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Bulk heating

Amirul Edham Roslee, Saifful Kamaluddin Muzakir, Jamil Ismail, Mashitah M Yusoff, Rajan Jose
This article addresses the heat capacity of quantum dots (QDs) using density functional theory (DFT). By analyzing the evolution of phonon density of states and heat capacity as CdSe clusters grow from a molecular cluster into larger quantum confined solids, we have shown that their heat capacity does not fit very well with the Debye T(3) model. We observed that the number of phonon modes, which is discrete, increases as the particles grow, and the dispersion relation shows a quadratic behavior in contrast to the bulk solids whose dispersion relation is linear and equal to the sound velocity...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
Olof Bäcke, Camilla Lindqvist, Amaia Diaz de Zerio Mendaza, Stefan Gustafsson, Ergang Wang, Mats R Andersson, Christian Müller, Per Magnus Kristiansen, Eva Olsson
We show by in situ microscopy that the effects of electron beam irradiation during transmission electron microscopy can be used to lock microstructural features and enhance the structural thermal stability of a nanostructured polymer:fullerene blend. Polymer:fullerene bulk-heterojunction thin films show great promise for use as active layers in organic solar cells but their low thermal stability is a hindrance. Lack of thermal stability complicates manufacturing and influences the lifetime of devices. To investigate how electron irradiation affects the thermal stability of polymer:fullerene films, a model bulk-heterojunction film based on a thiophene-quinoxaline copolymer and a fullerene derivative was heat-treated in-situ in a transmission electron microscope...
November 21, 2016: Ultramicroscopy
Philip Holthaus, Moritz Kappes, Wolfgang Krumm
Stricter regulatory requirements concerning end-of-life vehicles and rising disposal costs necessitate new ways for automobile shredder residue utilisation. The shredder granulate and fibres, produced by the VW-SICON-Process, have a high energy content of more than 20 MJ kg(-1), which makes energy recovery an interesting possibility. Shredder fibres have a low bulk density of 60 kg m(-3), which prevents efficient storing and utilisation as a refuse-derived fuel. By mixing fibres with plastic-rich shredder granulate and heating the mixture, defined granules can be produced...
November 23, 2016: Waste Management & Research
Omar Torres-Mendieta, Rosa Mondragron, Verónica Puerto-Belda, Omel Mendoza-Yero, Jesús Lancis, J Enrique Bolivar, Gladys Mínguez-Vega
Solar energy is extended over wide geographical areas and is becoming an essential tool to keep the ever-increasing demand of energy with minimal environmental impact. A solar nanofluid is a novel solar receiver concept for efficient harvesting of solar radiation based on volumetric absorption of directly irradiated nanoparticles in a heat transfer fluid. Herein, the fabrication of a solar nanofluid by pulsed laser ablation in liquids was explored. This study was conducted with the ablation of bulk tin immersed in ethylene glycol with a femtosecond laser...
November 22, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Xiuqiang Li, Weichao Xu, Mingyao Tang, Lin Zhou, Bin Zhu, Shining Zhu, Jia Zhu
Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications...
November 21, 2016: Proceedings of the National Academy of Sciences of the United States of America
Binita Pathak, Priti Xavier, Suryasarathi Bose, Saptarshi Basu
We report thermally induced rapid phase separation in PS/PVME polymer blends using a unique contact free droplet based architecture. De-mixing of homogeneous blends due to inter component dynamic asymmetry is aggravated by the externally supplied heat. Separation of polymer blends is usually investigated in the bulk which is a tedious process and requires several hours for completion. Alternatively, separation in droplet configuration reduces the process timescale by about 3-5 orders due to a constrained micron-sized domain [fast processing and high throughput] while maintaining similar separation morphologies as in the bulk...
November 30, 2016: Physical Chemistry Chemical Physics: PCCP
Trevor P Almeida, Adrian R Muxworthy, András Kovács, Wyn Williams, Leslei Nagy, Pádraig Ó Conbhuí, Cathrine Frandsen, Radchagrit Supakulopas, Rafal E Dunin-Borkowski
The thermal demagnetization of pseudo-single-domain (PSD) magnetite (Fe3O4) particles, which govern the magnetic signal in many igneous rocks, is examined using off-axis electron holography. Visualization of a vortex structure held by an individual Fe3O4 particle (~250 nm in diameter) during in situ heating is achieved through the construction and examination of magnetic-induction maps. Stepwise demagnetization of the remanence-induced Fe3O4 particle upon heating to above the Curie temperature, performed in a similar fashion to bulk thermal demagnetization measurements, revealed that its vortex state remains stable under heating close to its unblocking temperature and is recovered upon cooling with the same or reversed vorticity...
August 28, 2016: Geophysical Research Letters
Maximilian Schelden, William Lima, Eric Will Doerr, Martin Wunderlich, Lars Rehmann, Jochen Büchs, Lars Regestein
One of the most critical parameters in chemical and biochemical processes is the viscosity of the medium. Its impact on mixing, as well as on mass and energy transfer is substantial. An increase of viscosity with reaction time can be caused by the formation of biopolymers like xanthan or by filamentous growth of microorganisms. In either case the properties of fermentation broth are changing and frequently non-Newtonian behavior are observed, resulting in major challenges for the measurement and control of mixing and mass transfer...
November 14, 2016: Biotechnology and Bioengineering
Yean-Sheng Yong, Shanmugam Aravazhi, Sergio A Vázquez-Córdova, Joan J Carjaval, Francesc Díaz, Jennifer L Herek, Sonia M García-Blanco, Markus Pollnau
We study the spectroscopic properties of thin films of potassium ytterbium gadolinium double tungstates, KYb<sub>0.57</sub>Gd<sub>0.43</sub>(WO<sub>4</sub>)<sub>2</sub>, and potassium ytterbium lutetium double tungstates, KYb<sub>0.76</sub>Lu<sub>0.24</sub>(WO<sub>4</sub>)<sub>2</sub>, specifically at the central absorption line near 981 nm wavelength, which is important for amplifiers and lasers. The absorption cross-section of both thin films is found to be similar to those of bulk potassium rare-earth double tungstates, suggesting that the crystalline layers retain their spectroscopic properties albeit having >50 at...
November 14, 2016: Optics Express
Saikat Mukhopadhyay, Lucas Lindsay, David J Singh
The lattice thermal conductivity (κ) of hexagonal Ge2Sb2Te5 (h-GST) is studied via direct first-principles calculations. We find significant intrinsic anisotropy (κa/κc~2) of κ in bulk h-GST, with the dominant contribution to κ from optic phonons, ~75%. This is extremely unusual as the acoustic phonon modes are the majority heat carriers in typical semiconductors and insulators. The anisotropy derives from varying bonding along different crystal directions, specifically from weak interlayer bonding along the c-axis, which gives anisotropic phonon dispersions...
November 16, 2016: Scientific Reports
Sung Hoon Park, Seungki Jo, Beomjin Kwon, Fredrick Kim, Hyeong Woo Ban, Ji Eun Lee, Da Hwi Gu, Se Hwa Lee, Younghun Hwang, Jin-Sang Kim, Dow-Bin Hyun, Sukbin Lee, Kyoung Jin Choi, Wook Jo, Jae Sung Son
Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape...
November 11, 2016: Nature Communications
David Hwang, Benjamin P Yonkee, Burhan Saif Addin, Robert M Farrell, Shuji Nakamura, James S Speck, Steven DenBaars
We demonstrate a thin-film flip-chip (TFFC) process for LEDs grown on freestanding c-plane GaN substrates. LEDs are transferred from a bulk GaN substrate to a sapphire submount via a photoelectrochemical (PEC) undercut etch. This PEC liftoff method allows for substrate reuse and exposes the N-face of the LEDs for additional roughening. The LEDs emitted at a wavelength of 432 nm with a turn on voltage of ~3 V. Etching the LEDs in heated KOH after transferring them to a sapphire submount increased the peak external quantum efficiency (EQE) by 42...
October 3, 2016: Optics Express
Xinping Zhang, Haibin Wang, Meng Wang, Yuanhai Lin, Xiaoyan Song
Ultrafast optical excitation induced transient modification on the energy-band structures in tungsten, which resulted in the expansion and shift toward the Fermi-level of d-band. This process led to enhanced interband transitions at reduced photon energies. Meanwhile, enhanced interband excitation led to increased electron density above the Fermi level, resulting in enhanced optical scattering by localized surface plasmon resonance (LSPR). These mechanisms are responsible for balancing the direct heating of bulk electrons by optical pulses...
October 3, 2016: Optics Express
Jing Qian, Chengwei Wang, Yuanyuan Huang, Hongjing Li, Kongyu Lou, Guande Wang, Quan-Zhong Zhao
The nanoscale measurement of temperature in the bulk of dielectrics initiated by a single ultrashort laser pulse was first investigated by black-body radiation. A structureless broad continuum emission has been recorded at an interval delay of 2 ns with a temporal gate of 2 ns and spectral resolution of about 0.137 nm, which provides the highest temporal and spectral precision ever. The temporally resolved emission spectrum was proved to be black-body radiation in nature, and temperature was obtained by fitting the radiation with the Planckian formula...
October 10, 2016: Applied Optics
Malgorzata Jasiurkowska-Delaporte, Simone Napolitano, Jan Leys, Ewa Juszyńska-Gałązka, Michael Wübbenhorst, Maria Massalska-Arodź
The molecular dynamics of butyloxybenzylidine octylaniline (BBOA, abbreviated also as 4O.8) was studied by broadband dielectric spectroscopy (BDS) for samples that were exposed to various thermal treatments. Phase transitions between liquid crystalline phases (N, SmA, SmBhex and SmBCr) were evidenced by abrupt changes in the temperature dependence of the dielectric permittivity spectra and dielectric relaxation times. A particularly complex dynamic behaviour was revealed for the highly ordered SmBCr phase that showed clear evidence for cooperative dynamics of a glass forming liquid as manifested by a Vogel-Fulcher-Tammann (VFT) type temperature dependence of its structural relaxation time τ(T)...
November 3, 2016: Journal of Physical Chemistry. B
G M Revel, A Cavuto, G Pandarese
In this paper a Laser Ultrasonics (LUT) system is developed and applied to measure bulk density distribution of green ceramic tiles, which are porous materials with low heat conductivity. Bulk density of green ceramic bodies is a fundamental parameter to be kept under control in the industrial production of ceramic tiles. The LUT system proposed is based on a Nd:YAG pulsed laser for excitation and an air-coupled electro-capacitive transducer for detection. The paper reports experimental apparent bulk-density measurements on white ceramic bodies after a calibration procedures...
October 2016: Review of Scientific Instruments
Guilian Zhu, Jijian Xu, Wenli Zhao, Fuqiang Huang
Solar desalination driven by solar radiation as heat source is freely available, however, hindered by the low efficiency. Herein, we first design and synthesis the black titania with unique nanocage structure simultaniously with light trapping effect to enhance light harvesting, well-crystallized interconnected nanograins to accelerate the heat transfer from titania to water, and opening mesopores (4-10 nm) to facilitate the permeation of water vapour. Furthermore, the coated self-floating black titania nanocages film localizes the temperature increase at the water-air interface rather than uniformly heating the bulk of the water, which ultimately results in a solar thermal conversion efficiency as high as 70...
November 1, 2016: ACS Applied Materials & Interfaces
M Valix, S Katyal, W H Cheung
This study compared the upgrading of sugar bagasse by thermochemical and dry torrefaction methods and their corresponding combustion behavior relative to raw bagasse. The combustion reactivities were examined by non-isothermal thermogravimetric analysis. Thermochemical torrefaction was carried out by chemical pre-treatment of bagasse with acid followed by heating at 160-300°C in nitrogen environment, while dry torrefaction followed the same heating treatment without the chemical pretreatment. The results showed thermochemical torrefaction generated chars with combustion properties that are closer to various ranks of coal, thus making it more suitable for co-firing applications...
October 21, 2016: Bioresource Technology
Rakesh K Yadav, Thomas Gastine, Ulrich R Christensen, Scott J Wolk, Katja Poppenhaeger
Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints...
October 25, 2016: Proceedings of the National Academy of Sciences of the United States of America
Yipei Chen, Jiabin Luan, Wenjia Shen, Kewen Lei, Lin Yu, Jiandong Ding
Diabetes, a global epidemic, has become a serious threat to public health. The present study is aimed at constructing an injectable thermosensitive PEG/polyester hydrogel formulation of liraglutide (Lira), a "smart" anti-diabetic polypeptide, in long-acting treatment of type 2 diabetes mellitus. Three thermosensitive poly(ε-caprolactone-co-glycolic acid)-poly(ethylene glycol)-poly(ε-caprolactone-co-glycolic acid) (PCGA-PEG-PCGA) triblock copolymers with similar molecular weights but different ε-caprolactone/glycolide (CL/GA) ratios were synthesized...
October 27, 2016: ACS Applied Materials & Interfaces
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