Composition Of Surface Layer Research Articles

Layer-by-layer composition and structure of silicon subjected to combined gallium and nitrogen ion implantation for the ion synthesis of gallium nitride

The composition and structure of silicon surface layers subjected to combined gallium and nitrogen ion implantation with subsequent annealing have been studied by the X-ray photoelectron spectroscopy, Rutherford backscattering, electron spin resonance, Raman spectroscopy, and transmission electron microscopy techniques. A slight redistribution of the implanted atoms before annealing and their substantial migration towards the surface during annealing depending on the sequence of implantations are observed. It is found that about 2% of atoms of the implanted layer are replaced with gallium bonded to nitrogen; however, it is impossible to detect the gallium-nitride phase. At the same time, gallium-enriched inclusions containing ∼25 at % of gallium are detected as candidates for the further synthesis of gallium-nitride inclusions.

Pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium

The results from investigating the pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium are presented. It is shown that variations in the elemental and phase composition of surface layers, their microscopic characteristics, and their mechanical properties as a function of implantation time are not monotonous but follow certain patterns. The possibility of interpreting the obtained data in terms of surface modification by metallic clusters with at least ~100 atoms generated in the gas of metal atoms evaporated from cathode spots is discussed.

Measurements of deuterium retention and surface elemental composition with double pulse laser induced breakdown spectroscopy

Estimating the tritium amount retained in the plasma facing components and their surface layer composition is of crucial importance for ITER. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique suitable for in situ measurements of both these quantities. For improving its sensitivity, the double pulse (DP) variant can be used, instead of the standard single pulse (SP). In this work Mo samples coated with 1.5–1.8 μm thick W–Al (as a proxy for Be) mixed layer, with co-deposited deuterium were analyzed under vacuum (∼5 × 10−5 mbar) by SP and DP LIBS, showing enhancement of the spectral intensity for the latter. Calibration free method was applied to the LIBS data for getting the elemental concentration of W and Al. Results are in satisfactory agreement with those obtained from preliminary, ion beam analysis measurements. Deuterium concentration was tentatively estimated by accounting for the intensity ratio between Dα and nearby WI lines.

Enhanced corrosion resistance of magnesium alloy by a silane-based solution treatment after an in-situ formation of the Mg(OH)2 layer

A novel organic–inorganic Mg(OH)2/silane surface layer has been developed for corrosion protection of AZ31 magnesium alloy. The results of electrochemical impedance spectroscopy (EIS), the immersion tests, Fourier-transform infrared spectroscopy (FTIR) and sellotape tests showed that the Mg(OH)2/silane-based composite surface layer possessed excellent corrosion resistance and very good adhesion due to the formation of Si–O–Mg bond between Mg(OH)2 layer and silane layer. Electrochemical impedance spectroscopy tests results indicated that for the long-term corrosion protection of AZ31 the increase of the curing temperature improved the impedance of the composited layer when the curing temperature was lower than 130°С. However, the impedance of the composited layer deceased when the curing temperature was more than 130°С due to the carbonization of the silane layer.

Failure analysis of screw propellers and increase of fail safety by surface modification with multicomponent materials with shape memory effect

Based on the failures analysis of screw propellers we defined quantitative characteristics of the damage. It is shown that most failures are related to the cracks formation and corrosion-erosion lesions. To increase fail safety and prolong product life cycle,we suggested forming a composite surface layer by means of multicomponent materials with shape memory effect (SME) by high-velocity oxy-fuel spraying in a single technological cycle. We supplied the results of stress-strain state (SSS) numerical studies of a screw propeller with nanostructured composite surface layer. Experimental studies of surface-modified samples for fatigue strength, wear resistance, corrosion resistance in seawater confirmed increase in performance characteristics.

Increase in fatigue life of steels by electron-beam processing

Increase in fatigue life (by 3.5 times) of steels of different structural classes has been determined. By methods of transmission diffraction electron microscopy the variation of structure, phase composition and defective substructures parameters of material surface layer at different scale levels (from micro to nano) and the suppression of processes contributing to the formation of regions being the potential site of submicrocracks’ formation has been analyzed.

Formation of alpha and beta tantalum at the variation of magnetron sputtering conditions

Nano- and microdimensional surface layers of α and β tantalum on flat NiTi, Ti, glass, etc. substrates were created. Structure and composition of samples were defined by SEM, AES and x-ray diffractometry. With increase in deposition time surface layer thickness not linearly increases. The transitional layer provide high adhesion of a surface layer to a substrate. Irrespective of summary sputtering time the β phase is formed in the beginning and at sputtering time more than 20 min on it α tantalum is deposited, while temperature remains below 150°C. Keywords: composite materials, surface layer, tantalum, alpha and beta phase, nitinol, corrosion resistance.

High precision surface protection of Al-based alloy parts using laser micro cladding

Laser cladding is a well-known technique for wear protection coating tasks. Modern equipment for laser cladding enables material to be deposited with a lateral resolution of about 100 μ m and to produce high precision surface coating on small size parts. In this paper laser micro cladding process was investigated to produce wear protective coatings on Al-based alloy surface. Al-matrix composite (AlSi30) surface layers with thickness in the range 15–600 μ m were formed on AlMgSi0,5 alloy surface by laser micro cladding. The influence of laser cladding parameters (powder mass flow, vertical increment etc.) and layers number on quality of the deposited coatings was investigated. The homogeneous and free of pores and cracks coating microstructure was produced. The influence of the laser cladding parameters and layers number on functional characteristics of the deposited coatings (e.g. hardness, abrasive wear resistance and electrical conductivity) was investigated. It was found that hardness and wear resistance of the coatings increased with the decrease of powder mass flow. The technological possibility of AlSi30 wear protective layers production on surface of AlMgSi0,5 alloy with roughness up to Ra 1,2 μ m and microhardness up to 300 HV0,05 using laser micro cladding technology was demonstrated.

Surface layer composition of titania produced by various methods. The change of layer state under illumination

The comparative analysis of experimental data over titanium dioxide powders prepared by various ways under ambient air is carried out. The results over TiO2 prepared by high-temperature heating of anatase, produced by burning of titanium micro particles and grinding of rutile crystal are used for that comparison. Water and carbon dioxide were the main products released from the surface of the titania powders. It was found that under UV irradiation absorbed by titania, in absent oxygen, water effectively reacts with lattice oxygen of titanium dioxide.

Formation Structural Phase Gradients in Rail Steel During Long-Term Operation

The paper presents results of the structural and phase analysis of the surface layer composition in the type R65 rail steel in its original state and after long-term operation. It is shown that long-term operation of rail steel is accompanied by its structural and phase modification at a depth of not less than 2 mm. The structural elements are detected that can be stress concentrators.

The Assessment of a Material Life Cycle Based on an Analysis of Fracture Surfaces after Fatigue Failure

The service life of machine components exposed to cyclic loading below a yield point is a very significant factor for the assessment of material properties. One of the methods of enhancing material resistance to the initiation and course of a fatigue process is changing the chemical composition of the material surface layer. The paper is concerned with the prolongation of the life cycle of military vehicles machine components by means of a new technology based on the combination of chemical-heat (plasma nitriding) treatment and heat treatment with emphasis put on the increase in the fatigue strength and service life (resistance to corrosion) of originally soft-annealed steel ČSN 412061. The new technology allows reducing the probability of limit state occurrence in a component thus optimising financial means of the Armed Forces of the Czech Republic.

In English

Nanoporous b-cyclodextrin-containing silicas which differ in functional substituents of wide edge of attached cyclic oligosaccharide molecules (alcohol, bromoacetyl, thiosemicarbazidoacetyl groups) were synthesized. Сhemical composition of surface layer of organosilicas and their sorptional parameters were determined using IR spectroscopy, isotherms of nitrogen ad-desorption, elemental, chemical and thermogravimetric analyses. Ranges of thermal and chemical stability of synthesized b-cyclodextrin-containing silicas were defined; a method of organosilicas regeneration was proposed. Activation energies of water removal from the inner cavities of β-cyclodextrins and from the surface of functional organosilicas were calculated. Distribution and selectivity coefficients for sorption of mercury(II), copper(II), lead(II), cadmium(II), and zinc(II) cations were computed.

Evaluation of the microstructure and wear behaviour of AA6063-B4C/TiB2 mono and hybrid composite layers produced by friction stir processing

Friction stir processing (FSP) was used to produce mono and hybrid surface composite layers of aluminium matrix containing B4C and TiB2 particles. For this purpose the AA6063 was used as the base material. Different fractions of milled B4C and in situ TiB2–10 wt.%Al composite powder produced by mechanical alloying were incorporated into the matrix by FSP. The effect of different ratios of TiB2 and B4C reinforcing particles on the microstructure and wear resistance of surface layers was studied. Microstructural evaluation of the samples was conducted by optical microscopy and field emission scanning electron microscopy (FESEM) of the cross-sections of surface composite layers. Microhardness testing was conducted across the cross-sections of FSPed samples to obtain hardness profiles and pin on disk dry sliding wear test was conducted on FSPed samples. The results showed that the incorporation of B4C and TiB2 reinforcing particles to the surface increased the hardness and wear resistance of composite layers in comparison with FSPed AA6063 alloy. Moreover, 100%TiB2 surface composite layer exhibited the highest hardness and best wear behaviour compared to other fractions.

Composition and Microstructure of Surface Layers Produced by Ion Beam Assisted Deposition of Metals from a Pulsed Arc-Discharge Plasma onto Aluminum Substrates

Composition and Microstructure of Surface Layers Produced by Ion Beam Assisted Deposition of Metals from a Pulsed Arc-Discharge Plasma onto Aluminum Substrates

Effect of Chemical Exploitation Preparation on the Tribological Properties of CuSn10 Bronze within the Friction Process

The paper presents results of tribological properties of the kinematic pair: X210Cr12 steel / CuSn10 bronze, lubricated within the friction process by engine oil SAE 20W/40, and by the same lubricant modified by chemical exploitation preparation. Research of tribological properties were carried out using the tester T-05 (type tester roll - block). Tests have been carried out in two stages. In the first order - friction force, wear of the kinematic pair and the temperature of the friction area have been determined. The objective of the second phase was to micro roentgen spectral analysis of the surface friction zone. On the basis of these studies, the analysis of the elemental composition of the surface layer in the track wear have been made. The modification purposefulness of lubricant SAE 20W/40 by chemical exploitation preparation has been shown.

Modification of corrosion and tribological properties of 316L stainless steel by cathodic plasma electrolytic deposition of zirconia

Purpose – This paper aims to study the deposition of ZrO2 on 316L stainless steel surface using cathodic plasma electrolytic deposition (CPED) technique in potassium hexafluorozirconate (K2ZrF6) electrolyte solution to promote its corrosion and tribological properties. Design/methodology/approach – Plasma electrolytic oxidizing (PEO) technique is commonly used to form zirconium dioxide (ZrO2) on various substrates. But, in this paper, cathodic type of this technique (CPED) was used. Findings – Composition of the surface layer was analyzed by X-ray diffraction (XRD) and the formation of ZrO2 on the substrate was confirmed. Scanning electron microscope (SEM) was used to observe the unique morphology of the surface layer. The corrosion resistance of the coated surface was investigated by electrochemical methods involving cyclic voltammetery in Ringer’s solution. The treated sample showed a better pitting resistance. Pin-on-disk wear tests revealed that the friction coefficient of the coated sample is lower than that of the substrate. Also, it was shown that hardness and roughness of the coated sample increased after plasma electrolytic treatment. Originality/value – This paper considers the CPED of ZrO2 coating on 316L stainless steel. Some recent research works with ZrO2 coating have been prepared by PEO. There is limited or no record on the study of ZrO2 coatings by CPED process. In this study, the effort has been made to prepare a zirconia (ZrO2) coating on the stainless steel substrate through cathodic plasma electrolytic process under 200 V. Due to the excellent wear resistance, ZrO2 may be used as a high resistant and protective coating on stainless steels, which are widely used in industries and biomedical applications.

Effect of Ceramic Particles on Microstructure and Mechanical Properties of Aluminium Surface Composite Fabricated Using Friction Stir Processing

Friction stir processing (FSP) is a novel technique used to fabricate surface composites. This investigation is an attempt to made Al/Al2O3 and Al/SiC surface composite using FSP and compare the mechanical and metallurgical properties influenced by the types of reinforcement particles. Two plates were grooved with 0.8 mm in width, 5 mm in depth and 100 mm in length in the middle of the aluminium plate using wire EDM and compacted with Al2O3 and SiC powder. The FSP was carried out automatically on an indigenously built FSW machine at tool rotational speed of 1200 rpm, processing speed of 60 mm/min and axial force of 10 kN. The optical and Scanning Electron microstructures are precisely revealed the homogeneous distribution of Al2O3 and SiC particles in the stir zone of surface composite layer (SCL). The microhardness was measured across the cross section of SCL layers of Aluminium and Aluminium with SiC and Al2O3. The higher microhardness was obtained in Aluminium with SiC and Al2O3 composites fabricated by FSP. This is because of the higher hardness value of SiC particles than Al2O3 particles.

Silicate anodic coatings on aluminum containing oxides of cobalt and/or copper and/or cerium and their activity in CO oxidation

Coatings on aluminum alloy containing one or several crystalline oxides of cobalt, copper, and cerium deposited in different sequences have been obtained by a combination of methods of plasma electrolytic oxidation and impregnation followed by annealing. It has been established that the composition of surface layers and the catalytic activity of composites depend on the sequence of deposition of active components on the substrate. Cu2+, Cu+, Co3+, Ce4+, and Ce3+ are present in the surface and subsurface layers. All the studied composites are characterized by catalytic activity in the reaction of oxidation of CO into CO2. Of the studied composites, the following are most active: CexOy/CuO/SiO2 + Al2O3/Al, CexOy/Co3O4/CuO/SiO2 + Al2O3/Al, and CexOy/CuO/Co3O4/SiO2 + Al2O3/Al.

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.

Ion Beam Induced Modifications of Biocompatible Polymer

Ion beam bombardment has shown great potential for improving the surface properties of polymers. In this paper, the ion beam-polymer interaction mechanisms are briefly discussed. The main objective of this research was to study the effects of H-ion beam on physico-chemical properties of Ultra-high-molecular-weight polyethylene (UHMWPE) as it is frequently used in biomedical applications. UHMWPE was bombarded with 65 keV H-ions to fluences ranging from 1x1014–2x1016 ions/cm2. Changes of surface layer composition produced by ion bombardment of UHMWPE samples were studied. The hydrogen release and oxygen uptake induced by ion beam bombardment were determined by Nuclear reaction analysis (NRA) using the 1H(15N, αγ)12C and Rutherford backscattering spectrometry (RBS), respectively. Tribological and hardness properties at the polymer near surface region were studied by means of friction coefficient and micro-hardness testers, respectively. Wettability of the bombarded surfaces was determined by measuring the contact angle for distilled water. The obtained results showed that the ion bombardment induced hydrogen release increases with the increasing ion fluence. An important effect observed, was the rapid oxidation of samples, which occurs after exposure of bombarded samples to air. These effects resulted in important modifications of the surface properties of bombarded material such as change of friction coefficient, hardness and improved wettability.