Adding • Applied • Both • Ceramics • Cracks • Creating • Difference • Does • Easier • Expose • Glass • Hardening • Harder • Heating • Help • How • Impurities • Include • Its • Layer • Makes • Material • Metals • Mix • More • Most • Nanoparticles • Obstacles • Particles • Porous • Prevent • Propagating • Rapidly • Reducing • Refer • Refers • Relieve • Removing • Stress • Stresses • Techniques • Temperature • Tempering • Them • Then • They • Thing • Toughening • Under • Way