Coprecipitation synthetic methods

Typical coprecipitation synthetic methods involve the following stages (i) nanomaterials formation takes place from aqueous solutions, or by reduction from non-aqueous solutions, electrochemical reduction and decomposition of metal-organic precursors with templates (ii) metal chalconides are formed by the reactions of molecular precursors (iii) microwave/sonication assists the coprecipitation to take place at the microscale with the following advantages ... 

The factors which lengthen the pathway for diffusion not only slow the reaction, but also can lead to the formation of nonequilibrium intermediate phases. As an example, coarse particles of an equimolar mixture of BaC03 and Sn02 will lead to the initial formation of Ba2Sn04 rather than BaSn03. This aspect generally makes chemically prepared mixtures, for example, sol-gel, coprecipitation, and freeze- or spray-dried solution processes, more attractive as synthetic methods. 

Synthetic methods of preparing materials are broadly divided into two categories physical and chemical methods, and include coprecipitation, hydrothermal and solvothermal, sol-gel, microemulsion, microwave, sonochemical, impregnation, combustion, ball milling and so on. There are several parameters, which influence the size and morphology of the finished material.By controlling these parameters it is possible to make well-defined ceria-based oxides as shown in Fig. 8.1. 

The ability to tailor the structure of solid-state materials rationally depends upon control of reaction intermediates. Low temperature synthetic methods for preparing extended solids, such as coprecipitation, sol-gel, and hydrothermal techniques rely on the atoms being intimately mixed in a fluid phase before they are condensed into the... 

Elderfield and Greaves [629] have described a method for the mass spectromet-ric isotope dilution analysis of rare earth elements in seawater. In this method, the rare earth elements are concentrated from seawater by coprecipitation with ferric hydroxide and separated from other elements and into groups for analysis by anion exchange [630-635] using mixed solvents. Results for synthetic mixtures and standards show that the method is accurate and precise to 1% and blanks are low (e.g., 1() 12 moles La and 10 14 moles Eu). The method has been applied to the determination of nine rare earth elements in a variety of oceanographic samples. Results for North Atlantic Ocean water below the mixed layer are (in 10 12 mol/kg) 13.0 La, 16.8 Ce, 12.8 Nd, 2.67 Sm, 0.644 Eu, 3.41 Gd, 4.78 Dy, 407 Er, and 3.55 Yb, with enrichment of rare earth elements in deep ocean water by a factor of 2 for the light rare earth elements, and a factor of 1.3 for the heavy rare earth elements. 

Wang, Bejan and Bunce (2003) found that As(III) and As(V) could be removed from pH 2.0-2.1 synthetic acid mine drainage by raising the pH with electrochemical methods and coprecipitating the arsenic with iron (oxy)(hydr)oxides. In the presence of 260 mg L-1 of Fe(III), 40-42 mA of current lowered... 

Many synthetic processes and techniques to obtain IONPs have been developed, which are classified in physical and chemical methods. Initially, methods such as gas phase deposition and electron beam lithography were used. However, their main drawback is the inability to control the nanometric size of particles. In contrast, chemical routes are simpler, more efficient and tractable, with appreciable control over the size and, sometimes, the shape of particles. Most chemical syntheses are based on the coprecipitation of Fe2+ and Fe3+ aqueous salt solutions by addition of a base [32, 33]. 

The ACZ sample (AI2O3 doped Ceo sZro 502, the molar ratio of Al Ce Zr = 4 1 1) was synthesized by the coprecipitation method In a typical synthetic condition, the stoichiometric amount of ammonium cerium(IV) nitrate ((NH4)2Ce(N03)6, J.T. Baker, >99%), zirconiumflV) dinitrate oxide... 

High-surface-area homogeneous mixed oxides are widely required by industry for use as adsorbents, catalysts, and pigments, and in sensor and magnetic technologies [1-7]. These materials require preparation techniques that ensure an intimate mixture of the components, without high-temperature treatments, and the properties of the materials obtained are very different from those of the same solids synthetized using ceramic methods [8]. The synthesis of hydrotalcite-type (HT) anionic clays by coprecipitation, followed by thermal decomposition at moderate temperature, fulfills these requirements [7,9,10]. Synthetic HT... 

Nanostructured materials have attracted great interest for many different applications, due to their unusual or enhanced properties compared with bulk materials [9-12]. An example of enhanced property of nanomaterials producing ad-value is the ionic conductivity. Therefore, the investigation of the nanostructured solid conductors, also known as nanoionics, has recently become one of the hottest fields of research. These nanomaterials can be used for advanced energy conversion and storage applications, such as SOFCs. Various synthetic routes, such as thermal evaporation [13], wet chemical processes including coprecipitation [14], the modified sol-gel method [15], the hydrothermal process [11,16], mixing freeze-dried precursors [17], or the combustion [18], have already been developed to produce solid electrolytes composed from nanosized crystallites. 

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