Enhancement of Critical Current Density of Yttrium Barium Copper Oxide Thin Films by Introducing Nano dimensional Cerium Oxide Defects

The critical current density, Jc  has been the most important parameter used in the design and engineering of effective devices which is one of the implementation of high temperature superconductors (HTSC). In this work, an effort has been made to further improve the critical current density of YBa2Cu3O7-x (YBCO) thin films by preventing the magnetic flux line lattice against the Lorentz force by pinning it in place with the aid of nano-dimensional defects. These defects were generated by distributing nano sized CeO2 islands after YBCO layer was created on LaAlO3 substrates perpendicular to the film using pulsed laser deposition (PLD) technique. Three samples with buffer layers of CeO2 were prepared. CeO2 with 50 pulses, 100 pulses and 150 pulses, after each 1000 pulses of YBCO were prepared five layers for each of the samples. The structural characterization of YBCO/CeO2 and YBCO pristine films were carried out using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Superconducting proprieties were measured using a vibrating sample magnetometer (VSM). Jc  for the pure YBCO and the YBCO/CeO2 films were calculated from magnetization (M) versus Field (H) loops using Bean’s model. Jc  for the 50 pulses of YBCO/CeO2 films was found to be increased slightly by an order of magnitude of about 40% with respect to those of YBCO films without the nano dimensional defects.

Study on the Water Proof Seal for Underwater Robot Using MR Fluid

Water proofing is an obvious problem in developing successful underwater robots. In previous research, most underwater robots have used a mechanical seal for water proofing. However, this kind of seal has not proved reliable because of friction and wear between the stationary parts and moving parts. This paper presents a method to seal the moving parts in underwater robots, especially robot fish. The proposed seal for under water robots is developed using Magneto Rheology (MR) fluid. MR fluid is a kind of smart material, of which the viscosity varies with the external magnetic field. This fluid is composed of silicon oil and small magnetic particles, which are micrometer sized, and when an external magnetic field is applied to the fluid, the small particles align with the magnetic flux line. The arrays of magnetic particles in the fluid inhibit the fluid flow, which changes the viscosity of fluid. Taking advantage of this phenomenon, we devised a seal with a permanent magnet and MR fluid. Our analysis demonstrates the performance of the developed seal. The magnetic equivalent circuit method and FEM (Finite Element Method) are used to calculate the magnetic field and the analysis results show that the developed seal can sustain 10 atm pressure.