抄録
A preparation of hydrophobic metal oxide powders including TiO2, Ti-Fe-Al composite oxide and α-Fe2O3, using n-BTMS-EtOH-H2O with a mixing mass ratio of 10 : 6.8 : 3.2, was investigated in the pH range of 3.0 to 9.0 using CH3COOH and NH4OH. The main findings obtained were as follows :
(1) The hydrophobic degree of metal oxides is enhanced when the hydrolysis reaction of n-BTMS proceeds quickly and successive condensation is rather slow.
(2) In the plot of the average molecular weight of n-BTMS oligomer versus duration time on a log-log scale, no induction period followed by a slow increase in molecular weight was detected at pH 3.0, while at other pHs the induction period was followed by a linear increasing stage. The induction period was followed by the pH order 3.3<4.0<9.0<5.3 (de-ionized water exposed to air), and the slope of the linear portion increased in the pH order 3.3<4.0<9.0<5.3.
(3) The maximum M value, which is a parameter of the hydrophobic degree, obtained for Ti-Fe-Al composite oxide was 65% at pH 3.0, 3.3 and 4.0, while that for TiO2 was 60% at other pHs, except at pH 4.0 and with de-ionized water. The maximum M value determined with α-Fe2O3 was only 40% at the pHs of 3.0 and 3.3.
(4) To provide the maximum values of M for TiO2 and Ti-Fe-Al composite oxide, dimers to tetramers were required, whereas a polymerization degree above 2.5 was necessary for α-Fe2O3.
