Flexible organic-inorganic hybrids are promising thermoelectric materials to recycle waste heat in versatile formats. However, current organic/inorganic hybrids suffer from inferior thermoelectric ...properties due to aggregate nanostructures. Here we demonstrate flexible organic-inorganic hybrids where size-tunable Bi
Te
nanoparticles are discontinuously monodispersed in the continuous conductive polymer phase, completely distinct from traditional bi-continuous hybrids. Periodic nanofillers significantly scatter phonons while continuous conducting polymer phase provides favored electronic transport, resulting in ultrahigh power factor of ~1350 μW m
K
and ultralow in-plane thermal conductivity of ~0.7 W m
K
. Consequently, figure-of-merit (ZT) of 0.58 is obtained at room temperature, outperforming all reported organic materials and organic-inorganic hybrids. Thermoelectric properties of as-fabricated hybrids show negligible change for bending 100 cycles, indicating superior mechanical flexibility. These findings provide significant scientific foundation for shaping flexible thermoelectric functionality via synergistic integration of organic and inorganic components.
Delivering on the revolutionary promise of a universal quantum computer will require processors with millions of quantum bits (qubits)
. In superconducting quantum processors
, each qubit is ...individually addressed with microwave signal lines that connect room-temperature electronics to the cryogenic environment of the quantum circuit. The complexity and heat load associated with the multiple coaxial lines per qubit limits the maximum possible size of a processor to a few thousand qubits
. Here we introduce a photonic link using an optical fibre to guide modulated laser light from room temperature to a cryogenic photodetector
, capable of delivering shot-noise-limited microwave signals directly at millikelvin temperatures. By demonstrating high-fidelity control and readout of a superconducting qubit, we show that this photonic link can meet the stringent requirements of superconducting quantum information processing
. Leveraging the low thermal conductivity and large intrinsic bandwidth of optical fibre enables the efficient and massively multiplexed delivery of coherent microwave control pulses, providing a path towards a million-qubit universal quantum computer.
•Shape-stable and high-thermal conductivity c-PCMs composed of PEG and BPC are investigated.•Biological porous carbon materials not only shape PEG but also improve the thermal conductivity.•The ...maximum absorption of PEG reaches 85.36wt% without leakage in the PEG/BPC c-PCMs.•PEG/BPC c-PCMs show good thermal reliability even go through a 200 thermal cycles.
Shape-stable and high-thermal conductivity composite phase change materials (c-PCMs) composed of polyethylene glycol (PEG) and biological porous carbon (BPC) are investigated. BPC based on potatoes and white radishes are obtained by the carbonization method. The thermal conductivity of the BPC increases with the rising of the carbonization temperature due to the higher graphitization degree. Especially, BPC calcined at 1300°C for 2h resulted in the optimum PEG supporting matrix candidate, showing an attractive honeycomb-like microstructure. Calcination above 1300°C results in the destruction of the shape. BPC/PEG c-PCMs are synthesized via a vacuum impregnation approach. PEG equally distributed in the matrix material with a mass fraction of 85.36% approximately and it could keep its morphological stability after heating at 80°C for 40h. Moreover, the highest thermal conductivity is 4.5W/mK, which is about 10 times higher than the pristine PEG. Furthermore, no chemical interaction is found between the PEG and BPC. The melting and solidifying temperature, and enthalpy not vary upon a 200 thermal cycles test. This confirms the excellent chemical and structure stability for c-PCMs, which are within the most promising materials in the area of building heat preservation by being clean, energy-saving and recycled materials.
We consider the model of the Finnish high-voltage power grid in 1978-1979, for which the accurate parameters are available for calculating geomagnetically induced currents (GIC). Moving the grid at ...different locations across Europe gives estimates of GIC levels in this region. For calculating the geoelectric field driving GIC, we use different layered models of the ground conductivity and 1 min geomagnetic data of the year 2003. The results show a clear concentration of large GIC in north Europe, where the peak values are about 3-5 times larger than in Central and South Europe, being up to about 200 A in this specific power grid. There are two factors contributing to this finding. First, geomagnetic variations are generally stronger in the north. Second, there are regions in the north with clearly smaller ground conductivities than typically at other areas. Both of these reasons lead to larger electric fields in the north. A very similar behavior of GIC is found in the case when a single-layered ground conductivity model is assumed everywhere. We also show that the geographic characteristics of GIC are quite insensitive to the details of the power grid model by modifying various parameters of the Finnish grid. Key Points European-wide estimation of GIC Largest GIC in North Europe due to high magnetic activity Small ground conductivity further increases GIC in North Europe
High-performance thermally insulating materials from renewable resources are needed to improve the energy efficiency of buildings. Traditional fossil-fuel-derived insulation materials such as ...expanded polystyrene and polyurethane have thermal conductivities that are too high for retrofitting or for building new, surface-efficient passive houses. Tailored materials such as aerogels and vacuum insulating panels are fragile and susceptible to perforation. Here, we show that freeze-casting suspensions of cellulose nanofibres, graphene oxide and sepiolite nanorods produces super-insulating, fire-retardant and strong anisotropic foams that perform better than traditional polymer-based insulating materials. The foams are ultralight, show excellent combustion resistance and exhibit a thermal conductivity of 15 mW m(-1) K(-1), which is about half that of expanded polystyrene. At 30 °C and 85% relative humidity, the foams retained more than half of their initial strength. Our results show that nanoscale engineering is a promising strategy for producing foams with excellent properties using cellulose and other renewable nanosized fibrous materials.
Highly thermal conductivity materials with excellent electromagnetic interference shielding and Joule heating performances are ideal for thermal management in the next generation of communication ...industry, artificial intelligence and wearable electronics. In this work, silver nanowires (AgNWs) are prepared using silver nitrate as the silver source and ethylene glycol as the solvent and reducing agent, and boron nitride (BN) is performed to prepare BN nanosheets (BNNS) with the help of isopropyl alcohol and ultrasonication-assisted peeling method, which are compounded with aramid nanofibers (ANF) prepared by chemical dissociation, respectively, and the (BNNS/ANF)-(AgNWs/ANF) thermal conductivity and electromagnetic interference shielding composite films with Janus structures are prepared by the “vacuum-assisted filtration and hot-pressing” method. Janus (BNNS/ANF)-(AgNWs/ANF) composite films exhibit “one side insulating, one side conducting” performance, the surface resistivity of the BNNS/ANF surface is 4.7 × 10
13
Ω, while the conductivity of the AgNWs/ANF surface is 5,275 S/cm. And Janus (BNNS/ANF)-(AgNWs/ANF) composite film with thickness of 95 µm has a high in-plane thermal conductivity coefficient of 8.12 W/(m·K) and superior electromagnetic interference shielding effectiveness of 70 dB. The obtained composite film also has excellent tensile strength of 122.9 MPa and tensile modulus and 2.7 GPa. It also has good temperature-voltage response characteristics (high Joule heating temperature at low supply voltage (5 V, 215.0 °C), fast response time (10 s)), excellent electrical stability and reliability (stable and constant real-time relative resistance under up to 300 cycles and 1,500 s of tensile-bending fatigue work tests).
Complex conductivity of soils Revil, A.; Coperey, A.; Shao, Z. ...
Water resources research,
August 2017, Volume:
53, Issue:
8
Journal Article
Peer reviewed
Open access
The complex conductivity of soils remains poorly known despite the growing importance of this method in hydrogeophysics. In order to fill this gap of knowledge, we investigate the complex ...conductivity of 71 soils samples (including four peat samples) and one clean sand in the frequency range 0.1 Hz to 45 kHz. The soil samples are saturated with six different NaCl brines with conductivities (0.031, 0.53, 1.15, 5.7, 14.7, and 22 S m−1, NaCl, 25°C) in order to determine their intrinsic formation factor and surface conductivity. This data set is used to test the predictions of the dynamic Stern polarization model of porous media in terms of relationship between the quadrature conductivity and the surface conductivity. We also investigate the relationship between the normalized chargeability (the difference of in‐phase conductivity between two frequencies) and the quadrature conductivity at the geometric mean frequency. This data set confirms the relationships between the surface conductivity, the quadrature conductivity, and the normalized chargeability. The normalized chargeability depends linearly on the cation exchange capacity and specific surface area while the chargeability shows no dependence on these parameters. These new data and the dynamic Stern layer polarization model are observed to be mutually consistent. Traditionally, in hydrogeophysics, surface conductivity is neglected in the analysis of resistivity data. The relationships we have developed can be used in field conditions to avoid neglecting surface conductivity in the interpretation of DC resistivity tomograms. We also investigate the effects of temperature and saturation and, here again, the dynamic Stern layer predictions and the experimental observations are mutually consistent.
Plain Language Summary
Geophysical methods are increasingly popular in agriculture. Usually, DC (DIrect Current) resistivity is the preferred method but the interpretation of resistivity data suffers a major flaw: the inability to distinguish between bulk and surface conductivity. This has yield to unrealistc interpretation schemes in hydrogeophysics and an abuse of Archie's law. We propose a way to cure this flaw by extending the DC resistivity method to what is called induced polarization. This paper is the first work entirely focused on the study of induced polarization of soils including a comparison with a mechanistic model and a study of the influence of both temperature and saturation.
Key Points
A large data set of complex conductivity data on soils is presented
Complex conductivity data are explained to the light of the dynamic Stern layer model
Surface conductivity is related to the normalized chargeability or quadrature conductivity, which opens new perspectives in hydrogeophysics
Highly thermally conductive polymer composites are desirable for the thermal management of modern electronic devices. Although the thermal conductivity issue has been improved effectively with many ...methods, it always fails in maintaining the electrical insulation performance at the same time, which has become another great challenge. Here the sandwich-structured PVA/PVA-rGO/PVA (recorded as PVA/rGO) composite films simultaneously owning high thermal conductivity, excellent electrical insulation and outstanding flexibility were designed and prepared through self-construction strategy. The obtained results show that the prepared composite films achieved a high in-plane thermal conductivity of 4.00 W m−1 K−1 with only 5 wt% rGO loading, which was about 970% higher than that of pure PVA (0.413 W m−1 K−1). The high thermal conductivity is attributed to the formation of the homogeneous intermediate layer of PVA-rGO. In addition, the low filler loading makes the composite film remain excellent mechanical flexibility, and the PVA in the upper and lower layers of the composite film keeps good electrical insulation (volume resistivity beyond 109 Ω cm). The prepared composite films not only have great potential applications in the field of thermal management and flexible electronic devices but also have the possibility to conduct the mass production of polymer composites.
Display omitted
•The PVA/rGO composite films prepared through self-construction strategy own a sandwich structure.•The obtained polymer matrix composite films can simultaneously possess high thermal conductivity and good electrical insulation.•The anisotropy of the thermal conductivity could reduce the impact on adjacent electronic components when the composite films are applied in thermal management field.•The prepared composite films have great possibility to conduct the mass production by this simple preparation method.
In the present work, Janus monolayers WSSe and WSTe are investigated by combining first-principles calculations and semiclassical Boltzmann transport theory. Janus WSSe and WSTe monolayers show a ...direct band gap of 1.72 and 1.84 eV at K-points, respectively. These layered materials have an extraordinary Seebeck coefficient and electrical conductivity. This combination of high Seebeck coefficient and high electrical conductivity leads to a significantly large power factor. In addition, the lattice thermal conductivity in the Janus monolayer is found to be relatively very low as compared to the WS2 monolayer. This leads to a high figure of merit (ZT) value of 2.56 at higher temperatures for the Janus WSTe monolayer. We propose that the Janus WSTe monolayer could be used as a potential thermoelectric material due to its high thermoelectric performance. The result suggests that the Janus monolayer is a better candidate for excellent thermoelectric conversion.
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