• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.309-311
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• 2005

Single crystals of the new pentanary thiophosphate, $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ has been prepared through reactions of the elements with halide fluxes. The structure of $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ has been analyzed by single crystal X-ray diffraction technique. The structure of $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ is made up of one-dimensional ${^{\infty}_1}[Nb_2PS_{10}]$ chains along the [001] direction and these chains are separated from one another by $Ag^+$ and disordered $K^+$ ions. This chain is basically built up from bicapped trigonal prismatic [Nb2S12] units and tetrahedral [PS4] groups. The [$Nb_2S_{12}$] units are connected together to form the linear chain, ${^{\infty}_1}[Nb_2S_9]$ by sharing the S-S prism edge. Short (2.885(2) $\AA$ or 2.888(2) $\AA$) and long (3.743(1) $\AA$) Nb-Nb distances are alternating along the chain, and the $S_2{^2-}]\;and\;S^{2-}$anionic species are observed. The distorted octahedral coordination around the $Ag^+$ ion can be described as [2+4] bonding interaction.

• Journal of Korean Society on Water Environment
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• v.38 no.4
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• pp.177-189
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• 2022

Nature-based Solutions (NbS) are defined as practical and technical approaches to restoring functioning ecosystems and biodiversity as a means to address socio-environmental challenges and provide human-nature co-benefits. This study reviews NbS-related literature to identify its key characteristics, techniques, and challenges for its application in climate-adaptive water management. The review finds that NbS has been commonly used as an umbrella term incorporating a wide range of existing ecosystem-based approaches such as low-impact development (LID), best management practices (BMP), forest landscape restoration (FLR), and blue-green infrastructure (BGI), rather than being a uniquely-situated practice. Its technical form and operation can vary significantly depending on the spatial scale (small versus large), objective (mitigation, adaptation, naturalization), and problem (water supply, quality, flooding). Commonly cited techniques include green spaces, permeable surfaces, wetlands, infiltration ponds, and riparian buffers in urban sites, while afforestation, floodplain restoration, and reed beds appear common in non- and less-urban settings. There is a greater lack of operational clarity for large-scale NbS than for small-scale NbS in urban areas. NbS can be a powerful tool that enables an integrated and coordinated action embracing not only water management, but also microclimate moderation, ecosystem conservation, and emissions reduction. This study points out the importance of developing decision-making guidelines that can inform practitioners of the selection, operation, and evaluation of NbS for specific sites. The absence of this framework is one of the obstacles to mainstreaming NbS for water management. More case studies are needed for empirical assessment of NbS.

• Corrosion Science and Technology
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• v.21 no.4
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• pp.250-257
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• 2022

Transition metal sulfide materials have emerged as a new anode material for Li secondary batteries owing to their high capacity and rate capability facilitated by fast Li-ion transport through the layered structure. Among these materials, niobium disulfide (NbS₂) has attracted much attention with its high electrical conductivity and high theoretical capacity (683 mAh g^-1). In this study, we propose a facile synthesis of Fe_xNbS₂/C composite via simple ball milling and heat treatment. The starting materials of FeS and Nb were reacted in the first milling step and transformed into an Fe-Nb-S composite. In the second milling step, activated carbon was incorporated and the sulfide was crystallized into Fe_xNbS₂ by heat treatment. The prepared materials were characterized by X-ray diffraction, electron spectroscopies, and X-ray photoelectron spectroscopy. The electrochemical test results reveal that the synthesized Fe_xNbS₂/C composite electrode demonstrates a high reversible capacity of more than 600 mAh g^-1, stable cycling stability, and excellent rate performance for Li-ion battery anodes.

• Analytical Science and Technology
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• v.7 no.4
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• pp.493-504
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• 1994

The morphology and structure of precipitates of formed in Nb steels were investigated using SEM, TEM and XRD. The quantitative analysis of the precipitates was performed by ICP-AES. The potentiostatic etching method was employed as an extraction method using 10% AA-methanol and 15% Na-citrate electrolytes. The two selected potentials relative to SCE(Standard Calomel Electrode), -100mV in 10% AA-methanol solution and -250mV in 15% Na-citrate solution were found to be effective for the extraction. XRD analysis showed that composition of Nb carbonitride in Nb-steel(0.01% C-0.7% Nb-0.004N) was $NbC_{0.65}N_{0.2}$.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.161-167
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• 2011

The stress-strain responses and oxidation properties of cold-rolled Zr-1.5Nb-O and Zr-1.5Nb-O-S alloys were studied. The U.T.S. (ultimate tensile strength) of cold-rolled Zr-1.5Nb-O-S alloy with 160 ppm sulfur (765 MPa) were greater than that of Zr-1Nb-1Sn-0.1Fe alloy (750 MPa), achieving an excellent mechanical strength even after the elimination of Sn, an effective solution strengthening element. The addition of sulfur increased the strength at the expense of ductility. However, the ductile fracture behavior was observed both in Zr-Nb-O and Zr-Nb-O-S alloys. The beneficial effect of sulphur on the strengthening was observed in the cold rolled Zr-1.5Nb-O-S alloys. The activation volume of cold-rolled Zr-1.5Nb decreased with sulfur content in the temperature region of dynamic strain aging associated with oxygen atoms. Insensitivity of the activation volume to the dislocation density and the decrease of the activation volume at a higher temperature where the dynamic strain aging occurs support the suggestion linking the activation volume with the activated bulge of dislocations limited by segregation of oxygen and sulfur atoms. The addition of sulfur was also found to improve the oxidation resistance of Zr-Nb-O alloys.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.364-372
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• 2008

In this study, the circumferential creep behaviors ofpilgered advanced Zirconium alloy tubes such as Zr-Nb-O and Zr-Nb-Sn-Fe were investigated in the temperature range of $400\sim500^{\circ}C$ and in the stress range of 80$\sim$150MPa. The test results indicate that the stress exponent for the steady-state creep rate of the Zr-Nb-Sn-Fe alloy decreases with the increase of stress(from 6$\sim$7 to 4), while that of the Zr-Nb-O alloy is nearly independent of stress(5$\sim$6). The activation energy of creep deformation is found to be nearly the same as the activation energy for Zr self diffusion. This indicates that the creep deformation may be controlled by dislocation climb mechanism in Zr-Nb-O. On the other hand, the transition of stress exponent(from 6-7 to 4) in Zr-Nb Sn-Fe strongly suggests the transition of the rate controlling mechanism at high stresses. The lower stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained by the dynamic deformation aging effect caused by interaction of dislocations with Sn substitutional atoms.

• Ecology and Resilient Infrastructure
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• v.7 no.1
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• pp.15-25
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• 2020

We've compared and conceptually evaluated the newly emerging concept of nature-based solutions (NbS's), in the aspect of water management, and existing similar solutions of different naming, all of which are based on ecosystem functions. In this study, it is found that NbS's seem significant and meaningful both educationally and understandably in the aspect that it can comprehensively cover and include the existing methodologies and solutions using the functions of natural ecosystem to socio-environmental challenges. It, however, seems not quite different from the broad-meaning of green infra, including Eco-DRR, in terms of the approaching methodologies in water management. The conceptual and spatial hierarchy of each practice in water management considered in this study can be expressed in the narrowing order of NbS-(EE)-BGI-(CRT)-GI-LID. Last, the term LID, which is the best management practice for storm water management in the development project, can be replaced with the term GI for clarification and less confusion both in academia and practice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.63-66
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• 1998

Prototype MFSFET′s using ferroelectric oxide LiNbO$_3$ as a gate insulator have been successfully fabricated with the help of 2 sheets of metal masks and demonstrated nonvolatile memory operations of the MFSFET′s. The estimated field-effect electron mobility and transconductance on a linear region of the fabricated FET were 600 $\textrm{cm}^2$/V.s and 0.16 mS/mm, respectively. The drain current of the "on" state was more than 4 orders of magnitude larger than the "off" state current at the same "read" gate voltage of 0.5 V, which means the memory operation of the MFSFET. A write voltage as low as $\pm$3 V, which is applicable to low power integrate circuits, was used for polarization reversal.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1182-1190
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• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1968-1970
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• 1999

본 연구에서는 RF 마그네트론 스퍼터링법으로 CoNbZrPd 비정질 연자성 박막을 제조하여 Pd의 첨가 효과와 자장중 열처리에 의한 특성 변화에 대해 연구하였다. Pd가 4.34 at% 첨가된 $Co_{87.56}Nb_{6.45}Zr_{1.65}Pd_{4.34}$ 박막은 비정질 구조이며 Pd 첨가에 의해 보자력은 0.54 Oe으로 감소하였으며, 이방성 자계는 10.45 Oe로 Pd를 첨가하지 않은 CoNbZr 비정질 박막 보다 특성이 향상되었다. $Co_{87.56}Nb_{6.45}Zr_{1.65}Pd_{4.34}$ 비정질 박막은 $400^{\circ}C$까지 비정질 상을 유지하고 있지만, 연자기 특성이 열화되어 보자력이 증가하고 이방성자계가 급격히 감소하였지만, 포화 자화는 크게 변화지 않았다.