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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 31, Number 1
BKCSDE 31(1)
January 20, 2010 

The Powder Preparation of Blue Cobalt Aluminate at 210 oC Using the Malonate Method
Gong Yeol Lee, Dong Hoon Lee, Hong Gun Kim, Yoo Young Kim*
Blue CoAl2O4, Powder, Malonic acid, Low temperature, Ammonium hydroxide
A powder, containing 80 percent of blue cobalt aluminate (CoAl2O4) crystallites, was synthesized at 210 oC using a (metal nitrate-malonic acid-ammonium hydroxide-ammonium nitrate) system. The optimal amount of concentrated ammonia water and initial decomposition temperature were determined for the blue CoAl2O4 crystallites preparation. Three CoAl2O4 precursor pastes, corresponding to the various amounts of concentrated ammonia water, were prepared by evaporating the initial solutions in an electric furnace fixed at 80 oC under a vacuum of 25 torr. The initial solution was used to dissolve the starting materials. The powder with the maximum content (80%) of blue CoAl2O4 crystallites was prepared when the prepared precursor was decomposed at 210 oC. The blue CoAl2O4 crystallite content in the prepared sample decreased with increasing initial decomposition temperature. For 0.2 mole of the Al3+ ion, the chemical compositions of the precursor corresponded to molar ratios of 0.4, 1.40, 2.56 and 2.00 for the Co2+ ion, malonic acid, ammonia and ammonium nitrate per mole of the Al3+ ion, respectively. The blue CoAl2O4 crystallite content in the sample decreased with the amount of ammonia deviated from the optimal value. The characteristics of the powders were examined using X-ray diffraction, optical microscopy, Fourier transformation infrared spectroscopy and the Brunauer- Emmett-Teller technique.
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