Dear Waseem Abbas,

Urea is physiologically very important. It is the chief nitrogenous product of protein metabolism.Spherical micron sized porous particles of goethite FeO(OH), boehmite AlO(OH), anatase TiO2, Zn(OH)2 and binary mixtures of these oxides have been synthesized by homogeneous precipitation from aqueous solution containing urea in the presence of corresponding metal sulfates. Metal (hydrous) oxide particles obtained show spherical morphology and consist of agglomerated randomly oriented nanocrystallites. Synthesized metal oxide hydroxides were characterized using Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX)

prepared TiO2 spherical particles from a solution of TiOSO4 by homogeneous precipitation using urea as the precipitating agent at 70–90 °C. Uniform nanocrystalline iron hydrous oxide particles formed by hydrolysis of Fe2(SO4)2 with urea were describing synthesis of various hydrated metal oxide nanoparticles (Al, Sc, Ti, Y, Zr, etc.) using homogeneous precipitation of water-soluble metal salts with urea as the precipitating agent..At high temperature the role of Mn(II) ions in decomposing the coordinated urea in the form of [MnU2I2] could be understood according to the following reactions; at 90 0C

[MnU2I2] + 3H2O    =    MnCO3 + CO2 + 2NH4I + 2NH3

Adducts of ZnX2·2urea (X = Cl, Br, I), CdX2·2urea (X = Br, I), CdX2·urea (X = Cl, Br, I) and HgX2.urea (X = Cl, Br) have been characterized . The shifts of the stretching vibrations to low frequency (vCO) and to high frequencies (vCN and vNH) indicated that urea is oxygen-bonded to the metals. At high temperature the role of Zn(II) and Cd(II) ions in decomposing the coordination urea in the form of [Zn(urea)2I2] or [Cd(urea)2I2] could be understood as follows; at 90 0C

[ZnU2I2] + 3H2O   =    ZnCO3 + CO2 + 2NH4I + 2NH3

[CdU2I2] + 3H2O    =   CdCO3 + CO2 + 2NH4I + 2NH3

The x-ray studies on cobalt(II) salt-urea complexes  have confirmed the existence of the double compounds CoSO4.6CO(NH2)2, Co(NO3)2.CO(NH2)2, Co(NO3)2.4CO(NH2)2, Co(NO3)2.6CO(NH2)2, and of the triple compound Co(NO3)2.4Co(SO4)2.20CO(NH2)2.2H2O and CoSO4.2CO(NH2)2.6H2O. Complexes of N-ally urea (NAU) with cobalt(II) and nickel(II) halides and perchlorates have prepared and characterized by electrical conductance, magnetic susceptibility [42]. The infrared spectra of N-allyl urea complexes with Ni(II) and Co(II) salts, [Co(NAU)2X2]; (X= Cl, Br, and I), [Ni(NAU)4X2]; (X=Cl, Br), [Ni(NAU)4](ClO4)2 and [Ni(NAU)6](ClO4)2 are reported . A negative shift in the frequencies of n(C=O) and d(NH2) bands, and a positive shift in the frequency of n(C-N) band, suggest that carbonyl oxygen is the donor site. Moreover, the negative shift of the N-H stretching frequency is arise from hydrogen bonding between N-H and halogen and not to coordination. A small negative shift of the double bond on coordination is probably due to drain of electrons towards oxygen. The role of Co(II) ions in decomposing of coordinated urea at high temperature may be understood as follows, at 900C

[CoU2I2] + 3H2O   =    ZnCO3 + CO2 + 2NH4I + 2NH3

The (CO3) 2- ion is planar and therefore, it belongs to the D3h symmetry. It is expected to display four modes of vibrations, A`1 + A``2 + 2E` (E` is a doubly degenerate motion). The vibration A`1 is only Raman active while the other.

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regards,

Prem Baboo

Article Synthesis of spherical metal oxide particles using homogeneo...

 The samples of FeO(OH), AlO(OH) and TiO2, have been

prepared by the following procedure: The weighed amounts of

metal sulfates were suspended in 4 L of distilled water with 10mL

of 98%sulfuric acid. Urea was mixed with the above solution (see

Table 1). The resulting strongly acidic solution was heated so, that

the boiling point was reached after 1 h of heating. Then the

solution was kept under stirring at the boiling temperature for 6 h

until pH 7.0 was reached and the ammonia smell disappeared

from the steam. After aging, the precipitates were separated from

the mother liquor by filtration. Particles were washed with

distilled water and dried at laboratory temperature for several

hours. Fine powders of goethite FeO(OH), boehmite AlO(OH),

and anatase TiO2 as well as their mixtures were obtained.

Synthesis of spherical metal oxide particles using homogeneous precipitation

of aqueous solutions of metal sulfates with urea

Jan Šubrt ⁎, Václav Štengl, Snejana Bakardjieva, Lorant Szatmary

Powder Technology 169 (2006) 33–40