Scanning Electron Microsope Research Articles

Nitrate corrosion resistance of concrete with nanoparticles under dry–wet cycles

AbstractThe concrete of harbor wharf is in the environment of multifactor erosion. Under the coupled effects of dry–wet cycles and nitrate erosion, the durability of marine concrete gradually decreases. Therefore, it is an important issue to improve the durability of concrete. The changes of concrete durability are investigated under the coupled effects of dry–wet cycles and nitrate erosion, and the concrete durability are improved by adding nanoparticles. Nano‐concretes are made by adding different amounts of nano‐SiO2 and nano‐Al2O3 to plain concrete. The relative dynamic elastic modulus of nano‐concretes and the NO3− content are measured as indicators to evaluate the durability of nano‐concretes. The microstructure of nano‐concretes is analyzed through scanning electron microsope (SEM) and energy dispersive spectrometer (EDS）. The test results show that relative dynamic elastic modulus of nano‐concretes is increased obviously, and NO3− content of nano‐concrete at different depths is lower than that of plain concrete under the same number of dry–wet cycles. NO3− content of nano‐concrete is lower than that of plain concrete. Nanoparticles can optimize the pore structure of concrete and generate more C‐S‐H gels. Therefore, concrete durability can be efficiently increased through adding nano‐SiO2 and nano‐Al2O3 under the coupled effects of dry–wet cycles and nitrate erosion.

XRD Analysis for Characterization of Green Nanoparticles: A Mini Review

Plants are one of the richest sources of biomolecules on earth. In the last decade there has been an increasing interest of researchers and scientists on exploration of antimicrobial and medicinal properties of plants. It is with entry and amalgamation of nanotechnology with phytochemistry, which opened new dimensions. Synthesis of metallic nanoparticles mediated by plant extracts emerged rapidly and had significant explorations. The synthesized metallic nanoparticles are characterized for their size, shape and stability using several techniques such as UV-Visible spectrophotometer (UV-Vis), Fourier Transform Infrared (FTIR), Scanning Electron Microsope (SEM), Dynamic light scattering analysis (DLS). X-ray diffraction (XRD) analysis of nanoparticles is a comparatively new entry in this list. X-ray diffraction analysis provides concrete information regarding structure and crystalline size of nanoparticles, and it can play pivotal role in characterization of nanoparticles.

Screening and Optimisation of the Biodegradation Potential for Low Density Polyethylene (LDPE) Films by Fusarium Equiseti and Brevibacillus Parabrevis

The accumulation of low density polyethylene, used extensively in packaging for industrial and agricultural applications, in the ecosystem is a great threat. This study focuses on the isolation of micro-biota from the plastic polluted sites to screen and optimise their potential for low density polyethylene (LDPE) film biodegradation. Firstly, the plastic samples from soil dumping plastic debris and plastic polluted water were collected; then fungi and bacteria were isolated using potato dextrose agar media and nutrient agar media, respectively, while screening low density polyethylene film biodegradation performed on mineral salt media (MSM) using the isolated micro-biota. The measurement of the potential biodegradation was assessed by visual observation. The most microbial colonization for low density polyethylene films was identifying molecular which was then utilized for optimisation of the biodegradation processes with different parameters such as media type, inoculum size, shaking speed, different incubation temperature and pH at different incubation time. Then the weight loss in the LDPE films percentage was calculated measuring dry mycelium weight and bacterial absorbance. The results revealed that, among the isolated micro-biota fifteenth, the most colonization was Fusarium equiseti and Brevibacillus parabrevis depending on the scanning electron microsope (SEM) and Fourier transform infrared (FTIR) analysis, in addition to optimum media, inoculum size, shaking speed, incubation temperature, pH, MSM, 2 disks and 2 ml, 30˚ C and 35˚C, pH5 and pH7 for 30:20 days for F.equiseti and B.parabrevis, respectively. The overall results confirmed that F.equiseti and B.parabrevis from the plastic polluted sites play an essential role in low density polyethylene films biodegradation.

TUNGSTEN OXIDE DOPED TITANIA SUPPORTED ON TUD-C FOR PHOTOCATALYTIC REMOVAL OF METHYLENE BLUE

In this work, a series of mesoporous tungsten oxide (WO3) doped titania (TiO2) supported on Technische Universiteit Delft (TUD-C) (WO3-TiO2/TUD-C) were successfully prepared by the sol-gel method. X-ray diffraction (XRD) analysis showed that the samples’ crystallinity decreased after incorporation of WO3-TiO2 onto TUD-C, suggesting the successful incorporating WO3-TiO2 into the framework of TUD-C. N2 adsorption-desorption isotherm analysis indicated that the surface area, pore volume and pore size of WO3-TiO2/TUD-C increased significantly after loading onto TUD-C. The presence of tetrahedron frame structure Ti4+ and polytitanate in all the prepared samples were detected. Besides, all the WO3-TiO2 supported on TUD-C samples showed reduced band gap energy of 3.11 eV. The presence of zeolitic materials in the sample was confirmed by Fourier transform infrared spectroscopy, indicating the successfull formation of TUD-C. The Field Emission Scanning Electron Microsope (FESEM) images revealed the WO3-TiO2 were distributed uniformly on the surface of TUD-C. It has been demonstrated that the best photocatalytic activity for removal of methylene blue under UV light irradiation was achieved when WO3-TiO2/TUD-C was prepared with the molar ratio of Si to Ti is equal to 30 (WO3-TiO2/TUD-C(30)). The current research findings suggested that high pore size, surface area and crystallinity were the key factors for the high photocatalytic activity.Keywords: Photocatalyst, titania, TUD-C, tungsten oxide, methylene blue

Investigation of Mechanoluminescent Light-Emitting Devices Based on ZnS:Cu Composite Embedded Elastomer Film

A mechanically driven light-generating composite flims consisted of ZnS:(Cu,Al) and polydimethylsiloxane (PDMS) were fabricated by spin coating method. Effects of mechanical stresses on the structural, optical properties of composite films were investigated. X-ray diffraction(XRD) measurements showed the ZnS:(Cu,Al) microparticle based composite films showed a hexaginal zinc blende type crystal peaks without any other distinguishable phase. Field emission scanning electron microsope (FE-SEM) images showed that the ~ 900 um thick composite films fabricated and the mixed ZnS:(Cu,Al) microparticles were mostly surrounded by PDMS matrix. The mechanoluminescence intensity and color of composite films were strongly related to the external mechanical stress. The mechanoluminescence intensity increased with increasing mechanical stress and a color of the ZnS:(Cu,Al) based composite films shifted from green to blue [Commission internationale de L'Eclairage (CIE) color coordinates of (0.225, 0.444) to (0.171, 0.304)] as the increased mechanically stress. The best brightness of the composite films was 140 cd/m2 when it was exposed to external gas flow of 700 kPa.

Direct growth of CuO/ITO nanowires by the vapor solid oxidation method

In this paper, we report the synthesis results of cupric oxide nanowires (NWs) on the indium tin oxide (ITO) substrate by vapor solid oxidation method. In our study, a Cu layer of thickness 1.4 µm was deposited on ITO thin film substrates through the direct current DC magnetron sputtering method. Cupric oxide NWs grew on ITO after annealing Cu/ITO substrates at the temperatures with range from 350 to 500 °C in air for 3–5 h. The received peak shift of Cu2O to CuO NW phase depending on annealing temperatures was conducted by X-ray diffraction. Chemical atomic elements were obtained from energy dispersive X-ray spectroscopy. The morphology of nanowires were investigated using scanning electron microsope (SEM). The SEM images indicated that the NWs with length about 3–3.5 µm and diameter about 100 nm grew vertically over large area.

Weathering of submerged stressed calcarenites: chemo-mechanical coupling mechanisms

Long portions of the Apulian coast are steep cliffs in carbonate soft rocks. These, especially the calcarenite, are affected by weathering processes that markedly alter their mechanical properties with time, potentially leading to instability of coastal geomorphological structures. Such alterations are mainly due to chemical reactions between the solid and fluid phases, and are driven by chemical variables, which are internal variables and hence uncontrollable. In a search for the variables that drive the process of rock weakening, recourse is made to the micro scale, at which most of the chemical processes are observed and quantified. Observations using scanning electron microsope, thin sections and X-ray computed tomography analyses appear to be crucial for the understanding, interpretation and definition of the degradation mechanisms of the material. A chemo-mechanical coupled model at the meso scale of the chemically reactive stressed porous system is presented and framed in the context of a multi-scale scenario of an array of coupled phenomena. An analogous model at the macro scale is developed in parallel together with upscaling and identification procedures for meso-scale and macro-scale material constants. The main outcome of the study is a tool for predicting the progress of time-dependent weathering phenomena, potentially allowing the stability of geological structures to be assessed as it evolves with a progressing chemical degradation in a specific configuration and under a specific set of loads.

The use of energy dispersive X-ray spectroscopy to detect strontium marks in fish otoliths

Otolith marking provides a reference point for otolith growth patterns by validating the temporal significance of growth increments. This widespread method is primarily implemented using fluorescent dyes. The incorporation of a trace element that appears naturally in otoliths offers an alternative approach. Diplodus annularis and Serranus scriba otoliths were marked with an intramuscular injection of SrCl 2 diluted in 0.9% sterile saline solution (55 mg Sr ml -1 saline solution), given at a dose of 100 mg Sr kg -1 fish. At 277 to 366 days after marking, the fishes showed little or no mortality and experienced growth in length and weight. All of the otoliths analyzed showed a clear Sr mark detected with backscattered or secondary electron imaging during a scanning electron microsope (SEM) analysis. The mark was confirmed by Sr analysis using an X-ray detector and an energy dispersive spectrometer system with the SEM. The otoliths continued to grow after the mark, and background Sr values in this new growth were much lower than at the mark. This method was feasible and yielded good results. However, the method’s cost may limit its applicability to experimental studies.

Schoenoplectus hallii, S. saximontanus, and the Putative S. hallii X S. saximontanus Hybrid: Observations from the Wichita Mountains Wildlife Refuge and the Fort Sill Military Reservation 2002 - 2010

Schoenoplectus hallii, S. saximontanus, and the putative S. hallii × S. saximontanus hybrid are obligate wetland sedges that occur in the sparsely vegetated margins of ponds, ditches or swales with fluctuating water levels. The species are amphicarpic and have easily identified differences between spikelet and basal achenes. We surveyed selected sites at the refuge in 2001, 2002, and 2007 – 2010, surveyed 4 sites on the Fort Sill Military Reservation in 2009 and 2010, and collected voucher specimens from all populations. Scanning Electron Microsope (SEM) photographs of spikelet and basal achenes indicate distinct morphological differences between species and the presence of “winged” ridges on S. saximontanus. Field observations indicated that populations at all sites vary in size and species distribution annually, and that both parental species appeared to be declining in number. We concluded that in populations where S. hallii and S. saximontanus co-occur, hybridization may be a threat to one or both parental species. The distribution of achenes by waterfowl and ungulates indicates that management to prevent establishment of mixed populations, and therefore hybridization, is not practical. We recommend that S. hallii be evaluated for federal listing under the Endangered Species Act, a range-wide assessment be completed for S. saximontanus, and that all sites with mixed populations should be examined for the presence of hybrids.

Pilot-Scale Application of Attapulgitic Clay for Stabilization of Toxic Elements in Contaminated Soil

This study presents an in situ pilot-scale application of attapulgitic clay for stabilization of toxic metals and metalloids in contaminated soil. The selected field for the pilot-scale experiment was heavily contaminated with toxic metals and metalloids in total (Cu: 122 mg/Kg, Pb: 6,610 mg/Kg, Zn: 3,630 mg/Kg, Cd: 26.3 mg/Kg, Ag: 9.4 mg/Kg, As: 802 mg/Kg, Mn: 1,435 mg/Kg, Ba: 304 mg/Kg, Sb: 95.3 mg/Kg) and leachable concentrations. Geochemical and physical properties of treated soil were thoroughly studied before and after mixing with the attapulgitic clay. Soil mineralogy was determined by X-ray diffraction (XRD) and scanning electron microsope (SEM) techniques. On the basis of the site-specific soil geochemical properties, an appropriate proportion of specific grain-size attapulgitic clay was added and mixed in situ with simultaneous adjustment of soil moisture content to reach saturation. Analytical data of amended soil samples collected 1 month after the application showed a significant reduction of water leachable metal fraction (Cu: 17%, Pb: 50%, Zn: 45%, Cd: 41%, Ag: 46%, As: 18%, Mn: 47%, Ba: 45%, Sb: 29%). In addition, soil pH was stabilized at slightly alkaline conditions and remained constant during a 7-month monitoring period after amending the soil. Overall, the use of attapulgitic clay as a binder for immobilizing metals in contaminated land is a promising stabilization method at a competitive cost under present market conditions.

Structural characterisation of β‐cyclodextrin crosslinked by adipic acid

SummaryThis study was conducted to investigate the structural characterisation of β‐cyclodextrin (β‐CD) crosslinked by adipic acid. β‐CD was treated with different concentrations (0%, 5%, 10% and 15%, w/v) of adipic acid. Different instruments, such as scanning electron microsope (SEM), Fourier‐transform infrared (FT‐IR) spectroscopy and 1H and 13C nuclear magnetic resonance (NMR) spectra were used to find out chemical structure in the crosslinked β‐CD. SEM analysis suggested that crosslinking β‐CD with 15% adipic acid changed the original morphology and considerably increased the particle size of the raw material. FT‐IR spectroscopy data showed that an intensive absorption band at 1706 cm−1 was present in the β‐CD samples treated with 10% and 15% adipic acid, indicating a crosslinking between hydroxyl groups of β‐CD and carboxyl groups of adipic acid. NMR spectra revealed that the ester linkages between hydroxyl groups of β‐CD and carboxyl groups of adipic acid were formed after crosslinking of β‐CD with adipic acid.

Development of Patterns for Digital Image Correlation Measurements at Reduced Length Scales

Methods for patterning metal thin films at the microscale and nanoscale by applying the patterns to metallic and polymeric materials for use in shape and deformation measurements in a scanning electron microsope (SEM) or other high magnification imaging system are described. In one approach, thin films of metallic materials (e.g., Au, Ag, Cu, and Cr) are applied to a variety of substrates. The coated samples are then placed into a reaction vessel, where the specimens are heated and exposed to a nitrogen atmosphere saturated with selected volatile chemicals. This process results in nano-scale remodeling of the metallic films, thereby affording high contrast random patterns with different morphologies. In a second approach, thin films of metallic materials, including gold and silver, also have been applied using a simplified UV photolithographic method requiring a minimum amount of laboratory preparation. Using selected substrates, both methods have been used successfully to transfer patterns onto polymeric and metallic materials ranging from 50–500 nanometers with chemical vapor rearrangement and 2 to 20 microns with UV photolithography, providing a pattern that can be used with digital image correlation to quantify both the surface profile and also surface deformations at reduced length scales.

Effects of ultrasonic root end preparation on resected root surfaces: SEM evaluation

Objective The purpose of this study was to investigate the in vitro effect of ultrasonic retrotips on root end surfaces. Study design Root end resection was performed on 45 single-root teeth endodontically treated after extraction. Setting the ultrasonic device at full power, a retrograde cavity was made by a stainless steel tip in 9 specimens (SS-FP). In another 9 samples a diamond tip was used (D-FP). Setting the intensity of the ultrasonic device at half power, 9 specimens were treated using stainless steel tips (SS-HP) and 9 using diamond tip (D-HP). Nine teeth were only apically resected and used as controls. Histologic serial sections were examined by scanning electron microsope to assess the number of root-face cracking, the marginal quality, and the crack type. Results No significant difference between diamond and stainless steel groups was found at a given power setting. Significant differences were found between SS-FP and SS-HP group for both the number of cracks and the marginal quality.

607 電子顕微鏡内マイクロ加工機械の設計および実験報告

Micro-meso mechanical manufacturing (M4) technology has recently attracted attentions as an alternative micromachining solution because of its potentials of processing variety in materials into 3 dimensional form. A micro lathe, which is installable and operational in a SEM (scanning electron microsope) vacuum chamber, has been developed to understand surface chemistry effects and mechanics at the cutting point where the chip formation and defection take place or forces are applied.

Low-temperature deformation and fracture of bulk nanostructural titanium obtained by intense plastic deformation using equal channel angular pressing

The low-temperature plasticity and fracture of polycrystals of coarse-grained (CG) and nanostructural (NS) technical-grade titanium of two structural modifications with grain size 0.3 and 0.1 μm, which were prepared by equal channel angular pressing (ECAP) with additional thermomechanical treatment are studied. The measurements are performed at temperatures 300, 77, and 4.2 K with uniaxial compression at deformation rate 4×10−4 s−1. The “stress-plastic deformation” hardening curves are obtained, the macroscopic yield stress, and the ultimate plasticity are measured for samples with compression axis orientations parallel and transverse to the ECAP axis. It is found that the yield stress for NS titanium is 1.5–2 times higher than for CG titanium and the yield stress on cooling from 300 to 4.2 K. Plasticity anisotropy is also observed in NS titanium—the yield stress is 1.2–1.5 times greater when the compression axis is oriented perpendicular to the ESAP axis than for parallel orientation. The ultimate plasticity with such changes in the structure of samples and under the experimental conditions systematically decreases, but the deformation to fracture remains above 4%. Nanostructural titanium does not show cold-brittleness right down to liquid-helium temperatures, but at 4.2 K plastic flow becomes jumplike, just as in CG titanium. It is established that for low-temperature uniaxial compression NS titanium fractures as a result of unstable plastic shear accompanied by local adiabatic heating of the material. This phenomenon is not characteristic of CG titanium. A study of the morphology of the shear-fracture surfaces using a scanning electron microsope shows a characteristic “vein” pattern, attesting to local heating at temperatures ⩾800 °C. It is established that plastic deformation in NS titanium is thermally activated at low temperatures. It is shown that microstructural internal stresses due to thermal anisotropy and possible microtwinning affect the yield stress.

Scanning electron microscopy of nonconductive specimens at critical energies in a cathode lens system.

A method for scanning electron microscopy imaging of nonconductive specimens, based on measurement and utilisation of a critical energy, is described in detail together with examples of its application. The critical energy, at which the total electron yield curve crosses the unit level, is estimated on the basis of measurement of the image signal development from the beginning of irradiation. This approach, concentrated onto the detected signal as the only quantity crucial for the given purpose of acquiring a noncharged micrograph, evades consequences of any changes in an irradiated specimen that influence the total electron yield curve and possibly also the critical energy value. Implementation of the automated method, realised using a cathode lens-equipped scanning electron microsope (SEM), enables one to establish a mean rate of charging over the field of view and its dependence on the electron landing energy. This dependence enables one to determine the energy of a minimum damage of the image of the given field of view. Factors influencing reliability and applicability of the method are discussed and examples of noncharged micrographs of specimens from both life and material science fields are presented.

Fly ash in concrete — a microstructure study

The paper presents preliminary details of a laboratory study aimed at identifying the mechanism or mechanisms whereby the incorporation of fly ash influences the strength of lean concrete mixes suitable for use in the construction of concrete gravity dams. It involved a scanning electron microsope study and compressive strength evaluation of the paste fraction and covered a range of mixes containing various amounts of a single supply of fly ash. Test specimens were cured at 20°C and at 40°C, data being obtained at intervals of seven days up to the age of three months for the main part of the investigation. In addition, some autoclave tests were undertaken and, for specimens cured at 20°C, strength tests were also carried out at ages up to twelve months. Although it is not possible to propose a firm hypothesis, the study suggests that the early age strength development is largely influenced by the physical presence of the ash particles rather than by a compositional change of the particles as a result of chemical reaction. However, the continuing increase in strength at greater ages is believed to be pozzolanic in nature and the need for further work is emphasised.

A survey of epicuticular waxes among genera of Triticeae. I. Ultrastructure of glumes and some leaves as observed with the scanning electron microscope

This is the first part of an electron microscopic and chemical study on epicuticular wax. Epicuticular wax ultrastructural morphology (EWUM) of glumes of representatives of 21 genera of Triticeae was determined with the aid of a scanning electron microsope (SEM). Leaves of several genera were examined for specific comparisons to be done later when chemical results are available. This study is based on 120 out of 251 seed accessions obtained from various sources from natural habitats, all grown for the purpose of both SEM and chemical studies in a plot in Ottawa, Canada. Vouchers are preserved and have been critically identified. The results of EWUM demonstrate that the various genera can be characterized by patterns of relative frequencies of the basic wax crystal categories: plates (P), knobs (K), and filaments (F). The variation within each category is also described. Frequencies of P, K, and F have been summarized for each genus. The frequency data have been analysed by principal-coordinate analyses and by Jardine–Sibson Bk cluster analysis to assess and interpret the phenetic relationships between the generic EWUM frequency patterns.

A transmission and scanning electron microsope study of primary neural induction.

Normal primary neural induction has been further studied by TEM and SEM. A single mesoderm cell is usually in contact with several ectoderm cells. The mesoderm cells are also contacting other mesoderm cells. It is suggested that ectoderm cells are induced in groups and that induction is synchronized by these contacts. At the points of contact between mesoderm and ectoderm cells cytoplasmic changes are present in the induced tissue.

Scanning Electron Microscope Studies of EDTA-Treated Enamel

Enamel samples that were treated with EDTA for 2, 4, 7, and 24 hours respectively, were examined by a scanning electron microsope and were compared to the appearance of sound, untreated enamel. The following features were noted: a preferential decalcification pattern of EDTA on enamel prisms, characteristics of a superficial region of enamel suggestive of the "prismless" zone, differences in prisms from the striae of Retzius when compared with those in intervening areas, and enamel surface characteristics suggestive of a "coating" or cuticle resembling enamel matrix.