Search results for "thermal expansion"
showing 10 items of 101 documents
Prussian Blue Analogues of Reduced Dimensionality
2012
Abstract: Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule-based materials can combine physical and chemical properties associated with molecular-scale building blocks, their successful integration into real devices depends primarily on higher-order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced-dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is …
Bimodal velocity distribution of atoms released from nanosecond ultraviolet laser ablation
2005
We have investigated the velocity distributions of atoms released from a metallic gadolinium surface by UV laser ablation. The fluences of the nanosecond laser pulses were chosen for a pure release of neutrals and at a higher fluence level for the release of both neutrals and ions. In both cases a thermal Maxwell-Boltzmann slope has been observed for the low velocities, whereas for high velocities strong deviations from a thermal distribution have been seen. The observed velocity distribution has been explained by a bimodal structure including a thermal phase and a shockwave driven ``blow-off'' phase.
Behaviour of thermal expansion of (1-x)Pb(Ni1/3Nb2/3)O3–xPbTiO3 solid solutions
2017
The publication costs of this article were covered by the Estonian Academy of Sciences and the University of Tartu.
Metallic interconnects for solid oxide fuel cell: Effect of water vapour on oxidation resistance of differently coated alloys
2009
International audience; The need of interconnect to separate fuel and oxidant gasses and connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. Due to their high electrical and thermal conductivities, thermal expansion compatibility with the other cell components and lowcost, ferritic stainless steels (FSS) are nowconsidered to be among the most promising candidate materials as interconnects in SOFC stacks. Despite the formation at 800 ◦C of a protective chromia Cr2O3 scale, it can transform in volatile chromium species, leading to the lost of its protectiveness and then the degradation of the fuel cell. A previous…
Optical and Vibrational Spectra of CsCl-Enriched GeS2-Ga2S3 Glasses
2016
Optical and FTIR spectroscopy was employed to study the properties of 80GeS2-20Ga2S3-CsCl chalcohalide glasses with CsCl additives in a temperature range of 77–293 K. It is shown that CsCl content results in the shift of fundamental absorption edge in the visible region. Vibrational bands in FTIR spectra of (80GeS2-20Ga2S3)100 − х (СsCl) x (x = 5, 10, and 15) are identified near 2500 cm−1, 3700 cm−1,, around 1580 cm−1, and a feature at 1100 cm−1. Low energy shifts of vibrational frequencies in glasses with a higher amount of CsCl can be caused by possible thermal expansion of the lattice and nanovoid agglomeration formed by CsCl additives in the inner structure of the Ge-Ga-S glass.
EPR Study of Gd3+local structure in ScF3crystal with negative thermal expansion coefficient
2015
Zero field splitting (ZFS) of Gd3+ impurity in ScF3 is studied by electron paramagnetic resonance at 77 and 295 K. ZFS parameter b4 values obtained from angular dependence simulations show that regardless of negative thermal expansion in ScF3 temperature dependence of |b4| is similar to other cubic fluoroperovskites. Our analysis of ZFS parameters indicates that the local structure of Gd3+ centres expands positively with temperature.
Cooling-rate effects in amorphous silica: A computer-simulation study
1996
Using molecular dynamics computer simulations we investigate how in silica the glass transition and the properties of the resulting glass depend on the cooling rate with which the sample is cooled. By coupling the system to a heat bath with temperature $T_b(t)$, we cool the system linearly in time, $T(t)=T_i-\gamma t$, where $\gamma$ is the cooling rate. We find that the glass transition temperature $T_g$ is in accordance with a logarithmic dependence on the cooling rate. In qualitative accordance with experiments, the density shows a local maximum, which becomes more pronounced with decreasing cooling rate. The enthalpy, density and the thermal expansion coefficient for the glass at zero t…
Mathematical modelling of the industrial growth of large silicon crystals by CZ and FZ process
2003
The present paper gives an overview of the complex mathematical modelling of industrial Czochralski (CZ) and floating‐zone (FZ) processes for the growth of large silicon single crystals from melt. Extensive numerical investigations of turbulent Si‐melt flows in large diameter CZ crucibles, global thermal calculations in growth facilities and analysis of the influence of various electromagnetic fields on CZ process are presented. For FZ process, a complex system of coupled 2D and 3D mathematical models is presented to show the possibilities of modelling from the calculation of the molten zone shape till the resistivity distribution in the grown crystal. A special developed program code is pr…
Ab initio molecular dynamics simulations of negative thermal expansion in ScF3: the effect of the supercell size
2020
The authors sincerely thank S. Ali, A. Kalinko, and F. Rocca for providing experimental EXAFS data, as well as M. Isupova, V. Kashcheyevs, and A. I. Popov for stimulating discussions. Financial support provided by project No. 1.1.1.2/VIAA/l/16/147 (1.1.1.2/16/I/001) under the activity “Post-doctoral research aid” realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged by D.B. A.K and J.P. would like to thank the support of the Latvian Council of Science project No. lzp-2018/2–0353.
Two new members of the Silica-X family of materials: RUB-5, a silica zeolite with a very high framework density and RUB-6, a hydrous layer silicate
2020
Abstract The new zeolite RUB-5 and the new phyllo silicate RUB-6 were synthesized at temperatures between 130 °C and 200 °C from reaction mixtures consisting of SiO2/LiOH/B(OH)3/OA/H2O or SiO2/KOH/OA/H2O (OA = organic additive). Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and ATR-FTIR spectroscopy confirmed that RUB-5 is a framework silicate while RUB-6 is a layer silicate. The XRD powder patterns were indexed in monoclinic symmetry (space group: C2) with lattice parameters of a0 = 10.2699 (4) A, b0 = 10.6556 (4) A, c0 = 18.1551 (7) A and β = 106.35 (1)° (RUB-5), and a0 = 10.1100 (43) A, b0 = 10.6956 (51) A, c0 = 20.5448 (44) A and β = 105.79 (1)° (RUB…