Negative thermal expansion particles can compensate metal matrix composites to achieve near-zero thermal expansion materials. However, there are huge thermal residual mismatch stresses in the particles due to the thermal expansion mismatch between matrix and reinforcement. The use of hybrid reinforcement is required to solve the stress concentration problem. In this study, the hybrid Al matrix composites reinforced with ZrW 2 O 8 and SiC reinforcements (SiCp, SiCnw) were fabricated by the pressure infiltration process. The effect of SiC content on microstructure, phase composition, thermal expansion and mechanical properties were examined by a combination of XRD , SEM, thermal dilatometer and bending tests. The results showed that the high-pressure phase (γ-ZrW2O8) content of hybrid metal matrix composites decreased with increasing SiC fraction. Among them, the composites containing 61.7 vol%ZrW 2 O 8 and 3.3vol%SiCnw achieved the best performance with a bending strength of 100–150 MPa and a near-zero thermal expansion (2.0–3.0 ×10 –6 K −1 ) in a wide range of − 50–120 °C, which was attributed to the synergetic hybrid effects of SiCnw and ZrW 2 O 8 . This work opens up a new frontier for the design and preparation of lightweight zero-thermal expansion materials.
ZrW 2 O 8 with excellent negative thermal expansion coefficient and anti-reflective property, was successfully introduced onto VO 2 thermochromic films. With an increase in temperature, thermal expansion mismatch appears at the interface between VO 2 and ZrW 2 O 8 layers, and the concave-shaped structures are formed to collect more light. Additionally, ZrW 2 O 8 serves as an anti-reflective coating, which results in a significant enhancement in luminous transmittance . The luminous transmittance of VO 2 /ZrW 2 O 8 and ZrW 2 O 8 /VO 2 /ZrW 2 O 8 films is 71.9% and 75.7%, respectively, which have shown significant improvement compared to 39.8% for intrinsic VO 2 film. In addition, the solar modulation value of VO 2 /ZrW 2 O 8 and ZrW 2 O 8 /VO 2 /ZrW 2 O 8 films have also been improved compared to VO 2 film, and the obtained value for bi-layer film is higher than that of tri-layer film. The results obtained for VO 2 /ZrW 2 O 8 and ZrW 2 O 8 /VO 2 /ZrW 2 O 8 films have shown a remarkable improvement over other bi-layer or tri-layer structures. The described VO 2 /ZrW 2 O 8 and ZrW 2 O 8 /VO 2 /ZrW 2 O 8 films with enhanced luminous transmittance and solar modulation make them promising materials for the application in smart windows .
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