| 1. |
- 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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| 2. |
- Liu, Z. Y., et al.
(author)
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Micromechanical characterization of casting-induced inhomogeneity in an Al0.8CoCrCuFeNi high-entropy alloy
- 2011
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In: Scripta Materialia. - : Elsevier BV. - 1359-6462. ; 64:9, s. 868-871
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Journal article (peer-reviewed)abstract
- The microstructural features and micromechanical behavior of individual phases in a cast Al0.8CoCrCuFeNi high-entropy alloy (HEA) were characterized by high-resolution scanning electron microscopy and micro-compression tests. Use of neutron diffraction enabled the detection of a new phase which was otherwise unobservable by conventional X-ray diffraction. The identified phase constitution agreed well with the compositional analysis and the micro-compression results. The delicate microscale characterization of individual phase provides new insights for the design of novel HEAs with desirable mechanical properties. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 3. |
- Sun, S., et al.
(author)
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Thermal performance characterization of nano thermal interface materials after power cycling
- 2012
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In: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781467319669 ; , s. 1426-1430
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Conference paper (peer-reviewed)abstract
- The need for faster, smaller, and more reliable and efficient products has resulted in increase of heat generated in microelectronic components. The removal of the heat generated is an important issue in electronic packaging. A novel Nano-TIM was developed to improve the heat dissipation of electronics packaging. This paper aims at studying the heat dissipation performance of a new class of nano-structured polymer-metal composite film (Nano-TIM) after power cycling. The new Nano-TIM uses metal to provide continuous thermal pathways while using nano-polymer to control the elasticity of the TIM. Through semiconductor processing and RTD principle, chips including 5*5, 10*10, 20*20, 30*30 (mm 2), were developed to study different size's influence on heat dissipation effect of the Nano-TIM. Additional parameters studied include power effect. RTD is used respectively to measure the junction temperature, and then the R thJC (Junction-to-Case Thermal Resistance) is calculated afterwards. The Transient thermal resistances of the Nano-TIM were also tested by T3Ster method to further study heat dissipation effect of Nano-TIM. The morphologies and interaction between the Nano-TIM and chips were carefully studied using X-ray Scanning Microscope to analyze heat flow path. The result shows that Nano-TIMs can be used to 30 mm in chip length as the thermal interface material.
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| 4. |
- Van Eester, D., et al.
(author)
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Minority and mode conversion heating in (He-3)-H JET plasmas
- 2012
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In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 54:7, s. 074009-
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Journal article (peer-reviewed)abstract
- Radio frequency (RF) heating experiments have recently been conducted in JET (He-3)-H plasmas. This type of plasmas will be used in ITER's non-activated operation phase. Whereas a companion paper in this same PPCF issue will discuss the RF heating scenario's at half the nominal magnetic field, this paper documents the heating performance in (He-3)-H plasmas at full field, with fundamental cyclotron heating of He-3 as the only possible ion heating scheme in view of the foreseen ITER antenna frequency bandwidth. Dominant electron heating with global heating efficiencies between 30% and 70% depending on the He-3 concentration were observed and mode conversion (MC) heating proved to be as efficient as He-3 minority heating. The unwanted presence of both He-4 and D in the discharges gave rise to 2 MC layers rather than a single one. This together with the fact that the location of the high-field side fast wave (FW) cutoff is a sensitive function of the parallel wave number and that one of the locations of the wave confluences critically depends on the He-3 concentration made the interpretation of the results, although more complex, very interesting: three regimes could be distinguished as a function of X[He-3]: (i) a regime at low concentration (X[He-3] < 1.8%) at which ion cyclotron resonance frequency (ICRF) heating is efficient, (ii) a regime at intermediate concentrations (1.8 < X[He-3] < 5%) in which the RF performance is degrading and ultimately becoming very poor, and finally (iii) a good heating regime at He-3 concentrations beyond 6%. In this latter regime, the heating efficiency did not critically depend on the actual concentration while at lower concentrations (X[He-3] < 4%) a bigger excursion in heating efficiency is observed and the estimates differ somewhat from shot to shot, also depending on whether local or global signals are chosen for the analysis. The different dynamics at the various concentrations can be traced back to the presence of 2 MC layers and their associated FW cutoffs residing inside the plasma at low He-3 concentration. One of these layers is approaching and crossing the low-field side plasma edge when 1.8 < X[He-3] < 5%. Adopting a minimization procedure to correlate the MC positions with the plasma composition reveals that the different behaviors observed are due to contamination of the plasma. Wave modeling not only supports this interpretation but also shows that moderate concentrations of D-like species significantly alter the overall wave behavior in He-3-H plasmas. Whereas numerical modeling yields quantitative information on the heating efficiency, analytical work gives a good description of the dominant underlying wave interaction physics.
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| 5. |
- Zhang, L., et al.
(author)
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Study on the adhesion strength of new nano-structured polymer-metal composite for thermal interface material (Nano-TIM) under different pressures
- 2011
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In: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. - 9781457717680 ; , s. 426-429
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Conference paper (peer-reviewed)abstract
- With the continual increase in cooling demand for microprocessors, the microelectronics industry has been increasingly focused on the development of thermal solutions. Thermal Interface Material (TIM) plays a key role in reducing the thermal resistance of packaging and the thermal resistance between the electronic device and the external cooling components. Nano-TIM, a new type of thermal interface material, was developed to improve the heat dissipation of electronic devices. This paper describes work undertaken to research the reliability of Nano-TIM. Pull tests were used to investigate the shear strength of samples with Nano-TIM of different thicknesses coalesced between two PCBs with Sn coating made under different pressure. Scanning Electron Microscopy (SEM) analysis techniques were used to determine the morphology of the shear fracture section after pull tests and observe the structure of the cross section of Nano-TIM coalesced between two PCBs with Sn coating.
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| 6. |
- 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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| 7. |
- Carlberg, Björn, 1983, et al.
(author)
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Polymer nanofiber based continuous metal phase composite for thermal management applications
- 2010
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In: 3rd Electronics System Integration Technology Conference, ESTC 2010; Berlin; Germany; 13 September 2010 through 16 September 2010. - 9781424485536 ; , s. Art. no. 5642950-
-
Conference paper (peer-reviewed)abstract
- A new composite design approach for thermal interface materials is presented. A porous electro spun nanofiber network composed of temperature stable poly imide was infiltrated with liquid phase indium at a pressure of 30 MPa. The polymer phase defmes composition and geometry, while the continuous metal phase gives binding to surfaces and high thermal conductivity. The composite was characterized by assembly of tri-layer copper/TIM/copper sandwich structures and subsequent xenon flash measurements extracting the thermal properties of the intermediate TIM layer. The interfacial contact resistance was found to be 8 Kmm2/W and the thermal conductivity was 28 W/mK, indicating the potential for use in thermal management applications.
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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
-
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. |
- Casa, Marcello, et al.
(author)
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Development and characterization of graphene-enhanced thermal conductive adhesives
- 2014
-
In: 15th International Conference on Electronic Packaging Technology, ICEPT 2014; Wangjiang HotelChengdu; China; 12 August 2014 through 15 August 2014. - 9781479947072 ; :Art. no. 6922700, s. 480-483
-
Conference paper (peer-reviewed)abstract
- According to Moore's Laws, complexity and power densities of electronic devices are increased during the last decades, moreover their dimensions are shrinking to nanometers causing hot-spot temperature escalation. Thermal management, therefore, becomes a critical issue for next generation of electronics. This scenario motivates development of novel thermal conductive adhesive (TCA) with enhanced thermal conductivity. Conventional TCAs use polymers as the matrix (base material) and utilize large loading weight fraction of the filler, usually silver particles, to achieve the thermal conductivity of 1-4 W/ m K at room temperature [1]. Lately it was discovered that graphene exhibit superior thermal conductivity [2] even when they are incorporated with matrix materials [3], which offers a potential to develop high thermal conductive graphene-filled compound. In this paper, a new functionalized graphene and its filled TCA have been developed and characterized. Starting from pristine graphite flakes, graphene was prepared through chemical exfoliation and functionalized with a nano silver layer to form a special metal/graphene hybrid material. Moreover, an efficient method to uniformly disperse the nano-scaled graphene hybrid material in silver-epoxy matrix was developed. Cross-section view of SEM has shown a homogeneous component structure, and TGA analysis of hybrid material is given. The developed compound is based on a commercial TCA which is composed with epoxy matrix and micro-sized Ag flakes. Thermal characterization through Laser-flash equipment has indicated that a significant thermal conductivity improvement was achieved through adding functionalized graphene into the material. Different TCA samples with different weight percentages of functionalized graphene ranging from 0 % (reference) to 11.5 % were prepared and tested to study thermal conductivity change. Data show that a thermal conductivity value of 7.6 W/ m K is reached when the graphene/silver percentage is 11.5 % that is almost 4 times higher than our reference.
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| 10. |
- Chen, S., et al.
(author)
-
A solder joint structure with vertically aligned carbon nanofibres as reinforcements
- 2014
-
In: Proceedings of the 5th Electronics System-Integration Technology Conference, ESTC 2014. - 9781479940264 ; , s. Art. no. 6962851-
-
Conference paper (peer-reviewed)abstract
- In this paper, a solder joint structure was developed for the electronic packaging industry. Vertically aligned carbon nanofibres (VACNFs) were grown, transferred and used at the interface between Si/Au pads and Sn-3.0Ag-0.5Cu (SAC305) alloy as reinforcements in order to increase the solder joint thermal fatigue resistance. The transfer and assembly processes related to VACNFs were optimised and developed. The thermal cycling test results show that the thermal fatigue life of VACNF/SAC305 solder joints is 40% longer than that of pure SAC305. The dye and pry analysis and scanning electron microscopy observation prove that the VACNFs can effectively delay the crack propagation near the interface and consequently prolong the solder joint thermal fatigue life.
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