• 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.

• 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.

• 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.

• 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.

• 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.

• Journal of Environmental Science International
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• v.32 no.10
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• pp.731-739
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• 2023

In this study, lab-scale phosphorus coagulation/precipitation experiments were performed using three types of polyaluminum chloride (PAC) with different Al contents (10%, 12%, and 17%). The PO₄-P removal efficiencies at various operating conditions, such as initial PO₄-P concentration, initial pH, and Al/P molar ratio, were evaluated, and correlations among the operating factors affecting phosphorus coagulation/precipitation with PAC were derived to optimize the process efficiency. When the initial PO₄-P concentration was 0.065 and 0.161 mmol P/L under an initial pH of 8-10, the optimal PAC dose was 0.126-0.378 and 0.189-0.667 mmol Al/L, respectively. Under these conditions, the Al/P molar ratio was 2.16-6.18 and 1.28-4.30, respectively, and the PO₄-P removal efficiency was in the range of 40.2-92.5%. When the Al/P molar ratio was 2 or less under an initial pH condition of 6-8, the PO₄-P removal efficiency was approximately ≤40% owing to insufficient Al³⁺ ions. However, when the Al/P molar ratio is 3-5, the PO₄-P removal efficiency improved to approximately 80-90%. Thus, the optimal Al/P molar ratio to achieve a PO₄-P removal efficiency of over 90% was determined to be approximately 4 in the PO₄-P coagulation/precipitation process using PAC.

• 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.

• 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.

• 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.

• 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.