• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.13-14
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• 2014

Ultra high performance concrete (UHPC) consists of cement, silica fume (SF), sand, fibers, water and superplasticizer. Typical water/binder-ratios are 0.15-0.20 with 20-30% of silica fume. The development off properties of hardening UHPC relates with both hydration of cement and pozzolanic reaction of silicafume. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of UHPC. The degree of hydration of cement and degree of reaction of silica fume are obtained as accompanied results from the proposed hydration model. The properties of hardening UHPC, such as degree of hydration of cement, calcium hydroxide contents, and compressive strength, are predicted from the contribution of cement hydration and pozzolanic reaction. The proposed model is verified through experimental data on concrete with different water-to-binder ratios and silica fume substitution ratios.

• 한국세라믹학회지
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• 제13권2호
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• pp.24-30
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• 1976

To observe the influence of tetrahedral and octahedral preference of cations of Ni2+, Ti4+ upon the formation and the color development of the MgO-SnO2 spinel containing Ni2+ and Ti4+ ions, the gradual substitution of Ni2+ ions for Mg2+ ions and of Ti4+ ions for Sn4+ ions of the spinel in NiO-MgO-SnO2-TiO2 system was carried out. On samples prepared by calcining the oxide and basic carbonate mixtures at 130$0^{\circ}C$ for 1.5 hour, the X-ray analysis, measurement of reflectance and the test of their stability as a glaze pigment were also carried out. On samples prepared by calcining the oxide and basic carbonate mixtures at 130$0^{\circ}C$ for 1.5 hour, the X-ray analysis, measurement of reflectance and the test of their stabiality as a glaze pigment were also carried out. The results are summarized as follows. 1) As increasing the amounts of Ni2+ ions in the xNiO.(2-x)MgO.SnO2 system, spinel was not formed easily, and the mixed-spinel was formed in NiO.MgO.SnO2 of x=1 but the spinels was not formed completely in the range of x>1.5 2) The spinels was not more formed in NiO-MgO-TiO2 system than NiO-MgO-SnO2 system. Therefore, Ti4+ ions have strong octahedral preference than Sn4+ ions. The color changed the yellow region little. The mixed-spinel or non-spinel was formed easily NiO.TiO2, MgO.TiO2 of illmenite type as the gradual substitution of Ti4+ ions for Sn4+ ions. 3) The results of glaze test. The color changed from white through graish brown to brown as the gradual substitution of Ni2+ ions for Mg2+ ions in calcium-zinc glaze and calcium glaze, and from white through light yellowish beige to dull beige in tile glaze. Also, the color did not change generally as the gradual substitution of Ti4+ ions for Sn4+ ions in NiO-MgO-SnO2-TiO2 system.

• 한국결정성장학회지
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• 제30권6호
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• pp.244-250
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• 2020

β-삼인산칼슘(β-tricalcium phosphate, β-TCP, Ca3(PO4)2)은 뼈와 유사한 성분을 가지는 인산 칼슘계 세라믹 중 하나로, 생분해성과 골 전도성을 가지고 있어 골 대체재 등으로 다양하게 사용된다. 이러한 β-TCP의 생체 활성과 골유도성을 향상시키기 위해 다양한 이온 치환 연구가 진행되어왔으며 그 중 철 이온은 필수 미량 원소로 체내에서 다양한 기능을 한다. 본 연구에서는 β-TCP에 철 이온이 치환되었을 때 열처리 온도에 따른 구조의 변화를 분석하고, 이에 따른 생분해 특성을 평가하였다. 또한 분해 후의 구조를 분석하여 분해 거동을 확인하였다. 철 이온을 치환한 β-TCP는 공침법으로 합성을 하였고, 925℃와 1100℃에서 하소 처리를 실시하였다. X-선 회절 분석과 Rietveld refinement를 이용하여 구조 분석을 실시하였다. 철 이온은 온도에 따라 Fe2+ 또는 Fe3+ 상태로 바뀌기 때문에 β-TCP에 치환되었을 때 열처리 온도에 따라 치환 위치(Ca(4), Ca(5))가 바뀌고, 1100℃에서 열처리를 실시한 철 이온 치환 β-TCP의 분해 속도가 가장 빨랐다. 또한 세포 증식 특성이 향상된 것을 통해 β-TCP에 철 이온을 치환하는 것이 생체적합성과 생체 활성 특성을 향상시키고 골 결손부 회복 등 더욱 다양한 분야에 사용될 수 있을 것으로 기대된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.47-48
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• 2023

In the domestic industrial sector, greenhouse gases emitted from the cement industry account for about 10%, with most of them generated during the cement clinker calcination process. During the calcination process, 57% of carbon dioxide is emitted from the decarbonation reaction of limestone, 30% from fuel consumption, and 13% from electricity usage. In response to these issues, the cement industry is making efforts to reduce carbon dioxide emissions by developing technologies for raw material substitution and conversion, improving process efficiency by utilizing low-carbon alternative heat sources, developing CO₂ capture and utilization technologies, and recycling waste materials. In addition, due to the limitations in purchasing and storing industrial byproducts generated from industrial facilities, many studies are underway regarding the recycling of construction waste. Therefore, this study analyzes the manufacture of calcium silicate cement (CSC), which can store carbon dioxide as carbonate minerals in industrial facilities, and aims to contribute to the development of environmentally friendly regenerated cement using construction waste.

• 한국결정성장학회지
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• 제20권5호
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• pp.243-248
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• 2010

Si-BCP(si-substituted biphasic calcium phosphate)를 제조하기 위하여 $Ca(NO_3)_2{\cdot}4H_2O$, $(NH_4)_2HPO_4$, $Si(OC_2H_5)_4$을 출발 물질로 공침법(co-precipitation process)을 이용하여 합성하였다. 합성된 분말의 HAp/${\beta}$-TCP 결정상 비율 및 Si-P 치환 거동은 X-선 회절 상 분석을 이용하여 측정하였고, silicon ion 첨가 시 나타나는 BCP의 화학적 결합거동을 측정하기 위하여 FT-IR를 사용하여 분석하였다. 또한 Si-BCP 분말의 in-vitro 생분해거동 및 생체활성도를 측정하기 위하여 제조된 분말을 SBF(simulated body fluid) solution에 침적시킨 뒤 분말의 형상과 구성 성분은 SEM과 EDS를 통하여 확인하였다.

• Journal of Periodontal and Implant Science
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• 제33권1호
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• pp.13-26
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• 2003

Periodontal regeneration therapy with bone-substituting materials has gained favorable clinical efficacy by enhancing osseous regeneration in periodontal bony defect. As bone-substituting materials, bone powder, calcium phosphate ceramic, modified forms of hydroxyapatite, and hard tissue replacement polymer have demonstrated their periodontal bony regenerative potency. Bone-substituting materials should fulfill several requirements such as biocompatibility, osteogenecity, malleability, biodegradability. The purpose of this study was to investigate biocompatibility, osteo-conduction capacity and biodegradability of $Na_2O$, $K_2O$ added calcium metaphosphate(CMP). Beta CMP was obtained by thermal treatment of anhydrous $Ca_2(H_2PO_4)_2$. $Na_2O$ and $K_2O$ were added to CMP. The change of weight of pure CMP, $Na_2O$-CMP, and $K_2O$-CMP in Tris-buffer solution and simulated body fluid for 30 days was measured. Twenty four Newzealand white rabbits were used in negative control, positive control(Bio-Oss), pure CMP group, 5% $Na_2$-CMP group, 10% $Na_2O$-CMP goup, and 5% $K_2O$-CMP group. In each group, graft materials were placed in right and left parietal bone defects(diameter 10mm) of rabbit. The animals were sacrificed at 3 months and 6 months after implantation of the graft materials. Degree of biodegradability of $K_2O$ or $Na_2O$ added CMP was greater than that of pure CMP in experimental condition. All experimental sites were healed with no clinical evidence of inflammatory response to all CMP implants. Histologic observations revealed that all CMP grafts were very biocompatible and osseous conductive, and that in $K_2O$-CMP or $Na_2O$-CMP implanted sites, there was biodegradable pattern, and that in site of new bone formation, there was no significant difference between all CMP group and DPBB(Bio-Oss) group. From this result, it was suggested that all experimental CMP group graft materials were able to use as an available bone substitution.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권2호
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• pp.76-86
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• 2022

Calcium (Ca) and potassium (K) were introduced to remove Sr and Cs in soil, respectively. Four factor and three level Box-Bhenken design was employed to determine the optimal washing condition of Ca- and K-based solutions, and the ranges tested were 0.1 to 1 M of Ca or K, L/S ratio of 5 to 20, washing time of 0.5 to 2 h, and pH of 2 to 7. The optimal washing condition determined was 1 M of Ca or K, L/S ratio of 20, washing time of 1 h, and pH of 2, and Ca-based and K-based solutions showed 68 and 81% removal efficiency for Sr and Cs, respectively in soil. For comparison, widely used conventional washing agents such as 0.075 M EDTA, 0.01 M citric acid, 0.01 M oxalic acid, and 0.05 M phosphoric acid were tested, and they showed 25 to 30% of Sr and Cs removal efficiency. Tessier sequential extraction was employed to identify the changes in chemical forms of Sr and Cs during the washing. In contrast to the conventional washing agents, Ca-based and K-based solutions were able to release relatively strongly bound forms of Sr and Cs such as Fe/Mn-oxide and organic matter bound forms, suggesting the involvement of direct substitution mechanism, probably due to the physicochemical similarities between Sr-Ca and Cs-K.

• 에너지공학
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• 제28권1호
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• pp.10-16
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• 2019

본 연구에서는 경량기포콘크리트의 침하안정성 및 경제성을 확보하기 위해 수행되었다. OPC에 fly ash와 Calcium sulfaluminate(CSA)를 일정함량 치환한 배합비를 선정하고 기초물성을 검토하였다. CSA에 의해 조기 ettringite 생성으로 경량기포콘크리트의 플로우가 감소한 것을 확인하였다. 압축강도는 CSA 10%까지 혼입할 경우 경량기포콘크리트의 경화시간 단축으로 인해 초기강도는 증가한 것을 확인하였다. 침하깊이는 CSA를 치환할 경우 응결시간을 단축하여 기포가 소포되는 것을 방지하였기 때문에 침하안정성이 향상되었다.

• International Journal of Concrete Structures and Materials
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• 제8권1호
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• pp.15-26
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• 2014

In order to study the capacities of a new occurrence of Brazilian clay samples as partial replacements of cement, a bentonite sample was selected for utilization in the natural and modified forms for present study. The natural bentonite (BBT) was modified by anchorament of 3-aminopropyltrietoxisilane ($BBT_{APS}$) and 3,2-aminoethylaminopropyltrimetoxisilane (BBTAEAPS) in the surface of component minerals of bentonite sample. The original and organo-bentonite samples were characterized by elemental analysis, scanning electron microscopic and textural analyses. The values of micropore area were varying from $7.2m^2g^{-1}$ for the BBT to $12.3m^2g^{-1}$ for the $BBT_{AEAPS}$. The bentonite samples were characterized by the main variable proportion of bentonite in the natural and intercalated forms (2, 5, 10, 15, 20, 25, 30, and 35 % by weight of cement) in the replacement mode whiles the amount of cementations material. The workability, density of fresh concrete, and absorption of water decreased as the substitution of ordinary Portland cement by perceptual of natural and modified bentonite increased. The results reveal that workability decreased with decrease of the amount of natural bentonite in the concrete, same behavior is observed for bentonite functionalized, varying from 49 to 28 mm. The energetic influence of the interaction of calcium nitrate in the structure of blends was determined through the calorimetric titration procedure.

• 한국세라믹학회지
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• 제38권12호
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• pp.1132-1136
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• 2001

생체친화성이 증진된 생체재료를 얻기 위하여 실리콘 원료로 tetraethyl orthosilicate를 사용하여 실리콘이 치환된 hydroxyapatite를 합성하였다. XRD 분석결과 규산이나 다른 인산칼슘염을 포함하지 않는 순수한 hydroxyapatite상 만이 존재하는 것을 확인할 수 있었다. 성분분석 결과 3.32wt% 까지의 실리콘을 함유하였다. $^{29}$ Si MAS NMR 데이터 분석결과 실리콘은 수산화아파타이트의 결정 내에서 규산염 사면체구조를 가지는 것으로 확인할 수 있었다. FT-IR 분석결과 Si 치환 수산화아파타이트에서 수산기가 감소되는 것은 silicate group의 음전하를 보상하기위한 것으로 사료되었다.