Argon-nitrogen Atmosphere Research Articles

Preparation of tantalum-containing coatings on NiTi shape memory alloys with enhanced in vitro cytocompatibility and antibacterial effectiveness

In this work, the magnetron sputtering method is used to deposit tantalum-containing coatings on NiTi shape memory alloys under various sputtering atmospheres including (i) 100% argon, (ii) 16.6% oxygen and 83.4% argon, and (iii) 16.6% nitrogen and 83.4% argon. This research examines how the sputtering atmosphere can impact surface morphology, roughness, wettability, biocompatibility, in vitro cytocompatibility, and antibacterial performance of tantalum-containing coatings. The calculation of nickel ions release by coupled inductively coupled plasma-optical emission spectrometry displayed that none of the coated samples showed any traces of nickel, unlike the bare NiTi substrate. This has led to an improvement in biocompatibility. Topographical measurements demonstrated the formation of a smooth surface under the argon-oxygen atmosphere, whereas the deposited layer in the argon-nitrogen atmosphere exhibited irregular ups and downs. The coatings deposited under the argon-nitrogen atmosphere result in a hydrophobic surface with many hills and valleys which can considerably enhance protein and cellular absorption. Besides, the samples coated under an argon-oxygen atmosphere with a smooth surface exhibited excellent antibacterial efficiency only as early as 6 h of incubation. This is probably due to the formation of amorphous tantalum pentoxide.

Effects of Copper Content on the Microstructural, Mechanical and Tribological Properties of TiAlSiN–Cu Superhard Nanocomposite Coatings

The effects of the Cu content on the microstructural, mechanical and tribological properties of the TiAlSiN–Cu coatings were investigated in an effort to improve the wear resistance with a good fracture toughness for cutting tool applications. A functionally graded TiAlSiN–Cu coating with various copper (Cu) contents was fabricated by a filtered cathodic arc ion plating technique using four different (Ti, TiAl2, Ti4Si, and Ti4Cu) targets in an argon-nitrogen atmosphere. The results showed that the TiAlSiN–Cu coatings are a nanocomposite consisting of (Ti,Al)N nano-crystallites (~5 to 7 nm) embedded in an amorphous matrix, which is a mixture of TiOx, AlOx, SiOx, SiNx, and CuOx phase. The addition of Cu atoms into the TiAlSiN coatings led to the formation of an amorphous copper oxide (CuOx) phase in the coatings. The maximum nanohardness (H) of ~46 GPa, H/E ratio of ~0.102, and adhesion bonding strength between coating and substrate of ~60 N (LC2) were obtained at a Cu content ranging from 1.02 to 2.92 at.% in the TiAlSiN–Cu coatings. The coating with the lowest friction coefficient and best wear resistance was also obtained at a Cu content of 2.92 at.%. The formation of the amorphous CuOx phase during coating growth or sliding test played a key role as a smooth solid-lubricant layer, and reduced the average friction coefficient (~0.46) and wear rate (~10 × 10−6 mm3/N·m).

Optical Characterization of Non-Stoichiometric Silicon Nitride Films Exhibiting Combined Defects

The study was devoted to optical characterization of non-stoichiometric silicon nitride films prepared by reactive magnetron sputtering in argon-nitrogen atmosphere onto cold (unheated) substrates. It was found that these films exhibit the combination of three defects: optical inhomogeneity (refractive index profile across the films), uniaxial anisotropy with the optical axis perpendicular to the boundaries and random roughness of the upper boundaries. The influence of the uniaxial anisotropy was included into the corresponding formulae of the optical quantities using the matrix formalism and the approximation of the inhomogeneous layer by a multilayer system consisting of large number thin homogeneous layers. The random roughness was described using the scalar diffraction theory. The processing of the experimental data was performed using the multi-sample modification of the least-squares method, in which experimental data of several samples differing in thickness were processed simultaneously. The dielectric response of the silicon nitride films was modeled using the modification of the universal dispersion model, which takes into account absorption processes corresponding to valence-to-conduction band electron transitions, excitonic effects and Urbach tail. The spectroscopic reflectometric and ellipsometric measurements were supplemented by measuring the uniformity of the samples using imaging spectroscopic reflectometry.

Experimental and computational assessment of U[sbnd]Si[sbnd]N ternary phases

Uranium nitride-silicide composites are being considered as a high-density and high thermal conductivity fuel option for light water reactors. During development, chemical interactions were observed near the silicide melting point which resulted in formation of an unknown USiN ternary phase. In the present work, USiN composite samples were produced by arc-melting U3Si2 under an argon-nitrogen atmosphere to form the ternary phase. The resulting samples were characterized by SEM/EDS-EPMA and XRD, and demonstrated an equilibrium between U3Si2, UN, USi and a USiN phase with a distinct crystallographic structure. Rietveld refinement of the ternary structure was performed, considering the ternary structures existent in the analogue USiC system, and a good fit was obtained for the hexagonal U20Si16N3 phase. DFT + U calculations were performed in parallel to evaluate the thermodynamic and dynamic stability of the ternaries U20Si16N3 and U3Si2N2. The calculated enthalpy of formation and phonon dispersion support the existence of stable U20Si16N3 and U3Si2N2, although some soft modes in the U20Si16N3 phase phonons are observed. The results presented here thus demonstrate the occurrence of at least one ternary phase in the USiN system.

Microstructure and Mechanical Properties of Multilayer α-AlN/α-BCN Coating as Functions of the Current Density during Sputtering of a B4C Target

Multilayer AlN/BCN coating of nanometer scale have been prepared by magnetron sputtering of Al and B4C targets in an argon–nitrogen atmosphere during deposition on a Si substrate. These coating have an X-ray amorphous structure and the maximum Knoop hardness of 27 GPa (at the current density 100 mA). The first-principle molecular dynamics calculations show that the B4–BN layer is dynamically unstable; thus, it will not be epitaxial and will be amorphous or have a structure different from the B4–BN structure. The thermal vacuum annealing from 600 to 800°C of samples with multilayer nanosized coating leads to the decrease in the Knoop hardness to 18 GPa; however, the coating structure is retained X-ray amorphous.

Si doped GaN films grown by reactive co-sputtering of GaAs and Si

Si doped GaN films were grown on sapphire by RF reactive co-sputtering of GaAs and Si in argon–nitrogen atmosphere at 700 °C. The incorporation of Si in the films was controlled by varying Si area coverage on GaAs target and argon to nitrogen ratio in sputtering atmosphere. X-ray diffraction shows significant stress relaxation and improvement in structural quality with the incorporation of Si in films deposited with 2%–12% Si area coverage and 10%–20% nitrogen in sputtering atmosphere. Resistivity and Hall measurements show that the films deposited with 5%–12% Si area coverage and 20% nitrogen in sputtering atmosphere exhibit resistivity of ∼1.5 × 10−2 Ω cm, along with carrier concentration of ∼2 × 1019 cm−3 and mobility in the range of 20–22 cm2/V-s. The film deposited with 10% nitrogen in sputtering atmosphere and 8% Si area coverage, exhibits high carrier concentration of 1.5 × 1020 cm−3 along with mobility of 7.1 cm2/V-s, resulting in the lowest resistivity of ∼6 × 10−3 Ω cm. The behavior of electrical parameters is explained by invoking carrier trapping and scattering at the grain boundaries, in conjunction with the observed changes in their structural quality. The film with high carrier concentration ∼1020 cm−3, exhibits strong free carrier effects, such as, plasma resonance in NIR, high reflectivity in IR and significantly larger optical gap of 3.60 eV, due to the combined effect of Burstein-Moss shift and band gap narrowing.

Микроструктура и механические свойства многослойных alpha-AlN/alpha-BCN-покрытий в зависимости от плотности тока при распылении мишени B-=SUB=-4-=/SUB=-C

AbstractMultilayer AlN/BCN coating of nanometer scale have been prepared by magnetron sputtering of Al and B_4C targets in an argon–nitrogen atmosphere during deposition on a Si substrate. These coating have an X-ray amorphous structure and the maximum Knoop hardness of 27 GPa (at the current density 100 mA). The first-principle molecular dynamics calculations show that the B4–BN layer is dynamically unstable; thus, it will not be epitaxial and will be amorphous or have a structure different from the B4–BN structure. The thermal vacuum annealing from 600 to 800°C of samples with multilayer nanosized coating leads to the decrease in the Knoop hardness to 18 GPa; however, the coating structure is retained X-ray amorphous.

Atomization of UMo Particles under Nitrogen Atmosphere

Generally, the atomization of UMo particles is done under vacuum or argon atmosphere, and the surface modification of these UMo particles is, usually, carried on through a further process. The techniques for surface modification of atomized UMo particles, aimed to control the Fuel/Matrix interaction, involve, in some cases, complex methodologies and often with minor effect due to the limited solubility of third elements in solid UMo alloy. The atomization and surface conditioning, applied in separate stages, may affect the efficiency of powder production process. Then, the main goal of this study is to explore the surface modification of UMo particles in liquid state or during the solidification that follows the centrifugal atomization process. Through the change of atomization atmosphere, could be possible to promote liquid/gas reactions, with a higher solubility of the modifier element in micro drops of UMo alloy, before they become solid particles. This paper presents comparative results of centrifugal atomization of UMo particles, carried out under inert argon and reactive nitrogen atmospheres. Dissolved nitrogen contents, measured by SEM-EDS analyses, reached up to 7.57 wt% at the center of under nitrogen atomized particles, very higher than 0.84 wt% of nitrogen measured at the center of UMo particle atomized under argon. The presence of uranium nitride was partially verified by conventional XRD analysis. Nevertheless, Out-of-Pile interaction test result, reveals decreasing of aluminium contents into UMo particles atomized under nitrogen atmosphere; Just 3.77 wt% of Al was the maximum content detected in the center of these particles, very lower than 29.11 wt% of Al measured inside UMo particles atomized under argon. Finally, it is possible to conclude that the atomization under reactive atmosphere may modify the surface composition and the behavior of UMo fuel particles dispersed in aluminium, for dispersion type nuclear fuel application.

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N2atmosphere

A rhombohedral analysis method for analysing the lattice distortion in a (111)-textured face-centred cubic film under rotationally symmetric stress is proposed. Because no material constants, such as diffraction elastic constants, are required, the expressions of the distortion, namely the angle and the lattice parameter, are universal and can be readily used to compare different films. Using this rhombohedral distortion analysis method, (111)-textured Pt films deposited under argon–nitrogen atmosphere are systematically investigated, and the thickness-dependent lattice deformation in as-deposited and annealed films is described by the two geometrical parameters of the rhombohedral cell.

하이브리드 코팅 시스템에 의해 합성된 Zr-Al-N 박막의 미세구조와 기계적 특성, 산화 특성, 부식특성

Zr-Al-N coatings were synthesized by the hybrid coating system combining arc ion plating and DC magnetron sputtering from a Zr and an Al target in argon-nitrogen atmosphere, respectively. By changing the power applied on the Al cathodes, the Zr-Al-N coatings with various Al contents were deposited. The microstructure and chemical compositions of the Zr-Al-N coatings were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). With increasing of Al content in the coatings, the solid solution (Zr, Al)N crystallites were observed in the Zr-Al-N coatings. The nanohardness of the Zr-Al-N coatings exhibited a maximum value of 42 GPa for the Zr-Al (7.9 at.%)-N, and decreased with further increase in Al content in the coatings. The oxidation and corrosion behavior of the Zr-Al-N coatings revealed better properties compared than those of ZrN coatings due to the formation of a solid solution.

Effect of gas Pressure on the Mechanical Properties of Sputtered TaN Films

Abstract Tantalum nitride as a promising material for applications has attracted considerable interest due to such promising properties as superhardness and high temperature stability. In this paper, the TaN films were deposited on the single crystal superalloy by radio frequency (RF) reactive magnetron sputtering in an argon-nitrogen atmosphere. The effect of gas pressure on the mechanical property, morphology, phase structure, residual stress, tribological property of the films is investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray stress measurement and SRV friction and wear test, respectively. The results show that the partial pressure of N2 has a great influence on the phase structure, residual stress and nano-hardness.

A Novel Way to Prepare Silicon Oxide Nanomaterials with White Light Emission by Reactive Ladder Polyhydrosilsesquioxane

In the present work, we describe a simple and template-free preparation method of silicon oxide nanowires (SiOx-NWs) and silicon oxide nanotubes (SiOx-NTs) from a reactive ladder polyhydrosilsesquioxane (H-LPSQ) precursor. SiOx-NWs and SiOx-NTs were synthesized in large scale by high temperature (1100°C) reaction of ladder HLPSQ on silicon wafer substrate under wet hydrogen and argon (nitrogen) atmosphere. The SiOx-NWs and SiOx-NTs have a uniform diameter and long length. The as-prepared SiOx-NWs exhibits a particular white light emission rather than blue or green light emission found before. Keywords: Ladder polysilsesquioxanes, nanotubes, nanowires, silicon oxide, chemical vapor deposition (CVD), anodic aluminium, carboxylate crystals, sol-gel, Eclipse spectrometer, Si-OH groups, calorimetry, lamella

A Novel Way to Prepare Silicon Oxide Nanomaterials with White Light Emission by Reactive Ladder Polyhydrosilsesquioxane

In the present work, we describe a simple and template-free preparation method of silicon oxide nanowires (SiOx-NWs) and silicon oxide nanotubes (SiOx-NTs) from a reactive ladder polyhydrosilsesquioxane (H-LPSQ) precursor. SiOx-NWs and SiOx-NTs were synthesized in large scale by high temperature (1100°C) reaction of ladder HLPSQ on silicon wafer substrate under wet hydrogen and argon (nitrogen) atmosphere. The SiOx-NWs and SiOx-NTs have a uniform diameter and long length. The as-prepared SiOx-NWs exhibits a particular white light emission rather than blue or green light emission found before. Keywords: Ladder polysilsesquioxanes, nanotubes, nanowires, silicon oxide, chemical vapor deposition (CVD), anodic aluminium, carboxylate crystals, sol-gel, Eclipse spectrometer, Si-OH groups, calorimetry, lamella

Synthesis and magnetic properties of nanocolumnar nickel films deposited in argon-nitrogen atmosphere

Ferromagnetic nickel films with a structure comprising nanocolumns grown perpendicular to a substrate have been obtained by magnetron sputtering of a nickel target in argon atmosphere containing 2 vol % nitrogen. Measurements of X-ray diffraction and investigation of magnetic properties showed that the obtained films consist of a solid solution of nitrogen in nickel. The saturation magnetization of the films is 1.5–2 times smaller and their Curie temperature is 30 K lower than the corresponding values for pure nickel. The film material exhibits a dimensional effect: as the grain size decreases below 10 nm, the magnetization sharply drops; at a grain size of 0.5 nm, the film possesses no magnetic order.

Spectroscopic ellipsometry studies of reactively sputtered nitrogen-rich GaAsN films

Nitrogen-rich GaAsN thin films have been deposited at 500°C by reactive rf sputtering of GaAs target in argon–nitrogen atmosphere. The arsenic content of the films was varied by changing the nitrogen percentage in the sputtering atmosphere and the As/Ga ratio in the films was estimated by X-ray fluorescence measurements. Spectroscopic ellipsometry measurements have been carried out on these films and the measured ellispometric spectra were fitted with theoretical spectra generated by using suitable model sample structures. From the best fit parameters of the dispersion model, band-gap values and variation of refractive index and extinction coefficient as a function of wavelength have been obtained for films deposited with different percentages of nitrogen in the sputtering atmosphere. The films deposited with 12% to 100% nitrogen in the sputtering atmosphere, which are of hexagonal GaN, exhibit GaN-like optical properties, though effects due to excess arsenic in amorphous phase are seen in the films deposited with less than 40% nitrogen. The films deposited with 5% to 12% nitrogen in sputtering atmosphere are dominantly polycrystalline GaAsxN1−x (x≈0.01 to 0.08) and exhibit variations in optical parameters, which are consistent with their structure and composition. The films deposited with less than 5% nitrogen in sputtering atmosphere are arsenic-rich and amorphous.

Structural and morphological characterization WCxNy thin films grown by pulsed vacuum arc discharge in an argon–nitrogen atmosphere

Ternary WCN thin films were deposited on 304 stainless steel substrates by using the cathodic repetitive pulsed vacuum arc technique. Coatings were grown employing a WC (6N) target with nitrogen as gas of work and exploring the effect of the number of pulses on the plane orientations and phase transition by means of X ray diffraction (XRD). Results show different phases formation as WC, WCO, WCxNy and W. The number of pulses had strong influence not only on the phase transformation but also on the polycrystallinity. Values of x around 0.93 were obtained by using the Vegard's law, corroborating results extracting from XRD analysis as diffraction angles and lattice parameters that are closer to WC. Moreover, XRD analysis allowed confirming the formation of a composite material, due to the existence of different phases and plane orientations. Morphological analysis as grain size and thickness were calculated by using atomic force microscopy (AFM), observing an increase of these parameters as a function of the number of pulses.

Characteristics of tantalum nitride thin film strain gauges for harsh environments

This paper presents the characteristics of Ta–N thin film strain gauges that are suitable for harsh environments, which were deposited on thermally oxidized Si substrates by dc reactive magnetron sputtering in an argon–nitrogen atmosphere (Ar–N2 (4–16%)). These films were annealed for 1h in 2×10−6Torr in a vacuum furnace with temperatures that ranged from 500 to 1000°C. The optimized deposition and annealing conditions of the Ta–N thin film strain gauges were determined using 8% N2 gas flow ratio and annealing at 900°C for 1h. Under optimum formation conditions, the Ta–N thin film strain gauges obtained a high electrical resistivity, ρ=768.93μΩcm, a low temperature coefficient of resistance, TCR=−84ppm/°C and a high temporal stability with a good longitudinal gauge factor, GF=4.12. The fabricated Ta–N thin film strain gauges are expected to be used in micromachined pressure sensors and load cells that are operable under harsh environments.

Microstructure, composition and oxidation resistance of nanostructured NiAl and Ni–Al–N coatings produced by magnetron sputtering

Nanostructured NiAl and Ni–Al–N thin films were RF magnetron sputtered from a NiAl compound target in different argon–nitrogen atmospheres. The structure and stoichiometry of as-deposited coatings were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Differential thermal analysis (DTA) was also conducted to study the oxidation kinetics of the films at high temperatures. Microstructural and compositional changes of the coatings after isothermal oxidation were investigated using XRD, SEM, and Rutherford backscattering spectrometry (RBS). The results show that: (1) denser and more completely crystallized Ni–Al–N thin films can be tailored through controlled ion bombardment during deposition, (2) nano-composite NiAl–AlN thin films were synthesized with nitrogen atomic concentrations up to 30%, and (3) the NiAl and Ni–Al–N coatings exhibited good oxidation resistance even at temperatures above 1273 K. The addition of AlN to NiAl resulted in decreased activation energies for oxidation. The oxidation study also revealed different rate controlling mechanisms for NiAl and Ni–Al–N (21.4 at.% N) films isothermally oxidized in air at 1273 K.

질화탄탈 박막형 스트레인 게이지의 제작과 특성

This paper descibes on the characteristics of Ta-N(tantalum nitride) ceramic thin-film strain gauges which were deposited on Si substrates by DC reactive magnetron sputtering in an argon-nitrogen atmosphere (Ar-<TEX>$(4{\sim}16%)N_{2}$</TEX>) for high-temperature applications. These films were annealed in <TEX>$2{\times}10^{-6}$</TEX> Torr vacuum furnace at the range of <TEX>$500{\sim}1000^{\circ}C$</TEX>. Optimum deposition atmosphere and annealing temperature were determined at <TEX>$900^{\circ}C$</TEX> for 1 hr. in 8% <TEX>$N_{2}$</TEX> gas flow ratio. Under optimum formation conditions, the Ta-N thin-film for strain gauges was obtained a high-resistivity of <TEX>$768.93{\mu}{\Omega}{\cdot}cm$</TEX>, a low temperature coefficient of resistance (TCR) of -84 ppm/<TEX>$^{\circ}C$</TEX> and a good longitudinal gauge factor (GF) of 4.12.

Magnetic properties of weak itinerant ferromagnetic ζ-Fe2N film

We have studied magnetic properties of ζ-Fe2N film deposited onto surface-oxidized Si (100) substrates by reactive dc magnetron sputtering with an argon–nitrogen atmosphere. At the temperature less than 120 K, the magnetic moment of the 120 nm-thick ζ-Fe2N film is hard to be saturated at magnetic fields up to 50 kOe, and the magnetic moment is weak. The inverse susceptibility linearly increases as the temperature increases between 65 and 160 K, and the change of the inverse susceptibility obeys the Curie–Weiss law. From the results of magnetization measurements, the magnetic parameter of the Curie temperature, the spontaneous magnetic moment at 0 K and the effective magnetic moment can be estimated to be 35 ± 2.5 K, 0.028 μB/iron atom and 0.70 μB/iron atom, respectively. These parameters suggest that the ζ-Fe2N film is in the weak itinerant electron ferromagnetic state. These parameters can be also explained by self-consistently renormalization (SCR) theory.