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ENERGY (159 journals)                  1 2 | Last

Advances in Building Energy Research     Hybrid Journal   (10 followers)
Advances in High Energy Physics     Open Access   (12 followers)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (13 followers)
American Journal of Energy Research     Open Access   (2 followers)
Annals of Nuclear Energy     Hybrid Journal   (6 followers)
Annual Reports on NMR Spectroscopy     Full-text available via subscription   (1 follower)
Annual Review of Resource Economics     Full-text available via subscription   (10 followers)
Applied Nanoscience     Open Access   (7 followers)
Applied Solar Energy     Hybrid Journal   (9 followers)
Archives of Thermodynamics     Open Access   (3 followers)
Atomic Energy     Hybrid Journal   (4 followers)
Atoms for Peace: an International Journal     Hybrid Journal   (1 follower)
Biofuels     Full-text available via subscription   (7 followers)
Biomass Conversion and Biorefinery     Partially Free   (5 followers)
Bulletin de droit nucleaire     Full-text available via subscription   (1 follower)
Canadian Journal of Remote Sensing     Full-text available via subscription   (12 followers)
Canadian Water Resources Journal     Hybrid Journal   (17 followers)
Carbon Management     Full-text available via subscription   (4 followers)
Catalysis for Sustainable Energy     Open Access   (1 follower)
Chain Reaction     Full-text available via subscription  
Clefs CEA     Full-text available via subscription   (1 follower)
Computational Water, Energy, and Environmental Engineering     Open Access   (1 follower)
Continental Journal of Renewable Energy     Open Access   (8 followers)
Current Sustainable/Renewable Energy Reports     Hybrid Journal  
Dams and Reservoirs     Hybrid Journal   (2 followers)
Development of Energy Science     Open Access  
Distributed Generation & Alternative Energy Journal     Hybrid Journal   (1 follower)
E3S Web of Conferences     Open Access  
Electrical and Power Engineering Frontier     Open Access   (8 followers)
Electronic Journal of Energy & Environment     Open Access   (6 followers)
Energy     Partially Free   (17 followers)
Energy & Fuels     Full-text available via subscription   (21 followers)
Energy and Buildings     Hybrid Journal   (6 followers)
Energy and Environment Research     Open Access   (7 followers)
Energy and Power Engineering     Open Access   (6 followers)
Energy Conversion and Management     Hybrid Journal   (6 followers)
Energy Efficiency     Hybrid Journal   (9 followers)
Energy Materials: Materials Science and Engineering for Energy Systems     Hybrid Journal   (16 followers)
Energy Policy     Partially Free   (32 followers)
Energy Prices and Taxes     Full-text available via subscription   (4 followers)
Energy Procedia     Open Access   (2 followers)
Energy Science & Engineering     Open Access   (2 followers)
Energy Science and Technology     Open Access   (9 followers)
Energy Strategy Reviews     Partially Free   (4 followers)
Energy Studies Review     Open Access   (3 followers)
Energy Systems     Hybrid Journal   (7 followers)
Energy Technology     Partially Free   (2 followers)
Energy, Sustainability and Society     Open Access   (14 followers)
Environmental Progress & Sustainable Energy     Hybrid Journal   (3 followers)
EPJ Photovoltaics     Open Access  
Frontiers in Energy     Hybrid Journal   (2 followers)
Frontiers in Energy Research     Open Access  
Fuel and Energy Abstracts     Full-text available via subscription   (5 followers)
Functional Materials Letters     Hybrid Journal   (1 follower)
Gcb Bioenergy     Hybrid Journal   (1 follower)
Geothermal Energy     Open Access  
GeoWorld     Full-text available via subscription   (2 followers)
Green     Full-text available via subscription   (1 follower)
Hyperfine Interactions     Hybrid Journal   (2 followers)
IEA Electricity Information     Full-text available via subscription   (5 followers)
IEA Natural Gas Information     Full-text available via subscription   (4 followers)
IEEE Power and Energy     Full-text available via subscription   (7 followers)
IEEE Transactions on Energy Conversion     Hybrid Journal   (5 followers)
IEEE Transactions on Nuclear Science     Hybrid Journal   (7 followers)
IEEE Transactions on Power Systems     Hybrid Journal   (9 followers)
IET Power Electronics     Hybrid Journal   (7 followers)
IngenierĂ­a EnergĂ©tica     Open Access  
Innovations : Technology, Governance, Globalization     Hybrid Journal   (6 followers)
International Journal of Alternative Propulsion     Hybrid Journal   (1 follower)
International Journal of Ambient Energy     Hybrid Journal   (2 followers)
International Journal of Applied Power Engineering     Open Access  
International Journal of Clean Coal and Energy     Open Access   (3 followers)
International Journal of Critical Infrastructure Protection     Hybrid Journal   (5 followers)
International Journal of Electric and Hybrid Vehicles     Hybrid Journal   (3 followers)
International Journal of Emerging Electric Power Systems     Full-text available via subscription   (4 followers)
International Journal of Emerging Multidisciplinary Fluid Sciences     Full-text available via subscription  
International Journal of Energy and Environmental Engineering     Open Access   (2 followers)
International Journal of Energy and Power     Open Access   (4 followers)
International Journal of Energy Engineering     Open Access   (10 followers)
International Journal of Energy Research     Hybrid Journal   (8 followers)
International Journal of Energy Science     Open Access   (1 follower)
International Journal of Flow Control     Full-text available via subscription   (1 follower)
International Journal of Global Energy Issues     Hybrid Journal   (6 followers)
International Journal of Green Energy     Hybrid Journal   (5 followers)
International Journal of Hydrogen Energy     Partially Free   (7 followers)
International Journal of Marine Energy     Full-text available via subscription   (1 follower)
International Journal of Nuclear Desalination     Hybrid Journal   (2 followers)
International Journal of Nuclear Energy Science and Technology     Hybrid Journal   (1 follower)
International Journal of Nuclear Governance, Economy and Ecology     Hybrid Journal   (2 followers)
International Journal of Nuclear Hydrogen Production and Applications     Hybrid Journal   (2 followers)
International Journal of Nuclear Knowledge Management     Hybrid Journal   (1 follower)
International Journal of Power and Energy Conversion     Hybrid Journal   (3 followers)
International Journal of Regulation and Governance     Hybrid Journal   (2 followers)
International Journal of Sustainable Energy     Hybrid Journal   (8 followers)
International Journal of Sustainable Engineering     Hybrid Journal   (7 followers)
International Journal of Thermodynamics     Open Access   (1 follower)
ISRN Power Engineering     Open Access   (1 follower)
ISRN Renewable Energy     Open Access   (5 followers)
Journal of Alternate Energy Sources & Technologies     Full-text available via subscription  
Journal of Building Performance Simulation     Hybrid Journal   (3 followers)

        1 2 | Last

Journal of Renewable and Sustainable Energy    [14 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Online) 1941-7012
     Published by American Institute of Physics (AIP) Homepage  [30 journals]
  • Challenges and opportunities for multi-functional oxide thin films for
           voltage tunable radio frequency/microwave components
    • Abstract: There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.
      PubDate: 2013-11-15T12:00:00Z
  • Electrospun metallic nanowires: Synthesis, characterization, and
    • Abstract: Metals are known to have unique thermal, mechanical, electrical, and catalytic properties. On the other hand, metallic nanowires are promising materials for variety of applications such as transparent conductive film for photovoltaic devices, electrodes for batteries, as well as nano-reinforcement for composite materials. Whereas varieties of methods have been explored to synthesize metal nanowires with different characteristics, electrospinning has also been found to be successful for that purpose. Even though electrospinning of polymeric nanofibers is a well-established field, there are several challenges that need to be overcome to use the electrospinning technique for the fabrication of metallic nanowires. These challenges are mainly related to the multi-steps fabrication process and its relation to the structure evolution of the nanowires. In addition to reviewing the literature, this article identifies promising avenues for further research in this area with particular emphasis on the applications that nonwoven metal wires confined in a nano-scale can open.
      PubDate: 2013-11-01T12:00:00Z
  • Role of the early stages of Ni-Si interaction on the structural properties
           of the reaction products
    • Abstract: Nickel-silicon compounds, as most of the transition metal silicides, show peculiar thermodynamic and kinetic behaviours. The reason resides in the metastability of a rich variety of different phases, which are frequently favoured by the interaction with the substrate or by the limited amount of atoms available during the reactions (thin films). The large effort devoted to the comprehension of the phenomena governing Ni-Si interaction from the very beginning of the reaction process testifies the widespread interest in the field and it is driven by the need to push as far forward as possible the scaling down of micro/nano-electronics devices. Here, we provide a review on the crucial role of the early stages of the Ni-Si atomic interaction to show how this interaction has a huge impact on the reaction process and on the structural properties of the reaction products. The formation of a Ni-Si mixed layer at the deposition stage, its structure and its role in the further evolution of the reaction couple are discussed on [001] Si and amorphous Si substrates. Controlling the mixed layer properties becomes extremely important in a regime wherein kinetics upsets thermodynamic stability, i.e., in thin films interactions, and during low temperature and/or ultra-rapid thermal processes, as required by the scaling down of the devices. In the review, it is highlighted how the opportunity to control thickness and composition of the mixed (precursor) layer opens the field to tailor new materials possessing intriguing properties, such as the case of transrotational Ni-silicides. Compared to standard poly-Ni silicides, they offer large chemical and structural stability windows as well as a promising electrical behaviour.
      PubDate: 2013-09-23T12:00:00Z
  • Efficiency droop in InGaN/GaN blue light-emitting diodes: Physical
           mechanisms and remedies
    • Abstract: Physical mechanisms causing the efficiency droop in InGaN/GaN blue light-emitting diodes and remedies proposed for droop mitigation are classified and reviewed. Droop mechanisms taken into consideration are Auger recombination, reduced active volume effects, carrier delocalization, and carrier leakage. The latter can in turn be promoted by polarization charges, inefficient hole injection, asymmetry between electron and hole densities and transport properties, lateral current crowding, quantum-well overfly by ballistic electrons, defect-related tunneling, and saturation of radiative recombination. Reviewed droop remedies include increasing the thickness or number of the quantum wells, improving the lateral current uniformity, engineering the quantum barriers (including multi-layer and graded quantum barriers), using insertion or injection layers, engineering the electron-blocking layer (EBL) (including InAlN, graded, polarization-doped, and superlattice EBL), exploiting reversed polarization (by either inverted epitaxy or N-polar growth), and growing along semi- or non-polar orientations. Numerical device simulations of a reference device are used through the paper as a proof of concept for selected mechanisms and remedies.
      PubDate: 2013-08-15T12:00:00Z
  • Applications of high throughput (combinatorial) methodologies to
           electronic, magnetic, optical, and energy-related materials
    • Abstract: High throughput (combinatorial) materials science methodology is a relatively new research paradigm that offers the promise of rapid and efficient materials screening, optimization, and discovery. The paradigm started in the pharmaceutical industry but was rapidly adopted to accelerate materials research in a wide variety of areas. High throughput experiments are characterized by synthesis of a “library” sample that contains the materials variation of interest (typically composition), and rapid and localized measurement schemes that result in massive data sets. Because the data are collected at the same time on the same “library” sample, they can be highly uniform with respect to fixed processing parameters. This article critically reviews the literature pertaining to applications of combinatorial materials science for electronic, magnetic, optical, and energy-related materials. It is expected that high throughput methodologies will facilitate commercialization of novel materials for these critically important applications. Despite the overwhelming evidence presented in this paper that high throughput studies can effectively inform commercial practice, in our perception, it remains an underutilized research and development tool. Part of this perception may be due to the inaccessibility of proprietary industrial research and development practices, but clearly the initial cost and availability of high throughput laboratory equipment plays a role. Combinatorial materials science has traditionally been focused on materials discovery, screening, and optimization to combat the extremely high cost and long development times for new materials and their introduction into commerce. Going forward, combinatorial materials science will also be driven by other needs such as materials substitution and experimental verification of materials properties predicted by modeling and simulation, which have recently received much attention with the advent of the Materials Genome Initiative. Thus, the challenge for combinatorial methodology will be the effective coupling of synthesis, characterization and theory, and the ability to rapidly manage large amounts of data in a variety of formats.
      PubDate: 2013-06-17T00:00:00Z
  • Raman spectroscopy of piezoelectrics
    • Abstract: Raman spectroscopy represents an insightful characterization tool in electronics, which comprehensively suits the technological needs for locally and quantitatively assessing crystal structures, domain textures, crystallographic misalignments, and residual stresses in piezoelectric materials and related devices. Recent improvements in data processing and instrumental screening of large sampling areas have provided Raman spectroscopic evaluations with rejuvenating effectiveness and presently give spin to increasingly wider and more sophisticated experimental explorations. However, the physics underlying the Raman effect represents an issue of deep complexity and its applicative development to non-cubic crystallographic structures can yet be considered in its infancy. This review paper revisits some applicative aspects of the physics governing Raman emission from crystalline matter, exploring the possibility of disentangling the convoluted dependences of the Raman spectrum on crystal orientation and mechanical stress. Attention is paid to the technologically important class of piezoelectric materials, for which working algorithms are explicitly worked out in order to quantitatively extract both structural and mechanical information from polarized Raman spectra. Systematic characterizations of piezoelectric materials and devices are successively presented as applications of the developed equations. The Raman response of complex crystal structures, described here according to a unified formalism, is interpreted as a means for assessing both crystallographic textures and stress-related issues in the three-dimensional space (thus preserving their vectorial and tensorial nature, respectively). Statistical descriptions of domain textures based on orientation distribution functions are also developed in order to provide a link between intrinsic single-crystal data and data collected on polycrystalline (partly textured) structures. This paper aims at providing rigorous spectroscopic foundations to Raman approaches dealing with the analyses of functional behavior and structural reliability of piezoelectric devices.
      PubDate: 2013-06-03T00:00:00Z
  • Spin injection from Heusler alloys into semiconductors: A materials
    • Abstract: The notion of using electron spins as bits for highly efficient computation coupled with non-volatile data storage has driven an intense international research effort over the past decade. Such an approach, known as spin-based electronics or spintronics, is considered to be a promising alternative to charge-based electronics in future integrated circuit technologies. Many proposed spin-based devices, such as the well-known spin-transistor, require injection of spin polarized currents from ferromagnetic layers into semiconductor channels, where the degree of injected spin polarization is crucial to the overall device performance. Several ferromagnetic Heusler alloys are predicted to be half-metallic, meaning 100% spin-polarized at the Fermi level, and hence considered to be excellent candidates for electrical spin injection. Furthermore, they exhibit high Curie temperatures and close lattice matching to III-V semiconductors. Despite their promise, Heusler alloy/semiconductor heterostructures investigated in the past decade have failed to fulfill the expectation of near perfect spin injection and in certain cases have even demonstrated inferior behavior compared to their elemental ferromagnetic counterparts. To address this problem, a slew of theoretical and experimental work has emerged studying Heusler alloy/semiconductor interface properties. Here, we review the dominant prohibitive materials challenges that have been identified, namely atomic disorder in the Heusler alloy and in-diffusion of magnetic impurities into the semiconductor, and their ensuing detrimental effects on spin injection. To mitigate these effects, we propose the incorporation of half-metallic Heusler alloys grown at high temperatures (>200 °C) along with insertion of a MgO tunnel barrier at the ferromagnet/semiconductor interface to minimize magnetic impurity in-diffusion and potentially act as a spin-filter. By considering evidence from a variety of structural, optical, and electrical studies, we hope to paint a realistic picture of the materials environment encountered by spins upon injection from Heusler alloys into semiconductors. Finally, we review several emerging device paradigms that utilize Heusler alloys as sources of spin polarized electrons.
      PubDate: 2013-05-15T00:00:00Z
  • Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine
           structure and x-ray absorption near edge structure
    • Abstract: Ultrafast time resolved x-ray absorption and x-ray diffraction have made it possible to measure, in real time, transient phenomena structures and processes induced by optical femtosecond pulses. To illustrate the power of these experimental methods, we present several representative examples from the literature. (I) Time resolved measurements of photon/electron coupling, electron/phonon interaction, pressure wave formation, melting and recrystallization by means of time resolved x-ray diffraction. (II) Ultrafast x-ray absorption, EXAFS, for the direct measurement of the structures and their kinetics, evolved during electron transfer within molecules in liquid phase. (III) XANES experiments that measure directly pathway for the population of high spin states and the study of the operating mechanism of dye activated TiO2 solar cell devices. The construction and use of novel polycapillary x-ray lenses that focus and collimate hard x-rays efficiently are described.
      PubDate: 2013-04-17T09:24:52Z
  • Constructal law of design and evolution: Physics, biology, technology, and
    • Abstract: This is a review of the theoretical and applied progress made based on the Constructal law of design and evolution in nature, with emphasis on the last decade. The Constructal law is the law of physics that accounts for the natural tendency of all flow systems (animate and inanimate) to change into configurations that offer progressively greater flow access over time. The progress made with the Constructal law covers the broadest range of science, from heat and fluid flow and geophysics, to animal design, technology evolution, and social organization (economics, government). This review presents the state of this fast growing field, and draws attention to newly opened directions for original research. The Constructal law places the concepts of life, design, and evolution in physics.
      PubDate: 2013-04-15T00:00:00Z
  • Oxidation of Al-bearing III-V materials: A review of key progress
    • Abstract: Since the discovery of III-V oxidation by Dallesasse and Holonyak in 1989, significant progress has been made both technically and commercially in the use of oxides in compound semiconductor devices. Devices ranging from lasers to transistors have been fabricated that capitalize on the process-induced modification of refractive index and conductivity, allowing control of the two carriers of information in opto-electronic systems—the photon and the electron. Of particular note has been the use of oxidation for the fabrication of high-speed vertical-cavity surface-emitting lasers, which have extensive use in optical data links found in enterprise networks, data centers, and supercomputing applications. The discovery of III-V oxidation and key technical milestones in the fabrication of photonic and electronic devices that use oxidation are reviewed.
      PubDate: 2013-02-01T00:00:00Z
  • Plasma processing of low-k dielectrics
    • Abstract: This paper presents an in-depth overview of the present status and novel developments in the field of plasma processing of low dielectric constant (low-k) materials developed for advanced interconnects in ULSI technology. The paper summarizes the major achievements accomplished during the last 10 years. It includes analysis of advanced experimental techniques that have been used, which are most appropriate for low-k patterning and resist strip, selection of chemistries, patterning strategies, masking materials, analytical techniques, and challenges appearing during the integration. Detailed discussions are devoted to the etch mechanisms of low-k materials and their degradation during the plasma processing. The problem of k-value degradation (plasma damage) is a key issue for the integration, and it is becoming more difficult and challenging as the dielectric constant of low-k materials scales down. Results obtained with new experimental methods, like the small gap technique and multi-beams systems with separated sources of ions, vacuum ultraviolet light, and radicals, are discussed in detail. The methods allowing reduction of plasma damage and restoration of dielectric properties of damaged low-k materials are also discussed.
      PubDate: 2013-01-22T00:00:00Z
  • Mechanisms of boron diffusion in silicon and germanium
    • Abstract: B migration in Si and Ge matrices raised a vast attention because of its influence on the production of confined, highly p- doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (α-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In α-Si in the 450-650 °C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 × 1020 B/cm3. B migration in α-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of α-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identified with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 °C a large Is supersaturation. These aspects of B diffusion are presented and discussed, modeling the key role of point defects in the two different matrices.
      PubDate: 2013-01-16T00:00:00Z
  • Crystallinity of inorganic films grown by atomic layer deposition:
           Overview and general trends
    • Abstract: Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.
      PubDate: 2013-01-08T00:00:00Z
  • Small particles, big impacts: A review of the diverse applications of
    • Abstract: Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.
      PubDate: 2013-01-02T00:00:00Z
  • Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown
    • Abstract: The reversal time, superparamagnetic relaxation time, of the magnetization of fine single domain ferromagnetic nanoparticles owing to thermal fluctuations plays a fundamental role in information storage, paleomagnetism, biotechnology, etc. Here a comprehensive tutorial-style review of the achievements of fifty years of development and generalizations of the seminal work of Brown [Phys. Rev. 130, 1677 (1963)] on thermal fluctuations of magnetic nanoparticles is presented. Analytical as well as numerical approaches to the estimation of the damping and temperature dependence of the reversal time based on Brown's Fokker-Planck equation for the evolution of the magnetic moment orientations on the surface of the unit sphere are critically discussed while the most promising directions for future research are emphasized.
      PubDate: 2012-12-17T00:00:00Z
  • The effects of vacuum ultraviolet radiation on low-k dielectric films
    • Abstract: Plasmas, known to emit high levels of vacuum ultraviolet (VUV) radiation, are used in the semiconductor industry for processing of low-k organosilicate glass (SiCOH) dielectric device structures. VUV irradiation induces photoconduction, photoemission, and photoinjection. These effects generate trapped charges within the dielectric film, which can degrade electrical properties of the dielectric. The amount of charge accumulation in low-k dielectrics depends on factors that affect photoconduction, photoemission, and photoinjection. Changes in the photo and intrinsic conductivities of SiCOH are also ascribed to the changes in the numbers of charged traps generated during VUV irradiation. The dielectric-substrate interface controls charge trapping by affecting photoinjection of charged carriers into the dielectric from the substrate. The number of trapped charges increases with increasing porosity of SiCOH because of charge trapping sites in the nanopores. Modifications to these three parameters, i.e., (1) VUV induced charge generation, (2) dielectric-substrate interface, and (3) porosity of dielectrics, can be used to reduce trapped-charge accumulation during processing of low-κ SiCOH dielectrics. Photons from the plasma are responsible for trapped-charge accumulation within the dielectric, while ions stick primarily to the surface of the dielectrics. In addition, as the dielectric constant was decreased by adding porosity, the defect concentrations increased.
      PubDate: 2012-12-04T00:00:00Z
  • Nanophotonic light trapping in solar cells
    • Abstract: Nanophotonic light trapping for solar cells is an exciting field that has seen exponential growth in the last few years. There has been a growing appreciation for solar energy as a major solution to the world’s energy problems, and the need to reduce materials costs by the use of thinner solar cells. At the same time, we have the newly developed ability to fabricate controlled structures on the nanoscale quickly and cheaply, and the computational power to optimize the structures and extract physical insights. In this paper, we review the theory of nanophotonic light trapping, with experimental examples given where possible. We focus particularly on periodic structures, since this is where physical understanding is most developed, and where theory and experiment can be most directly compared. We also provide a discussion on the parasitic losses and electrical effects that need to be considered when designing nanophotonic solar cells.
      PubDate: 2012-11-19T00:00:00Z
  • Smart textiles: Challenges and opportunities
    • Abstract: Smart textiles research represents a new model for generating creative and novel solutions for integrating electronics into unusual environments and will result in new discoveries that push the boundaries of science forward. A key driver for smart textiles research is the fact that both textile and electronics fabrication processes are capable of functionalizing large-area surfaces at very high speeds. In this article we review the history of smart textiles development, introducing the main trends and technological challenges faced in this field. Then, we identify key challenges that are the focus of ongoing research. We then proceed to discuss fundamentals of smart textiles: textile fabrication methods and textile interconnect lines, textile sensor, and output device components and integration of commercial components into textile architectures. Next we discuss representative smart textile systems and finally provide our outlook over the field and a prediction for the future.
      PubDate: 2012-11-07T00:00:00Z
  • Ferrite film growth on semiconductor substrates towards microwave and
           millimeter wave integrated circuits
    • Abstract: It is widely recognized that as electronic systems’ operating frequency shifts to microwave and millimeter wave bands, the integration of ferrite passive devices with semiconductor solid state active devices holds significant advantages in improved miniaturization, bandwidth, speed, power and production costs, among others. Traditionally, ferrites have been employed in discrete bulk form, despite attempts to integrate ferrite as films within microwave integrated circuits. Technical barriers remain centric to the incompatibility between ferrite and semiconductor materials and their processing protocols. In this review, we present past and present efforts at ferrite integration with semiconductor platforms with the aim to identify the most promising paths to realizing the complete integration of on-chip ferrite and semiconductor devices, assemblies and systems.
      PubDate: 2012-10-16T00:00:00Z
  • Multi-functional dielectric elastomer artificial muscles for soft and
           smart machines
    • Abstract: Dielectric elastomer (DE) actuators are popularly referred to as artificial muscles because their impressive actuation strain and speed, low density, compliant nature, and silent operation capture many of the desirable physical properties of muscle. Unlike conventional robots and machines, whose mechanisms and drive systems rapidly become very complex as the number of degrees of freedom increases, groups of DE artificial muscles have the potential to generate rich motions combining many translational and rotational degrees of freedom. These artificial muscle systems can mimic the agonist-antagonist approach found in nature, so that active expansion of one artificial muscle is taken up by passive contraction in the other. They can also vary their stiffness. In addition, they have the ability to produce electricity from movement. But departing from the high stiffness paradigm of electromagnetic motors and gearboxes leads to new control challenges, and for soft machines to be truly dexterous like their biological analogues, they need precise control. Humans control their limbs using sensory feedback from strain sensitive cells embedded in muscle. In DE actuators, deformation is inextricably linked to changes in electrical parameters that include capacitance and resistance, so the state of strain can be inferred by sensing these changes, enabling the closed loop control that is critical for a soft machine. But the increased information processing required for a soft machine can impose a substantial burden on a central controller. The natural solution is to distribute control within the mechanism itself. The octopus arm is an example of a soft actuator with a virtually infinite number of degrees of freedom (DOF). The arm utilizes neural ganglia to process sensory data at the local “arm” level and perform complex tasks. Recent advances in soft electronics such as the piezoresistive dielectric elastomer switch (DES) have the potential to be fully integrated with actuators and sensors. With the DE switch, we can produce logic gates, oscillators, and a memory element, the building blocks for a soft computer, thus bringing us closer to emulating smart living structures like the octopus arm. The goal of future research is to develop fully soft machines that exploit smart actuation networks to gain capabilities formerly reserved to nature, and open new vistas in mechanical engineering.
      PubDate: 2012-08-28T00:00:00Z
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