Well corban was going to stab you in the back, so he was behind you. I stated in the last post that corban left the earth when he came to stabby stab. The aerogel is spread a foot around the blade. A foot is a decent amount of body coverage, and can cover majority of, if not all of the chest, which is where the attack is angled for, and the aerogel was specifically used as an insulator to account for the stray beam sparks. Plus the added protection of the disjunction, and the diamond field would leave corban himself believably unharmed. I also figured there would be some sparks flying like you suggested, too. That's why his barrier had several holes punched through it despite the aforementioned defenses.

Edit: I actually misquoted myself. The aerogel covered a whole two feet. Which is more than enough.