Large Diamond Research Articles

Effect of pressure on large size diamond single crystal synthesized by temperature gradient method under low nitrogen condition

Pressure is a vital condition in the synthesis of diamond crystals via the temperature gradient method. Exploring the effect of pressure on the growth of diamond crystals is vital. In this study, we investigated the synthesis of diamond crystals using iron–nickel alloy catalysts and analyzed the properties of the synthesized diamonds in the pressure gradient using a China-type large-volume cubic high-pressure apparatus. The synthesis temperature of 1600 K and pressure range of 5.5–6.5 GPa were used. The results of Raman spectra showed that increasing the pressure would increase the crystallinity of diamond crystals. The FTIR spectra of diamond samples featured peaks at 1332 (N+ ions), 1130, and 1344 cm−1, indicating that with increasing pressure, the concentration of nitrogen atoms and ions in diamonds significantly decreased. The photoluminescence spectra of nitrogen ions in diamond samples displayed a peak at 40–100 ppm. The 692 and 694 nm peaks and the phonon bands of NV-chromophores gradually weakened with increasing pressure, indicating that the 692 and 694 nm peaks are attributable to the NV-color center and phonon displacement energy of 165 meV occurred. The Electron paramagnetic resonance spectra displayed a phonon bands of the NV-color center phonon are expressed in EPR through the g-value of NV- .These test results indicated that the pressure featured a significant effect on the nitrogen concentration and the nitrogen-related defects in diamonds.

Friction and wear behaviors of polycrystalline diamond self-mated pairs in air and water lubrication conditions

Polycrystalline diamond (PCD) is one of the hardest man-made materials with excellent wear resistance, also a preferred friction pair material for sliding bearings on geological drilling and deep-sea energy development equipment which has demanding requirements for extreme load carrying and abrasive wear resistance. However, the friction and wear characteristics of PCD self-mated conformal contact sliding bearings are still not fully understood. PCD self-mated pairs may exhibit some special tribological characteristics, such as abnormal friction vibrations, even if the roughness of the friction surfaces is at the nanometer level, resulting in PCD damage and reliability problem of bearings. In order to reveal the cause of friction vibration and the wear mechanism of PCD self-mated pairs, the friction and wear behaviors of PCD self-mated pairs in air and water lubrication conditions were hereby studied using a ring-on-ring test apparatus. The friction torque at different rotational speeds and loads was measured, the wear surface features of the PCDs were examined, and the composition of the solid film formed during the test at the friction interface was identified. The results show that PCD self-matching pair tends to generate severe friction vibration due to the adhesion of diamond grains rather than the increase of friction interface roughness under the dry friction condition. Water matters considerably in reducing the adhesion. The wear forms of PCDs are adhesive and abrasive wear in dry friction, and abrasive wear in water. PCD with large diamond grains is provided with a better wear resistance.

Effects of B-NiS co-doping on diamonds growing along {1 1 1}-orientation under high pressure and high temperature

Large single diamonds were successfully synthesized from NiS or B-NiS co-doping FeNi-C system under high pressure and high temperature (HPHT) in this paper. In this study, the effects of different additive amounts of NiS doping alone or B-NiS co-doping on the crystal shape, color and quality of diamond were investigated. The color of NiS doped diamonds change from bright yellow to bright green and then to grayish yellow. The color of B-NiS co-doped diamonds change from yellowish green to grayish green and black. Besides, the shape of doped crystals gradually changes from plate to tower. Fourier transform infrared (FTIR) spectra shows that with the increase of additive NiS content, the entry of nitrogen is suppressed to some extent by the entry of S into the diamond lattice, while with B-NiS co-doping, the content of nitrogen impurities increase with the increase of B content. It can be found from the x-ray photoelectron spectroscopy (XPS) results that the obtained diamonds contain B/S/N elements, with S present in the diamond lattice in the form of C–S–O. Raman measurements show that with increasing B content, the peak positions of co-doped diamonds are shifted and the full width at half maximum (FWHM) become slightly larger, but still have a high quality sp3 structure. This study not only contributes to the investigation of the formation mechanism of natural diamond, but also has important implications for the enrichment of diamond species and the expansion of synthetic diamond applications.

Development and printability of diamond-containing composite filament for material extrusion

PurposeMaterial extrusion technology is considered to be an effective way to realize the accurate and integrated manufacturing of high-performance metal diamond tools with complex structures. The present work aims to report the G4 binder that can be used to create metal composite filament loading high concentrations of large diamond particles through comparative experiments.Design/methodology/approachThe quality of filaments was evaluated by surface topography observation and porosity measurement. And the printability of filaments was further studied by the tensile test, rheological test, shear analysis and printing test.FindingsThe results show that the G4 binder exhibits the best capacity for loading diamonds among G1–G4. The L4 filament created with G4 has no defects such as pores, cracks and patterns on the surface and section, and has the lowest porosity, which is about 1/3 of the L1. Therefore, the diamond-containing composite filament based on G4 binder exhibits the best quality. On the other hand, the results of the tensile test of L5–L8 filaments reveal that as the diamond content increases from 10% to 30%, the tensile strength of the filament decreases by 29.52%, and the retention force coefficient decreases by 15.74%. This can be attributed to the formation of inefficient bonding areas of the clustered diamond particles inside the composite filament, which also leads to a weakening of the shear strength. Despite this, the results of the printing test show that the diamond-containing composite filament based on the G4 binder has reliable printability.Originality/valueTherefore, the G4 binder is considered to solve the most critical first challenge in the development of diamond-containing filament.

High Performance of Normally‐On and Normally‐Off Devices with Highly Boron‐Doped Source and Drain on H‐Terminated Polycrystalline Diamond

AbstractDiamond exhibits large application potential in the field of power electronics, owing to its excellent and desirable electronic properties. However, the main obstacles to its development originate from the small‐sized single‐crystal wafers and the instability of the electrical conductivity. This work presents a metal‐oxide‐semiconductor field‐effect transistor (MOSFET) on a diamond substrate derived from a five‐inch (110) highly preferred polycrystalline diamond film. The MOSFETs with excellent performance are fabricated by combining an H‐terminated channel and an epitaxially grown boron‐doped layer as the source/drain contacts of the diamond devices. According to the electrical statistical results of ≈110 devices on the polycrystalline diamond substrate, 44% of devices show normally‐off operation with a maximum current density of 400 mA mm−1, while 56% of devices demonstrate normally‐on operation with a maximum current density of 525 mA mm−1. The normally‐off characteristics are more related to the higher amounts of nitrogen concentration than the grain boundaries. The stable boron‐doped source and drain provide a high concentration of holes, which facilitate transport in the surface p‐type channel induced by the H‐termination. The characteristics of the MOSFETs are inspiring for the fabrication of complementary inverter circuits on large diamond wafers.

The Prospecting Value of the Fractional Granulometric Analysis in the Study of Diamond-Bearing Placers

The article presents the novel data of fractional granulometric testing on the Syuzevskaya diamond placer located in the northern part of the Chikman-Nyar depression. The geological section was studied to a depth of 42,0 m. 18 samples weighing up to 200 kg each were taken, selected sectionally at two-meter intervals and graded into 10 granulometric classes on the gamma-Baturin scale. The obtained results have important search value: 1) the curve of the debris distribution by size is typical for the mature alluvium of the foothill river; 2) the paleo river alluvium is formed by a high dynamics flow and is fairly well sorted by size, which is a favorable sign for the concentration of large diamonds and indicates a slight dilution with non-diamond-bearing detrital material; 3) the presence of a typical mature alluvium in the paleovally indicates a long time of its existence, which is also a favorable search sign for industrial diamond placers. The methodology and results of the study can be used at various stages of the exploration cycle for placer minerals, including diamonds, all over the world.

Effect of catalyst composition on growth and crack defects of large diamond single crystal under high temperature and pressure

Under the condition of 5.6 GPa and 1250–1450 ℃, the diamond single crystals are synthesized in a cubic anvil high-pressure and high-temperature apparatus. High-purity FeNiCo solvents or NiMnCo solvents are chosen as the catalysts. High-purity (99.99%) graphite powders selected as a carbon source. High-quality abrasive grade diamond single crystals with relatively developed (100) or (111) crystal planes are used as crystal seeds. The effects of catalyst composition on crack defects in diamond single crystals are studied carefully. Firstly, using FeNiCo and NiMnCo catalysts respectively, we carry out the diamond single crystal growth experiments. It is found that under the same crystal growth condition, the probability of crystal crack defects in diamond single crystals grown with FeNiCo catalyst is significantly higher than that of crystals grown with NiMnCo catalyst. We believe that this is related to the high viscosity, poor fluidity of FeNiCo catalyst melt, and the large specific surface area of the crystal during growth, which leads to its high requirements for the stability of growth conditions. Secondly, the relationship between the growth time and the limit weight gain speed of the diamond single crystal synthesized, respectively, by FeNiCo catalyst and NiMnCo catalyst are investigated. The results are shown below. 1) The limiting growth rate of diamond single crystal increases with the growth time going by. 2) In the same growth time, the limit growth rate of diamond crystal grown with NiMnCo catalyst is higher than that of diamond crystal grown with NiMnCo catalyst. Thirdly, by scanning electron microscopy (SEM), we calibrate the surface morphology of the synthesized diamond single crystal. The test results show that the diamond single crystal has a high surface flatness. Even for the crystals with crack defects in the interior, the surface flatness is still good. However, Fourier transform infrared (FTIR) measurements show that the nitrogen impurity content of diamond crystal grown by FeNiCo catalyst with crack defect is about 3.66×10<sup>–4</sup>. The content of nitrogen impurity in the crystal grown by NiMnCo catalyst without crack defect is about 4.88×10<sup>–4</sup>. The results show that there is no direct correlation between nitrogen impurity content and crack defects in diamond crystal.

Dependence of static strength of large crystals of synthetic diamond type ib of octaedric habitus, after chemical-thermal time and time

Increasing demands on the quality of drilling tools are forcing us to revise the traditional methods of their production and develop new alternative technologies. Some issues related to the possibility of increasing the efficiency of a drilling tool using diamond single crystals are considered. It has been suggested that a further reserve for improving the quality of drill bits lies in the use of large, high-strength, non-magnetic diamonds. Scientific research in this area has shown that the efficiency of the drilling process largely depends on the mechanical properties of single crystals, such as tensile strength and hardness. The grains operate under a load close to critical, which can lead to the complete destruction of single crystals instead of gradual chipping with the formation of new cutting edges. The results of an experimental study of the influence of individual stages of the drilling tool manufacturing process, namely, chemical-thermal treatment and annealing at 1150°C, on the static strength of large type Ib synthetic diamond crystals with an octahedral habit are presented. The dependence of this quantity on the geometric dimensions of single crystals was obtained for the first time. The achieved maximum value of static strength was 8750 N. It was experimentally confirmed that with an increase in the breaking load, the size of the fragments decreases. In order to ensure sufficient strength of the cutting part of the drilling tool, it is advisable to limit the size of single crystals to 1000–1200 µm, since the critical load values ​​for them are higher than for crystals whose size is 1300 µm or more, which, according to the theory, is associated with an increase in the number of defects and inclusions in proportion to size. The performed analysis made it possible to make adjustments to aspects of the manifestation of the scale effect when testing the strength properties of diamond single crystals.

Distribution and geographic differences in stable isotope ratios of diamond squid Thysanoteuthis rhombus (Cephalopoda: Thysanoteuthidae) in Japanese waters

AbstractDiamond squid Thysanoteuthis rhombus (Troschel, 1857), which can grow to a dorsal mantle length of ~100 cm in 1 year, is an important fisheries resource in subtropical and temperate waters worldwide. Around Japan, it is an important resource in the East China Sea, Sea of Japan, and western North Pacific Subtropical Gyre, including the Kuroshio area. It is not known if linkages occur between these habitats. To clarify the species distribution, we estimated the habitat of young squid using a generalized additive model based on trawl surveys and analyzed carbon and nitrogen stable isotope ratios (δ13C and δ15N) in tissue samples. Based on trawl observations, young squid were distributed around northeastern Taiwan and the Okinawa Islands in June–July and in the Sea of Japan and the Kuroshio extension areas in August–September. We observed ontogenetic changes in the stable isotope ratios. The δ15N values in large diamond squid (dorsal mantle length > 400 mm) were significantly lower in the Pacific than those in other areas. Considering that the δ15N of forage fish is low in the Pacific and high in the East China Sea and Sea of Japan, large diamond squid in the northwest Pacific presumably have two distinct habitats.

Interaction mechanism of Ge, Ti, and N in diamond prepared by high pressure and high temperature conditions

In this paper, Ge-doped large single crystal diamond was synthesized under high pressure and high temperature (HPHT) conditions in NiMnCo-C and NiMnCo-Ti-C systems. The effects of Ge additives on the diamond morphology, nitrogen impurity content, and internal inclusions were investigated, and the interaction mechanism among germanium (Ge), nitrogen (N), and titanium (Ti) during the diamond growth process was discussed. The results show that the number of inclusions in diamond increase with increases in Ge addition in both systems. The N content of diamond grown in NiMnCo-C systems decreases with increases in Ge addition. However, Ge can more easily be doped into the diamond in a NiMnCo-Ti-C growth system. The experimental results show that the N can inhibit the amount of Ge entering the diamond lattice under HPHT conditions. When Ti was introduced into the system, it effectively removed N by combining with it, such that more Ge atoms could enter the diamond lattice.

Averting your gaze with sustainable, green marketing claims: a critique of luxury commodity production sustainability claims, with evidence from the diamond industry

The adverse impacts of capitalism on the global ecosystem are well-identified, and have created consumer interest in ecologically friendly commodities. One corporate response to this situation has been the development of green marketing strategies designed to convince consumers that products are ecologically sustainable and/or less ecologically harmful. One strategies suggests that luxury commodities are ecologically sustainable due to their durability and/or longevity. That argument ignores empirical assessments of the ecological impacts of luxury commodity production. To illustrate this point, we examine the use of green labeling claims within the context of capitalism. As an empirical example, we focus on sustainability claims constructed around luxury diamonds, and estimate the ecological harms of mining a large diamond in carbon equivalent terms. We also examine related production claims linked to sustainable supply chain certification. In our discussion, we draw from arguments in green criminology to suggest that diamond mining could be viewed as a crime of ecocide, and should be discouraged through influence campaigns and perhaps legal restrictions on diamond mining.

Realizing ultrahigh thermal conductivity in bimodal-diamond/Al composites via interface engineering

Bulk materials with high thermal conductivity are fundamentally important to heat dissipation of high-power devices. In this study, a record high thermal conductivity of 1021 ± 34 W m−1 K−1 is achieved in the diamond/Al composites reinforced with bimodal diamond particles. Meanwhile, a coefficient of thermal expansion (CTE) of 3.40 ± 0.10 × 10−6 K−1 is achieved that is compatible with the semiconductors applied in the high-power devices (∼13.7% and ∼3.7% lower than CTE of a-GaN and c-GaN, respectively). The excellent thermal transport property stems from the increased heat transport channels and well-bonded diamond/Al interfaces. Importantly, the thermal conductivity can also be retained as high as 557 ± 17 W m−1 K−1 at 673 K in the diamond/Al composites, which could greatly widen their applications at high temperatures. This study indicates that concurrently achieving high interfacial thermal conductance, high diamond content, large diamond particle size, and high relative density is the essential way to realize ultrahigh thermal conductivity and diamond/Al composites are promising thermal management materials.

Fabrication of high aspect ratio ceramic micro-channel in diamond wire sawing as catalyst support used in micro-reactor for hydrogen production

Ceramic is an ideal material for preparing micro-channel catalyst supports with their characteristics of high temperature resistance, corrosion resistance and mechanical strength. High aspect ratio micro-channel structure has the advantages of large specific surface area, strong mass and heat transfer performance and high material utilization. However, ceramic materials are hard and brittle, and it is difficult to fabricate micro-channel structures with aspect ratio more than 1.5:1 by traditional processing methods. In this paper, a cutting method of large diameter diamond wire sawing was proposed. The micro-channels with width of 520 μm and aspect ratio of more than 4:1 was successfully fabricated by this method. Furthermore, the integrity of the micro-channel structure processed by diamond wire sawing was analyzed. And than the effect of surface morphology in different processing parameters on the catalyst loading performance were studied. The catalyst loading strength of ceramic slices with different surface morphology was tested. Finally, the ceramic micro-channel array was used as the catalyst support in micro-reactor for hydrogen production via methanol steam reforming (MSR). The methanol conversion rate and H2 production rate could reach 87.8% and 74.6 mmol/h, respectively under GHSV 12600 ml/g·h at 300 °C. The experimental results show that the large-diameter diamond wire sawing technology can be used to process ceramic microchannels with high aspect ratio; using ceramic microchannel arrays as catalyst supports in hydrogen production can obtain better reaction performance; the feasibility of ceramic materials were broadened as microchannel catalyst supports.

A detailed study of industrially compatible, cost-effective and convenient texturization in large area diamond cut n-type C-Si

A detailed study of industrially compatible, cost-effective and convenient texturization in large area diamond cut n-type C-Si

A Newborn in Western Nepal with Harlequin Ichthyosis: A Case Report

Harlequin ichthyosis (HI) is a rare autosomal recessive congenital ichthyosis with an incidence of 1 in 300,000 live births. It is lethal in 44% of cases and the baby is usually prematurely born. These babies have thick, highly keratinized armor-like skin, which forms large diamond, trapezoid or rectangular plates separated by deep fissures. These affect the shapes of eyelids, nose, mouth and ears, and also limit movement of the arms, legs and chest. This condition is linked with a nonsense or frameshift mutation in the ABCA12 gene, which is responsible for lipid transport in the keratinocytes. This gene synthesizes a protein that transports a lipid, epidermoside, a glucosylceramide, out of stratum corneum cells in the epidermis. To our knowledge, this is the first case report on Harlequin ichthyosis from Nepal, which makes this case unique. The take away lesson from this case is that couples with consanguineous marriages should undergo screening of ABCA12 gene if they plan to conceive.

Triassic Diamondiferous Tuffaceous–Sedimentary Rocks in the Arctic Zone of Siberia

Abstract In the Arctic zone of Siberia, large diamond occurrences have been discovered in volcaniclastic, sedimentary–volcaniclastic, volcanosedimentary, and sedimentary rocks of the upper Ladinian strata and the base of the Carnian (Triassic) strata. They are confined to the Primorye mineragenic zone, which is traced along the Laptev Sea water area from the western Verkhoyansk area to eastern Taimyr. We have first identified a specific range of diamonds in these deposits. Among the rounded crystals of varieties I, II, V, and VII, there are grains with a light carbon isotope composition and high nitrogen contents. They have no analogues in typomorphic features in the known primary deposits of Yakutia but are completely similar to diamonds in the Rhaetian, Early Jurassic, Late Jurassic, Early Cretaceous, Neogene, and Quaternary commercial placers and placer occurrences, which suggests their formation as a result of the erosion of Triassic sources.

A Large Gain and High Resolution Diamond Radiation Detector With Au/Hydrogen Termination Ohmic Contact

Diamond radiation detector (DRD) with high performance in dose detection and energy resolution is demonstrated in this letter. Benefiting from a good ohmic contact between hydrogen terminated diamond surface and Au, and very low defects in single crystal diamond, this DRD achieves a large current gain factor of 151.83 (349.93 at 1 V/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>), a high specific sensitivity of <inline-formula> <tex-math notation="LaTeX">$41.441~\mu \text{C}$ </tex-math></inline-formula>/Gy<inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>mm³ and a linearity coefficient of 1.027 &#x00B1; 0.009 (1.011 &#x00B1; 0.001 at 0.16 V/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>) in X-ray dose detection when biased at 0.66V/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>. Furthermore, the optimal energy resolution of 0.76&#x0025; to ²⁴³Am-²⁴⁴Cm dual <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-source is shown in hole collection mode at the same bias. Meanwhile, owing to none of priming effect and persistent photoconductivity in the device, the on-state current fluctuations of dynamic switching measurements under steady X-ray irradiation are 0.929&#x0025; at 0.66V/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and 0.759&#x0025; at 0.16 V/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>, respectively. These results show that this DRD has a great potential for accurate and sensitive detection in medical application.

The novel and facile electrolysis method for removing the cobalt binder phase from large diameter polycrystalline diamond compacts

The thermal stability, wear resistance and impact toughness of polycrystalline diamond compact (PDC) are the primary determining variables in determining the performance. The cobalt binder contributes significantly to the PDC's thermal stability and wear resistance. To increase the thermal stability of the PDC, this paper used electrolysis to remove the cobalt binder from the polycrystalline diamond (PCD) layer of the PDC with a diameter of 62 mm. The optimal process parameters for cobalt removal via electrolysis were determined by examining the electrolyte concentration, the electrolytic voltage, and the electrolytic time. The cobalt removal impact was evaluated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), an X-ray diffraction (XRD), and thermogravimetric analysis-differential thermal analysis (TG-DTA). In addition, the abrasion ratio of the PDC samples were tested. The experimental results indicated that the optimal electrolysis parameters for cobalt removal were obtained when the concentration of cobalt sulphate was 4 g/100 mL, the electrolysis voltage was 2.5 V, and the electrolysis time was 10 h; in this case, the cobalt removal rate from the PCD layer exceeded 80%, and the cobalt removal depth was 372 μm. TG-DTA analysis revealed that the thermal stability of PDC was significantly enhanced as a result of the initial graphitization temperature of the cobalt removal sample being increased from 1071 °C to 1113 °C, but the abrasion ratio rose by more than 20%. It was discovered that electrolysis may efficiently remove the cobalt binder phase from the PCD layer, therefore improving the thermal stability and wear resistance of PDC.

Possible Nucleation and Synthesis of Large Diamonds in a Carbonate–Silicate Matrix without the Use of High Pressure

Possible Nucleation and Synthesis of Large Diamonds in a Carbonate–Silicate Matrix without the Use of High Pressure

Conformal description of near-horizon vacuum states

Motivated by recent work suggesting observably large spacetime fluctuations in the causal development of an empty region of flat space, we conjecture that these metric fluctuations can be quantitatively described in terms of a conformal field theory of near-horizon vacuum states. One consequence of this conjecture is that fluctuations in the modular Hamiltonian $\Delta K$ of a causal diamond are equal to the entanglement entropy: $\langle \Delta K^2 \rangle = \langle K \rangle = \frac{A(\Sigma_{d-2})}{4 G_d}$, where $A(\Sigma_{d-2})$ is the area of the entangling surface in $d$ dimensions. Our conjecture applies to flat space, the cosmological horizon of dS, and AdS Ryu-Takayanagi diamonds, but not to large finite area diamonds in the bulk of AdS. We focus on three pieces of quantitative evidence, from a Randall-Sundrum II braneworld, from the conformal description of black hole horizons, and from the fluid-gravity correspondence. Our hypothesis also suggests that a broader range of formal results can be brought to bear on observables in flat and dS spaces.