• 융합정보논문지
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• 제8권5호
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• pp.95-100
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• 2018

금속 산화물/그래핀 형태의 복합 나노소재는 높은 전기용량을 갖는 2차 전지의 전극용 소재 또는 고감도 가스 센서의 감지물질 등으로 활용되는 매우 유용한 기능성 소재이다. 본 논문에서는 열 화학기상증착(CVD, Chemical Vapor Deposition)으로 Cu Foil 위에 대면적으로 합성된 CVD 그래핀 및 고정렬 열분해 흑연(HOPG, Highly Oriented Pyrolytic Graphite)으로부터 기계적으로 박리된 그래핀 기판 위에 이산화바나듐($VO_2$) 나노구조물을 기상수송방법으로 직접 성장시키는 연구를 수행하였다. 연구결과 CVD 그래핀 기판의 경우, 그래핀 결정 경계에서 상대적으로 많이 존재하는 기능기들이 $VO_2$ 나노구조물에서 핵형성의 씨앗으로 작용하는 것이 확인되었다. 반면에 HOPG에서 기계적으로 박리된 그래핀 나노시트 표면에는 기능기가 균일하게 분포하기 때문에, 2차원과 3차원 형태로 $VO_2$ 나노구조물이 성장되었다. 이러한 연구결과는 고기능성 $VO_2$/그래핀 나노복합소재를 이용하여 높은 전기용량을 갖는 2차 전지 전극소재 및 고감도 가스 센서의 감지물질 합성에 유용하게 활용될 것으로 전망된다.

• 한국세라믹학회지
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• 제46권3호
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• pp.225-228
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• 2009

The processing and characterization of ceramic nanocomposites, which produce bulk nanostructures with attractive mechanical properties, have been emphasized and introduced at Prof. Mukherjee's Lab at UC Davis. The following subjects will be introduced in detail in Part II, III, and IV. In Part II, the paper will describe a three-phase alumina-based nanoceramic composite demonstrating superplasticity at a surprisingly lower temperature and higher strain rate. The next part will show that an alumina-carbon nanotube-niobium nanocomposite produced fracture toughness values that are three times higher than that of pure nanocrystalline alumina. It was possible to take advantage of both fiber-toughening and ductile-metal toughening in this investigation. In the fourth section, discussed will be a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method. This allowed the sintering to be completed at significantly lower temperatures and during much shorter times. These improvements in mechanical properties will be discussed in the context of the results from the microstructural investigations.

• 한국재료학회지
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• 제20권1호
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• pp.25-30
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• 2010

Si nanowire/multiwalled carbon nanotube nanocomposite arrays were synthesized. Vertically aligned Si nanowire arrays were fabricated by Ag nanodendrite-assisted wet chemical etching of n-type wafers using $HF/AgNO_3$ solution. The composite structure was synthesized by formation of a sheath of carbon multilayers on a Si nanowire template surface through a thermal CVD process under various conditions. The results of Raman spectroscopy, scanning electron microscopy, and high resolution transmission electron microcopy demonstrate that the obtained nanocomposite has a Si nanowire core/carbon nanotube shell structure. The remarkable feature of the proposed method is that the vertically aligned Si nanowire was encapsulated with a multiwalled carbon nanotube without metal catalysts, which is important for nanodevice fabrication. It can be expected that the introduction of Si nanowires into multiwalled carbon nanotubes may significantly alter their electronic and mechanical properties, and may even result in some unexpected material properties. The proposed method possesses great potential for fabricating other semiconductor/CNT nanocomposites.

• 한국분말재료학회지
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• 제26권2호
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• pp.119-125
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• 2019

Piezoelectric energy harvesting technology is attracting attention, as it can be used to convert more accessible mechanical energy resources to periodic electricity. Recent developments in the field of piezoelectric energy harvesters (PEHs) are associated with nanocomposites made from inorganic piezoelectric nanomaterials and organic elastomers. Here, we used the $BaTiO_3$ nanoparticles and piezoelectric poly(vinylidene fluoride) (PVDF) polymeric matrix to fabricate the nanocomposites-based PEH to improve the output performance of PEHs. The piezoelectric nanocomposite is produced by dispersing the inorganic piezo-ceramic nanoparticles inside an organic piezo-polymer and subsequently spin-coat it onto a metal plate. The fabricated organic-inorganic piezoelectric nanocomposite-based PEH harvested the output voltage of ~1.5 V and current signals of ~90 nA under repeated mechanical pushings: these values are compared to those of energy devices made from non-piezoelectric polydimethylsiloxane (PDMS) elastomers and supported by a multiphysics simulation software.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.99.1-99.1
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• 2016

The materials for an electronic packaging provide diverse important functions including electrical contact to transfer signals from devices, isolation to protect from the environment and a path for heat conduction away from the devices. The packaging materials composed of metals, ceramics, polymers or combinations are crucial to the device operating properly and reliably. The demand of effective charge and heat transfer continuous to be challenge for the high-speed and high-power devices. Nanomaterials including graphene, carbon nanotube and boron nitride, have been designed for the purpose of exploiting the high thermal, electrical and mechanical properties by combining in the matrix of metal or polymer. In addition, considering the inherent electrical and surface properties of graphene, it is expected that graphene would be a good candidate for the surface layer of a template in the electroforming process. In this talk, I will present recent our on-going works in nanomaterials for microelectronic packaging: 1) porous graphene/Cu for heat dissipations, 2) carbon-metal composites for interconnects and 3) nanomaterials-epoxy composites as a thermal interface materials for electronic packaging.

• Journal of Electrochemical Science and Technology
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• 제6권3호
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• pp.81-87
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• 2015

This study introduces a facile strategy to prepare metal oxide/conducting polymer nanocomposites that may have promising applications in energy storage devices. Ploy aniline/nano wire manganese dioxide (PANI/NwMnO₂) was synthesized by cyclic voltammetry on glassy carbon electrode. Morphology and structure of the composite, pure PANI, MnO₂ nanowires were fully characterized using XRD and SEM analysis. Electrochemical studies shows excellent synergistic effect between PANI and MnO₂ nanowires which results in its capacitance increase and cycle stability against PANI electrode. Specific capacitances of PANI/NwMnO₂ and PANI were 456 and 190 F/g respectively. The electrochemical performance of electrodes studied using cyclic voltammetry, Galvanostatic charge/discharge and impedance spectroscopy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.119-122
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• 2006

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of 1 vol.% carbon nanotube (CNT)-metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT-Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature. It was found by mechanical testing of the consolidated 1 vol.% CNT-Cu that high mechanical strength could be achieved effectively as a result of the Cu matrix strengthening and improved particle bonding during ECAP. The ECAP processing of powders is a viable method to achieve fully density CNT-Cu nanocomposites.

• Journal of Electrochemical Science and Technology
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• 제7권1호
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• pp.1-12
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• 2016

The production of oxygen and hydrogen from solar water splitting has been considered to be an ultimate solution for energy and environmental issues, and over the past few years, nano-sized semiconducting metal oxides alone and with graphene have been shown to have great promise for use in photocatalytic water splitting. It is challenging to find ideal materials for photoelectrochemical water splitting, and these have limited commercial applicability due to critical factors, including their physico-chemical properties, the rate of charge-carrier recombination and limited light absorption. This review article discusses these main features, and recent research progress and major factors affect the performance of the water splitting reaction. The mechanism behind these interactions in transition metal oxides and graphene based nano-structured semiconductors upon illumination has been discussed in detail, and such characteristics are relevant to the design of materials with a superior photocatalytic response towards UV and visible light.

• 소성∙가공
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• 제19권7호
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• pp.423-428
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• 2010

Carbon nanotubes(CNTs) are expected to be ideal reinforcements of metal matrix composite materials used in aircraft and sports industries due to their high strength and low density. In this study, a high pressure torsion(HPT) process at an elevated temperature(473K) was employed to achieve both powder consolidation and grain refinement of aluminummatrix nanocomposites reinforced by 5vol% CNTs. CNT/Al nanocomposite powders were fabricated using a novel molecular-level mixing process to enhance the interface bonding between the CNTs and metal matrix before the HPT process. The HPT processed disks were composed of mostly equilibrium grain boundaries. The CNT-reinforced ultrafine grained microstructural features resulted in high strength and good ductility.

• 공업화학
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• 제23권3호
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• pp.293-296
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• 2012

항균 활성도를 조사하기 위해 이산화티탄미립자 표면에 나노메탈(Au, Ag)을 균일하게 도핑한 나노복합체($Ag-TiO_2,\;Au-TiO_2,\;Ag-TiO_2$@$TiO_x$)를 초음파환원법과 졸-겔 법으로 제조하였다. 이렇게 제조된 나노메탈-이산화티탄 복합체의 항균 활성도는 고체배지 표면에 나노복합체와 함께 E. coli를 도말하여 $37^{\circ}C$에서 배양한 후 생존된 콜로니 개수의 측정을 통해서 이루어졌다. 나노복합체의 초기 항균 효율은 나노메탈이 도핑된 이산화티탄미립자($Ag-TiO_2,\;Au-TiO_2,\;Ag-TiO_2$@$TiO_x$)) 복합체가 도핑하지 않은 이산화티탄미립자($TiO_2$)에 비해 높은 항균 효율을 나타내주었다. 이후, 나노복합체를 $4^{\circ}C$에서 보관 후 장기보관에 따른 항균특성을 비교해본 결과, 나노메탈만 도핑된 복합체($Ag-TiO_2,\;Au-TiO_2$)보다는 $Ag-TiO_2,$의 표면을 다시 산화티탄막으로 코팅한 복합체($Ag-TiO_2$@$TiO_x$)의 항균특성이 오랫동안 유지되는 것을 알수 있었다. 이는 산화티탄막으로 다시 코팅한 $Ag-TiO_2$@$TiO_x$의 경우에 Ag 나노메탈의 산화방지 및 나노복합체의 콜로이드 안정성 향상이 이루어졌기 때문으로 사료된다.