Space Exploration Stack Exchange is a question and answer site for spacecraft operators, scientists, engineers, and enthusiasts. It only takes a minute to sign up.
Sign up to join this community
Following the incident on STS-107, three methods of dealing with damaged tiles were developed.
The method for large tile damage involved screwing a very thin plate over the hole, after loosely filling the gap with cotton balls.
What was the plate made of and how did its physical properties compare to the tiles?
Partial answer
This refers to the Overlay Tile Repair System (OTRS) provided to repair the ceramic tiles, not the plug system provided to repair the reinforced carbon-carbon portions of the heat shield.
The third method is a mechanical repair that uses insulating blankets to fill cavities that are then covered by an overlay of carbon silicon carbonate installed using augers that penetrate directly into healthy tiles. The overlay system consists of Saffil insulation blankets, pre-packaged in a variety of shapes and sizes, which provide radiant heat protection when installed in the cavity. A thin (0.03 inches) overlay cover made of a high- temperature resistant, flexible material such as carbon-silicon carbide -- which can hold its shape as a shield against plasma flow -- is installed over the damaged tile and insulation blanket using augers screwed directly into adjacent healthy tiles. Around the edges, between the overlay and the existing tile, a fabric gasket is used to prevent hot gasses from penetrating beneath the overlay.
(emphasis mine)
Source Inflight Inspection and Repair
Source STS-127 EVA checklist supplemental material
Not sure how to answer "how did its physical properties compare to the tiles?" because they were totally different materials.
