Annual Report of Cosmetology vol.7, 1999
Synopsis of Original Research PaperMorphology control of monodispersed inorganic
pigment particles and their characterization.
Kazuhiko Kandori
School of Chemistry Osaka University of Education

The morphology and texture of hematite particles producing from a forced hydrolysis
reaction of FeCl3-HCl solution were controlled by dimethylformamide (DMF) and dioxane(DX). The morphology of synthetic hematite particles was concentration dependent; theychanged from large sphere with diameter of ca. 600 nm to diamond-like shape with increasing
DMF concentration in the aging solution accompanying a reduction of their size to 80 nm
without incorporation of DMF in the particles. This fact was explained by an acceleration ofphase transformation from β-FeOOH to hematite with an elevation of the solution pH owing
to dimethylamine produced from a hydrolysis of DMF at an elevated temperature. TEM andXRD suggested that the diamond-like hematite particles formed above 6~10 vol% DMF
possess a single crystal nature. TG and FTIR indicated that the hematite particles producedwith DMF contained small amounts of OH− ions in the lattice though they provided a single
crystal nature. On the other hand, the spherical shape of haematite particles produced below
the DX concentration of 10 vol% (diameters: 600~1000 nm) was changed to cubic one after
producing the particles at more than 12 vol% DX (mean edge lengths: 900~1200 nm). The
rod-like β-FeOOH particles were precipitated to be cubic ones at the DX concentration ≳ 28vol%. TEM and XRD suggested that the haematite particles formed in the presence of DX arepolycrystalline with an enlarged c dimension in a unit cell. TG and FTIR indicated that thehaematite particles produced with DX are hydrohaematite possessing OH− ions in the lattice
as well as the particles produced with DMF. The results obtained in the present study revealed
that variation of the polarity of the medium with addition of DX is a determining factor of theparticle size and shape rather than the interfacial tension of the medium and the particles. In
the case of aluminum phosphate particles, the size of spherical particles was controlled by using
urea and isopropylamine (IPA) and their texture was investigated by various means. The mean
particle diameter (Dp) of the particles decreased with increase in the concentration of urea by
accelerating the precipitation reaction from decomposition of urea at elevated temperature. The
Dp decreased by addition of IPA up to 6 mol% to Al ions under a constant urea concentration,
while Dp increased above the concentration because IPA produced electrolytes by reactingwith HNO3; the electrolytes may reduce the range of coulombic repulsion between charged
primary particles. All the particles adsorbed selectively H2O molecules. IPA does not act as atemplate but operates as an effective additive for controlling the particle size without altering
the inner texture of spherical aluminum phosphate particles. It was revealed from the resultsthat both the hematite and aluminum phosphate particles are produced from the aggregation ofsmall primary particles.
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