Polypyrrole coated carbon nanotube aerogel composite phase change materials with enhanced thermal conductivity, high solar-/electro- thermal energy conversion and storage.

Phase change materials (PCMs) have been widely investigated as promising thermal management materials due to their high thermal storage capacity, satisfactory heat transfer rate and multi-responsive energy conversion and storage characteristics. In this work, a shape-stabilized solar-/electro- responsive thermal energy capture and storage system is proposed involving polypyrrole (PPy)-deposited carbon nanotubes (CNT) heterogeneous porous aerogel as a supporting matrix and the paraffin wax (PW) as a PCM. The composite PCMs obtained via integration of PW into aerogel supports present a relatively high thermal storage density of 160.9 J/g and outstanding phase transition stability even after 100 heating-cooling cycles. Furthermore, great enhancement of thermal conductivity (0.64 W/m-1·K-1, 2.56 times that of PW) is achieved in the composite PCMs by inducing PPy coating as a binder in the gap between CNTs. The mechanism of heat transport enhancement is explored by molecular dynamics simulation. It concludes that the in-situ polymerization of PPy through the vapor deposition method on the CNT aerogels effectively builds additional thermal transfer channels and enhances the heat transport between CNT by coordinating the carbon atom vibration. Herein, this reported stratagem may shed light on preparing composite PCMs with high thermal conductivity and multi-energy utilization functions.

Segmentation of Cerebrovascular Anatomy from TOF-MRA Using Length-Strained Enhancement and Random Walker.

Cerebrovascular rupture can cause a severe stroke. Three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) is a common method of obtaining vascular information. This work proposes a fully automated segmentation method for extracting the vascular anatomy from TOF-MRA. The steps of the method are as follows. First, the brain is extracted on the basis of regional growth and path planning. Next, the brain's highlighted connected area is explored to obtain seed point information, and the Hessian matrix is used to enhance the contrast of image. Finally, a random walker combined with seed points and enhanced images is used to complete vascular anatomy segmentation. The method is tested using 12 sets of data and compared with two traditional vascular segmentation methods. Results show that the described method obtains an average Dice coefficient of 90.68%, and better results were obtained in comparison with the traditional methods.

Effect of the loading amount and arrangement of iodine chains on the interfacial thermal transport of carbon nanotubes: a molecular dynamics study.

Due to their excellent electrical and thermal conductivity properties, the nano-scale characteristics of carbon nanotubes (CNTs) are expected to be suitable for very large-scale integrated circuits and for next-generation micro interconnected devices. Consequently, CNT-metal composite materials have been widely researched, and have shown excellent performance in terms of thermal conductivity, electrical conductivity, thermal expansion, and adaptability to microelectronic devices. However, there are few studies on halogen-CNT composite materials with characteristics similar to CNT-metal composites, including regarding the remarkable electrical compatibility of the halogen and CNT and the large number of low-frequency phonons that are beneficial for thermal transport. In this work, iodine chains were considered to explore the halogen effect on CNTs. Variation of the interfacial thermal conductance of CNTs as a function of the iodine chains loading amount and arrangement was explored by a molecular dynamics method. The heat transfer mechanism was further analyzed based on the phonon state difference. This research is expected to provide a new pathway for the application of CNT composite materials in the field of next-generation microelectronics.