Young's modulus and vibrational damping of sintered silicon carbide ceramics at high temperatures

Abstract

Silicon carbide-based advanced ceramics have good strength, high thermal conductivity, and good creep and environmental resistance at high temperatures [1]. These attractive thermomechanical properties have made them widely used ceramic material for a number of applications in aeronautics, energy, electronics, nuclear, and transportation industries. In the aeronautical arena, these materials are being considered for applications in jet engine components. Applications in the energy industries include radiant heater tubes, heat exchangers, heat recuperators, and components for land based turbines for power generation. These materials are also being considered for use in the first wall and blanket components of fusion reactors, in furnace linings, and bricks, and in components for diffusion furniture (boats, tubes) in the microelectronics industry. There are a number of critical issues related to the use of these materials. For a number of engineering applications, high temperature elastic modulus and damping behavior becomes very important. In earlier publications, dynamic Young’s modulus and damping behavior of a wide variety of reaction bonded and reaction formed silicon carbide ceramics have been reported [2–6]. The aim of the present work is to characterize the elastic modulus and vibrational damping behavior of a sintered silicon carbide (Hexoloy-SA; Carborundum Co., Niagra Falls, NY) material. These materials were fabricated by the pressureless sintering of alpha SiC powders with boron carbide or aluminum carbide as sintering aids. For the modulus and damping measurements, bend bars were machined from the as-supplied plates. These bars had dimensions of 50 mm× 4 mm× 3 mm. The dynamic Young’s modulus and vibrational damping were measured as a function of temperature. The vibrational damping was measured as Q−1, where: Q−1= energy dissipated per cycle 2π∗(maximum energy stored per cycle)