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Thermal equation of state of Molybdenum determined from in situ synchrotron X-ray diffraction with laser-heated diamond anvil cells
Abstract not provided
In situ measurement of power conversion efficiency and molecular ordering during thermal annealing in P3HT:PCBM bulk heterojunction solar cells
Bulk heterojunction organic solar cells hold much promise as commercially viable sources of renewable energy due to their relatively inexpensive fabrication. Developing a fundamental knowledge of how processing conditions influence solar power conversion efficiency will enable rational and efficient design, optimization, and control of new organic solar cell materials. In this report, we use a combination of in situ current–voltage measurements and grazing-incidence wide-angle X-ray scattering experiments at elevated temperature to correlate the changes in photoconversion efficiency to the changes in the molecular ordering of a poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction active layer. In situ measurements of current–voltage characteristics were used to optimize the power conversion efficiency and the resulting thermal processing was in agreement with studies from repeated heating and cooling cycles. The improvements in short circuit current with thermal annealing were correlated to an increase in the population of face-on oriented crystallites of P3HT rather than improvements in molecular ordering of PCBM.
Microscale solid-state thermal diodes enabling ambient temperature thermal circuits for energy applications
A micro-scale phase change thermal diode capable of ambient and solid-state operation is developed and incorporated into a thermal diode bridge circuit.
Nonmonotonic thickness-dependence of in-plane thermal conductivity of few-layered MoS 2 : 2.4 to 37.8 nm
The thermal conductivity of supported MoS 2 is discovered to first decrease with thickness (<9.2 nm), then increase with thickness.
Mechanical, thermal, and electrochemical properties of Pr doped ceria from wafer curvature measurements
This work demonstrates, for the first time, that a variety of disparate and technologically-relevent thermal, mechanical, and electrochemical oxygen-exchange material properties can all be obtained from in situ , current-collector-free wafer curvature measurements.
Impact of thermally dead volume on phonon conduction along silicon nanoladders
Silicon nanoladders show that thermally dead volume minimally impacts on the ballistic effects.
Tin–lead halide perovskites with improved thermal and air stability for efficient all-perovskite tandem solar cells
We report the fabrication of monolithic all-perovskite tandem solar cells with a stabilized power conversion efficiency of 19.1% and demonstrate improved thermal, atmospheric, and operational stability of the tin–lead perovskite (FA 0.75 Cs 0.25 Sn 0.5 Pb 0.5 I 3 ) used as the low gap absorber.
In situ formed polymer gel electrolytes for lithium batteries with inherent thermal shutdown safety features
An in situ formed poly(vinylene carbonate)–lithium iodide gel electrolyte enables stable cycling of lithium metal and a thermal shutdown function.
Flexible percolation fibrous thermal insulating composite membranes for thermal management
Flexible thermal insulating membranes are ubiquitous in thermal management.
Thermal properties and ultra-low thermal conductivity of Zn 2 GeSe 4
Analyses and modeling of the T -dependent thermal properties of Zn 2 GeSe 4 reveal an ultra-low thermal conductivity over a large temperature range due to low-frequency soft modes as well as strong lattice anharmonicity.
Thermal axion constraints in non-standard thermal histories
There is no direct evidence for radiation domination prior to big-bang nucleosynthesis, and so it is useful to consider how constraints to thermally-produced axions change in non-standard thermal histories. In the low-temperature-reheating scenario, radiation domination begins as late as {approx}1 MeV, and is preceded by significant entropy generation. Axion abundances are then suppressed, and cosmological limits to axions are significantly loosened. In a kination scenario, a more modest change to axion constraints occurs. Future possible constraints to axions and low-temperature reheating are discussed.
Laser assisted crystallization of ferromagnetic amorphous ribbons: A multimodal characterization and thermal model study
This paper focuses on laser-based de-vitrification of amorphous soft magnetic Fe-Si-B ribbons and its consequent influence on the magnetic properties. Laser processing resulted in a finer scale of crystallites due to rapid heating and cooling during laser annealing compared to conventional furnace annealing process. A significant increase in saturation magnetization is observed for laser-annealed ribbons compared to both as-received and furnace annealed samples coupled with an increase in coercivity compared to the as received samples. The combined effect of thermal histories and stresses developed during laser annealing results in the formation of nano-crystalline phase along the laser track. The phase evolution is studied by micro-XRD and TEM analysis. Solute partitioning and compositional variation within the phases are obtained by Local Electrode Atom probe analysis. The evolution of microstructure is rationalized using a Finite Element based heat transfer multi-physics model.
Molecular nonlinear dynamics and protein thermal uncertainty quantification
This work introduces molecular nonlinear dynamics (MND) as a new approach for describing protein folding and aggregation. By using a mode system, we show that the MND of disordered proteins is chaotic while that of folded proteins exhibits intrinsically low dimensional manifolds (ILDMs). The stability of ILDMs is found to strongly correlate with protein energies. We propose a novel method for protein thermal uncertainty quantification based on persistently invariant ILDMs. Extensive comparison with experimental data and the state-of-the-art methods in the field validate the proposed new method for protein B-factor prediction.
High thermal stability and low Gilbert damping constant of CoFeB/MgO bilayer with perpendicular magnetic anisotropy by Al capping and rapid thermal annealing
We demonstrate that the magnetic anisotropy of the CoFeB/MgO bilayer can be manipulated by adding an aluminum capping layer. After rapid thermal annealing, we can achieve large perpendicular magnetic anisotropy of CoFeB with a high thermal stability factor (Δ = 72) while the Gilbert damping constant can be reduced down to only 0.011 simultaneously. The boron and residual oxygen in the bulk CoFeB layer are properly absorbed by the Al capping layer during annealing, leading to the enhanced exchange stiffness and reduced damping. The interfacial Fe-O bonding can be optimized by tuning annealing temperature and thickness of Al, resulting in enhanced perpendicular anisotropy.
Phonon thermal transport through tilt grain boundaries in strontium titanate
In this work, we perform nonequilibrium molecular dynamics simulations to study phonon scattering at two tilt grain boundaries (GBs) in SrTiO{sub 3}. Mode-wise energy transmission coefficients are obtained based on phonon wave-packet dynamics simulations. The Kapitza conductance is then quantified using a lattice dynamics approach. The obtained results of the Kapitza conductance of both GBs compare well with those obtained by the direct method, except for the temperature dependence. Contrary to common belief, the results of this work show that the optical modes in SrTiO{sub 3} contribute significantly to phonon thermal transport, accounting for over 50% of the Kapitza conductance. To understand the effect of the GB structural disorder on phonon transport, we compare the local phonon density of states of the atoms in the GB region with that in the single crystalline grain region. Our results show that the excess vibrational modes introduced by the structural disorder do not have a significant effect on phonon scattering at the GBs, but the absence of certain modes in the GB region appears to be responsible for phonon reflections at GBs. This work has also demonstrated phonon mode conversion and simultaneous generation of new modes. Some of the new modes have the same frequency as the initial wave packet, while some have the same wave vector but lower frequencies.
Enhanced thermal stability of Ag nanorods through capping
Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. This letter proposes the use of a thin oxide capping layer to enhance the thermal stability of Ag nanorods beyond 100 °C. Using electron microscopy characterization and SERS tests, the authors show that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures.
Effects of rapid thermal annealing on the structural and local atomic properties of ZnO: Ge nanocomposite thin films
We have investigated the structural and local atomic properties of Ge nanocrystals (Ge-ncs) embedded ZnO (ZnO: Ge) thin films. The films were deposited by sequential sputtering of ZnO and Ge thin film layers on z-cut quartz substrates followed by an ex-situ rapid thermal annealing (RTA) at 600 °C for 30, 60, and 90 s under forming gas atmosphere. Effects of RTA time on the evolution of Ge-ncs were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), hard x-ray photoelectron spectroscopy (HAXPES), and extended x-ray absorption fine structure (EXAFS). XRD patterns have clearly shown that fcc diamond phase Ge-ncs of sizes ranging between 18 and 27 nm are formed upon RTA and no Ge-oxide peak has been detected. However, cross-section SEM images have clearly revealed that after RTA process, Ge layers form varying size nanoclusters composed of Ge-ncs regions. EXAFS performed at the Ge K-edge to probe the local atomic structure of the Ge-ncs has revealed that as prepared ZnO:Ge possesses Ge-oxide but subsequent RTA leads to crystalline Ge structure without the oxide layer. In order to study the occupied electronic structure, HAXPES has been utilized. The peak separation between the Zn 2p and Ge 3d shows no significant change due to RTA. This implies little change in the valence band offset due to RTA.