Search results for "Carbide"
showing 10 items of 139 documents
Al-SiC Metal Matrix Composite production through Friction Stir Extrusion of aluminum chips
2017
Abstract The production of most mechanical component requires machining operation, thus usually implying the cut material to be wasted as scrap. Traditional recycling techniques are not able to efficiently recycle metal chips because of some critical aspects that characterize such kind of scraps (shape, oxide layers, contaminating residues, etc). Friction Stir Extrusion is an innovative solid state direct-recycling technique for metal machining chips. During the process, a rotating tool is plunged into a hollows matrix to compact, stir and finally, back extrudes the chips to be recycled in a full dense rod. This process results to be particularly relevant since no preliminary treatment of t…
Friction Model for Tool/Work Material Contact Applied to Surface Integrity Prediction in Orthogonal Cutting Simulation
2017
Abstract Tribological behavior at both tool/chip and tool/work material interfaces should be highly considered while simulating the machining process. In fact, it is no longer accurate to suppose one independent constant friction coefficient at the tool/chip interface, since in reality it depends on the applied contact conditions, including the sliding velocity and pressure. The contact conditions at both above mentioned interfaces may affect the thermal and mechanical phenomena and consequently the surface integrity predictions. In this article, the influence of contact conditions (sliding velocity) on the tribological behavior of uncoated tungsten carbide tool against OFHC copper work mat…
Effect of graphene substrate type on formation of Bi2Se3 nanoplates
2019
AbstractKnowledge of nucleation and further growth of Bi2Se3 nanoplates on different substrates is crucial for obtaining ultrathin nanostructures and films of this material by physical vapour deposition technique. In this work, Bi2Se3 nanoplates were deposited under the same experimental conditions on different types of graphene substrates (as-transferred and post-annealed chemical vapour deposition grown monolayer graphene, monolayer graphene grown on silicon carbide substrate). Dimensions of the nanoplates deposited on graphene substrates were compared with the dimensions of the nanoplates deposited on mechanically exfoliated mica and highly ordered pyrolytic graphite flakes used as refer…
Crystallization kinetics of amorphous SiC films: Influence of substrate
2005
Abstract The crystallization kinetics of amorphous silicon carbide films was studied by means of X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The films were deposited by radio frequency (r.f.) magnetron sputtering on glassy carbon and single crystalline silicon substrates, respectively. TEM micrographs and XRD patterns show the formation of nano-crystalline β-SiC with crystallite sizes in the order of 50 nm during annealing at temperatures between 1200 and 1600 °C. A modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism was used to describe the isothermal transformation of amorphous SiC into β-SiC as an interface controlled, three-dimensional growth processes fr…
Study of tantalum hemicarbide (Ta2C) production by low pressure carburizing
2015
Tantalum is a very dense metal (d = 16.6) and has a very high melting temperature of 2996°C. This material is particularly required for crucibles used for pyrochemical applications. Early studies show that a carburizing treatment enhances corrosion resistance from liquid metals. Indeed, the intergranular attack of tantalum is stopped by Ta2C precipitates, which occupy the grain boundary regions. The production of the carbon saturated tantalum with Ta2C precipitates requires a good understanding of tantalum carburizing.A carburizing treatment on tantalum sample causes the emergence of a TaC layer on surface and Ta2C layer just below. A reduction of carbon flow has enabled the study of the fi…
Tuning the Magnetic Properties of Carbon by Nitrogen Doping of Its Graphene Domains
2015
Here we present the formation of predominantly sp-coordinate carbon with magnetic- and heteroatom-induced structural defects in a graphene lattice by a stoichiometric dehalogenation of perchlorinated (hetero)aromatic precursors [hexachlorobenzene, CCl (HCB), and pentachloropyridine, NCCl (PCP)] with transition metals such as copper in a combustion synthesis. This route allows the build-up of a carbon lattice by a chemistry free of hydrogen and oxygen compared to other pyrolytic approaches and yields either nitrogen-doped or -undoped graphene domains depending on the precursor. The resulting carbon was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM…
Minor Cutting Edge Wear in Finish Turning Operations
1999
In finish turning operation, it has already shown, that for the sake of control the dimensional accuracy and the micro-geometry of the worked surface, the wear parameters employed in rough turning operations are not suitable. In the present work the study of wear in fmish turning operations, is carried out, employing a particular groove survey methodology, already proposed in a previous paper, that is based on the techniques of acquirement and processing of images. In order to verify the applicability of the proposed technique two kind of alumina-based inserts and two kind of sintered carbide inserts have been tested. The experimental tests have confirmed the validity of the technique in th…
Itinerant Electron Metamagnetism in η-Carbide-Type Compound Co3Mo3C
2010
We report the magnetic properties of the cobalt molybdenum η-carbide-type compounds Co 3 Mo 3 C and Co 3 Mo 3 N. The magnetic susceptibility χ of Co 3 Mo 3 C shows a Curie–Weiss temperature dependence at high temperatures and a broad maximum at around 100 K, whereas that of Co 3 Mo 3 N shows a nearly temperature-independent enhanced Pauli paramagnetic behavior. The absence of a magnetic long-range order was confirmed by the nuclear magnetic resonance technique in both the compounds. As expected from the broad maximum of χ, we observed an itinerant electron metamagnetic transition at around 37 T in Co 3 Mo 3 C.
Discovery of new boron-rich chalcogenides: Orthorhombic B6X (X=S, Se)
2020
The authors thank T. Chauveau (LSPM) for help with Rietveld analysis, A. Jamali (LRCS) for assistance with SEM measurements, and Drs. Y. Tange (SPring-8) and N. Guignot (SOLEIL) for help in synchrotron experiments that were carried out during beamtimes allocated to proposals 2017A1047 & 2018A1121 at SPring-8 and proposal 20170092 at SOLEIL. Ab initio calculations have been performed using Rurik and Arkuda supercomputers. This work was financially supported by the European Union’s Horizon 2020 Research and Innovation Programme under Flintstone2020 project (grant agreement No. 689279). Z.W. thanks the National Science Foundation of China (grant No. 11604159). A.R.O. thanks the Russian Ministr…
Investigation of Silicon Carbide Polytypes by Raman Spectroscopy
2014
Abstract Polytypes of colourless and coloured single crystals of silicon carbide (SiC) grown on SiC substrates by chemical vapour deposition are studied using Raman spectroscopy supplemented by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The SEM analysis of the defect stacking faults, inclusions of defects and their distribution has shown that they correlate with the peak positions of the obtained Raman spectra and with the XRD data on the crystal structure