scholarly journals In situ TEM observation of FCC Ti formation at elevated temperatures

2017 ◽  
Vol 140 ◽  
pp. 9-12 ◽  
Author(s):  
Qian Yu ◽  
Josh Kacher ◽  
Christoph Gammer ◽  
Rachel Traylor ◽  
Amit Samanta ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
In Situ Tem

Small Lead and Indium Inclusions in Aluminium

1991 ◽  
Vol 235 ◽  
Author(s):  
E. Johnson ◽  
K. Hjemsted ◽  
B. Schmidt ◽  
K. K. Bourdelle ◽  
A. Johansen ◽  
...  
Keyword(s):  
Melting Point ◽  
Elevated Temperatures ◽  
Supersaturated Solution ◽  
In Situ Tem ◽  
Initial Growth ◽  
Heating And Cooling ◽  
Moiré Fringes ◽  
The Matrix ◽  
Spontaneous Phase

ABSTRACTIon implantation of lead or indium into aluminium results in spontaneous phase separation and formation of lead or indium precipitates. The precipitates grow in topotactical alignment with the matrix, giving TEM images characterized by moiré fringes. The size and density of the precipitates increase with increasing fluence until coalescence begins to occur. Implantations at elevated temperatures lead to formation of larger precipitates with well developed facets. This is particularly significant for implantations above the bulk melting point of the implanted species. Melting and solidification have been followed by in-situ TEM heating and cooling experiments. Superheating up to ∼ 50 K above the bulk melting point has been observed, and the largest inclusions melt first. Melting is associated with only partial loss of facetting of the largest inclusions. Initial growth of the inclusions occurs by trapping of atoms retained in supersaturated solution. Further growth occurs by coalescence of neighbouring inclusions in the liquid phase. Solidification is accompanied by a strong undercooling ∼ 30 K below the bulk melting point, where the smallest inclusions solidify first. Solidification is characterized by spontaneous restoration of the facets and the topotactical alignment.

An in situ TEM study of nucleation and growth of the Ω phase in an Al-4.0Cu-0.5Mg-0.5Ag alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 526-527
Author(s):  
A. Garg ◽  
J. M. Howe
Keyword(s):  
Elevated Temperatures ◽  
Cold Water ◽  
Nucleation And Growth ◽  
Age Hardening ◽  
In Situ Tem ◽  
Dislocation Loops ◽  
Ω Phase ◽  
Actual Mechanism ◽  
New Phase

Addition of small amounts of Ag to Al-Cu-Mg alloy with high Cu:Mg ratios stimulates precipitation of a new phase, designated Ω, which has an orthorhombic structure and forms as thin coherent hexagonal plates on {lll} α planes. This phase significantly increases the age hardening characteristics of the alloy, particularly at elevated temperatures. The mechanism of nucleation of Ω phase is not known but is believed to be fundamentally different from that of θ’ and S’ phases which also form in these alloys. The presence of Ag and Mg only in trace quantities makes the problem of finding the actual mechanism of nucleation of Ω phase difficult.An in situ hot stage TEM study was conducted on an Al-4.0Cu-0.5Mg-0.5Ag(wt.%) alloy in order to understand the nucleation and growth behavior of Ω phase. Two types of initial microstructures were used: 1) homogenized, solution-treated and cold water-quenched, 2) as-quenched and aged for 1 hr. at 190°C. The as-quenched structure shown in Fig. 1(a) consists of a high density of small dislocation loops, some helical dislocations and a few straight dislocations. When this foil was heated in the microscope, observable precipitation occured at about 205°C.

In situ TEM Observations of Grain Growth in Nanograined Thin Films

2004 ◽  
Vol 854 ◽  
Author(s):  
K. Hattar ◽  
J. Gregg ◽  
J. Han ◽  
T. Saif ◽  
I. M. Robertson
Keyword(s):  
Thin Films ◽  
Grain Growth ◽  
Elevated Temperatures ◽  
Critical Role ◽  
Grain Structure ◽  
In Situ Tem ◽  
Free Standing ◽  
Transmission Electron Microscopy Analysis ◽  
Cu Films

ABSTRACTIn situ transmission electron microscopy analysis is used to study the stability of nanograined and ultra-fine grained thin films at elevated temperatures. In the free-standing Au and Cu films, grain growth was dependent on annealing temperature and time with growth observed in both materials at temperatures greater than 373K. Both materials exhibited abnormal grain growth although it was more prevalent in Au than in Cu, which may be a consequence of pinning of the Cu grain boundaries by impurities. The formation and destruction of twins was observed to play a critical role in the grain growth, with the twins retarding the growth in gold, but not in Cu. In constrained Au films no grain growth was observed on annealing at temperatures below 636 K. At 636 K, the eutectic temperature, the microstructure transformed to the eutectic structure with the first stage being the annihilation of the grain structure.

scholarly journals Fabrication of a Simple Materials System for Study of Hg in a Stainless Steel

1998 ◽  
Vol 540 ◽  
Author(s):  
Charles W. Allen ◽  
Anthony W. Mccormick ◽  
Bernard J. Kestel ◽  
Peter M. Baldo ◽  
Nestor J. Zaluzec ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Elevated Temperatures ◽  
National Laboratory ◽  
In Situ Tem ◽  
Engineering System ◽  
Oak Ridge ◽  
Materials Engineering ◽  
Under Construction ◽  
Intense Radiation

AbstractThe Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory, is expected to employ a Hg target encased in a stainless steel. Little is known about the metallurgical behavior of this materials engineering system, which will occur in a service environment involving elevated temperatures and intense radiation. Under normal equilibrium conditions, however, Hg is known to be insoluble in and non-reactive with solid Fe and Cr but to form one or more intermetallics with Ni. Hg has been implanted into alloy 304L. After implantations at 400 and 500 °C to a fluence of 3×1016 cm−2 sub-micron sized precipitates of Hg are formed, as judged, for example, from their solidification behavior on cooling during TEM observation. The formation of such a system of microtargets and possible studies employing them as in situ TEM specimens are discussed, which can provide useful empirical information in conjunction with SNS target development.

scholarly journals In situ TEM Investigation of Anti-sintering Au@Pt Core-shell Nanostructures on MoS2 at Elevated Temperatures

2018 ◽  
Vol 24 (S1) ◽  
pp. 1892-1893 ◽  
Author(s):  
Boao Song ◽  
Yifei Yuan ◽  
Soroosh Sharifi-Asl ◽  
Yuzi Liu ◽  
Reza Shahbazian-Yassar
Keyword(s):  
Elevated Temperatures ◽  
Core Shell ◽  
In Situ Tem ◽  
Shell Nanostructures

In situ transmission electron microscopy of nano-sized metal clusters

2004 ◽  
Vol 839 ◽  
Author(s):  
Jeff Th. M. De Hosson ◽  
George Palasantzas ◽  
Tomas Vystavel ◽  
Siete Koch
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Self Assembly ◽  
Cluster Size ◽  
Elevated Temperatures ◽  
Crystal Habit ◽  
In Situ Tem ◽  
Transmission Electron ◽  
The Face

ABSTRACTThe paper concentrates on in situ transmission electron microscopy of nano-sized Mo and Nb clusters. In particular, this contribution presents challenges to control the microstructure in nano-structured materials via a relatively new approach, i.e. using a so-called nanocluster source. An important aspect is that the cluster size distribution is monodisperse and that the kinetic energy of the clusters during deposition can be varied. The deposited Mo clusters with sizes 5 nm or larger show a body-centered crystal (bcc) structure. The cubic clusters are self-assembled from smaller ones and forming distorted cubes of typical size 7.8 nm or larger. With reducing cluster size to ≤3 nm, the face centered crystal (fcc) structure appears due to dominance of surface energy minimization, while self-assembly into large cubes with sizes up to 20 nm is still observed. In situ TEM annealing leads to cluster coalescence at temperatures ∼800 °C, with the crystal habit changing to rhombic dodecahedron for isolated clusters, while large cubes change to faceted polyhedra. In situ TEM annealing studies on Nb clusters showed that cluster coalescence events were not observed even at rather elevated temperatures because of the formation of oxides.

In situ TEM studies of irradiation effects for materials improvement

1991 ◽  
Vol 49 ◽  
pp. 452-453
Author(s):  
Charles W. Allen
Keyword(s):  
Nuclear Reactor ◽  
Austenitic Stainless Steels ◽  
High Energy ◽  
Point Of View ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Tem Analysis ◽  
Radiation Induced ◽  
Analytical Tools

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.

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.

Sign in / Sign up

Export Citation Format

Share Document