Journal of Powder Materials

[Korean]
Functionally Gradient Materials (FGMs) for Improved Thermo-mechanical Properties: J Korean Powder Metall Inst. 2004;11(1):8-15.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.008

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Abstract PDF: The basic concept of functionally gradient materials (FGM) is to fabricate materials type having possibilities of applications in various fields by changing their intrinsic properties with continuous gradient. The present communication has reviewed the developments and applications of various FGMs designed for improved thermo-mechanical properties, in which the thermal protective and wear resistant materials are especially focused. Effects of thermo-mechanical properties and limits of FGMs designed for high temperature applications were mainly understood in terms of residual stress evolved from the design and fabrication. In addition, FGMs applied in structural parts were also introduced and discussed in terms of typical fabrication method for FGMs.

[Korean]
Effect of Carrier Gas on the Microstructure and Magnetic Properties of Co Nanoparticles Synthesized by Chemical Vapor Condensation: L. X.; J Korean Powder Metall Inst. 2004;11(1):16-21.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.016

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The nano-sized Co particles were successfully synthesized by chemical vapor condensation (CVC) process using the precursor of cobalt carbonyl (Co_2(CO)_8). The influence of carrier gases on the microstructure and magnetic properties of nanoparticles was investigated by means of XRD, TEM, XPS and VSM. The Co nano-particles with different phases and shapes were synthesized with a change of carrier gas : long string morphologies with coexistence of fcc and hcp structure in Ar carrier gas condition; finer Co core in a mass of cobalt oxide with only fcc structure in He; rod type cobalt oxide phase in Ar＋6vol％O_2. The saturation magnetization and coercivity was lower in Co nanoparticles synthesized in He carrier gas, due to their finer size.

Citations

Citations to this article as recorded by

The Fabrication of Cobalt Nanopowder by Sonochemical Polyol Synthesis of Cobalt Hydroxide and Magnetic Separation Method
Jong Min Byun, Myoung Hwan Choi, Chang Min Shim, Ji Young Kim, Young Do Kim
Journal of Korean Powder Metallurgy Institute.2015; 22(1): 39. CrossRef
Synthesis of Nano Sized Cobalt Powder from Cobalt Sulfate Heptahydrate by Liquid Phase Reduction
세환 안, 세훈 김, 진호 이, 현선 홍, 영도 김
Korean Journal of Materials Research.2011; 21(6): 327~333. CrossRef

[Korean]
Synthesis and Properties of ITO Nano Powders by Spray Drying Process: J Korean Powder Metall Inst. 2004;11(1):22-27.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.022

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Abstract PDF: The Indium Tin Oxide(ITO) nano powders were prepared by spray drying and heat treatment process. The liquid solution dissolved Indium and Tin salts was first spray dried to prepare chemically homogeneous recursor powders at the optimum spray drying conditions. Subsequently, the precursor powders were subjected to eat treatment process. The nano size ITO powders was synthesized from the previous precursor powders and the npuities also were decreased with increasing heat treatment temperature. Furthermore, the lattice parameter of TO nano powders was increased by doping Tin into Indium with increasing heat treatment temperature. The par icle size of the resultant ITO powders was about 20∼50nm and chemical composition was composed of In:Sn =86:10 wt.％ at 800°C.

[Korean]
Carbothermal Reduction of Spray Dried Titanium-Cobalt-Oxygen Based Oxide Powder by Solid Carbon: J Korean Powder Metall Inst. 2004;11(1):28-33.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.028

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Abstract PDF: In the present study, the focus is on the analysis of carbothermal reduction of the titanium-cobalt-oxygen based oxide powder by solid carbon for the optimizing synthesis process of ultra fined TiC/Co composite powder. The titanium-cobalt-oxygen based oxide powder was prepared by the combination of the spray drying and desalting processes using the titanium dioxide powder and cobalt nitrate as the raw materials. The titanium-cobalt-oxygen based oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and thermal gravity of the mixture during carbothermal reduction were analysed using XRD and TGA. The synthesized titanium-cobalt-oxygen based oxide powder has a mixture of TiO_2 and CoTiO_3. This oxide powder was transformed to a mixed state of titanium car-bide and cobalt by solid carbon through four steps of carbothermal reduction steps with increasing temperature; reduction of CoTiO_3 to TiO_2 and Co, reduction of TiO_2, to the magneli phase(Ti_nO_2n-1, n>3), reduction of the mag-neli phase(Ti_nO_2n-1, n>3) to the Ti_nO_2n-1(2≤n≤3) phases, and reduction and carburization of the Ti_nO_2n-1(2≤n≤3) phases to titanium carbide.

[Korean]
The Effect of Ni, Ce Addition and Extrusion Temperature on Al-Si Alloy: J Korean Powder Metall Inst. 2004;11(1):34-42.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.034

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Abstract PDF: The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized Al_81-(x＋y)Si_19Ni_xCe_y alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of Al_73Si_19Ni_7Ce_1 alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine Al_3Ni,;Al_3Ce compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 350°C and Al_73Si_19Ni_7Ce_1 alloy extreded at 350°C shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.

[Korean]
Effect of W Particle Size on the Electrical and Thermal Conductivity of W-Cu Composites: J Korean Powder Metall Inst. 2004;11(1):43-49.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.043

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Abstract PDF: The electrical and thermal conductivity of W-Cu composites were investigated as a function of the W-particle size and W-W contiguity. Powder mixtures were prepared by ball milling or mechanical alloying process, and then sintered at various temperatures. The electrical conductivity of sintered composite was increased with decreasing W grain size. Dependence of electrical conductivity on the W grain size was explained by the W-W contiguity concept. The thermal conductivity was increased with increasing the temperature up to 600°C but decreased at the temperature above 600°C Also, thermal conductivity value was influenced by the W particle size. Change of thermal conductivity in W-Cu composites was discussed based on the observed microstructural characteristics and theoretical considerations.

[Korean]
A Study on Magnetic Iron Oxide Nano Particles Synthesized by the Levitational Gas Condensation (LGC) Method: J Korean Powder Metall Inst. 2004;11(1):50-54.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.050

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Abstract PDF: Nanoparticles of iron oxides have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters were evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of iron oxide with particle size of 14 to 30 nm in a chamber filled with mixtures of Ar and O_2 gases. It was found that the phase transition from both gamma-Fe_2O_3 and alpha-Fe to Fe_3O_4, which was evaluated from the results of Mossbauer spectra, strongly depended on the O_2 flow rate. As a result, gamma-Fe_2O_3 was synthesized under the O_2 flow rate of 0.1≤Vo_2(Vmin)≤0.15, whereas Fe_3O_4 was synthesized under the O_2, flow rate of 0.15≤Vo_2(Vmin)≤0.2.

[Korean]
Sintering Behavior of (Ti＋Ni) Powder Mixture during Spark-Plasma Sintering: J Korean Powder Metall Inst. 2004;11(1):55-59.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.055

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Abstract PDF: TiNi bodies were produced from (Ti＋Ni) powder mixture by spark-plasma sintering procerg. The sintering behavior was investigated through the measurement of change in density, densification rate, phase analysis and microstructure. Irrespective of heating rate, sintered bodies with above 97％ relative density could be obtained. TiNi with B2 structure was confirmed as the major phase and Ti_2Ni,;TiNi_3, unreacted Ti, Ni as the second phase. Increase in heating rate suppressed a formation of intermediate phase during sintering process. Increase in holding time at sintering temperature led to a compositional homogenization.

[Korean]
A Study on the Nano Alloy Powders Synthesized by Simultaneous Pulsed Wire Evaporation (S-PWE) Method, Part I - Background: M. O., A. Yu.; J Korean Powder Metall Inst. 2004;11(1):60-68.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.060

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Abstract PDF: Pulsed wire evaporation (PWE) method is known as the promising production-technique for nanopowders. In this study, we developed and modified the previous single wire explosion equipment to the simultaneous two-wire explosion one for the fabrication of alloy or mixture of nano metallic powder. First of all, both the theoretical and empirical background of pulsed wire explosion of single wire were summarized, and compared with our experimental results for Cu and Al single wlre explosion. After then, the simultaneous wire evaporation equipment was designed, constructed, and tested. The current and voltage behavior were well matched between the calculated ones from the circuit equations, and the experimental results from simultaneous explosion of Cu and Al wire.

[Korean]
A study on Sintering Characteristics of Commercial 7xxx Series Al Alloy Powders: Panyu; J Korean Powder Metall Inst. 2004;11(1):69-73.; DOI: https://doi.org/10.4150/KPMI.2004.11.1.069

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The sintering characteristics of commercial 7xxx series Al-Zn-Mg-Cu alloy have been investigated. Sintering system of this blended elemental powder has aspects of both transient and supersolidus liquid phase sintering. Transient liquids occur when the constitution point during sintering lies in a solid phase region but where the sintering temperature is greater than either the melting point of one of the constituent or a eutectic temperature. Supersolidus liquid phase sintering occurs when a preblended powder is heated to a temperature between the solidus and liquids. However, these reaction were restrained their inter diffusion due to the appearance of the oxide film. Thus, 7xxx series Al alloy is extremely sensitive to process variables, including particle size, holding time and sintering temperature. Therefore, above phenomenons were observed formation and behaviour of the liquid by using SEM and DSC.

Citations

Citations to this article as recorded by

Sintering characteristic of Al2O3-reinforced 2xxx series Al composite powders
Kyung Ho Min, Shin Pil Kang, Dae-Gun Kim, Young Do Kim
Journal of Alloys and Compounds.2005; 400(1-2): 150. CrossRef

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