In-situ TEM Observation for Reaction Mechanism in MgH2 Hydrogen Storage Material

2009 ◽  
Vol 1216 ◽  
Author(s):  
Akifumi Ono ◽  
Shigehito Isobe ◽  
Yongming Wang ◽  
Naoyuki Hashimoto ◽  
Somei Ohnuki
Keyword(s):  
Hydrogen Diffusion ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Desorption Process ◽  
Voltage Electron ◽  
Transmission Electron ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Nano Size

AbstractIn-situ observation on the catalytic effect of Nb2O5 in MgH2 was carried out by using transmission electron microscopy (TEM). We prepared two kinds of samples, because we tried to observe the reaction from two kinds of viewpoints. MgH2 catalyzed with 1 mol% of Nb2O5 was prepared for an overall viewpoint on the desorption process of MgH2 with catalyst by conventional TEM. The dehydrogenation of the 1 mol% sample started at 150 °C and Mg nano-size particles were formed. However, Nb2O5 was not confirmed in diffraction patterns and images, because it was highly dispersed by ball-milled. So MgH2 catalyzed with 10 mol% of Nb2O5 was prepared for local viewpoint to focus the boundary between the catalyst and the Mg phase by high voltage electron micro scope (HVEM). The sample mixed in mortar was prepared for this, because it was difficult to find the boundary in the sample ball-milled. The high resolution images of the 10 mol% sample revealed that the dehydrogenation started from the interface of MgH2 and Nb2O5. The result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH2 phase to the interface between Mg and Nb2O5.

In-Situ TEM Observation for Dehydrogenation Mechanism in MgH2 with Catalyst

2010 ◽  
Vol 654-656 ◽  
pp. 2867-2870 ◽  
Author(s):  
Eri Morita ◽  
Akifumi Ono ◽  
Shigehito Isobe ◽  
Yong Ming Wang ◽  
Naoyuki Hashimoto ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Catalytic Effect ◽  
Hydrogen Diffusion ◽  
In Situ Observation ◽  
Transmission Electron ◽  
Milled Sample ◽  
High Resolution Images ◽  
Dehydrogenation Mechanism

We carried out in-situ observation on the catalytic effect of Nb2O5 in MgH2 by using a high voltage transmission electron microscope (HVEM). We synthesized two kinds of samples, which were prepared by ball milling and by hand mixing. In milled sample, Nb2O5 was not confirmed from high resolution images, however, NbO was identified. As the temperature increased, the decomposition of MgH2 proceeded, while Mg formed and grew. It suggested that NbO had the catalytic effect to promote the dehydrogenation of MgH2. In mixed sample, which was prepared to clearly observe the boundary between the catalyst and Mg phase, it was revealed that the dehydrogenation started from the boundary of MgH2 and Nb2O5. This result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH2 through Mg phase to the boundary.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

In-Situ Observation Of Aln Formation During Nitridation Of Sapphire By Ultrahigh Vacuum Transmission Electron Microscopy

1997 ◽  
Vol 482 ◽  
Author(s):  
M. Yeadon ◽  
M. T. Marshall ◽  
F. Hamdani ◽  
S. Pekin ◽  
H. Morkoc ◽  
...  
Keyword(s):  
Ultrahigh Vacuum ◽  
Ex Situ ◽  
In Situ Observation ◽  
Island Growth ◽  
Kinetic Measurements ◽  
Transmission Electron ◽  
Before And After ◽  
Subsequent Exposure ◽  
Diffraction Patterns

AbstractUsing a novel ultrahigh vacuum transmission electron microscope (UHV TEM) with insitu molecular beam epitaxy capability we have studied the nitridation of (0001) sapphire upon exposure to ammonia. Atomically flat sapphire surfaces for the experiments were obtained by high temperature annealing. Subsequent exposure to ammonia flow at 950°C led to the successful synthesis of epitaxial AIN; the films were characterized in-situ using TEM. Complimentary ex-situ atomic force microscopy (AFM) was also performed in order to characterize the surface morphology before and after nitridation.The experiments indicate that AIN grows by a 3D island growth mechanism. Electron diffraction patterns suggest an abrupt AIN/sapphire interface with no evidence of the formation of Al–O–N compounds. The rate limiting step in the nitridation reaction appears to be the diffusion of nitrogen and oxygen species between the free surface of the growing AIN film and the reaction interface. It is inferred from kinetic measurements that diffusion of these species occurs along the boundaries between coalescing AIN islands.

In-Situ TEM Studies of Sessile Dislocation Arrangements and N Vacancy Ordering in ZrN

2003 ◽  
Vol 779 ◽  
Author(s):  
P. Li ◽  
J.M. Howe
Keyword(s):  
Vacancy Concentration ◽  
Stacking Faults ◽  
In Situ Tem ◽  
Diffuse Intensity ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Vacancy Ordering ◽  
Short Range Ordering ◽  
Diffraction Patterns

AbstractDissociation of perfect 1/2<110> single dislocations into two 1/6<112> Shockley partial dislocations in ZrN was observed by transmission electron microscopy (TEM). The 1/2<110> single dislocations have a super-jog character and are not coplanar with the dissociated Shockley partials. This sessile arrangement of dislocations may be responsible for the brittleness of ZrN. The wide separation of the partial dislocations bounding stacking faults indicates that the stacking-faults energy (SFE) is low in ZrN. The low SFE can be explained on the basis of a high vacancy concentration, which was confirmed by the appearance of diffuse intensity maxima in electron diffraction patterns due to short-range ordering (SRO) of N vacancies. In-situ heating experiments in the TEM revealed that the diffuse intensity maxima disappear during heating and reappear on cooling. This indicates that N (or N vacancy) diffusion scrambles the SRO arrangement of N vacancies during heating. The width of the stacking faults in ZrN increases with temperature, indicating that the SFE decreases as the vacancy concentration increases.

In-situ TEM Observation for Reaction of LiH with NH3 by Means of Environmental Cell

2009 ◽  
Vol 1216 ◽  
Author(s):  
Hiroko Hirasawa ◽  
Shigehito Isobe ◽  
Yongming Wang ◽  
Hikaru Yamamoto ◽  
Hiroki Miyaoka ◽  
...  
Keyword(s):  
Volume Expansion ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Light Weight ◽  
Solid Reaction ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
Environmental Cell ◽  
Tem Transmission Electron Microscopy

AbstractIn-situ observation of the reaction between light weight hydride LiH and NH3 gas was performed by means of TEM (Transmission Electron Microscopy) with an environmental cell. This environmental cell was designed for the observation of the gas-solid reaction under 0 ∼ 0.2 MPa gas atmosphere at 20 ∼ 150 °C. It has been confirmed a volume expansion and generation of LiNH2, that is the reaction between LiH and NH3. Moreover, it was revealed that LiNH2 was generated at the surface of LiH particle at first process of the reactions.

Electronic Cone Illumination with the Conventional Transmission Electron Microscope

1977 ◽  
Vol 35 ◽  
pp. 72-73
Author(s):  
William Krakow
Keyword(s):  
Electronic Device ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Hollow Cone ◽  
Transmission Electron ◽  
Lissajous Figures ◽  
High Resolution Images ◽  
Imaging Mode ◽  
Diffraction Patterns ◽  
Transmission Microscope

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.

In situ TEM measurements of the electrical properties of interface dislocations

1992 ◽  
Vol 50 (2) ◽  
pp. 1338-1339
Author(s):  
F. M. Ross ◽  
R. Hull ◽  
D. Bahnck ◽  
J. C. Bean ◽  
L. J. Peticolas ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Electronic Device ◽  
In Situ Tem ◽  
Device Performance ◽  
Misfit Dislocations ◽  
Electrical Characteristics ◽  
Strained Layer ◽  
Transmission Electron ◽  
Interfacial Dislocations

We describe an investigation of the electrical properties of interfacial dislocations in strained layer heterostructures. We have been measuring both the structural and electrical characteristics of strained layer p-n junction diodes simultaneously in a transmission electron microscope, enabling us to correlate changes in the electrical characteristics of a device with the formation of dislocations.The presence of dislocations within an electronic device is known to degrade the device performance. This degradation is of increasing significance in the design and processing of novel strained layer devices which may require layer thicknesses above the critical thickness (hc), where it is energetically favourable for the layers to relax by the formation of misfit dislocations at the strained interfaces. In order to quantify how device performance is affected when relaxation occurs we have therefore been investigating the electrical properties of dislocations at the p-n junction in Si/GeSi diodes.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Growth kinetics of Al2Cu in an Al-1.5Cu thin film by in Situ TEM

1993 ◽  
Vol 51 ◽  
pp. 1172-1173
Author(s):  
M. Park ◽  
S.J. Krause ◽  
S.R. Wilson
Keyword(s):  
Thin Film ◽  
In Situ Tem ◽  
Collector Plate ◽  
Transmission Electron ◽  
Device Processing ◽  
Corrosion Susceptibility ◽  
Precipitation Phenomena ◽  
Semiconductor Chips ◽  
Kinetics Of

Cu alloying in Al interconnection lines on semiconductor chips improves their resistance to electromigration and hillock growth. Excess Cu in Al can result in the formation of Cu-rich Al2Cu (θ) precipitates. These precipitates can significantly increase corrosion susceptibility due to the galvanic action between the θ-phase and the adjacent Cu-depleted matrix. The size and distribution of the θ-phase are also closely related to the film susceptibility to electromigration voiding. Thus, an important issue is the precipitation phenomena which occur during thermal device processing steps. In bulk alloys, it was found that the θ precipitates can grow via the grain boundary “collector plate mechanism” at rates far greater than allowed by volume diffusion. In a thin film, however, one might expect that the growth rate of a θ precipitate might be altered by interfacial diffusion. In this work, we report on the growth (lengthening) kinetics of the θ-phase in Al-Cu thin films as examined by in-situ isothermal aging in transmission electron microscopy (TEM).

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