Graphite products are oxidized or melted, and covered with a graphite protective layer (the graphite protective layer is composed of a very fine graphite shell wrapped in one or several layers of graphite inner walls, and the graphite inside is usually black), after heating dissolved deposits. These hardened layers are resistant to corrosion by strong acids and are resistant to corrosion by very weak acids. Once the graphite layer is destroyed, thinner protective layers can be obtained, which will enhance its protective properties. Calcium has a single phase and a dual-phase, the dual phase is bound to crystalline carbon or directly bound to crystalline carbon.

That is, crystalline carbon forms a dual phase and crystalline carbon forms a single phase. Single-phase graphite is placed on top of a dual-phase protective layer, and when the calcium matrix dissolves into the graphite, a dual-phase will appear. Haha because the teacher in physics class was talking about this when I was young, and the teacher was a chemistry teacher. At that time, I was asked a very stupid question, why does graphite precipitate and not regenerate, much like a stubborn stone is heated to a certain extent and then cools down, the purpose of precipitation and gasification is to preserve energy so that energy The place continues to have energy.

But the strange thing is that such a stupid question, the teacher still asked us to do experiments to verify the answer. We know that the source of energy is not from graphite but from air. So through the action of air, you can get calcium. This may be the reason for this result.

From a physical point of view, it is probably like this: we all know that when graphite shows fluidity, it is protected by the energy-rich graphite structure. As the graphite structure begins to collapse, the pH of the small graphite rises, causing the graphite air to become polarized at high temperatures and begin to crystallize. When you dissolve graphite into water, because the pH value of the water will rise, the graphite crystal will be more fragile at the same temperature, resulting in brittleness. Of course, this also involves a factor that is the nature of water, but since I haven't seen any information on this, I can't conclude.