Abstract: A recent paper claiming "active thermitic material" in dust collected in the vicinity of the Twin Towers after their collapse is found to have shortcomings in its methodology. The paper also fails to explore adequately alternative, non-thermitic explanations for its findings.
Specifically, the paper's use of methyl ethyl ketone (MEK) to demonstrate the presence of elemental aluminum is known to yield inconsistent results because MEK reacts with aluminum; alleged elemental aluminum nanoparticles are claimed to remain unreacted after 55 hours of MEK bath, but also contradictorily to react violently already at 430°C; photographic and spectral comparisons between commercial thermite and spheroidal particles in Ground Zero dust omit any other comparison with possible alternative sources of such findings; DSC analysis was conducted in air, but should have been conducted in an inert gas environment in order to obtain reliable results for thermite, which does not require an external oxidizer.
The paper also does not consider the chemical composition of the corrosion-proofing paints and of the vermiculite used as thermal insulation and soundproofing at the World Trade Center and extensively documented by NIST. These products contain exactly the same elements and exhibit the same structural characteristics as the allegedly thermitic material found by the paper's researchers in their samples.
The researchers therefore appear to have been somewhat hasty in reaching their conclusions.
The debate regarding the collapse of New York's Twin Towers as a consequence of the 9/11 terrorist attacks has been revived by a study published by a US journal: "Active thermitic material discovered in dust from the 9/11 World Trade Center catastrophe" (Bentham Science Publishers).
Some of the authors of this study, such as Steven Jones and Kevin Ryan, are well-known for their strong support of so-called "conspiracy theories". The main author, Danish chemistry professor Niels Harrit, has also stated publicly his unorthodox views on 9/11 in writing and in TV appearances.
However, I will not deal with who supports these theories. Rather, I will simply assess the conclusions and facts stated by these researchers.
The authors claim to have analyzed debris dust from multiple New York sites located in the vicinity of Ground Zero, finding particles characterized by the presence of two layers, a red one and a gray one, joined in a wafer-like arrangement.
Analysis of these layers showed the presence of elements that can be observed in spectra.
The red layer shows the presence of carbon, oxygen, iron, zinc, aluminum, calcium, chromium, silicon and sulfur. The authors write that the presence of calcium and sulfur might be explained by the dust generated by the gypsum wallboard that was abundant in the Twin Towers. The other elements are always present in various analyses carried out on the four samples studied in the paper.
Therefore, attention is called to the constant presence of carbon, oxygen, iron, aluminum and silicon. Chromium and zinc are instead said to be present, but it is not clear in which samples they were found, since the caption of Figure 14 of the paper (shown below) suggests that the finding was occasional (note the word "sometimes").
The red layer appears to be porous and composed of particles having various shapes (faceted and laminar), embedded in a matrix that holds them. The faceted particles are rich in iron and oxygen (probably crystals) and the laminar ones are rich in silicon and aluminum. Carbon does not appear to be present specifically in the particles, but seems to be distributed within the matrix.
The porous region of the red layer, analyzed after soaking in a strong solvent, shows instead the presence of oxygen and silicon as well as carbon and iron.
Interface between red and gray layers
Spectral analysis of this separation region between the two layers shows the presence of oxygen and carbon.
This layer contains carbon, oxygen and iron. BSE (Back-Scattered Electron) imaging of this gray layer reveals lighter shades than the red layer. This means that the red layer is made of matter whose atomic number is, on average, lower than the matter that constitutes the gray layer.
Optical and electron microscope imaging also shows that the red layer has a larger particle size distribution than the gray layer, with evident porosities and heterogeneities, in sharp contrast with the compactness of the gray layer.
Both the red layer and the gray layer are sensitive to a magnetic field.
In summary, the two layers, despite their different appearance and color, are found to have an extremely similar chemical composition. In particular, the red layer has a carbon-rich matrix that embeds crystal-like particles rich in oxygen and iron and other laminar particles rich in silicon and aluminum (page 15 of the paper).
Use of methyl ethyl ketone (MEK)
The authors immersed samples of these particles in a bath of methyl ethyl ketone (MEK) for 55 hours in order to separate the elements of the red layer. They claim to have thus obtained, in addition to considerable swelling of the matrix of the red layer, segregation of the aluminum. They also claim that this demonstrates the presence of elemental aluminum.
However, it is trivial to find that the reactivity of MEK with light metals, and particularly with aluminum, is well-known, as reported for example in this Italian document, which states (in translation, emphasis added):
10. Stability and reactivity
The product is stable in normal conditions of storage and use. Heat or fire can cause the release of carbon oxides and vapors that can be harmful. Vapors can form explosive mixtures with air.
Methyl ethyl ketone reacts with light metals, such as aluminum, and with strong oxidizers: it attacks various kinds of plastic.
Unsuitable materials: natural rubber, butyl rubber, EPDM, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, Polyacrylonitrile. Suitable materials: stainless steel, carbon steel, polyester, Teflon.
If the intention of the researchers was to break up the carbon matrix of the red layer to allow analysis of the nanoparticles embedded in it, the result regarding the presence of aluminum does not appear to be compatible with this goal, since it is well-established that MEK might react more or less violently with elemental aluminum.
This appears to be a rather important methodological error by the researchers, since such a test might yield inconsistent results depending on whether the temperatures are suitable for the triggering of chemical reactions.
The logical conclusion is that one should therefore hypothesize the very opposite of what is claimed in the study, i.e., that there is no elemental aluminum in the compound and that aluminum is present in chemical bonds, or that elemental aluminum is present but in highly oxidized conditions and therefore scarcely reactive.
From a commodity point of view, MEK is sold for the following uses (translated from Italian):
"Methyl ethyl ketone - Used as a substitute of acetone when it is necessary to use a less volatile solvent, it dissolves shellac, rosin, cellulose resins, epoxy resins, many phenolic and acrylic resins, polystyrene etc.
It is a component of vinyl and nitrocellulose paints.
Methyl ethyl ketone is also suitable for cleaning instruments and tools and for washing impurities and chemical products off mechanical parts.
A data sheet of the product is available here (in Italian).
Going back to the analysis of the red player, the iron-rich particles exhibit a simultaneous abundance of oxygen, with a 2:3 proportion of iron to oxygen.
This means that these particles are Fe2O3, i.e., iron oxide. The simultaneous presence of iron oxide and elemental aluminum thus leads the authors to the conclusion that this is thermite. However, we have seen that the presence of reactive metallic aluminum is not at all beyond doubt.
I believe, therefore, there is good reason to question this forced conclusion, which contrasts with the rules of chemistry. The authors claim to have found nanoparticles of elemental aluminum, which cannot be all that reactive if they remain unchanged after 55 hours in a methyl ethyl ketone bath (in other words, one can deduce that they should be surrounded by a compact layer of aluminum oxide, a material that withstands extremely high temperatures and has a very high hardness), yet react violently already at 430°C to trigger a thermitic reaction.
In their study, the authors support their conclusions by showing charts of spectral analyses of various samples.
– Combustion products of commercial thermite:
- Spheroidal particles found in Ground Zero dust some time after the collapse and after work to demolish and clear the rubble had begun:
This is a clear attempt to influence the less than careful reader by suggesting explicitly the analogy between the analyzed samples and the products of thermite reaction, without investigating whether a similar spectrum might be due to other causes and reactions.
In other words, the authors jump immediately from the incorrect assessment of the presence of highly reactive elemental aluminum to the (evidently highly desired) conclusion that the collapse of the World Trade Center involved some sort of thermitic reaction of a mysterious product that is triggered at low temperature, provides twice the energy of ordinary thermite, and is characterized by the presence of nanoparticles that give explosive properties to a substance that otherwise is only an incendiary.
These are dramatic claims that need to be backed by equally dramatic evidence, not by suggestions.
Let's now consider the energy issue.
Thermal DSC analysis conducted in air
The authors analyze the behavior of the samples when heated in air in a differential scanning calorimeter (DSC). The result is that all the samples begin to burn in the temperature range between 415 and 435°C. In some cases, the heat generated by the exothermic reaction reaches 7.5 kJ/g.
After combustion, spheroidal particles are found in the porous burned residues. Some of these particles are rich in iron and other are rich in silicon (which is transparent and translucent). These particles indicate that high temperatures were reached as a result of an unspecified chemical reaction (which begins at 430°C!). According to the authors, this reaction can only be thermitic.
In particular, therefore, the authors claim (page 22 of the paper) that a highly exothermic reaction, such as to generate temperatures of approximately 1400°C, needed to melt iron and iron oxide, was triggered at only 430°C.
What this thermitic reaction that is triggered at 430°C might be is not known, since the ignition temperature of commercial thermite is higher than 900°C.
The authors seem to have failed to consider that the matrix of the red layer is highly abundant in carbon and that carbon has a lower heating value (or net calorific value) of 34.03 kJ/g, whereas thermite releases 3.9 kJ/g in combustion. In other words, one gram of carbon releases, in combustion at constant pressure, more than eight times the energy released by one gram of thermite.
Since the measurement was performed in air (why? Is this another rather embarrassing error in methodology, after the MEK blunder?), one cannot exclude the combustion of carbon, which is instead highly probable.
In order to obtain reliable results, since thermite does not require an oxidizer from the external environment, the DSC measurement should have been conducted in an inert gas environment (with nitrogen or argon).
The conclusions of the study are obviously favorable to the "alternative" hypotheses. In other words, they suggest that a nanothermite-based substance was used on 9/11 in the Twin Towers and was applied by unknown means, in unknown locations, at an unknown date by unknown individuals, yet was able to cause the collapse of the two giant steel buildings and of the comparatively smaller WTC7 building.
Here are the conclusions as stated in the article:
After examining the paper, which we can now describe as pro-conspiracy in its conclusions, I would like to present a few thoughts and consider whether there might be other working hypotheses that should be examined before jumping to the hasty conclusions presented in the paper.
My memory goes back to photographs like these:
These pictures show parts of the structural steel of the Twin Towers preserved by NIST.
Since these buildings were entirely made of steel and stood in a brackish environment, one of the builder's main concerns was to protect the steel adequately against corrosion by setting high quality standards for the protective coating.
Here are some documents related to the standards agreed by the Port Authority, owner of the Twin Towers, with the suppliers of the corrosion-proofing coating (source: NIST NCSTAR 1-6A, page 302 onward):
These documents and others presented in NIST's final report allow to determine the methods used to provide the corrosion-resistant coating and the quality control tests (source: NIST NCSTAR 1-1A, page 146):
It is very important to know the chemical composition of the paint used, which was the following (source: NIST NCSTAR 1-3C, page 147 onward, "Appendix D - Forensic thermometry tecnique development"):
Here we find that a substantially oily and resinous base (linseed oil and alkyd resin) contained a mixture of the following substances
- Iron oxide
- Zinc yellow (4ZnO.K2O.4CrO3.3H2O)
- Tnemec proprietary pigment ("Tnemec 99 Red Metal Primer")
- Fossil flour (Diatomaceous silica)
The dried resinous and oily base might be the organic matrix that constitutes the base of the red layer, which is rich in carbon and, as shown, may have a primary role in the release of energy during the combustion process.
In practice, the red layer of the wafers identified by the researchers contains exactly the same elements that we now know were present in the corrosion-resistant coating used during the construction of the World Trade Center, including the organic base constituted by linseed oil and alkyd resin.
It's not just a matter of the same chemical elements being present. The presence of fossil flour in the paint, too, is compatible with the porosity observed in the samples of the red layer. If one considers, moreover, that mica is also often present in fossil flour, then the presence of laminar particles mixed with crystalline particles of iron oxide might also be explained.
The gray layer, which as noted is rich in iron and oxygen, might be linked to a green corrosion-proofing paint (Tnemec Green Metal Primer, page 303), used extensively to provide markings on steel and explicitly listed in the materials supply specifications, or to a bonding agent used during construction to fix thermal insulation and soundproofing elements.
Could this type of paint peel off, forming the small flakes found in Ground Zero dust? We can refer to the photographs provided by NIST to document its research aimed at determining the temperatures to which the perimeter columns of the Twin Towers were exposed. Some of these pictures, shown below, show the behavior of the corrosion-resistant paint used in the WTC when exposed to heat.
These pictures show that the coating, when subjected to temperatures above 250°C, begins to break up in irregular patterns and can flake off surfaces if subjected to impacts. For temperature far above 250°C, the coating separates completely from the part to which it was applied and the organic component undergoes combustion, causing complete separation from the steel and simultaneously producing a layer of dark burned residues.
This result is compatible with the description given in the paper:
"Several paint samples were also tested and in each case, the paint sample was immediately reduced to fragile ashes by the hot flame. This was not the case, however, with any of the red/gray chips from the World Trade Center dust."
The corrosion-proofing paint used in the WTC was tested by NIST by subjecting it to 650°C for one hour. Combustion of the organic matrix occurred, but the paint was not reduced to ash.
Bearing in mind the passive fire-retardant protection of the perimeter columns, one can notice that the inward face of the many columns that composed the building faces was protected by panels of vermiculite, i.e., by panels of a lightweight aggregate of magnesium phyllosilicate, trivalent iron and aluminum, which is generally found in the form of laminar or sheet-like particles.
Vermiculite used in the building sector is obtained by baking micaceous rocks and is used as a heat insulation and soundproofing product.
One should also bear in mind that mica is a combination of chemical substances that have the following chemical characteristics:
Chemically, micas can be given the general formula
in which X is K, Na, or Ca or less commonly Ba, Rb, or Cs;
Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;
Z is chiefly Si or Al but also may include Fe3+ or Ti.
Structurally, micas can be classed as dioctahedral (Y = 4) and trioctahedral (Y = 6). If the X ion is K or Na the mica is a common mica, whereas if the X ion is Ca the mica is classed as a brittle mica.
These panels were bonded by means of adhesive to the internal face of the columns, in direct contact with the corrosion-proofing paint.
Vermiculite has practically no structural strength, and its use is limited to thermal insulation and soundproofing work. If impacted, it breaks into pieces.
The Twin Towers contained enormous amounts of vermiculite in direct contact, by means of adhesives, with the painted face of the perimeter columns. Yet the researchers that signed the study do not appear to have considered and investigated correctly this possibility before claiming residues of "active thermitic material" in Ground Zero dust.