Nickel Diamond Research Articles

Effect of Particle Concentration on the Microstructure and Properties of Electrodeposited Nickel–Diamond Composite Coatings

For the purpose of improving the wear properties of Ni composite coatings, diamond particles were co-electrodeposited into Ni–diamond composite coatings. The effect of diamond particle concentration in the electrolyte on the surface morphology, microstructure, and wear properties of Ni–diamond composite coatings was investigated. The electrodeposition behaviors of the composite coatings were simulated by COMSOL5.6. The results showed that the content of diamond particles in the coating was elevated by increasing the particle concentration in the electrolyte. The formation of [200] fiber texture was blocked and concurrently brought about crystallite refinement of the Ni deposits by the embedded particles. The COMSOL simulation findings indicated that embedded particles influenced the microstructure of the Ni deposits through processes such as heterogeneous nucleation, rearrangement, and concentration of local current density. The synergistic effect of the tailored microstructure and embedded particles substantially enhanced the wear resistance of the coating. By increasing the particle concentration in the electrolyte, the wear resistance of the coating was gradually enhanced, and the coating electrodeposited at 16 g/L possessed the lowest friction coefficient and the smallest profile of wear scratch owning to the strengthened synergistic effect.

Synthesis of Ni nanoclusters supported on diamond by plasma technique and their electrochemical properties

In this study, particles of synthetic undoped diamond (DN) obtained via the high pressure – high temperature method were coated with a nickel shell using metallic nickel plasma in a two-jet plasma generator with gas vortex and magnetic flux stabilization. Through the use of scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, we observed the formation of a nickel diamond composite with a core-shell structure, where DN serves as the core and Ni nanoclusters form the shell (DN@Ni). The results of voltammetric analysis indicated that DN@Ni, when deposited on a graphite electrode, exhibited significant electrocatalytic activity in the oxidation of methanol and paracetamol in an alkaline electrolyte.

Structure Integrity Analysis on Nickel–Diamond Blade in Dicing of Hard-brittle Ceramic Die

Dicing operation in cutting hard-brittle ceramic die using nickel–diamond blade causes cracked or chipped die, accelerated tool wear and, ultimately, shortage of blade lifetime. This study aims to analyse the structural integrity of dicing blade in terms of tool wear, surface roughness, microstructure and elements during dicing. The measurements of wear blade on the blade are made by confocal microscope, whereas surface and elemental analyses are carried out with EDX SEM. Results show that the volumetric wear rate of blade is 20%, similar to roughness. The microstructure of the blade changes with occurrence of Aluminium owing to abrasive wear mechanism during cutting.

Erratum to: Synthesis and characterization of nickel–diamond nanocomposite layers

Erratum to: Synthesis and characterization of nickel–diamond nanocomposite layers

Synthesis and characterization of nickel–diamond nanocomposite layers

Electrodeposition can be used in order to prepare nanocomposite coatings made of nanoparticles dispersed into a metallic matrix, onto a metallic substrate. These kinds of coatings can combine the properties of the matrix and of the dispersed nanoparticles, which can lead to some interesting properties of the mixture. Including diamond nanoparticles into a metallic matrix can take advantage of the diamond properties, especially of its hardness and inertness in many chemical media. Still, the proper control of the electrodeposition parameters is a must in order to obtain the best microhardness and corrosion behavior of such nanocomposite coating. This paper proposes the comparative analysis between Ni/diamond nanocomposite coatings, prepared by electrodeposition, by varying several deposition parameters and the corresponding pure nickel coatings onto the same type of substrate, namely copper. Microstructural and morphological analysis of the two kinds of coatings are also performed and studied, along with microhardness measurements and corrosion resistance tests. It is concluded that specific electrodeposition technique and corresponding parameters must be used in order to prepare those Ni/diamond nanocomposite coatings with the best microhardness and best corrosion resistance.

Study of the processing properties of a nickel-based diamond film in the development of a miniature circular diamond-blade array

This study presents a hybrid fabrication technique for developing a diamond-blade array used to directly generate a microgroove array onto NAK80 steel. The microgroove array on the NAK80 steel can be used as a biochip mold. The diamond-blade array is made by depositing a nickel-based diamond film onto a disk tool (substrate) through electrochemical co-deposition. The nickel–diamond wheel blank is then cut using RWEDM (Rotary Wire Electrical Discharge Machining) to produce a multi grinding-edge array from the blank. The developed diamond-blade array is then employed in machining a microgroove array on NAK80 steel to produce a biochip mold. The resultant dimensional accuracy, geometric accuracy, and surface finish of the grinding-edge and finished microgroove array are measured and evaluated. The factors influencing formability, thermal machinability, and mechanical properties of the diamond film are discussed in detail. Experimental results indicate that a lower current density and moderate diamond abrasive concentration create a diamond film of high-integrity. Increasing the thickness of the deposited film suppresses thermal fracturing and raises the rigidity of grinding-edges helping to keep the diamond cutting-edge accurate. Nano-metric scale grinding of microgrooves on the NAK80 steel is helpful in maintaining sharpness and slowing the wear rate of the diamond-film grinding-edges.

Rapid discharge sintering of nickel–diamond metal matrix composites

In this study rapid discharge sintering (RDS) and furnace sintering of nickel–diamond metal matrix composites (MMCs) is compared. Nickel–diamond powder composites (80–20% by weight respectively) were uniaxially pressed into 20 mm discs at compaction pressures of 100, 200 and 300 MPa. Discharge sintering was carried out using a microwave plasma formed with hydrogen and hydrogen/nitrogen as the discharge gases and tube furnace sintering carried out in a argon or a hydrogen/nitrogen (3:1) atmosphere. Discs pressed to 300 MPa were treated at both 850 and 1000 °C. The properties of the sintered nickel–diamond composites were characterized using density, approximate flexural strength, hardness, wear resistance, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The RDS samples sintered at 1000 °C achieved the maximum approximate disc flexural strength of 473 MPa within a 20 min treatment time compared with 6 h for furnace sintered samples. Samples sintered using the RDS technique exhibited increased hardness values and a finer nickel matrix over furnace sintered samples. Using the RDS technique it has been possible to process nickel–diamond MMCs without oxidation or graphitisation at temperatures above 900 °C. Minimal diamond destruction was observed during abrasive wear testing of the RDS samples compared with damage and pull-out observed for furnace sintering.

Lattice location of nickel in diamond by RBS channelling and PIXE

AbstractColour centres in diamond are important for potential applications in quantum information technology. Centres based on Ni have attractive properties but the structures are still not fully understood. One interesting colour centre is NIRIM‐2 which emits around 884 nm and is based on Ni preferentially incorporated into the <111> growth sector during high‐pressure high‐temperature diamond growth in the presence of a Ni catalyst. To help understand the structure of this colour centre a combination of Rutherford backscattering spectrometry (RBS) with ion channelling and particle induced X‐ray emission (PIXE) with 2 MeV H and He ions has been used to study the location of the Ni atoms in the diamond lattice. The Ni concentration, typically below 25 ppm, is well below the detection threshold for RBS, but the yield of characteristic Ni Kα X‐rays shows a decrease when the ion beam is channelled into the <111> growth sector of the diamond. This suggests a significant fraction of Ni is incorporated substitutionally in the diamond lattice. Correlation of Ni location in the diamond host with optical properties of Ni‐related centres in the same growth sector of the diamond offers the possibility of advancing our understanding of the structure of these important optical centres.

Preparation of composite electrochemical nickel–diamond and iron–diamond coatings in the presence of detonation synthesis nanodiamonds

In the work it is shown that addition of individual pure detonation synthesis nanodiamonds to nickel- and iron-plating electrolytes results in an increase in microhardness (2–3.5 times) and wear-resistance (3–6 times) and a decrease in porosity (3–4 times) of a coating. The use of nanodiamonds as a component of diamond-containing blend (a semi-product of synthesis of the nanodiamonds) results in deterioration of all of the above properties for a nickel–diamond coating and great improvement of the same properties for an iron–diamond coating.

Electronic properties of isolated nickel in diamond

Isolated nickel impurities in diamond have been investigated using the spin-polarized full-potential linearized augmented plane wave total energy method. The electronic and atomic structures, symmetries, transition energies, and formation energies of substitutional and interstitial Ni impurities in diamond were computed. The results were discussed in the context of the electrically active centers in synthetic diamond.

A study on the mechanism of formation of electrocodeposited Ni–diamond coatings

Co-deposition behavior of diamond particles and nickel onto a steel in nickel sulfamate baths has been investigated using both a rotating disc and wire geometries. Based on the zeta potential measurement and the change of diamond content of the deposits with electrical potential strength, diamond particles attracted to the cathode electrophoretically after adsorption of positive nickel ions. Results of polarization studies showed that since the rate of nickel deposition was controlled by both mass transfer of the nickel ions and electrochemical deposition, diamond content in nickel–diamond deposits decreased with increasing applied potential and stirring speed in the relatively high rotation speed ranges.

The Electronic States of Nickel ions in Diamond Calculated by a Discrete-Variational Xα Method

The electronic states of nickel in diamond were calculated by a discrete-variational Xα (DV-Xα) method. Model clusters used for substitutional and interstitial Ni sites were [ NiC28H36]- ( Ni\\sits- center) and [NiC30H40]+ ( Nii+ center), respectively. Superhyperfine constants for electron paramagnetic resonance (EPR) spectra were estimated from results of DV-Xα calculation and were compared with measured values. A triply degenerate state with total spin S=3/2 appears in the Nis--center and a half-filled doubly degenerate state with total spin S=1/2 appears in the Nii+-center. The total spin and electron occupancy of these clusters agree with the assignments of the EPR spectra. The electron population analysis result indicated that the Ni+ ion at the tetrahedral interstitial site formed more ionic bonding than the Ni- ion at the substitutional site. Superhyperfine interactions between Ni and the nearest-neighbor carbons were calculated as a function of Ni–C bond length, suggesting that a lattice relaxation occurred for the Ni–C bond to be elongated in the Nis- center.

Nickel defect centers in diamond.

Of all the first series transition metals, nickel in diamond gives strong optical features characteristic of the charge state of the defect. A multiplet structure for each of these charged states is deduced from results of cluster model calculations and shown to be consistent with experiment. The various defects found to date fall into a pattern centered on the neutrally charged form of the defect. This neutral form has completely filled energy levels and is therefore weakly bonded to the lattice. This could explain why only charged forms of the defect are apparently observed. It is also suggested that while interstitial nickel will have a transition-metal character, a substitutional nickel center will display characteristics not unlike a positively charged vacancy.

Nickel in diamond: an annealing study

Many papers have been published recently concerning the incorporation of nickel in diamond. In this paper we present results of an annealing study, carried out in the temperature range 1500–1900°C, of nickel-related optical centres in high-pressure synthetic diamond. We establish the temperature regime in which the well known 1.883 eV and 2.51 eV systems anneal out, and observe the concurrent growth of an array of structure which extends throughout the visible region of the absorption spectrum and gives the previously bright-yellow coloured diamonds a rich golden-yellow colour. By carrying out the annealing sequence on diamonds grown using various solvent-catalysts, we establish the conditions under which the annealed structure is maximized and propose that it involves nickel. Both the content and configuration of nitrogen present in diamond are shown to be critical in determining the stable form of nickel which results.

Optical dichroism of nickel in diamond

Recent optical measurements of a 1.4 eV doublet in diamond have revealed distinct optical polarization features which are associated with a nickel defect. A model for the defect is investigated taking into account the large electronic hybridization that will take place about the metal ion. Relative spectroscopic intensities and estimates of the spin-orbit interaction are considered within the LCAO approximation. Finally, a cluster model calculation is made specifically to investigate the electronic structure of the nickel defect and estimate the LCAO coefficients. From the results, suggestions are made about the possible charge states and lattice locations of nickel in diamond.

Optical polarization in strongly hybridized d electron states: Ni in diamond

When transition metals are incorporated into semiconductors the states become strongly hybridized. One important manifestation of this is that optical transitions are enhanced especially via strong 4p mixing. Optical polarization selection rules for d states at which there is spin-orbit coupling and a lowering of symmetry to C 3v are derived within a molecular orbital framework. The combined interactions indicate that important differences in the selection rules may arise due to ground and excited state hybridization effects. Application is finally made to recent results on the luminescence of nickel in diamond.

Optical Characterisation of Nickel in Diamond

ABSTRACTOptical absorption and luminescence with zero-phonon lines at 1.401 and 1.404 eV is shown to contain fine structure induced by the isotopes of natural Ni. Uniaxial stress and magnetic field perturbations establish that the optical center has trigonal symmetry. A relationship is estimated between the concentration of Ni in these optical centers and the strength of the optical absorption.

Variation with pressure of the nickel-carbon eutectic

The variation with pressure of the solubility of carbon in molten nickel and of their eutectic temperatures have been observed to about 60 kbars. The eutectic composition increases in carbon concentration from 2.0–2.2 wt.% at 1 atm to about 3.3% at 60 kbars. The eutectic temperature at 60 kbars of the nickel-garphite system as recorded by a platinum-platinum 10% rhodium thermocouple and corrected for its pressure e.m.f. error was ~1395°C. The slope of the eutectic fusion curve, dTe dP , was about half that of the pure metals. Evidence for nickel-carbide formation under pressure was found. The microstructures of several specimens from nickel-graphite and nickel diamond experiments are shown.