Three-Dimensional Atomic Structure of Supported Au Nanoparticles at High Temperature

Nanoscale ◽  
2021 ◽  
Author(s):  
Pei Liu ◽  
Ece Arslan Imran ◽  
Annick De Backer ◽  
Annelies de Wael ◽  
Ivan Lobato ◽  
...  
Keyword(s):  
High Temperature ◽  
Atomic Structure ◽  
Au Nanoparticles ◽  
Elevated Temperatures ◽  
Three Dimensional

Au nanoparticles (NPs) deposited on CeO2 are extensively used as thermal catalysts since the morphology of the NPs is expected to be stable at elevated temperatures. Although it is well...

Incommensurately modulated ordering of tetrahedral chains in Ca2Fe2O5 at elevated temperatures

2005 ◽  
Vol 61 (6) ◽  
pp. 656-662 ◽  
Author(s):  
Hannes Krüger ◽  
Volker Kahlenberg
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
X Ray ◽  
Left Handed ◽  
Lattice Periodicity

The basic building units of brownmillerite-type A 2 B 2O5 structures are perovskite-like layers of corner-sharing BO6 octahedra and zweier single chains of BO4 tetrahedra. A three-dimensional framework is formed by alternate stacking of octahedral layers and sheets of tetrahedral chains. The compound Ca2Fe2O5 is known to have Pnma symmetry at ambient conditions. The space group Imma was reported to be evident above 963 K. New high-temperature single-crystal X-ray diffraction experiments at 1100 K revealed that Ca2Fe2O5 forms an incommensurately modulated structure adopting the superspace group Imma(00γ)s00, with γ = 0.588 (2). The modulation affects the sequence of the enantiomorphic (right- and left-handed) oriented tetrahedral chains within the layer, breaking the lattice periodicity along c. This ordering can be modelled with crenel occupation modulation functions for the tetrahedrally coordinated Fe, as well as for the O atom interconnecting the tetrahedra.

scholarly journals Ta-Doped Sb2Te Allows Ultrafast Phase-Change Memory with Excellent High-Temperature Operation Characteristics

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yuan Xue ◽  
Shuai Yan ◽  
Shilong Lv ◽  
Sannian Song ◽  
Zhitang Song
Keyword(s):  
High Temperature ◽  
Phase Change ◽  
High Speed ◽  
Elevated Temperatures ◽  
Phase Change Memory ◽  
Three Dimensional ◽  
Amorphous Structure ◽  
Material System ◽  
Operation Speed ◽  
Change Memory

AbstractPhase-change memory (PCM) has considerable promise for new applications based on von Neumann and emerging neuromorphic computing systems. However, a key challenge in harnessing the advantages of PCM devices is achieving high-speed operation of these devices at elevated temperatures, which is critical for the efficient processing and reliable storage of data at full capacity. Herein, we report a novel PCM device based on Ta-doped antimony telluride (Sb2Te), which exhibits both high-speed characteristics and excellent high-temperature characteristics, with an operation speed of 2 ns, endurance of > 106 cycles, and reversible switching at 140 °C. The high coordination number of Ta and the strong bonds between Ta and Sb/Te atoms contribute to the robustness of the amorphous structure, which improves the thermal stability. Furthermore, the small grains in the three-dimensional limit lead to an increased energy efficiency and a reduced risk of layer segregation, reducing the power consumption and improving the long-term endurance. Our findings for this new Ta–Sb2Te material system can facilitate the development of PCMs with improved performance and novel applications.

High Thermo-Mechanical Stability in Polybenzoxazine Aerogels

2019 ◽  
Author(s):  
Sadeq Malakooti ◽  
Guoqiang Qin ◽  
Chandana Mandal ◽  
Chariklia Sotiriou-Leventis ◽  
Nicholas Leventis ◽  
...  
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
High Porosity ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Structural Applications

Abstract Aerogels are three-dimensional networks of nanoparticles with high specific surface area and high porosity. Following the significant improvement on the mechanical strengths and ductility of traditional aerogels with polymer cross-linking (i.e., X-aerogels), the emergence of pure polymeric aerogels has enabled unprecedented aerogel applications such as ballistic armor protection, which is quite surprising for such low-density materials. However, generally low glass transition temperatures (Tg) of polymeric aerogels hinder their structural applicability at service temperatures above their Tg temperatures. Thereby, developing novel polymeric aerogels with high Tg temperatures is crucial for high-temperature structural applications. As phenolic resins, polybenzoxazines are heat-resistant and mechanically strong with high glass transition temperatures. In this study, polybenzoxazine aerogels have been successfully synthesized, and their mechanical properties at different densities and elevated temperatures have been investigated. High thermo-mechanical stability has been observed over the entire temperature range of interest (i.e., below 250 °C) for their quasi-static compressive properties such as Young’s modulus and compressive strength. Moreover, the storage and loss moduli in shear of the aerogels have been studied at different temperatures and frequencies. The strong mechanical performance of these aerogels at elevated temperatures makes them an important, inexpensive, and advanced material for high-temperature applications, competitive with significantly more expensive polyimides.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

High temperature compressive behavior of three-dimensional five-directional braided composites

2018 ◽  
Vol 60 (7-8) ◽  
pp. 772-776 ◽  
Author(s):  
Jiayi Liu ◽  
Junmeng Zhou ◽  
Yu Wang ◽  
Jie Mei ◽  
Jialin Liu
Keyword(s):  
High Temperature ◽  
Three Dimensional ◽  
Compressive Behavior ◽  
Braided Composites

WIELAND-K88

Alloy Digest ◽  
2005 ◽  
Vol 54 (12) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Stress Relaxation ◽  
Copper Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
Relaxation Resistance ◽  
Temperature Performance ◽  
Very High

Abstract Wieland K-88 is a copper alloy with very high electrical and thermal conductivity, good strength, and excellent stress relaxation resistance at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-738. Producer or source: Wieland Metals Inc.

DOWMETAL HZ32XA

Alloy Digest ◽  
1956 ◽  
Vol 5 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Resistance ◽  
Zirconium Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
High Temperature Creep ◽  
Aged Condition ◽  
Chemical Company ◽  
Temperature Performance

Abstract DOWMETAL HZ32XA is a magnesium-thorium-zinc-zirconium alloy having good high temperature creep resistance, and is recommended for applications at elevated temperatures. It is used in the artificially aged condition (T5). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as heat treating, machining, and joining. Filing Code: Mg-26. Producer or source: The Dow Chemical Company.

UDIMET 105

Alloy Digest ◽  
1972 ◽  
Vol 21 (7) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Surface Treatment ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Nickel Base Alloy ◽  
Temperature Performance ◽  
Nickel Base

Abstract UDIMET 105 is a nickel-base alloy which was developed for service at elevated temperatures. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-175. Producer or source: Special Metals Corporation.

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