Metallurgy Topics or Metal Technology +
(terms about the science and technology of metals and metal processing)
Alkali metals are not very electronegative, meaning they attract electrons very weakly.
All of the alkali metals can act as electrolytes in solution, meaning that they conduct electricity. Many of these elements are found in alkaline batteries.
Lithium in particular is found in many types of batteries and it is also an important component of several drugs used to treat mental illness.
When these elements are combined with oxygen or water, they form compounds with a basic pH.
Alkaline earth metals are not very electronegative. They have just two valence electrons, and will lose them to become positively charged ions or cations.
Other well-known alloys include brass, an alloy of copper and zinc; and steel, an alloy of iron and carbon.
Alloys have been created by mixing metals with semi-metals like arsenic and antimony and with nonmetals like carbon and silicon.
Most alloys are developed for a specific physical characteristic; such as, malleability or strength.
In this process, ore that contains the aluminum, most often bauxite, is first purified to form a substance called alumina, which contains both aluminum and oxygen.
The alumina is placed in a bath of melted cryolite, whose constituents include fluorine and iron; fluorspar, a compound of calcium and fluorine, is added to lower the melting point.
The elemental aluminum that is produced by the Hall process has many uses because of its light weight, tensile strength, and good conductivity of heat and electricity.
Most notably, all of the modern aircraft that are flown by the military services and airlines have aluminum as their primary structural material.
Annealing is more often applied to the reduction of the hardness of a metal; however, annealing can also be done to change the microstructure of a metal or to achieve a specific set of physical or mechanical properties.
In the annealing process, the metal is first heated to a predetermined temperature and then it is allowed to cool to room temperature. It is often an important step in the production of specific metal types.
In the production of fine wires, there may be several intermediate annealing steps before the metal is drawn through fine openings to produce wirea with the desired properties.
Steel is made by introducing carbon from the coke used in the refinement of iron ore.
Alloys are also divided into ferrous (iron based) and non-ferrous, in which the base is usually copper, aluminum, or titanium.
While some metals; such as, gold and silver can be found uncombined with other elements in nature, most metals occur as minerals; that is, in chemical combination with nonmetallic elements.
When the combination is such that the extraction of a metal from a mineral is economically attractive, the combination is called an ore. The technique of producing metals from ore is called "process metallurgy" or "extraction metallurgy".
Metals are extracted from ores in three primary ways:
- Dry processes; such as, smelting, volatilization, or amalgamation; which is treatment with mercury.
- Wet processes, involving chemical reactions.
- Electrolytic processes, which work on the principle of eletcrolysis using electricity conducted by a solution or melt to effect chemical changes.
The principles involved in hydrometallurgy are those of physical chemistry, inorganic chemistry, electrochemistry and analytical chemistry.
Hydrometallurgical processes are used commercially because hey are convenient to operate, the recovery of metals is high, and operating costs usually are low; and especially, because of the variety of quantitative chemical separations that can be made in aqueous solutions much more readily than is possible with the melts used in pyrometallurgical processes.
In the head of the metal detector is a coil, that is part of an electronic circuit.
The presence of metal causes the frequency of the signal in the circuit to change, setting up an audible note in the headphones worn by the user.
The addition of metal halide gases results in higher light output, more lumens (unit of luminous flux) per watt, and better color rendition than from mercury gas alone.
The hydrogen can either be stored in the cavities of a grid of metal; such as, magnesium or titanium, or it can enter into an ionic bond with the metal.