Shenglei Che

Polarization-insensitive wide-angle multiband metamaterial absorber with a double-layer modified electric ring resonator array

In this letter, we report the design, demonstration and discussion of a multi- and broad- band metamaterial absorber (MMA) with wide angle polarization insensitive at microwave region. The MMA consisting of double layered electric ring resonator (ERR) with four fold rotational symmetry structure is used to realize a desirable absorption. Strong triple absorption peaks in 2∼8 GHz and broadband microwave absorption in 10∼18 GHz are demonstrated. The absorption can be reached as high as 0.73, 0.73 and 0.94 at 4.41, 5.15, 6.37 GHz, respectively. The multiband absorbing features originate from the synergetic effects of dipole resonance and Fabry-Perot interference between two or three metasurfaces. This design is of high practical for constructing broad band and multiband absorber for electromagnetic intereference/compatibility (EMI/EMC) applications.

An electrodeposition metal layers method for magnetic powders and warm-pressing preparation of Nd–Fe–B/Sn-bonded magnets

Abstract The method of magnetic stirring in fluid-bed galvanic deposits was used for cladding low-melting-point metallic tins onto the surface of rapid quenching Nd–Fe–B magnetic powders. This form of bonding was also used to make Nd–Fe–B/Sn composite magnets by warm pressing at 300 °C. The tin-plating layers of the Nd–Fe–B magnetic particles were observed by scanning electron microscope (SEM). The magnetic properties of the coated and uncoated powders were examined by vibrating sample magnetometer (VSM), respectively. Furthermore, both the compressive strength and magnetic properties of Sn-coated Nd–Fe–B/Sn-bonded magnets were measured. The results indicate that not only the tin plated and magnetic powders were bonded closely, but also the content of tin-plated layers can be controlled by the electrical current. The (BH)max and Br value of magnetic powders decrease with the increasing content of plated tin. An increase in the tin-plated content results in an elevation in magnetic properties of composite magnets by warm-pressing preparation. The composite magnets exhibit excellent integrated magnetic property when the content of Sn was 5.079 wt.%, at (BH)max = 113.7 kJ m−3, Br = 0.821 T, Hcj = 732.6 kA m−1. The results indicate that the required electrodeposited tin is less than 5 wt.% achieving the same magnetic properties and compressive strength which demands 10 wt.% tin in mechanical mixing method.

Mechanism of toughening polyphenylene sulphide by Al particles

Abstract Aluminium/polyphenylene sulphide (Al/PPS) composites were prepared using micrometre sized Al particles as toughening agents. The influences of the Al particles and of different coupling agents on the mechanical properties of the Al/PPS composites were studied using scanning electron microscopy (SEM), an electric testing machine and an impact testing machine. The results showed that the impact strength of the Al/PPS composites increased from 5·01 kJ m−2 to a maximum of 12·25 kJ m−2 when the Al addition increased from 0 to 35 wt-%. With further increase in the Al additions, the impact strength of the Al/PPS composites decreased. The impact strength further reached 35·96 kJ m−2 after the Al particles were treated with a 1 wt-% silane coupling agent (KH-560). The mechanism of toughening PPS using Al particles is proposed on the basis of the study’s SEM observations. Impact strength was increased because the cracks propagated through the PPS matrix around the Al particles by a longer pathway than when the Al particles were uniformly dispersed in the PPS matrix.

Low frequency and broadband metamaterial absorber with cross arrays and a flaked iron powder magnetic composite

In this paper, we present a design, simulation and experimental measurement of a cross array metamaterial absorber (MMA) based on the flaked Carbonyl iron powder (CIP) filled rubber plate in the microwave regime. The metamaterial absorber is a layered structure consisting of multilayer periodic cross electric resonators, magnetic rubber plate and the ground metal plate. The MMA exhibits dual band absorbing property and the absorption can be tuned from 1∼8GHz in the same thickness depending on the dimension and position of the cross arrays. The obviously broadened absorbing band of the designed structure is a result of the synergistic effects of the electrical resonance of the cross arrays and intrinsic absorption of the magnetic layer. The polarization and oblique incident angle in TE and TM model are also investigated in detail to explore the absorbing mechanisms. The resonance current of the cross array can excite the enhanced local magnetic field and dielectric field which can promote the absorption. T...

Synthesis of lithium ferrite and its solubility in water

Abstract The structural, electrochemical and magnetic properties of lithium ferrite have been widely studied, but the influence of structure on the solubility has seldom been reported. In this work, we investigated how structure affected the solubility of lithium ferrite in water. Lithium ferrites were synthesised by the solid state method. Structures of the reaction products were determined by X-ray diffraction. It was found that all products were mainly LiFeO2 and some had a few byproducts of LiFe5O8. Aqueous processing of the powders had little effect on the structure of lithium ferrite. The solubility of lithium ferrites in water was measured by induced couple plasma mass spectra (ICP-MS). The solubility decreased slightly with increasing molar ratio of α-Fe2O3 to Li2CO3, but solubility of all the products is lower than 1 wt-%. The solubility increases with the milling speed, but lower than 1 wt-%.

Double melting behaviour of PA46 matrix composites

Abstract Aluminium and alumina were chosen to mix with nylon 46 (PA46) to prepare Al/PA46 and Al2O3/PA46 composites by twin screw extruder. Differential scanning calorimeter, X-ray diffractometer and thermogravimetric analysis were adopted to analyse the melting behaviour of the as received composites. Scanning electron microscope was used to observe the microstructure of the fractural surface of the composites. The results show that two endothermic peaks separately appear at 282 and 289°C in the Al/PA46 and Al2O3/PA46 composites when the temperature rises. The double melting behaviour of the PA46 matrix composites is analysed and discussed by combining the experimental results. It is indicated that this double melting behaviour may be associated with the different crystalline regions in the PA46 matrix formed in the extruding process.