Single Diamond Research Articles

Retention and interfacial failure mechanism of single diamond grains in resin-bonded grinding tools

Abrasive grains and the associated bonding agent are the two significant components in the manufacturing of fixed abrasive machining tools. The material properties and interfacial bonding behavior between the grains and the bonding matrix determine machining performance. In precision machining processes with diamond abrasives, the primary failure modes of fixed abrasive tools are grain dislodgement and premature loss, leading to abrupt change in machining load and ultimately causing inaccurate and inefficient machining performance. This study develops a comprehensive model for understanding abrasive grain retention and interfacial failure mechanisms in resin-bonded diamond tools. Finite element analysis of a single diamond grain embedded in a resin matrix was conducted to examine the influence of the grain shape, protruding height, and orientation angle on critical interfacial failure force. A series of single diamond scratching experiments validated the model, revealing that the maximum retention force reached 43.56 N for grains with a 0.9 mm protruding height and a 60° orientation angle. The results also show that, within a specific grain size range, grain shape—quantified by the sphere deviation coefficient proposed in this paper, has the greatest impact on retention and failure behavior. Protruding height plays a secondary role, while the contribution of orientation angle is minimal. These findings provide valuable insights for the design, manufacture, and optimization of precision abrasive machining tools, particularly for applications requiring high precision and reliability.

Diamond Surfaces with Lateral Gradients for Systematic Optimization of Surface Chemistry for Relaxometry - a Low-Pressure Plasma-Based Approach.

Diamond is increasingly popular because of its unique material properties. Diamond defects called nitrogen vacancy (NV) centers allow for measurements with unprecedented sensitivity. However, to achieve ideal sensing performance, NV centers need to be within nanometers from the surface and are thus strongly dependent on the local surface chemistry. Several attempts have been made to compare diamond surfaces. However, due to the high price of diamond crystals with shallow NV centers, a limited number of chemical modifications have been studied. Here, we developed a systematic method to investigate the continuity of different local environments with varying densities and natures of surface groups in a single experiment on a single diamond plate. To achieve this goal, we used diamonds with a shallow ensemble of NV centers and introduced a chemical gradient across the surface. More specifically, we used air and hydrogen plasma. The gradients were formed by a low-pressure plasma treatment after masking with a right-angled triangular prism shield. As a result, the surface contained gradually more oxygen/hydrogen toward the open end of the shield. We then performed wide-field relaxometry to determine the effect of surface chemistry on the sensing performance. As expected, relaxation times and thus sensing performance indeed vary along the gradient.

Response Matching for Generating Materials and Molecules.

Diffusion models have recently emerged as powerful tools for the generation of new molecular and material structures. The key insight is that the noise in these models is related to the response of the atoms to displacement, and the denoising step is thus analogous to the geometry relaxation of atomistic systems starting from a random structure. Building on this, we present a generative method called Response Matching (RM), which leverages the fact that each stable material or molecule exists at the minimum of its potential energy surface. Any perturbation induces a response in energy and stress, driving the structure back to equilibrium. Matching this response is closely related to score matching in diffusion models. Another important aspect of state-of-the-art diffusion models is the incorporation of physical symmetries such as translation, rotation, and periodicity. RM employs a machine learning interatomic potential and random structure search as the denoising model, inherently respecting these symmetries and exploiting the locality of atomic interactions. RM handles both molecules and bulk materials under the same framework. Its efficiency and generalization are demonstrated on three systems: a small organic molecular data set, stable crystals from the Materials Project, and one-shot learning on a single diamond configuration.

Material removal characterization during axial ultrasonic vibration grinding SiCp/Al composites with a single diamond grain

Material removal characterization during axial ultrasonic vibration grinding SiCp/Al composites with a single diamond grain

Block Copolymer-Directed Single-Diamond Hybrid Structures Derived from X-ray Nanotomography.

Block copolymers are recognized as a valuable platform for creating nanostructured materials. Morphologies formed by block copolymer self-assembly can be transferred into a wide range of inorganic materials, enabling applications including energy storage and metamaterials. However, imaging of the underlying, often complex, nanostructures in large volumes has remained a challenge, limiting progress in materials development. Taking advantage of recent advances in X-ray nanotomography, we noninvasively imaged exceptionally large volumes of nanostructured hybrid materials at high resolution, revealing a single-diamond morphology in a triblock terpolymer-gold composite network. This morphology, which is ubiquitous in nature, has so far remained elusive in block copolymer-derived materials, despite its potential to create materials with large photonic bandgaps. The discovery was made possible by the precise analysis of distortions in a large volume of the self-assembled diamond network, which are difficult to unambiguously assess using traditional characterization tools. We anticipate that high-resolution X-ray nanotomography, which allows imaging of much larger sample volumes than electron-based tomography, will become a powerful tool for the quantitative analysis of complex nanostructures and that structures such as the triblock terpolymer-directed single diamond will enable the generation of advanced multicomponent composites with hitherto unknown property profiles.

Study on the grindability and removal mechanism of high volume fraction SiCp/Al composites based on single diamond grain grinding

Study on the grindability and removal mechanism of high volume fraction SiCp/Al composites based on single diamond grain grinding

Investigation of Single Grain Grinding of Titanium Alloy Using Diamond Abrasive Grain with Positive Rake Angle

Traditional grinding, which is predominantly performed with a negative rake angle (NRA), can be transformed into grinding with a positive rake angle (PRA) by employing femtosecond pulsed laser technology to modify the apex angle of the grains to be less than 90°. This innovative approach aims to reduce grinding forces and grinding temperatures while improving the surface quality of typical hard-to-machine materials. To assess the performance of PRA single grain grinding and to investigate the underlying mechanisms, the finite element simulation software ABAQUS 6.14 was employed to model the grinding of Ti6Al4V titanium alloy with a single diamond abrasive grain. The dependence of grinding force and temperature in single grain grinding with a PRA or an NRA under different grinding parameters was studied and compared. PRA and NRA single diamond grain grinding experiments on Ti6Al4V alloy were carried out, with grinding forces measured using a dynamometer and compared with the simulation results. The grinding surface morphology and surface roughness were observed and measured, and a comparison was made between PRA and NRA grinding. The results indicated that in single diamond grain grinding, transforming to a PRA significantly enhances grinding performance, as evidenced by reduced grinding forces, lower temperatures, improved surface morphology, and decreased surface roughness. These findings suggest that PRA single diamond grain grinding offers substantial benefits for the precision machining of hard-to-machine materials, marking a step forward in optimizing surface finishes.

Extrastrong aggregates of detonation nanodiamonds: structure and formation

Commercially available powders of detonation nanodiamond (DND) contain extrastrong 20–120 nm sized aggregates, in an amount sometimes up to 50% by mass sustainable to the conventional methods of deaggregation. It demonstrates the significant inhomogeneity structure of products of detonation synthesis and noticeably reduces the yield of 4.0 − 5.0 nm individual isolated particles obtained from DNDs. The presence of these aggregates is obviously related to the some essential features of detonation synthesis. This work presents the results of studying such extrastrong aggregates from DND powder. In order to determine the structure we applied the heat treatment of samples in vacuum and in air, and the subsequent study using Raman spectroscopy, X-ray diffraction, UV–vis spectroscopy, analysis of specific surface and dynamic light scattering (DLS). As a result, a structural model of extrastrong aggregates is proposed. It is shown that extrastrong aggregates consist notably of relatively large (∼8.0 nm) single crystalline diamond particles bonded by facets and covered by smaller 4.5 − 3.0 nm and less crystalline grains. Our results add the details for description of formation processes of diamond particles and aggregates in detonation synthesis from excessive carbon in the composition of explosives.

Influence of grit friability and grit distribution pattern on dry grindability of WC-6Co by single layered brazed diamond wheels

Single-layered brazed diamond wheels, composed of uni-layered diamond grits, metal binder, and metal core, have potentially good thermal conductivity to dissipate heat from the grinding zone. Considering this characteristic feature, the current study aims to explore the performance and suitability of various indigenously developed single-layered brazed diamond tools in plunge-grinding of fine-grained cemented carbide in a challenging dry atmospheric condition. Single crystalline synthetic diamond particles with different strengths and friability were utilized to develop indigenous diamond wheels with random and patterned grit distribution. The current study explores the role of diamond-grit friability and grit distribution patterns to identify the most suitable wheel for dry grinding of WC-6Co composite. Detailed analysis of the wheel morphology, signifying the fracture behavior of the diamond grit used, justified the variation in the grinding forces, tool life, and ground surface roughness. Irrespective of the grit and distribution type, all wheels showed saturation of dynamic changes in work-surface topography with the number of passes and more sensitively to the degree of increase of uncut chip thickness. Grinding wheels containing friable diamond grits with irregular granular structures performed better than the high-strength, cubo-octahedral grains during the dry grinding experiments.

Study on isotropic design of triply periodic minimal surface structures under an elastic modulus compensation mechanism

The energy absorption characteristics of the triply periodic minimal surfaces (TPMS) structure may vary significantly due to the anisotropy under multi-directional loading conditions. To address this issue effectively, an isotropic design strategy based on a precise elastic modulus compensation mechanism for different TPMS lattices is proposed. This strategy involves combining a TPMS lattice with a high elastic modulus in the axial direction with another TPMS lattice featuring a low elastic modulus in the same direction, leveraging the complementary effects of elastic modulus to achieve isotropy. The relationship between the relative density and the elastic modulus of six types of TPMS lattices is analyzed through homogenization simulation and finite element analysis. Mathematical expressions are then fitted using the Gibson-Ashby model. Additionally, a Kriging model is employed to establish the relationship between the Zener anisotropy values of hybrid TPMS structures and the relative density of their component lattices. This enables the precise complementary effect of elastic modulus in different TPMS lattice structures, providing a widely applicable selection rule for achieving isotropy. Using the Primitive-Diamond hybrid lattice as an example, the Zener anisotropy index after hybridization is reduced by 65.2 % and 31.37 % compared to single Primitive and Diamond lattices, respectively.

Tribological properties of HFCVD diamond coatings over wide temperature range

Single and gradient multilayered diamond coatings, deposited on silicon nitride (Si3N4), were prepared by hot filament chemical vapour deposition. The tribological properties were evaluated in a wide temperature range (26 °C–300 °C), against Si3N4 ceramic balls, as the friction counterpart. The results showed that with the increase of temperature from 26 °C to 300 °C, the wear rate of NCD (nanocrystalline diamond) and GCD (gradient diamond) coatings rapidly increases. When the temperature reaches 300 °C, obvious cracks and detachment appear on the surface of the NCD coatings. Due to the special interlayer, the wear rate of the GCD coatings is lower than that of the NCD coatings. In the range of 26 °C to 100 °C, GCD exhibits excellent wear resistance and low friction coefficient due to its special gradient structure. When the temperature increases to 200 °C, NCD films with smaller grain sizes exhibit higher wear rates. From the wear morphology, it can be seen that cracks are generated in the NCD film, and as the temperature increases, the cracks continue to expand until the film spalling. GCD shows relatively good wear resistance at high temperatures. This study found that gradient multilayered diamond coatings exhibited superior wear resistance at high temperatures, compared with single-layer coatings tested in identical conditions.

Modulation of Diamond PN Junction Diode with Double-Layered n-Type Diamond by Using TCAD Simulation

This study proposed a novel double-layer junction termination structure for vertical diamond-based PN junction diodes (PND). The effects of the geometry and doping concentration of the junction termination structure on the PNDs’ electrical properties are investigated using Silvaco TCAD software (Version 5.0.10.R). It demonstrates that the electric performances of PND with a single n-type diamond layer are sensitive to the doping concentration and electrode location of the n-type diamond. To further suppress the electric field crowding and obtain a better balance between breakdown voltage and on-resistance, a double-layer junction termination structure is introduced and evaluated, yielding significantly improved electronic performances. Those results provide some useful thoughts for the design of vertical diamond PND devices.

Microstructural characterisation and compound formation in rapidly solidified SiGe alloy

Severe Ge segregation to grain boundaries was observed in a Si–14.2 at% Ge thermoelectric alloy rapidly solidified using a drop-tube facility, manifesting itself as a series of regions with uniform stoichiometric compositions. The step change in composition at the interface between adjacent regions was ascribed to the formation of different SiGe pseudocompounds and contradicted the accepted thermodynamic description of the SiGe system as a continuous random solid solution. Rapid solidification increased, rather than decreased, the inhomogeneity degree of the solid product, and the Ge content of the most Ge-rich regions was positively correlated with the cooling rate, which suggested the absence of solute trapping. The transmission electron microscopy/selected area electron diffraction analysis of the most Ge-rich regions revealed superlattice spots indicative of chemical ordering. However, simple chemical ordering within a single diamond cubic unit cell could not explain the fact that most stoichiometries had compositions that were multiples of 5 at% Ge, which indicated the presence of superstructural ordering.

Investigation of friction and wear behavior of titanium alloy-diamond based on the morphology evolution of single abrasive clusters

This study investigates the wear mechanism of single diamond clusters during flexible scratching of titanium alloys. High-temperature rotary friction and wear tests were conducted using a flexible abrasive tool with bonded single diamond clusters. The study examined the impact of normal loads, rotation speeds, and temperatures on cutting ability and wear in titanium alloys. The percentage of abraded area in the annular cross-section was proposed as an index for evaluating diamond wear. The results indicate that the primary factors affecting diamond cluster wear are normal load and temperature, while friction speed has a relatively minor impact. At a 2 N load, the abrasive grains exhibited abrasive blunt wear without causing obvious damage to the titanium alloy surface. However, at a 4 N load and a temperature of 110 °C, adhesive wear became dominant, resulting in localized damage and oxidative wear on the diamonds. The annular cross-section abrasive wear profile revealed a nearly 30% increase in abrasive grain wear area as the normal load and temperature increased. This study aims to improve understanding of the abrasive grain wear at various stages and lays the foundations for grinding and polishing large-sized, high-precision parts.

Reticular liquid crystal design: Controlling complex self-assembly of p-terphenyl rods by side-chain engineering and chirality

A series of K-shaped bolapolyphiles, consisting of a p-terphenyl core, two polar glycerol end-groups and a swallow-tailed alkyl side-chain were synthesized and investigated. By increasing the side-chain volume an astonishing variety of very different liquid crystalline (LC) phases was observed, ranging from a rectangular (Colrec/c2mm) and a square honeycomb (Colsqu/p4mm) via a highly complex zeolite-like octagon/pentagon honeycomb filled with additional strings of rod-bundles (ColrecZ/c2mm), a new 3D-hexagonal (R3‾c) double network phase, a double and even a single network cubic phase (double gyroid Cub/Ia3‾d and single diamond Cub/Fd3‾m, respectively) to a correlated lamellar phase (LamSm/c2mm). Though these LC structures are highly complex and there is a delicate balance of steric and geometric frustration determining the phase formation, there is only a small effect of permanent molecular chirality in the glycerol groups ((R,R)-configuration) on them, which is attributed to a slightly different packing density of uniformly chiral and racemic glycerols, but not to an effect of induced helicity. Compared to related T-shaped bolapolyphiles with a single linear n-alkyl side-chain, which form exclusively honeycomb phases, the complexity of self-assembly is enhanced for the K-shaped compounds due to a competition between the requirements of space filling, chain stretching and geometric frustration, and affected by the shape of the polar glycerol domains at the junctions.

Effect of dislocation defects on the nano-scratching process of 4H–SiC

To investigate the influence of defects on the damage mechanism of 4H–SiC, this study primarily conducted molecular dynamics simulations of a single diamond abrasive indentation process and carried out subsequent nanoindentation experiments on 4H–SiC samples. The simulation and experimental results were compared, and the force–displacement curves showed consistent trends. On this basis, the scratching simulation of an ideal material and a single diamond abrasive particle containing 4H–SiC with dislocation defects was carried out to study the influence of internal dislocation (screw dislocation and edge dislocation) in 4H–SiC and its position on the material damage mechanism during scratching, and the development and evolution of internal dislocation were further analyzed. The results reveal that the presence of internal dislocations in the material is one of the causes of the formation of dislocation loops.

Study on the material removal mechanism and the exit breakage of ultrasonic vibration-assisted grinding for microcrystalline glass

With the aim of solving problems such as exit breakage and surface microcracks during microcrystalline glass machining, an ellipsoidal erosion model is established by analyzing the motion trajectory and characteristics of single diamond grit in ultrasonic vibration-assisted grinding (UVAG), and the material removal volume of single diamond grit particles is obtained. A simulation model of UVAG of microcrystalline glass is established by the finite element method. The effect of process parameters such as rotational speed, grinding depth, feed rate on grinding force and workpiece edge stress has been investigated. The experiment of UVAG for microcrystalline glass is performed on a five-axis CNC machine with the same process parameters, and the surface morphology, surface roughness, and exit breakage sizes of microcrystalline glass are observed. The results show that with the increase in grinding depth, the average grinding force between the tool and the workpiece increases, and the proportion of material removal in a brittle fracture increases. As the rotational speed increases, the grinding force between the tool and the workpiece gradually decreases and results in an improvement in the surface quality of the workpiece. As the feed rate increases, the surface roughness increases by 16.76%, the width of the edge breakage increases by 109.19%, and the thickness of the edge breakage increases by 104.49%.

Topological phase transition and surface states in a non-Abelian charged nodal line photonic crystal

Abstract Topological charges of nodal lines in a multigap system are represented by non-Abelian numbers, and the Euler class, a topological invariant, can be used to explain their topological phase transitions, such as pair-annihilation of nodal lines. Up until now, no discussion of phase transitions of nodal lines in photonic crystals using the Euler class has been reported, despite the fact that the Euler class and topological phase transition have recently been addressed in metallic or acoustic crystals. Here, we show how the deformation of a photonic crystal causes topological phase transitions in the nodal lines, and the Euler class can be used to theoretically predict the nodal lines’ stability based on the non-Abelian topological charge theory. Specifically, by manipulating the separation between the two single diamond structures and the extent of structural distortion, we numerically demonstrate the topological transition of nodal lines, e.g., from nodal lines to nodal rings. We then demonstrate that the range of surface states is strongly influenced by the topological phase transition of nodal lines. Moreover, the Zak phase was used to explain the surface states’ existence.

Fretting and Fretting Corrosion Behavior of Additively Manufactured Ti-6Al-4V and Ti-Nb-Zr Alloys in Air and Physiological Solutions.

Additive manufacturing (AM) of orthopedic implants has increased in recent years, providing benefits to surgeons, patients, and implant companies. Both traditional and new titanium alloys are under consideration for AM-manufactured implants. However, concerns remain about their wear and corrosion (tribocorrosion) performance. In this study, the effects of fretting corrosion were investigated on AM Ti-29Nb-21Zr (pre-alloyed and admixed) and AM Ti-6Al-4V with 1% nano yttria-stabilized zirconia (nYSZ). Low cycle (100 cycles, 3 Hz, 100 mN) fretting and fretting corrosion (potentiostatic, 0 V vs. Ag/AgCl) methods were used to compare these AM alloys to traditionally manufactured AM Ti-6Al-4V. Alloy and admixture surfaces were subjected to (1) fretting in the air (i.e., small-scale reciprocal sliding) and (2) fretting corrosion in phosphate-buffered saline (PBS) using a single diamond asperity (17 µm radius). Wear track depth measurements, fretting currents and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis of oxide debris revealed that pre-alloyed AM Ti-29Nb-21Zr generally had greater wear depths after 100 cycles (4.67 +/- 0.55 µm dry and 5.78 +/- 0.83 µm in solution) and higher fretting currents (0.58 +/- 0.07 µA). A correlation (R2 = 0.67) was found between wear depth and the average fretting currents with different alloys located in different regions of the relationship. No statistically significant differences were observed in wear depth between in-air and in-PBS tests. However, significantly higher amounts of oxygen (measured by oxygen weight % by EDS analysis of the debris) were embedded within the wear track for tests performed in PBS compared to air for all samples except the ad-mixed Ti-29Nb-21Zr (p = 0.21). For traditional and AM Ti-6Al-4V, the wear track depths (dry fretting: 2.90 +/- 0.32 µm vs. 2.51 +/- 0.51 μm, respectively; fretting corrosion: 2.09 +/- 0.59 μm vs. 1.16 +/- 0.79 μm, respectively) and fretting current measurements (0.37 +/- 0.05 μA vs. 0.34 +/- 0.05 μA, respectively) showed no significant differences. The dominant wear deformation process was plastic deformation followed by cyclic extrusion of plate-like wear debris at the end of the stroke, resulting in ribbon-like extruded material for all alloys. While previous work documented improved corrosion resistance of Ti-29Nb-21Zr in simulated inflammatory solutions over Ti-6Al-4V, this work does not show similar improvements in the relative fretting corrosion resistance of these alloys compared to Ti-6Al-4V.

Cutting of structured surface on titanium component

Titanium (Ti) has been used as a medical application such as an artificial bone or a dental implant. Generation of textured surface on the dental implant is effective to improve the fusion characteristics of the living body cell. However, it is difficult to machine Ti, because the tool wear is extremely high and precision texturing by cutting is very difficult. In this study, the tool wear and surface roughness characteristics of Ti were tested and the tool materials such as single crystalline diamond, cBN, and WC were compared. Finally cutting tests of micro textured patterns were tried to generate and feasibility of the micro tool for the texturing was tested.