Today we followed Lesker cleaning protocol, wipe off the oil of Li with paper wipe very quickly before going into hexane. And we also used a razor blade to scratch off a thin bad layer on the Li surface on the bar, under first hexane. Li bar was quite good before we load it into vessel, that is when it was in the last hexane bath it is still quite shiny I think (not 100% perfect, but quite shiny, we can demonstrate this later if needed. We also tested if we scratched Li surface under hexane the scratch surface can remain shiny under hexane for about 2 mins.)  Right after loading into the vessel and during the first pump down (again not 100% sure), some cut surfaces becomes grey, but not all. Here are some pictures:

Because some surfaces became grey during the first pump down, even before the first Ar fill, we think this might be due to the air that perturbs the Ar previously filled in the vessel. If this is the case then Chuanfu’s idea of putting a long tube may actually help because the perturbed interface between air and Ar can be raised to a high point, away from the vessel body. This is the reason why we are kind of thinking putting that tube. However, only partial surfaces became grey, and there are still quite many cut surfaces that are still shiny. We are not sure why, this is very weird! (You can see the stripes we created when we scratched the side cylindrical wall with a razor blade, that is the reason for the silver and dark stripes on the side, like a candy bar.)

The above is actually the second sample we prepared, the first one became quite dark when we load it into the vessel. It took us too long time to transport it from last hexane path to the beaker. So we immediately decided to discard that first one and prepared a second one. This is to say, the loading process is actually quite tricky and one needs to be very careful and quick, at the same time.

And then we heat it up. Now things are OK. The shiny surfaces actually stayed quite shiny until ~180 C(good signs here). At around ~190C Chuanfu first noticed melting sign, bar deforming. But when he checked it again 5 mins later, it became like the following pictures:

Some kind of explosion occurred. The bottom beaker broke. Li exploded into popcorns!!?! The surfaces of the Li popcorn are very shiny at this point. We had no idea how this can happen. There seems to be some kind of mist on the floor of the SS vessel and the top sight glass.

We kept on heating it up to 235C and wait for more time. Then the picture becomes:

At the end of the exp.

We are not sure about the reason for the explosion. One suspicion is we know there is a big temperature gradient on the vessel during the ramping stage. We changed the position of the TC from one side to the other (eg. from the right hand side of the picture, also where the heater is, to the left hand side), the temperature difference is about 20 degC. The beaker is loosely sitting in the SS ring, which is tightly fitted in the vessel, so it shouldn’t be due to the squeeze. Another one suspicion Chuanfu has is maybe the melted Li inside the bar vaporized and cause this explosion. Anyway, this is the first time we see this.

The popcorn Li did not seems to further melt much, they did become a bit more sagged, but not much. They seemed to resist to become liquid in this form.

Vitaly we are still thinking to try again, maybe without the glass, maybe with a metal tray. Because the first part of today’s exp still had some good signs, some shiny metal stripes can stay shiny all the way right before exploding. But should we? Or we should stop trying and start getting the circulating system?