• Title, Summary, Keyword: $AlPO_4$

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Analysis of adsorption behavior of lead ion on to surface modified AlPO4 materials (표면처리된 AlPO4에 대한 납 이온의 흡착 거동 분석)

  • Kim, Young-Ho;Kil, Hyun-Suk;Kang, Kwang-Cheol;Choi, Suk-Nam;Rhee, Seog-Woo
    • Analytical Science and Technology
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    • v.24 no.4
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    • pp.275-281
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    • 2011
  • $AlPO_4$-type material was synthesized by a reaction of $Al(OH)_3$ and H3PO4 with organic templates from wastewater of detergent manufacturer. The surface of material was coated with carboxylate groups by the reaction of succinic anhydride with surface amino groups which were formed by treatment of the material with APTMS. Powder XRD patterns showed the characteristic patterns of $AlPO_4$. Morphology of the material was examined using a SEM and the functional groups were investigated by FT-IR analysis. The surface charge of a aqueous suspension was analyzed: $AlPO_4-NH_2$ has positively charged surface while $AlPO_4$-COOH has negatively charged one. They were used for the removal of toxic metals from aqueous solution. The lead ions were adsorbed on the surface by the formation of complexes with carboxylate of surface and $K_d$ was 91.1 mL/g. In conclusion, the $AlPO_4$-COOH might be applicable in the removal of toxic metal ions from aqueous system.

Surface Treatment of LiFePo4 Cathode Material for Lithium Secondary Battery

  • Son, Jong-Tae
    • Journal of the Korean Electrochemical Society
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    • v.13 no.4
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    • pp.246-250
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    • 2010
  • In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

Synthetic Characteristics of AlPO$_4$-5 Molecular Sieve (AlPO$_4$-5 분자체의 합성 특성)

  • Sung Hwa Jhung;Suk Bong Hong;Young Sun Uh;Hakze Chon
    • Journal of the Korean Chemical Society
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    • v.37 no.10
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    • pp.867-873
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    • 1993
  • Influences of crystallization time and $H_2O/Al_2O_3$ ratio of the reaction mixtures on the synthesis of AlPO$_4$-5 molecular sieve have been studied by X-ray powder diffraction, nitrogen adsorption, scanning electron microscope (SEM), and solid state $^{27}$Al magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. The degree of crystallinity of AlPO$_4$-5 follows a sigmoid pattem as crystallization time increases. The induction period is shorter than 1 h when the crystallization process is carried out at 150$^{\circ}$C. The conversion of reactants to product, AlPO$_4$-5, can be clearly observed, and all of the determined physical properties change abruptly after about 2 h. It is found that increase in $H_2O/Al_2O_3$ ratio of the reaction mixtures not only changes the crystal morphology from aggregates to hexagonal single crystals, but also results in the formation of longer AlPO$_4$-5 crystals.

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Enhancement of Porosity and Strength of Porous Al2O3 Ceramics by Al(H2PO4)3 Addition

  • Bai, Jiahai;Piao, Jiasi;Gao, Jie;He, Jing;Du, Qingyang;Li, Chengfeng
    • Journal of the Korean Ceramic Society
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    • v.56 no.4
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    • pp.350-353
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    • 2019
  • Porous alumina ceramics with addition of 0, 5, 10, 15, and 20 wt% Al(H2PO4)3 were sintered at 1300, 1350, and 1400℃. The effects of the Al(H2PO4)3 addition on crystal phases, water absorption, open porosity, pore size distribution, microstructures, and flexural strength were studied extensively. The experimental results revealed that only characteristic peaks of corundum were indexed in the XRD patterns of the as-prepared porous ceramics. The water absorption and open porosity of the porous Al2O3 ceramics increased remarkably with an increase in Al(H2PO4)3 addition. The flexural strength first increased to a maximum value when 5 wt% Al(H2PO4)3 was added and then decreased as additional Al(H2PO4)3 was further added. SEM images showed that the average Al2O3 grain size in the porous ceramics changed in an opposite way as the flexural strength. The porous Al2O3 ceramics with 10 wt% Al(H2PO4)3 addition exhibited comparable flexural strength to the ceramics without Al(H2PO4)3 addition, although the latter had much higher porosity.

Synthesis of AlPO4-type Mesoporous Materials Using Alum Sludge (Alum 슬러지를 이용한 AlPO4-계 다공성 물질의 합성)

  • Kang, Kwang Cheol;Kim, Young Ho;Kim, Jin-man;Lee, Choul Ho;Rhee, Seog Woo
    • Applied Chemistry for Engineering
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    • v.22 no.2
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    • pp.173-177
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    • 2011
  • In this study, the formation of $AlPO_4$-type porous materials from alum sludge was investigated. The materials were synthesized by the reaction of aluminum hydroxide and phosphoric acid with an organic template. Cationic surfactant, natural humic acid, and amino acids were used for the organic template. The residual organic templates were removed by calcination at $600^{\circ}C$ in the air. Powder X-ray diffraction patterns showed the charicteristic patterns of the $AlPO_4$-type porous materials. The morphology of the material was examined using a scanning electron microscopy. The coordination environment of $Al^{3+}$ ion was investigated by $^{27}Al$ MAS NMR technique. Both tetrahedrally and octahedrally coordinated$Al^{3+}$ ions were found in the as-synthesized samples while all $Al^{3+}$ ions were tetrahedrally coordinated in the calcined products. The development of mesopore in the solid material was confirmed by the measurement of BET specific surface area. Finally, they were used for removal of toxic formaldehyde from the air and the formaldehyde molecules were adsorbed on the surface of pores. In conclusion, $AlPO_4$-type porous materials from alum sludge might be applicable in the removal of toxic volatile organic compounds from the air.

Effects of doping on the electrical conductivity and particle size in olivine type $LiFePO_4$ powders (올리빈형 $LiFePO_4$ 분말의 전기전도도와 입도 크기에 미치는 도핑의 영향)

  • Bai, Jin-Tao;Ha, Jung-Soo;Kim, Chang-Sam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.18 no.6
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    • pp.248-252
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    • 2008
  • To get a fine $LiFePO_4$ powder with high electrical conductivity, the influences of doping of aliovalent elements(Cr+B and Cr+Al) on electrical conductivity and of heat treatment conditions on particle size of the doped powders were studied. Two kinds of the doped powders $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.065}Cr_{0.03}Al_{0.005}PO_4$ were synthesized using mechanochemical milling and subsequent heat treatment at $675{\sim}750^{\circ}C$ for $5{\sim}10\;h$. The doping enhanced grain growth and electrical conductivity. The electrical conductivity at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$ in the doped with Cr and Al, and $5{\times}10^{-10}S/cm$ in the undoped one.

Electrochemical Properties and Thermal Stability of LiNi0.8Co0.15 Al0.05O2-LiFePO4 Mixed Cathode Materials for Lithium Secondary Batteries

  • Kim, Hyun-Ju;Jin, Bong-Soo;Doh, Chil-Hoon;Kim, Hyun-Soo
    • Journal of Electrochemical Science and Technology
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    • v.3 no.2
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    • pp.63-67
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    • 2012
  • We prepared various $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2-LiFePO_4$ mixed-cathode electrodes by changing the content of $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ and $LiFePO_4$ used, and we analyzed the electrochemical characteristics of the cathodes. We found that the reversible specific capacity of the cathodes increased and that the capacity retention ratios of the cathodes decreased during cycling as the content of $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2$ increased. Conversely, we found that although the reversible specific capacity of the cathodes decreased because of the material composition, the cycle property of the cathodes increased when the $LiFePO_4$ content increased. We analyzed the thermal stability of the $LiNi_{0.8}Co_{0.15}Al_{0.05}O_2-LiFePO_4$ mixed-material cathodes by differential scanning calorimetry and found that it increased as the $LiFePO_4$ content increased.

Synthesis and Electrochemical Performance of Reduced Graphene Oxide/AlPO4-coated LiMn1.5Ni0.5O4 for Lithium-ion Batteries

  • Hur, Jaehyun;Kim, Il Tae
    • Bulletin of the Korean Chemical Society
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    • v.35 no.12
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    • pp.3553-3558
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    • 2014
  • The reduced graphene oxide(rGO)/aluminum phosphate($AlPO_4$)-coated $LiMn_{1.5}Ni_{0.5}O_4$ (LMNO) cathode material has been developed by hydroxide precursor method for LMNO and by a facile solution based process for the coating with GO/$AlPO_4$ on the surface of LMNO, followed by annealing process. The amount of $AlPO_4$ has been varied from 0.5 wt % to 1.0 wt %, while the amount of rGO is maintained at 1.0 wt %. The samples have been characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The rGO/$AlPO_4$-coated LMNO electrodes exhibit better cyclic performance compared to that of pristine LMNO electrode. Specifically, rGO(1%)/$AlPO_4$(0.5%)- and rGO(1%)/$AlPO_4$(1%)-coated electrodes deliver a discharge capacity of, respectively, $123mAhg^{-1}$ and $122mAhg^{-1}$ at C/6 rate, with a capacity retention of, respectively, 96% and 98% at 100 cycles. Furthermore, the surface-modified LMNO electrodes demonstrate higher-rate capability. The rGO(1%)/$AlPO_4$(0.5%)-coated LMNO electrode shows the highest rate performance demonstrating a capacity retention of 91% at 10 C rate. The enhanced electrochemical performance can be attributed to (1) the suppression of the direct contact of electrode surface with the electrolyte, resulting in side reactions with the electrolyte due to the high cut-off voltage, and (2) smaller surface resistance and charge transfer resistance, which is confirmed by total polarization resistance and electrochemical impedance spectroscopy.

Theoretical Study of the Cobalt Substituting Site in the Framework of $AlPO_{4}-5$ Molecular Sieves

  • Sang Joon Choe;Dong Ho Park;Do Sung Huh
    • Bulletin of the Korean Chemical Society
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    • v.14 no.1
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    • pp.55-58
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    • 1993
  • In order to determine the cobalt substituting site in $AlPO_4-5$ framework, ASED-MO theory has been used. The substitution of cobalt for aluminum is energetically more favorable than that for phasphorous. The stabilized energy of the former is 51 eV lower than that of the latter. The calculated net charge was +1.27 for Al, +0.85 for P, and +1.56 for Co, respectively. The valence electron population (VEP), reduced overlap population (ROP) and net charge for the charged cluster models were compared for $AlPO_4-5$ and $CoAlPO_4-5$ systems. Then, twe find that the covalency of P-O bond was greater than that of Al-O bond.

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Electrical conductivity of olivine type LiFe0.965Cr0.03B0.005PO4 and LiFe0.965Cr0.03Al0.005PO4 powders (올리빈형 LiFe0.965Cr0.03B0.005PO4 and LiFe0.965Cr0.03Al0.005PO4 분말의 전기전도도)

  • Kim, Chang-Sam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.20 no.3
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    • pp.141-146
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    • 2010
  • $LiFePO_4$ doped with Cr showed improved electrochemical properties as a cathode material of lithium-ion batteries compared to the undoped. The improvement was thought that the doping would raise the electronic conductivity of the compounds. The electrical conductivity of $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder was measured in the temperature range from 30 to $80^{\circ}C$. The doped powders were synthesized via mechanochemical milling and subsequent heat treatment at 675~$750^{\circ}C$ for 5~10h. The doping enhanced grain growth and electrical conductivity. The electrical conductivity of the $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$, which was higher two orders of magnitude than that of the undoped.