Diamond Particles Research Articles

Enhancement Effect of a Diamond Network on the Flow Boiling Heat Transfer Characteristics of a Diamond/Cu Heat Sink

The use of a micro heat sink is an effective means of solving the problem of high-power chip heat dissipation. Diamond/Cu composites exhibit high thermal conductivity and a linear thermal expansion coefficient that is compatible with semiconductor materials, rendering them ideal micro heat sink materials. The aim of this study was to fabricate diamond/Cu and Cu separately as heat sinks and subject them to flow boiling heat transfer experiments. The results indicate that the diamond/Cu heat sink displayed a decrease in wall superheat of 10.2–14.5 °C and an improvement in heat transfer coefficient of 38–51% compared with the Cu heat sink under identical heat fluxes. The heat sink also exhibits enhanced thermal uniformity. Secondary diamond particles are incorporated into the gaps of the main diamonds, thereby constructing a three-dimensional heat conduction network within the composite material. The diamond network enhances the internal heat flux of the material while also creating more nucleation sites on the surface. These increase the boiling intensity of the diamond/Cu heat sink, leading to better heat transfer performance. By combining the transient thermal model with computational fluid dynamics, a heat transfer model based on the diamond/Cu heat sink is proposed. The efficient heat dissipation capability of diamond/Cu heat sinks can lower the working temperature of microelectronic devices, thereby improving device performance and reliability during operation.

Fabrication of diamond/copper composite thin plate based on a single-layer close packed diamond particles network for heat dissipation

High-efficiency heat dissipation is crucial for the reliability and durability of high-power electronics devices. Diamond/copper composites have drawn much attention as promising candidate materials for thermal management due to their high thermal conductivity and tunable coefficient of thermal expansion. In this work, a novel method was proposed to fabricate a thin plate of diamond/copper composite based on the construction of single-layer close packed diamond particles network. The composite with a sandwich structure was prepared by press-brazing method, which is cost-effective for both preparation and post-processing. The microstructures of the composite plate containing diamond, AgCuTi filler and Cu were examined. The influence of diamond particle size on thermal conductivity, coefficient of thermal expansion, and mechanical properties were also experimentally measured and theoretically simulated. The results show that a single-layer close packed diamond particles network is densely brazed between copper layers to form a composite thin plate. The interface TiC layer is in-situ formed between diamond and AgCuTi matrix. With increase in the diamond particle size to 1200 μm, thermal conductivity of 552.7 W⋅m−1⋅K−1, coefficient of thermal expansion of 10.1 × 10-6 K−1, and flexural strength of 204.3 MPa are achieved, which are in agreement with the theoretical simulated results. As a heat spreader substrate, the heat dissipation ability of diamond/Cu composite is increased by 5.7 °C in comparison with pure Cu plate. Finite element analysis and testing of actual scenarios further confirm the excellent thermal performance of the sandwich structured diamond/Cu composite thin plate, making it a prospective candidate for thermal management.

Molecular dynamics and experiment on ultraviolet-thermal curing abrasive tools for polishing microstructures

To achieve efficient polishing of the microstructure array, a preparation method of the UV-thermal curing abrasive tools with diamond was proposed. The properties of the UV-thermal curing system were studied using molecular dynamics (MD) and experiments. The time, frequency, and pressure parameters of the UV-thermal curing abrasive tool were optimized by polishing the copper plate. MD simulation results show that increasing the temperature to 340 K can improve the blending compatibility. With the increase of the bisphenol A acrylate, the tensile property enhances from 16.38 MPa to 42.98 MPa, and the size shrinkage and mass loss weaken. The addition of diamond particles improves the anti-friction coefficient. Finally, the microstructure is polished twice under the polishing pressure of 300 N and 200 N, resulting in a roughness of Ra61nm on the upper surface and Ra105nm on the lower surface. This study can be used to guide the preparation and application of UV-thermal curing abrasive tools for polishing microstructure.

In situ formation mechanism of the honeycomb structure of a vitrified-bond diamond composite

Vitrified-bond diamond composites are materials commonly used for grinding wheels in the grinding process of silicon wafer production. In this study, the mechanism of the in situ honeycomb structure formation in the sintering process of composite materials was explored by changing the binder content without adding a pore-forming agent.The results show when the content of vitrified bond is 55 wt%, the in situ honeycomb structure forms, resulting in a porosity of 60.68 % and bending strength of 23.03 MPa.The X-ray diffraction (XRD), Raman spectroscopy (RS), and thermogravimetry-differential thermal analysis (TG-DTA) results show that no graphitization of diamond grain occurs during sintering. The bonding ability between the vitrified bond and diamond grain, along with the microstructure of vitrified-bond diamond composites, was studied using scanning electron microscopy (SEM). Moreover, the results of energy spectrum analysis (EDS) show that the diffusion and segregation of Na at the interface between the diamond particles and the vitrified bond improve the bonding strength, and the vitrified bond can effectively bond with the diamond particles. Finally, the formation mechanism of the honeycomb structure was elucidated using the surface and interface sintering theory.

Tribological and Grinding Properties of Spherical Diamond Grown on a Rough Discontinuous Surface

Spherical diamond particles have great potential as additive materials for improving lubricity of lubricants, and yet the complicated preparation process is difficult to meet the current industrial demand. Therefore, a novel method was proposed to deposit mass spherical diamond on the discontinuous silicon nitride (Si3N4) powder substrate by the hot filament chemical vapor deposition method. The results revealed that the substrate was covered by the spherical diamond grains with a diameter of about 20 μm. Thereafter, they were used as lubricant additives to examine the tribological and grinding properties. Therein, the Si3N4 surface had a remarkable reduction in surface roughness by a factor of 124.62% as compared to that without spherical diamond powder, while GCr15 alloy had a 31.17% increase under the same condition. Hence, our method provides a promising way to deposit the mass spherical diamond powder that might become a great abrasive material for machining the ceramic.

Preparation of bimodal-diamond/SiC composite with high thermal conductivity

The excellent thermal properties of diamond/SiC composites are mainly attributed to the addition of diamond particles. In order to further increase the diamond content, a novel preparation method was used to regulate the distribution of bimodal diamond particles. Moreover, in order to achieve better performance, the effects of particle size ratios on the properties were studied. The results show that with the increase of small diamond particle size, the bimodal diamond packing will change from unmixing mechanism to mixing mechanism, and the critical ratio (small/large) of entrance for 400 µm diamond particles is between 0.37 and 0.5. When the particle size ratio is 0.25, the thermal conductivity reaches the maximum, reaching 812.27 W/mK (break through 800 W/mK for the first time). In addition, the influence of particle size ratio on coefficient of thermal expansion is also discussed.

Effect of tool wear on machining quality in milling Cf/SiC composites with PCD tool

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have great application potential in aerospace. But their high hardness and anisotropy cause rapid tool wear during machining, which affects machining quality and efficiency. However, tool wear mechanisms in milling Cf/SiC composites are still unclear. There is a lack of research on the relationship between tool wear and cutting performance. In this paper, milling experiments on 2.5D Cf/SiC composites were conducted using polycrystalline diamond (PCD) cutters. The tool wear mechanisms and effect of tool wear on surface roughness, milling force, burr damage, surface microstructure and chips were explored. The results show that abrasive wear caused by chips continuously scraping tool material and diamond particle fragmentation and falling off caused by sprouting and expansion of cracks inside grain were primary causes of tool failure. The formation mechanism of burr damage was analyzed. It was proved that the peak radius of cutting edge Rpeak and flank wear VB could reflect cutting capabilities. It was found that increasing flank wear had regrinding effects on the cutting edge, which affects the peak radius. The degree of burr damage was related to these two parameters. Tool wear changed the surface formation mechanism. Before tool wear, carbon fibers were primarily removed through the micro-brittle fracture, with low surface roughness. The flank face and chips scratched the workpiece like abrasive grains after tool wear, leaving scratches on the surface and increasing surface roughness from 1.27 μm to 2.25 μm.

Electrochemical recycling of diamond and precious metals from used diamond tools

The recycling of used diamond tools, which contain a large amount of unused diamond particles and precious metals, can not only realize the reuse of resources, but also reduce the pressure of environmental protection. In this paper, diamond particles were recovered by acid dissolution of aqua regia, and the current density, complexing agent concentration and pH value of the acid dissolution system were adjusted to recover Cu and Co by electrodeposition. Scanning electron microscope and energy spectrometer were used to study the changes of the composition and morphology of the plated layers, and the effects of the parameters such as current density, complexing agent concentration and pH on the organization and composition of the alloy plated layers were analyzed. The results showed that at the current density of 40 mA/cm², pH 4.5 and complexing agent concentration of 10 g/L, uniformly distributed, dense and moderately thick Cu-Co alloy plating was obtained, and the weight percentages of Cu and Co reached the peak respectively. The Cu and Co in the waste diamond tools can be recovered under this condition with good recovery effect.

Investigation of the Fabrication of Diamond/SiC Composites Using α-Si3N4/Si Infiltration.

Diamond/SiC (Dia/SiC) composites possess excellent properties, such as high thermal conductivity and low thermal expansion coefficient. In addition, they are suitable as electronic packaging materials. This study mainly optimized the diamond particle size packing and liquid-phase silicon infiltration processes and investigated a method to prevent the adhesion of the product to molten silicon. Based on the Dinger-Funk particle stacking theory, a multiscale diamond ratio optimization model was established, and the volume ratio of diamond particles with sizes of D20, D50, and D90 was optimized as 1:3:6. The method of pressureless silicon infiltration and the formulas of the composites were investigated. The influences of bedding powder on phase composition and microstructure were studied using X-ray diffraction and scanning electron microscopy, and the optimal parameters were obtained. The porosity of the preform was controlled by regulating the feeding amount through constant volume molding. Dia/SiC-8 exhibited the highest density of 2.73 g/cm3 and the lowest porosity of 0.6%. To avoid adhesion between the sample and buried powder with the bedding silicon powder, a mixed powder of α-Si3N4 and silicon was used as the buried powder and the related mechanisms of action were discussed.

A Novel Diamond/AlSi Composite Coating on Ti-6Al-4V SubStrate Made by Ultrasonic-Assisted Brazing

Ultrasonic-assisted brazing (UAB) technology has been introduced to prepare the diamond/AlSi composite coating on Ti-6Al-4V substrate. The microstructure and wear properties of the coating were studied. The results showed that AlSi filler metal had a certain spreading and climbing phenomenon on the diamond surface, indicating a significant improvement in wettability between AlSi filler metal and diamond by ultrasonic-assisted brazing. Under ultrasound action, the microstructure of AlSi brazing alloy was greatly refined, and the Ti atoms in the Ti-6Al-4V substrate diffused to the interface between diamond and AlSi brazing alloy and formed TiC on diamond particles. There was no thermal damage to diamond particles when the brazing temperature was 750 °C. UAB improved the microhardness of the coating alloy matrix due to the increasing quantity and distribution range of TiAl3 as reinforced particles but had no obvious effect on the microhardness of the Ti-6Al-4V substrate. The wear resistance of Ti-6Al-4V substrate with diamond/AlSi composite coating was promoted due to the dense diamond particles, the formed TiC on diamond particles, and the increase in microhardness of the alloy matrix of diamond/AlSi coating under ultrasound action.

Sintering window and sintering mechanism for diamond

High performance sintered diamond tools, such as those applied to wire drawing and rock drilling, represent a considerable advance in hard materials technology. A dense diamond-metal composite is produced using liquid phase sintering. With a cemented carbide substrate, a cobalt-rich liquid infiltrates between the diamond grains at temperatures near 1400 °C. For small diamond particles (nominally below 20 μm), a combination of high pressure (5 GPa or more) and high temperature (1400 °C or more) gives full density in minutes. A sintering window is defined by the pressure and temperature combination that avoids graphitization while ensuring cobalt melt infiltration. The sintering mechanism is carbon transport by dissolution of graphite from low pressure regions away from grain contacts with precipitation of diamond at grain contacts under high pressure. Sinter bonds preferentially nucleate at surface defects, such as screw dislocation spirals. Bonding rates depend on particle size, carbon solubility, temperature, pressure, and hold time. Calculations are shown for interface reaction site limited growth kinetics.

Freeform thermal-mechanical Bi-functional Cu-plated diamond/Cu metamaterials manufactured by selective laser melting

The leverage of selective laser melting (SLM) successfully fabricate metal matrix composites (MMCs) metamaterials with freeform intricate triply periodic minimal surface (TPMS) structures that are not possibly fabricated by conventional methods and exhibit exceptional mechanical properties. SLM fabricated high precision MMCs metamaterial TPMS structures are of great potential in energy conversion, heat management and lightweight applications. Due to the self-supporting geometric characteristics of TPMS, the metamaterial structures could effectively overcome the manufacturing constraints of SLM. Besides, their freeform capability offers great opportunities to be bi-functional or multi-functional through the selection of materials as well as the design optimization of structure. Diamond can offer unique advantages in the field of heat management due to its outstanding thermal and mechanical properties. The addition of micro-sized diamond particles into copper can tailor its coefficient of thermal expansion (CTE) while enhancing its thermal conductivity (TC). SLM fabricated diamond reinforced copper MMCs metamaterials with TPMS structure could bring outstanding thermal-mechanical bi-functional properties for prospective lightweight thermal management applications. In our previous work, the interfacial bonding issue between diamond particles and Cu matrix was resolved by a coating of copper on micro-sized diamond particle reinforcement. In this present work, 1 vol% Cu-plated diamond/Cu metamaterials with three various TPMS (Gyroid-G, Schwarz Primitive-P, Diamond-D) structures were successfully fabricated via SLM for the first time. Their bi-functional heat transfer and compression behaviors were evaluated by measurement and numerical simulation for three TPMS (G, P, D) structures and TPMS (D) structures with various lattice thicknesses. From the lightweight perspective of three TPMS structures with 0.2 mm wall thickness, the order of these structure is TPMS P structure, TPMS G structure, TPMS D structure (0.2 mm wall thickness, 0.2 P > 0.2 G > 0.2D). If heat transfer performance is an important consideration, The 0.2D structure can be selected from the three TPMS structures. This research also investigated the continuous design of TPMS D structure with various wall thickness and creatively proposed a flexible TPMS design paradigm toward advanced thermal-mechanical bi-functional Cu-plated Diamond/Cu metamaterials via SLM for prospective lightweight thermal management applications.

Properties of SiO2-B2O3-Li2O-ZnO-Al2O3 glass-ceramic-coated diamond particles prepared by sol-gel method

During the process of sintering diamond/ceramic composites, the wettability between diamond and the ceramic matrix is poor, and there are many irregular pores in the composites, which leads a low bending strength of the composites and easy shedding of diamond. In order to solve these problems, SiO2-B2O3-Li2O-ZnO-Al2O3 glass-ceramic coated diamond was prepared by a sol-gel method, and the properties of the coated diamond abrasive particles were studied. The SBLZA glass-ceramic-coated diamond exhibited high thermal stability and excellent oxidation resistance, making it a good protective material for diamond. The oxidation resistance of the SBLZA glass-ceramic-coated diamond was determined by thermogravimetric analysis (TGA). The uncoated diamond abrasive particles began to oxidize at 723 °C, while the coated abrasive particles were resistant to oxidation at temperatures up to 1000 °C. The glass-ceramic coating significantly improved the bonding between diamond and the ceramic matrix. The use of SBLZA glass-ceramic-coated diamond instead of uncoated diamond in the composites sintered at 750 °C resulted in a decrease in the volume expansion rate of the diamond/ceramic composites from 37.2 % to 28.5 %, and an increase in the bending strength from 38.4 MPa to 61.5 MPa.

Mechanical, Thermal, and Erosive Behavior of Recovered Inorganic Diamond Particles in Polyepoxide Composites

Mechanical, Thermal, and Erosive Behavior of Recovered Inorganic Diamond Particles in Polyepoxide Composites

Effect of uncoated and coated diamond on the compressive properties of porous aluminium composites

AbstractPorous aluminium composites are structural and functional materials that have vast potential, due to their lightweight and high energy absorption capacity, especially in automotive and aerospace applications. In this study, the effect of varying content of uncoated and titanium coated diamond particles on the compressive properties of porous aluminium composite was investigated. The composites were developed using powder metallurgy technique and porosity was attained by using polymethylmethacrylate (30 wt.%) as space holder material. The morphology of the pores was found to replicate the shape and size of polymethylmethacrylate particles, that were uniformly distributed in the composites. X‐ray diffraction analysis confirmed formation of aluminium carbide in uncoated diamond‐based aluminium composites while negligible amount was present in titanium coated porous composites during sintering. The porosities of composites decreased with an increase in diamond content due to the incomplete decomposition of polymethylmethacrylate particles. Moreover, the maximum plateau stress and energy absorption capacity of 9.96 MPa and 1.7 Mj/m3 were obtained for the composites with 8 wt.% of titanium coated diamond particles. Thus, coating inhibits the formation of undesirable compounds and contributes to better interfacial bonding between matrix and reinforcement.

Finite element based 3-D modelling of residual stress in high vacuum actively brazed diamond/Ni-Cr filler/C45 steel joint

In active brazing of diamonds, high brazing temperature and difference in the thermo-mechanical properties of the diamond grain, filler alloy, and substrate lead to the development of unfavorable residual stresses in the bonding region. This residual stress can potentially cause initiation of cracks within the interfacial reaction layer formed between diamond and filler-alloy, weakening the joint. Since the diamond particles used in diamond grinding tools are micro-sized and complex in shape, it is experimentally difficult to measure residual stress at the grit-filler interface. In the present investigation, a coupled thermo-mechanical three-dimensional finite element model has been developed to predict, map, and analyse the formation of residual stresses in diamond-bond-substrate systems. The presented model uniquely differs from those in literature, which are mostly 2-D type and did not consider the presence of interfacial reaction layer between diamond and filler. A Ni-Cr-Fe-B active brazing alloy has been selected as the filler and C45 steel as the substrate in the current simulation. Chromium carbide has been considered to be the interfacial compound. The numerical simulation suggests that the maximum value of residual stresses, predominantly tensile in nature, gets shifted from the diamond to the intermetallic zone at the bond level when the interfacial reaction compound is introduced between the diamond and filler. It also establishes that orientations of diamond during its placement on substrate for brazing have significant influence on the magnitude of induced residual stress. Approximately 40 % reduction has been observed in case of hexagon-base brazed diamonds when compared to that (1620 MPa) developed on square-base brazed diamonds. Raman spectral analysis of brazed specimen was conducted to experimentally validate the numerical simulation results. Residual stress was estimated from the peak shift of D-band in the spectra. The numerically computed residual stresses were found to deviate within the range of 3–15 % of the experimentally determined values.

Development of high thermal conductivity of Ag/diamond composite sintering paste and its thermal shock reliability evaluation in SiC power modules

Diamond has the highest thermal conductivity among naturally occurring materials and a relatively low coefficient of thermal expansion (CTE), making it a promising interconnected material for next-generation semiconductor power devices. In this study, Ag/diamond composite sintering paste was developed. The agglomerated diamond particles were uniformly dispersed in the sintered Ag porous structure, and the thermal conductivity was increased from 171.4 W/(m·k) for pure Ag sintering to 288 W/(m·k) for an Ag@2%diamond (2% of the total weight of Ag) specimen. The interfacial microstructure evolution and fracture behavior were investigated in detail for a SiC/Direct Bond Copper (DBC) joint structure during an extreme thermal shock test (TST) in the range of −50 °C–250 °C. Importantly, with a moderate amount of diamond additive, the microstructural degradation and severe deformation of the DBC substrate were effectively suppressed. This is mainly attributed to the diamond addition, which can block the migration pathways of Ag atoms toward long-term thermal shock and adjust the thermo-mechanical performance of the sintered layer. This detailed study about Ag/diamond composite paste can provide new guidance for strengthening sintered Ag interconnections for SiC power modules.

Effects of Particle Size and Solid Loading on Stereolithography for Preparation of Diamond-Based Composites

3D printing is a revolutionary technology that can easily produce complex shapes with low cost and high efficiency. In recent years, technologies for 3D printing have been developed rapidly for polymers, metals, ceramics, and composite materials. Due to its advantages in configuration, 3D printing has also been expected to be a powerful method for preparing diamond-based composites and promoting the applications of diamonds as well. In this paper, stereolithography printing technology is employed to prepare diamond-based composites with special attention to slurry preparation and its stereolithography performance. The impact of diamond particle size, solid loading, and exposure time on the photocuring performance of the diamond slurry are investigated systematically. In addition, the correlation between the thermal conductivity of the printed materials with particle size and solid loading is also studied. The highest thermal conductivity in this study is 1.32 W/(m·K), achieved with an average particle size of 15 μm and a solid loading of 75 wt%. The results show the great potential of preparing diamond-based composites by 3D printing and provide theoretical and technical guidance for further research.

Strengthening Mechanisms and Retention Properties of Sintered Iron-Based Matrix Material for Metallic-Diamond Tools.

This work presents the analysis of mechanisms controlling the deformation strengthening of the surface during abrasion and their impact on structural changes and mechanical properties of Fe-Mn-Cu-Sn-C matrix material, which was prepared by means of powder metallurgy (PM). The powder mixture was ball-milled for 8 h and densified to <1% porosity using hot pressing at 900 °C and 35 MPa. Phases and structural transformations taking place in austenite during plastic deformation were identified. The participation, distribution, and morphology of the phases, as well as the physicomechanical properties of the matrix material, were tested. It has been shown that during grinding, deformation twins are generated in areas where an austenitic microstructure is present. To test the ability of the matrix to keep diamond crystals firmly cylindrical (Ø11.3 mm× 5 mm), diamond-impregnated specimens containing diamond grits of 30/40 mesh in size and at a concentration of 20 (5% vol.) were prepared. It was finally determined by the diamond-retention index, which is the number of retained diamond particles compared to the total number of diamond particles and the pullouts on the working surface of the segment. This research shows that materials containing Ti- and Si-coated diamond particles, deposited by the CVD method, have the highest abrasion resistance and, therefore, have the best retention properties. In order to determine the bonding mechanism at the matrix-diamond interface, specimens were also analyzed by SEM and TEM.

Effect of Rough‐Surfaced Diamond Content on the Microstructure, Tribological Behavior, and Corrosion Resistance of Ni/Diamond Composite Coatings

This study fabricates certain Ni/diamond composite coatings using a coelectrodeposition method and then evaluates the effect of diamond content on the morphology, phase structure, microhardness, wear, and corrosion resistance of such coatings, while exploring their tribological and anticorrosion mechanisms. It is demonstrated that the addition of diamond can change the preferred orientation of Ni from (200) to (111), and its texture coefficient value can be boosted from 23.3% to 64.4% with the increase of diamond content. In the experiment, at a diamond content of 3 g L−1, the deposited diamond particles are more and evenly dispersed across the composite, with the microhardness of nickel‐based coatings reaching an optimum value of 613 HV. In addition, the coefficient of friction is reduced to a minimum value of 0.627, while the wear rate is kept at only 1.79 × 10−5 mm3 Nm−1, indicating a high wear resistance. Electrochemical test results demonstrate that the Ni/diamond composite coatings produced at 3 g L−1 create the maximum charge transfer resistance (5429.3 Ω cm2) and the minimum corrosion current density (2.19 μA cm−2), features that can deliver the best corrosion resistance.