• Journal of Powder Materials
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• v.29 no.6
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• pp.511-516
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• 2022

Electroless plating is widely utilized in engineering for the metallization of insulator substrates, including polymers, glass, and ceramics, without the need for the application of external potential. Homogeneous nucleation of metals requires the presence of Sn-Pd catalysts, which significantly reduce the activation energy of deposition. Therefore, rinsing conducted during Sn sensitization and Pd activation is a key variable for the formation of a uniform seed layer without the lack or excess of catalysts. Herein, we report the optimized rinsing process for the functionalization of Sn-Pd catalysts, which enables the uniform FeCo metallization of the glass fibers. Rinsing enables good deposition of the FeCo alloy because of the removal of excess catalysts from the glass fiber. Concurrently, excessive rinsing results in a complete removal of the Sn-Pd nucleus. Collectively, the comprehensive study of the proposed nanomaterial preparation and surface science show that the metallization of insulators is a promising technology for electronics, solar cells, catalysts, and mechanical parts.

• Current Applied Physics
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• v.18 no.12
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• pp.1528-1533
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• 2018

The trajectories of adsorption and dissociation process of $O_2$ on the Al (111) surface were studied by the spinpolarized ab initio molecular dynamics method, and the adsorption activation energy was clarified by the NEB method with hybrid functionals. Three typical dissociation trajectories were found through simulation of $O_2$ molecule at different initial positions. When vertically approaches to the Al surface, the $O_2$ molecule tends to rotate, and the activation energy is 0.66eV. If $O_2$ molecule does not rotate, the activation energy will increase to 1.43 eV, and it makes the O atom enter the Al sublayer eventually. When the $O_2$ molecules parallel approach to the Al surface, there is no activation energy, due to the huge energy released during the adsorption process.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.98-100
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• 2003

The efficiency of the adsorption of adsorbents depends on both pore size and shape. In other to adsorb hydrated ion in application of electric double layer capacitor (EDLC), mesopore is necessary[1,2]. Tamai et al.[3] reported that an increased portion of mesopore was introduced through addition of metal or organometallic compound in the precursor and following activation of the carbon fibers with steam. (omitted)

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.757-763
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• 1999

The metal specificity of D-xylose isomerase from Streptomyces rubiginosus was examined by site-directed mutagenesis. The activation constants for metal ion ($Mg^{2+},{\;}Mn^{2+},{\;}or{\;}Co^{2+}$) of wild-type and mutant enzymes were determined by titrating the metal ion-free enzyme with $Mg^{2+},{\;}Mn^{2+},{\;}and{\;}Co^{2+}$, respectively. Substitutions of amino acids either on coordinated or around the M2 site (His-22O, Asn-185, Glu-186, and Glu-221) dramatically affected the activation constants as well as activity. A decrease of metal binding affinity was most significant in the presence of $Mg^{2+}$. When compared with the wild-type enzymes, the binding affinity of H220S and Nl85K for Mg^{2+} was decreased by 10-15-fold, while the affinity for $Mn^{2+}{\;}or{\;}Co^{2+}$ only decreased by 3-5-fold. All the mutations close to the M2 site changed their metal preference from $Mg^{2+}{\;}to{\;}Mn^{2+}{\;}or{\;}Co^{2+}$. These altered metal preferences may be caused by a relatively weak binding affinity of $Mg^{2+}$ to the enzyme. Thermal inactivation studies of mutants at the M2 site also support the importance of the M2 site geometry for metal specificity as well as the thermostability of the enzyme. Mutations of other important groups hardly affected the metal preference, although pronounced effects on the kinetic parameters were sometimes observed. This study proposes that the metal specificity of D-xylose isomerase can be altered by the perturbation of the M2 site geometry, and that the different metal preference of Group I and GroupII D-xylose isomerases may be caused by nonconserved amino acid residues around the M2 site.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1920-1926
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• 2008

We investigated the C-H bond activation mechanism of aldimine by the [RhCl$(PPH_3)_3$] model catalyst using DFT B3LYP//SBKJC/6-31G*/6-31G on GAMESS. Due to their potential utility in organic synthesis, C-H bond activation is one of the most active research fields in organic and organometallic chemistry. C-H bond activation by a transition metal catalyst can be classified into two types of mechanisms: direct C-H bond cleavage by the metal catalyst or a multi-step mechanism via a tetrahedral transition state. There are three structural isomers of [RhCl$(PH_3)_2$] coordinated aldimine that differ in the position of chloride with respect to the molecular plane. By comparing activation energies of the overall reaction pathways that the three isomeric structures follow in each mechanism, we found that the C-H bond activation of aldimine by the [RhCl$(PH_3)_3$] catalyst occurs through the tetrahedral intermediate.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1500-1506
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• 2011

Tyrosinase is a widespread enzyme with great promising capabilities. The Lineweaver-Burk plots of the catecholase reactions showed that the kinetics of mushroom tyrosinase (MT), activated by $Co^{2+}$ and $Zn^{2+}$ at different pHs (6, 7, 8 and 9) obeyed the non-essential activation mode. The binding of metal ions to the enzyme increases the maximum velocity of the enzyme due to an increase in the enzyme catalytic constant ($k_{cat}$). From the kinetic analysis, dissociation constants of the activator from the enzyme-metal ion complex ($K_a$) were obtained as $5{\times}10^4M^{-1}$ and $8.33{\times}10^3M^{-1}$ for $Co^{2+}$ and $Zn^{2+}$ at pH 9 and 6 respectively. The structural analysis of MT through circular dichroism (CD) and intensive fluorescence spectra revealed that the conformational stability of the enzyme in these pHs reaches its maximum value in the presence of each of the two metal ions.

• Carbon letters
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• v.1 no.2
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• pp.69-75
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• 2000

Naphtha cracking bottom oil was reformed with heat treatment and then spun at $310^{\circ}C$. These pitch-based carbon fibers were carbonized at $1000^{\circ}C$ after oxidation at $280^{\circ}C$, for 90 min. These fibers were chemically activated with molar ratio of KOH/CF (1 : 1) at different temperatures ($250{\sim}900^{\circ}C$) for 1 hr. The process of activation was characterized with DTA, TGA, BET surface area and pore size distribution. The activation of fibers by KOH was performed by several process. One is the reduction process that carbon fiber was reacted with $K_2O$ produced from dehydration process above $400^{\circ}C$. The other is the process that $K_2CO_3$ was directly reacted with carbon fiber. At $800^{\circ}C$, the activation was performed by catalyzed mechanism that $K_2O$ was obtained from the reaction of metal potassium with $CO_2$, then was changed to $K_2CO_3$. At $870^{\circ}C$, the activation was also observed that activation mechanism was promoted by metal catalyst with $CO_2$ from decomposition of $K_2CO_3$. The specific surface area of prepared activated carbon fibers was dependent on the activation mechanism. The specific surface area was in the range of $1519{\sim}2000\;cm^3/g$ and was the largest prepared at $870^{\circ}C$. The pores developed were mostly micropores which was very narrow and uniform. The total pore volume was $0.58{\sim}0.77\;cm^3/g$.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.82-87
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• 2013

In this work, the 1L grade integrated metal DOC/DPF filter that can install in engine manifold position was developed to investigate the effect of platinum-coating amount of filter on the improvement of filter activation temperature and reduction of particulate matter (PM). This filter was installed in 2.9L CI engine which meets the EURO-4 emission regulation. Tests for PM reduction efficiency of filter were conducted under ND-13 mode with full-load test condition. It was revealed that the time to reach the activation temperature of metal filter ($280^{\circ}C$) was shorter as the amount of platinum-coating increased. This short activation time can be helpful for the reduction of CO and HC emissions during cold start condition. At the same time, PM reduced as the coating amount increased. The reduction percentage of $DOC_{40}$, $DOC_{20}$, and $DOC_0$ were 96.7% (2.34 mg/kW'h), 95.1% (3.47 mg/kW'h), and 94.5% (3.69 mg/kW'h) compared to previous result (71.4 mg/kW'h), respectively.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.617-623
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• 2002

In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{x}$ (x=0, 0.025, 0.05, 0.1), are prepared by adding the excess Zr in $MmNi_{4.5}$ $Mn_{0.5}$ / alloy for the strong resistance to intrinsic degradation. The hydrogen storage alloys of rare-earth metal such as $LaNi_{5}$ , and $MmNi_{5}$X and $MmNi_{4.5}$ /$_Mn{0.5}$ alloys which substituted La by misch metal properties were characterized as well. The hydrogen storage alloys were produced by melting each metal mixture in arc melting furnace, and the as-cast alloys were heat-treated at $1100^{\circ}C$ for 10 hr. The major elements of misch metal(Mm) were La, Ce, Pr and Nd with some impurities less than 1wt.% determined by ICP-AES. X-ray diffraction indicated that the structure for these samples was a single phase of hexagonal with $CaCu^{5}$ type. As the Zr contents increases, the activation time and the plateau pressure decrease and sloping of the plateau pressure increase. Amount of the 2nd phases increases with increase in Zr contents in $MmNi_{ 4.5}$$Mn_{0.5}$ $Zr_{0.1}$ alloy, This phenomenon indicated that $ZrNi_3$ in this phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage..

• Corrosion Science and Technology
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• v.21 no.5
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• pp.381-389
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• 2022

Cyclic Voltammetry and weight loss measurements were used to investigate corrosion prevention of tin in a 0.5M citric acid solution containing Anthocyanins extracted from grapes at various concentrations and temperatures. Results showed that the investigated chemicals, Anthocyanins extracted from grapes, performed well as tin corrosion inhibitors in 0.5M citric acid. Increasing the concentration of Anthocyanins increased their corrosion inhibition efficiencies. When the temperature dropped, their inhibition efficiencies, increased indicating that higher temperature tin dissolution predominated the adsorption of Anthocyanins at the surface of tin metal. When inhibitor concentrations were increased, their inhibition efficiencies were also increased. These results revealed that corrosion of tin metal was inhibited by a mixed type of adsorption on the metal surface. The adsorption isotherm of Langmuir governed the adsorption of Anthocyanins. Thermodynamic parameters such as the enthalpy of adsorption, the entropy of adsorption, and Gibbs free energy and kinetic parameters such as activation energy, enthalpy of activation, and entropy of activation were computed and discussed in this study.