• Bulletin of the Korean Chemical Society
• /
• 제15권5호
• /
• pp.341-346
• /
• 1994

The frameworks of $(Cu(NH_3)_3OH^+)_x(NH_4^+)_{12-x}-A{\cdot} zH_2O$ which were prepared by the ion-exchange of zeolite A with ammoniac cupric nitrate solution are more stable than those of $Cu_xNa_{12-2x} -A$ obtained by the ion exchange with aqueous cupric nitrate solution are more stable than those of $Cu_xNa_{12-2x} -A$ obtained by the ion exchange with aqueous cupric nitrate solution. An energetic calculation was made on the relatively stable $(CuOH^+)_2(NH_4^+)_{10}-A{\cdot} 2H_2O$ prepared by the partial evacuation of $(Cu(NH_3)_3OH^+)_2(NH_4^+)_{10}-A{\cdot} zH_2O$. The mean stabilization energies of water, OH-, and $NH_4^+$ ions are -30.23 kcal/mol, -60.24 kcal/mol, and -16.65 kcal/mol, respectively. The results of calculation were discussed in terms of framework stability. The $(Cu(NH_3)_3OH^+)_2(NH_4^+)_{10}-A{\cdot} zH_2O$ zeolite shows two step deammoniation reactions. The first deammoniation around 210 $^{\circ}$C (third DSC peak) was attributed to the decomposition of $[Cu(NH_3)_3OH^+]$ ion and the second one around 380 $^{\circ}$C (fourth DSC peak) was ascribed to the decomposition of $NH_4^+$ ion. The activation energies of the first and second deammoniation reactions were 99.75 kJ/mol and 176.57 kJ/mol, respectively.

• 공업화학
• /
• 제8권4호
• /
• pp.602-609
• /
• 1997

공기를 산화제로 하여 황산제일철 용액에 침전제로서 KOH, NaOH, $Na_2CO_3$및 $K_2CO_3$를 사용하여 산화침전반응을 행하여 생성되는 $\alpha$-ferric oxyhydroxide입자의 생성 및 성장과정을 자유 pH 변화시험을 통해서 관찰하였다. $\alpha$-ferric oxyhydroxide입자의 생성 및 성장과정은 모든 침전제에서 동일한 형태를 나타내었으며 KOH, NaOH에 의해 생성된 $\alpha$-ferric oxyhydroxide 결정입자의 길이는 $Na_2CO_3$및 $K_2CO_3$에 의해 생성된 것보다 약 1.5배 정도 짧았다. KOH를 침전제로 황산제일철을 공기 산화한 결과 초기침전제의 몰비 $(R_o=[Fe^{2+}]_o/[OH^-]_o)$ 값이 작아질수록 결정 입자의 길이가 종축 방향으로 길게 성장하였으며 생성물은 $1{\mu}m$ 이하의 균일한 침상형의 $\alpha$-ferric oxyhydroxide였다. 또한 황산제일철에 KOH를 침전제로 공기를 산화제로 하여 고정 pH 실험법에 의하여, 공기 유속, 초기 침전제의 몰비 $(R_o=[Fe^{2+}]_o/[OH^-]_o)$ 및 반응 온도의 변화에 따른 $\alpha$-ferric oxyhydroxide의 핵성장 반응속도에 관하여 알아보았다. 공기 유속, 반응 온도 및 $R_o$값이 증가할수록 $\alpha$-ferric oxyhydroxide 입자의 핵성장 반응속도는 점차적으로 증가하였으며, 핵성장의 활성화 에너지는 16.16 KJ/mol 이며, 공기 유속, $R_o$값 및 반응온도의 영향에 대한 핵성장 반응속도 관계식은 다음과 같다. $-\frac{d[Fe^{2+}]}{dt}=1.46{\times}10^4[P_{o2}]^{0.66}[OH^-]^{2.19}exp(-\frac{16.16}{dt})$.

• 한국광물학회지
• /
• 제27권1호
• /
• pp.17-30
• /
• 2014

폐콘크리트 처리 시 발생하는 시멘트 미분은 $CO_2$ 포집을 위한 광물탄산화 재료로 활용할 수 있다. 이번 연구에서는 폐콘크리트를 활용한 $CO_2$ 포집을 위한 기초연구로 수화시멘트의 수성탄산화 방안과 탄산염광물 형성 특성에 대한 자료를 확보하고자 하였다. 실험을 위해 물 : 시멘트 비를 6 : 4로 하여 28일간 수중 경화하여 시멘트 풀을 제작하고, 첨가제(NaCl과 $MgCl_2$)를 활용한 용출실험과 두 종류의 수성탄산화(직접수성탄산화와 간접수성탄산화)실험을 수행하였다. 용출실험 결과, $Ca^{2+}$ 이온의 용출은 시험된 최대 농도에서 보다 0.1 M NaCl과 0.5 M $MgCl_2$에서 최대로 나타났으며, $MgCl_2$는 NaCl에 비해 10배 이상의 $Ca^{2+}$ 이온을 용출력을 보였다. 미분(< 0.15 mm)의 시멘트 풀은 직접수성탄산화에 의해 1시간 이내에 탄산화에 의해 포트랜다이트가 거의 모두 탄산염 광물로 변화하고, CSH(calcium silicate hydrate)의 분해에 의한 탄산화도 진행되는 것으로 나타났다. 그러나 직접수성탄산화에는 NaCl과 $MgCl_2$와 같은 첨가제가 크게 효율적이지 못하였다. NaCl과 $MgCl_2$를 첨가제로 사용한 용출액에 대한 간접수성탄산화로 100% 순수한 방해석을 생성되었다. $MgCl_2$에 의한 용출액의 경우 탄산화를 위해 알칼리용액 의한 pH의 조절이 필요하였으며, $Mg^{2+}$ 이온의 영향으로 탄산화가 느리게 진행되었다. 수성탄산화 방법과 첨가제의 종류가 생성되는 탄산칼슘광물의 종류와 결정도 영향을 미치는 것으로 나타났다.

• Journal of Electrochemical Science and Technology
• /
• 제10권4호
• /
• pp.387-393
• /
• 2019

Activated carbons (ACs) are considered important electrode materials for supercapacitors because their large specific surface areas lead to high charging capacities. In the conventional synthesis of ACs, a substantial amount of carbon is lost during carbonization of a precursor. The development of a method to synthesize ACs in high yield would lower their manufacturing cost. Here, we demonstrate the synthesis of high-specific-surface-area NaOH-AC from carbon prepared via a hydrothermal carbonization (HTC) route, with a higher yield than that achieved through conventional pyrolysis carbonization. The amorphous carbon was derived from HTC of sugar and subsequently activated at 800℃ with various NaOH etchant/C ratios under a N₂ atmosphere. The AC prepared at 4:1 NaOH/C exhibited the highest surface area (as high as 2,918 ㎡ g^-1) and the highest specific capacitance (157 F g^-1 in 1 M aqueous Na₂SO₄ electrolyte solution) among the NaOH-AC samples prepared in this work. On the basis of their high specific capacitance, the NaOH-ACs prepared from HTC sugar are suitable for use as electrode materials for supercapacitors.

• Fibers and Polymers
• /
• 제3권1호
• /
• pp.1-7
• /
• 2002

Cellulose carbonate was prepared by the reaction of cellulose pulp and $CO_2$ with treatment reagents, such as aqueous $Zncl_2$ (20-40 wt%) solution, acetone or ethyl acetate, at -5-$0^{\circ}C$ and 30-40 bar ($CO_2$) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at -5-$0^{\circ}C$. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at $20^{\circ}C$ according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (-$5^{\circ}C$ and atmospheric pressure).

• 한국세라믹학회지
• /
• 제43권9호
• /
• pp.575-581
• /
• 2006

To precipitate the complex gel of flux and aluminum hydroxides gel, aqueous solution of the mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in aqueous solution of the mixture of $Al_2(SO_4)_3{\cdot}14{\sim}18H_2O,\;Na_2SO_4$, and then the complex gel was aged in $0{\sim}30h\;at\;90^{\circ}C$. As aging time passed, the aluminum hydroxides was grown into the acicular AlO(OH) gel. Also, aging time had an effect on physical properties of the AlO(OH) gel and on crystal growth of the flaky ${\alpha}-Al_2O_3$ prepared by molten-salt precipitation. In this study, the complex gel was crystallized in temperature range of $400{\sim}1,200^{\circ}C$ after drying at $110^{\circ}C$, and then it was investigated to effect of aging time on precipitation temperature, size, thickness, morphology and particle size distribution of the flaky ${\alpha}-Al_2O_3$ crystal. As aging time passed, the flaky a${\alpha}-Al_2O_3$ crystal showed a tendency toward an increase in size and thickness as result from an increase in BET surface area and pore volume of the acicular AlO(OH) gel.

• 한국의류산업학회지
• /
• 제3권3호
• /
• pp.277-282
• /
• 2001

The effect of chitosan on antibacterial activities of cotton, wool and polyester fibers was investigated by shake flask method. Chitosan was treated in 0.1%, 1% and 2% $NaBO_3$ solution to reduce the molecular weight in 4 steps, wadding of cotton, wool and polyester were treated in 0.1%, 0.3% and 0.5% of chitosan solution which were dissolved in 2% acetic acid aqueous solution. The antibacterial activities of the fiber wadding treated and untreated by chitosan against Escherichia coli, Proteus vulgaris and Stephylococcus aureus were measured by shake flask method. On the untreated waddings, cotton showed better antibacterial activities than wool, but on the treated ones, wool showed better than cotton. The antibacterial activity of polyester was better than that of cotton or wool which preserved before and after the chitosan treatment against the three kinds of bacteria. When the chitosan treated cotton waddings was retreated in NaOH aqueous solution, their bacterial activities decreased. After laundering, the antibacterial activities of the treated cotton and wool waddings kept good, but that of the treated polyester reduced by almost half.

• 대한기계학회논문집
• /
• 제13권3호
• /
• pp.411-418
• /
• 1989

본 연구에서는 물 및 물을 주성분으로 하는 NaCl, $Na_{2}$CO$_{3}$, NaOH 등의 비휘발성 수용액을 담금제로 하고 KS M 2172의 열처리유 냉각성능 실험 방법에서 채택하고 있는 은시편(순도 99.9%)을 이용한 표준냉각곡선으로부터 냉각 속도 열전달계수 및 담금강열도 등 담금제의 냉각성능 파라미터를 구하였으며, 각종 담금제의 온도 및 수용액의 농도 변화에 따른 냉각성능을 평가하였다. 그리고 실험에서 채택한 시편 및 담금제를 모델로 하여 축대칭 비정상 열전도방정식을 유한 요소법에 의하여 해석하고 냉각시간에 따른 시편의 온도분포를 계산하여 실험결과와 비교하였다.

• 한국재료학회지
• /
• 제18권8호
• /
• pp.438-443
• /
• 2008

SnO nanosheets were prepared at room temperature through a reaction between an aqueous solution of $SnCl_2$, $N_2F_4$, and NaOH and were converted into $SnO_2$ nanosheets without a morphological change. The SnO nanosheets were formed through a dissolution-recrystallization mechanism. Uniform and well-dispersed SnO nanosheets with the round-shape morphology were attained when the solution was treated by ultrasonic sound immediately after the addition of NaOH. The $SnO_2$ nanosheets prepared by means of solution reduction under the ultrasonic treatment, and subsequent oxidation at $600^{\circ}C$ showed a high level of gas sensitivity to $C_2H_5OH$ and $CH_3COCH_3$.

• 한국결정성장학회지
• /
• 제26권5호
• /
• pp.175-180
• /
• 2016

본 연구에서는 수용액 상에서 침전법과 수열합성법을 이용하여 나노크기의 ZnO 분말을 합성하였다. 두 합성방법 모두 출발원료로는 Zn-nitrate hexahydrate($Zn(NO_3)_2{\cdot}6H_2O$)와 NaOH 수용액을 사용하였고, 이들의 혼합용액에 합성조건 즉 반응 pH, 온도 및 Zn precursor의 몰 농도를 달리하여 ZnO 분말을 얻을 수 있었다. 두 합성법 모두에서 단일 상 ZnO는 낮은 Zn 농도 높은 pH 및 높은 온도 조건에서 합성되기 쉬웠다. 합성된 분말의 형상은 flake(plate), multipod 및 rod 형태로 합성 조건에 따라 그 형태의 조절이 가능하였다. 침전법에 비해 수열합성법은 $100^{\circ}C$ 이하인 비교적 낮은 합성온도에서도, 본 연구의 Zn 농도 전 구간(0.1~1 M)과 넓은 pH 범위에서 결정성이 우수한 ZnO 단일 상을 합성할 수 있는 장점을 보여주었다.