Backscattered Scanning Electron Microscopy Images Research Articles

Inventive Microstructural and Durability Investigation of Cementitious Composites Involving Crystalline Waterproofing Admixtures and Portland Limestone Cement.

The durability of a cement-based material is mainly dependent on its permeability. Modifications of porosity, pore-structure and pore-connectivity could have significant impacts on permeability improvement, which eventually leads to more durable materials. One of the most efficient solutions in this regard is to use permeability reducing admixtures (PRA). Among these admixtures for those structures exposed to hydro-static pressure, crystalline waterproofing admixtures (CWA) have been serving in the construction industries for decades and according to ACI 212—chemical admixtures’ report, it has proven its capability in permeability reduction and durability-enhancement. However, there is substantial research being done on its durability properties at the macro level but very limited information available regarding its microstructural features and chemical characteristics at the micro level. Hence, this paper presents one of the first reported attempts to characterize microstructural and chemical elements of hydration products for cementitious composites with CWA called K, P and X using Scanning Electron Microscopy (SEM). Backscattered SEM images taken from a polished-section of one CWA type—K—admixture were analyzed in ImageJ to obtain paste matrix porosity, indicating a lower value for the CWA-K mixture. X-ray analysis and SEM micrographs of polished sections were examined to identify chemical compositions based on atomic ratio plots and brightness differences in backscatter-SEM images. To detect chemical elements and the nature of formed crystals, the fractured surfaces of three different CWA mixtures were examined. Cementitious composites with K admixture indicated needle-like crystal formation—though different from ettringite; X and P admixtures showed sulfur peaks in Energy Dispersive Spectrum (EDS) spectra, like ettringite. SEM images and X-ray analyses of mixtures incorporating Portland Limestone Cement (PLC) indicated lower-than-average porosity but showed different Si/Ca and Al/Ca atomic ratios.

Surface modification of flax nonwovens for the development of sustainable, high performance, and durable calcium aluminate cement composites

The aim of this paper is to evaluate the influence of sustainable surface treatments —performed on flax nonwoven fabrics as textile reinforcement— on the durability of calcium aluminate cement (CAC) based composites. Two treatments are considered: an alkaline treatment (for increased stability and adhesion), and a treatment with soybean oil (to reduce fiber degradation). The cement hydration was studied by analysis of back-scattered scanning electron microscopy images, which revealed variations nearby the fibers owing their capacity for water absorption and presence of oil on the surface. A retarding effect on cement hydration was observed on the composites prepared with the oil-treated fabrics. The composites containing the alkali treated fabrics had better mechanical properties and also the highest durability. For these composites it was found an optimized fiber-matrix adhesion and penetrability of the cement to the fabric.

Development of novel Moving Wave Front image processing algorithm and microstructural quantification of Tungsten Heavy Alloy

Tungsten Heavy Alloy (WHA) is used in various aerospace applications. This alloy has a two-phase microstructure with a contiguous matrix dispersed with nearly spherical tungsten particles. The properties of this alloy depend on microstructural parameters such as tungsten particle size, tungsten-matrix and tungsten-tungsten interface. In this work, a novel Moving Wave Front (MWF) image processing algorithm was proposed for automatic detection of the interface boundary between coalesced tungsten particles. MWF algorithm was used to measure the size and orientation of the tungsten-tungsten interface from a two-dimensional montage of backscattered Scanning Electron Microscope images. The bivariate size-orientation distribution was measured for undeformed and deformed samples. The obtained distribution in 2D was used to estimate three dimensional size-orientation distribution. The evolution of the tungsten-tungsten interface in 3D was studied as a function of thermo-mechanical deformation. A characteristic evolution of the 3D size and orientation of the tungsten-tungsten interface with deformation was observed.

Use of backscattered scanning electron microscopy to quantify the bone tissues of midthoracic human ribs.

Novel information on apartheid health conditions may be obtained through the study of recent skeletal collections. Using a backscattered scanning electron microscopy (BSE-SEM) approach, this study aims to produce bone quality and tissue mineralization data for an understudied South African population from the Western Cape province. Using BSE-SEM imaging, cortical porosity (Ct.Po), osteocyte lacunar density (Ot.Lc.Dn), and the degree of tissue mineralization were quantified in midthoracic ribs from the Kirsten Skeletal Collection. Individuals ( n female = 75, n male = 68, and mean age = 46.3 years) were predominantly from the South Africa Colored (SAC) population group ( n SAC = 103, 72%). Full cross-sectional images of each rib were manually stitched together in Adobe Photoshop. Photomontages were imported into MATALB (Mathworks, Natick, MA) for image processing and analysis. Age-related changes in histomorphometric parameters and sex differences were examined using correlation analysis, as well as linear and nonlinear regressions. Young adult men have significantly less mineralized bone and fewer osteocyte lacunae, compared to women. Only men demonstrate a significant negative relationship between Ot.Lc.Dn and age. Average tissue mineralization decreases with age in women, while Ct.Po increases. Pore area (Po.Ar) does not vary with age, but pore density (Po.Dn) is highest in the perimenopause, when accelerated rates of bone turnover are first anticipated. Ct.Po is highest in the years following the predicted age of menopause, but levels off in the final decades of life. Men and women display disparate patterns of bone aging. Systemic disenfranchisement of non-white population groups affected bone health in South Africa, and may continue to do so today. Indicators of poor bone quality are evident in the full study sample, indicating that osteoporosis and fracture risk are not just of concern to the aged white female population.

Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations

The effect of polycarboxylate/nanosilica (nS) particles in quaternary cement formulations comprising Portland cement (PC), limestone powder (LS) and fly ash (FA) was investigated for the first time. The reference formulation contained 60% PC, 20% LS and 20% FA by mass of binder in an effort to minimise clinker and maximise the other constituents. nS particles were characterised by way of transmission and X-ray scanning electron microscopy (SEM). The nS was added at 0·3 or 0·6% by mass as a partial replacement for PC and different water-to-binder (w/b) ratios were explored. Compressive strength tests and thermal gravimetric analyses (TGA) performed at day 7, 28 and 56 testified to pozzolanic behaviour. Results suggest a mechanism of ‘de-activation’ of some FA particles with age. A new ratio: (compressive strength in MPa)/(calcium hydroxide content detected by TGA) was introduced, correlating microscale characteristics (hydration products) and macroscale performance (delivered compressive strengths). Back-scattered SEM images confirmed the calcium–silicate–hydrate (C–S–H) network formation, the presence of reacted/unreacted FA particles and the availability of calcium hydroxide for delayed hydration reactions. Tests on mortars also confirmed the enhancement offered by nS addition. The lower bound nS addition was determined to be 0·6% by mass of binder for pastes and 0·5% for mortars.

Processing of Ni-WC-8Co MMC casting through microwave melting

ABSTRACTThe melting and casting of nickel-based powder metal matrix composites (MMCs) through microwave energy is carried out in the present work. The nickel powder was mixed with 5% and 10% volume fraction of the WC-8Co reinforcement powder and processed in a microwave oven at 2.45 GHz and 900 W. The developed castings revealed complete melting of the nickel powder within 25 minutes of microwave exposure. The processing mechanism of MMC castings through microwave is explained and the developed castings were subjected to the microstructure and mechanical characterizations. The results of XRD analysis revealed the formation of some hard intermetallics such as NiSi and Cr23C6. The back-scattered scanning electron microscopy images of castings microstructures revealed the formation of nearly equiaxed grains of the matrix. It was observed that WC particles within the matrix were in agglomerated patterns, which were randomly dispersed. The presence of hard phases of WC reinforcement and formed intermetallic carbides enhanced the microhardness (788 ± 52 HV) of the developed composites.

Structural and Electrochemical Study of the Li–Mn–Ni Oxide System within the Layered Single Phase Region

The phase diagram of the Li–Mn–Ni-oxide pseudoternary system1 was used as a starting point to understand the influence of transition metal composition and lithium content on the structures and electrochemistry of materials with compositions: Li1+x(NiyMn1–y)1–xO2 (y = 0.2, 0.33, 0.4, 0.5, 0.6, and 0.7, 0 ≤ x ≤ 0.34). Mixed transition metal hydroxide precursors were synthesized via coprecipitation using a continuously stirred tank reactor. Powder X-ray diffraction results showed that additional spinel, rocksalt and/or layered phases were observed when the lithium content was less than that required for a single layered phase in agreement with ref 1. Additionally, residual Li2CO3 was detected in the backscattered scanning electron microscopy images for samples with relatively high lithium content. The boundaries of the single phase region were therefore defined and the contour plots of the lattice constants versus composition in the single phase region were generated. Electrochemical measurements showed that...

Post-oil solid bitumen network in the Woodford Shale, USA — A potential primary migration pathway

An important if not predominant component of porosity in many gas shales has been identified in organic matter. An organic network in shales has been described in the literature as organic matter (generalized term), kerogen (primary), or bitumen (secondary). Recognition of the type and origin of an organic network in shales has relevance in establishing the origin and timing of porosity and fracture development. The pervasive nature of the organic network adopting the shape of pores in Type II kerogen-rich Woodford Shale suggests it is the residue of primary oil migration. We use the term “post-oil solid bitumen” to distinguish this bitumen occurrence from “pre-oil solid bitumen” (defined as a precursor of oil). Three forms of this post-oil solid bitumen network are recognized in reflected white light at 500× magnification and confirmed in backscattered scanning electron microscope images at >2500× magnification, namely speckled (~1–2μm), wispy (~2–5μm), and connected (>5μm). The post-oil solid bitumen network demonstrates the prior occurrence of oil generation and migration within this hydrocarbon source rock, provides porosity for hydrocarbon storage sites, and forms hydrocarbon migration pathways.

Evaluation of a novel approach in the prevention of white spot lesions around orthodontic brackets

The purpose of this study was to evaluate and compare the relative efficacy of a resin fissure sealant, nano-filled self-adhesive protective coating, resin infiltrant, glass ionomer cement (GIC), and GIC containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) in preventing the formation of subsurface lesions of enamel (SLE) adjacent to orthodontic brackets by acting as an enamel surface sealant (ESS). Eighty-five enamel specimens with molar tubes bonded at their centre were randomly divided into five groups, each treated with a different material at the bracket's periphery. Specimens were stored in an acetate demineralization solution at pH 4.5 for 7days at 37 °C then imaged using quantitative light-induced fluorescence (QLF) to determine the difference in fluorescence (∆F) between sound- and acid-exposed enamel. Lesion cross-sections were then examined using backscattered scanning electron microscopy (SEM) to measure lesion depth. The use of GIC alone or incorporating CPP-ACP significantly reduced ∆F compared with other materials. Backscattered SEM images showed no measurable demineralization for enamel treated with either GIC material in contrast with other groups, which showed statistically significant demineralization levels. The fluoride-releasing effects and CPP-ACP benefits of the GIC materials show promise as an effective ESS in inhibiting enamel demineralization adjacent to orthodontic brackets.

A new standardized‐automatic method for bone‐to‐implant contact histomorphometric analysis based on backscattered scanning electron microscopy images

To establish an image analysis procedure for measuring the bone-to-implant contact (BIC) by a systematic non-subjective approach based on backscattered scanning electron microscopy (BS-SEM) images. A total of 36 dental implants (9 mm length, Ø 4.0 mm with a SBM surface) were implanted in six beagle dog mandibles. The implants were removed after 1, 2, 4, 6, and 8 weeks and then embedded in resin and cut along their long axis. Sample observation was performed by BS-SEM, acquiring 10 to 16 images per sample. Image processing and BIC determination were performed using the Fiji image processing package. Images were stitched, filtered, and thresholded to obtain a binary image of the whole implant that finally was dilated and outlined. The length of this outline was measured as the maximum possible BIC. The regions of coincidence between this line and the bone were measured as the real BIC. The proposed methodology for BIC determination, based on SEM, which has a much higher resolution than optical microscopy, allows the acquisition of highly discriminative images with great contrast between implant and bone. The high resolution and high contrast in SEM images provide more accurate results than those obtained by classical methods. Furthermore, the methodology of image analysis described in this study delineates precisely and automatically the contour of the implant, which results in non-biased measurements. The average percentage of BIC was 35%, ranging from 24.7 to 45.5%. These values were similar to the results documented in the literature for implants of similar roughness in animal models. A novel, non-subjective, and systematic method for measuring BIC is described based on BS-SEM images. The proposed methodology minimizes the shortcomings of the results obtained by previously described methods.

Earliest art in the Americas: incised image of a proboscidean on a mineralized extinct animal bone from Vero Beach, Florida

A fragmented fossil bone incised with the figure of a proboscidean was recently found at Vero Beach, Florida near the location where Late Pleistocene fauna and human bones were recovered from 1913 to 1916. This engraving may represent the oldest and only existing example of Terminal Pleistocene art depicting a proboscidean in the Americas. Because of the uniqueness, rarity, and potential antiquity of this specimen, caution demanded that a variety of tests be used in an attempt to verify its authenticity. The mineralized bone was identified as mammoth, mastodon, or giant sloth. Rare earth element analysis was consistent with the fossil bone being ancient and originating at or near the Old Vero site (8-IR-9). Forensic analysis suggests the markings on the bone are not recent. Optical microscopy results show no discontinuity in coloration between the carved grooves and the surrounding material indicating that both surfaces aged simultaneously. Scanning electron microscopy (SEM) revealed that the edges of the inscription are worn and show no signs of being incised recently or that the grooves were made with metal tools. In addition, the backscattered SEM images suggest there is no discontinuity in the distribution of light and heavy elements between the scribed region and the surrounding bone indicating that both surfaces aged in the same environment. This is very different from an intentional mark made on the bone for comparison. Energy dispersive x-ray spectroscopy (EDXS) shows that the surface contains significant amounts of calcium, phosphorus, oxygen, and carbon typical of a mineralized bone surface. Examination of a cast and mold of the incised bone by Reflectance Transformation Imaging (RTI) also provided no evidence that the engraving was made recently. All of these results are consistent with the mammoth engraving being authentic.

Site specific increase in heterogeneity of trabecular bone tissue mineral during oestrogen deficiency

Although osteoporosis reduces overall bone mass causing bone fragility, recent studies report that the remaining bone tissue is significantly stiffer. Preliminary studies indicate that alterations in bone tissue mineral content might explain these changes, albeit that other studies report conflicting observations. The objective of this study is to quantify whether the distribution of bone tissue mineral is altered during oestrogen deficiency. Individual trabeculae were harvested from the proximal femur of 7 ovariectomised sheep (OVX), sacrificed 12 months post-surgery, and 5 age-matched controls. Mineral content (wt% Ca) was determined using a quantitative backscattered scanning electron microscopy imaging approach. Mineral heterogeneity within individual trabeculae was compared by calculating the full width at half maximum (FWHM) of mineral density distributions. Mean calcium content, the spatial distribution of mineral within trabeculae and the inter-trabecular variation between regions of proximal femora were also compared. Oestrogen deficiency increased mineral heterogeneity within individual trabeculae compared to healthy controls, as measured by FWHM (3.57 ± 0.68 vs. 3.17 ± 0.36 wt% Ca, p = 0.04). In particular mineral variability increased between superficial and deep regions of trabeculae of OVX animals (p = 0.04). Interestingly, mineralisation variability between greater and lesser trochanters (i.e. intertrochanteric fracture line) was increased in OVX compared to CON, as indicated by a greater % difference in the standard deviation of trabecular mineral content (77.11 ± 11.70 vs. 45.64 ± 23.70 %, p = 0.03). Such changes are undetectable by evaluating the mean mineral content of bone tissue, but may contribute to changes in bone mechanical strength following osteoporotic bone loss.

Differences in the degree of bone tissue mineralization account for little of the differences in tissue elastic properties

Study of postmortem samples of cortical bone from the trochanters of 12 Caucasian females revealed that tissue mineral density (TMD) and tissue elastic modulus correlate weakly within and between individuals. Other material properties need to be taken into account to more fully predict variation in tissue elastic modulus. Bone is a composite material that varies in its material composition and structural organization at the macro-, micro-, and nano-scales. This hierarchical organization is essential for bone's resistance to crack initiation and propagation. We quantified the relationship between regional heterogeneity in TMD and tissue elastic modulus in cortical bone of the trochanter to determine whether TMD can be used as a predictor of tissue elastic modulus. Measurements of tissue elastic modulus and hardness were made using nanoindentation at 5 × 20 indent points spaced 100 μm apart. TMD at the same location was computed from quantitative backscattered scanning electron microscopy imaging of cortical samples from trochanters obtained at postmortem from 12 Caucasian females (mean age: 69 years; range: 29 to 85 years). Within an individual, the variance in tissue elastic modulus (CV = 18.7%; range: 9 to 41.5%) was five times greater than the variance in TMD (3.6%, range: 1.8 to 5.7%). On average, only 45% of the variance in tissue elastic modulus was explained by TMD. From individual to individual, the proportion of the variance in tissue elastic modulus explained by TMD ranged from 0 to 64%. In 6 of 12 samples, TMD explained less than 30% of the variance in tissue elastic modulus. Results were similar for tissue hardness. Tissue mineral density is an incomplete surrogate for tissue elastic modulus. Other material properties need to be accounted for to more fully predict regional variation in tissue elastic modulus.

A new approach for the characterization of the pore structure of dual porosity rocks

For the realistic representation of the pore space of dual porosity rocks, a new method of pore structure characterization is developed by combining experimental Hg intrusion/retraction curves with back-scattered scanning electron microscope (BSEM) images and inverse modeling algorithms. The pore space autocorrelation function measured by processing the digitized BSEM images is combined with the surface fractal dimension estimated from the high pressure Hg intrusion (MIP) data to derive a synthetic small-angle neutron scattering (SANS) intensity function, the inversion of which provides a volume-based pore body radius distribution (PBRD). The volume-based PBRD is fitted with a multimodal number-based PBRD consisting of two component distributions: one representing the macroporosity and another one representing the microporosity. Based on arguments of percolation theory, analytical mathematical models are developed to describe the Hg intrusion in and retraction from dual pore networks in terms of the complete PBRD, pore throat radius distribution (PTRD) of macroporosity, drainage accessibility functions (DAFs) of both porosities, and imbibition accessibility functions (IAFs) of both porosities. Inverse modeling of the Hg intrusion data set enables us to estimate the PTRD and DAFs. Inverse modeling of the Hg retraction datasets enables us to estimate a set of primary and secondary IAFs. The method is demonstrated by the pore structure characterization of four outcrop samples of carbonate and sandstone rocks. Analytic approximate equations developed from the critical path analysis (CPA) of percolation theory enable us to calculate explicitly the absolute permeability and the formation factor of the porous rocks using the estimated parameters (PBRD, PTRD, DAF) of the macroporosity. The measured permeability of cores is predicted satisfactorily and observed discrepancies may be attributed to large length-scale macro-heterogeneities which are not evident in BSEM images and Hg porosimetry data.

Dual‐porosity modelling of the pore structure and transport properties of a contaminated soil

SummaryWe have developed a new method to characterize the pore structure of mineral soils. We combined data from the analysis of back‐scattered scanning electron microscope (BSEM) images of resin‐impregnated pore‐casts, and mercury intrusion porosimetry (MIP) data, with analytical percolation models and inverse modeling algorithms. The pore space is regarded as a dual‐pore network consisting of a primary Euclidean pore‐and‐throat network and a secondary, fractal, pore system that is accessed through primary pores. The digitized 2‐D BSEM images of resin‐impregnated soil samples are employed to determine the autocorrelation function. The Fourier transform of this function provides the small‐angle neutron scattering (SANS) intensity function, which is extended by using the surface fractal dimension obtained from high‐pressure MIP data. Inversion of the extended scattering intensity function produces the volume‐based radius distribution function of spherical pore bodies (PBRD). The complete volume‐based PBRD is fitted with a composite number‐based PBRD composed of a lognormal primary PBRD and a power (fractal) secondary PBRD with upper and lower cut‐offs. Based on the concepts of invasion percolation, an analytic mathematical model that describes Hg intrusion into dual pore networks is developed. The complete PBRD and pore‐throat radius distribution (PTRD) functions of the primary network along with the drainage accessibility functions (DAFs) of the primary and secondary pore networks are estimated with inverse modelling of the Hg intrusion curve. Based on critical path analysis of percolation theory, approximate analytical relationships are developed to calculate explicitly the absolute permeability and electrical formation factor from the geometrical and topological parameters of the primary pore network. The method is demonstrated with application to four soil samples.

The effect of heavy oxidation upon flotation and potential remedies for Merensky type sulfides

Surface oxidation of sulfide minerals, such as that found in the regions of a sulfide ore body near the water table, can have a significant impact upon flotation. This theme has been explored for Merensky ore type sulfides where an ore containing pyrrhotite, pentlandite and chalcopyrite was thermally oxidised and the role of potential remedies investigated. Back-scattered scanning electron microscope images are presented showing the oxidation layer which formed in the mineral surfaces. These oxidation layers were depleted in both sulfur and iron with incorporated oxygen. Flotation recovery rapidly decreased with increasing oxidation, particularly after 27 days and reached a plateau after 50 days. Up to 27 days, this effect could be partially overcome with higher collector additions. Oxidation had more impact upon the finer size fractions, particularly for pyrrhotite. For more heavily surface oxidised samples, ultrasonic treatment prior to collector conditioning was found to improve flotation recoveries. This treatment had the greatest effect upon chalcopyrite particles. Sulfidisation was successful in restoring the flotation recovery of the heavily oxidised sulfide minerals. Longer sulfidisation conditioning times were not conducive to good flotation recoveries of both oxidised pyrrhotite and pentlandite due to oxidation of the freshly formed sulfide surfaces. For maximum flotation recoveries of oxidised pyrrhotite, pentlandite and chalcopyrite, different sulfidisation conditions are indicated. It appears likely that in a mineral processing operation treating oxidised Merensky type ores, two stages of sulfidisation employing different conditions would be required.

Articular calcified cartilage canals in the third metacarpal bone of 2‐year‐old thoroughbred racehorses

We describe morphological aspects of the articular calcified cartilage mineralizing front 'tidemark' in the distal joint surface of the third metacarpal bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the 'wedges' intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at one site on the sagittal ridge in all the horses. The site is one that is relatively less loaded during joint function. These canals through calcified cartilage result from osteoclastic resorption (cutting cones) penetrating from bone through to the non-mineralized hyaline articular cartilage. Their presence may indicate a pathway for connection between bone and cartilage extracellular fluid. In one horse, repair of such canals by plugging with new calcified cartilage was demonstrated. Differences in the degree of mineralization of regions of cartilage were seen in the combined compositional-cum-topographical backscattered SEM images of the macerated 'tidemark' front. More-or-less circular patches of lower mineralization density were frequently centred on (and may possibly originate from) canals. These microanatomical features should be searched for in other joints, at other ages and in other species to discover their frequency and significance.

Sub‐micron spongiform porosity is the major ultra‐structural alteration occurring in archaeological bone

AbstractTotal pore volume and pore size distribution are indicators of the degree of post‐mortem modification of bone. Direct measurements of pore size distribution in archaeological bones using mercury intrusion porosimetry (HgIP) and back scattered scanning electron microscopy (BSE‐SEM) reveal a common pattern in the changes seen in degraded bone as compared to modern samples. The estimates of pore size distribution from HgIP and direct measurement from the BSE‐SEM images show remarkable correspondence. The coupling of these two independent approaches has allowed the diagenetic porosity changes in human archaeological bone in the >0.01 µm range to be directly imaged, and their relationship to pre‐existing physiological pores to be explored. The increase in porosity in the archaeological bones is restricted to two discrete pore ranges. The smaller of these two ranges (0.007–0.1 µm) lies in the range of the collagen fibril (0.1 µm diameter) and is presumably formed by the loss of collagen, whereas the larger pore size distribution is evidence of direct microbial alteration of the bone. HgIP has great potential for the characterization of microbial and chemical alteration of bone. Copyright © 2002 John Wiley & Sons, Ltd.

Comparing X‐ray densitometry and BSE‐image analysis of thin section in varved sediments

A 10‐cm long section from varved sequence of Lake Nautajärvi, Finland, has been analysed using both X‐ray densitometry and image analysis of Backscattered Scanning Electron microscope Images (BSEI) of thin sections. Lake Nautajärvi's clastic‐organi c varves appear in X‐ray images as a succession of dark and pale stripes, pale ones being the spring detrital minerogenic layers and dark ones organic matter laid down during the time of summer, autumn and winter ice cover. Owing to the sharp contrast of the minerogenic spring layer, a semiautomatic tree‐ring width and density measurement DendroScan system was applied to obtain seasonal/annual data of relative X‐ray density. Mean density of BSEI was also acquired. Then BSEI were processed to produce black and white images, where white pixels represent the clay‐rich sedimentary matrix and black pixels the particles in the matrix: silt‐ or sand‐sized, terrigenous grains, authigenic particles and diatoms. Measurements of the size of the detrital particles forming the varves were obtained. For each varve, mean grey‐level values in BSEI correlated well with the mean grey‐level values of X‐ray images, but grain size obtained on BSEI did not correlate with any parameters computed from X‐ray radiography.

Image analysis and estimation of porosity and permeability of Arnager Greensand, Upper Cretaceous, Denmark

Arnager Greensand consists of unconsolidated, poorly sorted fine-grained, glauconitic quartz sand, often silty or clayey, with a few horizons of cemented coarse-grained sand. Samples from the upper part of the Arnager Greensand were used for this study to estimate permeability from microscopic images. Backscattered Scanning Electron Microscope images from polished thin-sections were acquired for image analysis with the software PIPPIN®. Differences in grey levels owing to density differences allowed us to estimate porosity, clay and particle content. The images were simplified into two phases, pores and particles, and the specific surface of the solid phase was calculated. We used the Kozeny Equation to calculate the permeability. The petrophysical properties, porosity and permeability obtained from image analysis were compared to results using laboratory methods. The 150x magnification of the image can not resolve the microporosity within the clay fraction, so we suggest that the imaged porosity at 150x magnification is close to the effective porosity for permeability assessment. The Heporosity, however, represents the total porosity of the Arnager Greensand. For permeability estimation, a local permeability was calculated for each image. For calculation of the plug scale permeability, we compare three different averaging methods: arithmetic, harmonic, and geometric mean. In every case the calculated permeability overestimates the measured permeability. Only the lowest calculated local permeabilities corresponds to the measured permeabilities, suggesting that the overall permeability for these samples is governed by the least permeable parts.