• 제목/요약/키워드: controlled synthesis

검색결과 625건 처리시간 0.024초

유기노의 항산화 활성 및 멜라닌 생성 억제 효과 (Effect of Artemisia anomala S. Moore on Antioxidant Activity and Melanogenesis)

  • 이범천;김진화;김진희;표형배;;박흠대;조영호
    • 생약학회지
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    • 제36권4호통권143호
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    • pp.273-277
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    • 2005
  • In mammalian melanocytes, melanin synthesis is controlled by tyrosinase, the key enzyme in the pigment synthesis. In this study, to develop a new whitening agent, we have investigated the antioxidant and the inhibitory effect of Artemisia anomala extract on tyrosinase activity and melanigenesis in the B16/F1 melanoma cells. The inhibition ratio of tyrosinase activity of butanol fraction from A. anomala was higher than that of arbutin ($97.5{\pm}0.5%$ at the concentration of 2 mg/ml). The butanol fraction was shown scavenging activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and superoxide anion radicals in a dose dependent manner. The highest inhibitory activity of melanogenesis was also butanol fraction ($25.0{\pm}3%$ at the concentration of $200\;{\mu}g/ml$). From these results, we suggest that the A. anomala extract might be used to be a potential agent for skin whitening.

초음파 분무 열분해 공정을 이용한 TiOF2 분말의 합성과 광학적 성질 (Synthesis and Optical Property of a TiOF2 Powder via an Ultrasonic Spray Pyrolysis Process)

  • 황보영;이영인
    • 한국분말재료학회지
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    • 제23권4호
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    • pp.307-310
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    • 2016
  • $TiOF_2$, which has remarkable electrochemical and optical properties, is used in various applications such as Li-ion batteries, electrochemical displays, and photocatalysts. In addition, it is possible to utilize the template which is allowed to synthesize fluorine doped $TiO_2$ powders with hollow or faceted structures. However, common synthesis methods of $TiOF_2$ powders have some disadvantages such as the use of expensive and harmful precursors and batchtype processes with a limited production scale. In this study, we report a synthetic route for preparing $TiOF_2$ powders by using an inexpensive and harmless precursor and a continuous ultrasonic spray pyrolysis process under a controlled atmosphere to address the aforementioned problems. The synthesized powder has an average size of $1{\mu}m$, a spherical shape, a pure $TiOF_2$ phase, and exhibits a band-gap energy of 3.2 eV.

Synthesis of Nickel and Copper Nanopowders by Plasma Arc Evaporation

  • Cho, Young-Sang;Moon, Jong Woo;Chung, Kook Chae;Lee, Jung-Goo
    • 한국분말재료학회지
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    • 제20권6호
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    • pp.411-424
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    • 2013
  • In this study, the synthesis of nickel nanoparticles and copper nanospheres for the potential applications of MLCC electrode materials has been studied by plasma arc evaporation method. The change in the broad distribution of the size of nickel and copper nanopowders is successfully controlled by manifesting proper mixture of gas ambiance for plasma generation in the size range of 20 to 200 nm in diameter. The factors affecting the mean diameter of the nanopowder was studied by changing the composition of reactive gases, indicating that nitrogen enhances the formation of larger particles compared to hydrogen gas. The morphologies and particle sizes of the metal nanoparticles were observed by SEM, and ultrathin oxide layers on the powder surface generated during passivation step have been confirmed using TEM. The metallic FCC structure of the nanoparticles was confirmed using powder X-ray diffraction method.

마이크로에멀젼을 이용한 은 나노입자의 합성 (Synthesis of Silver Nanoparticles by Microemulsion)

  • 윤인영;박흥조;곽광수;정노희
    • 한국응용과학기술학회지
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    • 제20권2호
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    • pp.118-124
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    • 2003
  • Silver nanoparticles was synthesized by the method of W/O microemulsions with AOT (bis(2-ethylhexyl) sodium sulfosuccinate). The nucleation particle growth and aggregation was controlled by the droplet exchange process. The intermicellar exchange reaction is varied by changing the AOT and the $H_2O$ concentration. The synthesized W/O microemulsions was found to give the nanoparticles, which was confirmed by SEM, TEM, particle-size-analyzer, and UV-spectrometer. The most stable particles was obtained at 0.056 mole AOT solution, and the particle size distribution was found in the range from 27 to 31 nm. The mean particle size was reduced by adding Tween 20 significantly, and distribution was found from 14 to 16 nm. And, It's size was reduced by cosurfactants as toluene and benzyl alcohol. In case of toluene and benzyl alcohol, the range of particle size was found 7${\sim}$11 nm and 8${\sim}$12 nm.

세미카바존의 전기적 산화에 의한 2-Amino-5-Substituted-1,3,4-Oxadiazoles 합성 (Synthesis of Some 2-Amino-5-Substituted-1,3,4-Oxadiazoles Through the Electrooxidation of Semicarbazone)

  • Kumar, Sanjeev
    • 대한화학회지
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    • 제53권2호
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    • pp.159-165
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    • 2009
  • 2-Amino-5-Substituted-1,3,4-Oxadiazoles의 합성은 비분활된 셀에서 포텐셜 전기분해의 제어하에 백금전극의 세미카바존 전기적 산화로부터 수행되었다. 이것은 유기화학 합성분야에서 환경적으로 양호한 방법이다. 아세트산 및 아세트니트릴, 무수용매와 리튬 과염소산염 이 전기적 산화에서 전기분해을 위하여 사용 되어졌다. 생성물은 IR, $^1H$-NMR, $^{13}C$-NMR 그리고 원소분석을 통해 구조분석 하였다.

고온자전합성과 확산 열처리를 이용한 V 이 첨가된 TiAl계 금속간화합물 복합판재의 제조 (Formation of a V-Added Ti Aluminide Multilayered Sheet by Self-Propagating High-Temperature Synthesis and Diffusion Annealing)

  • 김연욱
    • 한국재료학회지
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    • 제12권9호
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    • pp.696-700
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    • 2002
  • The Ti-aluminide intermetallic compound was formed from high purity elemental Ti and Al foils by self-propagating, high-temperature synthesis(SHS) in hot press. formation of $TiAl_3$ at the interface between Ti and Al foils was controlled by temperature, pressure, heating rate, and so on. According to the thermal analysis, it is known in this study that the heating rate is the most important factor to form the intermetallic compound by this SHS reaction. The V layer addition between Al and Ti foils increased SHS reaction temperatures. The fully dense, well-boned inter-metallic composite($TiA1/Ti_3$Al) sheets of 700 m thickness were formed by heat treatment at $1000^{\circ}C$ for 10 hours after the SHS reaction of alternatively layered 10 Ti and 9 Al foils with the V coating layer. The phases and microstructures of intermetallic composite sheets were confirmed by EPMA and XRD.

Sodium Flame Encapsulation 방법에 의한 초미립 Ti 분말 합성 및 공정개발 (Synthesis and Process Development of Ultrafine Ti Powder by Sodium Flame Encapsulation Method)

  • 맹덕영;이창규;김흥희
    • 한국재료학회지
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    • 제12권5호
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    • pp.391-397
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    • 2002
  • Synthesis and process development of nano-size Ti powder by SFE(Sodium/halide Flame Encapsulation) method were investigated. Four concentric coflow burner was used and its flame configuration was $TiCl_4/Ar/Na/Ar$ in order from the center. Flame has been controlled by the various processing parameters such as temperature of burner and flow rates of both $TiCl_4$(g) precursor and Na(g). It was found that yellow-colored flame was shown in the flow rates of 70cc/min of $TiCl_4$(g) precursor and 2 $\ell$ /min of Na(g) which were regarded as optimum flame condition. The powders encapsuled by NaCl were produced having the average powder size of 250nm. The results of X-ray diffraction showed that powders from the optimized condition consisted of pure Ti and NaCl. TEM analysis confirmed that the several Ti powders of 20-100nm were encapsulated with NaCl. After removing sodium chloride by heat treatment, the spherical Ti powders with the size range of 80 to 150nm were obtained.

Synthesis of One-dimensional Spinel LiMn2O4 Nanostructures as a Positive Electrode in Lithium Ion Battery

  • Lee, Hyun-Wook;Muralidharan, P.;Kim, Do-Kyung
    • 한국세라믹학회지
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    • 제48권5호
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    • pp.379-383
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    • 2011
  • This paper presents the synthesis of one-dimensional spinel $LiMn_2O_4$ nanostructures using a facile and scalable two-step process. $LiMn_2O_4$ nanorods with average diameter of 100 nm and length of 1.5 ${\mu}m$ have been prepared by solid-state lithiation of hydrothermally synthesized ${\beta}$-$MnO_2$ nanorods. $LiMn_2O_4$ nanowires with diameter of 10 nm and length of several micrometers have been fabricated via solid-state lithiation of ${\beta}$-$MnO_2$ nanowires. The precursors have been lithiated with LiOH and reaction temperature and pressure have been controlled. The complete structural transformation to cubic phase and the maintenance of 1-D nanostructure morphology have been evaluated by XRD, SEM, and TEM analysis. The size distribution of the spinel $LiMn_2O_4$ nanorods/wires has been similar to the $MnO_2$ precursors. By control of reaction pressure, cubic 1-D spinel $LiMn_2O_4$ nanostructures have been fabricated from tetragonal $MnO_2$ precursors even below $500^{\circ}C$.

주조접합법에 의한 TaC 직접합성에 관한 연구 (A Study on the Direct Synthesis of TaC by Cast-bonding)

  • 박홍일;이성열
    • 한국주조공학회지
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    • 제17권4호
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    • pp.371-378
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    • 1997
  • The study for direct synthesis of TaC carbide which was a reaction product of tantalum and carbon in the cast iron was performed. Cast iron which has hypo-eutectic composition was cast bonded in the metal mold with tantalum thin sheet of thickness of $100{\mu}m$. The contents of carbon and silicon of cast iron matrix was controlled to have constant carbon equivalent of 3.6. The chracteristics of microstructure and the formation mechanism of TaC carbide in the interfacial reaction layer in the cast iron/tantalum thin sheet heat treated isothermally at $950^{\circ}C$ for various time were examined. TaC carbide reaction layer was grown to the dendritic morphology in the cast iron/tantalum thin sheet interface by the isothermal heat treatment. The composition of TaC carbide was 48.5 at.% $Ti{\sim}48.6$ at.% C-2.8 at.% Fe. The hardness of reaction layer was MHV $1100{\sim}1200$. The thickness of reaction layer linearly increased with increasing the total content of carbon in the cast iron matrix and isothermal heat treating time. The growth constant for TaC reaction layer was proportional to the log[C] of the matrix. The formation mechanism of TaC reaction layer at the interface of cast iron/tantalum thin sheet was proved to be the interfacial reaction.

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벡터합성방법에 의한 디지털-무선 변환시스템 (Digital-Radio Conversion System using Vector Synthesis Method)

  • 주창복;김성호
    • 융합신호처리학회논문지
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    • 제1권2호
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    • pp.131-137
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    • 2000
  • 본 논문은 소프트웨어 무선에 적합한 전송장치로써 로직회로에 의해 생성되어지는 디지털신호를 직접 무선으로 변환시킬 수 있는 디지털-무선 변환장치를 제안한다. 이러한 회로가 실현되어지면 변조회로, RF회로와 안테나를 1개의 간단한 디바이스로 실현할 수 있어 소프트웨어무선의 본질인 소프트웨어처리에 의한 무선의 제어를 직접 수행할 수 있게 된다. 본 논문의 디지털-무선 변환장치는 채널화용 PN코드가 부여하는 위상각도에 의해 무수히 많은 채널화를 기할 수 있으며 디지털화에 의하여 설계에 유연성을 주게 되므로 하드웨어의 비중을 최소화시키고 소프트웨어 베이스의 유연한 기능을 갖는다.

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