• Korean Journal of Materials Research
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• v.22 no.6
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• pp.316-320
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• 2012

$Co_3O_4$, $Al_2O_3$ and $Co_3O_4$/$Al_2O_3$ mesoporous powders were prepared by a sol-gel method with starting matierals of aluminum isopropoxide and cobalt (II) nitrate. A P123 template is employed as an active organic additive for improving the specific surface area of the mixed oxide by forming surfactant micelles. A transition metal cobalt oxide supported on alumina with and without P123 was tested to find the most active and selective conditions as a heterogeneous catalyst in the reaction of styrene epoxidation. A bBlock copolymer-P123 template was added to the staring materials to control physical and chemical properties. The properties of $Co_3O_4$/$Al_2O_3$ powder with and without P123 were characterized using an X-ray diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), a Bruner-Emmertt-Teller (BET) surface analyzer, and $^{27}Al$ MAS NMR spectroscopy. Powders with and without P123 were compared in catalytic tests. The catalytic activity and selectivity were monitored by GC/MS, $^1H$, and $^{13}C$-NMR spectroscopy. The performance for the reaction of epoxidation of styrene was observed to be in the following order: [$Co_3O_4$/$Al_2O_3$ with P123-1173 K > $Co_3O_4$/$Al_2O_3$ with P123-973 K > $Co_3O_4$-973 K>$Co_3O_4$/$Al_2O_3$-973 K > $Co_3O_4$/$Al_2O_3$ with P123-1473 K > $Al_2O_3$-973 K]. The existence of ${\gamma}$-alumina and the nature of the surface morphology are related to catalytic activity.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.108-114
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• 2020

In this study, NH₃-selective catalytic oxidation (SCO) efficiencies according to calcination/reduction conditions were compared when preparing various Ru[1]/TiO₂ catalysts. The Ru[1]/TiO₂ red catalyst had better NH₃ conversion and NH₃ to N₂ conversion than those of Ru[1]/TiO₂ cal. Physico-chemical properties of Ru[1]/TiO₂ catalysts were confirmed by Brunauer Emmett Teller (BET), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (H₂-TPR) analyses, and the properties were shown to affect the dispersion and surface adsorption oxygen species (O_β) ratio of the active metal.

• Journal of the Korean Chemical Society
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• v.38 no.11
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• pp.833-840
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• 1994

8-Quinolinecarboxaldehyde (1) reacted with 1,5-hexadiene (2) in THF under Wilkinson's catalyst(3) and $AgBF_4(8)$ to give a mixture of 8-quinolinyl 5-hexenyl ketone (4) and 8-quinolinyl 5-hexen-2-yl ketone (9) at initial reaction stage. The reason for the formation of the branched alkenyl ketone 9 is supposed to be that the vacant coordination site, generated from Wilkinson's catalyst and $AgBF_4(8)$, makes it possible to form the 5.5 membered ring metallacycle intermediate. The higher the concentration of $AgBF_4(8)$ was used, the greater the ratio of 9 to 4 was observed. Longer reaction time and high temperature induced isomerization of 9 and 4 to 10 and 5. Especially the high reaction temperature increased the possibility of cyclization of the 5-hexenyl metal intermediate to give 8-quinolinyl cyclopentylmethyl ketone (11).

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.187-191
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• 2007

In this paper, the catalyst layer is deposited on silicon substrate using magnetron sputtering system and carbon nanotubes(CNTs) were grown in $NH_3\;and\; C_2H_2$ gas by hot-filament plasma enhanced chemical vapor deposition (HFPECVD) system. A growth temperature of carbon nanotubes was changed from $350^{\circ}C\;to\;650^{\circ}C\;by\;100^{\circ}C$. We observed the shape of CNTs by a field-emission scanning electron microscope(FE-SEM) measurement and analyzed the surface characteristic of CNTs layer by contact angle measurement. That is, the growth temperature of CNTs is the important factor leads to the variation of the properties.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.283-287
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• 2011

As the performance of microelectronic devices is improved, the use of copper as a heat dissipation member is increasing due to its good thermal conductivity. The high thermal conductivity of copper, however, leads to difficulties in the joining process. Satisfactory bonding with copper is known to be difficult, especially if high shear and peel strengths are desired. The primary reason is that a copper oxide layer develops rapidly and is weakly attached to the base metal under typical conditions. Thus, when a clean copper substrate is bonded, the initial strength of the joint is high, but upon environmental exposure, an oxide layer may develop, which will reduce the durability of the joint. In this study, an epoxy adhesive formulation was investigated to improve the strength and reliability of a copper to copper joint. Epoxy hardeners such as anhydride, dihydrazide, and dicyandiamide and catalysts such as triphenylphosphine and imidazole were added to an epoxy resin mixture of DGEBA and DGEBF. Differential scanning calorimetry (DSC) analyses revealed that the curing temperatures were dependent on the type of hardener rather than on the catalyst, and higher heat of curing resulted in a higher Tg. The reliability of the copper joint against a high temperature and high humidity environment was found to be the lowest in the case of dihydrazide addition. This is attributed to its high water permeability, which led to the formation of a weak boundary layer of copper oxide. It was also found that dicyandiamide provided the highest initial joint strength and reliability while anhydride yielded intermediate performance between dicyandiamide and dihydrazide.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.139-146
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• 2014

Sodium borohydride ($NaBH_4$) is considered as a secure metal hydride for hydrogen storage and supply. In this study, the interfacial friction of two-phase flow in the dehydrogenation of aqueous $NaBH_4$ solution in a microchannel with a hydraulic diameter of $461{\mu}m$ is investigated for designing a dehydrogenation chemical reactor flow passage. Because hydrogen gas is generated by the hydrolysis of $NaBH_4$ in the presence of a ruthenium catalyst, two different flow phases (aqueous $NaBH_4$ solution and hydrogen gas) exist in the channel. For experimental studies, a microchannel was fabricated on a silicon wafer substrate, and 100-nm ruthenium catalyst was deposited on three sides of the channel surface. A bubbly flow pattern was observed. The experimental results indicate that the two-phase multiplier increases linearly with the void fraction, which depends on the initial concentration, reaction rate, and flow residence time.

• Journal of Powder Materials
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• v.21 no.2
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• pp.119-123
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• 2014

Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

• Environmental Engineering Research
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• v.16 no.4
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• pp.187-203
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• 2011

Chlorophenols (CPs) are widely used industrial chemicals that have been identified as being toxic to both humans and the environment. Zero valent iron (ZVI) and iron based bimetallic systems have the potential to efficiently dechlorinate CPs. This paper reviews the research conducted in this area over the past decade, with emphasis on the processes and mechanisms for the removal of CPs, as well as the characterization and role of the iron oxides formed on the ZVI surface. The removal of dissolved CPs in iron-water systems occurs via dechlorination, sorption and co-precipitation. Although ZVI has been commonly used for the dechlorination of CPs, its long term reactivity is limited due to surface passivation over time. However, iron based bimetallic systems are an effective alternative for overcoming this limitation. Bimetallic systems prepared by physically mixing ZVI and the catalyst or through reductive deposition of a catalyst onto ZVI have been shown to display superior performance over unmodified ZVI. Nonetheless, the efficiency and rate of hydrodechlorination of CPs by bimetals depend on the type of metal combinations used, properties of the metals and characteristics of the target CP. The presence and formation of various iron oxides can affect the reactivities of ZVI and bimetals. Oxides, such as green rust and magnetite, facilitate the dechlorination of CPs by ZVI and bimetals, while oxide films, such as hematite, maghemite, lepidocrocite and goethite, passivate the iron surface and hinder the dechlorination reaction. Key environmental parameters, such as solution pH, presence of dissolved oxygen and dissolved co-contaminants, exert significant impacts on the rate and extent of CP dechlorination by ZVI and bimetals.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.4
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• pp.340-346
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• 2013

Study on clean and efficient utilization technology for low rank coal with high moisture content is actively ongoing due to limited reserves of petroleum and of high grade coal and serious climate change caused by fossil fuel usage. In the present study, supercritical water gasification of low rank coal was performed. With increasing reaction temperature, content of combustible gases such as $H_2$ and $CH_4$ in the syngas increased while the $CO_2$ content decreased. As the reaction pressure increased from 210 to 300 bar, the $CO_2$ content in the syngas increased while the hydrocarbon gas content decreased. The $H_2$ and $CH_4$ content in the syngas increased slightly with pressure. With the addition of Pd, Pt, and Ru catalysts, it was possible to improve the production of $H_2$. Moreover, the increase of active metal content in the catalyst increased the $H_2$ productivity. The Ru catalyst shows the best performance for increasing the $H_2$ content in the syngas, while decreasing the $CO_2$ content.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.24-34
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• 1992

Recent studies dealing with the fundamental understanding and applications of bimetallic catalysts are discussed. Bimetallic catalysts have had a major industrial impact, specifically for the reforming of petroleum naphtha, for the hydrogen reduction of carbon monoxide, and for the three way catalytic converter system. The action of the bimetallic catalysts in these reactions may be interpreted in terms of ensembles, electronic influences and surface structure. Various combinations of metal pairs have been considered in order to evaluate the role played by the added metals. For catalyst selectivity control, the possibility of surface enrichment of one element has been recognised. More generally, the influence of preparative variables on the formation of supported catalysts has been clarified, In particular by temperature programmed reduction (TPR). Information on the structure of bimetallic catalysts has been obtained with chemical probes, such as chemisorption and reaction rate measurement and physical probes, such as extended X-ray absorption fine structure (EXAFS), scanning transmission electron microscopy (STEM) and Xe-NMR.