• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.80.1-80
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• 2002

• 한국전자현미경학회:학술대회논문집
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• 2002.05a
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• pp.51-53
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• 2002

• Applied Microscopy
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• v.33 no.3
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• pp.195-204
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• 2003

The Experimental calibration method has been investigated to correct d-spacing estimation and to identify phases in the electron diffraction data acquired by imaging plates. When the diffraction data from the imaging plate was corrected by the d-spacing calibration method with the radial intensity distribution plotting in this experiment, The accuracy of d-spacing estimation was significantly increased in errors of about 0.5%. The experimental calibration equation followed up the first order exponential decay function was derived from the trace of d-spacing deviation between the measured and the calculated values. It was applied to the analysis of d-spacing and the phase identification of the transitional phases formed from [001] gibbsite specimen by electron beam irradiation effect. In this case more accurate phase identification and d-spacing evaluation is possible for the transitional phases whose diffraction patterns are complicatedly superimposed. It is concluded that ${\chi}$-alumina, ${\gamma}$-alumina and ${\sigma}$-alumina are clearly identified as the major transitional phases formed from gibbsite by electron beam irradiation for 120 min.

• Fire Science and Engineering
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• v.29 no.6
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• pp.76-83
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• 2015

EPS sandwich panel contains flame retardants that slow down ignition during fires,reduce the amount of heat generated, and block the spread of combustion. However, if a sandwich panel does not satisfy standards for fire-retardant performance, it may increase damage to property and human life. It is difficult to test the fire-retardant performance of a finishing material with the naked eye, so it is necessary to develop convenient and fast evaluation methods that are convenient and fast. In this study, a fire safety evaluation method for EPS sandwich panel was analyzed using X-ray to detect specific components related to the fire-retardant performance X-ray fluorescence analysis (XRF) indicated that suitable panel products contained more aluminum in comparison to unsuitable products. Gibbsite was identified as the main crystalline material of flame retardant EPS through X-ray diffraction analysis (XRD) and was included in both suitable products and unsuitable products, but there was a difference in crystalline structure. This study was verifies the possibility of evaluating fire-retardant performance using ultimate analysis and crystal analysis through these X-ray methods.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.11-11
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• 2003

전자현미경내에서 일부 무기 및 금속 시료들은 전자빔 조사에 의해 시료구조가 손상되거나 비정질화 또는 상전이 등과 같은 구조전이 현상들을 겪게 된다. 즉, 전자빔 조사에 의해 시료는 원자간 결합이 끊어져 나타나는 Knock-on damage, 시료 원자 주위의 전자들과의 상호 작용에 의해 나타나는 Ionization damage, 빔 에너지의 시료온도 상승 기여에 의한 Radiolysis damage 등의 현상들을 경험하게 된다. 이러한 현상은 전자현미경의 가속전압, 전자밀도, 시료 조건 등에 따라 그 지배기구가 다르며 동일한 시편이라도 시료의 두께와 시편온도를 결정하는 전자빔 조사선량에 따라 그 양상과 전이 속도가 달라진다. 본 연구에서는 전자빔 조사에 의해 구조 전이를 겪게 되는 대표적 무기수화물의 하나인 Cibbsite에 대해 전자빔 조사효과에 대한 정량적 고찰을 에너지 여과 투과전자현미경 (EF-TEM)을 이용하여 시도하였다. 전자빔 조사는 120분까지 실시하였고 각 시간별로 에너지 필터와 Imaging plate를 이용하여 Gibbsite의 회절패턴과 미세조직 변화를 기록하였다 빔조사 시엔 illumination angle을 1.25mrad(Dose rate : 334 × 10³ e/sup -//sec·n㎡)으로 하였으며 사진기록 시엔 최소 illumination angle인 0.04mrad(Dose rate : 413 e/sup -//sec·n㎡)을 사용하였다. 시료의 관찰방향은 [001]방향이고 관찰시료두께는 약 50nm로 평가되었으며 시료의 화학변화는 EDS를 이용하여 분석하였다. 회절자료의 Intensity는 ELD/CRISP 프로그램을 이용하였으며 빔조사선량은 평행조사빔이 시료와 상호 작용하는 면적과 상호작용하지 않을 때의 빔을 회절모드에서 faraday cup으로 측정한 빔전류로 부터 계산하였다. Gibbsite에 대한 전자빔 조사 시 1분 이내에 급격한 Hydroxyl Ion(OH-)의 이탈로 인해 Cibbsite의 구조는 거시적 비정질화가 되며 시간증가에 따라 χ-alumina → ν-alumina → σ-alumina or δ-alumina의 순으로 상전이를 겪는다. 전자빔 조사 시 관찰된 회절자료의 가시적 변화를 통해 illumination angle 1.25mrad(Dose rate : 334 × 10³ e/sup -//sec·n㎡)일 경우 약 3초 이내에 비정질화가 시작됨을 알 수 있었고 이는 약 1 × 10/sup 6/ e/sup -//sec·n㎡ 의 전자선량에 해당되며 이를 기준으로 각각의 illumination angle에 대한 임계전자선량을 평가할 수 있었다. 실질적으로 Cibbsite와 같은 무기수화물의 직접가열실험 시 전자빔 조사에 의해 야기되는 상전이 영향을 배제하고 실험을 수행하려면 illumination angle 0.2mrad (Dose rate : 8000 e/sup -//sec·n㎡)이하로 관찰하고 기록되어야 함을 본 자료로부터 알 수 있었다.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.3
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• pp.233-239
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• 1985

The identification works of the clay minerals in the Paju series soil of an alfisol, aquic hapludalf, which is derived from the basalt were carried out by the X-ray diffractometer and with the aid of the complete chemical analysis of the clay fractions as well. It also conducted to determine the contents of the identified minerals which correspond to peaks of the diffraction lines appeared at 0.72, 1.0, and 1.4nm respectively. The expansible 2:1 minerals, micas and micaceous minerals, kaolinite minerals, and gibbsite were identified by the X-ray method. Furthermore, the X-ray results are seemed to be partly supported by the chemical analysis because of the presence of illite in the fractions could be confirmed by the values of $SiO_2/A1_2O_3$ mole ratio which ranged from 2.33 to 2.61. The average contents of the 1.4nm minerals. montmorillonite and vermiculite, 1.0nm micas and micaceous minerals, and 0.72nm kaolinite minerals are 42%, 28%, and 30% respectively. The theoretical considerations for the formations of these minerals were also given and that seemed to be well coincided with the experimental results, The presence of the Bt horizons and the kaolinite with gibbsite equilibria in the soil could be interpreted that the weathering is deeply advanced so far under the given soil environmental conditions.

• Economic and Environmental Geology
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• v.22 no.3
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• pp.277-283
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• 1989

For the study of attenuation phenomena of the radioactive elements in solution, the adsorption experiment of thorium, uranium, barium and strontium on kaolinite, gibbsite, quartz, granite and shale as a function of time, pH and the surface area was conducted under the competition condition each other. There are two steps of adsorption kinetics. The first step is faster and completes in hours or a day, and the second step is slower eqiulibrium reaction. The adsorption rate which is considered to be related to CEC differs with adsorbent and decreases in the order of shale, kaolinite, granite, gibbsite and quartz. On the other hand, the adsorption rate for the same adsorbent differs with elements in the order of thorium,uranium, barium and strontium in decreasing rate. It is also affected by pH of the solution and the surface area of adsorbent. In conclusion, we didn't find any different between noncompetition condition and competition condition, and this means that we only have to consider the pH of ground water, the characteristics of the geological materials and the kinds of radioactive element in the case of selection of the places for the radioactive waste disposal.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.245-251
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• 2002

We prepared γ-alumina beads using the amorphous alumina, obtained by fast calcination of gibbsite, and its were immersed in aqueous solution of the mixture of 21.87% nitric acid and 28.57% acetic acid. The beads thus were hydrothermaly treated at 200$^{\circ}$C for 3h, and were investigated changes of crystal, pore characteristics, $N_2$ adsorption and desorption isotherms, mechanical strengths and thermal resistance. Acicular platelet crystals of 0.1∼0.3${\mu}$m were transformed into acicular boehmite crystals of 1∼2${\mu}$m having the same crystal structure. Through this changes, we found that reversible phase transformation due to hydrothermal reaction took placed between boehmite and ${\gamma}$-alumina. In comparison to the ${\gamma}$-alumina bead before hydrothermal treatment, $N_2$ adsorption capacity was increased from 450㎖/g to 670㎖/g, and pore volume between 100${\AA}$ and 1000${\AA}$ was increased form 0.15㎖/g to 0.77㎖g, and mechanical strength was increased form 1.4MPa to 2.2MPa. Also, it showed the remarkable thermal resistance which sustained ${\theta}$-alumina crystal structure and pores between 100${\AA}$ and 1000${\AA}$ at 1000$^{\circ}$C in 40vol% steam.

• Journal of the Korean Ceramic Society
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• v.17 no.1
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• pp.35-41
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• 1980

Alumina extraction from raw Hadong kaolin with sulfuric acid was studied to obtain relatively pure alumina. Factors as acid concentration, heating temperature and conditions of ammonium alum crystal formation from extracted solution are also surveyed and most of iron oxide in kaolin is eliminated in crystallization of ammonium alum. Pure crystal obtained from the extracted solution with ammonium sulfate is relatively free from iron containment in mother liquor. Alumina in ammonium alum crystal is converted to gibbsite form after complete hydrolysis in ammonia gas.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.272-276
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• 2004

Inorganic materials, including gemstones, also have characteristic vibrational energies in the infrared that can be used for identification. For infrared spectroscopy, absorptions associated with the vibrations of the crystal structure (lattice vibrations) are characteristic of the given combination of atoms constituting the gemstone. Natural turquoise $CuAl_6(PO_4)_4\cdot(OH)_8\cdot 5H_2O$ can be distinguished easily from its common substitutes in the infrared range 2000~450$\textrm{cm}^{-1}$ by features in the mid-infrared. Gilson turquoise, which is a synthetic, exhibits a significantly smoother pattern when compared with natural turquoise, because of a different state of aggregation. Also, because the natural turquoise and gibbsite are so different chemically, their patterns are very different. The technique, which is infrared spectroscopy, is nondestructive and, with Fourier transform instrumentation, extremely rapid.