• Korean Journal of Materials Research
• /
• v.20 no.3
• /
• pp.117-124
• /
• 2010

Titanium dioxide ($TiO_2$) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/$TiO_2$ composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/$TiO_2$ composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/$TiO_2$ composites. In particular, the photocatalytic activity of the Fe-CNT/$TiO_2$ composites under visible light was better than that of the CNT/$TiO_2$ composites due to the introduction of Fe particles.

• Macromolecular Research
• /
• v.15 no.3
• /
• pp.221-224
• /
• 2007

A silica-magnesium bisupport (SMB) was prepared by a sol-gel method for use as a support for a metal-locene/Ziegler-Natta hybrid catalyst. The prepared $rac-Et(Ind)_2ZrCl_2/TiCl_4$/MAO(methylaluminoxane)/SMB catalyst was applied to the copolymerization of ethylene with l-hexene using a variable triethylaluminum (TEA)/transition-metal (Ti) ratio and fixed MAO/transition-metal (Zr) ratio. The effect of the Al(TEA)/Ti ratio on the physical properties and chemical composition distributions (CCDs) of the ethylene-hexene copolymers produced by the hybrid catalyst was investigated. In the ethylene-hexene copolymers, two melting temperatures attributed to the metal-locene and Ziegler-Natta catalysts were clearly observed. The number of CCD peaks was increased from six to seven and the temperature region in which the peaks for the short chain branches of the ethylene-hexene copolymer were distributed became lower as the Al(TEA)/Ti ratio was increased from 300 to 400. Furthermore, the temperature regions corresponding to the lamellas in the copolymer became lower and those corresponding to the small lamellas in the copolymer became higher as the Al(TEA)/Ti ratio was increased from 300 to 400. In the copolymer produced with Al(TEA)/Ti = 500, however, only four CCD peaks were observed and the short chain branches were poorly distributed.

• Journal of Industrial and Engineering Chemistry
• /
• v.68
• /
• pp.187-195
• /
• 2018

$Sr_{0.92}Y_{0.08}Ti_{1-x}Ni_xO_{3-{\delta}}$ (SYTN) was investigated in the presence of $H_2S$ containing fuels to assess the feasibility of employing oxide materials as alternative anodes. Aliovalent substitution of $Ni^{2+}$ into $Ti^{4+}$ increased the ionic conductivity of perovskite, leading to improved electrochemical performance of the SYTN anode. The maximum power densities were 32.4 and $45.3mW/cm^2$ in $H_2$ at $900^{\circ}C$ for the SYT anode and the SYTN anode, respectively. However, the maximum power densities in 300 ppm of $H_2S$ decreased by 7% and by 46% in the SYT and the SYTN anodes, respectively. To enhance the sulfur tolerance and to improve the electrochemical properties, the surface of SYTN anode was modified with samarium doped ceria (SDC) using the sol-gel coating method. For the SDC-modified SYTN anode, the cell performance was mostly recovered in the pure $H_2$ condition after 500-ppm $H_2S$ exposure in contrast to the irreversible cell performance degradation exhibited in the unmodified SYTN anode.

• Korean Journal of Metals and Materials
• /
• v.50 no.3
• /
• pp.201-205
• /
• 2012

The effects of various manganese precursors for the low-temperature selective catalytic reduction (SCR) of $NO_x$ were investigated in terms of structural, morphological, and physico-chemical analyses. $MnO_x/TiO_2$ catalysts were prepared from three different precursors, manganese nitrate, manganese acetate(II), and manganese acetate(III), by the sol-gel method. The manganese acetate(III)-$MnO_x/TiO_2$ catalyst tended to suppress the phase transition from the anatase structure to the rutile or the brookite after calcination at $500^{\circ}C$ for 2 h. It also had a high specific surface area, which was caused by a smaller particle size and more uniform distribution than the others. The change of catalytic acid sites was confirmed by Raman and FT-IR spectroscopy and the manganese acetate(III)-$MnO_x/TiO_2$ had the strongest Lewis acid sites among them. The highest de-NOx efficiency and structural stability were achieved by using the manganese cetate(III) as a precursor, because of its high specific surface area, a large amount of anatase $TiO_2$, and the strong catalytic acidity.

• Journal of Magnetics
• /
• v.5 no.1
• /
• pp.16-18
• /
• 2000

The garnets $Nd_{1-x}Bi_xY_2Fe_5O_{12}$ ($\chi$=0.0, 0.25, 0.5, 0.75 and 1.0) have been studied by x-rays, electron microscopy, ferromagnetic resonance, vibrating sample magnetometer and Mossbauer spectroscopy, Ultra-fine polycrystalline cubic samples have been prepared by a melt-salt routed sol-gel method. The Mossbauer spectra consist of two sets of six-line patterns corresponding to $Fe^{3+}$ at the tetrahedral 24(d) and octahedral 16(a) sites. Magnetic hyperfine fields of $Nd_{0.5}Bi_{0.5}Y_2Fe_5O_{12}$ at 12 K are found to be 548 kOe (octahedral site) and 475 kOe (tetrahedral site), respectively, It is found that Debye temperatures for the tetrahedral and octahedral sites of $Nd_{0.75}Bi_{0.25}Y_2Fe_5O_{12}$ are $\theta_{tet}=436$ K and $\theta_{oct}=285$ K, respectively, The iron ions at both sites are highly covalent ferric. The Nel temperature decreases linearly with Bi concentration, from 630 K fur $\chi$=0.0 to 600 K for $\chi$=1.0, suggesting that the superexchange interaction for the Nd-O-Fe link is stronger than that for the Bi-O-Fe link. As a consequence, the coercivity of $Nd_{1-x}Bi_xY_2Fe_5O_{12}$ drastically decreases and the magnetization remains almost constant as x increases.

• Korean Journal of Materials Research
• /
• v.29 no.6
• /
• pp.385-391
• /
• 2019

In the present study, vanadium oxide($V_2O_5$) films for electrochromic(EC) application are fabricated using sol-gel spin coating method. In order to optimize the EC performance of the $V_2O_5$ films, we adjust the amounts of polyvinylpyrrolidone(PVP) added to the solution at 0, 5, 10, and 15 wt%. Due to the effect of added PVP on the $V_2O_5$ films, the obtained films show increases of film thickness and crystallinity. Compared to other samples, optimum weight percent(10 wt%) of PVP led to superior EC performance with transmittance modulation(45.43 %), responding speeds(6.0 s at colored state and 6.2 s at bleached state), and coloration efficiency($29.8cm^2/C$). This performance improvement can be mainly attributed to the enhanced electrical conductivity and electrochemical activity due to the increased crystallinity and thickness of the $V_2O_5$ films. Therefore, $V_2O_5$ films fabricated with optimized amount of PVP can be a promising EC material for high-performance EC devices.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.2
• /
• pp.77-81
• /
• 2019

Recently, as the problem of environmental pollution emerges, various methods of eco-friendly water treatment method are being developed. Polymer membranes, which are currently leading the market, are inexpensive, but have many problems in terms of chemical resistance and durability. Thus, ceramic membrane has been attracted great attention as high-efficiency water treatment due to excellent durability and chemical resistant. In this study, ceramic membranes were developed via pore structure, size control, and surface treatment. The pore size of the membrane was controlled through the formation of $ZrO_2$ and $TiO_2$ coating films. Tape casting and sol-gel process were used to form a ceramic coating film with nanopores on the surface of the membrane. Microstructure analysis of ceramic membrane and pore size analysis of the coating film were conducted and the change of water treatment characteristics was observed.

• Korean Journal of Medicinal Crop Science
• /
• v.27 no.2
• /
• pp.108-114
• /
• 2019

Background: Rutin is decomposed by rutin-degrading enzymes (RDE) during the processing of buckwheat groats, resulting in a decrease in rutin content and a further increase in the bitterness of processed products. Thus, the present study aimed to examine RDE activity in groats and various tissues of domestic buckwheat varieties and to develop a method to reduce the loss of rutin during the groat processing. Methods and Results: RDE activity and isozymes patterns were determined in Tartary and common buckwheat. RDE activity, measured by quercetin production rate, was 273 and $70{\mu}g/g$ fresh weight/min in mature Tartary and common buckwheat groats, respectively. A total of six RDE isozymes were detected in mature groats of Tartary buckwheat on a non-denaturing gel. In Tartary buckwheat groats, RDE activity decreased by approximately 81 or 71% with roasting or steaming for 5 min respectively. As the roasting or steaming time increased to 30 min, RDE activity decreased by over 95%. These results indicated that RDE was inactivated in groats by roasting or steaming. When untreated Tartary buckwheat groats were kneaded with powder, RDE was activated and the quercetin production rate increased by 62%. However, when roasted groats were kneaded with powder, the quercetin production rate decreased by 93%, mainly due mainly to inactivation of RDE, as indicated by a decrease in band intensities of the six isozymes. Conclusions: These results suggested that the loss of rutin, due to RDE activity during processing, may be reduced by 71 to 100% by roasting or steaming groats for 5 to 30 min, due in large part to the inactivation of RDE isozymes.

• Applied Chemistry for Engineering
• /
• v.22 no.1
• /
• pp.61-66
• /
• 2011

In this study, we prepared $TiO_2$ with the sol-gel method and controlled physico-chemical properties by a simple heat treatment. All materials were applied to photocatalytic decomposition of methylene blue and the material treated at 473 K showed the highest photocatalytic efficiency. The high performance resulted from a high adsorption amount of methylene blue due to a high surface area of $229.8m^2/g$. However, the material treated at 873 K, despite of a low surface area of $23.8m^2/g$ and a large particle size of 28.38 nm, exhibits a good photocatalytic performance due to the effect of mixed cyrstalline rutile and anatase phases formed by the high heat treatment temperature.

• Journal of the Korean Physical Society
• /
• v.73 no.10
• /
• pp.1444-1451
• /
• 2018

The surface-to-volume ratio of one-dimensional (1D) semiconductor metal-oxide sensors is an important factor for achieving good gas sensing properties because it offers a wide response area. To exploit this effect, in this study, we determined the optimal calcination temperature to maximize the specific surface area and thereby the sensitivity of the sensor. The $In_2O_3$ nanorods were synthesized by using vapor-liquid-solid growth of $In_2O_3$ powders and were decorated with the Pt nanoparticles by using a sol-gel method. Subsequently, the Pt nanoparticle-decorated $In_2O_3$ nanorods were calcined at different temperatures to determine the optimal calcination temperature. The $NO_2$ gas sensing properties of five different samples (pristine uncalcined $In_2O_3$ nanorods, Pt-decorated uncalcined $In_2O_3$ nanorods, and Pt-decorated $In_2O_3$ nanorods calcined at 400, 600, and $800^{\circ}C$) were determined and compared. The Pt-decorated $In_2O_3$ nanorods calcined at $600^{\circ}C$ showed the highest surface-to-volume ratio and the strongest response to $NO_2$ gas. Moreover, these nanorods showed the shortest response/recovery times toward $NO_2$. These enhanced sensing properties are attributed to a combination of increased surface-to-volume ratio (achieved through the optimal calcination) and increased electrical/chemical sensitization (provided by the noble-metal decoration).