Metal oxide formation

In a second paper from Kirillov et al., synthetic aspects of liquid phase precipitation reactions are discussed in relation to the factors responsible for metal-oxide formation. In particular the Pechini reaction, a sol-gel process, was examined. A good reference section is provided to introduce the reader to previous literature. The authors stress that more work needs to be done to establish what factors are important for producing the highest quality metal-oxide powders from such reactions. The conclusion specifically lists the criteria needed in order to accomplish this task. 

Since water molecules interact with a metal surface through their oxygen atoms, the enthalpy of the metal oxide formation should... 

Figure 11 Inductively coupled plasma mass spectra of (a) thorium demonstrates the propensity for metal oxide formation in the quadrupole ion trap. Cryogenic pumping (b) reduces the residual gases, resulting in dramatically reduced oxide formation. (From Ref. 50.)...

It is known that deposition on substrates where nonconductive metal oxide layers are formed at positive potentials is difficult. This includes electrodes made of stainless steel, tantalum, and aluminum. However, the rate of oxide formation is important because we have shown that stainless steel is an ideal substrate for deposition of some PPy s. The rate of oxide formation depends on the solution and the electrochemical conditions employed. If the polymer can deposit before the onset of metal oxide formation, then consistent films of excellent quality can be deposited. This is aptly demonstrated with the successful electrocoating of aluminum when the electrocatalyst Tiron 4 is used. 

Figure 5(a) shows results of BET measurement for the above two calcined sample series. When the hydroxide/hydrotalcite phases are converted to metal oxides, the surface area varies substantially. For example, the surface area of CR peaks at 250 C and later declines at higher temperatures since it is Co-rich and decomposes readily. In the CS series, however, the surface area maximizes only at 300°C since it is more stable to sustain thermal treatment. In both cases, maximum surface area is obtained when hydroxide/hydrotalcite framework collapses, i.e., it occurs at temperatures of metal oxide formation. The decrease in surface area at higher calcination temperatures can be explained as grain growth of oxides. 

In the adsorbed phase, in which the particles are mobile because of surface diffusion, the chemical reaction of the metal-oxide formation takes place via dissociative chemisorption of the oxygen. This means that, since the reaction takes place in the adsorption phase and the various reaction partners can have different condensation coefficients, the ratio of the rates of incidence is a necessary but not adequate criterion. According to Ritter [293, 298], the chemisorption rate of oxygen is the critical step for the completion of the reaction ... 

Material Melting temperature (°C) Affj for metal oxide formation per oxygen atom, -AH 298 K (kJ/mol) Temperatiure-programmed reduction, TPR (°C) Thermal stability in oxygen atmosphere... 

Metal or metal oxide formation with TMV templates... 

In Figure 10.19 reaction 1 recovers the metal oxide formation at lower potentials than monomer oxidation. From those oxides a catalytic monomer oxidation can occur. This parallel mechanism of monomer oxidation explains in part the large influence of anions on the polymerization process oxide formation is favoured by an increase in electrolyte concentration [48]. A second... 

The silica which is formed during the hydrothermal process of SiC is readily dissolved in water. This is, however, a very different situation for other metal oxides as most of them are insoluble in water thus, for other carbides, both carbon and metal oxide formations occur during hydrothermal reaction [62]. The type of carbide and the carbide-to-water ratio are the two most important controlling factors for the formation of carbon in hydrothermal reaction [63]. 

Another source of thermal instability arises from metal incorporation in the polymer via reaction of mercaptan with metal oxides. Formation of mercaptide groups can be minimized by incorporation of small amounts of sulfur. 

When a metal salt aqueous solution is heated up, metal (hydro) oxides are formed due to the shift of reaction equilibrium. At higher temperatures, the equilibrium shifts further toward the metal oxide formation side. 

The same group developed a one-pot microwave-assisted route to Sn02/RG0 composites using benzyl alcohol as a reactant for metal oxide formation and reducing agent for partial reduction of graphene oxide. Platinum nanoparticles... 

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