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Junxi Duan, Xiaoming Wang, Xinyuan Lai, Guohong Li, Kenji Watanabe, Takashi Taniguchi, Mona Zebarjadi, Eva Y Andrei
Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. Although passive cooling in graphene-based devices is quite effective due to graphene's extraordinary heat conduction, active cooling has not been considered feasible due to graphene's low thermoelectric power factor. Here, we show that the thermoelectric performance of graphene can be significantly improved by using hexagonal boron nitride (hBN) substrates instead of SiO2 We find the room temperature efficiency of active cooling in the device, as gauged by the power factor times temperature, reaches values as high as 10...
November 23, 2016: Proceedings of the National Academy of Sciences of the United States of America
William G Tobias, Jason S Rosenberg, Nicholas R Hutzler, Kang-Kuen Ni
We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to the spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64 °C, more than 85 °C below the ambient temperature...
November 2016: Review of Scientific Instruments
C Stoeckl, W Theobald, S P Regan, M H Romanofsky
A four-channel, time-resolved, hard x-ray detector (HXRD) has been operating at the Laboratory for Laser Energetics for more than a decade. The slope temperature of the hot-electron population in direct-drive inertial confinement fusion experiments is inferred by recording the hard x-ray radiation generated in the interaction of the electrons with the target. Measuring the energy deposited by hot electrons requires an absolute calibration of the hard x-ray detector. A novel method to obtain an absolute calibration of the HXRD using single photons from radioactive sources was developed, which uses a thermoelectrically cooled, low-noise, charge-sensitive amplifier...
November 2016: Review of Scientific Instruments
Y Li, C Cheng, Y Lei, M Wang, R D Wan
The antimony-doped half-Heusler thermoelectric bulk TiNiSb0.05Sn0.95 was prepared via ultra-fast 4.5 min microwave synthesis, cold-press forming and 20 min microwave pressureless sintering. The electrical properties i.e. the Seebeck coefficient (S), electrical resistivity (ρ), and carrier concentration (n) and mobility (μ) were measured on a Seebeck coefficient/resistance analysis system (S/RAs) and Hall effect measurement system (HEMS), respectively. The thermal conductivity (κ) was measured on a laser flash thermal analyzer (LFA)...
November 30, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Xinxin Yan, Wenwen Zheng, Fengming Liu, Shuhua Yang, Ziyu Wang
Nanostructures have the potential to exhibit good thermoelectric properties by tuning and controlling their size and thickness, and the competing electrical and thermal properties can be decoupled by engineering the interface and grain boundary. In the present study, Sb2Te3 nanoplatelets with different sizes were fabricated using a practical solvothermal method. The thickness of the platelets were regulated between sizes of 10 nm and 100 nm, and the opposite edge length was varied between 1 and 10 μm by altering chemical conditions...
November 29, 2016: Scientific Reports
Younghoon Shin, Minsu Yoo, Hyung-Sun Kim, Sung-Ki Nam, Hyoung-Ihl Kim, Sun-Kyu Lee, Sohee Kim, Hyuk-Sang Kwon
Understanding light intensity and temperature increase is of considerable importance in designing or performing in vivo optogenetic experiments. Our study describes the optimal light power at target depth in the rodent brain that would maximize activation of light-gated ion channels while minimizing temperature increase. Monte Carlo (MC) simulations of light delivery were used to provide a guideline for suitable light power at a target depth. In addition, MC simulations with the Pennes bio-heat model using data obtained from measurements with a temperature-measuring cannula having 12...
November 1, 2016: Biomedical Optics Express
Ramesh Ghosh, P K Giri
Semiconductor nanowires (NWs), in particular Si NWs, have attracted much attention in the last decade for their unique electronic properties and potential applications in several emerging areas. With the introduction of heterostructures (HSs) on NWs, new functionalities are obtained and the device performance is improved significantly in many cases. Due to the easy fabrication techniques, excellent optoelectronic properties and compatibility of forming HSs with different inorganic/organic materials, Si NW HSs have been utilized in various configurations and device architectures...
January 6, 2017: Nanotechnology
Gaël Bastien, Adrien Gourgout, Dai Aoki, Alexandre Pourret, Ilya Sheikin, Gabriel Seyfarth, Jacques Flouquet, Georg Knebel
We present high field magnetoresistance, Hall effect and thermopower measurements in the Ising-type ferromagnetic superconductor UCoGe. A magnetic field is applied along the easy magnetization c axis of the orthorhombic crystal. In the different experimental probes, we observed five successive anomalies at H≈4, 9, 12, 16, and 21 T. Magnetic quantum oscillations were detected both in resistivity and thermoelectric power. At most of the anomalies, significant changes of the oscillation frequencies and the effective masses have been observed, indicating successive Fermi surface instabilities induced by the strong magnetic polarization under a magnetic field...
November 11, 2016: Physical Review Letters
Xi Li, Zhenyuan Lu, Yves Fautrelle, Annie Gagnoud, Rene Moreau, Zhongming Ren
Effect of a weak transverse magnetic field on the microstructures in directionally solidified Fe-Ni and Pb-Bi peritectic alloys has been investigated experimentally. The results indicate that the magnetic field can induce the formation of banded and island-like structures and refine the primary phase in peritectic alloys. The above results are enhanced with increasing magnetic field. Furthermore, electron probe micro analyzer (EPMA) analysis reveals that the magnetic field increases the Ni solute content on one side and enhances the solid solubility in the primary phase in the Fe-Ni alloy...
November 25, 2016: Scientific Reports
Kevin F Garrity
Oxides have many potentially desirable characteristics for thermoelectric applications, including low cost and stability at high temperatures, but thus far there are few known high zT n-type oxide thermoelectrics. In this work, we use high-throughput first principles calculations to screen transition metal oxides, nitrides, and sulfides for candidate materials with high power factors and low thermal conductivity. We find a variety of promising materials, and we investigate these materials in detail in order to understand the mechanisms that cause them to have high power factors...
July 15, 2016: Physical Review. B
K Zberecki, M Wierzbicki, R Swirkowicz, J Barnaś
We analyze magnetic, transport and thermoelectric properties of narrow carbon polymers, which are chemically functionalized with nitroxide groups. Numerical calculations of the electronic band structure and the corresponding transmission function are based on density functional theory. Transport and thermoelectric parameters are calculated in the linear response regime, with particular interest in charge and spin thermopowers (charge and spin Seebeck effects). Such nanoribbons are shown to have thermoelectric properties described by large thermoelectric efficiency, which makes these materials promising from the application point of view...
February 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Tory M Schaaf, Kurt C Peterson, Benjamin D Grant, David D Thomas, Gregory D Gillispie
We have developed a microplate reader that records a complete high-quality fluorescence emission spectrum on a well-by-well basis under true high-throughput screening (HTS) conditions. The read time for an entire 384-well plate is less than 3 min. This instrument is particularly well suited for assays based on fluorescence resonance energy transfer (FRET). Intramolecular protein biosensors with genetically encoded green fluorescent protein (GFP) donor and red fluorescent protein (RFP) acceptor tags at positions sensitive to structural changes were stably expressed and studied in living HEK cells...
November 22, 2016: Journal of Biomolecular Screening
Rami T ElAfandy, Ayman F AbuElela, Pawan Mishra, Bilal Janjua, Hassan M Oubei, Ulrich Büttner, Mohammed A Majid, Tien Khee Ng, Jasmeen S Merzaban, Boon S Ooi
Knowledge of materials' thermal-transport properties, conductivity and diffusivity, is crucial for several applications within areas of biology, material science and engineering. Specifically, a microsized, flexible, biologically integrated thermal transport sensor is beneficial to a plethora of applications, ranging across plants physiological ecology and thermal imaging and treatment of cancerous cells, to thermal dissipation in flexible semiconductors and thermoelectrics. Living cells pose extra challenges, due to their small volumes and irregular curvilinear shapes...
November 23, 2016: Small
S Aminorroaya Yamini, D R G Mitchell, M Avdeev
Multiphase thermoelectric materials have recently attracted considerable attention due to the high thermoelectric efficiencies which can be achieved in these compounds compared to their single-phase counterparts. However, there is very little known on the structural evolution of these phases as a function of temperature. In this work we performed an in situ high temperature structural characterisation of recently reported high efficiency p-type multiphase (PbTe)0.65(PbS)0.25(PbSe)0.1 compounds by hot stage transmission electron microscopy and high-resolution neutron powder diffraction...
November 23, 2016: Physical Chemistry Chemical Physics: PCCP
Dongwook Lee, Sayed Youssef Sayed, Sangyeop Lee, Chris Adam Kuryak, Jiawei Zhou, Gang Chen, Yang Shao-Horn
Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) has high electrical conductivity (∼10(3) S cm(-1)) but it exhibits a low Seebeck coefficient (<15 μV K(-1)), resulting in a low power factor. Mixing PEDOT:PSS with nanostructured semiconductors can enhance the Seebeck coefficient and achieve an improved thermoelectric power factor. However, underlying mechanisms for those composite thermoelectric systems are scarcely understood so far. In this study, quantitative analyses on the electrical conductivity and Seebeck coefficient for the heterostructures of nanometer-thick PEDOT:PSS on single-crystal Si (001) on sapphire (SOS) are reported...
December 1, 2016: Nanoscale
Ying Pan, Giulia Tagliabue, Hadi Eghlidi, Christian Höller, Susanne Dröscher, Guo Hong, Dimos Poulikakos
Light detection and quantification is fundamental to the functioning of a broad palette of technologies. While expensive avalanche photodiodes and superconducting bolometers are examples of detectors achieving single-photon sensitivity and time resolutions down to the picosecond range, thermoelectric-based photodetectors are much more affordable alternatives that can be used to measure substantially higher levels of light power (few kW/cm(2)). However, in thermoelectric detectors, achieving broadband or wavelength-selective performance with high sensitivity and good temporal resolution requires careful design of the absorbing element...
November 22, 2016: Scientific Reports
Appala Naidu Gandi, Husam N Alshareef, Udo Schwingenschlögl
We solve numerically the Boltzmann transport equations of the phonons and electrons to understand the thermoelectric response in heterostructures of M2CO2 (M: Ti, Zr, Hf) MXenes with transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding, contribute significantly to the thermal transport, and compensate for the reduced contributions of the acoustic phonons (increased scattering cross-sections in heterostructures), such that the thermal conductivities turn out to be similar to those of the bare MXenes...
November 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
G Komisarchik, Y Gelbstein, D Fuks
Lead telluride based compounds are of great interest due to their enhanced thermoelectric transport properties. Nevertheless, the donor type impurities in this class of materials are currently mainly limited and alternative types of donor impurities are still required for optimizing the thermoelectric performance. In the current research titanium as a donor impurity in PbTe is examined. Although titanium is known to form resonant levels above the conduction band in PbTe, it does not enhance the thermo-power beyond the classical predictions...
November 30, 2016: Physical Chemistry Chemical Physics: PCCP
Sushma Santapuri
A unified thermodynamic framework for the characterization of functional materials is developed. This framework encompasses linear reversible and irreversible processes with thermal, electrical, magnetic, and/or mechanical effects coupled. The comprehensive framework combines the principles of classical equilibrium and non-equilibrium thermodynamics with electrodynamics of continua in the infinitesimal strain regime. In the first part of this paper, linear Thermo-Electro-Magneto-Mechanical (TEMM) quasistatic processes are characterized...
October 2016: Heliyon
Yani Chen, Minhong He, Bin Liu, Guillermo C Bazan, Jun Zhou, Ziqi Liang
Highly bendable n-type thermoelectric nanocomposites are successfully developed by embedding metallic Ni nanowires within an insulating poly(vinylidene fluoride) (PVDF) matrix in solution. These nanocomposites exhibit an abnormal decoupling of the electrical conductivity and Seebeck coefficient as a function of Ni contents. A maximum power factor of 220 µW m(-1) K(-2) and ZT of 0.15 can thus be obtained with 80 wt% Ni at 380 K.
November 11, 2016: Advanced Materials
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