• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1778-1782
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• 2017

The interaction of $NpO^+_2$ with $Cl^-$ was studied using visible-near-infrared spectroscopy in $NaCl-Ca-Cl_2-NaClO_4$, $NaCl-NaClO_4$, and $CaCl_2-NaClO_4$ solutions with ionic strength (I) of 6M. The spectra of $NpO^+_2$ around 980 nm varied with $Cl^-$ concentration in the $NaCl-CaCl_2-NaClO_4$ and $NaCl-NaClO_4$ solutions at [$Cl^-$] ${\geq}3.5M$, but not in the $CaCl_2-NaClO_4$ solution. Assuming the 1:1 interaction between $NpO^+_2$ and $Cl^-$, the apparent equilibrium constants at I = 6M were evaluated. The presence of $Ca^{2+}$ was found to destabilize overall interaction between $NpO^+_2$ and $Cl^-$. The observations were consistent with the density functional theory calculation.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.421-426
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• 2010

The transesterification of rapeseed oil, soybean oil, and mixed fat were conducted at $65^{\circ}C$ with $Al_2O_3$-supported CaO, 0.8 wt% KOH, 1 wt% NaOH and mixed catalyst. The overall conversion(%) of rapeseed oil indicated to be 96% at the 12:1 molar ratio of methanol to oil, 8 wt% CaO and 2 wt% water. The pH ranges of biodiesel for mixed fat using four catalysts and for three fats using 8wt% CaO were 7.3-9.1, 7.3-7.5, respectively. The volumes of water needed to wash biodiesel from rapeseed oil using 0.8 wt% KOH and 8 wt% CaO were 15 mL and 3 mL.

• 한국주조공학회지
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• 제28권6호
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• pp.282-287
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• 2008

The effect of CaO mold on the formation of reaction layer was investigated. CaO mold was prepared by mixing of Colloidal silica($NALCO^{(R)}$ 1130) and an $ZrO_2$, CaO at room temperature. The dried at $20{\pm}3^{\circ}C$, 75% humidity for 12hrs. Sample was prepared from the Cp-Ti(grade-2) and melted by high frequence induction melting system in the vacuum condition. The react ion layer of Ti was confirmed by optical microscopy, microhardness(Hv) and X-ray diffraction. Thickness of reaction layer using the CaO stabilized ZrO2 was thinner than the CaO added ZrO2. And thickness of reaction layer were decreased with decreasing pH of slurry. CaO addition in the slurry could not controlled reaction between molten Ti and investment mold. On the other hand, the CaO chemical bonded ZrO2 by stabilization treatment could controlled reaction between molten Ti and investment mold.

• 한국세라믹학회지
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• 제37권5호
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• pp.459-465
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• 2000

3CaO.3Al2O3.CaSO4(C4A3)clinker was prepared by solid state reaction and then its hydration property was investigated. C4A3 clinker was fired at various temperatures in the range of 700~135$0^{\circ}C$. The hydration of it was studied by XRD, DSC, Solid-state 27Al MAS NMR and SEM. According to the results, the Ca4A3 clinker was produced by reacting calcium aluminates with CaSO4 and Al2O3 and C4A3 was formed as a main phase after calcining at 120$0^{\circ}C$. The hydration products were mainly calcium monosulfoaluminate hydrate and Al(OH)3, and they were produced after 2hrs of hydration. However the hydration rate was about 74% at 3days.

• 대한치과기공학회지
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• 제21권1호
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• pp.5-14
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• 1999

Glass ceramics for dental crown prosthesis were prepared by crystallization of CaO-MgO-SiO2-$P_2O_5-TiO_2$ glasses. Their crystallization behaviors have been investigated as a function of heattreatment temperature, holding time and chemical composition in relation to mechinical properties. Crystallization peak temperatures were determined by differential thermal analysis(DTA). Crystalline phases and mircostructures of heat-treated sample were determined by the means of powder X-ray diffraction(XRD) and scanning electron microscopy(SEM). The final crystalline phase assemblages and the microstructures of the samples were found to be dependent on glass compositions, heattreatment temperature, and holding time. 1st crystallization peak temperature(TP), affected strongly by apatite, was found to be increased or decreased. From the experiment, the following results were obtained : 1. The crystallization peak temperature($T_P$) formed by apatite increased until adding up to 9wt% $TiO_2$ to base glass composition, then decreased above that. 2. Apatite($Ca_{10}P_6O_{25}$), whitlockite(${\beta}-3CaO-P_2O_5$), $\beta$-wollastonite($CaSiO_3$), magnesium tianate($MaTiO_3$) and diopside(CaO-MgO-$2SiO_2$) crystal phase were precipitated in MgO-CaO-$SiO_2-TiO_2-P_2O_5$ glass system containing 9wt% and 11wt% of $TiO_2$ 3. Vickers hardness of samples increased with increasing heat-treatment temperature and Vickers hardness of S415T9 samples heat-treated at 1075 was approxi-mately 813Kg $mm^{-2}$ as maximum value. 4. Vickers hardness of samples increased due to precipitation of apatite, whitlockite, $\beta$-wollastonite, magnesium titanate, and diopside crystal phases within glass matrix.

• 한국자기학회지
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• 제13권3호
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• pp.121-126
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• 2003

(N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$의 기본 조성에 첨가제 Sn $O_2$, CaO 첨가량과 ferrite의 공정을 변화시켜 시편의 전자기적 특성 및 미세구조를 조사하였다. 첨가제에 따른 입자크기의 변화는 거의 없었다. (N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$을 소결시 1300 $^{\circ}C$에서 소결하는 것보다 1150 $^{\circ}C$에서 소결한 소결체의 손실이 더욱 적었다. CaO만 첨가할 때 0.2 wt%가 소결밀도를 크게하여 손실을 줄여주는 첨가제로 사용 가능함을 확인하였다 Sn $O_2$차 Ca $O_2$함께 첨가시 SnO2$_2$ 0.06 wt%, CaO 0.4 wt%가 손실을 크게 줄여 주는 것으로 조사되었다.

• 한국건설순환자원학회논문집
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• 제11권4호
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• pp.324-331
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• 2023

본 연구에서는 유리석회 함량이 다른 순환유동층 보일러 애시의 수화특성 및 탄산화 특성에 대해 조사하였다. 또한, free-CaO 함량이 높은 CFBC ash를 탄산화 양생 전처리를 하여 시멘트계 재료로의 활용 가능성을 살펴보았다. Free-CaO 함량이 높은 CFBC ash를 혼합한 경우 급결의 양상을 보였으며 낮은 초기 압축강도를 나타냈다. Free-CaO 함량이 높은 CFBC ash를 탄산화 양생하였을 때, 양생 기간에 따라 이산화탄소 포집량이 증가하였다. 또한, free-CaO 값이 함께 감소하였으며 free-CaO가 이산화탄소와 반응한 것으로 보인다. Free-CaO 함량이 높은 CFBC ash를 탄산화 양생 전처리를 한 경우 급결이 나타나지 않았으며, 초기 압축강도도 향상된 것을 확인할 수 있었다. 연구 결과 free-CaO 함량이 높은 CFBC ash의 경우 적절한 탄산화 양생을 통해 시멘트계 재료로 활용 가능성이 높은 것으로 나타났다.

• 한국세라믹학회지
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• 제44권9호
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• pp.471-476
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• 2007

The hydration mechanism of the $3CaO{\cdot}Al_2O_3-CaSO_4{\cdot}2H_2O$ system in the presence of alkali sulfates has been investigated. The early hydration rate of $3CaO{\cdot}Al_2O_3$ was accelerated by the addition of $Na_2SO_4$ and $K_2SO_4$. This is closely related to the formation of syngenite $(CaSO_4{\cdot}K_2SO_4{\cdot}H_2O)$, and the U-phase added $K_2SO_4$ and $Na_SO_4$ in the $3CaO{\cdot}Al_2O_3-CaSO_4{\cdot}2H_2O$ system, respectively. The formation of the rigid syngenite and U-phase structure led to rapid setting and decreases the sulfate content in the liquid phase of the hydrating cement to the extent that it cannot adequately retard the hydration of $3CaO{\cdot}Al_2O_3$. In case of the alkali sulfate not added to the $3CaO{\cdot}Al_2O_3-CaSO_4{\cdot}2H_2O$ system, the ettringite was transformed to monosulfoaluminate immediately after the consumption of gypsum. However, when the alkali sulfates were added to this system, the ettringite did not transform to monosulfoaluminate immediately even though the gypsum was completely consumed. There was a stagnation period to transform to the monosufoaluminate after the consumption of gypsum because the syngenite and U-phase remained as the sulfate source.

• 한국세라믹학회지
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• 제31권11호
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• pp.1337-1345
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• 1994

Glasses in the system of 45CaO-25TiO2-30P2O5 containing 1 mole% of M2O(M=Li, Na, K) were melted and crystallized. And their crystal phases were Ca3(PO4)2, CaTi4(PO4)6, and TiO2. Porous glass-ceramics with skeleton of two crystal phase CaTi4(PO4)6 and TiO2 were prepared by selective leaching of Ca3(PO4)2 with 0.1 N-HCl. Glass transition temperature(Tg) and crystallization temperature(Tc) were decreased by addition of 1 mole% alkali metal oxide. Pore size of porous glass-ceramics was increased with increasing heat treatment temperature and its dependence on heat treatment temperature was decreased with addition of Na2O and K2O. It was found that porous glass-ceramics of parent glass and containing 1mole% M2O(M=Li, Na, K) composition had maximum specific surface area, porosity and maximum of crystallzed phase by heat treatment at 80$0^{\circ}C$, 76$0^{\circ}C$, 78$0^{\circ}C$, 80$0^{\circ}C$ respectively.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 2006년도 춘계임시총회 및 제27회 학술발표대회
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• pp.150-155
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• 2006

제강공정에서 발생되는 $CaO-Al_{2}O_{3}-SiO_{2}$계 조성을 갖는 2 차 정련슬래그 (래들 슬래그)를 이용하여 하수슬러지용 고화재개발 및 하수슬러지 고화체의 물성에 관한 연구를 수행하였다. 래들슬래그는 냉각과정에서 분화되는 성질이 있어 냉각후 분말상의 슬래그가 만들어진다. 분말상 슬래그의 주 결정상은 $12CaO{\cdot}7Al_{2}O_{3}$ 및 $2CaO{\cdot}SiO_{2}$로 구성되어 있다. $12CaO{\cdot}7Al_{2}O_{3}$ 상은 속경성 시멘트의 특징이 있다. 또한 $CaSO_{4}$와 혼합사용시 ettringite 상을 형성시켜 하수슬러지의 함수율 저감효과 및 강도발현 효과가 우수한 결과를 얻었다. $Cl^{-}$ 이온의 고정화면에서는 고화재중 래들슬래그의 혼합비가 높을수록 고화체 구조내에 $Cl^{-}$ 이온이 고정화되어 용출량은 감소하였다. 고화재로서 제강부산물을 사용하기 때문에 경제성이 있으며, $Cl^{-}$ 이온 함량이 높은 하수슬러지 고화재로서의 재활용이 기대된다.