Tribology in Full View

MRS Bulletin ◽  
2008 ◽  
Vol 33 (12) ◽  
pp. 1168-1173 ◽  
Author(s):  
Laurence D. Marks ◽  
Oden L. Warren ◽  
Andrew M. Minor ◽  
Arno P. Merkle
Keyword(s):  
Contact Mechanics ◽  
Mechanical Stability ◽  
Fundamental Problem ◽  
Interface Problem ◽  
The Novel ◽  
Sensors And Actuators ◽  
Force Sensitivity ◽  
Transmission Electron ◽  
New Information

AbstractFor many years, a fundamental problem in contact mechanics, both tribology and indentation problems, has been the inability to see what is taking place—the buried-interface problem. Over the past few years, there have been developments whereby it has become possible to perform contact mechanics experimentsin situwithin a transmission electron microscope. These new experiments have been enabled by both the miniaturization of sensors and actuators and improvements in their mechanical stability and force sensitivity. New information is now becoming available about the nanoscale processes of sliding, wear, and tribochemical reactions, as well as microstructural evolution during nanoindentation such as dislocation bursts and phase transformations. This article provides an overview of some of these developments, in terms of both the advances in technical instrumentation and some of the novel scientific insights.

In situ Tensile Testing of Nanoscale Freestanding Thin Films Inside a Transmission Electron Microscope

2005 ◽  
Vol 20 (7) ◽  
pp. 1769-1777 ◽  
Author(s):  
M.A. Haque ◽  
M.T.A. Saif
Keyword(s):  
Stress Measurement ◽  
Crystallographic Analysis ◽  
Uniaxial Tensile ◽  
In Situ Tem ◽  
Sensors And Actuators ◽  
Displacement Sensors ◽  
Thin Foils ◽  
Transmission Electron ◽  
Tensile Experiment

The unique capability of rendering opaque specimens transparent with atomic resolution makes transmission electron microscopy (TEM) an indispensable toolfor microstructural and crystallographic analysis of materials. Conventional TEM specimens are placed on grids about 3 mm in diameter and 10–100 μm thick. Such stringent size restriction has precluded mechanical testing inside the TEM chamber.So far, in situ testing of nanoscale thin foils has been mostly qualitative. Micro-electro-mechanical systems (MEMS) offer an unprecedented level of miniaturization to realize sensors and actuators that can add TEM visualization to nano-mechanical characterization. We present a MEMS-based uniaxial tensile experiment setup that integrates nanoscale freestanding specimens with force and displacement sensors, which can be accommodated by a conventional TEM straining stage. In situ TEM testing on 100-nm-thick freestanding aluminum specimens (with simultaneous stress measurement) show limited dislocation activity in the grain interior and consequent brittle mode of fracture. Plasticity at this size scale is contributed by grain boundary dislocations and partial dislocations.

Synthesis of Nanoflower Precursors in Two-Phase System via Microwave-Assisted Hydrothermal Method and their In Situ Thermal Convention to NiO

2012 ◽  
Vol 20 ◽  
pp. 43-52 ◽  
Author(s):  
Yan Bin Zhang ◽  
Zhen Feng Zhu ◽  
Wen Jia Zhang ◽  
Yan Li Zhang ◽  
Hui Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Process ◽  
Phase System ◽  
The Novel ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Microwave Hydrothermal ◽  
Transmission Electron ◽  
Average Size

The novel nanoflower precursors were successfully fabricated via microwave hydrothermal process in the presence of an anion surfactant Poly (N-vinyl-2-pyrrolidone). Nickel oxide (NiO) with the similar morphology of precursors was also obtained by a simple thermal decomposition of the as-prepared precursors at 400 °C for 2 h in air. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The synthesized NiO nanoclusters have a cubic structure with an average size 500-1000 nm. The specific capacitance of NiO is about 208.4 F/g.

Dynamic Behavior of Twins In BaTiO3

1994 ◽  
Vol 357 ◽  
Author(s):  
Kalpana S. Katti ◽  
Mehmet Sarikaya
Keyword(s):  
Room Temperature ◽  
Mechanical Stability ◽  
The Other ◽  
Ferroelectric Transition ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Lattice Planes ◽  
Microscopy Techniques ◽  
Dynamic Heating

AbstractThe most prominent lattice defects in barium titanate, i.e., twins on two distinct lattice planes { 111 } and { 110 }, were characterized using dynamic transmission electron microscopy techniques in the image and diffraction modes. In-situ heating experiments from room temperature up to 130°C and then cooling down to -168°C reveal a dependence of { 110 } twins on ferroelectric transition. On the other hand, { 111 } twins are found to be completely stable through the ferroelectric transition and exist in all phases. Streaking is observed in the diffraction spots leading to an estimation of { 1111 twin wall thickness to be about 10Å while no such streaking was observed corresponding to { 1101 twins. Based on these observations and the behavior of the twin boundaries under dynamic heating cycles, an estimate of the twin wall energies indicates that { 111 } walls have three orders of magnitude higher energy than that of { 110 } walls which explains their relative thermal and mechanical stability.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

An improved design for an Scanning Tunnelling Microscope (STM) for use in a Transmission Electron Microscope (TEM)

1991 ◽  
Vol 49 ◽  
pp. 384-385
Author(s):  
W.K. Lo ◽  
J.C.H. Spence
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Mechanical Stability ◽  
Scanning Tunnelling Microscope ◽  
Reflection Mode ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Tunnelling ◽  
Improved Design

An improved design for a combination Scanning Tunnelling Microscope/TEM specimen holder is presented. It is based on earlier versions which have been used to test the usefulness of such a device. As with the earlier versions, this holder is meant to replace the standard double-tilt specimen holder of an unmodified Philips 400T TEM. It allows the sample to be imaged simultaneously by both the STM and the TEM when the TEM is operated in the reflection mode (see figure 1).The resolution of a STM is determined by its tip radii as well as its stability. This places strict limitations on the mechanical stability of the tip with respect to the sample. In this STM the piezoelectric tube scanner is rigidly mounted inside the endcap of the STM holder. The tip coarse approach to the sample (z-direction) is provided by an Inchworm which is located outside the TEM vacuum.

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

In situ observations of electromigration induced void behavior

1995 ◽  
Vol 53 ◽  
pp. 244-245
Author(s):  
T. Marieb ◽  
J. C. Bravman ◽  
P. Flinn ◽  
D. Gardner ◽  
M. Madden
Keyword(s):  
Electron Microscopy ◽  
Void Nucleation ◽  
Plan View ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Microelectronics Industry ◽  
In Situ Observations ◽  
Backscatter Electron Detector ◽  
Voltage Scanning

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

P20 phosphor on polyimide as a large area high-resolution transmission screen for slow scan CCD systems

1995 ◽  
Vol 53 ◽  
pp. 20-21
Author(s):  
C. C. Ahn ◽  
S. Karnes ◽  
M. Lvovsky ◽  
C. M. Garland ◽  
H. A. Atwater ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
High Energy ◽  
Practical Implementation ◽  
Line Pair ◽  
Modulation Transfer ◽  
Large Area ◽  
Ccd Imaging ◽  
Transmission Electron ◽  
The One ◽  
Beam Broadening

The bane of CCD imaging systems for transmission electron microscopy at intermediate and high voltages has been their relatively poor modulation transfer function (MTF), or line pair resolution. The problem originates primarily with the phosphor screen. On the one hand, screens should be thick so that as many incident electrons as possible are converted to photons, yielding a high detective quantum efficiency(DQE). The MTF diminishes as a function of scintillator thickness however, and to some extent as a function of fluorescence within the scintillator substrates. Fan has noted that the use of a thin layer of phosphor beneath a self supporting 2μ, thick Al substrate might provide the most appropriate compromise for high DQE and MTF in transmission electron microcscopes which operate at higher voltages. Monte Carlo simulations of high energy electron trajectories reveal that only little beam broadening occurs within this thickness of Al film. Consequently, the MTF is limited predominantly by broadening within the thin phosphor underlayer. There are difficulties however, in the practical implementation of this design, associated mostly with the mechanical stability of the Al support film.

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