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Graphene oxide (GO) and nitrogen-doped graphene (NG) coated copper nanoparticles (NPs) have been developed in this work and investigated as nanofiller for water as Heat Transfer Fluids (HTFs). The morphology and composition of the coating were characterized to confirm the presence of functional groups and the nitrogendoping of the graphene coating. Different fractions of the two types of coated nanoparticles NPs between 0.1 and 10 wt.% were dispersed in water. The thermal conductivity of the dispersions was evaluated at temperatures between 20 and 50 °C. A positive correlation between the thermal conductivity of the HTFs and the fraction and temperature are observed as a result of the increase of the solid phase contribution into the heat transfer. At a concentration of 0.5 wt.%, the thermal conductivity of the NG-CuNPs nanofluid reached its maximum increase of 78%, compared to a 13% increase in the case of GO-CuNPs. However, due to the poor stability of the NG-CuNPs, further increase of the solid phase did not result in any additional improvement. In contrast, the thermal conductivity of the GO-based dispersion resulted in a 103% enhancement at 10 wt.% at a temperature of 50 °C.

This paper presents the improved thermal property of three-dimensional (3D) graphene network modified polydimethylsiloxane (PDMS) composites. It shows that with a 2 wt.% loading of graphene foams (GF), the thermal conductivity of GF/PDMS composite was successfully increased from 0.19 W/mK to 0.42 W/mK, which is 2.2 times higher than that of neat PDMS. However, if GF was transformed into graphene sheets (GS) by sonication, the thermal conductivity of GS/PDMS was decreased to 0.28 W/mK. The remarkable improvement of the thermal properties is attributed to the 3D interconnected graphene network in GF, which form continuous heat transfer networks. Furthermore, the finite element analysis was conducted to evaluate the effect of GFs in composites, where some parameters such as thickness and thermal conductivity were analyzed and discussed. Our results indicate that the continuous 3D GFs holds great potential as fillers to improve the thermal property of polymer materials.

Abstract: During the last decades, there has been growing interest in using therapeutic messager RNA (mRNA) together with drug delivery systems. Naked, unformulated mRNA is, however, unable to cross the cell membrane and is susceptible to degradation. Here we use graphene quantum dots (GQDs) functionalized with polyethyleneimine (PEI) as a novel mRNA delivery system. Our results show that these modified GQDs can be used to deliver intact and functional mRNA to Huh‐7 hepatocarcinoma cells at low doses and, that the GQDs are not toxic, although cellular toxicity is a problem for these first‐generation modified particles. Functionalized GQDs represent a potentially interesting delivery system that is easy to manufacture, stable and effective., Message delivered! A novel graphene quantum dots based mRNA drug delivery platform was prepared. The results show that these modified GQDs can deliver intact and functional mRNA to Huh‐7 hepatocarcinoma cells at low doses. The transfection efficiency for FGQDs/mRNA complexes was 25 % with a formulation concentration of 4000 ng mRNA/mL, but comparable transfection efficiencies could be achieved at much lower doses if the ratio between carrier and cargo was optimized. This work describes the first steps towards a potentially interesting preparation method for stable and effective mRNA delivery systems.

Carbon nanotube (CNT) array thermal interface materials (TIMs) are promising candidates for high-performance applications in terms of thermal performance. However, in order to be useful in commercial applications, the reliability of the interfaces is an equally important parameter, which so far has not been thoroughly investigated. In this study, the reliability of CNT array TIMs is investigated through accelerated aging. The roles of CNT array height and substrate configuration are studied for their relative impact on thermal resistance degradation. After aging, the CNT catalyst is analyzed using X-ray photoelectron spectroscopy to evaluate chemical changes. The CNT-catalyst bond appears to degrade during aging but not to the extent that the TIM performance is compromised. On the other hand, coefficient of thermal expansion mismatch between surfaces creates strain that needs to be absorbed, which requires CNT arrays with sufficient height. Transfer and bonding of both CNT roots and tips also create more reliable interfaces. Crucially, we find that the CNT array height of most previously reported CNT array TIMs is not enough to prevent significant reliability problems.

Heat pipe is one of the most efficiency tools for heat dissipation in power systems. Currently, heat pipes are usually made of copper or aluminum. However, due to their relatively high density and limited heat transmission capacity, heat pipes are facing urgent challenges in power electronics. In this paper, a new class of graphene enhanced heat pipe that can cope with these issues is reported. The graphene enhanced heat pipe is made of high thermal conductivity graphene assembled film with nanostructure enhanced inner surfaces. The study shows that the dramatically improved heat dissipation capacity, 7230 W m−2 K−1 g−1, about 3.5 times higher than that of copper based commercial heat pipes can be achieved. This paves the way for using graphene enhanced heat pipe in lightweight and large capacity cooling applications, as required in many systems such as automotive electronics, hand‐sets and space electronics.

This review focuses on the recent advances in the synthesis of graphene quantum dots (GQDs) and their applications in drug delivery. To give a brief understanding about the preparation of GQDs, recent advances in methods of GQDs synthesis are first presented. Afterwards, various drug delivery-release modes of GQDs-based drug delivery systems such as EPR-pH delivery-release mode, ligand-pH delivery-release mode, EPR-Photothermal delivery-Release mode, and Core/Shell-photothermal/magnetic thermal delivery-release mode are reviewed. Finally, the current challenges and the prospective application of GQDs in drug delivery are discussed.

With the increasing demand on integration and better performance of portable electronics devices, the system operation temperatures are expected to continue to increase, leading eventually to degeneration in functional performance and reliability. Therefore, demand for thermal management materials that effectively spread heat and reduce heat density is urgent. The existing solution of pyrolytic graphite film (PGF) is unsatisfactory due to their low heat flux carrying capacity or low thermal conductivity, as well as poor mechanical performance. This work solves the problem by substituting ultra-thick (≥75 μm) graphene film (GF) for PGF, offering more than three times higher heat flux carrying capacity. The conjugation of large crystallinity and firm structures endows GFs with excellent thermal conductive performance (up to 1204 ± 35 W m−1 K−1), great heat flux carrying capacity, and good foldability (5000 cycles folding). In addition to this, such a GF is produced based on an economically efficient and quasi-industrial method incorporating continuous high-pressure homogenization processing (HPH), indicating an enormous potential as a new pathway to thermal management applications.

A promising method of improving the densification of powder metallurgical steel components is to blend nanopowder with the otherwise typically used micrometre-sized powder. The higher surface-to-volume ratio of nanopowder is hypothesized to accelerate the sintering process and increase the inter-particle contact area between the powder particles. This is supposed to enhance the material transport and improve the densification. In the present investigation, water-atomized iron powder (− 45 μm) was mixed separately with pure iron and low-carbon steel nanopowder, each at a ratio of 95 to 5 pct. These powder mixes were compacted at different pressures (400, 600 and 800 MPa) and then sintered at 1350 °C in a pure hydrogen atmosphere. The sintering behavior of the powder blend compacts was compared to that of the compact with micrometre-sized powder only. Densification commenced at much lower temperatures in the presence of nanopowder. To understand this, sintering at intermittent temperatures such as 500 °C and 700 °C was conducted. The fracture surface revealed that the nanopowder was sintered at between 500 °C and 700 °C, which in turn contributed to the densification of the powder mix at the lower temperature range. Based on the sintering experiments, an attempt was made to calculate the activation energy and identify the associated sinter mechanism using two different approaches. It was shown that the first approach yielded values in agreement with the grain-boundary diffusion mechanism. As the nanopowder content increased, there was an increase in linear shrinkage during sintering.

With the development of electronic products towards high-density integration, high performance and multifunction, the working frequencies and power consumption rate of electronic components and devices increase substantially. The resulting temperature rise has a great impact on the operation and lifetime of electronic products. Transient temperature control and efficient heat dissipation are essential to the stability and reliability of the electronic components and products. Paraffin wax, as one of the most commonly used phase change materials, has been widely applied in many products requiring transient temperature control due to its melting temperature lying in the range of electronics operation conditions. However, the applicable scopes of phase change materials were limited due to their shortcomings of low thermal conductivity and heat dissipation. In the present paper, both metal forms and carbon nanomaterials are used as thermal enhancers to increase the conduction of paraffin wax, and the heat transfer characters of the composites are investigated by numerical method. The simulation results show that the introduction of Cu or Ni foam as heat conductive enhancers can significantly increase the effective thermal conductivity of paraffin wax composite. The thermal conductivity of the composite with Ni foams is 3.684 times higher than that of the paraffin wax, and the increase is 12.485 times when Cu foam is used instead of Ni foam. Furthermore, the heat transfer of the composites can be strengthened by adding carbon nanomaterials into the paraffin wax so as to increase the thermal conductivity of the matrix. The simulation results show that the impact of dispersed carbon nanomaterials on thermal enhancement of the composites is less significant than that of metal foams.

The chase of high performance by chip manufacturers has greatly increased the power consumption of integrated circuits, which brings great challenges to the heat dissipation of electronics systems. It has also slowed down following up of the Moore's Law, and it is expected to hit the wall soon [1]. Graphene film with high in-plane thermal conductivity is one of the key materials to make it possible for electronics industry to continue to follow the Moore's Law. However, there are few studies focusing on the longitudinal thermal conductivity of graphene films. The purpose of this study is to investigate the longitudinal thermal conductivity of graphene films according to ASTM D5470 [2]. The results show that the longitudinal thermal conductivity of the pressed graphene film is greater than that of the unpressurized graphene film. The longitudinal thermal conductivity is 10.6 W/m· K for the unpressurized graphene film and 20.6 W/m· K for the pressed graphene film.

Low-dimensional materials such as graphene exhibit superior electrical, mechanical and thermal properties. However, structural defects occur during the growth or treatment process of carbon nanomaterial and greatly affect the material properties. In this paper, molecular dynamics simulation methods are used to study the effects of atomic defects in graphene sheets on the tensile strength, and the vacancy type and defect orientation are considered in the cases of graphene sheets under various mechanical loadings. The simulation results show that for the graphene sheets with structural defects, the fracture starts near the original vacancy position. The tensile strength of the graphene sheets with X1-type vacancy defects under zigzag direction is reduced by about 26.9% compared with that of the defect-free graphene sheet, while the graphene sheet with X2-type vacancy defects shows the least decrease in magnitude, which is 9.5% lower than that of the perfect graphene sheet. When stretched in the armchair direction, the tensile strength of the graphene sheet with H2 vacancy defects was greatly reduced by 27.1%, and the X1 vacancy defects shows the least influence, where tensile strength of the graphene sheets was reduced by 11.2%.

The increasing need for high thermal dissipation in small electronic products puts tough requirements on effective cooling solutions. Two of the most effective passive cooling devices in electronics today are vapor chambers and heat pipes. With new advancements in materials science and nanotechnology comes the possibility to further increase cooling capacity and at the same time make devices lighter. This study is a critical assessment on recent progress in the field of nanomaterial enhanced wick structures in vapor chambers and heat pipes. In this paper, nano-enhanced wick structures are divided into five different sub-categories based on material type. Publication trends for the different types of nano-enhanced wicks are studied by plotting them on a timeline. It is found that nanostructured metal wicks is the most studied field in recent years. A plot showing wick performance in terms of superheat temperatures for given heat flux is created to be used for benchmarking of new wick structures when pool boil experiments are carried out. An attempt to find correlation between publication trends, type of wick and performance is done. On the basis of the gathered data it is deemed difficult to find a distinct correlation, this is mainly due to difficulty in comparing performance between different studies, especially when different heat fluxes are used. There is no unambiguous answer to which category of nano-enhanced wicks that should be target for future studies. Graphene coating and pure carbon nanomaterials such as aerogels and graphene foam are still relatively unexplored and believed to have great potential if they can be attached to envelope materials.

In recent years, laser-reduced graphene oxide (LRGO) has received widespread interest, however, the thermal properties of graphene films obtained by laser reduction of GO are rarely reported. In this paper, a pulsed laser was used to reduce the prepared GO films. The obtained LRGO films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS). The thermal diffusivity of the LRGO was measured as 7.3 mm2/s, higher than that of GO measured as 5.9 mm2/s. The heating performance of LRGO was performed under different DC voltages and the results show that the temperature can reach up to 91 °C with a response time of 14 s under the voltage of 18 V. The excellent electrothermal performance of LRGO films indicate that the LRGO films are promising as heating elements for various application such as defoggers.

The current development of the electronics system requires capabilities beyond conventional heat transfer approaches. New solutions based on advanced materials are being developed to tackle the current challenges in the development of electronics systems and the nanoscale 2D materials such as graphene are at the centre of the effort to exploit the intrinsic properties of carbon nanomaterials. In this work, we introduce a new concept of graphene-coated copper nanoparticles (G-CuNPs) and explore their multifunctional potential applications in metallic based paste used in electronics. The nanoscale powder was found to present a core/shell structure with the copper particle at its core and a disordered multilayer graphene structure continuously coating its surface. The composition of the particles was analysed, and the presence of the coating was found to provide oxidation protection for the metallic core. Thermogravimetric analysis (TGA) showed an additional role of the G-CuNPs with a reduction effect without the use of an additional reducing agent. Furthermore, due to the combined effect of the size of the particles and the oxidation-free metallic core, Differential Scanning Calorimetry (DSC) analysis revealed a melting depression at temperatures as low as $155 ^{\circ}\mathrm{C}$. Finally, the mechanical properties of the nanocoating were investigated and the results showed an enhanced ductility at the surface of the particles due to the presence of the multi-layered graphene structure, which might be exploited for powder flow and lubrication effect.

Thermal performance of an epoxy resin reinforced by carbon fibers is studied by numerical simulation method. Various carbon fiber structures are taken into consideration and the effective thermal conductivity of the composite carbon fiber waved structure is obtained. The influences of the number, size, shape, spacing and arrangement of the carbon fibers on the thermal conduction of the composites are analyzed. The deformation of the composite under mechanical loading and the corresponding the thermal conductivity of the carbon fiber-reinforced epoxy resin are also investigated.

In this work, laser-induced graphene (LIG)/ polyimide (PI) films with good thermal properties were prepared by directly inducing graphene on the bare PI substrates by a computer numerical control (CNC) laser engraving machine. The obtained samples were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The results showed that the laser energy density has a significant impact on the microstructures of the samples. Moreover, the thermal diffusivity of LIG/PI was increased from 0.5 mm2/s to 1.6 mm2/s, which is 3 times higher than bare PI. Finally, the electrothermal properties of the LIG films were investigated and the results showed that under a 12 V power supply, the equilibrium temperature of LIG films increases from 45°C to 74°C with the increase of laser energy density from 1.8 J/mm2 to 2.4 J/mm2. Our results indicate that this time-saving, low-cost, and environment-friendly method is promising for fabricating excellent graphene-based materials.

A flexible graphene and polyimide composite film was designed and fabricated in this study. A polyimide solution was used as an adhesive layer to connect graphene film and polyimide film by hot-pressing. Laser flash thermal analysis method was carried out to evaluate the thermal diffusion coefficient of different thicknesses of the fabricated films at various temperatures. Bending test was carried out to evaluate the stability and reliability of the composite film. Scanning electron microscopy was applied to characterize the cross-section of the composite film before and after the peel test. IR imaging was employed to compare the heat diffusion of the composite film and traditional flexible copper clad laminate. The results show that the composite film has significantly better thermal diffusion capacity than traditional flexible copper clad laminate.

Graphene attracts great attention due to its excellent properties. However, the mechanical of assembled graphene-based film is usually inferior than its inherent mechanical properties. Herein, we construct a high-performance graphene-based film via vacuum filtration process by using graphene as matrix and hydroxylated Carbon Nanotube (CNT) as reinforcement agent. The synergistic interaction of hydrogen bonds between CNT and graphene Oxide (GO) and ionic bonds between Fe2+ on CNT and GO significantly improve the mechanical properties of free-standing and flexible rGO/CNT film. Scanning Electron Microscopic (SEM) imaging and stress transfer mechanism analysis show that the introduction of CNT can hinder the slippage of GO sheets and promote the stress transfer under the continuous loading. The obtained rGO/CNT film shows high toughness of 3 MJ/m3, which is 3.6 times higher than that of GO sheets. This facile and scalable strategy can pave the way for the fabrication of high-performance graphene-based film in various applications.

A thin film Gold/Platinum/Titanium (Au/Pt/Ti) - based microheater with pectination construction and a four-point probe was fabricated on a silica substrate. A standard lithography process was used to transfer the circuit pattern onto the substrate, and then Au/Pt/Ti was deposited on the substrate by an evaporator. Standard calibration was carried out at various temperatures, which can be obtained the relationship between the temperature and the resistance of the microheater, the results show that the Au/Pt/Ti-based microheater has a good linear relationship between the temperature and the resistance, indicating the microheater can also be used as a temperature sensor. Furthermore, the effects of different input powers, the geometry, and the thickness of the thin-film metals of the microheater were investigated and discussed. Finally, a finite element model was set up to see the temperature distribution of the microheater after the electric potential is applied.

With increasing demands of high-performance and functionality, electronics devices generate a great amount of heat. Thus, efficient heat dissipation is crucially needed. Owing to its extremely good thermal conductivity, graphene is an interesting candidate for this purpose. In this paper, a two-step temperature-annealing process to fabricate ultrahigh thermal conductive graphene assembled films (GFs) is proposed. The thermal conductivity of the obtained GFs was as high as 3826 ± 47 W m−1 K−1. Extending the time of high-temperature annealing significantly improved the thermal performance of the GF. Structural analyses confirmed that the high thermal conductivity is caused by the large grain size, defect-free stacking, and high flatness, which are beneficial for phonon transmission in the carbon lattice. The turbostratic stacking degree decreased with increasing heat treatment time. However, the increase in the grain size after long heat treatment had a more pronounced effect on the phonon transfer of the GF than that of turbostratic stacking. The developed GFs show great potential for efficient thermal management in electronics devices.

Purpose This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated. Design/methodology/approach Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively. Findings Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles. Originality/value Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.

Thermally conductive materials with electrically insulating properties have been extensively investigated for thermal management of electronic devices. The combined properties of high thermal conductivity, structural stability, corrosion resistance and electric resistivity make hexagonal boron nitride (h-BN) a promising candidate for this purpose. Theoretical studies have revealed that h-BN has a high in-plane thermal conductivity up to 400 - 800 W m−1 K−1 at room temperature. However, it is still a big challenge to achieve high thermally conductive h-BN thick films that are commercially feasible due to its poor mechanical properties. On the other hand, many polymers exhibit advantages for flexibility. Thus, combining the merits of polymer and the high thermal conductivity of h-BN particles is considered as a promising solution for this issue. In this work, orientated PVP/h-BN films were prepared by electrospinning and a subsequent mechanical pressing process. With the optimized h-BN loading, a PVP/h-BN composite film with up to 22 W m−1 K−1 and 0.485 W m−1 K−1 for in-plane and through-plane thermal conductivity can be achieved, respectively. We believe this work can help accelerate the development of h-BN for thermal management applications.

Increased demand on the mechanical and thermal properties on the thermal interface and die attach material creates a demand for materials with tailored material properties. Solder matrix fiber composites (SMFCs) have been shown to address these challenges, but have, so far, required complicated procedures and components. In this paper, we present the fabrication of a new type of SMFC based on commercially available fiber networks infiltrated with Sn–Ag–Cu alloy (SAC305) or indium using equipment for large-volume production. The composite material exhibits similar thermal properties compared to pure solder, and mechanical properties that can be tailored toward specific applications. We also show that the handling properties of the SMFC allows it to be used in process flows where multiple reflow cycles are required and can achieve a well-defined bond line thickness (BLT) and good bonding using fluxless reflow under pressure.

As the feature size of integrated circuit devices is shrinking to sub-7 nm node, the chip power dissipation significantly increases and mainly converted to the heat. Vertically Aligned Carbon Nanotube arrays (VACNTs) have a large number of outstanding properties, such as high axial thermal conductivity, low expansion coefficient, light-weight, anti-aging, and anti-oxidation. With a dramatic increment of chip temperature, VACNTs and their composites will be the promising materials as Thermal Interface Materials (TIMs), especially due to their high thermal conductivity. In this review, the synthesis, transfer and potential applications of VACNTs have been mentioned. Thermal Chemical Vapor Deposition (TCVD) has been selected for the synthesis of millimeter-scale VACNTs. After that, they are generally transferred to the target substrate for the application of TIMs in the electronics industry, using the solder transfer method. Besides, the preparation and potential applications of VACNTs-based composites are also summarized. The gaps of VACNTs are filled by the metals or polymers to replace the low thermal conductivity in the air and make them free-standing composites films. Compared with VACNTs- metal composites, VACNTs-polymer composites will be more suitable for the next generation TIMs, due to their lightweight, low density and good mechanical properties.

Vertically aligned carbon nanotube arrays (VACNTs) show a great potential for various applications, such as thermal interface materials (TIMs). Besides the thermally oxidized SiO2, atomic layer deposition (ALD) was also used to synthesize oxide buffer layers before the deposition of the catalyst, such as Al2O3, TiO2, and ZnO. The growth of VACNTs was found to be largely dependent on different oxide buffer layers, which generally prevented the diffusion of the catalyst into the substrate. Among them, the thickest and densest VACNTs could be achieved on Al2O3, and carbon nanotubes were mostly triple-walled. Besides, the deposition temperature was critical to the growth of VACNTs on Al2O3, and their growth rate obviously reduced above 650 °C, which might be related to the Ostwald ripening of the catalyst nanoparticles or subsurface diffusion of the catalyst. Furthermore, the VACNTs/graphene composite film was prepared as the thermal interface material. The VACNTs and graphene were proved to be the effective vertical and transverse heat transfer pathways in it, respectively.

With the ever increasing demand for improved thermal management solutions in modern electronic devices, carbon nanotubes (CNTs) have been suggested as a candidate material for thermal interface materials (TIMs). However, the interfacial resistance between CNTs and matching substrate is huge due to poor interaction at the interface. With the help of chemical functionalization, these materials can be exploited to their full potential in TIM applications. By utilizing the epoxy-silane-based monolayers, covalent anchoring can be obtained between the CNTs and target substrate in order to bridge the interface, where high resistances, otherwise, would arise. To adapt CNT arrays to the epoxy chemistry, the CNTs have subsequently been subjected to nitrogen plasma in order to activate them with amino groups. The thermal interfaces were measured, and the thermal resistance was found to be decreased by 5% in comparison with the reference samples.

Functional fillers, such as Ag, are commonly employed for effectively improving the thermal or electrical conductivity in polymer composites. However, a disadvantage of such a strategy is that the cost and performance cannot be balanced simultaneously. Therefore, the drive to find a material with both a cost efficient fabrication process and excellent performance attracts intense research interest. In this work, inspired by the core–shell structure, we developed a facile manufacturing method to prepare graphene‐encapsulated Cu nanoparticles (GCPs) through utilizing an improved chemical vapor deposition (CVD) system with a cold wall reactor. The obtained GCPs could retain their spherical shape and exhibited an outstanding thermal stability up to 179 °C. Owing to the superior thermal conductivity of graphene and excellent oxidation resistance of GCPs, the produced GCPs are practically used in a thermally conductive adhesive (TCA), which commonly consists of Ag as the functional filler. Measurement shows a substantial 74.6 % improvement by partial replacement of Ag with GCPs.

SiC microparticles with various weight ratios (0.0, 0.5, 1.0 and 1.5 wt%) are incorporated into sintered silver nanoparticles (AgNP) as one of the promising packaging materials for high-power electronic devices. Mechanical properties and constitutive behaviour of sintered AgNP reinforced by SiC microparticles are investigated based on nanoindentation experiment and analytical approach. Nanoindentations were performed in the manner of continuous stiffness measurement for a maximum penetration depth of 2000 nm at a strain rate of 0.05 s−1. Particularly, a Berkovich indenter is utilized to evaluate the values of Young's modulus and hardness, and a spherical indenter is utilized to describe the constitutive behaviour. For sintered AgNP with 0.5 wt% SiC, the morphology exhibits uniformly compact microstructures to enable optimizing the heat conductivity, the yield strength and hardening capacity of sintered AgNP material is enhanced. To describe the constitutive behaviour, an analytical approach is proposed to simulate the indentation behaviour. The parameters in the modified power-law model are determined by fitting the average indentation responses. The developed correlation between microstructure and macroscopic properties facilitates the design of AgNP paste morphology and improves the mechanical properties of sintered AgNP in electronics packaging.

Graphene foam is a three-dimensional structure made up of graphene. It provides conductive network with excellent heat transfer performance due to the outstanding features of the graphene. The dimensions of the graphene sheets in the foam structure and their alignment have significant impact on the thermal properties of graphene foams. In the present paper, the heat transfer performances of graphene sheets with different alignment have been studied and molecular dynamics simulations were carried out to investigate the influence of alignment angle of graphene sheets on the thermal conductive characteristics. The alignment forms various patterns, and the change of thermal conductivity depends on the alignment pattern.

In this work, a graphene assembled film integrated heat sink and water cooling technology was used to build an experimental set-up of a thermal management system to demonstrate the possibility to achieve efficient cooling of the propulsion battery in electric vehicles. The experimental results showed that the temperature decrease of a Li-ion battery module can reach 11°C and 9 °C under discharge rates as of 2C and 1C, respectively. The calculated thermal resistance of the graphene based cooling system is about 76% of a similar copper based cooling system. Surface modification was carried out on the graphene sheet to achieve a reliable bonding between the graphene sheet and the battery cell surface. This work provides a proof of concept of a new highly efficient approach for electric vehicle battery thermal management using the light-weight material graphene.

In order to meet the ever more demanding requirements of modern thermal management with the increasing high power density, an easy-fabricated laminated graphene film/indium/aluminum (GF/In/Al) composite was developed. The GF was fabricated through assemble graphene oxide (GO) sheets in a layer-by-layer structure and then subjected to graphitization process at high temperature as well as press forming process. The fabricated GF exhibits ultrahigh in-plane thermal conductivity together with good tensile strength. The GF/In/Al laminated composite was fabricated by hot-pressing indium coated GF and Al layers in vacuum environment. The indium layer was easily coated onto the GF due to its low melting point along with good flowing property. The thermal resistance measurements show that the indium bonding possess greater preponderance of reducing contact resistance than without bonding material and thermal conductive adhesive (TCA) bonding, because indium layer could fill the gap between GF and Al layers, and provide more stable connection. The results show that the obtained laminated composite could be potentially used in the thermal management of high power systems.

With the rapid development of electronic materials and technologies, the working frequencies of electronic components and devices have been greatly improved and the volume of electronic products has been shrinking. The integration density has increased significantly, which puts forward higher requirements for thermal management. One of the keys to the heat dissipation of electronic components is to transfer the heat rapidly to the radiator through the heat conducting medium. Therefore, the development of high conductive materials has become a research hotspot of high-density integrated devices and systems. Due to their excellent heat transfer properties, carbon nanomaterials such as carbon nanotube and graphene have attracted extensive attention. The thermal conductivities of carbon nanotube and graphene have obvious anisotropy, which limited their applications to some extent. In this paper, three-dimensional composite structures composed of graphene sheets and carbon nanotubes are considered. The heat transfer processes are simulated by molecular dynamics method and the heat transfer characteristics of van der Waals interaction and chemical bond structures are analyzed. The effects of heat flow and nanotube layout on the thermal properties of three-dimensional composite structures are discussed.

During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m−1 K−1, while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.