Metal network

Classify each of the following solids as metallic, network covalent, ionic, or molecular. 

Molecular formula metal metal metal network solid Pi S6 Cls Ar... 

Consolidative reduction has been employed when the object is so badly corroded that it becomes extremely fragile and all surface details are just a mass of corrosion products. In this case, one must apply a low-current density over a prolonged period. In some instances, it is necessary to hold together the loose crusts during the electrolysis, which are then ultimately reduced in situ into a more coherent but porous metallic network. In the case of a completely mineralized silver lyre from the Royal Graves at Ur, partially-rectified current was used to reduce silver chloride [298]. 

Transition metal nitrides and carbides can be described, generally speaking, as insertion compounds of nitrogen or carbon in the metal network.1 In fact, strong metal-nonmetal interactions exist which induce structural modifications.1,2 These compounds form a class of materials with unique physical3,4 and catalytic1,5,6 properties. The term platinoids has been used to illustrate their potential in reactions traditionally catalysed by noble metals. 

Figure 2.2. Illustration of d-orbital overlap between adjacent metal atoms in an extended metallic network.

The second area that has exploded during the last decade concerns materials that involve open-frameworks that are constructed from both inorganic and organic components we shall refer to them collectively as hybrid materials and wUl cover them in two separate sections. The first will examine the so-called coordination polymers [14] in which molecular coordination compounds are connected by organic linkers to form chains, sheets or 3-D networks. The second class involves extended metal-oxygen-metal networks that are decorated by organic ligands we shall refer to these as hybrid metal oxides. 

Magnesium oxide, y-aluminum oxide, synthetic rutile, thorium dioxide, silica gels, barium sulfate, activated carbons, metallic network supporting structures, various silicates (especially of Mg, Al), etc. 

Nanoporous metallic networks combine these very interesting properties with an intricate spatial architecture for applications in electronics, optics (particularly as photonic crystals), optoelectronics, catalysis, fuel cells, and... 

Instead of infiltration with neat metal nanoparticles, the interstitial voids of the template opal can also be filled wifh a mefal precursor. The impregnation of the preformed colloidal crystals with the metal precursor, followed by transformation of the precursor to the neat metal and removal of the template, results in metallic inverse opals. For example, nickel oxalate was precipitated in a PS opal and converted into a NiO macroporous network by calcination of the metal salt and combustion of the polymer. In a subsequent step, the nickel oxide was reduced to neat Ni in a hydrogen atmosphere to yield a macroporous metal network [82]. It was further suggested by the authors that by the same technique other metal networks (e.g.. Mg, Mn, Fe, Zn from their oxides and Ca, Sr, Ba etc. from their carbonates) should be accessible. 

The nature of the chemical bonding within the metal network can be seen from a close examination of the four energy bands in fig. 48 which were calculated for a single [Gd CU] chain. Each band can be classified according to how it transforms with... 

Fig. 9.1 Schematic illustrating the preparation of metal-insulator-metal electrostatic nanocapacitors based on the double-gyroid morphology. Firstly, the DG templates are replicated via nickel electroplating. Subsequent to template dissolution the metal nanostructure is coated with a few nanometer thick electrictdly insulating alumina layer by ALD. Lastly, a liquified low-melting point tdloy is drop-cast onto the sample and allowed to infiltrate the mesopoies. The two interdigitated metal networks which ate separated by the electrically isolating metal oxide form the active volume V of the electrostatic capacitor...

Several X-ray crystal structures of two-dimensional oxalato-bridged mixed-metal networks have been reported since 1993. The first structural information on two-dimensional oxalates was obtained by Atovmyan et al who succeeded in growing single crystals of the compound... 

The first structure of a three-dimensional transition metal network incorporating the oxalate ion was that of [Ni(phen)3][KCo (ox)3] 2H20 (phen= 1,10-phenanthroline) reported by Snow and co-workers in 1971. The true dimensionality of this compound, however, went unrecognized during this period, and the potential of oxalate ions to form three-dimensional networks was not fully realized until 1993, when Decurtins et al. published the crystal structure of the iron(II)-oxalato complex with tris(2,2 -bipyridine)iron(II) cations. This compound has an overall stoichiometry of [Fe (bipy)3] [Fe 2(ox)3] " and forms a three-dimensional anionic polymeric network that is best described with the three-connected decagon network topology. A view of this anionic network is shown in Figure 43. 

Random metallic network model (RMN), 15-11 Rapidly mixed reactions, 7-7, 7-10-7-14, 7-29, 7-36,... 

Figure 5.3 also shows that there is no linear relationship between the quantity of filler content and conductivity. At a low filler content, the conductivity of the matrix polymer is dominant. With increasing fibre content, the contacts between the fibres increase and the specific conductivity escalates in a small window. The critical concentrations of volume required for this escalation - called the percolation threshold - range between 20-25 vol% for both the metal/thermoplastic hybrid material, and the polymer exclusively filled with copper. Above this concentration, the metal network becomes more dense to an extent where conductivity can be increased only marginally [3,16-18]. 

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