• 한국분말재료학회지
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• 제1권1호
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• pp.42-51
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• 1994

6061Al-SiCP metal matrix composite materials(MMCs) were fabricated by injecting SiCP particles directly into the atomized spray. The main attraction of this technique is the rapid fabrication of semi-finished, composite products in a combined atomization, particulate injection(10 $\mu\textrm{m}$, 40 $\mu\textrm{m}$, SiCP) and deposition operation. Conclusions obtained are as follows; The microstructure of the unreinforced spray formed 6061Al alloy consisted of relatively fine(50 $\mu\textrm{m}$) equiaxed grains. By comparision, the microstructure of the I/M materials was segregated and consisted of relatively coarse(150 $\mu\textrm{m}$) grains. The probability of clustering of SiCP particles in co-sprayed metal matrix composites increased it ceramic particle size(SiCP) was reduced and the volume fraction was held constant. Analysis of overspray powders collected from the spray atomization and deposition experiments indicated that morphology of powders were nearly spherical and degree of powders sphercity was deviated due to composite with SiCp particles. Interfacial bonding between matrix and ceramics was improved by heat treatment and addition of alloying elements(Mg). Maximum hardness values [Hv: 165 kg/mm2 for Al-10 $\mu\textrm{m}$ SiCp Hv--159 kg/mm2 for Al-40 $\mu\textrm{m}$SiCp] were obtained through the solution heat treatment at $530^{\circ}C$ for 2 hrs and aging at $178^{\circ}C$, and there by the resistance were improved.

• 전기화학회지
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• 제15권2호
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• pp.67-73
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• 2012

본 연구에서는 습식분쇄, 구형화 분무건조 및 열처리 공정을 통해 구형의 $LiMn_{2-x}M_xO_4$(M = Al, Mg, B) 스피넬계 양극소재를 합성하고, 이의 전기화학적 성능을 평가하였다. $MnO_2$ (Tosoh, 91.94%), $Li_2CO_3$ (SQM, 97%), $MgCO_3$ (Aldrich, 99%), $Al(OH)_3$ (Aldrich, 99%) 및 $B_2O_3$ (Aldrich, 99%)를 원료로 사용하였으며, 분무건조공정에서 전구체의 구형화도 증가를 위해 PAAH 바인더를 첨가하였다. 200~500 nm 크기로 분쇄된 혼합 슬러리 용액으로부터 분무건조법을 통해 구형의 전구체를 제조하고, 이를 다양한 조건에서 열처리하여 최종 스피넬계 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극소재를 제조하였다. 제조된 구형의 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극재료는 이종원소 치환량, 특히 Boron 치환량에 따라 입자 표면 및 내부의 치밀도가 변화하는 것을 확인할 수 있었으며, 치밀도가 증가함에 따라 소재의 출력특성이 향상되었으며, 최적 조성의 양극소재는 상온 5 C 용량이 0.2 C 용량 대비 90% 이상이 됨을 확인하였다. 또한 표면의 치밀도도 증가함에 따라 $60^{\circ}C$ 고온 충방전 조건에서 수명특성이 향상되어 500회 사이클 이후에도 초기용량의 80% 이상을 유지하였다.

• 한국응용과학기술학회지
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• 제31권4호
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• pp.731-739
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• 2014

투명 전도성 산화물로서 알루미늄과 붕소가 함께 도핑된 아연산화물(AZOB)이 $900^{\circ}C$에서 분무 열분해법에 의해 제조되었다. 얻어진 마이크론 크기의 AZOB 분말은 알루미늄, 붕소 및 아연의 수용액으로부터 얻어진다. 분무 열분해로 얻어진 마이크론 크기의 AZOB 분말은 $700^{\circ}C$에서 두 시간동안의 후 소성 과정과 24 시간 동안의 볼 밀링을 통해 나노 크기의 AZOB으로 변환된다. AZOB을 구성하는 일차 입자의 크기를 Debye-Scherrer 식에 의해 계산하였고 압축된 AZOB 펠렛의 표면 저항을 측정하였다.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.934-942
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• 1998

$^13CO$ chemisorbed on platinum particles in L-zeolite has been investigated by static and magic angle spinning NMR spectroscopy. The representative spectra are composed of a broad asymmetric peak with a center of gravity at 230±30 ppm and a sharp symmetric peak at 124±2 ppm which is tentatively assigned to physisorbed $CO_2$, on inner walls of L-zeolite. Overall, the broad resonance component is similar to our previous results of highly dispersed (80-96%) CO/Pt/silica or CO/Pt/alumina samples, still showing metallic characters. The principal difference is in the first moment value. The broad peak in the spectra is assigned to CO linearly bound to Pt particles in the L-zeolites, and indicates a distribution of isotropic shifts from bonding site to bonding site. The NMR results reported here manifest that the Pt particles inside of the L-zeolites channels are not collectively the same with the ones supported on silica or alumina with similar dispersion in terms of Pt particle shape and/or ordering of Pt atoms in a particle. As a result, Pt particles of CO/Pt/L-zeolite were agglomerated accompanying CO desorption upon annealing. There were no definite changes in the NMR spectra due to differences of exchanged cations. Comparison of our observation on CO/Pt/L-zeolite with Sharma et al.'s reveals that even when the first moment, the linewidtb, and the relaxation times of the static spectra and the dispersion measured by chemisorption are similar, the properties of Pt particles can be dramatically different. Therefore, it is essential to take advantage of the strengths of several techniques together in order to interpret data reliably, especially for the highly dispersed samples.

• 한국축산식품학회지
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• 제34권5호
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• pp.692-699
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• 2014

The aim of this study was to apply the external ionic gelation using an atomizing spray device comprised of a spray gun to improve the viability of Lactobacillus plantarum DKL 109 and for its commercial use. Three coating material formulas were used to microencapsulate L. plantarum DKL 109: 2% alginate (Al), 1% alginate/1% gellan gum (Al-GG), and 1.5% alginate/3% gum arabic (Al-GA). Particle size of microcapsules was ranged from 18.2 to $23.01{\mu}m$ depending on the coating materials. Al-GA microcapsules showed the highest microencapsulation yield (98.11%) and resulted in a significant increase in survivability of probiotic in a high acid and bile environment. Encapsulation also improved the storage stability of cells. The viability of encapsulated cells remained constant after 1-mon storage at ambient temperature. The external ionic gelation method using an atomizing spray device and the Al-GA seems to be an efficient encapsulation technology for protecting probiotics in terms of scale-up potential and small microcapsule size.

• 한국재료학회지
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• 제16권12호
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• pp.719-724
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• 2006

Ultrafine mullite powder was prepared from aluminium-secbutoxide and tetraethyl orthosilicate(TEOS) in the molar $Al_2O_3/SiO_2$=3/2. Sol-gel method by partial hydrolysis technique, as it were, first, TEOS was partially hydrolysized and then mixed with Al-secbutoxide for complete hydrolysis was used. X-ray diffraction, infrared spectroscopy and transmission electron microscopy, etc. confirmed that the mullite powder prepared by this method is in the stoichiometric $Al_2O_3/SiO_2$ ratio. Al-Si spinel was formed at $980^{\circ}C$ and ultrafine mullite powder with about 20 nm particle size was obtained above $1,200^{\circ}C$. Also mullite powders calcined at $1,600^{\circ}C$ had a stoichiometric composition, $3Al_2O_3{\cdot}2SiO_2$ and the lattice constants of the mullite powders calcined above $1,200^{\circ}C$ were almost coincided with theoretical values.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.306.1-306.1
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• 2014

정보화 시대의 발전에 따라 점점 더 많은 정보를 더욱 빠르게 처리할 수 있는 기기들이 요구되고 있다. 메모리는 그 중에서 핵심적인 부품으로써 소자의 고집적화와 고속화가 계속 진행되면서 기존의 메모리 소자들은 집적화에서 그 한계에 도달하고 있다. 기존 소자들의 집적화의 한계를 극복하기 위하여 새로운 비휘발성 메모리 소자들이 제안되었다. 그 중 resistive switching random access memory(ReRAM)은 저항의 변화특성을 사용하는 메모리로 간단한 구조를 가지고 있기 때문에 집적화에 유리하다는 장점을 가지고 있다. 그 외에도 빠른 동작 속도와 낮은 전압에서의 동작이 가능하여 차세대 메모리로써 각광받고 있는 추세이다. 본 연구실에서는 이미 nitride 물질을 기반으로 한 여러 ReRAM 소자들을 제안해 왔다. 그 중 AlN-based ReRAM 소자는 빠른 동작 속도와 좋은 내구성을 보인 바 있다. 하지만 상업화를 위해서 해결해야 할 문제점들이 아직 존재하고 있다. 대표적으로 소자의 배열에서 각 소자의 균일한 동작이 보증되어야 하기 때문에 소자의 셋/리셋 전압의 산포를 줄이고 동작 전류 레벨을 낮추어야 할 필요성이 존재한다. 이러한 ReRAM의 이슈를 해결하기 위해, 본 실험에서는 기존의 AlN-based ReRAM 소자에 Ti를 도핑 방법을 이용하여 소자의 동작 전압 및 전류의 산포를 줄이기 위한 연구를 진행 하였다. 본 실험은 co-sputtering 방법을 이용하여 Ti가 도핑된 AlN을 저항변화 물질로 사용하여 그 특성을 살펴보았다. Ti의 도핑 효과로 소자의 신뢰성 향상 및 동작 전압의 감소 등의 효과를 얻을 수 있었다. 이는 nitride 기반 물질에서 Ti dopant에 의해 형성된 TiN의 효과로 설명된다. TiN는 metallic한 특성을 지니고 있기에 저항변화물질 내에서 일종의 metallic particle의 역할을 수행할 수 있다. 따라서 conducting path의 형성과정에서 이러한 particle 들이 전계를 유도하여 좀 더 균일한 set/reset 특성을 나타내게 된다.

• Journal of Electrochemical Science and Technology
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• 제14권4호
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• pp.377-387
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• 2023

Ni-W/Al₂O₃ nano-composites were electrodeposited on mild steel substrate for mechanical and corrosion resistance applications. This study focused on the preparation of Ni-W/Al₂O₃ nano-composite coating with various quantity of Al₂O₃ incorporations. The addition of Al₂O₃ in the electrolytes were varied from 1-10 g/L in electrolytes and the Al₂O₃ incorporation in Ni-W/Al₂O₃ nano-composite coatings were obtained from 1.82 to 13.86 wt.%. The incorporation of Al₂O₃ in Ni-W alloy matrix influenced the grain size, surface morphology and structural properties were observed. The distributions of Al₂O₃ particle in alloy matrix were confirmed using electron microscopy (FESEM and TEM) and EDAX mapping analysis. The crystal structure informations were studied using X-ray diffraction method and it confirms that the deposits having cubic crystal structure. The better corrosion rate (0.87 mpy) and microhardness (965 HV) properties were obtained for the Ni-W/Al₂O₃ nano-composite coating with 13.86 wt.% of Al₂O₃ incorporations.

• 한국수소및신에너지학회논문집
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• 제25권5호
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• pp.459-467
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• 2014

The catalytic steam reforming of toluene, a major component of biomass tar, was studied using several catalysts at various temperatures $400-800^{\circ}C$, kind of metal, and metal loading content. Ru and K promoted Ni-base catalyst were prepared, and used for steam reforming of toluene with steam/toluene molar ratio of 25. Concentration of toluene in reactant flow is $30g/Nm^3$ that is usual content of tar from biomass gasifier. The result from experiments showed that $H_2$ content in product gas and toluene conversion increased with temperature. Where in high temperature range, CO and $CO_2$ content in product gas were affected mainly by Boudouard reaction. Ni/Ru-K(3wt%)/$Al_2O_3$ catalyst showed best performance on steam reforming of toluene than used catalysts in this study at whole temperature. Catalysts have been characterized by XRD, TG. XRD analysis displayed that Ni particle size on Ni/Ru-K (3wt%)/$Al_2O_3$ catalyst was 29.4nm. Activation energy of Ni/Ru-K (3wt%)/$Al_2O_3$ catalyst was calculated 36.8kJ/mol by Arrhenius plot.

• 한국세라믹학회지
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• 제43권9호
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• pp.575-581
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• 2006

To precipitate the complex gel of flux and aluminum hydroxides gel, aqueous solution of the mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in aqueous solution of the mixture of $Al_2(SO_4)_3{\cdot}14{\sim}18H_2O,\;Na_2SO_4$, and then the complex gel was aged in $0{\sim}30h\;at\;90^{\circ}C$. As aging time passed, the aluminum hydroxides was grown into the acicular AlO(OH) gel. Also, aging time had an effect on physical properties of the AlO(OH) gel and on crystal growth of the flaky ${\alpha}-Al_2O_3$ prepared by molten-salt precipitation. In this study, the complex gel was crystallized in temperature range of $400{\sim}1,200^{\circ}C$ after drying at $110^{\circ}C$, and then it was investigated to effect of aging time on precipitation temperature, size, thickness, morphology and particle size distribution of the flaky ${\alpha}-Al_2O_3$ crystal. As aging time passed, the flaky a${\alpha}-Al_2O_3$ crystal showed a tendency toward an increase in size and thickness as result from an increase in BET surface area and pore volume of the acicular AlO(OH) gel.