Diamond Particle Size Research Articles

Size effect in electron paramagnetic resonance spectra of impurity centers in diamond particles

The experiments have shown qualitative changes in electron paramagnetic resonance (EPR) spectra with decreasing average size of diamond particles from 100 μm to 18 nm. The characteristic hyperfine splitting in the EPR spectrum due to the interaction of an unpaired electron of a neutral impurity (nitrogen atom) in the diamond lattice with its nuclei disappears, and the resulting EPR spectrum is a superposition of two singlet Lorentzian lines. The reason for the observed effect is the indirect exchange interaction of electrons localized on bulk impurity centers through electrons localized on surface dangling bonds. Such an interaction of electrons localized on bulk centers becomes possible due to the resonant energy transfer between them. The transfer is result of the exchange interaction with electrons of surface centers. It is shown, that the energy of the indirect exchange interaction depends on the size of the diamond particle; therefore, the effect can be observed only in the case when particle size is smaller than a critical value R cr . The calculated value of the R cr based on the suggested model fitted well with experimental data.

Preliminary DOE Analysis of the Polishing Process of AISI P20 Mould Steel by Ultrasonic Erosion, Using Alumina and Diamond Hard Particles

The present work examines the surface finishing of AISI P20 tool steel, average hardness of 31.5 HRc, in the polishing process by ultrasonic erosion by loose abrasive particles. The study was performed in laboratory equipment, using various alumina and diamond hard particle sizes, ultrasonic frequencies and times. P20 steel is widely employed in the fabrication of polymer injection mould cavities due to its good machinability, homogeneous microstructure, hardness, corrosion and abrasion wear resistance. Mould cavity polishing processes represents the second longest manufacturing process time required to achieve the mould surface finish for good quality polymer parts. This time-consuming and largely artisanal polishing process contributes to high mould costs. Thus, several studies have been carried out in the literature to automate the mould polishing process, aiming to reducing surface roughness and polishing time. Present investigation was carried out in a surface cleaning equipment by the ultrasonic technique with commercial paste of abrasive hard particles used in mould polishing. Three factors were investigated: abrasive particle size, ultrasonic frequency and polishing time. The investigated alumina particle sizes were 0.05, 0.3, and 1.0 micron and the diamond particle size was 1.5 micron, which are the common sizes available in commercial paste for polishing metallography samples. The studied frequencies of the ultrasonic polishing process were 28 and 40 kHz, and the times of polishing process were 15, 30, and 45 minutes. Analysis of variance (ANOVA) of factor effects and two types of DOE analysis were employed to obtain the roughness Ra outcomes by empirical response surface modelling: 3x3 partial factorial design and 4x2 factorial design were used to investigate the surface roughness. The response surface modelling results indicate that the minimum surface roughness Ra of 0.21 micron obtained by ultrasonic polishing correspond to the frequency of 40 kHz, 20 minutes of polishing and alumina particle size of 0.7 microns.

Study on Polishing of Polycrystalline AlN Using Sol–Gel Polishing Tool

Polycrystalline aluminum nitride has extensive application prospects in substrate materials, insulating layer materials, and packaging materials. Polycrystalline aluminum nitride is sintered from powder. The traditional mechanical polishing method is easy to cause aluminum nitride grains to fall off to form pits. In this paper, to improve the polishing effect, based on the hydration of polycrystalline aluminum nitride, a sol-gel (SG) polishing tool was proposed to polish polycrystalline aluminum nitride. The polishing process was divided into rough polishing and fine polishing. The diamond particle size of the SG tool used for rough polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . The diamond particle size of the SG tool used for fine polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . Moreover, the polycrystalline AlN was processed with or without deionized water. The results showed that in the rough polishing stage, the material removal rate (MRR) of the polishing method without deionized water was four times higher than that of the polishing method with deionized water. However, in the fine polishing stage, the MRR of the polishing method with deionized water was slightly higher than that of the polishing method without deionized water. The results showed that mechanical removal is the primary material removal method in the rough polishing stage. In the fine polishing stage, hydration can improve the polishing effect of polycrystalline aluminum nitride.

Realizing ultrahigh thermal conductivity in bimodal-diamond/Al composites via interface engineering

Bulk materials with high thermal conductivity are fundamentally important to heat dissipation of high-power devices. In this study, a record high thermal conductivity of 1021 ± 34 W m−1 K−1 is achieved in the diamond/Al composites reinforced with bimodal diamond particles. Meanwhile, a coefficient of thermal expansion (CTE) of 3.40 ± 0.10 × 10−6 K−1 is achieved that is compatible with the semiconductors applied in the high-power devices (∼13.7% and ∼3.7% lower than CTE of a-GaN and c-GaN, respectively). The excellent thermal transport property stems from the increased heat transport channels and well-bonded diamond/Al interfaces. Importantly, the thermal conductivity can also be retained as high as 557 ± 17 W m−1 K−1 at 673 K in the diamond/Al composites, which could greatly widen their applications at high temperatures. This study indicates that concurrently achieving high interfacial thermal conductance, high diamond content, large diamond particle size, and high relative density is the essential way to realize ultrahigh thermal conductivity and diamond/Al composites are promising thermal management materials.

Drilling performance analysis of impregnated micro bit

Abstract. The cutting mechanical properties of impregnated diamond bit depend on the performance of its cutting elements. Aiming at the factors affecting the cutting element performance of impregnated diamond bit, the laboratory rock breaking experiment of impregnated micro bit is carried out. The results show that the breaking work ratio and unit wear first decrease and then increase with the increase of diamond particle size and concentration when drilling sandstone; the rock breaking efficiency and wear resistance are the highest when the concentration is 125 %. The breaking work ratio first decreases and then increases with the increase of diamond particle size when drilling limestone; the rock cutting efficiency is the highest when the concentration is 100 %. With the increase of diamond particle size, the breaking work ratio increases and the unit wear decreases when drilling granite; the rock cutting efficiency and wear resistance are the highest when the concentration is 150 %.

Diamond composites with Al-Co binder: Synthesis, structure, wear resistance

Wear-resistant diamond composites without a tungsten carbide substrate were obtained by sintering mixtures of micron and submicron diamonds at 7–8 GPa, 1550–1700 °C. Cobalt and aluminum powders were used as sintering activators in a proportion that ensures the formation of microstructure with binding phases in the form of intermetallic AlCo and carbide AlCo3C.The influence of the morphology and sizes of diamond particles on the microstructure and performance characteristics of composites is considered. The possibility of hard alloy turning with new composites from homogeneous mixtures in the quasi-ductile mode is demonstrated. The wear resistance of experimental samples with optimized initial composition and shape of diamond particles significantly exceeds the characteristics of high-quality commercial composites used in drill bits.

Influence of diamond parameters on microstructure and properties of copper-based diamond composites manufactured by Fused Deposition Modeling and Sintering (FDMS)

As an additive manufacturing technology, Fused Deposition Modeling and Sintering (FDMS) technology can give diamond tools some creative structures to be applied in more fields. To explore the influence of diamond parameters on diamond tools manufactured by FDMS, copper-tin-diamond composite samples with different diamond concentrations and particle size were prepared by FDMS technology in this paper. During the study, the morphological characteristics of diamond particles inside the samples during the debinding and sintering process are summarized and the influence of diamond parameters on the mechanical properties and structure of the samples was further explored. These influence laws were also verified by cutting experiments. The results show that most diamond particles are in an incomplete coating state because of the volatilization of the binder. Meanwhile, a higher concentration of diamond will lead to more pores and cavities in the samples; and the cavities can be connected to form a large area of cavity zone by the print layer, thereby resulting in a serious loss in the performance of the samples. On the other hand, a small diamond particle size can lead to agglomeration of particles. Subsequently, this will result in void generation and regional weakening of the holding ability. However, agglomeration and some pores or cavities will increase the wear of the matrix, expose more diamond particles, and finally improve the cutting efficiency of the dicing blades when cutting sapphire crystal. Excessive wear may reduce the life of the diamond tool, but improved of sharpness can be better applied in the field of precision machining.

Tailoring of Optical Properties of Methacrylate Resins Enriched by HPHT Microdiamond Particles.

Diamond particles have great potential to enhance the mechanical, optical, and thermal properties of diamond–polymer composites. However, the improved properties of diamond–polymer composites depend on the size, dispersibility, and concentration of diamond particles. In the present study, diamond–polymer composites were prepared by adding the microdiamond particles (MDPs) with different concentrations (0.2–1 wt.%) into polymers (acrylate resins) and then subjected to a photocuring process. The surface morphology and topography of the MDPs–polymer composites demonstrated a uniform high-density distribution of MDPs for one wt.% MPDs. Thermogravimetric analysis was employed to investigate the thermal stability of the MDPs–polymer composites. The addition of MDPs has significantly influenced the polymers’ thermal degradation. Absorption and emission spectra of thin layers were recorded through UV/Vis spectrophotometry and spectrofluorimetry. The obtained results revealed a significant increase in the fluorescence intensity of MDPs–polymer composites (at 1 wt.% of MDPs, a 1.5×, 2×, and 5× increase in fluorescence was observed for MDPs–green, MDPs–amber daylight, and MDPs–red resin, respectively) compared with the reference polymer resins. The obtained results of this work show the new pathways in producing effective and active 3D-printed optical elements.

Influence of Diamond Grain Size on the Basic Properties of WC-Co/Diamond Composites Used in Tools for Wood-Based Materials Machining.

The paper presents the effect of diamond particle size (varying between 2.5 µm and 20 µm) on the microstructure, density and hardness of WC-Co/diamond composites. The obtained materials contained 30% vol. diamond. The advanced sintering method Pulse Plasma Sintering (PPS) was used for the production of composites. The sintering process was carried out in two stages at a pressure of 50 and 100 MPa and a temperature of 1050 °C. Depending on the size of the diamond particles, composites with a density of 91–99% were obtained. Microstructure studies were performed employing scanning electron microscopy, along with an analysis of the chemical composition in micro-areas. Additionally, the phase composition was investigated by means of X-ray diffraction. In addition, hardness tests were performed. It was found that the size of the diamond particles significantly influenced the microstructure of the tested materials, as well as the density and hardness. As a result of PPS sintering of composites containing the finest diamond particles (2.5–5 µm), the presence of a metastable type of diamond—graphite was found.

A Biomimetic Strategy for the Fabrication of Micro- and Nanodiamond Composite Films

This investigation is motivated by increasing interest in diamond and composite films for applications in biomedical and electronic devices. A biomimetic strategy is based on the use of commercial bile acids, such as ursodeoxycholic acid (UDCA) and hyodeoxycholic acid (HDCA). Composite films are developed using UDCA and HDCA as solubilizing agents for poly(ethyl methacrylate) (PEMA) in isopropanol and as dispersing agents for micro- and nanodiamonds. In this approach, the use of traditional toxic solvents for PEMA dissolution is avoided. The ability to obtain high concentrations of high molecular mass PEMA and disperse diamond particles in such solutions is a key factor for the development of a dip-coating method. The PEMA dissolution and diamond dispersion mechanisms are discussed. The composition and microstructure of the films can be varied by variation of the diamond particle size and concentration in the suspensions. The films can be obtained as singular layers of different compositions, multilayers of similar composition, or alternating layers of different compositions. The films combine corrosion protection property and biocompatibility of PEMA with advanced functional properties of diamonds.

Research on maximizing the diamond content of diamond/SiC composite

Diamond content is a key factor affecting diamond/SiC composite performance, especially thermal and mechanical properties, but the composite with high diamond content manufacturing is still challenging issues. Hot mold pressing combined with liquid silicon infiltration to make diamond/SiC composites with high diamond content and relative density has been proposed in this paper. In addition, the effect of diamond particle size on the maximization of diamond content as well as properties of the composites were evaluated. The experiment shows that the content of diamond in the composites increases with the increase of the diamond particle size. When the particle size of diamond is 400 µm, the volume fraction of diamond reaches 59.08%. The highest thermal conductivity (ddia= 300 µm) and highest bending strength (ddia= 50 µm) are 616.77 W/m K (It is the maximum TC of diamond/SiC prepared by pressureless infiltration at present) and 380 MPa, respectively. This work provides a novel and efficient preparation method for further improving the thermal conductivity of diamond/SiC composites.

High thermal conductivity diamond-doped silver paste for power electronics packaging

A thermal management material with high thermal conductivity was prepared by sintering silver paste doped with Ag/TiC double-coated diamond at 5 MPa and 260 °C and the effects of diamond particle size, coating and concentration were investigated. The thermal conductivity of the composite sample doped with 25 vol% 40–50 μm double-coated diamond is 243 W/m·K, which is ∼74% higher than that of the undoped sample, i.e., 139 W/m·K. In addition, the resistivity and shear strength of the composite paste were characterized.

Purcell enhancement of fluorescence from silicon-vacancy color centers in Mie-resonant luminescent diamond particles

Over the past two decades, nanosized diamond particles with various luminescent defects have found numerous applications in many areas from quantum technologies to medical science. The size and shape of diamond particles can affect drastically the luminescence of embedded color centers. Here we study diamond particles of 250–450 nm in size containing silicon-vacancy (SiV) centers. Using dark-field scattering spectroscopy, we found that fundamental Mie resonances are excited in the spectral range of interest. We then measured the fluorescence saturation curves under continuous excitation to estimate the effects of the excitation and Purcell factor enhancement on the luminescent properties of the studied particles. The results show that the saturation excitation intensity differs by several times for particles of different sizes which is well explained by the numerical model that takes into account both the Parcell factor enhancement and resonant excitation.

Integration of Fluorescent, NV-Rich Nanodiamond Particles with AFM Cantilevers by Focused Ion Beam for Hybrid Optical and Micromechanical Devices

In this paper, a novel fabrication technology of atomic force microscopy (AFM) probes integrating cantilever tips with an NV-rich diamond particle is presented. Nanomanipulation techniques combined with the focused electron beam-induced deposition (FEBID) procedure were applied to position the NV-rich diamond particle on an AFM cantilever tip. Ultrasonic treatment of nanodiamond suspension was applied to reduce the size of diamond particles for proper geometry and symmetry. The fabricated AFM probes were tested utilizing measurements of the electrical resistance at highly oriented pyrolytic graphite (HOPG) and compared with a standard AFM cantilever performance. The results showed novel perspectives arising from combining the functionalities of a scanning AFM with optically detected magnetic resonance (ODMR). In particular, it offers enhanced magnetometric sensitivity and the nanometric resolution.

Study of deposition diamond to fill pores on cobalt removal surface adopting HFCVD method

While the presence of cobalt in conventional PCD tools had a detrimental effect on their cutting performance throughout the cutting process, cobalt removal PCD likewise had the issue of poor performance improvement. To address the issue of PCD's poor cutting performance, the pores remaining on the PCD surface after cobalt removal were filled using hot filament chemical vapor deposition (HFCVD). This relatively simple and effective approach was estimated to increase the cutting performance of PCD tools. For deposition, the carbon concentration was limited to 1%, 2%, 3%, 4%, and 5%, denoted by the numbers 1#, 2#, 3#, 4#, and 5#, respectively. SEM was used to observe the surficial and cross-sectional morphologies of the deposited PCD. The porosity of the deposited PCD surface was quantified using ImageJ software. X-ray diffraction and Raman spectroscopy were used to evaluate the diamond particle size and purity. The abrasion rate of the samples was determined using an abrasive rate tester. The flank wear of tools was then determined using a digital microscope, and the abrasion morphologies of tools were studied using an optical microscope following cutting. The results suggest that when the carbon concentration increases, the pores filling effect becomes superior and eventually inferior. The surface porosity of 2# is only 6.52%, which reaches the minimum, and that means 2# possesses the best pore filling effect. At the same time, 2# diamond grain size is the smallest, with relatively good purity and the smallest internal stress. When morphology and flank wear measures of cutting tools are compared, the tool life of 2# is almost double that of a general PCD tool. Thus, maintaining a carbon concentration of about 2% efficiently fills the pores of cobalt removal PCD, significantly improving the wear resistance and durability of the tools. In general, this study used HFCVD to deposit diamond to fill pores on the cobalt removal surface of the PCD tools. It was found that maintaining not too high carbon concentration can enhance the quality of diamond and filling ration, therefore improving the wearing performance of PCD tools. This experiment attempted to demonstrate the concept of utilizing diamond as a dense cover layer to deposit diamond grains into PCD tool pores. Then, carbon concentration was included as a significant factor in the deposition process in order to investigate the propensity of diamond pore nucleation and growth in order to fill the pores on the surface with the greatest possible quality. Finally, when the results of pore filling were compared to the results of real cutting, it was found that the cutting performance of PCD tools with improved filling was superior to that of conventional PCD tools.

Machining the Surface of Orthopedic Stent Wire Using a Non-Toxic Abrasive Compound in a Magnetic Abrasive Finishing Process

The orthopedic stent wire is one of the critical medical components, which is mainly used for the replacement of physically damaged parts in the human body. Therefore, a smooth surface and lack of toxic substances on the surface of this component are highly demanded. In this study, a magnetic abrasive finishing (MAF) process was carried out using a non-toxic abrasive compound (a mixture of iron powder, diamond particles, cold cream, and eco-friendly oils) to achieve high-quality surface finishing of orthopedic stent wire. The surface roughness (Ra) of the stent wire was investigated according to various processing parameters: different rotational speeds (500, 1000, and 2000 rpm), diamond particle sizes (1.0 µm), and three eco-friendly oils (olive oil: C98H184O10; grapeseed oil: C18H32O2; and castor oil: C57H104O9) within 300 s of the finishing time. The results showed that the surface roughness of the wire was reduced to 0.04 µm with a rotation speed of 1000 rpm and a diamond particle size of 1 µm when using grapeseed oil. SEM microimages and EDS analysis showed that the MAF process using a non-toxic abrasive compound could improve the surface quality of orthopedic Ni-Ti stent wire with a lack of toxic substances on the surface finish.

Preparation of SiO2-diamond composites by spark plasma sintering

ABSTRACT SiO2-diamond composites with 65–85 mass% diamond were fabricated by spark plasma sintering at 1873 K under 130 MPa for 300 s using bimodal diamond particle size of 2 and 25 µm in diameter. The diamond particles were coated with a SiC layer by chemical vapor deposition. The effects of diamond content on relative density, microstructure, and Vickers hardness of the SiO2-diamond composites were investigated. The SiO2-diamond composites exhibited relative density of 96%, and Vickers hardness of 36.2 ± 3.6 GPa at 75 mass% diamond content.

Interphase layer characteristics and thermal conductivity of hot-forged Cu-B/diamond composites

Copper/diamond composites are regarded as the next-generation heat sink materials and have great potential to be used for future high-power electronic devices. The interphase layer characteristics between the copper matrix and the diamond have a significant influence on the composite’s thermophysical properties. In this work, a cost-effective hot forging process is used to fabricate diamond particles (about 70 μm diameter) reinforced Cu-xB matrix (x = 0.3, 0.5 and 1.0 wt.%) composites. The results show that B4C particles are easier to nucleate on the diamond (100) facet than on diamond (111) facet during the hot forging. The morphology of the newly formed B4C interphase layer on the diamond (100) facet evolved from a fine dispersed particle (Cu-0.3B/diamond) to a continuous dense structure (Cu-1B/diamond). On the diamond (111) facet, the B4C nucleation is difficult due to relative stronger carbon bonds formed on the diamond (111) facet (three bonds) than on the diamond (100) facet (two bonds), the growth of previously nucleated B4C become predominated, resulting in forming a B4C interphase layer with large particle size and low density on the diamond (111) facet. The Cu-0.5B/diamond has the highest thermal conductivity among the three fabricated composites (440 W/mK), and a low coefficient of thermal expansion (6.57 × 10–6 /K) at 313 K is obtained. With increasing the diamond particle size to 200 μm, the hot-forged Cu-0.5B/diamond had an increased thermal conductivity (495 W/mK). It demonstrates that hot forging is a feasible method to fabricate Cu/diamond composites with acceptable thermal conductivity from powder mixture.

Fabrication and performance of brazing diamond using large size Ni[sbnd]Cr alloy as a bonding agent

To obtain the brazing effect of good exposure of abrasive particles and uniform thickness of the solder layer, the concept of vacuum brazing diamond with large particle size alloy solder was proposed, and the geometric model was established. The equation group of the relationship between large particle size alloy solder and diamond particle size was obtained, and the practical solution based on the wetting angle of alloy solder was obtained. In this study, NiCr alloy particles were used as the bonding agent and four sets of controlled experiments with different size combinations were conducted. The intermediate interface was analyzed by scanning electron microscopy and X-ray energy spectrometer. According to the test results, it demonstrated a large size NiCr alloy provides high consistency after brazing. Carbide chromium compound was also founded at the interface between diamond and alloy, which realized the firm control of diamond. This study showed that the new diamond brazing process based on the particle size matching mechanism was a feasible and promising method.

Deagglomeration of polycrystalline diamond synthesized from graphite by shock-compression

One of the industrially scalable methods for the synthesis of diamond crystals is shock compression of graphite. The method includes shock compression of graphite with explosives (RDX). Typical sizes of polycrystalline diamond particles produced by the method are in the range from 50 nm to 2 μm. We submit a method for deagglomeration of that diamond particles and production of stable hydrosol of monodisperse particles with positive electrokinetic potential. The mean size of isolated diamond particles in the hydrosol is 4 nm. The method includes chemical purification of the commercial diamond powder, annealing of purified powder in hydrogen, and followed centrifugation.