Metal oxide-based compounds particle size

The type and quality of the pigment are determined not only by the nature and concentration of the additives, but also by the reaction rate. The rate depends on the grades of iron used, their particle size, the rates of addition of the iron and nitrobenzene (or another nitro compound), and the pH value. No bases are required to precipitate the iron compounds. Only ca. 3 % of the theoretical amount of acid is required to dissolve all of the iron. The aromatic nitro compound oxidizes the Fe2 + to Fe3 + ions, acid is liberated during hydrolysis and pigment formation, and more metallic iron is dissolved by the liberated acid to form iron(II) salts consequently, no additional acid is necessary. 

Controlled hydrolysis is one of the most popular methods for processing silica spheres in the range of 10-1,000 nm. The method was developed by Stober, Fink, and Bohn (SFB) [226-229] and is based on the hydrolysis of TEOS in a basic solution of water and alcohol. Particle size depends on the reactant concentration, i.e., the TEOS/alcohol ratio, water concentration, and pH (>7). This method has been extended to other metal oxide systems with similar success, particularly for Ti02 synthesis [85,230]. The hydrous oxide particles precipitated by the hydrolysis of an alkoxide compound have the same tendency to agglomerate as that described for metal colloid systems. Different stabilizers can be used to stabilize these particles and prevent coagulation (step 2). These stabilizers control coagulation by electrostatic repulsion or by steric effects [44], similarly to the metal colloid systems. 

Studies have also revealed that the implementation of nanostmctured electrode materials can result in the initiation of new lithium storage mechanisms. These effects typically manifest either via a pseudocapacitive storage mechanism that accommodates lithium ions on the surface/interface of the particles below a critical particle size or through a conversion mechanism that involves the formation and decomposition of at least two separate phases [28-31]. The pseudocapacitive mechanism is more pronounced because of the more prominent role of surfaces and grain interfaces in nanomaterials. Reversible conversion reactions based on the reduction and oxidation of metal nanoparticles can ensue between binary compounds comprised of some second or third period element, a transition metal oxide, and metaUic lithium [32-37]. Nanoparticles are extremely effective toward this means because of their large specific surface area that is very active toward the decomposition of the lithium binary compound. Furthermore, reduction of some micrometer sized materials to the nanoscale has been shown to activate or enable reversible electrode reactions that would otherwise not take place, typically materials with low Li-ion diflEiision coefficients. 

---