• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4297-4303
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• 2011

Under solvent-free conditions, the synthesis of propargylic alcohols by direct addition of terminal alkynes to aldehydes promoted by ZnO as a novel, commercially, and cheap catalyst is described. Furthermore, the catalyst can be reused for several times without any significant loss of its catalytic activity.

• Clean Technology
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• v.22 no.3
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• pp.196-202
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• 2016

In this study, ceria- based catalysts were prepared for dimethyl carbonate (DMC) synthesis and reaction conditions were evaluated for finding the optimal reaction route. In order to find optimal catalysts for DMC synthesis, calcination temperature and Cu(II) impregnation amount were evaluated. The oxidative carbonylation using methanol, carbon monoxide and oxygen and the direct synthesis using methanol and carbon dioxide were introduced for producing DMC. Following the law of Le Chatelier, the dehydration reaction was applied for enhancing the reactivity (methanol conversion) as removing water during the reaction. 2-cyanopyridine, as a chemical dehydration agent, was used. In the case of the oxidative carbonylation, methanol conversion rate increased from 15.1% to 38.7% and the DMC selectivity increased from 0% to 98.8%. In the case of the direct synthesis, methanol conversion rate increased from 1.0% to 77.8% and the DMC selectivity increased from 41.2% to 100.0%.

• Fibers and Polymers
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• v.3 no.4
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• pp.147-152
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• 2002

Copper (II) salts are used as metallizing agents in the synthesis of new non-genotoxic direct dyes for cotton. Specifically, cotton fabric is dyed with non-genotoxic disazo direct dyes and then treated with copper salts. The complexes are characterized by neutron activation analysis, absorption spectrometry and standard Salmonella mammalian mutagenicity assay, and the after-treated fabrics are evaluated for lightfastness and washfastness. Direct dyes possessing ortho-propoxy and ortho'-hydroxy substituted systems formed the corresponding nonmutagenic 1:2 dye:metal complex and undergo significant improvement in lightfastness following metallization.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.291-296
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• 2018

Direct synthesis of methylchlorosilanes was developed by Rochow with addition of copper on the silicon surface as a catalyst and many research were followed. Most of research were focused on the increase of reaction activity through addition of promoters and concentrated on the increase of selectivity of DMDC. However, there are very few studies about the reaction mechanism. Although formation of DMDC was explained in literature, formation of other silanes were not mentioned at all. This reseach focused on the explanation about formation of all silanes obtained during direct reaction and TPD. Reaction paths were proposed by means of dissociative adsorption of methyl chloride and spillover of surface Cl and H. Surface silicon sites were considered as $=SlCl_2$ and $=Sl(CH_3)Cl$. The synthesis of all methylchlorosilanes were explained by the adsorption of methyl group on the silicon sites and by the surface diffusion of nearby Cl and H. The proposed reaction mechanism explains the formation of all silanes during the reaction and also during the TPD process.

• Journal of Powder Materials
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• v.17 no.5
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• pp.390-398
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• 2010

Aqueous gold nanoparticle dispersion was synthesized by chemical reduction method using diethanolamine as reducing agent and polyethyleneimine as dispersion stabilizer. The synthesis conditions for the stable dispersion of the gold nanoparticle suspension were determined by changing the amount of the reducing agent and dispersant during the wet chemical synthesis procedures. The face centered cubic lattice structure of the gold nanoparticles was confirmed by using X-ray diffraction and the morphologies of the nanoparticles were observed by transmission electron microscope. The synthesized gold nanoparticle dispersion was concentrated by evaporating the dispersion medium at room temperature followed by the addition of ethyleneglycol as humectant for the increase of the elastic properties to obtain gold nanoparticle inks for direct ink writing process. The line patterns were obtained with the gold nanoparticle inks during the writing procedures and the morphologies of the fine patterns were observed by scanning electron microscope.

• Journal of Power Electronics
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• v.18 no.1
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• pp.81-91
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• 2018

This paper proposes a double line voltage synthesis (DLVS) strategy for three-to-five phase direct matrix converters. In the proposed strategy, the input and expected output voltages are divided into 6 segments and 10 segments, respectively. In addition, in order to obtain the maximum voltage transfer ratio (VTR), the input line voltages and "source key" should be selected reasonably according to different combinations of input and output segments. Then, the corresponding duty ratios are calculated to determine the switch sequences in different segment combinations. The output voltages and currents are still sinusoidal and symmetrical with little lower order harmonics under unbalanced or distorted input voltages by using this strategy. In addition, the common mode voltage (CMV) can be suppressed by rearranging some of the switching states. This strategy is analyzed and studied by a simulation model established in MATLAB/Simulink and an experimental platform, which is controlled by a DSP and FPGA. Simulation and experimental results verify the feasibility and validity of the proposed DLVS strategy.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.344.1-344.1
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• 2016

Recently, graphene has shown great characteristic of electrical conductivity, strength, and elasticity. However, due to edge unstable and metallic properties, it is difficult to use as a semiconductor devices. The solution of such problems has been sought a way to use the boron nitride in a stacked layer structure. By graphene and boron nitride stacked layer structure on silicon substrate, the electron mobility is improved and deteriorated results in semiconductor properties. In this study, to make layered structure, we developed direct synthesis method for graphene on boron nitride. By using Raman technique, the directly stacked layer structure is in good agreement with measurements on each of the attributes.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.2
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• pp.113-122
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• 2014

The objective of the paper is to clarify a methodology based on the use of the existing component mode synthesis methods for the case of two damped substructures which are coupled through a linking viscoelastic flexible substructure and for which the structural modes with free geometrical interface are used for each main substructure. The proposed methodology corresponds to a convenient alternative to the direct use either of the Craig-Bampton method applied to the three substructures (using the fixed geometric interface modes) or of the flexibility residual approaches initiated by MacNeal (using the free geometric interface modes). In opposite to a geometrical interface which is a topological interface on which there is a direct linkage between the degrees of freedom of substructures, we consider a physical flexible interface which exists in certain present technologies and for which the general framework linear viscoelasticity is used and yields a frequency-dependent damping and stiffness matrices of the physical flexible interface.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.591-598
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• 2013

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.165-173
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• 1984

It is desirable to establish reliable synthetic methods for electro-ceramic materials. To synthesize $SrTiO_3$ in this study direct solid state reactions and wet chemical processes were used. Previous study of $SrTiO_3$ synthesis included oxalated-method($SrTiO(C_2O_4)_2$.$4H_2O$) co-precipitation$(SrCO_3+TiO(OH)_2)$ and direct solid state reaction$(SrCO_3+TiO(OH)_2)$ The methods in question lead to intermediate inclusion during the reactions and less controllable in particle sizes of $SrTiO_3$. To obtain highly pure $SrTiO_3$ so-called "direct wet process method" was added in this investigation. In the study the "direct wet process" was for the first time applied to synthesize chemically pure and fine particle $SrTiO_3$. $SrCl_2$ and $TiCl_4$<\ulcornerTEX> at KOH solution at room temperature to 10$0^{\circ}C$ precipitated $SrTiO_3$ The particle size increased as temperature increased.mperature increased.