• 대한화학회지
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• 제21권1호
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• pp.53-59
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• 1977

알루민산나트륨과 알루민산칼륨 용액에 $CO_2$가스 吹入法에 의해 $NaAlCO_3(OH)_2\;(Dawsonite)와\;KAlCO_3(OH)_2$를 合成하였다. 이 反應은 80 ∼ $90^{\circ}C$에서 $Na_2O/Al_2O_3,\;K_2O/Al_2O_3$의 몰比가 各 各 6∼8, 8∼10인 알루민산알칼리 용액중에 $CO_2$가스를 吹?하여 達成되었다. 알루민산알칼리 용액중에 $HCO_3^-$이 多量 存在하며 알루미나가 平衡固相으로서 Boehmite로 存在할 때 高純度의 Dawsonate와 $KAlCO_3(OH)_2$가 生成된다는 것을 알았다. 이런 條件下에서 合成된 Dawsonite와 $KAlCO_3(OH)_2$의 示性式은 赤外線吸收스펙트럼 分析結果 各各 $NaAlO(OH)HCO_3와\;KAlO(OH)HCO_3$로 나타내는 것이 妥當하다고 생각된다. 또 電子顯微鏡觀察로부터 Dawsonite는 纖維狀結晶, $KAlCO_3(OH)_2$는 針狀結晶으로 되어 있다는 것을 알았다.

• 자원리싸이클링
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• 제29권6호
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• pp.73-78
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• 2020

선탄 폐석의 유리 소재 원료로의 활용을 위해 선탄 폐석의 고온 상 전위 거동 및 Na2CO3의 첨가에 따른 유리질(비정질)화 실험을 실시하였다. 실험 결과 700~1,100 ℃에서 소성된 선탄폐석에는 mullite가 생성되고, 1,450 ℃에서는 mullite와 cristobalite만이 존재하였다. 선탄 폐석의 유리질화는 Na2CO3 첨가됨에 따라 진행되었으며, Na2CO3 10 wt.% 첨가 후 1,450 ℃ 온도에서 소성된 선탄 폐석의 유리질화는 97.9 wt.%로 나타났다. 그러나 Na2CO3가 20 wt.% 첨가된 선탄 폐석의 시료의 경우, 1,100 ℃에서의 2차 재소성 과정에서 nepheline(Na2O·Al2O3·2SiO2)이 생성되었으며, 이를 통해 선탄폐석의 유리질화를 위한 최적의 Na2CO3 첨가량은 10 wt.%로 나타났다.

• 한국자기학회지
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• 제6권4호
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• pp.204-210
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• 1996

제철소의 부산물인 mill scale과 $Fe_{2}O_{3}$, 그리고 이들의 혼합물을 사용하여 M형 ferrite를 제조하였다. $Fe_{2}O_{3}$와 $BaCO_{3}$의 몰비를 5.2~6.0으로 변화시킨 혼합물의 하소 및 소결은 각각 $1150^{\circ}C,\;1250^{\circ}C$에서 2시간 행하였으며, 하소시에 mill scale 중의 불순물 성분인 $SiO_{2},\;Al_{2}O_{3},\;MgO,\;CaO\;및\;Na_{2}O$를 적당량 첨가한 시편으로 자기적 특성과 형상을 조사하였다. $Na_{2}O$를 첨가한 시편은 미반응의 $Fe_{2}O_{3}$와 중간 화합물인 $BaFe_{2}O_{4}$의 영향으로 자기적 특성이 감소하였으나, $BaO.5.6Fe_{2}O_{3}$ 조성에 $SiO_{2}$와 $Al_{2}O_{3}$의 첨가는 특성의 증진을 보였으며, 특히 $Al_{2}O_{3}$는 $M_{s}$ 값은 감소시켰으나 $_{B}H_{c}$ 값을 증가시켰다. BM($BaCo_{3}$와 mill scale의 혼합물)과 BFM($BaCO_{3},\;Fe_{2}O_{3}$, mill scale의 혼합물) 소결 시편의 ${(BH)}_{max}$는 각각 0.86, 1.04 MGOe였으며, $440^{\circ}C$ 부근에서 자기 특성의 변화를 보였다.

• 한국분말재료학회지
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• 제21권5호
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• pp.377-381
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• 2014

This work describes the coloration, chemical stability of $SiO_2$ and $SnO_2$-coated blue $CoAl_2O_4$ pigment. The $CoAl_2O_4$, raw materials, were synthesized by a co-precipitation method and coated with silica ($SiO_2$) and tin oxide ($SnO_2$) using sol-gel method, respectively. To study phase and coloration of $CoAl_2O_4$, we prepared nano sized $CoAl_2O_4$ pigments which were coated $SiO_2$ and $SnO_2$ using tetraethylorthosilicate, $Na_2SiO_3$ and $Na_2SiO_3$ as a coating material. To determine the stability of the coated samples and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Blue $CoAl_2O_4$ solutions were tuned yellow color under all acidic/basic conditions. On the other hand, the chemical stability of $SiO_2$ and $SnO_2$-coated $CoAl_2O_4$ solution were improved when all samples pH values, respectively. Phase stability under acidic/basic condition of the core-shell type $CoAl_2O_4$ powders were characterized by transmission electron microscope, X-ray diffraction, CIE $L^*a^*b^*$ color parameter measurements.

• 자원리싸이클링
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• 제29권6호
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• pp.65-72
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• 2020

블랙 드로스는 알루미늄을 재활용하는 과정 중에 플럭스 사용에 의해 발생되는 짙은 회색의 드로스로서, NaCl, KCl, Al2O3, MgO 등이 포함되어 있다. 블랙 드로스는 용해(dissolution) 공정을 통하여 용해성 물질(NaCl, KCl)과 불용해성 물질(Al2O4, MgO)로 분리가 가능하다. 이중 용해성 물질의 경우 Salt flux로 재활용이 가능하며, Al2O3, MgO의 경우 합성 공정을 통하여 다양한 세라믹 소재로 업사이클링이 가능하다. 본 연구에서는 블랙 드로스로부터 회수한 Al2O3, MgO를 이용하여 Mayenite를 합성 하였으며, 배합 비율 및 반응 온도 조건에 따른 합성을 실시하였다. 블랙 드로스(spinel)와 CaCO3를 이용하여 Mayenite를 합성할 시 700 ℃에서 Mg0.4Al2.4O4, CaO로 변하며, 800 ℃ 이후부터 Ca12Al14O33(Mayenite)으로 변하는 것을 확인하였다. 배합 조건에는 CaCO3 함량이 증가함에 따라 Mayenite XRD 피크가 증가하며, Mg0.4Al2.4O4 XRD 피크는 감소하는 것을 확인하였다. 합성된 분말의 BET 분석 결과 Mayenite가 생성되는 과정에서 미세한 입자가 성장되고 응집됨에 따라 비표면적은 감소하는 거동을 보였다.

• 대한화학회지
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• 제13권2호
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• pp.149-156
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• 1969

$NaAl(OH)_2CO_3$was synthesized using colloidal earth (Allophane) as the starting material and some of its were studied in detail. It was found that Dawsonite was formed in the pH range (pH 12.5~12.0) that the concentration of $HCO_3^-$ was just begun to increase and the presence of $HCO_3^-$ in the product was clarified from the infrared absorption spectrum. The chemical formular of Dawsonite was therefore presumed as $NaAlO (OH) HCO_3$. From toahhe results of X-ray powder diffraction, both peaks at 5.7 $\AA$ and 2.8 $\AA$ were observed, and fibrous crystalline structure was observed from electron micrograph and also found from the microscopic electron diffraction at 5.7 $\AA.$ Therefore the fibrous axis was considered as =Al=O2=Al=O2=Al=(*image) direction. True specific gravity of Dawsonite was 2.44 and its porosity was 91.4%. It was practically insoluble in water, but decomposed in the boiling water to form Pseudo Boehmite. Stable pH range of Dawsonite was about 4.5~11.5. From the results of D.T.A. and T.G.A., it was observed that $CO_2$was liberated at $350^{\circ}C$, and $H_2O$ at $650^{\circ}C$, and converted into strongly hygroscopic $NaAlO_2$, which was easily decomposed in water into $\beta-Al(OH)_3(Bayerite)$ and NaOH.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.343-352
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• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.243-249
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• 2014

Three single crystals of fully dehydrated $Co^{2+}$-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of $Na_{75}$-Y ($|Na_{75}|[Si_{117}Al_{75}O_{384}]$-FAU) with aqueous streams 0.05 M in $Co(NO_3)_2$, pH = 5.1, at 294 K for 6 h, 12 h, and 18 h, respectively, followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3m at 100(1) K. They were refined to the final error indices $R_1/wR_2$ = 0.0437/0.1165, 0.0450/0.1228, and 0.0469/0.1278, respectively. Their unit-cell formulas are $|Co_{29.1}Na_{11.8}H_{5.0}|[Si_{117}Al_{75}O_{384}]$-FAU, $|Co_{29.8}Na_{11.0}H_{4.4}|[Si_{117}Al_{75}O_{384}]$-FAU, and $|Co_{30.3}Na_{9.5}H_{4.9}|[Si_{117}Al_{75}O_{384}]$-FAU, respectively. In all three crystals, $Co^{2+}$ ions occupy sites I, I' and II; $Na^+$ ions are also at site II. The tendency of $Co^{2+}$ exchange slightly increases with increasing contact time as $Na^+$ content and the unit cell constant of the zeolite framework decrease.

• 대한화학회지
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• 제13권2호
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• pp.157-164
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• 1969

Aoolphane was treated with 30% Hydrochloric acid at $18^{\circ}C$ for two hows with stirring in order to obtain the insoluble form of SiO2 gel and to extract quantitatively both $Al_2O_3$as and $Fe_2O_3AlCl_3{\cdot}6H_2O Fe$ and $Cl_3{\cdot}6H_2O$ forms, respectively, at the same time. $SiO_2$ gel was filtered and to the filterate Ammonia was added to precipitate $Al(OH)_3[Fe(OH)_3 Contaminated ]$ The precipitate was separated by filteration and the filterate was recovered as the form of $NH_4Cl$. The precipitate was treated with 200g (NaOH)/l Concentration of NaOH a little excessively to the equivalent at $65~70^{\circ}C$ as $Fe(OH)_3$ formed was insoluble, it was filtered of and to the filterate containing $NaAl(OH)_4(OH_2)_2$Carbon dioxide gas was bubbled at $50^{\circ}C~90^{\circ}C$ to obtain the precipitate with excellent filterability and crystallinity. The product was certified to be Dawsonite $(NaAl(OH)_2CO_3)$ by X-Ray diffraction analysis at below $40^{\circ}C$, when $CO_2$ gas was bubbled into the relatively lower concentration of $NaAl(OH)_4(OH_2)_2$ solution, the precipitate of very fine particles was formed, which was hard to filter and with the Composition of $\alpha-Al_2O_3-H_2O$ (Boehmite).

• 공업화학
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• 제4권1호
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• pp.144-152
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• 1993

${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$, $TiO_2$등에 고정화된 폴리에틸렌글리콜을 $Fe(CO)_5$에 의한 니트로벤젠의 상온 환원반응에 상이동 촉매로 사용하였다. 고정화된 PEG의 몰수는 담체의 비표면적에 따라 증가하였고 PEG/${\gamma}-Al_2O_3$가 가장 좋은 활성을 나타내었다. PEG의 사슬길이가 길고 NaOH 농도가 높을수록 반응속도가 증가하였다. 적외선분광기를 이용하여 반응기구에 대한 고찰도 함께 실시하였으며 폴리에틸렌글리콜 상이동 촉매는 본 반응의 활성물질로 알려진 $HFe(CO)_4{^{-}}$이온의 생성과 이의 유기상으로의 이동을 촉진시키는 것으로 판단되었다.