Do not forget about Aerographite  <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Aerographite" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Aerographite</a>
(only ~180g&#x2F;m3, much lower than a topicthing - 0.9kg&#x2F;m3)