Effects of nitrogen flow rate on the microstructure and mechanical and tribological properties of TiAlN films prepared via reactive magnetron sputtering

In this study, TiAlN ceramic films were fabricated via reactive magnetron sputtering on a Ti6Al4V titanium alloy substrate. The effects of N₂ flow rates on the microstructure and mechanical and tribological properties of the films were systematically studied. With increasing N₂ flow rate, the films underwent a morphological evolution from a fine columnar structure to a coarse structure with holes and microcracks. In addition, the preferred orientation of the films varied from TiAlN (220) to the (111) plane. However, a high N₂ flow rate (≥20sccm) resulted in target poisoning and reduced the deposition rate, which resulted in defects such as cavities and holes on the surface. Moreover, with increasing N₂ flow rate, the hardness and elastic modulus first increased and then reduced owing to grain refinement. The films deposited at a N₂ flow rate of 16 sccm exhibited the smallest wear width and the lowest wear rate. As the N₂ flow rate increased from 12 to 24 sccm, the wear mechanism of the films changed from abrasive and adhesion wear to abrasive wear caused by severe plastic deformation, which was directly related to the microstructural evolution and mechanical properties.     

Microstructural and optical properties of Ta-doped ZnO films prepared by radio frequency magnetron sputtering

Ta-doped ZnO films with different doping levels (0–5.02 at%) were prepared by radio frequency magnetron sputtering. The effects of the doping amount on the microstructure and the optical properties of the films were investigated. The grain size and surface roughness first significantly decrease and then slowly increase with the increase of Ta doping concentration. Both the grain size and the root mean square (RMS) roughness reach their minimum values at the doping content of 3.32 at%. X-ray Diffraction (XRD) patterns confirmed that the prepared Ta-doped ZnO films are polycrystalline with hexagonal wurtzite structure and a preferred orientation along the (002) plane. X-ray photoelectron spectroscopy (XPS) analysis reveals that Ta exists in the ZnO film in the Ta⁵⁺ and Ta⁴⁺ states. The average optical transmission values of the Ta-doped ZnO films are higher than those of the un-doped ZnO film in the visible region. The band gap energy extracted from the absorption edge of transmission spectra becomes large and the near band edge (NBE) emission energy obtained from PL spectra blueshifts to high energy when the Ta doping content grows from 0 at% to 5.02 at%, which can be explained by the Burstein–Moss shift.     

Electrochemical properties of boron-carbon-nitride films formed by magnetron sputtering

The electrochemical behavior of B_1.0C_2.4N_1.0 thin film was investigated in acidic, neutral and alkaline solutions. The anodic polarization curve of the film in 1 M NaOH showed the anodic dissolution of the film. The curve of the film in 1 M HCl showed no anodic dissolution. The cathodic polarization curve in 1 M NaCl showed shift to a negative potential side, but the anodic polarization curve was the same as that of Pt. The anodic dissolution in 1 M NaOH depended on potentials, that is, no anodic dissolution was recognized in a potential range of −0.2 to 0.1 V but the dissolution rate increased with increasing potential in a range of 0.1-0.6 V. The anodic current density of the film is directly proportional to the dissolution rate at potentials higher than 0.1 V. The dissolution rate of the film was increased with increasing solution pH.     

Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering

Tungsten and boron compounds belong to the group of superhard materials since their hardness could exceed 40?GPa. In this study, the properties of the tungsten boride WB_x coatings deposited by radio frequency magnetron sputtering were investigated. The sputtering was performed from specially prepared targets that were composed of boron and tungsten mixed in a molar ratio of 2.5 and sintered in Spark Plasma Sintering (SPS) process. WB films were deposited on silicon (100) and stainless steel 304 substrates at temperatures of 23 ÷ 770?°C. Microstructure, chemical and phase composition were investigated by using Scanning Electron Microscope (SEM), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The mechanical properties like Vickers hardness and Young's modulus were obtained by using nanoindentation test at a load of 5 ÷ 100 mN. The friction coefficient and wear resistance of αWB coatings were investigated in scratch test and reciprocal sliding wear instrumentation. Moreover, in order to investigate thermal properties, the αWB films were annealed at 1000?°C in argon/air for 1?h and at 250?°C for 2?h in air atmosphere. Results of our research confirm that αWB coatings can be considered as an alternative to superhard materials in the production of wear resistant, long-lasting tools.     

Microstructure evolution,mechanical and tribological properties of Ti3(Al,Sn)C2/Al2O3 composites

In this paper, in situ formed Ti₃(Al,Sn)C₂/Al₂O₃ composites were fabricated by sintering the mixture of Ti₃AlC₂ and SnO₂. The Al atoms could diffuse out of the Ti₃AlC₂ layered structure to react with SnO₂, resulting in the formation of Ti₃(Al,Sn)C₂ solid solution and Al₂O₃. When the SnO₂ content was 20?wt.%, the sintered Ti₃(Al,Sn)C₂/Al₂O₃ composite exhibited the best overall mechanical properties, because of the optimized cooperative strengthening effect of solution strengthening and Al₂O₃ enhancement. When the SnO₂ content increased up to 30?wt.%, the flexural strength and fracture toughness of Ti₃(Al,Sn)C₂/Al₂O₃ composite dramatically decreased on account of the large accumulation of generated Al₂O₃. Moreover, according to the SiC ball-on-flat wear tests, it was found that the wear resistance of Ti₃(Al,Sn)C₂/Al₂O₃ composites was significantly improved as the SnO₂ content increased.     

Microstructural,mechanical and tribological properties of suspension plasma sprayed YSZ/h-BN composite coating

Brittleness, relative high friction coefficient and wear rate limit the applications of ceramic coatings as wear-resistant layers. However, because embedding additives with ceramic matrix has demonstrated to be an effective way to improve coating performances, different contents and size of h-BN were added into an YSZ suspension. Afterwards, the YSZ/h-BN composite coatings were manufactured by suspension plasma spray and their tribological analysis indicated that: i) the reduction of the friction coefficient and wear rate can be achieved by incorporating h-BN into YSZ coating. ii) finer h-BN particle is more helpful to enhance the tribological properties of the coating. iii) the optimum content is dependent on h-BN particle sizes. iv) when the contents and the size of the h-BN inclusion increase, the probability distribution of the micro-hardness can become bi-modal. Three worn surface conditions were summarized and their wear mechanisms were discussed as well.     

Engineering of morphological,optical, structural,photocatalytic and catalytic properties of nanostructured CuO thin films fabricated by reactive DC magnetron sputtering

Nanostructured thin films of CuO were deposited on silica glass substrates using reactive DC magnetron sputtering technique. Microstructural, morphological, optical, catalytic and photocatalytic properties of the prepared CuO thin films were examined using FESEM, AFM, Rutherford backscattering spectrometry, XRD, XPS, UV–Vis absorption and PL spectroscopy. FESEM showed nanostructures in the thin films, which were confirmed to be of monoclinic CuO by XRD analysis. Substrate temperature variation (40 °C, 100 °C and 300 °C) was found to significantly alter the optical, morphological, photocatalytic and structural properties of the CuO nanostructured thin film coatings. FESEM and AFM analyses showed decrease in size of nanostructures and surface roughness increase with increase in substrate temperature. Increase in UV–Vis absorbance and PL intensity of CuO thin films with decrease in crystallite size were noticed as the substrate temperature was increased. The prepared nanostructured CuO thin films exhibited highly enhanced photocatalytic activities and degraded dyes (MB and MO) in water in just 40 min under solar exposure and catalytic transformation of 4-nitrophenol (4-NP) took place in just 15 min. The developed CuO nanostructured thin film coatings are very promising for large scale, practical and advanced catalytic reduction of toxic 4-NP and photocatalytic applications in solar driven water purification.     

O＇－Sialon－ZrO_2复合材料的显微结构与力学性能的研究

研究了Ｏ＇－Ｓｉａｌｏｎ－ＺｒＯ２复合材料的显微结构与力学性能的关系。结果表明，Ｏ＇－Ｓｉａｌｏｎ形成连续网络编织状结构。ＺｒＯ２加入量较少时充当填充结构骨架的作用；ＺｒＯ２加入量增多时（至４０％），会有更多的ＺｒＯ２形成聚集体。随着ＺｒＯ２引入量的增加，材料的常温抗折强度提高，但高温抗折强度下降。Ｏ＇－Ｓｉａｌｏｎ的编织状结构可能阻碍晶界滑移。这种复合材料的高温抗折强度在１４００℃为１１２～１７３ＭＰａ。     

Structure and high-temperature tribological properties of Pb-Cr-O composite films prepared by reactive magnetron sputtering

The formation of ternary composite oxides in a high-temperature environment has laid the foundation for the design of high-temperature wear-resistant self-lubricating film. A series of Pb-Cr-O films with different Cr contents were prepared by incorporating different ratios of Pb-Cr into a target in the reactive magnetron sputtering system. The results showed that the hardness of the Pb-Cr-O films is greatly improved compared to the pure Pb-O film. In addition, the Pb₂₉Cr₄O₆₇ film with the highest Cr content forms an amorphous structure due to the accumulation of Cr⁶⁺ at the grain boundary, which improves the H/E and H³/E² of the film. At 600 °C, in contrast with the single PbO lubricating phase formed by pure Pb₃₃O₆₇ film, the Pb₂₉Cr₄O₆₇ film forms a composite lubricating phase of Pb₅CrO₈ and PbO. This leads to a decreased wear rate as low as 7.2 × 10^?6 mm³N^?1m^?1 while maintaining low coefficient of friction comparable to pure Pb₃₃O₆₇ film. At higher temperature of 700 °C, Cr element in Inconel 718 matrix diffuses into the Pb-based oxide film and forms Pb₅CrO₈ phase similar to Pb₂₉Cr₄O₆₇ film, which improves the wear resistance of the Pb₃₃O₆₇ film while maintaining low friction coefficient of 0.15.     

Microstructure and properties of the AlCrMoZrTi/(AlCrMoZrTi)N multilayer high-entropy nitride ceramics films deposited by reactive RF sputtering

The AlCrMoZrTi/(AlCrMoZrTi)N multilayer high-entropy nitride ceramic films (HENCFs) fabricated by reactive RF magnetron sputtering presented (200) preferentially oriented FCC crystal structures. With the increase in the modulation period, the nitrogen content and surface roughness of the multilayer films gradually increased, the template effect between the nanocrystalline and amorphous forms was weakened, and the multilayer interface structure decreased. The S4 film with a modulation period of 1500 nm had the highest hardness and modulus (16.6 and 225.7 GPa, respectively) and the highest H/E* and H³/E*² values. The results of friction experiments showed that the S1 film with the smallest modulation period had a stable friction coefficient and small wear rate on both Si and Cu substrates, and it exhibited the best friction and wear performance due to its low surface roughness, high toughness and compressive yield resistance, and dense multilayer structure. The friction mechanisms of the HECNFs on Si and Cu substrates were mainly adhesive wear, abrasive wear, and a small amount of oxidative wear.     

Optical band gap shift in thin LiNbO3 films grown by radio-frequency magnetron sputtering

Thin polycrystalline LiNbO₃ films were deposited by the radio-frequency magnetron sputtering (RFMS) method and ion-beam sputtering (IBS) method under different conditions. Study of the adsorption band edge of fabricated films reveals direct and indirect optical transition. Depending on the particular technological sputtering RFMS regime, the direct energy gap varies from 3.8 to 4.4 eV. Band tails induced by the defects formation due to the reactive plasma effect on the film structure are responsible for indirect optical transitions in the studied films. Thermal annealing has a prominent effect on trap concentration and strain in as-grown films leading to rise in direct band energy up to 4.4 eV which is close to the value for bulk LiNbO₃.     

Effects of modulation ratio on the microstructure,mechanical and tribological properties of WB2/Cr multilayer films deposited by magnetron sputtering

WB₂/Cr multilayer films with different modulation ratios (λ = 1, 3, 5, 7, 12, and 20) were deposited by a combination of direct-current and pulse direct-current magnetron sputtering, and the number of bilayers was fixed at ten. The effect of the modulation ratio on the microstructure, mechanical and tribological properties of the multilayer films was investigated in detail. X-ray diffraction demonstrates that a preferred orientation of WB₂ (101) and Cr (110) exists, and WB₂ (101) dominates the film's growth with increasing of modulation ratio. The TEM results show that the multilayer films consist of nanograins dispersed in an amorphous matrix in WB₂ layers and polycrystalline grains in Cr layers. The hardness increases with the increasing modulation ratio, and the maximum hardness (31.1 GPa) is obtained at λ = 20. The indentation toughness presents an opposite changing trend, and the maximum indentation toughness (1.264 MPa m^1/2) is obtained in S1 at λ = 1 which conforms to the rule of mixture due to the relatively thick bilayer thickness (Λ = 160–192 nm). The wear mechanism is investigated, and the results suggest that the multilayer film with λ = 7 possesses the best wear resistance (2.06 × 10^?7 mm³/Nm), benefiting from the balance of hardness and indentation toughness.     

Effect of Ti particle size on mechanical and tribological properties of TiCN coatings prepared by reactive plasma spraying

Titanium carbonitride (TiCN) coatings were successfully fabricated by reactive plasma spraying (RPS) from agglomerated Ti-graphite feedstock. The effect of Ti particle size on the microstructure and phase composition of plasma sprayed TiCN coatings was investigated. The Vickers microhardness of coatings was measured by a Microhardness Test and the corresponding Weibull distribution were also analyzed. In addition, a pin-on-disk tribometer was employed to determine the trobological properties of coatings. Results show that all the coatings consist of TiC_xN_1−x (0 ≤ x ≤1) and minor Ti₂O phases, and the amount of Ti₂O increases with the increase of Ti particle size. The Weibull distribution of Vickers microhardness of all the coatings shows apparent scattering, while the coating sprayed with Ti particle size of 28 µm exhibits a relatively even distribution. Compared with the coating sprayed with Ti particle size of 14 µm or 48 µm, the coating sprayed with Ti particle size of 28 µm exhibits improved mechanical and tribological properties, which are attributed to the high microhardness and strong bonding strength.     

Effect of hBN addition on the fabrication,mechanical and tribological properties of Sialon materials

This work aims to investigate the effect of hBN on the friction and wear resistance of Sialon composite. Sialon and its composite with 10 wt% hBN were fabricated by SPS sintering. The effect of hBN additive on the phase composition, microstructure, densification behavior, mechanical and dry sliding tribological properties of Sialon material was studied. Being sintered at 1600 °C for 10 min, compared to monolithic Sialon, Sialon-hBN composite has more refined β-Sialon grains with smaller aspect ratios and slightly declined relative density. The hardness of the Sialon-hBN composite was reduced due to the weak bonding between Sialon and hBN grains. Nevertheless, its fracture toughness increased ascribing to the toughening mechanisms, including crack deflection and crack bridging. hBN had an essential impact on the tribological performances of the composite due to its lower friction coefficient and good lubrication action. Under the same densification level (i.e., with a relative density of around 97.5%), the friction and wear resistance of Sialon-hBN composite were much better than monolithic Sialon. The main wear mechanisms were tribolayer formation, oxidized wear, and abrasive wear.     

Fabrication,structural and vibrational properties,and physical and optical properties tailoring of nanocrystalline MoS2 films

The modification and tuning features of nanostructured films are of great interest because of controllable and distinctive inherent properties in these materials. Here, nanocrystalline MoS₂ films were fabricated on the stainless steels by a radio frequency magnetron sputtering at ambient temperature. X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and Raman scattering spectroscopy were used to study the chemical state, chemical composition, crystal structure and vibrational properties of the fabricated MoS₂ films. The bias voltage dependent structural evolution and its influence on the optical properties of MoS₂ nanocrystalline films were systematically investigated. Besides, the residual stresses of MoS₂ nanocrystalline films were explored by employing sin²ψ approach. X-ray diffraction demonstrates that the nanocrystalline MoS₂ films have single-phase hexagonal crystal structure. All MoS₂ films are polycrystalline in nature. The bandgap values are found to be intensively dependent on bias voltage. Our findings show that the nanocrystalline MoS₂ films with different physical properties and intense quantum confinement effect can be realized through adjusting bias voltages. This work may provide deep insight for realizing transitional metal dichalcogenide-based nanostructured film optoelectronic devices with tunable physical properties through a traditional, very cost-effective, and large-scale fabrication method.     

Evolution of microstructure of IGZO ceramic target during magnetron sputtering

In this study, influence of magnetron sputtering on indium gallium zinc oxide (IGZO) ceramic target was studied to improve its performance and utilization. Results indicated that state of the target such as target grain uniformity, micro defects, C element pollution, and secondary phase showed significant influence on magnetron sputtering process. Atoms located in small grains were easily bombarded out of IGZO target, and grains with slow sputtering rate protruded from target surface. Porous microstructure of IGZO ceramic created abnormal electric field of the target during sputtering, resulting in the poisoning of target. Moreover, more indium atoms were sputtered from the target, and the proportion of In after sputtering decreased by 0.62–0.97%. The difference in sputtering rates between secondary phase and main phase led to the formation of IGZO cladding layer with poor conductivity under the combined action of sputtering and re-sputtering. In sum, these findings may provide strong guidance for further improvement and performance enhancement of IGZO sputtering target.     

Improving the mechanical and tribological properties of TiB2/a-C nanomultilayers by structural optimization

A novel nanomultilayered architecture was developed through magnetron sputtering to simultaneously achieve excellent mechanical and tribological properties in TiB₂/a-C film. Structural optimization was conducted by adjusting the modulation period from 1 to 10.5 nm. Film hardness and toughness were significantly improved and reached the optimal value at Λ = 6.6 nm. Combination of a sufficient number of heterointerfaces and appropriate individual layer thickness played a key role in hardening and toughening. The internal stress increased linearly with the increase in modulation period, which may be related to the reduction in the number of interfaces. Furthermore, a low friction coefficient of about 0.1 was achieved in the steady state at Λ ≤ 6.6 nm due to the formation of a uniform and compact transfer film on the worn ball surface. The improved mechanical performance and the presence of an effective transfer film resulted in an outstanding anti-wear performance at Λ = 6.6 nm.     

Corrosion and friction resistance of TiVCrZrWNx high entropy ceramics coatings prepared by magnetron sputtering

High entropy alloy coatings have attracted much attention because of their high hardness, low-level fault energy, and chemical stability. Nevertheless, this type of coating would inevitably suffer from wear, corrosion, aging, and so on. Hence, a novel coating with corrosion and friction resistance would be constructed for broadening its application scenarios. In this work, TiVCrZrWN_x high entropy ceramics coatings were prepared by reactive magnetron sputtering. The microstructure, mechanical properties, friction, and corrosion resistance of the coatings deposited at different nitrogen flow rates have been studied. The microstructure of TiVCrZrWN_x coatings is strongly dependent on the nitrogen flow rate and forms a stable FCC structure when the nitrogen flow rate reaches 24 sccm. The pure TiVCrZrW coating is 15.65 GPa, with the increase of nitrogen flow rate (24 sccm), the coating hardness reaches 21.27 GPa. The corrosion resistance of the coatings also increases continuously. According to the results of the impedance spectrum and polarization curve, the charge transfer resistance value of the coating gradually increases with the content of nitrogen, the current density rapidly decreases to a minimum as the potential increases. In terms of tribological behavior, the formation of V₂O₅ during the sliding in seawater could significantly reduce the coefficient of friction from 0.603 to 0.383. Therefore, TiVCrZrWN_x HECs coatings simultaneously possess high hardness, toughness, and excellent resistance to friction and corrosion, which is expected to provide a new and reliable method for the research field of coatings in the maritime field.     

Correlation between micro/nano-structure,mechanical and tribological properties of copper-zirconia nanocomposites

Fine-grained copper (Cu) and copper-zirconia (Cu–ZrO₂) nanocomposites were produced by high-energy ball milling up to 20 h. Scan Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), microhardness, wear rate and coefficient of friction measurements were performed to investigate the correlation between micro/nano-structure changes of powder and consolidated samples and the properties of the produced nanocomposites. Cu and Cu–15%ZrO₂ nanocomposites with 49.3 and 24.4 nm crystal size, respectively, were produced after 20 h milling achieving 1.76- and 3-times larger hardness than the as received Cu. The wear rate of milled Cu was slightly decreased than the as received Cu, however, it was highly reduced for Cu–15%ZrO₂ nanocomposites reaching 10-times lower than the as received Cu. SEM, TEM and XRD analysis revealed that four main strengthening mechanisms lead to the great improvement of Cu–ZrO₂ nanocomposites properties. The major strength improvement occurred due to Orowan and dislocation strengthening mechanisms activated by the well dispersion of ZrO₂ nanoparticles in Cu matrix and their impedance to dislocation movement, respectively. Besides these two main strengthening mechanisms, work hardening and grain refinement acted as minor strengthening mechanisms for Cu–ZrO₂ nanocomposites while they are the main strengthening mechanisms of Cu samples.     

Synergistic optimization of mechanical and tribological properties of TiC modified copper-graphite composites by direct current in-situ sintering

The application of Cu-graphite composites in the field of friction materials is limited by the poor wettability between Cu and graphite and weakened mechanical properties. In this work, in-situ TiC layers were generated by interfacial resistance sintering with direct current to manipulate the interfacial bonding of the composites and enhance their comprehensive properties. The Ti added to the composites would react with graphite at the interface to generate TiC layers and form strong Cu–TiC-graphite interfaces due to interfacial reactions. When the added Ti content is 6 wt%, the composite demonstrates the most excellent mechanical properties and tribological characteristics, i.e., yield strength (168 MPa) and wear rate (2.7 × 10⁻¹⁰ m²/N) are 93.1% higher and 29.7% lower than those of the Cu-graphite composite without Ti addition, respectively. The dense TiC layer induces the strengthening of the Cu matrix and serves as the reinforcing phase to optimize the interfacial bonding and stress transfer, which not only greatly enhances the mechanical properties of the composite but also enables the composite to take full advantage of the hard TiC and graphite phases to obtain stable friction coefficient and low wear rate. This work provides a simpler technique to prepare modified Cu-graphite composites with excellent performance and contributes to the in-depth understanding of the enhancement mechanism of hard ceramic layers on the mechanical and tribological properties of composites.