Environmental Scanning Electron Micrographs Research Articles

Combination of biological pretreatment with deep eutectic solvent pretreatment for enhanced enzymatic saccharification of Pinus massoniana

Lignocellulosic biorefineries depended on effective pretreatment strategies to improve the conversion efficiency of the enzymatic hydrolysis. Here, this study coupled brown rot fungi and deep eutectic solvent (DES) to pretreat Pinus massoniana. The results showed that compared to fungal pretreatment and DES pretreatment alone, the combined ChCl-Lac/fungal pretreatments could effectively improve enzymatic saccharification of Pinus massoniana. The highest content of releasing reducing sugar reached 510.3 mg/g substrate. Environmental scanning electron micrograph (ESEM) showed that the surface structure of Pinus massoniana was almost completely torn and loose and FT-IR spectra and component analysis revealed that most of hemicellulose and lignin were selected removed and cellulose was enriched after ChCl-Lac/fungal pretreatments, which could account for the enhanced hydrolysis efficiency. The combination of biological pretreatment with DES pretreatment could be a mild and promising pretreatment approach for enzymatic saccharification of lignocellulose and had an extensive application prospect in the field of biorefinery.

Effects of repetitive firings on mechanical, optical, and phase formation changes of ceramic materials

Statement of problemStudies are sparse on how rapid heating and cooling negatively affect optical properties, including color and transparency, and mechanical properties, including hardness and durability, that affect esthetics and shorten the clinical usage period of the ceramics. PurposeThe purpose of this in vitro study was to determine the effects of repeated firing on the color difference, mechanical properties, and phase formation of different ceramic materials. Material and methodsA total of 160 disks (12×1.35 mm) were produced from 4 different ceramic materials: lithium disilicate glass-ceramic, zirconia-reinforced lithium silicate ceramic, zirconia core, and monolithic zirconia. Specimens from all groups were divided into 4 groups (n=10) with a different number of veneer porcelain firings (1 to 4) by simple randomization. After the firings, color measurement, X-ray diffraction analysis, environmental scanning electron micrograph analysis, surface roughness evaluation, Vickers hardness evaluation, and biaxial flexural strength tests were performed. Data were analyzed with analysis of variance (2-way ANOVA) (α=.05). ResultsRepeated firing did not affect the flexural strength of the specimens in any of the groups (P>.05), while the color, surface roughness, and surface hardness were significantly affected (P<.05). The specimens fired 4 times showed the highest mean Vickers hardness and ΔE00 values but the lowest mean surface roughness values. Zirconia core specimens showed the highest mean ΔE00 and flexural strength values, and lithium disilicate glass-ceramic specimens had the highest mean Vickers hardness values. ConclusionsThe increase in the number of firings affected the color, mechanical properties, and phase formation of the specimens; this change differed according to the ceramic tested.

Experimental Investigation of Microstructural Effects in Sn-Pb Solder Accumulated During Ten Years of Service Life

Aim: Solder joints of microelectronic devices are subjected to a wide range of loadings. They affect the microstructural evolution of the alloy. Long term investigations are commonly performed under thermally accelerated conditions, but are not available for real-life environmental conditions in literature yet. Therefore, the solder bumps of ten-year-old graphic cards are inspected here. Objectives: The primary objective of this study was the investigation of long-term accumulated effects in solder bumps. We classified the solder concerning its prior electrical functionality and analyzed theproperties of the microstructure. Methods: The image reconstruction is based on component identification, scratch elimination, and image stitching. Additionally, environmental scanning electron micrographs are employed to investigate the microstructure of the lead-rich phases. Results: Power supplying solder has the widest circularity distribution as a result of anisotropic diffusion and phase decomposition. On average, a bump with a cross-section of 0.12 mm2 contains 800 Pbrich phase islands. In the central region of the solder, broad Pb-rich platelets are present. Such platelets are typically perpendicular to the electric current flow and affected by the mechanical deformation of the bump. Additional electron-microscopy shows several micro-porous Pb-rich phase islands, which are induced by an uncalibrated diffusion of tin. Conclusion: We found the phase islands’ circularity to be the best indicator for the bulk dynamics. We conclude that device operation at normal working conditions leads to no hints for functional limitations at the end of the designed life span.

Effects of multiple firing processes on the mechanical properties of lithium disilicate glass-ceramics produced by two different production techniques

Statement of problemRepeated firings cause materials to be exposed to additional heat treatments. The effect of these additional heat treatments on the mechanical properties of lithium disilicate glass-ceramics is not fully known. PurposeThe purpose of this in vitro study was to determine the effects of repeated firing on the mechanical properties of lithium disilicate glass-ceramics produced by 2 different techniques, press and computer-aided design and computer-aided manufacturing (CAD-CAM). Material and methodsEighty rectangular (25×4×2 mm) lithium disilicate glass-ceramic specimens were used in this study, 40 produced by heat pressing and 40 by milling, and divided into 4 groups (n=10) with a different number of veneer porcelain firings (1 to 4). After firing, the Vickers hardness, flexural strength (3-point bend test), and fracture toughness were determined, and the specimens were analyzed with an environmental scanning electron micrograph. Data were analyzed with analysis of variance (ANOVA) (α=.05). ResultsThe repeat firing processes did not affect the flexural strength of the specimens in either group (P>.05), while the surface hardness and fracture toughness were significantly changed (P<.05). ConclusionsIncreasing the number of firings adversely affected the mechanical properties of lithium disilicate glass-ceramics.

Polymeric and non‐crosslinked acid self‐thickening agent based on hydrophobically associating water‐soluble polymer during the acid rock reaction

ABSTRACTDifferent from traditional crosslinked polymer diverting agents, a polymeric and non‐crosslinked acid self‐thickening agent (ZPAM) based on hydrophobically associating water‐soluble polymer of acrylamide (AM), [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (DMC) and N,N′‐dimethyl octadecyl allyl ammonium chloride (DOAC) was synthesized. The apparent viscosity variation of ZPAM acid solutions in acid rock reaction and rheological properties of ZPAM spent acid solutions were studied. Results showed that ZPAM acid solutions demonstrated good uninterruptedly thickening ability from low apparent viscosity to high apparent viscosity during the acid rock reaction. Meanwhile, ZPAM spent acid solutions showed good shear resistance, viscoelasticity and high temperature resistance. The thickening mechanism of ZPAM acid solutions during the acid rock reaction was explained by apparent viscosity change, rheological properties of simulative ZPAM acid solutions, and ZPAM aqueous solutions with different concentrations of CaCl2. The results showed increasing calcium chloride concentration enhanced the hydrophobic association strength of the thickener solution, resulting in increasing solution viscosity, in other words, the self‐thickening agent showed excellent salt resistance and acid resistance. In addition, the change of association strength of ZPAM acid solutions during the acid rock reaction was further confirmed via environmental scanning electron micrographs and UV spectrum. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47907.

Microwave irradiation with dilute acid hydrolysis applied to enhance the saccharification rate of water hyacinth (Eichhornia crassipes)

Abstract Sugar generated from aquatic plant biomass with high cellulose and hemicellulose content is considered as a dynamic progression towards the advancement in bio products. Hence, this study investigated the possibility of enhancing the saccharification rate of sugar from water hyacinth (Eichhornia crassipes) by microwave heating system. The method of full factorial experimental design was adopted to explore different parameters that influence the conversion rates of fibers into fermentable sugar. The structural changes of the fibers after microwave treatment with dilute sulfuric acid was observed on the residue by using X-ray Diffractometer (XRD), Fourier Transform Infrared Spectrometry (FTIR) and Environmental Scanning Electron Micrograph (ESEM) analysis. The results obtained illustrates that hydrolysis time reduces to approximately 40% and effectively improve the rate of saccharification to 13.94% with optimal sugar concentration of 4650 mg/L.

Bacterial nanocellulose as novel additive in low-lipid low-sodium meat sausages. Effect on quality and stability

Abstract Replacing animal fat with different oils has been proposed to improve fatty acid profile of meat emulsions. In this work a novel application of bacterial nanocellulose (BNC, 0–0.534 g of dry BNC/100 g batter) to low-lipid low-sodium meat emulsions formulated with pre-emulsified high-oleic sunflower oil is discussed. Process yield, water content, water activity, water holding capacity, color, texture, rheological characteristics, microstructure, and shelf-life were analyzed. Thermo-rheological curves showed a typical meat system gelation behavior where BNC addition produced a more solid-like three-dimensional network. Environmental Scanning Electron Micrographs of the systems revealed microstructure modifications in accordance with these results. Water-binding properties, hardness, cohesiveness, and chewiness increased when up to 0.267 g of dry BNC/100 g batter was added, while further additions had a negative impact on these attributes. Thus using oil pre-emulsified with BNC as fat mimetic had no negative effect on the quality properties of low-fat low-sodium meat sausages. A 45-days shelf-life under vacuum refrigerated storage was assured for this product.

X-ray diffraction investigation of amorphous calcium phosphate and hydroxyapatite under ultra-high hydrostatic pressure

The changes in the crystal structures of synthetically prepared amorphous calcium phosphate (ACP) and hydroxyapatite (HAP) in water (1:1 mass ratio) were studied by synchrotron X-ray diffraction (XRD) under ultra-high hydrostatic pressures as high as 2.34 GPa for ACP and 4 GPa for HAP. At ambient pressure, the XRD patterns of the ACP and HAP samples in capillary tubes and their environmental scanning electron micrographs indicated amorphous and crystalline characteristics for ACP and HAP, respectively. At pressures greater than 0.25 GPa, an additional broad peak was observed in the XRD pattern of the ACP phase, indicating a partial phase transition from an amorphous phase to a new high-pressure amorphous phase. The peak areas and positions of the ACP phase, as obtained through fitting of the experimental data, indicated that the ACP exhibited increased pseudo-crystalline behavior at pressures greater than 0.96 GPa. Conversely, no structural changes were observed for the HAP phase up to the highest applied pressure of 4 GPa. For HAP, a unit-cell reduction during compression was evidenced by a reduction in both refined lattice parameters a and c. Both ACP and HAP reverted to their original structures when the pressure was fully released to ambient pressure.

Impact of tank-mix adjuvants on deposit formation, cuticular penetration and rain-induced removal of chlorantraniliprole

Off-target deposits of agrochemicals impose a general risk for the environment while environmental factors such as rainfall might cause significant pesticide removal from agricultural crops and contribute to a requirement for a higher rate and frequency of applications in intensive agricultural systems. In the present study, we analyzed the impact of five tank-mix adjuvants (three organosilicones – one superspreader, one penetrating agent and one spreader-sticker – as well as one paraffinic oil and one vegetable oil with non-ionic surfactants) on the amount of active ingredient (AI) deposited, deposit characteristics at the microscale, and rain-induced removal of chlorantraniliprole from the hydrophobic leaf surfaces of wheat and maize. In addition, the cuticular penetration of the AI was determined on astomatous cuticles from the adaxial side of apple leaves. The tank-mix adjuvants with lower surface tension (organosilicone superspreader and organosilicone-based penetrating agent) caused a lower contact angle of sessile droplets, larger surface coverage, and higher AI amount on wheat and maize leaves. Heavy rain (5 mm h−1) removed zero to 60% of the chlorantraniliprole from wheat leaves, and 20–60% from maize leaves, the losses being more pronounced in those treatments with higher initial AI amount. Moreover, in wheat we observed a pronounced effect of the rain amount (5 mm or 10 mm) on the AI removal. Environmental scanning electron micrographs indicated the rain-induced displacement of the AI and adjuvants and their partial re-allocation within the droplet footprint. Moreover, the micrographs showed no residues in adjacent areas outside the primary droplet footprint. Cuticular penetration of chlorantraniliprole, which was demonstrated here for the first time, ranged from 15 to 30%, but no statistical differences (p ≤ 0.05) were found between the experimental groups. In summary, the evaluated tank-mix adjuvants positively influenced the AI amount and deposit formation of chlorantraniliprole on hydrophobic leaves. In the case of rain, the add-on value of adjuvants on retention and AI amount might be partially lost, since the highest wash-off was associated with the highest deposition; nevertheless, the AI concentration on the leaves after rain remained significantly higher, or in worst-case similar to, the control group. In specific cases, the cuticular penetration might be improved, while no information on stomatal infiltration and bio-efficacy is provided. Finally, we point to the need for further optimization of adjuvant-AI systems to increase both penetration and rainfastness, and in this way constrain AI losses and unnecessary environmental contamination.

Bioremediation of hexavalent chromium (VI) by a soil-borne bacterium, Enterobacter cloacae B2-DHA

Chromium and chromium containing compounds are discharged into the nature as waste from anthropogenic activities, such as industries, agriculture, forest farming, mining and metallurgy. Continued disposal of these compounds to the environment leads to development of various lethal diseases in both humans and animals. In this paper, we report a soil borne bacterium, B2-DHA that can be used as a vehicle to effectively remove chromium from the contaminated sources. B2-DHA is resistant to chromium with a MIC value of 1000 µg mL−1 potassium chromate. The bacterium has been identified as a Gram negative, Enterobacter cloacae based on biochemical characteristics and 16S rRNA gene analysis. TOF-SIMS and ICP-MS analyses confirmed intracellular accumulation of chromium and thus its removal from the contaminated liquid medium. Chromium accumulation in cells was 320 µg/g of cells dry biomass after 120-h exposure, and thus it reduced the chromium concentration in the liquid medium by as much as 81%. Environmental scanning electron micrograph revealed the effect of metals on cellular morphology of the isolates. Altogether, our results indicate that B2-DHA has the potential to reduce chromium significantly to safe levels from the contaminated environments and suggest the potential use of this bacterium in reducing human exposure to chromium, hence avoiding poisoning.

Novel Natural Sorbent for Oil Spill Cleanup

A novel sorbent was developed using the aligning of raw unprocessed cotton fibers leading to low-density, hydrophobic, oleophilic, and sustainable cotton batt. Cotton batting developed using immature cotton exhibited oil sorption capacity of 50.27 g/g, which is significantly higher than the oil sorption capacity of many commercial sorbents reported in the literature. Fundamental mechanisms such as adsorption, absorption, and capillary action govern the oil sorption phenomenon, which were verified using environmental scanning electron micrographs. In addition, optical microscopy was used to understand the difference in the longitudinal cross section of the mature (base range) and immature (low micronaire) cotton, which was determined quantitatively using Brunauer–Emmett–Teller surface area analysis. Effect of cotton characteristics such as fineness and maturity on the oil sorption capacity was also investigated. Nonwoven cotton batts consisting of immature and finer cotton fibers showed oil sorption capaci...

Synthesis and characterization of an associative polymer with an octylphenyl polyoxyethylene side chain as a potential enhanced‐oil‐recovery chemical

A novel nonionic surfmer, AGE‐TX‐100, was synthesized by the epoxide ring‐opening reaction of allyl glycidyl ether and polyoxyethylene (10) octylphenyl ether (TX‐100). Then a novel copolymer, acrylamide (AM)/acrylic acid (AA)/AGE‐TX‐100, was synthesized with AM, AA, and AGE‐TX‐100 in aqueous solution through free‐radical random polymerization. The structures of the novel surfmer and copolymer were characterized by IR and 1H‐NMR. The results of the salt‐resistance tests and the rheological tests indicate that the copolymer had good salt tolerance, thermal stability at high temperatures, and shearing resistance under high shear rates. The environmental scanning electron micrographs showed that the copolymer could form a tighter three‐dimensional network structure than partially hydrolyzed polyacrylamide (HPAM) in aqueous solution. Compared with the HPAM solution, the copolymer solution showed a good ability to emulsify organic components. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41024.

Ultrasound stimulated production of a fibrinolytic enzyme

The present study is aimed at enhanced production of a fibrinolytic enzyme from Bacillus sphaericus MTCC 3672 under ultrasonic stimulation. Various process parameters viz; irradiation at different growth phases, ultrasonication power, irradiation duration, duty cycle and multiple irradiation were studied for enhancement of fibrinolytic enzyme productivity. The optimum conditions were found as follows, irradiation of ultrasonic waves to fermentation broth at 12h of growth phase with 25kHz frequency, 160W ultrasound power, 20% duty cycle for 5min. The productivity of fibrinolytic enzyme was increased 1.82-fold from 110 to 201U/mL compared with the non sonicated control fermentation. Drop in glucose concentration from 0.41% to 0.12% w/v in ultrasonicated batch implies that, ultrasonication increases the cell permeability, improves substrate intake and progresses metabolism of microbial cell. Microscopic images before and after ultrasonic stimulation clearly signifies the impact of duty cycle on decreasing biomass concentration. However, environmental scanning electron micrograph does not show any cell lysis at optimum ultrasonic irradiation. Offshoots of our results will contribute to fulfill the demand of enhancement of microbial therapeutic enzyme productivity, through ultrasonication stimulation.

Thorium biosorption by Aspergillus fumigatus, a filamentous fungal biomass

Thorium biosorption by Aspergillus fumigatus was carried out in a batch reactor to study the effect of initial pH and metal ion concentration, contact time, biomass dose and kinetics and equilibrium Th uptake. Thorium(IV) uptake by A. fumigatus was pH dependent (pH range, 2.0–6.0) and maximum sorption was observed at pH 4.0. The uptake was rapid and the biosorption process reached equilibrium within 2 h of contact times at pH 2–4 and initial Th concentration of 50 and 100 mg/L. The kinetics data fitted well to Lagergren's pseudo-second-order rate equation ( r 2 > 0.99). A maximum initial sorption rate of 71.94 (mg/g min) and second-order rate constant of 7.82 × 10 −2 (g/mg min) were observed at pH 4.0, 50 mg Th/L. The observed maximum uptake of thorium was 370 mg Th/g at equilibrium. Biosorption process could be well described by Langmuir isotherm in comparison to Freundlich and Temkin isotherms. Sodium bicarbonate was the most efficient desorbing reagent with desorption efficiency of more than 99%. Environmental scanning electron micrograph (ESEM) showed that the surface of the biomass after desorption was intact.

Structural Effects of Crosslinking a Biopolymer Hydrogel Derived from Marine Mussel Adhesive Protein

In an effort to explore new biocompatible substrates for biomedical technologies, we present a structural study on a crosslinked gelatinous protein extracted from marine mussels. Prior studies have shown the importance of iron in protein crosslinking and mussel adhesive formation. Here, the structure and properties of an extracted material were examined both before and after crosslinking with iron. The structures of these protein hydrogels were studied by SEM, SANS, and SAXS. Viscoelasticity was tested by rheological means. The starting gel was found to have a heterogeneous porous structure on a micrometer scale and, surprisingly, a regular structure on the micron to nanometer scale. However disorder, or "no periodic structure", was deduced from scattering on nanometer length scales at very high q. Crosslinking with iron condensed the structure on a micrometer level. On nanometer length scales at high q, small angle neutron scattering showed no significant differences between the samples, possibly due to strong heterogeneity. X-ray scattering also confirmed the absence of any defined periodic structure. Partial crosslinking transformed the viscoelastic starting gel into one with more rigid and elastic properties.

Pitting corrosion induced current oscillations during electrodissolution of Al in HClO 4 solutions

In this paper, oscillatory electrodissolution of Al in perchloric acid solutions has been investigated. The Al/HClO 4 system is a new electrochemical oscillator and particularly, current oscillations occur over a large range of HClO 4 concentration and over a wide scale of applied potential. The effects of the applied potential and the HClO 4 concentration on the current oscillations have been studied. The results are discussed in terms of the formation and dissolution of the surface oxide film. During the anodic dissolution of the Al electrode in HClO 4 solutions, perchlorate ions are reduced to chloride ions, by which, pitting corrosion is induced. The surface morphologies of Al electrodes observed using an environmental scanning electron micrograph show that it is pitting corrosion that induces the current oscillations.

Development of a new thermoplastic laminate system

In this investigation an all-olefin thermoplastic laminate was developed and characterized. Commingled glass-fiber polypropylene (PP) composite was used as skin and HDPE (PE) foam with closed cells as core. Infra-red heating was used for melting the surfaces of the substrates for surface fusion bonding with a cold press. Two tie-layer films, viz., ethylene-propylene copolymer (EPC) and HDPE/elastomer blend were used as hot-melt adhesives for bonding the substrates. Singlelap shear joints were prepared from PP composite and PE foam adherends with a bonding area of 25.4 mm × 25.4 mm to determine the bond strength. EPC tie-layer adhesive provided higher bond strength (2.68 × 106 N/m2) to the all-olefin laminate than that based on HDPE/elastomer blend (1.93 × 106 N/m2). For EPC tie-layer-based laminates, a mixed mode of failure was observed in the failed lap shear samples: about 40% was cohesive failure through the tie-layer, and the rest of failure was interfacial, either at PP composite or PE foam surfaces. Environmental scanning electron micrographs (ESEM) revealed that in the process of surface fusion bonding, PE foam cells in the vicinity of interphase (800-μm-thick) were coalesced with high temperature and pressure. No macro-level penetration of the tie-layer melt front into the foam cells was observed. As the surface morphology of foam was altered due to IR surface heating and the PP composite bonding side had a resin-rich layer, the bonding situation was closer to that between two polymer film surfaces.

Development and characterization of an all‐olefin thermoplastic sandwich composite system

AbstractIn this investigation an all‐olefin thermoplastic sandwich system was developed and characterized. Commingled glass fiber polypropylene (PP) composite was used as skin and HDPE (PE) foam with closed cells as core. Infra‐red heating was used for melting the surfaces of the substrates for surface fusion bonding with a cold press. Two tie layer films, viz. ethylene‐propylene copolymer (EPC) and HDPE/elastomer blend, were used as hot melt adhesives for bonding the substrates. Single lap shear joints were prepared from PP composite and PE foam adherends with a bonding area of 25.4 mm × 25.4 mm to determine the interface strength. EPC tie layer provided higher bond strength (27.4 kg/cm2) to the all‐olefin sandwich system than HDPE/elastomer blend based one (19.7 kg/cm2). For EPC tie layer based sandwiches, a mixed mode a failure was observed in the failed lap shear samples; about 40% is cohesive failure through tie layer, and the rest of failure was adhesive either at PP composite or PE surfaces. Environmental scanning electron micrographs (ESEM) reveal that in the process of surface fusion bonding, PE foam cells in the vicinity of 0.80 mm interphase area were coalesced with high temperature and pressure. No macro level penetration of tie layer melt front into foam cells was observed. As the surface morphology of foam was altered on account of IR surface heating and the PP composite bonding side had a resin‐rich layer, the bonding situation was closer to that between two polymer film surface.

Characterization of Wood-Polypropylene Composite Sandwich System

A new wood-polypropylene composite sandwich was made by bonding unidirectional continuous glass fiber reinforced polypropylene (UCGPP) composite to oak wood using a thermoplastic tie layer. In order to evaluate the practical utility of wood-composite sandwich systems, the effects of moisture changes in both continuous and cyclic manner were investigated by monitoring the modulus change. Dynamic mechanical analysis (DMA) of neat wood and wood-composite sandwich was carried out under controlled relative humidity (RH) and isothermal conditions to simulate moisture desorption/sorption processes. It is observed that under continuous desorption condition the modulus increase is less in the case of wood-sandwich (20%) when compared with neat wood (35%). However, under desorption/sorption cycle conditions the wood-sandwich undergoes significant modulus change when compared with neat wood. It is inferred that while bonding wood with UCGPP composite helps reduce the variation in modulus under continuous desorption, it is not the case under cyclic moisture condition. The modulus behavior of both dry and normal wood-sandwiches at different end-use temperatures is also studied using DMA. Optical and environmental scanning electron micrographs show the distribution and penetration pattern of tie layer into wood as well as UCGPP composite, thus demonstrating the significance of micro-mechanical interlocking for bonding.

High resolution transmission soft X-ray microscopy of deterioration products developed in large concrete dams

In concrete structures, the reaction of certain siliceous aggregates with the highly alkaline concrete pore solution produces an alkali-silicate gel that can absorb water and expand. This reaction can lead to expansion, cracking, increased permeability, and decreased strength of the concrete. Massive concrete structures, such as dams, are particularly susceptible to the damage caused by the alkali-silica reaction because of the availability of water and because massive gravity dams usually do not contain steel reinforcement to restrain the expansion. Both the cement hydration products and alkali-silica reaction products are extremely sensitive to humidity. Consequently, characterization techniques that require high vacuum or drying, as many existing techniques do, are not particularly appropriate for the study of the alkali-silica reaction because artefacts are introduced. Environmental scanning electron micrographs and scanning electron micrographs with energy dispersive X-ray analysis results demonstrate the effect of drying on the morphology and chemical composition of the alkali-silicate reaction gel. Thus, the impetus for this research was the need to observe and characterize the alkali-silica reaction and its gel product on a microscopic level in a wet environment (i.e. without introducing artefacts due to drying). Only soft X-ray transmission microscopy provides the required high spatial resolution needed to observe the reaction process in situ. The alkali-silica reaction can be observed over time, in a wet condition, and at normal pressures, features unavailable with most other high resolution techniques. Soft X-rays also reveal information on the internal structure of the sample. The purpose of this paper is to present research, obtained using transmission soft X-ray microscopy, on the effect of concrete pore solution cations, namely sodium and calcium, on the product formed as a result of alkali attack. Alkali-silicate reaction (ASR) gel was obtained from the FURNAS Dam in Minas Gerais, Brazil. Images of the ASR gel in sodium hydroxide indicated dissolution and repolymerization of the silicate into a less dense form, demonstrating the expansive nature of the gel when exposed to alkalis. In the calcium hydroxide solution, ASR gel, silica fume, and chemical grade silica gel each reacted with the calcium ions in solution to produce a calcium silicate hydrate precursor with a lathlike, branching morphology. The distinctive spherulitic microstructure formed during this reaction was identified as the 'sheaf of wheat' morphology, previously described in the literature. In addition, the development of the sheaf of wheat morphology was documented over time. These results suggest that of the cations studied in this investigation, it is the alkalis in concrete pore solution that produce the expansive ASR gel, while reaction with calcium ions does not result in expansion or damage to the concrete structure. More broadly, these results demonstrate the advantage of transmission soft X-ray microscopy for the study of the alkali-silica reaction, indicating the value of this technique for further studies in concrete technology.