Chemical Composition Of Surface Layer Research Articles

Green corrosion inhibitors for drilling operation: New derivatives of fatty acid-based inhibitors in drilling fluids for 1018 carbon steel in CO2-saturated KCl environments

Corrosion of the oilfield drilling equipment can considerably affect its drilling effectiveness, service life, and operation safety as well as the surrounding environment. In this study, inhibition effects of three eco-friendly fatty acid-based inhibitors, Polyethylene glycol-2 oleamide (PEG-2 oleamide), Glycerol myristate (GM) and Glycerol linoleate (GL), in emulsion-based drilling fluids against corrosion of carbon steel were investigated. The inhibitors were characterized by Fourier transform infrared (FT-IR) spectroscopy and CHNS–O analysis. Effects of the inhibitors on corrosion of the steel were evaluated by means of electrochemical measurements of open circuit potential (OCP) and potentiodynamic polarization as well as electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectrophotometer (XPS) were employed to study morphology and the chemical composition of surface layer adsorbed on the metal surface. The study demonstrates remarkable performance of the green inhibitors especially PEG-2 oleamide, which shows an inhibition efficiency of 99.7%. The high inhibition capability results from a formed protective layer that blocks corrosive ions to attack the steel surface. First-principles calculations and molecular dynamics simulation were performed, which reveal chemical bonding between the inhibitors and iron surface, and stronger intermolecular attraction in the adsorbed film of, e.g., PEG-2 oleamide, which renders the PEG-2 oleamide–induced film particularly durable.

Devising criteria for the authenticity of historical cold weapons based on X-ray fluorescence analysis of their surface

This paper reports the results of studying the chemical composition of the surface of 4 objects of cold weapons of the 19th and early 20th centuries, made of iron – bayonet knives and sabers. This makes it possible to establish the signs of authenticity of cold weapon samples made of iron in that chronological period. An authentic procedure has been proposed for examining the chemical composition of the surface of historical objects of cold weapons by rubbing the samples with cotton wool swabs and their subsequent investigation. This makes it possible to explore objects of cold weapons, whose size is large, as well as simplify the very procedure for studying objects of historical and cultural value. Using the X-ray fluorescent chemical analyzer Expert Mobile, chemical elements were found at the surface of samples of cold weapons made of iron. The presence of such elements is the result of the process of re-crystallization and self-purification of metal during a long history of its life. Elements found in almost every rubbing sample were identified: calcium, ferrum, zinc, cuprum, and chlorine. The studies of cold weapons samples testify to the heterogeneity of the composition of patina formations on their surface, which confirms the authenticity of ancient objects. In addition, the studies have shown a difference in the chemical composition of surface layers of different parts of individual samples of antique cold weapons, which may indicate different times or different technology for their manufacture. The fluorescence spectra of the obtained rubbing of individual samples of cold weapons were compared with "pure" material, which made it possible to identify elements removed from the surface of objects. The study results are important indicators to confirm the authenticity of cultural monuments and the technology of their manufacture in the past.

The Influence of Ion Irradiation on the Morphology and Elemental and Chemical Composition of Surface Layers of Tungsten-Free Hard Alloys

The Influence of Ion Irradiation on the Morphology and Elemental and Chemical Composition of Surface Layers of Tungsten-Free Hard Alloys

Impact of the cycling temperature on electrode/electrolyte interfaces within Li4Ti5O12 vs LiMn2O4 cells

Reliable development of Li-ion Batteries requires a good understanding of the correlation between electrochemical performances and accurate aging interfaces phenomena. The present study focuses on the SEI characterization formed at both electrodes surface in LiMn2O4/Li4Ti5O12 (LMO/LTO) cells, depending on the cycling temperature, which is one of the major stress factors for batteries. LMO/LTO cells were cycled at 25 °C, 40 °C and 60 °C over 100 cycles and the chemical composition of surface layers was investigated by XPS, SAM and ToF-SIMS at the end of the 100th cycles. LTO electrodes are covered by surface layers since the first cycle (inducing an irreversible capacity loss) and the SEI thickness increases with the cycling temperature; moreover, organic (alkyl-carbonates, polyethylene oxides, oxalates) and inorganic species (LiF and (fluoro)-phosphates) of the solid interphase are present in different proportions depending on the temperature; more fluorophosphates are especially observed at 60 °C due to a higher chemical degradation of LiPF6 salt. Finally, small amounts of manganese, heterogeneously spread over the LTO electrode surface, are found at different oxidation states at higher temperatures; for the first time, metallic Mn0 was detected at the LTO surface after cycling at 60 °C which could explain the important capacity loss of the system at this temperature.

Deformation Microstructure and Chemical Composition of Surface Layers of Cu and Al Under Friction in Lubricated Conditions

Friction and wear are accompanied by severe plastic deformation of surface layers similar to that observed under different processes of grain refinement. Recently, a dependence of tribological properties for four fcc metals (Ag, Cu, Ni, and Al) under friction in boundary lubrication was reported. A connection between friction and wear properties and stacking fault energy (SFE) of the studied metals was considered. Steady-state friction is mainly determined by deformation microstructure and chemical interaction in thin surface layers. The objectives of this work are to study the evolution of the microstructure with the depth of plastic deformation after friction of Al and Cu, to evaluate the effect of SFE on microstructure and wear loss, and to analyze the chemical composition of thin surface layers of Cu and Al and their correlation with the microstructure and wear properties of the studied metals. Friction surfaces were examined with a field emission scanning electron microscope. The cross-sectional TEM lamellae were prepared using focused ion beam. Evolution of deformation microstructure and chemistry of surface layers of Cu and Al after friction in the lubricant conditions were estimated by STEM, TEM, and XPS analyses.

Electrochemical corrosion behavior of acid treated strip cast AM50 and AZX310 magnesium alloys in 3.5 wt.% NaCl solution

Abstract The influence of acid treatments on the surface morphology and electrochemical corrosion behavior of strip-cast AM50 and AZX310 alloys have been studied in the present investigation. The alloys were acid treated using H 3 PO 4 (AT-1) , HF (AT-2) and HNO 3 (AT-3) for different treatment durations viz., 60, 300 and 600 s. The acid treatments produced a surface layer consisting of corresponding magnesium salts of the acids and were confirmed from the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). AT-1 treatment produced cracked and network porous morphology for AM50 and AZX310 alloys respectively and AT-3 treatment exhibited dense creaked surface layer formation while AT-2 does not produce any significant change in the morphology. Polarization studies revealed that, the acid treatment significantly altered the corrosion process by altering anodic and cathodic reaction rates of AM50 and AZX310 alloys. The HNO 3 (AT-3) treatment was effective compared to other treatments to control the corrosion rate in the studied treatment conditions. The surface morphology and chemical composition of surface layer produced during the treatment was correlated to explain the corrosion results.

Plasma treatment of the surface of poly(hydroxybutyrate) foil and non-woven fabric and assessment of the biological properties

This paper deals with the poly(hydroxybutyrate) (PHB, foil and fabric) surface modification, characterization and the view of its possible application. The influence of Ar plasma treatment on surface polarity was studied. The changes of the surface parameters were determined immediately after treatment and after annealing related to plasma power, treatment time and heating. These surface-induced differences were studied by different analytic methods: polarity (wettability) was studied by contact angle measurement and surface energy calculation, the surface morphology analysis was done by atomic force microscopy and for determination of chemical composition of surface layer the XPS analysis was used. It was found that after plasma treatment the surface energy of both PHB foil and non-woven fabric significantly increased. PHB non-woven fabric exhibited almost immeasurable contact angle after the plasma treatment. The wettability of both types of PHB substrates after heating was completely inversed. The significant change in roughness of PHB foil was found. After the plasma treatment, the material ablation was determined, which was also connected with surface chemical changes, thus the surface was found to be corrugated. The heating procedure induced “little” crystallites on the surface. Positive effect of PHB foil modifications on surface biocompatibility was confirmed. The biocompatibility was also preserved when thermal stress was applied. Silver nanolayer sputtered on PHB fabric surface induced strong anti-microbial properties.

Investigation of the tribological properties of antifrictional aluminum alloys using sclerometry

The research is devoted to investigating new aluminum alloys that are promising substitutes of expensive bronzes in friction units. A procedure has been proposed for preselecting experimental alloys using sclerometry. Microcutting stress σmc was used as a criterion of score resistance. Two alloys based on the Al-Si-Cu-Sn-Pb system, which are closest to BrOTsS 4-4-17 bronze in their mechanical properties, have been selected from the series of test pieces with various compositions. Tribological investigations of the selected alloys by the shaft-partial bushing scheme have been carried out. The test results verified the possibility of using aluminum alloys for bearings as substitutes of bronze at pressures P ≤ 3 MPa. The structure and chemical composition of surface layers both of source samples and of samples after testing have been studied. The effect of the chemical property of the surface on the tribological properties of investigated alloys has been shown.

High alkali-resistant basalt fiber for reinforcing concrete

Abstract Basalt glasses and fibers with zirconia content in the range from 0 to 7 wt% were obtained using ZrSiO 4 as a zirconium source. Weight loss and tensile strength loss of fibers after refluxing in alkali solution were determined. Basalt fiber with 5.7 wt% ZrO 2 had the best alkali resistance properties. Alkali treatment results in formation of protective surface layer on fibers. Morphology and chemical composition of surface layer were investigated. It was shown that alkali resistance of zirconia doped basalt fibers is caused by insoluble compounds of Zr 4+ , Fe 3+ and Mg 2+ in corrosion layer. Mechanical properties of initial and leached fibers were evaluated by a Weibull distribution. The properties of basalt fibers with ZrSiO 4 were compared with AR-glass fibers. The performance of concrete with obtained fibers was investigated.

Surface of porous silicon under hydrophilization and hydrolytic degradation

Analysis of the IR absorption spectra is used to trace changes in the chemical composition of surface layers of mesoporous silicon crystals during the course of their hydrophilization via oxidation in hydrogen-peroxide solutions and as a result of indirect, by intermediate bromination, and direct nucleophilic substitution of bound hydrogen with a hydroxyl. The spontaneous process of atomic rearrangement with the transfer of oxygen atoms from adsorbed OH groups to lower-lying atomic layers of the crystalline skeleton, which yields Si-H bonds on its surface: -Si-Si-OH→-Si-O-Si-H, is revealed. The sequence of elementary processes that facilitate the hydrolytic degradation of porous silicon in weakly alkaline media is considered. The role played by the deformation of chemical bonds in a porous crystal in promoting the hydrolysis of silicon is noted. It is shown that the surface modification of porous silicon via bromination and subsequent treatment in water makes it possible to substantially increase the rate of its hydrolytic degradation in weakly alkaline solutions that are similar in pH values to biological fluids.

Characterization of oxygen and argon ion flux interaction with PET surfaces by in-situ XPS and ex-situ FTIR

The effects of low (2.5, 0.2 keV) energy reactive oxygen ion bombardment and argon ion bombardment on poly(ethylene terephthalate) thin film (PET) surface chemical composition were studied. PET films have a high potential as a material for biomedical and electrical industries. The source of ions was an ECR Ion Gun with settable acceleration voltages. PET films were sputtered by ion bombardment for variable process time and the modified films were investigated by in-situ X-ray Photoelectron Spectroscopy (XPS) and ex-situ Fourier transform infrared spectroscopy (FTIR). The significant changes in the chemical composition of surface layers were quantitatively studied by XPS. The ion bombardment scissions the chains in PET film surface layers. Selective sputtering of oxygen atoms from PET surface was observed when argon ion flux used. The 0.2 keV and 2.5 keV argon ion decreased O/C ratio from 0.37 to 0.25, 0.04 respectively. This phenomenon is responsible for the creation of carbon-rich up 96 at.% surface layer and the oxygen in ester bonds is detached first. The oxygen 2.5 keV ion bombardment had similar effect as argon ion bombardment; the ratio O/C was decreased. The ester bond was broken first. But oxygen 0.2 keV ion flux irradiation created an oxygen rich surface; the O/C ratio was in increased from 0.37 to 0.46. The changes in surface conductivity were investigated by shifts in C1s binding energy. Good agreement with atomic concentration of carbon in C–C bonds on the films surface was found. The FTIR analyses identified changes in chemical composition but with no obvious correlation to surface changes. Photons from the ion source irradiating the PET film during ion bombardment probably caused the observed changes in FTIR spectra.

Improvement of titanium alloy for biomedical applications by nitriding and carbonitriding processes under glow discharge conditions.

Although titanium alloys are used in medicine, they present low wear resistance. In this paper we present the results of studies on surface layers produced by nitriding at three different temperatures, and by carbonitriding under glow discharge conditions in order to improve wear resistance, hardness, and to modulate microstructure and chemical composition of surface layers. A cell culture model using human fibroblasts was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that nitrided and carbonitrided surface layers were cytocompatible. Modulation of surface microstructure by temperature in the nitriding process and chemical composition of surface layers by carbonitriding led to differences in cellular behaviour. Cell proliferation appeared to be slightly reduced from the 6th day of culture on nitrided surfaces produced at 730 degrees C and 1000 degrees C, however after 12 days of culture, the best growth was on surface layers produced at 850 degrees C. The best viability was observed on the carbonitrided layer. The orientation and shape of the cells corresponded to surface topography. Nitriding and carbonitriding under glow discharge conditions may constitute interesting techniques allowing the formation of surface layers on parts with sophisticated shapes. They may also permit modulating surface topography in a way improving the features of titanium alloys for various applications in medicine.

Combined chemical and bacterial leaching of ultrafine ground chalcopyrite

The changes in surface properties and the leaching of chalcopyrite CuFeS 2 after ultrafine grinding are examined. Surface area measurement and photoelectron spectroscopy (XPS) were used for characterization of the ground samples. A gradual decrease in the particle size, from 32 μm, for as received CuFeS2, to 2 μm, for the sample ground for 60 min, as well as increasing the surface area from 0.23 m 2 g −1 to 2.68 m2 g −1 for equal samples was observed. Analysis of the XPS line of sulphur S2 p electrons has shown the existence of sulphur in three different chemical forms: S 2-, So and S 6+. The ground samples exhibited a greater proportion of higher oxidation states. The samples were chemically preleached with an acid solution of Fe(III) sulphate to an equal conversion degree (ϵ cu = 25%), characterized and subsequently leached by the bacteria Thiobacillus thiooxidans. While the rate of chemical leaching is proportional to the increase in CuFeS 2 surface area, the rate of subsequent bacterial leaching is limited by 15 min grinding. The different behaviour of the samples ground for a long time may be explained by differences in the chemical composition of surface layers.

Ion implantation for cutting tools

The effects of ion implantation on surface contour, microhardness, micro-, and submicrostructures, as well as chemical composition of surface layers of cermet hard alloy tools and high-speed steel tools subjected to ion implantation were experimentally studied. The microhardness change and concentration profiles of implanted elements for the modified layer were measured. It was shown that a thin crystalline structure of carbide grains was formed in this layer and the residual compressive strains increased the fatigue resistance of the tools. Formation of high-strength compounds such as borides, oxides, nitrides, etc. in the surface layer was recorded. Data for many implanted cutting tools were obtained, and wear was compared with that of unimplanted tools. It was found that, in the process of tool degradation, the implanted impurity migrated inward to a distance which exceeds the ion range by an order of magnitude. Wear resistance tests for the implanted tools have shown that the implantation effect depends not only on its mode and the ion beam composition but also on the type of material being machined and on the machining conditions.

The influence of laser carbo-nitro-boriding on metallic surface properties

In this paper, the experimental procedures are presented for carbo-nitro-boroconizing in the #20 steel surface using a C0 2 laser with an output power of 500–2000W modulated CW. We also give a comprehensive analysis about the phase structure, the phase morphology, the distribution profile of the hardness and the resistance to abrasion of the sample after laser treatment. The experimental results indicate that the nicrostructure, the mechanical properties and the chemical composition in surface layer of material basically change.

High-resolution scanning electron microscopy of surface reactions

High-resolution ( < 10 A ̊ ) and high-quality secondary electron (SE) images can be obtained from specimens in the high-resolution imaging position of a HB5 dedicated STEM instrument, in parallel with STEM or SREM imaging and with microdiffraction and microanalysis using EELS. The additional information obtained by the SEM arises from the possibility of revealing three-dimensional morphology and sensitivity to the chemical composition of surface layers. Examples include evidence of a reaction between Pd and MgO substrate and the formation of Ni by reduction of NiO under electron beam irradiation.

Depth profiles of fluoride interactions in hyperfine subsurface layers of dental enamel

Information on chemical reactions of fluoride in topmost surface layers of dental enamel was obtained — in vitro — by analytical techniques with hyperfine depth resolution: electron spectroscopy combined with ion etching for depth profiling the chemical composition of surface layers and interference microscopy for measuring the depth of etching steps. From slightly acidic media, which are typical for some topical fluoride applications, the ion is taken up after apatite degradation in the form of calcium fluoride. Layers mixed of unreacted apatite and of calcium fluoride are formed. There is evidence that the calcium fluoride rich layer with less than 1 μm thickness, may contribute to the observed cariostatic effectiveness of fluorides. Only less attention has been paid till now to this effect.

Characterization of sediment reference materials by x-ray photoelectron spectroscopy

The chemical composition of surface layers of three sediment reference materials, Pond Sediment (Japan NIES CRM No. 2), River Sediment (US NBS SRM 1645) and Estuarine Sediment (US NBS SRM 1646), has been studied comparatively by X-ray photoelectron spectroscopy (XPS). The composition of River Sediment as determined by XPS is peculiar in that the concentration of Cr is much higher but that of Si is much lower than that expected from the bulk composition of the sample. This can be attributed to the structure of the sediment particles, which consist of silica-rich cores covered by surface layers rich in Cr(III). Organic substances are predominant in the surface layers of all three materials, as indicated by the C 1s and N 1s lines. The elemental composition of the surface layers can be reasonably related to the origin of the sediments. The bonding states of some elements in the sediment samples, deduced from the photoelectron binding energies, are briefly discussed.

Chemical composition of surface layers and fatigue resistance of plates of alloy D16

Chemical composition of surface layers and fatigue resistance of plates of alloy D16

On the equilibrium of coexisting sedimentary carbonates

The chemical composition of surface layers on calcite and an overgrowth on dolomite which proved to be calcitic have been determined in solutions of varying amounts of Mg 2+. It is demonstrated from the results that an apparent equilibrium between surface layers of the carbonates and solution is reached. Ca 2+ self diffusion and Na + diffusion coefficients in calcite were determined in order to study the ion mobility in the lattice. These D values suggest that cation replacement does not change the chemical composition of calcite to an appreciable extent. Thus, if recrystallization is absent, equilibrium between solid and solution is approached only at the surface layers or in the overgrowth. The bulk of solid might stay even on a geological time scale.