Diamond Particle Size Research Articles

Synergetic effect of diamond particle size on thermal expansion of Cu-B/diamond composite

Diamond particles reinforced Cu matrix (Cu/diamond) composites have promising applications for heat dissipation of high-power electronic devices because of their high thermal conductivity and suitable coefficient of thermal expansion. The effect of diamond particle size on thermal conductivity has been addressed; however, the effect of diamond particle size on thermal expansion still needs to be clarified. In this study, Cu-B/diamond composites with various diamond particle sizes ranging from 66 μm to 701 μm were fabricated to assess the impact of diamond particle size on the thermal expansion behavior. The composites exhibit low and adjustable coefficient of thermal expansion (CTE) values of 4.58–6.63 × 10−6 K−1, which align with 4–8 × 10−6 K−1 of widely employed semiconductors. The CTE of the Cu-B/diamond composites first decreases and then increases with increasing diamond particle size, which arises from a synergetic effect of interfacial bonding strength and matrix strengthening effect. As the diamond particle size is smaller than 272 μm, the interfacial bonding strength rises with increasing particle size, enabling the diamond particles to restrain the expansion of the Cu matrix more effectively and to reduce the CTE. As the diamond particle size exceeds 272 μm, the dislocation density in the Cu matrix continually decreases with increasing particle size, reducing the strength increment in the Cu matrix and increasing the CTE. The effect of thermal cycling on the thermal expansion of the Cu-B/diamond composites was also investigated, and all the composites show an increase in the CTE after 100 thermal cycles. Notably, the composite with 272 μm diamond particle size exhibits the lowest CTE increment. It shows a CTE value of 5.29 × 10−6 K−1 after thermal cycling, still compatible with the semiconductors for electronic packaging applications.

Ti6Al4V alloy with diamond particle-reinforced Cu-based coatings: Microstructure and tribological performance

To enhance the surface wear resistance of the Ti6Al4V alloy, diamond particles-reinforced Cu-based composite coatings (D500/D1000/D2000 coating: 500/1000/2000 mesh diamond: Cu-based alloy powder = 1:30 (wt%)) were fabricated by vacuum cladding. Cu-based alloys with liquid phase temperatures lower than the phase transition temperature of Ti6Al4V alloys were employed as cladding materials to avoid performance deterioration of Ti6Al4V substrates. The microstructure, mechanical properties, and dry-sliding tribological properties of the Cu-based composite coatings have been investigated systematically. The Cu-based composite coatings are composed of the ductile intermetallic compounds Ti3Sn and SnTi2 as the metal matrix, the hard and brittle intermetallic compounds CuTi, CuTi2, Ti(Cu, Al)2 and CuSn3Ti5, in situ generated TiC and the directly introduced diamond particle as the reinforced phases. In addition, a TiC hard phase protective layer was formed around the diamond particles, which retained the original properties of the diamond. The hardness of diamond particles-reinforced Cu-based composite coatings is much higher than that of the Ti6Al4V. Among them, the D2000 coating possesses the highest microhardness. The average Vickers hardness (HV0.5) on the coating surface and nanoindentation hardness (H) on the coating cross-section (the middle part without diamond particles) of the D2000 coating are 1329.8 HV0.5 and 16.87 GPa), which are 4–5 times higher than that of the Ti6Al4V substrate (333 HV0.5 and 3.37 GPa). Nevertheless, the D2000 coating (wear rate of 50.75 ×10−5 mm3/Nm) demonstrates slightly inferior tribological performance compared to the D500 coating. The wear rate of the latter is approximately 13.37 × 10−5 mm3/Nm, which is only 1/5.6 of the substrate (75.67 ×10−5 mm3/Nm). The larger the diamond particle size, the more the diamond serves as a bearing capacity support point to prevent the hard WC ball from further ploughing into the composite coating, and the better the wear resistance of the coating. Notably, D500 coating with excellent wear resistance has the potential for application in various fields of the machinery industry, marine engineering, and aerospace.

Cr-Diamond/Cu Composites with High Thermal Conductivity Fabricated by Vacuum Hot Pressing.

Chromium-plated diamond/copper composite materials, with Cr layer thicknesses of 150 nm and 200 nm, were synthesized using a vacuum hot-press sintering process. Comparative analysis revealed that the thermal conductivity of the composite material with a Cr layer thickness of 150 nm increased by 266%, while that with a Cr layer thickness of 200 nm increased by 242%, relative to the diamond/copper composite materials without Cr plating. This indicates that the introduction of the Cr layer significantly enhanced the thermal conductivity of the composite material. The thermal properties of the composite material initially increased and subsequently decreased with rising sintering temperature. At a sintering temperature of 1050 °C and a diamond particle size of 210 μm, the thermal conductivity of the chromium-plated diamond/copper composite material reached a maximum value of 593.67 W∙m-1∙K-1. This high thermal conductivity is attributed to the formation of chromium carbide at the interface. Additionally, the surface of the diamond particles in contact with the carbide layer exhibited a continuous serrated morphology due to the interface reaction. This "pinning effect" at the interface strengthened the bonding between the diamond particles and the copper matrix, thereby enhancing the overall thermal conductivity of the composite material.

Preparation and Property Modulation of Multi-Grit Diamond/Aluminum Composites Based on Interfacial Strategy

The development of electronic devices has a tendency to become more complicated in structure, more integrated in function, and smaller in size. The heat flow density of components continues to escalate, which urgently requires the development of heat sink materials with high thermal conductivity and a low coefficient of expansion. Diamond/aluminum composites have become the research hotspot of thermal management materials with excellent thermophysical and mechanical properties, taking into account the advantages of light weight. In this paper, diamond/Al composites are prepared by combining aluminum as matrix and diamond reinforcement through the discharge plasma sintering (SPS) method. The micro-interfacial bonding state of diamond and aluminum is changed by adjusting the particle size of diamond, and the macroscopic morphology performance of the composites is regulated. Through this, the flexible design of diamond/Al performance can be achieved. As a result, when 150 μm diamond powder and A1-12Si powder were used for the composite, the thermal conductivity of the obtained specimens was up to 660.1 W/mK, and the coefficient of thermal expansion was 5.63 × 10−6/K, which was a good match for the semiconductor material. At the same time, the bending strength is 304.6 MPa, which can satisfy the performance requirements of heat-sinking materials in the field of electronic packaging.

Refractometric method to study the coating thickness of diamond nanoparticles

A method based on refractometric measurements of liquid nanodisperse systems has been developed to determine the quantitative composition of diamond-amorphous carbon colloidal particles. It was demonstrated that by measuring the changes in the refractive index and density of sols caused by changes in particle concentration it is possible to determine the thickness of the particle surface layer, assuming its composition is known. Within the framework of the Mie theory, the influence of the size of diamond particles with carbon coating on the refractive index of hydrosols was quantified. The limits of applicability of the developed method have been determined. For several polydisperse sols with coated diamond particles the thickness of carbon coating was determined.

Effect of diamond particle size on thermal conductivity and thermal stability of Zr-diamond/Cu composite

The diamond particle size plays a critical role in regulating the thermal conductivity of diamond/Cu composite. However, the dependence of diamond particle size on thermal conductivity is generally interfered with interface carbides, and the effect of diamond particle size on the thermal stability of diamond/Cu composite has not been addressed. In this study, we fixed the thickness of the ZrC interlayer between Cu and diamond at around 60 nm and varied diamond particle size from 54 to 272 μm to investigate the relationship between diamond particle size and composite thermal conductivity. The thermal conductivity of the Zr-diamond/Cu composite increases with increasing diamond size. A high thermal conductivity of 820 W/mK is obtained with a diamond particle size of 272 μm. The thermal conductivities of all composites are decreased after 100 thermal cycles, and the diamond/Cu composite with large diamond particle size shows better thermal stability during thermal cycling. The findings emphasize the importance of tailoring diamond particle size to attain high thermal conductivity in the diamond/Cu composites and provide useful guidelines for their thermal management applications.

Effects of diamond particle size on microstructure and properties of diamond/Al-12Si composites prepared by vacuum-assisted pressure infiltration

Effects of diamond particle size on microstructure and properties of diamond/Al-12Si composites prepared by vacuum-assisted pressure infiltration

Rheology of magnetorheological shear thickening polishing fluids with micro diamond abrasive particles

Magnetorheological shear thickening polishing (MRSTP) has the dual effect of shear thickening and magnetization enhancement, thereby enhancing polishing efficiency. MRSTP fluids (MRSTPFs) were prepared using polyethylene glycol (PEG), silicon dioxide (SiO2), carbonyl iron particles (CIPs), and diamond micro-abrasive particles. MRSTPFs containing diamond particles of various sizes were prepared for rheological tests. A rheological hypothesis was proposed regarding the development of CIPs chains and the ability to aggregate PEG and SiO2. Rheological tests results indicated that each sample exhibited shear thickening and magnetization enhancement effects under the magnetic field and shear rate. The shear thickening effect decreased with increasing magnetic flux density, while the overall viscosity and shear stress increased. As the magnetic flux density increased from 0 mT to 112 mT, the thickening ratio of MRSTPFs containing 3 μm diamond particles decreased from 18.94 to 1.37, but the peak viscosity increased from 5.208 Pa·s to 3639 Pa·s. The thickening ratios of MRSTPFs with different abrasive sizes showed a slight variation from 0.11 to 1.76 at the same magnetic flux density of 22 mT, 45 mT, 68 mT, 90 mT, and 112 mT, respectively. It demonstrated that the diamond particle size did not have a significant effect on the rheological properties of MRSTPFs. The correctness of the hypothesis was confirmed. The storage modulus of MRSTPFs exceeded the loss modulus at non-zero magnetic flux density, indicating that the MRSTPFs had become semi-solid. The microscopic mechanism showed that the rheological characteristics were determined by the evolution of the chain structure of CIPs and the binding ability of PEG to SiO2. This study provided valuable insights into exploring mechanisms of MRSTPFs and demonstrating the potential application of MRSTP.

Densification and Surface Carbon Transformation of Diamond Powders under High Pressure and High Temperature.

A new type of poly-diamond plate without a catalyst was produced via the high-pressure high-temperature (HPHT) compression of diamond powders. The densification of diamond powders and sp3 to sp2 carbon on the surface under HPHT compression was investigated through the characterization of the microstructure, Raman spectroscopy analysis and electrical resistance measurement. The densification and sp3-sp2 transformation on the surface are mainly affected by the pressure, temperature and particle size. The quantitative analysis of the diamond sp3 and sp2 carbon amount was performed through the peak fitting of Raman spectra. It was found that finer diamond particles under a higher temperature and a lower pressure tend to produce more sp2 carbon; otherwise, they produce less. In addition, it is interesting to note that the local residual stresses measured using Raman spectra increase with the diamond particle size. The suspected reason is that the increased particle size reduces the number of contact points, resulting in a higher localized pressure at each contact point. The hypothesis was supported by finite element calculation. This study provides detailed and quantitative data about the densification of diamond powders and sp3 to sp2 transformation on the surface under HPHT treatment, which is valuable for the sintering of polycrystalline diamonds (PCDs) and the HPHT treatment of diamonds.

Diamond reinforced reaction-bonded boron carbide composites: Fabrication, microstructure, mechanical and tribological properties

Reaction-bonded boron carbide composites were fabricated by molten silicon infiltration of diamond-containing boron carbide preforms. The effects of diamond particle size on the microstructure, mechanical and tribological properties of reaction-bonded boron carbide composites were investigated. Fine diamond particles (≤7.7 µm) completely reacted with silicon generating nano silicon carbide particles, which bonded the boron carbide particles forming a 3-D ceramic skeleton and improving the flexural strength of the composites. Coarser diamond (≥24 µm) particles were retained protected by a dense SiC layer generated from the reaction of diamond and molten silicon. A “core-shell” structure with the retained diamond as the “core” and with the reaction formed silicon carbide as the “shell” formed. Relief structures were established on the composites’ surface during the wear process, greatly reducing the friction coefficient and improving the wear resistance.

Dynamic simulation of powder spreading processes toward the fabrication of metal-matrix diamond composites in selective laser melting

A novel method for the integrated production of structural and functional metal-matrix diamond composites is provided by selective laser melting (SLM) in the field of diamond tools. However, the uneven distribution of diamond particles and loose packing density in the powder bed can easily result in poor performance of diamond tools. In this work, a discrete element method model of diamond/CuSn composite powders is developed to simulate blade-spreading processes. It investigates how powder bed quality and particle dynamics are affected by diamond powder physical properties and powder spreading process parameters. The findings reveal that coarse diamond particles exhibit strong force chains at low velocities, whereas contact force chains are weak for fine CuSn particles at high velocities. It shows that diamond particles with irregular shapes have poor diffusivity and spreadability due to the large friction and mechanical locking forces, which causes diamond particles segregation. Therefore, the packing density and uniformity of the powder bed are both improved by reducing the volume fraction and particle size of diamond particles. In addition, the powder bed quality is improved by increasing the powder layer thickness and decreasing the translational speed of the blade, which weakens the shear expansion and jamming of diamond particles. The results have some significance for optimizing powder spreading processes toward the production of metal-matrix diamond composites in SLM.

Effect of Interfacial Coatings on Thermal Conductivity of Diamond/Al Composites

In this paper, the acoustic mismatch model and the differential effective medium scheme were applied to predict the influence of different interfacial coatings (Si and SiC) on the interfacial thermal conductivity and thermal conductivity of the Diamond/Al composites, respectively. With the increase of the thickness of interfacial coatings, the interfacial thermal conductivity and of the thermal conductivity of Diamond/Al composites decreased. In order to obtain ideal thermal conductivity of Diamond/Al composites, the thickness of the coating should be controlled below 1 μm. When the volume fraction of diamond was 60% and the average particle size was 100 μm, the interfacial thermal conductivity of Si and SiC coated Diamond/Al composites were in the range of 1.77×107∼1.1×108 W/(m2 · K) and 2.44×107∼1.29×108 W/(m2 · K), respectively; the thermal conductivity of Si and SiC coated Diamond/Al composites were in the range of 541.58∼764.15 W/(m· K) and 594.45∼777.3 W/(m· K), respectively. The thermal conductivity of Si and SiC coated Diamond/Al composites increased with the volume fraction and average particle size of Diamond, and the thermal conductivity of SiC coated Diamond/Al composites was higher than that of Si coated composites. SiC interface coating was proposed to be the most promising candidates to improve the thermal performance of Diamond/Al composites.

Influence of diamond matrix morphology on ZnO surface morphology and preferred orientation

The signal propagation loss and conversion efficiency are two critical performances of diamond/ZnO film-based surface acoustic wave (SAW) device, and depend on roughness and preferred orientation degree (POD) of ZnO surface layer at plane (002). In-situ improvement of operational performance of ZnO layer is achieved by adjusting morphology of diamond matrix layer via diamond particle size. Diamond layer is deposited on silicon substrate using hot-filament chemical vapor deposition (HFCVD) technique by varying Ar/(Ar+H2) ratio. The ZnO layer is then deposited on the diamond film using radio-frequency magnetron sputtering (RFMS). The results show that, by regulating the diamond particle size, it is possible to adjust morphology of the diamond layer and facilitate variation in morphology and preferred orientation of ZnO layer for a better operational performance of SAW device. When the diamond particle size is decreased from 1.38 to 0.12 µm, the root-mean-square (RMS) roughness of ZnO layer initially drops and then rises, and the lowest roughness is 6.4 nm. Also, POD of ZnO (002) increases from 2.61 to 2.89, and then drops to 2.83. For a diamond particle size of 0.35 µm, the RMS roughness of ZnO layer has minimum value of 6.4 nm, and the POD of ZnO (002) approaches the maximum of 2.89 with a half-peak width of 0.36˚. The influence of diamond layer morphology on ZnO morphology and POD is thus proposed.

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.

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.

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.

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.

Synergetic effect enabling high thermal conductivity in Cu/diamond composite

Diamond has a superior thermal conductivity, but the diamond particles reinforced Cu matrix composites exhibit thermal conductivities far from expected. Here an ultrahigh thermal conductivity of 1050 W/mK is realized in a Cu/diamond composite via a discrete in situ carbide interlayer and a bimodal diamond particle strategy. The high thermal conductivity stems from a synergetic effect of high interfacial thermal conductance, large diamond particle size, high diamond content, and high relative density in the composite, which are obtained simultaneously. The study highlights the fundamental role of synergetic effect in attaining high thermal conductivity in Cu/diamond composites. This methodology also provides guideline for preparing other diamond particles reinforced composites for thermal management applications.

Study of the hot-pressing sintering process of diamond/copper composites and their thermal conductivity

Diamond/copper composites have been widely studied as high thermal conductivity (TC) materials for heat dissipation in electronic integrated devices. In this study, diamond/copper composites with fin structures were prepared by hot-pressing sintering. The relative density and TC of the composites were analyzed for different diamond particle sizes, diamond volume fractions, sintering temperatures and sintering pressures. The relative density of the composites decreases significantly with increasing diamond particle size and volume fraction. The TC of the composite was found to be a maximum of 564.2 W/m·K at 1400 N sintering pressure and 900 °C sintering temperature when the diamond particle size was 230 µm and the volume fraction was 60%. In addition, the coefficient of thermal expansion (CTE) of the diamond/copper composite was 7.01 × 10−6 K−1 at 1400 N sintering pressure and 900 °C sintering temperature, which meets the packaging requirements for electronic integrated devices. The heat dissipation experiment of the diamond/Cu microchannel heat sink (MCHS) showed that the surface temperature of the heat source can be controlled at 59.9 °C when the inlet velocity was 0.4 m/s, achieving a cooling of 40.1 °C.

Thermal failure of diamond tools indicated by diamond degradation: Damage evaluation and property prediction on small image datasets

High temperature induced diamond degradation often leads to the failure of diamond tools. In this work, diamond samples holding different degrees of thermal damage were prepared by heating and sintering. The influence of diamond particle size and processing temperature was investigated through mechanical testing and micromorphology observation, meanwhile, a dataset containing 2870 SEM images showing diamonds with different degrees of degradation was constructed. By modification of VGG16 network, classification models and regression models were developed for thermal damage evaluation and sample property prediction. Training strategies including transfer learning and data augmentation were implemented and verified essential on the small dataset, where drop-out showed no positive effects. Two classification models (3-class and 65-class) were constructed and trained for damage evaluation. Visualized damage feature maps exported from Grad-CAM revealed the influential mechanism of thermal damage on diamonds, which proved the effectiveness of the classification models as well. Under the optimized training strategies, regression models were built for sample property prediction. The models towards toughness index, bending strength loss, relative density and Rockwell hardness were examined. Comparing the output results with real property values in test sets, the first two models matched well, and the latter two showed the opposite. It verified the validity of the regression models for property prediction as they were all established based on diamond damage image datasets. The loss in bending strength loss prediction model was smaller than that of toughness index, indicating bending strength easier to be shorten than impact toughness for diamond/metal composites suffering thermal impacts.