An article published by The Open Chemical Physics Journal in 2009 details that a team of scientists lead by a Danish University of Copenhagen researcher have found traces of what appears to be unreacted and partially reacted super-thermite, or nano-thermite, in four different samples of the World Trade Center dust collected by eyewitnesses. The unique compound shows immense reactivity to heat and ejects the same iron-rich spheroids observed in the ignition of commercial thermite.
An English-subtitled Danish television interview with the lead researcher, Niels Harrit, who believes that the discovery of this thermite compound implies foul play, is shown below, followed by an abstract from the research paper.
Abstract: We have discovered distinctive red/gray chips in all the samples we have studied of the dust produced by the destruction of the World Trade Center. Examination of four of these samples, collected from separate sites, is reported in this paper. These red/gray chips show marked similarities in all four samples. One sample was collected by a Manhattan resident about ten minutes after the collapse of the second WTC Tower, two the next day, and a fourth about a week later.
The properties of these chips were analyzed using optical microscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS), and differential scanning calorimetry (DSC). The red material contains grains approximately 100 nm across which are largely iron oxide, while aluminum is contained in tiny plate-like structures. Separation of components using methyl ethyl ketone demonstrated that elemental aluminum is present. The iron oxide and aluminum are intimately mixed in the red material. When ignited in a DSC device the chips exhibit large but narrow exotherms occurring at approximately 430 ˚C, far below the normal ignition temperature for conventional thermite. Numerous iron-rich spheres are clearly observed in the residue following the ignition of these peculiar red/gray chips. The red portion of these chips is found to be an unreacted thermitic material and highly energetic.