• 제목/요약/키워드: $MgB_{2}$ powder

검색결과 266건 처리시간 0.026초

Preparation and Characterization of Ordered Perovskite (CaLa) (MgMo) $_6$

  • Choy, Jin-Ho;Hong, Seung-Tae;Suh, Hyeong-Mi
    • Bulletin of the Korean Chemical Society
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    • 제9권6호
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    • pp.345-349
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    • 1988
  • The polycrystalline powder of (CaLa) (MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in $H_2/H_2O$ and $N_2$ flowing atmosphere. The powder X-ray diffraction pattern indicates that (CaLa) (MgMo)$O_6$ has a monoclinic perovskite structure with the lattice constants $a_0=b_0=7.901(1){\AA}$, $c =7.875(1){\AA}\;and\;{\gamma}=89^{\circ}$16'(1'), which can be reduced to orthorhombic unit cell, a = 5.551(1) ${\AA}$, b = 5.622(1) ${\AA}$ and c = 7.875(1) ${\AA}$. The infrared spectrum shows two strong absorption bands with their maxima at 590($ν_3$) and 380($ν_4$) cm, which are attributed to $2T_{1u}$ modes indicating the existence of highly charged molybdenum octahedron $MoO_6$ in the crystal lattice. According to the magnetic susceptibility measurement, the compound follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.83(1)$_{{\mu}B}$, which is well consistent with that of spin only value (1.73 $_{\mu}_B$) for $Mo^{5+}$ with $4d^1$-electronic configuration within the limit of experimental error. From the thermogravimetric analysis, it has been confirmed that (CaLa) (MgMo)$O_6$ decomposes gradually into $CaMoO_4,\;MoO_3,\;MgO,\;La_2O_3$ and unidentified phases due to the oxidation of $Mo^{5+}$ to $Mo^{6+}$.

고춧가루의 색도측정(色度測定)과 품질(品質)과의 관계(關係) (Color Measurement of Red Pepper Powder and its Relationship with the Quality)

  • 전재근;박상기
    • Applied Biological Chemistry
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    • 제22권1호
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    • pp.18-23
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    • 1979
  • 고춧가루의 품질(品質)을 평가(評價)할 수 있는 객관적(客觀的) 기준(基準)을 마련하기 위하여 고춧가루의 외관색도(外觀色度), 적색소(赤色素)인 capsanthin의 함량(含量)및 coliform bacteria의 오염도와의 관계를 연구(硏究)한 결과 다음과 같았다. 1. 고춧가루의 육안판별방법(肉眼判別方法)은 개인간(個人間)의 색감(色感)의 차이(差異)로 인(因)하여 객관성(客觀性)이 없었다. 2. Capsanthin 함량(含量)에 따라 분류한 등급방법(等級方法)은 객관성(客觀性)을 보였으며 고춧가루의 품질평가(品質評價)에 기준(基準)이 될 수 있었고 외관색도(外觀色度)는 이 capsanthin 함량(含量)에 비례(比例)하였다. 3. 고춧가루의 외관색도(外觀色度)는 색도계(色度計)의 Hunter 값 a/b을 사용하여 수치(數値)로 표현(表現)할 수 있었으며 capsanthin의 함량(含量)과의 관계는 다음 식과 같으며 Capsanthin 함량(含量) (mg/g-고춧가루)=$0.257{\times}10^{0.703}(a/b)$ 고춧가루의 품질평가(品質評價)의 방법(方法)으로 응용(應用)할 수 있다. 4. 색도(色度)와 미생물(微生物)의 오염과의 관계는 명확(明確)하지 않았다.

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캡사이신 분말을 첨가한 쿠키의 품질 특성 (Quality Characteristics of Cookies Added with Capsaicin Powder)

  • 정은자;오경은;이문수;김관필;방병호
    • 한국식품영양학회지
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    • 제27권5호
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    • pp.921-928
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    • 2014
  • This study investigated the quality characteristics of cookies containing capsaicin, the main source of spicy taste in pepper, which is well known for its various functions such as anti-oxidant, anti-cancer, anti-inflammatory, and anti-obesity activities, as well as pain-relief effect. Cookie samples were made by adding the capsaicin powder at different levels, including 40 mg% (C1), 85 mg% (C2), and 150 mg% (C3). In this study, measurement of the moisture, pH, color, spread factor, hardness, anti-oxidant activity, and sensory evaluation of the cookies was carried out. The results showed that the anti-oxidant activity increased when more capsaicin powder was added to the cookies (p<0.001). The moisture also increased with increasing capsaicin powder content (p<0.05), while the pH did not show any significant changes. As for the colors, the L value and b value decreased as more capsaicin powder was added, while the a value increased. The spread factor also increased significantly with the increase of capsaicin powder (p<0.01). Although the hardness increased with capsaicin powder content, no statistically significant differences were observed among the various cookies. In the sensory evaluation, Cookies containing 40 mg of capsaicin obtained the highest score in color, while cookies containing 150 mg of capsaicin showed the highest score in taste, texture, and overall acceptability.

에어로졸 증착법에 의한 $MgB_2$ 박막 제조 (Fabrication of Magnesium Diboride Thin Films by Aerosol Deposition)

  • ;정국채;장세훈;한병동;박동수
    • Progress in Superconductivity
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    • 제13권2호
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    • pp.122-126
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    • 2011
  • Superconducting $MgB_2$ thin films were fabricated by using a novel aerosol deposition technique wherein the pre-reacted powder is directly transformed into respective thin film. The formed thin films were characterized by X-ray diffraction technique and FE-SEM to understand its structure and morphology and the superconducting behavior has been characterized with the four probe resistivity measurement. The as-deposited thin films were formed into the frustrated amorphous structure, which were relaxed on the further heat treatment at $900^{\circ}C$ for 3 hrs. The relaxed amorphous $MgB_2$ thin films showed a comparatively high superconducting onset at about 38 K.

어트리션 볼 밀링에 의한 보론 분말의 미세화 및 $MgB_2$의 초전도특성 (Refinement of Crystalline Boron and the Superconducting Properties of $MgB_2$ by Attrition Ball Milling)

  • 이지현;신승용;전병혁;김찬중;박해웅
    • Progress in Superconductivity
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    • 제10권1호
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    • pp.23-28
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    • 2008
  • We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the $MgB_2$ pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the $MgB_2$ that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the $B_{2}O_{3}$ peak became stronger in the powders, resulting in an increase in the amount of MgO within the $MgB_2$ volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density ($J_c$), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

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