Oxide dispersion

Fig. 6. Properties of the ( ) oxide dispersion strengthening (ODS) materials MA-6000 and MA-754 and conventional (0) cast and (O) wrought superaHoys...

Table 7. Nominal Compositions of Oxide Dispersion Strengthened Alloys, wt %...

Table 8. Materials Properties of Oxide Dispersion Strengthened Superalloys ...

Oxide Dispersion StrengthenedSuperallojs, Inco Alloys International, Huntington, W. Va., 1990. 

In order to obtain a homogenous and stable latex compound, it is necessary that insoluble additives be reduced in particle size to an optimum of ca 5 )Tm and dispersed or emulsified in water. Larger-size chemical particles form a nucleus for agglomeration of smaller particles and cause localized dispersion instabiHty particles <3 fim tend to cluster with similar effect, and over-milled zinc oxide dispersions are particularly prone to this. Water-soluble ingredients, including some accelerators, can be added directly to the latex but should be made at dilute strength and at similar pH value to that of the latex concentrate. 

Sodium polymethacrylates are also anionic and are useful as iron oxide dispersants and iron stabilizers. Typical MWs range from 6,000 to 20,000. Examples include Polacryl F70-40S, Tamol 850, Tamol 960, and Aquatreat AR-232. 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Acrylic acid terpolymers have appeared on the market in recent years. With their broad spectrum of functions, they offer the potential for excellent waterside conditions. In particular, the terpolymers have proved to be very effective particulate iron oxides dispersants and colloidal iron stabilizers. Examples include acrylic acid/sulfonic acid/sodium styrene sulfonate (AA/SA/SSS), such as Good-Rite K781, K797, K798. A further example is acrylic acid/ sulfonic acid/substituted acrylamide (AA/SA/NI), such as Acumer 3100. 

As an example of the latter technique, Volkman et al. demonstrated the feasibility of using spin-cast zinc oxide nanoparticles encapsulated in 1-dodecanethiol to fabricate a functional transistor.44 The zinc oxide was deposited on a thermally grown silicon dioxide layer on a conventional silicon wafer, with thermally evaporated gold source and drain electrodes. As reported, the process requires very small particles (3nm or less) and a 400 °C forming gas anneal. A similar approach was also reported by Petrat, demonstrating n-channel thin-film transistor operation using a nanoparticle solution of zinc oxide dispersed onto a thermally grown silicon dioxide layer on a conventional... 

Oxidative damage, role of ascorbic acid in preventing, 25 769 Oxidative degradation, 70 682 of gasoline, 72 399-400 Oxidative dehydrogenation, 23 342-343 Oxidative pyrolysis, 27 466 Oxidative stability, of olefin fibers, 77 229 Oxidative stability test, 72 400 Oxide crystal glass-ceramics, 72 641 Oxide-dispersion-strengthened alloys, 77 103-104... 

Polyethyleneoxide-co-polypropyleneoxides, dispersants, S 710t Poly(ethylene oxide) film, physical properties of, 10 68It Poly(ethylene oxide) floe, 11 638 Poly(ethylene oxide)-poly(ethylene terephthalate) copolymers, bioresorbable polymers, 3 738 Poly(ethylene oxide) resins, molecular weight of, 10 684-685 Polyethylene oxides, dispersants, S 706t, 710t... 

As we have seen, the net surface charge of a hydrous oxide surface is established by proton transfer reactions and the surface complexation (specific sorption) of metal ions and ligands. As Fig. 3.5 illustrates, the titration curve for a hydrous oxide dispersion in the presence of a coordinatable cation is shifted towards lower pH values (because protons are released as consequence of metal ion binding, S-OH + Me2+ SOMe+ + H+) in such a way as to lower the pH of zero proton condition at the surface. 

In Fig. 3.5 we illustrated generally that an alkalimetric or acidimetric titration curve of a hydrous oxide dispersion becomes displaced by the adsorption of a metal ion or, - in opposite direction - by the adsorption of an anion (ligand). 

Fernandez-Merino, M.J., et al., Investigating the influence of surfactants on the stabilization of aqueous reduced graphene oxide dispersions and the characteristics of their composite films. Carbon, 2012. 50(9) p. 3184-3194. 

Evaluation of the Copolymers The polymer solutions were evaluated for their deposit control and dispersant activities. The tests included calcium phosphate inhibition, calcium carbonate inhibition, iron oxide dispersion, and clay dispersion. The procedures for these tests have been previously reported (12). A commercially available polyacrylic acid was also tested for comparison. The results are shown in Tables II to V. 

From the previous paragraphes it follows that a substantial amount of experimental data exist that illustrate the oxygenation properties of zeolite catalysts. In very general terms zeolites are used to heterogenize transition metal ions in ion exchange or lattice positions, to stabilize transition metal oxide dispersions and to prepare ship-in-bottle complexes. 

Vanadium oxide dispersed on supporting oxides (Si02 Al Oo, Ti02, etc.) are frequently employed as catalysts in reactions like partial oxidation and ammoxidation of hydrocarbons, and NO reduction. The modifications induced on the reactive properties of transition metal oxides like V20 when they are supported on an oxide carrier has been the subject matter of recent study. There is much evidence showing that the properties of a thin layer of a transition metal oxide interacting with the support are strongly modified as compared to the properties of the bulk oxide (1-3). In the recent past, increasing attention has been focussed... 

Despite the fact that the hydrolysis of the ferric ion is exceedingly sensitive to various experimental parameters (temperature, pH, etc.), hematite (a-Fe203) and akageneite ((3-FeOOH) were apparently the first reasonably uniform colloidal metal (hydrous) oxides dispersions reported in the literature, as already indicated in the introduction. Since then, this family of compounds has been the most extensively investigated, with specific emphases on particle uniformity, composition, and morphology. 

Finally, rod-like particles of indium hydrous oxide, dispersed in solutions of HfOCl2 and Na2S04, were coated with hafnium hydrous oxide by simply aging the entire system for 24 h at room temperature (149). 

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