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메틸피라진으로부터 시아노피라진으로의 암옥시화반응에서의 산화 바나듐 촉매에 관한 연구
권용승,박상언,이영길,Kwon Yong Seung,Park Sang-Eon,Lee Young K. 대한화학회 1990 대한화학회지 Vol.34 No.5
산화 바나듐(V$_2$O$_5$)이 알루미나에 담지된 촉매상에서 메틸피라진으로부터 시아노피라진으로의 암옥시화반응(Ammoxidation)을 연속흐름식 고정층 반응기에서 조사하였다. 알루미나에 담지된 산화 바나듐은 전처리의 환원온도에 따라 다양한 산화상태의 결정상을 형성하며, 이들 바나듐 산화물의 산화상태의 변화는 메틸피리진으로부터 시아노피라진으로의 반응활성에 영향을 준다. 알루미나에 10${\%}$ 산화 바나듐이 담지된 촉매를 600$^{\circ}C$ 수소기류하에서 2시간 환원처리하여 바나듐의 산화상태가 V$^{3+}$에 가까운, 즉 촉매상의 바나듐의 주된 결정상이 V$_2$O$_3$이며 V$_6$O$_{13}$및 V$_2$O$_4$(VO$_2$)가 공존할 때 메틸피라진으로부터 시아노피라진으로의 암옥시화반응에 최적의 반응활성과 선택도를 갖는 것으로 나타났다. The catalytic ammoxidation of methylpyrazine into cyanopyrazine over a supported vanadium oxides catalyst on ${\gamma}$-alumina was studied in a continuous-flow fixed bed reactor. Various crystalline phases of vanadium oxides were obtained depending on reduction temperatures. And also the activities for the reaction of methylpyrazine into cyanopyrazine were affected by their major oxidation states of the corresponding crystalline phases. The 10${\%}$ vanadium oxides loaded ${\gamma}$-alumina catalyst, which was reduced at 600$^{\circ}C$ under the hydrogen flow for 2 hours, showed the highest activity and the highest selectivity on cyanopyrazine in the ammoxidation of methylpyrazine.Its major crystalline phase was V$_2$O$_3$ with the presence of V$_6$O$_{13}$ and V$_2$O$_4$(VO$_2$) together. And this coexistance seemed to enhance the activity.
송유장,권용승,홍종범,민병훈,이규준,정명화,이종수,안중호 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.2
This paper reports the superconducting behavior of the tetragonal iron-chalcogenide superconductor FeSe. The electrical resistivity and the magnetic moment measurements confirmed its superconductivity with T^(zero)_c and T^(mag)_c of 9.4 K under ambient pressure. Electron probe macro analysis indicated that the sample had a stoichiometric Fe:Se ratio of 1:1. The Seebeck coefficient, which was 12.3 μV/K at room temperature, changed to a negative value near 200 K, indicating it to be a two-carrier material. Above T_c, the ρ(T) curve revealed an ‘S’ shape, and dρ(T)/dT and d^2ρ(T)/dT^2 showed two anomalous features, one near T_(an) = 30 K and the other near T^* = 110 K. The Seebeck coefficient, S(T), also displays peculiar behavior near the T_(an) and T^*. We also report a rather smaller critical current density, J_c = 10^2 ∼ 10^4 A/cm^2, compared to those observed forthe other pnictides and doped chalcogenides.
Hyung Sup Shin,Jun Kyu Jang,권용승,Ki Choong Mah 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6
Rigid gas permeable (RGP) contact lenses, based on fluorosilicone acrylate, were treated by using a plasma in air to improve surface wettability. As a function of the plasma exposure time, the wetting angles were estimated, the chemical compositions were analyzed by using X-ray photoelectron spectroscopy (XPS), and the surface morphology was observed by using atomic force microscopy (AFM). As the contact lenses were treated by the plasma, the wetting angle decreased significantly in the initial stage and decreased to 40 % of the wetting angle of the untreated lenses. The C, F, and N contents decreased significantly below 20 %, and the O and Si contents increased above 200 % on the surface. The rate of decrease of carbon was similar to the decrease in wetting angle. The number of oxygen-containing hydrophilic radicals (C-O and O-C=O) decreased because the carbons on the surface were oxidized and volatilized. The silica-like structure (SiOx, x = 1.5 ∼ 2.0) increased greatly (above 50 %), and the surface became hydrophilic. The surface roughness Rms decreased from 7 nm to about 4 nm, and the wetting angles decreased. The improved wettability of the contact lenses treated by using a plasma in air was affected more by the formation of a hydrophilic silica-like structure than by the change in surface morphology. Rigid gas permeable (RGP) contact lenses, based on fluorosilicone acrylate, were treated by using a plasma in air to improve surface wettability. As a function of the plasma exposure time, the wetting angles were estimated, the chemical compositions were analyzed by using X-ray photoelectron spectroscopy (XPS), and the surface morphology was observed by using atomic force microscopy (AFM). As the contact lenses were treated by the plasma, the wetting angle decreased significantly in the initial stage and decreased to 40 % of the wetting angle of the untreated lenses. The C, F, and N contents decreased significantly below 20 %, and the O and Si contents increased above 200 % on the surface. The rate of decrease of carbon was similar to the decrease in wetting angle. The number of oxygen-containing hydrophilic radicals (C-O and O-C=O) decreased because the carbons on the surface were oxidized and volatilized. The silica-like structure (SiOx, x = 1.5 ∼ 2.0) increased greatly (above 50 %), and the surface became hydrophilic. The surface roughness Rms decreased from 7 nm to about 4 nm, and the wetting angles decreased. The improved wettability of the contact lenses treated by using a plasma in air was affected more by the formation of a hydrophilic silica-like structure than by the change in surface morphology.