Papers by Author: Bo Li

Abstract: The ability to withstand axial hot compression at 700 °C of electropulsing-assisted ultrasonic surface rolling process (EUSRP) treated Inconel 718 was characterized by hot compression tests in this study. Results indicated that EUSRP induced ultra-fine microstructure on the near-surface regions of the sample and the formation of recrystallized ultra-fine grains in the near-surface regions was further promoted during hot compression test. In addition, a large number of nanoγ'' phases were precipitated on the broadened grain boundaries of the near-surface regions. In summary, EUSRP enhanced the ability to withstand axial hot compression of Inconel 718 at 700 °C.

Abstract: Three-dimensional (3-D) periodic hematite scaffold was successfully fabricated by direct writing method as a catalyst for degradation of organic contaminants. Photo-catalytically active α-Fe₂O₃ nanoparticles have been synthesized by sol-gel technique. Aqueous slurries of iron oxides were freeform fabricated to produce hematite scaffolds with a 3-D periodic architecture and multiscale porosity. The catalytic activity of the hematite scaffolds was evaluated in the degradation of Methylene Blue (MB). It was found that the degradation rate of MB dye was over 83%. The result strongly indicates that the hematite scaffolds exhibits a high catalytic activity. Moreover, this work provides an important step forward in the creation of suitable structures for photocatalyst.

Abstract: Inverse opal films (IOFs) of SnO₂ doped with Pd were prepared by the self-assembly technique using polystyrene microsphere (PS sphere) as template in combination with a sol-gel method. The photocatalysis properties of SnO₂ IOFs were estimated through measuring the rate of the degradation of methylene blue (MB). The result shows that SnO₂ IOFs have good photocatalytic activity, the solution of MB was degradated over 60% in 4 hours when it was dipped in SnO₂ IOFs and exposed in the UV light. The addition of Pd in SnO₂ IOFs improved the photocatalytic activity of the films and the degradation of MB can exceed 80% with the same condition. This sort of SnO₂ IOFs doped with Pd indicated a potential application in photocatalysis field.

Abstract: Methods of manufacturing Niobium oxide electrolytic capacitor were studied in this work. Some phenomena were found and the reasons or mechanisms were studied by using SEM(scanning electron microscope), EDS. In experiment, comparing with the type 6.3V/47μF tantalum capacitor, NbO powder were pressed to pellet as the capacitor anode, then the NbO capacitor was manufactured through the following processes: sintering, welding, anode oxidation, MnO₂ decomposition and cathode coating. Its capacitance, leakage current, ESR(equivalent series resistance) and tgδ were measured and compared with that of the simily type of tantalum capacitor, and the suitable technical parameters were chosen

Abstract: A EBG（Electromagnetic Bandgap） structure was prepared based on the theory of the high impedance surface photonic crystal and the HFSS emulating results. The measurement result showed that the bandgap of the EBG structure was in the Ultra Wideband range. The designed structure was fabricated by a method of low temperature co-fired ceramics technology（LTCC） using ceramics as the matrix and silver as the coils. The micro-structure was analyzed by microscope and scanning electron microscope which showed that these two kinds of materials were well connected. A bandgap between 4GHz~5.5GHz was found by the Vector Network Analyzer which was accord to the emulation.

Abstract: Barium titanate (BTO) inverse opal photonic crystals were fabricated by a process of self-assembly of polystyrene opal template in combination with electrophoretic deposition (EPD) of nanoparticles from BTO suspension. In this process, stable monodispersed suspension of BTO nanoparticles was prepared by dispersing BTO gel into a mixed solvent of 2-methoxyethanol and acethylacetone. Then the BTO nanoparticles were infilled into the interstices of the opal template formed by monodisperse polystyrene microspheres by electrophoretic deposition, and then polystyrene template was removed by calcining the specimen at a final temperature of 500oC. SEM images show that the inverse opals possess face-centered cubic (fcc) structure with center to center distant of the air spheres 310 nm. A photonic bandgap in the visible range is observed from reflection spectra of the sample. Such BTO inverse opals as photonic crystals should be useful in device applications.