Titanium oxide aggregates

Figure 12 shows the XANES and FT-EXAFS spectra of the titanium oxide catalysts chemically doped with Cr ions (a and A) and physically implanted with Cr ions (b and B). Analyses of these XANES and FT-EXAFS spectra show that in the titanium oxide catalysts chemically doped with Cr ions by an impregnation or sol-gel method, the ions are present as aggregated Cr oxides having an octahedral coordination similar to CriOs and tetrahedral coordination similar to CrOs, respectively. On the other hand, in the catalysts physically implanted with Cr ions, the ions are present in a highly dispersed and isolated state in octahedral... 

In carrier flotation, small-sized (several pm diameter) particles become attached to the surfaces of larger particles (perhaps 50 pm diameter, the carrier particles) [630]. The carrier particles attach to the air bubbles and the combined aggregates of small desired particles, carrier particles, and air bubbles float to form the froth. An example is the use of limestone particles as carriers in the flotation removal of fine iron and titanium oxide mineral impurities from kaolinite clays [630]. The use of a fatty acid collector makes the impurity oxide particles hydrophobic these then aggregate on the carrier particles. In a sense, the opposite of carrier flotation is slime coating, in which the flotation of coarse particles is decreased or prevented by coating their surfaces with fine hydrophilic particles (slimes). An example is the slime coating of fine fluorite particles onto galena particles [630],... 

Abruna HD (1991) X-ray Absorption Spectroscopy in the Study of Electrochemical Systems. In Electrochemical Interfaces. Abruna HD (ed) VCH Publishers, New York Albertini G, Carsughi F, Casale C, Fiori F, La Monaca A, Musci M (1993) X-ray and neutron small-angle scattering Investigation of nanophase vanadium-titanium oxide particles. Phil Mag B 68 949-955 Alexandrowicz Z (1993) How to reconcile classical nucleation theory with cluster-cluster aggregation. Physica A 200 250-257... 

Figure 3.2.6). Narrowly dispersed polystyrene (synthesized by atom transfer radical polymerization [polydispersity < 1.1]) was end fnnctionized with a phosphonate moiety that binds strongly to titanium oxide. The combination of narrowly dispersed titanium oxide and narrowly dispersed phosponate-terminated polystyrene generates a narrowly dispersed core-shell architecture as measured by dynamic light scattering, which can be spun into dielectric films. The covalent coating of polystyrene around titanium oxide is helpful at preventing aggregation of the nanoparticles in organic dispersion and in thin films.

A longer or a shorter time (y=60 or 10 min) for the second step made the band less intense and broader due to the aggregation of titanium oxides (Fig.3c,d). It can be considered that the longer the time for the second step, the higher the possibility of the aggregation to occur during the sol-gel process as follows. 

On the other hand, the shorter the time for the second step, the smaller the opportunity of the Si-O-Ti bond formation, leading to the aggregation of titanium oxide species during the calcination procedure. Thus, the optimum time to obtain highly dispersed titanium oxide species for each step was determined to be 30 minutes. 

The composition of CCP containedthe following phases Ti, TiOj (rutile), TiN (see Table 5.4). There were no other phases of titanium oxides except Ti02 (rutile). In accordance with SEM, the CCP of pTi consisted of fused aggregates (Figure 5.21c) formed from the melt, while the initial Ti particles were spheroidal. 

One example of the variation of the zeta potential with both pH and salt concentration is shown in Figure 10.13 for the titanium oxide particles, a well-known hydrophilic pigment, often used in paints (organic pigments are hydrophobic). The lEP where the potential is zero is around 7 in this case. The particles will aggregate close to this pH as the electrostatic repulsion will be very weak. We have positively charged surfaces at pH < lEP and negative ones at pH > lEP. 

These important results have stimulated many research workers in universities and industrial research laboratories in the world to investigate the particular state of aggregation and coordination that Tilv assumes when forced into framework positions of hydrophobic crystalline silicas. Researchers are also engaged in the search for other compounds containing titanium and silicon oxides with Tilv in the same coordination and environment, on the assumption that similar catalytic properties would be obtained. Relevant discoveries have been made, and additional valuable information has been obtained on this new class of materials and on their catalytic performance in many different reactions. 

Ti(II) tends to form polymers or aggregates upon increasing the Ti(II) concentration or the liquid acidity. Electrochemical, either galvanostatic or potentiostatic, oxidation of Ti metal produces either passive TiCl3 film or volatile TiCl4 which escapes from the liquid. The oxidation of metallic titanium to Ti(II) by direct anodization of Ti metal in this liquid has not yet been described. 

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