| 1. |
- Fu, Yifeng, 1984, et al.
(författare)
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A complete carbon-nanotube-based on-chip cooling solution with very high heat dissipation capacity
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- Heat dissipation is one of the factors limiting the continuous miniaturization of electronics. In the study presented in this paper, we designed an ultra-thin heat sink using carbon nanotubes (CNTs) as micro cooling fins attached directly onto a chip. A metal-enhanced CNT transfer technique was utilized to improve the interface between the CNTs and the chip surface by minimizing the thermal contact resistance and promoting the mechanical strength of the microfins. In order to optimize the geometrical design of the CNT microfin structure, multi-scale modeling was performed. A molecular dynamics simulation (MDS) was carried out to investigate the interaction between water and CNTs at the nanoscale and a finite element method (FEM) modeling was executed to analyze the fluid field and temperature distribution at the macroscale. Experimental results show that water is much more efficient than air as a cooling medium due to its three orders-of-magnitude higher heat capacity. For a hotspot with a high power density of 5000 W cm(-2), the CNT microfins can cool down its temperature by more than 40 degrees C. The large heat dissipation capacity could make this cooling solution meet the thermal management requirement of the hottest electronic systems up to date.
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| 2. |
- Fu, Yifeng, 1984, et al.
(författare)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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| 3. |
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| 4. |
- Nabiollahi, Nabi, 1983, et al.
(författare)
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FEM Simulation of Bimodal and Trimodal Thermally Conductive Adhesives
- 2009
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Ingår i: 2009 9th IEEE Conference on Nanotechnology, IEEE NANO 2009; Genoa; Italy; 26 July 2009 through 30 July 2009. - 9789810836948 ; , s. 422-425
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Konferensbidrag (refereegranskat)abstract
- A simulation with combination of a finite element analysis of Thermally Conductive Adhesive and contact resistance modeling has been presented. Using ANSYS and MATLAB software thermal conductivity and electrical resistivity of Conductive Adhesives with Ag filler and Epoxy matrix has been calculated. Thermally Conductive Adhesives are used as a thermal interface material to provide a better conduction and heat transfer between two surfaces. The results show that the conductivity dependency is relatively high for different filler shape and alignment. Discussed models are bimodal, Ag flakes and Ag spherical micro particles and trimodal with Multi-WallCNT nano particles.
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| 5. |
- Fan, Q., et al.
(författare)
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The effect of functionalized silver on properties of conductive adhesives
- 2011
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Ingår i: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. - 9781457717680 ; , s. 423-425
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Konferensbidrag (refereegranskat)abstract
- This research used low molecular surface modifiers and observed that chemisorptions took place through the formation of a bond between silver surface and an adsorbed molecule, which improved the dispersion of silver flakes in the organic resin. Results of shear viscosity, bulk resistivity etc. showed that by using these low molecular organic functionalizers, isotropic conductive adhesives (ICAs) with lower shear viscosity and better electrical conductivity at high silver fillers content were obtained. Different processing methods and different matrixes were compared.
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| 6. |
- Hu, Zhili, 1983
(författare)
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A Theoretical Study of Carbon Nanotubes in Electronic Packaging Applications
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The continuous decrease in size of transistors has allowed more components to be integrated in a single unit area and brings a range of opportunities as well as problems to the electronic packaging industry. To meet these challenges, the introduction of Carbon Nanotubes (CNT), which display a series of extraordinary properties, have attracted great interest. CNTs pose great difficulties to direct experimental study, thus theoretical study becomes a valuable alternative. This thesis presents several examples of theoretical studies aiming at CNT-based applications. Classic Molecular dynamics simulation (MDS) and continuum modeling are adopted as key methodologies in these studies. Although it is a theoretical work, this thesis presents exciting findings that point to possible practical applications.Chapter 2 presents two direct applications of CNT in electronic packaging, i.e. thermal management and interconnection. The thermal management is related to the use of CNTs in a micro-channel cooler construction due to its excellent thermal conductivity. In this example, the thermal interface resistance between CNT and adhesive could influence the heat transfer between the heat generator and the CNT fins in the cooler. This influence shall be evaluated. Thus in section 2.1, the thermal conductivity of epoxy matrix for thermal conductive adhesive (TCA) is studied by MDS using the Nonequilibrium Molecular Dynamics Method (NEMD). The thermal resistivity at the interface between the carbon nanotube and the polymer is estimated to be 33.262×10-8 m2K/W, which is consistent with previous studies. Both thermal management and interconnection with CNTs requires peeling off the CNT forest from the metal catalysts where CNTs were grown. Therefore an investigation of the bonding strength between metal and SWNT is presented. Two kinds of metal, i.e. iron and nickel are studied. Simulation results reveal that to debond the joint, a force greater than 31.7 nN is needed for Fe-SWNT joint, and for Ni-SWNT joint the required force is 3.5 nN.Then buckling behaviors of CNT are investigated and its potential applications presented. These investigations can be used in the electronic packaging applications. It starts from formulation work on the radial buckling of CNT. The results of this work are then verified with MDS which predicts an enhanced critical pressure for buckling of CNT due to an inserted linear carbon chain. This is followed by a theoretical analysis on the boundary condition effect on axial bucking of chiral CNT with MDS. It finds that boundary conditions can influence critical bucking strain by 20%. Hereafter a molecular gun that utilizes bending buckling of a telescope CNT is studied, which shows the inner tube of the doublewalled carbon nanotube (DWNT) can be shot out with a speed up to 500 m/s.After that another study concerning the effects of mechanical manipulation of CNT is undertaken. In this study, forced transverse vibrations of a single wall carbon nanotube (SWNT) containing atomic-size particles inside has been looked at, and the inertial trapping phenomenon in CNT resonators is discovered with MDS. This work reveals that when standing wave occurs by applying driving oscillation, particles inside the SWNT will be trapped near the anti-nodes or tip of SWNT if there are either one or two anti-nodes. A brief theory based on Fokker-Planck equation is proposed to explain this phenomenon. This trapping phenomenon is found to be highly sensitive to the external driving frequency i.e. that even a very small change of driving frequency can strongly influence the probability of the particle location inside the CNT. This effect can be potentially employed to achieve the atomic scale control of a particle position inside the SWNT via the finite adjustment of the external driving frequency. The thesis proposes that the inertia trapping phenomenon can be used to realize the concept of matter manipulation. Although it is not a true full three-dimensional (3D) maneuvering matter at the atomic level, the work could still be valuable in fields such as synthetic biology and molecule level data storage and hopefully offer a valuable tool for the realization of true 3D nanotechnology.
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| 7. |
- Hu, Zhili, 1983, et al.
(författare)
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Detecting single molecules inside a carbon nanotube to control molecular sequences using inertia trapping phenomenon
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:13, s. Art. no. 133105-
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Tidskriftsartikel (refereegranskat)abstract
- Here we show the detection of single gas molecules inside a carbon nanotube based on the change inresonance frequency and amplitude associated with the inertia trapping phenomenon. As its directimplication, a method for controlling the sequence of small molecule is then proposed to realize theconcept of manoeuvring of matter atom by atom in one dimension. The detection as well as theimplication is demonstrated numerically with the molecular dynamics method. It is theoreticallyassessed that it is possible for a physical model to be fabricated in the very near future.
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| 8. |
- Hu, Zhili, 1983
(författare)
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Enhanced critical pressure for buckling of carbon nanotubes due to an inserted linear carbon chain
- 2012
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Ingår i: Nanotechnology. - 1361-6528 .- 0957-4484. ; 19:30, s. 305703-
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Tidskriftsartikel (refereegranskat)abstract
- Recent findings of linear carbon-atom chains (C-chains) inside carbon nanotubes havestimulated considerable interest. In this work, molecular dynamics (MD) simulation and anelastic string–elastic shell model is adopted to study radial pressure-induced buckling ofsingle-walled carbon nanotubes (SWCNT) filled with a C-chain. The continuum model predictsthat the C-chain increases critical buckling pressure considerably (about 40%–160%) forSWCNTs of diameters ranging from 0.68 to 0.72 nm, in reasonable quantitative agreement withthe prediction of MD simulation. In particular, the MD simulation confirms that the originallycircular cross section of filled SWNTs becomes elliptical after buckling, as predicted by thecontinuum model.
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| 9. |
- Hu, Zhili, 1983, et al.
(författare)
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Influence of substrate on electrical conductivity of isotropic conductive adhesive
- 2011
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Ingår i: Proceedings of the IEEE International Symposium on Advanced Packaging Materials (APM), Xiamen, China, October 25-28, 2011. - 1550-5723. - 9781467301480 ; , s. 330 - 335
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Konferensbidrag (refereegranskat)abstract
- Isotropic conductive adhesive (ICA) is widely used with different kinds of substrates in electronics packaging applications. Therefore it is necessary to understand the influence of electrical conductivity of ICA from substrate. In this work, we investigated the electrical resistivity of ICA on quartz, PCB and glass substrate. The experimental data showed that the in-plane electrical conductivity of ICA on PCB is almost twice that of the glass substrate, while the conductivity of ICA on quartz is also significantly greater than that of glass, under the same curing temperature and with the same bond line thickness (BLT) of ICA. This paper later concludes that thermal conductive adhesive (TCA) on substrate with higher thermal expansion coefficient (CTE) is likely to give better performance. Finally, Finite Element Modeling (FEM) and analysis shows that this phenomenon could be universal to ICA and TCA.
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| 10. |
- Hu, Zhili, 1983, et al.
(författare)
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Molecular Gun Composed of Carbon Nanotube
- 2011
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Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 8:9, s. 1716-1719
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Tidskriftsartikel (refereegranskat)abstract
- Using molecular simulation, this paper predicts that by bending one end of the outer carbon nanotube (CNT) of a double-wall CNT (DWCNT), the inner CNT could possibly be shot out with a speed of several 100 m/s, and a kinetic energy of several eV from either left or the right end of the outer CNT, depending on the length of inner CNT. Analysis in this paper suggests that the outer CNT is a supplier of the CNT bullet's kinetic energy and the bullet can be shot out only if the outer CNT buckles while the inner CNT does not. Noticeably, such molecular gun could be practical in experiment environment since the bending of a CNT could be obtained by applying external electrical field.
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