Papers by Keyword: Diamond

Abstract: X-ray topography is an effective tool to investigate dislocations in semiconductor crystals. Due to low X-ray absorption coefficients of diamond, X-rays can penetrate deep into the crystal. Thus, deep three-dimensional (3D) dislocations are projected on two-dimension (2D) film, which makes dislocation analysis particularly challenging. Dislocation vectors from the films obtained using a set of the same diffraction vectors were identified using topographical and geometrical analyses. The depth and position of the dislocations in a crystal that was projected on a film were determined using geometrical relationship. The proposed analysis method was verified by analyzing several dislocations using four <404> diffraction films. The types of dislocation were identified through Burgers vector analysis.

Abstract: Diamond particle with tungsten boride (WB) coating was synthesized by the molten salt method. Three different diamond/Fe-Ni composites made from pristine diamond, B4C coated diamond and WB coated diamond with Fe-Ni powders were prepared by powder metallurgy. The composition and microstructure of the tungsten boride coating were investigated. Both bending strength and cutting performance of the composites were investigated. Addition of the WB coating provided an increased bending strength (871.2 MPa) and relative density (93.54%), compared with the composites consist of uncoated diamond and Fe-Ni (746.8 MPa, 92.81%). Three different Fe-Ni-based impregnated diamond drill bits contained 20 vol.% pristine diamond, B4C coated diamond and WB coated diamond were manufactured by powder metallurgy, respectively. Drilling rate of bits was measured by XY-4 geological core drill on granite. The test results show that the drilling rate of bits with WB coated diamond (2.42 m/h) was 40% higher than that with pristine uncoated diamond (1.72 m/h).

Abstract: Possible processes of the carbon isotopes fraction under hydrodynamic caviation at carbon-containing liquids are considered. We have made corresponding experiments with benzene, toluene and ethanol to provide carbon nanoforms with different crystal structures. Specific bonding forces for metals and n-diamond are modeled using developed numerical method. The task is to identify the key parameters affecting the pairs force potentials of carbon atoms and consider the application of the results to microelectronics and natural processes.

Abstract: A relationship between diamond synthesis and hydrogen production in in-liquid plasma method have been investigated. Approximately 60 % energy can be recovered by collecting hydrogen gas made by ingredient solution decomposition. The relationship is trade-off. When higher energy is used to maintain the substrate temperature, the hydrogen production rate gets faster, but the diamond synthesis rate gets slower. To increase diamond synthesis rate, a method should be established which maintains the substrate temperature by lower energy and generates less hydrogen gas.

Abstract: Diamond crystals are successfully synthesized by irradiating DC arc plasma jet to the substrate set in a methanol solution. It is the important procedure to preheat the substrate by inert Ar plasma jet before introducing the methanol solution gas to the plasma jet gun. The effects of two experimental conditions, the incident power and the substrates, are investigated. In the case of the Si substrate, cubic crystalline diamond grains of same size are synthesized at the plasma power of 470W. High speed hetero epitaxy is expected by using this method. In the case of the tungsten carbide substrate, diamond crystals and carbon nanotubes are simultaneously synthesized at the plasma power of 260W. The catalytic effect of Co binder in the substrate may cause the chemical reaction of the nanotube synthesis.

Abstract: The tribological characteristics of Electroless Ni-P and Ni-P/D (diamond) coatings were studied and analysed against AISI 52100 steel ball under dry reciprocating sliding conditions. Low and High Phosphorus Ni-P alloy coatings were deposited on steel substrate by Electroless deposition technique. Diamond particles were successfully reinforced into Ni-P matrix to produce Ni-P/D composite coatings. All coatings were subjected to heat treatment at 400^°. The micro-hardness, surface features and elemental composition of the coatings was analysed. The surface morphology of Ni-P and Ni-P/D coatings is detailed. Presence of dia mond particles in Ni-P matrix was confirmed by EDS analysis. Dry sliding wear tests showed a significant enhancement in wear resistance of Ni-P/D composite coatings compared to Ni-P coatings. Experimental results indicate that combined effect of diamond particles reinforcement and heat treatment play a crucial role in modifying the surface characteristics and tribological performance of the Ni-P coatings.

Abstract: In this paper, evolution of optical and electrical properties of diamond-like carbon (DLC) films deposited by ECR-CVD system are reported. By varying the deposition different substrates bias (0, -55, -100 V) and volume amount of C₂H₂ from 40 to 55 cc onto substrate Si/TiN and quarts. The structure of the DLC films were analyzed from Raman spectroscopy. DLC films deposited bias at-100 V and C₂H₂ at 40 cc show excellent optical transmittance and high resistivity. As a result, I_D/I_G ratio corresponds to the optical transmittance and resistivity with I_D/I_G ratio decreased making the film like to the diamond. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting substrates bias and volume C₂H₂, is important to many applications, which is improve film properties.

Abstract: Understanding thermos-physical properties of MMCs includes considering interfacial processes and interactions between the constituents in MMCs. In this context, interfacial bonding is of vital interest for a deeper understanding of composites. Neutron diffraction experiments on Al/diamond composites were performed and reconciled with their thermo-physical properties and quantification of interfacial carbides formation. To create different interfacial conditions both, the contact time during processing the MMCs by liquid metal infiltration and the nominal composition of the matrix were changed, thus creating different amounts of interfacial Al₄C₃ carbides. Neutron diffraction showed the increase in contact time and the addition of Si to Al both increase the bonding strength, although going with a significant decrease of the composite`s thermal conductivity.

Abstract: Micrometer-scale patterning was performed using the particle beam writing technique with a focused heavy-ion microbeam, allowing the creation of a unique two-dimensional distribution of fluorescent centers in single-crystalline diamond. The focused nitrogen microbeam was scanned over the target of single-crystalline diamond prepared by chemical vapor deposition to create nitrogen-vacancy (NV) centers at defined positions. Imaging using a custom-built confocal fluorescence microscopy system revealed that the desired NV distribution was generated in the target crystal with a spatial resolution similar to the beam resolution. A two-dimensional matrix barcode test pattern was successfully generated in a diamond substrate to demonstrate the encryption of information inside a solid-state target.

Abstract: Structure formation of diamond-containing composites with Sn-Cu-Co-W binders has been studied within the range of sintering temperatures of 780–820°C. The specimens were obtained by rolling the paste-like mixtures of metallic powders and diamonds on steel substrates, with sintering performed in vacuum. The structure of the sintered specimens was studied by optical metallography, X-ray diffractometry and electron probe microanalysis. Hardness of the materials was identified by Rockwell method (scale B). It has been found that the process of composites sintering is largely affected by oxide films available on the surface of the powders. In order to obtain composites having less than 10% porosity and up to 96–98 HRB hardness, they have to be sintered at the temperature of 820°C which eliminates the oxide films.