Fumed alumina/silica/titania

Figure 2. Optical spectra of (dimethylamino) azobenzene, DMAAB, adsorbed onto individual fumed alumina, silica A-300, and titania, and mixed oxides Si02/Ti02 (37 wt% Ti02), Al203/Si02 (30 wt% A1203) and Al203/Si02/Ti02 (22, 28, and 50 wt% res-pecttively).

Keywords fumed silica alumina/silica, titania/silica alumina/silica/titania Ni(II) Cd(II) Pb(II) polyethylene glycol) poly(vinyl alcohol) adsorption potentiometric titration surface charge density... 

Nanooxides such as fumed silica, titania, alumina, etc. (with spherical primary nanoparticles) are used as fillers for complex drugs, enterosorbents, vaccine adjuvants, food additives, etc.1,2 In general nonporous spherical nanoparticles can adsorb solutes in low amounts because the desolvation effect causes an... 

FIGURE 37.1 OPTPD spectra of water desorbed from (a) fumed silica A-300 and fumed titania (b) fumed silica/titania and CVD-Ti02/fumed Si02 and (c) fumed silica/alumina re-hydration (R) time is 0.5 h. 

FIGURE 2.3 Relationships between total and surface content Cx of (a) alumina and titania, (c) silica in SA, ST and AST samples (b) relationship between ratio C /Cx and the total content of the second phases, and (d) relationship between the surface content of alumina or titania and the peak temperature of TPD-MS thermograms of desorbed water. (Adapted from J. Colloid Interface Sci., 314, Gun ko, V.M., Blitz, J.P., Gude, K. et ah. Surface structure and properties of mixed fumed oxides, 119-130, 2007a, Copyright 2007, with permission from Elsevier.)... 

FIGURE 2.25 Dependence of surface charge density for mixed oxides on pH for fumed (a) titania/silica and (b) alumina/silica samples. 

FIGURE 2.48 Adsorption of different adsorbates onto (a) A-300 degassed at 200°C (b) fumed alumina (5bet,n2= 133 m /g) degassed at 200, 600, and 900°C and adsorption of (c) hexane and (d) acetonitrile onto A-50, A-200, alumina (5 bet,n2=89 m /g), and titania. (Adapted from J. Colloid Interface Sci., 348, Gun ko, V.M., G.R. Yurchenko, Turov, V.V. et al., Adsorption of polar and nonpolar compounds onto complex nanooxides with silica, alumina, and titania, 546-558, 2010d, Copyright 2010, with permission from Elsevier.)... 

Gun ko, V.M., Zarko, V.L, Chuikov, B.A. et al. 1998a. Temperature-programmed desorption of water from fumed silica, titania, sUica/titania, and sihca/alumina. Int. J. Mass Spectrvm. Ion Process. 172 161-179. 

These processes are very rapid and allow the preparation of inorganic supports in one step. This technique allows large-scale manufacturing of supports such as titania, fumed silica, and aluminas. Sometimes the properties of the material differ from the conventional preparation routes and make this approach unique. Multicomponent systems can be also prepared, either by multimetallic solutions or by using a two-nozzle system fed with monometallic solutions [22]. The as-prepared powder can be directly deposited onto substrates, and the process is termed combustion chemical vapor deposition [23]. 

Figure 9. Surface content of (a) A1 in fumed silica/alumina and (b) Ti in titania/silica and the maximum adsorption of (a) Pb(II) and (b) Ni(II) as a function of the total (a) alumina or (b) titania content in mixed oxides.

Abrasive particles are a key component in CMP slurry. The most commonly used abrasive particles include silica, alumina, ceria, zirconia, titania, and diamond. Table 21.1 listed a set of information on each type of abrasive particles such as density, microhardness, and isoelectric points (lEP). It is important to point out that the specific values for these properties depend highly on the preparation techniques and the specific states of the samples. The values listed in the table represent an average of the most commonly reported data. For example, the isoelectric point for silica is a function of the number of hydroxyl groups, type and level of adsorbed species, metal impurity in the solid matrix, and the treatment history of the materials [1]. There are three major types of silica according to their preparation methods fumed, colloidal, and precipitated. The common sources for obtaining these abrasive particles are listed in Table 21.2. As examples, some of the more specific information on... 

FIGURE 2.46 Surface content of (a) A1 in fumed silica/alumina and (b) Ti in titania/silica and the plateau adsorption (A) of (a) Pb(II) and (b) Ni(II) as a function of the total (a) alumina and (b) titania content in mixed nanooxides. (Adapted bom Appl. Surf. Sci., 253, Gun ko, V.M., Nychiporuk, Yu.M., Zarko, V.I. et ah, Relationships between surface compositions and properties of surfaces of mixed fumed oxides, 3215-3230, 2007b, Copyright 2007, with permission from Elsevier.)... 

The observation of individual AST particles with the hydrodynamic diameter of 10-20 nm (Figure 2.56), i.e., smaller than the average geometrical diameter of primary particles, is untypical for the aqueous suspensions of fumed silica, alumina, titania, or binary oxides (Gun ko et al. 2001e). This result can be caused by a very broad size distribution of primary particles of AST (broad primary particle size distribution is characteristic for nanooxides with a low specific surface area [vide supra Degussa 1997]). Therefore, one can assume that primary AST particles of strongly different sizes are characterized by different contributions of titania, alumina, and silica, since they can be formed in different zones of the flame during the synthesis. 

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