| 91. |
- Xu, Liang, et al.
(författare)
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Effect of substrates and underlayer on CNT synthesis by plasma enhanced CVD
- 2013
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Ingår i: Advances in Manufacturing. - : Springer Science and Business Media LLC. - 2095-3127 .- 2195-3597. ; 1:3, s. 236-240
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Tidskriftsartikel (refereegranskat)abstract
- Due to their unique thermal, electronic and mechanical properties, carbon nanotubes (CNTs) have aroused various attentions of many researchers. Among all the techniques to fabricate CNTs, plasma enhanced chemical vapor deposition (PECVD) has been extensively developed as one growth technique to produce vertically-aligned carbon nanotubes (VACNTs). Though CNTs show a trend to be integrated into nanoelectromechanical system (NEMS), CNT growth still remains a mysterious technology. This paper attempts to reveal the effects of substrates and underlayers to CNT synthesis. We tried five different substrates by substituting intrinsic Si with high resistivity ones and by increasing the thickness of SiO2 insulativity layer. And also, we demonstrated an innovative way of adjusting CNT density by changing the thickness of Cu underlayer. © 2013 Shanghai University and Springer-Verlag Berlin Heidelberg.
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| 92. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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Exploring Graphene Coated Copper Nanoparticles as a multifunctional Nanofiller for Micro-Scaled Copper Paste
- 2021
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Ingår i: 2021 23rd European Microelectronics and Packaging Conference and Exhibition, EMPC 2021.
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Konferensbidrag (refereegranskat)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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| 93. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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Graphene Fibres: Towards high mechanical, thermal and electrical properties state of art
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016, Tonsberg, Norway, 5-7 June 2016. - 9781510827226
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Konferensbidrag (refereegranskat)abstract
- Nowadays, tremendous efforts are made to enhance the thermal conductivity of materials and answer to demands for fast heat dissipation in various applications such as wearable electronics, photovoltaic energy conversion and advanced structural materials mounted on high power electronics. The main difficulty comes very often from the ability to simultaneously produce superior thermal, electrical and high mechanical properties. For this matter, graphene which owned the nickname of miracle material has attracted all the attention to exploit its outstanding properties at an industriel scale and the field of graphene fibre turned to be a very promising approach to produce a high quality 3D graphene material. In this review paper, we propose to summarize briefly the different advances and attemps made up to now in order the assemble graphene into macroscopic three-dimensional structures and apply the unique properties of its two-dimensional individuels in practical applications.
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| 94. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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Graphene Oxide and Nitrogen-Doped Graphene Coated Copper Nanoparticles in Water-Based Nanofluids for Thermal Management in Electronics
- 2022
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Ingår i: JOURNAL OF NANOFLUIDS. - : American Scientific Publishers. - 2169-432X .- 2169-4338. ; 11:1, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) and nitrogen-doped graphene (NG) coated copper nanoparticles (NPs) have been developed in this work and investigated as nanofiller for water as Heat Transfer Fluids (HTFs). The morphology and composition of the coating were characterized to confirm the presence of functional groups and the nitrogen-doping of the graphene coating. Different fractions of the two types of coated nanoparticles NPs between 0.1 and 10 wt.% were dispersed in water. The thermal conductivity of the dispersions was evaluated at temperatures between 20 and 50 degrees C. A positive correlation between the thermal conductivity of the HTFs and the fraction and temperature are observed as a result of the increase of the solid phase contribution into the heat transfer. At a concentration of 0.5 wt.%, the thermal conductivity of the NG-CuNPs nanofluid reached its maximum increase of 78%, compared to a 13% increase in the case of GO-CuNPs. However, due to the poor stability of the NG-CuNPs, further increase of the solid phase did not result in any additional improvement. In contrast, the thermal conductivity of the GO-based dispersion resulted in a 103% enhancement at 10 wt.% at a temperature of 50 degrees C.
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| 95. |
- Zehri, Abdelhafid, 1989, et al.
(författare)
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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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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 31:42
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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.
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| 96. |
- Zhang, Yong, 1982, et al.
(författare)
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2D HEAT DISSIPATION MATERIALS FOR MICROELECTRONICS COOLING APPLICATIONS
- 2016
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Ingår i: China Semiconductor Technology International Conference 2016, CSTIC 2016. - 9781467388047
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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.
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| 97. |
- Zhang, Yong, 1982, et al.
(författare)
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Characterization and simulation of liquid phase exfoliated graphene-based films for heat spreading applications
- 2016
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223. ; 106, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the thermal properties of graphene-based films for heat spreading applications. Following liquid phase exfoliation (LPE) films were made by two different methods, vacuum filtration and drop coating. Temperature decreases of up to 6 °C and 4 °C were measured at a heat flux density of 1200 W/cm2 for the vacuum filtrated and drop coated films respectively. For the first time in this paper, three different methods were combined to evaluate and predict the thermal performance of such graphene-based films. Resistance thermometers were used to monitor the hotspot temperature decrease versus the Joule heat flow as a result of using graphene-based heat spreaders. The 3ω method was used to experimentally determine the in-plane and through-plane thermal conductivities of such films. A finite element model of the hotspot test structure was setup using the in-plane and through-plane thermal conductivities (110 and 0.25 W/mK, respectively) obtained from the 3ω measurements. Simulations were performed to predict the hotspot temperature decrease with excellent agreement obtained between all methods. The results indicate that the alignment and purity of the graphene-based films, as well as their thermal boundary resistance with respect to the chip, are key parameters when determining the thermal performance of graphene-based heat spreaders.
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| 98. |
- Zhang, Yong, 1982, et al.
(författare)
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Chemical vapor deposition grown graphene on Cu-Pt alloys
- 2017
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 193, s. 255-258
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, the results from a series of experiments where graphene was grown on copper-platinum (Cu-Pt) alloy foils by chemical vapor deposition (CVD) are presented. By using Raman spectroscopy to analyze graphene films grown on Pt-Cu alloy foils with different Cu/Pt weight ratios (75/25, 50/50 and 25/75), we could show how the Cu/Pt weight ratio affected both the quality and the number of layers in the as-synthesized graphene films. Furthermore, graphene growth was shown to occur at temperatures as low as 750 °C due to what we believe is the strong catalytic ability of the Cu-Pt alloy foils. By keeping the flow rate of the CH4 precursor gas as low as 1.5 sccm, a low growth rate was obtained where the growth rates of monolayer and bilayer graphene could be controlled by simply adjusting the growth time.
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| 99. |
- Zhang, Yan, 1976, et al.
(författare)
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Experimental study of Electrical properties and stability of CNT bumps in high density interconnects
- 2013
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Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781479906758 ; , s. 1085-1088
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Konferensbidrag (refereegranskat)abstract
- With the minimization development of electronic devices and products, nanotechnology and nanomaterials are widely applied in different fields of electronic packaging. Carbon nanotube (CNT) is an ideal material due to its excellent electrical and thermal conductivities. In the present paper, the application of CNT bundles as chip bumps was experimentally investigated. The electrical resistances of the CNT interconnects were measured, and the thermal and humidity test were conducted. In addition, the CNT forests on fine pitch copper lines under various environmental test conditions were observed to evaluate the stability. © 2013 IEEE.
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| 100. |
- Zhang, Yong, 1982, et al.
(författare)
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Graphene-based heater
- 2016
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Ingår i: IMAPS Nordic Annual Conference 2016; Tonsberg; Norway; 5-7 June 2016. - 9781510827226
-
Konferensbidrag (refereegranskat)abstract
- The excellent thermal conductivity and optical transmittance of graphene make it tremendously interesting as a material for heating applications. In this paper, we demonstrate graphene can be used as a new heating element. The graphene is synthesized by chemical vapor deposition (CVD) on Cu foil. The heating performance is studied in terms of applied voltage, heating rate and input power density. A two-layer graphene film based heater can reach an equilibrium temperature up to 90C when 60 V voltage is applied for 2 min. A maximum heating rate of 1.1 C/s was observed under an applied voltage of 60 V. The results indicate that the graphene-based heater holds great promise for many applications such as defrosting and antifogging devices.
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