Nano titania

Kuo, C.S., Tseng, Y.H., Huang, C.H., and Li, Y.Y. (2007) Carbon-containing nano-titania prepared by chemical vapor deposition and its visible-light-responsive photocatalytic activity. Journal of Molecular Catalysis A Chemical, 270 (1-2), 93-100. 

Li, Y. and Kim, S.J. (2005) Synthesis and characterization of nano titania particles embedded in mesoporous silica with both high photocatalytic activity and adsorption capability. Journal of Physical Chemistry B, 109, 12309-12315. 

PREPARATION OF ULTRAFINE POWDERS BY REACTION-PRECIPITATION IN IMPINGING STREAMS III NANO TITANIA... 

Nano Titania is one of the earliest nano materials to be applied commercially. It has a number of superior properties, such as super strong scattering and anti-ultraviolet capabilities, special electromagnetism and catalysis characteristics, especially the photocatalysis ability decomposing microbes, and also extremely high surface activity... 

As for other inorganic nano materials, a number of preparation methods have been proposed for nano Titania. Because of its economic advantages and its simplicity, Li... 

The results on the particle sizes in the product calcined at 600°C measured by TEM are listed in Table 15.6, while those calcined at various temperatures are given in Table 15.7. The data listed in Table 15.6 show that the nano Titania product prepared by TiCl4 hydrolyzation-precipitation in the SCISR had very small sizes and a very narrow size distribution, the weighted mean size of which was calculated to be 9.64 nm. 

Average sizes of nano Titania products calcined at different temperatures... 

As can be seen from the discussions above, the sizes of the nano Titania products are affected most significantly by the pH of the reaction mixture. On the other hand, from the point of view of chemistry, the shift of titanium from the form of ion to complex-ion to precipitate is related closely to the pH. In order to examine the possibility of controlling the size of the product by NH3- neutralization operation and to obtain some information for understanding the reaction mechanism, the influence of the neutralization rate on the mean size and the regularity of pH variation during neutralization are studied experimentally. 

An investigation on the preparation of nano Titania by TiCl4-hydrorization-precipitation was carried out with the submerged circulative impinging stream reactor (SCISR) as the reaction device and the results compared with those obtained with the traditional stirred tank reactor (STR). The following can be concluded ... 

Li B, Liu X, Meng F, Chang J, Ding C. Preparation and antibacterial properties of plasma sprayed nano-titania/silver coatings. Mater Chem Phys 2009 118 99-104. 

Nanocomposite Nano silica, nano calcium carbonate, nano titania, nanoclay, carbon nanofibres, carbon nanotubes Mechanical mixing and sonication followed by casting or compression moulding... 

In this work nano-titania of anatase form has been added to mortars containing (a) binders of either lime and metakaolin or natural l draulic lime and, (b) fine aggregates of carbonate nature. The aim was to assess the adhesive performance of the above binders for reassembling fragmerrt pororrs stones and more specifically to explore the effect of nano-titania in the hydration and carbonation of the derived mortars. The nano-titania proportion was 4.5-6% w/w of binders. The physicochemical and mechanical properties of the nano-titania mortars were studied and corrtpared to the respective ones of the mortars without the nano-titania addition, used as reference. DTA-TG, FTIR, SEM and XRD analyses indicated the evolution of carbonation, hydration and hydraulic corrtpound formation dirring a period of one-year citring. The mechanical characterization indicated that the mortars with the nano-titania addition showed improved mechanical properties over time, when compared to the... 

Keywords Adhesive mortars, nano-titania, metakaolin-lime, hydraulic lime,... 

Binders of either lime (L by CaO Hellas) with metakaolin (M Metastar 501 by Imerys), or natural hydraulic lime (NHL NHL3.5z by Lafarge), as well as nano-titanium dioxide (T nano-structured nano-titania by NanoPhos), used as filler due to its photocatalytic activity, were employed for the design of the adhesive mortars. The already established improvement of hydration and carbonation process due to the photocatalytic activity of nano-titania in anatase form (Hyeon-Cheol 2010) added to cement mortars, was taken into consideration to assess whether the adhesion performance of the studied... 

In particular, Figme 2 depicts the DTA cmves for the NHL mortars without nano-titania at 1, 11 and 28 days of curing. The inset plot illustrates the evolution of the ratio mueacted-CH to formed-Cc at the same cming period for NHL mortars with and without nano-titania. As the setting process proceeds, mass losses attributed to the release of CO2 fixrm CaCOs increased. 

Figure 2. DTA curves for NHL mortars without nano-titania cured for 1, 11 and 28 days along with the evolution of carbonation in NHL mortars without and with nano-titania (NHLT) illustrated in the inset plot.

Figure 3 depicts the results of the FTIR analyses after curing time of 1, 11 and 28 days. In the ML samples without nano-titania, portlandite was identified, exhibiting the characteristic absorption at 3640 cm. Furthermore, the absorptions at 990 and 540 cm, which are indicative of the neo-formed hydraulic components, are more pronounced in the samples with nano-titania, confirming enhancement of the hydration process. 

Figure 3. FTIR for metakaolin-lime mortars with (a) and without nano-titania (b) cured for 1, 11 and 28 days. Portlandite (P) still exists in the ML mortars after 28 days of curing.

These variations can be explained by the Ti02 photocatalytie action for the mixtures with nano-titania the latter leads both to calcite formation and enhanced hydration of CSH and CAH products, similar to what was observed... 

Figure 5. Decrease of AE% of stains of methylene blue on mortars with metakalolin-lime and nano-titania (MLT) and metakaolin-lime (ML) after 59 h under UV irradiation.

The photocatalytic properties of the nano-titania mortars were tested by applying both stains of methylene blue and methyl orange to the mortars surfaees and observing their discoloration. The intensive decrease of the total color difference AE% observed on the mortar surface containing nano-titania stained with methylene blue after 59 h of UV irradiation, can be considered as an indication of the potential of nano-titania mortars to decompose organic pollutants (Figure 5). 

It seems that nano-titania with its hydrophylicity created an environment, which not only enhanced the hydraulie eomponent formation, but also controlled the shrinkage, thus avoiding mierocracking (Karatasios 2010). Further support to this statement is derived from the dense network of hydraulic components observed in the SEM micrographs (Figure 4b) for the MLT samples. 

Based on the physico-chemical and mechanical characterization of all the studied adhesive mortars the MLT mortars with metakaolin, lime and nano-titania and the natural hydraulic lime mortars with nano-titania (NHLT2) have been seleeted as the most appropriate for the adhesion of fragment porous stones. 

This research work addressed an important problem in the restoration sector concerning the reassembling of stone fragments from ancient monuments using non-eementitious mortars. The proposed adhesive mortars contain hydraulic lime or metakaolin and lime as binders, carbonate sand with grains between 250 and 63 pm and binder to aggregate ratio 1 or 2. The nano-titania as additive was employed in a binder replacement of 4.5-6% w/w. 

The mechanical characterization indicated that the mortars with nano-titania showed increased compressive and flexural strengths and moduli of elasticity over time, when compared to the specimens without nano-titania The results also indicate enhanced carbonation and hydration of mortar mixtures with nano-titania. The hydrophylicity of nano-titania improves the humidity retention of mortars, thus facilitating the carbonation and hydration processes. This property can be exploited into the fabrication of mortars... 

Maravelaki-Kalaitzaki, P., Agioutantis, Z., Lionakis, E., Stavroulaki, M., Perdikatsis, V. (2013) Physico-chemical and Mechanical Characterization of Hydraulic Mortars Containing Nano-Titania for Restoration Applications, Cement and Concrete Composites, 36 (1), 33-41. 

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