1 Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Key Laboratory for Advanced Energy Devices; Shaanxi Engineering Laboratory for Advanced Energy Technology; Institute for Advanced Energy Materials; School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, China; 2 State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Abstract Heat transfer is the foundation of freezing colloidal suspensions and a key factor for the interface movement. However, how the thermal conductivity of particles affects freezing microstructural evolution remains unknown. Here in this work, a mathematical model is built up to investigate thermal interactions among a growing particle layer, pulling speeds, and the freezing interface under a thermal gradient. Experiments are conducted to confirm the tendency predictions of the model. With the increase of pulling speeds, the drifting distance of the freezing interface increases and the time to finish drifting decreases. When the thermal conductivity of particles (k p) is smaller than that of the surrounding (k w), the freezing interface tends to go forward to the warm side. Contrarily, the freezing interface tends to go back to the cold side when the thermal conductivity of particles is larger than that of the surrounding (α =k p/k w >1). It originates from the shape of the local freezing interface: convex (α <1) or concave (α >1). These morphological changes in the local interface modify the premelting drag force F f. When α <1, F f decreases and the freezing morphology tends to be the frozen fringe. When α >1, F f increases and the freezing morphologies tend to be ice spears. These understandings of how the thermal conductivity of particles affect microstructural evolution may optimize the production of freeze-casting materials and their structural-functional properties.
Fund: Project supported by the National Key Research and Development Program of China (Grant Nos. 2018YFB1106003, 2017YFA0204800, and 2016YFA0202403), the National Natural Science Foundation of China (Grant No. 51901190), the China Postdoctoral Science Foundation (Grant No. 2020M673336), and the Peak Experience Program (2018) of Northwestern Polytechnical University, China.
Jia-Xue You(游家学), Yun-Han Zhang(张运涵), Zhi-Jun Wang(王志军), Jin-Cheng Wang(王锦程), and Sheng-Zhong Liu(刘生忠) Effects of heat transfer in a growing particle layer on microstructural evolution during solidification of colloidal suspensions 2021 Chin. Phys. B 30 028103
Altmetric calculates a score based on the online attention an article receives. Each coloured thread in the circle represents a different type of online attention. The number in the centre is the Altmetric score. Social media and mainstream news media are the main sources that calculate the score. Reference managers such as Mendeley are also tracked but do not contribute to the score. Older articles often score higher because they have had more time to get noticed. To account for this, Altmetric has included the context data for other articles of a similar age.
