Three-dimensional Conduction Research Articles

Simultaneously improving in-plane and through-plane thermal conductivity of insulted PVDF composite film using multi-layer and multi-filler strategies

In this paper, a multi-filler synergistic strategy combined with multi-layer hot pressing technology was developed to optimize the thermal conductivity and insulation properties of composite materials. Boron nitride nanosheets (BNNS), aluminium oxide (Al2O3) microspheres and silver (Ag) nanoparticles were incorporated to construct a three-dimensional thermal conduction network within a polyvinylidene fluoride (PVDF) thermally conductive composite film. An electrospun PVDF fiber film was first prepared to be used as a template. BNNS and Al2O3 were then electrostatically assembled on the surface of the PVDF fiber and in the film to obtain continuous BNNS/PVDF fiber film and Al2O3/PVDF fiber film, respectively. Ag nanoparticles were then prepared in situ on the Al2O3/PVDF fiber film to obtain an Ag-enhanced Al2O3/PVDF fiber film. A sandwich structured PVDF composite film (B-A@Ag-B/PVDF) was finally prepared by hot pressing, using the BNNS/PVDF fiber films as the top and bottom layers and the Ag-enhanced Al2O3/PVDF fiber film as the middle layer. The resulting B-A@Ag-B/PVDF composite film, with a total filler mass fraction of 32.1 %, had in-plane and through-plane thermal conductivities of 4.13 W m–¹ K–¹ and 1.05 W m–¹ K–¹, respectively, improvements of 1620 % and 452 % compared to those of pure PVDF. In addition, the through-plane electrical conductivity was as low as 5.38 × 10–¹¹ S/cm, matching the standards for insulating materials. The B-A@Ag-B/PVDF composite film demonstrates significant potential for advanced thermally conductive polymer composites.

Flexible wide-range, sensitive three-axis pressure sensor array for robotic grasping feedback

Flexible pressure sensors capable of detecting normal and tangential forces through physical contact have garnered considerable interest in the realm of human-interactive systems. However, simultaneous detection of multi-directional forces is still a challenge for current research. Herein, a capacitive flexible pressure sensor based on a sandwich structure for three-dimensional force detection is proposed. The fabrication process of the sensor array is straightforward, capable of effectively distinguishing between normal and tangential forces. Polyimide (PI) serves as the flexible substrate for depositing the metal electrode pattern, while Polydimethylsiloxane (PDMS) acts as the intermediate dielectric layer material and the three-dimensional force conduction block. Through a comparative study of the thickness of the hollow dielectric layer, a pressure sensor with superior performance was prepared, featuring high sensitivity across a wide working range. Test results demonstrate its capability to detect normal forces ranging from 0 to 46 N (0–520 kPa) with a sensitivity of 0.442 N−1 (0.031 kPa−1) and tangential forces from 0 to 10 N with a sensitivity of 0.08 N−1 (X-axis) and 0.07 N−1 (Y-axis). The designed acquisition system can simultaneously gather data from 6 sensor arrays, totaling 240 channels, with a response time of 11 ms. This sensor array, characterized by flexibility, versatility, and a wide range, is suitable for applications in robot tactile perception.

Thermal and thermo-mechanical post-buckling analysis of GNP-reinforced composite laminated plates

This research utilizes isogeometric analysis (IGA) method to analyze buckling and post-buckling responses of composite laminated plates embedded with graphene nanoplatelets (GNPs) subjected to three-dimensional (3D) conduction of heat or combined 3D heat conduction and mechanical edge compression. A formulation to determine temperature profile produced by 3D conduction of heat in the GNP-reinforced laminate is established, and a new function with smooth transition form of GNP volume fraction across the thickness is presented for dictating the volume fraction of layer. Shear deformable quasi-3D theory with the von Kármán type nonlinearity which takes initial geometric deformation and thermal effect into consideration is employed to construct the nonlinear equilibrium states. Four types of GNP arrangements encompassing uniform, O, X and V shapes are considered. The IGA approach presented, through the benchmark test, is evidenced to estimate the thermal buckling temperature accurately and to successfully trace the thermal post-buckling path. Additional parametric study is carried out to scrutinize the thermal and the thermo-mechanical post-buckling features of the GNP-reinforced composite laminated plates, and the new findings are sure to be served as the benchmark solutions.

MXene quantum dots modified pitaya peel-based composite phase change material with excellent thermal properties for building energy efficiency applications

Bio-based materials have attracted much attention because their application in the construction field is conducive to energy saving and emission reduction. In this paper, a bio-based composite phase change material (CPCM) was prepared by utilizing pitaya peel as a bio-based material, MXene quantum dots (MQDs) as a modified material, and polyethylene glycol (PEG) as a phase change medium. MXene quantum dots dispersed in the pitaya peel-based porous carbon skeleton enhanced the three-dimensional thermal conductivity network of the porous carbon skeleton somewhat improved the thermal conductivity (0.676 W/mK) of the polyethylene glycol/MXene quantum dots-modified pitaya peel-based porous carbon foam (PPF) composite phase change material (PEG/PPF@M). It is worth noting that PEG/PPF@M has excellent thermal stability and its enthalpy is basically unchanged after 100 cycles, which proves the recyclable stability of PEG/PPF@M in practical applications. PEG/PPF@M has great potential for thermal management of buildings and electronic components. Overall, a novel multifunctional CPCM was prepared in this study using a simple process method, which can not only be applied in electronic products to improve the service life of electronic components, but also in the field of construction to realize energy saving and emission reduction, as well as the recycling and reuse of waste.

Construction of three-dimensional proton-conduction networks with functionalized PU@PAN/UiO-66 nanofibers for proton exchange membranes

Proton exchange membranes (PEMs) play an important role in fuel cells. For realizing a nanofiber (NF) structure design in PEMs, the material should have tunable pores and a high specific area. In this study, we attempt to design a novel NF with synergistic architecture doped MOF for constructing three-dimensional (3D) proton conduction networks in PEMs. In this framework, UiO-66-COOH serves as a platform for proton sites to synergistically promote proton conductivity via polyvinylpyrrolidone dissolution, hydrolyzation of polyacrylonitrile, and sulfamic acid functionalization of the shell-layer NF. Benefiting from enriched proton-transfer sites in NFs, the obtained composite membrane overcomes the trade-off among proton conductivity, methanol permeability, and mechanical stability. The composite membrane with 50 % fiber (Nafion/S@NF-50) exhibited a high proton conductivity of 0.212 S cm−1 at 80 °C and 100 % relative humidity, suppressed methanol permeability of 0.66 × 10−7 cm2 s−1, and the maximum power density of direct methanol fuel cell is 182.6 mW cm−2. Density functional theory was used to verify the important role of sulfamic acid in proton transfer, and the activation energy barriers under anhydrous and hydrous conditions are only 0.337 and 0.081 kcal, respectively. This study opens up new pathways for synthesizing NF composite PEMs.

Comprehensive measurement of three-dimensional thermal conductivity tensor using a beam-offset square-pulsed source (BO-SPS) approach

Accurately measuring the three-dimensional thermal conductivity tensor is essential for understanding and engineering the thermal behavior of anisotropic materials. Existing methods often struggle to isolate individual tensor elements, leading to large measurement uncertainties and time-consuming iterative fitting procedures. In this study, we introduce the Beam-Offset Square-Pulsed Source (BO-SPS) method for comprehensive measurements of three-dimensional anisotropic thermal conductivity tensors. This method uses square-pulsed heating and precise temperature rise measurements to achieve high signal-to-noise ratios, even with large beam offsets and low modulation frequencies, enabling the isolation of thermal conductivity tensor elements. We demonstrate and validate the BO-SPS method by measuring X-cut and AT-cut quartz samples. For X-cut quartz, with a known relationship between in-plane and cross-plane thermal conductivities, we can determine the full thermal conductivity tensor and heat capacity simultaneously. For AT-cut quartz, assuming a known heat capacity, we can determine the entire anisotropic thermal conductivity tensor, even with finite off-diagonal elements. Our results yield consistent principal thermal conductivity values for both quartz types, demonstrating the method's reliability and accuracy. This research highlights the BO-SPS method's potential to advance the understanding of thermal behavior in complex materials.

Three-dimensional fracture space characterization and conductivity evolution analysis of induced un-propped fractures in shale gas reservoirs

Huge numbers of induced unpropped (IU) fractures are generated near propped fractures during hydraulic fracturing in shale gas reservoirs. But it is still unclear how their fracture space and conductivity evolve under in-situ conditions. This paper prepares three types of samples, namely, manually split vertical/parallel to beddings (MSV, MSP) and parallel natural fractures (NFP), to represent the varied IU fractures as well as their surface morphology. Laser scan and reconstruction demonstrate that the initial fracture spaces of MSVs and MSPs are limited as the asperities of newly created surfaces are well-matched, and the NFPs have bigger space due to inhomogeneous geological corrosion. Surface slippage and consequent asperity mismatch increase the fracture width by several times, and the increase is proportional to surface roughness. Under stressful conditions, the slipped MSVs retain the smallest residual space and conductivity due to the newly sharp asperities. Controlled by the bedding structures and clay mineral hydrations, the conductivity of MSPs decreases most after treated with a fracturing fluid. The NFPs remain the highest conductivity, benefitting from their dispersive, gentle, and strong asperities. The results reveal the diverse evolution trends of IU fractures and can provide reliable parameters for fracturing design, post-fracturing evaluation, and productivity forecasting.

Enhanced electrocatalytic CO2 reduction through constructing chemically homogeneous interfaces via ultrathin carbon encapsulated tin oxide

Electrocatalytic CO2 reduction to high-value chemicals has significant potential to combat environmental and energy crises. The strength and mode of adsorption of reaction species play a crucial role in determining the CO2 reduction products. Therefore, it is vital to construct catalytic interfaces with high catalytic activity, selectivity and chemically homogeneous for efficient CO2 reduction. Herein, ultra-thin carbon layer encapsulated sub-5 nm SnO2 quantum dots (SnO2@u-C) has been prepared by Sn-MOFs derivation for efficient electrocatalytic CO2 reduction. Specifically, the Faradaic efficiency of formate (FEformate) and energy efficiency of formate production (EEformate) exceed 80 % and 50 % respectively, over a wide potential range, with the highest value reaching 95.7 % for FEformate and 58.2 % for EEformate. Moreover, SnO2@u-C electrode shows excellent stability over 10 h with FEformate about 89 % at −1.17 V versus reversible hydrogen electrode. DFT calculations and experimental characterization reveal that the ultrathin carbon layer coating on the surface of SnO2 forms a chemically homogeneous catalytic interface, facilitating the adsorption and conversion of reaction species to achieve exceptional formate selectivity. Moreover, the carbon layer builds a three-dimensional rapid electron conduction network that supports electron transfer to CO2 molecules and suppressing SnO2 reduction.

Estimation of thermophysical properties of a pouch-type Li-ion battery using an inverse methodology

The growing popularity of electric vehicles highlights the crucial role of batteries. Effective battery thermal management is crucial for improving performance, reliability, and safety, especially in tropical areas where overheating is a key challenge. This necessitates a comprehensive understanding of the thermophysical properties of batteries. The present study concerns the estimation of the temperature-dependent orthotropic thermophysical properties (kx , ky , kz , cp ) of the active material in a pouch-type Li-ion battery using an inverse methodology. An experimental study is conducted on a commercial AMP20M1HD-A Li-ion battery to measure the surface temperature at various locations using thermocouples. The forward model consists of the three-dimensional unsteady conduction problem and is solved in COMSOL using experimental boundary conditions. The data generated is used to train an Artificial Neural Network, which acts as a replacement for the forward model. The Metropolis Hasting-Markov Chain Monte Carlo algorithm along with the Bayesian inference inverse model is used for analyzing the posterior distribution and the average estimates for thermophysical properties are obtained. The temperature dependence study shows a significant correlation between temperature and battery thermophysical properties. The accuracy of the employed inverse model is validated by obtaining the surface temperature using the estimated thermophysical properties and comparing it with the measured surface temperature.

Multi-dimensional nano-microstructures design of MOF-derived CoSe2@N–C composites toward excellent microwave absorption

Nano-microstructures design enabled the controlled tuning of electromagnetic parameters to obtain high-performance microwave absorption materials (MAM). Herein, Metal-Organic Frameworks-derived (MOFs-derived) CoSe2@Nitrogen-doped Carbon (CoSe2@N–C) materials with controllable nano-microstructures also exhibit tunable morphologies from dodecahedra-, cube-, fusiform-to sheet-like by adjusting the solvent and the molar ratio of cobalt/ligand. The organic frameworks are maintained by pyrolysis selenization, forming a unique CoSe2@N–C three-dimensional conduction network that broadens electron transport and electromagnetic wave multiple reflection routes, enhances conduction loss capability, and optimizes impedance matching. The confinement of ligand-derived carbon can avoid the agglomeration of CoSe2, forming rich heterogeneous interfaces within CoSe2@N–C, enhancing interfacial polarization loss. Symmetric models are developed to reveal the importance of destructive interference on the microwave absorption property. In addition, dipole polarization of defects and doped-nitrogen further encourages the enhancement of the microwave absorption properties of CoSe2@N–C. The CoSe2@N–C-d exhibits the best microwave absorption properties with a minimum reflection loss (RLmin) of −42.31 dB at 15.62 GHz in a thickness of 1.5 mm, and an effective absorption bandwidth of 4.25 GHz. The excellent absorption performance of CoSe2@N–C paves the way for the design and synthesis of high-performance absorbers.

Deep lithosphere-coupled surface deformation beneath Southeastern Brazil from amphibious magnetotellurics

The southeastern Brazilian onshore-offshore margin and underlying lithosphere are investigated by three-dimensional magnetotelluric imaging using 202 high-quality broadband and long-period amphibious MT-dataset, orthogonally traversing the regional surface deformation hills of Serra da Mantiqueira and Serra do Mar, as well as the coast-parallel onshore-offshore lineaments. Three-dimensional conductivity model reveals an electrically heterogeneous crust (up to 40 km) in the onshore Brasília and Ribeira Orogenic Belts, and ∼ 2–10 km thick-conductive-sedimentary-wedge beneath the offshore Santos Basin laying on top of a stretched and thinner resistive crust. Regionally, the lithosphere is found ∼130 km thick beneath the most northwestern part of the Brasília Orogenic Belt which is thinning out towards the deep-water Santos Basin (∼70 km). This thinning coincides with the lithosphere-asthenosphere boundary in recent seismic tomography results, reflecting the current state of the uplifted asthenosphere post-West Gondwana break-up. A major steeply dipping sub-lithospheric conductor, in conjunction with a confined asthenosphere upwelling (or lithospheric thinning), has been observed underneath Embu-Paraíba do Sul domain (Ribeira belt), which may be somehow associated with the continental scale rifting, surface uplift and the Cretaceous São Paulo-Rio de Janeiro dykes swarm. Our findings provide valuable insights into the formation of southeast Brazilian highlands and its association with mantle plume-induced lithospheric delamination (or removal) and the occurrence of alkaline magmatism, after reactivation of some pre-existing weak zones.

Hydraulic conductivity tensor of anisotropic soils: the impact on seepage flow

Natural or artificial changes in soil stratigraphic-plane (i.e., the deposition of soil and sediments into distinct layers) orientation can cause variations in hydraulic conductivity in different direction. Hydraulic conductivity must, therefore, be considered – in this case – as a nondiagonal, full tensor to appropriately represent the effect of the orientation of soil stratigraphic planes on the seepage flow pattern. This paper introduces the derivation of the formula for the three-dimensional nondiagonal hydraulic conductivity full tensor calculation in terms of azimuth and vertical angles. Furthermore, two-dimensional numerical simulations of the seepage flow beneath a concrete dam are presented to demonstrate the need to account for the nondiagonal elements of the hydraulic conductivity tensor in anisotropic soils of varying degrees of stratigraphic tilt with respect to the coordinate system.

Study on the potential of multi-performance enhanced phase change materials in battery thermal management

Lots of research has proved the effectiveness of flexible composite phase change material (CPCM) in thermal management of electronic products. However, the key properties of materials, e.g., flexibility, thermal conductivity and resistance are mutually restricted, further limiting its application in practical thermal management engineering. Unfortunately, the above performance has not been comprehensively considered in the existing research. In this work, a novel shape-stabilized flexible CPCM with considerable comprehensive performance was proposed. Styrene-b-ethylene-co-butylene-b-styrene (SEBS) was used as a flexible matrix to expand the flexible temperature range, and ALN was used to improving the thermal conductivity (0.786 W·m−1·K−1), strengthening the three-dimensional thermal conductivity skeleton of expanded graphite and improving the resistivity to 5.16 × 1010 Ω·m. Meanwhile, the CPCMs showed excellent performance in cycle stability, the melting enthalpy only decreased by 1.29 % after 500 cycles. The result of thermal management exhibited that the maximum temperature (Tmax) and maximum temperature difference (ΔTmax) of the battery at 6C discharge rate were 43.64 °C and 2.39 °C respectively with the help of CPCMs. More importantly, it was also obtained that the thermal conductivity played a major role in the battery temperature control in the long-term operation, the increase of the thermal conductivity reduced ΔTmax by 68.05 %. This work will further provide technical support for the practical engineering application of flexible CPCMs for electronic thermal management.

Inversion for 3D Conductivity and Chargeability Models Using EM Data Acquired by the New Airborne TargetEM System in Ontario, Canada

This paper introduces an original approach to the joint inversion of airborne electromagnetic (EM) data for three-dimensional (3D) conductivity and chargeability models using hybrid finite difference (FD) and integral equation (IE) methods. The inversion produces a 3D model of physical parameters, which includes conductivity, chargeability, time constant, and relaxation coefficients. We present the underlying principles of this approach and an example of a high-resolution inversion of the data acquired by a new active time domain airborne EM system, TargetEM, in Ontario, Canada. The new TargetEM system collects high-quality multicomponent data with low noise, high power, and a small transmitter–receiver offset. This airborne system and the developed advanced inversion methodology represent a new effective method for mineral resource exploration.

Three-dimensional active-control hygrothermal dynamic behavior of PFMLs structure subjected to laser heat treatment with dual-ellipse distribution form

Based on three-dimensional transient thermal conduction theory, the refined plate theory and Hamilton variational principle, the constitutive equations, geometrical equations, and governing equations for fiber metal laminates with piezoelectric layer (PFMLs) under hygrothermal environment is presented. Subsequently, the Newmark method and Galerkin method are used to solve the governing equations which in terms of displacement functions. The results show that electric potential function, fiber orientation, external load as well as thickness ratio have great influence on the deflection as well as normal stress. The selection of (45°/0°) fiber orientation is more resistance to deformation and normal stress.

Superionic lithium transport via multiple coordination environments defined by two-anion packing.

Fast cation transport in solids underpins energy storage. Materials design has focused on structures that can define transport pathways with minimal cation coordination change, restricting attention to a small part of chemical space. Motivated by the greater structural diversity of binary intermetallics than that of the metallic elements, we used two anions to build a pathway for three-dimensional superionic lithium ion conductivity that exploits multiple cation coordination environments. Li7Si2S7I is a pure lithium ion conductor created by an ordering of sulphide and iodide that combines elements of hexagonal and cubic close-packing analogously to the structure of NiZr. The resulting diverse network of lithium positions with distinct geometries and anion coordination chemistries affords low barriers to transport, opening a large structural space for high cation conductivity.

Thermal Conductivity Enhancement of Polymeric Composites Using Hexagonal Boron Nitride: Design Strategies and Challenges.

With the integration and miniaturization of chips, there is an increasing demand for improved heat dissipation. However, the low thermal conductivity (TC) of polymers, which are commonly used in chip packaging, has seriously limited the development of chips. To address this limitation, researchers have recently shown considerable interest in incorporating high-TC fillers into polymers to fabricate thermally conductive composites. Hexagonal boron nitride (h-BN) has emerged as a promising filler candidate due to its high-TC and excellent electrical insulation. This review comprehensively outlines the design strategies for using h-BN as a high-TC filler and covers intrinsic TC and morphology effects, functionalization methods, and the construction of three-dimensional (3D) thermal conduction networks. Additionally, it introduces some experimental TC measurement techniques of composites and theoretical computational simulations for composite design. Finally, the review summarizes some effective strategies and possible challenges for the design of h-BN fillers. This review provides researchers in the field of thermally conductive polymeric composites with a comprehensive understanding of thermal conduction and constructive guidance on h-BN design.

Construction of self-lapping three-dimensional thermal conduction network in epoxy resin thermosets by incorporating “dendritic” zinc oxide derived from metal-organic framework

Thermal management materials are the solution to heat dissipation issues in electronic devices, which are considered vital to the device's reliability and lifetime. Therefore, it was of great significance to develop a new type of epoxy resin composites with flame retardant, thermal conductivity and toxicity reduction. Here, dendritic zinc oxide (D-ZnO) was designed and synthesized after annealing the metal-organic framework (MOF) precursor and then using it to fabricate a thermally conductive epoxy resin (EP) thermoset. The synthesized d-ZnO reached a high specific surface area of 40.389 m2g−1, which is about 14 times higher than that of commercial ZnO (C-ZnO). Remarkably, the EP/D-ZnO thermosets reaches a thermal conductivity (TC) of 1.10 Wm−1K−1 at a low filler loading of 10 wt%, which is more than 4.5 times more than pure EP. In the meantime, the TC of the d-ZnO composite was 120 % higher than that of the commercial ZnO composite at the same loading. The coefficient of thermal expansion (CTE) of EP/10wt% d-ZnO thermoset decreased by 68.6 ppm K−1 compared to pure EP. The excellent thermal diffusion performance could be attributed to the polarized interfaces of d-ZnO, which forms heat conduction pathways. Thus, with addition of functionalized d-ZnO, the peak CO production and peak CO2 production were decreased from 0.036 gs−1 and 0.80 gs−1 for pure EP to 0.026 gs−1 and 0.50 gs−1(EP/D-ZnO thermosets). The EP/D-ZnO thermosets reported by this strategy demonstrate great potential as next generation thermal management materials.

Synergistic phase change and heat conduction of low melting-point alloy microparticle additives in expanded graphite shape-stabilized organic phase change materials

Organic phase change materials (PCMs) have great potential for efficient thermal energy storage and passive thermal management applications due to their non-corrosiveness, high heat storage capacity and stable operating temperature. However, low thermal conductivity and easy leakage seriously restrict the actual application. Meanwhile, heat transfer enhancers typically have a serious negative effect on the heat storage capacity of the PCMs. In this paper, a novel strategy for preparing high performance shape-stable composite phase change materials (CPCMs) is reported, utilizing paraffin wax (PW) as the energy storage material and expanded graphite (EG) as heat transfer enhancers and supporting material, especially in which low melting-point alloy (LMA) micro particles having same phase change temperature as PW are employed with two purposes: one is to provide extra latent heat, and another is to construct a hybrid three-dimensional thermal conduction network in microscale to achieve synergistic thermal conduction with EG. The resulting CPCMs exhibit excellent characteristics in energy storage capacity, thermal conductivity, and thermal cycling stability. The thermal conductivity of ternary CPCM can reach 5.842 W m−1 K−1 when the LMA and EG loading are 4.55 wt% and 9 wt%, which is about 16.4 times higher than that of pure PW, with no obvious volumetric latent heat reduction. This work provides a novel and promising approach for the preparation of CPCMs with high and fast storage properties.

AN EFFICIENT ALGORITHM FOR THE NUMERICAL SOLUTION OF A THREE-DIMENSIONAL THERMAL CONDUCTIVITY ISSUE

A mathematical model of slab heating based on a numerical solution of a three-dimensional thermal conductivity problem has been created and programmatically implemented in the work. To solve a system of difference equations, a layer-by-layer method is proposed that allows using the run-through method to solve a system of difference equations of a three-dimensional problem within a rapidly converging iterative procedure. Comparative calculations of slab heating are carried out using the proposed layer-by-layer method and the method of simple iteration with different degrees of grinding of the spatial grid. As a result, it was found that with the grinding of the mesh, the effectiveness of the layered method in relation to the simple iteration method increases.