Question

Question: Compare oxide ceramics such as alumina$\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$and magnesia (MgO), which have significant ionic character, with covalently bonded nonoxide ceramics such as silicon carbide (SiC) and boron carbide; (${\mathrm{B}}_4\mathrm{C}$see Problems 19 and 20) with respect to thermodynamic stability at ordinary conditions.

Short answer

Aluminium oxide is an electric insulator and has a relatively high thermal conductivity for a ceramic metal whereas pure MgO isn't conductive and have a high resistance to current at temperature.

Step-by-step solution

Step 1:

The most common form of Aluminium oxide is Corundum, which is insoluble in water. It is responsible for the resistance of metallic aluminium. Aluminium oxide is an electric insulator and has a relatively high thermal conductivity for a ceramic metal.

Aluminium oxide is answerable for the resistance of metallic aluminium to weathering. Metallic aluminium is incrediblyreactive with atmospheric oxygen, and a skinny passivation layer of aluminum oxide alumina is an amphoteric substance, meaning it can react with both acids and bases, like acid and caustic soda, acting as an acid with a base and a base with an acid, neutralising the opposite and producing a salt.

Step 2:

Pure MgO isn't conductive and have a high resistance to current at temperature. MgO is prized as a refractory material, i.e. a solid that's physically and chemically stable at high temperatures. it's two useful attributes: high thermal conductivity and low electrical conductivity. Filling the spiral Calrod range top heating elements on kitchen electric stoves are the major use.