Search

The mechanical properties especially the compression performance are very important for thermal interface materials (TIMs) to mitigate warpage failure caused by stress concentration and reduce contact resistance in practical applications. However, high thermal conductivity and excellent mechanical properties are generally incompatible in traditional TIMs. Herein, we fabricate a high-performance carbon fiber-based TIM by using an extrusion method based on the flow shearing effect. The vertically oriented composite shows a through-plane thermal conductivity up to 18.5 W·m−1·K−1 at 20 wt% carbon fiber content, which is 92.7 times that of pure matrix and 6.3 times that of the random structure. Moreover, the as-prepared material exhibits low hardness of 56 (Shore 00) and outstanding elastic compression performance of 51.4% compression under a pressure of 45 psi. These excellent properties are primarily attributed to the high orientation of the carbon fibers (CFs), thereby establishing a direct and effective thermal conductivity path in the vertical direction. In addition, the synergistic effect of carbon fibers and alumina particles is also beneficial for building thermal conduction pathways. Our work provides an insight to further research in fabricating high-performance flexible TIMs as a promising candidate for applying in advanced thermal management fields. • The composite achieves a thermal conductivity of 18.54 W·m−1·K−1. • The composites exhibit good elastic compliance under high through-plane thermal conductivity. • The synergistic effect of carbon fibers and alumina promotes the enhancement of thermal conductivity [ABSTRACT FROM AUTHOR]

• Thermal transport through SEI of Li-ion batteries was studied using MD simulations. • Three representative inorganic components of SEI were considered. • Impact of structural properties and temperatures were investigated. • Thermal conductivity of amorphous compounds is closely related to the components. • Results provide valuable insights for the design of electrolytes and SEI. The thermal behavior during operation of Lithium-ion batteries (LIBs) is widely concerned with respect to their electrochemical performance and safety. The solid electrolyte interphase (SEI) is a critical layer formed during electrochemical reactions in LIBs. A thorough understanding of SEI's thermal transport properties is essential to identify limitations within the internal heat transfer of LIBs. In this work, a computational study of the thermal transport through SEI was performed based on classical molecular dynamics (MD) simulations. Three representative inorganic components of SEI, namely Li 2 CO 3 , Li 2 O and LiF, were explored. First, the force fields were evaluated for accurate MD simulations. Subsequently, the impact of structural properties and temperatures on the thermal conductivities of SEI were investigated, followed by discussion on radial distribution functions and vibrational density of states. It was found that the comparison of thermal conductivity of the ordered crystals is Li 2 O > LiF > Li 2 CO 3. As temperature increases, the thermal conductivity of inorganic components decreases significantly. Additionally, it was discovered that the thermal conductivity of amorphous compounds is notably lower than that of ideal crystals and is closely related to the molar ratio of inorganic components. The results of this work can help understand the thermal transport properties of SEI and offer valuable insights for the design of electrolytes and SEI toward improving the thermal safety performance of LIBs. [ABSTRACT FROM AUTHOR]

The demand for biopolymer-based green packaging has attracted growing attention because of its outstanding properties and consistency with clean environmental principle, unfortunately, its slow crystallization rate and narrow processing window are challenging. Inspired by combined functions in nanocellulose-based conductive hybrids, this work developed high-performance polylactic acid (PLA) composites using conductive cellulose nanofiber (CNFene). Interestingly, CNFene has multiple functions as highly graphitized carbon and abundant hydroxyl groups, delivering stimulating properties to PLA composites. As nucleating agents, 3 wt% CNFene has a carbon layer on the surface combined with a hydrogen bonding network synergistically enhancing the tensile and crystallization properties of PLA-C3, with a tensile strength of ∼ 53.7 MPa, crystallinity of ∼ 33.9 %, and 6.6 °C decrease in the cold crystallization temperature. Additionally, the compatibility between CNFene and PLA can form a multi-level "reinforcement" network structure, further improving thermal stability and barrier properties. The resultant PLA-C3 showed higher thermal decomposition onset temperature (T 0), wider melt-processing window (197.6 °C) and extremely lower overall migration levels in ethanol (68.6 μg/kg) and isooctane (16.3 μg/kg), due to that improved interaction between CNFene and PLA positively affects crystallization ability and kinetic/mechanism of PLA to meet the requirements of industrial and green biopackaging applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-based copolyesters involving 2,6-pyridine structure with isosorbide as a second diol were synthesized. • Incorporation of isosorbide enhanced thermal properties of the pyridine-based polyesters. • Isosorbide significantly improved the mechanical properties of the pyridine-based polyesters. • The copolyesters showed high gas barrier properties. Driven by sustainable development and low-carbon policies, many high-performance bio-based polyesters are produced. Our previous work uncovered the high barrier but low thermal and mechanical properties of a renewable 2,6-pyridinedicarboxylic-based polyester. In this article, the copolymerization with isosorbide as a second diol is considered to ameliorate these properties. The chemical structures of copolyesters and the successful introduction of isosorbide were confirmed by FT-IR and 1H NMR. The 1H NMR spectra also allowed the calculation of isosorbide ratio in polymers. GPC revealed a decrease in molar masses with the increase of isosorbide ratio. Contact angle and water/gas permeation measurements disclosed an increase in hydrophilicity and water/gas permeability with the introduction of isosorbide. TGA and DSC analyses demonstrated an enhancement in thermal stability: 8 mol% of isosorbide to the total diol ratio increased the 5 % weight loss temperature (T 5%) by 9 °C, the maximum weight loss temperature (T max) by 8 °C and the glass transition temperature (T g) by 6 °C. DSC investigation showed that the incorporation of isosorbide significantly influenced the crystallization properties, particularly from the melt, by decreasing the crystallinity. XRD patterns indicated the presence of similar crystallization units in these polyesters. Tensile test revealed that incorporating 8 mol% of isosorbide greatly improved the mechanical properties by doubling Young's modulus and tripling the strength at break. Such enhancement in thermal and mechanical properties is important for high gas barrier food packaging applications of these polyesters. [ABSTRACT FROM AUTHOR]