Passive Oxide Film Research Articles

Evolution of Thermoelectric and Oxidation Properties in Lu-Substituted Yb14MnSb11

Yb14MnSb11 is one of the state-of-the-art high-temperature p-type thermoelectric materials with reported zTs of 1.2–1.3 at 1273 K. Site substitution of Yb14MnSb11 provides a means to control carrier concentration and impacts the oxidation kinetics. Substitution of Lu3+ for Yb2+ in Yb14MnSb11 single crystals has been shown to provide faster oxidation kinetics compared with the pristine phase, and it has been speculated that this may lead to surface passivation. Polycrystalline samples of Yb14–xLuxMnSb11 were synthesized from the elements and through a route utilizing YbH2, MnSb, and Yb4Sb3 as reactive precursors. The solubility of Lu was found to be less than x = 0.5, and at that composition and above LuSb impurities are observed in the powder X-ray diffraction. Because Lu3+ is substituting for Yb2+ in a p-type system, there is an increase in both the electrical resistivity and Seebeck coefficient with Lu substitution. As Yb14MnSb11 has been predicted to be optimally doped ∼1.5 × 1021 h+ cm–3, this reduction in carrier concentration in the solid solution of Yb14–xLuxMnSb11 decreases the peak zT. Oxidation of Yb13.7Lu0.3MnSb11 as a function of temperature was studied. At low temperatures, the Lu-substituted sample may have improved oxidation resistance through forming a passivating oxide film on the surface.

Effect of Cu additions on the microstructure, wear resistance and corrosion resistance of Fe-based/B4C composite coating by vacuum cladding

Fe-based/B4C composite coatings with different Cu contents were prepared on the surface of ASTM 1045 steel by vacuum cladding. The influence of Cu contents on the microstructure, hardness, wear behavior and corrosion resistance of coatings was investigated. The results demonstrated that the microstructure was finer owing to the dissolution and dispersion of Cu, although the type of boride M2B and carboboride M23(C, B)6 in Cu-free and Cu-added coatings did not change. Since the Cu additions improved the hardenability of coating matrix and transformed its microstructure into martensite, the microhardness of coating matrix reached over 600 HV, and the macrohardness also increased and reached the maximum of 57.85 HRC for 5Cu sample. The wear volume of Cu-added coating was significantly lower than that of Cu-free coating, and the wear rate of 5Cu sample decreased by 50.40 %. The number of spalling pits on the worn surface decreased, showing the best wear resistance, and the main wear mechanism was fatigue spalling. Furthermore, the coating with high Cu contents possessed higher Ecorr, lower Icorr and higher Rct, which was attributed to the composite oxide passive film formed on the corrosion surface effectively isolated the coating from corrosive medium and greatly improved the overall corrosion resistance of coating.

Effect of Sn content on the passivity of Ti-Ta-Sn alloys

In this work, Ti-13Ta-xSn samples were manufactured using the powder metallurgy technique with a porosity near 35 %. The microstructural analysis revealed that increased Sn content decreased the α-Ti and α’-Ti phases. Furthermore, scanning electron microscopy and X-ray photoelectron spectroscopy showed that the chemical composition of the passive oxide film was influenced by the Sn content. Moreover, the electrochemical analysis revealed that the protective properties of oxide film improved with the Sn addition.

Bimetallic Rechargeable Al/Zn Hybrid Aqueous Batteries Based on Al-Zn Alloys with Composite Electrolytes.

Aluminum is abundant and exhibits a high theoretical capacity and volumetric energy density. Additionally, the high safety of aqueous aluminum-ion batteries makes them strong candidates for large-scale energystorage systems. However, the frequent collapse of the cathode material and passive oxide film results in the difficult development of aqueous aluminum-ion batteries. This work provides a novel battery system, namely, Al-Zn/Al(OTF)3 +HOTF+Zn(OTF)2 /Alx Zny MnO2 ·nH2 O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Alx MnO2 ·nH2 O. Topology transformation alters the structure of the cathode material so that Zn2+ can be intercalated into the Alx MnO2 ·nH2 O spinel structure to provide support for the material structure. Regarding the anode, Zn2+ in the electrolyte is deposited onto Al of the anode to produce a regional Al-Zn alloy. Zn2+ is reduced to Zn metal during discharging, which adds a platform for secondary discharge beneficial for battery capacity enhancement. This system can provide a 1.6V discharge platform, while the first cycle discharge can reach 554 mAhg-1 , thereby maintaining a high capacity of 313 mAhg-1 after 100 cycles. This study provides a new idea for the further development of aqueous aluminum-ion batteries (AAIBs).

Transformation of amorphous passive oxide film on Zr65Cu17.5Ni10Al7.5 metallic glass ribbons

Zr-based metallic glass with favorable properties and a stable surface oxide layer is foreseen as an alternative material for water/nuclear reactor pressure systems. The high stability of Zr65Cu17.5Ni10Al7.5 metallic glass (MG) in anodic and cathodic regions within 0.5 M H2SO4 solution is evidenced by the negligible shift in the corrosion potential upon linear sweep voltammetry cycles. The recorded passivation current density of 15 mA cm–2 is very similar to 430 stainless steel. The formation of an amorphous Zr-rich oxide phase and slight dissolution of the native ZrO2 layer are confirmed by scanning transmission electron microscopy – energy dispersive X-ray analysis, which result from the interaction of hydronium ions (H3O+) with the oxide layer during linear polarization. Furthermore, promising hydrogen absorption of the produced Zr-based MG ribbons (1.33 %wt, non-reversible) by Sieverts-type apparatus were recorded at 400 °C and under 6 MPa, which evidences that this alloy can minimize the hydrogen evolution within the chamber due to the coverage with an oxide film and thereby prevent accidents.

Formation and Breakdown of Oxide Films in High-Rate Anodic Dissolution of Chromium–Nickel Steels in Electrolytes for Electrochemical Machining

It is shown that, in high-rate pulsed galvanostatic anodic dissolution of type CSN17335 and AISI 304 chromium–nickel steels in electrolytes for electrochemical machining (ECM) (chloride, nitrate, and mixed chloride–nitrate solutions with a conductivity of 0.15 S/cm) using microsecond pulses with a duration of 20–2000 μs and current densities in the range of 1–100 A/cm2, a substantial fraction of charge (up to ~40%) is spent on the formation of a passivating oxide film with a semiconducting behavior. The electrochemical treatment therefore directly involves the oxide film, not the alloy. As a consequence, the current efficiency of ECM of these materials is ~60–70%, depending on the alloy composition. When using direct current, the rate of machining increases as a result of the oxide film breakdown due to its thermokinetic instability (“thermal explosion”) caused by a rise in the surface temperature.

Effect of the Passive Oxide Films Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Their Electrochemical Machining. Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

An experimental study of the anodic dissolution of titanium and its alloys, including pulsed dissolution (up to 100 A/cm2) under control of hydrodynamic conditions and surface temperature in nitrate and chloride solutions, showed that the process is carried out through the electrochemical formation of anodic oxide films (AOF) which can be chemically dissolved. An AOF has a bilayered structure, i.e. two barrier films on the interface with a metal and a solution. Its model is PDM-III (Point Defect Model). At certain conditions, it is possible to achieve a steady state in which the film growth rate is compensated by the rate of its chemical dissolution (observed at pulsed conditions). In this case, over 100% current efficiency based on the ionization of titanium in the oxidation state is achieved. During the conducted experiments, when treated with the direct current, the rate of the electrochemical formation of an AOF exceeded the rate of its chemical dissolution, which led to a decrease in to current efficiency which did not exceed 75%. An increase of the dissolution rate takes place with an increase in the electrolyte flow rate. Upon reaching the thermokinetic instability (TKI) of the AOF (thermal explosion due to a feedback rate of the electrochemical reaction-surface tem-perature-rate of an electrochemical reaction), the interaction of electrolyte components with the surface free of the film takes place, and, as a result, an “anomalous” anodic dissolution is observed with the current efficiency greater than 100%. Regardless the nature of the electrolyte, TKI is achieved at a current density of 1 A/cm2. It is shown that in nitrate solutions with certain parameters of pulsed processing (duty factor 2, dc 50%), the dissolution rate, and, in the case of electrochemical machining, the feed rate of a cathode-tool, can be more than twice higher than the rate of machining with the direct current of the same density.

Single asperity sub-nano to nanoscale wear and tribocorrosion of wrought CoCrMo and additively manufactured CoCrMoW alloys

Wear and tribocorrosion of CoCrMo alloys have been associated with adverse local tissue reactions. The tribological and electrochemical processes that arise during single asperity contact at the scale of passive oxide films are poorly understood. An AFM-based ‘image-wear-image’ tribology method was applied to study the sub-nanoscale wear and tribocorrosion of traditional and additively manufactured CoCrMo and CoCrMoW alloys. Atomic wear and elasto-plastic driven wear were observed at wear depths near the oxide thickness. Contact stress, alloy, and environment significantly affected average nanowear depth. Surface degradation varied from grain to grain within LC CoCrMo and by intragranular cellular structures within AM CoCrMoW.

Mechanical, corrosion, nanotribological, and biocompatibility properties of equal channel angular pressed Ti-28Nb-35.4Zr alloys for biomedical applications

This study systematically investigated the effect of equal channel angular pressing (ECAP) on the microstructure, mechanical, corrosion, nano-tribological properties and biocompatibility of a newly developed β Ti-28Nb-35.4Zr (hereafter denoted TNZ) alloy. Results indicated that ECAP of the β TNZ alloy refined its microstructure by forming ultrafine grains without causing stress-induced phase transformation, leading to formation of a single β phase. The ECAP-processed TNZ alloy exhibited a compressive yield strength of 960 MPa, and high plastic deformation capacity without fracturing under compression loads. Potentiodynamic polarization tests revealed the higher tendency of ECAP-processed TNZ alloys to form passive oxide films on its surface, which exhibited a lower corrosion rate (0.44±0.07 µm/y) in Hanks’ balanced salt solution compared to its as-cast counterpart (0.71±0.10 µm/y). Nanotribological testing also revealed higher resistance of the ECAP-processed TNZ alloy to abrasion, wear and scratching, when compared to its as-cast counterpart. Cytocompatibility and cell adhesion assessments of the ECAP-processed TNZ alloys showed a high viability (111%) of human osteoblast-like SaOS2 cells after 7 d of culturing. Moreover, the ECAP-processed TNZ alloy promoted adhesion and spreading of SaOS2 cells, which exhibited growth and proliferation on alloy surfaces. In summary, significantly enhanced mechanical, corrosion, and biological properties of ECAP-processed TNZ alloy advocate its suitability for load-bearing implant applications. Statement of significanceEqual channel angular pressing (ECAP) provides a unique combination of enhanced mechanical and functional properties of materials by optimizing their microstructures and phase transformations. This study investigated the mechanical, nano-tribological, corrosion, and biocompatibility properties of a newly developed β Ti-28Nb-35.4Zr (TNZ) alloy processed via ECAP. Our findings indicated that ECAP of the β TNZ alloy refined its microstructure by forming ultrafine grains without causing stress-induced phase transformation. Compared to its as-cast counterpart, ECAP-processed TNZ exhibited significantly enhanced compressive yield strength, plastic deformation capacity, hardness, wear, and corrosion properties. Moreover, in vitro cytocompatibility and cell adhesion studies revealed high cellular viabilities, growth and proliferation of osteoblast-like SaOS2 cells on the ECAP-processed TNZ alloy.

Electrochemical and DFT Study of NaNO2/NaNO3 Corrosion Inhibitor Blends for Rebar in Simulated Concrete Pore Solution

The use of nitrite- and nitrate-based inhibitors provides corrosion protection by the development of passive oxide film on the metal surface in reinforced concrete applications. However, the impact of the nitrite and nitrate ratio in the mixture has not been widely studied. In this study, the corrosion protection provided by NaNO2:NaNO3 inhibitor blends with ratios of 0.5:1, 1:1, and 1:0.5 were studied to maximize corrosion inhibition efficiency. The nitrite species imparted higher corrosion protection, as shown by cyclic potentiodynamic polarization, with an icorr of 1.16 × 10–7 A/cm2 for the 1:0.5 mixture, lower than for both the 1:1 and 0.5:1 mixtures. Electrochemical impedance spectroscopy was also performed, with the 1:0.5 mixture consistently displaying high resistance values, showing an Rct of 1.31 × 105 Ω cm2. The effect of temperature was also assessed; the Ea’s of the corrosion reaction were calculated to be 12.1, 9.2, and 4.9 kJ/mol for the 0.5:1, 1:1, and 1:0.5 (NO2−:NO3−) mixtures, respectively. Density functional theory was applied to analyze the molecular properties and to determine the relationship between the quantum properties and corrosion inhibition. The ΔE of NO2− was found to be −5.74 eV, lower than that of NO3− (−5.45 eV), corroborating the experimental results. Lastly, commercially available inhibitor mixtures were investigated and nitrite/nitrate concentrations determined to evaluate their corrosion protection performance; amongst the two inhibitor blends tested, Sika was found to outperform Yara due to its greater NO2− concentration.

Effect of the Passive Oxide Films Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Their Electrochemical Machining. Part I. Anodic Dissolution of Chromium-Nickel Steel in a Nitrate Solution

Experimental study of the chromium-nickel steel Cr18Ni10 anodic dissolution in a nitrate solution with electrical conductivity 0.15 S/cm in a pulse – galvanostatic mode at pulse durations 20–100 µs and current densities 0.01–100 A/cm2, with a change in the duty cycle 10–100% (direct current) at various hydrodynamic conditions and control the surface temperature, that the results obtained are consistent with the hypothesis that the process proceeds through the formation of oxide films of a semiconductor nature with a different type of conductivity (a film containing point defects, Point Defect Model, PDM). Under sta-tionary conditions of the existence of PDM-II, the rate of its electrochemical formation is compensates by the rate of its chemical limiting value of the weight loss per unit of a passed charge (0.16–0.18 mg/C) (takes place under pulse conditions), which corresponds to a cur-rent efficiency close to 100% based on the highest degree of oxidation of the steel compo-nents. When transition to direct current takes place, thermokinetic instability of the film is observed (its formation and destruction due to thermal explosion). Under these conditions, the current efficiency can not only reach 100% based on the lowest degree of oxi-dation of the steel components (thermal activation) but also exceed this value due to the chemical interaction of the electrolyte with the film-free surface.

Effect of trace water in ammonia on breaking passive film of stainless steel during gas nitriding

The dense passive film on the surface of austenitic stainless steel isolates the corrosion medium from the matrix, which makes it have excellent corrosion resistance. However, it also hinders the penetration and diffusion of nitrogen atoms in the process of gas nitriding. During gas nitriding of stainless steel, we found a very interesting phenomenon. When trace water in ammonia is at a certain threshold, ammonia, water, and chromium oxide passivation film will undergo gas-solid reaction to break the passivation film on the surface of stainless steel. The results show that the trace water content in ammonia during gas nitriding is very important for in-situ breaking of passive film. When the trace water content exceeds the upper threshold, oxidation will occur on the surface of stainless steel. On the other hand, when the trace water content is lower than the lower threshold, the passivation film hinders the diffusion of nitrogen atoms, and the nitride layer cannot be obtained. The mechanism of in-situ removal of passive film by trace water during gas nitriding of stainless steel is revealed for the first time, which provides a new idea and method for the study of surface modification of stainless steel by gas nitriding.

Understanding the role of Ti addition on the corrosion and passive film characteristics of Nb stabilized AISI 347 weld

AbstractA multipass multilayer weld pad was fabricated on AISI 347 base metal with filler combinations of AISI 321 and AISI 347, to understand the role of Ti addition on metallurgical, corrosion, and passive film characteristics of the AISI 347 weld. Weld layers with Nb content of 0.53 wt.%, 0.47 wt.%, 0.23 wt.% and Ti of 0 wt.%, 0.21 wt.%, 0.33 wt.%, respectively, were extracted from fabricated weld pad. Selected weld metal compositions were subjected to thermal aging at 750°C for 24 h to investigate the influence of varying precipitation induced in these welds. Ti addition in AISI 347 weld showed lower enrichment of C and Cr at dendritic regions resulting in reduced Cr depletion, lower sensitization, enhanced pitting potential, and repassivation ability compared to conventional Nb stabilized AISI 347 weld. Passive film characteristics studied by electrochemical impedance spectroscopy and X‐ray photoelectron spectroscopy depicted formation of more protective, and dense passive film with higher Cr, Ni, and O concentrations for Ti added AISI 347 weld relative to conventional ones. Therefore, Ti addition via the use of Ti stabilized filler in the Nb stabilized AISI 347 weld proved to be efficient in enhancing its corrosion performance by forming a more protective passive oxide film.

X‐ray photoelectron spectroscopy‐based valence band spectra of passive films on titanium

Titanium (Ti) is always covered by thin passive films. Thus, valence band (VB) spectra, obtained using X‐ray photoelectron spectroscopy (XPS), are superpositions of the VB spectra of passive films and that of the metallic Ti substrate. In this study, to obtain the VB spectra only of passive films, angular resolution (for eliminating the substrate Ti contribution) and argon ion sputtering (for removing passive films) were used along with XPS. The passive film on Ti was determined to consist of a very thin TiO2layer with small amounts of Ti2O3, TiO, hydroxyl groups, and water with a thickness of 5.9 nm. The VB spectra of Ti were deconvoluted into four peak components: a peak at ~1 eV, attributed to the Ti metal substrate; a broad peak in the 3–10 eV range, mainly attributed to O 2p (~6 eV) and O 2p‐Ti 3d hybridized states (~8 eV), owing to the π (non‐bonding) and σ (bonding) orbitals in the passive oxide film; and a peak at ~13 eV, attributed to the 3σ orbital of O 2p as OH−or H2O. The VB region spectrum between approximately 3 and 14 eV from Ti is originating from the passive film on Ti. In particular, characterization of VB spectrum obtained with a takeoff angle of less than 24° is effective to obtain VB spectrum only from the passive film on Ti. The property as n‐type semiconductor of the passive film on Ti is probably higher than that of rutile TiO2ceramics.

Significance of waveform design to achieve bipolar electrochemical jet machining of passivating material via regulation of electrode reaction kinetics

Electrochemical machining (ECM) using the bipolar pulse technique shows significant potential for the effective machining of prone-to-passivation materials. However, despite its success in machining specific materials (e.g. tungsten carbide), the underlying mechanism remains unclear. This study presents an in-depth analysis of the interplay between cathodic polarisation (CP) and anodic oxidation in bipolar pulse electrochemical jet machining (bipolar-EJM). An observational study of the structural changes in the anodic oxide film indicated that the oxide broke down by electrochemical reduction and mechanical damage when subjected to CP. The electrochemical kinetics at the electrode interface, particularly the proton transport and discharge reactions, were discussed to elucidate the mechanism. This study first discloses that the bipolar pulse waveform plays a crucial role in overcoming the oxide film and achieving machining in bipolar-EJM. Variations in waveform shape result in distinct interactions of the cathodic pulse with the anodically formed surface oxide. A principal approach of bipolar-EJM was thus developed to effectively remove or eliminate passive oxide films by controlling the bipolar pulse. The material removal mechanism of the developed method is described and the corresponding kinetic model of the electrode reactions is presented. For verification, the bipolar-EJM of the strongly passivating metal niobium (Nb) is first demonstrated in a pH-neutral NaNO3 aqueous solution, demonstrating the effectiveness of the proposed method. The new insights into the bipolar pulse process established here will is believed to provide valuable guidance to advance the bipolar electrochemical process, including ECM and electrochemical polishing.

Formation and Destruction of Oxide Films during High-Speed Anodic Dissolution of Chromium-Nickel Steels in Electrolytes for Their Electrochemical Dimensional Machining

It is shown that at high-speed pulsed galvanostatic anodic dissolution of chromium-nickel steels Kh3N35VT (CSN17335), Kh18N10 (AIS1 304) in the regions of pulse durations of 20–2000 ms and current densities of 1–100 A/cm2 in electrolytes for their electrochemical dimensional machining (ECDM) (chloride, nitrate, and mixed chloride-nitrate with an electrical conductivity of 0.15 S/cm), a significant part of the charge (up to 50%) is spent on the formation of a passivating oxide film having a semiconductor character. As a result, the film, not the alloy, is subject to electrochemical treatment. As a result, the current output of the ECDM process of these materials under pulsed conditions is ~ 50–70%, depending on the composition of the alloy. The speed of the process increases with the transition to a constant processing current because of the destruction of the film due to its thermokinetic instability (“thermal explosion”) caused by an increase in the surface temperature.

Phase orientation improved the corrosion resistance and conductivity of Cr2AlC coatings for metal bipolar plates

In view of the Mn+1AXn (MAX) phase coatings benefiting the adaptive passivation film for good corrosion resistance and high electronic density of states for excellent electrical conductivity, here, we reported the Cr2AlC MAX phase coatings with different preferred orientations by a homemade technique consisting of vacuum arc and magnetron sputtering. The dependence of surface and interface microstructural evolution upon the corrosion and electrochemical properties of deposited coating was focused. Results showed that all the Cr2AlC coatings with different phase orientations greatly improved the performance of stainless steel (SS) 316 L substrate. Specifically, the lowest value of interface contact resistance (ICR) reached to 3.16 mΩ cm2 and the lowest corrosion current density was 2 × 10−2 μA cm−2, which were much better than those of bare SS316L. The combined studies of electrochemical properties and theoretical calculations demonstrated that the Cr2AlC coatings with preferred (103) orientation were easier to form oxide passivation film on their surface to increase the corrosion resistance.

Effect of Al surface oxide structures on oxidability of Al-peroxymonosulfate system

Al-peroxymonosulfate (PMS) system is an efficient way for removal of pollutants in aqueous solution. Al surface passive oxide film is a barrier to impede the electron transfer from inner metal Al to outside, whose compositions and phase structures are changed in different environment such as moisture or after recycling. In this work, for the first time, the effect of Al surface oxide structures on oxidability of Al-PMS system and its efficiency for removal of organic pollutant was investigated. It was found that if the passive oxide film on Al particles is hydrated and becomes hydroxides, the efficiency of Al-PMS system for degradation of bisphenol A (BPA) in aqueous solution decreases considerably, because the solubility of crystallized Al hydroxides is at least three orders of magnitude lower than that of amorphous Al oxides on pristine Al particles. Furthermore, the trace species in water have an influence on the hydration and structures of Al surface oxide film. For example, organics and F− ions in water will form complexes on Al particle surfaces and inhibit the hydration process, while Cl− ions corrode Al surface oxides and do not inhibit the hydration, based on the analyses of Al3+ ion concentration in their solution after BPA removal. It was also found that acid washing can remove the hydrated oxide film on Al surfaces and recover Al activity.

Passive Oxide Film Growth Observed On the Atomic Scale

AbstractDespite the ubiquitous presence of passivation on most metal surfaces, the microscopic‐level picture of how surface passivation occurs has been hitherto unclear. Using the canonical example of the surface passivation of aluminum, here in situ atomistic transmission electron microscopy observations and computational modeling are employed to disentangle entangled microscopic processes and identify the atomic processes leading to the surface passivation. Based on atomic‐scale observations of the layer‐by‐layer expansion of the metal lattice and its subsequent transformation into the amorphous oxide, it is shown that the surface passivation occurs via a two‐stage oxidation process, in which the first stage is dominated by intralayer atomic shuffling whereas the second stage is governed by interlayer atomic disordering upon the progressive oxygen uptake. The first stage can be bypassed by increasing surface defects to promote the interlayer atomic migration that results in direct amorphization of multiple atomic layers of the metal lattice. The identified two‐stage reaction mechanism and the effect of surface defects in promoting interlayer atomic shuffling can find broader applicability in utilizing surface defects to tune the mass transport and passivation kinetics, as well as the composition, structure, and transport properties of the passivation films.

Room-Temperature Preparation of Ta Ions-Containing Ionic Liquid and its Vapor Deposition toward Ta-Oxide Film Coating

Ta ions-containing solutions, which are brown in color with no precipitation, were successfully prepared through an electroelution process with ionic liquid (IL). An as-delivered Ta metal plate covered with a passivation oxide film could be easily eluted even at room temperature by simply applying an anodic potential of, e.g. +2.2 V vs Ag in [Bmim][PF6] IL. According to the quantity of electric charge required for oxidation of Ta, most Ta ions in the IL were suggested to be in an oxidation state of +5, which was also confirmed by X-ray photoemission spectroscopy (XPS). Ta ions in IL were found to thermally evaporate together with IL molecules by heating in a vacuum, forming a deposit of the Ta ions-containing IL on a substrate. The Ta concentrations in the deposits were reduced uniquely by about one order of magnitude from those in the original bulk source through the evaporation process under the present conditions. Furthermore, a possibility of the formation of thin film-like Ta oxide from such a Ta ions-containing IL deposit and its bulk droplet prepared on substrates by annealing in air at 1000 °C will be discussed.