다공성 금속-유기 골격체와 나노물질의 합성 및 가스 저장에의 응용 연구

학위논문 (박사)-- 서울대학교 대학원 : 화학부(무기화학전공), 2014. 2. 백명현.PART I. Hydrogen Storage in Metal - Organic Framework Incorporating Crown Ether Moieties: Cation Inclusion A doubly interpenetrated metal-organic framework (MOF) incorporating a 18-crown-6 ether (18C6) moiety, Zn5(μ3-OH)2(TBADB-18-Cr-6)2•4DMF]•13DMF•4H2O (SNU-200), has been synthesized. SNU-200 not only provides binding sites with various cations (K+, NH4+, methyl viologen(MV2+), and Eu3+) but also exhibits characteristic gas sorption property depending on the bound cation. Despite the inclusion of the cations, SNU-200 retains the structure and the surface areas of MOF do not decreased. The MOF undergoes single-crystal to single crystal transformations upon cation binding together with the inclusion or coordination of the counter anion in the pores or at the metal site, respectively. To investigate the effect of the crown ether moiety and metal ions incorporated in the MOF on gas sorption properties, the adsorption-desorption isotherms were measured for N2, H2, CO2, and CH4 gases at various temperatures. SNU-200 shows a higher isosteric heat (Qst) of the H2 adsorption (7.70 kJmol-1) compared to other Zn based MOFs. Among the cation inclusions, K+ is the best for enhancing the Qst of the H2 adsorption (9.92 kJmol-1) as well as the adsorption selectivity of CO2/N2 (22.6). PART II. Fabrication of Magnesium Nanocrystal in Highly Porous Materials for Hybrid Hydrogen Storage by Physi- and Chemisorption A 3D porous metal-organic frameworks, [Zn4O(atb)2]∙22DMF∙9H2O (SNU-90), have been prepared by the solvothermal syntheses from Zn(NO3)2 and aniline-2,4,6-tribenzoate (atb) ligand. SNU-90 is a non-interpenetrated (6,3)-connected net of a qom topology, similar to MOF-177 generating 3D channels. SNU-90 has Brunauer-Emmett-Teller (BET) and the Langmuir surface area of 4244 m2g-1 and 4914 m2g-1, respectively. Hexagonal-disk shaped magnesium nanocrystals of size 40 - 100 nm were embedded in a highly porous metal-organic framework, [Zn4O(atb)2] (SNU-90), where atb is aniline-2,4,6-tribenzoate, via chemical vapor deposition of Mg(cp)2 followed by thermal decomposition at 473 K under argon atmosphere. The shape and location of Mg nanocrystals were confirmed by HRTEM and tomography. Mg@MOF adsorbs hydrogen gas both by physi- and chemi- sorptions. The physisorption capacity at 77 K decreased as the amount of Mg embedded in MOF increased. However, the heat of H2 adsorption was increased from 4.55 kJmol-1 up to 11.6 kJmol-1 with increasing amount of Mg in the MOF. The hydrogen uptake capacity of the MOF at 298 K and 80 bar was also improved by the Mg nanocrystals from 0.45 wt% to 0.54 wt%. The Mg nanocrystals embedded in the MOF lowered the chemisorption temperature of hydrogen to 473 K, compared to 573 - 673 K for bare Mg powder of 50 - 100 µm. At 473 K and 30 bar, Mg@SNU-90 with a 10.5 wt% loaded amount of Mg chemisorbs hydrogen up to 0.71 wt%, which corresponds to 7.5 wt% of H2 adsorption in Mg alone. Highly porous covalent organic framework (Porous Aromatic Framework, PAF-1) has prepared by Ni catalyzed cross-coupling reaction of tetrakis (4-bromophenyl) methane. PAF-1 represents the diamondoid structure which consists of phenyl ring. It shows a high surface area (BET, 5640 m2g-1), exceptional thermal/ hydrothermal stability and the super hydrophobicity. The Mg nanocrystals (Mg NCs) were prepared in PAF-1 by reduction of Mg precursor that was vapor-deposited in the pore. The Mg of 11.87 wt% is included in PAF-1. The size of Mg NCs in PAF-1 is in a wide range from 17 to 400 nm, and it was characterized by HRTEM, and PXRD patterns. On exposure Mg NCs @PAF-1 to air for 10 days, the PXRD peak of Mg NCs still indicate a pure Mg peaks without any oxidation in nanosized Mg. In N2 and H2 gas sorption, as Mg incorporated in the PAF-1, surface area, pore volume, and H2 uptake capacity at 77 K and 1 atm decreased. However, the zero-coverage isosteric heats of the H2 adsorption is increased from 4.0 kJmol-1 to 5.8 kJmol-1.Abstracts i PART I. HYDROGEN STORAGE IN METAL-ORGANIC FRAMEWORK INCORPORATIONG CROWN ETHER MOIETIES: CATION INCLUSION I.1. Introduction 2 I.1.1. Synthesis of Metal-Organic Frameworks 3 I.1.1.1 Carboxylate-Based MOFs 3 I.1.2. Increase Isosteric Heat of Hydrogen Adsorption 10 I.1.2.1 Calculation of Isosteric Heat of H2 Adsorption 11 I.1.2.2. Creation of Active Open Metal Sites 14 I.1.2.3 Post – Synthetic Modifications 21 I.1.2.3.1. Ligand Functionalization 23 I.1.2.3.2 Inclusion of Metal Cation or Organic Molecules in the Frameworks 26 I.2. Experimental Section 30 I.3. Results and Discussion 38 I.4. Conclusions 57 Supporting Information 58 PART II. FABRICATION OF MAGNESIUM NANOCRYSTAL IN HIGHLY POROUS MATERIALS FOR HYBRID HYDROGEN STORAGE BY PHYSI- AND CHEMISORPTION II.1. Introduction 80 II.2. Physisorption and Chemisorption for Hydrogen Storage 82 II.3. Various Method for Preparation of Metal Nanoparticles in Metal Organic Frameworks or Covalent Organic Frameworks 83 II.3.1. Immersion of the Redox Active MOFs in Metal Salt Solution 84 II.3.2 Chemical Vapor Deposition of Organometallic Compounds Followed by Hydrogenolysis 91 II.3.3. Encapsulation of Presynthesized Metal Nanoparticles in MOFs 95 II.4. Experimental Section 96 II.5. Results and Discussion 104 II.6. Conclusions 127 Supporting Information 128 References 139 Publication 150 Abstract (in Korean) 237 Acknowledgement (in Korean) 241Docto

OFDM 시스템의 PAPR 감소 기법에 관한 연구

Thesis(doctoral)--서울대학교 대학원 :전기. 컴퓨터공학부,2006.Docto

핵자기공명 단층 촬영기를 이용한 뇌기능 연구에서 소리가 미치는 영향에 관한 연구

학위논문(석사) - 한국과학기술원 : 전기및전자공학과, 1997.2, [ v, 56 p. ]Acoustic or sound noise due to gradient pulsings has been one of the problems in MRI, both in patient scanning as well as in many areas of psychiatric and neuroscience research such as fMRI. Especially in fMRI, sound noise is one of the serious noise sources which obscures the small signals obtainable from the subtle changes occurring in oxygenation status in the cortex and blood capillaries in fMRI. Therefore, we have tested the effects of acoustic or sound noise arising in fMR imaging of the auditory, motor and visual cortices. It is known that the cerebral blood oxygenation responses to both sustained and repetitive functional activation differ profoundly between a visual and a motor paradigm. Our experimental results show that the acoustical noise effects on motor and visual responses were opposite also. During motor activity, it seems that sound noise makes the subject pay more attention to the mission, thereby resulting in increased total motor activation. For visual stimulation, however, visual stimuli can result in a diminished fMRI when loud acoustic noise exists. Two characteristic differences may be explained by the fact that the motor is self-motivated action while visual stimulation is an external driven stimulation (passive seeing). Although, the current observations are preliminary and requires more experimental confirmation, it appears that acoustic noise effects on brain functions in the motor and visual cortices have significant consequences in data observation and interpretation.한국과학기술원 : 전기및전자공학과

Influence of bone fracture incidence on the quality of pork semimembranous muscle

This study was conducted to investigate the incidence of bone-fracture from pig carcass slaughtered in eight processing plants located in Daejeon and Chungnam area, Korea, during the year 2013 and 2014, and to evaluate the quality of semimembranous muscle from bone-fractured carcasses. Twenty semimembranous muscles were collected from bone-fractured carcasses and none bone-fractured (control) ones, respectively, after storage of pig carcass at 5℃ for 24 h. The pH, cooking loss, and color of semimembranous muscle were measured as quality parameters. In total 4,865,502 of pig carcasses, the occurrence of bone fracture was 0.328% (15,975 heads) and scored the highest defect (26.31%) in total abnormal carcasses. The pH and cooking loss of semimembranous muscle from bone-fractured carcasses were significantly lower than those of control (p<0.05). L* and a* values of semimembranous muscle were not significantly different between bone-fractured carcass and control whereas that of b* values was significantly higher in bone-fractured carcass than control (p<0.05). Eight out of twenty semimembranous muscle collected from bone-fractured carcasses were confirmed as PSE whereas only one in control. In conclusion, the incidence of bone-fracture pre- and during slaughter of pig may cause serious defects in final meat quality. Therefore, the proper handling and treatment should be implicated to avoid and/or decrease the incidence of bone-fracture of pigs.N