• Journal of Magnetics
• /
• v.14 no.2
• /
• pp.75-79
• /
• 2009

Nickel (Ni) and ferrite ($Fe_3O_4$, $NiFe_2O_4$) nanoparticles were synthesized by LGC using both wire feeding (WF) and micron powder feeding (MPF) systems. Phase evolution and magnetic properties were then investigated. The Ni nanopowder included magnetic-ordered phases. The LGC synthesis yielded spherical particles with large coercivity while the abnormal initial magnetization curve for Ni indicated a non-collinear magnetic structure between the core and surface layer of the particles. Since the XRD pattern cannot actually distinguish between magnetite ($Fe_3O_4$) and maghemite (${\gamma}-Fe_2O_3$) as they have a spinel type structure, the phase of the iron oxide in the samples was unveiled by $M{\ddot{o}}ssbauer$ spectroscopy. The synthesized Ni-ferrite consisted of single domain particles, including an unusual ionic state. The synthesized nanopowder bore an active surface due to the defects that affected abnormal magnetic properties.

• Carbon letters
• /
• v.13 no.1
• /
• pp.44-47
• /
• 2012

We analyzed the effect of etchants for metal catalysts in terms of the characteristics of resulting graphene films, such as sheet resistance, hall mobility, transmittance, and carrier concentration. We found the residue of $FeCl_3$ etchant degraded the sheet resistance and mobility of graphene films. The residue was identified as an iron oxide containing a small amount of Cl through elemental analysis using X-ray photoelectron spectroscopy. To remove this residue, we provide an alternative etching solution by introducing acidic etching solutions and their combinations ($HNO_3$, HCl, $FeCl_3$ + HCl, and $FeCl_3+HNO_3$). The combination of $FeCl_3$ and acidic solutions (HCl and $HNO_3$) resulted in more enhanced electrical properties than pure etchants, which is attributed to the elimination of left over etching residue, and a small amount of amorphous carbon debris after the etching process.

• Journal of the Korean Ceramic Society
• /
• v.20 no.4
• /
• pp.289-296
• /
• 1983

The Wetting of fusion cast $Al_2O_3$ brick and $Al_2O_3 -ZrO_2$ brick by liquid Ag was studied by the sessile drop technique in Ar atmosphere. In this experiment the specimens were photographed per 2$0^{\circ}C$with increasing temperature from 96$0^{\circ}C$ melting point of Ag. And the method of photographing was carried out by shadow technique. The cosine of the contact angle increased linearly with increasing temperature in both systems. And the relation between the cosine of the contact angle and the temperature was Cos$\theta$=1.132+$0.75{\times}10^{-3}T$ for $Al_2O_3$ brick and Cos$\theta$=-1.706+$1.125{\times}10^{-3}T$ for $Al_2O_3 -ZrO_2$ brick In both systems the contact angle decreased as the surface of substrate became smoother. The work of adhesion which was 503.5ergs/$cm^2$ for $Al_2O_3$brick and 393.6 ergs/cm2 for $Al_2O_3 -ZrO_2$ brick at 96$0^{\circ}C$ increased parabolically with increasing temperature in both system.

• Resources Recycling
• /
• v.5 no.4
• /
• pp.17-24
• /
• 1996

The computer simulation model was established to verify the applicability of smelting reduction concept to treatment of industrial wastes which becomes issue on the enviromental and recycling view point. Computer simulation model provides as following results. The increase of post combustion ratio(PCR) and heat transfer efficiency of PC energy(HTE) is effective ways to save energy. But, in order to increase PCR, recovery efficiency of post combustion energy(HTE) have to be higher than 85% HTE considering refractory life and saving energy together. Coke is most useful fuel source because it shows lowest dependence of PCR and low hydrogen content. The quality of hot metal of current process would be expected to the similar level with that of blast furnace. The utilization of scrap and Al dross can be also possible to maximize the advantages of current process which is high temperature and chemical dilution with hot metal and slag. In case of scrap, energy consumption was slightly increases because of heating up energy of scrap. Consquently, current process concept provides the possibility of intergrating recycles of industrial wastes materials such as EAF slag, coke oven dust, life terminated acidic refractory, aluminium dross and scrap by smelting reduction process.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1628-1630
• /
• 2000

Vertically aligned multiwalled carbon nanotubes are grown on silicon oxide substrate at 950$^{\circ}C$ by thermal chemical vapor deposition using $C_{2}H_2$. Three catalytic metals such as iron(Fe), cobalt (Co), and nickel(Ni) are used as catalyst, we found that the growth rate of carbon nanotubes for three catalyst particles are in an order of Fe > Ni > Co. All carbon nanotubes are revealed to have bamboo structure with no encapsulated catalytic particles, the diameter of carbon nanotubes depend on the catalyst, the tip and the compartment sheets of bamboo structure also depend on the shape of catalytic particles.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.4
• /
• pp.905-909
• /
• 2010

Magnetic beads (Dynabeads$^{(R)}$) embedded in ~1 micron size polystyrene beads bearing surface carboxylic acid groups were modified with aminobenzyl ethylenediaminetetraacetic acid (ABEDTA) to concentrate or separate metal ions using pH gradients on micro and nano scales. The immobilization of ABEDTA was achieved by amide formation. The presence of the metal chelating functional group in the fully deprotonated form was confirmed by FT-IR. The chelation efficiency of beads was tested by determining metal ions in supernatant using GFAAS when pH gradients from 3 to 7. Mixtures of Cu and Mg and of Cd and Mn (at 10 ng/mL of metal) were separated as the difference in formation constant with the functional group of ABEDTA. The separation was repeated twice with relative standard deviation of <18%. A polydimethylsiloxane (PDMS) microchip column packed with EDTA-coated magnetic beads was optimized to concentrate metal ion for practical applications by eluting a Cu solution of micro scale at pH 3.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.761-763
• /
• 2015

Colors have been derived from the observed optical spectrum of Mars and Jupiter. It is known that the planets and the Moon emit reflected sunlight and thus their spectra are similar to the spectrum of solar radiation. The question was then why is the color of Mars different from that of other planets, i.e. red, although it would share the same spectrum of reflected sunlight. Can one derive color from the spectrum? Therefore, we observed the optical spectra of the scattered sunlight in day time for the Moon and Mars using a 1-D array spectrograph on the 12-inch reflecting telescope in the Korea Science Academy of KAIST in Busan, Korea. We adopted the International Commission on Illumination (CIE) in 1931 of three spectral sensitivity peaks for the human eye in short, medium and long wavelengths in visible light. The observed spectra were imposed on CIE sensitivities and the color detected by the human eye was derived. The Mars spectrum represents red color and the Moon white. It is a similar color to that which a human would see. This result means that color is easily derived from astronomical spectra. The appearance of the planets surface can be determined for Mars, which is the result of iron oxide.

• Journal of the Korean Magnetics Society
• /
• v.18 no.6
• /
• pp.217-220
• /
• 2008

We have investigated the magnetic properties of $ErFe_2O_4$. Stoichiometric polycrystalline sample of $ErFe_2O_4$ was prepared by solid-state reaction method in a stream of CO/$CO_2$ gas. The X-ray power diffraction pattern shows that the diffraction peaks are indexed with respect to the rhombohedral structure with a space group of R3m. The temperature dependent magnetization for $ErFe_2O_4$ shows two-step phase transitions at about 220 and 250 K. The transition at 250 K is an antiferromagnetic transition and that at 220 K is a structural transition.

• Journal of the Korean Ceramic Society
• /
• v.51 no.6
• /
• pp.570-574
• /
• 2014

Magnetic-graphene nanosheets have been synthesized via a simple effective chemical precipitation method followed by heat treatment. The composite nanosheets are super paramagnetic at room temperature and can be separated by an external magnetic field. The prepared magnetic-graphene nanosheets were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and BET surface area analysis. The results demonstrated the successful attachment of iron oxide nanoparticles to graphene nanosheets. It was found that the attached nanoparticles were mainly $Fe_3O_4$. The magnetic-graphene nanosheets showed near complete methyl orange removal within 10 mintues and would be practically usable for methyl orange separation from water.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.6 no.2
• /
• pp.33-40
• /
• 1982

The removal and redeposition of particulate soil occur simultaneously during the washing process. In order to investigate variables which affect on the redeposition of particulate soil, cotton lawn was soiled in the ion oxide black suspension using Launder-O meter. The amount of deposited soil was estimated by means of the spectrometric analysis of iron on the fabric after soiled. The results are as follows: 1. The presence of surfactants b suspension decreased the deposition of particulate soil and the most effective surfactant was soap and the descending order was NaDBS>CTAB>PONPE. 2. The influnce of temperature on soil deposition was considerable, soil deposition was gradually increased with elevating temperature in ionic surfactants solution such as NaDBS and CTAB but that was decreased above $40^{\circ}C$ in nonionic surfactant solution. 3. The tendency of soil deposition was dwindled by adding electrolytes especially in case of polyvalent anions. 4. From the results of the experiments redeposition of particulate soil was related with suspending power of surfactants and was influenced by factors varing zeta potential.