• Journal of the Korean Applied Science and Technology
• /
• v.29 no.3
• /
• pp.466-472
• /
• 2012

Visible-light-responding photocatalysts, $N-TiO_2$, were prepared by nitrogen doping onto $TiO_2$. The crystalline structure and morphology, doping state of the prepared photocatalysts were characterized by XRD, FE-SEM, and XPS. The activity of the prepared photocatalysts was examined by the decomposition of methyleneblue. The prepared catalysts were anatase type and the crystallinity was increased with pH. The particle sizes of the prepared catalysts were 5.42, 5.99, 7.58 nm at pH 2.2, 4.7, 9.0, respectively. The particle sizes of the prepared catalysts were slightly increased with pH. The activity of the photocatalysts was directly proportional to the crystallinity of the catalysts. $N-TiO_2$ prepared by nitrogen doping onto $TiO_2$ showed activity under visible light. The doped nitrogen was located not in the lattice but on the surface.

• Clean Technology
• /
• v.17 no.2
• /
• pp.142-149
• /
• 2011

The adsorption and desorption behaviors of NO and $N_2O$ over two mixed oxide catalysts, AlCoPd (1/1/0.05) and AlCoFe (1/1/2), have been investigated for the lean $NO_x$ trap applications. The catalysts showed good adsorption capabilities for NO and $N_2O$ without needing oxidation step. The adsorption decreased a lot when they are co-adsorbed with oxygen. While NO kept high adsorbability and selectivity with respect to oxygen, those of $N_2O$ decreased sharply. From the TPD results, NO and $N_2O$ are considered to decompose into nitrogen and oxygen in the higher temperature range and the oxygen seems to be strongly attached to the catalysts even at high temperature.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.264-264
• /
• 2011

Poly [(N, N'-oxydiphenylene) pyromellitimide], polyimide (PI) film은 기계적 강도가 매우 우수하고 열적, 화학적 안정성이 뛰어난 재료로서 전자제품의 소형화, 경령화, 고성능화를 위한 차세대 flexible electronic device에 적용하기 위하여 많은 연구가 진행되고 있다. 그러나 PI의 특성상, 매우 낮은 표면에너지로 인해 금속과의 접촉력이 좋지 않은 단점을 가지고 있다. 본 연구에서는, 금속박막과 PI film 과의 접촉력을 증가시키기 위해 remote-type modified dielectric barrier discharge (DBD) module을 이용하여 대기압 플라즈마 표면처리를 하였다. 실험에 사용된 gas composition은 각각 $N_2$/ He/ $SF_6$, $N_2$/ He/ $O_2$, $N_2$/ He/ $SF_6$/ $O_2$, $N_2$/ He/ $SF_6$/ $O_2$ 이다. $N_2$/ He/ $SF_6$/ $O_2$ gas composition을 이용하여 PI 표면을 플라즈마 처리한 경우, C=O 결합이 PI film 위에 생성됨으로써, 접촉각이 매우 낮게 형성됨을 관찰할 수 있었다. 이와는 반대로 $N_2$/ He/ $SF_6$ gas composition 을 사용하였을 경우에는 C-Fx 화학적 결합이 생성되기 때문에 가장 높은 접촉각이 형성됨을 관찰할 수 있었다. 특히, $N_2$ (40 slm)/ He (1 slm)/ $SF_6$ (1.2 slm) gas composition에 $O_2$ gas를 0.2 slm부터 1.0 slm까지 변화시켜가며 PI film 표면을 처리한 결과, $O_2$ gas를 0.9 slm 첨가하였을 때, 가장 낮은 $9.3^{\circ}$의 접촉각을 얻을 수 있었다. 이는 0.9 slm의 $O_2$ gas를 첨가하였을 때, 가장 많은 양의 $O_2$ radical이 생성되기 때문에 많은 양의 C=O 결합이 생성되기 때문이다. 최적화된 $N_2$ (40 slm)/ He (1 slm)/ $SF_6$ (1.2 slm)/ $O_2$ (0.9 slm) gas composition 조건에서 Ag film과 PI film과의 접촉력을 관찰할 결과, 111 gf/mm를 얻을 수 있었다.

• Journal of the Korean Chemical Society
• /
• v.55 no.2
• /
• pp.199-203
• /
• 2011

The title one-dimensional hydrogen-bonded coordination compound $[Cu^{II}(C_{13}H_{17}N_3OBr)(C_8H_5O_4)]{\cdot}2H_2O.CH_3OH$ has been synthesized and characterized by single crystal X-ray diffraction study. The monomeric unit contains a square-planar $Cu^{II}$ centre. The four coordination sites are occupied by a tridentate anionic Schiff base ligand (4-bromo-2-[(2-piperazin-1-yl-ethylimino)-methyl]-phenol) which furnishes an $N_2O$-donor set, with the fourth position being occupied by the oxygen atom of an adjacent terephthalate unit. Two adjacent neutral molecules are linked through intermolecular N-H---O and O-H---N hydrogen bonds and generate a dimeric pair. Each dimeric pair is connected with each other via discrete water and methanol molecules by hydrogen bonding to form a one-dimensional supramolecular network.

• Journal of Powder Materials
• /
• v.29 no.6
• /
• pp.492-498
• /
• 2022

N-doped Na₂Ti₆O₁₃@TiO₂ (denoted as N-NTO@TiO₂) composites are successfully synthesized using a simple two-step process: 1) ball-milling of TiO₂ with Na₂CO₃ followed by heat treatment at 900℃; 2) mixing of the prepared Na₂Ti₆O₁₃ with titanium isopropoxide and calcining with urea at 500℃. The prepared composites are characterized using XRD, SEM, TEM, FTIR, and BET. The N-NTO@TiO₂ composites exhibit well-defined crystalline and anatase TiO₂ with exposed {101} facets on the external surface. Moreover, dopant N atoms are uniformly distributed over a relatively large area in the lattice of the composites. Under visible light irradiation, ~51% of the aqueous methylene blue is photodegraded by N-NTO@TiO₂ composites, which is higher than the values shown by other samples because of the coupling effects of the hybridization of NTO and TiO₂, N-doping, and presence of anatase TiO₂ with exposed {101} facets.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.178-178
• /
• 2013

고체내의 결함을 분석하기 위한 장비로는 대표적으로 DLTS (deep level transient spectroscopy)를 이용하여 깊은 준위 결함의 활성화에너지를 구하는 분석법, 투과전자현미경을 이용한 박막의 결정살창 분석법, photoluminescence나 electroluminescence를 이용하여 광학적인 방법으로 결함을 분석하는 방법, 마지막으로 광전류 측정을 통하여 결함을 분석하는 방법 등이 있다. 이 중에서도 빛에 의해서 증가되는 광전류를 이용한 결함 분석 방법은 과거에는 종종 시행되어 왔으나 최근에는 거의 연구되어지고 있지 않고 있다. 고체 내의 많은 결함들이 빛에만 반응하는 결함도 있으며 전기적인 측정을 통해서만 발견되는 결함이 존재하기 때문에 모든 부분을 다 만족시키는 방법은 찾기가 힘들다고 알려져 있다. 한편, ZnO는 octahedral 구조로 공간이 비어있기 때문에 여러 가지 결함이 존재하는데, 그 중에서 valence band 바로 위 0.3~0.5 eV에 존재하는 결함 준위는 Zn 빈자리에 의한 결함으로 이론적으로만 밝혀졌을 뿐 실험적으로는 현재까지 발견되어지고 있지 않다. 본 연구에서는 광전류를 이용하여 n-ZnO/p-Si과 n-ZnO/p-GaN p-n 접합 다이오드 내의 결함에 대한 연구를 진행하였다. ZnO를 UHV 스퍼터링 방법으로 성장하였으며 ZnO의 결함의 양을 조절하기 위해 박막의 두께와 증착할 때의 기판 속도 등을 조절하였다. 이렇게 성장된 ZnO 기반의 다이오드를 광전류 측정을 이용하여 결함을 분석하였다. 실험결과 420 nm 파장의 빛을 다이오드에 주사하였을 때 광전류가 크게 증가하는 것을 확인하였으며 이것은 이론적으로만 주장되어져 왔던 Zn 빈자리 결함에 의한 것으로 판단되었다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.46-51
• /
• 1996

본 연구는 MDD(modified direct denitration)공정의 주 우라늄염인 암노늄 우라닐 나이트레이트의 화학특성을 밝히고 이들 화합물의 열분해 및 환원반응의 반응기구에 대하여 조사되었다. 암모늄 우라닐 나이트레이트는 제조 조건에 따라 N $H_4$$UO_2$N $O_3$와 (N $H_4$)$_2$$UO_2$(N $O_3$)$_4$.2$H_2O$의 두가지 형태의 복염으로 존재함이 화학 및 원소분석, X산 회절 분석, 그리고 적외선 분광분석에 의하여 확인되었다. 암모늄 우라닐 나이트레이트는 질소분위기에서 N $H_4$$UO_2$(N $O_3$)$_3$$\longrightarrow$ Amorphous $UO_3$$\longrightarrow$ a-$UO_3$$\longrightarrow$ U$_3$ $O_{8}$$\longrightarrow$ $\alpha$-U$_3$ $O_{8}$의 경로를 따라서 열분해 되며, 수소분위기에서는 N $H_4$$UO_2$(N $O_3$)$_3$$\longrightarrow$ $UO_3$$\longrightarrow$ U$_3$ $O_{8}$$\longrightarrow$ U$_4$ $O_{9}$ $\longrightarrow$ $UO_2$의 경로로 환원되었다.

• Journal of the Korean Ceramic Society
• /
• v.23 no.1
• /
• pp.44-50
• /
• 1986

Si-ZnO n-n heterojunction diodes were prespared by r.f diode sputtering of the sintered ZnO target on n-type Si single crystal wafers and their structures and electrical properties were studied. The films were grown orientedly with the c-axis of crystallites perpendicular to the substrate surface at low r.f. powder and grown to polycrystalline films with random orientation at high r. f. powder. The crystallite size increased with the increasing substrate temperture The oriented texture films only were used to prepare the photovoltaic diodes and these didoes showed the photovoltaic effect veing positive of the ZnO side for the photons in the wavelength range of 380-1450nm. The sign reversal of phootovoltage which is the property os isotype heterojunction was not observed because of the degeneration of the ZnO films. The diode showed the forward rectification when it was biased with the ZnO side positive. The current-voltage characteristics exhibited the thermal-current type relationship J∝exp(qV/nkT) with n=1.23 at the low forward bias voltage and the tunnelling-current type relationship J∝exp($\alpha$V) where $\alpha$ was constant independent of temperature at the high forward bias voltage. The crystallite size of ZnO films were influenced largely on the photovoltaic properties of diodes ; The diodes with the films of the larger crystallites showed the poor photovoltaic properties. This reason may be cosidered that the ZnO films with the large crystallites could not grow to the electrically continuous films because the thickness of films was so thin in this experiment.

• Korean Journal of Materials Research
• /
• v.25 no.10
• /
• pp.543-546
• /
• 2015

$TiO_2$ nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at $1000^{\circ}C$. The ratio of $O_2$ to $N_2$ in an ambient gas was changed to investigate the effect of the gas ratio on the growth of $TiO_2$nanowires. The oxidation process was carried out at different $O_2$/$N_2$ ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at $O_2$/$N_2$ ratios of less than 25/75. When the $O_2$/$N_2$ ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were $TiO_2$ with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of $TiO_2$were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.2
• /
• pp.267-271
• /
• 2009

The Marine Environment Protection Committee(MEPC) which is the IMO's specialized committee on marine pollution related matters deals with GHG related issues to discuss and compile possible approaches on technical, operational and market based measures to address GHG emissions from ships. The nitrous oxide($N_2O$) which remains generally in the atmosphere for around 114 years is one of the green house gases. The global warming potential of $N_2O$ is 310 times than $CO_2$ in the given period 100 years. It seems that the $N_2O$ formation is influenced by the nitrogen compound contained in the fuel which is named as "Fuel N" during the combustion process or the NOx, SOx and $H_2O$ through the emission gases before exhausted into the atmosphere. This paper has carried out an experimental study of the $N_2O$ concentration profiles by the change of $NH_3$ flows in the planner premixed combustion with using $C_3H_8$ and air.