Mechanical properties and corrosion resistance of nanocrystalline ZrNxOy coatings on AISI 304 stainless steel by ion plating

Transition metal oxynitrides have become emerging decorative coating materials due to their adjustable coloration and high hardness and corrosion resistance. This research studied the effect of oxygen content on the coloration, mechanical properties and corrosion resistance of ZrN_xO_y thin films deposited on AISI 304 stainless steel using hollow cathode discharge ion plating (HCD-IP). The Zr/N/O ratios of the ZrN_xO_y films were determined using X-ray photoelectron spectroscopy (XPS). The color of the ZrN_xO_y thin film changed from golden yellow to blue and then slate blue with increasing oxygen content. X-ray diffraction (XRD) patterns revealed that phase separation of ZrN and m-ZrO₂ occurred as the oxygen content reached 31.2 at.%. ZrN(O) (ZrN with dissolving oxygen) is dominant at oxygen content less than 18.1 at.%, while m-ZrO₂ phase was prevailed at oxygen content above 40.3 at.%. Phase separation lowered the hardness of the ZrN_xO_y films as the fraction of ZrO₂ was less than 40%. The residual stresses in ZrN phase was higher than that in ZrO₂, and the residual stress decreased for the specimen containing 30 to 37% ZrO₂. For the samples containing more than 44% ZrO₂, the average residual stress was close to that in ZrO₂ phase. The corrosion resistance was evaluated by salt spray test and potentiodynamic scan in two solutions: 0.5MH₂SO₄ + 0.05 M KSCN and 5% NaCl solutions. The results showed consistent trend in the two solutions. From the results of potentiodynamic scan, corrosion resistance increased as the packing density of the film increased, whereas the film thickness was not a crucial factor on corrosion current; moreover, the electrical conductivity of the film may be one of the significant factors in corrosion resistance. Results of salt spray tests suggested that the corrosion of ZrN_xO_y in NaCl may play an important role in corrosion resistance.     

Heat treatment induced phase separation and phase transformation of ZrNxOy thin films deposited by ion plating

Nanocrystalline ZrN_xO_y thin films were deposited on p-type Si (100) substrates using hollow cathode discharge ion-plating (HCD-IP) and the films were annealed at 700 and 900 °C in the controlled atmosphere. The purpose of this study was to investigate the phase separation, phase transformation and the accompanying change of properties of the heat-treated ZrN_xO_y films deposited by ion plating. With the increase of oxygen flow rate ranging from 0 to 10 sccm, the primary phase of the as-deposited films evolved from ZrN to nearly amorphous structure and further to monoclinic ZrO₂ (m-ZrO₂). After heat treatment at 700 and 900 °C, phase transformation occurred in the samples deposited at 8 and 10 sccm O₂, where a stoichiometric crystalline Zr₂ON₂ was found to derive from m-ZrO₂ with dissolving nitrogen (m-ZrO₂(N)). The hardness of the ZrN_xO_y thin films could be correlated to the fraction of Zr₂ON₂ + m-ZrO₂. The film hardness decreased significantly as the fraction of ZrO₂ + Zr₂ON₂ exceeded ~ 60%, which was due to phase transition by increasing oxygen flow rate or phase transformation induced by heat treatment. The phase separation of m-ZrO₂ from ZrN with dissolving oxygen (ZrN(O)) may relieve the residual stress of the ZrN_xO_y specimens deposited at 5 and 8 sccm O₂, while direct formation of m-ZrO₂ increased the stress of the film deposited at 10 sccm O₂. On the other hand, the phase transformation from m-ZrO₂(N) to Zr₂ON₂ by heat treatment at both 700 and 900 °C may effectively relieve the residual stress of the ZrN_xO_y films.     

Phase transition and mechanical properties of ZrNxOy thin films on AISI 304 stainless steel

ZrN_xO_y thin films were deposited on AISI 304 stainless steel (304SS) substrates by reactive magnetron sputtering. The specimens were produced by sputtering a Zr target at 500 °C and the reactive gasses were N₂ and O₂ at various flow rates (ranging from 0 to 2 sccm). The purpose of this study was to investigate the effect of oxygen flow rate on the phase transition and accompanying mechanical properties of the ZrN_xO_y thin films. The oxygen contents of the thin films increased significantly with increasing oxygen flow rate. X-ray diffraction (XRD) revealed that the characteristics of the films can be divided into three zones according to the major phase with increasing oxygen content: Zone I (ZrN), Zone II (Zr₂ON₂) and Zone III (m-ZrO₂). The hardness of the ZrN_xO_y films decreased with increasing oxygen content due to the formation of the soft oxide phase. Modified XRD sin²ψ method was used to respectively measure the residual stresses of ZrN, Zr₂ON₂ and m-ZrO₂ phases. The results showed that the residual stress in ZrN was relieved as the oxygen content increased, and Zr₂ON₂ and m-ZrO₂ were the phases with lower residual stress. Compositional depth profiles indicated that there was a ZrO₂ interlayer near the film/substrates interface for all samples except the mononitride ZrN specimen. Contact angle was used as an index to assess the wettability of the film on substrate. The contact angles of ZrN, Zr₂ON₂ and m-ZrO₂ on stainless steel were indirectly measured using Owens-Wendt method. The results showed that ZrO₂ possessed the lowest wettability on 304SS among the three ZrN_xO_y phases, indicating that the ZrO₂ interlayer may account for the spallation of the ZrN_xO_y films after salt spray tests.     

CuIn1−xAlxS2 thin films prepared by sulfurization of metallic precursors

CuIn_1−xAl_xS₂ thin films (x = 0, 0.09, 0.27, 0.46, 0.64, 0.82 and 1) with thicknesses of approximately 1 μm were formed by the sulfurization of DC sputtered Cu-In-Al precursors. All samples were sulfurized in a graphite container for 90 min at 650 °C in a 150 kPa Ar + S atmosphere. Final films were studied via X-ray diffraction (XRD), scanning electron microscopy (SEM) and micro-Raman spectroscopy. It was found that all samples were polycrystalline in nature and their lattice parameters varied slightly nonlinearly from {a = 5.49 Å, c = 11.02 Å} for CuInS₂ to {a = 5.30 Å, c = 10.36 Å} for CuAlS₂. No unwanted phases such as Cu_2−xS or others were observed. Raman were recorded at a room temperature and the most intensive and dominant A₁ phonon frequency varied nonlinearly from 294 cm⁻¹ (CuInS₂) to 314 cm⁻¹ (CuAlS₂).     

Structural, morphological and optical properties of Bi2−xSbxSe3 thin films grown by electrodeposition

Ternary single-phase Bi_2−xSb_xSe₃ alloy thin films were synthesized onto Au(1 1 1) substrates from an aqueous solution containing Bi(NO₃)₃, SbCl₃, and SeO₂ at room temperature for the first time via the electrodeposition technique. The electrodeposition of the thin films was studied using cyclic voltammetry, compositional, structural, optical measurements and surface morphology. It was found that the thin films with different stoichiometry can be obtained by controlling the electrolyte composition. The as-deposited films were crystallized in the preferential orientation along the (0 1 5) plane. The SEM investigations show that the film growth proceeds via nucleation, growth of film layer and formation of spherical particles on the film layer. The particle size and shape of Bi_2−xSb_xSe₃ films could be changed by tuning the electrolyte composition. The optical absorption spectra suggest that the band gap of this alloy varied from 0.24 to 0.38 eV with increasing Sb content from x = 0 to x = 0.2.     

Mechanical properties of SiOx gas barrier coatings on polyester films

This paper reports the impressive mechanical properties of 1 μm thick carbon-containing SiO_x gas barrier coatings, characterised using the uniaxial fragmentation test. Such coatings have been found to act as excellent barriers to water vapour permeation partly because they can be made so thick without stress induced cracking. The impressive mechanical properties are thought to be due in part to the high amount of carbon they contain, which gives them a more organic character, as well as the fact that they are deposited as a succession of thinner layers. The adhesion of the coatings to the polyester film is good in all cases, reflecting a high density of covalent bonding at the interface. Improvement of the mechanical properties of a SiO_x/PET composite can be achieved by altering the substrate. By replacing the PET with a heat-stabilised (HS) PET film, a HS film with an acrylate layer or PEN, it is found that the coating displays improved mechanical properties and adhesive strength (as well as barrier). This is thought to be due to the superior surface thermal and mechanical properties of these substrates. Deposition temperatures are at least 80 °C, which causes molecular motion at the surface of a plain PET film and creates defects in the SiO_x coating as it grows, making it more brittle and permeable to gas flow.     

Growth and characterization of chemical bath deposited Cd1−xZnxS thin films

Cd_1−xZn_xS (0 ≤ x ≤ 1) thin films have been deposited by chemical bath deposition method on glass substrates from aqueous solution containing cadmium acetate, zinc acetate and thiourea at 80 ± 5 °C and after annealed at 350 °C. The structural, morphological, compositional and optical properties of the deposited Cd_1−xZn_xS thin films have been studied by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), photoluminescence (PL) and UV-vis spectrophotometer, respectively. X-ray diffraction analysis shows that for x < 0.8, the crystal structure of Cd_1−xZn_xS thin films was hexagonal structure. For x > 0.6, however, the Cd_1−xZn_xS films were grown with cubic structure. Annealing the samples at 350 °C in air for 45 min resulted in increase in intensity as well as a shift towards lower scattering angles. The parameters such as crystallite size, strain, dislocation density and texture coefficient are calculated from X-ray diffraction studies. SEM studies reveal the formation of Cd_1−xZn_xS films with uniformly distributed grains over the entire surface of the substrate. The EDX analysis shows the content of atomic percentage. Optical method was used to determine the band gap of the films. The photoluminescence spectra of films have been studied and the results are discussed.     

Deposition of thick TiAlN coatings on 2024 Al/SiCp substrate by Arc ion plating

Aluminum-matrix composites with particulate SiC ceramic reinforcements (Al/SiC_p) have received much attention for space and aircraft propulsion applications. It is imperative to deposit thick hard coatings on these composites for protection. TiAlN coatings with a Ti interlayer were deposited by arc ion plating (AIP) on 2024 Al/SiC_p substrates at various nitrogen flow rates. It was found that when the nitrogen flow rate is increased from 100 sccm to 250 sccm, the deposition rate decreases, the coating hardness increases and the adhesion strength decreases. Based on the above results and the principle of gradient materials, the thick gradient TiAlN coatings with a Ti interlayer were successfully deposited on a 2024 Al/SiC_p substrate to a thickness of 60 μm by continuously increasing the nitrogen flow rate during deposition. Such an achievement can be attributed to the gradient distribution of elements, hardness, and stresses across the coating thickness.     

Study on nanocrystalline Cr2O3 films deposited by arc ion plating: II. Mechanical and tribological properties

In this work, the influence of substrate bias voltage on the microhardness, adhesive strength, friction coefficient, and wear rate of AIP Cr₂O₃ films deposited on AISI 304 stainless steel substrates was investigated systematically. In the meantime, the wear failure mechanism of AIP Cr₂O₃ films in dry sliding contact was also analyzed and discussed. The results showed that the mechanical properties, adhesive behaviors, and tribological performance of AIP Cr₂O₃ films were greatly altered by applying a negative bias voltage. With increasing the bias voltage, the hardness, critical load, and tribological performance of AIP Cr₂O₃ films first were improved gradually, and then were impaired slightly again. When the bias voltage is − 100 V, the Cr₂O₃ film possessed the highest hardness, the strongest adhesion, and the best wear resistance. The essence of above phenomena was attributed to the variations of microstructure and defect density in the films induced by the substrate bias voltage increase. The main wear failure mechanism of AIP Cr₂O₃ films is crack initiation and propagation under the high contact stresses, inducing the local film with small area to flake off gradually, and eventually leading to the formation of a wear scar.     

Electrical properties of binder-free thick film BaYxBi1−xO3 NTC thermistors

The microstructure and electrical properties of BaY_xBi_1−xO₃ thick film negative temperature coefficient thermistors, fabricated by screen printing, were investigated. The sintered thick films were the single-phase solid solutions of the BaY_xBi_1−xO₃ compounds with a monoclinic structure. The added Y₂O₃ led to a significant decrease in the grain size of the thermistors. The resistivity and coefficient of temperature sensitivity for the BaY_xBi_1−xO₃ (0 ≤ x ≤ 0.15) thick film NTC thermistors decreased first with increasing x in the range of x < 0.04 and then increased with further increase in x.     

Studies on the power factor of (Ba,Sr)Co2+xRu4−xO11 compounds

We have prepared polycrystalline single-phase ACo_2+xRu_4−xO₁₁ (A = Sr, Ba; 0 ≤ x ≤ 0.5) using the ceramic method and we have studied their structure, electrical resistivity and Seebeck coefficient, in order to estimate their power factor (P.F.). These layered compounds show values of electrical resistivity of the order of 10⁻⁵ Ωm and their Seebeck coefficients are positive and range from 1 μV K⁻¹ (T = 100 K) to 20 μV K⁻¹ (T = 450 K). The maximum power factor at room temperature is displayed by BaCo₂Ru₄O₁₁ (P.F.: 0.20 μW K⁻² cm⁻¹), value that is comparable to that shown by compounds such as SrRuO₃ and Sr₆Co₅O₁₅.     

Study on nanocrystalline Cr2O3 films deposited by arc ion plating: I. composition, morphology, and microstructure analysis

Nanocrystalline Cr₂O₃ thin films were deposited on silicon wafers with (100) orientation by arc ion plating (AIP) technique at various negative bias voltages. By virtue of X-ray diffraction analysis, scanning electron microscope, and high-resolution transmission electron microscope, the influence of substrate bias voltage on the film growth process, microstructure, and characteristics was investigated systematically, including the phase constituents, grain size, lattice constant, chemical compositions, as well as surface and cross-section morphologies. With increasing the bias voltage, the grain size and lattice constant of AIP Cr₂O₃ films first decreased slightly, and then increased gradually again. Both reached the minimum (35 nm and 13.57 Å) when the bias voltage was − 100 V. However, the bias voltage had little effect on the phase constituents and chemical compositions of AIP Cr₂O₃ films. During the film growth process, the surfaces of Cr₂O₃ films were getting smoother with the negative bias voltage increase, in the meantime, their microstructures evolved from coarse columnar grains to fine columnar grains, short columnar recrystallized grains, and fine columnar grains again.     

Transparent p-type CuxS thin films

The effect of different mild post-annealing treatments in air, at 270 °C, for 4-6 min, on the optical, electrical, structural and chemical properties of copper sulphide (Cu_xS) thin films deposited at room temperature are investigated. Cu_xS films, 70 nm thick, are deposited on glass substrates by vacuum thermal evaporation from a Cu₂S:S (50:50 wt.%) sulphur rich powder mixture. The as-deposited highly conductive crystalline CuS (covellite) films show high carrier concentration (∼10²² cm⁻³), low electrical resistivity (∼10⁻⁴ Ω cm) and inconclusive p-type conduction. After the mild post-annealing, these films display increasing values of resistivity (∼10⁻³ to ∼10⁻² Ω cm) with annealing time and exhibit conclusive p-type conduction. An increase of copper content in Cu_xS phases towards the semiconductive Cu₂S (chalcocite) compound with annealing time is reported, due to re-evaporation of sulphur from the films. However, the latter stoichiometry was not obtained, which indicates the presence of vacancies in the Cu lattice. In the most resistive films a Cu₂O phase is also observed, diminishing the amount of available copper to combine with sulphur, and therefore the highest values of optical transmittance are reached (65%). The appearance on the surface of amorphous sulphates with annealing time increase is also detected as a consequence of sulphur oxidation and replacement of sulphur with oxygen. All annealed films are copper deficient in regards to the stoichiometric Cu₂S and exhibit stable p-type conductivity.     

Synthesis of Ti3SiC2 by infiltration of molten Si

High-purity Ti₃SiC₂ compounds have been fabricated by infiltration of molten Si into a precursor, a partially sintered TiC_x (x = 0.67) preform. The Si source and the TiC_x preform were placed side by side on carbon cloth, and the system was heated to 1550 °C. Molten Si infiltrated the preform through the carbon cloth, and a direct reaction between TiC_x and molten Si immediately occurred at the reaction temperature to yield pure Ti₃SiC₂. We could observe phase formation and the microstructure of the bulk products with time, which were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS). Pure Ti₃SiC₂ compounds were formed on the exterior of the TiC_x preform at 1550 °C when the sintered TiC_x:Si ingot molar ratio was 3:1.4. At 1550 °C, no other minor phases were detected for any of the sintering time ranges.     

Thermoelectric properties of Bi2SexTe3−x prepared by Bridgman method

Bi₂Se_xTe_3−x crystals with various x values were grown by Bridgman method. The electrical conductivity, σ, was found to decrease with increasing Se content. The highest σ of 1.6 × 10⁵ S m⁻¹ at room temperature was reached at x = 0.12 with a growth rate of 0.8 mm h⁻¹. The Seebeck coefficient, S, was less dependent on Se content, all with positive values showing p-type characteristics, and the highest S was measured to be 240 μV K⁻¹ at x = 0.24. The lowest thermal conductivity, κ, was 0.7 W m⁻¹ K⁻¹ at x = 0.36. The electronic part of κ, κ_el, showed a decrease with increasing Se content, which implies that the hole concentration as the main carriers was reduced by the addition of Se. The highest dimensionless figure of merit, ZT, at room temperature was 1.2 at x = 0.36, which is attributed to the combination of a rather high electrical conductivity and Seebeck coefficient and low thermal conductivity.     

Relationships between Zr substitution for Ti and microwave dielectric properties in Mg(ZrxTi1−x)O3 ceramics

The influence of Zr substitution for Ti on the microwave dielectric properties and microstructures of the Mg(Zr_xTi_1−x)O₃(MZ_xT) (0.01 ≤ x ≤ 0.3) ceramics was investigated. The quality factors of Mg(Zr_xTi_1−x)O₃ ceramics with x = 0.01-0.05 were improved because the solid solution of a small amount of Zr⁴⁺ substitution in the B-site could increase density and grain size. An excess of Zr⁴⁺ resulted in the formation of a great deal of secondary phase that declined the microwave dielectric properties of MZ_xT ceramics. The temperature coefficient of resonant frequency (τ_f) of Mg(Zr_xTi_1−x)O₃ ceramics slightly increased with increasing Zr content, and the variation in τ_f was attributed to the formation of secondary phases.     

Influence of deposition conditions on mechanical and tribological properties of nanostructured TiN/CNx multilayer films

Nanostructured TiN/CN_x multilayer films were deposited onto Si (100) wafers and M42 high-speed-steel substrates using closed-filed unbalanced magnetron sputtering in which the deposition process was controlled by a closed loop optical emission monitor (OEM) to regulate the flow of N₂ gas. Multilayers with different carbon nitride (CN_x) layer thickness could be attained by varying the C target current (0.5 A to 2.0 A) during the deposition. It was found that the different bilayer thickness periods (i.e. the TiN layer thickness Λ_TiN was fixed at 3.0 nm while the CN_x layer thickness Λ_CNx was varied from 0.3 to 1.2 nm) significantly affected the mechanical and tribological properties of TiN/CN_x multilayer films. These multilayer films were characterized and analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), Rockwell-C adhesion test, scratch test, pin-on-disc tribometer, and nanoindentation measurements. XPS analyses revealed that the chemical states, such as TiN, TiC, TiN_xO_y and TiO_2, existed in a TiN layer. Nanoindentation results showed that the hardness was highly dependent on the bilayer thickness. A maximum hardness of ~ 41.0 GPa was observed in a multilayer film at bilayer thickness Λ_TiN = 3.0 nm and Λ_CNx = 0.9 nm. All multilayer films exhibited extreme elasticity with elastic recoveries as high as 80% at 5 mN maximum load. The compressive stresses in the films (in a range of 1.5-3.0 GPa) were strongly related to their microstructure, which depended mainly on the incorporation of nitrogen in the films. By scratch and Rockwell-C adhesion tests, the multilayer films with smaller bilayer thicknesses (Λ_TiN = 3.0 nm, Λ_CNx = 0.3 and 0.6 nm) exhibited the best adhesion and cohesive strength. The critical load value obtained was as high as ~ 78 N for the films with Λ_TiN = 3.0 nm, Λ_CNx = 0.9 nm. The friction coefficient value for a multilayer at Λ_TiN = 3.0 nm and Λ_CNx = 0.9 nm was found to be low 0.11. These adhesive properties and wear performance are also discussed on the basis of microstructure, mechanical properties and tribochemical wear mechanisms.     

Effect of non-magnetic doping on multi-step magnetization behavior of Dy50−xAlxAg50

The electrical transport and magnetization measurements have been carried out on Al-doped polycrystalline intermetallic compounds Dy_50−xAl_xAg₅₀ (x = 0, 0.3, 0.6, 1.2, 1.8) in a pulsed high magnetic field, in which multi-step magnetization is observed. Partial substitute of non-magnetic Al³⁺ for Dy³⁺ ions in the compounds increases the critical magnetic fields and the relative area of the magnetic hysteresis loop, which result from the pinning effect, lattice distortion, the change of coupling strength and dilution effect related to the Al³⁺ doping.The experimental results indicate that non-magnetic Al³⁺ ions and induced amorphous phase can pin the rotation and/or growth of magnetic domains, thus, the critical magnetic field can be enhanced by doping non-magnetic ions in the magnetic materials, especially in the permanent magnet materials.     

Ion beam energy effects on structure and properties of SiOx doped diamond-like carbon films

SiO_x doped diamond-like carbon (DLC) films were synthesized by direct ion beam from hexamethyldisiloxane vapor. Effects of ion beam energy were studied. Variation of atomic concentration of the oxygen versus carbon with ion energy has been observed. Raman scattering spectroscopy didn’t indicate essential changes in structure of the films deposited at different ion beam energies. The synthesized films were atomically smooth. Depending on the ion energy the refractive index of the SiO_x doped diamond-like carbon films varied within 2.1-2.5 and increased with increase of energy. The contact angle with water for all samples was only 61-64°.     

CFx thin solid films deposited by high power impulse magnetron sputtering: Synthesis and characterization

Fluorine containing amorphous carbon films (CF_x, 0.16 ≤ x ≤ 0.35) have been synthesized by reactive high power impulse magnetron sputtering (HiPIMS) in an Ar/CF₄ atmosphere. The fluorine content of the films was controlled by varying the CF₄ partial pressure from 0 mPa to 110 mPa at a constant deposition pressure of 400 mPa and a substrate temperature of 110 °C. The films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by applying elastic recoil detection analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and nanoindentation. First-principles calculations were carried out to predict and explain F-containing carbon thin film synthesis and properties. By geometry optimizations and cohesive energy calculations the relative stability of precursor species including C₂, F₂ and radicals, resulting from dissociation of CF₄, were established. Furthermore, structural defects, arising from the incorporation of F atoms in a graphene-like network, were evaluated. All as-deposited CF_x films are amorphous. Results from X-ray photoelectron spectroscopy and Raman spectroscopy indicate a graphitic nature of CF_x films with x ≤ 0.23 and a polymeric structure for films with x ≥ 0.26. Nanoindentation reveals hardnesses between ~ 1 GPa and ~ 16 GPa and an elastic recovery of up to 98%.