Lead nanopowders

Fievet et al. [225] have prepared and isolated metallic nanopowders of gold, palladium, iridium, osmium, copper, silver, nickel, cobalt, lead, and cadmium via polyol... 

Figure 3.5.15 gives a particularly instructive example [33, 34], It refers to Sn as anode material that even in the form of (commercial) nanopowders does not show a useful cyclability. This is in sharp contrast to the morphology shown in Figure 3.5.15. The morphology leads to optimization by improving not less than seven battery-relevant parameters (1) Sn particles are mechanically decoupled and do not suffer from pulverization upon volume change on cycling. (2) Carbon provides an efficient way of electron transport along the fiber to the tin particle. (3) Li+...

The oxidation rate of the micro- and nanopowders was found to be faster than that of bulk single-crystal silicon, hich can be rationalized as follows. At the initial stages of the oxide growth oxygen adsorption on micro- and nanoparticles leads to SiO formation. The oxidation is then due to an enhanced oxidant diffusion over the particle surface. During the oxidation of the powders, the amount of the oxidant penetrating into the bulk of a particle is so small that its contribution to the oxidation process in the bulk of the particle is insignificant. In this case, the oxidation of the micro- and nanopowders is... 

Let us start with nanopowders. The measurements were carried out by XRD method. In Fig. 2.2, the lattice constants a and c, measured on tetragonal BaTiOs nanopowder, are shown at room temperature [17]. One can see that at average particle size about 50 nm c = a, so that the symmetry becomes cubic and ferroelectric phase transforms into paraelectric one at room temperature. To estimate the average nanoparticle size, where the ferroelectric phase becomes unstable and transforms into paraelectric one, the Scherrer formula has been used. This formula relates the particle size to the XRD lines half-width. The average particle size leading to the symmetry breaking is called critical size and constitutes the important characteristic of nanomaterials. It turns out, that the critical size measured on different samples can be essentially different. To illustrate this, on Fig. 2.3 we report the ratio c/a at room temperature for BaTiOs nanopowder obtained in Ref. [18]. It is seen that ratio c/a= 1 was obtained in the samples with average size 120 nm. The difference between the critical sizes in the papers [17] and [18] can be related to the... 

The size-dependent properties of metal oxide nanopowder have generated diverse scientific interest. Their high surface area, shape, surface chanistry and intrinsic properties lead to their use in nanotechnology. 

The gelation of colloidal solution takes place at the pH dependence solution, which leads to the formation of metal oxide nanopowder... 

Cryogenic milling is a top-down approach to prepare nanoscale titanium of 100-300 nm size. Several mechanical deformations of large grains into nltra fine powder and degassing lead to nanopowder with improved characteristics. 

---