Method of treating joint in ceramic assembly

A method for forming a sealed joint between at least first and second formed or shaped ceramic structures, the method comprising:

• a) providing at least first and second joined ceramic structures, the first and second joined ceramic structures comprising silicon carbide and being joined together by a joint therebetween, the joint comprising one or more of silicon, a silicon alloy and a silicon compound, the joint including an exposed portion;
• b) converting at least a portion of the one or more of silicon, a silicon alloy, and a silicon compound of the joint to silicon nitride,
• wherein the step of converting at least a portion of the silicon, silicon alloy, or silicon compound of the joint to silicon nitride comprises heating in an inert atmosphere the at least first and second ceramic structures and the joint, to a temperature greater than 1300° C. and less than a melting point of the one or more of silicon, a silicon alloy, and a silicon compound of the joint, then, while the temperature is still less than the melting point of the one or more of silicon, a silicon alloy, and a silicon compound of the joint, switching from an inert to a reactive atmosphere, then, after switching to a reactive atmosphere, ramping the temperature of the first and second ceramic structures and the joint from less than the melting point of the one or more of silicon, a silicon alloy, and a silicon compound of the joint to greater than the melting point of the one or more of silicon, a silicon alloy, and a silicon compound of the joint.