Applied Sciences

7210 KiB

Open AccessReview

Graphene Thermal Properties: Applications in Thermal Management and Energy Storage

by Jackie D. Renteria, Denis L. Nika and Alexander A. Balandin

Appl. Sci. 2014, 4(4), 525-547; https://doi.org/10.3390/app4040525 - 28 Nov 2014

Cited by 281 | Viewed by 27652

We review the thermal properties of graphene, few-layer graphene and graphene nanoribbons, and discuss practical applications of graphene in thermal management and energy storage. The first part of the review describes the state-of-the-art in the graphene thermal field focusing on recently reported experimental and theoretical data for heat conduction in graphene and graphene nanoribbons. The effects of the sample size, shape, quality, strain distribution, isotope composition, and point-defect concentration are included in the summary. The second part of the review outlines thermal properties of graphene-enhanced phase change materials used in energy storage. It is shown that the use of liquid-phase-exfoliated graphene as filler material in phase change materials is promising for thermal management of high-power-density battery parks. The reported experimental and modeling results indicate that graphene has the potential to outperform metal nanoparticles, carbon nanotubes, and other carbon allotropes as filler in thermal management materials. Full article

(This article belongs to the Special Issue Towards Applications of Graphene)

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1926 KiB

Open AccessArticle

Broadband Continuous-Wave Multi-Harmonic Optical Comb Based on a Frequency Division-by-Three Optical Parametric Oscillator

by Yen-Yin Lin, Po-Shu Wu, Hsiu-Ru Yang, Jow-Tsong Shy and A. H. Kung

Appl. Sci. 2014, 4(4), 515-524; https://doi.org/10.3390/app4040515 - 26 Nov 2014

Cited by 2 | Viewed by 8016

Abstract

We report a multi-watt broadband continuous-wave multi-harmonic optical comb based on a frequency division-by-three singly-resonant optical parametric oscillator. This cw optical comb is frequency-stabilized with the help of a beat signal derived from the signal and frequency-doubled idler waves. The measured frequency fluctuation in one standard deviation is ~437 kHz. This is comparable to the linewidth of the pump laser which is a master-oscillator seeded Yb:doped fiber amplifier at ~1064 nm. The measured powers of the fundamental wave and the harmonic waves up to the 6th harmonic wave are 1.64 W, 0.77 W, 3.9 W, 0.78 W, 0.17 W, and 0.11 W, respectively. The total spectral width covered by this multi-harmonic comb is ~470 THz. When properly phased, this multi-harmonic optical comb can be expected to produce by Fourier synthesis a light source consisting of periodic optical field waveforms that have an envelope full-width at half-maximum of 1.59 fs in each period. Full article

(This article belongs to the Special Issue Multi-Color Laser Emission for the Generation of Ultrashort Optical Pulse)

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2660 KiB

Open AccessArticle

Continuous-Wave Molecular Modulation Using a High-Finesse Cavity

by David C. Gold, Joshua J. Weber and Deniz D. Yavuz

Appl. Sci. 2014, 4(4), 498-514; https://doi.org/10.3390/app4040498 - 18 Nov 2014

Cited by 6 | Viewed by 6193

Abstract

We demonstrate an optical modulator at a frequency of 90 THz that has the capability to modulate any laser beam in the optical region of the spectrum. The modulator is constructed by placing deuterium molecules inside a high-finesse cavity and driving a vibrational transition with two continuous-wave laser beams. The two beams, the pump and the Stokes, are resonant with the cavity. The high intra-cavity intensities that build up drive the molecules to a coherent state. This molecular coherence can then be used to modulate an independent laser beam, to produce frequency up-shifted and down-shifted sidebands. The beam to be modulated is not resonant with the cavity and thus the sidebands are produced in a single pass. Full article

(This article belongs to the Special Issue Multi-Color Laser Emission for the Generation of Ultrashort Optical Pulse)

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416 KiB

Open AccessEditorial

Greener and Sustainable Chemistry

by Rajender S. Varma

Appl. Sci. 2014, 4(4), 493-497; https://doi.org/10.3390/app4040493 - 29 Sep 2014

Cited by 28 | Viewed by 6304

Abstract

In the pursuit towards attaining sustainability, arrays of greener pathways are being carved to address the needs of the diverse chemical universe. The evolving area of green and sustainable chemistry envisions minimum hazard as the performance criterion while designing new chemical processes. Green Chemistry is defined as "the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture, and application of chemical products" [1]. Sustainable processes are being sought to explore alternatives to conventional chemical syntheses and transformations. Among several thrust areas for achieving this target includes: the utility of alternative feedstocks, preferably from renewable materials or waste from other industries; unconventional efficient reaction conditions and eco-friendly reaction media to accomplish the desired chemical transformations with minimized by-products or waste generation, and ideally avoiding the use of conventional volatile organic solvents, wherever possible. Other avenues for achieving this objective are to explore the generation of efficient catalytic processes, particularly magnetically retrievable nano-catalysts [1,2,3,4]. In addition to greener synthesis, the recyclability and reuse aspects for catalytic systems are extremely significant particularly when it boils down to the use of endangered elements and precious catalysts. Several friendlier applications in catalysis have been advanced via magnetically recoverable and recyclable nano-catalysts for oxidation, reduction, and multi-component condensation reactions [1,2,3,4] and this has made a terrific impact on the development of green chemical pathways [1]. The greener preparation of nanoparticles has been exemplified via the use of vitamins B1, B2, C, and tea [5] and wine polyphenols [6], beet juice [7] and other agricultural residues which function both as reducing and capping agents. This avoids the need to deploy toxic reducing agents, such as borohydrides or hydrazines and empowers simple and aqueous green synthetic methods to produce bulk quantities of nano-catalysts without the requirement for large amounts of insoluble templates [8]. [...] Full article

(This article belongs to the Special Issue Greener and Sustainable Chemistry)

489 KiB

Open AccessArticle

Derivation of Oscillators from Biquadratic Band Pass Filters Using Circuit Transformations

by Hung-Yu Wang, Huu-Duy Tran, Quoc-Minh Nguyen, Li-Te Yin and Chih-Yi Liu

Appl. Sci. 2014, 4(4), 482-492; https://doi.org/10.3390/app4040482 - 29 Sep 2014

Cited by 9 | Viewed by 7052

Abstract

Network transformations are the techniques to obtain new functional schemes from available circuits. They are systematic methodologies, since each transformation technique can be applied to many circuits to obtain the desired functions or characteristics. A convenient network transformation method, exploiting different circuit transformations, for deriving linear sinusoidal oscillators from biquadratic band pass filters is proposed. This method with generality can be applied to any band pass filter. The oscillation frequency of the new obtained oscillator is identical to the center frequency of the original band pass filter, and the useful properties of the selected band pass filter can be retained. Two examples are illustrated to confirm the feasibility of the proposed approach. The workability of the obtained oscillators is verified with PSPICE simulations. Full article

(This article belongs to the Special Issue Feature Papers)

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Appl. Sci., Volume 4, Issue 4 (December 2014) – 5 articles , Pages 482-547

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