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Based on the widely used wet metal-assisted electroless etching, we develop in this work a novel vapor-phase silver-assisted chemical etching (VP-Ag-ACE) suitable for the elaboration of highly doped p-silicon (Si) nanostructures with strong, visible, and multi-peak photoluminescence (PL) emissions. The lateral and vertical etching rates (LER and VER) were discussed based on the etching mechanism of the VP-Ag-ACE. The antireflective suitability of the vapor-etched layer has been evaluated by a reflectivity measurement and exhibits reflectivity values lower than 3%. The PL emission at both room and low temperatures emissions were deeply discussed and correlated with the structural properties of the Si morphologies and their surface states based on the FTIR results.

• The corrosion phenomenon in the PCHE flow channel is analyzed by coupling oxidation model and corrosion model. • As the lead–bismuth flow rate increases, the time required for oxygen equilibrium of lead–bismuth eutectic decreases. • Corrosion is trend to occur at the sharp corners of PCHE. The Printed Circuit Heat Exchanger (PCHE) is a key component essential for the small modular lead-cooled fast reactors. The corrosive charatersitics of lead–bismuth eutectic towards certain elements in stainless steel needs the surface oxidation processes to mitigate corrosion on structural materials. Hence, it becomes important to conduct a detailed analysis of the oxidation-corrosion characteristics within the heat exchanger. In this study, an oxidation kinetics model is embedded into Fluent to simulate the oxidation-corrosion behavior of a martensitic steel-made straight channel PCHE. Besides, the supercritical carbon dioxide is used as the coolant fluid in this PCHE simulation. According to the simulation result, the severe corrosion zones exist at sharp corners when the fluid flows through straight channels. The growth rate of the oxide layer increases with the increase of inlet flow velocity of the liquid alloy and decreases when the inlet flow velocity of supercritical carbon dioxide decrease. [ABSTRACT FROM AUTHOR]

Fe-based amorphous materials with the superiorities of high efficiency and low Fe sludge secondary pollution can be seen as a potential alternative to Fenton catalysts. However, catalyst deactivation on the catalyst surface hinders the sustainability of high degradation activity. In this study, the degradation capabilities of FeBCCr amorphous alloys in methylene blue (MB) solution by Fenton-like method were explored. The optimum (Fe 81 B 10 C 9) 99 Cr 1 ribbon with a more uniform Fe 3 B-like amorphous structure, which exhibits a thin and easily-peeled oxide layer, provides unique dynamic self-renewing to obtain excellent efficiency and recyclability. The degradation rate with 0.05 g/L (Fe 81 B 10 C 9) 99 Cr 1 ribbon reached 0.248 min−1 and the recyclability reached a charming record of over 90 times with a dosage of 0.1 g ribbon. The activation energy of (Fe 81 B 10 C 9) 99 Cr 1 ribbon (12.97 kJ mol−1) was found to be superior to that of most metallic catalysts. More importantly, the boron-rich film in the interfacial region can both retard further oxidation of iron and provides a channel for electron transmission, which can contribute to the persistence of a highly active microenvironment with more Fe(Ⅱ) sites and highly utilization of H 2 O 2. The limit segmentation method has verified the good performance in both heterogeneous and homogeneous reactions. This study introduces a strategy for designing high-performance non-noble metallic catalysts through cluster structure regulation, which provides a novel Fenton-like amorphous material with long recyclability of high degradation activity for water remediation. • B and C atoms coordination with Cr atoms to promote the formation of a more homogeneous structure. • The more homogeneous structure resulting in a thinner oxide layer to expose more active sites. • An Fe-based amorphous catalyst with excellent recycling performance and stable reaction rate. [ABSTRACT FROM AUTHOR]

The supercritical water-cooled reactors (SWCR) belong to Generation IV of reactors. These reactors have a number of advantages over currently operating WWERs and PWRs. These advantages include higher thermal efficiency, a more simplified unit design, and the possibility of incorporating it into a closed fuel cycle. It is therefore necessary to identify candidate materials for the SWCR and validate the safety and effectiveness of their use. 12Cr ferritic-martensitic (F/M) stainless steel is considered a candidate material for SWCR internals. Radiation embrittlement and corrosion cracking in the primary circuit coolant environment are the main mechanisms of F/M steels degradation during SWCR operation. Here, the stress corrosion cracking (SCC) in supercritical water at 390 and 550 °C of 12Cr F/M steel irradiated by neutrons to 12 dpa is investigated. Autoclave tests of specially designed disk specimens in supercritical water were performed. The tests were carried out under different constant load (CL), temperature 450 °C, and pressure in autoclave 25 MPa. The threshold stress, below which the SCC initiation of irradiated 12Cr F/M steel does not occur, was determined.

Type-II superlattices (T2SLs) are emerging as next-generation materials for infrared detectors. The epitaxial quality of T2SLs is of great importance to the performance of infrared detectors such as dark current and detectivity. Herein, we explore the effect of the native GaSb oxide layer on the surface morphology and crystal quality of InAs/GaSb T2SLs grown with molecular beam epitaxy. The experimental results demonstrate that the thickness of the oxidation layer on GaSb substrates gradually increases over time and is saturated at around 73 Å in the natural oxidation condition. Moreover, the oxidation process is sensitive to humidity. As the thickness of the GaSb oxide layer increases from 18.79 Å to 61.54 Å, the full width at half maximum of the first satellite peak increases from 38.44 to 61.34 arcsec in X-ray diffraction measurements, and the root mean square roughness increases from 0.116 nm to 0.171 nm in atomic force microscopy measurements. Our results suggest that the thickness of the GaSb oxide layer should be less than 55 Å to obtain smooth buffer layers and qualified superlattices. The work provides an optimized direction for achieving high-quality superlattices for infrared optoelectronic devices.

In this paper, a Cr-Al coating was deposited using multi-arc ion plating (MAIP) on 304 austenitic stainless steel. The Cr-Al-coated sample was treated by vacuum annealing at 600 °C for 12 h, and its corrosion behaviors against static LBE were carefully evaluated by SEM, EDS and XPS at a temperature of 600 °C for 1000 h, compared with an uncoated sample. The results showed that the uncoated sample was corroded by the dissolution and oxidation of LBE severely; a duplex-layered oxide layer consisting of an outer Fe3O4 magnetite layer and an inner FeCr2O4 spinel layer was produced on the surface of 304 stainless steel after LBE corrosion. For Cr-Al diffusion coating, an oxide layer was formed that separated the LBE into the 304 matrix. XPS detection showed that the oxide layer primarily included Al2O3. Besides this, the hardness of the coating was tested with a Vickers hardness tester, and the annealed Cr-Al diffusion coating exhibited an average hardness of 260 HV, about five times as high as the Al coating before annealing, of which the average hardness was 48 HV. [ABSTRACT FROM AUTHOR]

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• The oxide layer of SiBCN can be divided into outer and inner parts under 1300 °C. • The oxygen molecules diffused in SiC through the gaps in lattice, while diffused in SiBCN by substituting the O in SiO 2. • BN(C) phase in SiBCN can slow down the generation rate of gases such as CO, N 2 , NO 2 and B 2 O 3. SiBCN, SiC and SiC-BN ceramics/composites were prepared by mechanical alloyed combined hot-pressing sintering at 1900 °C, and the oxidation kinetics of SiBCN, SiC and SiC-BN were calculated based on the thickness of oxide layers at 1100∼1500 °C. The oxide layer can be divided into outer and inner parts under 1300 °C. At 1100 °C, the oxygen molecules diffused in SiC through the gaps in lattice, while diffused in SiBCN by substituting the O in SiO 2. Moreover, BN(C) phase in SiBCN can slow down the generation rate of gases such as CO, N 2 , NO 2 and B 2 O 3. [ABSTRACT FROM AUTHOR]

ZrB 2 /SiC, ZrB 2 /SiC/Si 3 N 4 and ZrB 2 /SiC/WC ceramic tool materials were prepared by spark plasma sintering technology, and their oxidation resistance was tested at different oxidation temperatures. When the oxidation temperature is 1300 °C, the oxide layer thickness, oxidation weight gain and flexural strength of ZrB 2 /SiC/Si 3 N 4 ceramic tool material after oxidation are 8.476 μm, 1.436 mg cm−2 and 891.0 MPa, respectively. Compared with ZrB 2 /SiC ceramic tool materials, the oxide layer thickness and oxidation weight gain are reduced by 8.2% and 11.8%, respectively, and the flexural strength after oxidation is increased by 116.1%. However, the addition of WC significantly reduces the oxidation resistance of the ceramic tool material. A dense oxide film is formed on the surface of ZrB 2 /SiC/Si 3 N 4 ceramic tool material during oxidation, which effectively prevents oxygen from entering the inside of the material, thereby improving the oxidation resistance of the ceramic tool material. [ABSTRACT FROM AUTHOR]

We studied the microstructure of the transfer layer and its effect on the wear mechanism and wear properties of an aged Cu-15Ni-8Sn alloy against 100Cr6 bearing steel during dry sliding by changing the applied load. The results indicate that the aged Cu-15Ni-8Sn alloy shows different wear behaviour and wear properties when the applied load changes; specifically, the average friction coefficient and specific wear rate decrease quickly with increasing applied load under steady wear conditions. The sample tested under a relatively high applied load showed the best wear performance because the oxide layer in the transfer layer. The main wear mechanisms were found to change with variation in the applied load. Metallic nanocrystalline particles and relatively ductile copper oxides promoted the formation of a thick and dense oxide layer. Changes in the thickness and morphology of the oxide layer under different loads can significantly affect the wear mechanisms. [ABSTRACT FROM AUTHOR]

The effect of temperature on surface oxidation characteristics of nickel-base superalloy GH4169 powder was investigated by field emission scanning electron microscope (FE-SEM)，energy-dispersive spectroscopy (EDS)，X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The results show that the surface of the GH4169 superalloy powder is partially oxidized at room temperature（RT），and on the surface there are elemental states dominated by Ni，Cr，Ti and Nb, and hydroxide/oxide dominated by Ni(OH)2，Cr2O3，TiO2 and Nb2O5。With the temperature increasing (150～250 °C) ，the peaks of Ni，Cr，Ti and Nb elements become weaker，the degree of oxidation is slightly increased and the surface of powder is partially oxidized. When the temperature reaches to 350 °C， the peaks of Ni，Cr，Ti，and Nb elements are all disappeared，and the surface of powder is fully oxidized. The oxide layer thickness is about 5 nm, and is mainly composed of Ni(OH)2，Cr2O3，TiO2and Nb2O5. The effect of temperature on oxidation characteristics of the GH4169 superalloy powder is significant，and the maximum treatment temperature of the GH4169 superalloy powder used for this study is no more than 250 °C exposed within 1 h under atmospheric conditions.

Abstract The main problem in metal oxidation is the spalling and de-cohesion of the oxide layer, which results in delamination due to strong compressive stress gradient through the layer. Present paper proposes the use of a modified process named Asymmetric Bipolar Pulsed Plasma (ABiPPS) for plasma-oxidation treatment of low carbon steel AISI-1006 samples. Results show that the ABiPPS process ensures high plasma stability and enables the growth of uniform oxide layers (with thickness up to 6 µm) on metal surfaces. Plasma generated through bipolar asymmetric voltage pulses provides better control on surface bombardment through interspersed jets of ions and electrons, during the oxidation process. The control of intermittent ions and electrons bombardment (through voltage peaks up to 1.5 kV and period about 1µs), during plasma oxidation, make it possible to improve the adhesion between the oxide layer and the substrate, moreover the control of crystalline phases, such as hematite and magnetite.

The influence of particle impact temperature and size on adhesion of soft particle/hard substrate material in cold spray has been scarcely studied. While the relationship between particle impact conditions and particle/substrate bonding is commonly established through FEM studies, they typically lack comparison to experimental data. In the current study, characterization was performed by post-mortem observation of removed adhered particles and collected rebounded particles contact surfaces. Observations are correlated to interfacial pressure and temperature using FEM, otherwise impossible to measure in situ. The influence of pressure and its temporal evolution with particle deformation on melting and bonding is evaluated. Evidence of anisotropic particle deformation associated with microstructural orientation and grain geometrical features has been observed. Experimental evidence confirms that the particle south pole experiences restricted deformation as the original powder grain morphology was observed even after impact. Interfacial melt features have been detected and the melt zone generation, propagation, stagnation and regression tracked through FEM have shown important influence on single impact adhesion processes. Observed metallic bonding features and FEM indicate that increasing particle velocity, i.e., decreasing particle size, accelerates particle bonding processes to occur within tens of nanoseconds. Contact compressive pressure and interfacial expansion increase with particle increasing velocity and temperature. [ABSTRACT FROM AUTHOR]

Introduction: Porcelain Fused to Metal (PFM) restorations offer aesthetics of ceramics and the strength of metal hence are the gold standards of fixed partial dentures. However, the fracture of porcelain-metal interface still remains a matter of concern. Aim: To study the porcelain-noble metal alloy interface of PFM restorations at different firing temperatures, using Scanning Electron Microscopy (SEM) and Energy Diffraction X-ray Spectroscopy (EDS). Materials and Methods: This in-vitro study was conducted between November 2018 to October 2019 at Prosthodontics Departments of Saraswati Dental College and Hospital and King George's Medical University Lucknow, Uttar Pradesh, India. A total of 75 strips of noble metal alloy were prepared and layered with 1mm of porcelain on one surface, conforming to American National Standard/American Dental Association Specifications (ANSI/ADA) specification no.38 for Metal-Ceramic Dental Restorative Systems: 2015. These were randomly divided equally into 3 groups. Specimens of each group (n=25) were fired at different temperatures that is 850oC, 900oC and 960oC, respectively. Scanning electron microscopy and Energy diffraction X-ray spectroscopy were performed at the noble metal alloy and ceramic interface of all specimens. Data was recorded and statistically analysed using one-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test. Results: Irregularities/Coarseness (50 µm) was seen on the noble metal alloy surface adjacent to ceramic layer in SEM images at all the three chosen temperatures. EDS study revealed intermingled zones of partial oxygen depletion at the interface region with formation of intermetallic compound, lead zirconate titanate and complete oxygen depletion zone near metal alloy end of interface. The mean value of Shear Bond Strength (SBS) was 16.31 MPa at 850oC, 24.33 MPa at 900oC and 19.41 MPa at 960oC (p-value <0.05). Conclusion: Difference in properties and location of the intermetallic compound formed at the interface, as well as the location of the oxygen depletion zone could account for the weaker bond formed between noble alloy-porcelain interface compared to base metal-porcelain interface. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of low alloyed Fe-Cr steels with 3 and 5% wt. of Cr in neutral Na2SO4 electrolyte combined with a detailed chemical and morphological characterization of these alloys performed by Auger electron spectroscopy, X-ray photoelectron spectroscopy, timeof- flight secondary ion mass spectrometry and scanning electron microscopy are presented here. The corrosion of low alloyed Fe-Cr steels proceeds in the prepassive range, with the formation of corrosion surface films having a duplex structure with outer iron oxide/hydroxide layer and inner Cr oxide-rich layer. The thickness, composition, and the morphology of the surface films vary as a function of chromium content in the alloy as well as conditions of electrochemical tests (temperature). Even a low chromium content shows a beneficial effect on the corrosion performances of the Fe-Cr steels. The chromium as a more active component than iron of ferrite increases the anodic activity of this phase, which results in a rapid saturation of the surface with the anodic reaction products forming a fine crystalline-like and compact layer of corrosion products. In this way, the chromium acts as a modifier of formation/crystallization of the iron-rich surface film (mainly magnetite) in the prepassive range. [ABSTRACT FROM AUTHOR]

Aluminum particle ignition behavior in open atmosphere rocket propellants fires is of particular interest for preventing accidents for rockets carrying high-value payloads. For nominal motor pressures, aluminum particles oxidize to aluminum oxide in the gas phase and release significant combustion energy while minimizing motor instability. During rocket abort or launch pad malfunction which occur under atmospheric or low pressure, behavior of aluminum particle combustion becomes complex and aluminum appears to melt, agglomerate or form a skeletal structure. Furthermore, an oxide shell of alumina instantly forms on any fresh aluminum surface which is exposed to an oxidizing environment. Aluminum combustion then strongly depends on the oxide layer growth, which is influenced by causative factors, including particle size, environmental gas composition, and heating rate. This work focuses on the effect of the oxide barrier which forms on the surface of aluminum that is recognized to impede combustion of aluminum in solid rocket propellants. Understanding the mechanism for breach of this barrier is deemed to be an important consideration in the overall process. In this discussion, results of various experiments will be discussed which have a bearing on this process. Basically, a recognized criterion is the melting of the oxide layer at 2350 K is sufficient. However, in other situations, depending on the mechanism of oxide formation, there will occur defects in the oxide shell which provide for aluminum ignition at lower temperatures. For slow heating in an oxidizing environment, where the oxide layer can grow thick, then ignition is more difficult. Because there is no uniform model to establish an ignition criterion due to the unknown history of an aluminum particle, this paper reports experimental findings involving oxyacetylene torch, thermogravimetric analysis with differential scanning calorimeter, aluminum particle heating, electric ignition and aluminum powder heating, to address the influence of the oxide layer on the aluminum particle ignition.

The cyclic stability of superelasticity in compression in [001]B2-oriented Ti49.3Ni50.7 single crystals is considered in this paper. The crystals were aged at 823 K for 1.0 h in air and helium. It has been experimentally shown that a two-layered surface thin film, consisting of a Ni-free oxide layer and a Ni-rich sublayer, appears after the oxidation at 823 K in air. The surface layers have a weak effect on the forward B2-R-B19’ martensitic transformation temperatures: TR temperature increases by 4 K; Ms and Mf temperatures decrease by 6 K. The oxide layer does not affect either the superelasticity response during fatigue tests or the temperatures of reverse B19’-B2 martensitic transformation. The cracking of the surface oxide layer during fatigue tests was not found in [001]B2-oriented single crystals aged in air. This is contributed by the relaxation of internal stresses. Such internal stresses are caused by both the formation of an oxide layer during aging and the matrix deformation at the stress-induced martensitic transformation. The main relaxation mechanisms of the internal stresses are the oriented growth of Ti3Ni4 precipitation near a thin surface film at aging in air, the formation of dislocations near the precipitation-matrix interface and a fine twinned B19’-martensite at fatigue tests.

Aluminum surfaces in a normal atmosphere are always coated with a native oxide layer. To prevent a new layer from forming after this oxide layer has been removed, an environment without oxygen must be created. This work uses a new method of doping an inert gas atmosphere with highly reactive silane to ensure technical freedom from oxygen. The influence of the surrounding atmosphere and the influence of the oxide layer on the tensile strength of an aluminum-aluminum joint are investigated. For this purpose, 2-component adhesives are used whose curing mechanisms are fundamentally not based on the reaction with the surrounding atmosphere. The tests are carried out in normal, pure argon, and an oxygen-free argon/silane atmosphere. The experiments show that the surrounding atmosphere influences the strength of the bonded joint. Compared to the oxidized surfaces, the joints of the deoxidized surfaces show a higher tensile strength under constant ambient conditions.

In this study, the SiBCN-Ti series ceramics with different Ti contents were fabricated, and the oxidation resistance and microstructural evolution of the ceramics at 1500 °C for different times were explored. The results show that with the increase in oxidation time, pores and bubbles are gradually formed in the oxide layer. When the oxidation time is less than or more than 4 h, the Ti(C, N) in the ceramics will maintain its initial structure or mostly transform to TiN. The introduction of Ti content can promote the formation of rutile silicate glass, thus healing the cracks and improving the oxidation resistance of the ceramics effectively., Competing Interests: The authors declare no conflict of interest.

Anion exchange membrane water electrolyzers (AEMWEs) have an intrinsic advantage over acidic proton exchange membrane water electrolyzers through their ability to use inexpensive, stable materials such as stainless steel (SS) to catalyze the sluggish oxygen evolution reaction (OER). As such, the study of active oxide layers on SS has garnered great interest. Potential cycling is a means to create such active oxide layers in situ as they are readily formed in alkaline solutions when exposed to elevated potentials. Cycling conditions in the literature are rife with unexplained variations, and a complete account of how these variations affect the activity and constitution of SS oxide layers remains unreported, along with their influence on AEMWE performance. In this paper, we seek to fill this gap in the literature by strategically cycling SS felt (SSF) electrodes under different scan rates and ranges. The SSF anodes were rapidly activated within the first 50 cycles, as shown by the 10-fold decline in charge transfer resistance, and the subsequent 1000 cycles tuned the metal oxide surface composition. Cycling the Ni redox couple (RC) increases Ni content, which is further enhanced by lowering the cycling rate, while cycling the Fe RC increases Cr content. Fair OER activity was uncovered through cycling the Ni RC, while Fe cycling produced SSF electrodes active toward both the OER and the hydrogen evolution reaction (HER). This indicates that inert SSF electrodes can be activated to become efficient OER and HER electrodes. To this effect, a single-cell AEMWE without any traditional catalyst or ionomer generated 1.0 A cm -2 at 1.94 V ± 13.3 mV with an SSF anode, showing a fair performance for a cell free of critical raw materials.

A new cutting method named "peel cutting" is proposed in this research to suppress notch wear in machining of metals with hard oxide surfaces. In general, metals are produced by hot deformation processes like rolling, forging, and extrusion, which cause hard oxide surfaces called scales on their surfaces. These hard scales need to be removed first in machining of precision parts. However, the machining causes the severe notch wear at the depth-of-cut position, where the tool contacts the hard scale. To solve this problem, the proposed peel cutting avoids this direct contact between the tool and the scale by inclining the end cutting edge at an extremely large inclination (oblique) angle. This extremely oblique cutting changes the material flow and generates a "burr-like chip". In the proposed cutting method, the tool contacts only soft non-oxide metal under the scale during cutting. Cutting of titanium alloy Ti–6Al–4V is conducted by modifying commercial tools to provide extremely large inclination angles, and it is clarified that an inclination angle of 70 deg or greater is required to realize the proposed cutting. Tool wear in the proposed cutting of the alloy with a hard scale is also observed in comparison with the ordinary cutting, and the result verifies that the notch wear can be suppressed successfully by the proposed peel cutting. • "Peel cutting" is proposed for machining of metals with hard scales. • Peel cutting avoids contact between tool and scale by generating "burr-like chip". • Peel cutting extends tool life by suppressing notch wear due to hard scales. [ABSTRACT FROM AUTHOR]

Inconel 600 alloy is widely utilized for high temperature environment application due to the corresponding good oxidation and corrosion resistance properties. In order to estimate the high temperature oxidation resistance of Inconel 600 alloy at various temperatures, the oxidation weight gain of all specimens was measured and fitted for the curve at the temperatures of 700, 800 and 900 °C for exposure time of 100 h. The surface morphology and the component of the oxide film were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that the high temperature oxidation resistance of Inconel 600 alloy is excellent blew 800 °C due to the oxidation kinetic curves at different temperatures corresponding to the parabola dynamic rules. This means that the oxidation film protects the substrate well. The dense oxide layer formation containing Cr2O3 and NiCr2O4 at 700 and 800 °C and MnCr2O4 at 900 °C, respectively, is the main reason for the good oxidation resistance. In contrast, the oxide layer peels off easily under applied force as the temperature increases beyond 800 °C, on account of the complicated compositions of the oxide film and the binding force between the oxide layer and the substrate weakening. Corresponding oxidation mechanism is expected to be understood and the oxidation resistance of Inconel 600 alloy is improved through binding force enhancement. [ABSTRACT FROM AUTHOR]

It is established that, when growing Si nanowires in a H2 flow that has not been additionally purified from residues of O2 and water vapor, SiO2 layers are formed on the crystal surface and growth substrate. The growth of Si nanowires is inhibited because of the presence of an oxide surface layer, and the crystals are characterized by strong morphological instability. The thermodynamic conditions for the formation of an oxide surface layer and its effect on the growth of Si nanowires are determined. At synthesis temperatures of 750–1400 K, Si nanowires are thermodynamically unstable in the gas phase containing any appreciably low O2 concentrations, and Si should completely transform into an oxide under favorable kinetic conditions. The thermal dissociation and hydrogen reduction of SiO2 under Si-nanowire growth conditions are practically unrealizable. [ABSTRACT FROM AUTHOR]

Investigations of the influence of the optimized process of wet chemical treatment on the optical characteristics of the silicon monocrystalline wafers surface have been carried out. It was found that chemical treatment of a silicon wafer surface with a KOH solution with a concentration of 45% in deionized water at a temperature of 75°C for 4 min leads to etching of the damaged surface layer, thereby reducing the number of surface recombination centers of charge carriers. The use of ozone for cleaning from organic and other contaminants and the replacement of isopropyl alcohol in a solution with KOH replaced by ALKATEX surfactant allows the plates to be textured at higher temperatures in a relatively short time and to reduce material costs. The use of an optimized wet chemical treatment process makes it possible to texture monocrystalline silicon wafers and obtain a pyramid on the surface with a base width from 1 to 4 μm and a height of ~1.5–3 μm, which will make it possible to reduce the reflection coefficient of electromagnetic radiation by more than 3 times in relation to plates with a smooth surface, in the spectral range of 600–800 nm, the reflection coefficient decreased to a value of 8.7%. A decrease in the reflection coefficient from the silicon wafer surface should lead to an increase in the transmittance of the supplying electromagnetic radiation of the silicon wafer, which will increase the number of the solar cell quanta penetrating the photoactive region, as a result of which the magnitude of the short-circuit current and the open-circuit voltage should increase. Investigation of the load current–voltage characteristic of a heterojunction with an intrinsic thin-layer (HIT) solar cell based on a textured monocrystalline silicon wafer showed an efficiency value of 22.92% under standard test conditions. [ABSTRACT FROM AUTHOR]

The procedure of hard anodizing is carried out at a temperature of (– 4)–0°C for 60 min. A 20% aqueous solution of H2SO4 is used as the base electrolyte. In the course of anodizing, the current density is equal to 5 A/dm2. To determine the influence of strong oxidants on the characteristics of anode layers (oxides), different amounts (30, 50, 70, and 100 g/liter) of hydrogen peroxide (H2O2) were added to the electrolyte. In some cases, it was blown off with an ozone-air mixture at a rate of 5 mg∙min/liter of ozone. It was discovered that the oxide layer (Al2O3∙H2O) is formed in the course of hard anodizing on aluminum alloys not only by oxygen ions appearing as a result of decomposition of water but also by neutral oxygen atoms formed as a result of decomposition of hydrogen peroxide and ozone. It is shown that both hydrogen peroxide and the procedure of blowing of the electrolyte with an air-ozone mixture increase the thickness and microhardness of the anodized layer by 50% due to the twofold reduction of the number of water molecules in aluminum oxide. Hydrogen peroxide and ozone clearly also decrease the thickness of the barrier layer of the coating through which oxygen and aluminum ions may penetrate and combine to form the oxide layer. It is demonstrated that the maximum microhardness of the anodized layer can be attained as a result of heat treatment, namely, as a result of heating of the anodized samples to 300°C. [ABSTRACT FROM AUTHOR]

Protic ionic liquids (PILs) being intrinsic proton conducting ionic species are considered as potential green electrolytes for study of electrocatalytic reactions and for fabrication of IL-based fuel cells (FCs) and batteries. We have prepared a sulfate anion based protic ionic liquid (PIL), triethylammonium sulfate (TEAS) through a reaction involving transfer of proton from H2SO4 to triethylamine (TEA). 1H NMR and FT-IR spectroscopic techniques were employed for confirmation of the synthesis of TEAS and water content of the PIL was quantified using coulometric Karl–Fischer (KF) titration. 1H NMR and FT-IR analysis confirm the synthesis of the PILs and KF-titration analysis shows that TEAS contains 1.43 w/w % water. Electrical conductivity of TEAS was determined at different temperatures showing that the PIL has excellent ionic conductivity that enhances with rise in temperature of the medium. The temperature dependence of the conductivity of the PIL follows the Arrhenius equation as the logσ versus 1/T plot is linear. The electrochemical windows (EWs) of the electrolyte were found using cyclic voltammetry at Pt and Au working electrodes and found to decrease with increase in temperature of the medium. The data revealed that the surfaces of the electrodes are covered with oxide layers due to oxidation of trace water (1.43 w/w %) present in the PIL. The oxide layers growth increase and their onset potential moves to less positive values as the temperature of the PILs is increased. The data was compared with the literature and would be helpful in understanding of the surface electrochemistry in this neoteric medium for being used as potential electrolyte in industry for various electrochemical applications. [ABSTRACT FROM AUTHOR]

As a lightweight construction material, aluminum plays a key role in weight reduction and, thus, sustainability in the transport industry. The brazing of aluminum and its alloys is impeded by the natural passivating oxide layer, which interferes with the brazing process. The presented study investigates the possibility of using a thermal silane-doped argon plasma to reduce this oxide layer in situ and thus eliminating the need to use hazardous chemical fluxes to enable high-quality brazing. Using plasma spectroscopy and an oxygen partial pressure probe, it was shown that a silane-doped argon plasma could significantly reduce the oxygen concentration around the plasma in a thermal plasma brazing process. Oxygen concentrations below 10−16 vol.-% were achieved. Additionally, metallographic analyses showed that the thickness of an artificially produced Al2O3-Layer on top of AlMg1 samples could be substantially reduced by more than 50%. With the oxide layer removed and inhibition of re-oxidation, silane-doped plasma brazing has the potential to become an economically efficient new joining method.

The article presents the effect of anodizing parameters of the EN AW-5251 aluminum alloy on the thickness and roughness of Al2O3 layers as well as their wettability and tribological properties in a sliding combination with the T7W material. The input variables were the current density of 1, 2, 3 A/dm2 and the electrolyte temperature of 283, 293, 303 K. The tribological tests were performed on the T-17 tester in reciprocating motion, in conditions of technically dry friction. The tests were carried out on a 15 km road with a constant average slip speed of 0.2 m/s and a constant unit pressure of 1 MPa. The measurement of the wettability of the layers was performed using the sitting drop method, determining the contact angles on the basis of which the surface free energy was calculated. The profilographometric measurements were made. The analysis of the test results showed that the anodizing parameters significantly affect the thickness of the Al2O3 layers. The performed correlation analysis also showed a significant relationship between the roughness parameters and the wettability of the surface of the layers, which affects the ability to create and maintain a sliding film, which in turn translates into sliding resistance and wear of the T7W material. The analysis of friction and wear tests showed that the layer with hydrophobic properties produced at a current density of 1 A/dm2 in an electrolyte at a temperature of 283 K is the most favorable for sliding associations with T7W material.

This paper investigated the solid particle erosion behavior of partially oxidized NiCrBSiFe and NiCr coatings by varying temperature and impact angle. The challenge in the current situation is to process a new system of powders containing metallic and oxide phases. Partially oxidized powders containing metallic and oxide phases were processed by flame spraying the alloy powders into distilled water and allowing the oxide layer to form while keeping the core in the middle of the particle. Partially oxidized coatings were developed on MDN321 steel using the plasma spray technique with feedstock of partially oxidized powders. An air jet erosion test was carried out using Al2O3 erodent of grit size 50 µm at room temperature, 200, 400, 600, and 800°C by varying 30, 45, 60, 75, and 90° impact angles. Coatings were characterized concerning bond strength, porosity, micro-hardness, and density. The effect of temperature and impact angle on volumetric erosion loss was studied using SEM, EDS, and XRD analysis. Partially oxidized NiCrBSiFe coating exhibited better erosion resistance compare with partially oxidized NiCr coating. NiCr coating demonstrates maximum volumetric erosion loss at 45° impact angle, whereas NiCrBSiFe at 60° impact angle under all tested temperatures. [ABSTRACT FROM AUTHOR]

The AA6061-T6 alloy is used in many industrial applications such as hydraulic pistons, aerospace and marine vehicle fittings, including the nuclear reactors due to their excellent joining and coating properties, high strength, good formability, high resistance to aquatic corrosion and neutron transparency. This study consists of high temperature oxidation for which the samples were oxidized using thermogravimetric analysis, at a temperature of 580°C in an atmosphere that contains air and argon. Exposure of exposure times at 580°C varied from 15 min to 8 h, which permitted to understand the mechanism of oxide formation mechanisms in this alloy and progressive formation of oxide layers on the surface. The chemistry, thickness and the morphology of the oxide layer formed on the surface was characterized by scanning electron microscopy (SEM-EDS), X-ray diffraction which revealed the existence of the following elements in the oxide layer, such as Al2O3, Al9Si, SiO2, MgO and Mg3O4. Results showed that the oxide layer becomes thicker with the increasing exposure time and is accompanied by a loss of weight compared to the mass formed at the beginning of the thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

This study investigates the cracking behavior of oxide layers formed on molten metals and alloys including pure zinc, Zn–4 wt%Al (ZAMAK3) and Al–(0.5–2) wt%Ca in dynamic oxidation condition by injecting gas bubbles into the molten metal during the pouring process. The crack characteristics of the oxide layers were studied using a field emission scanning electron microscope. The results show that various stresses initiated from turbulence flow in the molten metal promote the deformation of the oxide layer, particularly at the initial stages of oxidation. Different coefficients of thermal expansion of the oxide layers and the metals can also result in deformation/cracking the oxide layers. Simultaneous aspiration of the molten metal and solidification phenomenon within the casting process may lead to various morphological changes, e.g. folded-, wrinkled- and cracked-oxide layers. In addition, a splitting and reforming phenomenon of multiple oxide layers is observed, called as strips of 'ruffled tape'. An illustrative mechanism is suggested and discussed quantitatively for the formation of such phenomena. It is assumed that the unique appearance of these strips depends on the formation time and complex stress gradients on the oxide layers. [ABSTRACT FROM AUTHOR]

The laser shock peening without coating (LPwC) of medical grade Ti-6Al-7Nb titanium alloy was carried out and subsequently investigated for the role of oxide layer formed and microstructural changes concerning biocorrosion in simulated body fluid (SBF). Titanium alloy samples were treated using laser power densities of 3, 6 and 9 GW/cm2 with a spot diameter of 0.8 mm and an overlap percentage of 70 % using water as plasma confinement medium. The initial findings showed that LPwC resulted in formation of oxide layer predominantly comprising of TiO 2 , Al 2 O 3 and Nb 2 O 5 due to the thermal effect of laser interaction mediated oxygen diffusion. Increase in roughness and porosity was observed with increasing power density with a slight decrease for 6 GW/cm2 treated specimen. Even though 9 GW/cm2 condition attained a maximum hardness of 376 HV at sub surface, 6 GW/cm2 LPwC sample attained a consistent hardness (~ 342 HV) profile up to a depth of 700 μm. To evaluate the electrochemical stability, surface modified Ti-6Al-7Nb alloy were tested with potentiodynamic polarisation and electrochemical impedance spectroscopy by immersing in SBF at 37 °C. The I corr value of 6 GW/cm2 condition was improved by 4 times compared to unpeened Ti-6Al-7Nb alloy and the current densities of other samples indicated deterioration. The results show that for 6 GW/cm2 condition having high dislocation density, HAGB fraction and refined β phase present below the oxide layer act as site of passivation leading to superior anti-biocorrosion capability. • Oxide layer is formed due to laser shock peening without coating • TiO 2 , Al 2 O 3 and Nb 2 O 5 are the major constituents of the oxide layer • Strain hardening resulted in mechanical strength and electrochemical stability of subsurface • Passive layer formation along with oxide layer act as a barrier to biocorrosion [ABSTRACT FROM AUTHOR]

This study reveals the micro-structure of the naturally oxidized shot-blasting steel substrate surface and uses a simple resin pre-coating (RPC) approach to fully wet the substrate surface for a stronger adhesive bonding effect. RPC solutions are made of around 90% acetone and 10% resin without hardener, which can be sprayed or brushed onto the steel substrate surface. To demonstrate the wetting effect of RPC treatment on the oxide layer, a single lap shear (SLS) test is conducted to measure the shear strength of grit-blasting and naturally oxidized shot-blasting steel substrates under six different concentrations of RPC solutions. Results showed that after being treated with a 5 wt% RPC solution, the average shear strength of grit-blasting and naturally oxidized shot-blasting specimens increased by 27% and 20% respectively. Meanwhile, it has been observed that the average shear strength of naturally oxidized shot-blasting specimens treated with a 5 wt% RPC solution (15.53 MPa) is slightly higher than that of grit-blasting specimens without RPC treatment (15.45 MPa). This finding indicated that RPC treatment could effectively wet the oxide layer on the surface of shot-blasting steel substrates, removing the need of grit-blasting for steel substrates. Consequently, RPC treatment can simplify on-site processes and reduce environmental pollution. • The 5 wt% RPC solution greatly improves the wettability of oxidized shot-blasting steel substrates. • The RPC solution can penetrate the micro-cracks present in the oxide layer on the shot-blasting steel substrates. • RPC method can be used as an alternative to grit-blasting during the engineering bonding process. [ABSTRACT FROM AUTHOR]

In this study, the corrosion characteristics of essential materials used in supercritical water-cooled reactors (SCWRs) were investigated. Austenitic stainless steels 304 SS and 316 SS and nickel-based alloys 625 and 800 were exposed to supercritical water (SCW) at 500 °C and 25 MPa. The results showed that 304 SS, 316 SS, and Alloy 800 formed a double oxide layer, with the outer and inner layers enriched in Fe and Cr/Ni, respectively. Alloy 625 formed outer Ni-rich oxides (mainly NiO) and inner Cr-rich oxides and Ni-Cr oxides (mainly Cr 2 O 3 and NiCr 2 O 4 , respectively). The results indicated that the difference in the protective performance of the corrosion products was mainly due to the Cr content, and the order of corrosion resistance was Alloy 625 > Alloy 800 > 304 SS > 316 SS. In addition, a corrosion mechanism model was established, which lays a good foundation for corrosion prediction and protection in SCWRs. [Display omitted] • 304 SS, 316 SS, Alloy 625 and Alloy 800 formed different double corrosive oxides. • The Cr-poor zones were more prone to develop into the corrosion islands. • Holes and pits in Alloy 625 were mainly related to the precipitation of Nb-rich and Ti-rich phases. • A continuous Cr-rich oxide layer provided excellent protection for the matrix material. [ABSTRACT FROM AUTHOR]

Supercritical water (SCW) has strong reactivity and the ability to fuse non-polar substances, but it requires higher corrosion resistance of structural materials. To select reliable candidate materials for a supercritical water system, this study investigated the corrosion behavior of 304 stainless steel (304 SS) in supercritical water (798 K/24 MPa). After soaking 304 SS in supercritical water for 200 h, the oxidation kinetics, surface morphology, and element diffusion were studied by weight measurement, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface of 304 SS shows an isolated and discontinuous oxidation deposition. It is determined that the oxide layer is a single layer, mainly composed of Fe-Cr-rich spinel, with a small amount of magnetite attached to the surface of the oxide layer. Besides, the oxidation mechanism was also studied since some pores were found on the surface due to pitting. [Display omitted] • Corrosion behavior of 304 stainless steel is investigated in supercritical water. • Oxidation kinetics, surface morphology, and element diffusion were studied • Surface of 304 SS shows isolated and discontinuous oxidation deposition [ABSTRACT FROM AUTHOR]

Introduction, aim: The oxide layers on surface of titanium alloy are influencing corrosion resistance and biocompatibility. The compatibility between the bony tissue and titanium alloy is prevalently dependent on properties of a stable titanium dioxide layer. These layers can be prepared by various methods. The oxidation process (and its conditions) is resulting in different types of oxide layer: difference in chemical composition, mechanical properties, inner structure etc. The deviation inside of the layers structure may influence the stability of the layer, its adhesion or biocompatibility.The anodic oxidation of titanium alloys in appropriate electrolyte (under certain conditions) can lead not only to creation of the oxide layer, but to creation of an oxide layer with structured surface. This kind of structure is usually characterized by pores in nanometer scale. The structured surface radically changes the interaction between the titanium alloys surface and cells; and thus influencing its behavior inside a body. The cell interaction with the structured surfaces is not properly described yet. This work aims for better understanding of such structured layers. Methods: The anodic oxidation was carried out on Ti6Al4V ELI polished samples. The oxidation process was realized in 1M H2SO4 electrolyte with the voltage 100 V and current density 50 mA/cm2. The thickness and surface morphology of the resulting oxide layer were evaluated and documented using a scanning electron microscope (SEM). The changes of color and roughness of the surface after the oxidation were observed as well.The cytocompatibility of the materials surface is expressed by a surface area colonized by cells after the three days of cultivation. This method is standardly used and accredited by ČIA. The MG63 cells were used for the experiment and the percentage of colonized surface area was evaluated. The evaluation was done on polished and oxidized Ti6Al4V ELI samples and the results were compared. Result: The structure of samples prepared using the anodic oxidation consisted of pores with size ranging from tens to hundreds of nanometers.The cytocompatibility testings showed that the cells colonized larger area on the oxidized samples. The cells covered 56.9% of the surface area of the polished samples, while 63.5% of the surface area of the anodized samples. Results of all samples exhibited Gaussian distribution. Conclusion: The anodic oxidation lead to a creation of nanostructured oxide layer on Ti6Al4V ELI samples. The cytocompatibility of this layer was compared to polished samples. It was shown that cells are colonizing the larger surface area on the oxidized samples.

Owing to work at high temperature and high loadings, hot work die steels wear easily, and are especially susceptible to high temperature oxidative wear. Under severe oxidative wear conditions, the wear rate is high, which may lead to premature wear failure of the dies. Therefore, severe oxidative wear should be limited or avoided during the service life of hot work die steels. For service materials, wear resistance is affected by temperature, load, time on the oxide type, plastic deformation, and debris morphology of the surface and sub-surface. Pioneering researchers tended to focus on the influences of temperature, load, and time on wear resistance, and little is known about the wear mechanism of different materials. In this work, the wear mechanism and resistance differences between two hot work die steels, HTCS-130 and DAC55, were studied at temperatures of 100-700℃, using a high temperature friction and wear tester. Surface phase composition, worn surface and cross-section morphology were analyzed by white-light interferometer, scanning electron microscope (SEM), and X-ray diffraction (XRD). The results show that the wear rates of the two steels both increase at first and then decrease at temperatures of 100-700℃. The wear mechanisms of both steels appeared as adhesive wear at 100℃ and adhesive-oxidative wear at 300℃. Then, the wear mechanism changed into oxidative wear at 500℃ and an oxide layer comprising FeO, Fe2O3, and Fe3O4 was observed on the worn surface. Meanwhile, the subsurface started to soften slightly and a plastically deformed layer appeared. Subsequently, severe oxidative wear occurred at 700℃ and the number of oxides had sharply increased. The materials were severely softened owing to the recovery of the martensite matrix. Meanwhile, a continuous oxide layer formed on the worn surface. Due to the excellent thermal stability of HTCS-130 steel, the high hardness and narrow softened zone of matrix could better support the oxide layer. Therefore, HTCS-130 steel shows better wear resistance than DAC55 steel at 700℃.

A high-temperature water steam (H2O(g)) between 300 °C and 1000 °C reacted with the Al surface in this study. The Al surface states were characterized and analyzed using XRD °C, XPS, and SEM after and before the reaction, and the effects and mechanism of H2O(g) on the Al surface morphology and chemical composition were studied. The experiment showed that for an Al sheet reacting with H2O(g), its oxide layer morphology changed from nano-needle to flaky and granular oxides gradually with the rise of temperature, and finally the Al surface became porous as a whole. Its oxide crystals were amorphous and were determined to be aluminum oxide (Al2O3) using XPS. The needle-like oxide in the Al sheet surface tended to grow toward the surface, and no obviously inward oxidizing corrosion layer occurred in the aluminum substrate; the oxide layer between the oxide and Al sheet substrate was compact, and could effectively prevent the infiltration and corrosion of water molecules.

Photocatalysis-assisted chemical mechanical polishing, in which the photocatalysis oxidation and silica abrasives polishing are combined, is a novel finishing technique for 4H–SiC wafer. This paper characterizes the effect of pressure and abrasives on the MRR and surface quality and discusses mechanical and chemical interaction based three slurries that resulted in maximum material removal rate (1.18 μm/h) with PCMP slurry. The polished silicon carbide wafer was examined with atomic force microscope, transmission electron microscope and X-ray photoelectron spectroscopy for surface quality and material removal mechanism. The results show that an atomically smooth and flat 4H–SiC (0001) surface (Ra about 0.247 nm) was obtained by PCMP. The interface of crystal and amorphous layer of 4H–SiC wafer was flat without introducing crystallographic subsurface damage, and the atoms and lattice fringes of the crystal layer are arranged in regular order. The existence of a thin silicon oxycarbide layer, which are various forms of functional groups such as Si–C, Si–C–O, Si–O, Si4C4O4, C–O, and C = O, at the interface. And, it also demonstrates that the amorphous layer is composed of oxide layer (4–6 nm) and distorted layer. The silicon carbide surface is mechanically activated, oxidized and mechanically removed in turn, which is the main method of material removal. [ABSTRACT FROM AUTHOR]

In many areas of engineering, radiation heat transfer plays an important role and it is of great importance the knowledge of the thermal radiative properties of the surfaces involved. Radiation properties of solid materials are highly dependent on surface characteristics, e.g., surface roughness, surface damage, oxide layers, and deposited thin films, and cannot be assumed as those of pure materials, typically referred to optically smooth surfaces (OS). An experimental investigation of the thermal emittance of some metals (nickel, titanium, silver, and stainless steel) is presented. Experiments were conducted by using a radiometric apparatus able to measure the total normal emittance under different temperature and pressure conditions. The aim of this paper was to identify the separate roles of surface microgeometry alterations (surface roughness), surface damage, and surface coatings (i.e., presence of either thin films deposited onto a smooth surface or oxide layers formed on both smooth and rough surfaces) by undertaking carefully selected sets of experiments covering a relatively large temperature range. [ABSTRACT FROM AUTHOR]

The microstructures and corrosion behaviors of Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(0.25∼1.0)%Y in 3.5 wt.% NaCl solution are investigated via morphology observation, phase characterization, immersion and electrochemical methods. The experimental results suggest that yttrium alloying can improve the corrosion resistance of Mg-6%Al-3%Zn throughout the immersion. The initial enhanced corrosion resistance of magnesium alloy is attributed to the Y alloying, which gives rise to the increasing content of Al 2 O 3 in oxide layer. The promoted protectiveness of oxide layer on Mg-6%Al-3%Zn-1.0%Y alloy arouse a filiform corrosion as revealed by in-situ metallographic observation. Furthermore, the Y-containing magnesium alloys still perform higher corrosion resistance compared with that of Mg-6%Al-3%Zn alloy even if the oxide layer is exhausted. This phenomenon is owing to two factors, one is the gradual transformation of intermetallic phases from continuous Mg 17 Al 12 to discrete Al 2 Y in matrix, by which the micro-galvanic corrosion between α-Mg grains and intermetallic phases is alleviated; the other is the morphology variation of corrosion products, the uniform and compact products layer on Y-containing alloys provide a barrier that effectively prevent the corrosive ions from penetrating into and reacting with Mg matrix. [ABSTRACT FROM AUTHOR]

The characteristics of the oxide layer deposited by microarc oxidation (MAO) on Al – Si alloys in a silicate-alkaline electrolyte are studied. The thermal conductivity of the layer at 50 – 120°C is determined using a special facility by the method of stationary heat flow. The thickness, the porosity, the elemental composition, the content of the amorphous phase, and the size of the crystallites in the oxide layer are determined. The results obtained are analyzed and the conditions for the lowest thermal conductivity of the oxide layer are determined. [ABSTRACT FROM AUTHOR]

The surface microstructure and growth behavior of an Fe0.4 mass%C alloy formed by lithium-added salt-bath nitrocarburizing were investigated. The Fe0.4 mass%C alloy was prepared by arc melting and nitrocarburized by a salt-bath containing Li+, Na+, K+, CNO-, and CN- at 823K from 0.1 h up to 10 h. A compound layer forms on the surface at the beginning of nitrocarburizing, and then an oxide layer forms on the compound layer after nitrocarburizing for 1.0 h. Afterwards, the thickness of both layers increase. A grain boundary oxide forms at the interfaces of columnar crystals in the compound layer. The oxide consists of LixFe1-xO with an NaCl-type structure, and the growth of the oxide layer is controlled by the outward diffusion of iron in the oxide layer. Meanwhile, the compound layer consists mainly of an ε-Fe2(N,C)1-y phase and a slight £A-Fe4(N,C)1+z phase near the substrate. [ABSTRACT FROM AUTHOR]

Purpose: Ni-Ti alloy has been increasingly applied to dental and medical devices, however, it contains nickel, which is known to have adverse effects on the human body. The purpose of this study was to form a nickel-free surface oxide layer on Ni-Ti alloy by electrolytic treatment for better biocompatibility.Methods: Ni-49.15Ti (mol%) alloy was used, and the electrolytic treatment was performed in the electrolytes under 50 V for 30 minutes. The electrolytes were composed of lactic acid, water, and glycerol with different compositions. Surface analysis and characterization of Ni-Ti alloy were carried out by means of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).Results: Results indicated that the outmost surface oxide layer was nickel-free when using an electrolyte comprising 7.1% lactic acid, 57.2% water, and 35.7% glycerol by volume. The composition of this nickel-free surface oxide layer was determined as TiO1.92(OH)1.35 ∙ 0.43H2O by XPS, similar to that of unalloyed titanium. The thickness of this nickel-free layer was estimated at 6.4 nm by AES.Conclusion: The nickel-free surface oxide layer produced on Ni-Ti alloy is considered to improve the biocompatibility of medical and dental devices having shape memory effect and/or super-elasticity. [ABSTRACT FROM AUTHOR]