http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Prasad, D. Hari,Park, S. Y.,Ji, H.-I.,Kim, H.-R.,Son, J.-W.,Kim, B.-K.,Lee, H.-W.,Lee, J.-H. AmericanChemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.5
<P>In this study, Ce<SUB>0.65</SUB>Zr<SUB>0.25</SUB>RE<SUB>0.1</SUB>O<SUB>2−δ</SUB> (RE = Tb, Gd, Eu, Sm, Nd, Pr,and La)solid solutions were successfully prepared by the glycine-nitrateprocess and tested for CO oxidation activity. The X-ray diffractionresults confirmed the formation of complete Ce<SUB>0.65</SUB>Zr<SUB>0.25</SUB>RE<SUB>0.1</SUB>O<SUB>2−δ</SUB> solid solutions.The Raman spectroscopy measurements suggested the presence of oxygenvacancies due to defective structure formation and further evidencedthe formation of solid solution. The high-resolution transmissionelectron microscopy observations showed the nanocrystalline natureof the solid solutions. From X-ray photoelectron spectroscopy analysisit was revealed that the cerium, terbium, and praseodymium are presentin +3 and +4 oxidation states. The UV–vis diffuse reflectancespectroscopy indicated that the Pr<SUP>3+</SUP> ions in the Ce<SUB>0.65</SUB>Zr<SUB>0.25</SUB>Pr<SUB>0.1</SUB>O<SUB>2−δ</SUB> system provoked a significant increase in the Ce<SUP>3+</SUP> fractionon the surface. H<SUB>2</SUB> temperature-programmed reduction measurementsshowed an enhanced surface reduction at much lower temperatures forCe<SUB>0.65</SUB>Zr<SUB>0.25</SUB>Pr<SUB>0.1</SUB>O<SUB>2−δ</SUB> sample compared to others, indicating increased oxygen mobilityin these samples, which enable the enhanced oxygen diffusion at lowertemperatures. Significantly high CO oxidation activity is exhibitedby Ce<SUB>0.65</SUB>Zr<SUB>0.25</SUB>Pr<SUB>0.1</SUB>O<SUB>2</SUB> solid solution.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-5/jp207107j/production/images/medium/jp-2011-07107j_0007.gif'></P>
Chemical synthesis and characterization of CexZr1-xO2 powders by a modified solgel method
D.Hari Prasad,이종호,이해원,김병국,박종성 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.6
CexZr1-xO2 (x = 1, 0.7, 0.4, 0.2, 0) solid solution powders were successfully synthesized by a modified sol-gel method using a simple metal nitrate precursors as sources for cerium and zirconium which do not contain any hazardous and explosive precursor materials. X-ray diffraction (XRD) and Raman spectroscopy analyses revealed the formation of a solid solution depending on the ratio of the two oxides. In the modified sol-gel method, the composition range of the solid solution was wider than that from other methods. When the content of ZrO2 in the compound of CexZr1-xO2 was increased, the crystal structures were maintained as the cubic fluorite structures up to 60mol% of ZrO2 and the cubic phase was still predominant upto 80 mol% of ZrO2. A decrease in the crystallite size and an increase in the BET surface area were observed along with an increase of the Zr content in CexZr1-xO2 solid solutions. The powder morphologies were also investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis.
Ahn, Kiyong,Yoo, Dong Su,Prasad, D. Hari,Lee, Hae-Weon,Chung, Yong-Chae,Lee, Jong-Ho American Chemical Society 2012 Chemistry of materials Vol.24 No.21
<P>We combined first-principles calculations with several experimental studies to investigate the complex role for high oxygen storage capacity (OSC) in multivalent Pr-doped ceria. TPR and Raman spectra were measured for confirming oxygen vacancy concentration and oxygen mobility. The coordination number was fitted via EXAFS spectra, and it was the correlated DFT calculation that has been corrected as effective <I>U</I> (5.3 eV) to well express the reducing state (4+ → 3+) for both Ce and Pr elements. In our study, when Pr is incorporated into pure ceria, Pr<SUP>3+</SUP> and Pr<SUP>4+</SUP> ions are incorporated as majority and minority ions, respectively. Pr<SUP>3+</SUP> ions play a key role to create oxygen vacancies and induce a local distortion, which improves oxygen mobility, and Pr<SUP>4+</SUP> can contribute to diminishing reduction energy and a respectable OSC via the formation of an additional redox couple.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2012/cmatex.2012.24.issue-21/cm3022424/production/images/medium/cm-2012-022424_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm3022424'>ACS Electronic Supporting Info</A></P>
Ahn, Kiyong,Chung, Yong-Chae,Oh, Jin Hee,Prasad, D Hari,Kim, Hyoungchul,Kim, Hae-Ryoung,Son, Ji-Won,Lee, Hae-Weon,Lee, Jong-Ho American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.7
<P>In the present study, the catalytic partial oxidation of methane (CPOM) over various active metals supported on CeO2 (M/CeO2, M = Ir, Ni, Pd, Pt, Rh and Ru) has been investigated. The catalysts were characterized by X-ray diffraction (XRD), BET surface area, H2-temperature programmed reduction (H2-TPR), CO chemisorption and transmission electron microscope (TEM) analysis. Ir/CeO2 catalysts showed higher BET surface area, higher metal dispersion, small active metal nano-particles (approximately 3 nm) than compared to other M/CeO2 catalysts. The catalytic tests were carried out in a fixed R(mix) ratio of 2 (CH4/O2) in a fixed-bed reactor, operating isothermally at atmospheric pressure. From time-on-stream analysis at 700 degrees C for 12 h, a high and stable catalytic activity has been observed for Ir/CeO2 catalysts. TEM analysis of the spent catalysts showed that the decrease in the catalytic activity of Ni/CeO2 and Pd/CeO2 catalysts is due to carbon formation whereas no carbon formation has been observed for Ir/CeO2 catalysts.</P>