Environmental Scanning Electron Microscopy Observations Research Articles

Observation of asphalt binder microstructure with ESEM.

The observation of asphalt binder with the environmental scanning electron microscope (ESEM) has shown the potential to observe asphalt binder microstructure and its evolution with binder aging. A procedure for the induction and identification of the microstructure in asphalt binder was established in this study and included sample preparation and observation parameters. A suitable heat-sampling asphalt binder sample preparation method was determined for the test and several stainless steel and Teflon sample moulds developed, finding that stainless steel was the preferable material. The magnification and ESEM settings conducive to observing the 3D microstructure were determined through a number of observations to be 1000×, although other magnifications could be considered. Both straight run binder (PG 58-28) and an air blown oxidised binder were analysed; their structures being compared for their relative size, abundance and other characteristics, showing a clear evolution in the fibril microstructure. The microstructure took longer to appear for the oxidised binder. It was confirmed that the fibril microstructure corresponded to actual characteristics in the asphalt binder. Additionally, a 'bee' micelle structure was found as a transitional structure in ESEM observation. The test methods in this study will be used for more comprehensive analysis of asphalt binder microstructure.

The effect of heat treatments applied to superstructure porcelain on the mechanical properties and microstructure of lithium disilicate glass ceramics

The aim of this study was to investigate that heat treatments with different numbers applied to superstructure porcelain whether effects microstructure and mechanical properties of lithium disilicate ceramic (LDC). Eighty disc-shaped specimens were fabricated from IPS e.max Press. Specimens were fired at heating values of porcelain in different numbers and divided four groups (n=5). Initial Vickers hardness were measured and X-ray diffraction (XRD) analysis was performed. Different surface treatment were applied and then Vickers hardness, surface roughness and environmental scanning electron microscopy (ESEM) analysis were performed. Data were analyzed with Varyans analysis and Tukey HSD test (α=0.05). Initial hardness among groups was no significant different (p>0.05), but hardness and surface roughness after surface treatments were significant different (p<0.05). Lithium disilicate (LD) peaks decrease depended on firing numbers. ESEM observations showed that firing number and surface treatments effect microstructure of LDC. Increasing firing numbers and surface treatments effect the microstructure of LDC.

Observation of bitumen microstructure oxidation and blending with ESEM

There have been a several studies observing bitumen microstructure using the environmental scanning electron microscope (ESEM); however, these have been few and far between. Nevertheless, there have been findings that show microstructure under ESEM clearly evolving with bitumen ageing. The objective of this paper is to focus on sample conditioning, oxidation and blending. A conditioning procedure was produced and the effect of freezing (−18°C) on the bitumen microstructure for 19 h was examined. A straight-run PG 58-28 bitumen was sampled, with the same bitumen being oxidised using hot air. Additionally, these two bitumens were mixed at ratios of 25/75, 50/50 and 75/25. The microstructures were compared with ESEM observation for their relative density, organisation and fibril size, clearly showing an evolution in the microstructure with oxidation and with different blending ratios.

Whole-journey nanomaterial research in an electron microscope: from material synthesis, composition characterization, property measurements to device construction and tests

The whole-journey nanomaterial research from material synthesis, composition and structure characterizations, property measurements to device construction and tests in one equipment chamber provides a quick and unambiguous way of establishing the relationships between synthesis conditions, composition and structures, physical properties and nanodevice performances of nanomaterials; however, it still proves challenging. Herein, we report the whole-journey research of tungsten oxide nanowires in an environmental scanning electron microscope (ESEM) equipped with an x-ray energy dispersive spectrometer (EDS) and a multifunctional nanoprobe system. Tungsten oxide nanowires are synthesized by irradiating a tungsten filament using a high-energy laser in O2 atmosphere with the dynamic growth processes of nanowires being directly visualized under ESEM observation. The as-synthesized nanowires are then characterized to be monoclinic W18O49 nanowires by combing in situ EDS and ex situ transmission electron microscopy. Important physical parameters, i.e. Young’s modulus, breaking strength, and electrical conductivity, of W18O49 nanowires are determined based on in situ property measurements. Two-terminal electronic devices employing single W18O49 nanowires as the channel are in situ constructed and their performances as near-infrared photodetectors and water vapor sensors are studied. The whole-journey research establishes the relationships between synthesis conditions, composition and structures, physical properties and nanodevice performances of tungsten oxide nanowires, and can be applied to other nanomaterials.

Adhesion of surgical sealants used in cardiothoracic and vascular surgery

Surgical sealants are widely used in cardiothoracic and vascular surgery essentially for hemostasis and sealing. Their adhesive properties have mainly been studied by clinical experiments. The objective of this study is to measure adhesion of the three main types of surgical sealant used in cardiothoracic and vascular surgery under normalized realistic conditions.The bulge-and-blister test was used to quantify adhesive performances of three types of surgical adhesives: cyanoacrylates, polyethylene glycol (PEG), and aldehydes. Samples were composed of two circular layers of equine pericardium glued by the surgical sealant studied. Comparative adhesion testing was carried out in eight samples bonded with a Dermabond® (cyanoacrylate), five samples with Bioglue® (aldehyde), four samples with Coseal® (PEG), and thirteen samples bonded with an industrial cyanoacrylate. Scanning electron microscope (SEM) observations of cross-sections of samples glued by Dermabond® and environmental scanning electron microscopy (ESEM) images of samples composed of equine pericardium glued by Bioglue® were also performed.The average value of the adhesion energy is 2.3+/−1.5 J.m−2 for samples glued with Dermabond®, 6.04+/−1.61 J.m−2 with Bioglue®, 2.37+/−1.25Jm−2 with Coseal®, 3.74+/−1.33Jm−2 with the industrial cyanoacrylate glue in surgical conditions. SEM observations of cross-sections of samples glued by Dermabond® showed a failure at the interface between the glue and the pericardial layer. ESEM observations have revealed a majority of regions where the glue is not linked to the pericardium.Adhesive performance measurements and microscopy observations in surgical conditions show that surgical sealants adhesion is weak and explain their poor efficacy in clinical practice. To improve adhesion in the surgical field, we need to focus on achieving a better cohesion between the adhesive and the substrate by modifying conditions adhesive bonding and consequently tend toward cohesive failure.

In situ ESEM observations of spruce wood (Picea abies Karst.) during heat treatment

An environmental scanning electron microscope (ESEM) equipped with a hot stage was used to investigate how the anatomical features of spruce wood respond to heating in vacuum conditions. The ESEM allowed for continuously observing the swelling, shrinkage, and other deformations of certain anatomical elements during heating. Observations showed that, as the temperature increases, there is a slight initial swelling due to thermal expansion of wood and steam and gas release from the cell wall, up to a threshold of 90–100 °C. Subsequently, the size of the various anatomical elements remained stable up to 200 °C, after which the cell walls withdrew and deformed. There were few significant differences between earlywood and latewood, while the deformation of cell lumen was strongly influenced by the dimension and the arrangement of the walls that surrounded them. None of the observed cracks was directly attributable to the impact of increased heat. Nevertheless, existing intercellular spaces strongly increased in size, arriving to grow up to 300 % of the initial dimension. These results emphasize the importance of sound starting materials to avoid defects in the treated samples.

Environmental SEM and dye penetration observation on resin-tooth interface using different light curing method.

The aim of this study was the effects of different light curing methods on marginal sealing and resin composite adaptation to the cavity wall using the dye penetration test and environmental scanning electron microscope (SEM) observations. Cylindrical cavities were prepared on cervical regions. The teeth were restored with Clearfil Liner Bond 2 V adhesive and filled with Clearfil Photo Bright or Palfique Estelite resin composites. These resins were cured with a conventional light-curing method or a slow-start curing method. After thermal cycling, the specimens were subjected to the dye penetration test to evaluate marginal sealing and adaptation of the resin composites to the cavity walls. These resin-tooth interfaces were then observed using environmental SEM. The light-cured resin composite, which exhibited increased contrast ratios during polymerization, suggests high compensation for polymerization stress using the slow-start curing method. There was a high correlation between dye penetration test and environmental SEM observation.

In-Situ ESEM and EELS Observation of Water Uptake and Ice Formation in Multilayer Graphene Oxide.

Graphene oxide (GO) is hydrophilic and swells significantly when in contact with water. Here, we investigate the change in thickness of multilayer graphene oxide membranes due to intercalation of water, via humidity-controlled observation in an environmental scanning electron microscope (ESEM). The thickness increases reproducibly with increasing relative humidity. Electron energy loss spectroscopy (EELS) reveals the existence of water ice under cryogenic conditions, even in high vacuum environment. Additionally, we demonstrate that freezing then thawing water trapped in the multilayer graphene oxide membrane leads to the opening up of micron-scale inter-lamellar voids due to the expansion of ice crystals.

Erratum to: Psammoma bodies in two types of human ovarian tumours: a mineralogical study

Psammoma body (PB) is a common form of calcification in pathological diagnosis and closely relevant to tumours. This paper focuses on the mineralogical characteristics of PBs in ovarian serous cancer and teratoma by using polarization microscope (POM), environmental scanning electron microscope (ESEM), micro-Fourier transform infrared spectroscopy (micro-FT-IR), transmission electron microscope (TEM), micro-area synchrotron radiation X-ray powder diffraction (μ-SRXRD) and fluorescence (μ-SRXRF). Both the PBs in tissues and separated from eight typical cases were investigated. POM and ESEM observation revealed the inside-out growth pattern of PBs. μ-SRXRD and micro-FT-IR results demonstrated the dominant mineral phase of PBs in ovarian serous cancer and teratoma was AB-type carbonate hydroxyapatite (Ca10[(PO4)6-x-y(CO3)x(HPO4)y][(OH)2−u(CO3)u] with 0 ≤ x,y,u ≤ 2). As observed by ESEM and TEM, the layer-rich PBs in teratoma were up to 70 μm and mainly consisted of 5 nm-wide, 5-12 nm-long columnar crystals; the PBs in ovarian serous cancer with a maximum diameter of 35 μm were composed of slightly longer columnar crystals and granulates with 20-100 nm in diameter. The selected area electron diffraction patterns showed dispersed polycrystalline diffraction rings with arching behavior of (002) diffraction, indicating the aggregated nanocrystals grew in the preferred orientation of (002) face. The EDX and μ-SRXRF results together indicated the existence of Na, Mg, Zn and Sr in PBs. These detailed mineralogical characteristics may help uncover the nature of the pathological PBs in ovary.

Stress-dependent undrained shear behavior of remolded deep clay in East China

Consolidated-isotropically undrained triaxial compression (CIUC) tests were performed on the reconstituted deep clay from a mine in East China. It was consolidated to maximum stresses in the range of 0.3–2.6 MPa. The test results show that the stress-strain-strength properties of the clay during undrained shear are significantly stress-dependent. In particular, in the case of high consolidation pressure, the post-peak drop in strength on stress-strain curves and shear plane in soil specimens are more evident, the peak stress ratio and the axial strain at which this ratio was reached are smaller, and the relationship between pore pressure and axial strain is also significantly different from that for the case of low consolidation pressure. The environmental scanning electron microscope observations and micro analysis lead to an understanding of the physical mechanisms underlying the above stress-dependent mechanical behavior. In addition, the CIUC behaviors of the studied clay are discussed in the context of critical state soil mechanics.

Psammoma bodies in two types of human ovarian tumours: a mineralogical study

Psammoma body (PB) is a common form of calcification in pathological diagnosis and closely relevant to tumours. This paper focuses on the mineralogical characteristics of PBs in ovarian serous cancer and teratoma by using polarization microscope (POM), environmental scanning electron microscope (ESEM), micro-Fourier transform infrared spectroscopy (micro-FT-IR), transmission electron microscope (TEM), micro-area synchrotron radiation X-ray powder diffraction (μ-SRXRD) and fluorescence (μ-SRXRF). Both the PBs in tissues and separated from eight typical cases were investigated. POM and ESEM observation revealed the inside-out growth pattern of PBs. μ-SRXRD and micro-FT-IR results demonstrated the dominant mineral phase of PBs in ovarian serous cancer and teratoma was AB-type carbonate hydroxyapatite (Ca10[(PO4)6-x-y(CO3)x(HPO4 2−)y][(OH)2−u(CO3)u] with 0 ≤ x,y,u ≤ 2). As observed by ESEM and TEM, the layer-rich PBs in teratoma were up to 70 μm and mainly consisted of 5 nm-wide, 5–12 nm-long columnar crystals; the PBs in ovarian serous cancer with a maximum diameter of 35 μm were composed of slightly longer columnar crystals and granulates with 20–100 nm in diameter. The selected area electron diffraction patterns showed dispersed polycrystalline diffraction rings with arching behavior of (002) diffraction, indicating the aggregated nanocrystals grew in the preferred orientation of (002) face. The EDX and μ-SRXRF results together indicated the existence of Na, Mg, Zn and Sr in PBs. These detailed mineralogical characteristics may help uncover the nature of the pathological PBs in ovary.

Dissolution of Calcareous Phosphate Rock from Gafsa (Tunisia) Using Dilute Phosphoric Acid Solution

In the present study, porous structure of raw and calcined phosphate ore particles was examined. The specific surface area and the pore volume were determined by nitrogen adsorption. Raw particles and calcined ores were leached using dilute phosphoric acid solution (4% P2O5). In all cases, the ESEM (Environmental Scanning Electron Microscopy) observations show that the grain of phosphate holds its shape ovoidale. The sample heated at 780?C presented the lowest specific surface area 0.6 m2/g at each reaction time, and the unreacted phases were analysed using XRD, FT-IR, Nitrogen adsorption and ESEM observations. The selective leaching curves were evaluated in order to test the validity of kinetics models. A mathematical model in the following form was applied. The dissolution of the two samples (raw and calcined phosphate) has been observed to take place in two steps: the first being fast and the second being slow.

Effect of calcium phosphate-based fillers on the structure and bonding strength of novel gelatin–alginate bioadhesives

Interest in soft and hard tissue adhesives as alternatives for conventional wound closing and bone fixation applications has increased in recent decades as a result of numerous possible advantages such as better comfort and lower cost. A novel bioadhesive based on the natural polymers GA has recently been developed and studied in our laboratory. Hydroxyapatite and tricalcium phosphate are two bioactive ceramics known for their ability to enhance bone regeneration. In the current study, these two bioactive fillers were incorporated into the bioadhesive at concentrations of 0.125, 0.25 and 0.5% w/v, and their effects on the resulting adherence properties to soft and hard tissues were studied. Porcine skin and cortical portions of bovine femurs were used as soft and hard tissue specimens, respectively. The bonding strength was evaluated using an Instron universal testing machine in tensile mode, and the microstructure analysis was based on environmental scanning electron microscope observations. Both bioactive fillers were found to have a reinforcing effect on the adhesives, significantly improving their adhesion to soft tissues in certain concentrations. The best bonding strength results were obtained for 0.25% hydroxyapatite and 0.5% w/v tricalcium phosphate-18.1 ± 4.0 and 15.2 ± 2.6 kPa, respectively, compared with 8.4 ± 2.3 kPa for adhesive with no fillers. The improved adherence is probably related to the stiffness of the insoluble hydroxyapatite and tricalcium phosphate particles which reinforce the adhesive. These particles can clearly be observed in the environmental scanning electron microscope analysis. The potential of these fillers to increase the bonding strength of the adhesive to hard tissues was also demonstrated. Hydroxyapatite and tricalcium phosphate thus improve our new gelatin-alginate bioadhesives, which can be used for both soft and hard tissue adhesive applications.

Soot Cake Oxidation on a Diesel Particulate Filter: Environmental Scanning Electron Microscopy Observation and Thermogravimetric Analysis

The oxidation behavior of soot cake on the porous wall of a diesel particulate filter (DPF) was investigated. As a new experimental approach to observe the soot cake during its oxidation, an environmental scanning electron microscope (ESEM) was utilized. The dynamic deformation process of the soot cake was revealed, and the contact conditions between the soot cake and the DPF wall, which is important in catalytic soot oxidation, were examined. In addition, thermogravimetric analysis (TGA) was performed and the specific reaction rate was determined. The effect of gas diffusion into the soot cake on the overall oxidation reaction rate was demonstrated. The soot cake oxidation behavior was discussed based on the ESEM observation and TGA results.

Tuning the hydrophobicity of plasma polymer coated silica particles

The modification of particle hydrophobicity has been conventionally carried out using wet chemistry methods. This investigation has however applied plasma polymerisation as a novel approach to produce silica particles with tailored hydrophobicity. Deposition of plasma polymerised 1,7-octadiene (ppOD) was carried out using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerisation parameters were varied to study the hydrophobicity of hydrocarbon functionalised particles. The surface chemistry of the ppOD coated particles was analysed via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Deposition of ppOD coatings under low specific energy plasma conditions resulted in both chemically and hydrophobically heterogeneous ensemble of particles. Whereas optimised plasma conditions resulted in homogeneous ppOD coatings. Development of hydrophobicity in ppOD coated particles was confirmed by Washburn capillary rise measurements, film flotation tests and environmental scanning electron microscopy observations. Silica particles with a range of water contact angles from 36° to more than 90° were obtained by controlled deposition of ppOD films. Plasma polymerisation using a rotating reactor has shown to be an efficient approach in the surface modification of silica particles to obtain surfaces with controlled hydrophobicity, which are of direct interest in a diverse range of practical applications as well as fundamental studies.

Hydrophobic Plasma Polymer Coated Silica Particles for Petroleum Hydrocarbon Removal

In recent years, functionalized hydrophobic materials have attracted considerable interest as oil removal agents. This investigation has applied plasma polymerization as a novel method to develop hydrophobic and oleophilic particles for water purification. 1,7-Octadiene was plasma polymerized onto silica particles using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerized 1,7-octadiene (ppOD) films were deposited using plasma power of 40 W and monomer flow rate of 2 sccm, while polymerization time was varied from 5 to 60 min. The surface chemistry of ppOD coated particles was investigated via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy, while Washburn capillary rise measurements were applied to evaluate the hydrophobicity and oleophilicity of the particles. The effectiveness of ppOD coated particles for the removal of hydrophobic matter from water was demonstrated by adsorption of motor oil, kerosene, and crude oil. Petroleum hydrocarbon removal was examined by varying removal time and particle mass. The morphology of oil-loaded ppOD coated particles was examined via environmental scanning electron microscopy observations. Increasing the polymerization time increased the concentration of hydrocarbon functionalities on the surface, thus also increasing the hydrophobicity and oil removal efficiency (ORE). The ppOD coated particles have shown to have excellent ORE. These particles were capable of removing 99.0-99.5% of high viscosity motor oil in 10 min, while more than 99.5% of low viscosity crude oil and kerosene was adsorbed in less than 30 s. Plasma polymerization has shown to be a promising approach to produce a new class of materials for a fast, facile, and efficient oil removal.

Denitrification using PBS as carbon source and biofilm support in a packed-bed bioreactor

Biodegradable polymer was used as carbon source and biofilm support for nitrate removal from aqueous solution as an attractive alternative for biological denitrification. The objective of this paper was to investigate the denitrification performance and microbial community of a packed-bed bioreactor using poly (butanediol succinate) (PBS), a biodegradable polymer, as carbon source and biofilm support. NO(3)-N concentration was determined by UV spectrophotometer. NO(2)-N concentration was assayed by hydrochloric acid naphthyl ethylenediamine spectrophotometry method. Total organic carbon (TOC) was measured using a TOC analyzer. The morphology of the samples was observed using an environmental scanning electron microscope (ESEM). The microbial community was analyzed by pyrosequencing method. The experimental results showed that an average removal efficiency of nitrate was 95 %. ESEM observation and FTIR analysis indicated the changes of PBS granules before and after microbial utilization. Pyrosequencing results showed that Betaproteobacteria predominated, and most of PBS-degrading denitrifying bacteria were assigned to the family Comamonadaceae. Denitrifying bacteria accounted for 13.02 % in total population. The PBS granules were suitable support and carbon source for denitrifying bacteria.

Investigation of the role of biopolymer clusters in MBR membrane fouling using flash freezing and environmental scanning electron microscopy

The technique that employs flash freezing and environmental scanning electron microscopy (ESEM) was utilised for detailed investigation of the fouling materials in a membrane bioreactor (MBR). The method involves the flash freezing of a wet sample in liquid nitrogen for 10 s to preserve its structure for direct ESEM observation with a high image resolution. ESEM images show that the sludge cake formed by simple filtration of the MBR bulk sludge has a highly porous, sponge-like structure with a fairly low resistance. However, the fouling layer attached to the membrane surface contains a thin gel layer under the main body of the sponge-like sludge cake, which is similar to that formed by filtration of a dispersion of biopolymer clusters (BPCs). It is apparent that BPCs tend to accumulate on the membrane surface, and the gel layer is largely responsible for the high filtration resistance of the cake layer on the fouled membranes.

Microbial Deterioration of Artistic Tiles from the Façade of the Grande Albergo Ausonia &amp; Hungaria (Venice, Italy)

The Grande Albergo Ausonia & Hungaria (Venice Lido, Italy) has an Art Nouveau polychrome ceramic coating on its façade, which was restored in 2007. Soon after the conservation treatment, many tiles of the façade decoration showed coloured alterations putatively attributed to the presence of microbial communities. To confirm the presence of the biological deposit and the stratigraphy of the Hungaria tiles, stereomicroscope, optical and environmental scanning electron microscope observations were made. The characterisation of the microbial community was performed using a PCR-DGGE approach. This study reported the first use of a culture-independent approach to identify the total community present in biodeteriorated artistic tiles. The case study examined here reveals that the coloured alterations on the tiles were mainly due to the presence of cryptoendolithic cyanobacteria. In addition, we proved that the microflora present on the tiles was generally greatly influenced by the environment of the Hungaria hotel. We found several microorganisms related to the alkaline environment, which is in the range of the tile pH, and related to the aquatic environment, the presence of the acrylic resin Paraloid B72® used during the 2007 treatment and the pollutants of the Venice lagoon.

Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia

The oldest direct evidence of stone tool manufacture comes from Gona (Ethiopia) and dates to between 2.6 and 2.5 million years (Myr) ago. At the nearby Bouri site several cut-marked bones also show stone tool use approximately 2.5 Myr ago. Here we report stone-tool-inflicted marks on bones found during recent survey work in Dikika, Ethiopia, a research area close to Gona and Bouri. On the basis of low-power microscopic and environmental scanning electron microscope observations, these bones show unambiguous stone-tool cut marks for flesh removal and percussion marks for marrow access. The bones derive from the Sidi Hakoma Member of the Hadar Formation. Established (40)Ar-(39)Ar dates on the tuffs that bracket this member constrain the finds to between 3.42 and 3.24 Myr ago, and stratigraphic scaling between these units and other geological evidence indicate that they are older than 3.39 Myr ago. Our discovery extends by approximately 800,000 years the antiquity of stone tools and of stone-tool-assisted consumption of ungulates by hominins; furthermore, this behaviour can now be attributed to Australopithecus afarensis.