High-performance thermal management materials are essential in miniaturized, highly integrated, and high-power modern electronics for heat dissipation. In this context, the large interface thermal ...resistance (ITR) that occurs between fillers and the organic matrix in polymer-based nanocomposites greatly limits their thermal conductive performance. Herein, through-plane direction aligned three-dimensional (3D) MXene/silver (Ag) aerogels are designed as heat transferring skeletons for epoxy nanocomposites. Ag nanoparticles (NPs) were in situ decorated on exfoliated MXene nanosheets to ensure good contact, and subsequent welding of ice-templated MXene/Ag nanofillers at low temperature of ∼200 °C reduced contact resistance between individual MXene sheets. Monte Carlo simulations suggest that thermal interficial resistance (R 0) of the MXene/Ag–epoxy nanocomposite was 4.5 × 10–7 m2 W–1 K–1, which was less than that of the MXene–epoxy nanocomposite (R c = 5.2 × 10–7 m2 W–1 K–1). Furthermore, a large-scale atomic/molecular massively parallel simulator was employed to calculate the interfacial resistance. It was found that R MXene = 2.4 × 10–9 m2 K W–1, and R MXene‑Ag = 2.0 ×10–9 m2 K W–1, respectively, indicating that the Ag NP enhanced the interfacial heat transport. At a relatively low loading of 15.1 vol %, through-plane thermal conductivity reached a value as high as 2.65 W m–1 K–1, which is 1225 % higher than that of pure epoxy resin. Furthermore, MXene/Ag–epoxy nanocomposite film exhibits an impressive thermal conductive property when applied on a Millet 8 and Dell computer for heat dissipation.
Conventional polymer composites normally suffer from undesired thermal conductivity enhancement which has hampered the development of modern electronics as they face a stricter heat dissipating ...requirement. It is still challenging to achieve satisfactory thermal conductivity enhancement with reasonable mechanical properties. Herein, we present a three-dimensional (3D), lightweight, and mechanically strong boron nitride (BN)-silicon carbide (SiC) skeleton with aligned thermal pathways via the combination of ice-templated assembly and high-temperature sintering. The sintering has introduced atomic-level coupling at the BN-SiC junction which contributes to efficient phonon transport via the newly formed borosilicate glass BC x N3–x (0 ≤ x ≤ 3) and SiC x N4–x (0 ≤ x ≤ 4) phases, leading to much lower interfacial thermal resistance. Thus, the obtained BN-SiC skeleton shows satisfactory thermal performance. The prepared 3D BN-SiC/polydimethylsiloxane (PDMS) composites exhibit a maximum through-plane thermal conductivity of 3.87 W·m–1·K–1 at a filler loading of only 8.35 vol %. The thermal conductivity enhancement efficiency reaches 220% per 1 vol % filler when compared to pure PDMS matrix, superior to other reported BN skeleton-based composites. The feature of our strategy is to allow the oriented three-dimensional skeleton to be strongly bonded by a sintered ceramic phase instead of polymer-like adhesive, namely, to improve the intrinsic thermal conductivity of the skeleton to the greatest extent. This strategy can be applied to develop novel thermal management materials that are lightweight and mechanically tough that rapidly transfer heat. It represents a new avenue to addressing the heat challenges in traditional electronic products.
The thermal properties of body-centered tetragonal C4 (bct-C4), a new allotrope of carbon, were investigated using molecular dynamics (MD) simulations. The calculations gave a high and anisotropic ...thermal conductivity that is the first of its kind. The cross-plane thermal conductivity is 1209W/(mK) at room temperature, which is even higher than that of diamond. The thermal conductivity decreases as the temperature increases from 80 to 400K. The density of states of bct-C4 was analyzed, which has a prominent peak at 36THz. The relaxation times were calculated by fitting a heat flux autocorrelation function. The results showed that the acoustic phonons play the dominant role in the heat conduction, with a contribution of more than 99%. The relaxation times decrease with increasing temperature, as does the contribution of the acoustic phonons. Finally, the thermal conductivity based on lattice dynamics agreed well with that from the MD method, with which the group velocity and mean free path were deduced. This outstanding thermal property makes bct-C4 a promising substitute for diamond, especially as thermal interface materials in microelectronic packaging.
Hydrogenated graphene (HG)/hexagonal boron nitride (h-BN) heterobilayer is an ideal structure for the high-performance field effect transistor. In this paper, the carrier mobilities of HG/h-BN ...heterobilayer are investigated based on the first-principles calculations by considering the influence of stacking pattern between HG and h-BN, hydrogen coverage and hydrogenation pattern. With the same hydrogenation pattern, the electron mobility monotonously decreases when the hydrogen coverage increases. With the same hydrogen coverage, different hydrogenation patterns lead to significant changes of mobility. For 25% and 6.25% HGs, the μ
e
(ΓK) of 25% pattern I is 8985.85 cm
2
/(V s) and of 6.25% pattern I is 23,470.98 cm
2
/(V s), which are much higher than other patterns. Meanwhile, the h-BN substrate affects the hole mobilities significantly, but it has limit influences on the electron mobilities. The hole mobilities of stacking patterns I and II are close to that of HG monolayer, but much lower than that of stacking patterns III and IV.
Highlights
The flexible single-walled carbon nanotube/titanium carbide composite films exhibit excellent thermoelectric (TE), high-temperature stable and flame-retardant properties.
The assembled TE ...device achieves an ultrafast fire warning response time of ~ 0.1 s with a threshold voltage of 1 mV.
The fire warning device demonstrates exceptional repeatability and long-term stability.
The designed intelligent system is promising for next-generation self-powered remote IoT fire warning applications.
Fire warning is vital to human life, economy and ecology. However, the development of effective warning systems faces great challenges of fast response, adjustable threshold and remote detecting. Here, we propose an intelligent self-powered remote IoT fire warning system, by employing single-walled carbon nanotube/titanium carbide thermoelectric composite films. The flexible films, prepared by a convenient solution mixing, display p-type characteristic with excellent high-temperature stability, flame retardancy and TE (power factor of 239.7 ± 15.8 μW m
−1
K
−2
) performances. The comprehensive morphology and structural analyses shed light on the underlying mechanisms. And the assembled TE devices (TEDs) exhibit fast fire warning with adjustable warning threshold voltages (1–10 mV). Excitingly, an ultrafast fire warning response time of ~ 0.1 s at 1 mV threshold voltage is achieved, rivaling many state-of-the-art systems. Furthermore, TE fire warning systems reveal outstanding stability after 50 repeated cycles and desired durability even undergoing 180 days of air exposure. Finally, a TED-based wireless intelligent fire warning system has been developed by coupling an amplifier, analog-to-digital converter and Bluetooth module. By combining TE characteristics, high-temperature stability and flame retardancy with wireless IoT signal transmission, TE-based hybrid system developed here is promising for next-generation self-powered remote IoT fire warning applications.
The spectral phonon properties in defected graphene have been unclear due to the lack of advanced techniques for predicting the phonon-defect scattering rate without fitting parameters. Taking ...advantage of the extended phonon normal mode analysis, we obtained the spectral phonon relaxation time and mean free path (MFP) in defected graphene and studied the impacts of three common types of defects: Stone-Thrower-Wales (STW) defect, double vacancy (DV), and monovacancy (MV). The phonon-STW defect scattering rate is found to have no significant frequency dependence, and as a result, the relative contribution of long-wavelength phonons sharply decreases. In contrast, the phonon scattering by DVs or MVs exhibits a frequency dependence of (ProQuest: Formulae and/or non-USASCII text omitted) ~ omega super(1.1-1.3) except for a few long-wavelength phonons, revisiting the traditionally used ~ omega super(4) dependence. We note that although MV-defected graphene has the lowest thermal conductivity as compared to the other two defected graphene samples at the same defect concentration, it has a portion of phonons with the longest MFP. The contribution from the long-MFP and long-wavelength phonons does not decrease much as the vacancy concentration increases. STW defect and MV block more out-of-plane modes than in-plane modes, while DV has less bias for which mode to block. As the MV concentration increases from 0 to 1.1%, the relative contribution from out-of-plane modes decreases from 30% to 18%, while that of the transverse acoustic mode remains at around 30%. These findings of spectral phonon properties can provide more insight than the effective properties and benefit the prospective phononic engineering.
Graphite-related materials are commonly used as fillers in polymers to prepare thermal interface materials (TIMs) with high thermal conductivity. The thermal contact resistance (TCR) between graphite ...and polymer is a crucial factor affecting the thermal conductivity of TIMs. However, reducing the TCR is challenging due to the highly stable surface of graphite. Here, we propose a plasma-assisted strategy to form a self-assembled monolayer (SAM) on the surface of graphite films to reduce the TCR of the graphite film/silicone systems. A series of measurements, including the contact angle and Fourier infrared spectrum, confirm the formation of SAM. Using the non-contact photothermal technique, we investigate the effects of plasma bombardment times and powers on the TCR. Under 30 min bombardment, the TCR between modified graphite and silicone is reduced by almost one order of magnitude than the original one. Atomic-scale molecular dynamics simulations further confirm the effectiveness of SAM in reducing the TCR. This plasma-assisted SAM strategy can help graphite-based TIMs to provide better thermal performance to meet the requirements of future high-power devices.
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With the development of microprocessors toward higher power, larger chip, and higher frequency, heat dissipation is one of the central issues. Thermal interface materials (TIMs), which are used ...between the chip and the heat spreader and between the heat spreader and the heat sink, play an increasingly important role in microprocessor cooling. Currently, most of the research has primarily dealt with understanding the thermal conductivity of TIMs. For thermal design, elastic compliance is also important because excellent elastic compliance can reduce thermal contact resistance and relieve the warpage failure caused by stress concentration. However, high thermal conductivity and excellent elastic compliance are usually mutually exclusive in TIMs. Herein, we report a TIM made from vertically oriented graphite and polybutadiene that shows high through-plane thermal conductivity of 64.90 W·m–1·K–1, excellent elastic compliance with only 93 kPa stress at 50% compressive strain similar to soft biological tissues, and outstanding compression resilience performance (storage modulus 220 kPa and mechanical loss factor 0.226). These excellent properties result from the vertical orientation of graphite films in polybutadiene, strong interfacial strength between graphite films and polybutadiene, and the minimized negative impact of graphite on the intrinsic mechanical properties of polybutadiene by means of cross-stacking techniques. The optimal TIM is applied in CPU microprocessor cooling and exhibits superior heat dissipation capability, by up to 158 °C reduction of chip temperature comparing with polybutadiene. This work provides a high-performance TIM to meet specific requirements for high-performance computing, such as GPU, AI computing, and cloud computing.
With the ever-shrinking characteristic dimension of chips and the increasing of packaging density, heat dissipation has become the most critical technology challenge for electronic devices. The ...development of high-performance thermal interface materials (TIMs) for enhancing thermal coupling and minimizing thermal resistance between heterogeneous components is the key to achieving efficient thermal management of electronic devices. Herein, we report a high-performance carbon fiber/polydimethylsiloxane (CF/PDMS) TIM based on the construction of vertically oriented carbon fiber arrays and the modulation of PDMS's crosslinking density. The resulting CF/PDMS TIM exhibits highly desirable characteristics of through-plane thermal conductivity up to 43.47 W/m∙K (only 20 vol% loading), outstanding elastic compliance similar to soft biological tissues (stress ∼ 35 kPa at 35% compressive strain), and excellent resilience performance (resilience rate of 85% after compression cycles). In addition, the heat dissipation capability of CF/PDMS TIM is improved further by forming interconnected heat-conducting structures on the CF/PDMS TIM's surface. The optimal CF/PDMS TIM in microprocessor cooling application exhibits superior heat dissipation capability and stability during 1000 power cycles, resulting in a 68 °C reduction in the chip temperature compared with the state-of-the-art commercial TIM. This work opens up a new avenue for fabricating high-performance TIMs that meet the heat dissipation requirements of high-performance computing.
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