Complex sentence: Colossal carbon tubes (CCTs) are allotropes of carbon that are bigger than carbon nanotubes (CNTs), with a diameter of between 40 and 100 μm.
Split into simpler sentences: Colossal carbon tubes (CCTs) are a tubular form of carbon. In contrast to the carbon nanotubes (CNTs), colossal carbon tubes have much larger diameters ranging between 40 and 100 μm.