Diamond Particles Research Articles

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.

Controllable preparation of single-crystal diamond nanopillar clusters by metal cyclic dewetting process

Diamond nanopillars can effectively improve the spontaneous emission efficiency and coupling-out efficiency of diamond-color-center single-photon sources. In this paper, a low-cost and controllable method for preparing diamond nanopillar clusters is proposed. By choosing the crystal planting method and adjusting the methane concentration of the grown diamonds, isolated single-crystal diamond particles with a flat surface were prepared. Etching masks with individually controllable diameters and spacings were prepared through the cyclic deposition and dewetting of metal films on the surface of microcrystalline diamond particles. Using inductively coupled reactive ion etching technology, diamond nanopillar clusters were prepared through oxygen plasma etching. The nanopillars were uniform in diameter and densely arranged. The single-crystal properties of the diamond nanopillars and their enhancement effect on the photoluminescence of diamond color centers were confirmed through the analysis of Raman and photoluminescence spectra. The results provide a foundation for the deviceization of diamond-color-center single-photon sources.

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.

Electroplated waveguides to enhance DNP and EPR spectra of silicon and diamond particles.

Electroplating the waveguide of a 7 T polarizer in a simple innovative way increased microwave power delivered to the sample by 3.1 dB. Silicon particles, while interesting for hyperpolarized MRI applications, are challenging to polarize due to inefficient microwave multipliers at the electron Larmor frequency at high magnetic fields and fast electronic relaxation times. Improving microwave transmission directly translates to more efficient EPR excitation at high-field, low-temperature conditions and promises faster and higher Si polarization buildup through dynamic nuclear polarization (DNP).

Relaxometry for detecting free radical generation during Bacteria's response to antibiotics

Free radical generation plays a key role in killing bacteria by antibiotics. However, radicals are short-lived and reactive, and thus difficult to detect for the state of the art. Here we use a technique which allows optical nanoscale magnetic resonance imaging (MRI) to detect radical generation on the scale of single bacteria. We demonstrate that the radical generation in Staphylococcus aureus increases in the presence of UV irradiation as well as vancomycin and is dependent on the antibiotic's dose. With a method based on ensembles of nitrogen vacancy (NV) centers in diamond, we were able to follow the radical formation near individual bacteria over the whole duration of the experiment to reveal the dynamics of radical generation. Using this new approach, we observed free radical concentrations within nanoscale voxels around the diamond particles and determined its exact timing depending on the antibiotic dose. Since changes in the response to antibiotics emerge in only a few bacteria of the entire population, such a single-cell approach can prove highly valuable for research into drug resistance.

Investigation of Passivation, Pitting and Uniform Corrosion Performances of Chromium Coatings Reinforced with Nano Diamond Particles on Porous Powder Metallurgy Specimens

Investigation of Passivation, Pitting and Uniform Corrosion Performances of Chromium Coatings Reinforced with Nano Diamond Particles on Porous Powder Metallurgy Specimens

Gradient interface formation in Cu–Cr/diamond(Ti) composites prepared by gas pressure infiltration

Interface design is critical to enhance thermal properties of Cu/diamond composite as a promising thermal management material. Herein we combine Cr alloying in Cu matrix with Ti coating on diamond particles to prepare a Cu-0.5 wt%Cr/diamond(Ti) composite in an attempt to construct a TiC/Cr3C2 gradient interface to improve phonon transfer at the interface. The Ti-coating on diamond particles transforms to a TiC layer during deposition. As the TiC layer is 20 nm thick, a part of Cr atoms in the Cu matrix diffuse through the TiC layer to react with the C atoms on diamond particles to form a 30 nm-thick Cr3C2 layer, and a 28 nm-thick graphite layer is generated on diamond particle surface. With increasing the TiC layer thickness to 80 nm, a small part of Cr atoms can still pass through the TiC layer to form discrete chromium carbide particles and a 20 nm-thick graphite layer is generated. The interfacial structure of the Cu-0.5 wt%Cr/diamond(Ti) composite is characterized as diamond/graphite/TiC/Cr3C2/Cu, and the thermal conductivity for the Cu-0.5 wt%Cr/diamond(Ti) composite has a 549 W m−1 K−1 value lower than the 735 W m−1 K−1 value for the Cu/diamond(Ti) composite. The lowered thermal conductivity is attributed to the formed graphite layer and the thick Cr3C2 layer in the Cu–Cr/diamond(Ti) composite. This study provides guidance for designing and tailoring gradient interface for efficient phonon transport in Cu/diamond composites.

Dry sliding wear behavior of Poly Ether Ether Ketone (PEEK) reinforced with graphite and synthetic diamond particles

Tribo film modification by synthetic diamond filler is an important study in developing polymer composite-based tribo components to avoid material loss during the sliding process. Anti-wear and anti-friction responsiveness were investigated by adding synthetic diamond particles (0–1 wt%) and graphite particles (0–1 wt%) to a Poly Ether Ether Ketone (PEEK) matrix under dry sliding conditions. Adding high-strength synthetic diamond filler offers more resistance to deformation of the PEEK composite, significantly improving its hardness and wear resistance properties. Altering synthetic diamond and graphite filler concentrations changes the wear process by modifying the tribo film characteristics, specifically at 0.5 % diamond and 0.75 % graphite particles, showing the lowest friction. The measured ID/IG ratio of transfer film was 0.92 by Raman spectra analysis, referring to the crystallized graphitic structure in the tribo film. XPS and Raman spectra analyses show that the tribo-chemical products of tribo film improve the lubricity and load-bearing ability of the composite. The mechanical effects of synthetic diamond particles and the tribochemical interactions between the sliding pair release polymer chelates strongly bind the tribo film to the counter surface. This increases the strength of the tribo film bond, which significantly improves tribo performance.

Microstructure, Wear and Corrosion Behaviors of Electrodeposited Ni-Diamond Micro-Composite Coatings

For the micro-milling of hard and brittle materials, to avoid crack formation, a tool with ductile milling mode is required. Composite electrodeposition technology was used to prepare a Ni–diamond coating on the surface of brass. The surface microstructure, composition and surface roughness of the coating were studied with a scanning electron microscope, X-ray diffractometer and roughness tester. The adhesion strength was studied by scratch test, the wear resistance was analyzed by wear test, and the corrosion resistance was investigated by Tafel curves and electrochemical impedance spectra (EIS). It was found that the distribution of diamond particles of the Ni–diamond coating was relatively uniform, and the content was relatively high. The internal stress of the coating prepared by the composite electrodeposition technology was very low. With the incorporation of the diamond particles, the surface roughness of the coating tended to decrease. The wear experiment showed that the wear scar diameter of the corresponding glass ball for the Ni coating was 1.775 mm and the roughness was 13.88 ± 2.811 µm, while that for the Ni–diamond coating was 2.680 mm and 8.35 ± 0.743 µm, respectively, indicating that the tool coating with uniform diamond particles had a strong ability to process workpieces with significantly improved surface quality. The particle press-in mechanism not only improved the wear resistance of the coating, but helped to prolong the service life of the tool. The results of the EIS test and Tafel curves showed that the Ni–diamond coating had a lower corrosion current, and the corrosion resistance of the coating surface was improved. The experimental results showed that the micro-diamond coating prepared by the composite electrodeposition technology had good bonding strength, low internal stress, and significantly improved wear resistance and corrosion resistance.

Evaluation of diamond rotary instruments marketed for removing zirconia restorations

Statement of problemThe high strength of zirconia makes the removal of zirconia restorations challenging and time consuming. Whether diamond rotary instruments marketed for removing zirconia restorations are more efficient is unclear. PurposeThe purpose of this in vitro study was to compare the efficiency of diamond rotary instruments specifically marketed to cut zirconia with the efficiency of a conventional diamond rotary instrument. Material and methodsTwo diamond rotary instruments marketed to cut zirconia (JOTA Zirkon Cut Z838L [JOT] and Intensiv ZirconCut Zr02/10 [IZC]) and a conventional diamond rotary instrument (Intensiv FG 334/6 [IFG]) were tested on 2 zirconia materials: 3Y-TZP (IPS ZirCAD LT) and a multilayered 4Y-TZP (IPS ZirCAD MT Multi). Zirconia specimens (2 mm) were cut under water cooling using a force of 2 N or 6 N. Cutting times and maximum temperatures at the tip of the diamond rotary instruments were recorded. The surface roughness before and after use was measured, and the elemental composition was analyzed. ResultsOverall, cutting times were shorter for IFG (85 seconds) and IZC (100 seconds) than for the JOT (182 seconds). Cutting times were shorter for MT zirconia than for LT zirconia. Higher temperatures (2 N: 24.6 °C, 6 N: 36.7 °C) and lower surface roughness occurred with higher cutting loads. Impurities of diamond particles were seen for JOT. The diamond particle embedding materials were either nickel alloys (IFG and JOT) or a resin material (IZC). ConclusionsDiamond rotary instruments marketed for cutting zirconia did not perform better or generate less heat compared with a conventional diamond rotary instrument. A load of 2 N with sufficient water cooling is recommended for cutting zirconia to avoid an extensive temperature increase.

Wear characteristics of electroplated diamond dressing wheels used for on-machine precision truing of arc-shaped diamond wheels

The rapid wear of the dressing tools severely limits the further improvement of the truing accuracy and dressing sharpness of the arc-shaped diamond wheels used in ultra-precision grinding. This paper thoroughly investigated the wear characteristics of electroplated diamond dressing wheels used for on-machine precision truing of arc-shaped diamond wheels. Firstly, wear topography and protrusion height of the diamond particles were researched. Secondly, the wear evolution mechanism of diamond particles with different grain sizes was systematically researched. Then, the wear mechanism of the metal bonded matrix was studied. Subsequently, the Raman spectrum analysis of diamond particles before and after wear was carried out. Finally, the profile accuracy and surface topography of the trued arc-shaped diamond wheel were evaluated for distinguishing the wear resistance and sharpening performance of the electroplated diamond dressing wheels with different grain sizes.

Analysis of crack initiation load and stress field in double scratching of single crystal gallium nitride

Precision processing such as grinding of single crystal gallium nitride is processed through complex interactions between many diamond particles. However, single-grain scratching can only study the basic performance of abrasive grain processing, and cannot study the mutual influence of multi-abrasive grain processing. Therefore, this paper studies the situation of double scratching. The influence of the distance between two scratches on the crack initial load has been studied by the analysis model during simultaneous double scratching and continuous double scratching. During continuous double scratching, when the separation distance L < 1.8b, lateral cracks on adjacent side of the second scratch nucleate and expand under a smaller initial load than single-indenter scratching, and the smaller the L is, the smaller the corresponding initial load of lateral cracks will be. When the separation distance is 0.4b and 0.8b, the median crack nucleates at the middle of two scratches. During continuous double scratching, the median cracks always nucleate and expand at the bottom of the second scratch.

Facile formation of a thin chromium carbide coating on diamond particles via quaternary molten salt

In this paper, we introduced NaF into a NaCl-LiCl-KCl molten salt to reduce the thickness of chromium carbide coating on diamond particles. The effect of temperature of the quaternary salts (from 600 °C to 750 °C) on the chromium carbide coating was investigated by XPS, SEM, EDS, and XRD. The result indicates that a uniform and continuous Cr7C3 coating of about 160 nm in thickness forms when NaF is mixed with molten salt at 650 °C. Lower temperatures (<650 ℃) do not contribute to a continuous coating in the quaternary molten salt. As the temperature rises, the coating thickness gradually increases. Adding NaF reduces the reaction temperature, thereby preventing diamond surface graphitization. The cause of a thin Cr7C3 coating formation is discussed in terms of the viscosity of molten salt and Gibbs free energy. This study provides a low-cost method for forming a continuous thin carbide coating on diamond particles.

Thermal properties of diamond/Cu composites enhanced by TiC plating with molten salts containing fluoride and electroless-plated Cu on diamond particles

To improve the thermal properties of diamond/Cu composites for thermal management applications, we designed dual-coated diamond particles for preparing composites. A thin TiC coating is formed on diamonds using molten salt with NaCl-KCl-NaF, then electroless plating of Cu is applied. The effects of salt bath temperature on the formation of TiC coating and the percentage of modified diamonds on the thermal performance of the composites were investigated. At temperature as low as 700 °C, Ti and diamond particles forms a TiC coating with a thickness of 1 μm in molten salt containing fluoride. In response to an increase in temperature, the thickness of the formed TiC coating increases and is prone to cracking and flaking. Cu coating well coats the TiC/diamond by electroless plating. The hot-pressing diamond/Cu composite with 60 vol% modified diamonds exhibits the best thermal conductivity of 495.5 W·m−1·K−1, slightly below the values predicted by the model H-J and DEM, and lower thermal expansion coefficient of 5.86 × 10−6 K−1, corresponding to the Kerner model.

Irradiation enhanced the anti-friction performance of GO and FND codispersed nanofluids

Efficient lubrication technology is the basic method of ensuring the energy-saving and long-term stable operation of mechanical equipment. In particularly, it is difficult for a single lubricating solid phase to satisfy the anti-friction and wear resisting requirement of pumps in spacecraft. In this paper, two solid lubrication additives, graphene oxide (GO) and flake nanodiamond (FND), were added into water to form nanofluids, and their lubrication and irradiation properties were studied. Long-term stable GO-FND nanofluids were prepared by a two-step method. The friction test was carried out by a UMT5 tribometer. The irradiation experiment was carried out in the space charged particle irradiation environment simulation equipment. The mixed addition of GO and FND increased the anti-friction effect of nanofluids. The GO/FND nanofluids showed a 42.3 % reduction in the friction coefficient under the Al2O3-Si3N4 friction pairs. After irradiation, the lubrication stability of GO/FND nanofluids was further improved, and the friction coefficient decreased by 78.6 % compared with that of the base fluid. The excellent lubrication performance is attributed to the combined effect of GO and FND. After the friction test, graphene oxide was rolled up around the diamond particles to form a composite carbon film on the surface of the friction pair. The friction reduction effect was improved by forming a fluid film between the friction pair and fluid molecules. Electron irradiation treatment promotes the generation of hydrophilic CO bonds on the carbon nanoparticle surface, increases the affinity between carbon nanoparticles and deionized water, and further reduces the friction coefficient.

Active laser brazing of diamond onto 45 steel: Diamond flow behavior, microstructure and bonding strength

The paper investigated the influence of an active agent on the distribution and bonding properties of laser brazed abrasive particles experimentally in fabricating a diamond tool. In the design of experiments, fiber laser brazing was applied to make a single-layer diamond tool, 45 steel was used as a substrate, Cr2O3 was used as an active agent, and Ni-Cr alloy was used as a filler metal. The advantages of active laser brazing(A-LB) and conventional laser brazing (LB) are compared and analyzed from the aspects of flow behavior and mechanical properties. The experimental findings demonstrate that the molten metal flowing to the central will cause the diamond particles in A-LB to flow to the central of the molten pool. The diamond and Ni-Cr interface on the A-LB specimen is roughly 10 μm broader than on the LB. A-LB has a higher single particle shear strength than LB. Additionally, the sample of A-LB has superior wear resistance.

Fabrication of Boron-Doped Diamond Film Electrode for Detecting Trace Lead Content in Drinking Water.

This work aimed to fabricate a boron-doped diamond film electrode for detecting trace amounts of lead in drinking water so as to safeguard it for the public. Available detectors suffer from high costs and complex analytical processes, and commonly used electrodes for electrochemical detectors are subject to a short life, poor stability, and secondary pollution during usage. In this work, a boron-doped diamond (BDD) electrode was prepared on a porous titanium substrate, and the microstructure and electrochemical properties of the BDD electrode were systematically studied. Moreover, the stripping parameters were optimized to obtain a better signal response and determine the detection index. As a result, diamond particles were closely arranged on the surface of the BDD electrode with good phase quality. The electrode showed high electrochemical activity, specific surface area, and low charge transfer resistance, which can accelerate the stripping reaction process of Pb2+. The BDD electrode presented a low detection limit of 2.62 ppb for Pb2+ under an optimized parameter set with an enrichment time of 150 s and a scanning frequency of 50 Hz. The BDD electrode also has good anti-interference ability. The designed BDD electrode is expected to offer a reliable solution for the dilemma of the availability of metal electrodes and exhibits a good application prospect in the trace monitoring of Pb2+ content in drinking water.

Kinetic regularities of the formation of composite electrolytic coatings containing ultradispersed diamond particles

The paper formulates the problem of joint electrolytic co-deposition of metal ions and ultradispersed diamond particles into a metal matrix. It presents the developed mathematical model that describes the mechanism and kinetics of the cathode process, mass transfer of metal ions and ultradispersed diamond particles. A satisfactory correlation with experimental data was obtained. The contribution of the thermal action of laser radiation to the intensification of the process of co-deposition of dispersed particles and metal ions was determined. It was found that the more intense penetration of dispersed phase particles into the forming coating during the laser stimulation of the electrodeposition process is due to the presence of a temperature gradient, which provides an additional supply of metal ions in the irradiation region. Based on the theoretical and experimental studies, we established the regularities of the influence of the number and size of nanoparticles on the strengthening properties of composite metal coatings. It was found that an increase in the temperature of an aqueous electrolyte solution in the cathode region during a laser-stimulated deposition process leads to an increase in the flux density of ultradispersed diamond particles, and, as a result, to an increase in the concentration of the dispersed phase in nickel composite coatings, which contributes to the formation of a finer crystalline structure of coatings, an improvement in adhesion, strength properties and increased wear resistance of coatings.