Dielectric properties of spark plasma sintering AlN-W composite ceramics

Abstract

In order to develop AlN composites suitable for high average power electronic tube, AlN-W materials were prepared by spark plasma sintering. The effects of manufacture parameters on dielectric loss tangent and permittivity constant were investigated, which include powder-mixed method, milling time of high-energy ball milling, starting powder particle size, sintering temperature and holding time and adding amount of the conductive second phase. The results showed that AlN-W materials sintered at the temperature of 1700°C holding for 5 min with 10 vol.% W showed the best dielectric loss tangent larger than 0.81 at the frequency 1 kHz-1 MHz. In addition, magnetic stirring mixed powder and lower sintering temperature led to the better properties because of the higher porosity. The samples sintered from the starting AlN powder with smaller particle size also had the better properties.

Investigation on coordination number and geometrical conformation of rare earth complexes with catenulate aminopolycarboxylic acid ligands

“…Fdd2 space group [68][69][70][71][72][73][74][75][76][77]. The common characters in their geometrical conformation are as follows: first, they all are nine-coordinate MCSAP conformation; second, the EDTA is six-coordinate to the central REM ion; and third, there are generally three waters coordinated to the central REM, one occupying the capped site and the other two in composing the above plane of nine-coordinate MCSAP conformation.…”

Microstructure, Thermal and Mechanical Properties of AlN-MgO Composites Prepared by Spark Plasma Sintering

“…Research on AlNbased composites fabricated by SPS has attracted widespread attention in recent years to develop composite materials suitable for a range of applications. For example, Wang et al [17] fabricated AlN-W composites for high-average-power electronic tubes. Gao et al [18] reported that AlN-based composites containing Mo exhibited better overall performance than those without the additives.…”