Titanium
In today's (2016...2017) conventional technology Titanium is a good structural building material (light strong and corrosion resistant).
But today titanium but is rather expensive.
Titanium is not at all a rare element but
- it's more distributed than other elements.
- it's hard to extract and process
More advanced mining techniques enabled by atomically precise technology will allow a significant drop in price.
Contents
Why titanium is one of the most useful metals
In advanced atomically precise manufacturing titanium will be very useful since titanium's oxidized forms with nonmetals (it's gemstones) usually have:
- very high hardness and
- very high melting points (See refractory material).
So they form very useful structural building materials.
Some simple titanium gemstones are: TiN TiP TiC TiSi2 TiB2 TiO2 Ti2O3
- Aluminium the most common metal in earths crust (thus more common than titanium) forms much viewer binary nonmetal compounds that are useful as structural building material (most useful: leukosapphire Al2O3). carbides nitrides and phosphides of aluminum are no useful building materials.
- Binary nonmetal compounds with the second most common element in earth's crust iron Iron are usually not very hard and are usually metallic and non-transparent (Fe2O3 Hematite, Fe3O4 Magnetite, FeS2 Pyrite).
- Binary nonmetal compounds with the common alkali metals Sodium and Potassium K are all water soluble or worse (reactive).
- Many of the binary nonmetal compounds with the common earth alkali metals Magnesium and Calcium are water soluble with a few exceptions (CaF Fluorite, MgO Periclase).
Stuff that reacted with water to a stable compound is usually too soft for structural building materials (there are exceptions).
But what is the underlying reason for titanium to be so awesome?
See how silicon links to titanium in this slightly unconventionally plotted periodic table (top right)?
The titanium group (4th group) of the periodic table kind of forms a second branch of the carbon group (14th group).
Both groups have 4 electrons above their next lower closed noble gas electron shells.
- 14Si: [Ne] 3s23p2
- 22Ti: [Ar] 3d24s2
This may be part of the reason for why titanium (and zirconium) are:
- structurally so versatile and useful elements in that they from so many very hard and heat resistant materials.
- titanium and silicon sometimes form isostructural minerals: TiO2 Rutile and SiO2 Stishovite (not quartz here)
Then again, many titanium compound are in simple cubic rock salt structure (probably due to metallicness and ionicness)
while silicon likes to arrange in sparse covalent diamondoid structures (zincblende structure and wurzite structure).
Locations of occurrence and future usage
Titanium is especially abundant on the lunar lowlands.
So there titanium might find more use than on earth. (See: [1])
On the moon volatiles elements (including carbon and nitrogen) seem to be rather scarce so TiN and TiC may be less likely to find massive use there.
Limits of corrosion resistance
Pure metallic titanium:
Pure metallic titanium in macroscopic chunks forms a stable self protecting oxide layer. Similar to what happens with aluminum. (How thick and dense exactly?)
If machine parts out of titanium become so small that the oxide layers become almost the thickness of the parts themselves (as in advanced atomically precise technology) then elemental titanium can't be used in direct contact with the oxygen bearing atmosphere.
Even in a practically perfect vacuum or in an nonreactive noble gas environment elemental titanium (as probably most/all metals in elemental form)
may only be usable at very low temperatures where the atoms stay in place albeit the weakness of the undirected metallic bonds.
Suboxidic and nonoxidic artificial titanium gemstones (today mostly known as dislocation and impurity littered ceramics)
may or may not show some surface oxidation when exposed to (wet and possibly slightly acidic) air.
Related
Natural TiO2 mineral polymorphs:
