Titanium

See how silicon links to titanium in this slightly unconventionally plotted periodic table? 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

In today's (2016...2021) conventional technology Titanium is a good structural building material (light strong and corrosion resistant).
But today titanium 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.

Also compared to other metals and alloys titanium is harder to subtracrively machine.

Why titanium is maybe 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
Today (~2022) often ceramics rather than single crystalline gems are made.

Comparison of usefulness with the other most common metallic elements in Earth's crust

• 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 not especially useful as building materials. These are often quite chemical reactive even with water.
• 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 a few 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).

Named Titanium gemstone like compounds that occur as minerals

• TiC titanium end-member of khamrabaevit – Mohs 9 – hongquiit Mohs 5.5-6.0??
• TiN osbornite (wikipedia) – Mohs 8.5 – 5.43g/ccm

Titanium oxides:

• TiO [1] - hongquiite - simple cubic - 1,750C° - 4.95g/ccm - optically metallic (golden)
• Ti₂O₃ [2] - tistarite - hexagonal corundum structure (like sapphire) - 2,130°C (decomposes) - 4.49g/ccm - semiconducting to metallic at 200°C
• TiO₂ [3] - rutile, anatase, brookite, and more

Ternary compounds

A main titanium ore that also could be used as building material:

• Illmentite – FeTiO₃ – Mohs 5 to 6 – trigonal – (4.70 to 4.79)g/ccm – slightly magnetic

Locations of occurrence and future usage

Lots of titanium on our Moon?

On the lunar lowlands there are hot spots where Titanium is especially abundant.
(wiki-TODO: investgate overall abundance of titanium on Earth vs on the Moon)

There may be:

• easier refining to metallic state in the lunar vacuum and
• easier mining due to the the main resource (ilmenite) being magnetic grains in the lunar regolith

So overall titanium might find more use on the Moon than on Earth.

On abundance of partner elements in binary compounds:
On the moon volatile elements (including carbon and nitrogen) seem to be rather scarce.
So TiN and TiC may be less likely to find massive use there.
Unless locally high concentrations of volatiles in cold traps on the poles are tapped and not yet fully exploited.
How finite are cold trap volatiles on the moon compared to say
crude oil on Earth that we seem to manage to deplete eventually?

Related:

• wikipedia: Geology on the Moon
• The Surprising Lunar Maria – by G. Jeffrey Taylor – Hawai'i Institute of Geophysics and Planetology – mentioning a possible sampling bias
• The Chemical Composition of Lunar Soil (section on titanium) – Washington University in St. Louis
• (wiki-TODO: Are there lunar geologic maps depicting spacial distribution of titanium concentration?)

Where in the solar system is titanium the most accessible?

Generally the openly accessible silicatic celestial body crusts of our inner solar system and the main asteroid belt
likely give a higher chance of finding large quantities of titanium than the ice-crust-bearing celestial bodies of our outer solar system.

Titanium on Titan?

I case you wonder:
There is probably not much titanium in the outer crust of Saturns one and only giant moon Titan.
Most stuff there are likely light light volatile elements C,H,O,N,S.
Cryovolcanism (of yet unclear degree) might carry up some metal salts.
At least titanium is not siderophile (see: [4]).

Similar story

• on all jovian moons except Io
• on further out big ice moons like triton and
• on transpeptunian objects like pluto.

Limits of corrosion resistance

Pure metallic titanium (Ti):
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. The issue: Suface diffusion

Suboxidic and nonoxidic titanium based artificial gemstones (TiO, TiN, TiC, TiP):
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

• Chemical element
• Periodic table of elements
• Base materials with high potential

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Natural TiO₂ mineral polymorphs:

• Rutile
• Anatase
• Brookite
• Tistarite – Mohs 8.5

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• Mechadensite (not an official name)

External links

• Youtube: "Electron Configuration for Ti , Ti3+, and Ti4+ (Titanium and Titanium Ions)" by Wayne Breslyn 2019-07-01