Recent advances on 3D printing graphene-based composites

3D printing or additive manufacturing (AM) has revolutionized the way of manufacturing by designing complex structures in a customized feature which cannot be realized by traditional processing methods. Incoming materials are trying to adopt 3D printing techniques which directly fabricate sophisticated entities with multifunctionality like mechanical, electrical, thermal and magnetic properties etc. For the realization of advanced materials, 3D printing techniques are emerging from single material to composite materials manufacturing by simply introducing the nano- and micro-reinforcements with the matrix. In this review, we provide an outline of 3D printing graphene-based composites according to various AM techniques including fused deposition modeling (FDM), direct ink writing (DIW), stereolithography (SLA) and selective laser sintering (SLS). First a brief introduction of various AM techniques is given to get a basic understanding of the principles of 3D printing, and then the fabrication process, structural characteristics and applications of different 3D printing techniques for graphene-based composites are summarized. In addition, some effective simulation and characterization methods are also included. We hope that this review would clarify the potential of AM techniques for composite materials and can open new prospects for designing of novel materials.

Vertical Alignment of Anisotropic Fillers Assisted by Expansion Flow in Polymer Composites

Orientation control of anisotropic one-dimensional(1D)and two-dimensional(2D)materials in solutions is of great importance in many fields ranging from structural materials design,the thermal management,to energy storage.Achieving fine control of vertical alignment of anisotropic fillers(such as graphene,boron nitride(BN),and carbon fiber)remains challenging.This work presents a universal and scalable method for constructing vertically aligned structures of anisotropic fillers in composites assisted by the expansion flow(using2D BN platelets as a proof-of-concept).BN platelets in the silicone gel strip are oriented in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip surfaces.Due to the vertical orientation of BN in the central area of strips,a throughplane thermal conductivity as high as 5.65 W m^(-1) K^(-1) was obtained,which can be further improved to 6.54 W m^(-1) K^(-1) by combining BN and pitch-based carbon fibers.The expansion-flow-assisted alignment can be extended to the manufacture of a variety of polymer composites filled with 1D and 2D materials,which can find wide applications in batteries,electronics,and energy storage devices.

Recent progress on thermal conductivity of graphene filled epoxy composites

With the rapid development of the electronic industry, the requirements for packaging materials with high thermal conductivity(TC) are getting higher and higher. Epoxy is widely used as package material for electronic package applications. But it’s intrinsic TC can’t meets the increasing demands. Adding high TC graphene into epoxy matrix is a proper way to reinforce epoxy composites. This review focuses on the filler modification,preparation process and thermal properties of graphene-filled epoxy resin composites. Different ways of covalent and non-covalent modification methods are discussed. The various kinds of graphene coating layer are also summarized. Then we analysis the hybrid filler system in epoxy composite. We hope this review will provide guidance for the development and application of graphene-filled epoxy resin composites.

类施主效应调控与高择优取向织构提升n型Bi_(2)(Te,Se)_(3)材料热电性能

Thermoelectric materials have a wide range of application because they can be directly used in refrigeration and power generation. And the Bi_(2)Te_(3) stand out because of its excellent thermoelectric performance and are used in commercial thermoelectric devices. However, n-type Bi_(2)Te_(3) has seriously hindered the development of Bi_(2)Te_(3)-based thermoelectric devices due to its weak mechanical properties and inferior thermoelectric performance. Therefore, it is urgent to develop a high-performance n-type Bi_(2)Te_(3) polycrystalline. In this work, we employed interstitial Cu and the hot deformation process to optimize the thermoelectric properties of Bi_(2)Te_(2.7)Se_(0.3), and a high-performance thermoelectric module was fabricated based on this material. Our combined theoretical and experimental effort indicates that the interstitial Cu reduce the defect density in the matrix and suppresses the donor-like effect, leading to a lattice plainification effect in the material. In addition, the two-step hot deformation process significantly improves the preferred orientation of the material and boosts the mobility. As a result, a maximum ZT of 1.27 at 373 K and a remarkable high ZT_(ave) of 1.22 across the temperature range of 300–425 K are obtained. The thermoelectric generator(TEG, 7-pair) and thermoelectric cooling(TEC, 127-pair) modules were fabricated with our n-type textured Cu_(0.01)Bi_(2)Te_(2.7)Se_(0.3) coupled with commercial p-type Bi_(2)Te_(3). The TEC module demonstrates superior cooling efficiency compared with the commercial Bi_(2)Te_(3) device, achieving a ΔT of 65 and 83.4 K when the hot end temperature at 300 and 350 K, respectively. In addition, the TEG module attains an impressive conversion efficiency of 6.5% at a ΔT of 225 K, which is almost the highest value among the reported Bi_(2)Te_(3)-based TEG modules.

Rattling-like behavior and band convergence induced ultra-low lattice thermal conductivity in MgAl_(2)Te_(4) monolayer

Inspired by the excellent stability exhibited by experimentally synthesized two-dimensional(2D)MoSi_(2)N_(4) layered material,the thermal and electronic transport,and thermoelectric(TE)properties of MgAl2Te4 monolayer are systematically investigated using the First-principles calculations and Boltzmann transport theory.The mechanical stability,dynamic stability,and thermal stability(900 K)of the MgAl_(2)Te_(4) monolayer are demonstrated,respectively.The MgAl_(2)Te_(4) monolayer exhibits a bandgap of 1.35 eV using the HSE06 functional in combination with spin-orbit coupling(SOC)effect.Band convergence in the valence band is favorable to improve the thermoelectric properties.The rattling thermal damping effect caused by the weak bonding of Mgsingle bondTe bonds in MgAl2Te4 monolayer leads to ultra-low lattice thermal conductivity(0.95/0.38 W/(m·K)@300 K along the x-/y-direction),which is further demonstrated by the phonon group velocities,phonon relaxation time,Grüneisen parameters,and scattering mechanisms.The optimal zT of 3.28 at 900 K is achieved for the p-type MgAl_(2)Te_(4) monolayer,showing the great promising prospect for the excellent p-type thermoelectric material.Our current work not only reveals the underlying mechanisms responsible for the excellent TE properties,but also elaborates on the promising thermoelectric application of MgAl_(2)Te_(4) monolayer material at high temperature.

Enhancing through-plane thermal conductivity of fluoropolymer composite by developing in situ nano-urethane linkage at graphene–graphene interface

Attributed to the intense development and complexity in electronic devices,energy dissipation is becoming more essential nowadays.The carbonaceous materials particularly graphene(Gr)-based thermal interface materials(TIMs)are exceptional in heat management.However,because of the anisotropic behavior of Gr in composites,the TIMs having outstanding through-plane thermal conductivity(┴TC)are needed to fulfill the upcoming innovation in numerous devices.In order to achieve this,herein,nano-urethane linkage-based modified Gr and carbon fibers architecture termed as nanourethane linkage(NUL)-Gr/carbon fibers(CFs)is fabricated.Wherein,toluene diisocyanate is utilized to develop a novel but simple NUL to shape a new interface between graphene sheets.Interestingly,the prepared composite of NUL-Gr/CFs with polyvinylidene fluoride matrix shows outstanding performance in heat management.Owing to the unique structure of NUL-Gr/CFs,an unprecedented value of┴TC(~7.96 W·m^–1·K^–1)is achieved at a low filler fraction of 13.8 wt.%which translates into an improvement of^3,980%of pristine polymer.The achieved outcomes elucidate the significance of the covalent interaction between graphene sheets as well as strong bonding among graphene and matrix in the composites and manifest the potential of proposed NUL-Gr/CFs architecture for practical applications.