Negative thermal expansion Zr 2 WP 2 O 12 (ZWP) powder prepared by hydrothermal method was used as fillers to tailor the thermal expansion coefficient (TEC) of the polyimide (PI)-based composites. A series of PI-based composites containing different loading (0-40 wt% or 0-19.6 vol%) of ZWP powder were fabricated by the in-situ polymerization technique. Their structures and properties were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Impedance meter, Thermal mechanical analysis (TMA) and Thermogravimetric analysis (TGA). The additions of ZWP steadily reduced the TEC of the PI matrix at all loadings studied. A 40 wt% (19.6 vol%) ZWP loading gives a 32.5% (about 15×10 -6 /K) reduction of TEC. The thermal stability of the ZWP/PI composites can be enhanced with the increment of ZWP powder. The independence of the dielectric constant on frequency is improved by introduction of ZWP particles to PIs. The dielectric loss displays good stability, which indicates that the ZWP/PI composites 2 show potential applications in microelectronic and aerospace industries.
Zirconium tungsten phosphate (Zr2WP2O12 denoted as ZWP) is a negative thermal expansion material which can be used as filler in controlling the thermal expansion coefficient of other materials. In this study, dense ZWP ceramics without any additives was prepared via solid-state reaction method, by milling the as-synthesized powder for different times and sintering at 1300?C. The influence of the milling time, i.e. reduced particle sizes, on properties of the Zr2WP2O12 was investigated. The obtained samples were characterized by X-ray diffraction (XRD) method, scanning electron microscopy (SEM), thermal mechanical analysis (TMA), Raman spectroscopy and Vickers hardness tester. The results showed that the milled powders have high crystallinity with single phase orthorhombic structure. The ZWP ceramics exhibits NTE property with high density. With the increase of milling time the coefficient of thermal expansion changed from ?2.607 ? 10?6 1/K to ?3.914 ? 10?6 1/K. In addition, the grain sizes decrease and the relative density and HV hardness of the obtained ceramics increase confirming that grinding is an effective method to improve the performance of ZWP ceramics.
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