In situ characterisation of nanostructured multiphase thermoelectric materials at elevated temperatures

2016 ◽  
Vol 18 (48) ◽  
pp. 32814-32819 ◽  
Author(s):  
S. Aminorroaya Yamini ◽  
D. R. G. Mitchell ◽  
M. Avdeev
Keyword(s):  
High Temperature ◽  
Thermoelectric Materials ◽  
Single Phase ◽  
Elevated Temperatures ◽  
Chemical Interaction ◽  
Secondary Phases

Multiphase thermoelectric materials exhibit higher efficiencies than their single-phase counterparts. Here, we performed in situ high temperature structural characterisations and shown a strong chemical interaction between secondary phases and matrices at elevated temperatures.

Characterization of the Phase Evolution of Mosi2 - TiB2 Composites Produced by In-Situ Reactions Using Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and X-Ray Diffraction (XRD)

2000 ◽  
Vol 6 (S2) ◽  
pp. 374-375
Author(s):  
L. A. Dempere ◽  
M. J. Kaufman
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Molybdenum Disilicide ◽  
Phase Evolution ◽  
Secondary Phases ◽  
Temperature Oxidation ◽  
Structural Applications ◽  
In Situ Reactions

Intermetallics are playing an important role in the development of new materials able of sustaining the escalating demands of the aerospace industry. A significant improvement in weight, operating temperatures or mechanical performance is required for materials to be considered as replacements in the most demanding applications. Molybdenum disilicide is one such compound that has potential for high temperature applications. Its most attractive properties are its high melting point (2020°C), reasonable density (6.24 g/cm3), and excellent high temperature oxidation and corrosion resistance. However, low ambient fracture toughness and loss of strength at elevated temperatures have been the most significant limitations to the use of MoSi2 in structural applications.The more promising solutions for improving the mechanical properties of brittle intermetallics such as MoSi2 are based on the incorporation and control of secondary phases. To date, the artificial introduction of reinforcing phases or their generation via in-situ reactions have been explored.

Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

2000 ◽  
Vol 64 (2) ◽  
pp. 255-266 ◽  
Author(s):  
J. J. Reece ◽  
S. A. T. Redfern ◽  
M. D. Welch ◽  
C. M. B. Henderson
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
New York ◽  
High Temperature ◽  
Powder Diffraction ◽  
Elevated Temperatures ◽  
Neutron Powder Diffraction ◽  
Site Preference ◽  
A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

scholarly journals One-step ultra-rapid fabrication and thermoelectric properties of Cu2Se bulk thermoelectric material

RSC Advances ◽  
2019 ◽  
Vol 9 (19) ◽  
pp. 10508-10519 ◽  
Author(s):  
Tiezheng Hu ◽  
Yonggao Yan ◽  
Si Wang ◽  
Xianli Su ◽  
Wei Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermoelectric Properties ◽  
Single Phase ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Thermoelectric Energy ◽  
Rapid Fabrication ◽  
One Step ◽  
First Time

Cu2Se is a promising material for thermoelectric energy conversion. Fully dense single-phase bulk Cu2Se was prepared by the combination of self-propagating high-temperature synthesis with in situ quick pressing for the first time.

The local structure of Ta(v) aqua ions in high temperature fluoride- and chloride-bearing solutions: Implications for Ta transport in granite-related postmagmatic fluids

2019 ◽  
Vol 57 (6) ◽  
pp. 843-851
Author(s):  
Alan J. Anderson ◽  
Robert A. Mayanovic ◽  
Thomas Lee
Keyword(s):  
High Temperature ◽  
Local Structure ◽  
Elevated Temperatures ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Acidic Solutions ◽  
Diamond Anvil ◽  
X Ray Absorption ◽  
Photon Source

Abstract The local structure of Ta(V) in high-temperature fluoride- and chloride-bearing acidic solutions was investigated using in situ X-ray absorption spectroscopy (XAS). All XAS spectra were collected from two solutions, designated A and B, at beamline ID-20-C at the Advanced Photon Source, Argonne National Laboratory. Spectra were collected from solution A at 350 and 400 °C and from solution B at 25, 360, and 400 °C after the solutions were sealed in a hydrothermal diamond anvil cell. Solution A was prepared by dissolving Ta2O5 powder in 5% HF solution; solution B consisted of TaCl5 dissolved in 2% HF. The dominant tantalum species in solution A at elevated temperatures was TaF83–. In contrast, TaCl6–, which was the dominant complex in solution B at room temperature, disappeared as hydroxide complexes with an average ligand number between 5 and 7 became the dominant species at 350 and 400 °C. The XAS results confirm the previously recognized effect of fluoride activity on Ta speciation in hydrothermal fluids and suggest that both fluoride and hydroxide complexes play an important role in the transport of Ta in acidic fluoride-bearing solutions involved in the formation of mineralized mica-rich replacement units in granitic pegmatites.

scholarly journals Engineering Deinococcus geothermalis for Bioremediation of High-Temperature Radioactive Waste Environments

2003 ◽  
Vol 69 (8) ◽  
pp. 4575-4582 ◽  
Author(s):  
Hassan Brim ◽  
Amudhan Venkateswaran ◽  
Heather M. Kostandarithes ◽  
James K. Fredrickson ◽  
Michael J. Daly
Keyword(s):  
High Temperature ◽  
Radioactive Waste ◽  
Elevated Temperatures ◽  
Deinococcus Radiodurans ◽  
Nitrilotriacetic Acid ◽  
Thermophilic Bacterium ◽  
Prospective Development ◽  
Deinococcus Geothermalis ◽  
Radiation Resistant

ABSTRACT Deinococcus geothermalis is an extremely radiation-resistant thermophilic bacterium closely related to the mesophile Deinococcus radiodurans, which is being engineered for in situ bioremediation of radioactive wastes. We report that D. geothermalis is transformable with plasmids designed for D. radiodurans and have generated a Hg(II)-resistant D. geothermalis strain capable of reducing Hg(II) at elevated temperatures and in the presence of 50 Gy/h. Additionally, D. geothermalis is capable of reducing Fe(III)-nitrilotriacetic acid, U(VI), and Cr(VI). These characteristics support the prospective development of this thermophilic radiophile for bioremediation of radioactive mixed waste environments with temperatures as high as 55°C.

scholarly journals Amorphous Mg–Fe silicates from microwave-dried sol–gels

2019 ◽  
Vol 624 ◽  
pp. A136
Author(s):  
S. P. Thompson ◽  
A. Herlihy ◽  
C. A. Murray ◽  
A. R. Baker ◽  
S. J. Day ◽  
...  
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Microwave Drying ◽  
Drying Methods ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Context. Laboratory analogues can provide physical constraints to the interpretation of astronomical observations of cosmic dust but clearly do not experience the same formation conditions. To distinguish between properties intrinsic to the material and properties imprinted by their means of formation requires extensive characterisation. Aims. Sol–gel methods can produce amorphous silicates with potentially high reproducibility, but often require long drying times (24+ h) at elevated temperatures in air, controlled atmosphere, or vacuum. We investigate the possibility that microwave drying can be used to form amorphous silicate on a timescale of ∼10 min and characterise their structural and spectroscopic properties relative to silicates produced by other drying methods. Methods. Microwave-dried amorphous MgSiO3, Fe0.1Mg0.9SiO3 and Mg2SiO4 are characterised using X-ray powder diffraction, total X-ray scattering, small angle X-ray scattering and mid-IR FTIR spectroscopy, and compared to samples produced from the same gels but dried in-air and under vacuum. The development of crystalline structure in the microwave-dried silicates via thermal annealing up to 999°C is also investigated using in situ X-ray powder diffraction. Results. At the inter-atomic level the silicate structures are largely independent of drying method, however larger-scale structured domains, ranging from a ∼few × 10 Å to ∼100’s Å in size, are observed. These are ordered as mass fractals with discernible variation caused by the drying processes. The mid-IR 10 μm band profile is also found to be influenced by the drying process, likely due to the way removal of water and bonded OH influences the distribution of tetrahedral species. However, microwave drying also allows Fe to be easily incorporated into the silicate structure. In situ annealing shows that for amorphous MgSiO3 crystalline forsterite, enstatite and cristobalite are high temperature phases, while for Mg2SiO4 forsterite crystallises at lower temperatures followed by cristobalite at high temperature. For Fe0.1Mg0.9SiO3 the crystallisation temperature is significantly increased and only forsterite is observed. Crystalline SiO2 may be diagnostic of Mg-rich, Fe-poor grain mineralogies. The results are discussed in relation to the different thermal conditions required for dust to crystallise within protoplanetary disk lifetimes. Conclusions. Sol–gel microwave drying provides a fast and easy method of producing amorphous Mg- and Fe,Mg-silicates of both pyroxene and olivine compositions. Their structure and spectroscopic characteristics although similar to silicates produced using other drying methods, exhibit subtle variations which are particularly manifest spectroscopically in the mid-IR, and structurally over medium- and long-range length scales.

Single-phase nickel-doped ceria cathode with in situ grown nickel nanocatalyst for direct high-temperature carbon dioxide electrolysis

RSC Advances ◽  
2014 ◽  
Vol 4 (76) ◽  
pp. 40494-40504 ◽  
Author(s):  
Wentao Qi ◽  
Kui Xie ◽  
Min Liu ◽  
Guojian Wu ◽  
Yan Wang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Single Phase ◽  
Doped Ceria

In situ growth of Ni nanocatalysts on CeO2 surface has been achieved and the direct carbon dioxide electrolysis reaches high efficiencies using this material as cathode.

Ionic Transport under Chemical Potential Gradients - Kinetic Demixing and Decomposition in Metal Oxides and Scale Growth in High-Temperature Oxidation

2011 ◽  
Vol 696 ◽  
pp. 28-33
Author(s):  
Manfred Martin
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Elevated Temperatures ◽  
Chemical Potential ◽  
Transport Processes ◽  
Temperature Oxidation ◽  
X Ray ◽  
Kinetic Decomposition ◽  
Potential Gradients

In oxides which are exposed to thermodynamic potential gradients, transport processes of the mobile components occur. These transport processes and the coupling between different processes are not only of fundamental interest, but are also the origin of degradation processes, such as kinetic demixing, kinetic decomposition, and changes in the morphology of the material. The kinetics of high temperature oxidation processes of metals can be studiedin situby X-ray absorption spectroscopy (XAS), optical microscopy and X-ray diffraction (XRD) at elevated temperatures and defined oxygen partial pressures. As an example, thein situXAS investigation of the oxidation of cobalt, forming layers of CoO and Co3O4, will be discussed.

High-temperature oxidation of CoGa: Influence of the crystallographic orientation on the oxidation rate

2002 ◽  
Vol 17 (10) ◽  
pp. 2489-2498 ◽  
Author(s):  
U. Koops ◽  
D. Hesse ◽  
M. Martin
Keyword(s):  
High Temperature ◽  
Crystallographic Orientation ◽  
High Temperature Oxidation ◽  
Elevated Temperatures ◽  
Electron Backscatter Diffraction ◽  
Ex Situ ◽  
Temperature Oxidation ◽  
Transmission Electron ◽  
Backscatter Diffraction

The crystallographic orientation plays an important role in high-temperature oxidation of the intermetallic compound CoGa. When CoGa is exposed to air at elevated temperatures, the oxide β–Ga2O3 is formed, and different scale growth rates are observed, depending on the crystallographic orientation of the CoGa grains. This dependence is a consequence of the anisotropy of the gallium diffusion rate through the β–Ga2O3 scale and of a topotaxial orientation relationship occurring between β–Ga2O3 and CoGa. The combination of ex situ techniques, such as transmission electron microscopy and electron backscatter diffraction with optical microscopy, applied in situ resulted in a thorough understanding of these relations and of the oxidation process in general.

scholarly journals Recent Progress in Multiphase Thermoelectric Materials

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6059
Author(s):  
Raphael Fortulan ◽  
Sima Aminorroaya Yamini
Keyword(s):  
Conversion Efficiency ◽  
Thermoelectric Materials ◽  
High Performance ◽  
Degrees Of Freedom ◽  
Single Phase ◽  
Phonon Scattering ◽  
Secondary Phases ◽  
Beneficial Effects ◽  
Energy Filtering ◽  
New Compounds

Thermoelectric materials, which directly convert thermal energy to electricity and vice versa, are considered a viable source of renewable energy. However, the enhancement of conversion efficiency in these materials is very challenging. Recently, multiphase thermoelectric materials have presented themselves as the most promising materials to achieve higher thermoelectric efficiencies than single-phase compounds. These materials provide higher degrees of freedom to design new compounds and adopt new approaches to enhance the electronic transport properties of thermoelectric materials. Here, we have summarised the current developments in multiphase thermoelectric materials, exploiting the beneficial effects of secondary phases, and reviewed the principal mechanisms explaining the enhanced conversion efficiency in these materials. This includes energy filtering, modulation doping, phonon scattering, and magnetic effects. This work assists researchers to design new high-performance thermoelectric materials by providing common concepts.

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