• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3576-3580
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• 2012

Larva-like GaS nanostructures synthesized by the thermal evaporation of Ga metals and S powders were coated with $SiO_2$ by the sputtering technique. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the GaS-core/$SiO_2$-shell larva-like nanostructures were single crystal wurtzite-type hexagonal structured-GaS and amorphous $SiO_2$, respectively. Photoluminescence (PL) measurements at room temperature showed that the passivation of the larva-like GaS nanostructures was successfully achieved with $SiO_2$ without nearly harming the major emission from the wires. However, subsequent thermal annealing treatment was found to be undesirable owing to the degradation of their emission in intensity.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.420-421
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• 2006

In the present study, ultrafined Zr-V-Fe based alloy powder prepared by a plasma arc discharge process with changing process parameters. The chemical composition of synthesized powder was strongly influenced by the process parameters, especially the hydrogen volume fraction in the powder synthesis atmosphere. The synthesized powder had an average particle size of 50 nm. The synthesized Zr-V-Fe based particles had a shell-core structure composed of metal in the core and oxidse in the shell.

• Applied Microscopy
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• 제36권spc1호
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• pp.47-56
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• 2006

Improvements are made to existing primitive cell volume measurement method to provide a real-time analysis capability for the phase analysis of nanocrystalline materials. Simplification is introduced in the primitive cell volume calculation leading to fast and reliable method for nano-phase identification and is applied to the phase analysis of Mo-Si-N nanocoating layer. In addition, comparison is made between real-time and film measurements for their accuracy of calculated primitive cell volume values and factors governing the accuracy of the method are determined. About 5% accuracy in primitive cell determination is obtained from camera length calibration and this technique is used to investigate the cell volume variation in WC-TiC core-shell microstructure. In addition to chemical compositional variation in core-shell type structure, primitive cell volume variation reveals additional information on lattice coherency strain across the interface.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2017년도 임시총회 및 하계학술연구발표회
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• pp.217-217
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• 2017

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.96.1-96.1
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• 2007

• 한국분말재료학회지
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• 제23권1호
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• pp.38-42
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• 2016

$BaTiO_3$-coated Fe nanofibers are synthesized via a three-step process. ${\alpha}-Fe_2O_3$ nanofibers with an average diameter of approximately 200 nm are first prepared using an electrospinning process followed by a calcination step. The $BaTiO_3$ coating layer on the nanofiber is formed by a sol-gel process, and a thermal reduction process is then applied to the core-shell nanofiber to selectively reduce the ${\alpha}-Fe_2O_3$ to Fe. The thickness of the $BaTiO_3$ shell is controlled by varying the reaction time. To evaluate the electromagnetic (EM) wave-absorbing abilities of the $BaTiO_3@Fe$ nanofiber, epoxy-based composites containing the nanofibers are fabricated. The composites show excellent EM wave absorption properties where the power loss increases to the high frequency region without any degradation. Our results demonstrate that the $BaTiO_3@Fe$ nanofibers obtained in this work are attractive candidates for electromagnetic wave absorption applications.

• Korean Chemical Engineering Research
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• 제50권6호
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• pp.1068-1075
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• 2012

압출성형을 통한 core/shell 구조를 갖는 폴리부틸렌테레프탈레이트(PBT)/Nylon6,12 미세모를 제조함에 있어 최적의 압출조건을 규명하기 위하여, 압출온도와 배합비를 다르게 하여 제조한 블렌드 미세모의 상용성을 SEM 모폴로지와 DSC 분석을 통해 확인하고 UTM을 통해 압출속도에 따른 기계적 물성의 변화를 측정하였다. SEM 모폴로지 분석결과 압출온도가 증가할수록 분산상인 Nylon6,12 비드의 크기가 감소하였으며, Nylon6,12의 함량이 증가할수록 PBT 매트릭스 내 Nylon6,12의 상분리 현상이 감소하였다. DSC 분석 결과도 같은 경향을 나타냈는데, 압출온도가 상승함에 따라 녹는점에 해당하는 피크들의 경계가 사라지고, Nylon6,12의 비율이 증가할수록 두 피크의 간격이 좁아지는 것을 확인할 수 있었다. 한편 PBT/Nylon6,12 블렌드 미세모의 인장강도와 연신율 및 굴곡강도와 굴곡탄성률 모두 압출온도가 $260^{\circ}C$ 일 때까지 증가하였으나 그 이상의 온도에서는 오히려 감소하였다. $260^{\circ}C$에서의 인장강도와 연신율, 굴곡강도, 굴곡탄성률은 각각 560 $kg_f/cm^2$와 220%, 807 $kg_f/cm^2$, 22,146 $kg_f/cm^2$였는데 이는 PBT와 Nylon6,12의 중간 값을 상회하는 수치로 두 물질이 압출성형에 의한 블렌드 효과가 있다는 것을 확인할 수 있었다. 이처럼 우수한 상용성을 보일 때의 블렌드 압출 조건들을 토대로 하여 core/shell 구조의 이중구조 미세모를 제조하였다.

• 한국재료학회지
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• 제14권7호
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• pp.511-515
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• 2004

Fe nano powders were synthesized by plasma arc discharge (PAD) process and studied by means of X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Pure Fe rod($99.9\%$) was used as a source of metallic vapor under argon and hydrogen mixed atmosphere. The synthesized Fe nano powders had nearly spherical shapes and core-shell type structures. The influence of process parameters on the structure and size was investigated. The powder size increased with increasing of the chamber pressure and input current. High hydrogen gas ratio in chamber atmosphere affected the particle size and amount of Fe nanopowder.

• Journal of the Korean Wood Science and Technology
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• 제22권1호
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• pp.85-90
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• 1994

The flow properties of binder latices for paper coating were investigated, together with dynamic viscoelastic properties of latex films and electron micrographs of latices, under various conditions. The amphoteric latex, binder pigment latex and anionic latex were used in this work. The amphoteric latex has both anionic and cationic functional group on its surface. The binder-pigment with a core-shell structure has dual functions : plastic pigment and binder. The low shear viscosity of binder latices and clay slurry were measured with Brookfield vis cometer. At low-shear rates. the viscosity decreased with increasing particle size of latex. On the amphoteric latex surface, the carboxyl groups are assumed to be fully dissociated over the region of pH 9~12, but the density of negative groups seems to be increased because of the gradual decrease in the degree of dissociation of amino groups. Since the apparent particle size of latex increases with surface charge, the electroviscous effect can be observed. On the anionic latex surface, the charge density is assumed to be nearly constant above pH 8. However, below pH 8 the coagulation of particles could be observed probably because of the decrease in the charge density.

• Fibers and Polymers
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• 제7권3호
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• pp.229-234
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• 2006

Poly(vinyl acetate) (PVAc)/poly(vinyl alcohol) (PVA)/montmorillonite (MMT) clay nanocomposite microspheres with a core/shell structure have been developed via a suspension polymerization approach. In order to prepare the PVAc/ MMT and PVAc/PVA/MMT nanocomposite microspheres, which are promising precursor of PVA/MMT nanocomposite microspheres, suspension polymerization of vinyl acetate with organophilic MMT and heterogeneous saponification were conducted. A quaternary ammonium salt, cetyltrimethylammonium bromide, was mixed with the MMT in the monomer phase prior to the suspension polymerization. The rate of conversion decreased with an increase in MMT concentration. The incorporation of MMT into the PVAc was verified by FT-IR spectroscopy. Organic vinyl acetate monomers were intercalated into the interlayer regions of organophilic clay hosts and followed by suspension polymerization. Partially saponified PVA/MMT nanocomposite microspheres with a core/shell structure were successfully prepared by heterogeneous saponification.