• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1999.04a
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• pp.34-34
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• 1999

• Analytical Science and Technology
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• v.20 no.6
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• pp.502-507
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• 2007

X-ray diffraction method has been widely used for qualitative and quantitative analysis of a mixture of materials since every crystalline material gives a unique X-ray diffraction pattern independently of others, with the intensity of each pattern proportional to that material's concentration in a mixture. For determination of mixing ratios, extracting source spectra correctly is important and crucial. Based on the source spectra extracted, a regression model with non-negativity constraint is applied for determining mixing ratios. In some mixtures, however, X-ray diffraction spectrum has sharp and narrow peaks, which may result in partial negative source spectrum from independent component analysis. We propose several procedures of extracting non-negative source spectra and determining mixing ratios. The proposed method is validated with experimental data on powder mixtures.

• Journal of Sericultural and Entomological Science
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• v.41 no.1
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• pp.54-60
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• 1999

Antheraea pernyi silk powder was prepared by treatment with HCl and NaOH. The degree of hydrolysis of Antheraea pernyi silk fiber was examined. The morphology and structural characteristics of Antheraea pernyi silk powder were investigated by using SEM, FTIR and X-ray diffractometer. As the concentration of HCl and NaOH and tratment temperature increased, in general, the degree of hydrolysis of Antheraea pernyi silk fiber increased. On the other hand, the degree of hydrolysis of Antheraea pernyi treated with 3 N NaOH at 120$^{\circ}C$ for 24 hr was 70 wt%, which was lower than that of 90$^{\circ}C$(83 wt%). The morphology of acid/alkali resistance fraction of Antheraea pernyi silk fibroin was transformed from fiber form to powered one with an increase of hydrolysis. The conformation of Antheraea pernyi silk powder characterized by FT-IR spectrometer and X-ray diffractometer ${\beta}$-sheet and ${\alpha}$-helix structure.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.154.2-154
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• 2002

• Journal of the Mineralogical Society of Korea
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• v.13 no.3
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• pp.138-146
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• 2000

Using the ultrasonic interferometry on the single crystal MgO-periclase, adiabatic bulk moduli were determined to be 163.2 GPa and 162.6 GPa from (100) and (110) lattice plane measurements, respectively. Density was measured on polycrystalline MgO by the X-ray diffraction technique. Results from this study were compared with the previously reported values. Further, the present results were converted to the isothermal bulk moduli and, then compared with the published data available including the energy dispersive X-ray diffraction result which was performed on the same single crystal MgO. The principle and techniques ultrasonic interferometry were introduced too.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.129-132
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• 1992

The multiplicity factor, which is defined as the number of different planes in a form having identical interplanar spacing and identical intensity, is tabulated here for the eleven Laue groups on the basis of their symmetries.

• Korean Journal of Crystallography
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• v.9 no.1
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• pp.15-20
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• 1998

Single crystals of lithium heptaborate, Li3B7O12(M=288.49), have been grown and their structure was determined by the x-ray powder diffraction and the single crystal diffraction technique. It is found that the borate anion consists of two(B3O7)3- and (B3O8)5- groups a unit cell. The space group was determined to be P-1(Ci1) with a=6.500(3) Å, b=7.839(2) Å, c=8.512(1) Å, α=92.07(2)˚, β=104.97(2)˚, γ=99.35(3)˚, V=412.0(2) Å3, Z=2 Dx=2.32 g cm-3, MoKα, λ=0.71069 Å, μ=2.15cm-1, T=293K. The structure was refined to R=0.0339 and wR=0.0882 for 2296 unique reflections by the single crystal diffraction. By the x-ray powder diffraction, we could obtain the similar results.

• Journal of Sericultural and Entomological Science
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• v.44 no.2
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• pp.87-92
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• 2002

Dissolution of Antheraea pernyi silk fiber was carried out in a zinc chloride solution with various dissolving conditions. The solubility was significantly dependent on the concentration of zinc chloride, dissolving temperature and time. The proper conditions of dissolution were found as 8 M zinc chloride, 70$^{\circ}C$ temperature and 30 min dissolving time. Regenerated A. pernyi silk fibroin powder was obtained through dialysis. FTIR and XRD showed that regenerated A. pernyi silk powder was composed of a ${\beta}$-sheet as well as an ${\alpha}$-helix conformation.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.350-356
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• 1998

$Y_{3-x}La_xFe_5O_{12}$ (x=0.0, 0.25, 0.5, 0.75, 1.0) powders and thin films were fabricated by a sol-gel method and their magnetic properties and crystal structure were investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and Mossbauer spectroscopy. XRD and Mossbauer spectroscopy measurements show that garnet powders annealed at 900 $^{\circ}C$ for 8 hours were single-phased and that thin films fired at 800 $^{\circ}C$ for 2 hours were crystallized without any preferred direction. X-ray diffraction patterns of $Y_{3-x}La_xFe_5O_{12}$ powders annealed at 1000 $^{\circ}C$ had only peaks of the garnet structure in case of x$\leq$0.75 but those of $Y_2LaFe_5O_{12}$ powders consisted of peaks from garnets and $LaFeO_3$. Mossbauer sepectra of garnet powders grown by the sol-gel method had a similar shape of those of powders grown by a conventional ceramic method. Grain sizes of garnet powders were 200~300 nm and the averaged surface roughness was 3.17 nm. Results of VSM measurements show the powders and thin films had soft magnetic properties and that the garnet powders had the largest saturation magnetization, 30 emu/g, and the lowest coercivity, 52 Oe.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.167-167
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• 2000

전지 재료의 충방전 과정 연구에는 X-선 분말회절(x-ray powder diffraction techniques)과 중성자회절을 많이 사용하였다. 하지만 이러한 분석기술은 long-range order의 구조에 관한 정보를 제공하는데 유용하지만 atomic scale의 구조에 관한 정보를 얻기에는 한계가 있다. Li 전지에서의 전기화학적 반응에서는 cathode 물질에 포함된 전이금속의 산화, 환원 반응에 의한 Li 이온의 intercalation (charge process)과 deintercalation (discharge process) 현상이 일어난다. 이러한 충방전 과정은 알려지지 않은 다양한 형태의 위상 변화를 동반하게 되는데 x-선 이나 중성자를 이용한 powder diffraction techniques 로는 단지 정성적인 결정학적 정보를 얻을 수 있다. 따라서 최근에 원자 단위의 local structure에 관한 정보와 electrochemical state에 관한 정보를 동시에 얻을 수 있는 X-ray Absorption Fine Structure (XAFS) 분석기술을 Li 전지분석에 활용하기 시작하였다. XAFS는 하나의 x-ray 흡수원자에 대해서 주변원자들의 원자구조에 관한 정보와 구성 원소의 electrochemical state에 관한 정보를 얻을 수 있는 분석방법이다. X-ray Induced Electron Emission Spectroscopy (XIEES)는 x-ray에 의해서 방출된 전자를 검출하여 스펙트럼을 얻는 기능을 함축적으로 나타낸 것으로, x-ray를 물질 표면에 조사하여 발생하는 광전자, Auger 전자, 이차전자 등을 전자검출기(Channel Electron Multiplier: CEM)로 검출하는 기능과, 시료를 투과한 x-ray와 시료에서 발생하는 형광 x-ray를 비례계수기로 검출하는 기능을 가지고 있다. 이러한 검출 능력을 바탕으로 EXAFS, XANES, Standing Wave Technique, Elemental Composition Analysis, DXRD, Total Reflection Technique 등을 이용하여 물질을 구성하고 있는 원소의 성분, 미세원자구조, 전자구조에 관한 정보를 얻을 수 있는 새로운 spectrometer이다. 본 연구에서는 자체 개발한 XIEES의 XAFS 기능을 이용하여 여러 가지 방법으로 제조한 LiMn2-xO4와 LiMnO2, MnO2에서 Mn K-absorption edge에 대한 chemical state 변화를 측정하였다. Absorption edge에서 chemical shift를 측정하기 위해서는 방사광 가속기 수준의 에너지 분해능(~0.3eV)이 필요하다. 이번 연구에서는 SiO2(3140) monochromator를 사용하고 여기에 맞는 적절한 parameter를 적용하여 x-ray 에너지 분해능을 포항방사광가속기 수준으로 개선하였다. XIEES에서 얻은 스펙트럼과 포항방사광가속기에서 얻은 스펙트럼을 비교하였다. Chemical shift가 일어나는 경향은 두 실험 결과가 잘 일치하였다.