Magnification Scanning Electron Microscopy Research Articles

Mechanical Properties and Temper Resistance of Deformation Induced Ferrite in a Low Carbon Steel

The microstructures and mechanical properties of deformation induced ferrite (DIF) in the low carbon steel Q235 under different deformation temperatures have been investigated systematically. Through deformation induced ferrite transformation (DIFT), ferrite grain can be refined to 3 mu m and accounts for above 85% of the overall fraction. Yield strength of DIF (>500 MPa) is increased by up to 100% compared with the conventional low carbon steel. Comparison of microstructure and mechanical properties in the Q235 steel with DIF and tempered DIF microstructure illustrates that the strengthening mechanism of DIF microstructure is the combination of grain boundary strengthening and carbon supersaturated strengthening. Electron back-scattered diffraction (EBSD) analysis and high magnification scanning electron microscopy (SEM) observation denote that high-angle grain boundary among ultrafine ferrite grain and the transformation product of retain austenite membrane along ferrite boundaries are responsible for the stability of ferrite grain size during tempering process. Transmission electron microscopy (TEM) analysis demonstrates that the transformation product of retained austenite membrane between ferrite grain boundaries is cementite.

Growth Kinetics of Wall-Number Controlled Carbon Nanotube Arrays

We present a simple model for the growth and termination of carbon nanotube (CNT) arrays. This model was developed by modifying several submodels and provides a comprehensive predictive tool for the CNT growth process as a function of CNT wall number. Wall number, diameter, and areal density-controlled CNT arrays were grown on a reduced graphene film by combining block copolymer lithography and plasma-enhanced chemical vapor deposition (PECVD) method. The number of carbonaceous platelets required for the termination of CNT growth process was measured by high-resolution transmission electron microscopy (HRTEM), and the effective exposed catalyst surface area was measured by high magnification scanning electron microscopy (SEM). A parametric study showed that our simple kinetic model successfully predicted the kinetics of wall number-dependent CNT growth and could be used to optimize the PECVD process for CNT production.

Lagrange time delay estimation for scanning electron microscope image magnification

Interpolation techniques that are used for image magnification to obtain more useful details of the surface such as morphology and mechanical contrast usually rely on the signal information distributed around edges and areas of sharp changes and these signal information can also be used to predict missing details from the sample image. However, many of these interpolation methods tend to smooth or blur out image details around the edges. In the present study, a Lagrange time delay estimation interpolator method is proposed and this method only requires a small filter order and has no noticeable estimation bias. Comparing results with the original scanning electron microscope magnification and results of various other interpolation methods, the Lagrange time delay estimation interpolator is found to be more efficient, more robust and easier to execute.

Effectiveness of Three Different Retreatment Techniques in Canals Filled With Compacted Gutta-Percha or Thermafil: A Scanning Electron Microscope Study

IntroductionThis study evaluated the root canal wall morphology under scanning electron microscopy magnification after removal of 2 types of root canal fillings by using ultrasonic tips, nickel-titanium (NiTi) rotary instruments, and hand K-files. MethodsThirty-six extracted roots were filled by using AH Plus (DeTrey-Dentsply, Konstanz, Germany) as a sealer with Thermafil (Tulsa Dental Products, Tulsa, OK) (18 roots) or warm vertically condensed gutta-percha (18 roots). All fillings were removed up to the middle third by using Gates Glidden drills. The retreatment was completed by using K-files (group 1), M-Two NiTi rotary instruments (group 2), or ESI ultrasonic tips (group 3) in 12 roots each. Root canals were irrigated by using 10% ethylenediaminetetraacetic acid and 2.5% NaOCl. The samples were split longitudinally and observed by scanning electron microscopy (100–2000×). The presence of smear layer, filling debris, and the surface profile was evaluated in each picture. Kruskal-Wallis (analysis of variance) and Mann-Whitney tests were used to evaluate the differences between the obturation techniques, the 3 retreatment methods, and the canal thirds (P < .05). ResultsResin sealer tags were observed inside dentinal tubules. No statistical differences (P > .05) were found among the 3 retreatment methods. No statistical differences were observed between Thermafil and vertically compacted warm gutta-percha for each group or between the coronal third used as control, middle, and apical thirds. ConclusionsAll retreatment techniques showed similar performances in terms of smear layer morphology, debris, and surface profile. None of them completely removed filling debris from dentinal tubules of apical third.

331 Évaluation des bords carrés d’implants intra-oculaires hydrophobes et hydrophiles disponibles dans le commerce

Intraocular lenses (IOLs) with square optic edges were associated with lower rates of posterior capsule opacification. We evaluated the microstructure of the edges of currently available hydrophobic and hydrophilic IOLs, in terms of their deviation from an “ideal” square Ten designs of hydrophobic acrylic, 6 designs of silicone, and 24 designs of hydrophilic acrylic IOLs were used in this study. For each design, a +20 D IOL and a +0 D IOL (or the lowest available plus dioptric power) were evaluated whenever possible. The IOL edge was imaged under high magnification scanning electron microscopy (SEM) using a standardized technique. Low vacuum (0.7 Torr) and an environmental SEM was used for the hydrophilic lenses. The photographs were then imported to a digital computer program (AutoCAD LT 2000 system, Autodesk, San Rafael, CA, USA), and the area above the posterior-lateral edge, representing the deviation from a perfect square was measured in square microns. There was a large variation of the area values measured in currently available IOLs labeled as square edged lenses. The mean values for hydrophobic acrylic (N=19) and silicone (N=11) lenses were 183.38 +/−82.18, and 74.39 +/−88.54 square microns, respectively (all dioptric powers evaluated included). The area measurement values of hydrophilic acrylic lenses, as a group, were higher than the values reported for hydrophobic acrylic or silicone lenses (331.39 +/−218.90 square microns; N=47 lenses). Analysis of the microstructure of the optic edge of currently available square edged IOLs revealed a large variation of the deviation area from a perfect square. As a group, hydrophilic acrylic lenses were found to have less square edges than hydrophobic acrylic and silicone lenses.

Si-doped carbon nanostructured films by pulsed laser deposition from a liquid target

Ablation of a silicone oil, Dow Corning's DC-705 with laser pulses of sub-ps duration in high vacuum is a novel approach to fabrication of Si-doped carbon nanocomposite films. Gently focused, temporally clean 700 fs pulses @ 248 nm of a hybrid dye/excimer laser system produce power densities of the order of 10 11–10 12 W cm −2 on the target surface. The evolution of the chemical structure of film material is followed by comparing Fourier Transformed Infrared and X-ray Photoelectron spectra of films deposited at temperatures between room temperature and 250 °C. Despite the low thermal budget technique, in the spectrum of films deposited at room temperature the fingerprint of the silicone oil can clearly be identified. With increasing substrate temperature the contribution of the features characteristic of the oil gradually diminishes, but does not completely disappear even at 250 °C. This result is intriguing since the chance of oil droplets to survive in their original liquid form on the hot surface should be minimal. The results of the X-ray Photoelectron Spectroscopy suggest that the chemical structure of the film material resembles that of the oil. Both reflection mode optical microscopy and low magnification Scanning Electron Microscopy reveal that the films are inhomogeneous: areas of lateral dimensions ranging from a few to tens of micrometers, characterized by different contrasts can be identified. On the other hand, surface mapping by Scanning Electron and Atomic Force Microscopy unambiguously proves that all films possess a solid surface consisting of nanoparticles of less than 100 nm dimension, without the presence of any drop of oil. Possible explanations of the puzzling results can be that the films are polymers consisting mainly of the molecules of the target material, or composites of solid C:Si nanoparticles and oil residues.

Scanning Electron Microscope Evaluation of Vertical and Horizontal Discrepancy in Cast Copings for Single-Tooth Implant-Supported Prostheses

Despite careful attention to waxing, investing, and casting, marginal discrepancies are inevitable. Vertical and horizontal discrepancies can result in crestal bone resorption, peri-implantitis, and loss of osseointegration. The aim of this study was to evaluate marginal gap and overhang in 3 casting techniques for implant framework fabrication. A total of 24 frameworks, 8 each with the Burn-out Cap (ITI; Straumann) (group BC), with Impression Cap (ITI; Straumann) (group IC), and with conventional wax-up technique (group WX) were fabricated. All specimens were waxed on the analog abutments and cast with Type IV gold alloy. All castings were fixed on the analog abutments with cyanoacrylate and embedded in acrylic resin. Specimens were sectioned and prepared for scanning electron microscope evaluation. Frameworks were analyzed for vertical and horizontal discrepancies with x200 magnification (scanning electron microscopy). Data were analyzed statistically by multivariate analysis and the post hoc tests (alpha = 0.05). The vertical discrepancy measurements for the 3 groups showed mean values of 53.74 +/- 11.0 mum, 63.6 +/- 13.2 mum, and 50.1 +/- 17.3 mum, respectively. The interfacial gap differences were not statistically significant in all groups (P > 0.05). Waxing the frameworks with impression caps significantly increased the horizontal discrepancy at the interfaces (P < 0.001). Within the limitations of this experiment, it was demonstrated that the vertical discrepancy of the frameworks made with the 3 techniques were comparable in lack of accuracy with each other. Although conventional waxing produced the least horizontal discrepancy, the difference with burn-out cap group was not statistically different.

The effect of chemical and/or mechanical conditioning on the Er:YAG laser‐treated root cementum: Analysis of surface morphology and periodontal ligament fibroblast attachment

This study compared the surface morphology as well as the biocompatibility of dental root cementum treated with Er:YAG laser irradiation alone and with the laser irradiation followed by chemical and/or mechanical conditioning. Healthy cementum plates were randomly assigned to the following control and treatment groups: (1) untreated control (C), (2) Er:YAG laser irradiation (L), (3) laser plus tetracycline HCl (TC) placement (L+TP), (4) laser plus TC burnishing (L+TB), (5) laser plus EDTA gel placement (L+EP), (6) laser plus EDTA gel burnishing (L+EB), (7) laser plus saline solution burnishing (L+SB), and (8) laser plus minocycline-HCl paste placement (L+MP). Specimens were subjected to scanning electron microscopy (SEM), histological observation and attachment assay using periodontal ligament (PDL) fibroblasts. The laser irradiation produced a thin affected layer (5.7 microm thickness) with a superficial microstructure on the cementum surface. The characteristic microstructures of the lased surface were fragile and could be removed by chemical and/or mechanical conditioning treatments. The L+TB group exhibited marked exposure of collagen fibers after removal of the microstructures on the lased surface. The L+EP group presented a peculiar, smooth surface without exposure of collagen fibers and a uniform arrangement of spherical microparticles on the ultra-high magnification of SEM. In cell attachment assay, the L+TB group exhibited the greatest number of attached cells among all the groups, followed by the L+EP, L+SB and control group. The laser alone group exhibited the lowest number of cells. The characteristic microstructure of the root cementum surface after Er:YAG laser irradiation has a tendency to hinder the early attachment of PDL cells. However, chemical and/or mechanical root conditioning treatment may improve and increase the biocompatibility of the Er:YAG laser-treated root cementum by removing the microstructures of the surface and/or further exposing the collagen fibers.

A study on heat source modeling of scanning electron microscopy modified for material processing

Scanning electron microscopy (SEM) has been used as a surface measurement instrument and a tool for lithography in semiconductor processes due to its high-density localized beam. For those purposes, however, the maximum current of SEM is less than 100 pA, which is not enough for material processing. In this article, SEM was modified to increase the amount of current reaching a specimen from the gun part where the current is generated. The maximum current of SEM after modifications was measured at up to 10 µA, which is 105 times greater than before modifications. The current reaching the specimen is called the probe current, which can be defined as a heat source for material processing. The electron beam of the probe current scans rapidly over an area defined by SEM magnification. By considering the electron beam scanning period and the reaction between high-speed electrons and solid material, the heat source model of the rapidly scanning SEM electron beam was suggested. The simulation results with suggested heat source by ABAQUS were compared with the experiment results.

The durability of parylene coatings on neodymium-iron-boron magnets.

A parylene coating is frequently used to prevent corrosion of neodymium-iron-boron magnets when they are used intra-orally. This in vitro study was designed to test the durability of parylene coating in a simulated oral environment. Single and double parylene-coated magnets were subjected to grinding and crushing forces in an industrial ball mill. The results demonstrate that abrasion and wear was visible around the edges after 1 hour of testing, with a breach of the coating noted under high magnification scanning electron microscopy (SEM). The conclusion of the study is that parylene coating is unlikely to withstand intra-oral forces. The shape of the magnets, the manufacturing process involved in their production, and the thickness of the parylene coating are important factors to consider with respect to the durability of magnets used in the mouth.

Comparison of the Low and High Velocity Impact Response of Kevlar Fiber-Reinforced Epoxy Composites

Failure mechanisms of basket weave and 3-D braided Kevlar-fabric reinforced epoxy composites under low and high velocity impacts have been studied. The purpose of this study is to examine the initiation and development of damage under these two widely differing loading conditions on 2-D and 3-D structure fabric composites. The critical evaluation of post-damage composite panels was conducted using a combination of high magnification photography, optical microscopy, and scanning electron microscopy (SEM). The first objective, quantification, has been realized in principle with regards to laminated composites, and it has been demonstrated that dispersive failure occurs in these composites. The second objective in this work established the relationship between kinetic energy absorbed and the damage tolerance of inter-leaved composites as assessed by the impact tests. High velocity impact loading by a small projectile is generally more detrimental to the integrity of a composite structure than low velocity dropweight impact loading.

Operation Support System Driven by SEM Image for Micro Assembly

This paper proposes an operation support system using images of scanning electron microscope (SEM) for micro assembly, which is called “image driven operation system (IDOS)”. IDOS works as an interface between an operation site and a micro processing site. The authors designed the following three functions in IDOS for micro assembly using a real time image matching and a SEM magnification controlling: (1) indication of a deformed figure for easy operation, (2) image-driven manipulation using a visual pixel feedback, and (3) automatic operation of tasks which hides low magnification images. Through the experimental pick-and-place task using a 100μm-sized “micro torii” under SEM observation, we evaluated that IDOS worked effectively as intended.

High magnification SEM observations for two types of granularity in a high burnup PWR fuel rim

Rim microstructure of an UO 2 pellet irradiated up to 61 GWd/tU, observed with high magnification scanning electron microscopy, presented two types of subgrains: polyhedral and round subgrains. Round subgrains were also observed on the surface of fabrication pores along the pellet radius. These round-shaped subgrains seem to be associated to free surface rearrangement. This new type of round subgrains was proved to be independent of the rim effect. Observations of the fuel structure in the vicinity of rim area evidenced two types of defects specific to rim effect: planar defects and small intergranular pores. Hypothesis is made that the accumulation of planar defects could generate polyhedral subgrains, a new description of the rim effect is proposed including this planar defect. These observations prove that a careful examination of subgrains morphology is necessary to identify rim effect.

Fabrication issues for the prototype National Institute of Standards and Technology SRM 2090A scanning electron microscope magnification calibration standard

A new National Institute of Standards and Technology scanning electron microscope magnification calibration standard has been fabricated and distributed in production prototype form. The SRM 2090A samples contain structures ranging in pitch from 3000 to 0.2 μm and are useful at both high- and low-accelerating voltages. The design and fabrication of the samples has incorporated many of the improvements suggested through two previous prototype series. This article discusses optimization of the lithographic techniques in the fabrication process. We used electron beam lithography for fabrication because of the 0.1 μm features required on the samples. After liftoff, unexpected linewidth differences were measured among the smallest features. These differences were reduced through modification of the electron beam writing paths. We propose that the resist heating effect caused an axial dependence among features fabricated using the original electron beam writing paths. In addition, the susceptibility of the present prototype design to electron beam proximity effects was analyzed. Proximity effects from the 9 μm range of backscattered electrons have little effect on the pitch structures of the prototype but may impact development of the prototype as a linewidth standard.

Comparative Morphology of the Scolices and Microtriches among Five Species of Tetrabothrius (Eucestoda: Tetrabothriidae)

The structure of the scolex, neck, and adjacent strobila of 5 species of Tetrabothrius was evaluated using low to high magnification scanning electron microscopy. Species-specific patterns and morphotypes (spiniform, papilliform, and filiform) of microtriches were found on the scolices and strobilar tegument of Tetrabothrius (Oriana) affinis, Tetrabothrius (Oriana) filiformis, and Tetrabothrius (Culmenamniculus) laccocephalus; microtriches were absent in Tetrabothrius (Culmenamniculus) cylindraceus and Tetrabothrius (Tetrabothrius) sp. The presence, distribution, and form of microtriches may not be correlated with the subgeneric divisions of Tetrabothrius or the host taxon. Unique patterns do not appear to be shared with other groups of cestodes, particularly other tetraphyllideans. We suggest that the spiniform, filiform, and papilliform types of microtriches may be symplesiomorphic for the Eucestoda.

Interlaboratory Study on the Lithographically Produced Scanning Electron Microscope Magnification Standard Prototype.

NIST is in the process of developing a new scanning electron microscope (SEM) magnification calibration reference standard useful at both high and low accelerating voltages. This standard will be useful for all applications to which the SEM is currently being used, but it has been specifically tailored to meet many of the particular needs of the semiconductor industry. A small number of test samples with the pattern were prepared on silicon substrates using electron beam lithography at the National Nanofabrication Facility at Cornell University. The structures were patterned in titanium/palladium with maximum nominal pitch structures of approximately 3000 μm scaling down to structures with minimum nominal pitch of 0.4 (μm. Eighteen of these samples were sent out to a total of 35 university, research, semiconductor and other industrial laboratories in an interlaboratory study. The purpose of the study was to test the SEM instrumentation and to review the suitability of the sample design. The laboratories were asked to take a series of micrographs at various magnifications and accelerating voltages designed to test several of the aspects of instrument performance related to general SEM operation and metrology. If the instrument in the laboratory was used for metrology, the laboratory was also asked to make specific measurements of the sample. In the first round of the study (representing 18 laboratories), data from 35 instruments from several manufacturers were obtained and the second round yielded information from 14 more instruments. The results of the analysis of the data obtained in this study are presented in this paper.

Sem study of cell walls of 24 desmids (desmidiaceae, chlorophyta) from China

Surface ornamentations of the cell walls of 24 desmid species varieties and forms belonging to 7 genera were studied under a scanning electron microscope (SEM). Among these desmids, 1 species and 1 variety are new to science, 13 species, varieties and forms are recorded in China for the first time. These desmids are subdivided into homogeneous and heterogeneous types based on the characteristic ornamentations on their cell walls. A unique ornamentation pattern, the centre of each scrobiculation with a small punctum regularly arranged on the cell wall, and very fine puncta scattered on the cell wall can only be revealed under high SEM magnification.

PhiX174 protein E-mediated lysis of Escherichia coli

Bacteriophage PhiX174 encodes a single lysis gene, E, the function of which is necessary and sufficient to induce lysis of Escherichia coli. Here we present a novel model for E-lysis: physiological, genetic and biochemical data are presented which suggest that a transmembrane tunnel penetrating the inner and outer membrane is formed during the lytic action of protein E. Moreover, using high magnification scanning and transmission electron microscopy in this study, it was possible to visualize the transmembrane lysis structure directly.

High magnification scanning electron microscopy of bacterial cells and virions

When freeze-dried or critical point-dried cells of Escherichia coli and Bacillus sphaericus were coated with a 15 nm thick gold layer by means of sputtering, the surface of the bacteria appeared in the scanning electron microscope to consist of globules having a diameter of about 10–25nm. When the cells were coated with 3–5 nm of tungsten by sputtering, their surface appeared smooth or slightly grainy. Freeze-dried adenovirus type 2 virions sputtered with 15 nm gold exhibited an irregular surface, whereas virions sputtered with 3 nm tungsten looked smooth and had a more or less hexagonal shape. No capsomeres could be discerned.

Void nucleation and growth in dual phase steel wires

Composite ferrite–lath martensite dual phase steel is an alternative to high carbon pearlitic steel for producing high strength wire and may be drawn with no intermediate patenting treatments because of its high work hardening rate and formability. This paper presents the study of the relationships between the void density in drawn wires, the drawing limit, and the initial structure. An Fe–2Si–0·1C (wt-%) dual phase steel was treated to produce three different martensite morphologies at constant volume fraction, then wire drawn. The void density varied linearly with total drawing strain in all three conditions. High magnification scanning electron microscopy revealed that voids were initiated by decohesion at ferrite/martensite interfaces and by shear cracking of martensite particles. The voids grow to form cracks parallel to the drawing direction and affect the drawing limit. The character of the martensite, either dislocated lath or twinned plate, was determined by transmission electron microscopy. The void density was least in the fibrous lath martensite structure, where the lath martensite has a high degree of initial structural coherency with the surrounding ferrite, which hindered void formation and hence delayed the drawing limit.MST/1024