• Journal of the Korean Ceramic Society
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• v.51 no.2
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• pp.82-87
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• 2014

Due to the revised Korean standard KS L 5201 for Ordinary Portland Cement (OPC), the use of mixed cement has grown from 5% to 10%. This study investigates the hydration behavior of $C_3A$, asit is a cement mixture that is more commonly used than granulated blast furnace slag or limestone alone. Paste samples were prepared with either granulated blast furnace slag or limestone alone. Each sample was compared with the widely used Rietveld method with a cement mixture containing blast furnace slag or limestone. The hydration behavior of $C_3A$ in each OPC sample was assessed and results were analyzed. Granulated blast furnace slag promotes a high initial level of ettringite, but as the days passed, it promotes an increase in monosulfate, leading to cracks and expansion due to the penetration of sulfates in the solution. However, when limestone is added to the mixture, a transformation of ettringite to monosulfate occurs in the presence of the $CaCO_3$ in the limestone. It is considered that this produces hemi-carbonate and mono-carbonate and thus maintains the ettringite level.

• Journal of the Mineralogical Society of Korea
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• v.10 no.1
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• pp.50-59
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• 1997

the crystal structure of pale green gem-quality olivine from Bisbee mine,Arizona, (Mg1.83Fe0.18)Si0.99O4, a=4.7608(4)$\AA$, c=5.9903(6)$\AA$, c=5.9903(4)$\AA$, V=291.49(1)$\AA$, Pbnm, Z=4 has been refined by both single-crystal and Rietveld methods to R(%) indices of 2.20 and 9.07, respectively. Comparison of site occupancies, cell dimensions, atomic coordinations, and interatomic distances/angles obtained from both methods shows that the Rietveld method produces more accurate site scattering values, cell dimension, and atomic positions than the single-crystal method. This indicates that the Rietveld method is a useful technique for the structural characterization and crystal-chemical study of powdered samples of natural minerals and synthetic materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.514-519
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• 2020

In this study, cement clinkers were sintered at each temperature by replacing some of the clay components of cement clinkers with coal materials. The mineral phase change of sintered cement clinker was quantitatively analyzed by XRD-Rietveld method. As the sintering temperature of cement clinker increased, the amount of belite decreased, the amount of alite increased, and the amount of free-CaO decreased. The form of alite and belite could be distinguished at sintering temperature of 1450℃ or higher. The crystal size was greatly increased at 1500℃ sintering. It was confirmed that the excessive sintering was progressed. Free-CaO decreased with the increase of sintering temperature. At 1450 ℃ or higher, it was less than 0.5%. In 1450℃ or greater, it is determined that enough sintering is included. Therefore, the application of fly ash as a raw material of cement clinker was judged to be usable as a source of chemical components of alumina and iron raw materials.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.123-126
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• 2005

Barium Titanate (BT) powders were synthesized by solvothermal method with an ethanol as a solvent. The average particle size was increased with the feedstock concentration: the size was 59 nm at $6.25{\times}10^{-2}$ M and 89 nm at 0.5 M. The sample obtained at 0.5 M concentration was analysed by Rietveld refinement and the mole fraction of tetragonal phase was $75.5\%$ and lattice parameter of tetragonal phase was a=0.3999 (nm), c=0.4032 (nm), and cubic phase was a=0.4015 (nm). TEM analysis for the samples with condition of annealing at $500^{\circ}C$ for I h showed that hydroxyl ions on oxygen sites were not found for these experimental conditions.

• Korean Journal of Materials Research
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• v.6 no.5
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• pp.504-514
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• 1996

고상반응법과 sol-gel법으로 제조된 NASICON의 상온과 25$0^{\circ}C$에서의 X선 회절 데이터를 리트벨트 분석을 행하였다. monoclinic에서 rhombohedral로 상전이가 일어나도 원자들의 변위는 매우 작았다. 이들 상간의 ZrO6 팔면체와 Si(P)O4 사면체고 구성된 골격은 다소 다르게 나타남으로 인하여 Na 이온의 자리도 변하였다. 이들 방법으로 제조된 NASICON은 Zr이 부족한 비화학양론 화학식, Na 1+x+4yZr2-xSixP3-xO12으로 표현될 수 있었다. 제조법에 따라 Na 이온들의 자리 점유율이 변화하였다. 상온에서는 Na(1)과 Na(3)자리의 자리 점유율의 합이 거의 1에 가까웠으나, 25$0^{\circ}C$에서는 Na(1)과 mid Na 자리를 단위 화학식 당 한 개를 약간 상회하는 Na 이온이 점유하였다. 상온과 25$0^{\circ}C$에서의 Na 이온의 이동 경로가 다름을 알 수 있었다. 또한 25$0^{\circ}C$에서는 Na(1)자리와 Na(2)자리 사이에 mid Na가 존재하며, 이 자리가 Na 이온의 이동에 중요한 역할을 함을 알 수 있었다.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.780-786
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• 1995

For the execution of RIETAN program adopting Rietveld Analysis Method, the sample superconductor is made according to the solid state synthesis method at 920.deg. C for 24hrs, and was examined for the optimization of parameters needed to analyze Rietveld method with the input of the measured pattern data after measuring the pattern resulted from the X-ray diffraction. It was proven that the lattice constant of the superconductor which was consisted of Pmmm orthorhombic crystal structure in the analyzed space group correspond to the presented theoretical lattice constant a=3.8887(8).angs., b=3.8238(4).angs., c=11.7079.angs.. Therefore, it was examined and confin-ned that the R factor, which was compensated after analyzing the structure of superconductor resulted from this experimented data with the computer simulation, was refined to $R_{wp}$=8.83[%], $R_{P}$=6.47[%], $R_{I}$=10.08[%], $R_{F}$=7.19[%], $R_{E}$=3.76[%]. On the basis of these experimental data, the significant parameter such as the scale factor(S) and the zero point shift(Z) and FWHM value(U,V,W) were optimized as follows; S=2.0827E-3, Z=0.2146, U=4.2761E-2, V=1.7983E-2, and W=2.6768E-2.2.2.2.2.2.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.223-232
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• 2003

The co-precipitation method is applied to synthesize the cathode material Li[L $i_{x}$M $n_{1-x-y}$C $r_{y}$ ] $O_2$ for lithium rechargeable batteries at $650^{\circ}C$ (CR650) and 8$50^{\circ}C$ (CR850), respectively. Rietveld indices indicate that $R_{wp}$ with respect to $R_{exp}$ ( $R_{wp}$/ $R_{exp}$) are 9.2%/10.1% for CR650 and 15.9%/9.76% for CR850, respectively. $R_{B}$ and S (GofF) shows 10.9%, 8.54% and 1.9, 1.6, respectively. Rietveld structure refinement reveals that layer structure of LiMn $O_2$ (R3m) coexists with lower symmetry of Li[L $i_{1}$3/M $n_{2}$3/] $O_2$ (C2/c) due to superlattice ordering of Li and Mn in metal-transition containing layers. Unit-cell parameters are calculated as a=2.8520(2)$\AA$, c=14.248(2)$\AA$, V=100.40(l)$\AA^3$ for CR650, and a=2.8504(1)$\AA$, c=14.2371(7)$\AA$, V=100.179(8)$\AA^3$ for CR850. Final chemistry is obtained as Li[L $i_{0.35}$M $n_{0.56}$C $r_{0.09}$] $O_2$ (CR650) and Li[L $i_{0.27}$M $n_{0.61}$C $r_{0.13}$] $O_2$ (CR850), respectively.y...y..vely.y...y..

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.657-663
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• 2011

Structure directing agent(SDA) containing piperidine moiety such as piperidine(PI), 2-methylpiperidine (MPI), 2,6-dimethylpiperidine(DMPI) and 2,2,6,6,-tetramethylpiperidine(TMPI), respectively has been utilized to synthesize aluminophosphate zeolite using hydrothermal method. The gel composition was $1.0Al_2O_3:1.0P_2O_5:0.76SDA:45H_2O$ and the hydrothermal heating was performed in an oven at 443 K and for 7 days at static mode. The obtained zeolitic material contained a lamellar structure when PI was used as the SDA. With a progressive increase of the SDA size, various structures of aluminophosphate including AlPO-5 of AFI structure were obtained. The aluminophosphate of SAS structure was formed when the largest TMPI was utilized as the SDA, which was confirmed by the Rietveld refinement. The result of $^{27}Al$ and $^{31}P$ MAS NMR of the sample suggested that Al and P were incorporated into the framework of the aluminophosphate.

• Journal of the Mineralogical Society of Korea
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• v.13 no.1
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• pp.1-14
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• 2000

알루나이트는 포항지역의 제3기 연일층군의 이암 층내의 탄산염 결핵체 주변에서 할로이사이트와 함께 극미립 변질물 (1-2 $\mu\textrm{m}$)로서 산출된다. 알루나이트는 정육면체와 유사한 능면체 결정형을 이루고 침상 내지 단주상의 할로이사이트와 밀접한 공생관계를 이룬다. X-선회절 분석에 의해서 이 알루나이트는 a=6.9897(1) $\AA$, c=17.2327(4)$\AA$, V=728.75(3) $\AA$3의 격자상수값을 갖는 것으로 밝혀졌다. X-선형광된 이 알루나이트의 화학식은 (K0.94N0.06)(Al2.55Fe3+0.45)(SO4)2(OH)6 으로서, 나트로알루나이트 단성분을 6-7 mole%정도 함유하는 것으로 분석되었다. 또한 시차열분석 (TG-DTG-DTA)을 통해서 알루나이트의 승화성 성분들 (H2O와 SO3)의 존재와 함유 정도를 조사하였고, 고온X-선회절분석을 병행하여 이 광물의 OH기의 이탈 반응 (52$0^{\circ}C$)과 고온상으로의 전이 반응 ($600^{\circ}C$ 및 $700^{\circ}C$)을 감정 하였다. K/Ar 법으로 측정된 알루나이트의 생성 연대 ($0.342\pm$0.008 Ma)와 안정동위원소들의 분석 결과 ($\delta$18Oso4=-1.7, $\delta$DSMOW=-31, $\delta$34S=-10.8)는 이 알루미늄 황산염 광물이 연일충군의 융기 이후에 야기된 민물의 유입에 의한 표성기원의 변질작용의 결과로 생성되었음을 지시한다. 알루나이트+할로이사이트 공생군의 침전은 이암 내에서 조성된 강산성 (pH=2-3)의 알루미늄 황산염 용액이 탄산염 결핵체를 만나 반응하여 pH가 국지적으로 증가되어 (pH=4) 과포화되는 과정에 의해서 야기되었다. 컴퓨터를 이용한 Al3+의 포화지수에 관한 화학적 평형 모델링 실험 결과, 알루미늄 황산염 용액으로부터의 알루나이트와 할로이사이트의 침전은 pH=4 및 \ulcornerSO42-=10-4M 조건에서 K+과 Si(OH)4의 농도가 10-4M 이상 유지되어야 가능한 것으로 밝혀졌다.

• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.329-344
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• 2002

Mineralogical and chemical characterization of some domestic bentonites, such as quantitative XRD analysis, chemical leaching experiments, pH and CEC determinations, were done without any separation procedures to understand their relationships among mineral composition, characteristics, and cation exchange properties. XRD quantification results based on Rietveld method reveal that the bentonites contain totally more than 25 wt% of impurities, such as zeolites, opal-CT, and feldspars, in addition to montmorillonite ranging 30～75 wt%. Cation exchange properties of the zeolitic bentonites are deeply affected by the content of zeolites identified as clinoptilolite-heulandite series. Clinoptilolite is common in the silicic bentonites with lighter color. and occurs closely in association with opal-CT. Ca is mostly the dominant exchangeable cation, but some zeolitic bentonites have K as a major exchangeable cation, The values of cation exchange capacity (CEC) determined by Methylene Blue method are comparatively low and have roughly a linear relationship with the montmorillonite content of the bentonite, though the correlated data tend to be rather dispersed. Compared to this, the CEC determined by Ammonium Acetate method, i.e.‘Total CEC’, has much higher values (50～115 meq/100 g). The differences between those CEC values are much greater in zeolitic bentonites, which obviously indicates the CEC increase affected by zeolite. Other impurities such as opal-CT and feldspars seem to affect insignificantly on the CEC of bentonites. When dispersed in distilled water, the pH of bentonites roughly tends to increase up to 9.3 with increasing the alkali abundance, especially Na, in exchangeable cation composition. However, some bentonites exhibit lower pH (5～6) so as to regard as ‘acid clay’. This may be due to the presence of $H^{＋}$ in part as an exchangeable cation in the layer site of montmorillonite. All the works of this study ultimately suggest that an assesment of domestic bentonites in grade and quality should be accomplished through the quantitative XRD analysis and the ‘Total CEC’measurement.