Motor shaft heat block

3-3-23 I need a material that is strong and machinable so it will connect two 1/2 inch steel shafts like the picture below but can prevent heat from being transferred from one shaft to the other.

Specifically one shaft is a motor, the other is a steel propeller. The propeller will blow air that is 1000 degrees F and the motor shaft must not be heated by the propeller meaning this connector is a thermal barrier.

One idea is to use a 1 inch thick sheet of calcium silicate between two steel shaft couplers – similar to these –