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        검색결과 89

        21.
        2012.06 구독 인증기관·개인회원 무료
        Roll milled- and nano-powders were prepared from the freeze dried fruiting bodies of Hericium erinaceum and their hydration properties such as water solubility index, swelling capacity, water holding capacity, and water sorption isotherm were compared. Water content in freeze dried Nano-powder of Hericium erinaceum fruiting body was 8.17%. Nano-powder has higher water solubility index compared to roll mill powder by 58.41% and 39.06%, respectively. In the same way, swelling capacity of nano-powder was 10.21ml/g where as roll mill powder has only 4.42ml/g. In contrast, water holding capacity of nano-powder (3.87g/g) is lower than that of roll mill powder (6.81g/g). Water sorption isotherm of these powders was compared and the result shows no big difference at low relative humidity (below75%). However, a high relative humidity above 75%, these two kinds of powder showed comparable difference. At 84.34% relative humidity, roll mill powder has 30.41% of moisture content compared with 47.64% of nano-powder, and at the relative humidity of 97.3%, the moisture content of roll mill and nano-powder are 37.64% and 91.06% respectively.
        22.
        2011.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study, nano-sized tin oxide powder with an average particle size of below 50 nm is prepared by the spray pyrolysis process. The influence of air pressure on the properties of the generated powder is examined. Along with the rise of air pressure from 0.1kg/cm2 to 3kg/cm2, the average size of the droplet-shaped particles decreases, while the particle size distribution becomes more regular. When the air pressure increases from 0.1kg/cm2 to 1kg/cm2, the average size of the dropletshaped particles, which is around 30-50 nm, shows hardly any change. When the air pressure increases up to 3kg/cm2, the average size of the droplet-shaped particles decreases to 30 nm. For the independent generated particles, when the air pressure is at 0.1kg/cm2, the average particle size is approximately 100 nm; when the air pressure increases up to 0.5kg/m2, the average particle size becomes more than 100 nm, and the surface structure becomes more compact; when the air pressure increases up to 1kg/cm2, the surface structure is almost the same as in the case of 0.5kg/cm2, and the average particle size is around 80- 100 nm; when the air pressure increases up to 3kg/cm2, the surface structure becomes incompact compared to the cases of other air pressures, and the average particle size is around 80-100 nm. Along with the rise of air pressure from 0.1kg/cm2 to 0.5kg/cm2, the XRD peak intensity slightly decreases, and the specific surface area increases. When the air pressure increases up to 1kg/cm2 and 3kg/cm2, the XRD peak intensity increases, while the specific surface area also increases.
        4,000원
        23.
        2011.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Cemented tungsten carbide has been used in cutting tools and die materials, and is an important industrial material. When the particle size is reduced to ultrafine, the hardness and other mechanical properties are improved remarkably. Ultrafine cemented carbide with high toughness and hardness is now widely used. The objective of this study is synthesis of nanostructured WC-Co powders by liquid phase method of tungstate. The precursor powders were obtained by freezen-drying of aqueous solution of soluble salts, such as ammonium metatungstate, cobalt nitrate. the final compositions were WC-10Co. In the case of liquid phase method, it can be observed synthesis of WC-10Co. The properties of powder produced at various temperature, were estimated from the SEM, BET and C/S analyser.
        4,000원
        24.
        2011.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Inkjet printing was successfully done using Cu nano powder ink after these Cu nano powders were dry-coated with 1-octanethiol for oxidation prevention. 1-octanethiol, which is Self-Assembled Multi-layers (SAMs), was coated approximately 10-nm thick on the surface of Cu nano powders. 1-Octanol, which has the same chain length as that for 1-octanethiol, was used as a solvent to make the ink for inkjet printing. As a result, the fabricated ink was dispersed for about 4 weeks, and after printing and heat treatment at for 4 hours, the resistivity for the printed pattern was measured to be .
        4,000원
        25.
        2011.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study, by using tin chloride solution as a raw material, a nano-sized tin oxide powder with an average particle size below 50 nm is generated by a spray pyrolysis process. The properties of the generated tin oxide powder depending on the inflow speed of the raw material solution are examined. When the inflow speed of the raw material solution is 2 ml/min, the majority of generated particles appear in the shape of independent polygons with average size above 80-100 nm, while droplet-shaped particles show an average size of approximately 30 nm. When the inflow speed is increased to 5 ml/min, the ratio of independent particles decreases, and the average particle size is approximately 80-100 nm. When the inflow speed is increased to 20 ml/min, the ratio of droplet-shaped particles increases, whereas the ratio of independent particles with average size of 80-100 nm decreases. When the inflow speed is increased to 100 ml/min, the average size of the generated particles is around 30-40 nm, and most of them maintain a droplet shape. With a rise of inflow speed from 2 ml/min to 5 ml/min, a slight increase of the XRD peak intensity and a minor decrease of specific surface area are observed. When the inflow speed is increased to 20 ml/min, the XRD peak intensity falls dramatically, although a significant rise of specific surface area is observed. When the inflow speed is increased to 100 ml/min, the XRD peak intensity further decreases, while the specific surface area increases.
        4,000원
        26.
        2011.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Nanostructured cobalt materials have recently attracted considerable attention due to their potential applications in high-density data storage, magnetic separation and heterogeneous catalysts. The size as well as the morphology at the nano scale strongly influences the physical and chemical properties of cobalt nano materials. In this study, cobalt nano particles synthesized by a a polyol process, which is a liquid-phase reduction method, were investigated. Cobalt hydroxide (Co(OH)2), as an intermediate reaction product, was synthesized by the reaction between cobalt sulphate heptahydrate (CoSO4·7H2O) used as a precursor and sodium hydroxide (NaOH) dissolved in DI water. As-synthesized Co(OH)2 was washed and filtered several times with DI water, because intermediate reaction products had not only Co(OH)2 but also sodium sulphate (Na2SO4), as an impurity. Then the cobalt powder was synthesized by diethylene glycol (DEG), as a reduction agent, with various temperatures and times. Polyvinylpyrrolidone (PVP), as a capping agent, was also added to control agglomeration and dispersion of the cobalt nano particles. The optimized synthesis condition was achieved at 220˚C for 4 hours with 0.6 of the PVP/Co(OH)2 molar ratio. Consequently, it was confirmed that the synthesized nano sized cobalt particles had a face centered cubic (fcc) structure and with a size range of 100-200 nm.
        4,000원
        27.
        2011.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate (). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid () was used as reduction agent. Both the HCP and the FCC Co phase were developed while concentration ranged from 0.7 M to 1.1 M. Secondary phase such as and were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of , indicating that the amount of reduction agent was enough to reduce . Consequently, a homogeneous Co phase could be developed without second phase when the ratio exceeded 7.
        4,000원
        28.
        2011.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study investigated the effect of solvent on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid and compared the alloy particles fabricated by three different methods (PWE in liquid, PWE in Ar, plasma arc discharge), for high temperature oxidation-resistant metallic porous body for high temperature soot filter system. Three different solvents (ethanol, acetone, distilled water) of liquid were adapted in PWE in liquid process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. The alloy powder synthesized by PWE in ethanol has good particle size and no surface oxidation compared to that of distilled water. Since the Fe-based alloy powders, which were fabricated by PWE in Ar and PAD process, showed surface oxidation by TEM analysis, the PWE in ethanol is the best way to fabricate Fe-based alloy nano powder.
        4,000원
        29.
        2011.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study investigated the effect of wire diameter and applied voltage on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid, for high temperature oxidation-resistant metallic porous body for high temperature particulate matter (or soot) filter system. Three different diameter (0.1, 0.2, and 0.3 mm) of alloy wire and various applied voltages from 0.5 to 3.0 kV were main variables in PWE process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. It was controlled the number of explosion events, since evaporated and condensed nano-particles were coalesced to micron-sized secondary particles, when exceeded to the specific number of explosion events, which were not suitable for metallic porous body preparation. As the diameter of alloy wire increased, the voltage for electrical explosion increased and the size of primary particle decreased.
        4,000원
        30.
        2011.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Nano-technology is a super microscopic technology to deal with structures of 100 nm or smaller. This technology also involves the developing of TiO2 materials or TiO2 devices within that size. The aim of the present paper is to synthesize WOx doped nano-TiO2 by the Sonochemistry method and to evaluate the effect of different percentages (0.5-5 wt%) of tungsten oxide load on TiO2 in methylene blue (MB) elimination. The samples were characterized using such different techniques as X-ray diffraction (XRD), TEM, SEM, and UV-VIS absorption spectra. The photo-catalytic activity of tungsten oxide doped TiO2 was evaluated through the elimination of methylene blue using UV-irradiation (315-400nm). The best result was found with 5 wt% WOx doped TiO2. It has been confirmed that WOx-TiO2 could be excited by visible light (E<3.2 eV) and that the recombination rate of electrons/holes in WOx-TiO2 declined due to the existence of WOx doped in TiO2.
        4,000원
        31.
        2010.12 구독 인증기관 무료, 개인회원 유료
        For application of nano-sized material in various fields, toxicity evaluation of nano-sized material is important. In the current study, a suspension of 50 nm-sized zinc oxide (ZnO) nanoparticles at a dose of 1 g/kg body weight was injected intraperitonially into mice in order to identify the toxicity of ZnO nanoparticles. After 24 h, the blood and liver were taken and analyzed. According to the results of hematological analysis, white blood cell (p<0.001), mean corpuscular hemoglobin (p<0.001), and mean corpuscular hemoglobin concentration (p<0.05) in the ZnO nanoparticle treated group showed a significant decrease, compared to the control group. In serum biochemistry analysis, alanine aminotransferase (p<0.001) and aspartate amino-transferase (p<0.05) also induced a significant increase in the ZnO nanoparticle treated group, compared with the control group. In the histopathological examination, liver in mice treated with ZnO nanoparticles showed edema and degeneration in hepatocytes. Therefore, it is concluded that the liver is the target organ for 50 nm ZnO intraperitoneal exposure. In the future, greater attention should be paid to the potential toxicity induced by various routes and doses of ZnO nanoparticles.
        4,000원
        32.
        2010.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The optimum route to fabricate nano-sized Fe-50 wt% Co and hydrogen-reduction behavior of calcined Fe-/Conitrate was investigated. The powder mixture of metal oxides was prepared by solution mixing and calcination of Fe-/Co-nitrate. A DTA-TG and microstructural analysis revealed that the nitrates mixture by the calcination at 300˚C for 2 h was changed to Fe-oxide/Co3O4 composite powders with an average particle size of 100 nm. The reduction behavior of the calcined powders was analyzed by DTA-TG in a hydrogen atmosphere. The composite powders of Fe-oxide and Co3O4 changed to a Fe-Co phase with an average particle size of 40 nm in the temperature range of 260-420˚C. In the TG analysis, a two-step reduction process relating to the presence of Fe3O4 and a CoO phase as the intermediate phase was observed. The hydrogen-reduction kinetics of the Fe-oxide/Co3O4 composite powders was evaluated by the amount of peak shift with heating rates in TG. The activation energies for the reduction, estimated by the slope of the Kissinger plot, were 96 kJ/mol in the peak temperature range of 231-297˚C and 83 kJ/mol of 290-390˚C, respectively. The reported activation energy of 70.4-94.4 kJ/mol for the reduction of Fe- and Co-oxides is in reasonable agreement with the measured value in this study.
        4,000원
        33.
        2009.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The Zr-based bulk metallic glass matrix composites of a mixture of gas-atomized metallic glass powders and Fe-based nanostructured powders were fabricated by spark plasma sintering. The Fe-based nanostructured powders adopted for the enhancement of plasticity were well distributed in the matrix after consolidation, and the matrix remains as a fully amorphous phase. The successful consolidation of metallic glass matrix composite with high density was attributed to viscous flow in the supercooled liquid state during spark plasma sintering. Unlike other amorphous matrix composites, in which improved ductility could be obtained at the expense of their strength, the developed composite exhibited improvement both in strength and ductility. The ductility improvement in the composite was considered to be due to the formation of multiple shear bands under the presence of the Fe-based nanostructured particles.
        4,000원
        34.
        2009.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The compaction response of nano powders with an addition of Ti powders prepared by magnetic pulsed compaction and subsequent sintering processes was investigated. All kinds of different bulk exhibited an average shrinkage of about 12% for different MPCed pressure and sintering temperature, which were approximately 50% lower than those fabricated by general process (20%) and a maximum density of around 92.7% was obtained for 0.8GPa MPCed pressure and sintering temperature. The addition of Ti powder induced an increase in the formability and hardness of the sintered . But the lower densities were obtained on sintering with addition of over 10 (wt%) Ti powder due to generation of crack during sintering. Subsequently it was verified that the optimum compaction pressure in MPC and sintering temperature were 0.8GPa and , respectively
        4,000원
        35.
        2009.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In chemistry, the study of sonochemistry is concerned with understanding the effect of sonic waves and wave properties on chemical systems. In the area of chemical kinetics, it has been observed that ultrasound can greatly enhance chemical reactivity in a number of systems by as much as a million-fold. Nano-technology is a super microscopic technology in which structures of 100 nanometers or smaller can be investigated. This technology has been used to develop TiO2 materials and TiO2 devices of that size. Thus far, electrochemistry methods and photochemistry methods have generally been used to create TiO2 nano-size particles. However, these methods are complicated and create pollutants as a by-product. In the present study, nano-scale silver particles (5 nm) were prepared in a sonochemistry method. Sonochemistry deals with mechanical energy that is provided by the collapse of cavitation bubbles that form in solutions during exposure to ultrasound. TiO2 powders 25 nm in size doped with Ag were formed using an ultrasonic sound technique. The experimental results showed the high possibility of removing pollution through the action of a photocatalyst. This powder synthesis technique can be considered as an environmentally friendly powder-forming processing owing to its energy saving characteristics.
        4,000원
        36.
        2008.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this research, fine-structure TiO2 bulks were fabricated in a combined application of magnetic pulsed compaction (MPC) and subsequent sintering and their densification behavior was investigated. The obtained density of TiO2 bulk prepared via the combined processes increased as the MPC pressure increased from 0.3 to 0.7 GPa. Relatively higher density (88%) in the MPCed specimen at 0.7 GPa was attributed to the decrease of the inter-particle distance of the pre-compacted component. High pressure and rapid compaction using magnetic pulsed compaction reduced the shrinkage rate (about 10% in this case) of the sintered bulks compared to general processing (about 20%). The mixing conditions of PVA, water, and TiO2 nano powder for the compaction of TiO2 nano powder did not affect the density and shrinkage of the sintered bulks due to the high pressure of the MPC.
        4,000원
        37.
        2008.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        On the base of experience in development of Magnetic Powder Composites, and particularly Soft Magnetic Composites, authors are trying to systematize classification and indicate possible development prospective of Magnetic Nanocomposites (MN) technology and their applications in electrical converters. Clear classification and systematization, at an early stage of any materials and technology development, are essential and lead for better understanding and communication between researchers and industry involved. This concern MN as well and it seems to be the right time to make it at present stage of their development. Presented proposal of classification distinguishes various types of MN by their magnetic properties and area of possible applications. It is not a close set of types, and can be extended due to increase of knowledge concern these nanocomposites.
        4,200원
        38.
        2008.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        doped (GDC) solid solutions have been considered as a promising materials for electrolytes in intermediate-temperature solid oxide fuel cells. In this study, the nano-sized GDC powder with average panicle size of 69nm was prepared by a high energy ball milling process and its sintering behavior was investigated. Heat-treatment at of nano-sized GDC powder mixture led to GDC solid-solution. The enhanced densification over 96% of relative density was obtained after sintering at for 2h. It was found that the sinterability of GDC powder could be significantly improved by the introduction of a high energy ball milling process
        4,000원
        39.
        2007.12 구독 인증기관 무료, 개인회원 유료
        This study was perfomed to determine the feasibility of developing a healthy yogurt using tofu whey concentrates separated by nanofiltration (NF). The curd yogurt was prepared from whole milk with added skim milk powder, in which the NF powder was substituted at 0, 6.25, 12.5, or 25% for the skim milk powder. The quality characteristics were evaluated for pH, titratable acidity, viscosity, color, and viable cell counts. There were no significant differences in pH or titratable acidity between the control (yogurt with added skim milk powder only) and the yogurts with added NF powder, after 24 hr of fermentation at 370C. The apparent viscosities of the yogurts with added NF powder were higher (3,197~3,574 cps) than that of the control yogurt (3,196 cps). Lightness decreased, while yellowness increased, as the amount of NF powder increased. Sensory evaluations showed that the NF powder could be substituted for the skim milk powder at 6.25% without lowering the yogurt quality.
        4,000원
        40.
        2007.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        우리는 마이카, boron nitride, bismuthoxychloride와 같은 판상 분체에 ZnO 나노입자를 코팅한 고 기능성 무기 분체를 합성하였다. 본 실험에서 우리는 수열침전법을 이용하여 합성 분체를 합성하였다. 출발물질은 ZnCl2를 사용하였고 침전제로는 hexamethylenetetramine(HMT)와 urea를 사용하였다. 본 실험의 반응변수로는 출발물질의 농도, 침전제 및 반응온도를 변화시켜 실험하였다. 합성물의 형태, 결정성 및 UV-차단능은FE-SEM, XRD, FT-IR, TGA-DTA, in vitro SPF 테스트를 활용해 분석하였다. 본 실험의 결과, 나토입자 크기를 갖는 ZnO는 동일한 최적의 합성조건하에서 다양한 판상 분체의 종류에 관계없이 균일하게 코팅되었다.
        4,000원
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