The establishment of Boron nitride@sodium alginate foam/polyethyleneglycol composite phase change materials with high thermal conductivity, shape stability, and reusability

Adopting organic phase change materials(PCMs) for the management of electronic devices is restricted by low thermal conductivity. In this paper, the composite PCMs are established by freeze-drying and vacuum impregnation. Herein, polyethylene glycol(PEG) is induced as heat storage materials, boron nitride(BN) is embedded as filler stacking in an orderly fashion on the foam walls to improve thermal conductivity and sodium alginate(SA) is formed as supporting material to keep the shape of the composite stable. X-ray diffractometry, scanning electron microscopy-energy dispersive spectrometer, thermal gravimetric analysis, thermal conductivity meter, differential scanning calorimeter, and Fourier transform infrared were used to characterize the samples and thermal cycles were employed to measure the shape stability. The results exhibit the BN@SA/PEG composite PCMs have good chemical compatibility, stable morphology, and thermal stability. Due to the high porosity of foam, PEG endows the composite PCMs with high latent heat(149.11 and 141.59 J·g^(-1)). Simultaneously, BN@SA/PEG shows an excellent heat performance with high thermal conductivity(0.99 W·m^(-1)·K^(-1)), reusability, and shape stability, contributing the composite PCMs to application in the energy storage field. This study provides a strategy to manufacture flexible, long-serving, and shape-stable PCMs via introducing BN@SA foam as a storage framework, and these PCMs have great potential in thermal management in the electronic field.

The study on the mechanical properties of PU/MF double shell self-healing microcapsules

The self-healing microcapsules can be buried in the coating to improve the anticorrosive ability.In this paper,self-healing microcapsules of polyurea(PU)/melamine resin(MF)double shell were prepared by in-situ polymerization and interfacial polymerization with isocyanate as the core material.Scanning electron microscope was used to observe the microcapsule morphology.The structures of microcapsules prepared with different chain extenders were characterized by Fourier transform infrared spectroscopy.The micromanipulation system was used to loading–holding,loading–unloading and loading to rupture individual microcapsules,so as to explore the mechanical properties of microcapsules.The Young’s modulus corresponding to microcapsules was calculated by mathematical model fitting.The self-healing properties of microcapsule coating were characterized by optical microscope.The experimental results showed that the microcapsule shell prepared under optimized conditions had a complete morphology and good mechanical properties.The microcapsule was in the elastic deformation stage under small deformation,and the plastic deformation stage under large deformation.The Young’s modulus range of microcapsules was 9.29–14.51 MPa,and the corresponding Young’s modulus could be prepared by adjusting the process.The surface crack of the coating containing microcapsule could heal itself after48 h in a humid environment.

Tailoring the Microstructure and Mechanical Property of Mg-Zn Matrix Composite via the Addition of Al Element

The semi-solid stir casting method is adopted to prepare 10 wt%SiC_(p)/Mg-6Zn-0.5Ca-xAl(x=0,1,3 and 5 wt%)composites,and the microstructure evolution and mechanical property of composites with various Al content are investigated.The results show that the addition of 3 wt%Al improves the distribution of SiC_(p),whereas the SiC_(p) cluster occurs again with Al content greater than 3%.An abnormal phenomenon of twinning is observed in the cast composites in this work.The SiC_(p)/Mg-6Zn-0.5Ca composite possesses the highest twin content of~23%,for which tension twins(TTW)and compression twins(CTW)account for~19%and~3%,respectively.The CTW is only observed in ZXA600 composite.The addition of Al has an inhibiting effect for the generation and growth of twins.The content of twin decreases firstly and then increases with increase of Al content.The lowest twin content is obtained as Al increases to 3 wt%.It is found the existence of twin is detrimental to the mechanical property of composites.As-cast SiC_(p)/Mg-6Zn-0.5Ca-3Al composite with the lowest twin content exhibits the optimal mechanical property of yield strength,ultimate tensile strength and elongation for 100 MPa,188 MPa and 4.4%,respectively.The outstanding mechanical property is attributed to the uniform distribution of SiC_(p),the low twin content and the well-distributed fine second phases.

Efficient three-dimensional characterization of C/C composite reinforced with densely distributed fibers via X-ray phase-contrast microtomography

Carbon fiber(CF)/pyrolytic graphite(PG) composites are promising structural materials for molten salt reactors because of their superior performance.Due to the minor density difference between CF and PG, existing methods are impractical for efficient three-dimensional characterization of CF/PG composites.Therefore, in this study, a method based on in-line phasecontrast X-ray microtomography was developed to solve the aforementioned problem.Experimental results demonstrate that the method is suitable for comprehensive characterization of CF/PG composites.The relationship between the microporous defects and fiber orientations of such composites was also elucidated.The findings can be useful for improving the manufacturing process of CF/PG composites.

Megapixel X-ray ghost imaging with a binned detector in the object arm

At present,reconstruction of megapixel and high-fidelity images with few measurements is a major challenge for X-ray ghost imaging(XGI).The available strategies require massive measurements and reconstruct low-fidelity images of less than 300 × 300 pixels.Inspired by the concept of synthetic aperture radar,synthetic aperture XGI(SAXGI)integrated with compressive sensing is proposed to solve this problem with a binned detector in the object arm.Experimental results demonstrated that SAXGI can accurately reconstruct the 1200 × 1200 pixels image of a binary sample of tangled strands of tungsten fiber from 660 measurements.Accordingly,SAXGI is a promising solution for the practical application of XGI.