• 제목/요약/키워드: precursor solubility

검색결과 18건 처리시간 0.026초

알루미나-지르코니아 복합체의 제조공정 및 미세구조에 미치는 폴리머 첨가의 영향 (Effect of Polymer Content on Synthesis Process and Microstructure of Alumina-Zirconia Composite)

  • 이상진;권명도;이충효;조경식
    • 한국분말재료학회지
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    • 제10권5호
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    • pp.310-317
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    • 2003
  • Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

도판트 프리커서의 용해도 차이에 의한 Cr-doped Li4Ti5O12의 전기화학적 특성 변화 (Electrochemical Characteristic Change of Cr-doped Li4Ti5O12 due to Different Water Solubility of Dopant Precursors)

  • 윤수원;송한나;김용태
    • 전기화학회지
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    • 제18권1호
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    • pp.17-23
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    • 2015
  • $Li_4Ti_5O_{12}$는 우수한 안정성으로 자동차용 리튬 이온 이차전지의 음극 활물질로서 각광 받고 있다. 그러나 넓은 밴드갭에 기인한 절연체 특성으로 고율 충/방전을 가능하게 하기 위해서는 전자 전도도의 개선이 필수적이다. 본 연구에서는 Cr 도핑을 통해 $Li_4Ti_5O_{12}$의 전자 전도도 개선을 목표로 하였으며, wet-mixing법을 통한 물질 합성시 도판트인 Cr 프리커서의 용해도 차이에 의한 Cr-doped $Li_4Ti_5O_{12}$의 전기화학적 특성 변화를 고찰하고자 하였다. 시료의 물리적 특성은 ICP, XRD, SEM, EXAFS을 통하여 확인하였고 1.0V~3.0V (vs. $Li/Li^+$) 하에서 충/방전 특성을 조사하였다. 프리커서의 용해도는 합성된 물질의 상(phase) 및 모폴로지에 큰 영향을 미쳤으며, 가장 용해도가 높은 $Cr(NO_3)_2$ 프리커서로부터 합성된 경우 Bare $Li_4Ti_5O_{12}$와 비교하여 약 2배 개선된 고율 충/방전 특성(130 mAh/g @ 10 C)을 확인하였다.

A Water-Soluble Polyimide Precursor: Synthesis and Characterization of Poly(amic acid) Salt

  • Lee, Myong-Hoon;Jun Yang
    • Macromolecular Research
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    • 제12권3호
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    • pp.263-268
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    • 2004
  • We have synthesized a water-soluble polyimide precursor, poly(amic acid) amine salt (PAD), from pyromellitic dianhydride (PMDA), 4,4'-oxydianiline, and N,N -dimethylethanolamine (DMEA) and have investigated in detail its properties with respect to the degree of salt formation (D$\_$sf/). The maximum value of D$\_$sf/ we obtained upon precipitation of the precursor solution into acetone was 79%. We synthesized a PAD having a D$\_$sf/ of 100% (PAD100) by the solid state drying of an organic solution. The precursors showed different solubility depending on the D$\_$sf/ to make up to 4 wt% solutions in water containing a small amount of DMEA. PAD100 is completely soluble in pure water. We investigated the imidization behavior of PAD in aqueous solution using various spectroscopic methods, which revealed that PAD 100 has faster imidization kinetics relative to that of the poly(amic acid)-type precursors. The resulting polyimide films prepared from an aqueous precursor solution possess almost similar physical and thermal properties as those prepared from N-methyl-2-pyrrolidone(NMP) solution. Therefore, we have demonstrated that PAD can be used as a water-based precursor of polyimide; this procedure avoids the use of toxic organic solvents, such as NMP.

CuO의 첨가가 PMN-PT 세라믹스의 유전특성에 미치는 영향 (Effects of CuO Addition on the Dielectric Properties of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ Ceramics)

  • 김효태;변재동;김인태;김윤호
    • 한국세라믹학회지
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    • 제32권9호
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    • pp.1056-1064
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    • 1995
  • 95Pb(Mg1/3Nb2/3)O3-5PbTiO3 (hereinafter designated as 95PMN-5PT) system was prepared by the columbite-precursor method with 2 mol% excess PbO to compensate the PbO loss during thermal process. The amount of CuO was 1~10 mol%, and the effects of CuO addition on the dielectric properties of this system have been investigated. From the microstructures, XRD analysis and dielectric measurements, the solubility limit of CuO in 95PMN-5PT was found to be around 3 mol%. Lattice parameter and Curie temperature were found to be decreased as the amount of CuO increased up to the solubility limit. This result confirmed that the Cu2+-ions substituted the Pb2+-ions. It was revealed that the addition of CuO on 95PMN-5PT promoted the sinterability and properties. The room temperature dielectric constant, the loss factor and the specific resistivity of the specimens processed with optimum conditions were 23000, 1%, and 8$\times$1011Ω.cm, respectively.

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Properties of Synthesized Al2O3-CuO-ZnO/Ni Composite for Hydrogen Membranes

  • Rim, Saetbyol;Jung, Miewon
    • 한국세라믹학회지
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    • 제51권5호
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    • pp.477-480
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    • 2014
  • An $Al_2O_3$-CuO-ZnO (ACZ) precursor powder was synthesized by a facial sol-gel process using a nonionic surfactant span 80 as the chelating agent to improve the surface area and morphology. When creating a hydrogen membrane, several kinds of properties are required, such as easy dissociation of hydrogen molecules, fast hydrogen diffusion, high hydrogen solubility, and resistance to hydrogen embrittlement. ACZ-Ni composite membranes (cermet) were prepared with this precursor and pure Ni powder via the hot press sintering (HPS) method. The ACZ powder was characterized by XRD, BET, and FE-SEM. Hydrogen permeation experiments were performed by Sievert's type of hydrogen permeation membrane equipment. The hydrogen permeability of ACZ/Ni 10 wt% and ACZ/Ni 20 wt% was obtained as 7.2 and $10molm^{-2}s^{-1}$ at RT, respectively. These values of the corresponding membranes were slightly increased with increasing pressures.

Low Spin-Casting Solution Temperatures Enhance the Molecular Ordering in Polythiophene Films

  • Lee, Wi Hyoung;Lee, Hwa Sung;Park, Yeong Don
    • Bulletin of the Korean Chemical Society
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    • 제35권5호
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    • pp.1491-1494
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    • 2014
  • High-crystallinity poly(3-hexylthiophene) (P3HT) thin films were prepared by aging the precursor solutions, prepared using a good solvent, chloroform, at low temperatures prior to spin-casting. Lower solution temperatures significantly improved the molecular ordering in the spin-cast P3HT films and, therefore, the electrical properties of field-effect transistors prepared using these films. Solution cooling enhanced the electrical properties by shifting the P3HT configuration equilibrium away from random coils and toward more ordered aggregates. At room temperature, the P3HT molecules were completely solvated in chloroform and adopted a random coil conformation. Upon cooling, however, the chloroform poorly solvated the P3HT molecules, favoring the formation of ordered P3HT aggregates, which then yielded more highly crystalline molecular ordering in the P3HT thin films produced from the solution.

Molecular structure effects of the pitches on preparation of activated carbon fibers from electrospinning

  • Kim, Bo-Hye;Wazir, Arshad Hussain;Yang, Kap-Seung;Bang, Yun-Hyuk;Kim, Sung-Ryong
    • Carbon letters
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    • 제12권2호
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    • pp.70-80
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    • 2011
  • Two pitches with different average molecular structures were electrospun and compared in terms of the properties of their fibers after oxidative stabilization, carbonization, and activation. The precursor with a higher molecular weight and greater content of aliphatic groups (Pitch A) resulted in better solubility and spinnability compared to that with a lower molecular weight and lower aliphatic group content (Pitch B). The electrical conductivity of the carbon fiber web from Pitch A of 67 S/cm was higher than that from Pitch B of 52 S/cm. The carbon fiber web based on Pitch A was activated more readily with lower activation energy, resulting in a higher specific surface area compared to the carbon fiber based on Pitch B (Pitch A, 2053 $m^2/g$; Pitch B, 1374 $m^2/g$).

Thiazinogeldanamycin, a New Geldanamycin Derivative Produced by Streptomyces hygroscopicus 17997

  • Ni, Siyang;Wu, Linzhuan;Wang, Hongyuan;Gan, Maoluo;Wang, Yucheng;He, Weiqing;Wang, Yiguang
    • Journal of Microbiology and Biotechnology
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    • 제21권6호
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    • pp.599-603
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    • 2011
  • A new geldanamycin (GDM) derivative was discovered and isolated from the fermentation broth of Streptomyces hygroscopicus 17997. Its chemical structure was elucidated as thiazinogeldanamycin by LC-MS, sulfur analysis, and NMR. The addition of cysteine to the fermentation medium significantly stimulated the production level of thiazinogeldanamycin, suggesting cysteine as a precursor of thiazinogeldanamycin production. Although showing a decreased cytotoxicity against HepG2 cancer cells, thiazinogeldanamycin exhibited an improved water solubility and photostability. Thiazinogeldanamycin may represent the first natural GDM derivative characterized so far that uses GDM as its precursor. Its appearance also clearly indicates that an appropriate end-point of fermentation is of critical importance for the maximal production of GDM by Streptomyces hygroscopicus 17997.

Subphthalocyanine 화합물 유도체들의 합성 및 특성 비교 (Synthesis of Subphthalocyanine Compound Derivatives and Their Properties)

  • 김재환;허진;이윤이;김보현;이근대;홍성수;박성수
    • 공업화학
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    • 제20권1호
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    • pp.46-51
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    • 2009
  • 본 연구에서는 중간체인 여러 종류의 전구체를 사용하여 치환기의 종류와 위치가 상이한 subphthalocyanine (SubPc) 유도체를 성공적으로 합성하였다. 중간체 및 최종 생성물의 화학적 구조는 핵자기 공명 분광기 및 푸레어 변환 적외선 분광기를 이용하여 확인하였다. 또한, 분광학적 특성 및 결정상 특성은 자외선-가시광 분광기 및 XRD를 이용하여 측정 분석하였다. 합성한 SubPc 유도체들은 각각 560~600 nm 사이의 가시광을 선택적으로 흡수하였고, 치환기가 도입되면 용해도가 향상되었고, 치환기의 종류 및 위치에 따라 최대 흡수파장이 장파장 혹은 단파장으로 이동하였다.

Dimethylphenoxy와 MPEG 팬던트 그룹을 갖는 폴리벤즈옥사졸 전구체의 합성 및 특성 (Syntheses and Characterization of PBO Precursors Containing Dimethylphenoxy and/or MPEG Pendant Groups)

  • 윤두수;최재곤;조병욱
    • 폴리머
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    • 제29권5호
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    • pp.493-500
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    • 2005
  • Poly(ethylene glycol)methyl ether(MPEG)와 dimethylphenoxy 팬던트 그룹을 갖는 polybenzoxazoles(PBOs)의 중합 전구체인 poly(o-hydroxyamides)(PHAs)를 저온 용액 중축합에 의해서 합성하였다. 합성된 중합 전구체들의 고유점도는 $0.51\~2.31$의 값을 나타내었다. 중합전구체는 FT-IR, $1H-NMR$, DSC, 그리고 TGA를 이용하여 특성을 조사하였다. MPEG단위를 갖는 PHAs는 MPEG의 분자량이 증가할수록 용매특성이 증가하는데, 특히 분자량이 1100인 MPEG를 갖는 PHA의 경우 aprotic 용매뿐만 아니라 에탄올, 메탄올, H,0에도 용해되었으나, 열적 고리화 반응에 의해 PBOs로 전환되면 어떠한 용매에도 용해되지 않았다. 그리고 MPEG만을 갖는 중합 전구체의 경우, MPEG의 분자량이 증가할수록 고리화 반응온도는 감소함을 확인할 수 있었다.