| 1. |
- Li, Mengxiong, et al.
(author)
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Highly Oriented Graphite Aerogel Fabricated by Confined Liquid-Phase Expansion for Anisotropically Thermally Conductive Epoxy Composites
- 2020
-
In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 12:24, s. 27476-27484
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Journal article (peer-reviewed)abstract
- Graphene-based thermally conductive polymer composites are of great importance for the removal of the excess heat generated by electronic devices. However, due to the orientation of graphene sheets in the polymer matrix, the through-plane thermal conductivity of polymer/graphene composites remains far from satisfactory. We here demonstrate a confined liquid-phase expansion strategy to fabricate highly oriented confined expanded graphite (CEG) aerogels. After being incorporated into epoxy resin (EP), the resulting EP/CEG composites exhibit a high through-plane thermal conductivity (4.14 ± 0.21 W m-1 K-1) at a quite low filler loading of 1.75 wt % (0.91 vol %), nearly 10 times higher than that of neat EP resin and 7.5 times higher than the in-plane thermal conductivity of the composite, indicating that the CEG aerogel has a high through-plane thermal conductivity enhancement efficiency that outperforms those of many graphite/graphene-based fillers. The facile preparation method holds great industrial application potential in fabricating anisotropic thermally conductive polymer composites.
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| 2. |
- Fu, Yifeng, 1984, et al.
(author)
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Graphene related materials for thermal management
- 2020
-
In: 2D Materials. - : IOP Publishing. - 2053-1583. ; 7:1
-
Journal article (peer-reviewed)abstract
- Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.
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| 3. |
- Kaindl, Reinhard, et al.
(author)
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Aerosol Jet Printing of Graphene and Carbon Nanotube Patterns on Realistically Rugged Substrates
- 2021
-
In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 6:50, s. 34301-34313
-
Journal article (peer-reviewed)abstract
- Direct-write additive manufacturing of graphene and carbon nanotube (CNT) patterns by aerosol jet printing (AJP) is promising for the creation of thermal and electrical interconnects in (opto)electronics. In realistic application scenarios, this however often requires deposition of graphene and CNT patterns on rugged substrates such as, for example, roughly machined and surface oxidized metal block heat sinks. Most AJP of graphene/CNT patterns has thus far however concentrated on flat wafer-or foil type substrates. Here, we demonstrate AJP of graphene and single walled CNT (SWCNT) patterns on realistically rugged plasma electrolytic-oxidized (PEO) Al blocks, which are promising heat sink materials. We show that AJP on the rugged substrates offers line resolution of down to similar to 40 mu m width for single AJP passes, however, at the cost of noncomplete substrate coverage including noncovered mu m-sized pores in the PEO Al blocks. With multiple AJP passes, full coverage including coverage of the pores is, however, readily achieved. Comparing archetypical aqueous and organic graphene and SWCNT inks, we show that the choice of the ink system drastically influences the nanocarbon AJP parameter window, deposit microstructure including crystalline quality, compactness of deposit, and inter/intrapass layer adhesion for multiple passes. Simple electrical characterization indicates aqueous graphene inks as the most promising choice for AJP-deposited electrical interconnect applications. Our parameter space screening thereby forms a framework for rational process development for graphene and SWCNT AJP on application-relevant, rugged substrates.
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| 4. |
- Liu, Hao, et al.
(author)
-
Graphene oxide for nonvolatile memory application by using electrophoretic technique
- 2020
-
In: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 25
-
Journal article (peer-reviewed)abstract
- The experimental work presented here, for the first time using electrophoretic technique to fabricate graphene oxide (GO)-based resistive random access memory (RRAM). By using electrophoretic technique, nonvolatile RRAM devices with Aluminum (Al)/GO/Indium tin oxide (ITO) cross-bar sandwich-like structure were fabricated. The fabricated devices show typical bipolar resistant switching behavior with ON/OFF ratio more than 10, retention time more than 102 s, and transition voltage less than 1.7 V. The switching mechanism for the devices is ascribed to the formation and rupture of the conducting filament induced by the diffusion of oxygen ions. The results show that the electrophoretic technique holds great potential for film manufacturing for RRAM.
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| 5. |
- Liu, Hao, et al.
(author)
-
Thermally Conductive Graphene Film/Indium/Aluminum Laminated Composite by Vacuum Assisted Hot-pressing
- 2020
-
In: 2020 21ST INTERNATIONAL CONFERENCE ON ELECTRONIC PACKAGING TECHNOLOGY (ICEPT). - 9781728168265
-
Conference paper (peer-reviewed)abstract
- 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.
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| 6. |
- Liu, Ya, 1991, et al.
(author)
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A Novel Graphene Quantum Dot-Based mRNA Delivery Platform
- 2021
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In: ChemistryOpen. - : Wiley. - 2191-1363. ; 10:7, s. 666-671
-
Journal article (peer-reviewed)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.
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| 7. |
- Liu, Ya, 1991, et al.
(author)
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Graphene based thermal management system for battery cooling in electric vehicles
- 2020
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In: Proceedings - 2020 IEEE 8th Electronics System-Integration Technology Conference, ESTC 2020.
-
Conference paper (peer-reviewed)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.
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| 8. |
- Manchili, Swathi Kiranmayee, 1987, et al.
(author)
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Effect of Nanopowder Addition on the Sintering of Water-Atomized Iron Powder
- 2020
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In: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 51:9, s. 4890-4901
-
Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Zhang, Yong, 1982, et al.
(author)
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Properties of Undoped Few-Layer Graphene-Based Transparent Heaters
- 2020
-
In: Materials. - : MDPI AG. - 1996-1944. ; 13:1
-
Journal article (peer-reviewed)abstract
- In many applications like sensors, displays, and defoggers, there is a need for transparent and efficient heater elements produced at low cost. For this reason, we evaluated the performance of graphene-based heaters with from one to five layers of graphene on flexible and transparent polyethylene terephthalate (PET) substrates in terms of their electrothermal properties like heating/cooling rates and steady-state temperatures as a function of the input power density. We found that the heating/cooling rates followed an exponential time dependence with a time constant of just below 6 s for monolayer heaters. From the relationship between the steady-state temperatures and the input power density, a convective heat-transfer coefficient of 60 W·m−2·°C−1 was found, indicating a performance much better than that of many other types of heaters like metal thin-film-based heaters and carbon nanotube-based heaters.
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| 10. |
- Zhao, Changhong, 1982, et al.
(author)
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Synthesis of graphene quantum dots and their applications in drug delivery
- 2020
-
In: Journal of Nanobiotechnology. - : Springer Science and Business Media LLC. - 1477-3155. ; 18:1
-
Research review (peer-reviewed)abstract
- 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.[Figure not available: see fulltext.]
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| 11. |
- Chen, Jiajia, et al.
(author)
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Characterization of Longitudinal Thermal Conductivity of Graphene Film
- 2021
-
In: 2021 22nd International Conference on Electronic Packaging Technology, ICEPT 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 12. |
- Chen, Shujing, et al.
(author)
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Scalable production of thick graphene films for next generation thermal management applications
- 2020
-
In: Carbon. - : Elsevier BV. - 0008-6223. ; 167, s. 270-277
-
Journal article (peer-reviewed)abstract
- 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 mm) 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.
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| 13. |
- Cui, Luqing, et al.
(author)
-
Low Cycle Fatigue Behavior and Microstructural Evolution of Nickel-based Superalloy M951G at Elevated Temperatures
- 2020
-
In: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 163
-
Journal article (peer-reviewed)abstract
- Low cycle fatigue (LCF) tests of the newly developed nickel-based superalloy M951G have been conducted at 900 and 1000 °C under different total strain amplitudes. Results show that the fatigue properties, fracture mechanisms as well as coarsening of γ′ precipitates are dependent on testing temperatures and strain amplitudes. Fatigue life and cyclic stress response under the same total strain amplitude at 1000 °C are lower than that at 900 °C, which is due to the degradation of microstructures, shearing of γ′ precipitates by dislocations and serious oxidation. Fracture modes change from intergranular cracking to the mixed mode cracking as the strain amplitude increases. At low strain amplitudes, M951G alloy fails in the form of intergranular cracking owing to the oxidation of surface carbides and the relatively low deformation rate. At higher strain amplitudes, the strain localization in grain interior, the distribution of broken carbides and eutectics as well as the relatively higher strain rate are the main reasons for the formation of transgranular microcracks. Ultimately, the effects of fatigue conditions on coarsening of cubic γ′ precipitates are also analyzed from the aspect of γ′ volume fraction, fatigue life and flow stress difference between the γ/γ′ interfaces.
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| 14. |
- Enmark, Markus, 1991, et al.
(author)
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A Critical Assessment of Nano Enhanced Vapor Chamber Wick Structures for Electronics Cooling
- 2021
-
In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 15. |
- Fazi, Andrea, 1992, et al.
(author)
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Multiple growth of graphene from a pre-dissolved carbon source
- 2020
-
In: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:34, s. 345601-
-
Journal article (peer-reviewed)abstract
- Mono- to few-layer graphene materials are successfully synthesized multiple times using Cu-Ni alloy as a catalyst after a single-chemical vapor deposition (CVD) process. The multiple synthesis is realized by extracting carbon source pre-dissolved in the catalyst substrate. Firstly, graphene is grown by the CVD method on Cu-Ni catalyst substrates. Secondly, the same Cu-Nicatalyst foils are annealed, in absence of any external carbon precursor, to grow graphene using the carbon atoms pre-dissolved in the catalyst during the CVD process. This annealing process is repeated to synthesize graphene successfully until carbon is exhausted in the Cu-Ni foils. After the CVD growth and each annealing growth process, the as-grown graphene is removed using a bubbling transfer method. A wide range of characterizations are performed to examine the quality of the obtained graphene material and to monitor the carbon concentration in the catalyst substrates. Results show that graphene from each annealing growth process possesses a similar quality, which confirmed the good reproducibility of the method. This technique brings great freedom to graphene growth and applications, and it could be also used for other 2D material synthesis.
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| 16. |
- Gong, Xinjian, et al.
(author)
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Fabrication and Characterization of Graphene/polyimide Composite Film
- 2021
-
In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 17. |
- Guo, Sihua, et al.
(author)
-
Graphene-based films: Fabrication, interfacial modification, and applications
- 2021
-
In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 11:10
-
Research review (peer-reviewed)abstract
- Graphene-based film attracts tremendous interest in many potential applications due to its excellent thermal, electrical, and mechanical properties. This review focused on a critical analysis of fabrication, processing methodology, the interfacial modification approach, and the applications of this novel and new class material. Strong attention was paid to the preparation strategy and interfacial modification approach to improve its mechanical and thermal properties. The overview also discussed the challenges and opportunities regarding its industrial production and the current status of the commercialization. This review showed that blade coating technology is an effective method for industrial mass-produced graphene film with controllable thickness. The synergistic effect of different interface interactions can effectively improve the mechanical properties of graphenebased film. At present, the application of graphene-based film on mobile phones has become an interesting example of the use of graphene. Looking for more application cases is of great significance for the development of graphene-based technology.
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| 18. |
- Guo, Sihua, et al.
(author)
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Synergistic Toughening of Graphene Films by Addition of Hydroxylated Carbon Nanotube
- 2021
-
In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 19. |
- Hansson, Josef, 1991, et al.
(author)
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Bipolar electrochemical capacitors using double-sided carbon nanotubes on graphite electrodes
- 2020
-
In: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 451
-
Journal article (peer-reviewed)abstract
- The electrochemical capacitor (EC) is a key enabler for the miniaturized self-powered systems expected to become ubiquitous with the advent of the internet-of-things (IoT). Vertically aligned carbon nanotubes (VACNTs) on graphite holds promise as electrodes for compact and low-loss ECs. However, as with all ECs, the operating voltage is low, and miniaturization of higher voltage devices necessitates a bipolar design. In this paper, we demonstrate a bipolar EC using graphite/VACNTs electrodes fabricated using a joule heating chemical vapor deposition (CVD) setup. The constructed EC contains one layer of double-sided VACNTs on graphite as bipolar electrode. Compared to a series connection of two individual devices, the bipolar EC has 22% boost in volumetric energy density. More significant boost is envisaged for stacking more bipolar electrode layers. The energy enhancement is achieved without aggravating self-discharge (71.2% retention after 1 h), and at no sacrifice of cycling stability (96.7% over 50000 cycles) owing to uniform growth of VACNTs and thus eliminating cell imbalance problems.
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| 20. |
- Hansson, Josef, 1991, et al.
(author)
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Effects of high temperature treatment of carbon nanotube arrays on graphite : Increased crystallinity, anchoring and inter-tube bonding
- 2020
-
In: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 31:45
-
Journal article (peer-reviewed)abstract
- Thermal treatment of carbon nanotubes (CNTs) can significantly improve their mechanical, electrical and thermal properties due to reduced defects and increased crystallinity. In this work we investigate the effect of annealing at 3000 degrees C of vertically aligned CNT arrays synthesized by chemical vapor deposition (CVD) on graphite. Raman measurements show a drastically reduced amount of defects and, together with transmission electron microscope (TEM) diffraction measurements, an increased average crystallite size of around 50%, which corresponds to a 124% increase in Young's modulus. We also find a tendency for CNTs to bond to each other with van der Waals (vdW) forces, which causes individual CNTs to closely align with each other. This bonding causes a densification effect on the entire CNT array, which appears at temperatures >1000 degrees C. The densification onset temperature corresponds to the thermal decomposition of oxygen containing functional groups, which otherwise prevents close enough contact for vdW bonding. Finally, the remaining CVD catalyst on the bottom of the CNT array is evaporated during annealing, enabling direct anchoring of the CNTs to the underlying graphite substrate.
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| 21. |
- Jiang, Ziwei, et al.
(author)
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Characterterization of multi-scale nanosilver paste reinforced with SIC particles
- 2020
-
In: China Semiconductor Technology International Conference 2020, CSTIC 2020.
-
Conference paper (peer-reviewed)abstract
- Nanosilver paste with high operation temperature and low sintering temperature has attracted more and more attention for its promising application in high power devices. In this paper, the thermal properties of multi-scale nanosilver paste composed of nanometer and micrometer silver particles, and Ag-coated SiC particles were investigated. The thermal conductivity of multi-scale nanosilver paste increases with the increasing amount of SiC particles with Ag coating. The maximum value of Vickers hardness for multi-scale nanosilver paste with 0.5 wt.% Ag-coated SiC particles were 24.
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| 22. |
- Lu, Pei, et al.
(author)
-
Thermal Conduction of Fiber-Reinforced Polymer under Loading
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 23. |
- Lv, Zhen, et al.
(author)
-
Highly thermally conductive substrate based on graphene film
- 2021
-
In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021. ; , s. 195-199
-
Conference paper (peer-reviewed)abstract
- Heat dissipation has become one of the critical challenges of development for microelectronic products because of the increasing of heat accumulation in the devices. A novel laminated composite with high thermal conductivity was fabricated by hot-pressing using graphene films (GFs) and glass fiber reinforced epoxy resin (GFEP). The effect of GFs with different thicknesses and number of layers on the thermal properties of the composites was investigated. An in-plane thermal conductivity of 141 W · m-1 · K-1 for the laminated composites with GFs and GFEP were obtained. The heat dissipation capability of GFs/GFEP composites is evaluated by infrared thermal imaging technology. The maximum temperature difference between the heating elements on GFs/GFEP composites and GFEP increases with the rise of voltage applied to the heating elements. Moreover, the heat dissipation capability of the composite is enhanced with the increased of the number of layers of GFs. The temperature of the heating element assembled on GFs/GFEP composites is 144.3°C lower than that on GFEP at the same voltage. The results indicate that the GFs/GFEP composites is a promising candidate of substrate material with high heat dissipation capability.
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| 24. |
- Niu, Ziyu, et al.
(author)
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Enhanced electrochemical performance of three-dimensional graphene/carbon nanotube composite for supercapacitor application
- 2020
-
In: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 820
-
Journal article (peer-reviewed)abstract
- In this work, we developed a facile route to synthesize three-dimensional graphene/carbon nanotube (3DG/CNT) hybrids as electrodes for binder-free electrical double layer capacitor (EDLC) by using chemical vapor deposition (CVD) method. The 3DG/CNT composites have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). It was found that the 3DG/CNT with interconnected architecture exhibit improved capacitive characteristic and electrical conductivity compared to that of pure 3DG. The 3DG/CNT composites have high specific capacitance of 197.2 F/g and excellent capacity retention rate of 93% after 1000 cycles. The experiment results show that the as-synthesized 3DG/CNT hold great potential as candidate as electrode for binder-free EDLC. © 2019 Elsevier B.V.
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| 25. |
- Nylander, Andreas, 1988, et al.
(author)
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Degradation of Carbon Nanotube Array Thermal Interface Materials through Thermal Aging: Effects of Bonding, Array Height, and Catalyst Oxidation
- 2021
-
In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 13:26, s. 30992-31000
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Journal article (peer-reviewed)abstract
- 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.
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| 26. |
- Wang, Nan, 1988, et al.
(author)
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Improved Interfacial Bonding Strength and Reliability of Functionalized Graphene Oxide for Cement Reinforcement Applications
- 2020
-
In: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 26:29, s. 6561-6568
-
Journal article (peer-reviewed)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.
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| 27. |
- Yang, Fei, et al.
(author)
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Thermal Properties of Laser-induced Graphene Films Photothermally Scribed on Bare Polyimide Substrates
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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℃ to 74℃ 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.
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| 28. |
- Yin, Hang, et al.
(author)
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Analysis of heat dissipation characteristics of three-dimensional graphene-carbon nanotube composite structures
- 2020
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In: 2020 21ST INTERNATIONAL CONFERENCE ON ELECTRONIC PACKAGING TECHNOLOGY (ICEPT). - 9781728168265
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Conference paper (peer-reviewed)abstract
- 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.
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| 29. |
- Yu, Chen, et al.
(author)
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Thermal Properties of Laser Reduced Graphene Oxide Films
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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 ℃ 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.
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| 30. |
- Yuan, G., et al.
(author)
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Thermally reduced graphene oxide/carbon nanotube composite films for thermal packaging applications
- 2020
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In: Materials. - : MDPI AG. - 1996-1944. ; 13:2
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Journal article (peer-reviewed)abstract
- Thermally reduced graphene oxide/carbon nanotube (rGO/CNT) composite films were successfully prepared by a high-temperature annealing process. Their microstructure, thermal conductivity and mechanical properties were systematically studied at different annealing temperatures. As the annealing temperature increased, more oxygen-containing functional groups were removed from the composite film, and the percentage of graphene continuously increased. When the annealing temperature increased from 1100 to 1400 °C, the thermal conductivity of the composite film also continuously increased from 673.9 to 1052.1 W m-1 K-1. Additionally, the Young's modulus was reduced by 63.6%, and the tensile strength was increased by 81.7%. In addition, the introduction of carbon nanotubes provided through-plane thermal conduction pathways for the composite films, which was beneficial for the improvement of their through-plane thermal conductivity. Furthermore, CNTs apparently improved the mechanical properties of rGO/CNT composite films. Compared with the rGO film, 1 wt% CNTs reduced the Young's modulus by 93.3% and increased the tensile strength of the rGO/CNT composite film by 60.3%, which could greatly improve its flexibility. Therefore, the rGO/CNT composite films show great potential for application as thermal interface materials (TIMs) due to their high in-plane thermal conductivity and good mechanical properties.
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| 31. |
- Zehri, Abdelhafid, 1989, et al.
(author)
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Exploring Graphene Coated Copper Nanoparticles as a multifunctional Nanofiller for Micro-Scaled Copper Paste
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
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Conference paper (peer-reviewed)abstract
- 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 °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.
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| 32. |
- Zehri, Abdelhafid, 1989, et al.
(author)
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High porosity and light weight graphene foam heat sink and phase change material container for thermal management
- 2020
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In: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42
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Journal article (peer-reviewed)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.
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| 33. |
- Zhang, Emma, 1985, et al.
(author)
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Electrical monitoring of concrete using a novel structural sensor based on conductive cementitious mortar
- 2020
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In: ECCM 2018 - 18th European Conference on Composite Materials. - 9781510896932
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Conference paper (peer-reviewed)abstract
- This paper presents the development of a durable structural sensor based on cement-mortar modified with graphene and other carbon-based fillers. The purpose of the structural sensor is to indirectly monitor curing and service performance of concrete via electrical resistivity measurements. Electrical resistivity is an efficient parameter which can non-destructively capture intrinsic structural features of cementitious materials. The developed structural sensor is used to record electrical resistivity as a durability indicator during the whole service life of the concrete structure. To date, performance monitoring systems usually fail in the long-run before the failure of the actual monitored structure. The proposed sensor is embeddable in the interrogated structure and ensures sustainable consolidation with appropriate physico-chemical adherence and mechanical interlocking. This allows the monitoring system to surpass the expected service life of the parent concrete. Within this on-going work, the effects of different concentrations of carbon fillers on the electrical properties of cementitious mortars are reported. After an initial investigation to select the appropriate synthesis, the ability of the sensor to monitor the development of resistivity during setting and hardening was tested and the results are presented herein. Finally, the durability of the sensor was tested via electrical stability measurements under freeze-thaw cycles.
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| 34. |
- Zhang, Y., et al.
(author)
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Heat transfer analysis of phase change materials with metal foams
- 2021
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In: 2021 22nd International Conference on Electronic Packaging Technology, ICEPT 2021.
-
Conference paper (peer-reviewed)abstract
- 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.
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| 35. |
- Zhang, Y., et al.
(author)
-
MDS study on tensile properties of defective graphene sheet
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
-
Conference paper (peer-reviewed)abstract
- 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%.
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| 36. |
- Zhang, Yong, 1982, et al.
(author)
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Thermal Analysis of an Au/Pt/Ti-Based Microheater
- 2021
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In: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
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Conference paper (peer-reviewed)abstract
- 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.
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