Intermediate Si-Al spinel phase formation in phase transformation of diphasic mullite gel

1993 ◽  
Vol 28 (14) ◽  
pp. 3839-3844 ◽  
Author(s):  
A. K. Chakravorty
Keyword(s):  
Phase Transformation ◽  
Phase Formation ◽  
Spinel Phase

Is the olivine–spinel phase transformation martensitic?

Nature ◽  
1982 ◽  
Vol 298 (5872) ◽  
pp. 357-358 ◽  
Author(s):  
P. J. Vaughan ◽  
H. W. Green ◽  
R. S. Coe
Keyword(s):  
Phase Transformation ◽  
Spinel Phase

Improvement of the cyclic deterioration and structural evolution of Li[Li0.2Ni0.2Mn0.6]O2 cathode material by controlling initial charging voltages

RSC Advances ◽  
2016 ◽  
Vol 6 (28) ◽  
pp. 23677-23685 ◽  
Author(s):  
Wuwei Yan ◽  
Yongning Liu ◽  
Shaokun Chong ◽  
Yi-Fang Wu
Keyword(s):  
Phase Transformation ◽  
Cathode Material ◽  
Spinel Phase ◽  
Structural Evolution ◽  
Oxygen Release

The initial stepwise charging suppresses oxygen release and restrains the layered to spinel phase transformation.

TEM and Raman spectroscopy evidence of layered to spinel phase transformation in layered LiNi1/3Mn1/3Co1/3O2 upon cycling to higher voltages

2014 ◽  
Vol 733 ◽  
pp. 6-19 ◽  
Author(s):  
Prasant Kumar Nayak ◽  
Judith Grinblat ◽  
Mikhael Levi ◽  
Yan Wu ◽  
Bob Powell ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Phase Transformation ◽  
Spinel Phase

Enhancement of Aurivillius Phase Formation Kinetics in SBT Thin Films using Nanoparticle Seeding

2003 ◽  
Vol 784 ◽  
Author(s):  
Yun-Mo Sung ◽  
Woo-Chul Kwak ◽  
Se-Yon Jung ◽  
Seung-Joon Hwang
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Phase Transformation ◽  
Phase Formation ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Si Substrates ◽  
Formation Kinetics ◽  
Kinetics Of

ABSTRACTPt/Ti/SiO2/Si substrates seeded by SBT nanoparticles (∼60–80 nm) were used to enhance the phase formation kinetics of Sr0.7Bi2.4Ta2O9 (SBT) thin films. The volume fractions of Aurivillius phase formation obtained through quantitative x-ray diffraction (Q-XRD) analyses showed highly enhanced kinetics in seeded SBT thin films. The Avrami exponents were determined as ∼1.4 and ∼0.9 for unseeded and seeded SBT films, respectively, which reveals different nucleation modes. By using Arrhenius–type plots the activation energy values for the phase transformation of unseeded and seeded SBT thin films were determined to be ∼264 and ∼168 kJ/mol, respectively. This gives a key reason to the enhanced kinetics in seeded films. Microstructural analyses on unseeded SBT thin films showed formation of randomly oriented needle-like crystals, while those on seeded ones showed formation of domains comprised of directionally grown worm-like crystals.

An investigation on thermodynamics and kinetics of η phase formation in Nb-modified iron-nickel base A286 superalloy

2020 ◽  
Vol 118 (1) ◽  
pp. 105
Author(s):  
Reza Soleimani Gilakjani ◽  
Seyed Hossein Razavi ◽  
Masoumeh Seifollahi
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Phase Formation ◽  
Volume Fraction ◽  
Treatment Time ◽  
Diffusion Activation Energy ◽  
Phase Volume Fraction ◽  
Titanium Nickel ◽  
Nickel Base ◽  
Microstructural Studies

In this study, precipitation of η phase (Ni3Ti) in conventional and Nb-modified (Nb-A286) A286 superalloys was evaluated at different aging times and temperatures. The TTP curve of the η phase formation was plotted using thermodynamic analyses, kinetics and microstructural studies. Depending on temperature and heat treatment, the η phase precipitated at the grain boundaries or twin sites, as a result of the γ′ phase or matrix austenite transformation. Heat treatment of conventional A286 superalloy and Nb-A286 was performed within a temperature range of 650 to 900 °C for 2 to 30 h. The η phase transformation was evaluated by scanning electron microscope (SEM) which is equipped to energy dispersive X-ray spectroscopy (EDS) and optical microscopy (OM). In the analyses based on thermodynamic calculations, the interaction of the Gibbs free energy of η phase formation and the diffusion activation energy of the elements, especially titanium and niobium, was considered. The microstructural studies showed that increasing the heat treatment time results in increasing the volume fraction of the η phase. By increasing the aging temperature to 840 and 860 °C for conventional A286 superalloy and Nb-A286 superalloy, respectively, the η phase volume fraction increased, however, further increase led to volume fraction decrease. The results of the thermodynamic analyses showed the tip of the TTP diagrams at temperatures of 860 and 820 °C for the A286 and Nb-A286 alloys, respectively. Investigation of kinetics calculations showed that η phase transformation depends on the diffusion of titanium, nickel, and niobium.

scholarly journals X-Ray Powder Diffraction Studies of Mechanically Milled Cobalt

2012 ◽  
Vol 626 ◽  
pp. 913-917
Author(s):  
W.S. Yeo ◽  
Z. Nur Amirah ◽  
H.S.C. Metselaar ◽  
T.H. Ong
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Surface Energy ◽  
Phase Formation ◽  
Rietveld Method ◽  
High Energy ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Structure Defects ◽  
X Ray

The allotropic phase transformation of cobalt powder prepared by high-energy ball milling was investigated as a function of milling time. Measurement of crystallite size and micro-strain in the powder systems milled for different times were conducted by X-ray diffractometry. The X-ray diffraction (XRD) peaks were analyzed using the Pearson VII profile function in conjunction with Rietveld method. X-ray diffraction line broadening revealed that allotropic transformation between face-centred-cubic phase (fcc) and hexagonal close-packed phase (hcp) in cobalt is grain size dependent and also on the accumulation of structure defects. The results showed that the phase formation of cobalt depends on the mill intensity that influences of both the grain size and the accumulation of structure defects. However, this theory alone is not adequate to explain the effects in this work. It was found that the total surface energy (Ω) theory satisfactorily explains the phase transformation behavior of cobalt. The smaller value of surface energy (Ω) of the fcc crystal than the hcp phase when size decreases may alter the qualitative aspects of the phase formation.

Tem Study of Nanostructured Magnesium Aluminate Spinel Phase Formation

2012 ◽  
pp. 165-174
Author(s):  
Jafar F. Al-Sharab ◽  
James Bentley ◽  
Amit Singhal ◽  
Ganesh Skandan ◽  
Frederic Cosandey
Keyword(s):  
Phase Formation ◽  
Spinel Phase ◽  
Magnesium Aluminate ◽  
Magnesium Aluminate Spinel

Optimization of Phase Formation and Superconducting Properties in MgB2 Prepared by Phase Transformation from MgB4

2012 ◽  
Vol 41 (4) ◽  
pp. 673-678 ◽  
Author(s):  
K. L. Tan ◽  
K. Y. Tan ◽  
K. P. Lim ◽  
A. H. Shaari ◽  
S. K. Chen
Keyword(s):  
Phase Transformation ◽  
Phase Formation ◽  
Superconducting Properties

ASSESSMENT OF THE INFLUENCE OF R-PHASE FORMATION ON THE MATERIAL BEHAVIOR OF NiTi USING A MICROMECHANICAL MODEL

2012 ◽  
Vol 05 (01) ◽  
pp. 1250015 ◽  
Author(s):  
RAINER HEINEN ◽  
SHORASH MIRO
Keyword(s):  
Phase Transformation ◽  
Energy Dissipation ◽  
Phase Formation ◽  
Energy Minimization ◽  
Micromechanical Model ◽  
Strain Curve ◽  
Material Behavior ◽  
Cell Geometry ◽  
Stress Strain Curve ◽  
Geometrical Change

Shape memory alloys (SMA) show several interesting features in their material behavior which are due to martensitic phase transformation. In NiTi , this transformation covers the three crystallographic phases of austenite, martensite, and R-phase. This publication analyzes the influence of the R-phase formation on the overall material behavior by means of a micromechanical model. The model is based on energy minimization with the assumption of a certain energy dissipation when martensite is formed. To simplify the formulation, the dissipation associated with the transformation between austenite and R-phase is neglected, since the geometrical change in unit cell geometry is relatively small in this case. Numerical simulations show that especially the slope reduction in the stress–strain curve, which is known from experiments, can be explained by R-phase formation.

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