• Carbon letters
• /
• v.10 no.2
• /
• pp.114-122
• /
• 2009

Crushed, depitted peach stones were impregnated activated with 50% $H_3PO_4$ followed by pyrolysis at $500^{\circ}C$. Two activated carbons were produced, one under its own evolved gases during pyrolysis, and the second conducted with air flow throughout the carbonization stage. Physicochemical properties were investigated by several procedures; carbon yield, ash content, elemental chemical analysis, TG/DTG and FTIR spectra. Porosity characteristics were determined by the conventional $N_2$ adsorption at 77 K, and data analyzed to get the major texture parameters of surface area and pore volume. Highly developed activated carbons were obtained, essentially microporous, with slight effect of air on the porous structure. Oxygen was observed to be markedly incorporated in the carbon matrix during the air treatment process. Cation exchange capacity towards Cu (II) and Cd (II) was tested in batch single ion experimental mode, which proved to be slow and a function of carbon dose, time and initial ion concentration. Copper was up taken more favorably than cadmium, under same conditions, and adsorption of both cations was remarkably enhanced as a consequence of the air treatment procedure. Sequestration of the metal ions was explained on basis of the combined effect of the oxygen functional groups and the phosphorous-containing compounds; both contributing to the total surface acidity character.

• Resources Recycling
• /
• v.6 no.3
• /
• pp.28-35
• /
• 1997

Adsorption properities of hcavy metals (Cd, Cu, Fe, Mn, Pb, Zn) and organic compounds (Trichloroethylene and T Tetrachroethy len려 on sh$\xi$1I( oyster and ark shell) were investigated using wat$\xi$r treatment matenals, The shell powder (m띠or C crystal structurc is calcium hydroxide) showed the preference adsorption for heavy metals in order of Mn > Zn > Fe > Cd > eu > P Pb. The high removal capacities of heavy metals arc helicved to be largely due to precipitation by foonation of metal c carhonat,잃 and hydroxides at high pH caused by the $Ca(OH)_2$ component of sl1ell, immobilizatIon of heavy metals in a solid I matrix by calcium‘ and fixation by insoluble organic materials in the oystcr and ark shell. The use of sh려I in water treatment h has the potential to bc benefIcial as a source of inexpensive matcrials‘ moreover, not only treatment of waste but also e environmcntal business including environmental-purification ceramics could be better off by utili낌ng high-valued waste and d developed puri'fication ceramics and media.

• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.6
• /
• pp.701-717
• /
• 2003

The objective of this study was to extensively estimate the air quality trends of the study area by surveying con-centration trends in months or seasons, after analyzing the mass concentration of PM-10 samples and the inorganic lements, ion, and total carbon in PM-10. Also, the study introduced to apply the PMF (Positive Matrix Factoriza-tion) model that is useful when absence of the source profile. Thus the model was thought to be suitable in Korea that often has few information about pollution sources. After obtaining results from the PMF modeling, the existing sources at the study area were qualitatively identified The PM-10 particles collected on quartz fiber filters by a PM-10 high-vol air sampler for 3 years (Mar. 1999∼Dec.2001) in Kyung Hee University. The 25 chemical species (Al, Mn, Ti, V, Cr, Fe, Ni, Cu, Zn, As, Se, Cd, Ba, Ce, Pb, Si, N $a^{#}$, N $H_4$$^{+}$, $K^{+}$, $Mg^{2+}$, $Ca^{2+}$, C $l^{[-10]}$ , N $O_3$$^{[-10]}$ , S $O_4$$^{2-}$, TC) were analyzed by ICP-AES, IC, and EA after executing proper pre - treatments of each sample filter. The PMF model was intensively applied to estimate the quantitative contribution of air pollution sources based on the chemical information (128 samples and 25 chemical species). Through a case study of the PMF modeling for the PM-10 aerosols. the total of 11 factors were determined. The multiple linear regression analysis between the observed PM-10 mass concentration and the estimated G matrix had been performed following the FPEAK test. Finally the regression analysis provided source profiles (scaled F matrix). So, 11 sources were qualitatively identified, such as secondary aerosol related source, soil related source, waste incineration source, field burning source, fossil fuel combustion source, industry related source, motor vehicle source, oil/coal combustion source, non-ferrous metal source, and aged sea- salt source, respectively.ively.y.

• Journal of Korean Society for Atmospheric Environment
• /
• v.17 no.2
• /
• pp.133-145
• /
• 2001

The receptor modeling is one of the statistical methods to achieve reasonable air pollution strategies. The pur-pose of this study was to survey the concentration variability oi inorganic elements and ionic species in the PM-10 particles, to qualitatively characterize emission sources by an advanced algorithm called positive matrix factoriza-tion(PMF) as a receptor model that can strictly provide results in every loading matrix. A total of 254 samples was collected by a PM-10 high volume air sampler from Mar. 1997 to Feb. 1998 in Kyung Hee University at Suwon Campus. Fourteen chemical species(Zn, Cu, Fe, Pb, Al, Mn, $Na^{+}$, NH$_4$+, $K^{+}$, $Mg^{2+}$, $Ca^{2+}$, $SO_4^{2-}$, $NO_{3}^{-}$, and $Cl^{-}$) were determined by AAS and IC methods. The study results showed that the average monthly concentration of PM-10 particles were 86.3$\mu\textrm{g}$/$\textrm{m}^3$ in March (maximum) and 28.5$\mu\textrm{g}$/$\textrm{m}^3$ in August(minimum), respectively. The concentrations of Na+, NH$_4$+, $K^{+}$ and $Cl^{-}$ in winter, $Mg^{2+}$, $Ca^{2+}$ and $NO_{3}^{-}$, in spring, and $SO_4^{2-}$ in summer showed the largest peak concentration for the respective season. Through and app-lication of a PMF program of Pm-10 concentration data of Suwon, 9 sources were qualitatively identified , such as incineration source, oil burning source, soil related source, open burning source automobile source, coal burning sources, secondary sulfate related source, and secondary nitrate related source.

• Korean Journal of Environmental Agriculture
• /
• v.15 no.1
• /
• pp.1-10
• /
• 1996

The contents of heavy metals in soil near the Janghang smelter area were observed to understand present status and relationship between their fraction and the absorption by rice. The soil samples were taken from the eight sites of the paddy fields in 1982 and 1990, and analysis on heavy metals including Cd, Zn, Cu and Pb was performed. The results were as follows: Total contents of heavy metals in the samples of 1990 were higher than those of 1982. The order of increasing ratio was Cu > Zn > Pb > Cd and the variation of Cd content by sequential differente extracting was residual > exchangeable > dilute acid-extractable fractions and its increasing range was from 38 to 71% during nine years. The ratio of immobile heavy metals bound within an oxide or silicate matrix of Fe-Mn oxide bound and residual in surface soil was that Cd, Pb, Cu and Zn were 31.65, 42.22, 76.57 and 79.49%, respectively, and their mobile ratios of exchangeable, dilute acid-extractable and organically bound were more than 20.28%. Those of mobile Cd, Pb, Cu and Zn were 68.35, 55.78, 23.43 and 20.28%, respectively. Correlation between the heavy metal contents in surface soil and those in tissue of rice plant, such as leaf blade, leaf sheath, stem and panicle axis, were significant, but were not significant in subsurface soil. The dilute acid-extractable and organically bound fractions of Cd, Cu, Pb and Zn in surface soil were more significantly correlated with those in tissues of paddy rice.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.6
• /
• pp.265-272
• /
• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Proceedings of the Korean Magnestics Society Conference
• /
• 1991.05a
• /
• pp.73-74
• /
• 1991

The films with ferromagnetic fine particles dispersed in nonmagnetic matrix, such as $Fe-Al_2O_3$ and Fe-Cu have been studied for use of magnetic recording medium, optically device and sensor. Their magnetic properties depend strongly on structural parameter such as size and volume fraction of ferromagnetic particles. Fe-Cr-Ni alloy sputtered films also have microstructure with ferromagnetic -- b.c.c phase and nonmagnetic f.c.c phase grains. Magnetic properties of these films depend strongly on such a unique structure. These are depend on the ratio in volume of ferromagnetic particles to nonmagnetic ones $V_F/V_N$, the saturation magnetization Ms increased with increase of $V_F/V_N$. The coercivity Hc of the as-deposited films took maximum value of about 200 Oe at adequate $V_F/V_N$ and then Ms and Squareness S were 500 emu/cc and 0.5, respectively.(omitted)

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.975-985
• /
• 2011

Cu-Matrix sintered brake pads and low alloyed heat resistance steel are most applied to basic brake system for high energy moving machine. In this research, we analyzed tribological characteristics for influence of air velocity between disk and pad. At low brake pressure with air flow, friction stability was decreased due to no formation of tribofilm at disk surface. But there are no significant change of friction coefficient at all test conditions. Wear rate of friction materials were decreased with increasing of air flow velocity. In result, air flow velocity influenced friction stability, wear rate of friction materials and disk but not friction coefficient.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.99.1-99.1
• /
• 2016

The materials for an electronic packaging provide diverse important functions including electrical contact to transfer signals from devices, isolation to protect from the environment and a path for heat conduction away from the devices. The packaging materials composed of metals, ceramics, polymers or combinations are crucial to the device operating properly and reliably. The demand of effective charge and heat transfer continuous to be challenge for the high-speed and high-power devices. Nanomaterials including graphene, carbon nanotube and boron nitride, have been designed for the purpose of exploiting the high thermal, electrical and mechanical properties by combining in the matrix of metal or polymer. In addition, considering the inherent electrical and surface properties of graphene, it is expected that graphene would be a good candidate for the surface layer of a template in the electroforming process. In this talk, I will present recent our on-going works in nanomaterials for microelectronic packaging: 1) porous graphene/Cu for heat dissipations, 2) carbon-metal composites for interconnects and 3) nanomaterials-epoxy composites as a thermal interface materials for electronic packaging.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.1
• /
• pp.1-10
• /
• 2018

The improvement of critical current properties of $REBa_2Cu_3O_{7-x}$ (REBCO) coated conductors by introducing artificial pinning centers (APCs) is examined with respect to the field-angle anisotropy, high-field performance and relaxation property with time. Nano-rods along the c-axis introduced by PLD method and isotropic nano-particles introduced by TFA-MOD method are treated. The theoretical analysis is also shown to understand the effect of APCs quantitatively. The effects of superconducting layer thickness that influences the high-field performance and relaxation property are also discussed. It is shown that the upper critical field, which is another important factor to determine the high-field property, can be improved by introduction of APCs through electron scattering at interfaces with the superconducting matrix. The optimum critical current property can be obtained by properly designing the morphology and number density of APCs and the superconducting layer thickness.