Diamond Particle Size Research Articles

Preparation of Ni-P-diamond coatings with dry friction characteristics and abrasive wear resistance

The Ni-P-diamond composite coatings that contained diamond particles with various sizes in microns have been prepared by electroless plating. The effects of diamond particle size and heat-treatment on the microstructure, mechanical properties, dry friction behavior and abrasive wear performance of the Ni-P diamond composite coatings were investigated. It was discovered that a Ni-P diamond composite coating with the thickness of 30μm could be obtained. The diamond particles (2–9μm) could be homogeneously dispersed in the coatings with the volume fractions of 21%–25%. Subsequently to 400°C for 2h of heat treatment, the hardness of the Ni-P diamond coatings increased to approximately 1200HV. The friction coefficients of the Ni-P diamond composite coatings were stable in the range of 0.4–0.52, whereas the Ni-P coating coefficient increased with time and finally reached to beyond 0.50. The addition of diamond particles could improve the wear resistance significantly, whereas as the diamond particle sizes increased, the friction wear resistance and the abrasive wear resistance increased.

Experiment and Simulation for Rolling of Diamond–Cu Composites

We demonstrate an innovative preparation approach of diamond/Cu composites by powder-in-tube technique and rolling. A small copper tube was loaded with Ti- and Cu-coated diamond particles, and then the diamond particles were combined with Cu matrix by composite rolling. The morphology and element distribution of the interface between diamond and Cu were determined by scanning electron microscopy and energy-dispersive spectrometer. Finite element method (FEM) simulation was used to analyze the rolling process associated with experiment by DEFORM-3D. The final experimental results showed that homogeneous distribution of diamond particles could be observed in the center layer of the composites. According to the contrast experiments, the sample, whose diamond particle size is 0.12–0.15 mm and thickness of pre-rolling is 1.2 mm, showed relatively complete morphologies and homogeneous distribution. Experimental results indicated a poor efficacy of excessive rolling reduction. The thermal conductivity of the composites is about 453 W (m K)−1 by theoretical calculation. For FEM simulation, rolling strain and temperature field of the composites were simulated by DEFORM-3D. Simulation results were interpreted, and numerical results verified the reliability of the model. The simulation predicted that the local area of large strain, indicative of the strain along the thickness direction, could be intensified by adding diamond particles.

Improvement on the thermal conductivity of Diamond/CVI-SiC composites using large diamond particles

The Diamond/SiC composites were fabricated via slip casting and chemical vapor infiltration (CVI) approaches. The effects of diamond particle size (50–500μm) on microstructure, flexural strength, density, fracture toughness and thermal conductivity of Diamond/SiC composites were discussed. By using large-sized diamond particles, thermal conductivity of composites can be improved and the maximum value could reach up to 241W/(m·k), which is 2.1 times higher than that of the Diamond/SiC composites prepared by tape-casting and CVI process. With increasing of diamond particle size, the density of Diamond/SiC composites increased, and the mechanical properties decreased. The maximal density, flexural strength and fracture toughness were 3.18g/cm3, 287MPa and 5.0MPa·m1/2 respectively. The fracture mechanism of the composites transferred from diamond particles transgranular fracture to interfacial debonding.

Coagulation of carbon clusters in a detonation wave

The effect of the parameters of a charge of TNT/RDX alloys and their detonation conditions on the coagulation of carbon on the isentrope of the detonation products is analyzed. In the region of liquid nanocarbon, coagulation occurs by coalescence of nanodroplets and in the region of solid nanocarbon, by their joining (sintering) simultaneously with crystallization. Therefore, the specific surface area of nanodiamonds calculated from their sizes is always larger than the measured value. Separation of nanodroplets in detonation products accelerates their coagulation and cooling due to the flow of cooler products around them. Evaluation of the distance between the surfaces of nanodroplets in various TNT/RDX alloys shows that they are small, smaller than nanodroplets. The conditions of rapid coalescence of nanodroplets during different deceleration of the products by rigid barriers are analyzed. An increase of up to five orders of magnitude in the size of diamond particles was established experimentally. The factors responsible for the change in the coagulation rate with the transition from heterogeneous to homogeneous TNT/RDX alloy with decreasing size of TNT/RDX particles are discussed.

Morphological features of W- and Ni-containing coatings on diamond crystals and properties of diamond-copper composites obtained by Spark Plasma Sintering

In the present study, W- and Ni-containing coatings on diamond crystals were obtained by rotary chemical vapor deposition (RCVD) using tungsten carbonyl W(CO)6 and nickelocene Ni(C5H5)2 as precursors. Morphological features of the coatings deposited under different processing conditions were investigated. For obtaining bulk diamond-copper composites, mixtures of the coated and uncoated diamond crystals with a copper powder were subjected to Spark Plasma Sintering (SPS). The effects of the presence of the coatings on the diamond crystals and the size of the initial diamond particles on the microstructure, relative density and thermal conductivity of the consolidated diamond-copper composites were investigated.

Influence of magnetic field on the mass transfer of Ni–P-diamond electroless composite plating and deposit properties

Nickel–phosphorus (Ni–P)-diamond composite coatings were manufactured by the addition of sub-micrometre sized diamond particles to electroless nickel solution. In the process of this reaction, a magnetic field was introduced. This research studied the effect of the magnetic field on the Ni–P-diamond composite coatings by changing the concentration of sub-micrometre sized diamonds and the magnetic field intensity. The surface morphology, the coating composition and the coating adhesion were tested using scanning electron microscope and energy-dispersive spectrometer, a metalloscope and an automatic scratch tester. The results showed that the magnetic field influenced the mass transfer process of the composite plating by accelerating the oxidation rate of the hypophosphite, so that the deposition rate was increased, the coating morphology was improved and the bonding force between the coating and the matrix was improved.

Effect of Diamond Particle Size on the Thermal Shock Property of High Pressure High Temperature Sintered Polycrystalline Diamond Compact

Effect of Diamond Particle Size on the Thermal Shock Property of High Pressure High Temperature Sintered Polycrystalline Diamond Compact

Self-conditioning performance of hydrophilic fixed abrasive pad

Self-conditioning performance is one of the key properties of hydrophilic fixed abrasive (FA) pad, which affects greatly on lapping efficiency and surface quality of lapped work-piece. In order to explore the quantitative relationship between the self-conditioning performance of hydrophilic FA pad and process parameters, the material removal rate variation (MRRV) of work-piece was proposed to characterize the self-conditioning performance of the hydrophilic FA pad in a series of marathon tests. The correlations between MRRV and the factors, which are diamond particle size, pore forming additive, applied load, copper content in the pad, triethanolamine (TEA) content in the slurry and FA lapping parameters, were explored with the orthogonal regression experiments method. The results indicate that the relative significance factors affecting the self-conditioning performance are triethanolamine content of slurry and applied load, respectively.

Macroscale Superlubricity Enabled By Ensembles of Graphene on Diamond Nanoscrolls

The power of modern supercomputers together with the availability of highly scalable atomistic simulation codes have begun to revolutionize the modeling and computational analysis of materials. An enticing illustration of the same comes from our recent work where large-scale molecular dynamics (MD) simulations performed on Argonne’s supercomputer Mira closely coupled with experimentation led to a breakthrough in the field of tribology.1 An elusive phenomenon termed “Macroscale superlubricity” which refers to an extremely low friction state was shown to originate from an intriguing nanomechanical phenomenon: graphene patches wrap around nm sized diamond particles to form nanoscrolls that have significantly reduced contact area to an underlying surface. Atomistic simulations elucidated the overall mechanism and explained the mesoscopic link between the nanoscale mechanics and macroscale experimental observations. Given our recent success with nano-lubricants1, we will focus on accurately capturing ensemble effects across tribological interfaces using some representative lubricant materials (2-D materials, nanoparticles) and their combinations for different types of environments and operating conditions. This talk also will include brief discussion on our ongoing efforts towards development of a new class of force fields to enable high-fidelity large scale dynamical and statistical simulations of tribo-interfaces, properties and functionalities of new lubricants, as well as pathways and mechanisms of their in operando synthesis and assembly.

Surface microstructural changes of spark plasma sintered zirconia after grinding and annealing

Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140nm 372nm and 753nm grain sizes by sintering at 1250°C, 1450°C and 1600°C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60µm, under a pressure of 0.9MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after a ruff grinding of specimens at 1100°C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575°C for one hour, the nano-grain layer was not observed. The resulted grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.

Study on preparation and properties of mesh Ti/BDND electrode

ABSTRACTHigh-quality boron-doped nanocrystalline diamond (BDND) film was fabricated on mesh titanium substrate using hot filament chemical vapor deposition (HFCVD) system. Raman, X-ray diffraction (XRD), and scanning electron microscopy (SEM) spectroscopy were used to analyze the microstructure of the mesh Ti/BDND electrode. The SEM images show different parts of the mesh electrode surface are fully covered by the diamond film and particle sizes of that are nearly less than 1 μm on average. Additionally, the diamond film of the prepared electrode surface is relatively of high quality and the mesh electrode has a relatively small residual stress from Raman and XRD spectra, respectively. Cyclic voltammograms indicate that the mesh electrode has wide potential window, low background current and stable electrochemical properties in H2SO4 solution, suggesting that the prepared electrode is suitable for the application of wastewater treatment. The COD removal rate of the prepared mesh electrode increases by 10.4% compared with that of the plate electrode, which demonstrates that the ability of the mesh electrode in the wastewater treatment is relatively better.

Effect of (0–40) wt. % Si addition to Al on the thermal conductivity and thermal expansion of diamond/Al composites by pressure infiltration

This study pertained to the effect of (0–40) wt.% Si addition to Al on the thermal conductivities (TC) and the coefficient of thermal expansion (CTE) of diamond/Al composites by pressure infiltration. The fracture surfaces and interface microstructures by metal electro-etching were discussed with respect to Al matrix chemistry and diamond particles size. The results revealed that the diamond (single size)/Al–12.2Si (in wt.-pct) composites exhibited higher thermal conductivity of 532 W/m K due to the better interface bonding, which is over 90% of the theoretical prediction by the Hasselman–Johnson Scheme. At the interfaces, SiC was found and the undesired interface formation of Al4C3 was reduced. The CTE of diamond (single size)/Al–40Si (in wt.-pct) composites exhibited the average value of 4.5 × 10−6/K, but the TC value declined to 314 W/m K due to the inhomogeneous enrichment of Si. The bimodal mixtures of diamond particles (106–125 μm: 45–38 μm = 3:1) could improve TC and CTE of composites.

The Grain Size Effect of Polycrystalline Diamond on Surface Integrity by Using Micro EDM

In this study, the optimization of machining parameters and the effect of polycrystalline diamond (PCD) grain sizes on machining characteristics in micro electrical discharge machining (μEDM) are analyzed. There are four experimental factors, each parameter is set at three levels: current (0.5A, 2A and 4A), pulse-on time (2μs, 4μs and 8μs), pulse-off time (2μs, 4μs and 8μs) and PCD grain size (1.7μm, 4μm and 6μm). Voltage is fixed at 140V. Base on L9 orthogonal array and signal to noise ratio through Taguchi method, analysis of variance (ANOVA) is used to validate the significant experimental parameters. The results suggest that the PCD in grain size of 6μm is the best choice for maximum material removal rate and minimum for electrode wear ratio, meanwhile, the optimum condition of surface roughness is obtained at 1.7μm. The current and pulse on-time play as significant roles that affect machining performance. The discharge energy (current and pulse on-time) increases leading to the decrease of the material removal rate and the increase of the electrode wear ratio and the surface roughness. In addition to, the PCD grain size has a minor influence on electrode wear ratio and material removal rate and relatively affects surface roughness. The surface roughness increases as increasing the diamond particle size.

Evolution of the morphology of diamond particles and mechanism of their growth during the synthesis by chemical vapor deposition

The evolution of the surface morphology of diamond particles synthesized by chemical vapor deposition (CVD) on silicon substrates has been investigated. It has been found that, when the diamond particles reach a critical size of less than 800 nm, the surface of the diamond faces is transformed. Particles with sizes of no more than 100–300 nm have a well-faceted surface covered by the {100} and {111} faces. An increase in the size of diamond particles leads to a change in the structure of their surface. The surface is covered by the {100} faces surrounded by a disordered phase. With a further increase in the particle size (up to ∼2000 nm), the {100} faces disappear and the diamond particles are covered by high-index faces. A model explaining the evolution of the surface morphology of diamond particles has been proposed. According to this model, during the evolution of diamond particles with an increase in their size, the mechanism of layer-bylayer growth changes to normal growth, which leads to a significant transformation of the entire surface of the diamond particles. The critical size of a two-dimensional nucleus formed on the {100} and {111} faces, at which the change in the growth mechanism begins to occur, has been calculated. A method has been proposed for controlling the morphology of diamond particles during their synthesis.

Study of Electroplated Nickel Layer Thickness and Saw Parameters on Cutting Performance in Diamond Wire Sawing of Sapphire Ingots

A production-scale multiwire saw machine and 4 inch sapphire ingots were used in this study. The diamond wire used in the study had a core diameter of 0.1mm with an attached diamond particle size of 8–12μm. This study uses the Taguchi method and Grey relational analysis on the key diamond wire parameters which are electroplated nickel layer thickness, diamond wire tension, diamond wire speed and sapphire ingot feed rate, in order to simultaneously optimize the cutting performance in the diamond wire sawing of sapphire ingots. Based on the analysis, the nickel layer thickness and wire speed are the first and second most significant factors with 31.7 and 29.9% effects on cutting performances. The optimal control factors were then simultaneously evaluated for Ra, material removal rate, diamond wire wear rate and TTV and were found at optimization to be 14 μm nickel layer thickness, 15NT wire tension, 800m/min wire speed and 0.2mm/min feed rate, respectively. Compared with current standard condition, this improved process obtained from the optimization of diamond wire electroplated nickel layer thickness and saw machine parameters in the diamond wire sawing of sapphire ingots can achieve a 33% lower Ra, a 20% lower diamond wear rate, a 13% lower TTV and a 20% higher material removal rate, simultaneously.

Effects of diamond size on the deposition characteristic and tribological behavior of diamond/Ni60 composite coating prepared by supersonic laser deposition

Supersonic laser deposition (SLD) process, as a hybrid coating technique, which combines the benefits of both cold spray (CS) and laser irradiation, is a relatively new trend in the field of laser processing. The composite powder of Ni60 alloy powder mixed with diamond particles is deposited on medium carbon steel (AISI 1045 steel) substrate. Two sizes of diamond particles are used respectively in the composite coating. The diamond/Ni60 composite coating specimens prepared by SLD process are studied using scanning electron microscope (SEM), energy dispersive spectrum (EDS) and Raman spectra. The microstructures and interface bonding between the particles and Ni60 matrix are examined using indentation test and SEM. The hardness and tribological properties of the composite coatings are evaluated under Vickers indentation test and pin-on-disc wear test, respectively. The results show that the diamond/Ni60 composite coatings without graphitization of diamond exhibit better tribological properties, the smaller size of diamond is better than the larger one in the composite coatings for wear resistance. This research also demonstrates that SLD technique can deposit hard diamond/Ni60 composite on steel substrate successfully, which cannot be achieved via CS technique.

Thermal Conductivity Behaviour of Al/Diamond and Ag/Diamond Composites in the Temperature Range 4 K < T < 293 K

Two different systems, the non-reactive Ag–diamond and the reactive Al–diamond system, were assessed by their thermal conductivity behaviour, both were fabricated by gas pressure assisted infiltration of densely packed diamond bulks with aluminium or silver and different Si-concentration and diamonds of varying particle sizes. The effect of Si-concentration on the interface thermal conductance h between Al, Ag and diamonds was investigated in dependence of temperature by measuring thermal conductivity of composites with different sized diamond particles in the temperature range from 4 K up to ambient. Composite thermal conductivities κc(T) can be as high as 860 W m-1 K-1 at roughly 100 K for Al/diamond and 1100 W m-1 K-1 for Ag–Si/diamond at approx. 150 K. Although the Si concentration in the matrix plays an eminent role for κc(T), i.e. the lower the Si concentration, the higher κc(T), interface thermal conductance is almost unaffected in the reactive Al-diamond system. Furthermore, they are close to values determined on clean model systems, i.e. sputtered and evaporated metal layers on diamond monocrystals. For Ag–diamond composites, the matrix composition of Ag–1Si seems to reflect an optimal composition, as the highest thermal conductivity κc(T) and an extraordinary higher interface conductance was achieved compared to Ag–3Si/diamond composites.

다이아몬드 배열 무전해 니켈 도금층/무산소동 기판의 열전도도 특성

Abstract The monolayer engineering diamond particles are aligned on the oxygen free Cu plates with electroless Niplating layer. The mean diamond particle sizes of 15, 23 and 50 µm are used as thermal conductivity pathway for fab-ricating metal/carbon multi-layer composite material systems. Interconnected void structure of irregular shaped diamondparticles allow dense electroless Ni plating layer on Cu plate and fixing them with 37-43% Ni thickness of their meandiameter. The thermal conductivity decrease with increasing measurement temperature up to 150 o C in all diamond sizeconditions. When the diamond particle size is increased from 15 µm to 50 µm (Max. 304 W/mK at room temperature)tended to increase thermal conductivity, because the volume fraction of diamond is increased inside plating layer. Keywords: Thermal conductivity, Diamond, Multi-layer materials, Electroless plating ······························································································································· ·································································································

Preparation and characterization of diamond-silicon carbide-silicon composites by gaseous silicon vacuum infiltration process

Diamond-SiC-Si composites have been prepared using gaseous silicon vacuum infiltration. The evolution of the phases and microstructures of the composites have been analyzed using X-ray diffraction technique and scanning electron microscopy. It has been found that the diamond-SiC-Si composite is composed of β-SiC, diamond, and residual Si. The diamond particles were distributed homogeneously in the dense matrix of the composites. Besides, the effects of particle size and content of diamond on the properties of diamond-SiC-Si composites have been analyzed. The thermal conductivity of the composites increases with particle size and content of diamond. When the particle size and content of diamond are 300 μm and 80 wt %, respectively, the thermal conductivity of the composites approaches the value of 280 W·m−1·K−1.

Fabrication of High Thermal Conductivity Cu/Diamond Composites By Electrodeposition

Introduction Diamond has a very high thermal conductivity (1000-2000 W m-1 K-1). Metal/diamond composites have been extensively investigated for heat dissipation applications.1,2) Typically, metal/diamond composites are formed under high temperature and pressure conditions.3) However, composites made by sintering do not yield improved thermal conductivities because of the formation of gaps between the metal matrix and diamond particles due to low wettability. In comparison, fabrication of metal/diamond composites using an electrodeposition technique can be carried out at room temperature and atmospheric pressure, and there are no issues regarding wettability. We have already reported the fabrication of nickel/diamond composites by electrodeposition and an investigation of their thermal conductivities.4) In this study, Cu/diamond composites were fabricated by electrodeposition and their thermal conductivity was evaluated. Experimental The Cu/diamond composite plating bath was prepared using a copper sulfuric bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4) as the base, to which diamond particles (mean diameters of 10, 25, 45, 195 and 230 μm) were mixed. Electrodeposition was carried out under galvanostatic conditions. Pure copper plates were used for the cathode and the anode. The electrodes were arranged horizontally with the cathode set at the bottom position. First, diamond particles were precipitated on the cathode in the plating bath; electrodeposition was then carried out to fill the gaps between the diamond particles. Surface and cross-sectional morphologies of the composites were observed by field-emission scanning electron microscopy (FE-SEM). A cross-section polisher was used to prepare cross-sectional samples. The thermal conductivity was calculated as a product of the density, specific heat capacity and thermal diffusivity. The thermal diffusivity was measured by a xenon laser flash thermal property analyzer. In order to estimate the net current density during formation of the Cu/diamond composites, the Butler-Volmer equation was used. The exchange current density and the transfer coefficient were obtained from a Tafel plot.Simulation of the thermal conductivity of the Cu/diamond composites was carried out using the Hasselman-Johnson equation, for comparison with the measured values. Results and Discussion Figures 1 and 2 show cross-sectional SEM images of the Cu/diamond composite at two magnifications. No voids or cracks were observed between the Cu matrix and diamond. The thermal conductivities of the fabricated Cu/diamond composites were almost consistent with the simulation values. The largest value was 687 W m-1 K-1, using 230 μm size diamond particles with a diamond content in the composite of 61 vol%. Estimation of the net current density during the formation of the composites will be discussed at the meeting. References 1) J. Flaquer, A. Ríos, A. Martín-Meizoso, S. Nogales, H. Böhm, Computational Materials Science, 41, 156-163 (2007). 2) M-T. Lee, M-H. Fu, J-L. Wu, C-Y. Chung, S-J. Lin, Diamond & Related Materials, 20, 130-133 (2011).3) H. Feng, J. K. Yu, W. Tan, Materials Chemistry and Physics, 124, 851-855 (2010).4) S. Arai, Y. Tashiro, V. Hoang, Y. Suzuki, of the 220th ECS Meeting, #2337 (2011).