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김치형 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.2
Uniform ZrO2 nanoballs were synthesized at 700℃ using the inverse replication method through a colloidimprintedcarbon (CIC) template. The structural, dielectric, and conducting properties of the ZrO2 nanoballs wereinvestigated and compared with those of ZrO2 film prepared by sol-gel method and powdered ZrO2 chemical. Boththe monoclinic and cubic phases were found in the ZrO2 balls and film but the ZrO2 chemical showed a monoclinicphase, where the cubic structure is known to be formed at above 2,300℃. ZrO2 nanoballs showed the lowerdielectric property of k = 21.2 at 1 MHz because the 8-coordinated cubic phase in the ZrO2 nanoball produced lowerpolarization than the polarization of the 7-coordinated monoclinic ZrO2 chemical (k = 23.6). The dielectric stabilitywas maintained in each ZrO2 ball, film, and chemical under the applied forward and reverse voltage range (-5 to +5V) at 1 MHz. The ionic conductivities were 7.86 × 10-8/Ω·cm for ZrO2 nanoballs, 3.29 × 10-8 /Ω·cm for ZrO2 chemical,and 6.70 × 10-5/Ω·cm for the thickness of 1,053 nm ZrO2 film at room temperature with the electronic contributionbeing less than 0.006%.
김치형 청주대학교 산업과학연구소 2008 産業科學硏究 Vol.25 No.2
It is very difficult to treat the powder of mesoporous carbon replica, especially in measuring its electric property. The carbon power loses its compactness totally after the carbon pellet is annealed under inert nitrogen atmosphere. A new cell and an apparatus were designed for the electric measurement of mesoporous carbon replica. The powder sample, which is added into the tube-shaped quartz cell, can be compacted at constant pressure and kept its cylindrical shape from the designed apparatus. Two metal rods that work as electrodes entered both ends of the quartz tube, which made two- and four-probe electric measurements possible. The assembly is simple, easy to handle, costless, and semi-permanently useful. In addition, the designed cell and assembly can be applied on any powder samples that cannot be formed to dense pellets under the sintering conditions.
역MSU-H 구조를 가진 탄소화물과 Polypyrrole의 복합체에서 전기전도 활성화 에너지 및 등가회로에 관한 연구
김치형 청주대학교 2011 産業科學硏究 Vol.29 No.1
Although the electric conductivites of polypyrrole-intercalated composites increase as the temperature rises, their activation energies needed for conductivity go up with the increase of temperature and the augmentation of the intercalating ratio of polypyrrole to the three-dimensional mesopores of carbon replica, CMSU-H. The corresponding equivalent circuit represented by using the simplified resistance and capacitance elucidates the reduction of conductivity with the increment of polypyrrole contribution of the composite.
Graphitic Mesostructured Carbon from an Aliphatic Hydrocarbon Precursor
김치형,오데레사 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.9
A mesostructured form of carbon was fabricated from a template of mesostructured silica by using pentane, an aliphatic hydrocarbon precursor. To synthesize the mesostructured silica, a buffered (pH of 6.5) mixture of nonionic Pluronic P123 surfactant, sodium silicate, and acetic acid were used. The impregnated silica with Fe(CO)5 (wt 5%) and pentane was placed in a quartz tube, treated with pentane vapor at 800 °C for two hours to synthesize the mesostructured carbon. The XRD patterns of the carbon replica in the low/wide angle regions, its TEM images, and nitrogen adsorption-desorption isotherm revealed that the long-range framework order of mesostructure with the pore size centered on 2.8 nm was maintained to some extent mainly due to some portions of mesophase carbon that work as a support to fix the hexagonal frameworks by anchoring on the pore surface with an improved graphitic character. The dc conductivity of the mesostructured carbon in pressed powder form at 6.0 MPa was 2.08 S/cm.
김치형 청주대학교 산업과학연구소 2006 産業科學硏究 Vol.23 No.2
The carbon replica synthesized with the precursors, sucrose or phenol/aldehyde, using the silica MSU-H as a template were treated at 800℃ and 1000℃. According to the x-ray, nitrogen adsorption-desorption isotherm, and thermal analysis, the carbon treated at higher temperature showed higher thermal stability. The carbon replica synthesized with the sucrose was less stable thermally and less dense by producing more textural porosity with smaller pore size than the replica fabricated with the phenol/aldehyde.
김치형 청주대학교 산업과학연구소 2019 産業科學硏究 Vol.37 No.1
Hexagonally mesostructured SiC/cristobalite(SiO2) was synthesized though a diffusion reaction at the contact surface between silica and carbon composite at 1200°C in Ar gas and at 600°C in air, where SiC is coated on the wall surface of cristobalite frame and can be applied as a membrane or a molecular sieve due to its mechanical strength, uniform pore size, thermal shockand corrosion-resistant. Of the two carbon sources, sucrose and phenol, the latter showed a higher pore volume/surface area and a larger pore size of 5.3 nm, showing that the pore size can be controlled depending on a carbon source, reaction time, and temperatur
Mesostructure Replica의 탄소 Source로서 Sucrose, Phenol 및 Pluronic P123의 특성비교
김치형 청주대학교 2013 産業科學硏究 Vol.31 No.1
The properties of carbon replica synthesized with the precursors, sucrose, phenol, and pluronic p123 using the silica MSU-H as a template were investigated by x-ray, infrared, reflectance, nitrogen adsorption-desorption isotherm, and electric conductivity. Three C replicas showed amorphous phase, graphitic C=C stretching with lower reflectance and semiconducting electric property compared with graphite. Among the three C replicas, c-p123 showed graphitic C=C stretching the most, the lowest reflection and pore volume including micropores, and the highest electric conductivity.
Mesostructured Carbon의 제조를 위한 탄화수소 Precursor반응에서 촉매의 역할
김치형 청주대학교 2014 産業科學硏究 Vol.31 No.2
For the preparation of mesostructured carbon replica, H2SO4 was used as a catalyst on the precursors, sucrose, naphthalene, antracene, and pyrene. The H2SO4 eliminated H2O from sucrose producing carbon, and from acetone solvent with sulfonation forming the propylene system. The H2SO4 also sulfonated naphthalene, antracene, and pyrene creating ethylene and propylene systems. The Fe(CO)5 pyrolyzed into Fe and CO reacted with benzene and broke C-H bonds to generate carbon. The Fe surface provided catalytic sites to break the C-H bonds in benzene.
Polyurethane Elastomer Film의 두께변화에 따른 유전성 및 그 완화에 관한 연구
김치형 청주대학교 2018 産業科學硏究 Vol.35 No.2
Although the dielectric transitions of three polyurethane films (thickness = 2.2 mm, 381 and 41 μm) occurred at a similar Tg along with increases in dielectric constants and losses, the film thickness of 381 μm showed a dielectric constant higher than those of the other films. Based on the analyses of dielectric relaxations using Cole-Cole equation, its larger dielectric distribution (β =0.16) and shorter relaxation time (τ= 0.0008 s) come from loose arrangement of polymer chains, resulting in a less depressed dielectric relaxation compared with the other films.