Some Metals Today

as in ancient times, our source of raw materials is the earth s crust. However, because of our advanced chemical technology, exotic materials have become necessary for processes that are vital yet unfamiliar to most people. This is true even for students in 

An additional feature that makes obtaining many inorganic materials so difficult is that they are not distributed uniformly in the earth s crust. It is a fact of life that the major producers of niobium are Canada and Brazil, and the United States imports 100% of the niobium needed. The situation is similar for bauxite, major deposits of which are found in Brazil, Jamaica, Australia, and French Guyana. In fact, of the various ores and minerals that are sources of important inorganic materials, the United States must rely on other countries for many of them. Table 1.2 shows some of the major inorganic raw materials, their uses, and their sources. 

Material Major Uses of Products Sources Percentage Imported 

Bauxite Aluminum, abrasives, refractories, AI2O3 Brazil, Australia, Jamaica, Guyana 100 

Niobium Special steels, titanium alloys Canada, Brazil 100 

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Many years ago, geochemists recognized that whereas some metallic elements are found as sulfides in the Earth s crust, others are usually encountered as oxides, chlorides, or carbonates. Copper, lead, and mercury are most often found as sulfide ores Na and K are found as their chloride salts Mg and Ca exist as carbonates and Al, Ti, and Fe are all found as oxides. Today chemists understand the causes of this differentiation among metal compounds. The underlying principle is how tightly an atom binds its valence electrons. The strength with which an atom holds its valence electrons also determines the ability of that atom to act as a Lewis base, so we can use the Lewis acid-base model to describe many affinities that exist among elements. This notion not only explains the natural distribution of minerals, but also can be used to predict patterns of chemical reactivity. 

A number of electrolytic processes are used for the industrial production of metals. Some metals such as zinc, copper, manganese, gallium, chromium, etc. are electrowon from aqueous baths. Another common electrolytic process used is molten salt electrolysis. The most important application of molten salt electrolysis till now has been in the electrowinning of metals. Today aluminum, magnesium, lithium, sodium, calcium, boron, cerium, tantalum, and mischmetal are produced in tonnage quantities by molten salt electrolysis. As a representative example, the electrowinning process for aluminum is taken up. 

The period in human history beginning in about 1200 bce is called the Iron Age. It was at about this time that humans first learned how to use iron metal. But in some ways, one could refer to the current era as the New Iron Age. Iron is probably the most widely used and most important metal today. No other metal is available to replace iron in all its many applications. 

Few metals, particularly those in common technological applications, are stable when exposed to the atmosphere at both high and low temperatures. Consequently, most metals in service today are subject to deterioration either by corrosion at room temperature or by oxidation at high temperature. The degree of corrosion varies widely. Some metals, such as iron, will rust and oxidize very rapidly whereas other metals, such as nickel and chromium, are attacked relatively slowly. It wiU be seen that the nature of the surface layers produced on the metal plays a major role in the behaviour of these materials in aggressive atmospheres. 

Today, it is clear that aromaticity is possible in 3-dimensional, as well as planar, systems, such as quasi-spherical cages of fullerenes [43,44] and polyhedral boranes (e.g. Bi2Hi2 ) [44, 45], in carbon nanotubes and in some metal clusters (e.g., AusZn+, Au2o) [46], The 2( - -1) rule proposed by Hirsch [47] and successfully applied to design various novel aromatic compounds, serves as the 3-dimensional... 

Today, platinum-based catalysts are the state-of-the-art material in fuel cell applications. The costs of these catalysts, however, contribute by 33 % to the overall costs of a fuel cell stack [1]. This makes it reasonable to search for cheap alternatives, especially non-precious metal catalysts (NPMC). Some metal nitrides (Me = W, Mo) and oxynitrides (Me = Ta, Zr, Nb) are promising regarding the observed onset potentials (up to 0.8 V vs. NHE) and could be of interest for further investigation. In this respect, however, the readers are referred to the original contributions (W2N [2], M02N [3], ZrOxNy [4-6], TaOxNy [7], NbO Ny [8, 9]). 

The oxo-process is based on a hydroformylation reaction and uses an olefin, hydrogen, and carbon monoxide as raw materials and the transition metal hydrocarbonyl [HM(CO) ] as the catalyst cobalt is the most commonly used metal today. The resulting aldehydes are further converted to corresponding alcohols with special hydrogenation catalysts (based on nickel, copper, chromite, etc.). The derived oxo-alcohols are odd numbered and with some side branching. Some catalysts are used to limit the degree of 2-methyl branched alcohols to 25%. 

Sodium ethoxide was the first metal alkoxide described in 1837 (1). The alkoxides of many transition metals were developed after World War II (2—5). Today some alkoxides, including those of sodium, potassium, magnesium, aluminum, zirconium, and titanium, are commercially important. The name metal alkoxides is preferred, although metal alcoholates is also used. 

About the time that synthetic metals reached their apogee, twenty years ago, research began on semiconducting polymers. Today, at the turn of the century, such polymers have taken the center of the stage, and indeed promise some of the most important applications of polymers. 

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