备SiNx薄膜的XPS结构研究

利用微波电子回旋共振等离子体增强非平衡磁控溅射法在不同N₂流量下制备无氢SiN_x薄膜.通过X光电子能谱、纳米硬度仪等表征技术,研究了不同N₂流量下制备的SiN_x薄膜的化学键结构、化学键含量、元素配比及各元素沿深度分布.研究结果表明,N₂流量是影响SiN_x薄膜化学键结构、元素配比、元素延深度分布等性质的主要因素.在N_{2关键词： x}')" href="#">SiN_x 磁控溅射 XPS 化学键结构