Abstract
Zr2WP2O12/ZrO2 composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of Zr2WP2O12/ZrO2 composites with different mass ratio. Relative densities of all the resulting Zr2WP2O12/ZrO2 samples were also tested by Archimedes' methods. The obtained Zr2WP2O12/ZrO2 composites were comprised of orthorhombic Zr2WP2O12 and monoclinic ZrO2. As the increase of the Zr2WP2O12, the relative densities of Zr2WP2O12/ZrO2 ceramic composites increased gradually. The coefficient of thermal expansion of the Zr2WP2O12/ZrO2 composites can be tailored from 4.1 × 10−6 K−1 to −3.3 × 10−6 K−1 by changing the content of Zr2WP2O12. The 2:1 Zr2WP2O12/ZrO2 specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of −0.09 × 10−6 K−1. These adjustable and near zero expansion ceramic composites will have great potential application in many fields.
Highlights
Lots of materials known to show positive thermal expansion as temperature increase
For pure Zr2WP2O12 ceramics (Figure 1F), all diffraction peaks matched those expected for orthorhombic Zr2WP2O12 (JCPDS 43-0258)
The 2:1 Zr2WP2O12/ZrO2 specimen showed close to zero thermal expansion with an average linear coefficient of thermal expansion (CTE) of −0.09 × 10−6 K−1 in the temperature range of 25–700◦C. This near zero expansion ceramic composite will have a number of potential applications in many fields. These results suggest that the CTE of the Zr2WP2O12-ZrO2 composites can be modified in the range from 4.1 × 10−6 K−1 to −3.3 × 10−6 K−1, and that it is even possible to achieve zero thermal expansion by adjusting the mass ratios of Zr2WP2O12 and ZrO2. (Figure 2f) showed a wide size distribution of spherical grains with some residual porosity, which is in agreement with results reported earlier (Isobe et al, 2008, 2009; Cetinkol and Wilkinson, 2009)
Summary
Lots of materials known to show positive thermal expansion as temperature increase. In contrast, some materials show completely different thermal expansion properties and contract upon heating. This work is devoted to exploring the effects of mass ratio of Zr2WP2O12 and ZrO2 on the microstructure, density, and CTE values of the Zr2WP2O12/ZrO2 ceramic composites.
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