Near-net-shape fabrication of continuous Ag-clad Bi-based superconductors
We have developed a near-net-shape process for Ag-clad Bi-2212 superconductors. This alternative to the powder-in-tube process offers the advantages of nearly continuous processing, minimization of processing steps, reasonable ability to control the Bi-2212/Ag ratio, and early development of favorable texture of the Bi-2212 grains. The powder is rolled into an Ag channel, a cap is applied, and the assembly is lightly rolled. To minimize distortion during heat treatment, it is especially important that the Bi-2212 powder be nearly free of volatile species such as carbon. A vacuum-calcination process was developed to control CO/sub 2/ evolution during heating. Superconducting properties are discussed.
Critical current in Tl-base high-Tc oxides synthesized through a diffusion process
In the TBCCO diffusion composites, the 2223 phase is easily formed within a short reaction time. The critical current at 77 K is significantly improved by the F addition to the coating layer. The F addition decreases the degradation of critical current under magnetic field at 77 K, and shifts the irreversibility line to higher temperature. The XRD study reveals that the F addition clearly promotes the phase transformation from 2223 to 1223. Meanwhile, the annealing in flowing O/sub 2/ at 550/spl deg/C-600/spl deg/C also increases the critical current at 71 K. A J/sub c/ of about 10,000 A/cm/sup 2/ is obtained at 77 K in the TBCCO diffusion layer by the F addition and the O/sub 2/ annealing.<<ETX>>
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.