• 한국세라믹학회지
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• 제35권8호
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• pp.836-842
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• 1998

In this experiment well-know additives for Mn-Zn ferrites CaO and {{{{ { SiO}_{2 } }} were added at various content and their effects on microstructures and magnetic properties with sintering atmosphere were examined. By adding up to 0.04wt% {{{{ { SiO}_{2 } }} and and 0.06wt% CaO the sintered density was increased and then decreased gra-dually. Higher sintered density and initial permeability were observed by adding both CaO and {{{{ { SiO}_{2 } }} than by adding CaO or {{{{ { SiO}_{2 } }} alone. Without any additives initial permeability and tan$\delta$/${\mu}$ decreased at 1000kHz as oxidation degree(${\gamma}$) increased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.24-25
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• 2017

Gamma-C₂S (γ-C₂S) is a substance that is difficult to react with water under normal temperature but can absorb a large amount of CO₂ in the air. The addition of γ-C₂S to cementitious materials through the curing of CO₂ can improve the pore structure and improve the durability of the material. In this study, three kind of Ca-bearing materials : CaO, Ca(OH)₂, CaCO₃, were calcined 2.5h at 1450℃ to synthesize γ-C₂S after mixing with SiO₂ respectively. Among them, Ca(OH)₂ mixed with SiO₂ after calcining shows highest content. Synthesized γ-C₂S was added to the cement mortar, after water curing for 1 month, accelerated carbonation test was experimented. After 28d accelerated carbonation test, pore structure will be detectived by MIP. Based on the MIP result, following the calculation method of Fractal theory, the pore structure will be quantitative described.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.339-342
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• 2000

In the present study, we attempted to apply DV-X$\alpha$ method to expressing the reactivity of materials. The expression of reactivity was discussed by comparison between ${\gamma}$-C$_2$G having hydraulic activity and ${\gamma}$-C$_2$S not having hydraulic activity at normal conditions. It was found that the model cluster used for calculation can finely reproduce the bulk and surface states using with and without point charge, respectively. The hydration state was also represented by placing OH￣ on the surface of the cluster. It was calculated that the bond strength of the first layer (as surface) was bigger than that of inner layers (as bulk) for ${\gamma}$-C$_2$S while that of the first layer for ${\gamma}$-C$_2$G was smaller than that of inner layers. Subsequently a model in which OH￣ is coordinated on Ca at the surface was also calculated. The bond strength with OH￣ was stronger than that without OH￣, while for ${\gamma}$-C$_2$G the bond strength with OH￣ was weaker than that without OH￣. From these results, it is concluded that the hydraulic activity depends on whether the bond strength for hydrated state becomes weaker than that unhydrated state or not.

• 한국건축시공학회지
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• 제20권2호
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• pp.123-128
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• 2020

γ-C₂S(γ-Calcium Silicate)는 벨라이트(belite)의 다형성으로 알려져 있다. γ-C₂S는 CO₂ 고정 능력이 우수하고 제조 시 CO₂ 배출량이 적은 공정으로 인해 최근 많은 관심을 받고 있는 시멘트계 재료이다. 본 연구에서는 γ-C₂S의 건축재료로써 활용하기 위하여 γ-C₂S의 고순도 합성을 위한 다양한 합성방법을 조사하고 이를 기반으로 조건별 합성 실험 및 분석을 실시하였으며 γ-C₂S의 순도에 대한 다양한 원료와 소성 온도가 미치는 영향도 평가하였다. 여러 종류의 Ca 결합물 재료가 Ca 공급원으로 사용 되었고 Si 소스 공급원으로는 Si가 주성분인 SiO₂가 사용되었다. 각각의 원료는 혼합 후 다양한 조건에서 소성시켰다. 그 결과 Ca(OH)₂와 SiO₂ 분말을 원료로 합성하였을 때 최고 높은 γ-C₂S 순도를 얻을 수 있었다. 그리고 γ-C₂S 제조 실용화를 위해 천연 광물인 석회암 분말과 실리카 모래를 원료로 한 분말을 사용하여 다양한 소성온도에서 합성하였으며 그 결과 합성한 샘플의 γ-C₂S의 순도는 77.6%로 나타났다.

• 청정기술
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• 제9권3호
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• pp.125-132
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• 2003

본 연구에서는 이산화탄소 개질반응에 대한 연구의 일환으로 HY-zeolite를 주요 담체로 하여 니켈촉매의 활성화 개선에 대한 연구를 수행하였다. 메탄과 이산화탄소의 전환율은 반응온도가 증가함에 따라 증가하였고, $700^{\circ}C$ 이상이 되었을 때 80% 이상의 전환율을 얻었고, 니켈의 담지량이 증가함에 따라 촉매의 활성이 증가하였으며, 13wt%에서 가정 높은 활성을 보였다. 담체에 대한 영향으로 HY-zeolite 외에 ${\gamma}-Al_2O_3$와 $SiO_2$에 니켈을 담지시켜 반응활성을 비교한 결과 메탄과 이산화탄소의 초기 전환율은 HY-zeolite에 담지된 니켈 촉매를 사용했을 때가 가장 높았으나, 시간이 지남에 따라 ${\gamma}-Al_2O_3$에 담지된 니켈 촉매보다 비활성화가 빨랐지만 24시간 반응 후에도 메탄의 전환율이 80% 이상을 나타내었다. 그리고 13wt%Ni/HY-zeolite 촉매의 성능 향상을 위하여 Mg, Mn, K, Ca을 조촉매로 첨가하여 반응활성을 조사한 결과 Mg을 첨가한 촉매가 높은 활성과 안정성을 나타내었고, Mg의 최적 첨가량이 5wt%임을 확인하였다.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.282-293
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• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• Journal of Ceramic Processing Research
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• 제20권spc1호
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• pp.109-112
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• 2019

γ-dicalcium silicate(γ-C2S) is known as a polymorphism of belite. Due to its high CO2 fixed capacity and the low CO2 emission production process, γ-C2S has attracted more and more attention of researchers. For the further development of application of γ-C2S in building construction industry. In this study, we aim to investigate the method for synthesizing high purity of γ-C2S. The influence of different raw materials and calcination temperatures on the purity of γ-C2S was also evaluated. Several Ca bearing materials were selected as the calcium source, the materials which' s main component is SiO2 were used as the silicon source. Raw materials were mixed and were calcined under different temperatures. The results reveal that the highest purity could be obtained using Ca(OH)2 and SiO2 powder as raw materials. And for the practical application, a relatively economic synthesis method using natural mineral materials- limestone and silica sand as raw materials was developed, by this method, the purity of the synthetic γ-C2S was 77.6%.

• 한국환경보건학회지
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• 제49권5호
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• pp.251-261
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• 2023

Background: This paper deals with the study of natural radioactivity in rocks from Ogun State in Southwestern Nigeria. The aim is to determine radiation emissions from rocks in order to estimate radiation hazard indices. Objectives: The following objectives were targeted: 1. To determine radiation emissions from each type of rocks; 2. To estimate radiation hazard indices based on the rocks; 3. To correlate the activity concentrations of radionuclides with major oxides. Methods: The samples were analyzed using a NaI (Tl) gamma ray spectrometric detector and PerkinElmer AAnalyst 400 AAS spectrometer. Results: The activity of ⁴⁰K, ²²⁶Ra, and ²³²Th were found in order of decreasing magnitude from pegmatite>granite>migmatite. In contrast, lower concentrations were found in shale, phosphate, clay stone, sandstone and limestone. The mean absorbed doses were 125±23 nGyh^-1 (migmatite), 74±13 nGy/h (granite), 72±13 nGyh^-1 (pegmatite), 64±09 nGyh^-1 (quartzite), 45±16 nGyh^-1 (shale), 41±09 nGyh^-1 (limestone), 41±11 nGyh^-1 (clay stone), 24±03 nGyh^-1 (phosphate), and 21±10 nGyh^-1 (sandstone). The outdoor effective dose rates in all rock samples were slightly higher than the world average dose value of 0.34 mSvy^-1. The percentage composition of SiO₂ in the rock samples was above 50 wt% except for in the limestone, shale and phosphate. Al₂O₃ ranged from 4.10~21.24 wt%, Fe₂O₃ from 0.39~7.5 wt%, and CaO from 0.09-46.6 wt%. In addition, Na₂O and K₂O were present in at least 5 wt%. Other major oxides, including TiO₂, P₂O₅, K₂O, MnO, MgO and Na₂O were depleted. Conclusions: The findings suggest that Ogun State may be described as a region with elevated background radiation. It is recommended that houses should be constructed with good cross ventilation and residences should use home radiation monitoring instruments to monitor radon emanating from walls.

• 박물관보존과학
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• 제30권
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• pp.23-46
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• 2023

동아대학교 석당박물관 소장 지자총통은 조선 중기에 사용하던 전장유통식 중화기무기로 천자총통 다음으로 큰 화기류이다. 지자총통의 표면에는 표면 이물질들로 인해 고유의 색상이 가려져 있는 상태로, 보존처리가 필요한 상황으로 판단되었다. 안정적인 보존처리를 위해 감마선(γ선), X선 비파괴 투과조사, 내시경카메라 관찰을 실시하여 내부 구조와 보존상태를 파악하였고, p-XRF 성분분석, SEM-EDS 성분분석, XRD 분석 등을 활용하여 지자총통의 재질 성분과 표면 오염물 등에 관한 성분분석을 진행하였다. 휴대용현미경 관찰과 정밀 3D스캔으로 지자총통 표면 명문의 상태, 새김형태 등을 확인하였다. 감마선, X선 비파괴 투과조사 결과, 지자총통 내부에 다량의 기포가 관찰되었으며, 육안관찰로 확인되는 표면의 채플릿은 비파괴투과조사 결과로는 확인되지 않았다. p-XRF 성분분석 결과 지자총통은 구리(Cu), 주석(Sn), 납(Pb) 합금으로 만들어진 청동으로 확인되었으며, SEM-EDS를 활용한 표면 이물질 성분분석 결과, 백색이물질은 칼슘(Ca), 황(S), 티타늄(Ti)이 주성분으로 확인되었다. 티타늄은 백색수정액의 주성분인 이산화티타늄(TiO₂)으로 추정되었으며, 적색이물질은 바륨(Ba)이 주성분으로 확인되어 페인트의 체질안료인 황산바륨(BaSO₄)으로 추정되었다. 티타늄과 바륨을 주성분으로 하는 백색과 적색 오염물은 근래에 이르러 표면에 묻은 것으로 추정된다. 황색이물질은 알루미늄(Al), 규소(Si)로 확인되어 토양성분에서 유래한 것으로 추정했다. 백색이물질의 XRD 성분분석결과 황화칼슘(CaS)으로 확인되었고, SEM-EDS와 XRD 성분분석결과로 백색이물질은 석고(CaS)로 확인하였다. 성분분석의 결과를 토대로 표면 이물질 제거, 안정화처리, 강화처리를 진행하였다. 보존처리를 진행하던 중에 휴대용 현미경과 정밀 3D스캔을 통해 알려지지 않았던 명문 우(右), 병(兵), 상(上), 이(二)를 발견하였다. 또한, 명문의 새김방법과 깊이, 너비 등을 측정하였다. 우병상(右兵上)은 창원 합포성 내 위쪽이며, 이(二)는 두 번째 돈대로 파악할 수 있다.