Layer Of Oxide Film Research Articles

Effects of temperature and heating method on the performance of Ti/Ru0.25Ir0.25Ti0.50O2 anodes applied toward Bisphenol S removal

One of the challenges faced by environmentally-related electrochemical techniques and which limit their industrial application is the lack of efficient and economically viable electrodes. This paper reports the development and application of a microwave-assisted hybrid heating method for the production of mixed metal oxide (MMO) anodes aiming at obtaining low-cost, highly catalytic, and durable anodes with reduced production time. The Ti/Ru0.25Ir0.25Ti0.50O2 electrodes were prepared by the Pechini method using two calcination temperatures (350 and 400 °C) and two heating mechanisms (conventional in an electric furnace and hybrid heating using microwaves). The electrodes developed were applied toward the electrochemical degradation of Bisphenol S (BPS); this is the first report involving the application of MMO electrodes for BPS removal in the literature. The calcination temperature and type of heating influence the electrodes physical and electrochemical characteristics, as well as the film compositions and catalytic activities. With the exception of the anode produced in the furnace at 400 °C (CM-400), which exhibited a crack-free compact surface, the oxide film layers covered the Ti substrates entirely, displaying a typical “cracked mud” morphology. The morphological characteristics of CM-400 contributed toward obtaining low voltammetric charge (88 mC) and high resistivity (194 Ω) for the film. In contrast, the electrode developed by microwave-assisted hybrid heating at 350 °C was produced in a relatively shorter time (4.6-fold), presented the lowest charge transfer resistance (24 Ω), the highest voltammetric charge (240 mC), and the highest stability (with 51 h – accelerated life test). Overall, the electrodes produced in furnace were slightly more efficient when applied toward the electrochemical removal of BPS; to be precise, the electrode calcined at 400 °C showed total BPS removal in 10 min at 100 mA cm–2. About 20% of TOC removal was obtained in 60 min of electrolysis; this is the highest TOC rate reported for BPS under such short treatment time. Thus, the anodes developed are found to be suitable and highly promising for the electrochemical removal of BPS from water.

A Comprehensive Review on the Corrosion Pathways of Titanium Dental Implants and Their Biological Adverse Effects

The main aim of this work was to perform a comprehensive review of findings reported by previous studies on the corrosion of titanium dental implants and consequent clinical detrimental effects to the patients. Most studies were performed by in vitro electrochemical tests and complemented with microscopic techniques to evaluate the corrosion behavior of the protective passive oxide film layer, namely TiO2. Results revealed that bacterial accumulation, dietary, inflammation, infection, and therapeutic solutions decrease the pH of the oral environment leading to the corrosion of titanium. Some therapeutic products used as mouthwash negatively affect the corrosion behavior of the titanium oxide film and promote changes on the implant surface. In addition, toothpaste and bleaching agents, can amplify the chemical reactivity of titanium since fluor ions interacting with the titanium oxide film. Furthermore, the number of in vivo studies is limited although corrosion signs have been found in retrieved implants. Histological evaluation revealed titanium macro- and micro-scale particles on the peri-implant tissues. As a consequence, progressive damage of the dental implants and the evolution of inflammatory reactions depend on the size, chemical composition, and concentration of submicron- and nanoparticles in the surrounding tissues and internalized by the cells. In fact, the damage of the implant surfaces results in the loss of material that compromises the implant surfaces, implant-abutment connections, and the interaction with soft tissues. The corrosion can be an initial trigger point for the development of biological or mechanical failures in dental implants.

Study on micro-arc oxidation coating of magnetic metal powder composite magnesium alloy

Purpose The purpose of this paper is to prepare composite micro-arc oxide coatings with better wear resistance and corrosion resistance. Design/methodology/approach A nickel powder composite micro-arc oxide film was prepared on the surface of the magnesium alloy by the method of organically combining ultra-fine Ni powder with micro arc oxidation film layer. In this experiment, the changes in the corrosion resistance and microstructure of the composite film layer after adding Ni powder were studied, and the effect of the addition of glycerin on the corrosion resistance of the film layer was analyzed. Findings The results show that the ultra-fine nickel powder was successfully prepared by the liquid phase reduction method, and the micro-arc oxidation process was modified under the optimal addition amount. The surface of the micro-arc oxide film made of ultra-fine nickel powder was found by SEM to have smooth surfaces and few holes. According to X-ray diffraction analysis, the phase composition of the micro-arc oxide film layer was Mg, Ni, NiSiO4, MgNi (SiO4) and Mg2SiO4. According to the results of electrochemical tests, the corrosion resistance of the micro-arc oxidation composite film layer was improved after the addition of ultra-fine Ni powder, the corrosion current was greatly reduced and the impedance has been improved. And after adding glycerin, the surface of the film layer becomes denser, and the corrosion resistance of the micro-arc oxide film is significantly improved. Originality/value Through this experimental research, a micro-arc oxide coating of powder composite magnesium alloy was successfully prepared. The corrosion resistance of the micro-arc oxidation film layer has been improved, and certain functions had been given to the micro-arc oxidation composite film, which has increased the application field of magnesium alloys.

The effect of different turbulent flow on failure behavior in secondary loop of the pressurized water reactor

To investigate the effect of different two-phase turbulent flow on the failure behavior, two areas with different distances from the orifice, which suffered from different degrees of two-phase turbulent flow, were studied by transmission electron microscope (TEM) and computational fluid dynamic (CFD). The results indicated that the two-phase turbulent flow affected the wall thinning by accelerating increase of the mass transfer rate. The Erosion at pipe head adjacent to the orifice was found to form cavitation, forming a single layer of nanocrystalline Fe3O4 film on the ferrite matrix; while a moderate Flow accelerated corrosion (FAC) was found in the middle of the pipe, producing a four-layer Fe3O4 film, which consisted of an inner thin nanocrystalline oxide layer, a second dense blocky-shaped oxide layer, a third loose particle layer, an outermost layer deposited large particle layer. Obviously, the four-layer oxide film structure had better protection than the single layer oxide film due to low mass transfer rate.

Humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer.

A relative humidity sensor based on a graphene oxide-coated few-mode fiber Mach-Zehnder interferometer (MZI) is proposed in this paper. The MZI was made by splicing a segment of the few-mode fiber (FMF) between two segments of a no-core fiber (NCF) and two segments of a single mode fiber (SMF) located outside the two NCFs. The core and cladding of the FMF acted as interferometric arms, while the NCFs acted as couplers for splitting and recombining light due to mismatch of mode field diameter. The cladding of the FMF was corroded with hydrofluoric acid, and a layer of graphene oxide (GO) film was coated on the corroded cladding of FMF via the natural deposition method. The refractive index of GO varied upon absorption the water molecules. As a result, the phase difference of the MZI varied and the wavelength of the resonant dip shifted with a change in the ambient relative humidity (RH). High humidity sensitivity of 0.191 and 0.061 nm/%RH in the RH range of 30-55% and 55-95%, respectively, were achieved experimentally. The high sensitivity, compact size, and simple manufacturing of the proposed sensor could offer attractive applications in fields of chemical sensors and biochemical detection.

White-light interferometry for early-stage metal oxide growth characterization

Oxidation of metals can provide a functional oxide film or an oxide layer that can lead to material degradation causing performance limiting concerns. Because of the technological and economic impacts of oxidation, understanding early-stage oxidation growth and its mechanisms is of high importance. Unfortunately, poor empirical data during early-stage oxidation has left our current understanding of oxidation incomplete and woefully inadequate. Measurement techniques previously used for oxidation kinetics characterization include microbalance, x-ray diffraction, Fourier-transform infrared spectroscopy, and spectroscopic ellipsometry. However, these techniques lack the necessary time-resolution or vertical resolution in addition to not providing any spatial data, which is essential to early-stage oxidation studies to understand both oxidation kinetics and mechanisms. A novel rapid and surface-sensitive data collection technique that provides three-dimensional spatial data of a growing oxide layer with sub-nanometer thickness resolution using white-light interferometry has been developed here. This technique will be the first technique capable of providing real-time spatial results of early-stage oxidation growth. The effectiveness of this characterization tool is shown by observing the early-stage oxidation kinetics and film cracking of uranium heated to 90 °C under 500 torr of pure O2. Initially a parabolic oxidation growth is observed. Once the oxide layer reaches ≈30 nm, the epitaxial stresses between the uranium substrate and oxide film layer causes localized cracking in addition to the observed transition of the parabolic growth rate to a linear growth rate. The results of the white-light interferometry are verified by glancing incidence x-ray diffraction.

Effect of hydrothermal treatment on porous anodic alumina generated by one-step anodization

Abstract The effects of the hydrous oxide film obtained from the hydrothermal treatment of the electropolished aluminum sheet on the porous anodic alumina produced by the first step of anodization in oxalic acid were investigated. It is indicated that the dense barrier layer within the hydrous oxide film can bring about a nearly exponential decrease of the current as a function of time. As to the porous layer of the hydrous oxide film, namely the ‘cornflake’ structure onto the barrier layer, it can optimize the initially nucleated site of the nanoporous during the anodization, which is beneficial to the self-ordered array of the nanoporous generated on the PAA film. It is concluded that the hydrous oxide film produced by the hydrothermal treatment can facilitate the self-assembly of the porous anodic alumina even if the applied potential is 60 V in oxalic acid.

Insights into the zinc effect on radio-cobalt deposition on stainless steel piping surfaces under BWR conditions from experiment guided 1st principles modelling

The beneficial effect of zinc to mitigate radio-cobalt uptake on stainless steel piping surfaces under BWR conditions is revisited by means of 1st principles modelling. A viable generic hydroxylated grain boundary interface (HGBI) model for magnetite, i.e., an inverse spinel, is formulated and interrogated in order to unravel how Zn may cause exclusion of Co by competing for the same sites. While Co2+ as well as Ni2+ reside preferentially in the octahedral lattice sites of the inverse spinel lattice, Zn2+ prefers to reside at the HGBI. The difference is consolidated for M(II), M being Cr, Mn, Fe, Co, Ni, Cu, or Zn. Similar affinities as well as mobilities of Co2+ and Zn2+ in the HGBI are taken to explain how, upon Fe2+ dissolution, Zn2+ may compete with Co2+ for the Fe2+ sites in the inner layer of the duplex oxide film. Impacts of Zn2+ and Ni2+ on Co2+ uptake in the outer oxide layer is also addressed. Zn2+ guided precipitation is found to be less effective than the Ni2+ guided process. Reported beneficial effects on radio-cobalt uptake upon sealing off the stainless steel acting Ni2+ source by coating with magnetite as well as hematite are discussed.

The Effect of Electrolyte Concentration and Electric Current on the Quality of Surface Coloring on Anodized Aluminum

The use of aluminum metal in daily life has widely used coloring techniques to enhance the aesthetic value of the metal. Aluminum anodizing process can produce porous on the metal surface. The formed porous can be used to store and hold the coloring agent to make them more durable. The research intends to observe the coloring characteristics on the aluminum surface influenced by several parameters of the anodizing process, including electrolyte concentration and electric current. In this study the current H2SO4 concentration was used as a variable to improve the quality of staining on anodized aluminum surfaces. The anodization process was carried out on H2SO4 electrolyte solution with variations in concentrations of 10% to 20% and the current density used was 3 A to 5 A. The tests were carried out using micro Vickers to observe the hardness value. The hardness was higher at lower concentration of electrolyte solution due to thinner layer of oxide film, scanning electron microscope to observe the structure and visual observations for anodized color quality. From the results given, the tendency of the lower current density the size and density of porous lower. With the same condition, the color was darker than higher current density.

Performance of protective oxide films on Fe–Ni alloy anodes in molten KF–AlF3–Al2O3 salts at 700 °C

An oxide film containing NiFe2O4 was prepared by oxidizing Fe–Ni alloy in hot air, and the performance of the protective oxide film in molten KF–AlF3–Al2O3 salts at 700 °C was characterized by electrochemical methods, including electrochemical impedance spectroscopy, capacitance measurements, linear sweep voltammetry, and chronoamperometry to clarify the breakdown and growth process of the oxide film. For the pre-oxidized 57Fe–43Ni, 50Fe–50Ni, and 43Fe–57Ni alloys, the oxide films, with a thickness of 5 μm, are composed of Fe2O3 and NiFe2O4, according to X-ray diffraction and scanning electron microscopy analysis. The transfer resistance of ions in the oxide film increases with increasing nickel content, and reaches its maximum value of 91.39 Ω⋅cm2 for the pre-oxidized 43Fe–57Ni alloy based on electrochemical impedance spectroscopy measurements. Moreover, the carrier density in the oxide film determined from Mott–Schottky plots decreases as the nickel content increases. Under anodic polarization, the breakdown of oxide film follows the generation of metal cation vacancies and condensation of excess cation vacancies. Concurrently, a new oxide layer forms along the substrate owing to the annihilation of oxygen vacancies and diffusion of oxygen anion in the oxide film. After oxygen evolution, a new oxide film layer containing NiFe2O4 forms on the alloy substrate, leading to the passivation observed in the anodic polarization curves. The maximum polarization resistance in the passivation region is 4.86 Ω⋅cm−2 for the pre-oxidized 43Fe–57Ni alloy, indicating that the pre-oxidized 43Fe–57Ni alloy possesses better corrosion resistance to molten fluorides than the other two pre-oxidized Fe–Ni alloys. Chronoamperometry measurements show that the oxide film on the 43Fe–57Ni alloy is in a dynamically stable state during oxygen evolution.

Analysis of the Microstructure, Phase Composition, and Oxidation Kinetics of Heat-Resistant Titanium Alloys with Gadolinium

The structure, phase composition, and local chemical composition of half-finished products (rods) made from Ti–Al–Mo–Zr–Si- and Ti–Al–Mo–Zr–Sn–Si-based alloys additionally microalloyed with 0.4 wt % gadolinium have been studied in this work. The structure of the rod made from the Gd-alloyed Ti–Al–Mo–Zr–Si composition was found to be characterized by the presence of Gd2O3 gadolinium oxide particles. The structure of the rod made from the Gd-alloyed Ti–Al–Mo–Zr–Sn–Si composition, which contains tin as a low-melting element, is characterized by the presence of Gd–Sn–O complex oxide particles, whose cores and shells are Gd5Sn3 intermetallics and Gd2O3 gadolinium oxide, respectively. The formation of such particles in both alloys occurs at the stage of ingot solidification, and the particles remain in the materials at all stages of their subsequent treatment. The oxidation kinetics of the alloys upon isothermal holding in a temperature range of 600–800°С is studied depending on the structure of half-finished products. The oxidation processes of the Ti–Al–Mo–Zr–Sn–Si alloy are less intensive than those of the Ti–Al–Mo–Zr–Si alloy. The alloying with gadolinium up to 0.4 wt % leads to the accelerated oxidation of the tin-free alloy, which is due to the presence of Gd2O3 particles precipitated at grain boundaries and interfaces. The alloying of the tin-containing composition with gadolinium almost does not affect the oxidation kinetics at 600–700°С and slightly decelerates the oxidation at 750–800°С; this is related to the presence of the Gd–Sn–O oxide particles in the structure, which are uniformly distributed over the grain body. The laws of oxidation of both the compositions free from gadolinium and alloyed with gadolinium were determined. It was shown that the oxide film formed upon the oxidation of both alloys is multilayer and consists of alternating layers of aluminum and titanium oxides. In this case, the progressive growth of oxide film layers alters the film exfoliation owing to the high brittleness of aluminum oxides. The presence of gadolinium oxide particles in both alloys leads to the porosity of diffusion zone of the base metal upon oxidation.

The effect of nickel on corrosion behaviour of high-strength low alloy steel rebar in simulated concrete pore solution

The effect of nickel on the corrosion behaviour of high-strength low alloy steel reinforcement was investigated by electrochemical measurement techniques, X-ray photoelectron spectroscopy, and auger electron spectroscopy. The results demonstrate that 3 wt% of nickel addition reduced the corrosion rate to 17 nA/cm2 compared to 730 nA/cm2 of carbon steel in the contaminated concrete condition. The enhancement of corrosion resistance for nickel-bearing steel was attributed to the formation of protective oxide film. The oxide film exhibited n-type semiconductivity in which oxygen vacancy was the main defect. The involvement of nickel in the formation process of oxide film changed its structure and composition. Nickel was enriched in the oxide film, simultaneously decreasing the defects density and the whole thickness of oxide film, and together with the increase of the Fe2+/Fe3+ ratio and the inner barrier oxide film thickness. The protective inner barrier layer of oxide film on the nickel-bearing steel can strongly inhibited the corrosive attack.

Ultrasensitive negative capacitance phototransistors

Sensitive photodetection is crucial for modern optoelectronic technology. Two-dimensional molybdenum disulfide (MoS2) with unique crystal structure, and extraordinary electrical and optical properties is a promising candidate for ultrasensitive photodetection. Previously reported methods to improve the performance of MoS2 photodetectors have focused on complex hybrid systems in which leakage paths and dark currents inevitably increase, thereby reducing the photodetectivity. Here, we report an ultrasensitive negative capacitance (NC) MoS2 phototransistor with a layer of ferroelectric hafnium zirconium oxide film in the gate dielectric stack. The prototype photodetectors demonstrate a hysteresis-free ultra-steep subthreshold slope of 17.64 mV/dec and ultrahigh photodetectivity of 4.75 × 1014 cm Hz1/2 W−1 at room temperature. The enhanced performance benefits from the combined action of the strong photogating effect induced by ferroelectric local electrostatic field and the voltage amplification based on ferroelectric NC effect. These results address the key challenges for MoS2 photodetectors and offer inspiration for the development of other optoelectronic devices.

Economical Si-Bearing, Nearly Ni-Free 19Cr TRIP-Aided Duplex Stainless Steels with Better High-Temperature Oxidation Resistance

A novel series of Si-bearing, nearly Ni-free economical TRIP-aided duplex stainless steels (DSSs) 19Cr-5.5Mn-0.3Ni-0.2N-xSi (x = 0.5-2.5) have been prepared to investigate effect of silicon on microstructure, tensile mechanical property and high-temperature oxidation behavior. The results have shown that the designed economical alloys have a balanced ferrite/austenite dual-phase structure after suitable solution treatment. Volume of ferrite phase increases with an increase in silicon content. Ferrite deforms by dislocation slip during tensile plastic deformation process at room temperature. However, transformation-induced plasticity effect dominates deformation mode of metastable austenite phase. The designed DSS with 1.5 wt.% Si content exhibits good combination of tensile mechanical properties, exceeding 50% in elongation and 800 MPa in ultimate tensile strength, with a sequential γ → e-martensite → α′-martensite transformation in deformed austenite phase. High-temperature oxidation resistance of DSSs could be enhanced with an increase in silicon content at 1100 °C in air due to the formation of compact and continuous Cr- and Si-rich oxide film in the inner oxide film layer.

Effective Medium Model of Periodic Nanolayered Transparent Shields

An innovative effective medium model based on the transfer matrix method is proposed for the simulation of 1D-periodic subwavelength metal–dielectric laminated structures excited by TM- or TE-polarized plane wave with oblique incidence angles. The homogeneous medium of each period is characterized by TM or TE complex effective permeability and conductivity. The resulting effective single layer (ESL), having the same total thickness of the multilayer laminate, is represented by a transfer matrix given by the product of the transmission matrices of the periods composing the structure. Notice that this model allows the homogenization of n -layer periods, while the effective medium approximation method is formulated for only two-layer periods. The ESL is used to compute the transmission and reflection coefficients and the shielding effectiveness of 1D-periodic nanolayered transparent coatings made by alternating layers of silver, zinc oxide, or titanium dioxide films, in the frequency range from 100 MHz up to 10 THz. The propagating wave performances of the ESL are compared with the ones given by the rigorous multilayer model. Finally, two different screens made of transparent coatings over glass are proposed and analyzed.

The effect of electrolyte concentration and electric current on the quality of surface colouring on anodized aluminium

The use of aluminium metal in daily life has widely used colouring techniques to enhance the aesthetic value of the metal. Aluminium anodizing process can produce porous on the metal surface. The formed porous can be used to store and hold the colouring agent to make them more durable. The research intends to observe the colouring characteristics on the aluminium surface influenced by several parameters of the anodizing process, including electrolyte concentration and electric current. In this study the current H2SO4 concentration was used as a variable to improve the quality of staining on anodised aluminium surfaces. The anodization process was carried out on H2SO4 electrolyte solution with variations in concentrations of 10% to 20% and the current density used was 3 A to 5 A. The tests were carried out using micro Vickers to observe the hardness value. The hardness was higher at lower concentration of electrolyte solution due to thinner layer of oxide film, scanning electron microscope to observe the structure and visual observations for anodised colour quality. From the results given, the tendency of the lower current density the size and density of porous lower. With the same condition, the colour was darker than higher current density.

Effect of Alcohol Addition to Sulfuric Acid on Efficiency for Formation of Anodic Alumina

Anodization of aluminum in electrolytes containing alcohols as an additive has been studied for improvement of coating properties such as corrosion and wear resistance, and hardness. The influence of the addition of alcohols on the pore arrangement in anodic alumina was also investigated. However, the essential understanding of the effect of alcohol addition is still insufficient. In this study, we used the sulfuric acid-based electrolyte containing various alcohols (e.g., methanol, ethanol, glycerol, and ethylene glycol) as an additive and investigated the effects of types and concentrations of alcohols on the efficiency for the oxide formation and the structure of the porous alumina. High purity aluminum sheets were used as a starting material and anodized at constant current of 100 A m-2 in 1.5 mol dm-3 sulfuric acid with alcohol concentration in the range of 0~50 vol%. The formation of porous alumina film on the aluminum substrate was investigated by measuring voltage transient. In the case of ethanol concentration less than 10 vol%, voltage-time curve shows the steady-state voltage of approximately 15.7 V. When ethanol concentration exceeded 20 vol%, the steady-state voltage obviously increased with increasing ethanol concentration. In sulfuric acid without ethanol addition, the surface layer of oxide film was excessively dissolved after anodization for 220 min. The film thickness was approximately 65 μm. While using sulfuric acid with 50 vol% ethanol, chemical dissolution of the outer surface was significantly suppressed and the film thickness increased from 65 μm to 70 μm at the same anodization time, i.e., the same electric charge. Even in other type of alcohols, chemical dissolution of oxide was suppressed, resulting in improvement of coulombic efficiency for the oxide formation. The variation of dissociation constant of the electrolyte by addition of alcohols might affect the chemical dissolution and formation efficiency of anodic film. K. Kuroda, M. Ozawa, J. Met. Finish. Soc. Jpn., 15, 3 (1965).Y. Li, M. Zheng, L. Ma, W. Shen, Nanotechnology, 17, 5101 (2006).

Numerical simulation of periodic cracking mechanism in microscopic surface films during roll bonding processes

AbstractThe microscopic surface films existing on the top of metallic layers play an important role in the process of joining by plastic deformation. The bond formation during cold welding processes is basically associated with the fracturing of surface films to produce intimate metallic contacts. The present paper aims at providing a numerical model to describe the cracking pattern of brittle surface films bonded to the ductile substrates. A microscale finite element model is developed which takes into account the fracturing mechanisms of thin surface films in roll bonding processes. The presented model is calibrated by using the existing experimental data for an aluminum alloy covered by a thin layer of oxide film. The model is also validated against a well‐known analytical model for periodic cracking. The distribution of stresses within the fractured surface film demonstrates that the generated cracks in the surface film have essentially a periodic pattern. Moreover, it is shown that the crack spacing is highly dependent on the properties of the surface film. Finally, the obtained results for the roll bonding show that a crack density saturation takes place at the entry of the roll bite where a small surface expansion is applied to the rolled samples.

A Highly Robust Silicon Ultraviolet Selective Radiation Sensor Using Differential Spectral Response Method.

This paper presents a silicon ultraviolet radiation sensor with over 90% UV internal quantum efficiency (QE) and high selectivity to the UV waveband without using optical filters. The sensor was developed for applications that require UV measurement under strong background visible and near-infrared (NIR) lights, such as solar UV measurement, UV-C monitoring in greenhouses or automated factories, and so on. The developed sensor is composed of monolithically formed silicon photodiodes with different spectral sensitivities: a highly UV responsive photodiode with internal quantum efficiency (QE) of nearly 100% for UV light, and a lowly UV responsive photodiode with UV internal QE lower than 10%. The photodiodes were optimized to match their visible and NIR light responsivity, and the UV signal is extracted from the background radiation by using the differential spectral response method. With this approach, an internal QE of over 90% for UV light was obtained, with a residual internal QE to non-UV light lower than 20% for 400 nm, 5% for 500 nm, 2% for 600 nm and 0.6% to NIR light. The developed sensor showed no responsivity degradation after exposure towards strong UV light. It was confirmed by the simulation results that the residual responsivity is further suppressed by employing an on-chip band-rejection optical layer consisting of several layers of silicon oxide and silicon nitride films.

Spheroidization of tantalum powder by radio frequency inductively coupled plasma processing

In this work, we used radio frequency (RF) plasma spheroidization to transform irregularly shaped tantalum powders to spherical ones. After RF plasma treatment, the majority of particles were spheroidized with the presence of a small number of irregular particles. The mean particle size becomes finer and the particle size distribution narrower, as compared with the starting powder. A few non-spherical or even irregular tantalum powders still existed. Although argon gas was used in the plasma chamber, oxygen contamination still occurred. A thin layer of oxide film was found on the surface of particles, while the particle interiors were inferred free of oxygen. The powder characteristics had been significantly improved. After spheroidization treatment, the apparent density, tap density and powder flowability significantly increased from 7.03 g/cm3 to 8.9 g/cm3, 8.6 g/cm3 to 10.05 g/cm3, and 12.41 s/(50 g) to 7.96 s/(50 g), respectively, in comparison with that of raw powders. This study presents a feasible method for fabricating spherical tantalum powders, which may potentially broaden the application for metal additive manufacturing.