Controlling the Chemical Order in PMN-Type Relaxors

1998 ◽  
Vol 541 ◽  
Author(s):  
P. K. Davies ◽  
M. A. Akbas
Keyword(s):  
Solid Solution ◽  
Thermal Treatment ◽  
Dielectric Response ◽  
Random Distribution ◽  
Domain Growth ◽  
Site Model ◽  
Charge Model ◽  
Random Site ◽  
Space Charge Model ◽  
The Stability

AbstractInvestigations of pure and chemically substituted tantalate and niobate members of the Pb(Mg1/3 Nb2/3)O3 (PMN) family of perovskite relaxors demonstrate that the degree of cation ordering and size of the chemically ordered domains can be extensively modified by thermal treatment. These observations and refinements of the cation occupancies in well ordered samples conflict with the predictions of the widely accepted “space charge model”, and instead support a “random site” model for the 1:1 B-site ordering. In this model one of the positions in the ordered structure is occupied by Ta (or Nb) and the other contains a random distribution of Mg and the remaining Ta cations. The stability of the order and magnitude of the domain growth can be enhanced by relatively small concentrations of selected solid solution additives (e.g. Zr in Pb(Mg1/3Ta2/3)O3 (PMT); Th or Sc in PMN). Correlations between the stability of the 1:1 order and the size of the solid solution additive can be used to understand the different responses of the cation order in PMN and PMT to thermal treatment. Results are also presented for the dielectric response of fully ordered relaxors in the (l–x) Pb(Mg1/3Ta2/3)O3 – (x) Pb(Sc1/2 Ta1/2)O3 system. While large domain samples of PMT-rich compositions exhibit a relaxor response, a crossover to normal ferroelectric behavior is observed for x = 0.5. The change in the dielectric response can be rationalized in terms of the effect of the chemistry of the random site sub-lattice on the correlation length of the ferroelectric coupling.

A review on phase prediction in high entropy alloys

2021 ◽  
pp. 095440622110089
Author(s):  
Vinay Kumar Soni ◽  
S Sanyal ◽  
K Raja Rao ◽  
Sudip K Sinha
Keyword(s):  
Solid Solution ◽  
Phase Formation ◽  
Single Phase ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Modeling Tools ◽  
High Entropy ◽  
Recent Developments ◽  
Phase Prediction ◽  
The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

Influence of Force Chains Behaviors on Strength of Al/W/PTFE Granular Composite

2021 ◽  
Vol 324 ◽  
pp. 94-99
Author(s):  
Le Tang ◽  
Die Hu ◽  
Sheng Zhou ◽  
Chao Ge ◽  
Hai Fu Wang ◽  
...  
Keyword(s):  
Random Distribution ◽  
Force Chains ◽  
Metal Particles ◽  
Fracture Mechanisms ◽  
Mesoscale Simulation ◽  
Dynamic Simulations ◽  
Granular Composite ◽  
Compressive Response ◽  
Cracks Propagation ◽  
The Stability

Mesoscale simulation is conducted to investigate the effect of force chains between metal particles on the mechanical behavior of aluminum-tungsten-polytetrafluoroethylene (Al/W/PTFE) granular composite under a strain-controlled loading. A two-dimensional model followed the random distribution of particles is developed. Dynamic simulations are performed with variations in the size of Al particles to reveal the strength and fracture mechanisms of the composites. The results indicate that, force chains governed by the number and the size of metal particles significantly affects the global compressive response and macro-cracks propagation. The stability and reconstruction of mesoscale force chains explain the phenomenon that a higher strength is observed in the material with fine Al particles. Combined with the angle between particles, we examine the properties of force chains and the network as they evolve during the course of the deformation. Findings indicate that reactive composites tend to produce shorter chains, and straighter force chains with a smaller force angle result in a macroscopically stronger granular material.

Perovskite structure and low frequency relaxor- like- dielectric response of (Sr,Ce)TiO3 solid solution

2017 ◽  
Vol 43 (18) ◽  
pp. 16376-16383 ◽  
Author(s):  
Burhan Ullah ◽  
Wen Lei ◽  
Xiao-Qiang Song ◽  
Xiao-Hong Wang ◽  
Wen-Zhong Lu
Keyword(s):  
Solid Solution ◽  
Dielectric Response ◽  
Perovskite Structure ◽  
Low Frequency

Thermal Treatment as a Means of Improving the Stability of Earth Masses

Géotechnique ◽  
1958 ◽  
Vol 8 (4) ◽  
pp. 158-165 ◽  
Author(s):  
A. A. Beles ◽  
I. I. Stănculescu
Keyword(s):  
Thermal Treatment ◽  
The Stability

scholarly journals Carbonitration of a Tool for Pressing Stainless Steel Pipes

2020 ◽  
Vol 7 (2) ◽  
pp. C17-C21
Author(s):  
I. V. Ivanov ◽  
M. V. Mohylenets ◽  
K. A. Dumenko ◽  
L. Kryvchyk ◽  
T. S. Khokhlova ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Treatment ◽  
Heat Resistance ◽  
Alkali Metals ◽  
Matrix Ring ◽  
High Hardness ◽  
Operating Conditions ◽  
Matrix Rings ◽  
Conventional Heat Treatment ◽  
The Stability

To upgrade the operational stability of the tool at LLC “Karbaz”, Sumy, Ukraine, carbonation of tools and samples for research in melts of salts of cyanates and carbonates of alkali metals at 570–580 °C was carried out to obtain a layer thickness of 0.15–0.25 mm and a hardness of 1000–1150 НV. Tests of the tool in real operating conditions were carried out at the press station at LLC “VO Oscar”, Dnipro, Ukraine. The purpose of the test is to evaluate the feasibility of carbonitriding of thermo-strengthened matrix rings and needle-mandrels to improve their stability, hardness, heat resistance, and endurance. If the stability of matrix rings after conventional heat setting varies around 4–6 presses, the rings additionally subjected to chemical-thermal treatment (carbonitration) demonstrated the stability of 7–9 presses due to higher hardness, heat resistance, the formation of a special structure on the surface due to carbonitration in salt melts cyanates and carbonates. Nitrogen and carbon present in the carbonitrided layer slowed down the processes of transformation of solid solutions and coagulation of carbonitride phases. The high hardness of the carbonitrified layer is maintained up to temperatures above 650 °C. If the stability of the needle-mandrels after conventional heat treatment varies between 50–80 presses, the needles, additionally subjected to chemical-thermal treatment (carbonitration) showed the stability of 100–130 presses due to higher hardness, wear resistance, heat resistance, the formation of a special surface structure due to carbonitration in melts of salts of cyanates and carbonates. Keywords: needle-mandrel, matrix ring, pressing, heat treatment, carbonitration.

scholarly journals Optimisation of functional properties in lead-free BiFeO3–BaTiO3 ceramics through La3+ substitution strategy

2018 ◽  
Vol 6 (13) ◽  
pp. 5378-5397 ◽  
Author(s):  
Ilkan Calisir ◽  
Abdulkarim. A. Amirov ◽  
Annette K. Kleppe ◽  
David A. Hall
Keyword(s):  
Solid Solution ◽  
Thermal Treatment ◽  
Functional Properties ◽  
Lead Free ◽  
Chemical Homogeneity ◽  
La Substitution

The structure and key functional properties of a promising lead-free solid solution, BiFeO3–BaTiO3, have been optimised by controlling chemical homogeneity via La-substitution strategies and thermal treatment.

Influence of Quenching Parameters on the Stability of the β Solid Solution in a High-Strength Titanium Alloy

2019 ◽  
Vol 120 (5) ◽  
pp. 476-482
Author(s):  
A. G. Illarionov ◽  
I. V. Narygina ◽  
S. M. Illarionova ◽  
M. S. Karabanalov
Keyword(s):  
Solid Solution ◽  
Titanium Alloy ◽  
High Strength ◽  
The Stability
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