Liu Lie
Email Address
tslll@nus.edu.sg
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Publication Shift of resonance frequency of long conducting fibers embedded in a composite(2003-07-15) Matitsine, S.M.; Hock, K.M.; Liu, L.; Gan, Y.B.; Lagarkov, A.N.; Rozanov, K.N.; TEMASEK LABORATORIESAn experimental study on the dipole resonance of long high-conducting fibers embedded in an inhomogeneous composite sheet was presented. It was shown that the resonance frequency is determined completely by the thickness and permittivity of the composite sheet, particularly with the anisotropy of the permittivity. No effect due to inhomogeneity of the environments is observed, which is in disagreement with the scale-dependent effective medium theory (SDEMT) that is conventionally exploited to model the permittivity of fiber-filled composites.Publication Electromagnetic smart screen for tunable transmission applications(2008-06) Liu, L.; Matitsine, S.; Tan, P.K.; TEMASEK LABORATORIESElectromagnetic smart screen containing conductive strip array loaded with pin diodes was investigated with numerical and experimental approaches. Transmission coefficient was simulated using finite element method with validation by free space measurement. Tunable EM properties are observed between 3 and 8 GHz, which can be useful for antenna applications. © 2008 Wiley Periodicals, Inc.Publication Frequency dependence of effective permittivity of carbon nanotube composites(2007) Liu, L.; Matitsine, S.; Gan, Y.B.; Chen, L.F.; Kong, L.B.; Rozanov, K.N.; TEMASEK LABORATORIESDependence of the permittivity of single-walled and multiwalled carbon nanotube composites on frequency and concentration was investigated experimentally using the coaxial air-line method over 0.1-10 GHz. The results are in good agreement with that obtained using the impedance method. It is found that scaling law based on the percolation theory provides a good description of the frequency dependence of measured permittivity in carbon nanotube composites. Parameters of the scaling law and deviations from the percolation theory are also discussed. © 2007 American Institute of Physics.Publication Electromagnetic smart screen with extended absorption band at microwave frequency(2011-04) Liu, L.; Matitsine, S.; Huang, R.F.; Tang, C.B.; TEMASEK LABORATORIESElectromagnetic smart screen (ESS) containing conductive patch array loaded with pin diodes was investigated experimentally and numerically. Reflectivity of smart screen was measured with free space method and calculated through finite element simulation. The reflectivity of ESS with thickness about 2.3. mm can be as low as -40. dB and the absorption peak can be tuned from 3. GHz to 4. GHz. The relative absorption bandwidth (less than -7.5. dB) can be as large as 40% which is much wider than non-tunable metamaterials. © 2010 Elsevier B.V.Publication FEM analysis of frequency selective composites with regularly or randomly distributed conductive fibers(2005) Liu, L.; Matitsine, S.M.; Gan, Y.B.; Rozanow, K.N.; TEMASEK LABORATORIESFinite element method (FEM) was used to calculate the transmission coefficient of frequency selective composites with regularly or randomly distributed conductive fibers for various volume concentrations of the fibers. Transmission coefficient was also measured with free space measurement system. The computed results are consistent with measured data. It also demonstrated that FEM is an accurate tool to predict the microwave performance of frequency selective composites, as compared to the Method of Moment. © 2005 IEEE.Publication NiCuZn ferrite flakes prepared using a sol-gel bubble method and its magnetic properties(2011-02-10) Yang, Z.H.; Li, Z.W.; Liu, L.; Kong, L.B.; TEMASEK LABORATORIESNi0.23Cu0.11Zn0.66Fe2O 4 ferrite flakes, with thickness of about 8 μm and average diameter of 20-35 μm, were prepared using a sol-gel bubble method. Morphology, phase evolution, static and dynamic magnetic properties of the flakes and their composites were studied. Magnetic measurements showed that easy magnetization direction of the flaky filler composite was parallel to its sample plane. Composites made of silicone resins and flakes had higher complex permeability, which can be attributed to the reduction in demagnetization factor due to their flaky shapes. This sol-gel bubble method should be also applicable to fabricating flakes of other multi-component oxides. © 2010 Elsevier B.V. All rights reserved.Publication High permittivity and shielding effectiveness of microwire composites with optical transparency(2012) Liu, L.; Yang, Z.H.; Kong, L.B.; Li, P.; Poo, C.H.; TEMASEK LABORATORIESFlexible composites with optical transparency were fabricated with glass-coated nanocrystalline ferromagnetic microwires and transparent silicone matrix. Free space method was employed to measure the effective permittivity and shielding effectiveness of samples fabricated from 4 to 20 GHz. Due to resonance phenomena of the embedded microwires with certain lengths, both dielectric permittivity and loss of the composite are quite high at designed microwave frequency. Broadband shielding effectiveness (SE) of the transparent shielding layer with 0.5wt% of microwires and thickness less than 0.75mm can be 10 to 14 dB. The maximum SE of combining two layers of sheets (∼1.5mm) with microwires of different length could be better than 20dB © 2012 IEEE.Publication Comment on "high microwave permittivity of multiwalled carbon nanotube composites" [Appl. Phys. Lett. 84, 4956 (2004)](2005-07-04) Matitsine, S.M.; Liu, L.; Chen, L.F.; Gan, Y.B.; Ong, C.K.; TEMASEK LABORATORIES; PHYSICSThe phenomena of high microwave permittivity of multiwalled carbon nanotube (MWCNT) composites was investigated. Resonance peaks at about 1.8 GHz were found using the impedance method. The complex permittivity were measured for composite sheets with a single wall carbon nanotube using both the impedance analyzers and the 7 mm coaxial line method. It was shown that the origin of the resonance cannot be attributed to the dielectric properties of the nanotube materials.Publication Bandwidth extension of metamaterials with low reflectivity(2011) Huang, R.; Li, Z.-W.; Liu, L.; Kong, L.B.; TEMASEK LABORATORIESFollowing introduction of a figure of merit to quantify the thickness-normalized bandwidth of metamaterials for reflectivity reduction from metallic surfaces, possible methods are explored to design broadband metamaterials with low reflectivity. It is presented that the static permeability of substrate, the frequency-dispersion of permeability and permittivity of substrate, and the metallic resonant patterns all determine the figure of merit, and in turn the bandwidth of broadband metamaterials. Both numerical and experimental examples are included to validate the designs. © 2011 Engineers Australia.Publication High frequency properties of composite membrane with in-plane aligned Sendust flake prepared by infiltration method(2012-05) Liu, L.; Yang, Z.H.; Deng, C.R.; Li, Z.W.; Abshinova, M.A.; Kong, L.B.; TEMASEK LABORATORIESComposite membranes (with thickness around 100200 μm) containing highly in-plane aligned Sendust flakes embedded in polyvinyl alcohol matrix were prepared with a novel infiltration method. As compared with tape-casting method, infiltration method results in enhanced magnetic permeability, which could be caused by better alignment and less porosity. Annealing process could modify the grain size, improve saturation magnetization and coercivity of Sendust flakes. Hence, the radio and quasi-microwave frequency permeability (between 10 MHz to 3 GHz) of composites membranes with annealed Sendust flakes could be enhanced significantly as compared with that of the as-prepared flakes. Infiltration method is especially suitable for composites with high concentration of flaky fillers. The composite membranes prepared have potential applications, including electromagnetic shielding, noise reduction and wave absorption. © 2012 Elsevier B.V. All rights reserved.