Search Results (44)

This study proposes a laser texturing method to optimize adhesion and minimize residual stresses in CVD diamond films deposited on tungsten carbide (WC-Co). WC-5.8 wt% Co substrates were textured with quadrangular pyramidal patterns (35 µm) using a 1064 nm nanosecond-pulsed laser, followed by chemical treatment (Murakami’s solution + aqua regia) to remove surface cobalt. Diamond films were grown via HFCVD and characterized by Raman spectroscopy, EDS, and Rockwell indentation. The results demonstrate that pyramidal texturing increased the surface area by a factor of 58, promoting effective mechanical interlocking and reducing compressive stresses to −1.4 GPa. Indentation tests revealed suppression of interfacial cracks, with propagation paths deflected toward textured regions. The pyramidal geometry exhibited superior cutting post-deposition cooling time for stress relief from 3 to 1 h. These findings highlight the potential of laser texturing for high-performance machining tool applications. Full article

Background/Objectives: The increasing demand for total hip arthroplasty (THA), due to aging populations and active lifestyles, necessitates advancements in implant materials and design. This review evaluates the role of surface coatings in enhancing the performance, biocompatibility, and longevity of hip implants. It addresses challenges like wear, corrosion, and infection, focusing on innovative surface engineering solutions. Methods: The review analyzes various surface modification techniques, including physical vapor deposition (PVD), chemical vapor deposition (CVD), electrophoretic deposition (EPD), plasma spraying, and ion implantation. It also examines their effectiveness in improving tribological properties, biocompatibility, and resistance to infection. Computational methods such as finite element analysis (FEA) are discussed for predicting potential coating failures. Results: The findings underscore the challenges posed by wear debris and corrosion in common configurations, like metal-on-metal (MoM) and metal-on-polyethylene (MoP). Innovative coatings, such as diamond-like carbon (DLC) films and hydroxyapatite (HA) layers, demonstrate enhanced performance by reducing friction, wear, and bacterial adhesion, while promoting osteogenic cell attachment. Surface textures and optimized tribological properties further improve implant functionality. Multifunctional coatings exhibit potential in balancing biocompatibility and infection resistance. Conclusions: Surface engineering plays a critical role in advancing next-generation hip implants. The integration of advanced coatings and surface modifications enhances implant durability, reduces complications, and improves patient outcomes. Future research should focus on combining innovative materials and computational modeling to refine coating strategies for long-term success in THA. Full article

With the development of diamond technology, its application in the field of electronics has become a new research hotspot. Hydrogen-terminated diamond has the electrical properties of P-type conduction due to the formation of two-dimensional hole gas (2DHG) on its surface. However, due to various scattering mechanisms on the surface, its carrier mobility is limited to 50–200 cm²/(Vs). In this paper, the effects of process parameters (temperature, CH₄ concentration, time) on the electrical properties of hydrogen-terminated diamond were studied by microwave plasma chemical vapor deposition (CVD) technology, and hydrogen-terminated diamond with a high carrier mobility was obtained. The results show that homoepitaxial growth of a diamond film on a diamond substrate can improve the carrier mobility. Hydrogen-terminated diamond with a high carrier mobility and low sheet resistance can be obtained by homoepitaxial growth of a high-quality diamond film on a diamond substrate with 4% CH₄ concentration and hydrogen plasma treatment at 900 ℃ for 30 min. When the carrier concentration is 2.03 × 10¹²/cm², the carrier mobility is 395 cm²/(Vs), and the sheet resistance is 7.82 kΩ/square, which greatly improves the electrical properties of hydrogen-terminated diamond. It can enhance the transmission characteristics of carriers in the conductive channel, and is expected to become a potential material for application in devices, providing a material choice for its application in the field of semiconductor devices. Full article

Diamonds produced using chemical vapor deposition (CVD) have found many applications in various fields of science and technology. Many applications involve polycrystalline CVD diamond films of micron thicknesses. However, a variety of optical, thermal, mechanical, and radiation sensing applications require more bulky CVD diamond samples. We report the results of a magnetic resonance and structural study of a thick, sizable polycrystalline CVD diamond disc, both as-prepared and treated with e-beam irradiation/high-temperature annealing, as well as gamma irradiation. The combination of various magnetic resonance techniques reveals and enables the attribution of a plentiful collection of paramagnetic defects of doublet and triplet spin origin. Analysis of spectra, electron, and nuclear spin relaxation, as well as nuclear spin diffusion, supports the conclusion of significant macro- and micro-inhomogeneities in the distribution of nitrogen-related defects. Full article

Low-temperature growth of diamond films using the chemical vapor deposition (CVD) method is not so widely reported and its initial periods of nucleation and growth phenomenon are of particular interest to the researchers. Four sets of substrates were selected for growing diamond films using linear antenna microwave plasma-enhanced CVD (LA-MPCVD). Among them, silicon and sapphire substrates were pre-treated with detonation nanodiamond (DND) seeds before diamond growth, for enhancement of its nucleation. Carbon nanotube (CNT) films on Si substrates were also used as another template for LA-MPCVD diamond growth. To enhance diamond nucleation during CVD growth, some of the CNT films were again pre-treated by the electrophoretic deposition (EPD) of diamond nanoparticles. All these substrates were then put inside the LA-MPCVD chamber to grow diamond films under variable processing conditions. Microwave input powers (1100–2800 W), input power modes (pulse or continuous), antenna-to-stage distances (5–6.5 cm), process gas recipes (with or without CO₂), methane gas percentages (3%–5%), and deposition times (11–120 min) were altered to investigate their effect on the growth of diamond film on the pre-treated substrates. The substrate temperatures were found to vary from as low as 170 °C to a maximum of 307 °C during the alteration of the different processing parameters. Contrary to the conventional MPCVD, it was observed that during the first hour of LA-MPCVD diamond growth, DND seeds and the nucleating structures do not coalesce together to make a continuous film. Deposition time was the most critical factor in fully covering the substrate surfaces with diamond film, since the substrate temperature could not become stable during the first hour of LA-MPCVD. CNTs were found to be oxidized rapidly under LA-MPCVD plasma conditions; therefore, a CO₂-free process gas recipe was used to reduce CNT burning. Moreover, EPD-coated CNTs were found to be less oxidized by the LACVD plasma during diamond growth. Full article

This review of the tribocorrosion of coatings and surface modifications covers nearly 195 papers and reviews that have been published in the past 15 years, as compared to only 37 works published up to 2007, which were the subject of a previous review published in 2007. It shows that the research into the subject area is vibrant and growing, to cover emerging deposition, surface modification and testing techniques as well as environmental influences and modelling developments. This growth reflects the need for machines to operate in harsh environments coupled with requirements for increased service life, lower running costs and improved safety factors. Research has also reacted to the need for multifunctional coating surfaces as well as functionally graded systems with regard to depth. The review covers a range of coating types designed for a wide range of potential applications. The emerging technologies are seen to be molten-, solution-, PVD- and PEO-based coatings, with CVD coatings being a less popular solution. There is a growing research interest in duplex surface engineering and coating systems. Surface performance shows a strong playoff between wear, friction and corrosion rates, often with antagonistic relationships and complicated interactions between multiple mechanisms at different scale lengths within tribocorrosion contacts. The tribologically induced stresses are seen to drive damage propagation and accelerate corrosion either within the coating or at the coating coating–substrate interface. This places a focus on coating defect density. The environment (such as pH, DO₂, CO₂, salinity and temperature) is also shown to have a strong influence on tribocorrosion performance. Coating and surface modification solutions being developed for tribocorrosion applications include a whole range of electrodeposited coatings, hard and tough coatings and high-impedance coatings such as doped diamond-like carbon. Hybrid and multilayered coatings are also being used to control damage penetration into the coating (to increase toughness) and to manage stresses. A particular focus involves the combination of various treatment techniques. The review also shows the importance of the microstructure, the active phases that are dissolved and the critical role of surface films and their composition (oxide or passive) in tribocorrosion performance which, although discovered for bulk materials, is equally applicable to coating performance. New techniques show methods for revealing the response of surfaces to tribocorrosion (i.e., scanning electrochemical microscopy). Modelling tribocorrosion has yet to embrace the full range of coatings and the fact that some coatings/environments result in reduced wear and thus are antagonistic rather than synergistic. The actual synergistic/antagonistic mechanisms are not well understood, making them difficult to model. Full article

The complexity of milling metal matrix composite alloys based on aluminum like Al/SiC is due to their low melting point and high abrasive ability, which causes increased wear of carbide tools. One of the effective ways to improve its reliability and service life is to modify the surface by plasma chemical deposition of carbon-based multilayer functional layers from vapor (CVD) with high hardness and thermal conductivity: diamond-like (DLC) or polycrystalline diamond (PCD) coatings. Experiments on an indexable mill with CoroMill 200 inserts have shown that initial tool life increases up to 100% for cases with DLC and up to 300% for multilayered MCD/NCD films at a cutting speed of 800 m/min. The primary mechanism of wear of a carbide tool in this cutting mode was soft abrasion, when wear on both the rake and flank surfaces occurred due to the extrusion of cobalt binder between tungsten carbide grains, followed by their loss. Analysis of the wear pattern of plates with DLC and MCD/NCD coatings showed that abrasive wear begins to prevail against the background of soft abrasion. Adhesive wear is also present to a lesser extent, but there is no chipping of the base material from the cutting edge. Full article

Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH₃)₂CO in a main gas flow of argon. We performed experiments at two ((CH₃)₂CO + Ar)/Ar) ratios and observed that two visually distinct types of layers were deposited after a one-hour deposition process. The first layer type, which appears more inhomogeneous, has areas of SiO₂ (about 5% of the surface area substrates) beside shiny bright and rough paths, and its Raman spectrum corresponds to diamond-like carbon, was deposited at a (CH₃)₂CO+Ar)/Ar = 1/5 ratio. The second layer type, deposited at (CH₃)₂CO + Ar)/Ar = a 1/0 ratio, appears homogeneous and is very dark brown or black in color and its Raman spectrum pointed to defect-rich multilayered graphene. The performed structural studies reveal the presence of diamond and diamond polytypes and seldom SiC nanocrystals, as well as some non-continuously mixed SiC and graphene-like films. The performed molecular dynamics simulations show that there is no possibility of deposition of sp³-hybridized on sp²-hybridized carbon, but there are completely realistic possibilities of deposition of sp²- on sp²- and sp³- on sp³-hybridized carbon under different scenarios. Full article

In this work, a diamond/Ti/diamond multilayer structure has been fabricated by successively following thin-film CVD and PVD routes. It has been found that a combined pre-treatment of the silicon base substrate, via argon plasma etching for creating surface roughness and, thereafter, detonation nanodiamond (DND) seeding, helps in the nucleation and growth of well-adherent CVD diamond films with a well-defined Raman signal at 1332 cm⁻¹, showing the crystalline nature of the film. Ti sputtering on such a CVD-grown diamond surface leads to an imprinted bead-like microstructure of the titanium film, generated from the underlying diamond layer. The cross-sectional thickness of the titanium layer can be found to vary by as much as 0.5 µm across the length of the surface, which was caused by a subsequent hydrogen plasma etching process step of the composite film conducted after Ti sputtering. The hydrogen plasma etching of the Ti–diamond composite film was found to be essential for smoothening the uneven as-grown texture of the films, which was developed due to the unequal growth of the microcrystalline diamond columns. Such hydrogen plasma surface treatment helped further the nucleation and growth of a nanocrystalline diamond film as the top layer, which was deposited following a similar CVD route to that used in depositing the bottom diamond layer, albeit with different process parameters. For the latter, a hydrogen gas diluted with PH₃ precursor recipe produced smaller nanocrystalline diamond crystals for the top layer. The titanium layer in between the two diamond layers possesses a very-fine-grained microstructure. Transmission electron microscopy (TEM) results show evidence of intermixing between the titanium and diamond layers at their respective interfaces. The thin films in the composite multilayer follow the contour of the plasma-etched silicon substrate and are thus useful in producing continuous protective coatings on 3D objects—a requirement for many engineering applications. Full article

The high-concentration N doping of diamond film is still a challenge since nitrogen is limited during diamond growth. In this work, a novel method combined with the thermal decomposition of silicon nitride was proposed to form the activated N and Si components in the reactor gas that surrounded the substrate, with which the high-concentration N and Si doping of diamond film was performed. Meanwhile, graphene oxide (GO) particles were also employed as an adsorbent to further increase the concentration of the N element in diamond film by capturing the more decomposed N components. All the as-deposited diamond films were characterized by scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. For the pure diamond film with a growth time of 0.5 h, the N and Si concentrations were 20.78 and 41.21 at%, respectively. For the GO-diamond film, they reached 47.47 and 21.66 at%, which set a new record for super high-concentration N doping of diamond film. Hence, thermal decomposition for the substrate can be regarded as a potential and alternative method to deposit the chemical vapor deposition (CVD) diamond film with high-concentration N, which be favorable for the widespread application of diamond in the electric field. Full article

With the increase in the modulation rate of thin-film lithium niobate ($LiNb{O}_3$, LN) modulators, the multi-physical field coupling effect between microwaves, light, and heat becomes more significant. In this study, we developed a thin-film LN modulator model using undoped pure LN thin film and T-shaped slow-wave electrodes. Furthermore, we utilized this model to simulate the microwave heating and light heating situations of the modulator. The temperature of the LN modulator was analyzed over time and with different signal frequencies. We also studied the influence of temperature rise on microwave and light signals, and we analyzed the change of S parameters and the Phase Shift of the light signal caused by temperature rise. Finally, we improved the thermodynamic characteristics of the modulator by adding a diamond heat dissipation layer. The diamond was obtained through the Chemical Vapor Deposition (CVD) technique and was a polycrystalline diamond. After adding the diamond heat dissipation layer, the temperature rise of the modulator was significantly improved, and the adverse effects of temperature rise on microwave signals were also significantly reduced. Full article

Diamond-like carbon (DLC) films are generally used in biomedical applications, mainly because of their tribological and chemical properties that prevent the release of substrate ions, extend the life cycle of the material, and promote cell growth. The unique properties of the coating depend on the ratio of the sp³/sp² phases, where the sp² phase provides coatings with a low coefficient of friction and good electrical conductivity, while the share of the sp³ phase determines the chemical inertness, high hardness, and resistance to tribological wear. DLC coatings are characterized by high hardness, low coefficient of friction, high corrosion resistance, and biocompatibility. These properties make them attractive as potential wear-resistant coatings in many compelling applications, including optical, mechanical, microelectronic, and biomedical applications. Another great advantage of DLC coatings is that they can be deposited at low temperatures on a variety of substrates and can thus be used to coat heat-sensitive materials, such as polymers. Coating deposition techniques are constantly being improved; techniques based on vacuum environment reactions are mainly used, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD). This review summarizes the current knowledge and research regarding diamond-like carbon coatings. Full article

Polycrystalline diamond (PCD) films are usually grown by chemical vapor deposition (CVD) in hydrogen–methane mixtures. The synthesis conditions determine the structure and quality of the grown material. Here, we report the complex effect of the microwave plasma CVD conditions on the morphology, growth rate and phase composition of the resulting PCD films. Specifically, we focus on the factors of (i) increased methane concentrations (${\nu }_c$) that are varied over a wide range of 4%–100% (i.e., pure methane gas) and (ii) substrate temperatures (${\mathrm{T}}_{\mathrm{s}}$) varied between 700–1050 °C. Using scanning electron microscopy, X-ray diffraction and Raman spectroscopy, we show that diamond growth is possible even at ultrahigh methane concentrations, including ${\nu }_c$ = 100%, which requires relatively low synthesis temperatures of ${\mathrm{T}}_{\mathrm{s}}$ < 800 °C. In general, lower substrate temperatures tend to facilitate the formation of higher-quality PCD films; however, this comes at the cost of lower growth rates. The growth rate of PCD coatings has a non-linear trend: for samples grown at ${\mathrm{T}}_{\mathrm{s}}$ = 800 °C, the growth rate increases from 0.6 µm/h at ${\nu }_c$ = 4% to 3.4 µm/h at ${\nu }_c$ = 20% and then falls to 0.6 µm/h at ${\nu }_c$ = 100%. This research is a step toward control over the nature of the CVD-grown PCD material, which is essential for the precise and flexible production of diamond for various applications. Full article

As a significant parameter in tuning the structure and performance of the boron-doped diamond (BDD), the thickness was focused on the mediation of the boron doping level and electrochemical properties. BDD films with different thicknesses were deposited on silicon wafers by the hot filament chemical vapor deposition (HFCVD) method. The surface morphology and composition of the BDD films were characterized by SEM and Raman, respectively. It was found that an increase in the BDD film thickness resulted in larger grain size, a reduced grain boundary, and a higher boron doping level. The electrochemical performance of the electrode equipped with the BDD film was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in potassium ferricyanide. The results revealed that the thicker films exhibited a smaller peak potential difference, a lower charge transfer resistance, and a higher electron transfer rate. It was believed that the BDD film thickness-driven improvements of boron doping and electrochemical properties were mainly due to the columnar growth mode of CVD polycrystalline diamond film, which led to larger grain size and a lower grain boundary density with increasing film thickness. Full article

A dynamic magnetic field (DMF) with different angular frequencies (50, 100, and 150 π rad/s) was introduced during diamond growth via hot filament chemical vapor deposition (HFCVD). The effects of the dynamic magnetic field on the growth rate, diamond quality, growth orientation, and deposition uniformity of large-area diamond films were investigated with scanning electron microscopy (SEM), X-ray diffractometry (XRD), and Raman spectroscopy. The correlation between diamond growth and angular frequency was discussed. The results showed that a faster growth rate (about 2.5 times) and higher diamond quality were obtained by increasing the angular frequency of the DMF. A (100) textured polycrystalline diamond film was achieved, and the preferential orientation was found to evolve from (110) to (100), while the expected uniform deposition of a large-area diamond film under DMF was not achieved. The enhancement effect of the DMF was ascribed to the activation of more gas molecules, which participated in CVD diamond growth. Full article