PAPERmaking! g FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 2, Number 1, 2016
Figure 7 shows the PL spectra of TiO 2 nanopigments collected after an excitation at wavelength of 320nm. As seen from the spectra, relatively broad bands at 358nm and at 380nm are detected for all samples. These emission bands are most probably originated from quantum confinement in nanocrystals.
Fig. 7 Photoluminescence spectra of TiO 2 nanopigments. a Anatase, b anatase + brookite and c rutile samples. The samples are excited at wavelength of 320nm Application in paper coating Optical properties The optical properties of paper products are very important parameters, mostly due to their aesthetic aspects; however, they also play an important role in print or writing showing through paper product. The properties are defined by reflecting ability, absorbing capacity and penetration of light through paper. Table 2 illustrates the effect of the prepared nano titanium dioxide phases in conjunction with clay on brightness and opacity of the prepared coated paper. It can be clearly seen that along with the increase in the amount of titanium dioxide in relation to clay, the paper ISO brightness and the opacity increased compared with pure clay-coated paper, because the inherent high light scattering coefficients of titanium dioxide pigment led to higher brightness and opacity as it limits the amount of light that can be transmitted through the paper. Comparing the three prepared nano titanium dioxide pigments, Table 2 shows that rutile pigment has the highest brightness value. This is in consistent with the results of UV – visible spectra in Fig. 6 which reveal that rutile pigment has the highest intensive peak. No significant difference in brightness appears upon changing the addition level of titanium dioxide from 30 to 50% for sample rutile, a mixture (Anatase + Brookite) and anatase, respectively (Table 2). The opacity of the coated paper slightly increased upon using the prepared nano titanium dioxide pigments. Physical properties Table 2 summarised the data obtained for optical and physical properties of coated papers having the prepared nanopigments. It shows that an increase in the addition levels of nano titanium dioxide pigments leads to substantial decrease in coated paper roughness. When
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Article 3 – Titanium Coating Pigments
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