In Situ TEM Studies of Metal–Carbon Reactions

2002 ◽  
Vol 8 (4) ◽  
pp. 288-304 ◽  
Author(s):  
Robert Sinclair ◽  
Toshio Itoh ◽  
Richard Chin
Keyword(s):  
Amorphous Carbon ◽  
Crystallization Process ◽  
Metal Layer ◽  
In Situ Tem ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Precipitation Type ◽  
Silicon And Germanium ◽  
Film Form

The reactions which occur between amorphous carbon and a number of first transition metals (Ti, Cr, Fe, Co, Ni, and Cu) have been studied by transmission electron microscopy (TEM). The materials are in thin-film form with the metal layer sandwiched between thicker carbon layers. In four cases, the predominant reaction is the graphitization of the amorphous carbon, at temperatures well below 800°C. This is brought about by the elements themselves in the case of Co and Ni, and by metastable carbides in the case of Fe (Fe3C) and Cr (Cr3C2−x). The Ti–C and Cu–C systems do not exhibit graphitization. For the former, only TiC is produced up to 1000°C, while the carbon does not react at all with copper. In situ TEM studies show the mechanism to be of the dissolution-precipitation type, which is equivalent to the metal-mediated crystallization process for amorphous silicon and germanium. The heat of graphitization is found to be 18–19 kcal/mol-C by differential scanning calorimetry.

scholarly journals In situ TEM-исследование фазовых превращений в нестехиометрическом сплаве Гейслера Ni-=SUB=-46-=/SUB=-Mn-=SUB=-41-=/SUB=-In-=SUB=-13-=/SUB=-

2021 ◽  
Vol 63 (11) ◽  
pp. 1725
Author(s):  
Д.Д. Кузнецов ◽  
Е.И. Кузнецова ◽  
А.В. Маширов ◽  
А.С. Лошаченко ◽  
Д.В. Данилов ◽  
...  
Keyword(s):  
Residual Austenite ◽  
Austenite Phase ◽  
In Situ Tem ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Direct Transition ◽  
Scanning Calorimetry ◽  
Characteristic Temperatures ◽  
Transmission Electron

This paper presents a study of the metamagnetostructural transition of the martensitic type in the Ni46Mn41In13 alloy with magnetic shape memory and inverse magnetocaloric effect. The characteristic temperatures of the direct transition starting Ms = 253 K and its finishing Mf = 164 K, as well as the reverse temperatures As = 203 K and Af = 236 K, respectively, were determined by differential scanning calorimetry. The characteristic peculiarities of the transition: a decrease of the Ms and the presence of a residual austenite phase, as well as pre-martensitic states, were studied using transmission electron microscopy. The estimated the thickness of alloy was 50 nm, when martensitic transition suppressed.

Nickel Mediated Transformation of Amorphous Carbon to Graphite

1994 ◽  
Vol 349 ◽  
Author(s):  
Toshio Itoh ◽  
Robert Sinclair
Keyword(s):  
Amorphous Carbon ◽  
Glassy State ◽  
Temperature Peak ◽  
Scanning Calorimetry ◽  
Precipitation Mechanism ◽  
Transmission Electron ◽  
Nickel Carbide ◽  
Higher Temperature ◽  
In Situ Heating

ABSTRACTReactions between Ni and amorphous carbon (a-C) below 600°C have been investigated using differential scanning calorimetry (DSC) and in situ annealing in a transmission electron microscopy (TEM) of Ni/a-C layered films deposited by DC sputtering. DSC data show that there are two exothermic peaks in the temperature range around 200-600°C. One is a weak and broad peak below 500°C and the other is a strong and sharp peak at around 530°C. In situ heating in the TEM revealed that the low temperature peak corresponds to a series of reactions for nickel carbide (Ni3C) formation and decomposition into Ni and carbon, most likely in a glassy state. The higher temperature peak was found to correspond to graphitization of a-C by a solution-precipitation mechanism. Graphite formed in this process is strongly textured with the (0002) graphite basal planes parallel to the original Ni/a-C interface.

In Situ Tem Study of Reactions in Iron/amorphous Carbon Layered Thin Films

1995 ◽  
Vol 382 ◽  
Author(s):  
Toshio Itoh ◽  
Robert Sinclair
Keyword(s):  
Grain Size ◽  
Amorphous Carbon ◽  
Layered Structure ◽  
Annealing Temperature ◽  
In Situ Tem ◽  
Dc Sputtering ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Deposited Films

ABSTRACTReactions between Fe and amorphous carbon (a-C) below 600ºC have been investigated. In situ annealing in a transmission electron microscopy (TEM) was performed on a-C/Fe/a-C trilayer films deposited by DC sputtering. As-deposited films showed a well defined tri-layered structure and an average Fe grain size of about 50Å. Cementite (Fe3C) grains appeared in the Fe layer by annealing around 300ºC. As the annealing temperature was raised, the number and size of the cementite grains increased. When the annealing temperature reached 500ºC, the Fe layer completely turned into cementite with an average grain size of 1000Å. At this point the film still kept a well defined tri-layered structure even though some parts of the cementitelayer agglomerated. Above 500ºC, the cementite layer started to “move” into the a-C leaving graphite behind. Graphite formed in this process is strongly textured with the (0002) graphite basal planes parallel to the surface of the moving cementite. This process is concluded to be carbide mediated crystallization of a-C, similar to silicide mediated crystallization of silicon in Ni-Si and Pd-Si systems.

scholarly journals In-situ TEM annealing of amorphous Fe-24at.%W coatings and the effect of crystallization on hardness

2020 ◽  
Vol 56 (5) ◽  
pp. 4006-4012
Author(s):  
Antonio Mulone ◽  
Inga Ennen ◽  
Andreas Hütten ◽  
Uta Klement
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Amorphous Structure ◽  
In Situ Tem ◽  
Amorphous Coating ◽  
Scanning Calorimetry ◽  
Plating Bath ◽  
Maximum Value ◽  
Transmission Electron

AbstractThis paper describes the crystallization which occurs upon annealing of an amorphous Fe-24at.%W coatings, electrodeposited from a glycolate-citrate plating bath. A combination of Differential Scanning Calorimetry and in-situ Transmission Electron Microscopy annealing is used to study the onset of crystallization of the amorphous coating. The in-situ TEM analyses reveal the formation of first crystallites after annealing at 400 °C for 30 min. Upon a temperature increase to 500–600 °C, the crystallites develop into Fe-rich nanocrystals with ~ 40 nm grain size. The nanocrystals are dispersed in the remaining amorphous Fe-W matrix, which results in the formation of a mixed nanocrystalline-amorphous structure. The observed crystallization can be held responsible for the increase in the hardness obtained upon annealing of Fe-24at.%W coatings. In fact, the hardness of the as-deposited material increases from 11 to 13 GPa after annealing at 400 °C, and it reaches the maximum value of 16.5 GPa after annealing at 600 °C.

Crystallization of Amorphous Germanium in a Silver Germanium Layered System

1993 ◽  
Vol 311 ◽  
Author(s):  
Toyohiko J. Konno ◽  
Robert Sinclair
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Differential Scanning Calorimetry ◽  
Layered System ◽  
In Situ Tem ◽  
Heat Of Reaction ◽  
Scanning Calorimetry ◽  
Amorphous Germanium ◽  
Transmission Electron

ABSTRACTWe studied crystallization of amorphous germanium (a-Ge) induced in a Ag/a-Ge layered system, using in situ transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Amorphous Ge was found to crystallize at about 270°C with the heat of reaction of 10±lkJ/mol. In situ TEM revealed that Ag grains migrate into the a-Ge phase leaving the crystalline Ge (c-Ge) phase behind. From this observation, we propose a model whereby the Ag provides the fastest path for the Ge atoms to diffuse from a-Ge to c-Ge phases.

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 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.

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).

scholarly journals In-Situ TEM Annealing Observation of Helium Bubble Evolution in Pre-Irradiated FeCoNiCrTi0.2 Alloys

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3727
Author(s):  
Huanhuan He ◽  
Zhiwei Lin ◽  
Shengming Jiang ◽  
Xiaotian Hu ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Vacuum Arc ◽  
In Situ Tem ◽  
Face Centered Cubic ◽  
Helium Bubble ◽  
High Entropy ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
Bubble Evolution ◽  
Face Centered

The FeCoNiCrTi0.2 high-entropy alloys fabricated by vacuum arc melting method, and the annealed pristine material, are face centered cubic structures with coherent γ’ precipitation. Samples were irradiated with 50 keV He+ ions to a fluence of 2 × 1016 ions/cm2 at 723 K, and an in situ annealing experiment was carried out to monitor the evolution of helium bubbles during heating to 823 and 923 K. The pristine structure of FeCoNiCrTi0.2 samples and the evolution of helium bubbles during in situ annealing were both characterized by transmission electron microscopy. The annealing temperature and annealing time affect the process of helium bubbles evolution and formation. Meanwhile, the grain boundaries act as sinks to accumulate helium bubbles. However, the precipitation phase seems have few effects on the helium bubble evolution, which may be due to the coherent interface and same structure of γ’ precipitation and matrix.

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