Climate Guy has peer reviewed the paper by Harrit et al. (Open Chemical Physics Journal, 2, 2009, 7-31) and finds no conclusive evidence for nanothermite.
Here is the peer review report.
There is much wrong with this article. It would not have passed my expert peer review in its published state.
Particles were separated from untreated dust using magnetic separation (a simple bar magnet). The separate contained small bi-layer (grey-layer + red-layer) flakes.
The red layers were concluded to be synthetic nanothermite.
Separated particles were examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA). Samples were mounted for the SEM/EDXA measurements using carbon tape adhesive on bulk aluminum plugs, the standard simplest mounting for SEM/EDXA work.
The authors argued that since the red layers were seen by SEM (back scattered electron images) to be aggregates of dense nanoparticles and less dense nanoflake-like particles and since the EDXA spectra showed the presence of both Fe (iron) and Al (aluminum) that the flake-like particles must be elemental aluminum, whereas the smaller nanoparticles were presumed to be iron oxide.
They further argued that a nano-scale mixture of Fe-oxide and Al-metal is by definition a nanothermitic material.
The authors also provided differential scanning calorimetry (DSC) measurements of bi-layer grey-red flakes and observed exothermic peaks at approximately 420 C (degrees Celsius) for all four WTC dust samples.
There are more problems with all of this than I have the patience to outline but here are some main points.
- The Al slugs would give inhomogeneous background Al signals in the EDXA spectra. This was not considered or discussed in the paper. There could be no or little Al in the red-layer.
- The carbon adhesive tape will give inhomogeneous background C signals in the EDXA spectra. This was not considered or discussed in the paper. There could be no or little C in the red-layer.
- There is as much or more Si (silicon) in the EDXA results than Al in all the red-layer results and Si and Al are closely correlated in their spatial distributions (e.g., their Figure 10). No probable explanation is given for this. This is not consistent with the presence of metallic Al.
- Oxygen (O) is more closely spatially correlated with Al and Si than with Fe (e.g., their Figure 10). No probable explanation is given for this. This contradicts the conclusion of the presence of metallic Al.
- No effort was made to estimate the Fe:Al elemental ratio in the red-layer. Synthetic thermite or nanothermite would have a ratio of 1:1. The point is never discussed.
- The exothermic peak in the DSC traces occurs at a temperature (420 C) approximately 90 C below the temperature for the thermite reaction. No explanation is proposed for this. Chemical activation energies of known reactions cannot be so sample dependent, whether nano-sized or not. This is not the thermite reaction.
- In the reacted product (after heating in DSC), no Al-oxide is observed as a residue, as required by the thermite reaction. No explanation is given for this.
- The obvious needed measurement of X-ray diffraction was not used to confirm the solid mineral species (oxides or metals). This is unacceptable in a materials chemistry paper. This is not considered by the authors.
- Much is made of the fact that Fe-rich spheroids are present after reaction but there is no discussion of the grey-layer or of the origin of the Si-rich spheroids. Heating causes many things and there is an exothermic reaction so the conclusions about the presence of Fe-rich spheroids (which are reported to contain oxygen) as evidence for the thermite reaction is tenuous.
Steel rusts. Rust crusts crack and blow off the steel when physically disrupted.
Rusting steel is one of the most studied materials science problems in engineering.
When steel rusts in a humid building environment it grows a crust composed of layers of different Fe-oxides and Fe-oxyhydroxides. These are stratified micro-layers with successive layers of different Fe-oxides species (wustite, maghemite, hematite, etc.). In a humid atmosphere the outer layers will be Fe-oxyhydroxides such as goethite, lepidocrocite and akaganeite. The latter three Fe-oxyhydroxides have the same chemical formula: FeOOH, and differ only in their crystal structures.
These Fe-oxyhydroxides typically form as nanoparticles and have the same needle and nanoflake-like morphologies as observed here.
When these Fe-oxyhydroxides are heated in a DSC they undergo a solid to solid exothermic reaction of dehydroxilation (loss of OH) and transform from FeOOH to Fe2O3 (hematite) at a temperature of approximately 400 C. The temperature of the transformation can vary depending on exact chemical composition, and on the crystal structure, but it is always at approximately 400 C.
Looks like our boys may have been discovering the properties of rusted steel. Steel contains C and Si which would end up in its oxidation products, especially in the oxyhydroxides.
I may be wrong but if I had been a reviewer I would have required that the authors prove the presence of metallic Al nano-flakes by X-ray diffraction (or electron diffraction) and that they be much more careful in their EDXA work. I think they would have seen FeOOH not metallic Al.
I would have also required that they make nanothermite by known recipes and measure its DSC trace and look for the Al-oxide residue after reaction.
In my opinion the Open Chemical Physics Journal did a very sloppy job on this paper, especially given the importance of 911 as a historic event and societal phenomenon.