• Title/Summary/Keyword: amorphous $Al(OH)_3$

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Immobilization of Thermomyces lanuginosus Xylanase on Aluminum Hydroxide Particles Through Adsorption: Characterization of Immobilized Enzyme

  • Jiang, Ying;Wu, Yue;Li, Huixin
    • Journal of Microbiology and Biotechnology
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    • v.25 no.12
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    • pp.2016-2023
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    • 2015
  • Xylanase plays important roles in a broad range of industrial production as a biocatalyst, and its applications commonly require immobilization on supports to enhance its stability. Aluminum hydroxide, a carrier material with high surface area, has the advantages of simple and low-cost preparation and resistance to biodegradation, and can be potentially used as a proper support for xylanase immobilization. In this work, xylanase from Thermomyces lanuginosus was immobilized on two types of aluminum hydroxide particles (gibbsite and amorphous Al(OH)3) through adsorption, and the properties of the adsorbed enzymes were studied. Both particles had considerable adsorptive capacity and affinity for xylanase. Xylanase retained 75% and 64% of the original catalytic activities after adsorption to gibbsite and amorphous Al(OH)3. Both the adsorptions improved pH and thermal stability, lowered activation energy, and extended lifespan of the immobilized enzyme, as compared with the free enzyme. Xylanase adsorbed on gibbsite and amorphous Al(OH)3 retained 71% and 64% of its initial activity, respectively, after being recycled five times. These results indicated that aluminum hydroxides served as good supports for xylanase immobilization. Therefore, the adsorption of xylanase on aluminum hydroxide particles has promising potential for practical production.

Photoluminescence and Thermal Characteristics of SrAl2O4:Eu+2, Dy+3 Phosphors Synthesized with Various Aluminum Compounds (SrAl2O4:Eu+2, Dy+3 장잔광 형광체 합성에 있어서 알루미늄 화합물에 따른 열적거동 및 발광특성 변화)

  • Lee, Young-Ki;Lee, You-Kee
    • Korean Journal of Materials Research
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    • v.17 no.11
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    • pp.612-617
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    • 2007
  • Both photoluminescence and thermal characteristics for $SrAl_2O_4:Eu^{+2},\;Dy^{+3}$ phosphors synthesized with various aluminum compounds (${\alpha}-Al_2O_3$, ${\gamma}-Al_2O_3$, amorphous-$Al_2O_3$ and $Al(OH)_3)$ were investigated in this study. The formation temperature of the host $SrAl_2O_4$ crystal is changed by these various aluminum compounds, as a result of the different thermal decomposition temperature of $SrCO_3$ phase. Among these compounds, the amorphous-$Al_2O_3$ phase shows the lowest formation temperature of the host $SrAl_2O_4$ crystal. The PL emission and excitation spectra of $SrAl_2O_4:Eu^{+2},\;Dy^{+3}$ phosphor are not affected by these aluminum compounds. After the removal of the Xenon lamp excitation (360 nm), however, the excellent longphosphorescent property of the phosphor is obtained by the amorphous-$Al_2O_3$ phase, although the decay time for all phosphors decrease exponentially.

Effect of Heat Treatment on Magnetic and Electrical Properties of AlN Films with Co Particles

  • Oh, Chang-Sup;Han, Chang-Suk
    • Korean Journal of Metals and Materials
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    • v.50 no.3
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    • pp.248-255
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    • 2012
  • AlN thin films containing various amounts of Co, AlN-Co, and Al-Co alloy particles were prepared using a two-facing-target type dc reactive sputtering (TFTS) system. The as-deposited films exhibited the variable nature expected from an AlN-rich phase, and an amorphous-like phase, depending on the Co content in the films. Specific favorable microstructures were prepared by optimizing annealing conditions. Those microstructures and their magnetic properties and resistivity were investigated. As-deposited films showed very small saturation magnetization and an amorphous-like structure. However, when annealed, the as-deposited amorphous-like phase decomposes into phases of AlN, Co and Al-Co. These annealing induced changes in the microstructure improve the magnetization and resistivity of the films. Further improvement of soft magnetic properties could lead to the material being used for high density magnetic recording head material.

Effects of Sintering Additives on the Microstructure Development in Silicon Oxynitride Ceramics

  • Kim, Joosun;Chen, I-Wei
    • The Korean Journal of Ceramics
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    • v.6 no.3
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    • pp.224-228
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    • 2000
  • Using a small amount of additives and amorphous Si₂N₂O powders, O-SiAlON ceramics have been hot-pressed and its microstructure and mechanical properties were investigated. Scandium oxide was demonstrated to be an effective densification additive for O-SiAlON. Amorphous Si₂N₂O was densified at relatively low temperatures and a microstructure with acicular grains was developed. Fine grains found in materials obtained from amorphous powders suggest that nucleation and crystallization of O-SiAlOH is relatively easy compared with the Si₃N₄-SiO₂reaction.

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Properties of Alumina Powder Prepared by Precipitation Method(I): Aluminum Hydrate (침전법으로 제조한 Alumina 분말의 특성(1): 알루미늄 수산\ulcorner루)

  • 홍기곤;이홍림
    • Journal of the Korean Ceramic Society
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    • v.25 no.2
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    • pp.111-116
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    • 1988
  • Aluminum hydrates were prepared by precipitation method using Al2(SO4)3$.$18H2O as a starting material and NH4OH as precipitation agent. The phases of aluminum hydrate were changed from amorphous aluminum hydrate to pseudo-boehmite of AlOOH form and bayerite, gibbsite, hydragillite and norstrandite of Al(OH)3 form with increasing pH. As pH increased, agglomeration phenomena were reduced. Aluminum hydrates of AlOOH and Al(OH)3 form represented dehydration of structural water near 175$^{\circ}C$ and 385$^{\circ}C$, and 280$^{\circ}C$, respectively. As the ratio of Al(OH)3 to AlOOH increased, specific surface area was reduced.

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A Study on the Morphology of Carbon Nanomaterials prepared by Thermal CVD on the Mechanochemical Treated Catalysts

  • Ryu, Ho-Jin;Yi, Hyung-Kyun;Saito, Fumio;Lee, Byuung-Il;Chang, Ho-Jung
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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    • 2002.11a
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    • pp.75-78
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    • 2002
  • CNTs have been grown by the thermal CVD process in which $C_{2}H_{2}$ gas was deposited on the Fe - $Al(OH)_3$ mixture pretreated by mechanochemical treatment with a high energy mixer mill. As the duration time of grinding fer $Fe-(Al(OH)_3$ mixture by the mixer mill increased, amorphous $Al(OH)_3$ and more smaller Fe particles agglomerated into spheres. With unground and ground mixtures of $Fe-Al(OH)_3$, CNTs were grown at $700^{\circ}C$. As a result, CNTs grown on ground mixtures have more uniform diameter and morphology than those of unground mixture. The characterization of $Fe-Al(OH)_3$ mixture and as-grown CNTs were done by XRD, SEM and TEM.

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Early Hydration Properties of Calcium Aluminosulfate (3CaO · 3Al2O3 · CaSO4) Prepared by Chemical Synthesis

  • Kim, Hoon-Sang;Kim, Hyung-Chul;Song, Jong-Taek
    • Journal of the Korean Ceramic Society
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    • v.39 no.7
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    • pp.617-621
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    • 2002
  • Calcium aluminosulfate (3CaO.3Al$_2$O$_3$.CaSO$_4$or $C_4$A$_3$S) was prepared by chemical synthesis from the nitrate salts and aluminum sulfate. $C_4$A$_3$S was the main phase after calcination at 110$0^{\circ}C$. The specific surface areas after calcination at 110$0^{\circ}C$ and 130$0^{\circ}C$ were about 2.5 and 1.0 $m^2$/g, respectively. Hydration was investigated by XRD, DSC, SEM, EDS, conduction calorimetry and analysis of the liquid phase. Calorimetry showed that the induction period was longer than that of a sample prepared by conventional solid state sintering and this was attributed to the formation of amorphous coatings in abundance of $Al_2$O$_3$ and SO$_3$. Crystalline hydration products, principally calcium monosulfoaluminate hydrate and Al(OH)$_3$, appeared subsequently.

A study on the synthesis of amorphous aluminium phosphate powders by hydrothermal precipitation method (수열침전법에 의한 비정질 인산알루미늄 분말의 합성에 관한 연구)

  • 김판채;최종건;황완인;이충효
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.11 no.5
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    • pp.185-189
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    • 2001
  • Amorphous aluminium phosphate powders were synthesized as a single phase by neutralization reaction of a stoichiometric mixture of $Al_2(SO_4)_3$ and $H_3PO_4$ using the NaOH or KOH solution and subsequently by the hydrothermal precipitation method. The synthesis conditions were as follows : starting materials; $Al_2(SO_4)_3$ and $H_3PO_4$,pH ranges of neutralization reaction; between 5.6 and 6.0, temperature ranges of hydrothermal reaction; between 170 and $180^{\circ}C$,time ranges of hydrothermal reaction; between 4 and 5hs. Under such synthesis conditions, the products are obtained as amorphous aluminium phosphate powders of 0.1~0.3$\mu\textrm{m}$ in size and are Eitted to USP (United Standard Pharmacopoeia) test.

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Preliminary Study on the Phase Transition of White Precipitates Found in the Acid Mine Drainage (산성광산배수에서 발견되는 흰색침전물의 상전이에 대한 예비 연구)

  • Yeo, Jin Woo;Kim, Yeongkyoo
    • Journal of the Mineralogical Society of Korea
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    • v.32 no.2
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    • pp.79-86
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    • 2019
  • The white aluminum phases in acid mine drainage usually precipitates when mixed with stream waters with relatively high pH. The minerals in white precipitates play important roles in controlling the behavior of heavy metals by adsorbing and coprecipitation. By the phase transition of these minerals in white precipitates, dissolution and readsorption of heavy metals may occur. This study was conducted to obtain preliminary information on the phase transition of the mineral phases in white precipitates. In this study, the mineral phase changes in the white precipitates collected from the stream around Dogye Mining Site over time were investigated with different pH values and temperatures. White precipitates consist mainly of basaluminite, amorphous $Al(OH)_3$ and a small amount of $Al_{13}$-tridecamer. During aging, the incongruent dissolution of the basaluminite occurs first, increasing the content of the amorphous $Al(OH)_3$. After that, pseudoboehmite is finally precipitated following the precursor phase of pseudoboehmite. At $80^{\circ}C$, this series of processes was clearly observed, but at relatively low temperatures, no noticeable changes were observed from the initial condition with coexisting basaluminite and amorphous $Al(OH)_3$. At high pH, the desorption of $SO{_4}^{2-}$ group in basaluminite was initiated to promote phase transition to the pseudoboehmite precursor. Over time, the solution pH decreases due to the dissolution and phase transition of the minerals, and even after the precipitation of pseudoboehmite, only the particle size slightly increased but no clear cystal form was observed.

Effect of pH and Initial Phosphorus Concentration on Phosphorus Removal by Aluminum Salts (알루미늄염에 의한 인 제거 시 pH와 초기 인 농도의 영향)

  • Park, Jeongwon;Kwak, Hyoeun;Min, Sojin;Chung, Hyung-Keun;Park, Pyung-Kyu
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.2
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    • pp.123-130
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    • 2016
  • Phosphorus (P) removal by aluminum sulfate solution was investigated with varying pH and initial P concentrations. P removal was the highest at around pH 6. The pH range where P removal occurred was slightly wider at higher initial P concentrations. Compared to theoretical calculations, it was confirmed that $AlPO_4$ precipitation was the main reason for P removal at low pH. At high pH, where there should be no $AlPO_4$ precipitates, the P removal by adsorption of amorphous $Al(OH)_3$ precipitates was experimentally observed. The P removal by adding amorphous $Al(OH)_3$ precipitates prepared before the adsorption experiments, however, was lower than that by injecting aluminum sulfate solution because the prepared precipitates became larger, leading to less specific surface area available for adsorption. Ions other than sulfate had little influence on P removal.