High thermal conductivity polymer composites at low filler loading are of considerable interest because of their wide range of applications. The construction of three-dimensional (3D) interconnected ...networks can offer a high-efficiency increase for the thermal conductivity of polymer composites. In this work, a facile and scalable method to prepare graphene foam (GF)
via
sacrificial commercial polyurethane (PU) sponge templates was developed. Highly thermally conductive composites were then prepared by impregnating epoxy resin into the GF structure. An ultrahigh thermal conductivity of 8.04 W m
−1
K
−1
was obtained at a low graphene loading of 6.8 wt%, which corresponds to a thermal conductivity enhancement of about 4473% compared to neat epoxy. This strategy provides a facile, low-cost and scalable method to construct a 3D filler network for high-performance composites with potential to be used in advanced electronic packaging.
A facile, low-cost and scalable method is developed to construct three-dimensional thermal transport channels like highways in polymer composites.
AD is the abbreviation for Alzheimer's Disease, which is a neurodegenerative disorder that features progressive dysfunction in cognition. Previous research has reported that mitophagy impairment and ...mitochondrial dysfunction have been crucial factors in the AD's pathogenesis. More recently, literature has emerged which offers findings suggesting that the nicotinamide adenine dinucleotide (short for NAD+) augmentation eliminates the defective mitochondria and restores mitophagy. Meanwhile, as an enzyme which is rate-limiting, the Nicotinamide phosphoribosyltransferase, or NAMPT, is part of the salvage pathway of NAD+ synthesis. Therefore, the aim of the research project has been to produce proof for how the NAMPT-NAD +-silent information-regulated transcription factors1/3 (short for SIRT1/3) axis function in mediating mitophagy in APP/PS1 mice aged six months. The results revealed that the NAMPT-NAD+-SIRT1/3 axis in the APP/PS1 mice's hippocampus was considerably declined. Surprisingly, P7C3 (an NAMPT activator) noticeably promoted the NAD+-SIRT1/3 axis, improved mitochondrial structure and function, enhanced mitophagy activity along with the ability of learning and memory. While FK866 (an NAMPT inhibitor) reversed the decreased NAD+-SIRT1/3 axis, and even exacerbated Aβ plaque deposition level in the APP/PS1 mice's hippocampus. The findings observed in this study indicate two main points: avoiding downregulation of the NAMPT activity can prevent AD-related mitophagy impairment; on the other hand, NAMPT characterizes a potential therapeutic intervention regarding AD pathogenesis.
•FK866, an inhibitor of NAMPT, could exacerbate mitochondrial dysfunction and even Aβ plaque loads in the hippocampus of APP/PS1mice.•P7C3, an activator of NAMPT, could increase mitophagy activity in the hippocampus, and improve cognitive impairment in APP/PS1 mice.•Targeting NAMPT may serve as an important strategy for preventing AD.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Display omitted
•Size-dependent assembly of graphene sheets constructs vertical heat pathways across the graphene paper.•GHGP exhibits both high through-plane thermal conductivity and good ...compressibility.•The cooling efficiency of GHGP was 2.2 times that of the state-of-the-art commercial TIM.
Graphene-based papers have recently triggered considerable interests in developing the application as thermal interface materials (TIMs) for addressing the interfacial heat transfer issue, but their low through-plane thermal conductivity (κ⊥), resulting from the layer-by-layer stacked architecture, limits the direct use as TIMs. Although various hybrid graphene papers prepared by combining the graphene sheets and the thermally conductive insertions have been proposed to solve this problem, achieving a satisfactory κ⊥ higher than that of commercial TIMs (>5 W m−1 K−1) remains challenging. Here, a strategy aimed at the construction of heat pathways along the through-plane direction inside the graphene paper for achieving a high κ⊥ was demonstrated through the simultaneous filtration of graphene sheets with two different lateral sizes. The as-prepared graphene paper presented a hierarchical structure composed of loosely stacked horizontal layers formed by large graphene sheets, intercalated by a random arrangement of small graphene sheets. Due to the heat pathways formed by small graphene sheets along the through-plane direction, the hierarchically structured graphene paper exhibited an improved κ⊥ as high as 12.6 W m−1 K−1 after a common graphitization post-treatment. In the practical test, our proposed paper as an all-graphene TIM achieved an enhancement in cooling efficiency of ≈ 2.2 times compared to that of the state-of-the-art TIM, demonstrating its superior performance to meet the ever-increasing heat dissipation requirement.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Abstract The challenges associated with heat dissipation in high‐power electronic devices used in communication, new energy, and aerospace equipment have spurred an urgent need for high‐performance ...thermal interface materials (TIMs) to establish efficient heat transfer pathways from the heater (chip) to heat sinks. Recently, emerging 2D materials, such as graphene and boron nitride, renowned for their ultrahigh basal‐plane thermal conductivity and the capacity to facilitate cross‐scale, multi‐morphic structural design, have found widespread use as thermal fillers in the production of high‐performance TIMs. To deepen the understanding of 2D material‐based TIMs, this review focuses primarily on graphene and boron nitride‐based TIMs, exploring their structures, properties, and applications. Building on this foundation, the developmental history of these TIMs is emphasized and a detailed analysis of critical challenges and potential solutions is provided. Additionally, the preparation and application of some other novel 2D materials‐based TIMs are briefly introduced, aiming to offer constructive guidance for the future development of high‐performance TIMs.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•Treadmill exercise alleviates Aβ burden and altered Aβ metabolism in APP/PS1 mice.•Treadmill exercise alleviates hippocampal ER stress in APP/PS1 mice.•Treadmill exercise down-regulates ...PERK/eIF2α/BACE1 pathway in APP/PS1 mice.•Treadmill exercise down-regulates PERK/eIF2α/ATF4/PS1 pathway in APP/PS1 mice.
The accumulation of β-amyloid protein (Aβ) in the brain is one of major pathological hallmarks of Alzheimer's disease (AD). Overactivation of the unfolded protein response (UPR) signaling has been reported to lead to β-amyloidogenesis. The current study aimed to investigate the effects of treadmill exercise on UPR signaling and the Aβ production and to demonstrate whether exercise-induced Aβ reduction was associated with changes in UPR signaling. Three-month old male APP/PS1 transgenic and wild-type mice were subjected to treadmill exercise for 3 months. At the end of exercise (6 months old), the levels of Aβ plaques and soluble forms of Aβ, and proteins involve in the unfolded protein response (UPR) were analyzed in the hippocampus. Three months of treadmill exercise resulted in a robust reduction in Aβ plaques and soluble forms of Aβ in the hippocampus of APP/PS1 mice. This was accompanied by a significant decrease in β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and presenilin-1 (PS1) expression. Meanwhile, we found that treadmill exercise down-regulated the expression of GRP78 and inhibited activation of PERK, eIF2α, and ATF4, reflecting the involvement of the UPR signaling. Overall, our findings suggest that treadmill exercise may suppresse the overactivation of the UPR signaling as well as inhibit the amyloidogenic pathway in APP/PS1 mice, thus may serve as an useful approach for the prevention and treatment of AD.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Phase change materials with considerable heat effect during phase change have been regarded as one of the most promising candidates for latent thermal energy storage and thermal management. Although ...intensive efforts have been dedicated to the high-efficiency application, challenges remain in enhancing the thermal response due to their intrinsically low thermal conductivity. Here, continuous diamond-carbon nanotube foams are designed and fabricated as thermal conductive reinforcement. The unique diamond foam with extremely high thermal conductivity act as the “main channel” for thermal flow transportation, and the directly-grown, well-distributed carbon nanotube networks plays role of the “second heat channel”. Benefiting from this stable hierarchical structure, thermal conductivity of the phase change composite has been enhanced to 9.72 W m−1 K−1 from 0.105 W m−1 K−1 of paraffin matrix, representing one of the highest enhancement ever-reported. Besides this conceptual advance, we discover that the hybrid structure considerably suppresses subcooling, a common problem that causes a much lower crystallization temperature than the melting temperature of many phase change materials. The special design promises to be one of the most efficient solutions for thermal response promotion of phase change materials and their extensive application.
Display omitted
•A continuous hierarchical thermal conductive reinforcement based on diamond and directly-grown carbon nanotubes was proposed and developed.•Thermal conductivity and heat charging rate of the composites were markedly promoted.•Good phase change reversibility and thermal stability were achieved.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
With the explosive development in integration of electronic components and the increasing complexity of packaging systems, semiconductor chips own extremely high operation temperatures given by the ...horrible heat accumulation attributed to the drastically increasing power density. Therefore, highly efficient heat dissipation with the help of rationally designed thermal interface materials (TIMs) is the key to maintaining the device performance and lifespan. Graphene exhibits an ultrahigh intrinsic thermal conductivity, which has attracted a large amount of academic interest due to its significant potential for developing high-performance TIMs. In this tutorial review, we summarize the recent advances in graphene-based TIMs, especially emphasizing the determinate effects of graphene structure and alignment in enhancing the heat transfer capacity of corresponding samples, with detailed discussion in the superiorities and limitations of various graphene skeletons. In addition, we also provide prospects for the challenges and opportunities in the future development of graphene-based TIMs.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
AbstractThe applicability of microwave-assisted ball milling for the treatment of p-nitrophenol (PNP) was investigated in this study. The degradation process of PNP was studied by using UV-vis ...(ultraviolet-visible) spectra, total organic carbon (TOC), fluorescence intensities, electroconductivity, and X-ray diffraction (XRD). PNP was degraded 99.1% after microwave-assisted ball milling for only 15 min at pH 3 when the initial concentration of PNP was 300 mg/L. When the pH value of solution was 3, PNP can be mineralized completely in 12 min by microwave-assisted ball milling and adding hydrogen peroxide. The new high-activity nanoscale zero-valent iron (NZVI) was produced constantly in the process of stirring, collision, and spalling, preventing nanoparticles from reuniting. Further, the hydroxyl radical generated in the coupling effect of microwave and mechanical force also improved the reaction rate.
The rapid development of highly integrated microelectronic devices causes urgent demands for advanced thermally conductive adhesives (TCAs) to solve the interfacial heat‐transfer issue. Due to their ...natural 2D structure and isotropic thermal conductivity, metal nanoflakes are promising fillers blended with polymer to develop high‐performance TCAs. However, achieving corresponding TCAs with thermal conductivity over 10 W m−1 K−1 at filler content below 30 vol% remains challenging so far. This longstanding bottleneck is mainly attributed to the fact that most current metal nanoflakes are prepared by “bottom‐up” processes (e.g., solution‐based chemical synthesis) and inevitably contain lattice defects or impurities, resulting in lower intrinsic thermal conductivities, only 20–65% of the theoretical value. Here, a “top‐down” strategy by splitting highly purified Ag foil with nanoscale thickness is adopted to prepare 2D Ag nanoflakes with an intrinsic thermal conductivity of 398.2 W m−1 K−1, reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibits a thermal conductivity of 15.1 W m−1 K−1 at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat‐transfer efficiency of the Ag/epoxy achieves ≈1.4 times that of the state‐of‐the‐art commercial TCA.
2D Ag nanoflakes with intrinsic thermal conductivity (398.2 W m−1 K−1) close to theoretical value are prepared using the “top‐down” method. After directly blending with epoxy (18.6 vol%) without any complex surface modification, hybridization, and structural design, the interfacial heat‐transfer efficiency of the obtained gap‐filling adhesive is ≈1.4 times that of the state‐of‐the‐art counterpart.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Combining the advantages of high thermal conductivities and low graphene contents to fabricate polymer composites for applications in thermal management is still a great challenge due to the high ...defect degree of exfoliated graphene, the poor orientation of graphene in polymer matrices, and the horrible phonon scattering between graphene/graphene and graphene/polymer interfaces. Herein, mesoplasma chemical vapor deposition (CVD) technology was successfully employed to synthesize vertically aligned graphene nanowalls (GNWs), which are covalently bonded by high-quality CVD graphene nanosheets. The unique architecture leads to an excellent thermal enhancement capacity of the GNWs, and a corresponding composite film with a matrix of polyvinylidene fluoride (PVDF) presented a high through-plane thermal conductivity of 12.8 ± 0.77 W m
−1
K
−1
at a low filler content of 4.0 wt%, resulting in a thermal conductivity enhancement per 1 wt% graphene loading of 1659, which is far superior to that using conventional graphene structures as thermally conductive pathways. In addition, this composite exhibited an excellent capability in cooling a high-power light-emitting diode (LED) device under real application conditions. Our finding provides a new route to prepare high-performance thermal management materials with low filler loadings
via
the rational design of the microstructures/interfaces of graphene skeletons.
We report a unique graphene architecture combining the advantages of highly vertical alignments and covalently bonded interfaces to improve the heat transfer ability of PVDF, achieving a thermal conductivity enhancement per 1 wt% filler loading of up to 1659.
