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Synthesis, effect of γ-ray and electrical conductivity of uranium doped nano LiMn2O4 spinels for applications as positive electrodes in Li-ion rechargeable batteries

El-Metwaly F G, Abou-Sekkina M. M, Saad F A, Khedr A. M.

Materials Science Poland

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2014

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Vol. 32, No. 4

571--577

EN

LiMn2O4 is an attractive candidate cathode material for Li-ion rechargeable batteries, but it suffers from severe capacity fading, especially at higher temperature (55 ◦C) during charging/discharging processes. Recently, many attempts have been made to synthesize modified LiMn2O4. In this work, a new study on the synthesis of pure and U4+-doped nano lithium manganese oxide [LiMn2−xUxO4, (x = 0.00, 0.01, 0.03)] via solid-state method was introduced. The synthesized LiMn1.97U0.03O4 was irradiated by γ-radiation (10 and 30 kGy). The green samples and the resulting spinel products were characterized using thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared (IR), and scanning electron microscopy (SEM) measurements. XRD and SEM studies revealed nano-sized particles in all prepared samples. Direct-current (DC) electrical conductivity measurements indicated that these samples are semiconductors and the activation energies decrease with increasing rare-earth U4+ content and γ-irradiation. ∆Ea equals to 0.304 eV for LiMn1.99U0.01O4, ∆Ea is 0.282 eV for LiMn1.97U0.03O4 and decreases to ∆Ea = 0.262 eV for γ-irradiated LiMn1.97U0.03O4 nano spinel. The data obtained for the investigated samples increase their attractiveness in modern electronic technology.

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Synthesis, characterization, DC-electrical conductivity and γ-ray effect on Ag1+, Y3+ double doped nano lithium manganates (LiMn2−2x Ag x Y x O4) for rechargeable batteries

Abou-Sekkina M. M, Saad F A, El-Metwaly F G, Khedr A. M.

Materials Science Poland

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2014

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Vol. 32, No. 3

315--323

EN

Pristine lithium manganate (LiMn2O4) and Ag1+, Y3+ double doped nano lithium manganate [LiMn2−2x Ag x Y x O4, (x = 0.025, 0.05)] spinels were synthesized via a coprecipitation method for rechargeable batteries applications. The synthesized LiMn1.9Ag0.05Y0.05O4 was exposed to different doses of γ-irradiation (10 and 30 kGy). The resulting spinel products were characterized by using thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), electronic (UV-Vis) and electron spin resonance (ESR) spectra. LiMn2O4 exhibited a discharge capacity of 124 mAhg−1 while LiMn1.9Ag0.05Y0.05O4 had discharge capacities of 129 and 137 mAhg−1 for non irradiated and γ-irradiated (30 kGy) samples, respectively. The effects of the dopant cations and γ-irradiation on the discharge capacity and DC-electrical conductivity of some synthesized spinels were studied.

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Spectroscopic investigation of cobalt(II) complexes with some triazole azo dyes for microdetermination of cobalt(II) in pharmaceutical products

Khedr A. M.

Chemia Analityczna

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2009

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Vol. 54, No. 4

783-793

EN

By coupling diazonium salt of 3-amino-l,2,4-triazole with resorcinol, p-hydroxy-toluene, p-hydroxyethylbenzoate, p-hydroxybenzophenone, p-hydroxybenzaldehyde and p-bromo-phenol, six triazole azo dyes HL1-HL were obtained. They represented good complexing properties towards Co(II) ions, resulting in colored complexes. In this paper, the use of the synthesized triazole azodyes as reagents in spectrophotometric determination of Co(II) was presented. Absorption maxima, optimum pH values, molar extinction coefficients, sto-ichiometric ratios, apparent stability constants for the complexes, and coresponding free energy of formation were determined. HL1 was found to be the best chromogenic reagent due to its high selectivity and sensitivity towards Co(II) ion. HL1 was successfully applied with high precession and good accuracy to the spectrophotometric determination of Co(Il) ion in injection solutions, tablets, capsules, and liquid formulations. Bonding type in the formed complexes was studied.

PL

Otrzymano sześć triazolowych barwników Azo HL1—HL6. Otrzymano je przez przyłączenie rezorcyny, p-hydroksytoluenu, benzoesanu p-hydroksyetylu, p-hydroksybenzaldchydu i p-bromofenolu do diazoniowej soli 3-amino-l,2,4-triazolu. Otrzymane ligandy dobrze kompleksowały jony Co(II), a otrzymane kompleksy były kolorowe i zostały użyte w tej pracy do oznaczania Co(II). Wyznaczono maksima absorpcji, optymalne pH, współczynniki ekstynkcji, stechiometrię reakcji kompleksowania i jej stałą trwałości oraz odpowiednie wartości entalpii swobodnej. HL1 okazał się najlepszym ligandem pod względem selektyw-ności i czułości. Został on zastosowany z dużą precyzją i dokładnością do spektrofotome-trycznego oznaczania Co(II) w zastrzykach, tabletkach, kapsułkach i ciekłych preparatach. Dyskutowano również typ wiązania w związkach kompleksowych.