• Analytical Science and Technology
• /
• v.13 no.4
• /
• pp.534-538
• /
• 2000

The title compound, $[Co(H_2O)_6](CH_3C_6H_4SO_3)_2$, has been prepared and characterized by X-ray crystallography. The crystal structure of the compound demonstrates a layered material constituted by hexaaquacobalt (II) cations and p-toluenesulfonate anions. Geometrical environment of the cobalt atom is octahedrally coordinated by water molecules. The p-toluenesulfonate anions are arranged with the sulfonate groups turned toward opposite side of the layer, alternately. The layered structure is stabilized by the hydrogen bondings between the ligated water molecules and the anionic sulfonate oxygen atoms.

• Korea-Australia Rheology Journal
• /
• v.19 no.1
• /
• pp.1-5
• /
• 2007

By combining ultrasonic energy which is essential for the chain scission of polymer molecules and a multifunctional agent (MFA) having double bonds at its ends, we were able to modify the molecular structure of polycarbonate (PC) from linear to a branched structure during melt processing. The three double bonds in chain ends of MFA were expected to act as sites for trapping macroradicals of PC during the course of ultrasound-assisted mixing process. The transformation of molecular structure of PC was confirmed by the measurements of rheological properties of the modified PC. After the ultrasonic irradiation of PC together with MFA, increase in complex viscosities and shear-thinning behavior were observed. The Cole-Cole plot and measurement of extensional viscosities revealed the characteristic features of branched structure with well-defined extensional behavior which is comparable to that of a commercial branched PC.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.9
• /
• pp.2684-2688
• /
• 2014

Two two-dimensional cyanide- and phenoxo-bridged heterometallic M(II)-Mn(III) (M = Ni, Pd) coordination polymers $\{[Mn(saltmen)]_4[Ni(CN)_4]\}(ClO_4)_2{\cdot}CH_3OH{\cdot}H_2O$ (1) and $\{[Mn(saltmen)]_4[Pd(CN)_4]\}(ClO_4)_2{\cdot}CH_3CN{\cdot}H_2O$ (2) ($saltmen^{2-}$ = N,N'-(1,1,2,2-tetramethylethylene)bis(salicylideneaminato)dianion) have been obtained by using $K_2[M(CN)_4]$ as building blocks and a salen-tpye Schiff-base manganese(III) compound as assembling segment. Single X-ray analysis reveals their isostrutural cyanide-bridged $MMn_4$ pentanuclear cationic structure. The four Schiff base manganese units of the pentanuclear entity are self-complementary through the phenoxo oxygen atoms from the neighboring complex, therefore forming cyanide- and phenoxo-bridged 2D sheet-like structure. Investigation over magnetic susceptibilities reveals the overall ferromagnetic coupling between the adjacent Mn(III) ions bridged by the phenoxo oxygen atoms with J = 2.13 and $2.21cm^{-1}$ for complexes 1 and 2, respectively.

• Carbon letters
• /
• v.12 no.1
• /
• pp.21-25
• /
• 2011

A novel electrode for an NO gas sensor was fabricated from electrospun polyacrylonitrile fibers by thermal treatment to obtain carbon fibers followed by chemical activation to enhance the activity of gas adsorption sites. The activation process improved the porous structure, increasing the specific surface area and allowing for efficient gas adsorption. The gas sensing ability and response time were improved by the increased surface area and micropore fraction. High performance gas sensing was then demonstrated by following a proposed mechanism based on the activation effects. Initially, the pore structure developed by activation significantly increased the amount of adsorbed gas, as shown by the high sensitivity of the gas sensor. Additionally, the increased micropore fraction enabled a rapid sensor response time due to improve the adsorption speed. Overall, the sensitivity for NO gas was improved approximately six-fold, and the response time was reduced by approximately 83% due to the effects of chemical activation.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1893-1895
• /
• 2001

In this paper, novel release technique using wet etch is proposed. The results of this technique and the results of SAMs (Self-Assembled monolayers) coated after release using this technique are compared. Fabricated structure have 100 um in width and experimental length is from 100 um to 1 mm. Thickness of aluminum sacrificial layer is 2 um and structure thickness is 2.5 um. Cantilevers and bridges are fabricated with electroplated gold and silicon nitride deposited on substrate. An aluminium sacrificial layer was evaporated thermally and removed in various wet etching solutions. Detachment length of cantilever is 200 um and detachment length of bridge is 1 mm after isooctane rinsing. And the SAMs coating condition which is appropriate for gold and nitride are studied respectively.

• The Korea Journal of Herbology
• /
• v.31 no.5
• /
• pp.25-39
• /
• 2016

Objectives : Atractylodes rhizomes, which have been widely used to treat gastrointestinal disorders, consist of numerous chemical compounds. Polyacetylenes are the parts of characteristic compounds of importance required to understand the therapeutic properties of Atractylodes rhizomes. It is necessary to understand the physicochemical and pharmacological properties of polyacetylenes in the Atractylodes rhizomes.Methods : The literatures from 1970 to January 2016 were searched using Korean and international electronic databases. The chemical structures of polyacetylenes were drawn by structure-drawing software.Results : The reported polyacetylenes were classified by their chemical skeletons and original resources, and their physicochemical and pharmacological features were discussed. Polyacetylenes with skeletal moieties were reported, such as diene-diyne types (two double and two triple carbon-bonds), triene-diyne types (three double carbon bonds and two triple carbon bonds), and monoene-diyne types (one double carbon bonds and two double carbon bonds), with various functional groups. Atractylodin was most frequently reported from many Atractylodes species. Atractylodin-related polyacetylenes showed chemical instability in both high and freezing temperatures. Processing of the Atractylodes rhizomes by stir-frying with bran could affect the contents of polyacetylenes and their bioavailability in vivo. Several polyacetylenes showed structure-related anti-inflammatory activities and gastrointestinal activities.Conclusion : Polyacetylene compounds in Atractylodes rhizomes were based on three chemical backbones and showed diverse physicochemical and pharmacological features. The present study provides structural, physicochemical, and pharmacological information of polyacetylene from Atractylodes rhizomes. This information provides fundamental data for further research.

• Journal of the Korean Applied Science and Technology
• /
• v.24 no.1
• /
• pp.67-73
• /
• 2007

Methane combustion over perovskite catalysts was investigated. For the preparation of catalysts, Co, Mn, Fe, and Ni were used as B-site components of the perovskite catalysts $(ABO_3)$ and La was used as A-site component. The effect of calcination temperature on methane combustion and perovskite structure was also investigated. The structure of perovskites, surface area, and adsorbed oxygen species were tested with XRD, BET apparatus, and $O_2-TPD$, respectively. The formation of perovskite structure was affected by the calcination temperature. The catalyst desorbing oxygen at a lower temperature showed better activity for the methane combustion, therefore, the oxygen species desorbing at lower temperatures is responsible for the methane combustion.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.12
• /
• pp.1009-1016
• /
• 2007

Numerical study on preferential diffusion effects in flame structure in $CH_4-H_2$ diffusion flames is conducted with detailed chemistry. Comparison of flame structures with mixture-averaged species diffusion and suppression of the diffusivities of $H_2$ and H was made. Discernible differences in flame structures are displayed with three species diffusion models. The behaviors of maximum flame temperatures with those species diffusion models are not explained by scalar dissipation rate but by the nature of chemical kinetics. It is seen that the modifcation of flame structure is mainly due to the preferential diffusion of H2 and thereby the nature of chemical kinetics. It is also found that the behaviors of major species with the three species diffusion models are addressed to the nature of chemical kinetics, and this is evident by examining importantly contributing reaction steps to the production and destruction of those chemical species.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.8
• /
• pp.1241-1243
• /
• 2004

• Bulletin of the Korean Chemical Society
• /
• v.25 no.12
• /
• pp.1937-1940
• /
• 2004