Making Iron Microspheres - Grinding, Impacts, Welding, Burning

[Mick West]

Iron rich microspheres can be made in various ways. In this thread I investigate some of them, and try to make some microspheres of my own.

Burning Methods (external ignition heat from flames)

• Burning Paint Chips #1. https://www.metabunk.org/posts/218647/
• Steel Wool #1: https://www.metabunk.org/posts/219558/
• Iron Filings #1: https://www.metabunk.org/posts/219574/
• Toner: https://www.metabunk.org/posts/219612/
• Steel Wool #2: https://www.metabunk.org/posts/219648/
• Burning Paint Chips #2: https://www.metabunk.org/posts/219649/
• Iron Powder 320 Mesh: https://www.metabunk.org/posts/225668/
• Iron Filings 50 Mesh: https://www.metabunk.org/posts/225672/
• *Pyrophoric iron: https://www.metabunk.org/posts/219592/
• Steel Wool #3 (physics investigation): https://www.metabunk.org/threads/what-happens-when-you-burn-steel-wool.10002/

Sparking methods (impact causing both scraping and ignition heat)

• Steel on steel impact. https://www.metabunk.org/posts/219454/
• Angle Grinder: https://www.metabunk.org/posts/219490/
• Bic Lighter: https://www.metabunk.org/posts/219555/
• Flint Striker: https://www.metabunk.org/posts/219584/
• Rust on aluminum impact: https://www.metabunk.org/posts/219689/
• 1600's Flint: https://www.metabunk.org/posts/219589/

Melting Methods (External Energy/Heat Melting steel/iron)

• Arc Welding #1 (Magnet capture): https://www.metabunk.org/posts/219499/
• Arc Welding #2 (Water capture): https://www.metabunk.org/posts/219888/
• *Oxy cutting
• *Thermal lance cutting

Chemical Reaction Method (chemical reaction with molten or vapor iron as a product)

• Thermite (Al + Fe2O3): https://www.metabunk.org/posts/219775/

* = Methods I've not personally tried

 

[Mick West]

I bashed off a bunch of pain chips from my red painted steel wheelbarrow and waved a butane flame over them. Result = iron microspheres

Here's a scale comparison with the Harrit microspheres (left) and mine (right).

Of note, in both their photos and mine the red layer appears undamaged. Curious, since that's supposed to be the one that's nanothermite. What seems to have happened is the iron oxide layer has "burnt" (perhaps with some of the paint, of some intermediate layer), and created some iron microspheres.

 

[Mick West]

I've hit my wheelbarrow with a hammer a few more times. Interestingly I seem to have found an iron microsphere without even heating it!

Lighting in other direction to show the spherical nature.

Context:

These iron microspheres just pop up everywhere!

Another one from hammering. What does the presence of iron microspheres indicate?

 

[DasKleineTeilchen]

I've hit my wheelbarrow with a hammer a few more times. Interestingly I seem to have found an iron microsphere without even heating it!

What does the presence of iron microspheres indicate?

so it seems to me that if the force of a hammer slamming on iron is enough to delivering the necessary heat trough friction to generate ironspheres, it seems plausible to assume that steelbeams just from scratching and falling onto each other can generate these ironspheres as well. no "nanothermite" needed.

 

[Mick West]

so it seems to me that if the force of a hammer slamming on iron is enough to delivering the necessary heat to generate ironspheres, it seems plausible to assume that steelbeams just from scratching and falling onto each other can generate these ironspheres as well. no "nanothermite" needed.

Agreed. And me hitting something with a hammer is several order of magnitude less energetic than what happened during the WTC collapse - especially toward the end. Multi-ton steel sections hitting steel and concrete at 100mph is going to make a few sparks.

 

[DasKleineTeilchen]

Multi-ton steel sections hitting steel and concrete at 100mph is going to make a few sparks.

so, absolutly not surprising at all why these spheres were nearly everywhere on site. quite the opposite, it would be highly suspicious if there were no ironspheres to be found.

 

[Mick West]

so, absolutly not surprising at all why these spheres were nearly everywhere on site. quite the opposite, it would be highly suspicious if there were no ironspheres to be found.

It would be impossible to find none. At the very least there would be billions from the angle grinding done during construction. I just made a few thousand with a few second of grinding, used a magnet to catch the sparks.

 

[Nada Truther]

It would be impossible to find none. At the very least there would be billions from the angle grinding done during construction. I just made a few thousand with a few second of grinding, used a magnet to catch the sparks.

Not to mention all of the ones created during the construction from welding too.

 

[Mick West]

Not to mention all of the ones created during the construction from welding too.

Yeah, I should get my welder out, see if it makes similar spheres.

 

[Mick West]

Microspheres from about 10 seconds of arc welding:

(Magnet under the paper is catching spheres.

Zoomed on the clump on the right:

 

[Mick West]

And reciprocating saw (Sawzall) with a metal blade is NOT a source of microsphere. Just just end up with a bunch of partially melted iron filings.

I heated this up with a butane flame, some of the very smallest pieces fused into microblobs. There were some sparks, but I did not have a good magnet set up to catch them. I suspect filings + fire woudl produce spheres under different conditions. However probably not a significant factor in the WTC fires.

 

[benthamitemetric]

Mick--what is the range of sizes for the microspheres your experiments are producing? I think it would be helpful to know that in order to better understand how they compare to the microspheres observed in the WTC dust.

 

[Mick West]

Mick--what is the range of sizes for the microspheres your experiments are producing? I think it would be helpful to know that in order to better understand how they compare to the microspheres observed in the WTC dust.

I was just doing that. Here's a WTC sphere, note the 10 µm scale:

Here's my image, with a 100 µm scale, with the WTC sphere just under the scale. Full frame:

Here's a wider shot

So it seems to be in the ballpark. Most of my spheres are large, but a good proportion are smaller.

Note this was taken directly under the welder. Many WTC dust samples were carried by wind, so smaller particles would predominate.

 

[Mick West]

AE911 talk of "billions" of microspheres. How much is that exactly?

The volume of a sphere is 4/3*PI*r^3, so a billion spheres of radius 25 µm (1 µm = 1/1000000 meters) is

4/3*PI*(25/1000000)^3*1000000000 cubic meters of iron.

= 0.00006545 cubic meters of iron

= a cube of iron 4cm cubed.

= a cube of iron about 1.5" cubed.

or about a 8cm or 3" cube per billion spheres, if the average size is 50µm radius (like the larger spheres in my sample)

(Verifying this backwards. 8cm = 80,000 µm, so you can fit 80,000/100 of 100 µm = 800 cubes along an edge. 800^3 = half a billion cubes, approx a billion worth in volume of spheres)

So "billions" of microspheres really isn't very much iron. How much would a few tons of thermite be expect to produce?

How much would thousands of hours of arc welding produce?

 

[Mick West]

Some perspective. Here's the spheres from welding, with a ballpoint pen and a dollar bill to scale. The rule marking are 1mm

The tip of the ballpoint pen is a tiny steel sphere. Compare with the microspheres scattered below.

 

[Mick West]

I should note I also lost a lot of my welding microspheres due to a small fire on the collection apparatus. I might try to improve the collection method tomorrow. Magnet under tempered glass sounds good.

The flames were invisible with the welding mask and the sun, so I just saw these curious growing brown spots. Took me a second to realize what it was.

 

[Redwood]

I wonder what you would get if you placed a small quantity of hematite pigment (available in any artist's supply shop) in a fireproof dish, poured a small quantity of kerosene (essentially the same as jet fuel) over it, and ignited it?

 

[Mick West]

I wonder what you would get if you placed a small quantity of hematite pigment (available in any artist's supply shop) in a fireproof dish, poured a small quantity of kerosene (essentially the same as jet fuel) over it, and ignited it?

Heck, now I may as well get some aluminum powder as well.

Fun awaits!

 

[Nada Truther]

Heck, now I may as well get some aluminum powder as well.
View attachment 31915

Fun awaits!

You better be careful! Buying all these chemicals might put up some red flags, and put you on a watch list for potentially making bombs or thermite or some such.

 

[Oystein]

Be careful with words like "burn" or "melt" (I notice Mick has indeed used quote marks here and there). Also with the word "iron".

Iron and iron oxides come in different crystalline phases and also amorphous. When you heat them in the presence of oxygen AND organic fuels (whether kerosine, butane or paint binder), existing iron or iron oxides may change phase, oxidize or get reduced, all of which require some topological re-organization of atoms and molecules - processes where microparticles have a chance to try for the energetically preferred spherical shape.

What I am saying in short is: I doubt that oxidation and / or melting are required for such "iron-rich" "spheres" to form.



Another thing you can try: Burn stacks of printed office paper (laser printer, ideally) in a hot furnace (fire place - add plain wood if you can't get paper alone to burn hot), and do the same with unprinted office paper, then sift through the ashes with a magnet. I know that burning wood alone will yield a small amount of magnetically attracted particles in the ash. I suspect that laser printer toner will yield some amount of very small shiny spheres, iron-rich.

 

[Mick West]

Another thing you can try: Burn stacks of printed office paper (laser printer, ideally) in a hot furnace (fire place - add plain wood if you can't get paper alone to burn hot), and do the same with unprinted office paper, then sift through the ashes with a magnet. I know that burning wood alone will yield a small amount of magnetically attracted particles in the ash. I suspect that laser printer toner will yield some amount of very small shiny spheres, iron-rich.

Lacking a laser printer, I'm thinking that just a spoonful of this on a stack of blank paper will work.

Toner is iron oxide and carbon, but wikipedia suggests newer type of toner have other chemicals.

 

[Mick West]

Of course some of the laser printers in the building themselves would have burnt. Also with everything being crushed, there would be toner spread around in bulk in some areas, which might then have burnt.

 

[Oystein]

Of course some of the laser printers in the building themselves would have burnt. Also with everything being crushed, there would be toner spread around in bulk in some areas, which might then have burnt.

True, though I'd estimate that in any old office building, there is much more toner fixed on paper than fresh in the printers and spares. Much of that paper would have burned, much of the iron oxide pigment remained.

 

[Jedo]

And me hitting something with a hammer is several order of magnitude less energetic than what happened during the WTC collapse

Just a small remark: I think you need to compare energy density scales, not energies. So I'd expect the orders of magnitude for energy densities to differ much less then those for the energies.

 

[Mick West]

Just a small remark: I think you need to compare energy density scales, not energies. So I'd expect the orders of magnitude for energy densities to differ much less then those for the energies.

I'm not sure what you mean. I was thinking about difference between hitting painted sheet metal with a hammer and "Multi-ton steel sections hitting steel and concrete at 100mph". So what I was considering was the energy involved at the regions of contact. Which is suppose is a local energy density?

 

[Jedo]

Iron and iron oxides come in different crystalline phases and also amorphous. When you heat them in the presence of oxygen AND organic fuels (whether kerosine, butane or paint binder), existing iron or iron oxides may change phase, oxidize or get reduced, all of which require some topological re-organization of atoms and molecules - processes where microparticles have a chance to try for the energetically preferred spherical shape.

What I am saying in short is: I doubt that oxidation and / or melting are required for such "iron-rich" "spheres" to form.

I disagree with that; microspheres are still macroscopic bodies with respect to crystalline structure. You have about 20·10¹² iron atoms in a microsphere of 10 µm diameter (if i did not miscalulate). So how should boundary effects play a role there energetically?

Moreover, the crystalline reorganisation between phases below the melting point usually happens as functions of temperature if there is only iron, and functions of temperature and the composition of elements if you have an eutectic system like steel. However, crystalline reorganization below the melting point takes much time, so annealing processes in steel production take up several hours of slow temperature changes.

My guess is that the spheres result from surface tension in the liquid state, so you need sufficient energy densities for melting small iron particles.

 

[Oystein]

I disagree with that; microspheres are still macroscopic bodies with respect to crystalline structure. You have about 20·10¹² iron atoms in a microsphere of 10 µm diameter (if i did not miscalulate). So how should boundary effects play a role there energetically?

Let's see: Atomic radius of iron is on the order of 125 pm. 10 µm is 10,000 nm is 10,000,000 pm. That's 80,000 iron radii. An iron sphere of 10 µm is thus on the order of 80,000^3 = 512,000,000,000,000 - 5*10^14. Hmmm ok ^^

Moreover, the crystalline reorganisation between phases below the melting point usually happens as functions of temperature if there is only iron, and functions of temperature and the composition of elements if you have an eutectic system like steel. However, crystalline reorganization below the melting point takes much time, so annealing processes in steel production take up several hours of slow temperature changes.

Is it correct that such annealing involves no chemical reactions? I have a feeling that oxidation and reduction should have more effect on the shape of micro-particles, as density and thus volume changes when you oxidize iron or reduce iron oxide. Or oxidized iron oxide that's not yet fully -III.

But I'll quickly add that this is layman's conjecture.

My guess is that the spheres result from surface tension in the liquid state, so you need sufficient energy densities for melting small iron particles.

"Sufficient energy densities" = local temperature, not?

Harrit et al (2009) say that heating and burning paint chips in a DSC, the temperature of which is controlled to a maximum of 700 °C, creates iron-rich microspheres (Mick reproduces micrographs in the opening post) where there weren't any before.
I find it hard to believe that either
- those chips attained a local temperature in excess of 1000 °C at any point in time during the DSC experiment
- the gray layer (from whence the spheres appear to have formed), which was mostly iron oxide, had a eutectic melting point not much higher than 700 °C.
That's why I have always thought that recution and/or phase changes played a role.

 

[Leifer]

Sometimes my job is to paint recently welded or cut steel. Often I'll have to clean off the "slag" and "spatters (balls)" from the welding or torch cutting.
The slag or spatters (balls) can stick/adhere to the hot cut (or welded) metal area. But most of the spheres are shot away, cooled in air, before landing, and stuck to nothing.
Often, the floor in a welding shop is covered in these spheres, and can become a slip hazard.
Slag and spheres produced....acetylene torch....


Plasma cutting...

I would expect to find slag and spatter particles from the construction of the WTCs. The construction of welds during 1960's construction was "stick welding" of the beams, no ?
Building are constructed from the ground-up, so many small particles fall the lower floors, and can get trapped when these raw walls are encased for finish-work.
(spheres that land on weather-exposed areas at ground-level, will have likely rusted away by now)

And DURING welding, similar slag and spatters happen...

 

[Mick West]

Another thing to consider is if the microspheres where there all along in the paint chip, and were simply revealed by the substance burning/evaporating away.

Both arc welding and grinding produce abundant microspheres. Is it possible that since they are simply a common component of dust in steelworks (and construction sites) and so simply tend to get mixed in when things are painted?

I know there's at least a thousand microsphere on the floor of my office right now. I probably have quite a few on my clothing too.

 

[Leifer]

Is it possible that since they are simply a common component of dust in steelworks (and construction sites) and so simply tend to get mixed in when things are painted?

I've had to paint floors that were beneath areas of steel welding. I would have to not only sweep or vacuum the welding dust, but often scrape these balls off non-steel surfaces.
They might not stick to the welded hot metal, but these "steel embers" (balls) are often hot enough to embed themselves into/onto non-metal surfaces.
.....then you could be correct, many get painted-over, or flashed-over (covered) by high-rise (I-beam) protective fire coatings.

 

[Redwood]

Heck, now I may as well get some aluminum powder as well.
View attachment 31915

Fun awaits!

I would say, do both!

 

[Mick West]

A new method suddenly occurred to me:

Strike a lighter over a piece of paper with a magnet underneath:

Four or five strikes and you've got enough residue to form a visible ring around the edge of the disk magnet.

It's full of microspheres!

Similar ranges of sizes as before 10 to 100 microns (µm) in diameter.

The Bic lighter contains a small bit of flint [17] that's pressed firmly (with a spring [19]) against a steel wheel [16]. Turing the wheel grinds off tiny bits of steel (and flint), the friction ignites the steel, this creates iron microspheres.

I suspect the yellow is flint. There's also some bits of unmelted iron there attached to spheres, which suggests the formation mechanism is very similar to the burning of steel wool. Longer strands of shaved steel ignite. The combustion moves rapidly along the shaving, forming a ball (not enough oxygen to fully combust it, heat melts adjacent steel).

 

[Mick West]

Probably not be a significant factor, but it's certainly another potential source. An ironworker's flint striker produces far more sparks than a Bic lighter

 

[Mick West]

A few years ago I did some experiments with steel wool, you can actually see the combustion and the formation of iron microspheres

This is what I wrote in 2013:

If you ignite some steel wool with a hydrocarbon flame, then you get lots of iron spheres, some of the same size as these microspheres. Note this is not from the flame melting the steel, but from the steel itself burning, and melting itself. This is only possible with a sufficiently large surface area to mass ratio - i.e. with very small or very thin particles.

Here's a video of one of my experiments burning wool. Again it's just igniting it, then the steel wool itself burning does the melting. This is the video the above GIF came from. If you view it full screen in HD you can see that each orange circular glow is a microsphere forming.

Filmed thusly: (100mm, field of view is about 20mm wide)

Now I've got a proper microscope I might redo the steel wool burning experiment

 

[Jedo]

I'm not sure what you mean. I was thinking about difference between hitting painted sheet metal with a hammer and "Multi-ton steel sections hitting steel and concrete at 100mph". So what I was considering was the energy involved at the regions of contact. Which is suppose is a local energy density?

Sorry, I have sloppy language here as well. To be more precise in the language, we should talk about the work done at impact in each case, which then is partially transferred to heat.

Then we can talk about the corresponding work done and heat transferred per unit volume (which is what I meant misleadingly by energy density).

By just guessing I would say the work done per unit volume to a nail hit by a hammer is comparable (up to say 2 orders of magnitude maybe) to that of the impact of a multi-ton steel beam falling from several hundred meters. But you do not expect blue light flashes to appear like in the case of Argon welding, which then obviously has a heat transfer per unit volume several orders of magnitude higher.

 

[Mick West]

Could not wait. Steel wool (0000 size) burning on a glass slider over a magnet.

Source: https://www.youtube.com/watch?v=rlpHdyvcLkc


Produced two types of microspheres, which I'll call sparked and wired

Sparked spheres seem like they form from sparks, like with the lighter, but probably an entirely different physical mechanism. They seem smaller, more perfect, having formed in the air.

And wired spheres, formed by the flame traveling along the wire, larger and a bit irregular. Usually attached to a "wire"

 

[Mick West]

I'm still using that same bag of steel wool from five years ago. It has not gone rusty.

Why would microspheres inside the building rust away? Seems like they could easily last 40 years is they are not getting wet.

 

[Mick West]

What is the physical mechanism of an iron spark? What propels it? How does it form a microsphere? Why do sparks shoot away from the steel wool?

Hypothesis: It seems like a spark there is like a micro rocket, a tiny bit of fuel that is burning on one side, so it gets propelled away. The burning can't combust the entire thing, but produces enough heat to entirely melt what remains. Surface tension forms a sphere, and it solidifies in a fraction of a second.

But how does the rocket form?

What's the exact limiting mechanism that stops larger pieces of steel combusting?

 

[Tedsson]

Love the experiments.

As a historical note we have been producing well ordered homogenous spheres from falling molten metal for centuries. What I might dub mesospheres.

I used to live near a shot tower built in 1760. Very tall and narrow building with a long drop internally. Molten lead was poured through a sieve and dropped 30m. It cooled and condensed into a sphere (surface tension) on the way down where it was set in a pool of water. Result: shotgun pellets.

Some of results were not suitable (droplets that coagulated) and were in turn sieved out. I have little doubt that there were far more lead microspheres than shot size spheres. All of these were recycled through the process.

Here it is:

 

[Oystein]

What is the physical mechanism of an iron spark? What propels it? How does it form a microsphere? Why do sparks shoot away from the steel wool?

Hypothesis: It seems like a spark there is like a micro rocket, a tiny bit of fuel that is burning on one side, so it gets propelled away. The burning can't combust the entire thing, but produces enough heat to entirely melt what remains. Surface tension forms a sphere, and it solidifies in a fraction of a second.

But how does the rocket form?

Do you picture some hot gas emenating the spheres?

I'd guess there is tension within the material as iron is a) suddenly heated and b) suddenly oxidized. Both processes increase volume, which cannot be fully accomodated by the old shape - tension arises. Once the future sphere is melted loose from substrate, released tension flings it away.