Galerkin-based quasi-smooth manifold element(QSME)method for anisotropic heat conduction problems in composites with complex geometry

The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.

Deformation characterization of conductive particles in anisotropically conductive adhesive simulated by FEM

The deformation behavior and the contact area of conductive particles in anisotropically conductive adhesives (ACA) were investigated by finite element method (FEM). The solid conductive particles are made of pure Ni and Cu. The results indicate that the deformation of the conductive particles is inhomogeneous during fabrication. When the reduction in height is small the deformation concentrates in the area near the contact area. As the reduction in height increases, the strain in the area near the contact area increases, and the metal flows toward the circumference, resulting in the increase of the contact area between the conductive particles and pad. The higher the degree of deformation, the larger the contact area. The regression equations were offered to express the relations between the bounding force and the contact area or the reduction in height. An approach of how to obtain the maximum contact area in ACA was discussed.

Reliability aspects of electronics packaging technology using anisotropic conductive adhesives

Anisotropic conductive adhesive technology for electronics packaging and interconnect application has significantly been developed during the last few years. It is time to make a summary of what has been done in this field. The present paper reviews the technology development, especially from the reliability point of view. It is pointed out that anisotropic conductive adhesives are now widely used in many applications and the reliability data and models have been developed to a large extent for anisotropic conductive adhesives in various applications.

The Improved Element-Free Galerkin Method for Anisotropic Steady-State Heat Conduction Problems

In this paper,we considered the improved element-free Galerkin(IEFG)method for solving 2D anisotropic steadystate heat conduction problems.The improved moving least-squares(IMLS)approximation is used to establish the trial function,and the penalty method is applied to enforce the boundary conditions,thus the final discretized equations of the IEFG method for anisotropic steady-state heat conduction problems can be obtained by combining with the corresponding Galerkin weak form.The influences of node distribution,weight functions,scale parameters and penalty factors on the computational accuracy of the IEFG method are analyzed respectively,and these numerical solutions show that less computational resources are spent when using the IEFG method.

Periodic transparent nanowires in ITO film fabricated via femtosecond laser direct writing

This paper reports the fabrication of regular large-area laser-induced periodic surface structures(LIPSSs)in indium tin oxide(ITO)films via femtosecond laser direct writing focused by a cylindrical lens.The regular LIPSSs exhibited good properties as nanowires,with a resistivity almost equal to that of the initial ITO film.By changing the laser fluence,the nanowire resistances could be tuned from 15 to 73 kΩ/mm with a consistency of±10%.Furthermore,the average transmittance of the ITO films with regular LIPSSs in the range of 1200-2000 nm was improved from 21%to 60%.The regular LIPSS is promising for transparent electrodes of nano-optoelectronic devices-particularly in the near-infrared band.

An emerging quaternary semiconductor nanoribbon with gate-tunable anisotropic conductance

Two-dimensional noble transition metal chalcogenide(NTMC)semiconductors represent compelling building blocks for fabricating flexible electronic and optoelectronic devices.While binary and ternary compounds have been reported,the existence of quaternary NTMCs with a greater elemental degree of freedom remains largely unexplored.This study presents the pioneering experimental realization of a novel semiconducting quaternary NTMC material,AuPdNaS_(2),synthesized directly on Au foils through chemical vapor deposition.The ribbon-shaped morphology of the AuPdNaS_(2)crystal can be finely tuned to a thickness as low as 9.2 nm.Scanning transmission electron microscopy reveals the atomic arrangement,showcasing robust anisotropic features;thus,AuPdNaS_(2)exhibits distinct anisotropic phonon vibrations and electrical properties.The field-effect transistor constructed from AuPdNaS_(2)crystal demonstrates a pronounced anisotropic conductance(σ_(max)/σ_(min)=3.20)under gate voltage control.This investigation significantly expands the repertoire of NTMC materials and underscores the potential applications of AuPdNaS_(2)in nano-electronic devices.

A high-strength self-healing nano-silica hydrogel with anisotropic differential conductivity

Soft nano electronic materials based on conductive hydrogels have attracted considerable attention due to their exceptional properties.Particle deposition and poor interface compatibility often diminish the mechanical strength and electron transport capabilities of the conductive hydrogel.Mechanical damage can severely impact the performance of the conductive hydrogel and can even damage electronic devices based on the conductive hydrogel.In the current study,a transparent nano-silica hydrogel is prepared by employing an extremely easy-to-operate method.This approach can preclude the deposition of particles via strong mechanical force.In addition,controlling the concentration of the reaction interface makes the hydrogel grow along the mechanical force in the direction with a special directional hole structure formed.The hydrogel is transparent,showing excellent self-healing properties—it can self-heal within 15 seconds.Remarkably,the hydrogel after self-healing maintains its performance.Moreover,it has excellent mechanical properties and can be stretched in length.Up to 1,200%of the original length,the tensile strength of the gel spline can reach 7 MPa.The viscosity of the hydrogel can reach 1.67×10^(8)(MPs).In addition,a large amount of Na+in this hydrogel endow it a conductivity of 389 ps/cm.The conductivity of this hydrogel is adjustable result from the special pore structure.Lastly,the difference between the horizontal and vertical conductivity of the same sample can reach 3-4 times,thus this hydrogel can be used in the field of nano conductive materials.

ANALYSIS AND CHARACTERIZATION OF MICROSCOPIC MORPHOLOGY AND ORIENTATION STRUCTURE OF POLYANILINE POLYMERIZED IN A CONSTANT MAGNETIC FIELD

Conductive polyaniline(PAn-_M and PAn-_O) doped with dodecylbenzene sulfonic acid(DBSA) was synthesized by using emulsion polymerization method in the presence of a constant magnetic field(0.4 T) and the absence of magnetic field, respectively.The effects of magnetic field on the microscopic morphology and orientation structure of PAn were generally analyzed and characterized by using transmission electron microscope(TEM),X-ray diffraction(XRD) and through the conductivity anisotropy of unit resistance of t...

Boosting electromagnetic wave absorption of Ti_(3)AlC_(2) by improving effective electrical conductivity

Electromagnetic wave-absorbing(EMA)materials at high temperatures are limited by poor conduction loss(L_(c)).However,adding conductors simultaneously increases the conduction loss and interfacial polarization loss,leading to a conflict between impedance matching(Z_(in)/Z_(0))and electromagnetic wave loss.This will prevent electromagnetic waves from entering the EMA materials,finally reducing overall absorbing performance.Here,the effective electrical conductivity(σ)is enhanced by synchronizing particle size and grain number of Ti_(3)AlC_(2) to increase the conduction loss and avoid the conflict between the impedance matching and the electromagnetic wave loss.As a result,the best-absorbing performance with an effective absorption bandwidth(EAB)of 4.8 GHz(10.6–15.4 GHz)at a thickness of only 1.5 mm is realized,which is the best combination of wide absorption bandwidth and small thickness,and the minimum reflection loss(RL_(min))reaches−45.6 dB at 4.1 GHz.In short,this work explores the regulating mechanism of the EMA materials of effective electrical conductivity by simulated calculations using the Vienna ab-initio Simulation Package(VASP)and COMSOL as well as a series of experiments,which provide new insight into a rational design of materials with anisotropic electrical conductivity.

Tunable Anisotropic Lattice Thermal Conductivity in One-Dimensional Superlattices from Molecular Dynamics Simulations

Engineering nanostructured superlattices provides an effective solution toward the realization of high-performance thermoelectric device and thermal management materials,where the anisotropic thermal conductivity is critical for designing orientation-dependent thermal devices.Herein,the lattice thermal conductivity anisotropy of Al/Ag superlattices as one typical example of superlattice materials is investigated utilizing non-equilibrium molecular dynamics simulations.The cross-plane and in-plane lattice thermal conductivities of one-dimensional superlattices are in the ranges of 0.5–3.2 W/(m·K)and 1.8–5.1 W/(m·K)at different period lengths,respectively,both of which are smaller than those of bulk materials.More specifically,the cross-plane lattice thermal conductivity of superlattices increases with the period length,while the in-plane phonon thermal conductivity first increases and then trends to convergence,resulting in the non-monotonic thermal anisotropy value.To further reveal the microscopic phonon transport mechanism,the interfacial phonon thermal resistance,density of states and spectral phonon transmission coefficient including anharmonic phonon properties under different period lengths are calculated.Our results can be helpful for understanding phonon transport in low-dimensional materials and provide guidance for optimizing the thermal conductivity anisotropy of superlattice materials in the application ranging from thermoelectric devices to thermal management in micro/nano systems.

Design strategy for ferroelectric-based polar metals with dimensionality-tunable electronic states

Since LiOsO_3 was discovered, obtaining easy-accessible polar metals for research and applications has been challenging. In this paper, we present a multilayer design strategy, which is configured as ferroelectric layer/carrier reservoir layer/isolation layer/substrate, for obtaining polar metals by electrostatically doping a strained ferroelectric material in a more effective way. In the proposed configuration, both 1 unit-cell thick BaTiO_3 and PbTiO_3 exhibited considerable Ti off-centering with various strains,which should extend the applicability of ferroelectric-based polar metals in ultra-thin devices. Moreover, engineered by the compressive strain and the BaTiO_3 thickness, the design strategy effectively achieved polar metallicity and dimensionalitytunable electronic states associated with the modulation of highly anisotropic properties such as electrical and electronic thermal conductivity, which may be helpful for designing ultra-thin, ultrafast, and low-power switch devices.

Layered material GeSe and vertical GeSe/MoS2 p-n heterojunctions

GroupqV monochalcogenides are emerging as a new class of layered materials beyond graphene, transition metal dichalcogenides （TMDCs）, and black phosphorus （BP）. In this paper, we report experimental and theoretical investigations of the band structure and transport properties of GeSe and its heterostructures. We find that GeSe exhibits a markedly anisotropic electronic transport, with maximum conductance along the armchair direction. Density functional theory calculations reveal that the effective mass is 2.7 times larger along the zigzag direction than the armchair direction; this mass anisotropy explains the observed anisotropic conductance. The crystallographic orientation of GeSe is confirmed by angle- resolved polarized Raman measurements, which are further supported by calculated Raman tensors for the orthorhombic structure. Novel GeSeflVIoS2 p-n heterojunctions are fabricated, combining the natural p-type doping in GeSe and n-type doping in MoS2. The temperature dependence of the measured junction current reveals that GeSe and MoS2 have a type-II band alignment with a conduction band offset of N 0.234 eV. The anisotropic conductance of GeSe may enable the development of new electronic and optoelectronic devices, such as high-efficiency thermoelectric devices and plasmonic devices with resonance frequency continuously tunable through light polarization direction. The unique GeSe/MoS2 p-n junctions with type-II alignment may become essential building blocks of vertical tunneling field-effect transistors for low-power applications. The novel p-type layered material GeSe can also be combined with n-type TMDCs to form heterogeneous complementary metal oxide semiconductor （CMOS） circuits.

Highly in-plane anisotropy of thermal transport in suspended ternary chalcogenide Ta_(2)NiS_(5)

Energy dissipation has always been an attention-getting issue in modern electronics and the emerging low-symmetry two-dimensional(2D)materials are considered to have broad prospects in solving the energy dissipation problem.Herein the thermal transport of a typical 2D ternary chalcogenide Ta_(2)NiS_(5) is investigated.For the first time we have observed strongly anisotropic in-plane thermal conductivity towards armchair and zigzag axes of suspended few-layer Ta_(2)NiS_(5) flakes through Raman thermometry.For 7-nm-thick Ta_(2)NiS_(5) flakes,theκz i g z a g is 4.76 W·m^(−1)·K^(−1) andκa r m c h a i r is 7.79 W·m^(−1)·K^(−1),with a large anisotropic ratio(κa r m c h a i r/κz i g z a g)of 1.64 mainly ascribed to different phonon mean-free-paths along armchair and zigzag axes.Moreover,the thickness dependence of thermal anisotropy is also discussed.As the flake thickness increases,theκa r m c h a i r/κz i g z a g reduces sharply from 1.64 to 1.07.This could be attributed to the diversity in phonon boundary scattering,which decreases faster in zigzag direction than in armchair direction.Such anisotropic property enables heat flow manipulation in Ta_(2)NiS_(5) based devices to improve thermal management and device performance.Our work helps reveal the anisotropy physics of ternary transition metal chalcogenides,along with significant guidance to develop energy-efficient next generation nanodevices.