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Taejin Choi,Daehyeon Kim,Bo-An Jang,Seong-Seung Kang 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.6
The influence of microorganisms on the physical properties and strength of ilmenite and magnetite ores was determined in culture studies and laboratory tests of rock parameters such as absorption, porosity, elastic wave velocity, and uniaxial compressive strength. Initial pH condition was determined in the culture experiments, and then abiotic and biotic oxidation tests were performed to determine variations in pH, physical properties, and the strengths of the two ferruginous ore rocks. For ilmenite and magnetite ores, average initial values were, respectively, 0.185% and 0.496% for porosity, 0.046% and 0.123% for absorption, 1919 m/s and 1467 m/s for elastic wave velocity, and 432 MPa and 168 MPa for uniaxial compressive strength. The pH of ilmenite ore at the end of the abiotic and biotic oxidation tests was in the range of 3.82–4.26 and 2.20–2.57, respectively, while that of magnetite ore was 4.02–5.16 and 1.50–1.90, respectively. In magnetite ore, the changes in porosity and absorption due to the biotic oxidation test were larger than those observed in the abiotic oxidation test, while the variations in ilmenite ore due to both tests (abiotic and biotic oxidation) were small. The differences in porosity and absorption between the abiotic and biotic oxidation tests were larger in magnetite ore than in ilmenite ore, while the elastic wave velocity was smaller in magnetite ore than in ilmenite ore. In addition, the variations in uniaxial compressive strength due to the abiotic oxidation test were not significantly different than initial values in both ilmenite and magnetite ores, while variations caused by the biotic oxidation test were relatively large in both ferruginous ore rocks. Our results suggest that variations in the physical properties and strength of ilmenite and magnetite ores are largely dependent on microbial activity.
Taejin Choi,Yong Il Lee 한국지질과학협의회 2006 Geosciences Journal Vol.10 No.3
Apatite and zircon fision track (FT) analyses werecarried out to reconstruct the thermal histories of the CretaceousPungam and Yeongdong basins, Korea. These basins were formedalong the sinistral strike-slip faults in the Early Cretaceous andwere compressed in the Late Cretaceous by transpressional stressesdue to the change in subduction direction of the Kula/Pacific Plate.sistent FT ages of ca. 50 Ma and ca. 63 Ma, respectively, muchyounger than their stratigraphic ages. In contrast, the zircon FTages of both basins show relatively wide ranges, i.e., from 89 to70 Ma in the Pungam Basin, and from 83 to 64 Ma in the Yeo-ngdong Basin. Zircon single-grain age spectra also show multipleage populations. Co-existence of both the older and younger FTages in comparison to the depositional age (Pungam Basin: ~70Ma, Yeongdong Basin: ~100 Ma) indicates that the zircon samplesfrom both basins were partially annealed. The Pungam Basin wasvolcanic activity and associated hydrothermal fluid, then cooledbelow the apatite closure temperature at ca. 50 Ma. The Yeong-dong Basin was also heated into the ZPAZ after deposition byburial and volcanic activity, then cooled down below the apatiteclosure temperature at ca. 63 Ma, and was uplifted to the presentsurface. Comparing these data with those of the GyeongsangBasin, the response to transpressional stresses seems not to be con-trolled by the distance of the basin from the active continentalmargin. Further studies are needed to clarify such tectonic inver-sion of the sedimentary basins in the active continental margin.
Hydrogen plasma-enhanced atomic layer deposition of hydrogenated amorphous carbon thin films
Choi, Taejin,Yeo, Seungmin,Song, Jeong-Gyu,Seo, Seunggi,Jang, Byeonghyeon,Kim, Soo-Hyun,Kim, Hyungjun Elsevier 2018 Surface & coatings technology Vol.344 No.-
<P><B>Abstract</B></P> <P>Hydrogenated amorphous carbon (a-C:H) thin films were prepared by hydrogen plasma-enhanced atomic layer deposition (PE-ALD). The a-C:H thin films were grown at low temperatures in the range of 150–350 °C using CBr<SUB>4</SUB> as the precursor and hydrogen plasma as the reactant. Raman spectroscopy, secondary ion mass spectrometry, X-ray photoelectron spectroscopy and Fourier transform infrared measurements showed that the a-C:H films consist of hydrogenated nanocrystalline sp<SUP>3</SUP> diamond, disordered sp<SUP>3</SUP> carbon and sp<SUP>2</SUP>-hybridized graphitic carbon incorporated with oxygen as a main contaminant. Moreover, the incorporation of bromine and oxygen in the a-C:H films was significantly reduced upon increasing the growth temperature from 200 to 300 °C. Surface hydroxylation and precursor exposure pretreatments were employed to saturate the adsorption of CBr<SUB>4</SUB> precursors and enhance the initial nucleation of carbon during the deposition of the a-C:H thin film by the PE-ALD process. In addition, the conformal growth of a-C:H thin films on three-dimensional structures was confirmed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen plasma-enhanced atomic layer deposition of hydrogenated amorphous carbon (a-C:H) thin films was developed. </LI> <LI> Substrate pretreatments by plasma hydroxylation and CBr<SUB>4</SUB> exposure are helpful for the uniform deposition of a-C:H films. </LI> <LI> a-C:H thin films can be deposited on three-dimensional structures in a conformal manner. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>