Does divorce take place if I playfully said to my sick wife: "If you don't recover by tomorrow at noon, I will divorce you," knowing that I was not aware of what I uttered?

This phrase is a promise of divorce, and divorce does not occur merely by promising it, nor is one obligated to fulfill it. So, nothing is binding upon you because of it. However, one should avoid such phrases and be gentle with one's wife using kind words.