In the study, two kinds of nanomaterials [hexagonal nitride nanopowder (hBN) and graphene nanosheets (GNs)] were chosen as resin fillers due to their similar structures and excellent thermal properties. The hBN/CE, GNs/CE and hBN/GNs/CE resin nanocomposites with different hBN and/or GNs contents were prepared by a solution blended method. The structures of hBN and GNs, thermal and electrical conductivities, and thermal properties of the hBN/CE, GNs/CE and hBN/GNs/CE resin nanocomposites were observed with different test instruments. The results showed that the hBN had an analogous structure with GNs. The addition of hBN and GNs in the CE resin made the fractural surfaces of the resin nanocomposites rougher and more fold than that of the pure CE resin. For thermal conductivity, the synergistic effect of the hBN and GNs in the CE resin nanocomposites was better than the hBN or GNs filling the CE resin alone. The thermal diffusivity of GNs was good, meanwhile, the electrical conductivity of GNs was excellent as well. It indicated that the electrical conductivity of the GNs/CE resin nanocomposites was higher than that of the hBN/GNs/CE resin nanocomposites at a given volume contents. The data calculated from the TGA test was roughly corresponding to the experimental hBN and GNs volume content of the hBN/GNs/CE resin nanocomposites.
Cuicui Wang,Yuchen Geng,Jie Zhang,Jing Ren,Maolian Guo,Huazhang Zhao,Jianfeng Li
A superhydrophilic C-hBN layer was coated on PVDF membrane via PVA-CNT crosslinking. • The membrane has notable flux increase and rapid PMS activation for fouling control. • Enhanced flux was due to the increased heat unitization efficiency of C-hBN layer. • PMS was priorly adsorbed to generate singlet oxygen for selective organic removal. • The membrane is able to reduce heat and mass transfer resistance simultaneously. How to get membranes with high water flux and sustainable long-term operation remains a key challenge for membrane distillation (MD) in treating high-salinity organic wastewater. Herein, a novel carbon-doped hexagonal boron nitride (C-hBN) catalytic membrane was developed to boost water flux and enable in-situ cleaning for membrane distillation via selective peroxymonosulfate (PMS) oxidization. Experimental results showed that the membrane achieved a 28.3% increase in water flux and an 83.8% reduction in flux decline rate. The numerical COMSOL simulations and membrane surface calculation using heat and mass transfer equations revealed that the enhanced flux was mainly attributed to the increased heat unitization efficiency during water evaporation in superhydrophilic C-hBN layer. Density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) indicated that C-hBN exhibited a strong interaction with PMS, and 1 O 2 was selectively generated, leading to the efficient organic removal in high salinity environment. This study offers a viable pathway to engineer high-performance, in-situ cleaning membranes for sustainable operation of membrane distillation. Download: Download high-res image (194KB) Download: Download full-size image
Muhammad Awais,Xiangrong Chen,Zelin Hong,Qilong Wang,Yiwen Shi,Fan-Bo Meng,Chao Dai,Ashish Paramane
Epoxy (EP) resin insulations are widely used in electronic devices and power systems . They are gradually finding their way as winding insulation material for medium frequency transformers (MFT) due to their attractive insulating and adhesive properties along with low cost and easy processing. However, their dielectric insulation properties are compromised at high frequencies and high temperatures due to poor thermal properties. In this context, the surface-treated hexagonal boron nitride (h-BN) micro fillers and core-shell TiO 2 @SiO 2 nanofillers are doped in epoxy (EP) to enhance their thermal and electrical insulation properties under high frequencies and high temperatures. Results reveal that the thermal conductivity of the EP increases continually, whereas the electrical breakdown strength is reduced above the threshold content of micro/nano fillers. Particularly, the micro h-BN addition is beneficial for thermal conductivity enhancement, whereas the core-shell structure of TiO 2 @SiO 2 improves the electrical insulation properties of the EP. The multi-layer core model is used to explain the dynamics of the fillers. The homogeneous dispersion and optimal content of suitable micro-nano fillers can produce efficient EP composites as the electrical insulation for medium frequency transformers.
Jun Zhao,Ziliang Rui,Zhiwei Hu,Zhen Shangguan,Shuai Yin,Hao Peng
In battery thermal management (BTM), flexible phase change materials (FPCMs) emerge as highly promising substances, owing to their simple installment and low contact thermal resistance. However, FPCMs based on high thermal conductivity fillers and polymers always suffer from the enduring challenges of poor high-temperature resistance and poor filler-matrix compatibility. To solve these problems, a novel strategy is reported in this work, wherein FPCMs with excellent filler-matrix compatibility and satisfactory high-temperature resistance are synthesized by two steps: functionalizing the hexagonal boron nitride (hBN) surface and inducing the inter crosslinking between Styrene-Butadiene-Styrene(SBS) and Low-density polyethylene(LDPE). Vinyltrimethoxysilane (VTMS) molecules were introduced on the surface of raw hBN by hydroxylation and silanization surface modification to improve the compatibility of hBN with the matrix. Concluding from the results, the addition of 6.7 wt% LDPE doubled the high-temperature resistance of FPCMs, enabling them to maintain their structural integrity even at 200 °C for 1 h. The prepared FPCMs also exhibited higher thermal conductivity (increased by 20.5 %), low leakage rate (<0.6 wt% after 70 heating–cooling cycles), high enthalpy (122 J g −1 ), and strong adhesion (>0.1 MPa), etc. In terms of BTM performance, the FPCMs-based passive cooling BTM presents remarkable temperature control capabilities (maximum temperature reduction by 16.3 ℃) and uniform temperature performance (maximum temperature difference < 2.5 ℃). Collectively, this work will provide a promising approach for the fabrication of high-performance FPCMs in BTM and other thermal management applications for electronic devices.
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