• Korean Journal of Materials Research
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• v.13 no.8
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• pp.491-496
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• 2003

Fe-Ni alloy nanoparticles were prepared by ERC (Evaporation and Rapid Condensation) method, and the crystal structure and the behavior of martensite for the nanosized alloy particles were investigated by X-ray diffraction analysis. The relation between the rate of martensite transformation and the internal strain of austenite was discussed. The lattice spaces of austenite and martensite for the nanoparticles agreed with those of the bulk materials. The rate of martensite transformation from austenite and the internal strain of austenite was reduced with decreasing the average size of Fe-Ni nanoparticles. It was thought that the residual austenite in the Ni content range of 11∼l5at% was caused by the internal strain, and the residual martensite in the Ni content range of 32∼36at% had its origin in the high surface energy of nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.128-128
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• 2013

Fabrication of heterogeneous catalysts using Atomic Layer Deposition (ALD) has recently been attracting attention of surface chemists and physicists. In this talk, I will present recent results about structures and chemical activities of various catalysts prepared by ALD, particularly focusing on Ni-based catalysts. Ni has been considered as potential catalysts for $CO_2$ reforming of methane (CRM); however, Ni often undergoes rapid decrease in catalytic activity with time, and therefore, application of Ni as catalysts for CRM has been regarded as difficult so far. Deactivation of Ni catalysts during CRM reaction is from either coke formation on Ni surface or sintering of Ni particles during reaction. Two different strategies have been used for enhancing stability of Ni-based catalysts; $TiO_2$ nanoparticles were deposited on micrometer-size Ni particles by ALD, which turned out to reduce coke formation on Ni surfaces. Ni nanoparticles deposited by ALD on mesoporous silica showed high activity and long-term stability from CRM without coke deposition and sintering during CRM reaction. Ni-based catalysts have been also used for oxidation of toluene, which is one of the most notorious gases responsible for sick-building syndrome. It was shown that onset-temperature of Ni catalysts for toluene oxidation is as low as $120^{\circ}C$. At $250\circ}C$, total oxidation of toluene to $CO_2$ with a 100% conversion was found.

• Journal of Surface Science and Engineering
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• v.22 no.2
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• pp.78-87
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• 1989

Mechanism of formation of electroless composite coatings is similar to that of electrodeposited composite coating, but the amount of particles entraped in electroless coating is higher that the one of electrodeposited coatings. The methol of entrapment by the metal for SiC and Al2O3 particles is different from that for WC particles. In the former case the particles are gracually engulfed by the depositing metal, wheran with WC a metal envelope is rapidly fomed around each particles. This difference can be attributed to the difference in electrical resistivity of the particles. Inclusion density of SiC and Al2O3 particles during copeposition depend on the particle size, agitation condition, vabration conditions and electrolyte temperatures.

• Analytical Science and Technology
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• v.24 no.2
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• pp.61-68
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• 2011

Ni-coated alumina was prepared by sonochemical method. To increase an efficiency of Ni coating on alumina, amorphous alumina was prepared by sol-gel method and Ni was coated to fine particles of alumina. Ni-coated alumina was prepared from various calcination temperatures ($500^{\circ}C$, $1,000^{\circ}C$), concentrations of Ni solution (0.01 M~0.2 M) and sonochemical reaction times (30 min, 2h). The prepared fine particles were characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), and Particle Size Analyzer (PSA). The coating amount of Ni increased, as Ni concentration and ultrasonication time increased. The maximum amount of Ni was coated to fine particles of alumina, when Ni-coated alumina was prepared with 0.1 M concentration of Ni solution for 2 h of sonication time at $1000^{\circ}C$ of calcination temperature. The average particle size was in the range of 835.9 to 986.7 nm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.311-316
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• 2002

Two different approaches, namely two-step deposition process and Bias-Enhanced Nucleation (BEN) technique have been examined for deposition of high quality diamond thin film on polycrystalline Ni which has low chemical activity with the carbon neutrals provided from the $CH_4/H_2$mixtures. A two-step deposition process, consisted of pre-deposition of soot layer at lower temperatures and subsequent deposition at higher temperature condition, has been developed to deposit diamond layer directly on Ni substrate. Diamond particles were observed after deposition step at $925^{\circ}C$ for 5 hours and those particles seem to be nucleated from the soot layer pre-deposited at lower temperatures ($810^{\circ}C$). Diamond particles of a substantial size were found on Ni substrate after biasing -220 V for 10 minutes and subsequent deposition for 2 hours while no diamond particles were observed under the conditions without applied bias.

• Journal of Powder Materials
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• v.10 no.3
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• pp.195-200
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• 2003

Ni coated $Al_2O_3$ composite was successfully Prepared by the electroless deposition Process. The average size of Ni particles coated on the $Al_2O_3$ matrix powder was about 20 nm. It was hard to find any reaction compound as an impurity at interface between $Al_2O_3$ and Ni particles after sintering. The characterization of microstructure crystal structure and fracture behavior of the sintered body were investigated using XRD, TEM and Victors hardness tester, and compared with those of the sintered $Al_2O_3$ monolithic body. Many dislocations were observed in the Ni phase due to the difference of thermal expansion coefficient between $Al_2O_3$ and Ni phase, and no observed microcracks at their $Al_2O_3$ and Ni interface. In the $Al_2O_3$/Ni composite, the main fracture mode showed a mixed fracture with intergranular and transgranuluar type having some ,surface roughness. The fracture toughness was slightly increased due to the plastic deformation mechanism of Ni phase in the $Al_2O_3$/Ni composite.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.217-220
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• 1991

Ni-Zn ferrite powders in the few hundred angstrum size range and up have been synthesized by a wet direct method. The coprecipitate were prepared by adding alkaline solution into the constituent metal ions solution. and subsequent calcined at various temperature. At 95, the particles were ultrafine spherical shaped particles of about 500(A) in diameter.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.411-417
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• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.894-898
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• 2016

Solution plasma is a unique method which provides a direct discharge in solutions. It is one of the promising techniques for various applications including the synthesis of metallic/non-metallic nanomaterials, decomposition of organic compounds, and the removal of microorganism. In the context of nanomaterial syntheses, solution plasma has been utilized to produce carbon nanoparticles and metallic-carbon nanoparticle systems. The main purpose of this study was to synthesize nickel nanoparticles embedded in a matrix of carbon particles by solution plasma in one-step using waste vegetable oil as the carbon source. The experimental setup was done by simply connecting a bipolar pulsed power generator to nickel electrodes, which were submerged in the waste vegetable oil. Black powders of the nickel nanoparticles-embedded carbon (NiNPs/Carbon) particles were successfully obtained after discharging for 90 min. The morphology of the synthesized NiNPs/Carbon was investigated by a scanning electron microscope, which revealed a good dispersion of NiNPs in the carbon-particle matrix. The X-ray diffraction of NiNPs/Carbon clearly showed the co-existence of crystalline Ni nanostructures and amorphous carbon. The crystallite size of NiNPs (through the Ni (111) diffraction plane), as calculated by the Scherrer equation was found to be 64 nm. In addition, the catalytic activity of NiNPs/Carbon was evaluated by cyclic voltammetry in an acid solution. It was found that NiNPs/Carbon did not show a significant catalytic activity in the acid solution. Although this work might not be helpful in enhancing the activity of the fuel cell catalysts, it is expected to find application in other processes such as the CO conversion (by oxidation) and cyclization of organic compounds.

• Journal of Korea Foundry Society
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• v.23 no.1
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• pp.30-39
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• 2003

Porous hybrid preforms were fabricated by reactive sintering using the compacts consisting of SiC particles, Fe and Al powders. Squeeze casting processing was employed to produce the composite in which the matrix phase is Al-Si7Mg. The microstructural change and wear resistance of the composites were investigated in terms of an amount of SiC particles. The wear loss was increased with increasing the contact pressure in the alloy containing SiC particles coated with Cu. The most drastic change was found to the specimen tested at 2.5 MPa of contact pressure. Concerning the alloys containing SiC particles coated with Ni-P, a drastic increase in the wear loss exhibited at 2 MPa of contact pressure in those alloys containing 4 and 8 wt. % of SiC particles coated with Ni-P. In the alloy containing 16 wt. % a proportional increase in wear loss was observed to the change of contact pressure. With respecting to the sliding velocity, the wear loss of the alloy containing SiC particles coated with Cu increased at the initial stage of wear process and then decreased. Similar result was found in the alloys containing SiC particles coated with Ni-P. On the basis of the present results obtained, it was found that wear resistance of the alloys tested was improved to show in the order of the alloy reinforced by coated SiC particles > by uncoated SiC particles > by intermetallic compound without SiC particles.