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Journal ArticleDOI

Dynamic nanofin heat sinks

TL;DR: In this article, a magnetophoretically formed high aspect ratio nano-nodes are used for hot-spot cooling in microfluidic environments, which can be dynamically chained and docked onto the hot spots to establish tuneable high-aspect ratio nanofins for the heat exchange between these hot spots and the liquid coolant.
Abstract: The limitation of hot spot cooling in microchips represents an important hurdle for the electronics industry to overcome with coolers yet to exceed the efficiencies required. Nanotechnology-enabled heat sinks that can be magnetophoretically formed onto the hot spots within a microfluidic environment are presented. CrO2 nanoparticles, which are dynamically chained and docked onto the hot spots, establish tuneable high-aspect-ratio nanofins for the heat exchange between these hot spots and the liquid coolant. These nanofins can also be grown and released on demand, absorbing and releasing the heat from the hot spots into the microfluidic system. It is shown that both high aspect ratio and flexibility of the fins have a dramatic effect on increasing the heat sinking efficiency. The system has the potential to offer a practical cooling solution for future electronics.
Citations
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Journal ArticleDOI
01 Aug 2016-Carbon
TL;DR: An in-depth historical and current review is presented on the science of lithium-ion battery (LIB) solid electrolyte interphase (SEI) formation on the graphite anode, including structure, morphology, composition, electrochemistry, and formation mechanism.

1,217 citations

Journal ArticleDOI
TL;DR: The essential Raman scattering processes of the entire first- and second-order modes in intrinsic graphene are described and the extensive capabilities of Raman spectroscopy for the investigation of the fundamental properties of graphene under external perturbations are described.
Abstract: Graphene-based materials exhibit remarkable electronic, optical, and mechanical properties, which has resulted in both high scientific interest and huge potential for a variety of applications. Furthermore, the family of graphene-based materials is growing because of developments in preparation methods. Raman spectroscopy is a versatile tool to identify and characterize the chemical and physical properties of these materials, both at the laboratory and mass-production scale. This technique is so important that most of the papers published concerning these materials contain at least one Raman spectrum. Thus, here, we systematically review the developments in Raman spectroscopy of graphene-based materials from both fundamental research and practical (i.e., device applications) perspectives. We describe the essential Raman scattering processes of the entire first- and second-order modes in intrinsic graphene. Furthermore, the shear, layer-breathing, G and 2D modes of multilayer graphene with different stacking orders are discussed. Techniques to determine the number of graphene layers, to probe resonance Raman spectra of monolayer and multilayer graphenes and to obtain Raman images of graphene-based materials are also presented. The extensive capabilities of Raman spectroscopy for the investigation of the fundamental properties of graphene under external perturbations are described, which have also been extended to other graphene-based materials, such as graphene quantum dots, carbon dots, graphene oxide, nanoribbons, chemical vapor deposition-grown and SiC epitaxially grown graphene flakes, composites, and graphene-based van der Waals heterostructures. These fundamental properties have been used to probe the states, effects, and mechanisms of graphene materials present in the related heterostructures and devices. We hope that this review will be beneficial in all the aspects of graphene investigations, from basic research to material synthesis and device applications.

1,184 citations

Journal ArticleDOI
TL;DR: In this article, the recent developments and the characteristics of membrane separators for rechargeable lithium-ion batteries are reviewed and the outlook and future directions in this research field are also given.
Abstract: In this paper, the recent developments and the characteristics of membrane separators for lithium-ion batteries are reviewed. In recent years, there have been intensive efforts to develop advanced battery separators for rechargeable lithium-ion batteries for different applications such as portable electronics, electric vehicles, and energy storage for power grids. The separator is a critical component of lithium-ion batteries since it provides a physical barrier between the positive and negative electrodes in order to prevent electrical short circuits. The separator also serves as the electrolyte reservoir for the transport of ions during the charging and discharging cycles of a battery. The performance of lithium-ion batteries is greatly affected by the materials and structure of the separators. This paper introduces the requirements of battery separators and the structure and properties of five important types of membrane separators which are microporous membranes, modified microporous membranes, non-woven mats, composite membranes and electrolyte membranes. Each separator type has inherent advantages and disadvantages which influence the performance of lithium-ion batteries. The structures, characteristics, manufacturing, modification, and performance of separators are described in this review paper. The outlook and future directions in this research field are also given.

1,077 citations

Journal ArticleDOI
TL;DR: In this article, recent developments in understanding and overcoming stability concerns of metal halide perovskite solar cells are highlighted and an overview of possible instability issues due to electrical, atmospheric, heat, and light stresses is provided and the different implications to the most commonly used device architectures are discussed.
Abstract: In recent years, there has been an unprecedented rise in the performance of metal halide perovskite solar cells. They are now in a position to compete on performance with traditional crystalline solar cells, and as such the most pressing questions concern the long term operational stability of this class of solar cell. Here, recent developments in understanding and overcoming stability concerns of metal halide perovskite solar cells are highlighted. An overview of possible instability issues due to electrical, atmospheric, heat, and light stresses is provided and the different implications to the most commonly used device architectures are discussed.

1,006 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the effects of variations in the temperature and volume fraction on the steady-state effective thermal conductivity of two different nanoparticle suspensions were examined and the results indicated that the nanoparticle material, diameter, volume fraction, and bulk temperature, all have a significant impact on the effective thermalconductivity of these suspensions.
Abstract: An experimental investigation was conducted to examine the effects of variations in the temperature and volume fraction on the steady-state effective thermal conductivity of two different nanoparticle suspensions. Copper and aluminum oxide, CuO and Al2O3, nanoparticles with area weighted diameters of 29 and 36nm, respectively, were blended with distilled water at 2%, 4%, 6%, and 10% volume fractions and the resulting suspensions were evaluated at temperatures ranging from 27.5to34.7°C. The results indicate that the nanoparticle material, diameter, volume fraction, and bulk temperature, all have a significant impact on the effective thermal conductivity of these suspensions. The 6% volume fraction of CuO nanoparticle/distilled water suspension resulted in an increase in the effective thermal conductivity of 1.52 times that of pure distilled water and the 10% Al2O3 nanoparticle/distilled water suspension increased the effective thermal conductivity by a factor of 1.3, at a temperature of 34°C. A two-factor ...

749 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental single stage heat transformer (SSHT) with water/carrol mixture was analyzed. But the performance of the SSHT was not evaluated. But four test runs were carried out in order to evaluate the performance and the heat powers were measured from 0.99 to 1.35.

721 citations

Journal ArticleDOI
TL;DR: Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995 as mentioned in this paper, and there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10).
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.

679 citations

Journal ArticleDOI
TL;DR: This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.
Abstract: There is a significant need for site-specific and on-demand cooling in electronic, optoelectronic and bioanalytical devices, where cooling is currently achieved by the use of bulky and/or over-designed system-level solutions. Thermoelectric devices can address these limitations while also enabling energy-efficient solutions, and significant progress has been made in the development of nanostructured thermoelectric materials with enhanced figures-of-merit. However, fully functional practical thermoelectric coolers have not been made from these nanomaterials due to the enormous difficulties in integrating nanoscale materials into microscale devices and packaged macroscale systems. Here, we show the integration of thermoelectric coolers fabricated from nanostructured Bi2Te3-based thin-film superlattices into state-of-the-art electronic packages. We report cooling of as much as 15 degrees C at the targeted region on a silicon chip with a high ( approximately 1,300 W cm-2) heat flux. This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.

678 citations

Journal ArticleDOI
TL;DR: In this paper, experimental investigations and theoretical determination of effective thermal conductivity and viscosity of Al 2 O 3 /H 2 O nanofluid are reported and it is found that the viscoverage increase is substantially higher than the increase in thermal conductivities.

672 citations