Diamond Morphology Research Articles

Phase-field modeling of facet growth of diamond using a modified anisotropic coefficient of interfacial energy

In the present work, a modified anisotropic coefficient of interfacial energy is used to simulate the anisotropic facet crystal growth along non-orthogonal directions by phase-field method. The modified anisotropic coefficient of interface anisotropy is simulated and evaluated against the theoretical prediction of equilibrium shape. The simulation results are compared between the modified form and classic form. Subsequently, the modified anisotropic coefficient is employed to simulate the Wulff construction of facet growth of diamond, encompassing both pristine diamond and diamond with reconstructed surfaces. The dynamics of diamond morphology and the reconstructed surface area and proportion are thoroughly evaluated, demonstrating agreement with experimental records. The effect of the reconstruction surface on the growth of diamond grain is analyzed in terms of the total energy reduction, and the range of interfacial energies for more stable diamond reconstructions is also summarized. By introducing the modified anisotropic coefficient, anisotropic facet growth can be described and the simulation results are verified both theoretically and experimentally.

Colossal Core/Shell CdSe/CdS Quantum Dot Emitters.

Single-photon sources are essential for advancing quantum technologies with scalable integration being a crucial requirement. To date, deterministic positioning of single-photon sources in large-scale photonic structures remains a challenge. In this context, colloidal quantum dots (QDs), particularly core/shell configurations, are attractive due to their solution processability. However, traditional QDs are typically small, about 3 to 6 nm, which restricts their deterministic placement and utility in large-scale photonic devices, particularly within optical cavities. The largest existing core/shell QDs are a family of giant CdSe/CdS QDs, with total diameters ranging from about 20 to 50 nm. Pushing beyond this size limit, we introduce a synthesis strategy for colossal CdSe/CdS QDs, with sizes ranging from 30 to 100 nm, using a stepwise high-temperature continuous injection method. Electron microscopy reveals a consistent hexagonal diamond morphology composed of 12 semipolar {101̅1} facets and one polar (0001) facet. We also identify conditions where shell growth is disrupted, leading to defects, islands, and mechanical instability, which suggest synthetic requirements for growing crystalline particles beyond 100 nm. The stepwise growth of thick CdS shells on CdSe cores enables the synthesis of emissive QDs with long photoluminescence lifetimes of a few microseconds and suppressed blinking at room temperature. Notably, QDs with 80 and 100 CdS monolayers exhibit high single-photon emission purity with second-order photon correlation g(2)(0) values below 0.2.

Closed-form analytical relationships for pentamode metamaterials

Pentamode metamaterials are a class of extremal materials exhibiting fluid-like mechanical behavior. The mechanical properties of pentamode metamaterials arise from their unique micro-architecture, rather than their constituent material. In this research, we present closed-form analytical relationships for the elastic modulus and Poisson’s ratio of pentamode lattice structures with double-cone struts based on cubic diamond morphology. To validate our analytical solutions, we performed numerical simulations and experimental tests, which confirmed the accuracy of the derived relationships. Our findings indicate that increasing the smaller diameter (d) and the larger-to-smaller diameter ratio (α) of the double-cones increases the elastic modulus of pentamode metamaterials. However, within the considered range of d and α, the Poisson’s ratio is nearly constant and lies within the range of approximately 0.5. These analytical relationships provide valuable insight into the mechanical behavior of pentamode metamaterials, which can aid in the design and optimization of new materials with unique properties.

Controlling the morphology of polycrystalline diamond films via seed density: Influence on grain size and film texture

Controlling the morphology of polycrystalline diamond (PCD) films is crucial for various applications, including thermal management and quantum sensors. PCD films are typically produced by plasma-enhanced chemical vapor deposition on substrates seeded with nanodiamonds. Different film morphologies can be achieved by controlling growth rates of crystal-forming facets, which is commonly managed through deposition temperature and hydrocarbon concentration in the plasma. However, the impact of seed density on film morphology remains largely unexplored. In this study, we observed that reducing seed density on silicon substrates has a similar effect on PCD film morphology as increasing hydrocarbon concentration in the plasma. Specifically, as seed density decreases, deposition rate increases, and film texture transitions from (1 1 1) to (1 0 0), followed by the formation of large grains with (1 0 0) facets surrounded by clusters of small grains. These changes were observed using electron microscopy, Raman spectroscopy, and X-ray diffraction. To explain our results, we hypothesize that the silicon–plasma interface surrounding the growing diamond seeds acts as a diamond precursor source. Our proposed explanation requires relatively long precursor migration lengths compared to those assumed in standard diamond deposition theory. Finally, we also propose two new mechanisms for diamond precursor adsorption based on well-established physical phenomena and recent publications. Our findings may open new avenues in diamond research, applicable not only to polycrystalline but also to single-crystal diamond deposition.

Fragmentation behavior of diamond particles with different particle size and ratio under high pressure compaction

The fragmentation behavior of mixed diamond particles with different grain sizes under high pressure is important to guide the design of raw material diamond powder ratios and obtain high performance polycrystalline diamond compact (PDC). In this study, five different grain size diamond powders commonly used for the preparation of PDCs were selected, and the single and mixed diamond particles were cold pressed at 7.7 GPa for 60s. The particle size variations of diamond powders with different principal particle sizes and ratios after cold pressing were analyzed by a laser particle size scanner, and the crushing behavior was observed by scanning electron microscopy. The results showed that the larger the initial grain size, the more significant the degree of fragmentation under high pressure. The crushing morphology of fine-grained diamond showed that the majority of grains were locally fractured at the edge, and the peak of the grain size distribution curve was shifted to the left after high pressure. In comparison, the coarse-grained diamond produced a large number of cracks and fractures along the weak grain boundaries under high pressure, which generated a large number of fine grains, and multiple secondary peaks in the particle size distribution curve. The addition of fine-grained diamond as filler particles to coarse-grained diamond could inhibit the crushing phenomenon to some extent. As the proportion of filler particles increased, the crushing of coarse-grained diamond was inhibited more significantly. When the proportion of filler particles was 30 wt%, the crushing under high pressure was greatly limited, especially when the size difference between filler particles and main particles was large. The results of the cold pressing experiments provided preliminary evidence that 30 wt% of filler particles were too high, and that a better ratio should be between 10 wt% and 20 wt%.

Dissolution of synthetic diamonds to produce morphologies similar to natural diamonds: an experimental study

Abstract The results on dissolution of flat-faced synthetic diamond crystals of octahedral habit in an Fe-Ni-S melt at 4.0 GPa and 1 400°C are presented. It has been established that the resulting diamond morphology is similar to some natural kimberlitic diamonds and follows the particular sequence: flat-faced octahedron – laminar octahedron – trisoctahedroid with parallel striations in the <110> direction (“O1-D1”). Comparing the obtained results with earlier experimental works it is concluded that oxidisation of octahedral diamonds by means of ditrigonal etching layers and formation of tetrahexahedroid form is a result of diamond interaction with the fluidised kimberlite magma. We suggest that formation of octahedral diamonds with trigonal etching layers does not occur in kimberlite magma, and that diamonds of the O1-D1 morphological series avoided natural oxidation in kimberlite magma, but, like flat-faced octahedrons, were enclosed within xenoliths. Most probably, this dissolution process took place in the mantle prior to their capture by kimberlite. The results support an idea that metal-sulphide melts could be considered not only as a growth place for the world’s largest Cullinan-like diamonds found in South Africa (CLIPPIR type), but also as a mantle agent producing crystal morphologies typical for common kimberlitic diamonds: it depends upon carbon content in metal-sulphide melt – with supersaturation of the melt, the growth of diamond occurs while at the undersaturation conditions the dissolution begins.

Effect of SPS frequency on the transformation of diamond to graphite in WC-Co composite

(WC–6wt%Co)/5Vol% diamond composites were successfully fabricated at 1150–1300 °C and 40 MPa for 5 minutes under the thermodynamically unstable conditions of the Spark Plasma Sintering method. The influence of on-off time, and frequency of the DC pulse of SPS on diamond stability, microstructure, and mechanical properties of WC–Co/diamond composites were investigated. The diamond particles are strongly bounded with the cemented carbide matrix by a transition layer composed of a solid solution of tungsten and carbon in cobalt. The amount of graphitization was low in the sintered composites at 1300 °C due to the low temperature and short sintering time. Reduction of SPS frequency effectively inhibited graphite preformation, and no graphite was detected in the sintered composites at 1150 °C. Diamond morphology was not affected during SPS as examined by SEM, and Raman scattering spectra. The uniform dispersion of the super-hard diamond phase in matrix which good bonded, caused the high hardness, fracture toughness and flexural strength of this composite. The reduction of pulse frequency of SPS leads to a significant enhancement in the hardness, fracture toughness, and flexural strength of the composites, overcoming the graphitization of diamond typically observed in SPS. The sample sintered with 4 Hz showed simultaneously the highest hardness (23.6 GPa), the highest fracture toughness (24.6 MPa.m½), and the highest flexural strength (2050 MPa).

Effect of Diamond Morphology on Construction of Thermal Conduction Path in Flexible Thermal Interface Materials

Effect of Diamond Morphology on Construction of Thermal Conduction Path in Flexible Thermal Interface Materials

Laser induced diamond/graphite structure for all-carbon deep-ultraviolet photodetector

Graphite was formed by in-situ structural conversion from sp3 to sp2 hybridized carbon via KrF excimer. The surface morphology of diamond was changed to nanoparticles after laser irradiation. Raman peak related to amorphous carbon emerged after laser treatments with energy of 10 ∼ 25 mJ cm−2. X-ray photoelectron spectroscopy exhibited that surface graphitization could take place under low laser energy of 2 mJ cm−2. The structural transformation of diamond after laser irradiation was further studied by cross-sectional transmission electron microscopy (TEM) analysis. The TEM results displayed that the diamond/graphite interface was gradually transformed from diamond to graphite, and the transformation process was verified by molecular dynamics simulations. The specific contact resistance of 7.83 × 10-5 Ω cm2 for the diamond/graphite structure was acquired by transmission line model. Meanwhile, the barrier height of the graphite/diamond contact was obtained to be 0.54 eV. In the end, an all-carbon deep-ultraviolet photodetector with diamond/graphite structure was developed. The all-carbon photodetector exhibited relatively high responsivity of 15 mA/W under 220 nm illumination, and a fast transient response of 86 μs.

Is the Imposition of Diamond Morphology on Mineral Inclusions a Syngenetic or Post-Genetic Process with Respect to Diamond Formation?

Is the Imposition of Diamond Morphology on Mineral Inclusions a Syngenetic or Post-Genetic Process with Respect to Diamond Formation?

Facile Preparation of Porous Diamond Films via Microwave Plasma Based on Metal Particles Heterogeneous Catalysis Etching

The porous diamond film was fabricated via a self-developed microwave plasma chemical vapor deposition (MPCVD) system in H2/Ar plasma by utilizing micrometer-sized diamond films coated with nickel as starting material. SEM and Raman spectroscopy were used to evaluate the evolution of the morphology and sp3 phase of porous diamond with changes in the surface treatment process parameters, including the etching temperature and time. The results indicate that once the etching temperature exceeds 700 °C, the pitting etching phenomenon can be observed on the surface of diamond film. In a certain range, increasing the etching time increases the depth of surface holes on diamond film, whereas the microporous density exhibits an inverted parabolic change pattern. The porous diamond films with uniform pores structure can be obtained by adopting optimal etching process parameter when the H2/Ar plasma temperature is determined at 900 °C for 30 min. The porous formation mechanism of diamond film is attributed to the nickel particles’ heterogeneous catalysis behavior, which promotes the transition route from diamond phase to graphite phase, followed by the preferential etching of graphite phase by H2/Ar plasma.

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.

Surface Morphology and Properties of Diamond Etched by MnO2 Powder

Surface Morphology and Properties of Diamond Etched by MnO2 Powder

Caught in the act: Diamond growth and destruction in the continental lithosphere

Abstract Diamonds can form within eclogite (remnants of ancient subducted oceanic crust) in the subcontinental lithospheric mantle (SCLM), pieces of which may then be transported to the surface as xenoliths in kimberlites. These diamond-bearing xenoliths offer a rare opportunity to study diamonds in their host lithology. The morphology and surface features of diamonds record evidence of attack by diamond-aggressive melts/fluids, which results in resorption, rounding, and destruction of octahedral growth forms. The location and timing of such diamond-destruction processes remain controversial, and the kimberlite magma itself is often considered to be the primary culprit. We used X-ray computed tomography scanning to present a view of diamond morphology and distribution within 24 diamondiferous eclogites in unprecedented detail. These scans clearly capture diamond growth and destruction that occurred within the SCLM, prior to kimberlite entrainment. We show that euhedral diamonds in these eclogites are predominantly step-faced octahedra. This morphology is preserved even when the diamonds are exposed at the surface of the eclogites, indicating that kimberliteinduced resorption was not significant. Six eclogites contain only rounded diamonds with no distinct crystal faces, and their exposed surfaces on the exterior of the xenoliths are highly irregular, indicating diamond-destruction in the SCLM. In three cases, single xenoliths host both resorbed diamonds and step-faced octahedra, indicating multiple metasomatic events, some of which were diamond-aggressive and others diamond-friendly. These diamondiferous xenoliths provide snapshots of diamond growth and destruction in the SCLM, caught in the act.

Geometric-kinematic model for reinforced concrete core drilling

Since diamond-impregnated tools have a big share on tools for construction, the development of more efficient ones is necessary in the near future. The drilling speed performance is one of the concerns during the development of new diamond-impregnated segments in concrete core drilling. However, observations only based on experiments can be very costly, considering a quite demanding amount of material and workforce. One of the solutions to overcome these issues is the development of a geometric-kinematic model (containing a kinematic process model, material model, and drilling force model) to simulate the tangential and normal forces of diamond-impregnated segments in core drilling process. Such model is regularly used in the literature for the simulation of a bonded-abrasives process. The main purpose of the geometric-kinematic model is to generate simulations for the concrete core drilling for the tool performance estimation. This allows an evaluation of the geometric characteristics’ (diamond morphology, orientation, size, and positioning) impact of diamond-impregnated segments and of drilling parameters on the drilling force. The geometric-kinematic model will use detailed segment descriptions with stochastic and deterministic variables. The drilling simulation delivers a consistent drilling forces prediction in Utliberg concrete and ASTM A615 steel at the frequently used core drilling feed window. Besides, the model shows the competence to evaluate the impact of a diamond layer characteristics (diamond size and number of rows), allowing the comparison of distinct diamond arrangements designs between each other.

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.

Analysis of diamond wear morphology and segment wear evolution during the process of hard granite sawing

Diamond circular sawblade has been widely used in hard granite processing. In this study, the wear mechanism and wear evolution of the diamond segment were investigated. The wear morphologies of diamond grits were classified as emerging diamond, whole diamond, crack diamond, blunt diamond, micro-fractured diamond, macro-fractured diamond, wear flat diamond, and pull-out diamond, which is based on sufficient observation data. The main form of diamond wear is fracture. The fracture morphology of diamond grit dominates by cleavage, which is brittle transgranular fractures, and the microscopic features are fracture steps and river-like patterns. Since the {111} crystal plane has the largest interplanar spacing among all the crystal planes, cleavage fractures tend to occur on this crystal plane. Through the scratches and pitting on the diamond grit surface, it proved that the wear process is a mixed type of two-body wear and three-body wear. However, some diamond grits exhibit special fracture morphology and are without the typical characteristics of cleavage fracture. Combined with internal factors (including microstructures and internal defect) and external factors (including chip flow, thermal load and mechanical load), the mechanism of various diamond wear morphologies and segment wear phenomena observed in the sawing experiment is clarified. Finally, the evolution process of the diamond failure and segment wear are described. The research systematically revealed the mechanism of segment wear and the fracture morphology characteristics of diamond grits in the sawing granites, which can further improve the understanding of segment wear and provide theoretical guidance for segment design.

Electroplating technology of suspended diamond particles surface based on rotating electrode

In view of the difficulty of fine-grained diamond surface electroplating, a method of diamond barrel plating based on rotating electrode is proposed, which is to make the cathode rotate during the rolling process. The mechanism of dynamic contact between fine-grained particle in suspension electroplating solution and electrode is analyzed. And the force model and motion equation of diamond abrasive particles in electroplating fluid were established. The single factor experiments were carried out to study the effects of the rotation speed of the plating bottle, the rotation speed of the electrode, and the diameter of the diamond particles on the weight gain rate and the surface morphology of the suspended fine-grained diamond. The results show that the contact time between the suspended particles and the electrode can be increased when the electrode direction is opposite to that of the plating bottle, and the rotation speed should be matched with the flow rate of the plating solution to obtain a good electroplating result. The weight gain rate decreased with the decrease of particle size. For 25–36 μm diamond particles, the optimal process parameters are as follows: the rotation speed of plating bottle is 20 r/min, the electrode speed is 50 r/min, and the electrode turns opposite to the plating bottle. The smallest size range of diamond particles that can be electroplated by this method is 5–10 μm.

3D Tomographic Analysis of the Order-Disorder Interplay in the Pachyrhynchus congestus mirabilis Weevil.

The bright colors of Pachyrhynchus weevils originate from complex dielectric nanostructures within their elytral scales. In contrast to previous work exhibiting highly ordered single‐network diamond‐type photonic crystals, here, it is shown by combining optical microscopy and spectroscopy measurements with 3D focused ion beam (FIB) tomography that the blue scales of P. congestus mirabilis differ from that of an ordered diamond structure. Through the use of FIB tomography on elytral scales filled with platinum (Pt) by electron beam‐assisted deposition, it is revealed that the red scales of this weevil possess a periodic diamond structure, while the network morphology of the blue scales exhibit diamond morphology only on the single scattering unit level with disorder on longer length scales. Full wave simulations performed on the reconstructed volumes indicate that this local order is sufficient to open a partial photonic bandgap even at low dielectric constant contrast between chitin and air in the absence of long‐range or translational order. The observation of disordered and ordered photonic crystals within a single organism opens up interesting questions on the cellular origin of coloration and studies on bio‐inspired replication of angle‐independent colors.

Diamond Supercapacitors: Towards Durable, Safe, and Biocompatible Aqueous-Based Energy Storage.

Durable and safe energy storage is required for the next generation of miniature bioelectronic devices, in which aqueous electrolytes are preferred due to the advantages in safety, low cost, and high conductivity. While rechargeable aqueous batteries are among the primary choices with relatively low power requirements, their lifetime is generally limited to a few thousand charging/discharging cycles as the electrode material can degrade due to electrochemical reactions. Electrical double layer capacitors (EDLCs) possess increased cycling stability and power density, although with as-yet lower energy density, due to quick electrical adsorption and desorption of ions without involving chemical reactions. However, in aqueous solution, chemical reactions which cause electrode degradation and produce hazardous species can occur when the voltage is increased beyond its operation window to improve the energy density. Diamond is a durable and biocompatible electrode material for supercapacitors, while at the same time provides a larger voltage window in biological environments. For applications requiring higher energy density, diamond-based pseudocapacitors (PCs) have also been developed, which combine EDLCs with fast electrochemical reactions. Here we inspect the properties of diamond-related materials and discuss their advantages and disadvantages when used as EDLC and PC materials. We argue that further optimization of the diamond surface chemistry and morphology, guided by computational modelling of the interface, can lead to supercapacitors with enhanced performance. We envisage that such diamond-based supercapacitors could be used in a wide range of applications and in particular those requiring high performance in biomedical applications.