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1.	Hansson, Josef, 1991, et al. (författare) Synthesis of a Graphene Carbon Nanotube Hybrid Film by Joule Self-heating CVD for Thermal Applications 2018 Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2018-May Konferensbidrag (refereegranskat)abstract Hybrid films based on vertically aligned carbon nanotubes (CNTs) on graphene or graphite sheets have been proposed for application as thermal interface materials and micro heat sinks. However, the fabrication of these materials are limited to small scale, expensive and complicated chemical vapor deposition (CVD) for CNT synthesis. We present a new method for direct growth of CNTs on one or both sides of a thin graphene film (GF) using joule self-heating of the graphene film to provide the necessary heat for the thermal breakdown of carbon feedstock in a CVD process. The resulting CNT forests show good density and alignment consistent with regular CVD synthesis processes on silicon surfaces. The resulting double sided GF/CNT hybrid film is directly applicable as a thermal pad. The CNT forest has a thermal conductivity of 30 W/mK, measured by pulsed photothermal reflectance, and the total thermal interface resistance between aluminum blocks was measured to be 60 Kmm 2 /W using an ASTM D5470 compliant 1-D measurement setup. This method of directly synthesizing CNTs on graphene films is more energy efficient and capable of larger volume production compared to traditional CVD methods. It is also compatible with scaling up towards continuous roll-to-roll production for large scale commercial production, one of the major limitations preventing CVD-grown CNTs from commercial applications
2.	Huang, Shirong, et al. (författare) Reliability of Graphene-based Films Used for High Power Electronics Packaging 2015 Ingår i: 16th International Conference on Electronic Packaging Technology, ICEPT 2015, Changsha, China, 11-14 August 2015. - 9781467379991 ; , s. 852-855 Konferensbidrag (refereegranskat)abstract Graphene-base film was fabricated with chemical conversion process, including graphene oxide (GO) prepared by Hummer's method, graphene oxide reduced with L-ascorbic acid (LAA), graphene based film deposited by vacuum filtration process. Meanwhile, the functionalization of the graphene-based film was performed to decrease the thermal interface resistance between the graphene-based film and substrate. Characterization data showed that the graphene-based film possessed high reliability after 500 hours under 85°C aging test. In summary, the graphene-based film can be a promising solution in thermal management of high power electronics.
3.	Jiang, Di, 1983, et al. (författare) Embedded Fin-Like Metal/CNT Hybrid Structures for Flexible and Transparent Conductors 2016 Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 12:11, s. 1521-1526 Tidskriftsartikel (refereegranskat)abstract In this paper, an embedded fin-like metal-coated carbon nanotube (Fin-M/CNT) structure is demonstrated for flexible and transparent conductor wire applications. Embedded in a polydimethylsiloxane polymeric substrate, Fin-M/CNT wires with a minimum width of 5 μm and a minimum pitch of 10 μm have been achieved. Direct current resistances of single Fin-M/CNT wires, where the supporting CNT structures have been covered by Ti/Al/Au metal coatings of different thicknesses, have been measured. The high aspect ratio of the fin-like structures not only improves the adhesion between the wires and the polymeric substrate, but also yields a low resistance at a small surface footprint. In addition, transparent Fin-M/CNT grid lines with hexagonal patterns, with a sheet resistance of as low as 45 Ω sq−1, have been achieved at an optical transmittance of 88%. The robustness of the Fin-M/CNT structures has been demonstrated in bending tests up to 500 cycles and no significant changes in wire resistances are observed.
4.	Nylander, Andreas, 1988, et al. (författare) RF properties of carbon nanotube / Copper composite through silicon via based CPW structure for 3D integrated circuits 2019 Ingår i: 2019 IEEE 14th Nanotechnology Materials and Devices Conference, NMDC 2019. Konferensbidrag (refereegranskat)abstract The development of integrated circuits (ICs) has seen exponential growth in performance over the last couple of decades and has pushed the boundaries for how we use our electronics in our daily lives. The scaling of ICs, and therefore also the performance development, is now starting to slow down when the physical designs are reaching critical dimensions where quantum effects starts to become noticeable. One proposed route to circumvent these issues for a continued scaling is based on the implementation of 3D integration by chip stacking for an increased miniaturization potential. Miniaturisation will soon also result in interconnect dimensions that surpass the mean free path (MFP) in Cu, the commonly used material for interconnects today, with a sharp increase in resistivity as a result. By changing the through silicon via (TSV) interconnect material from Cu to a carbon nanotube (CNT)/Cu composite, continued scaling can be ensured both in terms of electrical conductivity, ampacity and signal delays. Furthermore, a reduced skin effect can be achieved ensuring lower signal losses at higher RF frequencies making the CNT/Cu composite an ideal candidate to replace tranditional Cu interconnects. In this paper, we are demonstrating a coplanar waveguide (CPW) test structure using CNT/Cu filled TSVs connected to Au transmission lines on SiO2-passivated high resistivity Si substrates. The parasitic losses of the CNT/Cu TSV based CPW test structure were measured using a Sparameters test setup. The results showed that the CNT/Cu TSVs with affiliated contacts increased the signal losses up to S21 = -5.5 dB compared to Au reference transmission lines. These results are in line with previous results using CNT based TSVs and will serve as a basis for future improvements of CNT based interconnect technology for 3D integration.
5.	Wang, Nan, 1988, et al. (författare) Improved Interfacial Bonding Strength and Reliability of Functionalized Graphene Oxide for Cement Reinforcement Applications 2020 Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 26:29, s. 6561-6568 Tidskriftsartikel (refereegranskat)abstract Poor bonding strength between nanomaterials and cement composites inevitably lead to the failure of reinforcement. Herein, a novel functionalization method for the fabrication of functionalized graphene oxide (FGO), which is capable of forming highly reliable covalent bonds with cement hydration products, and therefore, suitable for use as an efficient reinforcing agent for cement composites, is discussed. The bonding strength between cement and aggregates was improved more than 21 times with the reinforcement of FGO. The fabricated FGO also demonstrated many important features, including high reliability in cement pastes, good dispersibility, and efficient structural refinement of cement hydration products. With the incorporation of FGO, cement mortar samples demonstrated up to 40 % increased early and ultimate strength. Such results make the fast demolding and manufacture of light constructions become highly possible, and show strong advantages on improving productivity, saving cost, and reducing CO2 emissions in practical applications.
6.	Zehri, Abdelhafid, 1989, et al. (författare) High porosity and light weight graphene foam heat sink and phase change material container for thermal management 2020 Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42 Tidskriftsartikel (refereegranskat)abstract 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.
7.	Zhang, Yong, 1982, et al. (författare) 2D HEAT DISSIPATION MATERIALS FOR MICROELECTRONICS COOLING APPLICATIONS 2016 Ingår i: China Semiconductor Technology International Conference 2016, CSTIC 2016. - 9781467388047 Konferensbidrag (refereegranskat)abstract The need for faster and smaller, as well as more reliable and efficient consumer electronic products has resulted in microelectronic components that produce progressively more heat. The resultant reliability issues from the increased heat flux are serious and hinder technological development. One solution for microelectronics cooling applications is 2D materials applied as heat spreaders and these include monolayer graphene, graphene based films, and monolayer hexagonal boron nitride and BN based films. In addition, thermal performances of the graphene heat spreader were also studied under different packaging structures, including wire bonding, cooling fins and flip chips. Finally, 2D hexagonal Boron nitride (h-BN) heat spreaders, fabricated by different methods, had their heat dissipation performances characterized by different thermal characterization methods, such as resistance temperature detector (RTD) and Infrared (IR) methods. In conclusion, these new novel 2D materials developed show great potential for microelectronics cooling applications.
8.	Casa, Marcello, et al. (författare) Development and characterization of graphene-enhanced thermal conductive adhesives 2014 Ingår i: 15th International Conference on Electronic Packaging Technology, ICEPT 2014; Wangjiang HotelChengdu; China; 12 August 2014 through 15 August 2014. - 9781479947072 ; :Art. no. 6922700, s. 480-483 Konferensbidrag (refereegranskat)abstract According to Moore's Laws, complexity and power densities of electronic devices are increased during the last decades, moreover their dimensions are shrinking to nanometers causing hot-spot temperature escalation. Thermal management, therefore, becomes a critical issue for next generation of electronics. This scenario motivates development of novel thermal conductive adhesive (TCA) with enhanced thermal conductivity. Conventional TCAs use polymers as the matrix (base material) and utilize large loading weight fraction of the filler, usually silver particles, to achieve the thermal conductivity of 1-4 W/ m K at room temperature [1]. Lately it was discovered that graphene exhibit superior thermal conductivity [2] even when they are incorporated with matrix materials [3], which offers a potential to develop high thermal conductive graphene-filled compound. In this paper, a new functionalized graphene and its filled TCA have been developed and characterized. Starting from pristine graphite flakes, graphene was prepared through chemical exfoliation and functionalized with a nano silver layer to form a special metal/graphene hybrid material. Moreover, an efficient method to uniformly disperse the nano-scaled graphene hybrid material in silver-epoxy matrix was developed. Cross-section view of SEM has shown a homogeneous component structure, and TGA analysis of hybrid material is given. The developed compound is based on a commercial TCA which is composed with epoxy matrix and micro-sized Ag flakes. Thermal characterization through Laser-flash equipment has indicated that a significant thermal conductivity improvement was achieved through adding functionalized graphene into the material. Different TCA samples with different weight percentages of functionalized graphene ranging from 0 % (reference) to 11.5 % were prepared and tested to study thermal conductivity change. Data show that a thermal conductivity value of 7.6 W/ m K is reached when the graphene/silver percentage is 11.5 % that is almost 4 times higher than our reference.
9.	Gutierrez, Martí, 1993, et al. (författare) Sintering of SiC enhanced copper paste for high power applications 2017 Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging (NordPac). - 9781538630556 ; , s. 151-156 Konferensbidrag (refereegranskat)abstract In this work a Cu paste consisting in both micro and nanoparticles was produced. The copper paste was produced with different additive weight percentages of Ag coated SiC and sintered for 30min at 500°C under 6,5MPa in N2 atmosphere. The thermal resistance and composition of the resulting joints was studied. XPS and EDX measurements show no significant oxidation of the Cu after sintering, which is attributed to the combination of reductive agents in the paste and the inert atmosphere. SEM images of cross sections show contacts with no voids between the SiC particles and the copper matrix. Thermal conductivity measurements with laser flash analysis (LFA) show that the additive increases the effective thermal conductivity to more than double of that of the pure copper paste at 2% additive weight percentage, but bigger amounts yield smaller improvements and presumably would eventually worsen it.
10.	Han, H. X., et al. (författare) Functionalization mediates heat transport in graphene nanoflakes 2016 Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 7 Tidskriftsartikel (refereegranskat)abstract The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by similar to 28 degrees C for a chip operating at 1,300 Wcm(-2). Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene-graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.
11.	Jiang, Di, 1983, et al. (författare) A flexible and stackable 3D interconnect system using growth-engineered carbon nanotube scaffolds 2017 Ingår i: Flexible and Printed Electronics. - : IOP Publishing. - 2058-8585. ; 2:2 Tidskriftsartikel (refereegranskat)abstract One of the critical challenges for realizing flexible electronic systems for a wide range of applications is the development of materials for flexible and stackable interconnects. We propose and demonstrate a three-dimensional (3D)interconnect structure embedded in a polymeric substrate using metal-coated carbon nanotube (CNT)scaffolds. By using two different underlayer materials for the catalyst, onestep synthesis of a dual-height CNT interconnect scaffold was realized. The CNT scaffolds serve as flexible cores for both annular metal through-substrate-vias and for horizontal metal interconnect. The 3D-CNT network was fabricated on a silicon substrate, and once the scaffolds were covered by metal, they were embedded in a polymer serving as a flexible substrate after peel-off from the silicon substrate. The 3D-CNT interconnect network was exposed to mechanical bending and stretching tests while monitoring its electrical properties. Even after 300 cycles no significant increase of resistances was found. Electrically there is a trade-off between flexibility and conductivity due to the surface roughness of the scaffold. However, this is to some extent alleviated by the metalized sidewalls giving the horizontal wires a cross-sectional area larger than indicated by their footprint. For gold wires 200 nm thick, measurements indicated a resistivity of 18 μΩ.cm, a value less than one order of magnitude larger than that of bulk gold, and a value that is expected to improve as technology improves. The mechanical properties of the metalized scaffolds were simulated using a finite element model. The potential scale-up capability of the proposed 3D-CNT network was demonstrated by the stacking of two such polymer-embedded interconnect systems.
12.	Kuzmenko, Volodymyr, 1987, et al. (författare) Cellulose-derived carbon nanofibers/graphene composite electrodes for powerful compact supercapacitors 2017 Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 7:73, s. 45968-45977 Tidskriftsartikel (refereegranskat)abstract Herein, we demonstrate a unique supercapacitor composite electrode material that is originated from a sustainable cellulosic precursor via simultaneous one-step carbonization/reduction of cellulose/graphene oxide mats at 800 degrees C. The resulting freestanding material consists of mechanically stable carbon nanofibrous (CNF, fiber diameter 50-500 nm) scaffolds tightly intertwined with highly conductive reduced graphene oxide (rGO) sheets with a thickness of 1-3 nm. The material is mesoporous and has electrical conductivity of 49 S cm(-1), attributed to the well-interconnected graphene layers. The electrochemical evaluation of the CNF/graphene composite electrodes in a supercapacitor device shows very promising volumetric values of capacitance, energy and power density (up to 46 F cm(-3), 1.46 W h L-1 and 1.09 kW L-1, respectively). Moreover, the composite electrodes retain an impressive 97% of the initial capacitance over 4000 cycles. With these superior properties, the produced composite electrodes should be the "looked-for" components in compact supercapacitors used for increasingly popular portable electronics and hybrid vehicles.
13.	Kuzmenko, Volodymyr, 1987, et al. (författare) FREESTANDING CARBON NANOFIBERS/GRAPHENE COMPOSITE ELECTRODES FOR SUPERCAPACITORS 2016 Ingår i: The World Conference on Carbon - Carbon 2016, July 10-15, State College, PA, USA. Konferensbidrag (refereegranskat)
14.	Liu, Johan, 1960, et al. (författare) 1. Thermal Characterization of Power Devices Using Graphene-based Film 2014 Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781479924073 ; , s. 459 - 463 Konferensbidrag (refereegranskat)abstract Due to its atomic structure with sp2 hybrid orbitals and unique electronic properties, graphene has an extraordinarily high thermal conductivity which has been reported to be up to 5000 W/mK. As a consequence, the use of graphene-based materials for thermal management has been subject to substantial attention during recent years in both academia and industry. In this paper, the development of a new type of graphene-based thin film for heat dissipation in power devices is presented. The surface of the developed graphene based film is primarily composed of functionalized graphene oxide, that can be bonded chemically to the device surface and thus minimize the interface thermal resistance caused by surface roughness. A very high in-plane thermal conductivity with a maximum value of 1600 W/mK was detected by laser flash machine regarding to the graphene-based films. To investigate the structure of the graphene-based films, scanning electron microscopy (SEM) and raman spectroscopy were carried out. Finally, LED demonstrators were built to illustrate the thermal performance of graphene-based film and the functional layers. IR camera recorded a 5°C lower temperature of a LED demonstrator with SHT G1000 as the binding layer instead of a commercial thermal conductive adhesive.
15.	Liu, Ya, 1991, et al. (författare) Graphene based thermal management system for battery cooling in electric vehicles 2020 Ingår i: Proceedings - 2020 IEEE 8th Electronics System-Integration Technology Conference, ESTC 2020. Konferensbidrag (refereegranskat)abstract 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.
16.	Liu, Ya, 1991, et al. (författare) Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader 2019 Ingår i: Proceedings - 2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019. ; , s. 1-5 Konferensbidrag (refereegranskat)abstract 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.
17.	Liu, Ya, 1991, et al. (författare) Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader 2019 Ingår i: Advancing Microelectronics. - 2222-8748. ; 2019:NOR, s. 1-5 Tidskriftsartikel (refereegranskat)abstract 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.
18.	Shi, Yuqing, et al. (författare) Fabrication and characterization of graphene based film 2017 Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 162-166 Konferensbidrag (refereegranskat)abstract Large area, freestanding graphene papers fabricated from 2D graphene nanosheets with optimized microstructure, graphene sheet alignment and superior properties have a wide range of functional applications. In this paper, we propose a novel approach to fabricate graphene film by Electro-spray deposition (ESD), which is considered as the preparation for a roll-to-roll industrial production of the further. Expanded graphite, as the raw materials, was dispersed into N-Methyl-2-pyrrolidone (NMP) which is used as the feeding solution for ESD. It is also shown that high-shear mixing and high ultra-sonication of graphite powder in NMP solvent result in large-scale exfoliation, giving good dispersions of graphene nanosheets. The fabrication of the film with different thicknesses is based on ESD onto the surface of a heated aluminum foil at around 140°C. Brunauer-Emmett-Teller method is used to test the surface area of raw material, which has been reported to reach 1200 m2/g. Raman spectroscopy and scanning electron microscope (SEM) are used to characterize the microstructure and morphology of the film, contributing to the optimization of electrospray's parameters. Joule heating was utilized to quantify thermal conductivity of the film.
19.	Sun, Shuangxi, 1986, et al. (författare) Heat dissipation of a hybrid CNT/Graphene based heat spreader 2016 Ingår i: IMAPS Nordic Annual Conference 2016, Tonsberg, Norway, 5-7 June 2016. - 9781510827226 Konferensbidrag (refereegranskat)abstract Graphene and Carbon Nanotube have been received much attention in the microelectronics application, due to their intrinsic unique performance in the thermal and electronic conduction. In this paper, a free standing three dimensional (3D) carbon nanotube (CNT)/graphene (G) hybrid material was synthesized through chemical vapor deposition (CVD) process for heat dissipation application. Scanning electron microscope (SEM) was employed to characterize the morphology of this hybrid material. Thermal test chip was designed and fabricated to test the cooling effect of this CNT/G hybrid material. The temperature of the hot spot on the chip can decreased around 10 oC with the help of this hybrid material.
20.	Tang, Luping, 1956, et al. (författare) Pre-Study of Graphene-Enhanced Cementitious Materials 2014 Rapport (övrigt vetenskapligt/konstnärligt)abstract In the pre-study the bonds between graphene and cement hydrates are analyzed and two types of functionalized graphene oxides with potential covalent bonds, that is, silica coated GO (GO-SiO2) and silane functionalized GO (FS-GO), are tested.
21.	Wang, Nan, 1988, et al. (författare) Development and Characterization of Graphene Enhanced Thermal Conductive Adhesives 2016 Ingår i: 2016 6th Electronic System-Integration Technology Conference (Estc). - 9781509014026 ; , s. Article no 7764682- Konferensbidrag (refereegranskat)abstract In this paper, a graphene enhanced thermal conductive adhesive (G-TCA) was developed for thermal management of power devices. The developed G-TCA has many advantages, including high thermal conductivity, lower density, good dispensing ability. and cost effective. To fabricate G-TCAs. few-layer graphene was utilized as fillers to improve the thermal conductivity of the TCA. The graphene nanosheets were fabricated through a high-speed shear mixing process in a mixed solvent. Compared to many reported liquid exfoliation process, the graphene fabrication process shows many advantages, such as high process efficiency, mass production, low-cost, clean and safe process. G-TCA sample with a hybrid filler ratio of 73% Ag and 3% graphene shows the highest thermal conductivity of 8 W/m K, which is almost four times higher than reference TCAs. A Joule heating setup was built to simulate G-TCA's function in a real electronic component and demonstrate the superior heat dissipation properties of the G-TCAs. Viscosities of the G-TCA samples were regulated in an acceptable range of many dispensing processes to be able to make uniform and fine patterns. Therefore, the developed G-TCA could be widely used for thermal management of power devices and electronic packaging area to decrease their working temperatures and extend the lifetime of devices.
22.	Wang, Nan, 1988, et al. (författare) Efficient surface modification of carbon nanotubes for fabricating high performance CNT based hybrid nanostructures 2017 Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 111, s. 402-410 Tidskriftsartikel (refereegranskat)abstract Carbon nanotubes (CNTs) were chemically modified to achieve strong binding strength with the attached functional components as well as good dispersability and nanoparticle size-uniformity. An efficient multi-oxidation process was developed to create porous out layer with many nanoscale defects on the surface of CNTs for metallic nanoparticle close attachment and bond sufficient oxygen-containing groups, which assisted the dispersion of CNTs in the aqueous solution. The surface modified CNTs have advantages of strong binding capability, large surface area, high mechanical strength and good dispersability, which show great potential as building blocks for hybrid nanomaterials. Monodispersed silver nano particles with an average size of 3 nm were formed from inside the created nanoscale defects on the surface of CNTs without any obvious agglomerations. The fabricated hybrid exhibited much enhanced anti-bacterial performance compared to commercial silver nanoparticles due to the combined antibacterial effects of CNTs and silver nanoparticles. With these superior properties, the developed surface modification process could be widely used for improving the performances of many CNT based hybrid nanomaterials in diverse applications.
23.	Wang, Nan, 1988, et al. (författare) Flexible Multi-functionalized Carbon Nanotubes Based Hybrid Nanowires 2015 Ingår i: Advanced Functional Materials. - 1616-3028 .- 1616-301X. Tidskriftsartikel (refereegranskat)
24.	Wang, Nan, 1988, et al. (författare) Flexible Multifunctionalized Carbon Nanotubes-Based Hybrid Nanowires 2015 Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 25:26, s. 4135-4143 Tidskriftsartikel (refereegranskat)abstract In this work, flexible multifunctionalized carbon nanotube (CNT)-based hybrid nanowires are synthesized through surface modification processes. The good dispersability of the hybrid nanowire in polar solvents facilitates directly making fine patterns with a minimum width of 40 μm for applications of flexible and stretchable circuits (FSCs). The hybrid nanowire possesses a flexible and highly conductive structure which demonstrates stable electro-mechanical properties on polydimethylsiloxane (PDMS) substrates under large structural deformation. FSCs fabricated from the hybrid nanowires show a constant resistance of 0.096 Ω □-1 (equivalent of a resistivity 0.96 Ω μm) under repeated bending cycles. The FSCs also have a low and stable sheet resistance of 0.4 Ω □-1 for strains up to 30%, which is almost four orders of magnitude lower than that of pure CNT samples (1316 Ω □-1). Further improved stretchability and electro-mechanical properties (0.1 Ω □-1, at the strain of 100%) are achieved with a prestrain PDMS substrate. Repeated deformation tests demonstrate the high reliability of FSCs. The observed stable and reliable electro-mechanical performance of FSCs suggests the potential use of the material in wearable and portable electronics. Multifunctionalized hybrid nanowires based on carbon nanotubes are prepared through different surface modification processes. These hybrid nanowires exhibit both the high electrical conductivity of metal and excellent mechanical properties of carbon nanotubes together with good dispersability. Flexible and stretchable electrodes based on the hybrid nanowires demonstrate stable electro-mechanical properties under large structural deformations.
25.	Wang, Nan, 1988 (författare) Functionalization and Characteization of Carbon-based Nanomaterials 2015 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Surface functionalization of nanomaterials opens up unlimited possibilities to combine the distinct properties of inorganic, organic, or even bioactive components in a single material and bring novel functionalities in a wide range of applications ranging from electronics to catalysts and medicine carriers. So far, a variety of organic and inorganic nanomaterials have been explored to construct different functionalized nanomaterials. Among them, carbon nanomaterials (CNMs), such as carbon nanotubes (CNTs) carbon nanofibers (CNFs) and graphene, are believed to be promising building blocks for constructing nanoscale functionalized materials, owing primarily to their large surface area and extraordinary electrical and mechanical properties. In this thesis, flexible and scalable chemical approaches to functionalize CNMs are developed for different applications. According to the bonding difference between CNMs and the functional components, these approaches can be divided into two groups, including covalent functionalization and non-covalent functionalization. In addition, a variety of characterization methods are utilized to characterize the structures and properties of the as-fabricated functionalized CNMs. Covalent functionalization of CNMs surface is based on reactions with the oxygen-containing groups of CNMs which are bonded directly to the π-conjugated skeleton of the CNMs. The first part of the work in the thesis is to functionalize CNTs surface via simultaneously oxidation and ultrasonication treatments and fabricate metal nanoparticle decorated CNT hybrid. As a result, finely grained and uniform silver nanoparticles were successfully deposited on the surface of activated CNTs. The other part of covalent functionalization of CNMs is about the fabrication of free-standing graphene based films (GBFs) via self-assembly and functionalization to improve GBF’s heat spreading performance. The results show efficient cooling performance of the functionalized GBF which could offer potential solutions for the thermal management of high power devices. Non-covalent functionalization utilizes various functional molecules or active species as assembly mediators to functionalize the surface of CNMs via non-covalent interactions. In the thesis, non-covalent functionalization of CNTs was realized through polymer wrapping. The targeted wrapping of APTES and silica layers on the surface of CNTs enabled homogeneous CNT dispersion in various polar solvents, and also facilitated the silver nanoparticle’s deposition. The synthesized multi-functionalized CNT based hybrid nanowires demonstrated superior mechanical and electrical performance in the application of flexible and stretchable circuits (FSCs) due to a highly conductive and flexible structure, which show great potential in the field of wearable and portable electronics.
26.	Wang, Nan, 1988 (författare) Functionalization and Characterization of Carbon Based Nanomaterials for Electronics, Composite and Biomedical Applications 2017 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Surface functionalization of nanomaterials to combine different material’s properties together opens up unlimited possibilities for both academic research and industrial applications. In this thesis, flexible and scalable chemical approaches to functionalize carbon nanomaterials (CNMs) are developed for different applications, including electronics, composite and biomedical applications. According to the bonding difference between CNMs and functional components, these approaches can be divided into two groups, including covalent functionalization and non-covalent functionalization. Covalent functionalization of CNMs surface is based on reactions of different components with the oxygen-containing groups of CNMs. The first part in this section introduced the covalent functionalization of carbon nanotubes for biomedical application. The surface of CNTs was modify by a multi-oxidation process and coated by silver nanoparticles to improve CNT’s antibacterial property. The developed silver/CNT composites show strong antibacterial property to bacteria. The second part presents covalent functionalization of graphene oxide for cement reinforcement. The developed surface functionalized GO (FGO) can improve both the early and ultimate strength of the Portland cement mortar efficiently. The key benefit of FGO lies in its ability to form covalent bonds with C-S-H whilst having minimum effect on the workability of mortar paste. The third part introduced the covalent functionalization of graphene based films (GBFs) that act as heat spreaders for hotspot cooling. The applied covalent bonding between GBF and the substrate can significantly reduce the thermal interface resistance, showing great advantages on cooling of high-power density devices. Non-covalent functionalization utilizes various functional molecules or active species as assembly mediators to functionalize the surface of CNMs via non-covalent interactions. The first part of this section presents a method of non-covalent self-assembly of high-thermal-conductivity of graphene films (GFs). The fabricated smooth, large-grain and turbostratic-stacking GFs shows excellent thermal and mechanical properties, which is superior to most of currently existing thermally conductive materials. The second part introduced the non-covalent functionalization of graphene for high thermal conductive adhesive. Liquid exfoliated few-layer graphene was utilized as fillers to improve the thermal conductivity of the thermal conductive adhesive which showed an improvement of 400 %. The third part presents a non-covalent functionalization process for synthesizing intrinsically flexible multi-functionalized CNT based hybrid nanowires. The synthesized multi-functionalized CNT based hybrid nanowires possess many excellent properties, such as good dispersability and stability in various polar solvents, large flexibility and high electrical conductivity. These extraordinary properties facilitate the application of hybrid nanowires in the fabrication of flexible and stretchable circuits (FSCs) with high resolution.
27.	Wang, Nan, 1988, et al. (författare) Reliability investigation of nano-enhanced thermal conductive adhesives 2012 Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781467321983 Konferensbidrag (refereegranskat)abstract This paper deals with silver (Ag) coated silicon carbide nanoparticles (SiC@Ag NPs) for thermal conductive interconnect and die attach applications.
28.	Wang, Nan, 1988, et al. (författare) Synthesis of highly conductive and mechanically strong silver coated silk bundles for flexible electronic applications 2016 Ingår i: IMAPS Nordic Annual Conference 2016 Proceedings. - 9781510827226 Konferensbidrag (refereegranskat)abstract Portable and wearable electronics that feature lightweight, highly compact and low cost can enable a wide variety of new applications, such as paper-like displays, smart clothing, stretchable solar cells, camera eyes and biomedical sensors. The applications for these types of system require conductive materials that are both highly conductive and mechanically robust enough to have large deformation stability. In this work, silver coated silk hybrid fibers were fabricated to meet the above requirements. As one of natural polymers used by human at the earliest stage, silk fiber has many advantages, such as light weight, good comfortability and mechanically robust. The chemical structure of silk fiber is composed of two main proteins, fibroin and sericin. Importantly, the sericin layer shows the special sol-gel property under temperature difference and therefore can be used for adhesion between the deposited silver nanoparticles and the surface of silk bundles. The silver coating layer on the surface of silk fiber can significantly improve the electrical conductivity of the hybrid structure to 1600 S/cm. Such a good conductivity is attributed to a complete silver shell structure. Importantly, the fabricated silver coated silk hybrid fibers demonstrated stable electro-mechanical properties under different structural deformations, including bending, compressing, and twisting. The observed stable and reliable electro-mechanical performance of silver coated silk hybrid fibers suggests the potential use of the material in future wearable and portable electronics.
29.	Wang, Nan, 1988, et al. (författare) Tailoring the Thermal and Mechanical Properties of Graphene Film by Structural Engineering 2018 Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 14:29 Tidskriftsartikel (refereegranskat)abstract Due to substantial phonon scattering induced by various structural defects, the in-plane thermal conductivity (K) of graphene films (GFs) is still inferior to the commercial pyrolytic graphite sheet (PGS). Here, the problem is solved by engineering the structures of GFs in the aspects of grain size, film alignment, and thickness, and interlayer binding energy. The maximum K of GFs reaches to 3200 W m−1K−1and outperforms PGS by 60%. The superior K of GFs is strongly related to its large and intact grains, which are over four times larger than the best PGS. The large smooth features about 11 µm and good layer alignment of GFs also benefit on reducing phonon scattering induced by wrinkles/defects. In addition, the presence of substantial turbostratic-stacking graphene is found up to 37% in thin GFs. The lacking of order in turbostratic-stacking graphene leads to very weak interlayer binding energy, which can significantly decrease the phonon interfacial scattering. The GFs also demonstrate excellent flexibility and high tensile strength, which is about three times higher than PGS. Therefore, GFs with optimized structures and properties show great potentials in thermal management of form-factor-driven electronics and other high-power-driven systems.
30.	Yang, Y., et al. (författare) Heat dissipation performance of graphene enhanced electrically conductive adhesive for electronic packaging 2017 Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 125-128 Konferensbidrag (refereegranskat)abstract Electrically conductive adhesive is a new type of environmentally interconnect material which can be used in electronic packaging to replace the traditional solders due to its advantages of simple applying process and low curing temperature. Silver coated graphene is employed in this work to enhance the thermal conductivity of the current commercial electrically conductive adhesive with very low thermal conductivity. Thermal conductivity of the electrically conductive adhesive was measured by laser flash thermal analyzer. The infrared thermal imager was utilized to obtain the temperature distribution of chip surface. The results indicated that the developed graphene enhanced electrically conductive adhesive has perfect heat performances. It can be believed that this new kind of electrically conductive adhesive possesses promising application in electronic packaging in the future.
31.	Yuan, G., et al. (författare) Graphene-based heat spreading materials for electronics packaging applications 2017 Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. - 9781538630556 ; , s. 172-174 Konferensbidrag (refereegranskat)abstract Graphene-based heat spreading materials, including graphene-based film (GBF) and graphene-based electrically conductive adhesive (G-CA), were applied to electronics packaging. The thermal performances of GBF and G-CA were analyzed by resistance temperature detector (RTD) and thermal infrared imager. When the chip was covered by GBF and G-CA, the temperature of hotspot could be reduced by 3.1°C, at heat flux of 580 W/cm2. To analyze the thermal performances of G-CA and GBF in 3D electronics packaging, the distribution of temperature and temperature profiles on the top surface of chip were analyzed by COMSOL. Both of GBF and G-CA could obviously reduce the temperature of hotspot on the top surface of chip, compared with that on the bare chip. With G-CA and GBF, the temperature of hotspot could be reduced by 8°C. It suggests that both of G-CA and GBF are good heat spreading materials for electronics packaging application.
32.	Zhang, Q., et al. (författare) Effect of sintering method on properties of nanosilver paste 2017 Ingår i: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. ; , s. 186-189 Konferensbidrag (refereegranskat)abstract Nanoscale silver paste has a good application prospect in heat dissipation of high-power chips due to the characteristics of low temperature sintering and high temperature service. The properties of the nanosilver paste including thermal conductivity, electrical conductivity, and shear strength are affected greatly by the sintering process. The influence of different sintering methods on the performance of the nanosilver paste was studied in this article. The nanosilver paste with 80.5 wt% nano-scale silver particles, 1.5 wt% submicron-scale SiC particles with Ag coating, 0.9 wt% dispersion agent, 10 wt% organic carrier and 7.1 wt% diluting agent was sintered at 260°C for 30 min with three different methods, heating table sintering, heating furnace sintering, and mixed sintering. The samples obtained by mixed sintering process have higher thermal conductivity than the ones obtained by heating furnace sintering method and heating table sintering method. The effect of sintering methods on shear strength of nanosilver paste was also investigated subsequently. Shear testing equipment was used to measure the shear strength of the samples gained by heating table sintering, heating furnace sintering, and air dry oven sintering. The maximum shear strength was obtained for the samples by heating table sintering method. The shear strength of samples by air dry oven sintering method was the minimum one.
33.	Zhang, Q., et al. (författare) Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles 2019 Ingår i: Soldering and Surface Mount Technology. - 1758-6836 .- 0954-0911. ; 31:4, s. 193-202 Tidskriftsartikel (refereegranskat)abstract © 2019, Emerald Publishing Limited. 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.
34.	Zhang, Xiangnan, et al. (författare) Gut Bacterial Indole-3-acetic Acid Induced Immune Promotion Mediates Preventive Effects of Fu Brick Tea Polyphenols on Experimental Colitis 2023 Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 71:2, s. 1201-1213 Tidskriftsartikel (refereegranskat)abstract Ulcerative colitis has been consistently associated with gut microbiota imbalance and disturbed immune system. Emerging research suggests a protective function of polyphenols on prevention and treatment of ulcerative colitis, yet underlying mechanisms remain unclear. Fu brick tea, a postfermented tea, contains abundant polyphenols with anti-inflammatory and antioxidant properties. In the present study, we found that prophylactic supplementation of polyphenols extracted from Fu brick tea (FBTP) dose-dependently alleviated colitis symptoms, immune cells infiltration, and pro-inflammatory cytokines secretion in mice suffering dextran sulfate sodium induced murine colitis. FBTP substantially reshaped gut microbiota and promoted microbial transformation of tryptophan into indole-3-acetic acid (I3A), thereafter leading to aryl hydrocarbon receptor (AHR)-mediated protection from colitis through enhanced expressions of IL-22 and tight junction proteins (i.e., ZO-1, occluding and claudin-1) in colon. Multiomics integration analyses revealed strong connections between I3A, tryptophan-metabolizing bacteria, AHR activity, and pathological phenotypes of colitis. Notably, FBTP failed to significantly alleviate colitis symptoms in the absence of gut microbiota, while intragastric administration of I3A could imitate benefits of FBTP on colitis alleviation and intestinal epithelial homeostasis through a direct enhancement in AHR activity in microbiota-depleted mice. These findings further determine the key role of gut microbiota controlled I3A-AHR signaling in mediating the FBTP on colitis alleviation. This study provides the first data proposing the FBTP as a natural prebiotic for colitis alleviation through the gut microbiota-dependent modulation of the AHR pathway. Most importantly, we also identified I3A as a key microbial metabolite targeted by FBTP for exhibiting health-promoting effects.
35.	Zhang, Yong, 1982, et al. (författare) Improved Heat Spreading Performance of Functionalized Graphene in Microelectronic Device Application 2015 Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 25:28, s. 4430-4435 Tidskriftsartikel (refereegranskat)abstract It is demonstrated that a graphene-based film (GBF) functionalized with silane molecules strongly enhances thermal performance. The resistance temperature detector results show that the inclusion of silane molecules doubles the heat spreading ability. Furthermore, molecular dynamics simulations show that the thermal conductivity () of the GBF increased by 15%-56% with respect to the number density of molecules compared to that with the nonfunctionalized graphene substrate. This increase in is attributed to the enhanced in-plane heat conduction of the GBF, resulting from the simultaneous increase of the thermal resistance between the GBF and the functionalized substrate limiting cross-plane phonon scattering. Enhancement of the thermal performance by inserting silane-functionalized molecules is important for the development of next-generation electronic devices and proposed application of GBFs for thermal management.
36.	Zhang, Yong, 1982, et al. (författare) Use of graphene-based films for hot spot cooling 2014 Ingår i: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962834- Konferensbidrag (refereegranskat)abstract Efficient heat dissipation is becoming an urgent demand in electronics and optoelectronics because of increasing power density, which is generating more heat than ever. Graphene, an atomic layer of carbon, has been shown to have high thermal conductivity, which makes this material a promising candidate for heat dissipation in electronics. Here, we demonstrate a new type of graphene-based film on a test platform to alleviate the thermal issues. Taking advantage of its high in-plane thermal conductivity, CVD-grown graphene has been observed to possess a strong heat-spreading ability. In this paper, a chemical conversion process, including chemical oxidation, exfoliation and reduction, is utilised to fabricate the graphene-based films. Additionally, functionalisation of the film was also performed to diminish the interface thermal resistance between the chip surface and the graphene-based films. Thermal characterisation showed a capacity for effective heat removal, which was indicated by the decrease in the hot spot temperature at the same power loading. In summary, this facile approach may technologically enable large-scale fabrication of graphene-based films for thermal management in high power density devices.

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