Understanding Precursor Phenomena for the R-Phase Transformation in Ti-Ni-Based Alloys

MRS Bulletin ◽  
2002 ◽  
Vol 27 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Daisuke Shindo ◽  
Yasukazu Murakami ◽  
Takuya Ohba
Keyword(s):  
Phase Transformation ◽  
Diffuse Scattering ◽  
Parent Phase ◽  
Martensitic Transformations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements ◽  
Transmission Electron ◽  
Critical Issues ◽  
Structural Modulation

AbstractPrecursor phenomena are critical issues for martensitic transformations. In this article, we show recent progress in understanding precursor phenomena to the R-phase transformation, which is important for both fundamentals and applications. Structural modulation in the parent phase was intensively studied by means of detailed analyses of the weak diffuse scattering of electrons with the aid of recently developed energy-filtered transmission electron microscopy coupled with x-ray diffraction. A peculiar domain-like structure, which originates from static transverse atomic displacements in the parent phase, was discovered by virtue of these advanced methods. The characteristics of this structure (e.g., size, shape, and temperature-dependence), as well as its role in the subsequent R-phase transformation, are discussed.

Phase Transformation of Powdered Material by Using Metal Jet

2012 ◽  
Vol 706-709 ◽  
pp. 741-744 ◽  
Author(s):  
Akio Kira ◽  
Ryuichi Tomoshige ◽  
Kazuyuki Hokamoto ◽  
Masahiro Fujita
Keyword(s):  
Phase Transformation ◽  
Powdered Material ◽  
Scanning Transmission Electron Microscope ◽  
Ultrahigh Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Metal Jet ◽  
Very High

The various techniques of phase transformation of the material have been proposed by many researchers. We have developed several devices to generate the ultrahigh pressure by using high explosive. One of them uses metal jets. It is expected that the ultrahigh pressure occurs by the head-on collision between metal jets, because the velocity of the metal jet is very high. By mixing a powdered material with metal jets, the pressure of the material becomes high. The purpose of this study is to transform the phase of the powdered material by using this high pressure. The powders of the graphite and hBN were applied. The synthesis to the diamond and cBN was confirmed by X-ray diffraction (XRD). In this paper, the mechanism of the generation of the ultrahigh pressure is explained and the results of the observation of the powder by using scanning transmission electron microscope (STEM) are reported.

Crystalline phase transformation of colloidal cadmium sulfide nanocrystals

2017 ◽  
Vol 31 (06) ◽  
pp. 1750037
Author(s):  
M. Ghali ◽  
A. M. Eissa ◽  
M. M. Mosaad
Keyword(s):  
Phase Transformation ◽  
Optical Absorption ◽  
Crystalline Phase ◽  
Growth Conditions ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
X Ray ◽  
Ph Values ◽  
Transmission Electron

In this paper, we give a microscopic view concerning influence of the growth conditions on the physical properties of nanocrystals (NCs) thin films made of CdS, prepared using chemical bath deposition CBD technique. We show a crystalline phase transformation of CdS NCs from hexagonal wurtzite (W) structure to cubic zincblende (ZB) when the growth conditions change, particularly the solution pH values. This effect was confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) measurements. The optical absorption spectra allow calculation of the bandgap value, [Formula: see text], where significant increase [Formula: see text]200 meV in the CdS bandgap when transforming from Hexagonal to Cubic phase was found.

STUDY OF HYDROTHERMAL SYNTHESIS AND PROPERTIES OF Bi2Fe4O9

2010 ◽  
Vol 03 (03) ◽  
pp. 173-176 ◽  
Author(s):  
YIBO WANG ◽  
HUAJUN SUN ◽  
JING ZHOU ◽  
BO LI ◽  
CHENGYONG ZHANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Dielectric Properties ◽  
X Ray Diffraction ◽  
Impedance Analyzer ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Highly oriented Bi2Fe4O9 nanosheets can be fabricated with Fe(NO3)3 ⋅ 9H2O and Bi(NO3)3 ⋅ 5H2O using the low-temperature hydrothermal method. The as-prepared powders are characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), which exhibit an excellent orientation along the (00l) planes. The leakage current density and dielectric properties of the nanosheet samples are measured by Radiant Precision Workstation and HP4291B Impedance Analyzer, respectively. The effects of NaOH concentration on the phase transformation, sheet size and morphologies of the Bi2Fe4O9 crystallites are studied in this paper.

scholarly journals Structures of AlN/VN Superlattices with Different AlN Layer Thicknesses

2002 ◽  
Vol 17 (5) ◽  
pp. 1224-1231 ◽  
Author(s):  
Quan Li ◽  
I. W. Kim ◽  
S. A. Barnett ◽  
L. D. Marks
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Structural Model ◽  
Hexagonal Wurtzite Structure ◽  
X Ray Diffraction ◽  
Rock Salt Structure ◽  
X Ray ◽  
Transmission Electron ◽  
Salt Structure

AlN/VN superlattices with different periods were studied using x-ray diffraction and transmission electron microscopy (TEM). A phase transformation of the AlN from an epitaxially stabilized rock-salt structure to a hexagonal wurtzite structure was observed for an AlN layer thickness greater than 4 nm. A structural model is proposed on the basis of TEM results for the orientation of the transformed phase. The VN layer grown on top of the hexagonal AlN was observed to be reoriented compared to that in the stabilized B1-AlN/VN. The VN nucleated by taking the w-AlN(002) plane as its (111) plane instead of the (002) plane.

Ferricoxychloride and Hematite Nanoparticles: Synthesis and Phase Transformation

2006 ◽  
Vol 518 ◽  
pp. 63-66 ◽  
Author(s):  
M. Marinović-Cincović ◽  
Guillaume Wang ◽  
Michel Fedoroff ◽  
Z.V. Šaponjić ◽  
S.K. Milonjić ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Precise Determination ◽  
Recrystallization Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Synthetic Procedure ◽  
Vis Spectroscopy ◽  
Hydrolysis Of

A synthetic procedure based on thermal hydrolysis of iron(III) chloride solutions for the preparation of hematite (α-Fe2O3) and ferricoxychloride (FeOCl) colloids consisting of nanoparticles (NPs) is described. Transmission electron microscopy indicated that both colloids consisted of particles smaller than 10 nm. X-ray diffraction measurements revealed transformation of FeOCl NPs into α-Fe2O3 NPs after a few months. The phase transformation was explained in terms of redissolution – recrystallization process. UV-vis spectroscopy was used for precise determination of the band gap of α-Fe2O3.

scholarly journals Microstructure And Texture Evolution During Cold-Rolling In The Fe-23Mn-3Si-3Al Alloy

2015 ◽  
Vol 60 (3) ◽  
pp. 1789-1794 ◽  
Author(s):  
J. Kowalska ◽  
W. Ratuszek ◽  
M. Witkowska ◽  
A. Zielińska-Lipiec ◽  
M. Kowalski
Keyword(s):  
Cold Rolling ◽  
Texture Evolution ◽  
Martensitic Transformations ◽  
Mechanical Twinning ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Cold Rolled ◽  
Hot Rolled

Abstract Fe–23wt.%Mn–3wt.%Si–3wt.%Al alloy was cast, homogenized at 1150ºC, hot-rolled at temperatures between 1200ºC and 900ºC and next cold-rolled from 5% up to 40% reductions in thickness. Microstructure and texture of this alloy, which has a low stacking fault energy, were defined after cold-rolling. Investigation of transmission electron microscopy and X-ray diffraction showed that mechanical twinning and martensitic transformations (γfcc→εhcp and γfcc→εhcp→α′bcc) took place during cold-rolling. The crystallographic Shoji-Nishiyama (S-N) {00.2}ε║{111}γ, <11.0>ε ║ <110>γ and Kurdjumov-Sachs (K-S) {111}γ║{101}α’, <101>γ║<111>α’ relations between martensite (ε, α’) and austenite (γ), were found in the coldrolled material.

Phase Transformations on Aging Cu-Al-Ni β Phase Alloys

1983 ◽  
Vol 21 ◽  
Author(s):  
S. W. Husain ◽  
P. C. Clapp ◽  
M. Ahmed
Keyword(s):  
Martensitic Transformation ◽  
Phase Transformations ◽  
Parent Phase ◽  
Isothermal Kinetics ◽  
X Ray Diffraction ◽  
Subsequent Aging ◽  
X Ray ◽  
Β Phase ◽  
Transmission Electron ◽  
Equilibrium Phases

ABSTRACTThe phase transformations occurring on quenching and subsequent aging of a Cu-Al-Ni β phase alloy have been studied using transmission electron microscopy, x-ray diffraction and optical microscopy. Quenching produces an ordered solid solution, β1, based on the DO3 structure of Cu3A1. X-ray and electron diffraction show satellite diffraction peaks. On aging, these satellite peaks disappear and the parent phase undergoes a martensitic transformation. It is suggested that the parent phase undergoes a process of phase separation through the mechanism of spinodal decomposition before the martensitic transformation occurs. The martensitic transformation shows isothermal kinetics for which a transformation diagram is presented. Prolonged aging results in the formation of equilibrium phases.

The Debye Temperature of Carbonyl Iron

1960 ◽  
Vol 4 ◽  
pp. 93-107
Author(s):  
Charles P. Gazzara
Keyword(s):  
Temperature Gradient ◽  
Ambient Temperature ◽  
Diffraction Study ◽  
Carbonyl Iron ◽  
Diffuse Scattering ◽  
Characteristic Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Displacements ◽  
Integrated Intensities

AbstractThe Debye characteristic temperature, θ, of carbonyl iron has been determined as being between 433 and 445°K at an ambient temperature of 310°K from an X-ray diffraction study utilizing both monochromatlzed and filtered radiation by both stationary and scanning slit methods.In computing θ, several factors have been taken into consideration; the diffracted integrated intensities have been corrected for temperature diffuse scattering (TDS); the temperature gradient through the specimen was found to be critical and given as 160°K/in. at 95°K; corrections for the temperature dependence of θ have been made; and extinction effects were investigated, and results contrary to those of U'lna, Krltskaya, and Kurdyumov have been found.The TDS corrected values for static and dynamic atomic displacements are also given.

Microstructures of Fe-Pd Alloy Ribbons Subjected to Rapidly Solidified Melt Spinning

2013 ◽  
Vol 738-739 ◽  
pp. 431-435
Author(s):  
Yoichi Kishi ◽  
Takeshi Kubota ◽  
Zenjiro Yajima ◽  
Teiko Okazaki ◽  
Yasubumi Furuya ◽  
...  
Keyword(s):  
Pole Figure ◽  
Melt Spinning ◽  
Room Temperature ◽  
Parent Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Oriented Texture ◽  
Pd Alloy ◽  
Rapidly Solidified

Microstructures of the Fe-29.6at%Pd alloy ribbons were observed with an X-ray diffractometer and a transmission electron microscope. The X-ray diffraction profiles at room temperature showed that the ribbon consists of FCT martensitic phase and FCC parent phase. Moreover, the ribbon exhibits a strongly 200-oriented texture analyzing with pole figure measurements. TEM bright field images for the cross section of the ribbon showed high-density striation in the FCT martensite variants. Twin-related two sets of reflections were observed in the SAED patterns taken of the FCT martensite variants. FCT was nearly parallel to the thickness direction according to the analysis of the SAED patterns. This result corresponds to the pole figure measurements.

The effect of TiO2 addition on the thermal behavior of sol-gel derived β-spodumene powders

1999 ◽  
Vol 14 (1) ◽  
pp. 97-102 ◽  
Author(s):  
Moo-Chin Wang
Keyword(s):  
Phase Transformation ◽  
Sol Gel ◽  
Transformation Process ◽  
X Ray Diffraction ◽  
Crystallization Sequence ◽  
X Ray ◽  
Transmission Electron ◽  
Tio2 Addition ◽  
A Minor ◽  
Increasing Temperature

The effect of TiO2 addition on the crystallization and phase transformation process in Li2O · Al2O3 · 4SiO2 gels with various TiO2 contents was investigated using differential thermal analysis, x-ray diffraction, and transmission electron microscopy. The activation energy increased from 98.2 to 184.6 kcal/mol as the TiO2 content rose from 2.0 to 8.0 wt. %. The crystallization sequence and phase transformation were similar in LAS gels with various wt.% of TiO2 additions, except in the case of a 2.0 wt.% TiO2 content. During calcination from 800 to 1200 °C, crystallization of the β-spodumene phase progressed with increasing temperature, and a minor crystalline phase, rutile, also appeared.

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