• Journal of the Korean Magnetic Resonance Society
• /
• v.22 no.4
• /
• pp.144-148
• /
• 2018

Catalytic enzyme Pyrazinamidase (PncA) from Mycobacterium tuberculosis can hydrolyze substrate pyrazinamide (PZA) to pyrazoic acid (POA) as active form of compound. Using NMR spectroscopy, pH-dependent catalytic properties were monitored including metal binding mode during converting PZA to POA. There seems to be a conformational change through zinc binding in active site from the perturbation of peak intensities in series of 2D HSQC spectra the conformation changes through zinc binding.

• Korean Journal of Materials Research
• /
• v.19 no.6
• /
• pp.319-324
• /
• 2009

The deposition behavior and structural and magnetic properties of electroless Co-B and Co-Fe-B deposits, as well as the amorphous ribbon substrates, were investigated. These Co-based alloy deposits exhibited characteristic polycrystalline structures and surface morphology and magnetic properties that were dependent on the type of amorphous substrates. The catalytic activity sequence of the amorphous ribbon electrodes for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath that did not contain the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of the substrates. The deposition rate linearly varied against the deposition time. The initial deposition potential may have also determined the structural and magnetic properties of the deposit based on the thickness of ${\mu}m$ order. Furthermore, a basic study of the electroless deposition processes on an amorphous ribbon substrate has been carried out in connection with the structural and magnetic properties of the deposits.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.9
• /
• pp.840-845
• /
• 1996

Rate constants have been measured spectrophotometrically for the reactions of p-and m-nitrophenyl 2-thiophenecarboxylate (5a and 5b, respectively) with alkali metal ethoxides (EtO-M+) in absolute ethanol at 25.0±0.1 ℃. The reactivity of EtO-M+ exhibits dependence on the size of alkali metal ions, i.e. the reactivity of EtO-M+ toward 5a decreases in the order EtO-K+ ≥ EtO-Na+ > EtO-Li+ > EtO-, while the one toward 5b does in the order EtO-Na+ ≥ EtO-K+ > EtO-Li+ > EtO-. This result indicates that ion paired EtO-M+ is more reactive than dissociated EtO-, and alkali metal ions form complexes with the substrate more strongly at the transition state than at the ground state. The catalytic effect shown by alkali metal ions appears to be less significant in the reaction of 5 than in the corresponding reaction of 4, indicating that complexation of alkali metal ions with 5 is not as strong as the one with 4.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.213-213
• /
• 2000

Direct laser vaporization of transition-metal(Co, Ni)/graphite composite pellet produced single wall carbon naotubes(SWNT) in the condensing vapor in a heated flow cylinder-type tube furnace, Transition metal/graphite composite pellet target was made by mixing graphite, Co, and Ni in 98:1:1 atomic weight ratios, pressing the mixed powder, and curing it. The target was placed in a tube furnace maintained at 1200$^{\circ}C$ and Ar inert collision gas continuously flowed into the tube. The 2nd harmonic, 532nm wavelength light from Nd-YAG laser was used to vaporize the tube. The carbon nanotubes produced by the laser vaporization were accumulated on quartz tube wall. The raw carbon nanotube materials were purified with surfactants(Triton X-100) in a ultrasonicator. These carbon nanotubes were analyzed using SEM, XRD, and Raman spectroscopic method. The carbon nanotube growth on the Ni-patterned Si substrate was investigated by the CVD process. Transition-metal, Ni and CH4 gas were used as a catalyst and a reactant gas, respectively. The structure and the phonon frequencies of the carbon nanotubes formed on the patterned Si substrate were measured by SEM and Raman spectrometer.

• Journal of ILASS-Korea
• /
• v.18 no.4
• /
• pp.196-201
• /
• 2013

SCR(Selective Catalytic Reduction) is a major after-treatment solution to reduce NOx emission in recent diesel engines. In this study, a metal foam is applied as an alternative SCR substrate and tested in a commercial diesel engine to compared with a conventional ceramic SCR system. Basic engine test from ND-13 mode shows that a metal foam catalyst has lower NOx conversion efficiency than a ceramic catalyst especially over $350^{\circ}C$. A metal foam catalyst has characteristics of high exhaust gas pressure before a SCR catalyst and high heat transfer rate due to its material and structure. NOx conversion efficiency of a metal foam catalyst shows an increasing tendency along with the increase of exhaust gas temperature by $500^{\circ}C$. The effect of urea injection quantity variation is also remarkable only at high exhaust gas temperature.

• Carbon letters
• /
• v.6 no.2
• /
• pp.79-85
• /
• 2005

The work reported in this paper relates to preparation and characterization of carbon nanomaterials by CVD method on different substrates by decomposition of certain hydrocarbons at 550-$800^{\circ}C$ using a horizontal quartz tube reactor. Monometallic and bimetallic catalyst system of iron and nickel were used for the preparation of different carbon nanomaterials. The influence of various parameters such as substrate/catalyst preparation parameters, the nature of substrate, catalyst concentration, reaction time and temperature on the growth, yield and alignment of carbon nanotubes has been studied. The characterization of carbon nanomaterials has been carried out using SEM, TEM and TGA. The carbon nanomaterials developed were vertically aligned on a large area of flat quartz substrate.

• Proceedings of the KIEE Conference
• /
• 2005.11a
• /
• pp.191-193
• /
• 2005

This study has investigated the effects of the etching method of a Ti substrate for a metal oxide electrode on the electrochemical characteristics of the electrode. The HCl etching develops a fine and homogeneous roughness on the Ti substrate. Fabrication and material properties of the catalytic oxide electrode, which is known to be so effective to destruct refractory organics in aqueous waste, were studied. A method to enhance the fabrication reproducibility of the oxide electrode was tested for Ru, Zr, Sn oxide on the Ti substrate using SEM, XRD, Cyclic voltammetry.

• Electrical & Electronic Materials
• /
• v.16 no.9
• /
• pp.63.1-63
• /
• 2003

Catalytic chemical vapor deposition (Cat-CVD) has been developed to deposit alumina(Al$_2$O$_3$) thin films on silicon (Si) crystal using N$_2$ bubbled tir-methyl aluminium [Al(CH$_3$)$_3$, TMA] and molecular oxygen (O$_2$) as source species and tungsten wires as a catalyzer. The catalyzer dissociated TMA at approximately 600$^{\circ}C$ The maximum deposition rate was 18 nm/min at a catalyzer temperature of 1000 and substrate temperature of 800$^{\circ}C$. Metal oxide semiconductor (MOS) diodes were fabricated using gates composed of 32.5-nm-thick alumina film deposited as a substrate temperature of 400oC. The capacitance measurements resulted in a relatively dielectric constant of 7, 4, fixed charge density of 1.74*10e12/$\textrm{cm}^2$, small hysteresis voltage of 0.12V, and very few interface trapping charge. The leakage current was 5.01*10e-7 A/$\textrm{cm}^2$ at a gate bias of 1V.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.68-68
• /
• 2018

Nanoporous or nanotubular metal oxide can be fabricated by anodization of metal substrate in fluoride contained electrolytes. The approach allows various transition metals such as Zr, Hf, Nb, Ta to form highly ordered oxide nanostructures. These oxide nanostructures have various advantages such as high surface area, fast electron transport rate and slow recombination in semiconductive materials. Recently, vanadium oxide nanostructures have been drawn attentions due to their superior electronic, catalytic and ion insertion properties. However, anodization of vanadium metal to form oxide layers is relatively difficult due to ease formation of highly soluble complex in water contained electrolyte during anodization. Yang et al. reported $[TiF_6]^{2-}$ or $[BF_4]^-$ in electrolyte helps to formation of stable oxide layer [1, 2]. However, the reported approaches are very sensitive in other parameters. In this presentation, we deal with the other important key parameters to form ordered anodic vanadium oxide such as pH, temperatures and applied potential.

• Journal of Electrochemical Science and Technology
• /
• v.11 no.1
• /
• pp.92-98
• /
• 2020

SnO₂-based high-capacity anode materials are attractive candidate for the next-generation high-performance lithium-ion batteries since the theoretical capacity of SnO₂ can be ideally extended from 781 to 1494 mAh g^-1. Here 3D etched Cu foam is applied as a current collector for electron path and simultaneously a substrate for the SnO₂ coating, for developing an integrated electrode structure. We fabricate the 3D etched Cu foam through an auto-catalytic electroless plating method, and then coat the SnO₂ onto the self-supporting substrate through a simple sol-gel method. The catalytic dissolution of Cu metal makes secondary pores of both several micrometers and several tens of micrometers at the surface of Cu foam strut, besides main channel-like interconnected pores. Especially, the additional surface pores on etched Cu foam are intended for penetrating the individual strut of Cu foam, and thereby increasing the surface area for SnO₂ coating by using even the internal of Cu foam. The increased areal capacity with high structural integrity upon cycling is demonstrated in the SnO₂-coated 3D etched Cu foam. This study not only prepares the etched Cu foam using the spontaneous chemical reactions but also demonstrates the potential for electroless plating method about surface modification on various metal substrates.