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ABSTRACT: Using plasma-based ion implantation, two types of gradient layers have been prepared on 2024 Al alloy. One is prepared by N-implantation then C-deposition, the other adds an interlayer composed of a Ti layer and a Ti–N layer between N-implantation and C-deposition. C-deposition is carried out at various implanting voltages or C2H2/H2 ratios. The composition depth profiles of these layers were characterized by x-ray photoelectron spectroscopy. The structure, morphologies and microstructure of the C layers were studied using Raman spectroscopy, atomic force microscope and transmission electron microscope, respectively. The surface hardness was measured with a Knoop tester and a mechanical property microprobe. The dry ball-on-disc wear tests were performed in ambient air. The gradient layer without interlayer is composed of an N-implanted layer rich in AlN and a diamond-like carbon (DLC) layer (film), and the two layers are connected with a C–Al transition layer containing Al4C3. The Ti layer rich in α -Ti and the N-implanted layer are connected by a Ti–Al transition layer containing TiAl3, while the Ti–N layer rich in TiN and the DLC film are connected by a C–Ti transition layer containing TiC, TiCN, etc. Thus, the gradient layer with interlayers has optimized the gradient structure. DLC films are compact and amorphous, contain high sp3/sp2 ratios and depend on the implanting voltage and the C2H2/H2 ratio. Similarly, these gradient layers exhibit significant improvement in morphologies, surface hardness and tribological properties; the interlayer, the implanting voltage and the C2H2/H2 ratio all have prominent effects on these properties.
Journal of Physics D Applied Physics 01/2004; 37(3):392. · 2.54 Impact Factor
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Sheng li xue bao: [Acta physiologica Sinica] 09/1987; 39(4):373-9.
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ABSTRACT: The in situ radical transfer addition polymerization of styrene from silica nanoparticles was carried out by the free radical polymerized of styrene in the presence of mercaptopropyl-modified silica nanoparticles as chain-transfer agent. The effects of the amount of the initiator, polymerizing temperature and polymerizing time on the convention of styrene (C) and the percentage of grafting were investigated. Results of elemental analysis, IR, X-ray photoelectron spectrometer and transmission electron microscope demonstrated that the desired polymer chains have been covalently bonded to the surface of the silica nanoparticles. A C of 42.56% and a PG of 38.10% could be achieved with the optimal condition. The polystyrene grafted silica nanoparticles could be separated and used as nanofiller for polymers.
European Polymer Journal 40(2):267-271. · 2.74 Impact Factor
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ABSTRACT: Ni–Co/Si3N4 composite coatings with various contents of Si3N4 nano-particulates were prepared by electrodeposition in a Ni–Co plating bath containing Si3N4 nano-particulates to be co-deposited. The shape and size of the Si3N4 nano-particulates were observed and determined on a transmission electron microscope. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat/galvanostat device. The friction and wear behaviors of the Ni–Co/Si3N4 composite coatings were evaluated on a ball-on-disk UMT-2MT test rig. The worn surface morphologies of the Ni–Co/Si3N4 composite coatings wear observed using a scanning electron microscope. It was found that the Si3N4 nano-particulates appeared as microspheres of a diameter about 20 nm. The cathodic polarization potential of the composite electrolyte increased with increasing Si3N4 concentration in the plating bath, and the addition of Si3N4 particulates led to changes in the morphologies of the composite coatings. Namely, the Ni–Co alloy coating was composed of needle-like micro-crystallites, while the Ni–Co/Si3N4 composite coatings were characterized by particulate-like structure and had more compact and fine granular morphologies. At the same time, the morphologies of the composite coatings changed from fibril to granular, which implied that the co-deposited Si3N4 nano-particulates at a larger content could agglomerate to some extent. The co-deposited Si3N4 nano-particulates were uniformly distributed in the Ni–Co matrix and contributed to greatly increasing the microhardness and tribological properties of the Ni–Co alloy. The microhardness of the composite coatings increased and the friction coefficients and wear rates decreased with increasing content of the nano-Si3N4 in the composite coatings. This was attributed to the grain fining and dispersive strengthening effects of the co-deposited hard Si3N4 nano-particulates. At the same time, the hydroxylated silicon oxide formed by the tribochemical reaction between the nano-Si3N4 of high reactivity and water vapor in the air also contributed to decreasing the friction coefficient.
Materials Science and Engineering: A.
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ABSTRACT: Four carbon nanometer films ranging from 5 to 60 nm have been prepared by plasma-based ion implantation (PBII) with C on Si (1 0 0) wafers. Raman spectra and X-ray photoelectron spectroscopy (XPS) indicate these films are diamond-like carbon (DLC) films with high sp3/sp2 bonds ratio. Atomic force microscopy shows that their appearances are smooth and compact, and improved to some extent. Meanwhile, XPS displays that they are naturally connected with the Si substrate by a C–Si transition layer where the implanted C+ ions react with Si to form SiCx. Infrared spectra reveal they contain some hydrogen, and hydrogen mainly combines with carbon to form sp3 CH, CH2 and CH3 bonds. Proper DLC films will be obtained and used as the qualified candidates in some particular engineering applications by actively optimizing PBII parameters.
Applied Surface Science.
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ABSTRACT: A generalized Ritz vector inverse iteration algorithm (GRI) for the solution of some extreme eigenvalues and corresponding eigenvectors of quadratic eigenvalue problems is proposed. The new method preserves banded and sparse properties of the matrices and does not invoke complex arithmetics. Iterations are performed on the original n order scale while the quadratic eigenvalue problem is efficiently reduced to a lower order linear one. The algorithm applies to both symmetric and unsymmetric cases and thus has a wide range of application. Numerical results show the excellent stability and accuracy of the algorithm.
Computers & Structures.
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ABSTRACT: As an interlayer in the gradient layers such as AlN/Ti/TiN/DLC prepared by plasma-based ion implantation (PBII) on 2024 aluminum alloy, titanium layer plays an important role in enhancing adhesion, reducing thermal stress, limiting the crack propagation, etc. A series of dual-layers prepared by PBII with nitrogen then titanium at various sputtering currents of titanium target on 2024 aluminum alloy have been reported in this paper. The composition distributions and the chemical states are analyzed using X-ray photoelectron spectroscopy (XPS). The structures are studied with grazing X-ray diffraction (GXRD). The results show that PBII with titanium strongly depends on the sputtering current. It is found that there exists a critical sputtering current corresponding only to a titanium-implanted layer containing TiAl3. When the sputtering current exceeds the critical value, a titanium-deposited layer rich in α-Ti is formed on a titanium-implanted layer. By controlling the sputtering current an appropriate titanium interlayer can be prepared to meet the requirement of forming a proper gradient layer.
Applied Surface Science.
