Pure Diamond Research Articles

Purification and tailored functionalities in detonation nanodiamond

Abstract Nanodiamonds (NDs) offer immense potential in various fields, but graphitic or metal-based impurities hinder their widespread adoption. Conventional purification methods often employ harsh chemicals or high temperatures, raising concerns about ND integrity and surface properties. Herein, we compared various strategies to purify and tailor the surface functional groups in the detonation-derived NDs. A facile 2-step purification strategy combining salt-assisted air oxidation (SAAO) and Fenton chemistry is particularly interesting for efficient and selective removal of graphitic impurities while preserving the diamond lattice structure. SAAO selectively burns off graphitic impurities at 450 °C under controlled oxygen flow, minimizing damage to the diamond core. Subsequently, Fenton's reagent (H2O2/Fe2+) introduces hydrophilic functional groups onto the ND surface, further enhancing diamond purity and promoting subsequent functionalization. This synergistic approach enables (i) highly efficient removal of graphitic impurities while preserving ND morphology and crystal structure, (ii) controlled introduction of surface functionalities, and (iii) improved colloidal stability of purified NDs. This green and efficient purification protocol is beneficial for tailoring ND properties and unlocking their full potential in diverse applications ranging from biomedicine and electronics to catalysis and quantum technologies.

Characterization of a HPHT boron ion-implanted diamond X-ray mirror following high vacuum annealing

The incorporation of boron into a diamond lattice holds the potential to advance X-ray optics, offering the capability to manipulate various parameters of the lattice. This includes enhancing near-infrared absorption relative to pure diamond, thereby enabling Q-switchable optics. The use of MeV boron implantation emerges as a promising method for precisely doping the diamond lattice. However, for these optics to function effectively as Bragg-reflecting mirrors, ion implantation must be executed with meticulous attention to maintaining a strain-free, perfect diamond lattice. This study aimed to investigate the feasibility of utilizing a 9 MeV ion beam for high energy boron implantation. Different areas of a high-pressure, high-temperature (HPHT) diamond sample were subjected to irradiation with 9 MeV Boron ions, ranging in fluences from 5×1015 to 2.5×1016ions/cm2. Following boron implantation, high-temperature vacuum annealing was performed to restore the diamond lattice. Our assessment utilized X-ray rocking curve imaging, surface profilometry, and micro-Raman spectroscopy, with additional observations on near-infrared transmission properties. Our measurement of high-quality Bragg reflection through X-ray rocking curve imaging, sensitive to implantation-induced strain and defects, served as an key diagnostic for the effectiveness of this ion-implanted sample as a Bragg-reflecting optic.

New understandings of the applications of PDC cutters in oil and gas drilling

Today, the polycrystalline diamond compact (PDC) cutters have already reached a pretty high level of quality and are still keeping advancing. The formations drillability is positively related to the quality of PDC cutters. With advances in PDC cutters, most formations have become easy-to-drill. Years of improvements in the PDC cutter quality and the drilling techniques have also upended some long-hold knowledge and understandings about the cutter applications. PDC designs abandoned long ago are once again applicable, such as unleached, thin diamond table, small chamfer, and non-pure diamond mix. From the perspective of saving money and environmental protection, these long-abandoned PDC designs are worth a shot, but are suggested to be used in the well-understood formations and lithologies. On the other hand, why do PDC cutters always perform poorly in challenging formations? The results revealed that this is mainly due to the irregular dynamic impacts and inefficient rock cutting, which are the primary causes of the premature failure of PDC cutters and bits. The challenging formations as well as the unknown formations in the exploratory wells still prefer the cutters with the best quality, such as pure diamond mix, thicker diamond table, deep leaching, excellent residual stress management, and the ones from the best manufacturer. In addition, how to select the right cutters depends highly on the bit failure forensics and the multi-index evaluation. The emphasis of cutter selection is on selecting the right design and the right materials for the right formations, rather than the most expensive ones.

Structural, Energetic, and Electronic Properties of H-Interstitial in C-Monovacancy: A First-Principles Density Functional Theory

We discover a unique structural-modified diamond that exhibits similar symmetry and band gap energy to that of the pure diamond. We study a complex carbon-vacancy-hydrogen in the diamond using the density-functional-theory method. The defective models are created by adding H-interstitial (Hi, where i = 1, 2, 3 and 4) in the 3D diamond C-monovacancy. The result shows that carbon-vacancy-hydrogen defects significantly decreased the symmetry from Td to C2V. Likewise, the volumetric size of the systems is widening up to 48.70 %, while the optimized band gap energies are narrowing. Additional states appeared in the C-monovacancy, H1-V, H2-V, and H3-V systems which further improved electron mobility. The Hi compensates the C-monovacancy which further serves as a deep donor. Interestingly, H4-V exhibits similar symmetry and band gap energy to that of the pure diamond, but its volumetric size is 48.70 % wider. HIGHLIGHTS Study of complex carbon-vacancy-hydrogen defects through density-functional-theory calculations Discover a unique structural-modified diamond that is 48.70 % wider than the pure diamond, but exhibits similar symmetry and band gap energy. Complex carbon-vacancy-hydrogen defects significantly lower the symmetries, widening the volumetric sizes, and narrowing the band gap energies. The H-interstitial acts as a deep donor. GRAPHICAL ABSTRACT

Single-crystal vs polycrystalline boron-doped diamond anodes: Comparing degradation efficiencies of carbamazepine in electrochemical water treatment

The ongoing challenge of water pollution by contaminants of emerging concern calls for more effective wastewater treatment to prevent harmful side effects to the environment and human health. To this end, this study explored for the first time the implementation of single-crystal boron-doped diamond (BDD) anodes in electrochemical wastewater treatment, which stand out from the conventional polycrystalline BDD morphologies widely reported in the literature. The single-crystal BDD presented a pure diamond (sp3) content, whereas the three other investigated polycrystalline BDD electrodes displayed various properties in terms of boron doping, sp3/sp2 content, microstructure, and roughness. The effects of other process conditions, such as applied current density and anolyte concentration, were simultaneously investigated using carbamazepine (CBZ) as a representative target pollutant. The Taguchi method was applied to elucidate the optimal operating conditions that maximised either (i) the CBZ degradation rate constant (enhanced through hydroxyl radicals (•OH)) or (ii) the proportion of sulfate radicals (SO4•−) with respect to •OH. The results showed that the single-crystal BDD significantly promoted •OH formation but also that the interactions between boron doping, current density and anolyte concentration determined the underlying degradation mechanisms. Therefore, this study demonstrated that characterising the BDD material and understanding its interactions with other process operating conditions prior to degradation experiments is a crucial step to attain the optimisation of any wastewater treatment application.

Effect of Fe: Cu ratio on microstructure and mechanical properties of Fe-Co-Cu-based diamond tools

Co-based diamond tools are widely appreciated for their exceptional mechanical properties and good holding ability for diamonds. However, the reliance on cobalt (Co) poses challenges due to its high cost and scarcity as a strategic resource. A potential alternative is the Fe–Co–Cu alloy, emerging as a promising substitute for Co matrix alloys. In this work, hot-press sintering was utilized to create pure matrix and diamond tools utilizing Fe–Co–Cu pre-alloyed powders of varying compositions as raw materials without the use of any sintering additives. The investigation explores the influence of different Fe: Cu ratios on the mechanical properties of diamond tools produced from Fe–Co–Cu alloys, focusing on the diamond holding force, microstructure, and phase structure evolution. Results indicate that at a Co content of 15 wt% and Fe: Cu ratios ranging from 7.5:1 to 1:7.5, the Fe–Co–Cu alloy's phase structure primarily comprises α-Fe and a Cu-rich phase. Co predominantly exists in α-Fe as a solid solution. As the Fe: Cu ratio decreases, the alloy's phase structure gradually transitions from α-Fe to a Cu-rich phase, accompanied by a progressive decline in both bending strength and hardness, while the densities gradually increase. The matrix's holding force on the diamond exhibits an increasing and then diminishing trend, peaking at the Fe: Cu ratio of 6:1. The Fe–Co–Cu alloy sintered by hot-pressing has a nearly equiaxed grain structure with no obvious texture.

Optical characteristics and wavefront control of femtosecond laser pulses and their effect on the performance of diamond graphite electrodes

High purity diamond is an excellent material for making radiation hard detectors suitable for high-energy particle detection, cancer treatment and other fields. Electrodes are formed by the localized graphitization of the diamond bulk, where fine control of the manufacturing process is essential to the performance of the detector. The resistivity of the electrode formed by diamond graphitization significantly affects the performance of the detector. Femtosecond laser pulses interact with the material for a very short time (10-13 s), exhibiting a cold processing. In this paper, we utilize Spatial Light Modulators (SLM) to optimize the optical characteristics of the 800 nm femtosecond laser pulse and control the graphitization process. Our research focuses on the analysis of the influence exerted by the pulse characteristics on the diameter and resistivity of inscribed graphite structures. By examining these parameters, the study aims to refine the graphitization process, thereby optimizing the functional characteristics of the diamond-based detectors.

Study of the Acoustic Characteristics of Suspensions Based on Glycerol and Synthetic Diamond Microparticles Using a Resonator with a Longitudinal Electric Field

The acoustic properties of suspensions based on pure glycerol and diamond powder with a particle size of 1–2 μm and different concentrations were studied using a resonator with a longitudinal electric field. A disk resonator made of langasite with round electrodes on both sides of the plate with a frequency of 4.1MHz, operating on a longitudinal acoustic wave, was completely immersed in a liquid container with the studied suspension. Based on the measured frequency dependences of the real and imaginary parts of theelectric impedance of the resonator using an equivalent electromechanical circuit, the longitudinal elastic modulus and longitudinal viscosity coefficient of the samples were determined. Comparison of the experimental dependences of the longitudinal elastic modulus, viscosity coefficient, and longitudinal acoustic wavevelocity on the volume concentration of diamond particles in the suspension with the calculated dependences demonstrated good agreement.

14C diamond as energy converting material in betavoltaic battery: A first principles study

The application of radioactive semiconductors is a potential way to improve the performance of betavoltaic battery. The stability and band structure of decayed 14C diamond are investigated by density functional theory. After the decay, the 14C atoms are substituted by nitrogen atoms, and it can be seen that the corresponding C63N1 and C62N2 structures have larger lattice constants and become more unstable. The C63N1 structure is a metallic system instead of an indirect bandgap semiconductor. Different C62N2 configurations have either metallic or indirect bandgap semiconductor properties, and the bandgaps are significantly lower than those of pure diamond. The 14C diamond–12C diamond betavoltaic battery switches between a pn-junction and p-type Schottky diode with higher short-circuit current.

Analysis of the microstructural and magnetodielectric behavior in multiferrioc Cr1.3Fe0.7O3 nanoparticles

Single phase Cr1.3Fe0.7O3 has been successfully prepared by wet chemical method, accompanied by the surface morphology with pure diamond shaped structure of corundum and uniform grain growth. The splitting of magnetization curves at ∼220 K during varying temperature measurement indicates the magnetocrystalline anisotropy with the coexistence of antiferromagnetic and ferromagnetic phases. The obvious dielectric relaxation behavior has been determined above ∼125 K with the activation energy of 0.0318 eV, which is attributed to the dipolar relaxation caused by short-range polaron range hopping in the magnetic grains. The arresting magnetoelectric coupling effect near room temperature is certified in Cr1.3Fe0.7O3 from ∼125 K, with the maximum coupling coefficient of 5 % at ∼212 K. These characteristics mean that the sample has potential application value in fields such as spintronics devices and magnetoelectric memories.

Super High-Concentration Si and N Doping of CVD Diamond Film by Thermal Decomposition of Silicon Nitride Substrate.

The high-concentration N doping of diamond film is still a challenge since nitrogen is limited during diamond growth. In this work, a novel method combined with the thermal decomposition of silicon nitride was proposed to form the activated N and Si components in the reactor gas that surrounded the substrate, with which the high-concentration N and Si doping of diamond film was performed. Meanwhile, graphene oxide (GO) particles were also employed as an adsorbent to further increase the concentration of the N element in diamond film by capturing the more decomposed N components. All the as-deposited diamond films were characterized by scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. For the pure diamond film with a growth time of 0.5 h, the N and Si concentrations were 20.78 and 41.21 at%, respectively. For the GO-diamond film, they reached 47.47 and 21.66 at%, which set a new record for super high-concentration N doping of diamond film. Hence, thermal decomposition for the substrate can be regarded as a potential and alternative method to deposit the chemical vapor deposition (CVD) diamond film with high-concentration N, which be favorable for the widespread application of diamond in the electric field.

Research and Application Progress of Boron-doped Diamond Films

Thanks to its unique structure, diamond has many excellent properties, such as high hardness, low birefringence, high thermal conductivity, good chemical stability, etc., but pure diamond has extremely high resistivity (up to 1012 Ω∙m ), which is an insulator, so it is usually doped to expand the application of diamond in the electrochemical field. B atoms have a very small radius, which is an ideal material for doping diamond, and B-doped diamond has good electrical conductivity. In this paper, on the basis of introducing the phase composition and structure of boron-doped diamond (BDD) film, the common methods for preparing BDD film are analyzed, and the application status and prospect of its application in electrochemistry and other fields are summarized.

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

Various HFCVD diamond coatings synergistically tuned using CH4 gas flow and working pressure and key merit evaluation of their coated tools

Diamond-coated tools can meet the service requirements of high precision, high efficiency and long life with multi-element coupling, but the milling characteristics of graphite materials with high spindle speed, feed speed and high force may require tools with a high number of micro-edges and good adhesion strength. In the present study, microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and gradient composite diamond (GCD) coatings were deposited on commercial end mills subjected to distinct CH4 gas flows and working pressure by hot filament chemical vapor deposition. The adhesion strength, erosion resistance and milling performance of the diamond coatings in milling graphite materials were evaluated. Besides, the effect of CH4 gas flows and working pressure on the growth model of diamond coatings and the mechanism of crack propagation when subjected to stress concentration were studied. The results show that the combination of high CH4 gas flows and low working pressure achieves the re-nucleation of diamond particles, the smaller grain, more graphite/amorphous carbon in the boundaries and larger residual stresses lead to continuous crack propagation, causing poor adhesion strength, erosion resistance and milling performance in NCD and GCD coatings. Conversely, the low CH4 gas flows to ensure the epitaxial growth required for MCD coating, the larger grain, higher diamond purity, columnar structure and smaller residual stresses allow the pinning effect between coating and substrate, altering and increasing the path of crack propagation, making it suitable for milling conditions with high speed and high force. This study provides significant insights into the links between diamond morphology, structure, grain size, boundaries, and phase composition and the mechanical properties of adhesion strength, erosion resistance, and milling properties by synergistically tuning or alternating the CH4 gas flows and working pressure.

Study on material removal mechanism of sapphire wafer with CeO2 coated diamond composite abrasives via green polishing

Toxic and polluted ingredients are normally employed in the chemical mechanical polishing of sapphire wafers, which results in widespread environmental pollution. Thus, developing a novel green polishing technology is a significant challenge to achieve ultra-smooth and efficient polishing. In this study, novel CeO2 coated diamond composite abrasives were used in the semi-fixed abrasive polishing of sapphire wafers, which were successfully synthesized by a modified precipitation approach without using explosive hazardous chemicals. During the whole polishing process, the polishing slurry only contains deionized water, without any other chemical reagents, to avoid environmental pollution. Polishing results showed that the surface roughness of sapphire polished by the composite abrasives was reduced to 6.1 nm, which was 26.5 % lower than that of pure diamond. Meanwhile, the material removal rate was 1.46 nm/min, with an improvement of 10.6 %, as well as a reduction in residual stress by approximately 29.8 %. Combined with the theory of micro-contact mechanics, the polishing mechanism and interfacial contact behavior of composite abrasives were investigated in depth through the analysis of polished sapphire surface and wear debris. The improvement of polishing performance may be attributed to the enhancement of solid-state reaction and its mutual balance with the mechanical removal action of composite abrasives.

The Effect of Glycerol-Based Suspensions on the Characteristics of Resonators Excited by a Longitudinal Electric Field

This study examines the effect of suspensions based on pure glycerol and diamond powder with different concentrations on the characteristics of resonators with a longitudinal electric field. We used two disk resonators made of the quartz and langasite plates with round electrodes on both sides of the plate and resonant frequencies of 4.4 and 4.1 MHz, operating in shear and longitudinal acoustic modes, respectively. Each resonator was mounted on the bottom of a 30 mL liquid container. During the experiments, the container was filled with the suspension under study in such a way that the resonator was completely immersed in the suspension, and the frequency dependences of the real and imaginary parts of the electrical impedance of the resonator were measured. As a result, the shear modulus of the elasticity and shear coefficient of the viscosity of the studied suspensions were determined. The material constants of the suspensions were found by fitting the theoretical frequency dependences of the real and imaginary parts of the electrical impedance of the resonator to the experimentally measured ones, which was calculated using Mason's equivalent circuit. As a result, the dependencies of the density, shear modulus of elasticity, shear viscosity coefficient, and velocity of the shear acoustic wave on the volume concentration of the diamond particles were constructed.

Polishing Performance and Removal Mechanism of Core-Shell Structured Diamond/SiO2 Abrasives on Sapphire Wafer.

Corrosive and toxic solutions are normally employed to polish sapphire wafers, which easily cause environmental pollution. Applying green polishing techniques to obtain an ultrasmooth sapphire surface that is scratch-free and has low damage at high polishing efficiency is a great challenge. In this paper, novel diamond/SiO2 composite abrasives were successfully synthesized by a simplified sol-gel strategy. The prepared composite abrasives were used in the semi-fixed polishing technology of sapphire wafers, where the polishing slurry contains only deionized water and no other chemicals during the whole polishing process, effectively avoiding environmental pollution. The experimental results showed that diamond/SiO2 composite abrasives exhibited excellent polishing performance, along with a 27.2% decrease in surface roughness, and the material removal rate was increased by more than 8.8% compared with pure diamond. Furthermore, through characterizations of polished sapphire surfaces and wear debris, the chemical action mechanism of composite abrasives was investigated, which confirmed the solid-state reaction between the SiO2 shell and the sapphire surface. Finally, applying the elastic-plastic contact model revealed that the reduction of indentation depth and the synergistic effect of chemical corrosion and mechanical removal are the keys to improving polishing performance.

Role of Hydrogen Flow Rate for the Growth of Quality Nanodiamonds via Microplasma Technique

Nanodiamonds (NDs) were prepared by utilizing a microplasma facility. Ethanol and Argon mixture was decomposed in microplasma for the formation of NDs. In order to stabilize the NDs growth, the Hydrogen was added in the mixture during the growth process. Hydrogen flow rate was changed from 1 to 5 L/min to find out the optimum flow rate for the growth of stabilized NDs. The experiments were also performed without the introduction of Hydrogen for the comparison. TEM and Raman analysis confirm that the highest quality diamonds are obtained at Hydrogen flow rate of 3L/min. In the case of Hydrogen, the SAED patterns reveal the presence of pure diamond phases which in turn envisages the etching of graphitic shell. TEM micrographs reveal that the size of NDs produced at 3 L/min Hydrogen flow rate ranges from 1~20 nm which is much smaller than that of without Hydrogen (4-32 nm). EDX spectra also disclose the Carbon peak with a maximum intensity for 3 L/min flow rate. UV-Visible and PL spectroscopy analysis indicate the presence of Nitrogen-Hydrogen defect centers. However, a decrease in defect density at 3L/min indicates the production of improved quality NDs. FTIR also verifies the removal of graphitic shell around NDs at 3 L/min flow rate. Moreover, high hydrogen flow rates effectively incorporate nitrogen vacancy (NV) defects. Prepared NDs offer emerging applications in optoelectronic systems, biomedical nanodevices and nanoscale sensors for electric field, magnetic field & temperature.

Effect of stress state on graphitization behavior of diamond under high pressure and high temperature

Pure diamond powder and mixed powder of diamond and sodium chloride were treated at high pressures (5 GPa and 10 GPa) and high temperatures (1000–2700 °C), and then the graphitization behavior of diamond powder under non-hydrostatic (pure diamond powder) and quasi-hydrostatic (mixed powder of diamond and sodium chloride) compression was quantitatively studied by analyzing the X-ray diffraction peaks' area of treated samples. It is found that the graphitization under non-hydrostatic compression is much more easily triggered by heating due to the heterogeneous stress distribution within the diamond grains. Under the quasi-hydrostatic compression of 5 GPa, the starting graphitization temperature is about 1600 °C, which is 300 °C higher than that under non-hydrostatic compression. Under a pressure of 10 GPa, graphitization could be observed after pure diamond powder was treated at 1400 °C, but no graphitization occurred in the mixed powder even after a high temperature treatment at 2300 °C. Optimizing the stress distribution among diamond grains by the mixing of grain-size can significantly reduce the graphitization at high temperature even under non-hydrostatic compression.

INTERFACE MODIFICATION OF SUBSTRATE FOR ENHANCING ADHESIVE STRENGTH OF CVD DIAMOND COATING BY SOLID PARTICLES

The strong adhesive strength is essential for the widespread applications of diamond coating in the mechanical field. In this paper, a novel method combining conventional chemical vapor deposition (CVD) diamond technique with solid particles was proposed to modify the interface material properties of substrate to improve the adhesive strength of the diamond coating. Prior to deposition, wet dispersion was adopted to uniformly distribute solid particles on the substrate, with which the diamond coatings with the WC, TiC and BN particles embedded at the interface were fabricated on Co-cemented tungsten carbide (WC-Co) substrate. In addition, the pure diamond coating was also fabricated for comparison. The as-deposited diamond coatings were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. The results indicated that the diamond coating with TiC exhibited the highest residual stress, which may be due to the larger lattice mismatch between TiC and diamond as compared to WC and BN. The indentation test suggested that WC and BN particles were favorable for the improvement of the adhesive strength and the crack resistance of diamond coating, while this phenomenon was not observed in the diamond coating with TiC particle. This might be caused by the large lattice parameter, high lattice mismatch, and high thermal expansion coefficient mismatch of TiC as compared with diamond. Furthermore, the lattice parameter of additional particles might be an important factor to determine whether or not the adhesive strength of diamond coating can be enhanced, because it determined the compressive stress or tensile stress generated inside diamond coating. Hence, interface modification of substrate by dispersing the solid particles with low lattice parameter or similar material properties of diamond may be an effective and convivence approach to improve the adhesive strength of the diamond coating.