• 한국대기환경학회지
• /
• 제16권4호
• /
• pp.309-316
• /
• 2000

Chemical compositions of air pollutants with fine particles (<2.5 ${\mu}{\textrm}{m}$, PB2.5) were evaluated at background site. Kangwha. in Korea during the winter season. The data set was obtained for seventeed days with 24-hour sampling from December 11 to 16, 1996 and from January 9 to 1997. The chemical species have been measured {{{{ {SO }`_{4 } ^{2- } }}}}, {{{{ { NO}`_{3 } ^{- } }}}}, {{{{ { NH}`_{4 } ^{+ } }}}}. OC and EC in the particulate phase, NH3 HNO3, HCl and SO2 in the gas phase using the three stage filter pack method. Mean concentration ($\mu\textrm{g}$/m3) of this study were : 35.42 for PM2.5 8.78 for organic carbon (OC) 7.25 for nss {{{{ {SO }`_{4 } ^{2- } }}}}, 4.94 for {{{{ { NO}`_{3 } ^{- } }}}}, 3.58 for {{{{ { NH}`_{4 } ^{+ } }}}} and 1.48 for elemental carbon (EC) respectively. Contributive rates of major particulate components in PM2.5 were OC (25%) nss- {{{{ {SO }`_{4 } ^{2- } }}}}(20%) ,{{{{ { NO}`_{3 } ^{- } }}}}(14%) {{{{ { NH}`_{4 } ^{+ } }}}}(10%) and EC (4%) respectively and these components could be accounted for 73% of PM2.5 mass. Reactive forms of {{{{ { NH}`_{4 } ^{+ } }}}} were considered as NH4HO3 and NH4{{{{ {SO }`_{4 } ^{2- } }}}} during the sampling periods. {{{{ { NO}`_{3 } ^{- } }}}}/({{{{ { NO}`_{3 } ^{- } }}}} + HNO3) and {{{{ {SO }`_{4 } ^{2- } }}}}/({{{{ {SO }`_{4 } ^{2- } }}}} + SO2) were calculated 0.8 and 0.9 respectively. Most of these compounds might be formed in partiiculate phase in the air. Correlation coefficient between OC and EC was 0.866 which might have the same sources during the sampling periods,.

• 한국분말재료학회지
• /
• 제4권4호
• /
• pp.243-251
• /
• 1997

Engine valve-shaped TiAl-Mn intermetallics containing 43.5 to 47.5at%Al (Mn/Al=0.036) are successively fabricated by reactive sintering the elemental powder mixtures near-net shaped by extrusion and die forging. A duplex structure consisted of lamellar grains and equiaxed $\gamma$ grains is developed for all compositions, and the areal fraction of the lamellar grains(or equiaxed $\gamma$ grains) decreases (or increases) with increasing Al content. As Al content increased, the elongation increases with accompanying decrease in yield strength and ultimate tensile strength at both room temperature and 80$0^{\circ}C$. This indicates that the suitable composition is Ti-45at%Al-1.6at%Mn in considering the balance of ambient and elevated tensile properties. The reactive-sintered Ti-45Al-1.6Mn alloy shows superior oxidation resistance not only to the plasma arc melted one but also to the heat resistance steel STR35(representative exhaust valve head material for automotive engine). The reactive-sintered Ti-45Al-1.6Mn alloy coated with an oxidizing scale exhibits a better wear resistance than induction hardened martensitic steel STR11(representative exhaust valve tip material for automotive engine).

• 한국입자에어로졸학회지
• /
• 제12권3호
• /
• pp.57-63
• /
• 2016

The laser-induced breakdown spectroscopy (LIBS) has been used for rapid detection of elemental compositions of various materials in multi-media (solid, liquid, gas, and aerosols). In this study, the aerosol-LIBS has been developed for real-time monitoring of process-induced particles produced during the semiconductor manufacturing. The developed aerosol-LIBS mainly consists of laser, optics, spectrometer, and aerosol chamber. A new aerosol chamber was constructed for the aerosol-LIBS to be applied for various semiconductor manufacturing process, including exhaust tubes, and low pressure and high temperature chamber. The aerosol-LIBS was evaluated by using laboratory generated aerosols for detection of various elements. As a result, P, Fe, Mg, Cu, Co, Ni, Ca, Na, and K emission lines were successfully detected by the aerosol-LIBS. Further evaluation of the aerosol-LIBS is being conducted.

• Bulletin of the Korean Chemical Society
• /
• 제35권12호
• /
• pp.3601-3608
• /
• 2014

RGB light emitting ZnSe based nanocrystals: ZnSe (blue), ZnSe:Cu (green) and ZnSe:Mn (red) were synthesized by capping the surface of the nanocrystals with oleic acid. The obtained nanocrystal powders were characterized by using XRD, HR-TEM, ICP-AES, FT-IR, and FT-Raman spectroscopies. The optical properties were also measured by UV/Vis and photoluminescence (PL) spectroscopies. The PL spectra showed broad emission peaks at 471 nm (ZnSe), 530 nm (ZnSe:Cu) and 665 nm (ZnSe:Mn), with relative PL efficiencies in the range of 0.7% to 5.1% compared to a reference organic dye standard. The measured average particle sizes from the HR-TEM images for those three nanocrystals were 4.5 nm on average, which were also supported well by the Debye-Scherrer calculations. The elemental compositions of the ZnSe based nanocrystals were determined by ICP-AES analyses. Finally, the drawn CIE diagram showed the color coordinates of (0.15, 0.16) for ZnSe, (0.22, 0.57) for ZnSe:Cu, and (0.62, 0.35) for ZnSe:Mn respectively, which were fairly well matched to that of the RGB color standards.

• 한국대기환경학회지
• /
• 제11권3호
• /
• pp.279-290
• /
• 1995

Recently in Korea, due to the significant drop of lead and bromine levels as a marker of autoemission source in the urban areas, the conventional application of receptor methods has many difficulties to properly apportion mass contribution of some sources. It is then needed to urgently develop alternative source profiles and identify new emission markers. Thus, the study has extensively examined the results obtained from using PAHs and elemental data for receptor modeling and has provided an opportunity to identify alternative source compositions and to determine a proper number of the ambient emission sources in Seoul area. The purpose of the study is to identify the sources of PM-10 and to estimate their mass contributions in Seoul area. Thus, a receptor model, target transformation factor analysis(TTFA) has been massively applied. The TTFA offers the possibility of determining the number of sources and their mass contributions. The input data used in this study are composed of two separate sets: fine (d$_{p}$ < 2.5.mu.m) and coarse (2.5.mu.m < d$_{p}$ < 10.mu.m) mode aerosol samples. Each sample was simultaneously collected by a PM-10 dichotomous sampler during the daytime(8 AM to 8 PM) and the nighttime(8 PM to 8 AM) from February to October 1993 on the Sungdong-Gu, Seoul. All the samples were analyzed to determine the levels of 10 inorganic elements by an XRF system as well as 14 PAHs by a HPLC. However, only 8 inorganic elements and 7 PAHs were used for the various statistical analysis.sis.

• 한국재료학회지
• /
• 제21권10호
• /
• pp.542-545
• /
• 2011

Half-Heusler alloys are a potential thermoelectric material for use in high-temperature applications. In an attempt to produce half-Heusler thermoelectric materials with fine microstructures, TiCoSb was synthesized by the mechanical alloying of stoichiometric elemental powder compositions and then consolidated by vacuum hot pressing. The phase transformations during the mechanical alloying and hot consolidation process were investigated using XRD and SEM. A single-phase, half- Heusler allow was successfully produced by the mechanical alloying process, but a minor portion of the second phase of the CoSb formation was observed after the vacuum hot pressing. The thermoelectric properties as a function of the temperature were evaluated for the hot-pressed specimens. The Seebeck coefficients in the test range showed negative values, representing n-type conductivity, and the absolute value was found to be relatively low due to the existence of the second phase. It is shown that the electrical conductivity is relatively high and that the thermal conductivities are compatibly low in MA TiCoSb. The maximum ZT value was found to be relatively low in the test temperature range, possibly due to the lower Seebeck coefficient. The Hall mobility value appeared to be quite low, leading to the lower value of Seebeck coefficient. Thus, it is likely that the single phase produced by mechanical alloying process will show much higher ZT values after an excess Ti addition. It is also believed that further property enhancement can be obtained if appropriate dopants are selectively introduced into this MA TiCoSb System.

• 대한수의학회지
• /
• 제45권2호
• /
• pp.151-154
• /
• 2005

The purpose of this study is to examine the elemental compositions, antioxidant and antitumor activity of water, 20%, 40%, 60%, and 80% ethanol extracts obtained from the fruiting body of Phellinus gilvus. In electron donating ability test, the strong activities more than 70% were observed in $80{\mu}g/ml$ of 20%, 40%, 60% and 80% ethanol extracts from the fruiting body of P. gilvus grown in oak and sawdust. The antitumor activity was evaluated by sulforhodamine B (SRB) in terms of cell survival level. The tumor cells (sarcoma 180) were treated with various ethanol extracts (water, 20, 40, 60 and 80%). The results showed that all extracts inhibited proliferation showing a dose-dependent manner against tumor cells.

• Nuclear Engineering and Technology
• /
• 제53권6호
• /
• pp.2025-2037
• /
• 2021

The influence of lead cations on natural quartz (QZ) from Egypt as a glass shielding material for the composition with nominal formula (10Na₂O - (90 - x) QZ - xPbO (where x = 30, 35, 40, 45 and 50 mol %)) was examined. The studied samples are synthesized via the melt quenching method at 1050 ℃. The X-ray diffraction XRD patterns were confirmed the glass nature for studied samples. Moreover, the optical properties, and the transparency for all compositions were examined by UV-Vis spectroscopy. Also, the major elemental composition of the natural quartz were estimated via the X-ray fluorescence (XRF) technique. Further, the density and molar volume were determined. Furthermore, the nuclear shielding parameters such as, mass attenuation coefficient, effective atomic number, electronic density, the total atomic, and electronic cross sections as well as the mean free path, and the half value layer with different gamma ray energies (81 keV-1407 keV) were calculated. Besides, the results showed that the shielding behavior towards the gamma ray radiation for all glass samples was increased as the increment in PbO concentration in the glass system.

• Nuclear Engineering and Technology
• /
• 제55권8호
• /
• pp.2889-2896
• /
• 2023

The waste acceptance criteria for heavy metals in mixed waste should be developed by reflecting the leaching behaviors that could highly depend on the repository design and environment surrounding the waste. The current standards widely used to evaluate the leaching characteristics of heavy metals would not be appropriate for the silo-type repository since they are developed for landfills, which are more common than a silo-type repository. This research aimed to explore the leaching behaviors of cementitious waste with Pb, Cd, and Sb metallic and oxide powders in an environment simulating a silo-type radioactive waste repository. The Toxicity Characteristic Leaching Procedure (TCLP) and the ANS 16.1 standard were employed with standard and two modified solutions: concrete-saturated deionized and underground water. The compositions and elemental distribution of leachates and specimens were analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES) and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy (SEM-EDS). Lead and antimony demonstrated high leaching levels in the modified leaching solutions, while cadmium exhibited minimal leaching behavior and remained mainly within the cement matrix. The results emphasize the significance of understanding heavy metals' leaching behavior in the repository's geochemical environment, which could accelerate or mitigate the reaction.

• 분석과학
• /
• 제19권5호
• /
• pp.376-382
• /
• 2006

In this work, pitch/activated carbon/$TiO_2$ composite were prepared by $CCl_4$ solvent method with different mixing ratios. The BET surface area of pitch/activated carbon/$TiO_2$ composite has a significantly increase with increasing activated carbon content in pitch/activated carbon/$TiO_2$ composite. The surface structure and elemental compositions of the composite were studied by SEM and EDX, respectively. The SEM results were presented to the characterization of porous texture on the pitch/activated carbon/$TiO_2$ composite. And EDX data was shown the presence of C, O, S, Ti and other elements. The structural properties of the composite were studied in XRD measurements. The $TiO_2$ crystal phases of the pitch/activated carbon/$TiO_2$ composite had lots of rutile-type structure which transforms from anatase-type with a little of anatase-type structure. The photocatalytic activities of the composite were evaluated using a photo-decomposition method under UV lamp. The pitch/activated carbon/$TiO_2$ composites were observed better photocatalytic activity than that of pristine $TiO_2$.