scholarly journals The failure process of mortars during sulfate attack

2019 ◽  
Vol 39 (3) ◽  
pp. 221-228
Author(s):  
Kaiwei Liu ◽  
Aiguo Wang ◽  
Daosheng Sun ◽  
Yan Li ◽  
Jinhui Tang
Keyword(s):  
Failure Process ◽  
Surface Damage ◽  
Scattered Electron ◽  
Transition Zones ◽  
Strength Failure ◽  
Wide Range ◽  
Deterioration Process ◽  
Damage Process ◽  
Electron Image ◽  
Back Scattered Electron Image

External sulfate attacks on concrete structures may cause serious damage and it has attracted a wide range of attention from numerous researchers over the past decades. However, many studies have been concentrated on the sample which has been already destroyed. This paper investigated the entire deterioration process of mortars that were immersed in Na2SO4 solution containing 3 gSO4 2-/L and 33.8g SO4 2-/l at 20 o C up to 600 days. The study on time-varying regularity of expansion, cracks, compressive strength and mineral phases was investigated. Back scattered electron image was used to further examine the evolution of microstructures of the mortars during the attack process. The results showed that damage process of mortars can be described as induction stage, surface damage, bulk damage and then completely damage stage. Fine ettringites that were formed in restricted spaces, approximately 2-5 μm, result in surface damage. At the bulk damage stage, cracking was the main characteristic of mortar which leads to obvious expansion. In this stage, some large ettringite crystals (>20μm) were just deposited in the formed cracks. At the later stage, gypsum can be easily formed at interfacial transition zones as the consumption of calcium hydroxide, which mainly contributed to completely strength failure rather than expansion.

Microstructure Evolution During Alternating-Current-Induced Fatigue

Materials ◽  
2004 ◽  
Author(s):  
R. R. Keller ◽  
R. H. Geiss ◽  
Y.-W. Cheng ◽  
D. T. Read
Keyword(s):  
Electron Backscatter Diffraction ◽  
Failure Process ◽  
Low Frequency ◽  
Surface Damage ◽  
Alternating Current ◽  
Fiber Texture ◽  
Electrical Failure ◽  
Damage Process ◽  
Current Densities ◽  
Interconnect Lines

Subjecting electronic interconnect lines to high-density, low-frequency alternating current creates cyclic thermomechanical stresses that eventually cause electrical failure. A detailed understanding of the failure process could contribute to both prevention and diagnostics. We tested unpassivated Al-1Si traces on the NIST-2 test chip; these are 3.5 μm wide by 0.5 μm thick by 800 μm long, with a strong (111) as-deposited fiber texture and an initial average grain diameter of approximately 1 μm. We applied rms current densities of 11.7 to 13.2 MA/cm2 at 100 Hz. Resistance changes in the lines indicated that such current densities produce temperature cycles at 200 Hz with amplitude exceeding 100 K. Open circuits occurred in under 10 minutes, with substantial surface damage seen after only one minute. A few failures initiated at lithography defects initially present in the lines, but most were produced by the current alone. In one detailed example presented in this paper, we monitored the damage process by interrupting the current at 10, 20, 40, 80, 160, and 320 s in order to characterize an entire line by scanning electron microscopy and automated electron backscatter diffraction (EBSD); failure took place after 697 s. Results are described in terms of deformation, grain growth, and orientation changes.

scholarly journals Hf-Zr interdiffusion in single crystal zircon II: determination by back-scattered electron image.

1995 ◽  
Vol 29 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Hiroshi Nagasawa ◽  
Hisayoshi Yurimoto ◽  
Masana Morioka
Keyword(s):  
Single Crystal ◽  
Scattered Electron ◽  
Electron Image ◽  
Back Scattered Electron Image

The effect of specimen tilt on back-scattered electron image contrast in scanning electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 506-507
Author(s):  
X. Meng-Burany ◽  
A.E. Curzon
Keyword(s):  
Electron Beam ◽  
Image Contrast ◽  
Reference Specimen ◽  
Scattered Electron ◽  
Simple Method ◽  
Sputtered Films ◽  
Electron Image ◽  
Backscattered Electron ◽  
Back Scattered Electron Image ◽  
Image Position

The present work concerns the back-scattered electron image contrast of a thin film of Cu64Mo36 on a silicon substrate. The contrast is defined by the ratio(1)where If and Ib are the backscattered electron signals from the film and from an adjacent bulk reference specimen. In previous work on thin sputtered films of Cu-Mo, Cu-W and Cu-Al both the film and the bulk reference specimen were perpendicular to the incident electron beam. It was found that the dependence of r on the accelerating voltage of the electron beam could be used to obtain both the thickness and the composition of the films. It is the purpose of the present work to determine whether the simple method previously used to extract the required information can be extended to include tilted specimens. As will be seen the method can be adapted to films tilted by less than 50°.

Dentin Caries Recording with Schiff's Reagent, Fluorescence, and Back-scattered Electron Image

1993 ◽  
Vol 72 (12) ◽  
pp. 1588-1592 ◽  
Author(s):  
E.-L. Hietala ◽  
L. Tjaderhane ◽  
M. Larmas
Keyword(s):  
Ultraviolet Light ◽  
Scattered Electron ◽  
Mineral Contents ◽  
Mandibular Molar ◽  
Electron Image ◽  
Back Scattered Electron Image ◽  
Tetracycline Labeling ◽  
Normal Light ◽  
Carious Process ◽  
Caries Lesions

After being weaned, the Wistar rats (12) were fed on a sucrose diet for five weeks to induce dental caries. Tetracycline was injected intraperitoneally into 7 of them to label the mineralizing dentin front. Five rats without tetracycline injection were used to verify spontaneous fluorescence. The evidently carious area under one prominent fissure from each mandibular molar hemisected sagittally in the midline was photographed under ultraviolet light so that autofluorescence would be revealed. The jaws were then stained with Schiff's reagent and photographed under normal light and again under ultraviolet light. The areas of all the lesions were quantified planimetrically as they appeared on the photographs. The mineral contents of the areas were verified with the back-scattered electron images. The caries lesions revealed with Schiff's reagent also exhibited a change in the color of the dentin fluorescence regardless of the tetracycline labeling. The areas of these lesions followed the shapes of the lesions stained by Schiff's reagent but they were greater. Staining with Schiff's reagent was repeatable after the specimen was washed with ethanol for a few weeks. The loss of minerals was seen in the areas stained with Schiff's reaction but was also related to the change in dentin fluorescence, which seems to be a more sensitive indicator of the caries progression than Schiff's reagent, especially in the early phase of the carious process.

Reactive Ion Etching Induced Surface Damage of Silicon Carbide

2005 ◽  
Vol 483-485 ◽  
pp. 765-768 ◽  
Author(s):  
Jun Hai Xia ◽  
E. Rusli ◽  
R. Gopalakrishnan ◽  
S.F. Choy ◽  
Chin Che Tin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Reactive Ion Etching ◽  
Surface Damage ◽  
Textured Surface ◽  
Rf Power ◽  
Power Devices ◽  
Ion Etching ◽  
Maximum Value ◽  
Wide Range ◽  
Coarse Surface

Reactive ion etching of SiC induced surface damage, e.g., micromasking effect induced coarse and textured surface, is one of the main concerns in the fabrication of SiC based power devices [1]. Based on CHF3 + O2 plasma, 4H-SiC was etched under a wide range of RF power. Extreme coarse and textured etched surfaces were observed under certain etching conditions. A super-linear relationship was found between the surface roughness and RF power when the latter was varied from 40 to 160 W. A further increase in the RF power to 200 W caused the surface roughness to drop abruptly from its maximum value of 182.4 nm to its minimum value of 1.3 nm. Auger electron spectroscopy (AES) results revealed that besides the Al micromasking effect, the carbon residue that formed a carbon-rich layer, could also play a significant role in affecting the surface roughness. Based on the AES results, an alternative explanation on the origin of the coarse surface is proposed.

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