Pigments anatase

During calcination, water is removed at temperatures between 200 and 300°C sulfur trioxide is removed at temperatures between 480 and 800°C. At about 480°C the crystals of Ti02 are being formed and continue to grow with increasing temperature. To prepare the anatase pigment, the final calcination temperature of the hydrolysate prepared in the presence of anatase seeds should reach about 800—850°C. 

There is a difference of a factor of five in energy consumption between the two processes, largely due to the avoidance of evaporation of large amounts of water in the latter process. Despite this both processes still operate, although the chloride process does dominate. There are two main reasons for this first the sulfate process can use lower grade and therefore less expensive ores and secondly it produces anatase pigments as well as rutile, which is the sole product of the chloride process. 

Photoactivities of Commercial Pigments. The photoactivities of titanium dioxide pigments, as indicated by the quantum yields for photooxidation of isopropyl alcohol to acetone, vary by a factor of 10 (Table 1). The observation of generally lower photoactivity of the rutile relative to the anatase pigment is consistent with previous observations ( 5). 

Figure 4. Total weight loss dependence of anatase pigmented paint films on wavelength and on p.v.c. (1)...

Figure 14. Ti02 anatase pigmented coating, chalk rating 4, general view (2)...

The early technological interest in anatase pigments was probably why anatase powder was for a time favoured as a non-porous adsorbent. Thus, anatase was one of the few finely divided crystalline solids used by Harkins and Jura (1944) in the development of new procedures for surface area determination. Anatase was also featured... 

The starting material is an anatase pigment or a Ti02 hydrolyzate, which is calcined with oxides of transition metals to form chromium mtile or nickel rutile pigments (see Section 3.1.3.). 

Fig. 5.42 Scattering of anatase pigments as a function of particle size (daylight).

Casual inspection of Figures 2 and 6 indicates that both the CO2 photogeneration and the conventional carbonyl development methods show that PP is more photoactive than PE. Also, CO2 photogeneration and carbonyl development both show the high photoactivity of anatase pigmented films of both PE and PP. 

Figure 8. CO2 absorbance after 3 hours UV exposure versus 1713 cm absorbance after 658 hours UVA-340 illumination for PE (solid symbols) and PP films (open symbols). A, A unpigmented M, rutile pigmented , O anatase pigmented.

Figures 2.69-2.71 show the morphology of anatase pigment and rutile with and without coating. The layer of coating can be distinguished on micrograph.

Malati, M.A., Fassam, R.A., and Henderson, LR., Mechanism of phosphate interaction with two reference clays and an anatase pigment, J. Chem. Tech. Biotechnol., 58, 387, 1993. 

Although quite a number of the map s details have been debated as evidence both for authenticity and forgery, the presence of modem anatase pigment is recognized as the smoking-gun argument for forgery. Nonetheless, there are still many scholars who find the evidence on both sides to be equivocal. 

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