Effective Thermal and Electrical Conductivities of AgSnO 2 During Sintering. Part I: Experimental Characterization and M
- PDF / 4,694,195 Bytes
- 15 Pages / 593.972 x 792 pts Page_size
- 100 Downloads / 184 Views
urgy techniques combined with sintering can lead to the fabrication of almost dense materials with optimized properties (high thermal and electrical conductivities, good wear resistance, and high strength). Thanks to these good characteristics, these weakly porous materials are used successfully to produce, for example, contact materials for switches and circuit breakers,[1–8] or heat pipes.[9,10] To tailor the desired properties in the case of contact materials, metallic powders, with high thermal and electrical conductivity (Ag, or Cu), are mixed with a small amount of high strength powders issued mainly from metal oxides, such as SnO2, CdO, ZnO or from W, or WC, acting as reinforcement. These composite powders are elaborated by chemical or mechanical processes and sintered by specific techniques. In the field of materials science, non-conventional sintering techniques for granular media have been ELODIE BRISSON, Postdoctoral Student, PATRICK CARRE, HENRI DESPLATS, and PHILIPPE ROGEON, Doctor Lecturers, and VINCENT KERYVIN, Professor, are with the Laboratory IRDL FRE CNRS 3744, University of South Brittany, 56321, Lorient, France. Contact e-mail: [email protected] ALEXANDRE BONHOMME, Doctor-Engineer, is with the Schneider Electric Electropole, 31 rue Pierre Mendes France, 38050, Grenoble Cedex 9, France. Manuscript submitted February 28, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
developed to improve traditional techniques. In particular, RS techniques using pulsed or continuous currents, whose advantages are described in detail in the Orru review,[11] have had considerable success over the last 10 years. Pulsed or continuous currents provide a Joule effect directly in the tools and in the granular medium (for conductors), with a fast rise in temperature, and consequently reducing the process time, compared to Hot Pressing (HP) or free sintering. Furthermore, several authors like Inoue,[12] Omori,[13] Stanciu,[14] Chaim,[15] and Zhang,[16] have attributed the best results obtained with pulsed currents to a specific phenomenon called ‘Spark Plasma Sintering’ (SPS) based on an electromagnetic effect. Williams[17] and more recently Montes et al.,[18] have shown that numerical simulation of the RS process appears of great interest for a better understanding of the involved physical phenomena, but requires the knowledge of porous medium properties evolutions during the process, in particular, the thermal and electrical conductivities. Indeed, thermal conductivity will influence the thermal gradient, which could occur inside the material especially during fast sintering processes. Furthermore, during RS of metallic powders, the current can run directly through the porous material and the electrical conductivity can influence directly the heat power generated inside the material. High-temperature gradients can cause density gradients, as well as nonuniformity in grain size distribution and properties.[19] Therefore, a first objective of this work presented in the Part I is to provide all the essential information
Data Loading...
