Multi-metallic

FIG. 18-117 Section of precoated wire filter leaf. (Multi Metal Wire Cloth.)... 

Substrate Steel Steel Zinc Multi-metal Aluminium... 

In modern practice, inhibitors are rarely used in the form of single compounds — particularly in near-neutral solutions. It is much more usual for formulations made up from two, three or more inhibitors to be employed. Three factors are responsible for this approach. Firstly, because individual inhibitors are effective with only a limited number of metals the protection of multi-metal systems requires the presence of more than one inhibitor. (Toxicity and pollution considerations frequently prevent the use of chromates as universal inhibitors.) Secondly, because of the separate advantages possessed by inhibitors of the anodic and cathodic types it is sometimes of benefit to use a formulation composed of examples from each type. This procedure often results in improved protection above that given by either type alone and makes it possible to use lower inhibitor concentrations. The third factor relates to the use of halide ions to improve the action of organic inhibitors in acid solutions. The halides are not, strictly speaking, acting as inhibitors in this sense, and their function is to assist in the adsorption of the inhibitor on to the metal surface. The second and third of these methods are often referred to as synergised treatments. 

PNNL has a long history studying hydrogenolysis as a means to form value-added products from sugar alcohols including glycerol. In this paper we will report on a subset of this work, focused on rhenium-based multi-metallic catalysts supported on carbon. 

Chojnacka, K., Biosorption and bioaccumulation of microelements by Riccia fluitans in single and multi-metal system, Bioresource Technology, 98 (15), 2919-2925, 2007. 

One of the more recent innovations for the use of dichalcogenophosphates in coordination chemistry is in the synthesis of multi-metallic cluster compounds, in particular those involving d10 copper(I) or silver(I) metal centres. These clusters can be conveniently prepared from the reaction of the ammonium salt of the dichalcogenophosphate with the appropriate metal PF6 salt. The most... 

On the other hand, hi- or multi-metallic supported systems have been attracting considerable interest in research into heterogeneous catalysis as a possible way to modulate the catalytic properties of the individual monometalUc counterparts [12, 13]. These catalysts usually show new catalytic properties that are ascribed to geometric and/or electronic effects between the metalUc components. Of special interest is the preparation of supported bimetallic catalysts using metal carbonyls as precursors, since the milder conditions used, when compared with conventional methods, can render catalysts with homogeneous bimetallic entities of a size and composition not usually achieved when conventional salts are employed as precursors. The use of these catalysts as models can lead to elucidation of the relationships between the structure and catalytic behavior of bimetalUc catalysts. 

The examples are shown in Figure 9.1.10, which gives x-ray diffractograms of three types of physical mixtures of PVP-stabilized Pd, Pt, and Au monometallic nanoparticles, and the corresponding PVP-stabilized bimetallic nanoparticles (53). The diffraction patterns of the physical mixtures are consistent with the sum of two individual patterns, and are clearly different from those of the bimetallic nanoparticles, which have two broader peaks, indicating that several interatomic lengths exist in a single particle. By XRD one can easily understand if the obtained multi-metallic nanoparticles have an alloy structure or are simple physical mixtures of monometallic particles. 

There is increasing interest in the study of multi-metallic systems for several reasons. They are potential catalysts in many industrial processes and, because of the common occurrence of multi-metallic species as active sites in many metalloenzymes, they may be used as models for these molecules. In addition, these complexes offer the possibility of studying multi-electron charge transfer and magnetic coupling phenomena. 

The determination of arsenic is discussed under Multi-Metal Analysis of Soils in Sect. 2.55. 

The determination of chromium is also discussed under Multi-Metal Analysis of Soils in Sect. 2.55 (atomic absorption spectrometry), Sect. 2.55 (inductively coupled plasma atomic emission spectrometry), Sect. 2.55 (emission spectrometry), Sect. 2.55 (photon activation analysis), Sect. 2.55 (neutron activation analysis), and Sect. 2.55 (differential pulse anodic stripping voltammetry). 

The determination of lanthanum in soil by neutron activation analysis is discussed under Multi-Metal Analysis of Soils in Sects. 2.55 (neutron activation analysis) and 2.55 (column chromatography). 

---