Decipher Ultrasonic Signals from Defects in Thick Aluminum Extrusions to Identify Type and Origin of Defects

2021 ◽  
Vol 875 ◽  
pp. 248-255
Author(s):  
Lubaba Batool ◽  
Zukhruf Nawaz ◽  
Irsa Jahangir ◽  
Zeeshan Abbasi ◽  
Anjum Tauqir
Keyword(s):  
Ultrasonic Testing ◽  
Quality Criteria ◽  
Ultrasonic Signals ◽  
Eds Analysis ◽  
Aluminum Extrusions ◽  
Metallographic Preparation ◽  
Microscopic Studies ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Defect Morphology

Manufacturing of thick seamless pipes of age-hardenable aluminum alloys are a specialized technology since their application is limited to specific hi-tech areas. Quality criteria for their inspection are propriety items of the very few production facilities that develop these criteria in-house. Present study relates ultrasonic signals reflecting back from non-continuities in the thickness of seamless pipes with their microstructural features. Detailed study of defects leads to the source of their formation and will ultimately help to systematically control them. Signals from ultrasonic testing trace defects as UT waves reflect back from discontinuities in the material. Defective sections of seamless pipes were cut with precision to reveal the defects. The sectioned surfaces were subjected to metallographic preparation and revealed defects were studied using Optical and Field Emission Scanning Electron Microscopes (FESEM). Defects are grouped based on the shape of UT signals as well as the defect morphology as revealed by microscopic studies. Most of the observed cracks are found to grow in the direction of extrusion. Energy Dispersive Spectroscopy (EDS) analysis was conducted to determine the composition of inclusions in the vicinity of the defects. Data from elemental analysis is used to identify the potential sources. The study recommends measures to control the defects and improve the yield.

Scanning Electron Microscopic Studies on the Tegument of Trematodes

1974 ◽  
Vol 32 ◽  
pp. 182-183
Author(s):  
J. E. Ubelaker ◽  
R. D. Specian ◽  
V. F. Allison
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Host Response ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Microscopic Studies ◽  
Physiological Demands ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Among the parasitic flatworms, only members of the trematoda have exploited nearly every conceivable niche. Since physiological demands in each habitat present special problems in eluding the host response as well as obtaining nourishment the surface epithelia of such organisms warrant special attention. To gain an appreciation of tegumental diversity in the trematoda, representative trematodes from numerous habitats in their respective hosts were examined by scanning electron microscopySpecimens were collected from natural infections, fixed in paraformaldehyde and dehydrated in alcohol. Ethanol was exchanged with amyl acetate prior to CO2 drying in a Denton DCP-1 critical point dryer. The dried specimens were mounted on metal holders, outgassed and rotary coated with gold-palladium. These were then examined with the ISI Mini-SEM and AMR 1000 scanning electron microscopes.

Toward High-Resolution Low-Voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 218-219
Author(s):  
Zhifeng Shao
Keyword(s):  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Limiting Factor ◽  
Operating Voltage ◽  
Probe Radius ◽  
Non Local ◽  
Electron Microscopes ◽  
Image Position ◽  
Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

Current State of Biological High-Resolution Scanning Electron Microscopy

1988 ◽  
Vol 46 ◽  
pp. 180-181 ◽  
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Performance ◽  
Low Voltage ◽  
Backscattered Electrons ◽  
Lens Position ◽  
Low Voltage Operation ◽  
Signal Collection ◽  
Probe Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

A new generation of high performance field emission scanning electron microscopes (FSEM) is now commercially available (JEOL 890, Hitachi S 900, ISI OS 130-F) characterized by an "in lens" position of the specimen where probe diameters are reduced and signal collection improved. Additionally, low voltage operation is extended to 1 kV. Compared to the first generation of FSEM (JE0L JSM 30, Hitachi S 800), which utilized a specimen position below the final lens, specimen size had to be reduced but useful magnification could be impressively increased in both low (1-4 kV) and high (5-40 kV) voltage operation, i.e. from 50,000 to 200,000 and 250,000 to 1,000,000 x respectively.At high accelerating voltage and magnification, contrasts on biological specimens are well characterized1 and are produced by the entering probe electrons in the outmost surface layer within -vl nm depth. Backscattered electrons produce only a background signal. Under these conditions (FIG. 1) image quality is similar to conventional TEM (FIG. 2) and only limited at magnifications >1,000,000 x by probe size (0.5 nm) or non-localization effects (%0.5 nm).

Chromatic aberration and low-voltage SEM

1987 ◽  
Vol 45 ◽  
pp. 546-547
Author(s):  
Zhifeng Shao ◽  
A.V. Crewe
Keyword(s):  
Electron Energy ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Primary Electron ◽  
Probe Size ◽  
Non Local ◽  
Optical Treatment ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

For scanning electron microscopes, it is plausible that by lowering the primary electron energy, one can decrease the volume of interaction and improve resolution. As shown by Crewe /1/, at V0 =5kV a 10Å resolution (including non-local effects) is possible. To achieve this, we would need a probe size about 5Å. However, at low voltages, the chromatic aberration becomes the major concern even for field emission sources. In this case, δV/V = 0.1 V/5kV = 2x10-5. As a rough estimate, it has been shown that /2/ the chromatic aberration δC should be less than ⅓ of δ0 the probe size determined by diffraction and spherical aberration in order to neglect its effect. But this did not take into account the distribution of electron energy. We will show that by using a wave optical treatment, the tolerance on the chromatic aberration is much larger than we expected.

High-resolution observation of sintered alumina (Al2O3) using the specimen-heated and electron-beam-induced conductivity method in a UHR-SEM

1994 ◽  
Vol 52 ◽  
pp. 1046-1047
Author(s):  
K. Ogura ◽  
T. Suzuki ◽  
C. Nielsen
Keyword(s):  
Electron Beam ◽  
High Resolution ◽  
Specimen Preparation ◽  
Conductivity Method ◽  
Fine Grain ◽  
Grain Structures ◽  
Resolution Observation ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Charging Effect

In spite of the complicated specimen preparation, Transmission Electron Microscopes (TEM) have traditionally been used for the investigation of the fine grain structures of sintered ceramics. Scanning Electron Microscopes (SEM) have not been used much for the same purpose as TEM because of poor results caused by the specimen charging effect, and also the lack of sufficient resolution. Here, we are presenting a successful result of high resolution imaging of sintered alumina (pure Al2O3) using the Specimen Heated and Electron Beam Induced Conductivity (SHEBIC) method, which we recently reported, in an ultrahigh resolution SEM (UHR-SEM). The JSM-6000F, equipped with a Field Emission Gun (FEG) and an in-lens specimen position, was used for this application.After sintered Al2O3 was sliced into a piece approximately 0.5 mm in thickness, one side was mechanically polished to get a shiny plane for the observation. When the observation was started at 20 kV, an enormous charging effect occured, and it was impossible to obtain a clear Secondary Electron (SE) image (Fig.1).

High resolution at low voltage: A new approach

1989 ◽  
Vol 47 ◽  
pp. 76-77
Author(s):  
Arthur V. Jones
Keyword(s):  
Low Voltage ◽  
Emission Sources ◽  
New Approach ◽  
Design Concepts ◽  
Probe Diameter ◽  
Low Voltage Operation ◽  
Sufficient Intensity ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Immersion Type

With the introduction of field-emission sources and “immersion-type” objective lenses, the resolution obtainable with modern scanning electron microscopes is approaching that obtainable in STEM and TEM-but only with specific types of specimens. Bulk specimens still suffer from the restrictions imposed by internal scattering and the need to be conducting. Advances in coating techniques have largely overcome these problems but for a sizeable body of specimens, the restrictions imposed by coating are unacceptable.For such specimens, low voltage operation, with its low beam penetration and freedom from charging artifacts, is the method of choice.Unfortunately the technical dificulties in producing an electron beam sufficiently small and of sufficient intensity are considerably greater at low beam energies — so much so that a radical reevaluation of convential design concepts is needed.The probe diameter is usually given by

Observation of GaAs/AlAs Superlattice Structures in both Secondary and Backscattcred Electron Imaging Modes with an Ultrahigh Resolution Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 404-405
Author(s):  
K. Ogura ◽  
A. Ono ◽  
S. Franchi ◽  
P.G. Merli ◽  
A. Migliori
Keyword(s):  
Gaas Layer ◽  
Objective Lens ◽  
Superlattice Structure ◽  
Backscattered Electron ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Superlattice Structures ◽  
Electron Imaging ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the last few years the development of Scanning Electron Microscopes (SEM), equipped with a Field Emission Gun (FEG) and using in-lens specimen position, has allowed a significant improvement of the instrumental resolution . This is a result of the fine and bright probe provided by the FEG and by the reduced aberration coefficients of the strongly excited objective lens. The smaller specimen size required by in-lens instruments (about 1 cm, in comparison to 15 or 20 cm of a conventional SEM) doesn’t represent a serious limitation in the evaluation of semiconductor process techniques, where the demand of high resolution is continuosly increasing. In this field one of the more interesting applications, already described (1), is the observation of superlattice structures.In this note we report a comparison between secondary electron (SE) and backscattered electron (BSE) images of a GaAs / AlAs superlattice structure, whose cross section is reported in fig. 1. The structure consist of a 3 nm GaAs layer and 10 pairs of 7 nm GaAs / 15 nm AlAs layers grown on GaAs substrate. Fig. 2, 3 and 4 are SE images of this structure made with a JEOL JSM 890 SEM operating at an accelerating voltage of 3, 15 and 25 kV respectively. Fig. 5 is a 25 kV BSE image of the same specimen. It can be noticed that the 3nm layer is always visible and that the 3 kV SE image, in spite of the poorer resolution, shows the same contrast of the BSE image. In the SE mode, an increase of the accelerating voltage produces a contrast inversion. On the contrary, when observed with BSE, the layers of GaAs are always brighter than the AlAs ones , independently of the beam energy.

Pollen morphology of some Tamarix (Tamaricaceae) species of Iran

2020 ◽  
Vol 62 (1-2) ◽  
pp. 151-161
Author(s):  
T. Shagholi ◽  
M. Keshavarzi ◽  
M. Sheidai
Keyword(s):  
North Africa ◽  
Pollen Grains ◽  
Ecological Niches ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
Qualitative And Quantitative ◽  
Petal Length ◽  
Electron Microscopes ◽  
High Level ◽  
Scanning Electron Microscopes

Tamarix L. (Tamaricaceae) is a halophytic shrub in different parts of Asia and North Africa. Taxonomy and species limitation of Tamarix is very complex. This genus has three sections as Tamarix, Oligadenia, and Polyadenia, which are mainly separated by petal length, the number of stamens, the shape of androecial disk and attachment of filament on the androecial disk. As there was no palynological data on pollen features of Tamarix species of Iran, in the present study 12 qualitative and quantitative pollen features were evaluated to find diagnostic ones. Pollen grains of 8 Tamarix species were collected from nature. Pollen grains were studied without any treatment. Measurements were based on at least 50 pollen grains per specimen. Light and scanning electron microscopes were used. Multivariate statistical methods were applied to clarify the species relationships based on pollen data. All species studied showed monad and tricolpate (except some individuals of T. androssowii). Some Tamarix species show a high level of variability, in response to ecological niches and phenotypic plasticity, which make Tamarix species separation much more difficult. Based on the results of the present study, pollen grains features are not in agreement with previous morphological and molecular genetics about the sectional distinction.

scholarly journals Characteristics of Lightweight Cellular Concrete and Effects on Mechanical Properties

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2678 ◽  
Author(s):  
Wei Yu ◽  
Xu Liang ◽  
Frank Mi-Way Ni ◽  
Abimbola Grace Oyeyi ◽  
Susan Tighe
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
High Definition ◽  
Pore Characteristics ◽  
Software Applications ◽  
Solid Part ◽  
Electron Microscopes ◽  
Lab Test ◽  
Scanning Electron Microscopes ◽  
Cellular Concrete

This study investigated the pore structure and its effects on mechanical properties of lightweight cellular concrete (LCC) in order to understand more and detailed characteristics of such structure. As part of investigation, environment scanning electron microscopes (ESEM) and industrial high-definition (HD) macro photography camera were separately used to capture and compare images of specimens. Physical properties of the pore structure, including pore area, size, perimeter, fit ellipse, and shape descriptors, were studied based on the image processing technology and software applications. Specimens with three different densities (400, 475, and 600 kg/m3) were prepared in the laboratory. Firstly, the effects of density on the characteristics of pore structure were investigated; furthermore, mechanical properties (compressive strength, modulus of elasticity and Poisson’s ratio, flexural strength and splitting tensile strength of LCC) were tested. The relationships among pore characteristics, density, and mechanical properties were analyzed. Based on the results obtained from the lab test—comparisons made between specimens with high-densities and those with low-densities—it was found significant variability in bubble size, thickness, and irregularity of pores. Furthermore, the increase of density is accompanied by better mechanical properties, and the main influencing factors are the thickness of the solid part and the shape of the bubble. The thicker of solid part and more regular pores of LCC has, the better mechanical properties are.

Discoasters of the Blue Clay (Middle Miocene) of Malta and Gozo

1978 ◽  
Vol 115 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Minoo Hojjatzadeh
Keyword(s):  
Middle Miocene ◽  
The Family ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

SummaryTwenty-three species of the Family Discoasteraceae Vekshina, 1959 recovered from 18 samples of the Blue Clay at Fort Chambray, Gozo, and 31 samples from Fomm-Ir-Rih Bay, Malta, have been studied under light and scanning electron microscopes. Fourteen Middle Miocene species are reviewed, their stratigraphical ranges and importance as marker species discussed. Nine species are described as new. On the basis of the discoaster species present, a Middle Miocene age (NN.6 Discoaster exilis Zone – NN.7 Discoaster kugleri Zone) for the Blue Clay in Malta and Gozo is suggested.

Sign in / Sign up

Export Citation Format

Share Document