Posted 11 March 2006 - 11:13 AM
Tungsten was used because it is more durable and chemically resistant at high temperatures than steel-- the same reason it's used in light bulb filiaments. However, tungsten also has a lower electrical conductivity than steel, so replacing the thinner tungsten-steel wires with somewhat thicker steel (alloy?) wires woulkd allow greater current for a given voltage.
Tungsten is an element -- a pure substance made of a single type of atom. Steel is a alloy of the element iron with a few percent of carbon for strength. Quite often, other elements are added for other properties. Stainless steel, for example, generally contains at least 10.5% of the element Chromium (for greater resistance to chemical attack) and various stainless steel "recipes" contains small amounts of nickel, molybdenum, titanium, copper and other elements, to optimize other properties.
Magnetite is simply one name for a mineral form of the element iron. As a natural mineral, it is generally not pure iron (which, as we know, is highly oxidizable) but is a mixture of relatively pure iron with some iron oxide and various trace compounds (depending on source)
Magnetite really doesn't have any special properties that aren't generally shared by bulk iron, because iron and iron oxides are "ionic" (the chemical bonds are omnidirectional charge attractions, rather than electron pair sharing between two specific atoms) Though iron does have some mesoscale structure (local microscrystals organized in a specific direction) it doesn't have anything like the versatility of carbon, which has *covalent bonds, and whose natural mineral forms can have dramatically different properties depending on their structure (e.g. diamond, graphite and buckministerfullerene are all pure carbon with consistent patterns of chemical bonds; coal and charcoal are amorphous carbon (no uniform structure) with some impurities from their natural origin; activated charcoal is high purity amorphous carbon, made in factories)
To envision this, you can think of iron atoms as little magnetic balls. You can imagine how these balls will tend to organize themselves in a nice tight orderly crystalline packing over short distances. Carbon (and covalent compounds) have direct bonds, like the sticks of a tinkertoy set. While a pile of iron magnet balls will have some interesting properties, the number of distinctly different things it can do is fairly small. Tinkertoys allow for much more versatile and different structures
[If you build flat hexagonal grids of tinkertoys, and stack them so the layers ccan slide easily over each other, you'd have the structure of graphite (often used as a lubricant). If, instead, you built a 3-D hexagonal grid (it's actually based on tetrahedrons -- but it's NOT a tetrahedral grid) then you'd have something that was very rigid in 3 dimensions -- a diamond. If you took the basic hexagon grid of graphite, but removed or doubled-up some, so the flat grid started to curl up, you'd get the basic curved structures seen in buckminsterfulleres (buckyballs, buckytubes, etc) -- Buckminister Fuller geodesic dome or tubes are classic tinkertoy projects. Buckyballs are actually exactly the pattern of pentagons and hexagons seen on the outside of a soccer ball. Magnet balls, by contrast, don't organize themselves in amy different ways]
I don't think magnetite would have any substantial effect. It has a lower tensile strength than steel (requiring thicker wires) and a comparable electical conductivity (depending on the steel alloy used) but the magnetic properties of the magnetite itself will vanish at relatively low temperatures. The so-called "curie point" of pure iron is 1043 K ( ~1400 F), and above that temperature iron *isn't* spontaneously magnetic, as it is at room temperature-- it's only magnetic the same way *any other* moving ion or plasma would be. The organization of charges in the outer shell of iron atoms simply gets wrecked at high temps.
And we're not talking thousands of degrees in this experiment, or merely millions, but *billions*. At those temperatures, the room temperature properties of iron are even less relevant than the magical superfluid properties of liquid helium at 2.17K are to a child's party balloon.
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