Type IIa Diamond Research Articles

Compressibility behavior of CoxB: Experiment and computation

Structural stability studies on Co2B and Co3B are performed using Mao-Bell type diamond anvil cell. The tetragonal structure of Co2B and the orthorhombic structure of Co3B are stable up to 41 and 43 GPa, respectively. The bulk modulus obtained from high-pressure XRD experiments is 282 ± 21 GPa and 254 ± 10 GPa for Co2B and Co3B, respectively, which reasonably agrees with the computed value. The first principle calculations are carried out to understand the elastic and mechanical properties of CoxB (x: 1, 2, and 3). Adding B into Co enhances the elastic and mechanical properties marginally up to Co2B. Whereas in CoB, a significant increase in the elastic and mechanical properties was observed. The electronic density of states of CoB reveals the presence of a pseudo gap at Fermi energy leading to higher bulk modulus among the cobalt borides. Bader charge analysis shows a transfer of charge from Co to B. The valence charge variation indicates the strengthening of B–B bonds at the expense of Co–Co bonds leading to enhanced elastic properties.

Temperature/laser dependence of N3 optical centers in natural type Ia diamonds through photoluminescence spectroscopy

In this work, low-temperature photoluminescence spectroscopy was employed to investigate the N3 optical color center in natural type Ia diamond. The optical properties of the N3 center with regular changes in testing temperature and laser power were studied, and the energy level transition was also discussed. The results showed that the PL intensity of the N3 center enhanced sub-linearly with laser power increased, indicating that the electron transition of the N3 center was mainly radiative recombination with weak Auger recombination participation. In addition, the physical model was employed to analyze the change in the zero phonon line with the increase in the test temperature; it obtained thermal quenching activation energy (25.2 meV), bond softening, and strong interaction with acoustical phonons of the N3 center. The theoretical analysis of the broadening parameters revealed that the longitudinal optical phonon energy was 55.1 meV, and the electron–optic phonon coupling strength was 2.3 meV.

Thermal conductivity of type-Ib HPHT synthetic diamond irradiated with electrons

The effect of irradiation with 3 MeV electrons and subsequent high-temperature annealing on the thermal conductivity κT of synthetic HPHT diamond containing impurity nitrogen at a concentration of about 100 ppm was studied at temperatures from 5 to 410 K. At each stage of the experiment, the optical absorption and photoluminescence spectra, magnetization and thermal conductivity were measured on two plates from the same diamond single crystal. Color centers and their concentration in different locations in the samples were determined from the optical spectra. The concentration of paramagnetic impurities in the samples was determined from the temperature and field dependencies of the paramagnetic magnetization. Thermal conductivity is suppressed by two orders of magnitude at temperatures from 35 to 50 K after irradiation to a fluence of 5×1018 cm−2. Annealing at a temperature of 1800° C restored the thermal conductivity of diamond at moderate and high temperatures, but not at temperatures below 120 K. The measured data on thermal conductivity were analyzed within the framework of the phenomenological Callaway model in order to understand the role of various phonon scattering processes and how it changes during irradiation and annealing.

Characterization on the occurrence state of nitrogen getter Ti in HPHT grown synthetic diamond crystals

Type IIa diamonds are the most promising gem grade, optical and electronic grade materials with high quality and low defects, however natural type IIa diamonds are rare and therefore the synthetic methods to obtain the high quality type IIa diamonds have been a hot issue. Nitrogen getters play a crucial role in the synthesis of type IIa high temperature high pressure (HPHT) diamonds crystals by reacting with the nitrogen in the system and effectively removing it from the growth process. However, the occurrence state of nitrogen getter introduced after diamond crystal growth remains to be investigated. In this study, a group of HPHT synthetic diamond crystals with different mass fractions of Ti as a nitrogen getter were examined by scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS) and X-ray fluorescent spectroscopy (micro-XRF) to observe the occurrence state of the nitrogen getter Ti within the synthetic diamond crystal, it was found that at the end of crystal growth, There are two forms of Ti present in the process: (i) Ti reacts with C to form TiC, which was deposited on the surface of the diamond crystal in the dendritic pattern, and (ii) Ti enters the diamond crystal to form metallic inclusions. This study provides reliable data to support a comprehensive analysis of the effect of Ti as a nitrogen getter in the growth procession of HPHT synthetic diamond crystal, and it will have a positive effect on the development of synthetic diamond technology.

A novel strategy for improving the wear resistance of electrodeposited Ni-diamond composite coatings by diamond surface morphology modification

Ni-based composite coatings have been extensively adopted in the automotive, printing and aerospace fields. However, numerous significant engineering components necessitate protective coatings with increased wear resistance. In the present study, the modification of the diamond surface morphology for improving the wear resistance of Ni-diamond composite coatings was experimentally verified. A new type of rough-surfaced diamond was obtained by applying the thermochemical corrosion method, and a Ni-diamond composite coating (#2) and Ni-rough-surfaced diamond composite coating (#3) were prepared by means of direct current electrodeposition. The present research shows that rough-surfaced diamond has a larger surface area and higher electronegativity than ordinary diamond, which enhances the adhesion between the Ni-based bond and the rough-surfaced diamond. Compared with the #2 coating, the microhardness of the #3 coating was increased to 613 HV and the coefficient of friction was reduced to 0.63. Due to the synergistic influence of augmented microhardness and bond strength, the wear rate of the #3 composite coating experienced a decline of 15.6 %, resulting in a reduction to 1.79 × 10−5 mm3/Nm. Such enhancement consequently led to an improvement in the wear resistance of the coating. The application of rough-surfaced diamonds offers a new direction for the development of new high wear-resistant coatings with broad application prospects.

Comparison of the I and IV Diamond Types (According to Orlov’s Classification) from the Snap Lake Deposit (Slave Craton, Canada)

Comparison of the I and IV Diamond Types (According to Orlov’s Classification) from the Snap Lake Deposit (Slave Craton, Canada)

On the creation of near-surface nitrogen-vacancy centre ensembles by implantation of type Ib diamond

Dense, near-surface (within ∼10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 10$$\\end{document} nm) ensembles of nitrogen-vacancy (NV) centres in diamond are moving into prominence as the workhorse of many envisaged applications, from the imaging of fast-fluctuating magnetic signals to enacting nuclear hyperpolarisation. Unlike their bulk counterparts, near-surface ensembles suffer from charge stability issues and reduced formation efficiency due to proximity to the diamond surface. Here we examine the prospects for creating such ensembles by implanting nitrogen-rich type Ib diamond, aiming to exploit the high bulk nitrogen density to combat surface-induced band bending. This approach has previously been successful at creating deeper ensembles, however we find that in the near-surface regime there are fewer benefits over nitrogen implantation into pure diamond substrates. Our results suggest that control over diamond surface termination during annealing is key to successfully creating high-yield near-surface NV ensembles generally and implantation into type Ib diamond may be worth revisiting once that has been accomplished.Graphical

Nitrogen centers in single crystal diamond grown by chemical vapor deposition

The single crystals of diamond grown by chemical vapor deposition (CVD) are getting wider acceptance in the market for gem purposes and various other applications. Most popular applications are gems, particle detectors, high pressure anvils, and laser windows. It is widely accepted that, unless specifically made, the CVD diamond single crystals are type IIa, which implies that they have a nitrogen concentration of less than 5 ppm in the diamond. The concentration of nitrogen in CVD grown single crystal diamond is a serious deterrent for certain applications such as particle detectors, high pressure anvils, and laser windows. The threshold of nitrogen for these specific applications is subparts per billion (less than 1 ppb). On the other hand, the CVD single crystal diamonds for gems could hold nitrogen in subparts per million (less than 1 ppm) range and would still qualify as excellent gems. In this paper, an attempt is made to understand the nature of nitrogen in two types of CVD single crystal diamonds: one that shows very week fluorescence in the PL spectrum (light color or white color) with low nitrogen concentration and the other with high nitrogen concentration that shows strong fluorescence in the PL spectrum (brown to dark brown color). The correlation of nitrogen in different forms of vacancy centers in these two types of single crystals of CVD diamonds is studied. The results indicate that a strong relationship exists in concentrations of the (NVH)0 and NS+ centers in brown and dark brown color CVD grown single crystal diamonds.

High-pressure phase of cold-compressed bulk graphite and graphene nanoplatelets

We have studied the high-pressure vibrational and structural behavior of bulk graphite and graphene nanoplatelets at room temperature by means of high-pressure Raman spectroscopic and x-ray diffraction probes. We have detected a clear pressure-induced structural transition in both materials, evidenced by the appearance of new Bragg peaks and Raman features, deviating from the starting hexagonal graphitic structure. The high-pressure phase is identified as a partially disordered orthorhombic structure, consisting of mixed $s{p}^{2}$- and $s{p}^{3}$-type bonding. Our experimental findings serve as direct evidence for the existence of a metastable transient modification in cold compressed carbon, lying between the $s{p}^{2}$-type graphite and ${sp}^{3}$-type diamond allotropes.

HTHP synthesis and characterization of 5–8 mm diamond large crystal by Fe-Co alloy catalyst

IIa-type diamonds with 5–8 mm edge lengths were successfully synthesized under the catalytic action of Fe-Co catalyst. The effects of Fe-Co and Fe-Ni catalysts on the synthesis of type Ib diamonds were compared and analyzed. Moreover, the effects of different levels of nitrogen-getter agents on the synthesis of type IIa diamonds were discussed. When we characterized the single diamond crystals, Optical microscopy, Raman spectroscopy, Fourier infrared absorption spectroscopy, and photoluminescence spectroscopy were used. The experimental results showed that the nitrogen content of the diamonds synthesized using Fe-Co alloy catalyst was reduced by 127 ppm compared with those synthesized using Fe-Ni alloy catalyst. When the amount of nitrogen-getter added was increased from 0.4 wt% Ti + 0.5 wt% Cu to 0.7 wt% Ti + 0.8 wt% Cu in the Fe-Co-C system, the nitrogen content in the diamond was reduced from 20 ppm to 1 ppm, the internal crystal stress decreased from 238.1 MPa to 147.4 MPa, and the crystal quality was significantly improved. In addition, the Fe-Co alloy catalysts have a lower V-shaped growth zone of diamond, so its growth region is closer to the graphite-diamond equilibrium line, resulting in slower crystal growth and less impurity content in the crystal. Thus, Fe-Co alloy catalysts can synthesize gem-quality diamonds more easily.

Studies of Dislocations in Type Ib, Type IIa HPHT and CVD Single Crystal Diamonds

In this review, the X-ray topography results of various types of single crystal diamonds (SCDs) are reported. Dislocations and dislocation bundles are present in all types of SCDs, the only exception being type IIa high-pressure, high-temperature (HPHT) SCDs. The technology of growing HPHT type IIa SCDs has advanced to a level where the samples show almost no dislocations or dislocation bundles. However, very few groups appear to have perfected the process of HPHT growth of type IIa SCDs. There appears to be a characteristic difference in the dislocations present in type Ib HPHT and chemical vapor deposited (CVD) SCDs. The dislocations in CVD SCDs are mostly in aggregate form, while in HPHT type Ib diamonds there are line dislocations which propagate in <111> or <112> directions. The CVD SCDs growth appears to be in the early stage in terms of the control of dislocations and dislocation bundles, compared to other semiconductor wafers. The dislocations and dislocation bundles and aggregates in SCDs limit their applications in electronic and optical devices. For instance, high-power laser windows must have low dislocations and dislocation bundles. For electronic devices such as high-power diodes, dislocations reduce the breakdown voltage of SCDs, limiting their applications. The knowledge of dislocations, their identification and their origin are, therefore, of utmost importance for the applications of SCDs, be they HPHT or CVD grown.

Test and Analysis of the Protection Efficiency of a New Type Thermal Sleeve

As an additional part of the artillery barrel, the thermal sleeve is a cladding made of insulation or thermal conductive material mounted on the outer surface of the barrel, which can greatly reduce the bending deformation caused by sunlight exposure of the barrel, thus improving the shooting accuracy of the artillery. In this paper, a new type diamond thermal sleeve on the barrel thermal protection efficiency is tested and analyzed, after testing, the protection efficiency can be as high as 71.6%, much higher than the ordinary thermal sleeve’s protection performance, so research of thermal sleeve is of great significance to improve the shooting accuracy of the artillery.

New aerosol-decreasing dental handpiece functions sufficiently decrease pulp temperature: An in vitro study.

To assess the changes in intrapulpal temperature between electric high-speed handpieces of different coolant functions ('Water Jet' and 'Water Spray'), coolant port designs (1- and 4-port), suction use, and bur and tooth types using an experimental in vitro setup. Forty-four extracted anterior and posterior teeth were collected. A total of 18 groove cuts (n = 18/coolant port spray design, bur and tooth type group) and 12 groove cuts (n=12/tooth type and suction use) were completed, with a total of 264 groove cuts. Real-time temperature and duration were recorded at 1-s intervals throughout the preparation process using a thermocouple and digital data logger setup (GFX Data Logger Series and EL USB-TC; Lascar Electronics Inc., USA), and the data retrieved using EasyLog Software (EasyLog USB; Lascar Electronics Inc., USA). Statistical analysis was performed (SPSS V.27) for the change in temperature using the analysis of variance and post hoc analysis. The majority of the specimen cuts, regardless of tooth (anterior or posterior) and bur (diamond or carbide) types, handpiece coolant port design, and suction use showed an overall decreasing trend in intrapulpal temperature. No cuts caused a mean temperature change that reached the critical temperature of 42.5°C or resulted in an overall increase in intrapulpal temperature when the 60-s duration was completed. The tested electric handpieces efficiently reduced intrapulpal temperature, with the majority displaying a decreasing trend. A greater decrease in intrapulpal temperature was observed in canines compared to premolars; carbide burs compared to diamond; and with no suction preparations compared to when suction was used.

Design and analysis of strut-based lattice structure cranial implant

A specialized medical cranioplasty procedure entails the use of implants of various materials, forms, and sizes. Computational technologies such as modelling and simulation, have refined the technique for creating these implants catering to patient specific needs. Superior qualities of lattice structures have considerable usage in implants. This study mainly focuses on three distinct types of strut-based lattice structures, Octet, Diamond, and Kelvin, for constructing cranial implant models using CAD tools like Solidworks and nTopology. Titanium alloy (Ti6Al4V) is used to test the behaviour of the designed implants in two cases: impact of external force and increase in intracranial pressure. Level of porosity is compared to determine extent of porosity of these implants, as porosity is significant in osseointegration. According to the study, these lattice structures give satisfactory results and can be utilized to make the implant more porous while satisfying the load bearing capacity.

Phenomenon of photo-regulation on gold/diamond Schottky barriers and its detector applications

A thickness asymmetric electrode structure on an oxygen-terminated type IIa diamond was designed and prepared (one electrode was semitransparent to ultraviolet light and the other blocked the transmission of ultraviolet light). This structure exhibited an apparent photo-induced rectification property under irradiation by a deuterium lamp. This is attributed to the mechanism by which the light penetrating the electrode reduces the metal–diamond contact barrier. Furthermore, we developed a light-modulated Schottky barrier diamond photodetector based on this mechanism. Solar-blind light can lower the Schottky barrier height in situ in the presence of light, which significantly enhances the photocurrent. However, the Schottky barrier is not reduced by light regulation when there is no light; therefore, the low dark current of the detector is still guaranteed. Compared with the non-photo-regulated Schottky barrier detector, the photo-regulated Schottky barrier detector exhibits a 128% increase in responsivity at 220 nm under a 1.6 V/μm bias. For such an obvious difference in detection performance, this mechanism has rarely been a focus of studies on diamond detectors. In addition to diamond detectors, light-modulated barrier technology can also be applied to other fields related to the diamond surface potential, such as color center control and Schottky diodes; it can also be used to control or evaluate device performance.

HPHT-Treated Impact Diamonds from the Popigai Crater (Siberian Craton): XRD and Raman Spectroscopy Evidence

Phase change and graphitization of diamonds from the Popigai impact crater (Krasnoyarsk Territory, Siberian platform, Russia) exposed to high-pressure high-temperature (HPHT) conditions of 5.5 GPa and 2000–2200 °C are studied by Raman spectroscopy and X-ray diffractometry (XRD). Light-color diamonds of type 1, free from inclusions, with 0 to 10 % lonsdaleite, are more resistant to HPHT effects than dark diamonds of type 2 rich in lonsdaleite and graphite. The lonsdaleite/diamond ratios in lonsdaleite-bearing impact diamonds become smaller upon annealing, possibly because lonsdaleite transforms to cubic diamond simultaneously with graphitization. Therefore, lonsdaleite is more likely a structure defect in diamond than a separate hexagonal phase.

Design and characterization of 3-D printed hydrogel lattices with anisotropic mechanical properties

The goal of this study was to design, fabricate, and characterize hydrogel lattice structures with consistent, controllable, anisotropic mechanical properties. Lattices, based on three unit-cell types (cubic, diamond, and vintile), were printed using stereolithography (SLA) of polyethylene glycol diacrylate (PEGDA). To create structural anisotropy in the lattices, unit cell design files were scaled by a factor of two in one direction in each layer and then printed. The mechanical properties of the scaled lattices were measured in shear and compression and compared to those of the unscaled lattices. Two apparent shear moduli of each lattice were measured by dynamic shear tests in two planes: (1) parallel and (2) perpendicular to the scaling direction, or cell symmetry axis. Three apparent Young's moduli of each lattice were measured by compression in three different directions: (1) the “build” direction or direction of added layers, (2) the scaling direction, and (3) the unscaled direction perpendicular to both scaling and build directions. For shear deformation in unscaled lattices, the apparent shear moduli were similar in the two perpendicular directions. In contrast, scaled lattices exhibit clear differences in apparent shear moduli. In compression of unscaled lattices, apparent Young's moduli were independent of direction in cubic and vintile lattices; in diamond lattices Young's moduli differed in the build direction, but were similar in the other two directions. Scaled lattices in compression exhibited additional differences in apparent Young's moduli in the scaled and unscaled directions. Notably, the effects of scaling on apparent modulus differed between each lattice type (cubic, diamond, or vintile) and deformation mode (shear or compression). Scaling of 3D-printed, hydrogel lattices may be harnessed to create tunable, structures of desired shape, stiffness, and mechanical anisotropy, in both shear and compression.

Synthesis, characterization and cutting performances of gradient gradual changing (GGC-) MCD/SMCD/NCD/UNCD diamond coatings with tailored interfacial integrity on CFRP drilling tools

Drilling holes is a common mechanical processing method in the high-precision machining of carbon fiber reinforced plastic (CFRP) material. Diamond coatings can be deposited on the drilling tools to enhance the tool life and improve the machining quality. However, traditional multilayer diamond coatings, such as MCD/NCD etc., easily suffer from interfacial separation in actual applications due to the sharp interfaces of diamond layers. Novel gradient gradual changing (GGC-) structure without clear interfaces is applied to tailor the architecture of diamond coatings, which can lead to superior interfacial integrity and the reduction of sp2 phase content at the transition between distinct diamond layers. Various diamond films, containing monolayer diamond films (MCD, SMCD, NCD, UNCD) and gradient gradual changing multilayer diamond films (GGC-MCD/SMCD/NCD, GGC-MCD/SMCD/NCD/UNCD), were fabricated on WC-Co samples. The deposition of tailored gradient gradual changing coating interfacial architecture can be accomplished by controlling the linear variation of carbon concentration and gas pressure simultaneously. The complementary characteristics of high coating-substrate adhesive strength, superior frictional and wear resistance, good interfacial integrity and favorable crack propagation resistance are concentrated on GGC-MCD/SMCD/NCD and GGC-MCD/SMCD/NCD/UNCD coatings compared to monolayer MCD, SMCD, NCD and UNCD coatings. Moreover, because of the existence of UNCD layer, GGC-MCD/SMCD/NCD/UNCD coating performs lower surface roughness, frictional coefficient and higher surface smoothness than GGC-MCD/SMCD/NCD coating. Besides, the cutting performances in high-speed drilling experiments of CFRP laminates using different types of diamond coated drilling tools were compared systematically, showing that the dominant wear modes are abrasive wear and adhesive wear, and the GGC-MCD/SMCD/NCD/UNCD coated drilling tool exhibits the longest tool lifetime and best machining quality because of the overall interfacial integrity and high surface smoothness.

Boron isotopes in blue diamond record seawater-derived fluids in the lower mantle

Boron is a quintessential crustal element but its conspicuous presence in diamond – a mantle mineral – raises questions about potential subduction pathways for boron and other volatiles. It has been a long-standing goal to characterize the isotopic composition of boron in blue, boron-bearing (Type IIb) diamonds to reveal its origin. Mineral inclusions indicate that Type IIb diamonds crystallize at transition zone to lower mantle depths, meaning that if the boron is subducted it would trace a pathway of volatile elements into the deep mantle. Here, using off-line laser ablation sampling, we present the first boron isotope compositions, along with trace element contents and carbon isotope compositions, of a suite of blue diamonds mainly sourced from the Cullinan diamond mine in South Africa. The ten analyzed blue diamonds have a wide range in δ11B, between −9.2 ± 2‰ and −0.5 ± 2‰, compared to the more restricted range for mid-ocean ridge basalts (−7.1 ± 0.9‰). Carbon isotope values for the blue diamonds range between −20.6 and −1.8‰, with a mode at −17‰, significantly more negative than the main mantle mode at −5‰. Combined, the boron and carbon isotope compositions require fluid input from subducted oceanic lithosphere down into deep mantle source regions of blue diamonds. This finding highlights a deep subduction pathway for volatiles to stoke the source regions of deeply-derived magmas.

N-type diamond synthesized with tert-butylphosphine for long spin coherence times of perfectly aligned NV centers

The longest spin coherence times for nitrogen-vacancy (NV) centers at room temperature have been achieved in phosphorus-doped n-type diamond. However, difficulty controlling impurity incorporation and the utilization of highly toxic phosphine gas in the chemical vapor deposition (CVD) technique pose problems for the growth of n-type diamond. In the present study, n-type diamond samples were synthesized by CVD using tert-butylphosphine, which is much less toxic than phosphine. The unintentional incorporation of nitrogen was found to be suppressed by incrementally increasing the gas flow rates of H2 and CH4. It was found that the spin coherence time (T2) increased with decreasing the nitrogen concentration, which suggests that the nitrogen concentration limits the length of T2. In the sample with the lowest nitrogen concentration, T2 increased to 1.62 ± 0.10 ms. Optically detected magnetic resonance spectra indicated that all of the measured NV centers were aligned along the [111] direction. Hall measurements confirmed n-type conduction in three measured samples prepared under different growth conditions. The highest measured Hall mobility at room temperature was 422 cm2/(V s). This study provides appropriate CVD conditions for growing phosphorus-doped n-type diamond with perfectly aligned NV centers exhibiting long spin coherence times, which is important for the production of quantum diamond devices.