• Membrane Journal
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• v.34 no.2
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• pp.154-162
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• 2024

Anion exchange membranes (AEMs) are essential components in water electrolysis systems, serving to physically separate the generated hydrogen and oxygen gases while enabling the selective transport of hydroxide ions between electrodes. Key characteristics sought in AEMs include high ion conductivity and robust chemical and mechanical stability in alkaline. In this study, quaternized Poly(terphenyl piperidinium)/cellulose nanocrystals (qPTP/CNC) mixed matrix membrane was fabricated. The polymer matrix, PTP, was synthesized via super-acid polymerization, known for its excellent ion conductivity and alkaline durability. The qPTP/CNC membrane showed a dense and uniform morphology without significant voids or large aggregates at the polymer-nanoparticle interface. The qPTP/CNC membrane containing 2 wt% CNC demonstrated a high ion exchange capacity of 1.90 mmol/g, coupled with low water uptake (9.09%) and swelling ratio (5.56%). Additionally, the qPTP/CNC membrane showed significantly lower resistance and superior alkaline stability (384 hours at 50℃ in 1 M KOH) compared to the commercial FAA-3-50 membrane. These results highlight the potential of hydrophilic additive CNC in enhancing ion conductivity and alkaline durability of ion exchange membranes.

• Journal of Magnetics
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• v.11 no.1
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• pp.30-35
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• 2006

A thorough study about the influences of Mn substitution for Fe on the microstructure and magnetic characteristics of $Fe_{73.5-x}Mn-{x}Si_{13.5}B_{9}Nb_{3}Cu_1$ (x = 1, 3, 5) alloys prepared by the melt-spinning technique has been performed. Nanocomposites composed of nanoscale $(Fe,Mn)_{3}Si$ magnetic phase embedded in an amorphous matrix were obtained by annealing their amorphous alloys at $535^{\circ}C$ for 1 hour. The addition of Mn causes a slight increase in the mean grain size. The Curie temperatures of the initial amorphous phase and of the nanocrystals phase decreased, while the Curie temperature of the remaining amorphous phase remained nearly constant with increasing Mn content. Soft magnetic properties of the crystallized samples have been significantly improved by a proper thermal treatment. Accordingly, the giant magnetoimpedance effect is observed and ascribed to the increase of the magnetic permeability, and the decrease of the coercivity of the samples. The increased magnetic permeability is resulted from a decrease in the magnetocrystalline anisotropy and saturation magnetostriction.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.100.1-100.1
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• 2010

고효율 실리콘 양자점 태양전지를 제작하기 위해 Si과 C target을 co-sputtering 방식으로 제조한 SiC matrix를 열처리하여 박막 내에 Si nanocrystal들을 생성하였다. Si nanocrystal의 특성은 다양한 요인에 영향을 받는 데 barrier 물질인 SiC matrix가 가장 큰 영향을 준다. SiC는 900도 이상에서 열처리하는 동안 Si과 C과 SiC으로 재배열 혹은 재결합하는 데 이 때 가장 작은 carbon이 빠르게 diffusion하는 현상에 의해 Si nanocrystal의 성장과 특성에 영향을 주게 된다. 이 현상을 연구하기 위해 stoichiometric SiC/Si-rich SiC/stoichiometric SiC의 3층 구조로 시료를 제작하여 이를 SIMS의 depth profiling을 통하여 열처리 전보다 열처리 후에 Si-rich SiC layer내에 carbon이 약 2~3%정도 증가한 것으로 carbon이 diffusion된 것을 확인하였다. 이 시료를 UV-VIS-NIR spectroscopy, Raman, GIXRD 등의 다양한 측정을 통하여 carbon diffusion에 의한 Si nanocrystal의 특성변화를 연구하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.77.1-77.1
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• 2010

반도체 나노 결정은 크기와 모양에 따라 다른 광학적 전기적 성질을 보이는 독특한 특성 때문에 태양전지, 발광 다이오드, 레이저, 바이오메디컬 레이블링 등에 응용될 수 있는 저가격의 차세대 광전기 재료의 개발을 위한 구조체로 각광받고 있다. 최근에는 하나의 나노 결정에 type-II band offset을 가지는 두 개의 물질을 결합한 이종접합 나노 결정체의 연구가 활발하게 진행되고 있는데, 이는 나노 결정 내에서 빛에 의해 생성된 전하들을 공간적으로 분리해 낼 수 있는 장점을 가지고 있기 때문에 태양전지나 광촉매로의 응용에 매우 유용하다. 우리는 나노 결정과 고분자 하이브리드 태양전지의 제작에 있어서 성분과 type-II 이종접합 반도체 나노 결정의 영향을 조사하기 위하여 CdSe, CdTe, type-II CdTe/CdSe tetrapod을 합성하였다. CdSe tetrapod과 P3HT의 블렌딩에 의해 만들어진 태양전지는 AM 1.5, 100mW/$cm^2$ 조건에서 1.03%의 가장 높은 변환 효율, 그리고 415nm에서 43%의 IPCE를 나타내었다. 그리고 CdTe/CdSe type-II tetrapod 이종접합과 P3HT 블렌딩으로 만들어진 태양전지는 CdTe를 이용하여 만든 태양전지에 비해 4.4배의 변환효율과 3.9배의 단락전류를 나타내었다.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.19-22
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• 2008

In recent years, much attention has been paid to "Photocatalytic oxidation" as an alternative technique, where the pollutants are degraded by UV-irradiation in the presence of a semiconductor suspension such as titanium dioxide. $TiO_2$ is the most often used photocatalyst due to its considerable photocatalytic activity, high stability, non-environmental impact and low cost. 1n this research, the photocatalytic degradation of humic acid, acetaldehyde and methylene blue in $UV/TiO_2$ systems has been stydied. The effect of calcination temperature for manufacturing of $TiO_2$ photocatalysts and type of photocatalysts on photodegradation has been investigated. Photocatalysts with various metal ions(Mn, Fe, Cu and Pt) loading are tested to evaluate the effects of metal ions impurities on photodegradation. The photodegradation efficiency with $Pt-TiO_2$ or $Fe-TiO_2$ or $Cu-TiO_2$ is higher than Degussa P-25 powder. However, the photodegradation efficiency with $Mn-TiO_2$ is lower than Degussa P-25 powder. The photocatalytic properties of the nanocrystals were strongly dependent upon the crystallinity, particle size, standard reduction potential of various transition metal and electronegativity of various transition metal. As a result photocatalysts with various metal ion loading evaluated the effect of photodegradation.

• Advances in nano research
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• v.2 no.3
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• pp.157-172
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• 2014

The three-dimensional Nano-Electronic Modeling toolkit (NEMO 3-D) is an open source software package that allows the atomistic calculation of single-particle electronic states and optical response of various semiconductor structures including bulk materials, quantum dots, impurities, quantum wires, quantum wells and nanocrystals containing millions of atoms. This paper, first, describes a software module introduced in the NEMO 3-D toolkit for the calculation of electronic bandstructure and interband optical transitions in nanowires having wurtzite crystal symmetry. The energetics (Hamiltonian) of the quantum system under study is described via the tight-binding (TB) formalism (including $sp^3$, $sp^3s^*$ and $sp^3d^5s^*$ models as appropriate). Emphasis has been given in the treatment of surface atoms that, if left unpassivated, can lead to the creation of energy states within the bandgap of the sample. Furthermore, the developed software has been validated via the calculation of: a) modulation of the energy bandgap and the effective masses in [0001] oriented wurtzite nanowires as compared to the experimentally reported values in bulk structures, and b) the localization of wavefunctions and the optical anisotropy in GaN/AlN disk-in-wire nanowires.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.267.2-267.2
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• 2016

Semiconductor photo-catalysis offers the potential for complete removal of toxic chemicals through its effective and broad potential applications. Various new compounds and materials for chemical catalysts were synthesized in the past few decades. As one of the most important II-VI group semiconductors, zinc sulfide (ZnS) with a wide direct band gap of 3.8 eV has been extensively investigated and used as a catalyst in photochemistry, environmental protection and in optoelectronic devices. In this work, the ZnS films and nanostructures have been successfully prepared by wet chemical method. We show that the agglomerates with four successive scales are always observed in the case of the homogeneous precipitation of zinc sulfide. Hydrodynamics plays a crucial role to determine the size of the largest agglomerates; however, other factors should be invoked to interpret the complete structure. In addition, studies of the photocatalytic properties by exposure to UV light irradiation demonstrated that ZnS nanocrystals (NCs) are good photo-catalysts as a result of the rapid generation of electron-hole pairs by photo-excitation and the highly negative reduction potentials of excited electrons. A combination of their unique features of high surface-to volume ratios, carrier dynamics and rich photo-catalytic suggests that these ZnS NCs will find many interesting applications in semiconductor photo-catalysis, solar cells, environmental remediation, and nano-devices.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.386-388
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• 2009

차세대 에너지로 연료전지가 각광을 받고 있는 현재, 세계 각국에서는 연료전지의 상용화를 위해 노력하고 있다. 그러나 촉매분야에서 백금계 촉매의 사용량의 문제에 따른 매장량 한계점과 귀금속이라는 문제점이 존재하기 때문에 이에 대하여 대책강구가 필요한 시점이다. 이에 백금 촉매의 활성을 증대하고자 나노 크기의 제어 연구가 진행되고 있다. 또한, 촉매의 구조적인 면에 따라 촉매의 활성이 달라지는 점을 착안하여 백금계의 나노 형상 조절 연구와 백금계 촉매를 대체할 비백금계의 촉매 개발 연구가 활발히 진행되어지고 있다. 이에 본 연구는 백금계 촉매 중 Pd을 polyol process에 의한 나노 형상 조절을 통하여 단위 질량당(or 단위 부피당) 촉매의 활성을 높이고자 하였다. Polyol process에서는 환원제, 계면활성제, 온도, 시간, 기타 첨가제에 따라 나노 형상이 다르게 조절되는데, 이에 계면활성제로 PVP를 사용하고, 반응속도 및 형상조절을 위해 다양한 첨가제를 이용하여 polygonal Pd NPs을 형성하였다. 본 나노 형상 조절에서는 첨가제와 온도가 가장 큰 영향을 미치는 요인으로 착안하여 그에 따른 polygoanl Pd NPs의 사이즈 조절을 통해 전기화학 특성이 차이의 연구에 중점을 두었다. 이에 따라 나노 형상 조절이 된 Pd촉매를 이용하여 상용화된 촉매(Pd/C(XC-72R))에 비하여 전기화학적인 특성의 차이와 Pd 촉매의 촉매적 특성의 효과를 보고자 한다.

• Advances in nano research
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• v.5 no.3
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• pp.203-214
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• 2017

In this study we present the reaction mechanism of $Cu_2ZnSnSe_4$ (CZTSe) nanoparticles synthesized by microwave-assisted chemical synthesis. We performed reactions every 10 minutes in order to identify different phases during quaternary CZTSe formation. The powder samples were analyzed by x-ray diffraction (XRD), Raman spectroscopy, energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results showed that in the first minutes copper phases are predominant, then copper and tin secondary phases react to form ternary phase. The quaternary phase is formed at 50 minutes while ternary and secondary phases are consumed. At 60 minutes pure quaternary CZTSe phase is present. After 60 minutes the quaternary phase decomposes in the previous ternary and secondary phases, which indicates that 60 minutes is ideal reaction time. The EDS analysis of pure quaternary nanocrystals (CZTSe) showed stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. In conclusion, the evolution pathway of CZTSe synthesized by this novel method is similar to other synthesis methods reported before. Nanoparticles synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.433-440
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• 2005

The hydrogen sorption speed of $Zr_{57}V_{36}Fe_7$ nanocrystalline and amorphous alloys was evaluated at room temperature. Nanocrystalline alloys of $Zr_{57}V_{36}Fe_7$ were prepared by planetary ball milling. The hydrogen sorption speed of nanocrystalline alloys was higher than that of the amorphous alloy. The enhanced sorption speed of nanocrystalline alloys was explained in terms of surface oxygen stability which has been known to retard the activation of amorphous alloys. The retardation can be reduced by formation of nanocrystals, which results in the observed increase in sorption properties.