A final speaker for today, last but by no means least, Igor Shatinin from the National

University of Science and Technology in Moscow, who's going to be talking about steels modified

by fullerenes and carbon nanotubes. Ladies and gentlemen, dear colleagues, I would like to present the report devoted to a study of structure and properties of chromium or molybdenum steel modified by fullerenes

and carbon nanotube addition. The work was carried out in the National University of Science and Technology and the Bolshor High Technology Research Institute of organic materials. In recent years, nanostructured carbon forms such as fullerenes and carbon nanotubes

were very often used for modifying and preparation of carbon composite based on different metals, alloys, polymers and ceramics. Production process used for these materials exhibit a great work. More frequently for modification using high energy milling and hot pressing.

However, information about studies related to the modifying of high alloy steels, in particular industrial steels, chromium molybdenum steel isn't available in literature.

Thus, the complex studies of structure and properties formation the steels which were prepared by high energy milling with fullerenes and carbon nanotube addition. Subsequent hot pressing and hot treatment is topical both research and practical points of view.

And the goal of this work to achieve the goal of the following task were formulated. First, to instigate futures of structure formation of powders produced by high energy milling process,

chromium molybdenum steel with addition of fullerene and carbon nanotubes. Second, to study the structure transformation during hot pressing and rolling of steel samples. Next, to instigate the effect of heat treatment on the morphology of the resulting compacts

to evaluate the mechanical properties and to identify the effect of carbon modifiers on the structure and properties of the materials. In this work, we used the next materials. It's industrial chromium molybdenum steel with about 12% of chromium and about 2% of molybdenum.

We used multiple carbon nanotubes, the same image you can see on the slide. And fullerene, in this work we used fullerene in the form of fluoride concentrate powder

containing 85% of C60, 10% of C70 and 5% of higher fullerenes. And the fullerene we added as a solution in toluene. The amount of additive was about one and five percent.

On the next slide, you can see the experimental scheme. On the first step, including centrifugal spring and pre-mill, was necessary to obtain the powder from a bulk initial state, chromium molybdenum steel.

Centrifugal spring was carried out in a helium atmosphere and cooling rate of this process was about one million Kelvin per second. And pre-mill was carried out in an argonium atmosphere during one hour.

The amount, on the next step, in the obtained powders, in the first part, we added fullerene on the second part, multi-walled carbon nanotubes, and the third part, without addition.

The quantity, the amount of the additives was one and five percent. In the next step, the obtained mixture was milled in a high-energy milling in a bulk mill in an argonium atmosphere. Maximum milling time was five hours.

Next, the milled powders was subjected hot-prey sinker, 1050 degree hot rolling, 900 degree and final hot treatment. Now I'd like to discuss results.

After centrifugal spring, the steel has a flake shape with lengths about one to three centimeters, widths about half centimeters, and thickness about ten micrometers. According to XRD data, the steel consisted of alpha phase and a small quantity of gamma phase.

The lattice spacing of alpha phase increased due to formation of solid solution. You can see the term image of the steel on this slide.

There are grains with size about two to six micrometers. Nussbauer data confirms the presence of austenite. You can see austenite singlet and sextet of alpha phase with distribution of hyperfine magnetic field

because of formation of solid solutions. On the next slide, the result of XRD after premill. According to XRD data, austenite singlet is absent,

and lattice spacing of alpha phase is the same of before premill. According to Nussbauer data, austenite is absent too, and distribution of hyperfine magnetic field for alpha phase sextet is same,

as initial state. XRD data of rhenium molybdenum steel after milling with five personal fullerene and carbon nanotube additions shows that halo around the line of 110 of alpha phase formed after two hour

in the case of fullerene additions, and after half hour in the case of carbon nanotubes added.

Longer milling resulted in the formation of carbides, different types of carbides. The particle size of alpha phase and carbides was about 10 nanometers. It's the analysis of line bordering. Transmission electron microscopy data images you can see on the slide,

powder particles with size about one micrometer, and these particles contain the mixture of equiaxed particles of alpha phase and carbides with size 10 and 15 nanometers.

Nussbauer spectroscopy shows that there are alpha phase with distribution of hyperfine magnetic field, sextet with smaller hyperfine magnetic fields, and doublet associated with unknown paramagnetic phases.

Structure of chromium molybdenum steel after milling with one percent of fullerene and carbon nanotube addition. X-ray diffraction data obtained for the steel powder modified with one percent of addition

show the formation of only weak halo near the line of 110 reflection of alpha phase. We observed the same halo at the initial stage of milling of the steel with five percent of addition.

And the TEM data shows diffraction reflection of carbides are not detected. Powder particles is about one micrometer, and the powder particle contains small

equiaxed crystallites of alpha phase with size about 10 to 20 nanometers. Nussbauer spectra taken for the steel samples milled for four and a half hour with one percent of addition exhibit a paramagnetic doublet,

here and here, formed along with the sextet corresponding of the alpha phase. The analogous doublet was formed from the samples milled with five percent of fullerenes and carbon nanotube additions. However, intensity of this doublet observed in the spectrum taken for the

samples with one percent of fullerene and carbon nanotube addition is substantially lower. Thus, we can conclude that the structure changes with a cue in the samples with one percent and five percent addition of fullerene and carbon nanotubes during high energy milling is similar.

However, in the case of one percent addition, these changes can be interpreted as the initial stage of interaction between steel's component and carbon containing condition. Besides, same data shows that powder particles size about one to five micrometers.

We carried out some experiment with pure iron. According X-ray data, the milling of carbonil iron powder with one percent of fullerene and carbon nanotube addition for two to five hour does not lead to the formation of any new phases.

And Nussbauer data shows that hyperfine parameters of almost all ions is same from pure iron.

This fact indicates that in the case of milling carbon with fullerene of carbon nanotubes, no chemical reaction between the components take place.

In the next step, the samples with and without carbon addition were compacted. According to X-ray data, diffraction data, samples free additions contain the alpha phase and traces of carbides, special carbides, metal C.

In the case of samples with addition, carbon nanotubes and fullerenes, samples contain alpha phase and metal and carbides, two types of carbides, gamma phase.

Detailed analysis of profile of two peaks of alpha phase observed for the samples modified with fullerene carbon nanotubes exhibit the asymmetry,

which manifests itself in the more substantial bordering of the reflection in the low angle range. This can be explained by the formation of martensite. Scanning electron microscope studies show in this slide, and there are different morphological structure components.

In the compact seams prepared with different modifiers, fullerenes and carbon nanotubes, you can see this in the presented images.

In contrast to carbides found in samples modified with fullerenes, carbides present in sample modified with carbon nanotubes are characterized by pronounced elongated shape with size, with this size.

And smaller carbides in the grains, you can see. The existence of large microstructure typical of the martensite was confirmed by atomic for microscopic studies.

The image you can see on the slide. The microhardness of samples after hot pressing and high and close to that of hardness steel.

This fact along with x-ray diffraction data and atomic force microscopy data confirm on again the presence of martensite in the samples. The higher hardness of steel samples modified with carbon nanotubes and fullerenes is likely

to be due to the higher carbon content in martensite in presence of carbides. To increase the density of samples, the additional hot rolling at 900 degree was performed.

The result of XRD data shows that the hot rolling changes the phase composition and microstructure of samples. X-ray diffraction data of samples shows that both before and after hot rolling, the

samples free from carbon containing modifiers consist of alpha phase and small amount of special carbide. The hot rolling samples modified with fullerenes and carbon nanotubes demonstrate the disappearance of carbide metal 763 or C3 carbide and formation of special carbide metal C.

They further precipitated and formation of more aqueous carbide inclusions. In this case, large carbide inclusions are presented in grain boundaries.

And metal and smaller carbides are presented in the grains.

It's case one. And the size of alpha phase grain was 5 to 10 micrometers.

Determining the final annealing temperature, we conducted the following experiment and found the dependence of the steel microhardness on temperature. It was found the microhardness on temperature samples decreases continuously with the increased temperature.

In the case of samples prepared in the absent of modifiers, the main decrease in the microhardness take place at temperature of 500 to 700 degree. The microhardness of samples modified with the fullerenes and carbon nanotubes is higher at all temperatures.

And understudies for samples free from modifying condition, but it begins a market decreases annealing temperature for both 300 degree.

However, at temperature below 400 degree, their hardness remains equal to 1,000 MPa. The decrease in hardness is likely to be related to the decomposition of martensite.

Since the main decrease in the hardness of modified steel samples start at annealing temperature above 400 degree. And this temperature was taken as annealing temperature.

And the samples annealed on this temperature was studied by scanning electron microscopy and the micro end images you can see on the slide. This is image with fullerenes addition, it's carbon nanotube addition.

The samples contain alpha phase, but in case of samples with fullerenes addition, metal of 23C6 carbide precipitates with size half to 2 micrometers located and grain boundaries of alpha phase.

In the case of samples with multi-well carbon nanotube addition, these carbides precipitates with size 1 to 2 micrometers located in grain boundaries of alpha phase.

And carbides with size 100 to 300 nanometers are absorbed within grains. In addition, 10 data samples with carbon nanotube additions, you can see structure like bainite and smaller carbides.

And I think at last slide, it's mechanical properties of these materials.

You can see that it's a typical curio deformation of this sample.

We was two type of measure, tensile stress and bending test. Figure on the left shows typical deformation diagram for...

The comparison data obtained by attention and bending test allows us to conclude that they relate with each other.

Difference in the mechanical properties can be explained by different structures, state of the samples. And general conclusion, you can see on the slide, it's my presentation is completed. Thank you for your attention.

Thank you, Igor. Fantastic presentation. Something completely different to everything else we've had today. Certainly this afternoon, we've had five completely different presentations. And finally, I'd just like to invite any questions for Igor from his work.

It's interesting work to put carbon nanotube and do a pyrometallurgy. What you're really doing is carbon going into the austenite, is that correct? The part of carbon obtained the solution in austenite is true.

So why do we need to go through so much pain to get the carbon into the austenite? I'm curious about it. I was wondering whether it is because of the stability of fullerene and multi-wall nanotube. Scientifically, it's very interesting because stability is very important.

But I don't understand why do we need to go through this route to increase the hardness. Any idea on that? What would have happened if you used graphite?

I think it's the next work because in this work, we won't show how to carbon nanotubes and fullerenes interaction with steels.

You can see that interaction is different if you use carbon nanotubes or fullerenes. Results is different. Mechanical properties is different. I think if you will use graphite or amorphous carbon, its result will be another.

Okay. We've got a couple here. Steve, you want to bring the microphone? Thank you for the nice talk.

In the previous slide, you showed the tensile test curves. You have kind of a strange difference in your elastic part of the curve, your young models. Do you have an explanation about that, with and without modification? Curves one and two and three, completely different elastic parts.

And green and blue. Yeah, exactly. Materials have different model. So, it's something, inter-atomic connection is changing there, yes? Yes. Its phase consist is different, its model is different.

Okay. My question is, what is the amount of boron in your alloy? I think for these alloys, and also when you talk about carbides like M23C6, the boron amount can be influential.

Okay. As I told, this is industrial steels and chemical composition of steel, it's industrial.

Boron on this steel, use it for... Yeah, you showed it less than 0.005. I mean, for me, even for an amount of less than that, it can have a dramatic effect, especially on the coarsening of this kind of carbides.

Yeah, I mean, if that means no boron, then that's no boron.

Okay, ladies and gentlemen, I think we might just have time for one more question, if anyone has anything to ask. Yeah, Steve, one behind you there. And maybe we'll come to you quickly at the end, Martin. Just a quick comment, no questions. The purpose of his study may be to make a steel nanocomposite with the introduction of carbon nanotubes,

because I am working similar on some other materials, not steel. But the problem is, he has chosen steel in which carbon has high diffusivity, and he finally ended up with pictures. I didn't see any of the pictures of TEM with individual carbon nanotubes after your hot pressing or rolling or anything,

because most of the carbon you add in the form of carbon nanotubes reacted and formed carbides. But if you take elements like aluminum or magnesium, where you can add carbon nanotubes, and that is tremendously increasing the properties of the material, and that is where the carbon nanotube composites is coming into the picture.

But in your case, since it is steel, most of the carbon is not retained as single individual carbon nanotube, but mostly converted into your carbides. In this work we used the industrial steels and chemical composition, its presence.

The goal of this work is to study from structure, from relation with high energy milling, this steel and carbon additives.

I just wanted to go back to the tensile curves, because clearly if you look at the composition of this steel,

you'd expect to get pretty good elongation out of it. So I wonder if you could comment, is it the root itself that's giving you the poor properties, rather than the actual addition of the carbon nanotubes and the fullerene? In pure iron? The actual manufacturing root itself.

Because the composition is good. I mean, the composition itself, you'd expect good properties, including good ductility.

The mechanical properties are presented here. Yeah, if you go back to the tensile curve, your summary there. Plasticity, in the case of... But you've got elongation there, which I presume is your failure elongation.

You've got it down as 2.4 to 2.7% for the base steel, which is quite low. So it may put the results for the two additive steels into perspective. If you sort of... You know, that 2.4, 2.7 should be closer to, I don't know, 10, 15%, something like that at least,

from a normal conventional root. It's only got 0.1 to 0.2% carbon in it. Yeah, no, if you look at the... I'm talking about the base composition. Okay, maybe this is something that we should be talking about afterwards,

if we're going to be discussing it in depth. Because I'm afraid we are actually out of time. We've overrun by about three minutes, which I don't think is bad for a whole day of talks. So we'd just like to say thank you to Igor for a fantastic talk. Thank you very much.