• 한국재료학회지
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• 제21권1호
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• pp.67-71
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• 2011

La doped CuO-ZnO-$Al_2O_3$ powders are prepared by sol-gel method with aluminum isopropoxide and primary distilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such as copper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-$Al_2O_3$ powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at various temperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with the calcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-ray Diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET), Thermogravimetry-Differential Thermal analysis (TG/DTA), $^{27}Al$ solid state Nuclear Magnetic Resonance (NMR) and transform infrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-$Al_2O_3$ powders from $25m^2$/g to $41m^2$/g.

• 공업화학
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• 제10권4호
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• pp.620-627
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• 1999

리튬이온전지용 Al 집전체와 비수용성 전해질의 전기화학적 특성을 연구하기 위하여 1 M $LiBF_4$ EC : DMC, 1 M $LiBF_4$ EC : EMC. 1 M $LiPF_6$ EC : DMC. 1 M $LiPF_6$ EC : EMC의 4가지 전해질에서 전압전류 및 임피던스 특성을 조사하였다. Al 집전체는 비교적 넓은 전위창(0.5~4.1 V)에서 안전하지만, 첫 싸이클의 저 전위에서(<2.0 V vs. $Li/Li^{+}$)에서 전해질 내 미량 존재하는 불순물($H_2O$, $O_2$ 등)과 반응하여 계면물질을 생성하며, 리튬염 및 유기용매 또한 일정 전위 범위(<1.5 V vs. $Li/Li^{+}$)에서 Al 집전체와 반응하였다. 특히 전해질내 존재하는 미량의 불순물로 인하여 고 전위에 노출된 Al 집전체의 국부부식이 진행되었다.

• Advances in environmental research
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• 제1권1호
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• pp.83-96
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• 2012

The water sludge is generated from the treatment of water with alum. Disposing of sludge again to the streams raises the concentrations of aluminum oxides in water, which has been linked to Alzheimer's disease. The use of water treatment plant (WTP) sludge in manufacturing of constructional elements achieves both the economical and environmental benefits. Due to the similar mineralogical composition of clay and WTP sludge, this study investigated the complete substitution of brick clay by sludge incorporated with some of the agricultural and industrial wastes, such as rice husk ash (RHA) and silica fume (SF). Three different series of sludge to SF to RHA proportions by weight were tried, which were (25: 50: 25%), (50: 25: 25%), and (25: 25: 50%), respectively. Each brick series was fired at 900, 1000, 1100, and $1200^{\circ}C$. The physical and mechanical properties of the produced bricks were then determined and evaluated according to Egyptian Standard Specifications (E.S.S.) and compared to control clay-brick. From the obtained results, it was concluded that by operating at the temperature commonly practiced in the brick kiln, a mixture consists of 50% of sludge, 25% of SF, and 25% of RHA was the optimum materials proportions to produce brick from water sludge incorporated with SF and RHA. The produced bricks properties were obviously superior to the 100% clay control-brick and to those available in the Egyptian market.

• 대한금속재료학회지
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• 제48권6호
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• pp.506-513
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• 2010

The composite coatings of $(ZrO_2-8Y_2O_3)$/(Ni-22Cr-10Al-1Y) were prepared by the air plasma spraying method. They consisted of (Ni,Cr)-rich regions,$(ZrO_2-Y_2O_3)$-rich regions, and $Al_2O_3$-rich regions that were formed by oxidation of Al from (Ni-22Cr-10Al-1Y) during spraying. The coatings corroded at 800 and $900^{\circ}C$ in NaCl-$Na_2SO_4$ molten salts up to 50 hr. Ni, Cr and Al oxidized to NiO, $Cr_2O_3$ and ${\alpha}-Al_2O_3$, respectively. These oxides and $(ZrO_2-Y_2O_3)$ were dissolved off into the molten salts during hot corrosion, which resulted in the ever-lasting corrosion of the composite coatings. Chromium diffused out from the (Ni,Cr)-rich regions and oxidized to $Cr_2O_3$, which was most frequently found as surface scales. Aluminum retained in the (Ni,Cr)-rich regions were similarly diffused out.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권2호
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• pp.62-69
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• 2008

본 연구에서는 제조방법이 다른 여러 종류의 망간코팅사(MCS)들의 물리화학적 특성과 내산성을 비교하고 이들에 의한 독성 3가 비소의 산화특성을 평가하였다. 실험에 사용된 MCS는 4종류로서 실험실에서 고온가열처리에 의하여 제조한 B-MCS, 접촉/건조(wetting and dry) 방법으로 제조한 W&D-MCS, 정수처리장 수 처리 과정에서 자연발생적으로 생성된 N-MCS, 그리고 철 및 망간제거용으로 시판되는 Birm을 사용하였다. 각 망간사내의 망간함유량은 Birm (63,120 mg/kg) > N-MCS(10,400 mg/kg) > W&D-MCS(5,080 mg/kg) > B-MCS(2,220 mg/kg) 순으로 나타났다. 내산성 실험결과 Birm에 함유된 망간이 산성조건에서 가장 적은 용출분율(% 기준)을 보였다. 3가 비소산화 결과, B-MCS의 경우 반응용액의 pH가 낮을수록 산화율이 지속적으로 증가하였지만, N-MCS와 Birm의 경우는 이와는 달리 pH 6 부근에서 산화율이 최소가 되며 강산성 및 강알카리 영역에서는 산화율이 증가하는 것으로 나타났다. N-MCS와 Birm의 경우에는 산화망간 외에 상당량의 산화알루미늄을 함유하고 있어서 As(III) 산화와 동시에 망간산화물의 환원에 의해서 생성되는 $Mn^{2+}$가 산화망간 및 산화알루미늄 두 반응점으로 경쟁흡착이 되기 때문에 기인한 것으로 여겨진다.

• 한국광물학회지
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• 제15권4호
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• pp.315-327
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• 2002

벤토나이트에 포함된 몬모릴로나이트의 층간에 Al산화물의 기둥(pillar)을 만든 Al-층간가교 점토를 합성하였다. 이 Al-층간가교점토에 대해 XRD, DTA, 화학분석 등을 실시하여 광물학적 특성을 검토하였으며, 그리고 이 가교점토에 대하여 Batch법의 흡착실험을 통하여 인산이온의 흡착성을 검토하였다. X-선 회절분석의 결과, Al-층간가교점토는 상온에서 층간격이 $18.03 \AA$으로 증가되어 나타났고, $550\AA$가열에서도 약 $17\AA$을 나타내어 열적 안정성이 크며, 글리세롤에 의한 층간격의 팽윤은 매우 미약한 것으로 나타났다. 열분석 결과, 이 점토에는 pillar부분에 관련된 물의 탈수에 의한 것으로 보이는 $270^{\circ}C$와 $420^{\circ}C$의 특징적인 흡열반응이 나타났다. Al-층간가교 점토의 인산 이온에 대한 흡착실험의 결과, 몬모릴로나이트는 거의 흡착능력을 보이지 않는데 비하여 월등히 우수한 인산이온($PO_{4}^{3－}$ /)성을 나타냈다. 시료 2 g에 용액 20 mL의 실험에서 300 mg/L 이하의 인산 농도에서는 거의 100%의 흡착효율을 나타냈다. 그리고 인산 이온에 흡착된 시료를 $500^{\circ}C$로 가열한 후 재차 흡착실험을 행한 결과, 역시 매우 높은 흡착효율을 나타냈다. 따라서 Al-층간가교 점토의 인산 이온 흡착에 대한 재활용의 가능성이 큰 것으로 나타났다

• 한국분말재료학회지
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• 제9권6호
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• pp.394-408
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• 2002

Nanostructured high strength metastable Al-, Mg- and Ti-based alloys containing different amorphous, quasicrystalline and nanocrystalline phases are synthesized by non-equilibrium processing techniques. Such alloys can be prepared by quenching from the melt or by powder metallurgy techniques. This paper focuses on one hand on mechanically alloyed and ball milled powders containing different volume fractions of amorphous or nano-(quasi)crystalline phases, consolidated bulk specimens and, on the other hand. on cast specimens containing different constituent phases with different length-scale. As one example. $Mg_{55}Y_{15}Cu_{30}$- based metallic glass matrix composites are produced by mechanical alloying of elemental powder mixtures containing up to 30 vol.% $Y_2O_3$ particles. The comparison with the particle-free metallic glass reveals that the nanosized second phase oxide particles do not significantly affect the glass-forming ability upon mechanical alloying despite some limited particle dissolution. A supercooled liquid region with an extension of about 50 K can be maintained in the presence of the oxides. The distinct viscosity decrease in the supercooled liquid regime allows to consolidate the powders into bulk samples by uniaxial hot pressing. The $Y_2O_3$ additions increase the mechanical strength of the composites compared to the $Mg_{55}Y_{15}Cu_{30}$ metallic glass. The second example deals with Al-Mn-Ce and Al-Cu-Fe composites with quasicrystalline particles as reinforcements, which are prepared by quenching from the melt and by powder metallurgy. $Al_{98-x}Mn_xCe_2$ (x =5,6,7) melt-spun ribbons containing a major quasicrystalline phase coexisting with an Al-matrix on a nanometer scale are pulverized by ball milling. The powders are consolidated by hot extrusion. Grain growth during consolidation causes the formation of a micrometer-scale microstructure. Mechanical alloying of $Al_{63}Cu_{25}Fe_{12}$ leads to single-phase quasicrystalline powders. which are blended with different volume fractions of pure Al-powder and hot extruded forming $Al_{100-x}$$(Al_{0.63}Cu_{0.25}Fe_{0.12})_x$ (x = 40,50,60,80) micrometer-scale composites. Compression test data reveal a high yield strength of ${\sigma}_y{\geq}$700 MPa and a ductility of ${\varepsilon}_{pl}{\geq}$5% for than the Al-Mn-Ce bulk samples. The strength level of the Al-Cu-Fe alloys is ${\sigma}_y{\leq}$550 MPa significantly lower. By the addition of different amounts of aluminum, the mechanical properties can be tuned to a wide range. Finally, a bulk metallic glass-forming Ti-Cu-Ni-Sn alloy with in situ formed composite microstructure prepared by both centrifugal and injection casting presents more than 6% plastic strain under compressive stress at room temperature. The in situ formed composite contains dendritic hcp Ti solid solution precipitates and a few $Ti_3Sn,\;{\beta}$-(Cu, Sn) grains dispersed in a glassy matrix. The composite micro- structure can avoid the development of the highly localized shear bands typical for the room temperature defor-mation of monolithic glasses. Instead, widely developed shear bands with evident protuberance are observed. resulting in significant yielding and homogeneous plastic deformation over the entire sample.

• 공업화학
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• 제16권4호
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• pp.491-495
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• 2005

Al이 0.01에서 0.05 몰 도핑된 오산화바나듐을 졸-겔법을 이용하여 제조하였고, Al이 도핑된 오산화바나듐의 화학적성질과 전기화학적 특성을 조사하기 위하여 $Li/Al_xV_2O_5$ 전지를 만들었다. $Al_xV_2O_5$ xerogel의 표면형상은 비등방성의 주름진 판상을 이루며 층간거리는 약 $11.5{\AA}$이었다. IR 스펙트럼에 의하면 도핑된 Al이 $V_2O_5$의 vanadyl기에 결합하고 있는 것으로 나타났다. $Al_xV_2O_5$ xerogel은 가역성과 에너지밀도가 $V_2O_5$보다 향상되었다. 또한 10 mA/g의 방전율로 얻은 $Al_{0.05}V_2O_5$ xerogel의 비용량은 200 mAh/g 이상이었으며, 1.9 V에서 3.9 V 전위영역에서 31회의 연속 충방전 실험을 한 결과 약 90%의 사이클효율을 나타내었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.183-184
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• 2013

Two main MBE growth techniques have been used: plasma-assisted MBE (PA-MBE), which utilizes a rf plasma to supply active nitrogen, and ammonia MBE, in which nitrogen is supplied by pyrolysis of NH3 on the sample surface during growth. PA-MBE is typically performed under metal-rich growth conditions, which results in the formation of gallium droplets on the sample surface and a narrow range of conditions for optimal growth. In contrast, high-quality GaN films can be grown by ammonia MBE under an excess nitrogen flux, which in principle should result in improved device uniformity due to the elimination of droplets and wider range of stable growth conditions. A drawback of ammonia MBE, on the other hand, is a serious memory effect of NH3 condensed on the cryo-panels and the vicinity of heaters, which ruins the control of critical growth stages, i.e. the native oxide desorption and the surface reconstruction, and the accurate control of V/III ratio, especially in the initial stage of seed layer growth. In this paper, we demonstrate that the reliable and reproducible growth of GaN on Si (110) substrates is successfully achieved by combining two MBE growth technologies using rf plasma and ammonia and setting a proper growth protocol. Samples were grown in a MBE system equipped with both a nitrogen rf plasma source (SVT) and an ammonia source. The ammonia gas purity was ＞99.9999% and further purified by using a getter filter. The custom-made injector designed to focus the ammonia flux onto the substrate was used for the gas delivery, while aluminum and gallium were provided via conventional effusion cells. The growth sequence to minimize the residual ammonia and subsequent memory effects is the following: (1) Native oxides are desorbed at $750^{\circ}C$ (Fig. (a) for [$1^-10$] and [001] azimuth) (2) 40 nm thick AlN is first grown using nitrogen rf plasma source at $900^{\circ}C$ nder the optimized condition to maintain the layer by layer growth of AlN buffer layer and slightly Al-rich condition. (Fig. (b)) (3) After switching to ammonia source, GaN growth is initiated with different V/III ratio and temperature conditions. A streaky RHEED pattern with an appearance of a weak ($2{\times}2$) reconstruction characteristic of Ga-polarity is observed all along the growth of subsequent GaN layer under optimized conditions. (Fig. (c)) The structural properties as well as dislocation densities as a function of growth conditions have been investigated using symmetrical and asymmetrical x-ray rocking curves. The electrical characteristics as a function of buffer and GaN layer growth conditions as well as the growth sequence will be also discussed. Figure: (a) RHEED pattern after oxide desorption (b) after 40 nm thick AlN growth using nitrogen rf plasma source and (c) after 600 nm thick GaN growth using ammonia source for (upper) [110] and (lower) [001] azimuth.

• Korean Chemical Engineering Research
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• 제53권3호
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• pp.372-381
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• 2015

본 연구에서는 $Ni/Al_2O_3$ 촉매를 사용한 에틸렌글리콜의 수증기 개질반응에서 제조 방법에 따른 영향을 알아보았다. 촉매들은 건식 함침법, 습식 함침법 그리고 공침법을 사용하여 제조하였다. 공침법을 사용하여 촉매 제조시 침전제를 KOH, $K_2CO_3$, $NH_4OH$를 각각 사용하여 침전제에 따른 영향 또한 알아보았다. 제조한 촉매들은 질소 물리흡착, 유도결합 플라즈마 질량분석법(ICP-AES), X선 회절법(XRD), 수소 승온 환원법(TPR), 수소 화학흡착, 승온 산화법(TPO), 주사전자현미경(SEM), 열분석법(TGA)을 사용하여 촉매의 물리화학적인 특성을 분석하였다. 773 K에서 환원한 촉매의 경우 KOH 혹은 $K_2CO_3$를 침전제로 사용하여 공침법으로 제조한 촉매가 가장 높은 활성을 보였다. 촉매 제조 방법은 Ni의 입자크기, Ni 산화물의 환원도, 반응에서의 활성과 안정성, 반응 중 탄소 침적의 형태 등에 영향을 끼치는 것을 확인할 수 있었다. KOH를 침전제로 사용하여 공침법으로 제조한 촉매의 경우 환원온도를 773~1173 K까지 증가시켰을 때, Ni 입자크기의 증가에도 불구하고 Ni 산화물의 환원도가 증가하므로 반응활성이 증가하는 것으로 나타났다.