Crack propagation and deformation behavior of Al2O3-24 vol. % ZrO2 composite studied by transmission electron microscopy

Crack propagation and deformation behavior of a pressureless-sintered Al2O3-24 vol. % ZrO2 composite have been studied by transmission electron microscopy on Vickers-indented specimens from room temperature to 1200 °C. Hardness of the composite gradually decreases with increasing temperature, whereas the ratio of indent to crack lengths, which corresponds to the apparent toughness of materials, decreases up to about 1000 °C and then quickly increases with increasing temperature. In the samples indented at room temperature and 1000 °C, most of the cracks propagate along Al2O3/ZrO2 interfaces and Al2O3 grain boundaries, but a few monoclinic ZrO2 grains are transgranularly fractured. These fractured grains are heavily deformed and produce a marked reduction of the driving force for propagation of cracks at room temperature. In the sample indented at 1200 °C, cracks are hardly observed, but on the other hand, formation of subgrain boundaries, elongation of grains, and grain boundary sliding are observed both in the Al2O3 and ZrO2 grains located around the indentation site.

Download Full-text

Dislocations Produced by Indentation Deformation of HPVE GaN Films

MRS Proceedings ◽

10.1557/proc-622-t6.18.1 ◽

2000 ◽

Vol 622 ◽

Cited By ~ 3

Author(s):

M. H. Hong ◽

P. Pirouz ◽

P. M. Tavernier ◽

D. R. Clarke

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Plastic Zone ◽

Room Temperature ◽

Prism Plane ◽

Weak Beam ◽

Transmission Electron ◽

Hardness Tests ◽

Increasing Temperature ◽

Gan Film

ABSTRACTVickers hardness tests on {0001} and (1120) faces of a relatively thick GaN film grown on a (0001) sapphire substrate have been performed in the temperature range 25-1200°C. The microstructure of the plastic zone around the indentation sites has been investigated by transmission electron microscopy (TEM). At room temperature, the hardness was measured to be 12.3 GPa on the basal plane, and 11.1 GPa on the prism plane. The hardness decreases gradually with increasing temperature up to ∼800°C and then shows a plateau between ∼800 and ∼1050°C after which it decreases again above ∼1100°C. In contrast to the rather straight dislocations produced by room-temperature indentation of the (0001) face, the dislocations generated by indenting the (1120) face at room temperature were curved and in the shape of half-loops emanating from the indentation sites on the prism planes. Such dislocations were not dissociated within the resolution of weak-beam TEM.

Download Full-text

A TEM Study of Bubbles Growth with Temperature in Xenon and Krypton Implanted Uranium Dioxide

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.323-325.191 ◽

2012 ◽

Vol 323-325 ◽

pp. 191-196 ◽

Cited By ~ 1

Author(s):

Amélie Michel ◽

C. Sabathier ◽

G. Carlot ◽

M. Cabié ◽

S. Bouffard ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Uranium Dioxide ◽

Microstructure Evolution ◽

Room Temperature ◽

Number Density ◽

Thin Foils ◽

Transmission Electron ◽

Growth Phenomenon ◽

Increasing Temperature

Transmission electron microscopy (TEM) characterizations were carried out on a set of UO2 thin foils previously implanted at room temperature with 400 keV Xe2+ and 250 keV Kr2+ ions at the fluence 7.1015 at.cm-2 (equivalent to 1 at.%/at. UO2). The experiment was devoted to the study of the evolution of the fission gases bubbles populations with increasing temperature. Annealings were performed in the laboratory furnace at 600°C, 800°C, 1000°C for 12h, 1400°C for 4h and 1500°C for 2h under Ar-5%H2 atmosphere. For each annealing condition and for as-implanted specimens the bubble population has been characterized in size and number density. A comparison between Xe and Kr has been done that showed a similar behaviour. Globally, from the as-implanted sample to the 1500°C annealed, the bubbles growth phenomenon and the microstructure evolution with temperature was put in relieve.

Download Full-text

Scanning and Transmission Electron Microscopy of Human Red Blood Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062129 ◽

1969 ◽

Vol 27 ◽

pp. 44-45

Author(s):

A.J. Tousimis ◽

T.R. Padden

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Blood Cells ◽

Room Temperature ◽

Type Specimen ◽

New Combination ◽

Human Red Blood Cells ◽

Transmission Electron ◽

Microscope Slides ◽

Scanning Electron

The size, shape and surface morphology of human erythrocytes (RBC) were examined by scanning electron microscopy (SEM), of the fixed material directly and by transmission electron microscopy (TEM) of surface replicas to compare the relative merits of these two observational procedures for this type specimen.A sample of human blood was fixed in glutaraldehyde and washed in distilled water by centrifugation. The washed RBC's were spread on freshly cleaved mica and on aluminum coated microscope slides and then air dried at room temperature. The SEM specimens were rotary coated with 150Å of 60:40- gold:palladium alloy in a vacuum evaporator using a new combination spinning and tilting device. The TEM specimens were preshadowed with platinum and then rotary coated with carbon in the same device. After stripping the RBC-Pt-C composite film, the RBC's were dissolved in 2.5N HNO3 followed by 0.2N NaOH leaving the preshadowed surface replicas showing positive topography.

Download Full-text

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096618 ◽

1972 ◽

Vol 30 ◽

pp. 672-673

Author(s):

S. Mahajan

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Ambient Temperature ◽

Room Temperature ◽

Channel Formation ◽

Early Stages ◽

Transmission Electron ◽

Three Stages ◽

Two Stages ◽

Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

Download Full-text

A crystallographic analysis of the CoSi/Si(111) interface using Transmission Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176009 ◽

1990 ◽

Vol 48 (4) ◽

pp. 574-575

Author(s):

A.C. Daykin ◽

C.J. Kiely ◽

R.C. Pond ◽

J.L. Batstone

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Defect Structure ◽

Room Temperature ◽

Theoretical Method ◽

Crystallographic Analysis ◽

Si Substrate ◽

Transmission Electron ◽

Theoretical Predictions

When CoSi2 is grown onto a Si(111) surface it can form in two distinct orientations. A-type CoSi2 has the same orientation as the Si substrate and B-type is rotated by 180° degrees about the [111] surface normal.One method of producing epitaxial CoSi2 is to deposit Co at room temperature and anneal to 650°C.If greater than 10Å of Co is deposited then both A and B-type CoSi2 form via a number of intermediate silicides .The literature suggests that the co-existence of A and B-type CoSi2 is in some way linked to these intermediate silicides analogous to the NiSi2/Si(111) system. The phase which forms prior to complete CoSi2 formation is CoSi. This paper is a crystallographic analysis of the CoSi2/Si(l11) bicrystal using a theoretical method developed by Pond. Transmission electron microscopy (TEM) has been used to verify the theoretical predictions and to characterise the defect structure at the interface.

Download Full-text

Synthesis and TEM study of Ag–In–(Eu, Ce) ternary approximants

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.2009.1110 ◽

2009 ◽

Vol 224 (1-2) ◽

Cited By ~ 1

Author(s):

Kazue Nishimoto ◽

Miki Muraki ◽

Ryuji Tamura

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Room Temperature ◽

Transmission Electron

AbstractTernary Ag–In–(Eu, Ce) 1/1 approximants are synthesized and their structures are studied by transmission electron microscopy (TEM). For both the approximants, superlattice spots are clearly observed at room temperature, and the superstructures of the Ag–In–(Eu, Ce) approximants are found to be similar to those of Cd

Download Full-text

Preparation of Straight and Orderly Polypyrrole Microrods through Soft Template Methods

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.306-307.679 ◽

2011 ◽

Vol 306-307 ◽

pp. 679-683

Author(s):

Li Bo Sun ◽

Yuan Chang Shi ◽

Lin Ya Chu ◽

Bing Chang Zhang ◽

Jiu Rong Liu

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Cetyltrimethylammonium Bromide ◽

Growth Process ◽

Room Temperature ◽

Oxidative Polymerization ◽

Soft Template ◽

Microemulsion System ◽

Transmission Electron ◽

The Impact

The straight and orderly microrods of polypyrrole(PPy) was synthesized in a microemulsion system consisted of cetyltrimethylammonium bromide(CTAB), n-pentanol, water and pyrrole by chemical oxidative polymerization, in which CTAB was used as soft templates and APS was used as the oxidant. Fourier-transform infrared spectroscopy (FTIR) was used to characterize the structure of the PPy microrods. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) was used to characterize the morphology of the samples. We discussed the impact of temperature, the adding way of the oxidant, the amount of cosurfactant n-pentanol to the morphology of PPy microrods. The results showed that straight and orderly PPy microrods with a diameter about 300nm and a length up to 20μm were synthesized when the temperature was kept at room temperature (25°C), the dropping time of APS was more than 1.5h, the ratio of CTAB to n-pentanol was 0.6:1, and the polymerization time was about 24h. We studied the growth process of PPy microrods by HTEM analysis. HTEM images revealed that the growth process of PPy changed from hollow microrods, semi-hollow microrods, and finally solid microrods.

Download Full-text

Nanotwinned Surface on a Ternary Titanium Alloy with Increased Hardness Induced under Nanoindentations

Materials Science Forum ◽

10.4028/www.scientific.net/msf.874.323 ◽

2016 ◽

Vol 874 ◽

pp. 323-327

Author(s):

Hong Xiu Zhou ◽

Ming Lei Li ◽

Neng Dong Duan ◽

Bo Wang ◽

Zhi Feng Shi ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Surface Roughness ◽

Titanium Alloy ◽

Chemical Mechanical Polishing ◽

Material Removal ◽

Room Temperature ◽

Chemical Reagents ◽

Transmission Electron ◽

High Temperature High Pressure

A nanotwinned surface is formed on a titanium alloy under nanoindentations. Prior to nanoindentation, blocks of a ternary titanium alloy are machined by chemical mechanical polishing. The surface roughness Ra and peak-to-valley values are 1.135 nm and 8.82 nm, respectively. The hardness in the indented surface is greatly increased, indicated from the load-displacement curves compared to the polished surfaces. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is uniformly generated by nanoindentations at room temperature, which is different from previous findings, in which high temperature, high pressure, or chemical reagents are usually used. The nanotwinned surface is produced by pure mechanical stress, neither material removal nor addition.

Download Full-text