| 1. |
- Fu, Yifeng, 1984, et al.
(author)
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Selective growth of double-walled carbon nanotubes on gold films
- 2012
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In: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 72, s. 78-80
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Journal article (peer-reviewed)abstract
- Growth of high-quality vertical aligned carbon nanotube (CNT) structures on silicon supported gold (Au) films by thermal chemical vapor deposition (TCVD) is presented. Transmission electron microscopy (TEM) images show that the growth is highly selective. Statistical study reveals that 79.4% of the as-grown CNTs are double-walled. The CNTs synthesized on Au films are more porous than that synthesized on silicon substrates under the same conditions. Raman spectroscopy and electrical characterization performed on the as-grown double-walled CNTs (DWNTs) indicate that they are competitive with those CNTs grown on silicon substrates. Field emission tests show that closed-ended DWNTs have lower threshold field than those open-ended.
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| 2. |
- Fu, Yifeng, 1984, et al.
(author)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Journal article (peer-reviewed)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. |
- Sun, Jie, 1977, et al.
(author)
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Direct Chemical Vapor Deposition of Large-Area Carbon Thin Films on Gallium Nitride for Transparent Electrodes: A First Attempt
- 2012
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In: IEEE Transactions on Semiconductor Manufacturing. - : Institute of Electrical and Electronics Engineers (IEEE). - 0894-6507 .- 1558-2345. ; 25:3, s. 494-501
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Journal article (peer-reviewed)abstract
- Direct formation of large-area carbon thin films on gallium nitride by chemical vapor deposition without metallic catalysts is demonstrated. A high flow of ammonia is used to stabilize the surface of the GaN (0001)/sapphire substrate during the deposition at 950 degrees C. Various characterization methods verify that the synthesized thin films are largely sp(2) bonded, macroscopically uniform, and electrically conducting. The carbon thin films possess optical transparencies comparable to that of exfoliated graphene. This paper offers a viable route toward the use of carbon-based materials for future transparent electrodes in III-nitride optoelectronics, such as GaN-based light emitting diodes and laser diodes.
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| 4. |
- Zhang, Xia, 1980, et al.
(author)
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Design of Printed Monopole Antennas on Liquid Crystal Polymer Substrates
- 2010
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In: Journal of Infrared, Millimeter, and Terahertz Waves. - : Springer Science and Business Media LLC. - 1866-6892 .- 1866-6906. ; 31:4, s. 469-480
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Journal article (peer-reviewed)abstract
- In this paper, a compact printed monopole antenna with an extremely wide bandwidth has been realized on Liquid Crystal Polymer (LCP) substrates by using standard processing technology. Both laminated and directed metalized LCP substrates were used in this experiment. The antenna made on the direct metalized LCP substrate performed well compared to on the laminated LCP substrate. To improve the adhesion, the surface of the LCP was further roughened and a certain adhesion layer was used prior to the deposition of Cu. The measured antenna on a metalized LCP substrate could cover this frequency band with an impedance bandwidth from 0.51 GHz to 14.4 GHz (28.2:1) for VSWRa parts per thousand currency sign2. Moreover, the antenna exhibits a nearly omni-directional radiation pattern. The size of this antenna is only about 0.18 lambda(1) x 0.13 lambda(1), where lambda(1) is the wavelength of the lowest operating frequency. The results show that LCP is a promising candidate for high frequency applications.
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| 5. |
- Zhang, Yan, et al.
(author)
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Numerical investigation on thermal properties of micro-pin-fin cooler
- 2011
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In: Journal of Shanghai University. - 1007-6417. ; 15:4, s. 273 - 278
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Journal article (peer-reviewed)abstract
- Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes (CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.
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| 6. |
- Carlberg, Björn, 1983, et al.
(author)
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Direct Photolithographic Patterning of Electrospun Films for Defined Nanofibrillar Microarchitectures
- 2010
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:4, s. 2235-2239
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Journal article (peer-reviewed)abstract
- In this letter, a method of generating spatially defined electrospun microarchitectures by direct photolithographic patterning of electrospun Films is described, A photoinitiator, benzoin methyl ether, is incorporated into a solid thermoplastic electrospun polyurethane matrix selectively photo-cross-linked by standard photolithographic methods. Subsequent development in in organic solvent yields spatially defined electrospun microstructures oil a single substrate. Utilizing a multilayer approach, the method allows for the assembly of complex hierarchical electrospun structures on single substrates using methods analogous to the conventional microfabrication of solid-state devices.
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| 7. |
- Carlberg, Björn, 1983, et al.
(author)
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Polymer-metal nanofibrous composite for thermal management of microsystems
- 2012
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In: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 75, s. 229-232
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Journal article (peer-reviewed)abstract
- In this letter, a composite structure based on a porous electrospun polyimide structure infiltrated with indium aimed at thermal interface material applications is presented. A porous nanofibrous structure was prepared by electrospinning of polyimide. An interfacial nanocomposite layer of silver nanoparticles partially or fully embedded in the polyimide matrix was synthesized on the fiber surfaces, followed by autocatalytic deposition of a uniform silver coating (using the interfacial layer as an anchored seed layer) serving as a reactive wetting layer for the infiltrating melt. The thermal performance of the composite was evaluated and the thermal conductivity was determined to be 27 W/mK, accompanied by low contact resistance of the metallurgical bond (
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| 8. |
- Carlberg, Björn, 1983, et al.
(author)
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Surface-Confined Synthesis of Silver Nanoparticle Composite Coating on Electrospun Polyimide Nanofibers
- 2011
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In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:21, s. 3057-3066
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Journal article (peer-reviewed)abstract
- A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1)). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO(3) solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.
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| 9. |
- Chen, S., et al.
(author)
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A Reliability Study of Nanoparticles Reinforced Composite Lead-Free Solder
- 2010
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In: Materials Transactions. - 1347-5320 .- 1345-9678. ; 51:10, s. 1720-1726
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Journal article (peer-reviewed)abstract
- This work looks at the development and investigation of a reinforced composite solder with low melting point The composite solder was prepared by adding Sn 3 0Ag 0 5Cu nanoparticles Into Sn 58BI solder paste 1 he Sn 3 0Ag 0 5Cu nanoparticles were manufactured using a self developed Consumable electrode Direct Current Arc (CDCA) technique The test FR 4 Printed Circuit Board (PCB) with Cu pad and Electroless Nickel Immersion Gold (ENIG) surface finish were fabricated and fifty SR1206 chip resistors were mounted on pads of test PCB with the reinforced composite solder paste by using conventional surface mount technology The differential scanning calorimetry (DSC) was used to analyze the constituent of the composite solder Joint after reflow A scanning electron microscope (SEM) transmission electron microscope (TEM) and optical microscope (OM) were employed in order to observe the morphology of nanoparticles the microstructure of reinforced composite solder Joint the crack initiation and propagation in solder Joint and the fracture mode after shear test The thermal cycling (TC) was carried out with a temperature range of 40 degrees C and 125 C The contract resistance of the solder Joint was measured during thermal cycling and the shear test of solder Joints was performed before and after 500 thermal cycles After the shear test all fracture surfaces were inspected to identify the fracture mode of the composite solder joint The results of the experiments detailed in this work indicate that the shear strength of the composite solder increased 2 times in comparison to Sn 58B(1) Meanwhile the thermomechanical fatigue (TMF) resistance of the composite solder with 1 mass% nanoparticles was 16 times stronger than Sn 58BI and 4 times stronger than Sn 3 0Ag 0 5Cu However the tendency of forming micro cracks between nanoparticles and solder matrix and the fracture within solder was increased for solder joints with more than 3 mass% nanoparticles after thermal cycling.
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| 10. |
- Fu, Yifeng, 1984, et al.
(author)
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A complete carbon-nanotube-based on-chip cooling solution with very high heat dissipation capacity
- 2012
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In: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 23:4
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Journal article (peer-reviewed)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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