Base materials with high potential

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Very good materials

Best of the best

All diamondoids come in:

  • cubic zincblende structure
  • hexagonal wurzite structure

Related main page: Diamond like compounds

Best diamondoid compounds

C – pure carbon "dialondeite" this includes the allotropes:

  • C in zincblende structure is called diamond of the normal cubic variety
  • C in wurzite structure is called lonsdaleite "hexagonal diamond"

SiC – gemstone quality optically transparent silicon carbide aka moissanite.
The structure of natural moissanite is in-between the zincblende and the wurzite structure.
This is part of what makes natural moissanite more though than natural diamond.
This does not apply to piezochemically mechanosynthesized and very small structures like some crystolecules though.
A main advantage of moissanite over diamond is it's high heat and oxidation resistance.


Si – pure silicon (eventually)
Not optically transparent since a semiconductor with low enough bandgap.
Lower mechanical chemical and thermal stability then the above.


BN – diamondoid boron nitride (cubic c-BN and hexagonal w-BN)
Boron is not super extremely abundant and available.
There is a rare natural mineral of the cubic variety called – quingsongit (de) – cubic – Mohs 9-10
Like graphene in the case of carbon there's a graphitic polymorph of BN. This is not counted as "diamondoid" here.


BC2N – heterodiamond
Basically an intermediate between dialondeite and "diamondoid boron nitride".


AlN – aluminum nitride – optically transparent due to big bandgap (visible light)
A main advantage compared to boron nitride is that aluminium is much more common than boron.
Disadvantages are lower mechanical (thermal?) and chemical stability.
The surface is not stable against water at the nanoscale level (powders hydrolyse to amonniak NH3 and aluminum hydroxide).
Nanomachinery out of AlN must thus be sealed into a product internal environment like e.g. PPV.


Phosphides: Phosphorus has a similar abundance/acessibility problem as boron.
It's by no means scarce (see fertilizer) but by no means anywhere near accessible as nitrogen. (See:Air as a resource).
Plus some compounds can be a huge health hazard. Like (AlN aluminum nitride) releasing highly toxic phosphine (PH3) gas on contact with water.
Out of these reasons they are not listed here as materials with high potential here.
Diamondoid phosphides are listed on the page: Diamond like compounds

Best SiO2 polymorphs

Metastable ultrahard and dense SiO2 polymorphs:

Simple titanium gemstones

Titanium combined with all sorts of abundant non-metal elements forms astoundingly many gemstone like compounds with exceptionally good mechanical and thermal properties. (Unlike the extremely abundant element iron that disappointingly underperforms in this regard). Titanium is reasonably abundant in Earths crust. Not as common as iron though. Titanium is especially common on our moon. There is also lack of non-volatile non-metal elements (like carbon and nitrogen) to combine it with though. Well, even for a quite big moonbases the volatiles in polar moon craters will suffice.

Titanium compounds with second row elements

  • TiB2 titanium diboride - hexagonal 2D layered - 3230°C - 4.52g/ccm - optically metallic - highly refractory compound
  • TiC titanium carbide - simple cubic - 3160°C (800°C in air) - 4.93g/ccm Mohs 9 to 9.5 - water insoluble (almost)
  • TiN titanium nitride - simple cubic - 2,947°C - 5.21 g/cm3 - optically metallic (golden) - "barrier metal" - water insoluble (almost)

Associated minerals:

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

Titanium compounds with third row elements:


  • TiSi2 titanium disilicide - orthorhombic (complex unit cell) - 1,470°C - 4.02g/ccm - water insoluble - optically metallic and electrically conductive - C54 phase (researchgate) - More titanium silicides ...
  • Ti3Si - tetragonal - (isotype to Ti3P - see above and Zr3P)(can this form a cubic A15 phase too ??)
  • Ti5Si4 - 2120°C - tetragonal (isotype to Zr5Si4)
  • TiSi titanium monosilicide - 1760 °C - orthorhombic (isotype to FeB)
  • Ti5Si9 - spacegroup Cmcm (Nr. 63) - 3.9g/ccm
  • Ti5Si3

Given silicon is a semi-metal and titanium is a metal titanium silicides should come with quite metallic properties (optically and electrically).
But mechanically still gemstone like like inter-metallic compounds.

Simple zirconium gemstones

Zirconium Zr compounds (maybe)

  • Zr (fifth row) is the element below Titanium (fourth row)
  • Zr is the most abundant fifth and below row non alkali element (Earth's crust).
  • Zr makes similarly good compounds with various other elements as Ti

Quite simple rutile structure & Hard

And neo-polymorphs with rutile structure. These include:

  • Silicon group: GeO2, SnO2, β-PbO2 – (germanium Ge is rather rare)
  • Other: MnO2, FeSbO4 – (antimony Sb is rather rare)

See: rutile structure. There is also a mention on that on the page about silicon
This could be called the the stishovite continuum or the rutile continuum'.

Corundum structure & hard

The corundum structure has lower symmetry than the rutile structure
which can be but not necessarily is a downside in that the design of crystolecules
based on these materials might be more difficult and or more limited.


  • Eskolatite (Cr2O3) – Mohs 8 – optically metallic – Chromium is less common
  • Hematite (Fe2O3) – Mohs 5.5 to 6.5 – optically metallic – Iron compounds are usually weaker

For more examples including less performant ones see:
Corundum structure – corundum is a term for low grade sapphire (and polymorphs: deltalumite)

Mono metal monoxides (simple cublic NaCl salt structure)

Earth alkali based

  • MgO periclase
  • CaO anhydrous lime - questionable - highly reactive with water - ok if well sealed inside of products

Transition metal based

Some transition metal monoxides (Typical: Max 1300-1900°C - Mohs 5-6)

  • TiO hongquiite
  • MnO manganosite - (Mn is less abundant)
  • FeO wüstite
  • NiO bunsenite - (Ni is not too abundant on earth but very abundant on metallic asteroids)

V vanadium, Cr chromium, Co cobalt do that too but
these elements are more scarce thus
not included as pure high volume base materials here

Other quite interesting compounds

Decently hard iron nitrides:

  • Fe4N Roaldite 3D structure (de)cubic – Mohs 5.5-6.0 – (very simple crystal structure)
  • Fe9N4 Siderazot 3D structure (de) – triclinic – Mohs ?? – (not as complex as formula suggests)

Silicon oxynitride:

Corundum/sapphire polymorphs (See: Leukosapphire#Polymorphs):

  • Al2O3 Deltalumite (δ form of corundum, polymorph of sapphire) – tetragonal – Mohs ?? (likely quite hard) – [6]

Spinel minerals (they all have nice cubic unit cells)

  • Spinel MgAl2O4 – Mohs 7.5 to 8.0 – cubic
  • Ulvöspinel TiFe2O4 – Mohs 5.5 to 6.0 – optically metallic

Ambient pressure stable high pressure modificaions of olivine:

  • High pressure modification of iron olivine γ-Fe2SiO4: Ahrensite[7] – (Mohs 6 – 4.26g/ccm)
  • High pressure modification of magnesium olivine Mg2SiO4: Ringwoodite – (Mohs ? – 3.9g/ccm)

Quite good materials with some hampering weakness(es)

Con: low crystal structure symmetry

Con: Somewhat soft materials

Saving graces: very common or acessible elements, some degradability, nature friendliness (common biomineral – sea shells)

  • CaCO3 calcite – trigonal – Mohs 3 (defining mineral)
  • CaCO3 aragonite – ortorhombic – Mohs 3.5-4.0 – (a bit harder and somewhat higher symmetry crystal structure)

Other compounds

B4C – boron carbide High mechanical thermal and chemical resistance.
Boron is not as common and almost everywhere accessible as carbon though.

BeO brommelite [8] – excellent material – hexagonal – simple minimal unit cell (de) – very hard Mohs 9
Problems:

  • beryllium is quite scarce
  • beryllium is quite poisonous – it's can be quite well sealed in a macroscopic gemstone though – how well a nanomachinery metamaterial out of many nanoscale brommelite crystolecules will seal the beryllium: not so clear

  • Sodalih [9] – cubic – Mohs 5.75
  • And (almost?) isostructural ones like: Haüyn, Nosean, Bicchulith, ...

Garnets

X3Y2(SiO4)3 the class of garnet gemstones [10] – typically hard Mohs 6.6-7.5 – and cubic – but big unit cell

  • Andradite – Ca3Fe2Si3O12iron but no aluminum garnet – HUGE unit cell 3D structure (de)

  • Almandine – Fe3Al2Si3O12 – iron and aluminum garnet
  • Pyrope – Mg3Al2Si3O12 – aluminum but no iron
  • Grossular – Ca3Al2Si3O12 – aluminum but no iron

  • Spessartine – Mn3Al2Si3O12 – (less abundant manganese)
  • Uvarovite – Ca3Cr2Si3O12 – (less abundant chromium – neither aluminum nor iron)

Wikipedia:

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External links

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