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Bulk heating

Weiwei Cao, Xiaoyan Yang, Fengqi Lu, Wenfeng Zhu, Laijun Liu, Xiaojun Kuang, Mathieu Allix
Isovalent substitution of Zr4+ for smaller Ti4+ was performed in the 8-layer twinned hexagonal perovskite (referred to as 8H) tantalate Ba8 Ti3 Ta4 O24 , which stabilizes a 10-layer twinned hexagonal perovskite (referred to as 10H). The formation of the 10H phase occurs at low substitution concentration ( x = 0.1) in Ba8 Zrx Ti3- x Ta4 O24 at 1300 °C and reverts back to the 8H phase upon heating at elevated temperatures. Such a 10H-to-8H phase transformation is suppressed at higher Zr-substitution contents ( x > 0...
March 19, 2018: Inorganic Chemistry
Zhili Wan, Yingen Sun, Lulu Ma, Feibai Zhou, Jian Guo, Song-Qing Hu, Xiao-Quan Yang
Nanofibrils from self-assembly of the naturally occurring saponin glycyrrhizic acid (GA) can be used to create an oil-in-water emulsion foam with long-term stability. Through a homogenization and aeration followed by a rapid cooling, stable emulsion foams can be produced from the mixtures of sunflower oil and saponin nanofibrils. At high temperature, the GA fibrils form a multilayer assembly at the interface, creating an interfacial fibrillar network to stabilize the oil droplets and air bubbles generated during homogenization...
March 16, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Yupeng Shen, Fancy Qian Wang, Jie Liu, Yaguang Guo, Xiaoyin Li, Guangzhao Qin, Ming Hu, Qian Wang
A new two-dimensional (2D) carbon allotrope, Hexa-C20, composed of C20 fullerene is proposed. State-of-the-art first principles calculations combined with solving the linearized phonon Boltzmann transport equation confirm that the new carbon structure is not only dynamically and thermally stable, but also can withstand temperatures as high as 1500 K. Hexa-C20 possesses a quasi-direct band gap of 3.28 eV, close to that of bulk ZnO and GaN. The intrinsic lattice thermal conductivity κlat of Hexa-C20 is 1132 W m-1 K-1 at room temperature, which is much larger than those of most carbon materials such as graphyne (82...
March 16, 2018: Nanoscale
Morgane Dolhen, Masayuki Tanaka, Vincent Couderc, Sébastien Chenu, Gaëlle Delaizir, Tomokatsu Hayakawa, Julie Cornette, François Brisset, Maggy Colas, Philippe Thomas, Jean-René Duclère
We report on the laser emission of the polycrystalline ceramic obtained from the full and congruent crystallization of the parent glass 1Nd3+ :75TeO2 -12.5Bi2 O3 -12.5Nb2 O5 composition. In particular, the current work underlines the importance of carefully controlling the heat treatment in order to solely crystallize the Bi0.8 Nb0.8 Te2.4 O8 cubic phase and consequently avoid the formation of the BiNbTe2 O8 orthorhombic phase that would be detrimental for optical purpose. The structure, microstructure and photoluminescence properties of the resulting transparent tellurite ceramics are characterized...
March 15, 2018: Scientific Reports
Maxime Markov, Jelena Sjakste, Giuliana Barbarino, Giorgia Fugallo, Lorenzo Paulatto, Michele Lazzeri, Francesco Mauri, Nathalie Vast
Bismuth is one of the rare materials in which second sound has been experimentally observed. Our exact calculations of thermal transport with the Boltzmann equation predict the occurrence of this Poiseuille phonon flow between ≈1.5 and ≈3.5  K, in a sample size of 3.86 and 9.06 mm, consistent with the experimental observations. Hydrodynamic heat flow characteristics are given for any temperature: heat wave propagation length, drift velocity, and Knudsen number. We discuss a gedanken experiment allowing us to assess the presence of a hydrodynamic regime in any bulk material...
February 16, 2018: Physical Review Letters
Krzysztof B Beć, Yusuke Morisawa, Kenta Kobashi, Justyna Grabska, Ichiro Tanabe, Erika Tanimura, Harumi Sato, Marek J Wójcik, Yukihiro Ozaki
We investigated the surface (<50 nm) of poly(3-hydroxybutyrate) (PHB) and its nanocomposite with graphene by attenuated total reflection far- and deep-ultraviolet (ATR-FUV-DUV; 145-300 nm; 8.55-4.13 eV) spectroscopy and quantum mechanical calculations. The major absorption of polymers occurs in FUV and is related to Rydberg transitions. ATR-FUV-DUV spectroscopy allows for direct measurements of these transitions in the solid phase. Using ATR-FUV-DUV spectroscopy, periodic density functional theory (DFT) and time-dependent DFT (TD-DFT), we explained the origins of the FUV-DUV absorption of PHB and provided insights into structural changes of PHB which occur upon formation of a graphene nanocomposite and upon heating of the pure polymer...
March 15, 2018: Physical Chemistry Chemical Physics: PCCP
Reka Horvath, Gyorgy Hantal, Sylvain Picaud, Milán Szőri, Pal Jedlovszky
The adsorption of methylamine at the surface of amorphous ice is studied at various temperatures, ranging from 20 K to 200 K, by grand canonical Monte Carlo simulations under conditions that are characteristic to the interstellar medium (ISM). The results are also compared with those obtained earlier on crystalline (Ih) ice. We found that methylamine has a strong ability of being adsorbed on amorphous ice, involving also multilayer adsorption. The decrease of the temperature leads to a substantial increase of this adsorption ability, thus, considerable adsorption is seen at 20-50 K even at bulk gas phase concentrations that are comparable with that of the ISM...
March 14, 2018: Journal of Physical Chemistry. A
Dominique Laniel, Gunnar Weck, Gabriel Gaiffe, Gaston Garbarino, Paul Loubeyre
Polynitrogen compounds have been actively pursued driven by their potential as ultra-high performing propellants or explosives. Despite remarkable breakthroughs over the past two decades, the two figures of merit for a compelling material, namely a large fraction of nitrogen by weight and a bulk stability at ambient conditions, have not been achieved yet. Here, we report the synthesis of a lithium pentazolate solid by compressing and laser-heating lithium embedded in molecular N2 around 45 GPa along with its recovery at ambient conditions...
March 13, 2018: Journal of Physical Chemistry Letters
David Portehault, Simon Delacroix, Guillaume Gouget, Rémi Grosjean, Tsou-Hsi-Camille Chan-Chang
The design of inorganic nanoparticles relies strongly on the knowledge from solid-state chemistry not only for characterization techniques, but also and primarily for choosing the systems that will yield the desired properties. The range of inorganic solids reported and studied as nanoparticles is however strikingly narrow when compared to the solid-state chemistry portfolio of bulk materials. Efforts to enlarge the collection of inorganic particles are becoming increasingly important for three reasons. First, they can yield materials more performing than current ones for a range of fields including biomedicine, optics, catalysis, and energy...
March 13, 2018: Accounts of Chemical Research
Naohiro Kameta, Jiuchao Dong, Hiroharu Yui
A series of nanotubes with a dense layer of short poly(ethylene glycol) (PEG) chains on the inner surface are prepared by means of a coassembly process using glycolipids and PEG derivatives. Dehydration of the PEG chains by heating increases the hydrophobicity of the nanotube channel and fluorescent-dye-labeled amino acids are extracted from bulk solution. Rehydration of the PEG chains by cooling results in back-extraction of the amino acids into the bulk solution. Because of the supramolecular chirality of the nanotubes, amino acid enantiomers can be separated in the back-extraction procedure, which is detectable with the naked eye as a change in fluorescence as the amino acids are released from the nanotubes...
March 13, 2018: Small
L J Bae, U Zastrau, H-K Chung, A C Bernstein, M S Cho, G M Dyer, E Galtier, Z-H He, P A Heimann, G B Kang, M Kim, Y H Kim, H J Lee, J W Lee, B Nagler, A G R Thomas, B I Cho
Warm dense conditions in titanium foils irradiated with intense femtosecond laser pulses are diagnosed using an x-ray imaging spectroscopy technique. The line shapes of radially resolved titanium Kα spectra are measured with a toroidally bent GaAs crystal and an x-ray charge-coupled device. Measured spectra are compared with the K-shell emissions modeled using an atomic kinetics - spectroscopy simulation code. Kα line shapes are strongly affected by warm (5-40 eV) bulk electron temperatures and imply multiple temperature distributions in the targets...
March 5, 2018: Optics Express
Yaser Khorrami, Vahid Ahmadi, Mohammad Razaghi, Narottam Das
In this paper, we numerically analyze nonlinear asymmetric switching using a semiconductor optical amplifier (SOA) phase-shifter-based Mach-Zehnder interferometer (MZI), for the first time, to the best of our knowledge. The self-phase modulation (SPM) effect and nonlinear phase shift in each MZI arm are investigated for different input pulse intensities and linear gains in both picosecond and femtosecond regimes. The input light signal is split unequally over the two arms, where SOAs are placed and act as nonlinear phase shifters in each arm...
March 1, 2018: Applied Optics
Chenxi Han, Changchun Chai, Qingyang Fan, Jionghao Yang, Yintang Yang
The structural, mechanical, anisotropic, electronic, and thermal properties of t -Si₃N₄, t -Si₂GeN₄, t -SiGe₂N₄, and t -Ge₃N₄ in the tetragonal phase are systematically investigated in the present work. The mechanical stability is proved by the elastic constants of t -Si₃N₄, t -Si₂GeN₄, t -SiGe₂N₄, and t -Ge₃N₄. Moreover, they all demonstrate brittleness, because B/G < 1.75, and v < 0.26. The elastic anisotropy of t -Si₃N₄, t -Si₂GeN₄, t -SiGe₂N₄, and t -Ge₃N₄ is characterized by Poisson's ratio, Young's modulus, the percentage of elastic anisotropy for bulk modulus AB , the percentage of elastic anisotropy for shear modulus AG , and the universal anisotropic index A U ...
March 7, 2018: Materials
F Nestola, N Korolev, M Kopylova, N Rotiroti, D G Pearson, M G Pamato, M Alvaro, L Peruzzo, J J Gurney, A E Moore, J Davidson
Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth's mantle. Discoveries of some of these minerals in 'super-deep' diamonds-formed between two hundred and about one thousand kilometres into the lower mantle-have confirmed part of this picture. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3 ). This mineral-expected to be the fourth most abundant in the Earth-has not previously been found in nature...
March 7, 2018: Nature
Ibrahim Alhroub, Evguenii Kozliak, Alena Kubatova, Mark Sulkes
There has been a limited understanding of high MW polycyclic aromatic hydrocarbon (PAH) product chemistry in the pyrolysis of triglycerides (TGs), though the subject has important implications for both fuel production from TGs and food science. Previous TG pyrolysis studies have been able to identify only relatively low MW GC-elutable aromatics occurring in the bulk liquid phase; products occurring in the solid phase have remained inaccessible to chemical analysis. In contrast, cold gas expansion molecular beam methods, where pyrolysis products are analyzed in real time as they are entrained in gas expansions, remove product collection difficulties, thereby allowing for analysis of coke/tar PAH precursors...
March 7, 2018: Journal of Physical Chemistry. A
Dominique Laniel, Agnès Dewaele, Gaston Garbarino
The high pressure chemistry of transition metals and nitrogen was recently discovered to be richer than previously thought, due to the synthesis of several transition metal pernitrides. Here, we explore the pressure-temperature domain of iron with an excess of nitrogen up to 91 GPa and 2200 K. Above 72 GPa and 2200 K, the iron pernitride FeN2 is produced in a laser-heated diamond anvil cell. This iron-nitrogen compound is the first with a N/Fe ratio greater than 1. The FeN2 samples were characterized from the maximum observed pressure down to ambient conditions by powder X-ray diffraction and Raman spectroscopy measurements...
March 5, 2018: Inorganic Chemistry
Yanhui Feng, Runzhi Wei, Zhi Huang, Xinxin Zhang, Ge Wang
Carbon nanotubes (CNTs) filled with lauric acid (LA) as a kind of shape-stabilized phase change material were prepared and their structures and phase change properties were characterized. The results showed that the melting point and latent heat of LA confined in carbon nanotubes were lower than those of the bulk material, and both decrease as the diameters of CNTs and the filling ratios of LA decrease. Molecular dynamics (MD) simulations indicated that LA molecules form a liquid layer near pore walls and crystallize at the pore center...
March 5, 2018: Physical Chemistry Chemical Physics: PCCP
Danuta Barnat-Hunek, Marcin K Widomski, Małgorzata Szafraniec, Grzegorz Łagód
The aim of the research that is presented in this paper was to evaluate the physical and mechanical properties of heat-insulating mortars with expanded cork aggregates and different binders. In this work, the measurements of surface roughness and adhesion strength, supported by determination of basic mechanical and physical parameters, such as density, bulk density, open porosity, total porosity, absorbability, thermal conductivity coefficient, compressive strength, flexural strength, and frost resistance of mortars containing expanded oak cork, were performed...
March 1, 2018: Materials
Alicia M Leon, Wenceslao T Medina, Dong J Park, José M Aguilera
Designing soft, palatable and nutritious texture-modified foods for the elderly is a challenge for food technologists. The aim of this work was to produce and characterize emulsion-gelled microparticles (EGM) made from whey protein isolate (WPI) and sodium alginate (NaAlg) that may be used to modify the rheology of liquid foods and as carriers of lipids and lipophilic nutrients and bioactives. Olive oil microdroplets became embedded in the WPI/NaAlg gel matrix in the form of an emulsion produced by ultrasound (US) or high-speed blending (HSB)...
January 1, 2018: Food Science and Technology International, Ciencia y Tecnología de Los Alimentos Internacional
Xuan Hu, Poya Yasaei, Jacob Jokisaari, Serdar Öğüt, Amin Salehi-Khojin, Robert F Klie
Two-dimensional materials, including graphene, transition metal dichalcogenides and their heterostructures, exhibit great potential for a variety of applications, such as transistors, spintronics, and photovoltaics. While the miniaturization offers remarkable improvements in electrical performance, heat dissipation and thermal mismatch can be a problem in designing electronic devices based on two-dimensional materials. Quantifying the thermal expansion coefficient of 2D materials requires temperature measurements at nanometer scale...
February 2, 2018: Physical Review Letters
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