Papers by Keyword: XPS

Abstract: Ethylene propylene diene monomer (EPDM) rubber was exposed to an accelerated thermal aging environment produced by an air-circulating oven for different time periods. The changes of thermal stability and chemical structures of EPDM were monitored by thermo-gravimetric analysis (TGA), Attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS). The results showed that the accelerated thermal aging environment did not obviously affect the thermal stability of EPDM. FTIR and XPS confirmed the formation of hydroxyl, carbonyl and ester groups in the test environment.

Abstract: Titanium dioxide (TiO₂), belonging to the family of transition metal dichalcogenides (together with molybdenum disulfide (MoS₂) and tungsten disulphide (WS₂)), is well known for its solid lubricating behaviour. Thin films of TiO₂ exhibit extremely low coefficient of friction in dry environments, and are typically applied by mixed in oil, grease or impregnated into porous matrix of powdered materials. Current researches in many areas imply the using of different types of nanoparticles in the composition of oily lubricants. Results of these researches upon the friction couples show that nanoparticles contained by lubricant can improve the tribological properties, the friction-wear reduction and the lubrication effect. When nanomaterials are used to improve lubrication effect, the selection of metal is very important. In this paper, the authors chose for investigating the tribological properties of two samples of TiO₂ with the mean diameter of 15 nm (n-TiO₂) and 250 nm (m-TiO₂), under different friction conditions. The tribological properties of TiO₂ nanoparticles mixed in the ecological lubricant oil were investigated using a four-ball tribometer and a block-on-ring tribometer and show the lowering of the friction coefficient in comparison to the lubricant base oil. The finally obtained lubricant is not considered toxic for the environment. The analyses of surface film composition, characterized with the help of X-ray photoelectron spectroscope (XPS) and scanning electron microscopy (SEM) images showed that the deposed nanoparticles form a protective film (TiO₃) allowing for an increase in the load capacity of friction couple. XPS and SEM were used to examine the morphology of the wear track, after the four-ball experiment. The main advantage of the nanoparticles is ascribed to the release and furnishing of the nanoparticles from the valley onto the friction metal surface and their confinement at the interface. The TiO₂ nanoparticles showed lower frictions coefficient and higher wear resistance as compared to the common TiO₂ particles (about 1.5 μm in diameter(c- TiO₂)) on a four-ball machine, which were caused by the microstructure of the protective film and serve as perfect intermediate lubricants between the contact surfaces.

Abstract: This paper describes the effect of oil-immersion treatment on the surfaces of cutting tools. In this study, the ‘oil-immersion treatment’ refers to the modification of the tool’s surface by immersing the tool in a treatment solution and heating under pressure. Our previous study demonstrated that such treatment reduces the wear on cutting tools. In this study, the effect of oil-immersion treatment on a carbide cutting tool was investigated by EPMA (electron probe microanalysis) and XPS (x-ray photoelectron spectroscopy). SEM (scanning electron microscope) and EPMA examination revealed that oil-immersion treatment reduces the amount of cobalt on the tool’s surface and forms sulphur deposits. XPS analysis of the chemical bonds on the surfaces revealed the presence of cobalt sulphide and inorganic carbon. In addition, friction tests showed that the oil-immersion treatment reduces the friction coefficient of the tool.

Abstract: The mechanism of the increased crystallization stability (the difference between glass incipient crystallization temperature and transition temperature) of Sb₂O₃ —doped vanadium phosphate sealing glass investigated by X-ray photoelectron spectroscopy (XPS) is reported in the present study. Experimental results showed that after doping with Sb₂O₃, the rate of bridging oxygen increased while the rate of no-bridging oxygen decreased, and the ratio of V⁴⁺/V_total also increased, too. This two changes led to the break of V=0 bond which is essential for the formation of V₂O₅ crystalline phase, thus inhibited the formation of that crystalline phase and improved glass crystallization stability.

Abstract: ZnO microspheres with complete and perforated morphologies were synthesized by a simple solvothermal method via regulating solvent composition. Material characterization has included XRD, SEM, XPS, Raman spectrum and Brunauer–Emmet–Teller (BET) methods. The introduction of ethanol into the solvent resulted in the morphology change from complete to perforated spheres, meanwhile generated more surface adsorption sites and larger specific surface area as demonstrated by XPS and BET analysis. A possible formation mechanism of ZnO microspheres is proposed to explain the perforation development process. The gas sensing performances of the sensors prepared using the complete and perforated spheres were compared to reveal the positive impact of morphology change.

Abstract: This paper introduces a real case from construction practice illustrating extensive damage to concrete slit drains, followed by the relevant computer simulation. From the computer simulation and lab tests it follows that the failures of concrete slit drains can be easily caused by deformations of the concrete slabs constituting the surrounding multi-layer road system. Thermally-induced expansions and contractions, as well as concrete shrinkage, produce, in non-dilating connection, stress in the link between the multi-layer road system and the lateral walls of the slit drains. The slit drains are highly sensitive even to a very small malfunction of the expansion joints (e.g. clogging of the slit by solid materials), or their bad installation. It is apparent that failures (cracks) in the slits arise even by the slight compression of a slit drain (to the order of tenths of a millimetre). The analysis presented shows the necessity for a careful installation of expansion joints during the placement of the slit drains into the surrounding multi-layer system, which could induce horizontal pressures on the drains. The study is concluded by recommendations for designers.

Abstract: A new gemini surfactant containing long chain alkyl ammonium headgroups have been used as corrosion inhinbitor for copper in 3.5% NaCl solution. The weight loss and electrochemical methods results showed that presence of inhibitor greatly decrease corrosion rate, gemini surfactant acted as an excellent corrosion inhibitor with inhibition efficiency greater than 96% at an optimum concentration of 30 mg·L^-1. X-ray photoelectron spectroscopy reveals that the gemini surfactant molecules adsorb onto the copper surface through the two ammonium head groups (N⁺).

Abstract: A family of TeO₂-based glasses is known to have high third-order nonlinear properties and expected as nonlinear optical devices. In the present study, we fabricated Ag₂O-TeO₂ and Ag₂O-Nb₂O₅-TeO₂ glasses, and estimated their structures and linear/nonlinear optical properties. The main results showed that the absorption-edge of the glasses was shifted to longer wavelength side with increasing Ag₂O content. By Raman spectroscopy, it was found that an increase in Ag₂O content promoted to change TeO₄ to TeO₃/TeO₃₊₁ units. X-ray photoelectron spectroscopy (XPS) revealed the presence of an electronic state of Ag²⁺ ions, which was supposed to have a large influence on the absorption-edge wavelength. In Ag₂O-Nb₂O₅-TeO₂ glass system, the third-order nonlinear susceptibility χ⁽³⁾ increased with increasing Ag₂O content at the expense of Nb₂O₅ content.

Abstract: Carbon based materials have attracted much for its unique surface microstructure and nanomechanical properties among researchers. In this study, the influence of microstructure on the nanomechanical properties of thin carbon based films was studied in detail. For which amorphous Carbon nitride (a-CN) and Titanium incorporated amorphous Carbon nitride (Ti/a-CN) thin films were prepared with a thickness of less than 100 nm using hybrid ion beam deposition technique. The incorporation of Ti into the a-CN matrix greatly modified the sp³/sp² hybridized bonding ratio and it is reflected in the mechanical hardness of Ti/a-CN thin film. Most of the incorporated Ti reacts with carbon and nitrogen to form TiN and TiCN phases respectively. On the other hand, owing to the usage of energetic ion bombardment and the presence of TiN/TiCN phases in the carbon nitride matrix, the Ti/a-CN nanocomposite film shows improved adhesion strength compared to that of pure a-CN film. Overall the presence of hard metallic phase in the amorphous carbon network alters the microstructure and improves the adhesion strength of a-CN films suitable for protective coating applications.

Abstract: Nanostructured manganese oxide films were obtained by electro-oxidation of manganese films electrodeposited at two typical cathodic currents of 65 mA cm^-2 (EDM-65 oxide) and 150 mA cm^-2 (EDM-150 oxide) from sulfate solutions with additives. Obtained Mn oxide films were studied by scanning electron microscope, X-ray photoelectron spectroscopy, cyclic voltammetry and AC impedance. SEM study revealed that the Mn oxide films were mesoporous nanostructures on the EDM-150 oxide surface, while the EDM-65 oxide coating is homogeneous and compact. XPS results indicate that EDM-150 oxide had a higher content of anhydrous Mn oxide and structure water, which means that it had more anhydrous characteristics as compared to EDM-65 oxide. It was shown that porous nanostructured films showed good capacitive behavior for applications in electrochemical supercapacitors. The porous nanostructured films prepared at 150 mA cm^-2 showed higher specific capacitance (SC) compared to the SC of the EDM-65 oxide films. The highest SC of 148 F g^-1 in a voltage window of 0.8 V was obtained in 0.1 M Na₂SO₄ solutions at a scan rate of 25 mV s^-1.