Precipitants homogeneous

Main uses of lithium alloys. Li additions often change completely the properties of metals to which it is added, for instance hardness of A1 and Pb (addition of Li to Pb results in the formation of Pb solid solution and a eutectic at 15.7 at.% Li with LiPb) and ductility of Mg. Al-alloys can be of great interest in aerospace industry Li (as Be) simultaneously reduces the density of A1 and increases its modulus of elasticity. Each 1 mass% Li up to the solubility limit (4.2 mass%) reduces density by about 3% and increases modulus by 5%. Precipitates homogeneously distributed of spherical LiAl3 in diluted Li-alloys during heat treatment may improve strength. 

Thus rate laws for precipitation reactions tend to be complicated, even in pure solutions. Mixed precipitates can be inhomogeneous solids with one component restricted to a thin outer layer because of slow diffusion. New solid phases can precipitate homogeneously onto the surfaces of existing solid phases. Weathering solids may provide host surfaces onto which more stable phases may precipitate. 

It should be noted that, in the natural subsurface solid phase, differentiation between adsorption and precipitation can be very difficult, because the new sohd phase may precipitate homogeneously onto the surface of an existing sohd phase. Weathering may provide host surfaces for the more stable phase into which they transform chemically. 

The effect of reactant concentration can be divided into two separate influences. The simplest is obvious Lower overall concentrations result in a slower rate. This does not necessarily mean a thinner fihn, however—sometimes the opposite. The reason for this is clear if we return to our introductory discussion on the CD process—rapid precipitation. It is clear that if the reaction is too fast, it will terminate with most of the product precipitating homogeneously in solution rather than depositing on the substrate (which requires time to occur). This results in a very thin film, if any fihn at all. Similarly, for the less extreme case of a CD reaction that terminates, not within a second, but still in a short time, the final fihn thickness will be small. At the other extreme, if the reaction is extremely slow, a thick fihn can be built up, but it may take a very long time for this to occur (weeks, even months). It is therefore evident that there is an optimum rate for the reaction, which can be controlled by a combination of reactant concentrations, temperature, and pH. 

Finally, even if these criteria are satisfied, there remains the question of whether the product will adhere to form a film or just precipitate homogeneously in the solution. This is the most difficult criterion to answer a priori. The hydroxide and/or oxy groups present on many substrates in aqueous solutions are likely to be quite different in a nonaqueous solvent (depending on whether hydroxide groups are present or not). Another factor that could conceivably explain the general lack of film formation in many organic solvents is the lower Hamaker constant of water compared with many other liquids this means that the interaction between a particle in the solvent and a solid surface will be somewhat more in water than in most other liquids (see Chapter 1, van der Waals forces). From the author s own experience, although slow precipitation can be readily accomplished from nonaqueous solutions, film formation appears to be the exception rather than the rule. The few examples described in the literature are confined to carboxylic acid solvents (see later). 

Precipitation/homogenization with hydrochloric acid and MeCN was presented for the milk, muscle, liver, and kidney samples. The extract was partially evaporated, and TCs were analyzed in separate ion-pair chromatographic systems, depending on the kind of sample and analyzed compound (47). 

Precipitation or hydrolysis a. Neutralization and precipitation Homogeneous precipitation Coprecipitation Salts solution Alkoxides Sol-gel Hydrothermal... 

Unique nanocrystalline microstructures can be produced by controlled crystallization of the fully amorphous product, including nanocrystalline precipitates homogeneously distributed in an amorphous alloy matrix. In some systems, both the strength and ductility increase in this partially crystalline state [24], Other alloys produce nanocrystalline intermetallic or quasicrystalline precipitates, providing a credible path for increasing the specific stiffness. Thus, a significant effort is required to study the kinetics of crystallization, the devitrification pathways and the microstructures and properties that may be produced upon devitrification. The potential for exploration of novel compositions and microstructures in this class of materials is clearly promising. 

Zhi et al. [41] investigated the effect of synthesis method on the WGS activity of Cu-Ce-La catalysts. They prepared the catalysts using co-precipitation, homogeneous precipitation and deposition-precipitation techniques. Among the various catalysts, the catalysts synthesized by co-precipitation method exhibit better activity. Then, they investigated the effect of precipitator. The sequence of activities are NaOH (61.10%)>NaOH-h(NH2)2CO (60.98%)> (NH2)2C0 (57.4%) NH3 X H2O (5.35%) at 300 °C. 

Before the polymerization starts, the initiator molecules can either be located in monomer-swollen micelles, in monomer droplets, or in the continuous aqueous phase [35]. The distribution depends on several factors, including first of all the hydrophilic properties of the initiator. But even when oil-soluble initiators are used, radicals are very Ukely to be present in the aqueous phase [35-37]. Those radicals in the aqueous phase either (re)enter a droplet and lead to droplet nucleation, enter a micelle and lead to micellar nucleation, or start polymerizing monomer molecules dissolved in the aqueous phase. Those oligomers can either enter a droplet or precipitate (homogeneous nucleation) [38]. 

A PEG precipitated homogenate of avocado was prepared and subjected to anion exchange on a Pharmacia Mono Q column. 0.5ml fractions were collected and assayed for binding of [1-f C] from [1-f"fC] acetyl CoA in the presence and absence of E.coli ACP. The first peak was absolutely dependent on the presence of ACP for incorporation of [1- C], confirming this... 

On the other hand, if the drops are sprayed against the substrate with sufficiently high strength, spread lightly, maintain an evaporation rate equivalent to the solute precipitation rate, the solute nucleates and precipitates homogeneously, creating a dense and continuous film (Yu Liao, 1998). 

Various CaTiOs samples having diEfeient particle sizes, shapes, crystal defects and impurity phases were prepared by three methods, i.e., co-precipitation, homogeneous precipitation and solid-state reaction methods. The CaTiOs samples were loaded with Pt co-catalyst (0.1 wt%) and examined for both the photocatalytic water decomposition (WD) and the photocatalytic steam reforming of methane (PSRM). The highest activities for the WD and the PSRM were obtained over the samples prepared by the solid-state reaction method from mtile and anatase Ti02, respectively. The controlling factors in their activity were discussed. 

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