Samples of TiO 2 of various colours (bluish black to yellowish white) were obtained by heating TiO2 at 1400 °C. under oxygen of increasing pressure. At that temperature the dissociation pressure is about 2/3 arm. (in oxygen). The homogeneity region of the phase extends from about TiO~.gsa to TiO2.000 (39.845 to 40.05% b.w. of oxygen). The composition of the samples was determined from lattice parameter and density measurements. TiO2 of stoichiometric composition has a sound lattice with n' = 1.9999 +_ 0.0009 molecules per unit cell. The structure of the grayish and deeper coloured samples is imperfect, caused by missing oxygen ions (up to 0.034 ions per unit cell or 0"85% of all oxygen positions are vacant at the left phase border).The lattice constants of the tetragonal TiO2-phase varied only slightly with increasing oxygen content (a increased and c decreased). The constants of stoichiometric TiO2 were obtained by extrapolation : a.~ 5 = 4.5937a and c2s = 2.95812 (precision : _+ 0"00005 A) : c/a = 0.64395 : v2~ = 62.423 _+ 0"004 A 3 ; the expansion coefficients between 10 and 60 °C. were (X a ----6"9 x 10 -6 and ac = 9"9 x 10 -s along the a-and c-axes respectively. The macroscopic density of TiO 2 was: de5 = 4.2493 + 0.0005 g.cm. -3. The density of the preparations decreased with decreasing oxygen content; their expansion coefficients were within the limits of error independent of composition.

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SynopsisAlkali-metal oxides and fluorides were substitutionally added into a commercial mold flux currently used in China Steel Corp. to examine their effects on the flux viscosity. The solution mechanism of alkali-metal oxides and that of fluorides into the molten flux were discussed. The correlations between polymerization coefficient (K) and the break points, viscosities and activation energies were presented. It was found that the effect of all the alkali-metal oxide and fluoride additions on the flux viscosity continually became less pronounced with increasing temperatures. And based on the result of this study, the additions of Li20 and Na2SiFs to the mold flux could be the best choices, provided a low-viscosity and low-break point flux was desired.

We investigated the effects of guest molecules of the gel particles on the volume phase transition properties of bulk gels. The guest molecules are the microspheres of poly(N-isopropylacrylamide) (NIPA) gel with submicron diameter, synthesized by the emulsion-polymerized reaction in water. We prepared several cylindrical NIPA gels with sub-millimeter diameter by the incorporation of the submicron NIPA gel particles of various concentrations at gelation, where the total NIPA monomer concentration (from the host networks and the guest particles) was fixed. In order to make clear the distribution of the gel particles immobilized in the bulk polymer networks, the fractured surfaces of the gels were observed by tapping mode atomic force microscopy in water. It was found that the gel particles aggregate in the host homogeneous networks to form domains with densely connected structure, which become larger with increasing particle concentration. We measured the macroscopic swelling curves, which indicate that the presence of guest NIPA particles with lower concentration does not strongly affect the transition temperature as well as the discontinuity of the phase transition in the bulk gels. On the other hand, when the amount exceeds a threshold concentration, the transition becomes continuous, and the swollen diameter rapidly increases. These results have been compared with the network inhomogeneities in pure NIPA gels (without particles) introduced at gelation, which depend on the gelation temperature below or above the cloud point of the linear polymer. We discussed qualitatively the macroscopic swelling behavior of the NIPA gels in terms of the inhomogeneities introduced artificially by the incorporation of the submicron gel particles.

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