Average Diamond Research Articles

Geological mapping of kimberlite magmatism as an assessment of diamond-bearing objects in Western Yakutia

Тhe results of generalization and GIS integration of the results of the study of all known indigenous deposits and manifestations of diamonds located in the distributed and undistributed fund of the subsoil of the Russian Federation are presented. The work takes into account the results of prospecting, exploration and exploitation works, minutes of meetings of regional (TKZ) and federal (RKZ and GKZ) commissions on mineral reserves and published data. As a result, a GIS-integrated database was created containing 1,319 objects, for each of which key parameters were determined: coordinates, shape, size, age, average diamond content, forecast resources, and diamond reserves. It was established that the indigenous diamond deposits are concentrated in the Central Siberian subprovincia and account for 2.3 % of all known kimberlite bodies, diamond-bearing kimberlite bodies in the Yakut diamond-bearing province – 282, the predominant body shape is a pipe (59 %). There is no correlation between the size of kimberlite bodies and their diamond content, small pipes, as well as large diatremes, can be industrially diamondiferous, the prevailing absolute age of industrially diamondiferous kimberlites is 329-382 million years.

Wear evolution of metal bond diamond tool in grinding of sapphire

The wear characteristics of the metal bond diamond tools changes with the grinding process, resulting in affecting the grinding efficiency, tool's life, and surface integrity of the workpiece. In this study, the wear evolution of a metal bond diamond tool, for the case of grinding of sapphire, is investigated by using a novel design of the grinding setup. The wear characteristics of the diamond grits and the metal bond at a fixed zone of the grinding tool were examined. In addition, the evolution of the grinding process, the grinding force, the grinding ratio, and the surface integrity of the sapphire were also evaluated. As the material removal volume increases, the number of participating diamond grits, the proportion of micro-fractured diamond grits, and the average diamond grit protrusion height increase during the grinding process. And the proportion of newly exposed diamond grits decreases and the distribution of protrusion height of diamond grits becomes narrower during the grinding process. Consequently, a higher grinding ratio, stable grinding force, and excellent ground surface integrity are achieved positively when the wear of the metal bond diamond tool transforms from the initial stage to the stable stage with the material removal volume of up to 3600 mm3.

Quantum Simulation of Dissipative Collective Effects on Noisy Quantum Computers

Dissipative collective effects are ubiquitous in quantum physics, and their relevance ranges from the study of entanglement in biological systems to noise mitigation in quantum computers. Here, we put forward the first fully quantum simulation of dissipative collective phenomena on a real quantum computer, based on the recently introduced multipartite collision model. First, we theoretically study the accuracy of this algorithm on near-term quantum computers with noisy gates, and we derive some rigorous error bounds that depend on the timestep of the collision model and on the gate errors. These bounds can be employed to estimate the necessary resources for the efficient quantum simulation of the collective dynamics. Then, we implement the algorithm on some IBM quantum computers to simulate superradiance and subradiance between a pair of qubits. Our experimental results successfully display the emergence of collective effects in the quantum simulation. In addition, we analyze the noise properties of the gates that we employ in the algorithm by means of full process tomography, with the aim of improving our understanding of the errors in the near-term devices that are currently accessible to worldwide researchers. We obtain the values of the average gate fidelity, unitarity, incoherence and diamond error, and we establish a connection between them and the accuracy of the experimentally simulated state. Moreover, we build a noise model based on the results of the process tomography for two-qubit gates and show that its performance is comparable with the noise model provided by IBM. Finally, we observe that the scaling of the error as a function of the number of gates is favorable, but at the same time reaching the threshold of the diamond errors for quantum fault tolerant computation may still be orders of magnitude away in the devices that we employ.

Bright silicon vacancy centers in diamond/SiC composite films synthesized by a MPCVD method

SiC is always produced forming diamond/SiC composite films owing to the oversaturated doping of Si atoms during the preparation of high emission SiV centers. As a higher refractive index material (n = 2.72), the presence of SiC could possibly lead to inefficient photo-luminescent (PL) collection of SiV centers with total internal reflection. In order to understand such effect, different diamond/SiC films were deposited in a 915 MHz microwave plasma CVD (MPCVD) using the reactive gas of tetramethylsilane (TMS). The microstructure and photoluminescence of SiV centers were systematically investigated. It is found that the addition of TMS gas leads to the formation of cubic β-SiC and the refinement of diamond crystals. At the TMS gas flow of 5 sccm, the concentration of β-SiC is about 10% and the average diamond size is about 98 nm. The film exhibits the optimized PL emission of SiV centers, with the ratio of SiV PL to diamond Raman peak being 21.4. Increasing TMS gas flow leads to the increase of the concentration of β-SiC and the deterioration of PL emission of SiV centers. These results reveal that the introduction of TMS gas at a low flow advances the formation of diamond/SiC film containing high-brightness SiV centers.

A novel economic-filter for evaluating sub-Saharan diamondiferous kimberlites

SYNOPSIS Because of their high degree of geological complexity, kimberlite-hosted diamond deposits are exceedingly difficult to evaluate for economic viability. Accordingly, standard mineral asset evaluation protocols (e.g., the Cost-, Market-, and Income Approaches defined in the SAMREC Code) may not hold sufficient predictive abilities for these deposit types, especially at the early stages of exploration. Here we present a novel tool, a cost filter approach towards preliminary evaluation of economic viability of southern African kimberlite-hosted diamond deposits, using the AK6 and BK11 diamond deposits from the Orapa diamond field as case studies. The development of this cost filter is underpinned by elements of both the Market Approach (i.e., comparisons to similar deposits) and the Income Approach (i.e., use of net present value (NPV) calculations) for mineral asset evaluation. Importantly, the cost filter is constrained through modification of only two primary variables (the average diamond value and the diamond grade) and thus differs significantly from other cost filters that rely on estimation and assumptions for every parameter input into an NPV calculation. The cost filter correctly predicts the sub-economic status of the BK11 diamond pipe, and is thus presented as a useful geo-economic tool for early stage kimberlite evaluation within the local southern African context. The approach and its theoretical underpinning foreseeably hold vast potential for use in the economic evaluation of other ore commodities, particularly where socio-economic and political risk factors can be negated by employing a geographic constraint. Keywords: diamond, economic viability, kimberlites, southern Africa, cost models filter.

Growth of polycrystalline and single-crystal CVD diamonds with bright photoluminescence of Ge-V color centers using germane GeH4 as the dopant source

Germanium-Vacancy (Ge-V) color center in diamond possesses a narrow band photoluminescence (PL) emission in the orange spectral range interesting as a single-photon source for quantum optical technologies and thermometry, therefore, development of methods for the controllable doping of diamond with Ge is of high importance for such applications. Here, we report on the synthesis of polycrystalline and epitaxial single crystal Ge-doped films using microwave plasma chemical vapor deposition (CVD) technique by addition of the germane GeH4 gas into the H2-CH4 plasma. It is demonstrated, that GeH4 addition affects the CVD growth of microcrystalline diamond, reducing the film growth rate and increasing the average diamond grain size. The films show bright photoluminescence of Ge-V centers at ≈602 nm under the optimized GeH4 concentration, with a zero-phonon line width of 1.6 nm (FWHM) for Ge-V ensemble at low temperatures (5 K). The developed in-situ doping from the germane gas opens a way for a better control of the Ge-V color center formation in diamond for photonic applications.

Geology and resource development of the Kelvin kimberlite pipe, Northwest Territories, Canada

The early Cambrian to late Neoproterozoic Kelvin kimberlite pipe is located in the southeast of the Archean Slave Craton in northern Canada, eight km northeast of the Gahcho Kue diamond mine. Kelvin was first discovered in 2000 by De Beers Canada. Subsequent exploration undertaken by Kennady Diamonds Inc. between 2012 and 2016 resulted in the discovery of significant thicknesses of volcaniclastic kimberlite that had not previously been observed. Through extensive delineation drilling Kelvin has been shown to present an atypical, steep-sided inclined L-shaped pipe-like morphology with an overall dip of 15 to 20°. With a surface expression of only 0.08 ha Kelvin dips towards the northwest before turning north. The body (which remains open at depth) has been constrained to a current overall strike length of 700 m with varying vertical thickness (70 to 200 m) and width (30 to 70 m). Detailed core logging, petrography and microdiamond analysis have shown that the pipe infill comprises several phases of sub-horizontally oriented kimberlite (KIMB1, KIMB2, KIMB3, KIMB4, KIMB7 and KIMB8) resulting from multiple emplacement events. The pipe infill is dominated by Kimberley-type pyroclastic kimberlite or “KPK”, historically referred to as tuffisitic kimberlite breccia or “TKB”, with less common hypabyssal kimberlite (HK) and minor units with textures transitional between these end-members. An extensive HK sheet complex surrounds the pipe. The emplacement of Kelvin is believed to have been initiated by intrusion of this early sheet system. The main pipe-forming event and formation of the dominant KPK pipe infill, KIMB3, was followed by late stage emplacement of additional minor KPK and a hypabyssal to transitional-textured phase along the upper contact of the pipe, cross-cutting the underlying KIMB3. Rb-Sr age dating of phlogopite from a late stage phase has established model ages of 531 ± 8 Ma and 546 ± 8 Ma. Texturally and mineralogically, the Kelvin kimberlite is similar to other KPK systems such as the Gahcho Kue kimberlites and many southern African kimberlites; however, the external morphology, specifically the sub-horizontal inclination of the pipe, is unique. The morphology of Kelvin and the other kimberlites in the Kelvin-Faraday cluster defines a new type of exploration target, one that is likely not unique to the Kennady North Project area. Extensive evaluation work by Kennady Diamonds Inc. has resulted in definition of a maiden Indicated Mineral Resource for Kelvin of 8.5 million tonnes (Mt) of kimberlite at an average grade of 1.6 carats per tonne (cpt) with an average diamond value of US$ 63 per carat (ct).

Investigation of cutting forces, surface integrity, and tool wear when high-speed milling of high-volume fraction SiCp/Al6063 composites in PCD tooling

This paper focused on high-speed milling of Al6063 matrix composites reinforced with high-volume fraction of small-sized SiC particulates and provided systematic experimental study about cutting forces, thin-walled part deformation, surface integrity, and tool wear during high-speed end milling of 65% volume fraction SiCp/Al6063 (Al6063/SiCp/65p) composites in polycrystalline diamond (PCD) tooling. The machined surface morphologies reveal that the cutting mechanism of SiC particulates plays an important role in defect formation mechanisms on the machined surface. In high-speed end milling of Al6063/SiCp/65p composites, the cutting forces are influenced most considerably by axial depth of cut, and thus the axial depth of cut plays a dominant role in the thin-walled parts deformation. Increased milling speed within a certain range contributes to reducing surface roughness. The surface and sub-surface machined using high-speed milling suffered from less damage compared to low-speed milling. The milling speed influence on surface residual stress is associated with milling-induced heat and deformation. Micro-chipping, abrasive wear, graphitization, grain breaking off, and built-up edge are the dominated wear mechanism of PCD tools. Finally, a series of comparative experiments were performed to study the influence of tool nose radius, average diamond grain size, and machining parameters on PCD tool life.

Synthesis of and characterization of freestanding, high-hierarchically structured graphene-nanodiamond films

A novel carbon structure is synthesised during the interaction of solid organic precursors as d-glucose with a molten metallic zinc catalyst under a layer of molten alkali chlorides at air atmosphere. Scanning electronic microscopy studies show that the formed pure carbon film is non-isomorphic and smooth on one side, but highly evolved, with square steps, on the other. The Raman spectrum of the smooth side resembles that of multilayer graphene. The Raman spectrum of the developed side shows a typical sharp and narrow diamond peak at 1332cm−1 along with graphene peaks. XPS data show that the most of the carbon atoms are at diamond sites. According to the results of an Auger spectroscopy investigation, obtained carbon film is composed of carbon atoms of sp2 and sp3 hybridisation in a ratio of 1:1. From the average graphene cluster size of 5nm and average diamond crystal diameter of 2–7nm, it may be concluded that the formation of graphene-nanodiamond films in this system is thermodynamically possible at this temperature range without application of increased pressure. Chemically induced transition to the nanodiamond structure occurs in graphene layers due to presence of large quantities of atomic hydrogen in the molten salt media.

Synthesis and Characterization of Monocrystalline GaPSi3 and (GaP)y(Si)5–2y Phases with Diamond-like Structures via Epitaxy-Driven Reactions of Molecular Hydrides

Hybrid (III–V)–(IV) alloys described using the general formula (GaP)y(Si)5–2y have been synthesized as epitaxial layers on Si(100) using specially designed chemical vapor deposition methods. Reactions of [D2GaN(CH3)2]2 with P(SiH3)3 between 525 and 540 °C gave GaPSi3 (y = 1) with a fixed Si content of 60%, while analogous reactions of [H2GaN(CH3)2]2 at >590 °C produced Si-rich derivatives with tunable Si contents in the range of 75–95% (y < 1). In both cases, diffraction studies and optical characterizations demonstrate single-phase, monocrystalline structures with an average diamond cubic lattice akin to Si. Raman scattering supports the presence of a tetrahedral structure containing isolated Ga–P pairs randomly embedded within the parent Si matrix. This outcome is consistent with theoretical simulations of a crystal growth mechanism involving interlinking GaPSi3 tetrahedra in a manner that precludes the formation of energetically unfavorable Ga–Ga bonds. Ellipsometry measurements of the dielectric funct...

Influence of Surface Finishing on High-Temperature Oxidation of AISI Type 444 Ferritic Stainless Steel Used in SOFC Stacks

This research is focused on the study of the samples, approximatively 15 × 30 mm2 sized, that were mechanically cut from two sheets (0.4 and 0.2 mm thick, respectively) of AISI 444 Type ferritic stainless steel (FSS) (DIN 1.4521, Eu designation X2CrMoTi18-2); this material was in the ‘as-rolled’ state. Part of these specimens were treated superficially on one side using abrasive SiC papers with different average grit sizes (i.e., 46.2, 30.2, 18.3 μm) and diamond suspension (up to 1 μm) in order to obtain various surface roughness. Both the ‘as-rolled’ and superficially treated samples were then aged in a muffle furnace in static air according to a thermal cycle corresponding to the curing phase of an experimental glass used as sealing in the solid oxide fuel cell stacks. After aging, the chemical compositions and morphological peculiarities of the scale formed depending on the thickness of the samples and their surface state were studied by scanning electron microscopy, energy-dispersive spectroscopy, micro-Raman spectroscopy, bright field light optical microscopy. The obtained results show that all scales formed consist of an inner Cr2O3 subscale and an outer (Mn,Cr)3O4 spinel layer; the relationship between FSS grain size and scale microstructural features is consistent on the samples with mirror-like surface only; the scale thicknesses on SiC grinded samples are comparable; the scales covering the ‘as-rolled’ surfaces are morphologically similar to those grown on the surfaces finished with the 30.2 and 18.3 μm SiC papers, and their thicknesses show an intermediate situation between the abraded and the mirror-like specimens. The last described characteristics depend mainly on the surface and microstructural peculiarities resulting from the rolling process.

Surface microstructural changes of spark plasma sintered zirconia after grinding and annealing

Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140nm 372nm and 753nm grain sizes by sintering at 1250°C, 1450°C and 1600°C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60µm, under a pressure of 0.9MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after a ruff grinding of specimens at 1100°C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575°C for one hour, the nano-grain layer was not observed. The resulted grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.

Tool wear behaviour and workpiece surface integrity when turning Ti–6Al–2Sn–4Zr–6Mo with polycrystalline diamond tooling

The paper details the performance of a range of polycrystalline diamond (PCD) tools (∼1.3–39μm average diamond grain size) when turning Ti–6Al–2Sn–4Zr–6Mo with 150bar cutting fluid. The alloy is used for aeroengine components such as turbine discs due to its superior mechanical and elevated temperature properties. Tool life improved from ∼30 to 80min with increasing grain size except with the ultra-coarse (∼39μm) PCD grade, which failed via chipping/edge fracture after ∼8min. In general, the principal wear modes were crater formation and workpiece adhesion. Workpiece integrity assessment showed no major subsurface damage with surface compressive residual stresses of ∼600MPa.

Ge1-ySny (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties

Novel hydride chemistries are employed to deposit light-emitting Ge1-ySny alloys with y ≤ 0.1 by Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD) on Ge-buffered Si wafers. The properties of the resultant materials are systematically compared with similar alloys grown directly on Si wafers. The fundamental difference between the two systems is a fivefold (and higher) decrease in lattice mismatch between film and virtual substrate, allowing direct integration of bulk-like crystals with planar surfaces and relatively low dislocation densities. For y ≤ 0.06, the CVD precursors used were digermane Ge2H6 and deuterated stannane SnD4. For y ≥ 0.06, the Ge precursor was changed to trigermane Ge3H8, whose higher reactivity enabled the fabrication of supersaturated samples with the target film parameters. In all cases, the Ge wafers were produced using tetragermane Ge4H10 as the Ge source. The photoluminescence intensity from Ge1−ySny/Ge films is expected to increase relative to Ge1−ySny/Si due to the less defected interface with the virtual substrate. However, while Ge1−ySny/Si films are largely relaxed, a significant amount of compressive strain may be present in the Ge1−ySny/Ge case. This compressive strain can reduce the emission intensity by increasing the separation between the direct and indirect edges. In this context, it is shown here that the proposed CVD approach to Ge1−ySny/Ge makes it possible to approach film thicknesses of about 1 μm, for which the strain is mostly relaxed and the photoluminescence intensity increases by one order of magnitude relative to Ge1−ySny/Si films. The observed strain relaxation is shown to be consistent with predictions from strain-relaxation models first developed for the Si1−xGex/Si system. The defect structure and atomic distributions in the films are studied in detail using advanced electron-microscopy techniques, including aberration corrected STEM imaging and EELS mapping of the average diamond–cubic lattice.

In situ doping of diamond coatings with silicon, aluminum and titanium through a modified laser-based CVD process

Abstract The aim of this study was to demonstrate the feasibility of in situ doping of chemical vapor deposition (CVD) fabricated diamond coatings through simultaneous evaporation of solids in a CVD plasma-based process. In order to achieve maximum flexibility and energy density, a laser-based plasma-jet CVD process was chosen, and expanded with the introduction of dopant rods. The rods, with diameters varying from 0.5 mm to 3.0 mm, were fed at rates from 0.25 mm/min to > 100 mm/min, and positioned 3 mm below the optical breakthrough which generates the plasma. Gas flows of 20.0 slm (standard liters per min) argon, 2.0 slm hydrogen and 0.02 slm methane were used for diamond coating deposition. At a surface temperature of about 1100 °C, an average linear diamond growth rate of 20 μm/h was achieved. The materials selected as solid precursors for the rods were SiO2, Al2O3, and Ti due to their differing electrical characteristics, as they are an insulator, semiconductor, and conductor, respectively. The evaporation rate of these rods varied by more than six orders of magnitude, from 7 × 10− 2 g/min (SiO2). The doped diamond coatings were produced by simultaneous evaporation and CVD. To prove that the precursors were vaporized and the atomic bonds were broken by the plasma, the optical emission spectra are compared with published and calculated spectral lines. Analyses of the layers were performed using EDX (energy-dispersive X-ray) spectroscopy and WDS (wavelength dispersive X-ray spectroscopy). As a result, the maximum doping densities in the diamond coating were determined, and were 3.460 wt.% for silicon, 0.957 wt.% for aluminum, and 0.03 wt.% for titanium. To prove the diamond-like characteristics of these coatings, Raman measurements were performed.

Nanoscale assembly of silicon-like [Al(As1−xNx)]ySi5−2yalloys: Fundamental theoretical and experimental studies of structural and optical properties

Ab initio theoretical simulations of Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)Si${}_{3}$ alloys, a new class of optoelectronic materials, confirm that these compounds are likely to be disordered via a mechanism that preserves the integrity of the constituent III-V-Si${}_{3}$ tetrahedra but randomizes their orientation in the average diamond lattice of the compound. This type of disorder is consistent with experimental structural data and with the proposed growth mechanism for such alloys, according to which ``III:V(SiH${}_{3}$)${}_{3}$'' intermediate complexes are formed in the gas phase from reactions between group-III atomic beams and V(SiH${}_{3}$)${}_{3}$ molecules, delivering the entire III-V-Si${}_{3}$ tetrahedra to the growing film. Experimental optical studies of these Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)Si${}_{3}$ alloys as well as more general [Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)]${}_{y}$Si${}_{5\ensuremath{-}2y}$ compounds grown on Si substrates were carried out using spectroscopic ellipsometry. The resulting dielectric functions are found to be similar to broadened versions of their counterparts in pure Si. This broadening may have important practical applications, particularly in photovoltaics, because it dramatically enhances the optical absorption of Si in the visible range of the electromagnetic spectrum. A critical point analysis reveals the existence of direct optical transitions at energies as low as 2.5 eV, well below the lowest direct absorption edge of Si at 3.3 eV. Such transitions are predicted theoretically for perfectly ordered III-V-Si${}_{3}$ compounds, and the experimental results suggest that they are robust against tetrahedra orientational disorder.

Grazing-incidence small-angle X-ray scattering study on ultrananocrystalline diamond films

In this work, an ultrananocrystalline diamond film was studied with grazing-incidence small-angle X-ray scattering (GISAXS) to determine the diamond grain size and average distance of the grains with a non-destructive method and with excellent sampling statistics. The measured 2D GISAXS patterns were modelled with the assumption of monodisperse spheres. The best fits were obtained with the "buried layer" model where the spheres are correlated within the film plane. This correlation was approximated with a two-dimensional Percus–Yevick structure factor. The average diamond grain size of D=8.0–8.5nm and a centre-to-centre distance of the grains with 10.4–11.9nm agrees well with transmission electron microscopy results of comparable samples.

Effect of diamond growth rate on carbon isotope fractionation in Fe–Ni–C system

The carbon isotope fractionation factor between diamond and carbon dissolved in the Fe–Ni metal melt varies from 4.1‰ down to 2.4‰ in HTHP crystallization experiments with the average diamond growth rates ranging from 1 to 12.5 mg/h. The observed fractionation of heavy carbon isotope is in agreement with the Burton–Prim–Slichter model for the compatible impurity distribution associated with crystallization. The variations in the carbon isotope composition within a single diamond crystal can result from appropriate variations of the crystal growth rate. The scale of the observed fractionation effect is comparable with the internal isotope inhomogeneity of natural stones.

Effect of Input Power on the Deposition of Optical Grade Thick Diamond Film in a DCPJ CVD Jet System

High quality optical grade thick diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. Three different powers, 13.65, 15.40 and 17.94kW, were employed during the investigation. The aim was to investigate the effect of these powers on the deposition of thick diamond film. The controlled system was discussed together. The results show that the average diamond grain size and growth rate increase with input plasma power, but a further increase in input power, diamond thick-film defects and amorphous carbon content increased.

Study on Performance of Hot Pressed High Phosphorus-Boron Iron-Based Bit Matrix and Diamond Bit

Formula uniform design method was adopted to study the performance of iron-based matrix with high content of phosphorus and boron. Two forms of regression models on matrix hardness and wear resistance and the optimum matrix formulae were obtained respectively by regression analysis and constrained nonlinear programming using MATLAB. Regression analyses indicate that matrix hardness was mainly affected by the factor of Ni, Co and Fe; matrix hardness and brittleness increased with the increment of P-Fe alloy, but decreased with the increase of 663-Cu. These results can be used as a rough guide for design of highly adaptive diamond bits for different rock formations. After the indoor experiments, diamond bit based on 3# matrix formula was made to perform field drilling tests. The results were that the penetration rate was 1.91m/h and the average diamond bit life was 67.37m.