Large Diamond Research Articles

Морфология и структурное состояние частиц нанопорошков, полученных измельчением природного алмаза и методом детонационного синтеза

A complex of high-resolution methods has revealed that the nanopowder particles obtained by milling natural diamonds have a wider variety of sizes and predominantly of lamellar shape in contrast to detonation synthesis nanopowder, which consists mainly of similar-sized and isometric particles. The primary particles of the nanopowder obtained by milling, as well as detonation synthesis nanodiamonds, consist of diamond nuclei with cubic crystal lattices surrounded by shells with complex structures, which are formed from carbon atoms in the sp2-state and impurities. A noticeable increase in interatomic distances in nanodispersed diamond crystals has been established compared with those for large diamond crystals.

Особенности распределения крупных алмазов в россыпях ЮАР

Особенности распределения крупных алмазов в россыпях ЮАР

Transformation of the radionuclides composition of river sediments in the area of the exploited Lomonosov diamond deposit (NW Russia)

The article is devoted to the study of the activity of the natural radionuclides 40K, 232Th, 226Ra and technogenic 137Cs radionuclide in the river sediments of watercourses around the Lomonosov diamond deposit (northwestern Russia). This is the only large diamond mining and beneficiation complex in Europe. Samples of river sediments and surface waters were taken from the Zolotitsa River and its tributaries in the area of the diamond deposit. Samples of rocks were taken from quarries. Samples of kimberlites used for enrichment and rocks entering the dumps were selected. Measurements of the activity of radionuclides in bottom sediments and rocks were conducted using the low-background semiconductor gamma spectrometry method. For measurements, a detector from high-purity germanium was used. The study of uranium isotopes in bottom sediments and waters was conducted using the alpha spectrometry method. The average activity of 137Cs, 226Ra, 232Th and 40K were 5.4, 9.0, 11.2, 318.8 Bq·kg−1 respectively. The impact of the development of the field on the change in the radioecological state of the bottom sediments was evaluated. Several patterns of radionuclide accumulation have been found depending on the physicochemical parameters of river sediments. These patterns are due to the technogenic influence of the mining and beneficiation complex. The performed studies present the first evaluation of the impact of diamond mining on natural radionuclides' distribution and accumulation in the river sediments within the adjacent territories.

Synthesis and characterization of gem diamond single crystals in Fe-C system under high temperature and high pressure

• High-quality gem diamond were successfully synthesized in the pure Fe-C system. • There are no NV 0 , NV − center in diamond synthesized in pure Fe-C system. • Our findings are greatly helpful for the synthetic high-purity diamond crystal. In this paper, the diamond large single crystals were successfully synthesized in the pure Fe-C system by temperature gradient growth (TGG) method in China-type cubic anvil high-pressure apparatus (CHPA) at 5.8 GPa and 1550 °C. The synthesized diamonds were characterized by Optical microscopy, Infrared spectroscopy, Raman spectroscopy and Photoluminescence (PL) spectroscopy. The results show that the nitrogen concentration of type Ib diamonds synthesized in pure Fe-C system is about 80 ppm, which is much lower than diamonds synthesized by Ni-based and Fe-based alloys. PL spectra result indicated that there were no peaks related to the NV centers in diamonds synthesized by Fe-C system. In addition, high-quality type IIa gem diamond can be synthesized by adding a small amount of nitrogen getter in the pure Fe-C system. We believe that this work is of great significance for the synthesis of high-purity large single type IIa diamonds without impurities such as nitrogen and metals.

Growth characteristics of type IIa large single crystal diamond with Ti/Cu as nitrogen getter in FeNi–C system**Project supported by the Natural Science Foundation of Henan Province of China (Grant No. 182300410279), the Key Science and Technology Research Project of Henan Province of China (Grant No. 182102210311), the Key Scientific Research Project in Colleges and Universities of Henan Province of China

High-quality type IIa large diamond crystals are synthesized with Ti/Cu as nitrogen getter doped in an FeNi–C system at temperature ranging from 1230 °C to 1380 °C and at pressure 5.3–5.9 GPa by temperature gradient method. Different ratios of Ti/Cu are added to the FeNi–C system to investigate the best ratio for high-quality type IIa diamond. Then, the different content of nitrogen getter Ti/Cu (Ti : Cu = 4 : 3) is added to this synthesis system to explore the effect on diamond growth. The macro and micro morphologies of synthesized diamonds with Ti/Cu added, whose nitrogen concentration is determined by Fourier transform infrared (FTIR), are analyzed by optical microscopy (OM) and scanning electron microscopy (SEM), respectively. It is found that the inclusions in the obtained crystals are minimal when the Ti/Cu ratio is 4:3. Furthermore, the temperature interval for diamond growth becomes narrower when using Ti as the nitrogen getter. Moreover, the lower edge of the synthesis temperature of type IIa diamond is 25 °C higher than that of type Ib diamond. With the increase of the content of Ti/Cu (Ti : Cu = 4 : 3), the color of the synthesized crystals changes from yellow and light yellow to colorless. When the Ti/Cu content is 1.7 wt%, the nitrogen concentration of the crystal is less than 1 ppm. The SEM results show that the synthesized crystals are mainly composed by (111) and (100) surfaces, including (311) surface, when the nitrogen getter is added into the synthesis system. At the same time, there are triangular pits and dendritic growth stripes on the crystal surface. This work will contribute to the further research and development of high-quality type IIa diamond.

C3H6N6 doping effect of synthetic diamond under high pressure and high temperature

In this paper, large diamond crystals were successfully synthesized under 5.6 GPa at temperature 1513 and 1553 K with melamine (C3H6N6) additive. Fourier transform infrared spectroscopy (FTIR) indicated C3H6N6 is an ideal nitrogen source for large diamond crystal synthesized by temperature gradient method (TGM), but its hydrogen is not absorbed by diamond. With the increase of C3H6N6 content, the colour of diamond changed from yellow to green, and the highest nitrogen content of diamond is 2300 ppm. High synthesis temperature can effectively reduce the formation of defects and play a key role in the formation of C-centers during diamond growth. Surprisingly, diamond is likely to grow into twin crystal when the C3H6N6 content is 0.1 wt%. In the process of diamond growth, carbon atoms of C3H6N6 are likely to serve as carbon source to form plane dislocations, which eventually lead to the formation of twin diamond. Raman spectra show that there are few crystal defects in diamond synthesized with C3H6N6 as dopant.

Fundamental study of ductile-regime diamond turning of single crystal gallium arsenide

Gallium arsenide (GaAs) components, ranging from the planar substrate to those possessing complicated shapes and microstructures, have attracted extensive interest regarding their applications in photovoltaic devices, photodetectors and emerging quantum devices. Single point diamond turning (SPDT) is regarded as an excellent candidate for an industrially viable mechanical machining process, as it can generate nano-smooth surfaces, even on some hard-to-machine brittle materials such as silicon and silicon carbide, with a single pass. However, the extremely low fracture toughness and strong anisotropic machinability of GaAs makes it difficult to obtain nano-smooth, crack-free machined surfaces. To bridge the current knowledge gaps in understanding the anisotropic machinability of GaAs, this paper studied the mechanical material properties of (001)-oriented GaAs through indentation tests, assuming the diagonals of the indenter acted in the similar way of the cutting edge of a diamond tool with a negative rake angle. The results showed that the (001) plane of the GaAs material displayed harder and more brittle when indented along direction I (one diagonal of indenter parallel to the <110> orientation) compared to direction II (one diagonal of indenter parallel to the <100> orientation), which coincides with anisotropic machined surface quality by SPDT. This finding reveals, for the first time, that the crystallographic orientation dependence of both hardness and fracture toughness represents the underlying mechanism for the anisotropic machinability of GaAs. The paper presents a novel approach to evaluate the critical depth of cut under a high cutting speed comparable to SPDT and to determine the maximum feed rate for ductile-regime diamond turning. The 26.57 nm critical depth of cut was obtained for the hardest cutting direction using a large negative rake angle diamond tool. Finally, a nano-smooth surface was successfully generated along all the orientations in ductile-regime diamond turning, in which the material removal mechanism is considered as plastic deformation caused by high-density dislocations. The subsurface layer remains to its single crystal structure and no cracks are found under a transmission electron microscope (TEM). The results proves the proposed evaluation approach for the critical depth of cut and the maximum allowed feed rate is highly effective for guiding the ductile-regime machining of brittle materials.

Design an effective solution for commercial production of 18/20 mesh diamond grits using large volume cubic high pressure apparatus

The recent developments in the mass production of high-grade large diamond grits utilizing the China-type large-volume, cubic-anvil, high-pressure apparatus (LV-CHPA) are discussed. Some new technologies for the synthesis of large diamond grits have been proposed. The temperature distribution in high-pressure synthetic cell is optimized by adjusting the sample assembly and the technical process. The finite element (FE) modeling is used to visualize the temperature fields. Compared with running experimental methods or testing prototypes, FE modeling allows for quicker and often more efficient and accurate optimization of assembly and technical process. With this improvement, the large diamond grits will become inexpensive benefiting the global construction industry in the near future.

Evaluation of diamond mosaic wafer crystallinity by electron backscatter diffraction

A mosaic substrate is a promising candidate to create large size single crystal diamonds for various types of applications. In this study, the crystal orientations of the joint areas of four single crystal plates of a mosaic substrate were measured using the high resolution electron backscatter diffraction method. The lattice rotation of [110] to [–110] (X-Y direction) was less than 0.5° and the lattice rotation mappings of [001] to [110] (Z-X direction) and [1–10] (Z-Y direction) were less than 0.2°. Considering that plate alignment is not particularly considered during the fabrication process, further improvement can be expected to realize a well- aligned mosaic substrate.

Tracking of Blood Movement in the Heart using Elongated Horizontal Large Diamond Search Pattern and Optical Flow Technique for Enabling the Detection of Atrial Septal Defect

In major congenital heart ailments comes Atrial Septal Defect (ASD). Many techniques viz. ECG, MRI, Ultrasound etc., are in use to detect ASD. Performance of heart is analyzed by the Doctors through test results or observations of heart Ultrasound. In this research work it is proved that the disorder ASD is detected using the technique of block matching and optical flow. These algorithms enables the doctors or experts to detect ASD automatically and hence reduces the dependency on humans. This paper proposes a new Elongated Horizontal Large Diamond Search Pattern (EHLDSP) and Optical Flow algorithm for detection of ASD based on MV. Experimentation was carried out on A4C view of 2D Echo Cardiogram, collected form the hospitals as well as from open available database. Ground truth image is used by the cardiologist to compare the results. In this paper, performance of the proposed Elongated Horizontal Large Diamond Search Pattern (EHLDSP) method is compared with other techniques on the basis of cost functions like PSNR and computation complexity. EHLDSP algorithm is used to check the pixel movements and to calculate Motion Vector (MV), followed by the estimation of the displacement of blood cells from either right to left or vice versa. This will help in the reduction of dependency on specialized doctors or human factor can be reduced. For automatic detection of abnormality, research is going on in this area to make it fast and accurate. Proposed algorithm reduces the average computation by providing speed improvements of about 91% over FS/ES and about 6% over existing DS. Also, EHLDSP has shown improvements in the PSNR value in comparison with other methods.

Bargains in the diamond market? How to take advantage from online information

AbstractThis paper empirically analyses the price of diamonds from different perspectives. The sample data contains detailed information on more than 165,000 diamonds certified by Gemological Institute of America, which can be purchased since July 2016 from a large online diamond supplier. Our empirical analysis allows to extend the classic 4Cs model in several directions as follows: (a) the classical 4Cs model is insufficient in order to explain the price, so that other attributes, such as polishing, symmetry, and fluorescence, must be incorporated to accurately estimate the price of a particular piece; (b) the large sample size allows us to analyse specific price ranges characterized by high market activity; (3) a very detailed analysis has been conducted for round diamonds, incorporating interactions between attributes within the regression model and studying the marginal rates of substitution between diamond weight and alternative characteristics given a certain price. Our model is able to detect diamonds that could constitute a clear market opportunity for buyers. This model can help to select efficient demand options taking advantage of the information available on the website, improving the overall efficiency of exchange in this sector.

The new Massadou diamondiferous kimberlite field in Guinea

A new kimberlite field, called Massadou, has been discovered in southeastern Guinea near Macenta city. The field consists of numerous ~1 m thick kimberlite dikes with low diamond contents; altogether 16 dikes have been found so far. Mineralization occurs along a 600 m wide zone distinct in satellite images, which is oriented in the same way as the K4 kimberlite reported by Huggerty. The Massadou kimberlite is covered by a thick laterite weathering profile. Main kimberlite indicator minerals found in the area are pyrope, chromite, and ilmenite. The latter occurs as zoned grains with a high-Fe core (hemoilmenite) surrounded by a parallel-columnar aggregate in the rim. The aggregate has a composition of ordinary kimberlitic Mg ilmenite and results from interaction of hemoilmenite with the kimberlite melt. The kimberlite age is estimated as 140—145 Ma by analogy with the surrounding fields. The dikes independent products of kimberlite magmatism in the Guinea-Liberia shield rather than being roots of pipes as interpreted by Skinner (2004). Therefore, the erosion cutout is moderate, and there are no reasons to expect the presence of large and rich diamond placers.

Operation and performance of the active target of PADME

The PADME experiment at the Laboratori Nazionali di Frascati of the INFN searches for a hypothetical dark photon A′, produced in the annihilation between a positron of a beam with an electron of a target. The target is an active component of the experiment; it consists of a thin and large size diamond detector with a pattern of graphitic strips on both sides acting as ohmic electrodes for detector polarization and signal readout. In this paper the operation and performance of the active diamond target, as observed in the first PADME physics run, are reported.

Origin of Conductive Nanocrystalline Diamond Nanoneedles for Optoelectronic Applications.

Microstructural evolution of nanocrystalline diamond (NCD) nanoneedles owing to the addition of methane and nitrogen in the reactant gases is systematically addressed. It has been determined that varying the concentration of CH4 in the CH4/H2/N2 plasma is significant to tailor the morphology and microstructure of NCD films. While NCD films grown with 1% CH4 in a CH4/H2/N2 (3%) plasma contain large diamond grains, the microstructure changed considerably for NCD films grown using 5% (or 10%) CH4, ensuing in nanosized diamond grains. For 15% CH4-grown NCD films, a well-defined nanoneedle structure evolves. These NCD nanoneedle films contain sp3 phase diamond, sheathed with sp2-bonded graphitic phases, achieving a low resistivity of 90 Ω cm and enhanced field electron emission (FEE) properties, namely, a low turn-on field of 4.3 V/μm with a high FEE current density of 3.3 mA/cm2 (at an applied field of 8.6 V/μm) and a significant field enhancement factor of 3865. Furthermore, a microplasma device utilizing NCD nanoneedle films as cathodes can trigger a gas breakdown at a low threshold field of 3600 V/cm attaining a high plasma illumination current density of 1.14 mA/cm2 at an applied voltage of 500 V, and a high plasma lifetime stability of 881 min is evidenced. The optical emission spectroscopy studies suggest that the C2, CN, and CH species in the growing plasma are the major causes for the observed microstructural evolution in the NCD films. However, the increase in substrate temperature to ∼780 °C due to the incorporation of 15% CH4 in the CH4/H2/N2 plasma is the key driver resulting in the origin of nanoneedles in NCD films. The outstanding optoelectronic characteristics of these nanoneedle films make them suitable as cathodes in high-brightness display panels.

The regulating effect of cooling water temperature on the axial growth rate of large single crystal diamond under HPHT conditions

In this work, we use finite element simulations to investigate the influence of cooling water temperature on the axial growth rate of the large single crystal diamond with the convex shape catalyst under high pressure and high temperature (HPHT) conditions. The simulation results show that adjusting the axial cooling water temperature can change the axial temperature gradient and the convection velocity in the catalyst, which lead to the different axial growth rate of the diamond crystal. The different axial growth rates lead to the change of crystal morphology. Simulation results are confirmed by our synthesis experiments. Morphology and structural properties of the synthesized diamonds are characterized by optical microscope and Raman spectrum. This result not only provides a theoretical explanation for the regulation mechanism of cooling water on the axial growth rate of diamond, more importantly, adjusting the axial cooling water can further improve the morphology of the synthetic diamond, which is of great guiding significance in the commercial production of diamond.

Si Doping Effects on the Growth of Large Single-Crystal Diamond in a Ni-Based Metal Catalyst System under High Pressure and High Temperature

Si powder was added to Ni-based metal catalysts under high pressure and high temperature conditions to investigate its effects on the growth of large single-crystal diamonds. As the Si content increased, the internal inclusions of the diamonds showed a trend in the distribution of point-like → sheet-like → string-like, illustrating that it is ultimately difficult to grow intact crystals. The results show that the first-order Raman peak shifted from 1331.71 to 1329.76 cm–1, and its full width at half-maximum increased from 3.945 to 4.976 cm–1. These results indicate that the Si doping caused an increase in the stresses inside the crystal and that the crystalline quality of the diamond became worse. The Raman and X-ray photoelectron spectroscopy results confirm that the inclusion impurities (graphite, amorphous carbon, and Si3N4) in diamond increase with the Si content. There are significant interactions between silicon and nitrogen in the synthesis process. The addition of Si reduces the nitrogen concentration in diamond. Meanwhile, the presence of nitrogen also reduces the effectiveness of Si doping into diamond.

Overview of recent gyrotron R&D towards DEMO within EUROfusion Work Package Heating and Current Drive

Gyrotron R&D within the EUROfusion Work Package Heating and Current Drive (WPHCD) is addressing the challenging requirements posed on gyrotrons by the European concept for a demonstration fusion power plant (EU DEMO). These requirements, as specified within WPHCD, ask for highly reliable and robust long-pulse operation of the gyrotron, delivering 2 MW of microwave power at frequencies above 200 GHz with a high overall efficiency above 60% and the option for fast frequency step-tunability. To meet these targets, which are clearly beyond today’s state-of-the-art, the R&D activities within WPHCD are organized in five main branches: these are the experimental verification of the advanced coaxial gyrotron technology at long pulses, the development of a coaxial gyrotron meeting the EU DEMO requirements, the development of multi-stage depressed collectors for enhanced energy recovery, the development of large broadband diamond windows to allow fast frequency tunability of the gyrotron, and the studies on further innovations and improvement of critical gyrotron components, in view of optimization of performance, reliability, and industrialization. The paper presents the progress made on these activities, the recent results, and the near-term planning. The major recent achievements include (i) the experimental validation of the fabrication of the new, water-cooled components for the longer-pulse coaxial gyrotron at Karlsruhe Institute of Technology, by demonstrating 2.2 MW at 170 GHz with 33% efficiency without depressed collector, (ii) the design of key components for a 2 MW, 170/204 GHz dual-frequency coaxial gyrotron, (iii) the design of a two-stage depressed collector with 77% efficiency, (iv) the first-ever production, in an industrial plasma reactor, of large chemical vapor deposition diamond wafers of 180 mm diameter, (v) the procurement of an advanced electron gun with coated emitter edges, and (vi) advances in the theoretical and numerical modelling for investigating improved concepts for the gyrotron beam tunnel and cavity.

Critical effect and enhanced thermal conductivity of Cu-diamond composites reinforced with various diamond prepared by composite electroplating

Abstract Despite the great potential value as heat sink materials, their practical application of high thermal conductivity (TC) Cu-diamond composites is limited since high temperature and high pressure (above 1000 K and 60 MPa) were requisite in the conventional process. In this study, high TC void-free Cu-diamond composites reinforced with various diamond particles were prepared via composite electroplating. The impacts of diamond particle sizes (ranged from 10 to 400 μm) on microstructure, interface and TC of the composites were investigated. The TC of Cu-diamond composites was improved with the increase of diamond particle sizes and well-combined interface. Interestingly, a critical size for improved the TC of Cu-diamond composites was clearly observed and the critical value (22 μm) was derived from Kipitza theory. Based on the TC results and critical analysis, the Cu-diamond composite reinforced with large diamond particles (400 μm) was synthesized, which possessed the TC of 846.52 W m−1 K−1 and the thermal expansion coefficient of 7.2 × 10−6 K−1. Such attractive thermal properties suggested that electroplating Cu-diamond composites showed the promising application as heat sink materials in microelectronic industry.

Micro-diamonds: Proposed origins, crystal growth laws, and the underlying principle governing resource predictions

The origin of micro-diamonds is controversial and although the application to determine the grade and value of macro-diamonds in kimberlite/lamproite bodies continues to receive widespread usage there are several outstanding factors generally not considered, the most important of which is genesis. The issue is addressed in this study in the context that two classes of small diamonds (generally <0.5 mm and rarely <1 mm) are recognized. Micro-diamonds sensu-stricto (MDS) are typically sharp-edged octahedra, free of mineral inclusions and surface etching or corrosion, increase exponentially with decreasing size and are in overwhelming larger concentrations, by orders of magnitude, relative to macro-diamonds (>0.5 mm). The second class of small diamonds (SD <0.5 mm), used in industrial applications, may have modified solution-growth morphologies (e.g. dodecahedra, tetrahexahedra and related forms), and include loosely bonded polycrystalline diamonds (framesite), boart, fibrous cubes and broken fragments. There are large differences in volume to surface-area ratios between MDS and SD, demonstrating unequivocally that pristine and solution-modified forms could not have co-existed in equilibrium under the same P-T-t-fO2 conditions in the mantle. From detailed studies of N and C in diamond, and experimental results on the redox-partitioning of N in the presence of metallic Fe, it is concluded that MDS are plume-related from the D″ core-mantle boundary, and are melt-derived in lower mantle proto-kimberlite. The lower mantle is expectedly saturated in metallic Fe, and is highly depleted in N which is siderophile under very low f O2 conditions, a setting in which excessively large (∼100 to 3000 ct), but rare Type II mega-diamonds (but also MDS) are inferred to have originated. These diamonds (Type II, Ib, IaA) are distinct from the majority of N-rich Type Ia upper mantle macro-diamonds that grew slowly by metasomatic processes and annealed over long periods. Two crystal growth laws are possibly applicable to the size-distribution of diamonds encountered in kimberlites/lamproites. Gibrat’s Law of proportionate, short-term crystal growth in open systems by advection is applicable to magmatic MDS, whereas macro-diamonds bear some relation to McCabe’s Law of long-term, relatively constant crystal growth, by diffusion metasomatism. The range from small to large diamonds (SFD size-frequency-distribution) is lognormal but is composed of two segments: the smaller size (<0.5 mm) fraction has an overall linear distribution, whereas macro-diamonds (>0.5 mm) are quadratic. The two distributions meet or overlap in a marked discontinuity, implying but not proving distinct origins. The power law governing SFD lognormal distributions is fundamental and is widespread across an enormous number of disciplines (from biology to economics), and may be universal (e.g. it is applicable to planetary scale meteorite impact craters, and to the SFD of cosmic-diamonds from supernovae explosions). Industry applications in resource predictions are from mixtures of diamonds (MDS and SD), and extrapolation to larger stones is valid because the fundamental law is independent of origins.

Correction to: 2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.

Correction to: 2018 AHA/ACC Guideline for the Management of Adults With Congenital Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.