Tough adhesive hydrogels find broad applications in engineering and medicine. Such hydrogels feature high resistance against both cohesion and adhesion failure. The superior fracture properties may, however, deteriorate when the hydrogels swell upon exposure of water. The underlying correlation between the polymer fraction and fracture properties of tough adhesive hydrogels remains largely unexplored. Here we study how the cohesion and adhesion energies of a tough adhesive hydrogel evolve with the swelling process. The results reveal a similar scaling law of the two quantities on the polymer fraction ( ). Our scaling analysis and computational study reveal that it stems from the scaling of shear modulus. The study will promote the investigation of scaling of hydrogel fracture and provide development guidelines for new tough adhesive hydrogels.
Core-shell structured composites of Zn-doped CoFe 2 O 4 cubes @CNTs were in situ synthesised using a CVD method at 450°C with Zn-doped CoFe 2 O 4 cubes as catalysts and ethanol as carbon source. The as-obtained products were characterised using an X-ray diffractometer, transmission electron microscope, thermogravimetric analyser and vibrating sample magnetometer. Results demonstrated that CNTs uniformly grew on the surface of Zn doped CoFe 2 O 4 cubes to form the shell with average diameter of 20-80 nm. The average diameter of the core/shell Zn-doped CoFe 2 O 4 @CNTs cubes range from 3 to 10 µm. The magnetic hysteresis curves of Zn-doped CoFe 2 O 4 cubes @CNTs illustrated the strong magnetic response to a varying magnetic field and the saturation magnetisations for the composites obtained at 450 and 600°C were 33.55 and 10.05 emu g −1 , respectively. A minimum reflection loss of −9.98 dB was observed at 9.2 GHz for the Zn-doped CoFe 2 O 4 @CNTs core/shell composites with a thickness of 2 mm. The Zn-doped CoFe 2 O 4 @CNTs core/shell composites prepared at a higher temperature exhibited better microwave absorbing performance than the sample prepared at a lower temperature.
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