Diamond Core Research Articles

Effect of Grit Size and Wall Thickness of Core Drill on Machining Quality at Hole Exit in Drilling Carbon Fiber Reinforced Plastics Laminate

This article focuses on the drilling of carbon fiber reinforced plastics (CFRP) laminate with brazed diamond core drill under no cooling condition. The effect of grit size, wall thickness of core drill and feed speed on machining quality at the hole exit is studied. The experimental results indicate that the grit size has a significant influence on the diameter of the hole exit. The expanding factor of diameter at hole exit increases with the decrease of grit size. Both large wall thickness and high feed speed lead to serious drilling-induced defects of the hole exit. The drilling-induced defects at hole exit are transformed from broken-edge and burr to local tear.

Ion irradiation-induced modifications of diamond nanorods synthesised by microwave plasma chemical vapour deposition

Diamond nanorods (DNRs) synthesised by the high methane content in argon rich microwave plasma chemical vapour deposition (MPCVD) have been implanted with nitrogen ions. The nanorods were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The DNRs consist of single-crystalline diamond cores of 3–5 nm in diameter and several tens of nanometres in length. For purification from non-diamond contents, hydrogen plasma etching of DNRs was performed. Structural modifications of etched DNRs were studied after irradiating with 50 keV nitrogen ions under the fluence of 5 × 1014, 1 × 1015, 5 × 1015 and 1 × 1016 ions cm−2. Nitrogen-ion implantation changes the carbon–carbon bonding and structural state of the nanocrystalline diamond (NCD). Raman spectroscopy was used to study the structure before and after ion irradiation, indicating the coexistence of diamond and graphite in the samples. The results indicated the increase in graphitic and sp2-related content, at the expense of decrease in diamond crystallinity, for ion implantation dose of 5 × 1015 cm−2 and higher. The method proves valuable for the formation of hybrid nanostructures with controlled fractions of sp3–sp2 bonding.

Nuclear Magnetic Resonance Study of Hydroxylated Detonation Nanodiamond

We report on a detailed nuclear magnetic resonance (NMR) study of hydroxylated diamond nanoparticles. 13C and 1H NMR reveal signals originated from diamond core, hydroxyl, hydrocarbon groups and moisture on the diamond surface. In order to distinguish between the contributions of moisture and other hydrogen-containing groups to the NMR spectra and spin–lattice relaxation, as-prepared and exhausted down to 10-5 Torr samples have been studied. This approach is shown to be useful for correct analysis of the NMR data. Significant reduction in the 13C spin–lattice relaxation time compared with natural diamond and non-exponential behavior of the 13C magnetization recovery were observed similar to the findings on other detonation nanodiamond samples and attributed to the interaction of nuclear spins with paramagnetic defects.

Hole drilling in ceramics/Kevlar fiber reinforced plastics double-plate composite armor using diamond core drill

Both engineering ceramics and Kevlar fiber reinforced plastics (KFRPs) are difficult to cut, so is the ceramics/KFRP double-plate composite armor. In this work, an experimental study of drilling the ceramics/KFRP double-plate composite armor by using a special sintering diamond core drill has been carried out on a general-purpose drilling machine. Machining mode, drilling sequence, and machining efficiency have been discussed based on drilling experiments. According to the discussed experimental results, machining using manual step feed, drilling the KFRP backboard firstly, and selecting the reasonable technical parameters could greatly facilitate the hole drilling in the ceramics/KFRP double-plate composite armor. The results achieved show that the machining method presented in this work is applicable for small order production.

Surface modification and electrochemical behaviour of undoped nanodiamonds

Surface modifications of undoped nanodiamond (ND) particles were carried out through different annealing treatments. The methods of Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy were used to characterize the ND surface before and after the annealing process. The electrochemical properties of the modified ND powders in aqueous solution were investigated with Fe(CN)63−/4− as a redox probe. When the annealing temperature was below 850°C, vacuum annealing removed parts of the oxygen-containing surface functionalities from the ND surface and produced more sp2 carbon atoms in the shell. The charge transfer of the Fe(CN)63−/4− redox couple decreased with increasing annealing temperature. Re-annealing in air restored the original surface conditions: few sp2-bonded carbon atoms and similar surface functionalities, and thus the electrochemical activity. When ND was annealed in vacuum at 900–1100°C, more serious graphitization produced a continuous fullerenic shell wrapped around a diamond core, which had a high conductivity and electrochemical activity. This provides a novel nanoparticle with high conductivity and high stability for electrochemical applications.

EFFECT OF OPERATING PARAMETERS AND FORMATION PROPERTIES ON PENETRATION RATE IN SOME SANDSTONE ROCKS USING DIAMOND CORE BIT

In this study four sandstone rocks were drilled by diamond core bit using a fixed laboratory-drilling machine at 400 and 1200 rpm, rotary speed, over a range of weights on bit (WOB) 12,18,24,30,…….,150 kg. Operating parameters of the drill bit such as WOB, penetration rates (PR), torque (T) and specific energy (SE) were continuously monitored during the drilling trials. Besides the effects of formation properties on the penetration rate were monitored. Relationships between WOB and both PR, torque T and SE were determined and the relationship between PR and SE was given. Graphs are presented and can be used to predict diamond-drilling performance easy and fast.

Bucky diamond produced by annealing nanodiamond as a support of Pt electrocatalyst for methanol electrooxidation

Bucky diamond (BD) with a nanoscale diamond core surrounded by a fullerene shell was used as a support of Pt electrocatalyst for methanol electrooxidation. BDs were prepared by annealing detonation-synthesized nanodiamond (ND) powders in 10−3 Pa vacuum at 900–1100 °C. The electrochemical properties of the BD powders in aqueous solution were investigated. The BDs and NDs supported platinum (Pt) electrocatalysts were prepared using a microwave-assisted reduction method. Higher dispersion of Pt nanoparticles was observed on the BDs than the pristine NDs, indicating a high affinity between BDs and Pt metal. The Pt/BD catalyst had better catalytic activity and higher stability for the methanol electrooxidation in comparison to the Pt/ND prepared at the same conditions. This provides a novel nanoparticle with a high conductivity and a high stability for electrochemical applications.

Reactivity of Divalent Germanium Alkoxide Complexes Is in Sharp Contrast to the Heavier Tin and Lead Analogues

The chemistry of β-diketiminate germanium alkoxide complexes has been examined and shown to be in sharp contrast to its heavier congeners. For instance, (BDI)GeOR (BDI = [{N(2,6-(i)Pr(2)C(6)H(3))C(Me)}(2)CH], R = (i)Pr, (s)Bu, (t)Bu) does not react with carbon dioxide to form a metal carbonate complex. Addition of aliphatic electrophiles, such as methyl iodide or methyl triflate, results in the net oxidative addition to the germanium, giving cationic tetravalent germanium complexes, [(BDI)Ge(Me)OR][X] (X = I, OTf). An examination of the contrasting reactivities of the alkoxide ligand and the germanium loan pair with Lewis acids yielded the unusual germanium(II)-copper(I) adduct, {μ(2)-Cu(2)I(2)}[(BDI)GeO(t)Bu](2). This complex not only displays a rare example of a divalent Ge-Cu bond, but is the first example in which a planar Cu(2)I(2) diamond core possesses a three-coordinate copper bound to another metal center.

Oxygen hole doping of nanodiamond

Surface-graphitized nanodiamonds (NDs) are promising hybrid nanomaterials which appear to combine core properties of diamond with surface properties of graphene-based materials. Here we demonstrate that NDs covered by graphene islands, so-called Fullerene-Like Reconstructions (FLRs), are sensitive to hole doping by molecular oxygen in water. NDs covered by FLRs (NDs-FLRs) are prepared by annealing under vacuum of detonation NDs at 750 °C. We propose that oxygen hole doping is promoted on FLRs due to a unique electronic interaction between the diamond core and the outer graphene layer. As a consequence, NDs-FLRs exhibit positive zeta potential in water, unlike NDs surrounded by several graphitic layers. Surface hole-doped NDs may be promising nanomaterials for new electronic and biomedical applications.

An Analysis of Noise Characteristics of Drill Bits

There have been papers that analyze the relationship between bit design and a bit’s vibrational characteristics. These papers typically are based on the analysis of three-axis near-bit down-hole vibration sensors. In this paper, the authors take a simpler approach. Using a standard microphone literally pointed at the bit, they record the noise of the bit/rock interaction while drilling and analyze the resulting noise for these bit vibrational characteristics. The data were gathered at the Colorado School of Mines in Golden, CO. The noise of a PDC core, roller cone, and diamond core bits were recorded under various weight and rotary speeds using a microphone and a vertically mounted uniaxial geophone (used for confirming the data recorded on the microphones). Using a Fast Fourier Transform, the frequency spectra were extracted from the recorded data and analyzed. The data were normalized for rotational speed. The results of the frequency analysis of the roller cone, the PDC, and the natural diamond bits are presented in this paper. The major differences in the three bit frequency characteristics could be detected and furthermore, for drag bits, the frequency characteristics could be related to the bit’s design. The frequency spectra of the roller cone bit can best be described with a general high amplitude level that is relatively evenly distributed over the whole frequency spectrum. The drag bit data showed a strong relationship between the number and arrangement of cutting elements and frequency peaks on a plot of amplitude versus cycles per revolution. Frequency peaks were observed at multiples of the number of cutting elements. In general this relationship was strongly visible on the PDC bit data but not as strongly visible on the diamond bit data. The conclusion is that bit characteristics can be determined using only the noise of a bit. Potential applications of this research include detecting and diagnosing bit problems (e.g., broken teeth and bit balling) in real time using simple microphone based acoustic data.

Early stages of surface graphitization on nanodiamond probed by x-ray photoelectron spectroscopy

We have investigated the early stages of graphitization on detonation nanodiamond during sequential annealing treatments under vacuum using x-ray photoelectron spectroscopy. Two different temperature-dependent regimes were observed. Below 900 \ifmmode^\circ\else\textdegree\fi{}C, the nanodiamond surface reconstructs into graphitic domain but does not alter the diamond core. Above 900 \ifmmode^\circ\else\textdegree\fi{}C, graphitization, i.e., carbon hybridization changes from $s{p}^{3}$ to $s{p}^{2}$, occurs from the nanodiamond surface toward the diamond core. Graphitization is observed at much lower temperatures on nanodiamonds than on bulk diamond due to the high concentration of structural defects on their surface. These results indicate that low-temperature annealing under vacuum is an efficient method to uncouple surface and bulk graphitization. Hybrid nanocarbons formed in these conditions, constituted of a diamond core with a thin graphitic outer shell, may have interesting catalytic and chemical properties.

Structure and Bonding of the Manganese(II) Phosphide Complex (t-BuPH2)(η5-Cp)Mn{μ-(t-BuPH)}2Mn(Cp)(t-BuPH2)

Rather than achieving bis-deprotonation of the phosphine, reaction of Cp2Mn (Cp = cyclopentadienyl) with t-BuPH2 at room temperature yields monodeprotonation of half of the available phosphine in the product (t-BuPH2)(η5-Cp)Mn{μ-(t-BuPH)}2Mn(Cp)(t-BuPH2) (1). This complex comprises a Mn(II) phosphide and is a dimer in the solid state, containing a Mn2P2 diamond core. Consistent with the observation of a relatively short intermetal distance of 2.8717(4) A in 1, DFT analysis of the full structure points to a singlet ground state stabilized by a direct Mn–Mn single bond. This is in line with the diamagnetic character of 1 and an 18-electron count at Mn.

Molecular dynamics investigation of the lubrication mechanism of carbon nano-onions

Carbon nano-onions have been shown to provide exceptional friction and wear reduction through a rolling and sliding mechanism of the nano-onions at the interface, but the influence of this behavior on the their tribological properties is not well documented. Understanding the lubrication mechanisms of such nanostructured materials aids in determining their frictional properties and promotes the use of these materials in tribological applications. Here, we characterize the mechanisms of rolling and sliding through which carbon nano-onions provide low coefficients of friction by performing atomistic molecular dynamics simulations of carbon nano-onions sliding between diamond-like carbon substrates. The results indicate that the ability of the nano-onions to roll is inhibited both by increased contact pressure and the presence of a diamond core within the nanoparticles that enhances the formation of interfacial bonds during friction. The transition from rolling to sliding behavior is accompanied by a significant increase in the coefficient of friction.

The coordination chemistry of unsymmetric N-capped tripodal NO3 ligands with iron(III), oxo-vanadium(V) and dioxo-molybdenum(VI) metal centres

The synthesis and characterisation of iron(III) [Fe(L1)]2 (1), oxo-vanadium(V) [VO(L1)] (2) and dioxo-molybdenum(VI) K[MoO2(L1)] (3) complexes supported by a partially unsymmetric N-capped tripodal NO3 ligand (L1) are reported. Complexes 1 and 2 were prepared by reactions of a proligand [H3L1] and their corresponding metal precursor (FeCl3 and VOCl3, respectively) in the presence of triethylamine in THF, while 3 was obtained in a similar manner by treating [MoO2(acac)2] (acac=acetylacetonate) with the same proligand and potassium hydroxide in methanol. The X-ray crystal structure of 1 illustrates a dimeric structure with a bis-(μ-phenoxo) Fe2O2 diamond core, and each iron centre bears a rare NO4 coordination sphere. The preparation of a previously unknown, fully unsymmetric N-capped tripodal NO3 proligand [H3L2] featuring three different phenolic arms is also described. Reaction of [H3L2] with VOCl3 yielded the oxo-vanadium(V) complex [VO(L2)] (4). Complexes 2–4 exist as monomers in solution and were characterised by NMR (1H and 13C), IR (for 3), mass spectrometry, and elemental analysis.

Quantification of Ni laterite mineralogy and composition: a new approach

Quantification of the chemical and mineralogical composition of Ni-bearing laterites is challenged by their complex nature, with the distribution of Ni and other metals controlled by a number of phases. Anew approach to predict the Ni (and Fe, Mg) composition of Ni laterites more reliably was tested using samples from drill holes from the Siberia North and Highway deposits. These deposits, selected as examples of (siliceous) oxide-style lateritic deposits, form part of the Kalgoorlie Nickel Project (KNP) in the north-eastern Yilgarn, Western Australia. Diffuse reflectance spectra over the 380–2500 nm wavelength range, measured using the CSIRO HyChips™ automated scanning system, were integrated with a multi-element dataset for 1 m-composite pulp samples using partial least-squares regression (PLSR) analysis. PLSR cross-validation models were developed to predict Ni, MgO and FeO, contents in samples with bulk composition limits of >0.08 wt% Ni and <6 wt% MgO. Calibration and validation models showed a strong, linear trend for characterising FeO and, to a lesser extent, Ni content, whereas reflectance spectroscopic-chemical models for predicting MgO content were less reliable. This reflected the prevailing mineralogy and associated element distribution within the oxide laterite profiles. For example, Fe and Ni distribution is controlled by relatively few minerals—predominantly goethite and, to a lesser extent, the Fe3+-bearing smectite, nontronite. Magnesium is associated with a range of Mg-bearing minerals, some of which are compositionally complex and include serpentine, talc, chlorite, smectite and carbonates (e.g. dolomite and magnesite). The MgO abundance alone does not reflect the varied mineralogy of samples with relatively high MgO contents, which can be spectrally distinct. Hence, samples with similar Mg contents, although comprising Mg-bearing minerals with distinct reflectance spectra, were difficult to model (e.g. smectite vs Mg carbonates). The findings of this study demonstrate that characterisation of Ni laterite chemistry may be achieved as part of routine logging of either drill cuttings or diamond drill core using PLSR analysis, but a detailed understanding of the mineral–element association is essential for reliable predictive analysis.

Transformation of nano-diamonds to carbon nano-onions studied by X-ray diffraction and molecular dynamics

The transformation of ultra-dispersed diamond nanoparticles of about 50 Å in diameter into carbon nano-onions has been studied by high-energy X-ray diffraction and molecular dynamics simulations using the reactive empirical bond order potential. Structural models have been constructed for pristine nano-diamonds and nano-diamonds annealed at 1673 K, 1973 K and 2273 K. These models have been relaxed using the molecular dynamics method and the model based structure factors and the pair correlation functions are compared with the experimental data. All model relaxations and the X-ray diffraction experiments have been carried out at 300 K. Two starting models consisting of 5460 atoms with a single diamond core and an amorphous-like outer shell and for a twinned diamond core and a similar amorphous outer shell containing in total about 13,500 atoms reproduced correctly features of the experimental data. The atomic models of two intermediate and final fully graphitized structures, consisting of the same numbers of atoms and containing the series of defected icosahedral fullerenes describe satisfactorily the atomic arrangements for the samples annealed at 1673 K, 1973 K and 2273 K. The generated models of the nano-diamonds and the nano-onions are related to the previous observations by high-resolution transmission electron microscopy.

Substrate-Triggered Activation of a Synthetic [Fe2(μ-O)2] Diamond Core for C–H Bond Cleavage

An [Fe(IV)(2)(μ-O)(2)] diamond core structure has been postulated for intermediate Q of soluble methane monooxygenase (sMMO-Q), the oxidant responsible for cleaving the strong C-H bond of methane and its hydroxylation. By extension, analogous species may be involved in the mechanisms of related diiron hydroxylases and desaturases. Because of the paucity of well-defined synthetic examples, there are few, if any, mechanistic studies on the oxidation of hydrocarbon substrates by complexes with high-valent [Fe(2)(μ-O)(2)] cores. We report here that water or alcohol substrates can activate synthetic [Fe(III)Fe(IV)(μ-O)(2)] complexes supported by tetradentate tris(pyridyl-2-methyl)amine ligands (1 and 2) by several orders of magnitude for C-H bond oxidation. On the basis of detailed kinetic studies, it is postulated that the activation results from Lewis base attack on the [Fe(III)Fe(IV)(μ-O)(2)] core, resulting in the formation of a more reactive species with a [X-Fe(III)-O-Fe(IV)═O] ring-opened structure (1-X, 2-X, X = OH(-) or OR(-)). Treatment of 2 with methoxide at -80 °C forms the 2-methoxide adduct in high yield, which is characterized by an S = 1/2 EPR signal indicative of an antiferromagnetically coupled [S = 5/2 Fe(III)/S = 2 Fe(IV)] pair. Even at this low temperature, the complex undergoes facile intramolecular C-H bond cleavage to generate formaldehyde, showing that the terminal high-spin Fe(IV)═O unit is capable of oxidizing a C-H bond as strong as 96 kcal mol(-1). This intramolecular oxidation of the methoxide ligand can in fact be competitive with intermolecular oxidation of triphenylmethane, which has a much weaker C-H bond (D(C-H) 81 kcal mol(-1)). The activation of the [Fe(III)Fe(IV)(μ-O)(2)] core is dramatically illustrated by the oxidation of 9,10-dihydroanthracene by 2-methoxide, which has a second-order rate constant that is 3.6 × 10(7)-fold larger than that for the parent diamond core complex 2. These observations provide strong support for the DFT-based notion that an S = 2 Fe(IV)═O unit is much more reactive at H-atom abstraction than its S = 1 counterpart and suggest that core isomerization could be a viable strategy for the [Fe(IV)(2)(μ-O)(2)] diamond core of sMMO-Q to selectively attack the strong C-H bond of methane in the presence of weaker C-H bonds of amino acid residues that define the diiron active site pocket.

Hydroxylated Detonation Nanodiamond: FTIR, XPS, and NMR Studies

Detailed and unambiguous characterization of the surface structure of detonation nanodiamond (DND) particles remains one of the most challenging tasks for the preparation of chemically functionalized nanodiamonds. In the present paper, a combination of FTIR, NMR, and XPS was used to characterize DND particles that were treated in a reduction reaction that results in the enrichment of hydroxyl and hydroxymethyl functional groups. FTIR spectra and quantum-chemistry modeling demonstrated that the vacuum treatment of the sample, with the purpose of the removing adsorbed water and other volatile contaminates, is mandatory to obtain the correct data on the nature and relative content of the −OH surface groups on DND. 13C and 1H NMR spectra show signals from the diamond core, hydroxyl, hydrocarbon groups, and moisture on the diamond surface. NMR data were taken for as-prepared DNDs, as well as those that were dried under vacuum conditions of 10–4 Torr, in order to distinguish between the NMR signal contributions...

Optical properties of nanodiamond suspensions

The optical properties of nanodiamond suspensions have been calculated. The main supposition is that carbon dimers, which in many aspects are analogous to Pandey chains (2 × 1) on the surface of bulk diamond, are formed on the surface of nanodiamonds due to the surface reconstruction. All experimentally observed features of the absorption of nanodiamond suspensions have been explained on the basis of these ideas. Whereas the diamond nucleus does not absorb light in the visible spectral range, dimers on the surface of the diamond core absorb light in the entire range of optical wavelengths. In addition, there are two features at energies close to 1.5 and 5 eV in their absorption spectrum.

Diamond growth from oxidized carbon sources beneath the Northern Slave Craton, Canada: A δ 13C–N study of eclogite-hosted diamonds from the Jericho kimberlite

Diamonds from high- and low-MgO groups of eclogite xenoliths from the Jericho kimberlite, Slave Craton, Canada were analyzed for carbon isotope compositions and nitrogen contents. Diamonds extracted from the two groups show remarkably different nitrogen abundances and δ 13C values. While diamonds from high-MgO eclogites have low nitrogen contents (5–82 ppm) and extremely low δ 13C values clustering at ∼−40‰, diamonds from the low-MgO eclogites have high nitrogen contents (>1200 ppm) and δ 13C values from −3.5‰ to −5.3‰. Coupled cathodoluminescence (CL) imaging and SIMS analysis of the Jericho diamonds provides insight into diamond growth processes. Diamonds from the high-MgO eclogites display little CL structure and generally have constant δ 13C values and nitrogen contents. Some of these diamonds have secondary rims with increasing δ 13C values from −40‰ to ∼−34‰, which suggests secondary diamond growth occurred from an oxidized growth medium. The extreme negative δ 13C values of the high-MgO eclogite diamonds cannot be produced by Rayleigh isotopic fractionation of average mantle-derived carbon (−5‰) or carbon derived from typical organic matter (∼−25‰). However, excursions in δ 13C values to −60‰ are known in the organic sedimentary record at ca. 2.7 and 2.0 Ga, such that diamonds from the high-MgO eclogites could have formed from similar organic matter brought into the Slave lithospheric mantle by subduction. SIMS analyses of a diamond from a low-MgO eclogite show an outer core with systematic rimwards increases in δ 13C values coupled with decreases in nitrogen contents, and a rim with pronounced alternating growth zones. The coupled δ 13C-nitrogen data suggest that the diamond precipitated during fractional crystallization from an oxidized fluid/melt from which nitrogen was progressively depleted during growth. Model calculations of the co-variation of δ 13C–N yielded a partition coefficient ( K N) value of 5, indicating that nitrogen is strongly compatible in diamond relative to the growth medium. δ 13C values of diamond cores (−4‰) dictate the growth medium had higher δ 13C values than primary mantle-derived carbon. Therefore, possible carbon sources for the low-MgO eclogite diamonds include oxidized mantle-derived (e.g. protokimberlite or carbonatite) fluids/melts that underwent some fractionation during migration or, devolatilized subducted carbonates.