Papers by Keyword: XPS

Abstract: The hydrolytic lignin derivatives have been prepared via its physical activation (high-temperature heating in vacuum) followed by chemical modification (fluorination). The obtained products were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the graphitized product of thermal activation up to 1000 °C at a low rate of < 2 °C/min under high vacuum shows an enhanced specific surface area (215 m²/g), that makes its potentially useful as sorbent, catalytic substrate or electrode material. To clarify the potentialities of hydrolytic lignin derivatives for energy storage and conversion, the electrochemical system with metallic lithium anode was applied. The galvanostatic discharge of battery at a current density of 100 μA/cm² between 3.0 and 0.5 V shows that the specific capacity of thermally activated derivative is equal to 845 mA·h/g, while the untreated lignin yields only 190 mA·h/g. The improve of the electrochemical performance of product originates from its graphitization, increasing electronic conductivity, and, possibly, enhanced ability to adsorb of oxygen. The fluorination of both the lignin and its thermally activated form results in higher operating voltage of battery, as seems, due to the involvement of fluorine bound to carbon in electrochemical process.

Abstract: Percolation networks of electrically connected nanographenes are the promising structures for solving the problem of the transfer of their peculiar quantum properties to the macroscopic level. In this work we report the results of investigations, conducted with using a set of complementary physical methods, on the origin, structural motifs and properties of such networks revealed in thermally reduced graphene oxide films. The presence of zero modes, which may be π-electronic states stabilized at the zigzag edges of network elements, has been established.

Abstract: In this work, we investigated interfacial properties of InP, which is a typical group III-V compound used for semiconductors, by using a chemical-treated metal oxide semiconductor (MOS) capacitor. The interfacial properties of InP is more affected by interface state density than the surface roughness and is greatly affected by In₂O₃ in particular. Additionally, we evaluated In₂O₃ growth during 24-hour rinsing and air exposure and found that In₂O₃ on an InP surface grows larger during rinsing than during air exposure. To reduce In₂O₃, the rinse needs to be optimized.

Abstract: This paper presents possible deviations between advanced (performance-based or ‘realistic’) and simplified calculations of initiation and spread of a fire in a factory for the production of insulation panels made of extruded polystyrene (XPS). Simplified procedures, discussed in the paper, are founded on several assumptions regarding the evolution of the fire. They are normally based on a great deal of practical experience of the fire designer and/or reports of eyewitnesses of similar fires. Provided that the latter are easily accessible, such procedures are fast and can provide a reasonably good first impression regarding the expected fire as the paper shows. However, they also almost inevitably lead to temperatures which are somewhat underestimated in the most intense fire phase but are overestimated in the decaying phase. Hence, for a more reliable calculation, advanced procedures are recommended.

Abstract: In this study, bioleaching experiments, X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) were conducted to investigate the intermediates and surface species of bornite leached by mesophilic mixed bacteria of Leptospirillum. ferriphilum and Acidithiobacillus. caldus. Bioleaching experiments results showed that the mixed bacteria induced higher redox potential and significantly increased the copper extractions. In the presence of mesophilic mixed bacteria, bornite bioleaching was not inhibited by jarosite and S₈. The evolution of intermediates during bornite dissolution was proposed: Cu₅FeS₄→ Cu₉Fe₉S₁₆→CuFe₂S₃→CuS→Cu²⁺, the presence of mesophilic mixed bacteria accelerated the dissolution process. XPS spectra showed that the Cu was existed as Cu(I) species in different period, and confirmed that the presence of polysulfide and jarosite.

Abstract: In the present study, we investigated the bioleaching of arsenopyrite with or without pyrite by moderate thermophiles. In both chemical leaching and bioleaching, the addition of pyrite decreased the leaching rate of arsenopyrite. The arsenic speciation and minerology changes in the residues were analysed by X-ray Absorption Near Edge Structure (XANES) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and powder X-ray Diffraction (XRD). The XANES analysis showed no detectable arsenopyrite in the final residues from the experiments without pyrite. However, there was still 21.7% of arsenic species presented as arsenopyrite after bioleaching, when the initial arsenopyrite/pyrite ratio was 1:5. The XPS analysis revealed there was only As(V) on the surface of most of the residues, except on one chemically leached sample where As(III) was found.

Abstract: In this research, the possibility of applying multilayer multielement super hard coatings by Cathodic Arc is investigated. More precisely the structure of the coating consisting of quaternary CrAlSiN and ternary AlSiN layers is examined by electron microscopy, X-ray diffraction and X-ray photoelectron microscopy analytical methods. The as-deposited samples were found to have distinguishable layers. The CrAlSiN layer is characterized by an extra sequence of repeated nanolayers. The AlSiN layer consisted of nanosized grains having a preferential orientation. Finally the surface layer was found to contain a solid solution of CrxAl1-xN, while Si3N4was identified only by XPS most probably due to its amorphous structure.

Abstract: Normally-on MOSFETs were fabricated on 3C-SiC epilayers using high temperature (1300 °C) wet oxidation process. XPS analysis found little carbon at the MOS interface yet the channel mobility (60 cm²/V.s) is considerably low. Si suboxides (SiO_x, x<2) exist at the wet oxidised 3C-SiC/SiO₂ interface, which may act as interface traps and degrade the conduction performance.

Abstract: To characterize the properties of the as-grown Al_xGa_1-xN material for producing high property Al_xGa_1-xN photocathode in ultraviolet (UV) detection, the Ar⁺ sputtering and X-ray photoelectric spectroscopy (XPS) scan are performed. XPS spectra indicates that although processed with chemical solutions, Al_xGa_1-xN still contains large amount of carbon and oxide on the surface, which can be completely removed by Ar⁺ sputtering within few minutes. Ga3d and Al2p curves show that there are other compounds of Ga and Al on the surface but both become very concentrated when sputtering continues. The proportion of Al increases and that of Ga decreases gradually from surface to AlN bulk, which testify the graded band gap profile of the Al_xGa_1-xN sample. There is always a very slight amount of oxygen in the AlN layer, which is regarded as native element during material growth. At the interface of AlN and sapphire, an abrupt transition appears which can influence the properties of the Al_xGa_1-xN photocathode when it works with the transmittance mode

Abstract: La_0.67Sr_0.33MnO₃ (LSMO) films were prepared on SrTiO₃ single-crystal substrates by the pulsed laser deposition method. X-ray photoelectron spectra (XPS) were measured for the LSMO films as-prepared and annealed in vacuum, respectively. Multiple peak fitting for Mn 2p_3/2 XPS spectra shows that Mn³⁺ and Mn⁴⁺ proportionally decrease on the surface of the LSMO film annealed in vacuum compared with the as-prepared film. And the saturation magnetization (M_s) slightly decreases. Analysis indicates that a small amount of Mn²⁺, as surface defects of LSMO films, hardly changed after vacuum annealing. The total of Mn³⁺, Mn⁴⁺ and the low-binding energy peak (LEP) remains unchanged before and after annealing in vacuum, which suggests that LEP should be related with Mn³⁺ and Mn⁴⁺ when the magnetic properties are considered.