As you can see from all my previous posts, I have many first-hand sources. When I prepared the book “E-Cat – The New Fire”, I contacted one of the people who had worked on the development of the E-Cat (therefore, not Rossi). He told me that the Hot-Cat running was a sort of “Sun in a box” and that once he had also seen the reactor sublimate!
Also Andrea Rossi, later, has described this type of event in a comment posted on JoNP:
December 28th, 2013 at 8:32 PM
Very sorry, I cannot answer to this question exhaustively, but I can say something. Obviously, the experiments are made with total respect of the safety of my team and myself. During the destructive tests we arrived to reach temperatures in the range of 2,000 Celsius degrees, when the “mouse” excited too much the E-Cat, and it is gone out of control, in the sense that we have not been able to stop the raise of the temperature (we arrived on purpose to that level, because we wanted to study this kind of situation). A nuclear Physicist, analyzing the registration of the data, has calculated that the increase of temperature (from 1,000 Celsius to 2,000 Celsius in about 10 seconds), considering the surface that has increased of such temperature, has implied a power of 1 MW, while the Mouse had a mean power of 1.3 kW. Look at the photo you have given the link of, and imagine that the cylinder was cherry red, then in 10 seconds all the cylinder became white-blue, starting from the white dot you see in the photo (after 1 second) becoming totally white-blue in the following 9 seconds, and then an explosion and the ceramic inside (which is a ceramic that melts at 2,000 Celsius) turned into a red, brilliant stone, like a ruby. When we opened the reactor, part of the AISI 310 steel was not molten, but sublimated and condensed in form of microscopic drops of steel.
The photo cited by Rossi: a Hot-Cat exhibits a hot-spot during a destructive test, in 2012.
Sublimation is a process during which a solid on heating changes directly into the vapor phase without passing through the intermediate liquid state. When the vapors are cooled, they condense to form solid. The temperature at which a solid changes into vapor is called the sublimation point (and corresponds to the boiling point of the liquid).
Typically, the pressure at which a material sublimate is atmospheric pressure, so the sublimation points are normally referred to the standard pressure of 760 mm Hg, and the temperature is the determining factor to the change of state in those cases. However, more in general, a material will change from solid state to gas state at specific combinations of temperature and surrounding pressure.
The temperature of a material will increase until it reaches the point where the change takes place. It will stay at that temperature until that change is completed. Some substances sublime at room temperature. A common example of this is dry ice, where solid carbon dioxide becomes gaseous without being a liquid during the process.
You can see below its phase diagram:
The phase diagram for carbon dioxide (from Wikimedia).
For each solid, raising temperature at low enough pressure takes the material directly from solid to gas, but at higher pressure it will go through the liquid between. The pressure where that behavior changes turns out to be a lot different for different materials, so at atmospheric pressure some behave some way, some the other. For water, if you lower pressure to about 1/160 of atmospheric pressure, it will go straight from solid to gas.
It is interesting that metals exhibit evidence of a tendency to sublimate – or, more exactly, show volatility – at temperatures considerably below their melting points. Krafft already in 1903 investigated in some detail the volatilization of a number of metals at low pressures. Rosenhain obtained beautiful crystals of sublimed zinc by heating a piece of zinc to 300 °C for some weeks in a glass tube containing hydrogen (!) at atmospheric pressure.
From the book “Hot-Cat 2.0 – How last generation E-Cats are made” we know that the reactors used in these destructive tests were made of metallic and non metallic materials: steel (external cylinder and inner cylinder), a ceramic material (between the two steel cylinders), some heating resistors (made of metal) and nickel (main component of the charge). So it is interesting to check what are the sublimation points for some of such materials.
The sublimation point for nickel is 2800 °C. However, very few metals are used in pure, or even relatively pure, forms. Steel, for example, is the name for a whole family of iron alloys (containing carbon and often some other elements). The boiling point of iron (not steel) is 2750 C, so the sublimation (or boiling) point of steel is likely to be close for most steels: around 3000 °C. Steel melts at much lower temperatures: around 1300-1500 °C.
The phase diagram for pure iron (from Wikipedia).
In the phase diagram above you can see that iron is solid at room pressure and at standard temperature (25 °C), but melts around 1540 °C and sublimate around 2750 °C. Alpha (α) iron, or ferrite, is the name given in material science to pure iron with a body-centered cubic crystal structure. It is this structure which gives steel its magnetic properties and is the classic example of a ferromagnetic material. Mild steel consists mostly of ferrite.
Regarding the ceramic materials contained in Rossi’s type of Hot-Cat used in the destructive tests (different from the alumina used in the Lugano test, as described in the cited book), their melting point is around 1900-2000 °C, and their sublimation point is about 3000-3500 °C.
Therefore, at the end of this “exploration” we can conclude – taking into account also the temperature gradient along the reactor from inside to outside – that the temperature reached in the destroyed Hot-Cats was well beyond 3000 °C! This is extremely interesting, because there is no way to obtain such a result using electrical heating resistors…
This post has been written with the kind collaboration of the physicist Alessandro Cavalieri.