uhp grade graphite electrodes

What is the multi-type phase change control technology of uhp grade graphite electrodes?

Yesterday, Mr. Wan asked about what is the multi-type phase change control technology? Let’s get to know it together: uhp grade graphite electrodes common polytypes include 4H, 6H, 15R. 15R and 4H, 15R and 6H are lattice mismatches, which are prone to cracks. However, there are two types of problems in growth: 4H crystal growth is prone to 6H and 15R impurity phases; 6H crystal growth is prone to 15R impurity phases.

Possible mechanism analysis: the plane area of the (0001) plane is too large, and the resulting SiC layer is easy to adopt a stacking method different from the previous layer, causing the c-direction stacking to not continue and appear random. Reduce the size of the plane area to form more steps, so that at least in the short term, no new layers will appear, or reduce the area where new layers appear at the same time. Possible response methods:

Scheme 1. Adjust the atmosphere. Nitrogen atmosphere can build more steps;

Scheme 2. Seed crystal processing. (001) The crystal plane grows by 4°. It is also used for stacking fault control technology. In fact, this is called multi-type phase change control technology, which is actually based on the results.

The technical point has two directions: one is to focus on controllable things, and the other is to focus on results.

Change the controllable things, this is the technology; and after the technology is displayed, the result will be achieved. Here, it can also be disassembled into two technologies: atmosphere type control technology, and seed crystal direction control technology. Generally, achieving one result requires the integration of multiple technologies; however, one technology may achieve multiple desired results. For example, the introduction of seed crystals upgraded the Lely method to a physical vapor transport method, and created the industrialization of uhp grade graphite electrodes single crystals. It not only enlarges the size of uhp grade graphite electrodes single crystal, but also increases the quality of graphite electrode single crystal.