Low Vacuum Mode Research Articles

Deposition of Boron nitride nanoparticles on polyamide fabrics

Purpose of research. Fixation of Boron nitride nanoparticles on polyamide fabric.Methods. Colloidal systems were stirred and dispersed in an ultrasonic bath QUICK 218-35 with an emitter power of 50 W and an ultrasonic technological disperser “Volna” UZTA-0.4/22-OM. The activation of the polyamide fabric surface and its cleaning were carried out by plasma treatment in a low-pressure PICO system. Deposition of nanoparticles using the Langmuir-Blodgett method was performed on a KSV Nima 2002 setup. The morphology and elemental composition of the polyamide fabric before and after the application of boron nitride nanoparticles were studied using a JEOL 6610LV scanning electron microscope equipped with an Oxford Instruments X-Max energy-dispersive X-ray analyzer. The research methodology included the use of a low-vacuum mode, which was important for preventing the accumulation of surface electrical charge on dielectric samples.Results. Sediment-resistant colloidal systems were synthesized based on boron nitride nanoparticles stabilized with stearic acid and an aqueous solution of Boron nitride nanoparticle powder with the addition of an oiling agent. Nano-particles from the first colloidal system were deposited on polyamide fabric using the Langmuir-Blodgett method, while nanoparticles from the second system were applied by immersing the fabric in the system with ultrasonic dispersion. SEM images of the polyamide fabric and its energy-dispersive analysis confirm the uniform fixation of boron nitride nanoparticles on the fibers by these methods.Conclusion. In this work, boron nitride nanoparticles were fixed onto polyamide fabric using the Langmuir-Blodgett method and by immersing the fabric in a colloidal system with ultrasonic dispersion. This allowed for uniform deposition of nanoparticles both on the surface of the polyamide fabric and between the fibers, enhancing its performance characteristics.

Development of a microfurnace dedicated to in situ scanning electron microscope observation up to 1300 °C. III. In situ high temperature experiments.

The FurnaSEM microfurnace was installed in the chamber of a scanning electron microscope to carry out in situ experiments at high temperatures and test its limits. The microfurnace was used in combination with different types of detectors (Everhart-Thornley for the collection of secondary electrons in a high vacuum, gas secondary electron detector for the specific collection of secondary electrons in the presence of gas, and Karmen© detector for the collection of backscattered electrons at high temperature). Experiments carried out on various samples (metal alloys and ceramics) show that the microfurnace operates in both high-vacuum and low-vacuum modes. Temperature ramp rates during temperature cycles applied to the sample range from 1 to 120 °C/min (temperature rise) and 1 to 480 °C/min (controlled and natural cooling). The maximum temperature at which images were recorded up to 25k × magnification was 1340 °C, with a residual air atmosphere of 120Pa. The choice of a flat furnace with the sample placed directly above it has enabled innovative experiments to be carried out, such as low-voltage imaging (using a shorter working distance-up to 10 mm-than is possible with conventional furnaces), 3D imaging (by tilting the stage by up to 10°), and high-temperature backscattered electron imaging (using a dedicated detector).

Transverse Loading on Single High-Performance Fibers by Round-Head Indenters and the Fibers’ Failure Visualization

High-performance fibers are well-known for their high stiffness and strength under axial tension. However, in their many applications as critical components of textiles and composites, transverse loads widely exist in their normal service life. In this study, we modified a micro material testing system to transverse load single fibers using round-head indenters. By integrating the loading platform with the Scanning Electron Microscopy (SEM) operating at a low-vacuum mode, we visualized the failure processes of fibers without conductive coatings. Post-fracture analysis was conducted to provide complementary information about the fibers’ failure. The energy dissipation was compared with the axial tensile experiments. Three inorganic and two organic fibers were investigated, namely carbon nanotube, ceramic, glass, aramid, and ultrahigh molecule weight polyethylene fibers. Different failure characteristics were reported. It is revealed that the organic fibers had higher energy dissipation than the inorganic fibers under the transverse loading by the round-head indenters. The fiber’s energy dissipation under transverse loading was no more than 17.9% of that subjected to axial tension. Such a reduced energy dissipation is believed to be due to the stress concentration under the indenter. It is suggested that the fiber’s material constituent, structural characteristics, and stress concentration under the indenter should be considered in the fiber model for textiles and composites.

A new sample preparation protocol for SEM and TEM particulate matter analysis

A new methodology has been developed to prepare electron microscopy, both SEM and TEM, specimens starting from particulate matter collected using environmental sampling systems. The approach is based on the extraction of the particles to be analyzed from the harvesting substrates. The extracted particles can be directly observed in an SEM, possibly in low-vacuum mode to prevent electrical charging. In order to prepare electron transparent samples, TEM observations require a further step, consisting in embedding the particles in an electron transparent carbon film deposited before dissolving the acetate extracting substrate. The protocol has been tested by analyzing particles collected during bench tests on brake pads and discs, carried out on a dynamometer equipped with a particulate matter sampling apparatus. The main advantages of the approach are: the complete extraction of the particulate matter specimens from the original substrates, that in this way do not interfere with the analyses; the extracted samples retain the topological information of the collection in the specimens prepared for SEM; possibility to be applied to any kind of particulate matter harvesting substrates.

Structural features of mineral carriers of medicinal substances

The aim of the work is to investigation of the structural features of mineral carriers of medicinal substances. Tasks: conduct electron microscopy and study the structural features of mineral sorbents; develop a classification of sorption interaction. The materials are Smectite Dioctahedral (registration certificate N 015155/01, France), Kaolin (state standard 19608-84, Russia), Montmorillonite Clay (technical specifications 9296-001-62646221-2012, Russia). The methods are scanning electron microscopy on a FEI Quanta 600 microscope with a low vacuum mode and an LFD detector. Results. Electron microscopy of objects was performed using segmentation of elements as subsystems, inside which the morphological description does not penetrate. The morphology of objects is studied. It is established that the studied substances are microstructural objects. Porosity was determined in samples of Smectite, Kaolin and Montmorillonite Clay. The classification of sorption interaction is developed. According to the presented classification, the materials under study are divided into two groups according to their porous characteristics: Group 1-sorption interaction in pores and by ion exchange (Smectite, Montmorillonite Clay); Group 2-sorption in secondary pores and by means of Oxygen and Hydroxyl centers (Kaolin).

Evaluation and application of a new scintillator-based heat-resistant back-scattered electron detector during heat treatment in the scanning electron microscope.

A new high-temperature detector dedicated to the collection of backscattered electrons is used in combination with heating stages up to 1050°C, in high-vacuum and low-vacuum modes in order to evaluate its possibilities through signal-to-noise ration measurements and different applications. Four examples of material transformations occurring at high temperature are herein reported: grain growth during annealing of a rolled platinum foil, recrystallisation of a multiphased alloy, oxidation of a Ni-based alloy and complex phase transformations occurring during the annealing of an Al-Si coated boron steel. The detector could be potentially adapted to any type of SEM and it offers good opportunities to perform high-temperature experiments in various atmospheres.

AGGREGATION OF MS-MONOPYRIDYL-Β-OCTAALKYLPORPHYRINS IN DICHLOROMETHANE IN PRESENCE OF Pd(II)

Aggregation of 13,17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-4-yl) porphyrin (I), 13,17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-3-yl)porphyrin (II) and 13.17-diethyl-2,3,7,8,12,18-hexamethyl-5-(pyridin-2-yl)porphyrin (III) in the presence of trans-bis(benzonitrile)palladium(II) dichloride was studied by dynamic light scattering and electronic absorption spectroscopy in dichloromethane at 293 K. The average aggregate size and the nature of their distribution were determined. Using scanning electron microscopy, it was determined the size and composition of clusters formed by aggregates of complexes of the palladium(II) cation with the studied porphyrins. It was shown that minimal acetic acid additions lead to the destruction of the corresponding clusters. At the same time, complete destruction of the aggregates does not occur even with a 100-fold molar excess of acid.We used the Zetasizer Nano ZS (model ZEN3600, Malvern Instruments), equipped with a 633nm laser and non-invasive backscattering (NIBS) technology when the scattered light detector is positioned at an angle of 173° to the incident light. Confirmation of porphyrin aggregation was performed by additional study of the structure using a Hitachi TM4000Plus desktop electron microscope equipped with a 4-segment highly sensitive semiconductor detector and a secondary electron detector for low vacuum mode. Elemental analysis of the obtained aggregates in the cluster was performed using a silicon drift detector with a working area of 30 mm2, combined with a Hitachi TM4000Plus microscope. It was found that aggregates consisting of a para-pyridyl derivative of alkylporphyrin and trans-bis (benzonitrile) palladium (II) dichloride are formed in dichloromethane at 293 K. The best results of porphyrin structures were observed for mixtures of 13,17-diethyl-2,3,7,8,12,18-5-hexamethyl-5-(pyridine-4-yl)porphyrin with TRANS-bis(benzonitrile)- palladium (II) dichloride in a ratio of 1:3, which is probably due to less spatial shielding of the reaction center of the macrocycle and, as a result, better stabilization of the resulting particles. The size of a cluster consisting of individual aggregates was measured using scanning electron microscopy. An elemental analysis of a single aggregate was obtained.

Simultaneous Visualization of Wet Cells and Nanostructured Biomaterials in SEM using Ionic Liquids.

This work presents a successful methodology to image mammalian cells adhered to nanostructured titanium by using scanning electron microscopy (SEM) operating in low-vacuum mode following ionic liquid treatment. Human osteoblast-like Saos-2 cells were treated with a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate, and subsequently imaged on titanium by SEM. Titanium substrates were modified to create laser-induced periodic surface structures (LIPSS) for visualization at the submicron scale. By using a combination of fluorescence-based cell metabolism along with light microscopy and SEM image analysis, the shape and location of irradiated cells were confirmed to be unchanged after multiple irradiation sessions; the viability of minimally irradiated cells was also unaltered. The wet imaging conditions combined with a rapid facile protocol using ionic liquid allows this technique to fulfill a niche in examining cellular behavior on biomaterials with submicron surface features. The demonstrated method to track observed cell adhesion to submicron surface features by SEM has great implications for understanding cell migration on nanostructured surfaces as well as the exploration of simpler SEM preparation methods for cellular imaging.

Ionosilica-based anion exchangers for low-temperature thermochemical storage of energy under mild conditions of adsorbent regeneration and saturation

Three ionosilica materials have been tested for low-temperature thermochemical storage of energy under mild conditions of adsorbent regeneration and saturation. The previous synthesis procedures were adapted to prepare materials possessing an organosilica framework with silylated cationic blocs and Cl-, HSO4-, SO42- anions in various proportions as extra-framework compensating counter-ions. Transmission and Scanning Electron Microscopy, Wavelength Dispersive X-Ray Fluorescence, Energy Dispersive X-ray Spectroscopy, Thermogravimetric analysis, adsorption of gaseous nitrogen at 77 K, 29Si Solid-State Nuclear Magnetic Resonance spectroscopy were employed to establish the key characteristics of the three ionosilica samples in terms of elemental composition, particle morphology and textural properties, thermal stability and regenerability, or variability of surface activity during repeated hydration-dehydration cycles. Their capacity to adsorb water vapor at cool and moderate ambient temperatures after incomplete surface drying was demonstrated by means of the scanning microscopy operating in low-vacuum mode at 275 K, or more precisely by measuring the water adsorption isotherms at 313 K and the related differential heats under static conditions. Finally, flow calorimetry operating in the moist-gas flow mode was used to measure the integral heat accompanying the adsorption of water vapor at its partial pressure of 2.8 kPa and 296 K as well as the kinetics of heat release in three drying-saturation cycles. After a drying procedure carried out under helium flow at 353 K, the thermal performance of two ionosilica samples containing both HSO4- and SO42- counter-ions was sufficient enough to consider them as potential adsorbents for auxiliary space heating in homes, small businesses, or public buildings.

Microscopic imaging of human bloodstains: testing the potential of a confocal laser scanning microscope as an alternative to SEMs

The forensic interest on human bloodstains derives from their relation to crime investigation, whereas an archaeological and ethnographic concern arises from their occurrence because of warfare and ritual. The development of digital reflected light microscopes provided an opportunity to use ligh microscopy to study surface topographies in a more accurate way than previously. However, this enhancement has been focused on increasing magnification rather than resolution. An advanced type of light microscope is the confocal laser scanning microscope (CLSM). Its potential as an alternative to scanning electron microscopes (SEMs) for imaging human bloodstains was tested. A fragment of stone (brown chert) was smeared with human peripheral blood, air-dried, and stored indoors. After nearly two years, the sample was examined and imaged using an Olympus LEXT OLS4000 CLSM. The surface detail of CLSM images appeared to be comparatively lower than that of SEM micrographs of coated bloodstains taken at high-vacuum mode and high accelerating voltage, similar to that of SEM micrographs of uncoated bloodstains taken at low-vacuum mode and high accelerating voltage, and similar to or even higher than that of SEM micrographs of uncoated bloodstains taken at high-vacuum mode and low accelerating voltage. These results suggest that a CLSM is a practical alternative to SEMs for imaging human bloodstains when a very-high level of surface detail is not required.

Environmental gas impact on the emission volume of X-rays near the interface in the variable pressure scanning electron microscopy

In this paper, our previously developed model to account for the secondary X-ray fluorescence and absorption effects near the interface of two adjacent materials in a high-vacuum scanning electron microscope (Zoukel & Khouchaf, 2014) is adapted and extended to experimental conditions of low-vacuum mode (in the presence of a gaseous environment in the SEM analysis chamber). The position shifting effect of the two Gaussian peaks issued from the first derivative equation that can fit the experimental low-vacuum EDS profiles is investigated. The impact of the medium gas on the emission volume of secondary X-rays near the interface is qualitatively discussed. Water vapour and helium are successively used as gas environment, in order to link the resolution of microanalysis profiles with the effects of the X-ray fluorescence and absorption phenomenon. A close agreement between Monte Carlo simulation and experimental results is found.

Microscopy tools for product innovation

Microscopy tools for product innovation

Quantitative analysis of the effect of environmental-scanning electron microscopy on collagenous tissues

Environmental-scanning electron microscopy (ESEM) is routinely applied to various biological samples due to its ability to maintain a wet environment while imaging; moreover, the technique obviates the need for sample coating. However, there is limited research carried out on electron-beam (e-beam) induced tissue damage resulting from using the ESEM. In this paper, we use quantitative second-harmonic generation (SHG) microscopy to examine the effects of e-beam exposure from the ESEM on collagenous tissue samples prepared as either fixed, frozen, wet or dehydrated. Quantitative SHG analysis of tissues, before and after ESEM e-beam exposure in low-vacuum mode, reveals evidence of cross-linking of collagen fibers, however there are no structural differences observed in fixed tissue. Meanwhile wet-mode ESEM appears to radically alter the structure from a regular fibrous arrangement to a more random fiber orientation. We also confirm that ESEM images of collagenous tissues show higher spatial resolution compared to SHG microscopy, but the relative tradeoff with collagen specificity reduces its effectiveness in quantifying collagen fiber organization. Our work provides insight on both the limitations of the ESEM for tissue imaging, and the potential opportunity to use as a complementary technique when imaging fine features in the non-collagenous regions of tissue samples.

Specific Features of Energy Dispersive X-Ray Electron Probe Microanalysis in the Low Vacuum Mode

Experimental data on the generation and detection of characteristic X-radiation of elements in electron probe microanalysis of dielectric samples in the low vacuum mode without the deposition of conducting coatings are discussed. The main advantage of the considered method of analysis is the stability of the intensity ratio between diagnostic analyte lines in the wide range of currents of the electron probe and gas phase pressure in the chamber in the range 60–130 Pa, sufficient for obtaining undistorted images of the surface of dielectrics. The stability of the intensity ratio ensures obtaining correct data of the quantitative analysis of nonconducting samples without the deposition of conducting coatings. The main features of low-vacuum microanalysis for the range of gas phase pressures used are discussed, which can create additional difficulties in the study. Among such features is a possibility of the manifestation of reflexes of gas-phase elements, significant underestimation of the relative emission intensity from lighter elements in the composition of the studied samples, loss of scanning locality in the analysis of small sites on the sample surface. An example of the correct quantitative elemental analysis of a dielectric surface without the deposition of an electroconductive coating for a number of aluminosilicates is presented.

The effect of different workplace nanoparticles on the immune systems of employees

Currently, nanoparticles are widely present in the environment and are being used in various industrial technologies. Nanoparticles affect immune functions, causing different immune responses. The aim of the current study was to evaluate several cytokines, interleukin (IL)-1b, IL-6, IL-8, tumour necrosis factor-a (TNF-α), interferon-γ, adhesive molecule sICAM-1, macrophage inhibitory protein 1a (MIP1a) and secretory immunoglobulin A, in nasal lavage fluid and in the peripheral blood of healthy subjects exposed to workplace nanoparticles. Thirty-six employees from three different environments were examined: 12 from a metalworking company, 12 from a woodworking company and 12 office workers. The nanoparticles in the different workplaces were detected in the air in the immediate vicinity of the employees. The particle number concentration and surface area values were significantly higher in the workplaces of the metal- and woodworking industries, but concentrations of mass were lower (the measurements were performed by an electrical low-pressure impactor ELPI+). Energy dispersive X-ray spectroscopy (EDS, an attachment to a high-resolution SEM) was used to provide elemental analysis or chemical characterization of the dust particles in a low-vacuum field-free mode operating at a potential of 15 kV spot 3.0. The technique used provided quantitative and spatial analyses of the distribution of elements through mapping (two to three parallel measurements) and point analysis (four to five parallel measurements). Samples from the metal industry contained more ultramicroscopic and nanometric particles, e.g. toxic metals such as Zn, Mn and Cr, and fewer microscopic dust particles. The nasal lavage and peripheral blood were taken at the beginning and the end of the working week, when immune indices were measured. Our data showed a statistically significant increased level of the pro-inflammatory cytokine TNF-α in serum in both exposed groups compared with office workers as well as a higher level of TNF-α in workers from the woodworking company compared with the metalworking employees. We found an elevated level of IL-6 in the exposed groups as well as an elevated level of IL-8 in the nasal lavage in woodworking employees after work.

Detection of glass particles on bone lesions using SEM-EDS.

The problem of identifying the wounding agent in forensic cases is recurrent. Moreover, when several tools are involved, distinguishing the origin of lesions can be difficult. Scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDS) equipment is increasingly available to the scientific and medical community, and some studies have reported its use in forensic anthropology. However, at our knowledge, no study has reported the use of SEM-EDS in forensic cases involving glass tools, whether in case reports or experiments. We performed an experimental study on human rib fragments, on which we manually created wounds using fragments of window and mirror glass. SEM-EDS was executed on samples without any further preparation on low vacuum mode, then on the same samples after defleshing them completely by boiling them. Window and mirror glass particles were detected on experimental wounds. Both had silica in their spectra, and the opaque side of the mirror contained titanium, allowing for their identification. Boiling and defleshing the bone samples involved a loss of information in terms of the number of wounds detected as positive for glass particles and in the number of glass particles detected, for both window and mirror glass. We suggest the analysis of wounds with suspected glass particles using low vacuum mode and with no defleshment by boiling.

Focus on analytical equipment, sensors, and detectors

Focus on analytical equipment, sensors, and detectors

Ultrastructural analyses of the novel chimeric hemostatic agent generated via nanotechnology, ABS nanohemostat, at the renal tissue level.

Ankaferd Blood Stopper (ABS), a hemostatic agent of plant origin, has been registered for the prevention of clinical hemorrhages. Currently there is no data regarding the ultrastructural analysis of ABS at the tissue level. The aim of this study is to assess renal tissue effects via scanning electron microscopy (SEM) analyses for the ABS and ABS nanohemostat (formed by the combination of self-assembling peptide amphiphile molecules and ABS). SEM experiments were performed with FEI Nova NanoSEM 230, using the ETD detector at low vacuum mode with 30 keV beam energy. SEM analyses revealed that significant erythroid aggregation are present inside the capillary bed of the renal tissue. However, neither the signs of necrosis nor any other sign of tissue damage are evident in the surrounding renal tissue supplied by the microcapillary vasculature. Our study is important for several reasons. Firstly, in our study we used ABS nanohemostat which was recently developed. This study adds valuable information to the literature regarding ABS nanohemostat. Secondly, this study is the first ultrastructural analysis of ABS that was performed at the tissue level. Thirdly, we disclosed that ABS nanohemostat could induce vital erythroid aggregation at the renal tissue level as detected by SEM. Lastly, we detected that ABS nanohemostat causes no harm to the tissues including necrosis and any other detrimental effects.

Human bloodstains on bone artefacts: an SEM intra- and inter-sample comparative study using ratite bird tibiotarsus

Apart from their forensic significance in crime investigation, human bloodstains have an anthropological interest due to their occurrence on certain traditional weapons and ritual objects. Previously, a guiding study of erythrocytes in experimental samples including domestic sheep (Ovis aries) tibia was carried out using a scanning electron microscope (SEM). Here, a comparative SEM study to reveal the potential differences in bloodstain surface morphology as a function of intra-sample (smear region) and inter-sample (individual smear, smearing mechanism, bone origin) parameters is reported. A fragment of emu (Dromaius novaehollandiae) tibiotarsus was smeared with an adult man’s peripheral blood. After air-drying and storing indoors, the boundary and neighbouring inner areas of the three individual bloodstains obtained were examined via secondary electrons in a variable-pressure SEM working in low-vacuum mode. As a whole, desiccation microcracks were present, the limits between the smear and the substrate appeared poorly defined, and no erythrocyte negative replicas were observed in the examined areas. In addition, a putative fibrin network, more or less embedded in the dried plasma matrix, was observed in the smears’ boundary. Regarding the smear region in sliding smears, the periphery and boundary revealed to be different, while the head and tail were similar. Considering individual sliding smears, they had similar characteristics. Relating to the smear region as a function of the smearing mechanism, the periphery was different whether sliding or touching, while the boundary was similar in sliding and touching smears. Concerning the smear region as a function of the bone origin, the periphery revealed to be similar in both ratite and mammalian bone, while the boundary did different in ratite and mammalian bone. The results of this study show that SEM examination can be used fruitfully to detect bloodstains on ratite bone. Combined with previous SEM results in domestic sheep bone, they suggest, further, that blood remains can be detected on objects made of bone irrespectively of the mammalian or ratite origin of this raw material.

Applications of scanning electron microscopy in earth sciences

This paper expounds upon the basic principle of scanning electron microscopy (SEM), the main features of image types, and different signals, and the applications and prospects in earth sciences research are reviewed. High-resolution field emission SEM allows observation and investigation of a very fine micro area in situ. Using low-vacuum mode SEM, geological insulating samples can be analyzed directly without coating, demonstrating the wide application prospect. Combined with backscatter detector (BSE), energy dispersal X-ray spectroscopy (EDS), cathodoluminescence spectrometry (CL), and electron back-scattering diffraction (EBSD), SEM can yield multiple types of information about geological samples at the same time, such as superficial microstructure, CL analysis, BSE image, component analysis, and crystal structure features. In this paper, we use examples to discuss the geological application of SEM. We stress that we should not only focus on the CL image analysis, but strengthen CL spectrum analyses of minerals. These results will effectively reveal the mineral crystal lattice defects and trace element composition and can help to reconstruct mineral growth conditions precisely.