Surface Of Diamond Particles Research Articles

Effect of carbon fiber structure of Marimo carbon on polymer electrolyte fuel cell performance

Fibrous carbon has attracted attention for use as a carbon support of polymer electrolyte fuel cells (PEFC). In this study, Marimo carbon (MC), a fibrous carbon, was used as the carbon support. The MC has a higher order structure in which many carbon nanofilaments (CNFs) are grown on the surface of diamond particles (dia.). The MC was synthesized by the contact reaction between a Ni supported oxidized diamond (Ni/O-dia.) and CH4 gas, the carbon source of the CNFs. The flow rate of the CH4 gas during the MC synthesis altered the structure of the CNFs. A thick CNFs was observed in the MC with a low CH4 gas flow rate, which was not observed in the MC with a high CH4 gas flow rate. The MC with the thicker CNFs had wider interspaces between the CNFs and higher Pt supporting amounts. Electrochemical measurements of the Pt support MC (Pt/MC) were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and current–voltage (I–V) measurements. The lower CH4 gas flow rate of the MC indicated faster charge transfer. The MC structural and charge transfer changed with the flow rate of the CH4 gas altered the electrochemical active surface area (ECSA), the oxygen reduction reaction (ORR) catalytic activity and the I–V performance of the Pt/MC.

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Sputtering Coating on the Surface of Diamond Particles Using High Temperature Generated by Thermal Explosion Reaction

Effects of the In Situ Growth of CNTs on Ti-Coated Diamond Surfaces on the Mechanical Properties of Diamond/Aluminum Composites.

Diamond/aluminum composites have attracted significant attention as novel thermal management materials, with their interfacial bonding state and configuration playing a crucial role in determining their thermal conductivity and mechanical properties. The present work aims to evaluate the bending strength and thermal conductivity of CNT-modified Ti-coated diamond/aluminum composites with multi-scale structures. The Fe catalyst was encapsulated on the surface of Ti-coated diamond particles using the solution impregnation method, and CNTs were grown in situ on the surface of Ti-coated diamond particles using the plasma-enhanced chemical vapor deposition (PECVD) method. We investigated the influence of interface structure on the thermal conductivity and mechanical properties of diamond/aluminum composites. The results show that the CNT-modified Ti-coated diamond/aluminum composite exhibits excellent bending strength, reaching up to 281 MPa, compared to uncoated diamond/aluminum composites and Ti-coated diamond/aluminum composites. The selective bonding between diamond and aluminum was improved by the interfacial reaction between Ti and diamond particles, as well as between CNT and Al. This led to the enhanced mechanical properties of Ti-coated diamond/aluminum composites while maintaining acceptable thermal conductivity. This work provides insights into the interface's configuration design and the performance optimization of diamond/metal composites for thermal management.

Selective laser melting and mechanical behavior of Mo-coated diamond particle reinforced metal matrix composites

Defects, such as pores, microcracks, and thermal damage, pose significant challenges in the selective laser melting (SLM) process of diamond reinforced metal matrix composites. To address these issues, this study utilizes Mo-coated diamond particles prepared via salt bath plating for SLM processing of CoCr-diamond composites. The SLM process parameters including laser power, scanning speed, and hatch spacing were systematically optimized using the response surface method (RSM). Subsequently, the microstructure and mechanical properties of the SLMed CoCr-diamond composites were thoroughly investigated. Notably, a protective layer of Mo2C is formed on the surface of diamond particles during the salt bath plating process. When compared to the SLMed CoCr-15 vol% Mo-uncoated diamond composite, the Mo coating significantly enhances the compressive strength by 69 % and flexural strength by an impressive 345 % for the CoCr-15 vol% Mo-coated diamond composite.

Improvement in effectiveness of diamond in strengthening the porous aluminium composite

In this study, an aluminum (Al) alloy matrix reinforced with uncoated and titanium (Ti) -coated diamond were developed using powder metallurgy technique where polymethylmethacrylate (PMMA) particles were employed as space holders. The weight % of uncoated and coated diamond varied as (0, 6, 9, 12, 15, and 20 wt.%). Microstructural and elemental analysis was examined using scanning electron microscopy and energy dispersive spectroscope, respectively. The relative density and porosity that were in the range of 0.72–0.92 and 31–44% respectively, were measured using Archimedes principle. The compressive properties were measured and correlated with microstructure observations. The microstructure of the composite samples revealed presence of well-defined macro pores with good interfacial integrity. The X-ray diffraction revealed the presence of strengthening phases such as Al2Ti, Mg2Sn, AlB12, Cu5Sn6, Al12Mg17 and MgB2 phases formed as a result of addition of metal additives in Al matrix. Further improvement in the strength was obtained by using Ti-coated diamond particles as reinforcement. As Ti formed a good interface between the Al alloy matrix and the diamond thereby preventing the formation of undesirable carbide phases. There was an improvement in plateau stress and energy absorption capacity of 82 and 88% as compared to unreinforced porous sample. The maximum values obtained for the plateau stress and energy absorption capacity were 45.12 MPa and 13.68 MJ/m3 respectively for 9 wt.% of Ti-coated diamond reinforced composites. Uncoated diamond reinforced composites, on the other hand, reduced the strength of porous Al alloy matrix due to the formation of brittle intermetallic compound such as carbides (Al2C3) at the interface. As a result, the coated diamond particle surface modifies and improves the wettability of the Al alloy matrix and diamond interface.

Effect of Nano-SiC coating on the thermal properties and microstructure of diamond/Al composites

A 20 nm SiC nanocoating was prepared on the surface of crushed diamond particles using a combination of sol-gel and in situ reaction methods. 50 vol% SiC-coated diamond particles reinforced 6061Al composites were fabricated by vacuum hot pressing method. Part of the SiC, with a crystallographic orientation relationship of (-11-1)Diamond//(-11-1)SiC and [-110]Diamond//[-110]SiC between SiC and diamond, remains at the interface, which reduces the mismatch of phonon vibration modes between the diamond and Al matrix. Thus, the interfacial thermal conductance of the composite was greatly improved compared to that of composite prepared by diamond without coating. The thermal conductivity of the composite is 485 W/mK, which is the highest among the crushed diamond/Al composites and similar to that composite fabricated by single-crystal diamond. It is significant for the industrial application of diamond/Al composites that obtain a composite with well machinability and TC using the crushed diamond with nano-SiC coating.

Interface formation evolution of the hot-forged copper-(Cr)diamond composite and its thermal conductivity

Due to the distinction of (111) and (100) faces on the diamond particle, the preferential formation of interface layers on the diamond particle is discovered when adding metal additives like titanium, chromium, aluminum in copper/diamond composites. The formed interface would affect the thermal conductivity of the copper/diamond composites. In this study, copper-55 vol%(Cr-coated) diamond composites were successfully produced by hot forging under 800 ℃, 900 ℃ and 1050 ℃. Heat treatment of Cr-coated diamond powders was conducted under a series of temperatures for studying the evolution of the carbide interface formation on surfaces of diamond particles. It was found that the average grain size of the Cr7C3 on diamond (111) faces was larger than that on (100) faces when the temperature is below 850 ℃, and the opposite trend was observed when the heat treatment temperature is above 850 ℃. The Cr layer was fully transformed into Cr7C3 when the temperature was above 950 ℃. Unlike the results obtained after heat treatment, the interface layers was directly transformed into Cr3C2 due to the non-equilibrium phase transformation after hot forging. The Cr3C2 interface layers were preferentially kept on (100) diamond faces, and exfoliated on (111) faces after hot forging. The grain size of the formed Cr3C2 on diamond (100) faces was increased with raising the hot forging temperature. The 1050 ℃-hot-forged sample showed the highest thermal conductivity, attributed to large grain sizes of the Cr3C2 interface layer. This study elaborates the mechanisms of the evolution of the interface layer formed under different temperatures on the diamond surfaces in copper-(Cr-coated) diamond composites, and the phenomenon of preferential formation of the interface layers is verified.

Effects of CuSn on the diamond particle holding force of pressureless sintered FeCuCo-based diamond tools

Gas atomized FeCuCo (Cu 28.7 wt% Cu, 12.1 wt% Co) prealloyed powder was used as matrix of diamond tools, and CuSn (15. wt% Sn) prealloyed powder was used as sintering aids. The content of diamond particles was 0.35 wt%. The alloys were prepared through pressureless sintering. Effects of CuSn addition on mechanical properties, microstructure, and holding force of diamond particle were studied. The results show that the FeCuCo alloy is mainly composed of α-Fe phase and Cu-rich phase. Co and Sn are solid solution atoms of α-Fe phase and Cu-rich phase respectively. The fracture morphology of FeCuCo alloy mainly fine dimple and quasi cleavage fracture, as well as sintered pore surface and crack. With the increase of CuSn addition, the density, hardness, bending strength and diamond particle holding force of the alloy increase first and then decrease. The hardness, bending strength, and relative density of FeCuCo alloy with 8 wt% CuSn reach the peak. The bending strength of this alloy added with diamond particles reaches 871 MPa, and the strength loss rate is only 21.7%. There is an obvious gap between the diamond particles and the matrix, indicating that the holding mechanism is mainly mechanical encapsulation. After the addition of CuSn, there are more attachment on the surface of diamond particles, resulting in metallurgical bonding.

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.

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.

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.

Coating diamond surfaces in a Ti/Si/carbon black/diamond system via thermal explosion

By using Ti/Si/graphite/diamond powders as the raw material, a coating was formed on the surfaces of diamond particles via thermal explosion. The phase composition and microstructure of the coating on the surfaces of the diamond particles were analyzed and observed by using X-ray diffraction and scanning electron microscopy. Results showed that Ti3SiC2 and TiC were the main components of the matrix after thermal explosion. The addition of diamond particles to the raw material had little effect on the phase composition of the matrix. A good coating that was mainly composed of TiC and SiC was obtained on the surfaces of the diamond particles after the reaction.

Coating on the Surface of Diamond Particles by Thermal Explosion Reaction Method

Coating on the Surface of Diamond Particles by Thermal Explosion Reaction Method

Fabrication of Titanium and Copper-Coated Diamond/Copper Composites via Selective Laser Melting.

The poor wettability and weak interfacial bonding of diamond/copper composites are due to the incompatibility between diamond and copper which are inorganic nonmetallic and metallic material, respectively, which limit their further application in next-generation heat management materials. Coating copper and titanium on the diamond particle surface could effectively modify and improve the wettability of the diamond/copper interface via electroless plating and evaporation methods, respectively. Here, these dense and complex composites were successfully three-dimensionally printed via selective laser melting. A high thermal conductivity (TC, 336 W/mK) was produced by 3D printing 1 vol.% copper-coated diamond/copper mixed powders at an energy density of 300 J/mm3 (laser power = 180 W and scanning rate = 200 mm/s). 1 and 3 vol.% copper-coated diamond/copper composites had lower coefficients of thermal expansions and higher TCs. They also had stronger bending strengths than the corresponding titanium-coated diamond/copper composites. The interface between copper matrix and diamond reinforcement was well bonded, and there was no cracking in the 1 vol.% copper-coated diamond/copper composite sample. The optimization of the printing parameters and strategy herein is beneficial to develop new approaches for the further construction of a wider range of micro-sized diamond particles reinforced metal matrix composites.

Preparation of oxazoline-group-functionalized diamond using poly(2-vinyl-2-oxazoline) based on a model reaction between oxazoline and carboxylic acid

We conducted research aimed at combining diamond particle surfaces with external moieties using a polymer. We here propose an effective solution using a reactive polymer, poly (2-vinyl-2-oxazoline) (Pvozo), with a large amount of reactive oxazoline as side chains. The idea is that some of the oxazoline groups react with carboxylic acid at the surface and the other oxazoline groups remain as available unreacted groups for further reaction with external moieties. The chemical reactivity of oxazoline with carboxylic acid was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy using model low-molecular-weight molecules, followed by reaction between Pvozo and the surface. The amount of acid groups on the surface was determined by titration. Diamond particles reacted with Pvozo in a solvent, followed by a washing step, which resulted in the formation of a uniform monolayer of nanosized Pvozo on micron-sized diamond particles, which was confirmed by thermogravimetric analysis (TGA) and by a visible-marker method with scanning electron microscopy (SEM) using carbon nanotubes. The amounts of reacted and unreacted oxazoline of Pvozo on the surface were quantified using nonanoic acid in conjunction with TGA.

Influence of sputtering and electroless plating of Cr/Cu dual-layer structure on thermal conductivity of diamond/copper composites

Highly uniform, dense and tightly-bonded Cr/Cu dual-layer films are successfully deposited on the surface of diamond particles combined with magnetron sputtering and electroless plating. Then, Cr/Cu-coated diamond particles and Cu powders are utilized to synthesis diamond/Cu composites by the spark plasma sintering. Scanning electronic microscope, transmission electron microscope and optical microscope are employed to examine the structure and morphology of the as-prepared diamond/Cu composites. The results reveal the formation of an interfacial zone between diamond particles and Cu matrix, which is mainly composed of Cr-Cu-C. One should note that the growth of interlayer mainly depends on the electro-plating time. Moreover, a laser thermal conductivity meter is employed to measure the thermal conductivity (TC) of diamond/Cu composites, reaching a value of 613 W/m·K due to the formation of an excellent interface between diamond particles and Cu matrix. The diamond/Cr-C/Cr/Cr-Cu/Cu interface structure can significantly decrease the interface thermal resistance and, in turn, enhance the thermal conductivity.

Titanium coating on the surface of diamond particles by a novel rapid low-temperature salt bath plating method

Titanium coating on diamond surface was treated with conventional and microwave salt bath plating methods. The composition and morphology of the coatings were analyzed by XRD, SEM, EDS and TEM. The results indicated that uniform and dense coatings were obtained on diamond particles after microwave-assisted salt bath plating at 850 °C for 20 min, while the deposition of titanium was incomplete by conventional heating salt bath treatment at 850 °C for 120 min. It indicates that a complete and dense titanium coating can be obtained on diamond surface at a lower temperature and a shorter time by microwave heating.

Unveiling the interface characteristics and their influence on the heat transfer behavior of hot-forged Cu–Cr/Diamond composites

Cu–Cr/55 vol% diamond composites with 1 wt % (Cu–1Cr/55Dia), 2 wt % (Cu–2Cr/55Dia), and 3 wt % (Cu–3Cr/55Dia) Cr additives, respectively, are fabricated by a hot forging method. The diamond particle surfaces are nearly completely covered by the formed carbides interface for the Cu–3Cr/55Dia composite, and the Cu–3Cr/55Dia has the highest measured thermal conductivity among the three fabricated composites (433 Wm−1K−1). High Resolution Transmission Electron Microscopy analyses suggest that a double-layered interface structure is formed between the copper matrix and the diamond particle in the Cu–3Cr/55Dia, which is composed of 160 nm-thick Cr3C2 and 2 nm-thick Cr23C6. This interface structure, together with high relative density of the composite, high interface coverage of diamond, thin interface layer, and formation of coherent atomic boundaries, significantly contributes to obtaining high thermal conductivity for the Cu–3Cr/55Dia composite. The Diffuse Mismatch Model and Differential Effective Medium model are modified for establishing the quantitative relationship among interface characteristics, interface thermal conductance, and the composite’s thermal conductivity, based on considering the composite’s interface structure and phonon transmission theory. The predicted thermal conductivity value is well matched with the measured value for the Cu–3Cr/diamond (487 Wm−1K−1 vs 433 Wm−1K−1). This helps understand heat transfer behavior in the Cu–Cr/diamond composites.

Enhanced thermal conductivity of copper/diamond composites by fine-regulating microstructure of interfacial tungsten buffer layer

In this paper, tungsten (W) coatings were deposited on surface of diamond particles by magnetron sputtering for fabricating copper/diamond composites with high thermal conductivity. To reveal the influence of interfacial microstructure on performance of the composites, the W coated diamond particles subjected different annealing process before the composites were fabricated via pressure-assisted infiltration. The evolution of interfacial microstructure and composition of the coating layer were studied. Thermal conductivity of the composites exhibited increasing firstly and decreasing subsequently with the interfacial phase transformed from metallic W to corresponding carbides. Compared with diamond/WC/Cu interfacial microstructure, constructing diamond/WC/W2C/Cu interfacial microstructure via fine regulation is a critical factor for the optimized thermal conductivity of the composites. When the interfacial coating layer was composed of WC phase (97.6 wt.%) and W2C phase (2.4 wt.%), the highest thermal conductivity of the composite reached to 836 W⋅m−1⋅K−1. Based on the theoretical calculation, the W2C sublayer in diamond/WC/W2C/Cu interfacial microstructure reduces the acoustic impedance mismatch between Cu and the carbide buffer layer, resulting in higher interfacial thermal conductance.

Microstructure and thermo-physical properties of Cu[sbnd]Ti double-layer coated diamond/Cu composites fabricated by spark plasma sintering

Diamond/Cu composites were fabricated by spark plasma sintering (SPS) process with CuTi double-layer coated on the surface of diamond particles as the reinforcement phase. The effect of sintering temperature, pressure and holding time on the microstructure and thermo-physical properties of the composites were investigated. The results showed that the interface between diamond and copper matrix were tightly bonded with the increase of sintering temperature, the fracture surface morphologies were consisted of ductile fracture on copper matrix and diamond particles falling out from the bonding interface. As the double-layer coated on the surface of diamond particles made the interface present tightly bonding, which improved the interfacial bonding between diamond and copper matrix. It was found that the temperature, pressure and holding time together can accelerate the densification process and further improve the thermo-physical of the composites. Comprehensive consideration of process parameters, the process parameters conducive to strengthening the interface bonding are 900 °C, 60 MPa and 40 min, and the relative density, bending strength, hardness and thermal conductivity of CuTi double-layer coated diamond/Cu composites were 99.77%, 153.52 MPa, 148.63 HV and 258.04 W/m·K, respectively. Moreover, higher sintering temperature, larger pressure and longer holding time could cause copper matrix to melt and grain growth as well as the graphitization of diamond, which reduced the densification and lowered the thermo-physical of the composites.