Effect of pre-treatment polishing on fabrication of anodic aluminum oxide using commercial aluminum alloy

김기범,김병찬,하석재,조명우 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9

Aluminum anodizing is a process in which metal is oxidized with an electrochemical method to make a metallic oxide. Because it can be used to manufacture an Anodic aluminum oxide (AAO) with dozens to hundreds of nanoscale pores that are vertically and uniformly arranged, it is widely applied in a variety of fields. In particular, most of the pre-treatment methods in the anodic oxidation processes using a high-purity aluminum adopt surface treatment through electrolyte polishing. In this study, complex polishing was performed using an abrasive film and Magnetorheological (MR) fluid for a commercial aluminum alloy to produce a uniform porous oxidized aluminum. The surface roughness and surface integrity were analyzed after each process to investigate the production behavior of AAO in relation to the pre-treatment of the surface. In addition, a study was conducted on the nano-pore production by the anodizing process in accordance with the pre-treatment polishing, in terms of the work-hardening and residual stress. Thus, in the anodic oxidation process, it was possible to generate uniform nano-pores when surface integrity including surface roughness and residual stress distribution of the aluminum alloys are excellent. Test results showed that the polishing process using the MR fluid did not generate process scratches and pits, but could effectively remove the work-hardening and compressive residual stress, proving that MR fluid polishing method is a suitable pre-treatment process to produce nano-pores in the anodizing process.

<i>In Situ</i> Determination of the Pore Opening Point during Wet-Chemical Etching of the Barrier Layer of Porous Anodic Aluminum Oxide: Nonuniform Impurity Distribution in Anodic Oxide

Han, Hee,Park, Sang-Joon,Jang, Jong Shik,Ryu, Hyun,Kim, Kyung Joong,Baik, Sunggi,Lee, Woo American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.8

<P>Wet-chemical etching of the barrier oxide layer of anodic aluminum oxide (AAO) was systematically investigated by using scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and a newly devised experimental setup that allows accurate <I>in situ</I> determination of the pore opening point during chemical etching of the barrier oxide layer. We found that opening of the barrier oxide layer by wet-chemical etching can be significantly influenced by anodization time (<I>t</I><SUB>anodi</SUB>). According to secondary ion mass spectrometry (SIMS) analysis, porous anodic aluminum oxide (AAO) samples formed by long-term anodization contained a lower level of anionic impurity in the barrier oxide layer compared to the short-term anodized one and consequently exhibited retarded opening of the barrier oxide layer during the wet-chemical etching. The observed compositional dependence on the anodization time (<I>t</I><SUB>anodi</SUB>) in the barrier oxide layer is attributed to the progressive decrease of the electrolyte concentration upon anodization. The etching rate of the outer pore wall at the bottom part is lower than that of the one at the top part due to the lower level of impurity content in that region. This indicates that a concentration gradient of anionic impurity in the outer pore wall oxide may be established along both the vertical and radial directions of cylindrical pores. Apart from the effect of electrolyte concentration on the chemical composition of the barrier oxide layer, significantly decreased current density arising from the lowered concentration of electrolyte during the long-term anodization (∼120 h) was found to cause disordering of pores. The results of the present work are expected to provide viable information not only for practical applications of nanoporous AAO in nanotechnology but also for thorough understanding of the self-organized formation of oxide nanopores during anodization.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-8/am400520d/production/images/medium/am-2013-00520d_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am400520d'>ACS Electronic Supporting Info</A></P>

Evaluation of natural organic matter adsorption on Fe-Al binary oxide: Comparison with single metal oxides

Kim, Kyung-Jo,Jang, Am Elsevier 2017 CHEMOSPHERE - Vol.185 No.-

<P><B>Abstract</B></P> <P>The adsorption characteristics of three types of standard natural organic matter (NOM) on iron-aluminum (Fe-Al) binary oxide (FAO) and heated aluminum oxide (HAO) under natural surface water condition were investigated using various adsorption isotherms and kinetic models. FAO was synthesized by Fe oxide and Al oxide, mixed using the sol-gel hydrothermal method, and aluminum sulfate was used to make HAO. The amount of adsorbed NOM was increased to 79.6 mg g<SUP>−1</SUP> for humic acid (HA), 101.1 mg g<SUP>−1</SUP> for sodium alginate (SA) in the FAO, but the maximum adsorption capacity of bovine serum albumin (BSA) (461.3 mg g<SUP>−1</SUP>) was identified on the HAO. The adsorption of HA, BSA, and SA dramatically increased (>70%) on FAO in 5 min and HA was significantly removed (90%) among the three NOM. Mutual interaction among the adsorbed NOM (BSA) occurred on the HAO surface during adsorption due to formation of monolayer by protein molecules at neutral pH. The pseudo second order clearly represented the adsorption kinetics for both adsorbents. The equilibrium isotherm data of FAO was better exhibited by the Langmuir isotherm model than by the Freundlich isotherm, but HAO was a slightly non-linear Langmuir type. Also, the free energy, enthalpy, and entropy of adsorption were determined from the thermodynamic experiments. Adsorption on FAO was spontaneous and an exothermic process. Fluorescence excitation-emission matrix (FEEM) spectra were used to elucidate the variation in organic components. The results obtained suggests that the significant changes in the surface property of the adsorbent (large surface area, increased crystalline intensity, and fine particle size) were effectively determined by the Fe-synthesized Al oxide mixed using the sol-gel hydrothermal method. The results also suggest that the changes enhanced the adsorption capacity, whereby three NOM were notably removed on FAO regardless of NOM characteristics (hydrophobic and hydrophilic).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Substantial natural organic matter (NOM) is removed after iron-synthesized aluminum oxide adsorption. </LI> <LI> The adsorption of NOM on iron-synthesized aluminum oxide indicates spontaneous and exothermic processes. </LI> <LI> The synthesized metal oxide can remove the both hydrophobic and hydrophilic NOM. </LI> </UL> </P>

알루미늄 분말의 열적 산화거동에 미치는 니켈 코팅의 영향

김경태 ( Kyung Tae Kim ),우재열 ( Jae Yeol Woo ),최윤정 ( Yoon Jeong Choi ),김창기 ( Chang Kee Kim ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.12

Aluminum powders with average diameters of 24, 45, and 75 μm were homogeneously coated with nickel through an electroless plating process. The effect of nickel coating on the thermal oxidation behavior of the aluminum powders was clearly confirmed by observing the variation of the weight gain during thermal gravimetric analysis in an air atmosphere. The results obtained from differential scanning calorimetry showed that the exothermic enthalpy values of the aluminum powders increased significantly with decrease in the powder size from 75 μm to 25 μm. Furthermore, the nickel-coated aluminum powders exhibited much higher exothermic enthalpy values than those of pure aluminum powders. It was found that nickel coated onto aluminum powders plays an important role as a protective layer, preventing pure aluminum powders from undergoing surface oxidation while also providing exothermic heat through a self-propagating high-temperature synthetic reaction between the nickel and the aluminum. These results indicate that nickel coating should be considered to achieve high reactivity in aluminum powders for energetic applications.

Solution-Processed Aluminum-Zirconium Oxide as a Gate Dielectric for InGaZnO Thin Film Transistors

Han Jeong Hun,Lee So Young,Kim Hyo Eun,Jeon Jae-Hong,Park KeeChan,Moon Kook Chul,Im Hwarim,Kim Yong-Sang 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1

This study presents a solution-processed aluminum-zirconium oxide (AlZrOx) dielectric for amorphous indium-gallium-zinc oxide (a-IGZO) thin-flm transistors (TFTs). Solution-processed AlZrOx thin flms exhibit overall improved dielectric properties, such as leakage current characteristics of 1.10× 10–8 A/cm2 at 0.5 MV/cm and high dielectric constants of approximately 9.1 by combining the advantages of aluminum oxide (AlOx) and zirconium oxide (ZrOx). Solution-processed IGZO TFTs using the AlZrOx flm as a gate insulator layer exhibited a threshold voltage of 0.64 V, feld-efect mobility of 3.06 cm2 /V s, and a subthreshold slope of 0.26 V/dec. In addition, the IGZO TFTs with the AlZrOx flms exhibited a higher on/of current ratio of 1.05× 106 than devices with the AlOx and ZrOx gate insulator layers. The improvement of device properties is mainly attributed to the interface properties. The IGZO TFTs with the AlZrOx gate insulator exhibited the lowest interface trap density of 2.07× 1012 cm−2 eV−1, compared to the devices with the AlOx and ZrOx gate insulators of 3.30× 1012 and 5.06× 1012 cm−2 eV−1, respectively, because of the smooth surface roughness and reduced residual hydroxyl groups in the flms. The IGZO TFTs with the AlZrOx gate insulator also improved hysteresis characteristics with the hysteresis window of 0.17 V. This study presents a signifcant step toward developing low-cost, low-power-consumption, and high-performance oxide electronic device.

알루미늄 함량에 따른 알루미늄 주철의 내산화성에 관한 연구

김동혁 ( Dong-hyuk Kim ) 한국주조공학회 2020 한국주조공학회지 Vol.40 No.6

Aluminum cast iron has excellent oxidation resistance, sulfurization resistance, and corrosion resistance. However, the ductility at room temperature is insufficient, and at temperatures above 600?, the strength drops sharply and practicality is limited. In the case of heat-resistant cast iron, high-temperature materials containing Cr and Ni account for 30 to 50% or more. However, these high-temperature materials are expensive. Aluminum heat-resistant cast iron is considered as a substitute for expensive heat-resistant materials. Oxidation due to the aging temperature and holding time conditions increases more in 0 wt.% Al-cast iron than in 2 and 4 wt.% Al-cast iron according to oxidized weight and gravimetric oxide layer thickness measurements. As a result of observing the cross-section of the oxide layer, it was found to contain 0 wt.% of Al-cast iron silicon oxide-containing SiO₂ or Fe₂SiO₄ oxide film. In cast iron containing aluminum, the thickness of the internal oxide layer due to aluminum increases as the aging temperature and retention time increase, and the amount of the iron oxide layer generated on the surface decreases.

Aluminum-Copper(II) Oxide Composite의 정전기에 의한반응 특성 연구

김민준,김성호,김자영,임예슬 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.5

The reaction characteristics of aluminum-copper(II) oxide composites initiated by the electrostatic discharge were studied as changing the aluminum particle size. Three different sizes of aluminum particles with nano-size copper(II)-oxide particle were used in the study. These composites were manufactured by two methods i.e. a shock-gel method and a self-assembly method. The larger aluminum particle size was, the less sensitive and less violent these composites were based on the electrostatic test. On the analysis of high speed camera about ignition appearances and burning time, the burning speed was faster when aluminum particle size was smaller.

Preparation and Analysis of High Functional Silicone Hydrogel Lens Containing Metal Oxide Nanoparticles by Photopolymerizaion

허지원,성아영 한국재료학회 2022 한국재료학회지 Vol.32 No.4

In this study, lenses are fabricated using various nanomaterials as additives to a silicone polymer made with an optimum mixing ratio and short polymerization time. In addition, PVP is added at a ratio of 1% to investigate the physical properties according to the degree of dispersion, and the compatibility with hydrophobic silicone and the possibility of application as a functional lens material are confirmed. The main materials are SIU as a silicone monomer, DMA, a hydrophilic copolymer, EGDMA as a crosslinking agent, and 2H2M as a photoinitiator. Holmium (III) oxide, Europium (III) oxide, aluminum oxide, and PVP are used. When Holmium (III) oxide and Europium (III) oxide are added based on the Ref sample, the characteristics of the lens tend to be similar overall, and the aluminum oxide shows a tendency slightly different from the previous two oxides. This material can be used as a silicone lens material with various nano oxides and polyvinylpyrrolidone (PVP) acting as a dispersant.

Effect of Oxide Dispersion on Dendritic Grain Growth Characteristics of Cast Aluminum Alloy

Kim, Gwang-Ho,Hong, Sung-Mo,Lee, Min-Ku,Kim, Soon-Ho,Ioka, Ikuo,Kim, Byoung-Suhk,Kim, Ick-Soo The Japan Institute of Metals 2010 Materials transactions Vol.51 No.10

<P>The dispersion characteristics of the nano-sized Y<SUB>2</SUB>O<SUB>3</SUB> powders in molten aluminum were investigated from the viewpoint of changes in microstructure and mechanical property as a function of oxide contents. As the solidification structure, the oxide nanoparticles dispersed in the columnar crystal was mainly segregated on the grain boundary, whereas the oxide nanoparticles dispersed in the equiaxed crystal was uniformly dispersed on both grain boundary and inside the crystal. The most uniform dispersion of oxide nanoparticles was observed at Y<SUB>2</SUB>O<SUB>3</SUB> content of 2 mass%. As Y<SUB>2</SUB>O<SUB>3</SUB> content of 3 mass%, the size of oxide nanoparticles in metal matrix increased due to the particle aggregation, as confirmed by SEM analysis. Moreover, it was found that the mechanical properties such as hardness and tensile strength were improved at Y<SUB>2</SUB>O<SUB>3</SUB> content of 2 mass%, indicating the well-dispersion of nano-sized Y<SUB>2</SUB>O<SUB>3</SUB> powders in cast aluminum. The hardness was increased by 1.2 times up to 57 <I>H</I><SUB>V</SUB> and tensile strength was increased by 1.55 times up to 80 MPa, compared with the case of pure aluminum. However, at Y<SUB>2</SUB>O<SUB>3</SUB> content of 3.0 mass%, tensile strength was sharply decreased by 0.6 times due to aggregation of oxide nanoparticles, while the hardness was increased to 57 <I>H</I><SUB>V</SUB>, which is the same as the case of Y<SUB>2</SUB>O<SUB>3</SUB> content of 2.0 mass%.</P>

Improvement of oxidation resistance of graphite by aluminosilicate coating with aluminum metaphosphate interlayer

M. Fekri,K. Jafarzadeh,S. A. Khalife Soltani,Z. Valefi,H. Mazhari Abbasi 한국탄소학회 2023 Carbon Letters Vol.33 No.7

In this research, in order to increase the oxidation resistance of graphite, kaolin and alumina powder with different ratios (26A-74S, 49A-51S, 72A-28S) and slurry method were used to create an aluminosilicate coating on the graphite substrate. In order to reduce the difference in the coefficients of thermal expansion of graphite with aluminosilicate coating, aluminum metaphosphate coating as an interlayer was prepared on the surface of graphite by cathodic electrochemical treatment. The isothermal oxidation test of the samples was carried out in air at a temperature of 1250 °C for 1, 3 and 5 h. The microstructure, chemical composition, and phase components of the coating were, respectively, analyzed by scanning electron microscope equipped with an energy-dispersive spectrometer and X-ray diffraction. The results indicated that, by increasing the withdrawal speed of the samples in slurry method, the amount of changes in the weight of the samples has increased and therefore had a direct effect on oxidation. In addition, it was approved that, at high-temperature oxidation, AlPO4 glass phase forms on aluminum metaphosphate interlayer which retards graphite oxidation. Along with aluminum metaphosphate, aluminosilicate coating also produces a glass phase which fills and seals the voids on the surface which prevents the oxygen to reach the surface of graphite. The created double-layer coating including an interlayer of aluminum metaphosphate + slurry coating prepared with the ratio of 26A-74S as the optimal coating in this research was able to increase the oxidation resistance of graphite by 73% at a temperature of 1250 °C.