In-Situ Heating Observations on Superlattice Dislocation in A Ni3(Al, Zr) Single Crystal

1994 ◽  
Vol 364 ◽  
Author(s):  
Yi Liu ◽  
Yuefeng Gu ◽  
Dongliang Lin ◽  
Shipu Chen ◽  
Xiaoning Zhao ◽  
...  
Keyword(s):  
Single Crystal ◽  
Significant Variation ◽  
Room Temperature ◽  
Peak Temperature ◽  
Burgers Vector ◽  
Superlattice Dislocation ◽  
Weak Beam ◽  
In Situ Heating ◽  
Beam Technique

AbstractThe TEM weak-beam technique has been used to investigate the behavior of dissociated superlattice dislocation in Ni3Al single crystal as a function of temperature. The observed dislocation with the Burgers vector of [110] partly dissociated on the (001) plane forming Kear-Wilsdorf (KW) lock. The dissociated pair did not indicate significant variation of separation in the temperature range from room temperature to 773K. but turned to form a jog at 773K. At 898K, which is near the peak temperature, the dissociated segment constricted completely. The experimental observations are discussed.

Electron microscope studies of climb of dissociated dislocations

1978 ◽  
Vol 36 (1) ◽  
pp. 324-325
Author(s):  
C.B. Carter ◽  
D. Cherns ◽  
P.B. Hirsch ◽  
H. Saka
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Point Defects ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Al Alloys ◽  
Weak Beam ◽  
High Supersaturation ◽  
Beam Technique

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.

Tem Study of Dislocations in Plastically Deformed AlN

1992 ◽  
Vol 242 ◽  
Author(s):  
V. Audurier ◽  
J. L. Demenet ◽  
J. Rabier
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Compound Semiconductors ◽  
Burgers Vector ◽  
Weak Beam ◽  
Deformation Substructure ◽  
Transmission Electron ◽  
Doping Effects ◽  
Electronic Doping ◽  
Beam Technique

ABSTRACTAlN ceramics were plastically deformed using uniaxial compression under hydrostatic pressure between room temperature (RT) and 800°C. Deformation microstructures have been studied by Transmission Electron Microscopy (TEM) using the weak beam technique. The deformation substructure at RT is characterized by perfect glide loops with 1/3<1120> Burgers vector in (0001) elongated in the screw direction. When deformation temperature increases, the screw character is associated to cross slip events and dislocation dipolesare found. In the investigated temperature range, slip of dislocations with 1/3<1120> Burgers vector is also evidenced on prismatic planes. Weak beam observations failed to evidence any dislocation splitting. Some of these dislocation properties, similar to those of III-V compound semiconductors, suggest that electronic doping effects could be used to control plastic behaviour of covalent ceramics.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

scholarly journals Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 202
Author(s):  
Miranda Martinez ◽  
Anil R. Chourasia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Interaction ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Increasing Trend ◽  
Substrate Temperatures ◽  
Beam Technique

The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

An In Situ Observation of Slip Deformation in a Compressed Ti-Mo-Al Single Crystal

2018 ◽  
Vol 941 ◽  
pp. 1463-1467
Author(s):  
Ryotaro Hara ◽  
Masaki Tahara ◽  
Tomonari Inamura ◽  
Hideki Hosoda
Keyword(s):  
Martensitic Transformation ◽  
Slip System ◽  
Single Crystal ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Martensite Phase ◽  
Slip Direction ◽  
Β Phase ◽  
Slip Deformation

The stress-induced martensitic transformation and slip deformation behavior were investigated by the compression test with anin-situobservation in a Ti-6Mo-10Al (mol %) alloy single crystal. Owing to the stress-induced martensitic transformation from the parent β phase to the α′′ martensite phase, the single crystal of α′′ martensite without internal twinnings was successfully obtained at room temperature. By further compression, the slip deformation occurred in the single crystal of α′′ martensite. The operated slip system in the α′′ martensite was analyzed by the two face trace analyses, and the slip direction was determined to be []o.

Experimental Tem and Image Simulation of Dislocations in Ti3A1

1994 ◽  
Vol 364 ◽  
Author(s):  
JÖrg M.K. Wiezorek ◽  
S. A. Court ◽  
C.J. Humphreys
Keyword(s):  
Fine Structure ◽  
Room Temperature ◽  
Stacking Faults ◽  
Antiphase Boundary ◽  
Computational Techniques ◽  
Image Simulation ◽  
Prism Plane ◽  
Weak Beam ◽  
Transmission Electron ◽  
Beam Technique

AbstractThe fine structure and the character of a dislocations on prism planes have been determined for room-temperature deformed polycrystalline Ti3Al using a combination of experimental and computational techniques of transmission electron microscopy (TEM). Within the resolution limits of the weak-beam technique the fine structure of prism plane a dislocations in Ti3Al is found to be planar and to comprise only a single ribbon of antiphase boundary and no experimentally observable stacking faults.

Phase Transformations in Sol-Gel PZT Thin Films

2000 ◽  
Vol 623 ◽  
Author(s):  
D.P. Eakin ◽  
M.G. Norton ◽  
D.F. Bahr
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Room Temperature ◽  
Structural Changes ◽  
Sol Gel ◽  
Ex Situ ◽  
Ambient Conditions ◽  
Crystalline Films ◽  
In Situ Heating

AbstractThin films of PZT were deposited onto platinized and bare single crystal NaCl using spin coating and sol-gel precursors. These films were then analyzed using in situ heating in a transmission electron microscope. The results of in situ heating are compared with those of an ex situ heat treatment in a standard furnace, mimicking the heat treatment given to entire wafers of these materials for use in MEMS and ferroelectric applications. Films are shown to transform from amorphous to nanocrystalline over the course of days when held at room temperature. While chemical variations are found between films crystallized in ambient conditions and films crystallized in the vacuum conditions of the microscope, the resulting crystal structures appear to be insensitive to these differences. Significant changes in crystal structure are found at 500°C, primarily the change from largely amorphous to the beginnings of clearly crystalline films. Crystallization does occur over the course of weeks at room temperature in these films. Structural changes are more modest in these films when heated in the TEM then those observed on actual wafers. The presence of Pt significantly influences both the resulting structure and morphology in both in situ and ex situ heated films. Without Pt present, the films appear to form small, 10 nm grains consisting of both cubic and tetragonal phases, whereas in the case of the Pt larger, 100 nm grains of a tetragonal phase are formed.

scholarly journals Lactide polymerization with iron alkoxide complexes

2015 ◽  
Vol 93 (6) ◽  
pp. 594-601 ◽  
Author(s):  
Arek Keuchguerian ◽  
Berline Mougang-Soume ◽  
Frank Schaper ◽  
Davit Zargarian
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Side Reactions ◽  
X Ray Diffraction ◽  
Iron Cluster ◽  
X Ray ◽  
H Nmr ◽  
Exchange Product

This report presents the results of a study on the preparation of iron alkoxide complexes chelated by diiminopyridine ligands and their role in the room temperature polymerization of rac-lactide. Reaction of N,N′-(p-R-C6H4CH2)2-diiminopyridines (R = H (1), F (2)) with FeX2 (X = Cl, Br) yielded the homoleptic complexes [(1)2Fe][FeX4] or [(2)2Fe][FeX4], respectively. Treating the latter with Na[BPh4] afforded the anion exchange product [(2)2Fe][BPh4]2, which was characterized by 1H NMR and absorption spectroscopy, combustion analysis, and single crystal X-ray diffraction. Various attempts to grow crystals of [(1)2Fe][FeX4] and [(2)2Fe][FeX4] culminated in the isolation of single crystals of [(2)2Fe][Cl6Fe2O] that was characterized by X-ray diffraction. Attempted synthesis of well-defined, mononuclear alkoxide derivatives from [(1)2Fe]2+ or [(2)2Fe]2+ gave mostly intractable products, but in one case we obtained the crystallographically characterized sodium iron cluster Na4Fe2(OC6H4F)8(THF)2. An aryloxide derivative proved accessible by reaction of NaOC6H4F with the mono-ligand precursor LFeCl2 (L = N,N′-dimesityl-diiminopyridine), but characterization of LFe(OC6H4F)2 was limited to a single crystal X-ray diffraction analysis, owing to unsuccessful attempts at isolating pure samples. The difficulties encountered in the isolation of pure alkoxide derivatives prompted us to use in-situ generated LFe(OEt)2 for studying the polymerization of rac-lactide. This system was found to be moderately active at room temperature and with a slight preference for the formation of a heterotactic polymer (Pr = 0.54–0.65). Large polydispersities of 1.5–2.0 indicated the presence of transesterification side-reactions, which were confirmed by the presence of peaks with m/z = n 144 + M(EtOH) + M(Na+) and m/z = (n + 0.5) 144 + M(EtOH) + M(Na+) in MALDI-MS.

Weak beam image of a superlattice dislocation in deformed Ni3 (AlHfB)

1990 ◽  
Vol 48 (4) ◽  
pp. 476-477
Author(s):  
X. F. Wu
Keyword(s):  
Dislocation Structure ◽  
Room Temperature ◽  
Deformation Behaviour ◽  
Temperature Deformation ◽  
Superlattice Dislocation ◽  
Weak Beam ◽  
Beam Image ◽  
Spark Erosion ◽  
Work Hardening Rate ◽  
Increasing Temperature

A number of intermetallic compounds with the L12 structure exhibit a strange increase in the flow stress and work-hardening rate with increasing temperature. Despite the success of some model in explaining macroscopic properties, the detailed dislocation processes of model that are assumed to take place have not been observed in microscope. This work is an attempt to determine how the dislocation fine structure is related to the deformation behaviour of L12.Single crystal Ni-23Al-1Hf-0.1B(at%) was used in the present study. direction was chosen as compression axis. Samples were deformed to plastic strain of 6%, specimens were cut parallel to by spark erosion. Fined electropolishing was donein solution of 1% perchloric acid in methanol at −50°c and 30V. The g/3g diffraction condition used in weak beam observation.Fig1 shows the dislocation structure in foil. Long fairly straight screw dislocations with b=a[011] are imaged. The formation of dipoles is regarded as a characteristic and unusual feature of the dislocation structure. This indicates that annihilation is difficult at room temperature deformation. Weak beam images of superlattice dislocations are shown in fig.2 by using different reflections. The dislocation CC is long straight screw dislocation.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2019 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.51 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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