• Title, Summary, Keyword: $CaCO_3$ preparation

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Preparation and Sound Insulation Properties of Thermoplastic Elastomer Composites with CaCO3 Filler (탄산칼슘 분말을 충진시킨 열가소성 탄성체 복합재의 제조 및 차음 특성)

  • Choi, Jung-Woo;Hwang, Yeon
    • Korean Journal of Materials Research
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    • v.20 no.9
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    • pp.467-471
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    • 2010
  • Composites of ceramic powders and an elastomer-based matrix were prepared by mixing $CaCO_3$ powders with polyethylene and polypropylene elastomers, and their mechanical and sound insulation properties were measured. $CaCO_3$ powders with 0.7 ${\mu}m$ and 35 ${\mu}m$ particle size were added to elastomers up to 80 wt%. Scanning electron microscopy photographs showed uniform distribution of the $CaCO_3$ powders in the matrix. While density and surface hardness increased, melt index, tensile strength and elongation of the composites decreased as the amount of added $CaCO_3$ powders increased. As more $CaCO_3$ powders were added sound transmission loss of the composites increased owing to the increase of density. Addition of 0.7 ${\mu}m$ sized $CaCO_3$ powders resulted in a slightly higher transmission loss than the addition of 35 ${\mu}m$ sized powders because of the increased interface area between the elastomer matrix and the $CaCO_3$ powders. Composites with a polyethylene matrix showed higher transmission loss than those with a polypropylene matrix because the tensile strength and hardness of the polyethylene-based composites were low and their elongation was high.

Preparation and Characterization of $CaCO_3$ Encapsulation by PMMA Core-Shell latex (PMMA와 캡슐화된 $CaCO_3$ Core-Shell 라텍스 제조와 물성연구)

  • Lim, Jong-Min;Seul, Soo-Duk
    • Elastomers and Composites
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    • v.38 no.4
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    • pp.303-315
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    • 2003
  • Inorganic/organic composite particles were also synthesized by changing an initiator an it's concentration, concentration of an adsorbed surfactant, reaction temperature, and agitation speed in the presence of $CaCO_3$ adsorbed SDBS. The polymerization conditions were optimized according to the conversion of the core-shell composite particles. In the inorganic/organic core-shell composite particle polymerization, $CaCO_3$ absorbed surfactant SDBS of 0.5 wt % was prepared first and then core $CaCO_3$ was encapsulated by sequential emulsion polymerization using MMA, concentration of APS $3.16{\times}10^{-3}mol/L$ to minimize the formation of new PMMA particle during MMA shell polymerization. The structure characterization of the inorganic/organic core-shell particles was verified by measuring the decomposition degree of $CaCO_3$ using HCl solution. It was found that $CaCO_3$ was encapsulated by shell PMMA due to having excellent dispersion in the epoxy resin, smooth surface distinctly from spindle shape, and broad particle distribution after the capsulation.

Preparation of Fine-particle $(PbCa)ZrO_3$ for Resonator (동축형 공진기용 $(PbCa)ZrO_3$ 분말의 합성)

  • 이병하;이경희;윤성화
    • Journal of the Korean Ceramic Society
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    • v.30 no.8
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    • pp.635-642
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    • 1993
  • To obtain a higher dielectric constant material, we investigated Ca substitution for Pb in PbZrO3. In this study, the four mixtures of (Pb0.68Ca0.32)ZrO3, (Pb0.65Ca0.37)ZrO3, (Pb0.63Ca0.37)ZrO3, and (Pb0.60Ca0.40)ZrO3 were prepared by coprecipitation reaction of Pb(NO3)2, ZrOCl2, and CaCl2 with (NH4)2CO3 and NH4OH in aqueous solution. The (Pb1-xCax)ZrO3 with different x mole fractions (x=0.35, 0.37) showed not only high dielectric constant, but also high Q values and low temperature coefficient of the capacitance.

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High Cell Density Cultivation of Bifidobacterium longum Using a Calcium Carbonate-Alginate Beads System

  • Yu, Won-Kyu;Kim, Ji-Youn;Lee, Ki-Yong;Heo, Tae-Ryeon
    • Journal of Microbiology and Biotechnology
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    • v.12 no.3
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    • pp.444-448
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    • 2002
  • A $CaCO_3$-alginate beads system was developed for high cell density cultivation of Bifidobacterium longum and the cost-effective media were also screened. In batch process with $CaCO_3$, beads, two strains of B. longum showed both the highest viable cells and optical density in TPY medium, resulting in maximum optical density and viable cell counts of 12.40, $2.22{\times}10^10$ cfu/ml for B. longum ATCC 15707 and 13.71, $3.93{\times}10^10$ cfu/ml for B. longum HLC 3742. Released size distribution, according to $CaCO_3$-alginate bead size preparation, was smaller than others. These results were also examined by observing their morphology. The skim milk-based medium was most adequate to cultivate B. longum as the cheapest medium, and $10\%$ skim milk supplemented with $2\%$ glucose and $1\%$ yeast extract was a suitable medium, supporting the growth to $5.57{\times}10^10$ cfu/ml for ATCC 15707 and $6.82{\times}10^9$ cfu/ml for HLC 3742. During the long-term storage at $4^{\circ}C\;and\;-20{\circ}C$, B. longum cultivated with $CaCO_3$ beads had the highest stability. Consequently, $CaCO_3$-alginate beads buffer was found to be useful not only to cultivate B. longum but also to preserve cultures.

Properties of Polypropylene/CaCO3 Composites from the Shape of Calcium Carbonate (Polypropylene/CaCO3 복합재료에 있어서 입자 형태에 따른 물성)

  • Lyu, S.G.;Bae, K.S.;Sur, G.S.
    • Applied Chemistry for Engineering
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    • v.8 no.5
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    • pp.771-776
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    • 1997
  • The various shape of calcium carbonate were prepared. For the preparation of the PP/$CaCO_3$ composite, these synthetic calcium carbonate(cubic, spheric and neddle type) and PP were mixed on a two roll mill and the mixture were pressed into plate. The effect of particle shape in the prepared composite on the crystallization temperature, heat of fusion, size of spherulite and mechanical properities were investigated. It was found that the former four were strongly influenced by that. When, especially, vaterite was mixed with PP, the size of spherulite was smaller and the degree of crystallinity was higher than others. Therefore, the tensile strength and Young's modulus were higher.

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Sorption-enhanced reforming of tar: Influence of the preparation method of CO2 absorbent

  • Xie, Huaqing;Zhang, Weidong;Zhao, Xiangnan;Chen, Hao;Yu, Qingbo;Qin, Qin
    • Korean Journal of Chemical Engineering
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    • v.35 no.11
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    • pp.2191-2197
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    • 2018
  • To remove tar and produce environment-friendly $H_2$, one of the promising routes is the sorption-enhanced steam reforming (SESR) process, in which the $CO_2$ sorbent is a key element. We prepared the $CO_2$ sorbents with $Ca_{12}Al_{14}O_{33}$ as carrier with various methods. Their characterizations were examined, and the sample prepared by solgel (SG) method showed the strongest CaO and $Ca_{12}Al_{14}O_{33}$ phases and the most excellent pore structure among all the samples. Then, a thermogravimetric experiment was conducted, and the results showed that the sample prepared by sol-gel (SG) method had the best $CO_2$ adsorption capacity and excellent long-term cyclic stability. Finally, the sorbent was used into the steam reforming experiments of tar. Under the action of the sorbent, the reforming reaction was enhanced in-situ, with the $H_2$ yield and concentration improved obviously, and especially, $H_2$ concentration can reach over 98.85%.

Studies on the Preparation of Aragonite (Ⅰ). Formation of Aragonite of Pillar Shape (Aragonite의 제조에 관한 연구 (Ⅰ). 주상형 아라고나이트의 생성)

  • Park, Seoung-Sik;Ha, Ho;Lee, Hee-Cheol
    • Journal of the Korean Chemical Society
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    • v.39 no.7
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    • pp.578-584
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    • 1995
  • An aqueous solution of $Ca(OH)_2$ containing a small amount of dissolved $Sr(OH)_2$ was carbonated with $CO_2$ gas, and the effects of the reaction temperature and $Sr(OH)_2$ on the carbonation were investigated. The higher the reaction temperature and the larger the ratio of $Sr(OH)_2(aq)$ to $Ca(OH)_2(aq)$, which amounts to the larger the ratio of $OH^-$ to $CO_2(aq)$, the better pillar aragonite was formed. $Sr(OH)_2$ played an important role in the formation of pillar aragonite, because it is easily formed itself into rhombic $SrCO_3$ during the initial period of carbonation process and acting as a seed for the pillar aragonite of similar morphology. In addition, due to its substantially higher solubility compared with $Ca(OH)_2$, $OH^-$ concentration in the carbonation mixture and subsequently $CO_3^{2-}$ necessary for the crystal growth are increased.

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Preparation and Photoluminescent Properties of NaCaPO4 Activated by Divalent Europium (2가 유로피움으로 활성화된 NaCaPO4의 합성과 광 특성)

  • Kim, Dong-Jin;Park, In-Yong;Lee, Jong-Won;Kim, Kyu-Jin;Kim, Byoung-Gyu
    • Korean Journal of Materials Research
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    • v.16 no.10
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    • pp.624-628
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    • 2006
  • In this study, divalent europium-activated $NaCaPO_4$ green phosphor powders were prepared by the chemical synthetic method followed by heat treatment in reduced atmosphere, and the crystal structures, morphologies and photoluminescent properties of the powders were investigated by x-ray powder diffraction, scanning electron microscope and spectrometer for the first time. The effects of Ca/P and Na/Ca mole ratios on the final products were also investigated. The influences of input amount change of europium as the activator on the light emission intensity were studied, and the resulting concentration quenching phenomenon was observed. The optimized synthesis conditions obtained in this study were Ca/P mole ratio 1.2, Na/Ca mole ratio 3.0 and 4 mole%Eu. The peak wavelength was 505 nm for all the samples. The result of excitation spectrum measurement indicated that the excitation efficiency was high for the long-wavelength UV region. It was thus concluded that the samples prepared in this study can be successfully applied for the light-emitting devices such as LED excited with long-wavelength UV light sources.

Preparation and characterization of a porous silicate material from silica fume

  • Zhang, Yinmin;Qi, Haiping;Li, Yaqiong;Zhang, Yongfeng;Sun, Junmin
    • Korean Journal of Chemical Engineering
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    • v.34 no.12
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    • pp.3185-3194
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    • 2017
  • A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), $N_2$ adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that $SiO_2$ in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the $SiO_3^{2-}$ leachate from raw silica fume. The maximum value of $SiO_3^{2-}$ extraction yield was obtained under the following conditions: reaction temperature of $120^{\circ}C$, reaction time of 120 min, NaOH concentration of 15%, and alkali to $SiO_2$ molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of $SiO_3^{2-}$ leachate and $Ca(OH)_2$ suspension liquid. The optimum preparation conditions were as follows: preparation temperature of $90^{\circ}C$, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were $220.7m^2{\cdot}g^{-1}$ and $8.55cm^3/g$, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of $Ca^{2+}$, $SiO_3^{2-}$, $CO_3^{2-}$ and $Na^+$ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The $N_2$ adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01 mg/g for 140 min at $25^{\circ}C$.