Silicone rubber composites filled with FeSiAI alloys and multi-walled carbon nanotubes （MWCNT）/graphite have been prepared for the first time by a coating process. The complex permittivity and permeability of the composites were measured with a vector network analyzer in a 1-4 GHz frequency range, and the DC electric conductivity was measured by a standard four-point contact method. These parameters were then used to calculate the reflection loss （RL） and shielding effectiveness （SE） of the composites. The results showed that the added MWCNT increased the permittivity and permeability of composites in the L-band, while the added graphite increased only the permittivity. The variation lies in the interactions between two carbonous absorbents. Addition of 1 wt% MWCNT enhanced the RL in the L-band （minimum -5.7 dB at 1 ram, -7.3 dB at 1.5 ram）, while the addition of graphite did not. Addition of MWCNT as well as graphite reinforced the shielding property of the composites （maximum SE 13.3 dB at 1 ram, 18.3 dB at 1.5 ram） owing to the increase of conductivity. The addition of these carbonous materials could hold the promise of enforcing the absorption and shielding property of the absorbers.
Diatom frustules,considered as novel bio-functional materials,display a diversity of patterns and unique micro-and nanostructures which may be useful in many areas of application.Existing devices directly use the original structure of the biosilica frustules,limiting their function and structural scale.Current research into the shapes,materials and structural properties of frustules are considered;a series of frustule processing methods including structure processing,material modification,bonding and assembly techniques are reviewed and discussed.The aim is to improve the function of diatom frustules allowing them to meet the design requirements of different types of micro devices.In addition,the importance of the comprehensive use of diatom processing methods in device research is discussed using biosensors and solar cells as examples,and the potential of bio-manufacturing technology based on diatom frustules is examined.
The electromagnetic （EM） wave absorbing property of silicone rubber filled with carbonyl iron particles （CIPs） and multi-walled carbon nanotubes （MWCNTs） was examined. Absorbents including MWCNTs and spherical/ flaky CIPs were added to silicone rubber using a two-roll mixer. The complex permittivity and complex permeability were measured over the frequency range of 1-18 GHz. The two EM parameters were verified and the uniform dispersion of MWCNTs and ClPs was confirmed by comparing the measured reflection loss （RL） with the calculated one. As the MWCNT weight percent increased, the RL of the spherical CIPs/silicone rubber composites changed insignificantly. It was attributed to the random distribution of spherical ClPs and less content of MWCNTs. On the contrary, for composites filled with flaky ClPs the absorption bandwidth increased at thickness 0.5 mm （RL value lower than -5 dB in 8-18 GHz） and the absorption ratio increased at lower frequency （minimum -35 dB at 3.5 GHz）. This effect was attributed to the oriented distribution of flaky CIPs caused by interactions between the two absorbents. Therefore, mixing MWCNTs and flaky CIPs could achieve wider-band and higher-absorption ratio absorbing materials.
The growth characteristics of Sphaerotilus natans and Leptothrix discophora SS-1(ATCC43182) were first used to fabricate the ferrite and manganese ferrite.The scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),X-ray diffraction(XRD),and vibrant sample magnetometer(VSM) were used to make clear their morphology microstructure,chemical composition,crystal structure,and magnetostatic characteristic.The result showed that the hollow ferrite fibers were prepared successfully,whose crystal structures were close to α-Fe2O3 and the average aspect ratio was over 50.Moreover,the soft magnetic manganese ferrite was fabricated with the saturation magnetization Ms at 25 emu/g and coercive force Hc at 796 A/m.
