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1.
  • Abgrall, N., et al. (author)
  • The large enriched germanium experiment for neutrinoless double beta decay (LEGEND)
  • 2017
  • In: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 1894
  • Conference paper (peer-reviewed)abstract
    • The observation of neutrinoless double-beta decay (0νββ) would show that lepton number is violated, reveal that neu-trinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of ∼0.1 count /(FWHM·t·yr) in the region of the signal. The current generation 76Ge experiments GERDA and the Majorana Demonstrator, utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0νββ signal region of all 0νββ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale 76Ge experiment. The collaboration aims to develop a phased 0νββ experimental program with discovery potential at a half-life approaching or at 1028 years, using existing resources as appropriate to expedite physics results.
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2.
  • Chen, Shujing, et al. (author)
  • Manufacturing Graphene-Encapsulated Copper Particles by Chemical Vapor Deposition in a Cold Wall Reactor
  • 2019
  • In: ChemistryOpen. - : Wiley. - 2191-1363. ; 8:1, s. 58-63
  • Journal article (peer-reviewed)abstract
    • Functional fillers, such as Ag, are commonly employed for effectively improving the thermal or electrical conductivity in polymer composites. However, a disadvantage of such a strategy is that the cost and performance cannot be balanced simultaneously. Therefore, the drive to find a material with both a cost efficient fabrication process and excellent performance attracts intense research interest. In this work, inspired by the core-shell structure, we developed a facile manufacturing method to prepare graphene-encapsulated Cu nanoparticles (GCPs) through utilizing an improved chemical vapor deposition (CVD) system with a cold wall reactor. The obtained GCPs could retain their spherical shape and exhibited an outstanding thermal stability up to 179 degrees C. Owing to the superior thermal conductivity of graphene and excellent oxidation resistance of GCPs, the produced GCPs are practically used in a thermally conductive adhesive (TCA), which commonly consists of Ag as the functional filler. Measurement shows a substantial 74.6 % improvement by partial replacement of Ag with GCPs.
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3.
  • Cometto, O., et al. (author)
  • Control of Nanoplane Orientation in voBN for High Thermal Anisotropy in a Dielectric Thin Film: A New Solution for Thermal Hotspot Mitigation in Electronics
  • 2017
  • In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:8, s. 7456-7464
  • Journal article (peer-reviewed)abstract
    • High anisotropic thermal materials, which allow heat to dissipate in a preferential direction, are of interest as a prospective material for electronics as an effective thermal management solution for hot spots. However, due to their preferential heat propagation in the in-plane direction, the heat spreads laterally instead of vertically. This limitation makes these materials ineffective as the density of hot spots increases. Here, we produce a new dielectric thin film material at room temperature, named vertically ordered nanocrystalline h-BN (voBN). It is produced such that its preferential thermally conductive direction is aligned in the vertical axis, which facilitates direct thermal extraction, thereby addressing the increasing challenge of thermal crosstalk. The uniqueness of voBN comes from its h-BN nanocrystals where all their basal planes are aligned in the direction normal to the substrate plane. Using the 3 omega method, we show that voBN exhibits high anisotropic thermal conductivity (TC) with a 16-fold difference between through-film TC and in-plane TC (respectively 4.26 and 0.26 W.m(-1).K-1). Molecular dynamics simulations also concurred with the experimental data, showing that the origin of this anisotropic behavior is due to the nature of voBN's plane ordering. While the consistent vertical ordering provides an uninterrupted and preferred propagation path for phonons in the through-film direction, discontinuity in the lateral direction leads to a reduced in-plane TC. In addition, we also use COMSOL to simulate how the dielectric and thermal properties of voBN enable an increase in hot spot density up to 295% compared with SiO2, without any temperature increase.
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4.
  • Jing, Lin, et al. (author)
  • Thermal Conductivity Enhancement of Coaxial Carbon@Boron Nitride Nanotube Arrays
  • 2017
  • In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:17, s. 14555-14560
  • Journal article (peer-reviewed)abstract
    • We demonstrate the thermal conductivity enhancement of the vertically aligned carbon nanotube (CNT) arrays (from ?15.5 to 29.5 W/mK, ?90% increase) by encapsulating outer boron nitride nanotube (BNNT, 0.97 nm-thick with ?3-4 walls). The heat transfer enhancement mechanism of the coaxial C@BNNT was further revealed by molecular dynamics simulations. Because of their highly coherent lattice structures, the outer BNNT serves as additional heat conducting path without impairing the thermal conductance of inner CNT. This work provides deep insights into tailoring the heat transfer of arbitrary CNT arrays and will enable their broader applications as thermal interface material.
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5.
  • Liu, Ya, 1991, et al. (author)
  • Effect of Boron Nitride Particle Geometry on the Thermal Conductivity of a Boron Nitride Enhanced Polymer Composite Film
  • 2019
  • In: THERMINIC 2019 - 2019 25th International Workshop Thermal Investigations of ICs and Systems.
  • Conference paper (peer-reviewed)abstract
    • Hexagonal Boron Nitride (h-BN) has been considered as a promising enhancement filler for thermal management due to its high thermal conductivity, structural stability, and super electrical resistivity. Numerus studies have reported using BN as an enhancement filler to achieve high thermally conductive polymer based thermal management materials. However, there are limited data regarding the influence of the flake size of BN sheets to the thermal management property of BN filled composites. In this work, three h-BN size geometries, including microscale h-BN powder, h-BN nanosheets, and a mixture of micro and nanoscale h-BN, were studied regarding its thermal transfer performance. The results show that h-BN nanosheets are able to achieve the highest in-plane thermal conductivity with loading from 0 - 5 wt% while for the through-plane thermal conductivity, all three geometries show similar thermal property when the filler loading less than 5 wt%. Through-plane thermal conductivity exhibits a sudden increase to 5.69 W m-1 K-1 at a loading of 5 wt%..
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6.
  • Liu, Ya, 1991, et al. (author)
  • Egg albumen templated graphene foams for high-performance supercapacitor electrodes and electrochemical sensors
  • 2018
  • In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 6:37, s. 18267-18275
  • Journal article (peer-reviewed)abstract
    • We demonstrate a simple and scalable strategy to obtain N, S and Si co-doped biocompatible graphene foams (GFs) with different shapes using egg albumen as the template. The unique porous structure and element doping endow the GFs with a high charge-discharge rate and good wettability, which largely improve the electrochemical performance of the electrodes, including ultrahigh specific capacitance (534 F g-1at 1 A g-1), and excellent rate capability (308 F g-1at 100 A g-1) and cycling performance (96.1% retention of the initial capacitance after 10000 cycles at a high current density of 10 A g-1). Besides, when used as an electrochemical sensor for dopamine, the GF exhibits a detection limit as low as 1.2 μM with a linear response up to 70 μM, due to the low equivalent series resistance. These reveal great potential for promoting the application of 3D graphene in energy storage and electrochemical sensors.
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7.
  • Liu, Ya, 1991, et al. (author)
  • Surface modification of graphene for use as a structural Fortifier in water-borne epoxy coatings
  • 2019
  • In: Coatings. - : MDPI AG. - 2079-6412. ; 9:11
  • Journal article (peer-reviewed)abstract
    • Graphene, the typical two-dimensional sp2 hybridized carbon allotrope, is widely used as a filler for improving the mechanical performance of polymers. However, its superhydrophobic surface makes it a big challenge to obtain stable graphene dispersions, especially in water-borne systems. On the contrary, graphene oxide (GO) shows excellent dispersibility in water, but strong oxidants and acids destroy its structure and degrade its mechanical properties. This largely limits its application in water-borne coatings. In this work, graphene from mechanical exfoliation was surface modified by p-aminophenol derived diazonium salt to achieve a homogenous dispersion. Moreover, the hydroxyl groups in p-aminophenol are able to combine with epoxy resins during the curing process to improve mechanical performance of the final coatings. The result shows that functionalized graphene shows a lower coefficient of friction and better abrasion resistance compared to GO.
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8.
  • Liu, Ya, 1991, et al. (author)
  • Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader
  • 2019
  • In: Proceedings - 2019 IMAPS Nordic Conference on Microelectronics Packaging, NORDPAC 2019. ; , s. 1-5
  • Conference paper (peer-reviewed)abstract
    • Thermally conductive materials with electrically insulating properties have been extensively investigated for thermal management of electronic devices. The combined properties of high thermal conductivity, structural stability, corrosion resistance and electric resistivity make hexagonal boron nitride (h-BN) a promising candidate for this purpose. Theoretical studies have revealed that h-BN has a high in-plane thermal conductivity up to 400-800 W m-1 K-1 at room temperature. However, it is still a big challenge to achieve high thermally conductive h-BN thick films that are commercially feasible due to its poor mechanical properties. On the other hand, many polymers exhibit advantages for flexibility. Thus, combining the merits of polymer and the high thermal conductivity of h-BN particles is considered as a promising solution for this issue. In this work, orientated PVP/h-BN films were prepared by electrospinning and a subsequent mechanical pressing process. With the optimized h-BN loading, a PVP/h-BN composite film with up to 22 W m-1 K-1 and 0.485 W m-1 K-1 for in-plane and through-plane thermal conductivity can be achieved, respectively. We believe this work can help accelerate the development of h-BN for thermal management applications.
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9.
  • Liu, Ya, 1991, et al. (author)
  • Thermally Conductive and Electrically Insulating PVP/Boron Nitride Composite Films for Heat Spreader
  • 2019
  • In: Advancing Microelectronics. - 2222-8748. ; 2019:NOR, s. 1-5
  • Journal article (peer-reviewed)abstract
    • Thermally conductive materials with electrically insulating properties have been extensively investigated for thermal management of electronic devices. The combined properties of high thermal conductivity, structural stability, corrosion resistance and electric resistivity make hexagonal boron nitride (h-BN) a promising candidate for this purpose. Theoretical studies have revealed that h-BN has a high in-plane thermal conductivity up to 400 - 800 W m−1 K−1 at room temperature. However, it is still a big challenge to achieve high thermally conductive h-BN thick films that are commercially feasible due to its poor mechanical properties. On the other hand, many polymers exhibit advantages for flexibility. Thus, combining the merits of polymer and the high thermal conductivity of h-BN particles is considered as a promising solution for this issue. In this work, orientated PVP/h-BN films were prepared by electrospinning and a subsequent mechanical pressing process. With the optimized h-BN loading, a PVP/h-BN composite film with up to 22 W m-1 K-1 and 0.485 W m-1 K-1 for in-plane and through-plane thermal conductivity can be achieved, respectively. We believe this work can help accelerate the development of h-BN for thermal management applications.
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10.
  • Middeldorp, Christel M., et al. (author)
  • The Early Growth Genetics (EGG) and EArly Genetics and Lifecourse Epidemiology (EAGLE) consortia : design, results and future prospects
  • 2019
  • In: European Journal of Epidemiology. - : Springer Science and Business Media LLC. - 0393-2990 .- 1573-7284. ; 34:3, s. 279-300
  • Journal article (peer-reviewed)abstract
    • The impact of many unfavorable childhood traits or diseases, such as low birth weight and mental disorders, is not limited to childhood and adolescence, as they are also associated with poor outcomes in adulthood, such as cardiovascular disease. Insight into the genetic etiology of childhood and adolescent traits and disorders may therefore provide new perspectives, not only on how to improve wellbeing during childhood, but also how to prevent later adverse outcomes. To achieve the sample sizes required for genetic research, the Early Growth Genetics (EGG) and EArly Genetics and Lifecourse Epidemiology (EAGLE) consortia were established. The majority of the participating cohorts are longitudinal population-based samples, but other cohorts with data on early childhood phenotypes are also involved. Cohorts often have a broad focus and collect(ed) data on various somatic and psychiatric traits as well as environmental factors. Genetic variants have been successfully identified for multiple traits, for example, birth weight, atopic dermatitis, childhood BMI, allergic sensitization, and pubertal growth. Furthermore, the results have shown that genetic factors also partly underlie the association with adult traits. As sample sizes are still increasing, it is expected that future analyses will identify additional variants. This, in combination with the development of innovative statistical methods, will provide detailed insight on the mechanisms underlying the transition from childhood to adult disorders. Both consortia welcome new collaborations. Policies and contact details are available from the corresponding authors of this manuscript and/or the consortium websites.
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11.
  • Wang, Nan, et al. (author)
  • Highly thermal conductive and electrically insulated graphene based thermal interface material with long-term reliability
  • 2019
  • In: Proceedings - Electronic Components and Technology Conference. - 0569-5503. ; 2019-May, s. 1564-1568
  • Conference paper (peer-reviewed)abstract
    • High density packaging in combination with increased transistor integration inevitably leads to challenging power densities in terms of thermal management. The conventional TIMs that are widely used in the microelectronic industry today are experiencing more and more stress due to their limited thermal performance and poor reliability. Composed by particle laden polymer matrix, thermal conductivity (K) of conventional TIMs is generally limited to 5 W/mK, and such values can be even lower for electrically insulated TIMs. Conventional TIMs also suffer from severe pump-out and dry-out failures, which brought great threat to the performance and lifetime of the electronic devices. Here, we solve these problems by applying a novel highly thermal conductive, electrically insulated and reliable graphene based TIMs (I-GTs). Composed by vertical graphene structures, I-GTs provide a continuous heat pathway from top to bottom, which enables superfast heat dissipation at through-plane direction. The highest bulk through-plane thermal conductivity of the conductive body can reach up to 1000 W/mK, which is orders of magnitude higher than conventional TIMs, and even outperforms the pure indium TIMs by over ten times. The highly flexible and foldable nature of I-GT enables at least 100% compressibility upon small applied pressures. As excellent gap fillers, I-GT can provide complete physical contact between two surfaces and thereby minimize the contact resistance to heat flow. The measured minimum thermal resistance for I-GTs reaches about 30 Kmm2/W. Such values are significantly higher than the randomly dispersed composites presented above. To ensure fully electrical insulation, a smooth and soft adhesive layer with a thickness of few microns was coated on the surface of I-GT. The breakdown voltage of I-GT reaches up to 950 V. Thermal cycling test shows the highly stable nature of I-GT. The good compressibility and elasticity of I-GT ensures continued proper TIM contact with substrates, which counteracts the effect of internal stress induced by the mismatch of coefficient of thermal expansion (CTE) during temperature cycling. In addition, the I-GTs have the advantages of low density and good maintainability. The resulting I-GTs thus opens new opportunities for addressing large heat dissipation issues for form-factor driven electronics and other high power driven systems.
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12.
  • Wang, Nan, et al. (author)
  • Highly Thermal Conductive and Light -weight Craphene-based Heatsink
  • 2019
  • In: 2019 22ND EUROPEAN MICROELECTRONICS AND PACKAGING CONFERENCE & EXHIBITION (EMPC). - 2165-2341. - 9780956808660
  • Conference paper (peer-reviewed)abstract
    • With the developing trend ofminiaturization and integration of modem electronic devices, commercial hearsinks ivaterigh, like copper and ii iv are facing mare and mare challenges, such as inefficient cooling performance, large size turd heavy weight. Here, we salve the probletn by developing a novel highly thermal conductive and 11Mo-weight graphene heatsink. Cornposed by vertically-aligned and continUOUS graphene structures, heat transport was highly efficiero from the base 1o fin Ii: ininside the heatsink, The maximum through-platre thermal catuluctivity ofgraphene heatsink can be up to 1000 1500 Ward( which is over 7 times higher than aluminum, and even outperforms copper about 4 times_ Gmphene heatsink demonstrated outstanding cooling perffrmance which wm superior to copper heatsink with the same dimension and same power input. Noticeably, the graphene hearsink also has anportant advantagas of light-weight and high emissions,. The measured density (1 1 g cmli is only onroeighth of copper and lam than hoor of aluminum and emissivity is about ten times hiher than pure rapper and aluminum. The resulting graphene heatsink thus opertS rim opportunities for addressing large heat dissMatMn issues in weight' driven electronics and othm high power smions.
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13.
  • Zhang, Dongsheng, et al. (author)
  • Thermal properties of TIM using CNTs forest in electronics packaging
  • 2016
  • In: 2016 17th International Conference on Electronic Packaging Technology, ICEPT 2016; Wuhan Optics Valley Kingdom Hotel Wuhan; China; 16 August 2016 through 19 August 2016. ; , s. 1355-1359
  • Conference paper (peer-reviewed)abstract
    • Thermal interface material (TIM) is applied to fill the air gaps of interfaces, which provides a path for interfacial heat transfer. Owing to the exceptional thermal properties of carbon nanotubes (CNT), TIMs based on CNTs have received much attention in recent years. In this study, heat dissipation performance of vertically aligned carbon nanotubes (VACNT) arrays as TIM in electronic packing was analyzed. Vertically aligned carbon nanotubes with length of 245?m and 763?m were synthesized on a silicon substrate by chemical vapor deposition respectively. Morphology of the vertically aligned carbon nanotubes was characterized by scanning electron microscope. The hotspot temperature of thermal test chip with vertically aligned carbon nanotubes were characterized by resistance temperature detector method and infrared imaging method.
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14.
  • Zhang, Maomao, et al. (author)
  • Effect of pressure during graphitization on mechanical properties of graphene films
  • 2019
  • In: 2019 20th International Conference on Electronic Packaging Technology, ICEPT 2019.
  • Conference paper (peer-reviewed)abstract
    • Graphene films (GFs) can be used in the field of electronics cooling, owing to many outstanding properties. In the present paper, GFs samples were graphitized at different pressures to study their effect on the mechanical properties. The elastic modulus and hardness of GFs were measured by nanoindentation and the tensile strength of GFs were obtained by stretching GFs in a tensile tester. Meanwhile, GFs were characterized by X-ray diffraction(XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. The results show that the modulus, hardness and tensile strength of GFs were strongly influenced by the defect and wrinkles among other things.
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15.
  • Zhang, Q., et al. (author)
  • Effect of sintering method on properties of nanosilver paste
  • 2017
  • In: 2017 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2017, Goteborg, Sweden, 18-20 June 2017. ; , s. 186-189
  • Conference paper (peer-reviewed)abstract
    • Nanoscale silver paste has a good application prospect in heat dissipation of high-power chips due to the characteristics of low temperature sintering and high temperature service. The properties of the nanosilver paste including thermal conductivity, electrical conductivity, and shear strength are affected greatly by the sintering process. The influence of different sintering methods on the performance of the nanosilver paste was studied in this article. The nanosilver paste with 80.5 wt% nano-scale silver particles, 1.5 wt% submicron-scale SiC particles with Ag coating, 0.9 wt% dispersion agent, 10 wt% organic carrier and 7.1 wt% diluting agent was sintered at 260°C for 30 min with three different methods, heating table sintering, heating furnace sintering, and mixed sintering. The samples obtained by mixed sintering process have higher thermal conductivity than the ones obtained by heating furnace sintering method and heating table sintering method. The effect of sintering methods on shear strength of nanosilver paste was also investigated subsequently. Shear testing equipment was used to measure the shear strength of the samples gained by heating table sintering, heating furnace sintering, and air dry oven sintering. The maximum shear strength was obtained for the samples by heating table sintering method. The shear strength of samples by air dry oven sintering method was the minimum one.
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16.
  • Zhang, Q., et al. (author)
  • Mechanical property and reliability of bimodal nano-silver paste with Ag-coated SiC particles
  • 2019
  • In: Soldering and Surface Mount Technology. - 1758-6836 .- 0954-0911. ; 31:4, s. 193-202
  • Journal article (peer-reviewed)abstract
    • © 2019, Emerald Publishing Limited. Purpose: This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated. Design/methodology/approach: Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively. Findings: Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles. Originality/value: Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.
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17.
  • Banerjee, Debashree, et al. (author)
  • Elevated thermoelectric figure of merit of n-type amorphous silicon by efficient electrical doping process
  • 2018
  • In: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 44, s. 89-94
  • Journal article (peer-reviewed)abstract
    • The currently dominant thermoelectric (TE) materials used in low to medium temperature range contain Tellurium that is rare and mild-toxic. Silicon is earth abundant and environment friendly, but it is characterized by a poor TE efficiency with a low figure of merit, ZT. In this work, we report that ZT of amorphous silicon (a-Si) thin films can be enhanced by 7 orders of magnitude, reaching ∼0.64 ± 0.13 at room temperature, by means of arsenic ion implantation followed by low-temperature dopant activation. The dopant introduction employed represents a highly controllable doping technique used in standard silicon technology. It is found that the significant enhancement of ZT achieved is primarily due to a significant improvement of electrical conductivity by doping without crystallization so as to maintain the thermal conductivity and Seebeck coefficient at the level determined by the amorphous state of the silicon films. Our results open up a new route towards enabling a-Si as a prominent TE material for cost-efficient and environment-friendly TE applications at room temperature.
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18.
  • Bao, Jie, et al. (author)
  • Application of two-dimensional layered hexagonal boron nitride in chip cooling
  • 2016
  • In: Yingyong Jichu yu Gongcheng Kexue Xuebao/Journal of Basic Science and Engineering. - 1005-0930. ; 24:1, s. 210-217
  • Journal article (peer-reviewed)abstract
    • © 2016, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.Research into layered hexagonal boron nitride(h-BN)has recently intensified, due to its superior physicochemical properties compared to that of a typical two-dimensional material. H-BN can be utilized in power chips as both an insulating layer as well as a heat spreader for local hotspots with high heat flux. Single layer h-BN film grown by CVD and h-BN microparticles are respectively transferred onto the surfaces of the thermal evaluation chips, where the influence of h-BN on the heat dissipation performance of the chips can be observed at different power values. The resistance-temperature curve method and infrared thermal imager are both used to measure the temperature of hotspots on the thermal evaluation chips, which can be reduced by between 3~5℃ at 1W after the transfer of h-BN. The cooling efficiency is improved and it can be found that single layer h-BN film shows better heat dissipation ability.
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19.
  • Bao, Jie, et al. (author)
  • Measurement of Dielectric Properties of Ultrafine BaTiO3 Using an Organic-Inorganic Composite Method
  • 2015
  • In: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 44:7, s. 2300-2307
  • Journal article (peer-reviewed)abstract
    • Ultrafine BaTiO3, unlike traditional ferroelectric materials, demonstrates some interesting dielectric properties, such as a gradual transition from paraelectric to ferroelectric phase, which is similar to dielectric relaxation ferroelectrics. Although several methods have been recently proposed to measure the dielectric properties of ultrafine BaTiO3, the problem still remains unsolved. This paper proposes a new method to estimate the dielectric properties of ultrafine BaTiO3 by measuring and analyzing the dielectric properties of BaTiO3-epoxy composites. The Novocontrol dielectric measuring system was employed to measure the dielectric response of the composites. The dielectric behavior and relaxation characteristics of the BaTiO3 filler were estimated by modeling and calculating the dielectric constant based on different mixture theories. Results reveal that the effect of surface states yields dielectric relaxation in ultrafine BaTiO3.
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20.
  • Bao, Jie, et al. (author)
  • Synthesis and Applications of Two-Dimensional Hexagonal Boron Nitride in Electronics Manufacturing
  • 2016
  • In: Electronic Materials Letters. - : Springer Science and Business Media LLC. - 1738-8090 .- 2093-6788. ; 12:1, s. 1-16
  • Research review (peer-reviewed)abstract
    • In similarity to graphene, two-dimensional (2D) hexagonal boron nitride (hBN) has some remarkable properties, such as mechanical robustness and high thermal conductivity. In addition, hBN has superb chemical stability and it is electrically insulating. 2D hBN has been considered a promising material for many applications in electronics, including 2D hBN based substrates, gate dielectrics for graphene transistors and interconnects, and electronic packaging insulators. This paper reviews the synthesis, transfer and fabrication of 2D hBN films, hBN based composites and hBN-based van der Waals heterostructures. In particular, this review focuses on applications in manufacturing electronic devices where the insulating and thermal properties of hBN can potentially be exploited. 2D hBN and related composite systems are emerging as new and industrially important materials, which could address many challenges in future complex electronics devices and systems.
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21.
  • Bao, Jie, 1982, et al. (author)
  • Two-dimensional hexagonal boron nitride as lateral heat spreader in electrically insulating packaging
  • 2016
  • In: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 49:July 2016, s. 265501-
  • Journal article (peer-reviewed)abstract
    • The need for electrically insulating materials with a high in-plane thermal conductivity for lateral heat spreading applications in electronic devices has intensified studies of layered hexagonal boron nitride (h-BN) films. Due to its physicochemical properties, h-BN can be utilised in power dissipating devices such as an electrically insulating heat spreader material for laterally redistributing the heat from hotspots caused by locally excessive heat flux densities. In this study, two types of boron nitride based heat spreader test structures have been assembled and evaluated for heat dissipation. The test structures separately utilised a few-layer h-BN film with and without graphene enhancement drop coated onto the hotspot test structure. The influence of the h-BN heat spreader films on the temperature distribution across the surface of the hotspot test structure was studied at a range of heat flux densities through the hotspot. It was found that the graphene-enhanced h-BN film reduced the hotspot temperature by about 8–10°C at a 1000 W/cm2 heat flux density, a temperature decrease significantly larger than for h-BN film without graphene enhancement. Finite element simulations of the h-BN film predict that further improvements in heat spreading ability are possible if the thermal contact resistance between the film and test chip are minimised.
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22.
  • Bistarelli, Silvia, et al. (author)
  • Evaluating CNT-Based Interconnects : A Nummerical Tool to Characterize Hybrid CNT-Copper Interconnects
  • 2017
  • In: IEEE Microwave Magazine. - 1527-3342 .- 1557-9581. ; 18:4, s. 124-129
  • Journal article (peer-reviewed)abstract
    • Nanotechnologies offer a vast number of applications due to the unique features of nanostructured materials [1]. In the electronics field, this new technology could open innovative ways to go beyond Moore's law [2], but progress in manufacturing technology still limits the wide dispersion of nanotechnology-based circuits. The bridge between nanoscience and realized devices can be achieved by modeling the multiphysics phenomena at the nanoscale, which will aid in the development of the technology.
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23.
  • Casa, Marcello, et al. (author)
  • Conductive adhesive based on mussel-inspired graphene decoration with silver nanoparticles
  • 2018
  • In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880. ; 18:2, s. 1176-1185
  • Journal article (peer-reviewed)abstract
    • Decoration with silver nanoparticles was obtained by coating graphene with a polydopamine layer, able to induce spontaneous metallic nanoparticles formation without any specific chemical interfacial modifier, neither using complex instrumentation. The choice of dopamine was inspired by the composition of adhesive proteins in mussels, related to their robust attach to solid surfaces. The synthesis procedure started from graphite and involved eco-friendly compounds, such as Vitamin C and glucose as reducing agent and water as reaction medium. Silver decorated graphene was inserted as secondary nanofiller in the formulation of a reference conductive adhesive based on epoxy resin and silver flakes. A wide characterization of the intermediate materials obtained along the step procedure for the adhesive preparation was carried out by several techniques. We have found that the presence of nanofiller yields, in addition to an improvement of the thermal conductivity (up to 7.6 W/m· K), a dramatic enhancement of the electrical conductivity of the adhesive. In particular, starting from 3 · 10 2 S/cm of the reference adhesive, we obtained a value of 4 · 10 4 S/cm at a nanofiller concentration of 11.5 wt%. The combined double filler conductivity was evaluated by Zallen’s model. The effect of the temperature on the resistivity of the adhesive has been also studied.
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24.
  • Casa, Marcello, et al. (author)
  • Silver decorated graphene-polyvinyl alcohol hybrid hydrogel as catalyst for benzonitrile conversion
  • 2017
  • In: Advanced Science Letters. - : American Scientific Publishers. - 1936-7317 .- 1936-6612. ; 23:6, s. 5980-5983
  • Journal article (peer-reviewed)abstract
    • In this work, we have synthetized a reduced graphene oxide functionalized with silver nanoparticles (G/Ag) by a method developed in our previous study and incorporated it in a hydrogel based on polyvinyl alcohol (PVA) as gelator through a freezing/thawing method. The hydrogel has been tested to catalyze the reduction at room temperature of nitrile group of benzonitrile in water by using glucose as a natural and mild reducing agent.
  •  
25.
  • Chen, Si, 1981, et al. (author)
  • A High Performance Ag Alloyed Nano-scale n-type Bi2Te3 Based Thermoelectric Material
  • 2015
  • In: Materials Today: Proceedings. - : Elsevier BV. - 2214-7853. ; 2:2, s. 610-619
  • Conference paper (peer-reviewed)abstract
    • A silver alloyed n-type bismuth telluride (Bi2Te3) thermoelectric (TE) bulk material with nano crystalline structure was studied and characterized in this paper. The Bi2Te3 nanopowders used in this study were first fabricated via a patented explosion based process. Then, the various concentrations of Ag nanoparticles (0-20 wt. %) were added into the Bi2Te3 nanopowders in order to increase the electrical conductivity. Combining the benefits of high electrical conductivity (1.51x10(5) S.m(-1)) and low thermal conductivity (0.441 W.m(-1).K-1), the dimensionless figure of merit (ZT value) of 1.48 for this n-type Bi2Te3 TE material is achieved at 300 K temperature.
  •  
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