Search Results (407)

This research numerically investigates the cooling performance of Diamond-type triply periodic minimal surface (TPMS) networks as a gas turbine effusion cooling layer, augmented with various jet impingement configurations. The study analyzes the internal and external flow characteristics, pressure loss, and overall cooling effectiveness using conjugate heat transfer simulations. The Diamond design is compared to conventional film cooling and micro-hole models within a blowing ratio range of 0.5 to 2.0. The jet hole diameter and jet-to-plate distance are varied to identify an optimal double-wall cooling configuration. The results reveal that the Diamond hole mitigates the strong discharge of coolant, resulting in a more adherent cooling film, which provides excellent surface coverage. While jet impingement enhances internal heat transfer, its contribution to cooling effectiveness is minor compared to the benefit of film coverage. At an equivalent total pressure loss coefficient, the Diamond with impinging jets demonstrates 101% higher cooling effectiveness than the film hole. The thermal-mechanical analysis indicates that the Diamond model exhibits a more uniform distribution of thermal stress and displacement. The average stress is reduced by 44.7% compared to the film hole. This work confirms the TPMS-based effusion as an advanced cooling solution for next-generation gas turbines. Full article

This study deals with diamond films grown via the microwave plasma-enhanced chemical vapor deposition technique (MWPECVD) on molybdenum (Mo) substrates of different roughness. This work is motivated by the necessity of overcoming the poor adhesion of diamond films on smooth Mo substrates, to ensure their effective application as cathodes for aerospace propulsion. The deposition process was monitored in situ using pyrometric interferometry (PI), thus enabling the real-time monitoring of both the rate and the temperature of deposition. The characterization of the obtained diamond films was performed using different techniques, such as Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The poor adhesion of diamond films on Mo substrates was solved by roughening their surface, which promotes residual stress reduction in the diamond films. In this work, the PI technique was also exploited to support the prediction of the adhesion and stability of diamond films before their exposure in air through the monitoring of the deposition temperature. This represents a novel point of our work that has never been discussed in other research papers, as pyrometric interferometry is generally mainly used to assess the rate and the temperature of deposition. Full article

This study presents a highly effective method for depositing diamond-like carbon (DLC) films onto pipe substrates using a scanning deposition by plasma enhanced chemical vapor deposition. A microwave–sheath voltage combination plasma was employed to generate local high-density plasma along a rotating pipe. While conventional contact-mode deposition using a metal contactor suffers from arcing and surface damage due to unstable sliding contact during rotation, a non-contact deposition using a metal antenna was developed to overcome these limitations. Electromagnetic field simulations were conducted to evaluate microwave power absorption in various antenna geometries, showing that the flat-plate antenna demonstrated the most effective power coupling. Subsequent scanning deposition experiments to a rotating pipe using flat-plate antennas of different lengths revealed that the 100 mm configuration achieved the highest deposition volume rate (exceeding that of the contact-mode) while avoiding arcing. Optical emission observations during deposition confirmed the formation of high-density plasma surrounding the flat-plate antenna and Raman spectroscopy of the deposited film showed typical spectra of DLC films. The deposition rates of DLC-coated pipe showed no significant variation with respect to rotational angle, suggesting that rotation during deposition contributes to achieving uniform film thickness along the circumferential direction of the pipe. Full article

The inherent brittleness and poor fracture toughness of diamond-like carbon (DLC) films significantly limit their long-term reliability in mechanical and tribological applications. Among various strategies to enhance toughness, doping with non-carbide-forming metals (e.g., Ag, Cu) has emerged as a highly effective approach due to their ductile properties and compatibility with carbon matrices. This review comprehensively examines the underlying toughening mechanisms induced by non-carbide metal doping in DLC films. We systematically analyze how metal incorporation influences film microstructure, stress state, and crack behavior throughout the entire lifecycle—from deposition to mechanical testing. Five primary toughening mechanisms are identified and discussed: (I) bombardment-induced compressive stress relaxation during film growth; (II) refinement of carbon atomic clusters and enhancement of grain boundary sliding; (III) inhibition of dislocation accumulation through moderated carbon atom repulsion; (IV) plastic deformation, crack bridging, and strain field relaxation at crack tips; (V) shear-induced stress relief via soft metal particles. Among these, Mechanism IV (ductile phase toughening) is identified as the dominant contributor, and their synergistic action can lead to orders of magnitude improvement in wear resistance and a significant increase in crack propagation resistance. Furthermore, the critical role of doping content is emphasized, revealing an optimal concentration range (e.g., ~10–15 at.% for Ag and Cu) beyond which toughness may deteriorate due to excessive boundary formation or hardness loss. This work provides a mechanistic framework for designing toughened DLC films and guides future efforts in developing high-performance, durable carbon-based coatings. Full article

By alternately depositing hydrogen-free amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) nanolayers on HSLA-100 steel through arc-ion plating, multilayer diamond-like carbon (DLC) architectures were engineered, with the modulation period adjusted from 1 to 10 cycles. SEM and Raman spectroscopy served as the analytical tools for characterizing the microstructure. For assessing key functional behaviors, nanoindentation was used to test mechanical properties, dry-sliding tribometry and in-situ tribocorrosion tests targeted tribological and tribocorrosion performance, and polarization tests focused on corrosion resistance. Introducing C₂H₂ increased the sp³ fraction and hardness relative to pure a-C. The ten-period film (S5) yielded the highest H/E (0.0767) and H³/E² (0.171), reflecting the best hardness–toughness synergy. All coatings lowered the dry friction coefficient to 0.08–0.10 and cut wear by more than 1 order of magnitude versus the substrate; the ten-period film (S5) showed the minimum dry wear rate (1.39 × 10⁻⁷ mm³·N⁻¹·m⁻¹) and tribocorrosion wear rate (4.53 × 10⁻⁷ mm³·N⁻¹·m⁻¹) in 3.5 wt% NaCl. The superior performance is due to interlayer interfaces that dissipate stresses, arrest crack propagation, and block electrolyte ingress through defects. These findings indicate that the rational stacking of a-C/a-C:H significantly improves the tribological and tribocorrosion resistance of HSLA-100, providing a reliable protective approach for components used in marine services. Full article

Diamond-like carbon (DLC) films exhibit superior tribological properties; however, their widespread adoption in precision manufacturing is hampered by inherent brittleness and a lack of reliable toughness characterization methods at the micrometer scale. This review critically examines existing techniques for evaluating DLC film toughness, highlighting limitations due to film thickness constraints and subjective failure definitions. We focus on two prominent micro-scale methods: impact testing and scratch testing. Impact toughness is assessed through energy absorption analysis based on impact crater morphology, including crack patterns and delamination areas. Scratch toughness is evaluated using critical loads (Lc₁, Lc₂) and the derived Crack Propagation Resistance (CPRS) parameter, complemented by microscopic failure analysis. We argue that neither method alone suffices for comprehensive toughness assessment. Instead, we propose a synergistic strategy integrating both techniques to provide a practical and comprehensive evaluation encompassing energy- and stress-based failure mechanisms under varying loading conditions. This approach offers a practical framework for developing tougher DLC coatings. Full article

Conductivity sensors play a vital role in monitoring production data in oil wells to ensure efficient oilfield operations, and their service performance depends on the durability of Invar alloy electrodes. The alloy electrodes are susceptible to damage from abrasive solid particles, corrosive media, and oil fluids in downhole environments. The degradation of the alloy electrodes directly compromises the signal stability of conductivity sensors, resulting in inaccurate monitoring data. Inspired by the intrinsic oleophobic properties of fish scales, we developed a fluorinated boron-doped diamond (FBDD) film with biomimetic micro–nano structures to enhance the wear resistance, corrosion resistance, and amphiphobicity of Invar alloy electrodes. The fish scale architecture was fabricated through argon-rich hot-filament chemical vapor deposition (90% Ar, 8 h) followed by fluorination. FBDD-coated electrodes surpass industrial benchmarks, exhibiting a friction coefficient of 0.08, wear rate of 5.1 × 10⁻⁷ mm³/(N·mm), corrosion rate of 3.581 × 10⁻³ mm/a, and oil/water contact angles of 95.32°/106.47°. The following underlying improvement mechanisms of FBDD films are proposed: (i) the wear-resistant matrix preserves the oleophobic nanostructures during abrasive contact; (ii) the corrosion barrier maintains electrical conductivity by preventing surface oxidation; (iii) the oil-repellent surface minimizes fouling that could mask corrosion or wear damage. Full article

Due to the outstanding thermal stability of diamond film, diamond films have extensive application prospects in fields such as electronics, optics, biomedicine, and aerospace, and are one of the important materials driving the development of modern science and technology. Moreover, the cost of single-crystal diamond substrates is high, and it is difficult to achieve large-scale batch production. A direct current arc plasma jet chemical vapor deposition method, combined with post-treatment steps such as nano-diamond seed crystal implantation, surface modification, and high-temperature annealing, is used to prepare high-quality diamond films. The relationship between the thermal conductivity and optical properties of diamond films is analyzed in detail. The experimental results showed that diamond film has a relatively smooth surface, with a surface roughness that can reach 3 nm. As the temperature rises, diamond films exhibit good crystal orientation and thermal stability, the FWHM of reflection peaks become smaller, and thermal conductivity can reach 1734 W/(m·K). The infrared testing analysis also confirmed that the diamond film has excellent thermal diffusion properties. When the diamond film is applied to power device chips, it can effectively reduce the junction temperature of 30 °C. The preparation method proposed in this paper is expected to break through the cost and scale limitations of high-performance diamond films, thereby promoting the wide application of diamond films in industries. Full article

In this work, diamond/Si heterojunctions were fabricated by synthesizing a diamond layer directly on a monocrystalline n-type Si substrate. The diamond layers were characterized using micro-Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The current–voltage (I–V) characteristics of the heterojunctions were measured at room temperature. The heterojunctions exhibited rectifying behavior, confirming their diode-like nature. Based on thermionic emission theory, key electrical parameters of the heterojunction diodes—including the ideality factor (n) and carrier mobility (μ)—were estimated from the I–V characteristics. The I–V curves revealed large ideality factors ranging from 1.5 to 6.5, indicating the presence of deep trap states with densities between 2 × 10¹⁵ and 8 × 10¹⁶ eV⁻¹·cm⁻³. These variations were attributed to differences in the structural quality of the diamond layers and the effects of surface hydrogen termination. Full article

Diamond-like carbon (DLC) films are valued for their high hardness and wear resistance, but their application in harsh environments is limited by high internal stress and poor corrosion resistance. Co-doping with transition metals offers a promising route to overcome these drawbacks by tailoring microstructure and enhancing multifunctional performance. However, the synergistic effects of Ni and Cr co-doping in DLC remain underexplored. In this study, Ni and Cr co-doped DLC (NiCr-DLC) films were fabricated using filtered cathodic vacuum arc deposition (FCVAD). By varying the C₂H₂ flow rate, the carbon content and microstructure evolved from columnar to fine-grained and compact structures. The optimized film (F55) achieved an ultralow surface roughness (Sa = 0.26 nm), even smoother than the Si substrate. The Ni–Cr co-doping promoted a nanocomposite structure, yielding a maximum hardness of 15.56 GPa and excellent wear resistance (wear rate: 4.45 × 10⁻⁷ mm³/N·m). Electrochemical tests revealed significantly improved corrosion resistance compared to AISI 304L stainless steel, with F55 exhibiting the highest corrosion potential, the lowest current density, and the largest impedance modulus. This work demonstrates that Ni-Cr co-doping effectively enhances the mechanical and corrosion properties of DLC films while improving surface quality, providing a viable strategy for developing robust, multifunctional protective coatings for demanding applications in aerospace, automotive, and biomedical systems. Full article

This study investigated how Ti6Al4V substrate topography affects the performance of diamond-like carbon (DLC) coatings. Substrates with four finishes (unpolished, #100, #400, #800 grit) were coated, and their morphology, wettability, bonding structure, mechanical properties, and biological response were examined. Characterization was performed using AFM, SEM, contact angle tests, Raman spectroscopy, and nanoindentation. Biocompatibility was evaluated with A549 epithelial cells. DLC deposition reduced roughness while partly preserving surface features. Increasing Ra was associated with lower surface free energy and ID/IG ratios. It also correlated with higher hardness and modulus, reflecting greater sp³ bonding. Biological results, however, indicated that surface organization was more decisive than Ra magnitude. The #100-grit surface, with aligned anisotropic grooves, supported uniform wetting, protein adsorption, and sustained proliferation. In contrast, the unpolished and smoother surfaces did not maintain long-term growth. These findings suggest that anisotropy, rather than Ra alone, plays a key role in optimizing DLC-coated Ti6Al4V implants. Full article

The scalable synthesis of high-quality single-crystal diamond films remains pivotal for next-generation extreme-performance devices. Iridium substrates offer exceptional promise for heteroepitaxy, yet early-stage growth mechanisms limiting crystal quality are poorly understood. An integrated multiscale investigation combining first-principles DFT calculations, molecular dynamics simulations, and experimental validation is presented to resolve the oriented attachment process governing diamond growth on Ir(100). Robust interfacial bonding at the interface and optimal carbon coverage are revealed to provide thermodynamic driving forces for primary nucleation. A critical angular tolerance enabling defect-free coalescence through crystallographic realignment is identified by molecular dynamics. Concurrent nucleation growth pathways are experimentally confirmed through SEM, AFM, and Raman spectroscopy, where nascent crystallites undergo spontaneous orientational registry to form continuous epitaxial domains. Grain boundary annihilation is observed upon lattice rotation aligning adjacent grains below the critical angle. Crucially, intrinsic atomic steps are generated on the resultant coalesced layer, eliminating conventional etching requirements for homoepitaxial thickening. This work advances fundamental understanding of single-crystal diamond growth mechanisms, facilitating enhanced quality control for semiconductor device manufacturing and quantum applications. Full article

Aluminum nitride (AlN) ceramic materials have relatively low thermal conductivity and poor heat dissipation performance, and are increasingly unsuitable for high-power LED packaging. In this study, diamond films were deposited on AlN ceramic substrates by microwave plasma chemical vapor deposition (MPCVD). The effects of different process parameters on the crystal quality, surface morphology and crystal orientation of diamond films were studied, and the high thermal conductivity of diamond was used to enhance the heat dissipation ability of AlN ceramic substrates. Finally, the junction temperature and thermal resistance of LED devices packaged on AlN ceramic–diamond composite substrate, AlN ceramic substrate and aluminum substrate were tested. The experimental results show that compared with the traditional aluminum and AlN ceramic substrates, AlN ceramic–diamond composite substrates show excellent heat dissipation performance, especially under high-power conditions. Full article

Technological advancements for the miniaturization of electronic components highlight a critical role of thin and durable stencils in advanced surface mount technology. Here, we report a transparent and fine film stencil consisting of a clear polyimide film and a functional diamond-like carbon coating layer for the fine-pitch surface mount technology process. High-quality and burr-free apertures in the thin film result from the thermally stable laser-cut process using a repetitive and low-power irradiation of nanosecond pulse laser, enhancing the printing accuracy of solder paste with fewer solder joint defects. The carbon coating layer with an electrostatic discharge composition facilitates smooth and robust surfaces and sidewalls of the apertures for the high solder paste release and high mechanical durability of the fine film stencil. The low-cost and easy fabrication of the fine film stencil accelerates the potential industrial replacement of the conventional metal stencils at a reduced thickness and further open a new opportunity for the mass production of the fine-pitch surface mount technology process. Full article

In response to the demand for advanced materials in extreme environments, researchers have developed a variety of bulk and thin-film materials. One of the best-known processes for altering the mechanical and tribological properties of materials is surface engineering techniques. These involve various approaches to synthesize thin-film coatings, along with post-deposition treatments. The need for self-lubricating materials in extreme situations such as high-temperature applications, cryogenic temperatures, and vacuum systems has attracted the attention of researchers. They have fabricated several types of thin films using CVD and PVD techniques to meet this demand. Among the various techniques used for fabricating self-lubricating coatings, sputtering stands out as a special one. It contributes to developing smooth, homogeneous, and crack-free dense microstructures, which further enhance the coatings’ properties. This review explains the need for self-lubricating materials and the different techniques used to synthesize them. It discusses and summarizes the concept of synthesizing various types of self-lubricating films. It shows the different types of self-lubricating material systems, like transition metal-based nitrides and carbides, diamond-like carbon-based materials, and so on. This work also reflects the governing factors like the deposition temperature, doping elements, thickness of the film, deposition pressure, gas flow rate, etc., that influence the deposition results and, consequently, the properties of the film, as well as their advanced applications in different areas. This work reflects the self-lubricating properties of different kinds of films exposed to various environments in terms of their coefficient of friction and wear rate, emphasizing how the friction coefficient affects the wear rate. Full article