Tu Mingjing

Study on shielding functionally gradient materials with low reflection loss and high absorption loss for electromagnetic wave

In this paper, the double gradient model for shielding functionally gradient materials (SFGMs) with low reflection loss and high absorption loss in less than 1 GHz is put forward to reduce pollution of the electromagnetic wave. In SFGMs, double impedance matching layers on the surface and high absorption layer in center and double impedance transition layers between the surface and center are designed. The based on nickel and (Ni,Zn)Fe/sub 2/O/sub 4/ gradient composite shielding coatings are prepared. The test results of the coatings showed that, the reflection loss was decreased 6/spl sim/8 dB and the absorption loss was increased 6/spl sim/14 dB.

Preparation of a Core-Shell Structured Al2O3/YAG:Ce Phosphor by a Spray Drying Method and Formation Mechanism

Abstract The core-shell structured Al 2 O 3 /YAG:Ce phosphor was prepared by a spray drying method. The obtained samples show cubic Y 3 Al 5 O 12 structure, have a spherical shape with the size in the range of 1~8 μm and exhibit higher internal quantum yield compared to the samples prepared by co-precipitation. Based on the fact that the spray drying method can be employed to fabricate microencapsulate particles, the formation mechanism of the core-shell structured Al 2 O 3 /YAG:Ce phosphor was formulated. The slurry, which was mixed with micrometer Al 2 O 3 particles and polycations consisting of Y 3+ , Al 3+ and Ce 3+ , was atomized and shaped by the evaporation of droplets. In the process of solvent evaporation, the interparticle capillary forces make the self-assembly of polycations into the close-packed shell surrounding the Al 2 O 3 particles, because the polycations have a bigger diffusion rate than Al 2 O 3 particles. At last, the precursor was calcined at the temperature from 850 o C to 1250 o C for 2 h and then the core-shell structured phosphor was produced. Therefore, a novel idea for preparing core-shell structured phosphor is proposed.