A binder-free ice template method for vertically aligned 3D boron nitride polymer composites towards thermal management.

Hexagonal boron nitride (BN) is an attractive filler candidate for thermal interface materials, but the thermal conductivity enhancement is limited by the anisotropic thermal conductivity of BN and disordered thermal pathways in the polymer matrix. Herein, a facile and economic ice template method is proposed, wherein BN modified by tannic acid (BN-TA) directly self-assemble to form vertically aligned nacre-mimetic scaffold without additional binders and post-treatment. The effects of the BN slurry concentration and the ratio of BN/TA on three-dimensional (3D) skeleton morphology are fully investigated. The corresponding polydimethylsiloxane (PDMS) composite via vacuum-impregnation achieves a high through-plane thermal conductivity of 3.8 W/mK at a low filler loading of 18.7 vol%, which is 2433% and 100% higher than that of pristine PDMS and the PDMS composite with randomly distributed BN-TA, respectively. The finite element analysis results theoretically demonstrate the superiority of the highly longitudinally ordered 3D BN-TA skeleton in axial heat transfer. Additionally, 3D BN-TA/PDMS exhibits excellent practical heat dissipation capability, lower thermal expansion coefficient, and enhanced mechanical properties. This strategy offers an anticipated perspective for developing high-performance thermal interface materials to address the thermal challenges of modern electronics.

Enhancing computing skills of low-achieving students via e-learning: a design experiment of Web-based, problem-based learning and self-regulated learning.

A design experiment was conducted applying Web-based problem-based learning (PBL), self-regulated learning (SRL), or their combination to help low-achieving students improve their skills of deploying application software in a compulsory course at a vocational school in Taiwan. The effects were encouraging and mostly positive. However, students' inertia to change routines of learning inherited from a culture of taking standard tests found in e-learning practice is quite common. A teacher's awareness of these changes and associated resistance may increase likelihood of e-learning success for future trials. Some modifications of the design are thus suggested for the next round of the experiment.