Insulating diamond coatings on tungsten electrodes

The undoped and B-doped polycrystalline diamond thin film was synthesized by hot filament chemical vapor deposition and microwave plasma, respectively. The structural characterization was performed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The electrical properties of synthesized diamond layer were characterized by dc-conductivity method and charge deep level transient spectroscopy. The B-doped diamond layers show higher sp2/sp3 ratios in comparison with that of undoped layers what can have an essential influence on the localized density of states associated with shallow hydrogen acceptor states what is reflected in the values of activation energies which reached the values of 38 meV for B-doped and 55 meV for undoped diamond layers, respectively. The existence of deep level traps, as, for example, associated with B-related acceptors, was not observed.

Porous diamond (PD) films have been grown on sintered WC‐13 wt.%Co substrates by bias enhanced hot filament (HF) chemical vapour deposition (CVD) methods and characterized by scanning electron microscopy (SEM), laser Raman spectroscopy and X‐ray diffraction (XRD). The PD films show excellent adhesion under Rockwell indentation testing. Factors encouraging the growth of diamond film with high porosity are discussed. magnified image

Diamond icosahedron on a TiN-coated steel substrate

In tungsten inert gas welding, the tungsten electrode plays a crucial role in guiding current and transmitting electrical energy. However, the tungsten electrode is susceptible to abrasion during welding. Accurately obtaining the abrasion length of the tungsten electrode is of great significance for further optimizing the tungsten electrode replacement cycle and improving welding quality and efficiency. This paper proposes a novel detection method for the abrasion length of welding tungsten electrodes based on semantic segmentation and tip restoration. This method first uses the DeepLabV3+ model for semantic segmentation to obtain the masks of the tungsten electrode column and tip; then, based on these masks, it performs angle correction and restoration of the tungsten electrode tip; finally, by comparing the masks of the tungsten electrode tip before and after restoration, the abrasion length of the tungsten electrode is obtained. Experimental results show that this method can accurately obtain the abrasion length of the welding tungsten electrode, providing precise and objective data on the abrasion state of the tungsten electrode for welding equipment.

Novel structuring technique for diamond coatings

Structure and photoluminescence properties of graphene nanoflakes grown on zinc oxide films by hot filament chemical vapor deposition

Electrochemical behaviour of graphite- and molybdenum electrodes modified with thin-film diamond

The hot filament chemical vapor deposition (HFCVD) process is used to synthesize diamond crystals on cemented carbide (WC–Co) SPUN inserts. Diamond (Dia.), carbon (GC-glassy spherical form), iridium (Ir), molybdenum (Mo), palladium (Pd), platinum (Pt), tungsten (W), and tantalum (Ta) powders were used as seeding materials for crystal growth. Scanning electron microscopy (SEM) data revealed the development of a few diamond crystals in platinum, iridium, and tungsten powders. The seeding with carbon, tantalum, and diamond powders formed clustered microcrystalline diamond (MCD) crystals, although other powders produced discrete crystals. Tantalum and diamond-seeded powders produced the most significant number and size of crystals. According to micro-Raman spectroscopy (µ-RS), tantalum powder had the lowest ID/IG ratio and the most excellent sp3 bonding. X-ray diffraction (XRD) revealed the maximum diamond intensity in the (111) plane. According to atomic force microscopy (AFM), diamond and molybdenum powders had the largest grains, whereas tantalum powder had the smallest root mean square roughness value with a homogeneous grain distribution. The Vickers microhardness (VHN) test confirmed the highest hardness value for diamond and tantalum seeded powder coatings with the least amount of radial cracking. Field emission scanning electron microscopy (FESEM) revealed that both powders had higher film thickness values.

By using the Hot Filament Chemical Vapor Deposition (HFCVD) technique tungsten thin films were deposited on amorphous quartz substrates. To achieve this, a tungsten filament was heated at 1300 °C during 30 minutes maintaining a constant pressure inside the chamber at 460 mTorr and substrate at 700 °C. Transition from tungsten oxide deposits to tungsten thin films, by varying the substrate temperature, were characterized by means of Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), X-Ray Diffraction and, micro-Raman spectroscopy. The SEM micrographs reveal that the tungsten films have no more than 200 nm in thickness while XRD show evidence of the films crystallize in the á-tungsten modification. On the other hand, AFM shows that the tungsten thin films exhibit a uniform and smooth surface composed with semi-spherical shapes whose diameters are below than 50 nm. Furthermore, to the naked eye, the as-deposited tungsten films exhibit a high mirror-like appearance.

Nucleation studies of thin diamond films on model substrates

A study of diamond synthesis on glassy carbon by the hot filament chemical vapour deposition technique

Defects in nitrogen-doped diamond films, produced by hot filament chemical vapour deposition have been studied by Electron Spin Resonance (ESR), Raman spectroscopy and Scanning Electron Microscopy (SEM). The peak-to-peak ESR line width (ΔHpp) varies in the range 0.36-0.52 mT and depends on the nitrogen concentration in the process gas. In the case of nitrogen-doped diamond films ESR spectrum shows a hyperfine structure typical of NS0 paramagnetic centre. The shape of the central ESR line shows that it is a superposition of two components: a narrower Lorentzian and a broader Gaussian one, characterized by different saturation behaviour. With increasing nitrogen concentration in process gas the ratio of integral intensities AG/AL (Gausian to Lorentzian) of ESR spectrum also increases. The Raman spectra show that with increasing doping level the diamond Raman line at 1332.5 cm-1 broadens, the broad band at about 1530 cm-1 becomes more pronounced what indicate on degradation of diamond crystallinity and it is in agreement with SEM observation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The mechanism of the negative bias enhanced nucleation of diamond on silicon has been studied by a set of experiments using hot filament chemical vapor deposition. Nucleation enhancement was achieved for experimental configurations either with or without the application of a negative bias to the mirror-polished Si substrates. The obtained nucleation density ranged from 108 to 1010 cm−2. The as-deposited films were characterized by scanning electron microscopy and Raman spectroscopy. Our results demonstrate that the electron emission from the diamond coating the substrate holder, which is speculated to greatly increase the concentration of atomic hydrogen and dissociated hydrogen radicals on/near the substrate surface is responsible for the nucleation enhancement during the bias pretreatment.

The substrate temperature has great influence on the growth rate and quality of diamond films by hot filament chemical vapor deposition (HFCVD). In order to deposit polycrystalline diamond films of uniform thickness over large areas and improve the growth rate of diamond films, the substrate temperature uniformity need to be further improved. Thus three-dimensional finite volume simulation has been developed to predict substrate temperature distribution, and optimize the deposition parameters like the size and arrangement of filaments which have a profound effect on the substrate temperature. Based on the simulation results, the optimum parameters of diamond deposition are found. Subsequently, experiments of depositing diamond films on silicon (100) wafers are done when the deposition parameters are fixed at optimum values gained from the simulation results. According to the results of scanning electron microscopy (SEM) and Raman spectroscopy, the thickness and quality of diamond films are homogeneous, which validate that the simulated deposition parameters are conducive to fabricate the high quality diamond films.

Growth and characterization of integrated nano- and microcrystalline dual layer composite diamond coatings on WC–Co substrates