• Title/Summary/Keyword: dimethyl oxalate

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Chemical Factors on the Homogeneous Precipitation of Barium Titanyl Oxalate by Dimethyl Oxalate and Their Effects on the Charateristics of Barium Titanate (Dimethyl oxalate에 의한 barium titanyl oxalate의 균일 침전에 미치는 화학적 인자와 이들이 티탄산 바륨의 특성에 미치는 영향)

  • Ryu, Kyoungyoul;Huh, Wooyoung;Lee, Chul
    • Analytical Science and Technology
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    • v.12 no.3
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    • pp.230-234
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    • 1999
  • Barium titanyl oxalates (BTO) has been homogeneously prepared by thermal decomposition of dimethyl oxalate (DMO) in hydrochloric solution containing $Ba^{2+}$ and $Ti^{4+}$. Particles of BTO settled on the bottom of the beaker were collected at the aging time of 120 min using hydroxy propyl cellulose (HPC) as a dispersant. The reaction temperature, the concentration ratio of $[DMO]_0/([Ba^{2+}]_0+[Ti^{4+}]_0)$ and the existence of HPC were found to influence on morphologies of BTO, chemical yields and characteristics of barium titanates formed from their precursors.

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Morphology of Barium Titanyl Oxalate Produced by Homogeneous Precipitation from Acidic Solution of Dimethyl Oxalate (Dimethyl Oxalate에 의한 균일 침전법으로 생성된 Barium Titanyl Oxalate의 형태학적 연구)

  • Min, Chonkyu;Lee, Chul
    • Analytical Science and Technology
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    • v.10 no.3
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    • pp.203-208
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    • 1997
  • Barium titanyl oxalate(BTO) was precipatated by utilizing the thermal decomposition of dimethyl oxalate in acidic aqueous solution having $BaCl_2$ and $TiCl_4$. Particle morphology of BTO was influeneced by the various experimental factors. i.e.. the faster rate to nucleation with higher temperature and the higher ratio of [DMO]/[$Ba^{2+}+Ti^{4+}$] was found to correspond to the faster rate of transformation of particle size distribution from unimodal to broad unimodal through bimodal. The BT powder obtained by calcination at $900^{\circ}C$ in air consists of larger particles than BT generated by general coprecipitation method and shows tetragonal symmetry. The stirring during reaction was also found to have much effect upon characteristics of BTO and BT.

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Homogeneous Preparation of Barium Titanate by Dimethyl Oxalate in Ethanol Solution (에탄올 용액에서 Dimethyl Oxalate에 의한 티탄산바륨의 균일한 제조)

  • Ryu, Kyoung-Youl;Lim, Myoung-Hee;Huh, Woo-Young;Lee, Chul
    • Analytical Science and Technology
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    • v.12 no.5
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    • pp.382-386
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    • 1999
  • Spherical particles of barium titanyl oxalate(BTO) were homogeneously precipitated by thermal decomposition of dimethyl oxalate in hydrochloric mixture solutions of water and ethanol. The experimental parameters such as composition of the mixture solvents. the eoncentration of hydrochloric acid and reaction temperature had the paramount effect on the size of panicles collected from the bottom of the reaction vessel at the aging time of 120 min and the composition of BTO. Stoichiometric BTO powders were obtained under certain conditions as relatively low alcohol content in the mixtures, high chloride concentration and high temperature, Monosized, submicrometer, but titanium excess particles were obtained under certain reverse conditions.

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Effect of Supporting Anions on Particle Characteristics of Barium Titanyl Oxalate Formed by Homogeneous Precipitation (지지 음이온이 균일 침전법에 의해 생성된 Barium Titanyl Oxalate의 입자특성에 미치는 영향)

  • Ryu, Kyoungyoul;Huh, Wooyoung;Lee, Chul
    • Analytical Science and Technology
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    • v.11 no.4
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    • pp.260-265
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    • 1998
  • Spherical, ${\mu}m$-sized particles of barium titanyl oxalate were prepared by thermal decomposition of dimethyl oxalate in acidic barium and titanium solutions. Precipitation was carried out in the presence of several supporting anions. Spherical particles having a specific type of particle size distribution. i.e., unimodal or bimodal distribution, with mean size in the range of $0.2{\sim}3{\mu}m$, were formed depending on the supporting anions, oxalate ion generation rate and aging time. Particles of barium titanyl oxalate settled on the bottom of the beaker at the aging time of 120 min grew to the critical monosize of about $1.5{\sim}3{\mu}m$. XRD spectra and chemical analyses of barium titanate showed that barium titanyl oxalate with high qualities could be synthesized by choosing chloride ion as a supporting anion and increasing the reaction temperatures.

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Electrical properties of La-doped BaTiO3 synthesized by homogeneous precipitation (균일침전법으로 제조된 란탄이 혼입된 $BaTiO_3$의 전기적 특성)

  • Huh, Woo-Young;Ryu, Kyoung-Youl;Kim, Seung-Won;Lee, Chul
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.5
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    • pp.498-503
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    • 1999
  • La-doped $BaTiO_3$ ceramics were prepared from BaTiO(C_2O_4)_2\;{\cdot}\;XH_2O(BTO)$, which was synthesized by homogeneous precipitation using dimethyl oxalate. The electrical properties of La-doped $BaTiO_3$ were investigated with variation of La-contents and particle size. It was found that a large PTCR (positive temperature coefficient of resistivity) effect was appeared in the conditions at the 0.6 mol% of La-content and at small particle size of BTO as 1.0$\mu\textrm{m}$. The plot of temperature vs. 1/$\varepsilon_m$(T) above Curie temperature $(T_c)$ was agreed with Curie-Weiss law. The potential barrier calculated from measured resistance and capacitance of specimen, also gave higher value at small particle size of BTO as 1.0 $\mu\textrm{m}$ and at La-content of 0.6 mol%.

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