BSE Image Research Articles

A 2D Irregular Shape Model of Random Packing for Cement Particles

In this paper, an area-oriented algorithm based on a cellular automaton (CA) is proposed firstly to generate random irregular particles in a special area. The algorithm is used to reconstruct a 2D image with numerous irregular particles, the particles information is extracted from a 2D original image reprocessed from a BSE image of Cement CCRL-133 (NIST, USA). To make it more comparable, a uniform size 2D image is reconstructed by random packing of circle cement particles. In addition, the influence of cement particle shapes (circle and irregular) on initial surface areas and pore size information of initial cement paste microstructure is presented. Comparative results demonstrate that the 2D image reconstructed by irregular particles generating from the new algorithm is consistent with the original one.

SEM-backscattered electron imaging and image processing for evaluation of unhydrated cement volume fraction in slag blended Portland cement pastes

Proper parameters for image taking and minimum field number for image processing were investigated to evaluate volume fraction of unhydrated cement(UHC) in both neat cement paste and slag blended cement paste. Our research suggested that magnification 250× was sufficient for the two pastes, and accelerating voltage should be set as 15 kV and 20 kV for BSE image taking of neat cement paste and slag blended cement paste respectively; the minimum field number increased while the total imaging area stayed the same as the magnification increased within certain statistical bias.

철근 부식 방식을 위한 굳지 않은/굳은 콘크리트의 전기방식 적용에 관한 연구

본 연구에서는 전기방식 종류에 따른 문헌 고찰 및 굳지 않은/굳은 상태의 콘크리트에 대해 전기방식 적용 시 방식 효과와 관련하여 연구를 실시하였다. 굳은 콘크리트의 경우 우선적으로 철근의 부동태피막 파괴를 유도하기 위하여 NaCl을 혼입한 후, 2주일동안 250, 500, $750mA/m^2$ 의 방식전류를 통전하였다. 그 후 부동태피막 복원화와 염소 이온 추출에 대해서 정량화를 실시하였다. 동시에, 굳지 않는 상태의 콘크리트에 대해서는 굳은 상태와 동일한 양의 방식전류를 타설 직후부터 동일한 기간동안 통전하여 전기방식을 실시하였다. 후광산란(Backscattered electron; BSE) 이미지를 이용하여 철근-콘크리트 계면을 관찰하였으며, 염소이온 확산에 대해서 염소이온 이동 속도와 철근 부식 저항성에 대한 콘크리트의 성질 변화에 대해 측정하였다. 결과적으로 보면, 전기 방식은 부동태피막 복원화에 매우 효육적이며, 콘크리트 내의 염소이온 중 63-73% 정도가 추출되는 것으로 확인 되었다. 굳지 않는 상태의 콘크리트에 전기방식을 적용할 경우, 철근 표면에서 $Ca(OH)_2$ 층이 조밀하게 되어 철근 부식 저항성이 향상되었다. 다만, 방식 전류에 따라 콘크리트 표면 염화물량이 증가하는 경향이 나타나는 것을 확인 할 수 있다. 【In this study, the inhibitive effect of electrochemical treatment subjected to fresh and hardened concrete and literature reviews in terms of the treatment were performed. In hardened concrete, chloride ions are mixed during casting to destroy the passivity of steel, and then the current was provided for 2 weeks with 250, 500 and $750mA/m^2$ . After completion of electrochemical treatment, the extraction of chloride ions was quantified and repassivation of steel was observed. Simultaneously, the equated levels of current density for 2 weeks were applied to fresh concrete. Steel-concrete interface in concrete was observed by BSE image analysis and the concrete properties in terms of the diffusivity of chloride ions and the resistance of steel corrosion was measured. As the result, electrochemical treatment is very effectiveness to rehabilitate the passive film on the steel surface and 63-73% of chloride ions in concrete were extracted by the treatment. As the treatment was applied to fresh concrete, the resistance of steel corrosion was improved due to the densification of $Ca(OH)_2$ layers in the vicinity of steel. However, an increase in the current density resulted in an increase in surface chloride content of concrete.】

Realistic pore structure of Portland cement paste: experimental study and numerical simulation

In this study, the pore structure of Portland cement paste is experimentally characterized by MIP (mercury intrusion porosimetry) and nitrogen adsorption, and simulated by a newly developed status-oriented computer model. Cement pastes with w/c=0.3, 0.4 and 0.5 at ages from 1 day to 120 days are comprehensively investigated. It is found that MIP cannot generate valid pore size distribution curves for cement paste. Nevertheless, nitrogen adsorption can give much more realistic pore size distribution curves of small capillary pores, and these curves follow the same distribution mode. While, large capillary pores can be effectively characterized by the newly developed computer model, and the validity of this model has been proved by BSE imaging plus image analysis. Based on the experimental findings and numerical simulation, a hypothesis is proposed to explain the formation mechanism of the capillary pore system, and the realistic representation of the pore structure of hydrated cement paste is established.

Timing of Variscan HP-HT metamorphism in the Moldanubian Zone of the Bohemian Massif: U-Pb SHRIMP dating on multiply zoned zircons from a granulite from the Dunkelsteiner Wald Massif, Lower Austria

In an attempt to better constrain the timing of Variscan HP-HT metamorphism in the SE Bohemian Massif we have dated zoned zircons from a garnet-kyanite granulite of granitic composition from the Dunkelsteiner Wald Massif, Lower Austria, by means of sensitive high-resolution ion microprobe (SHRIMP) technique. In order to combine isotopic information with crystal growth textures, CL and BSE images were systematically taken from the dated zircons. A characteristic threefold concentric zoning was found in many zircons. This involves pre-Variscan protolithic cores followed by two distinct metamorphic/anatectic overgrowth shells of Variscan age. The inner overgrowth shell is characterized by a weak CL but bright BSE signal, and yields high contents of uranium (0.1 to 0.2 wt.%). A pooled U-Pb Concordia age for this zone is 342.0 ± 3.0 Ma (n = 11, MSWD = 0.12). The second, outer, overgrowth shell is always bright in the CL image, dark in the BSE image, and has generally low uranium contents (mostly <500 ppm). A pooled U-Pb Concordia age for this zone is 337.1 ± 2.7 Ma (n = 11, MSWD = 0.22). These results imply that the Variscan HT crystallisation history of the Moldanubian granulites took place over a period of a few million years and was not an extremely rapid subduction-exhumation process. SHRIMP measurements in the protolithic cores yield a cluster of (sub)concordant ages between ∼390 and 460 Ma and a few outliers at higher ages mostly represented by cores in cores. Core domains, which are large, homogeneous and with undisturbed igneous oscillatory zoning, yielded preferentially ages between 430 and 460 Ma. We therefore consider that granitic protolith formation took place at that time. The still older inner cores are interpreted as inherited into the granitic melt.

Experimental Investigation on the Phase Equilibria of the Nb-Ti-Si-B System at 1500 °C

The phase equilibria at 1500 °C of the Nb-Ti-Si-B quaternary at the Nb-rich region were carefully studied. Seven alloys were arc-melted and subsequently annealed at 1500 °C for 150 h. BSE image, XRD and EPMA results show that Nbss + T2 + Nb3B2, Nbss + T2 + Nb3Si and Nbss + T2 + Nb3B2 + Nb3Si were present in these alloys. Extensive solubility of Ti and Si were found in the Nb3B2 phase. The experimental findings were compared favorably with the calculated phase equilibria. The phase equilibria in the Nb-rich region of the Nb-Ti-Si-B system have Nbss + T2, Nbss + T2 + Nb3B2, Nbss + T2 + Nb3Si and Nbss + T2 + Nb3B2 + Nb3Si. This work provides important guide lines on the effect of B addition to the microstructure of the Nb-rich Nb-Ti-Si alloys.

Influence of self heating and Li 2SO 4 addition on the microstructural development of calcium aluminate cement

Hydrated Calcium Aluminate Cement (CAC) is known to have a complex microstructure involving different phase assemblages strongly dependant on the temperature. This work presents an experimental approach to study the microstructure of CAC pastes from the first minute of hydration with controlled time–temperature histories up to several months of curing. The self heating usually occurring in the CAC concrete is considered and its influence on the growth and assemblage of the hydration products and subsequent space filling is shown. Quantification of the degree of CA hydration by BSE image analysis is used to understand the evolution of phases throughout the hydration process. Lithium sulphate is commonly used to control the setting time of CAC based materials. It is shown that this promotes the formation of more stable hydrates, but slightly reduces the extent of CA hydration.

RECONSTRUCTION OF MAGMATIC TO SUBSOLIDUS PROCESSES IN AN AGPAITIC SYSTEM USING EUDIALYTE TEXTURES AND COMPOSITION: A CASE STUDY FROM TAMAZEGHT, MOROCCO

The Eocene Tamazeght (or Tamazert) complex, situated in the High Atlas Mountains of Morocco, comprises a suite of ultramafic to syenitic alkaline to peralkaline units cross-cut by carbonatite diatremes, and dyke rocks of both carbonatite and silicate lithology. In spatially restricted areas, the most evolved silicate unit of the complex (malignites) contains eudialyte-group minerals (EGM) as index phases for agpaitic systems. The chemical composition of EGM is closely related to their textural position; the EGM are stable over a wide range of temperature and chemical composition and readapt their composition to changing subsolidus conditions, including infiltration of external fluids. Therefore, EGM are a powerful petrogenetic indicator in agpaitic systems. Petrography and compositions of EGM record all stages of the (late-) magmatic to subsolidus history including (1) effects of an autometasomatic fluid, (2) infiltration of a fluid derived from associated carbonatites, and (3) opening of the system to meteoric fluids. During the late-magmatic stage 1, the crystallization of interstitial EGM is accompanied by intensive albitization of surrounding feldspars. The replacement of nepheline by sodalite occurs at the postmagmatic stage 2, when primary sector-zoned EGM are cross-cut by irregular bright zones in BSE image that are enriched in Sr, Mn, rare-earth elements (REE) and high field-strength elements (HFSE). Enrichment of these elements in distinct schlieren-like zones in EGM combined with the formation of Ca- and CO2-rich minerals of the cancrinite group points to the associated carbonatites as the potential source of fluid. The latest modifications (3) include the formation of zeolite-group minerals and calcite, which are believed to be a result of the interaction of the rocks with low-temperature meteoric fluids, probably in equilibrium with the surrounding country-rocks.

Diagenesis and reservoir quality of Bhuban sandstones (Neogene), Titas Gas Field, Bengal Basin, Bangladesh

This study deals with the diagenesis and reservoir quality of sandstones of the Bhuban Formation located at the Titas Gas Field of Bengal Basin. Petrographic study including XRD, CL, SEM and BSE image analysis and quantitative determination of reservoir properties were carried out for this study. The sandstones are fine to medium-grained, moderately well to well sorted subfeldspathic arenites with subordinate feldspathic and lithic arenites. The diagenetic processes include clay infiltration, compaction and cementation (quartz overgrowth, chlorite, kaolinite, calcite and minor amount of pyrite, dolomite and K-feldspar overgrowth). Quartz is the dominant pore occluding cement and generally occurred as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Pressure solution derived from grain contact is the main contributor of quartz overgrowths. Chlorite occurs as pore-lining and pore filling cement. In some cases, chlorite helps to retain porosity by preventing quartz overgrowth. In some restricted depth interval, pore-occlusion by calcite cement is very much intense. Kaolinite locally developed as vermiform and accelerated the minor porosity loss due to pore-occlusion. Kaolinite/chlorite enhances ineffective microporosity. Kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene or deeper Oligocene source rocks. The relation between diagenesis and reservoir quality is as follows: the initial porosity was decreased by compaction and cementation and then increased by leaching of the metastable grains and dissolution of cement. Good quality reservoir rocks were deposited in fluvial environment and hence quality of reservoir rocks is also environment selective. Porosity and permeability data exhibit good inverse correlation with cement. However, some data points indicate multiple controls on permeability. Reservoir quality is thus controlled by pore occluding cement, textural parameters (grain size, pore size and sorting) and depositional environment. The reservoir finally resumed partly its pre-cementation quality after development of secondary porosity.

Size and Volume Relationship of Pore for Construction Materials

A general relationship between cumulative pore volume and pore sizes as measured through mercury intrusion porosimetry (MIP) and BSE image analysis technique is presented in this paper. From the results of the MIP study conducted on hardened cement paste, cement silica fume paste, cement silica fume sand mortar, brick, soil cement, and concrete, it is observed that a general relationship exists between applied pressure and intruded volume of mercury. This relationship closely follows the MMF (Morgan, Mercer and Flodin) model. The general relationship between pore sizes and intrusion volume in MIP is then derived from this relationship using Washburn's equation. A similar model is also observed to describe the relationship between cumulative volume and pore sizes obtained through BSE image analysis. The variations of the parameters namely median pore radius and dispersion coefficient (a measure of the spread of pore sizes), with silica fume content, ratio of water-to cementitious material and age are then discussed to demonstrate the utility of the model.

Study of Experiments on Cutting Difficult-to-Machine Materials with Ultrafine-Grained Waved-Edge Milling Insert

For the cutting of the difficult-to-machine materials, such as stainless steel and dead-hard steel, is always puzzling and restricting manufacturing, it is necessary to deeply study and search after new machining methods in respect of both theory and practice. This paper chose waved-edge milling inserts and flat-groove milling inserts of different materials to make cutting force contrast experiments on stainless steel ZG0Cr13Ni5Mo, chose ultrafine-grain inserts, YT14 inserts (local product) and CY250 inserts(foreign product) to make cutting life contrast experiments on dead-hard steel ZG35CrMo, then researched in theory the disrepair appearance, the BSE image and the granularity. The research results show that the integrated cutting capability of ultrafine grain waved-edge milling insert is excellent for difficult-to-machine materials.

Influence of corrosion inhibitors on concrete transport properties

The effect on transport properties of admixing corrosion inhibitor in Portland cement based concrete is studied experimentally in this paper. Two commonly available types of corrosion inhibitor have been evaluated: an organic corrosion inhibitor and a nitrite based inhibitor. The gas permeability, water permeability and chloride migration of the resulting concrete were evaluated by means of standard test methods. In some cases, 1% sodium chloride was added to the concrete. It is found that both types of corrosion inhibitor lead to higher transport coefficients. The increment caused by the nitrite based inhibitor is higher than for the amine-ester based inhibitor. The influence of sodium chloride addition during mixing is not prominent. The obtained transport properties are analysed and discussed by means of BSE experiments and image analysis.

シミュレーションにより再現された組織と電子顕微鏡観察像の空間構造の比較

Microstructure in cement pastes revealed by BSE image analysis was quantitatively compared with a structure simulated by CEMHYD3D. At a water/cement ratio of 0.25, the spatial structures of unhydrated cement particles and coarse capillary pores were sufficiently simulated by the model. At water/cement ratios of 0.40 and 0.60, judging from visual impression, the simulated structures are similar to real ones. However, its geometric features in terms of spatial statistics, especially capillary pores do not agree with the real structure. This discrepancy results from the differences in porosity and pore size to be compared in the two methods. It should be noted that quantitative comparison between real and simulated structures is meaningful only when there are little pore finer than the resolution in each image.

Corrosion Resistance of AZ91D Magnesium Alloy Modified by Rare Earths-Laser Surface Treatment

To improve the corrosion resistance of magnesium alloy AZ91D which is widely applied in the realm of aviation and aerospace in industry, a composite way was adopted for its surface modification, namely the laser heating of pre-coated sample by sol-gel method. Experiments for testing its corrosion resistance were carried out, accordingly, it could be concluded that this composite technique was able to improve the corrosion resistance against uniform corrosion. Surface morphology observed by SEM image was analyzed, and it could be seen clearly that laser heating was fairly favorable for improving the cohesion between coating and the substrate. XRD spectrum and BSE image were studied which gave out the information that the main compositions were mainly CeO 2 and a small quantity of MgO CeO 2. According to all the experimental evidence, the anticorrosion mechanism of samples treated by composite techniques and the effects of laser heating on corrosion resistance of magnesium alloys AZ91D were discussed.

Influence of limestone powder used as filler in SCC on hydration and microstructure of cement pastes

Abstract In recent years, self-compacting concrete (SCC) has gained wide application in the construction industry. As for high performance concrete (HPC) and traditional concrete (TC), the microstructural properties of SCC are the main factors, which determine the material properties, i.e. the mechanical properties, transport properties and the durability behaviour. In order to investigate the development of the microstructure of SCC, the microstructural parameters of the paste including porosity, pore size distribution and phase distribution are determined by means of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The thermogravimetric analysis (TGA) and the derivative thermogravimetric analysis (DTG) are used to identify the phase constituents. These parameters as studied for self-compacting concrete are compared with high performance concrete and traditional concrete. The specimens of self-compacting cement paste (SCCP) are made with water/binder ratio 0.41 and 0.48, the high performance cement paste (HPCP) with w/c 0.33 and traditional cement paste (TCP) with w/c 0.48. The measurements are performed at different hydration stages, i.e. at 1, 3, 7, 14, 28 and 56 days. The result of this research shows that the pore structure, including the total pore volume, pore size distribution and critical pore diameter, in the SCCP is very similar to that of HPCP. The fact that limestone powder does not participate in the chemical reaction was confirmed both from thermal analysis and BSE image analysis.

Modern SEM-based mineral liberation analysis

Modern digital mine planning, plant design and mineral processing operations demand detailed characterisation of the ore and plant feed. Textural parameters, such as mineral liberation size and mineral association, combine with modal mineralogy data to strongly influence mineral processing conditions and recovery. Traditionally, the measurement of these ore characteristics employed the tools of an optical microscope and/or a semi-automated SEM. These methods are time consuming, costly and frequently produce semi-quantitative results from data sets that are too small to be statistically valid. Thus, the results cannot be used reliably and effectively in digital mine planning and design. In the last 10 years, modern SEM-based quantitative mineralogy tools have advanced rapidly with increasing computer power, improved SEM hardware and the development of sophisticated image analysis methods. Texture resolutions can now be submicron and SEM measurement times have reduced to less than an hour for simple analyses, where previously they required many hours. Through image analysis, particle sections are recognised and separated, and the mineral grains within are delineated for discrete X-ray analysis to determine mineralogy. The modern tools not only increase the speed and accuracy of liberation analysis, but also enhance measurement automation. Automated standard collection assists with the setup of new ore types for routine analysis and automated elemental quantification of target minerals enables the tracking of variations in the composition of the minerals of interest. The key to success for any modern SEM-based mineral liberation analysis system is the close integration of BSE image and EDS X-ray analyses. Integration of the SEM-based quantitative mineral liberation analysis with optical microscope, dual beam systems and X-ray tomography will further enrich the analysis results and the derived user experience.

Reply to the discussion by Sidney Diamond of the paper “Patch microstructure in cement-based materials: Fact or artefact?”

A reply to a discussion of an earlier paper published in this journal (Volume 36, Number 5, May 2006), written by H.S. Wong and N.R. Buenfeld and commenting on work by S. Diamond, is presented. The authors of the reply posit that the micro-scale inhomogeneities described by the discusser are not considered to be what is termed patch microstructure (PM). PM refers instead to broad areas, in the order of several hundred microns or more of dense, almost nonporous paste, and dark, highly porous paste, separated by sharp and distinct boundaries. These patches are irregularly shaped and occur randomly in 'bulk' and classical 'ITZ' paste. The most striking feature of PM is the sharp boundary between the porous and dense paste. It is emphasized that the characteristics of PM given in this reply and in the authors' paper are identical to those originally reported in Refs. [1] and [2]. It is reiterated that the appearance of PM is an artefact of sample preparation and does not reflect the true nature of the hydrated cement paste. The appearance of dense patches comes from areas that have been ground beyond the epoxy intrusion depth. In a BSE image, non-resin filled pores are not visible as backscatter electrons are generated from the base or side walls of the pores.

Low-Speed Sliding Test on New Cu-Sn-Based Composite Materials

The author prepared new composition of Cu-Sn based composite materials containing lamellar solid lubricants, and measured their performance with focus on contact resistance and the coefficient of friction using a low-speed tribometer. Among three kinds of composite materials, the composite material containing 26wt.% of total solid lubricants was lower in both of contact resistance and the coefficient of friction and showed stable characteristics compared with those containing 25wt.% and 35wt.% respectively. The author analyzed the characteristics of these materials using several techniques including BSE image, element analysis through EPMA, and mapping analysis, and examined why the composite material containing 26wt.% of total solid lubricants showed higher performance.

Combining confocal and BSE SEM imaging for bone block surfaces

The present report presents a method for the correlation of qualitative and quantitative BSE SEM imaging with confocal scanning light microscopy (CSLM) imaging modes applied to bone samples embedded in PMMA. The SEM has a proper digital scan generator: we leave the BSE image unchanged, and match the CSLM image to it, because the CSLM scan mechanism is not digital, though the signal is digitised. Our overlapping program uses a linear transformation matrix which projects one system to the other, calculated by finding three corresponding points in BSE and CSLM pictures. BSE images are empty where cells and osteoid are present. Fluorescence mode CSLM fills in these gaps. The combination images enhance our understanding of what is going on - and re-establish the need for good cellular preservation.

An Improved Method for the Dispersion Assessment of Flame Retardant Filler/Polymer Systems Based on the Multifractal Analysis of SEM Images

AbstractSummary: The dispersion quality of filler particles in highly loaded, flame retardant filled (FRF) polymer composites has been quantified using a complementary multifractal image analysis method. The use of an alternative imaging signal, backscattered electrons, greatly reduced the time required for image capture, relative to energy dispersive X‐ray signals discussed previously. Characteristic Dq multifractal spectra were calculated from BSE image data and multifractal curve width was once again observed to be a good indicator of dispersion quality. Numerically derived data was in strong agreement with a visual interpretation of images exhibiting variations in dispersion quality. This new method was used to study a series of FRF/EVA composite compounds based on aluminium hydroxide and magnesium hydroxide, both uncoated and coated with isostearic acid. Results from a screening experimental design were used to investigate the effect of material formulation on dispersion quality. Variations in dispersion quality observed in formulations based on isostearic acid treated filler could be related to the differing isostearic acid adsorption characteristics of the two metal hydroxides.Observed versus predicted scatter plot for the linear model describing the dependence of mean Dq curve width on material formulation.magnified imageObserved versus predicted scatter plot for the linear model describing the dependence of mean Dq curve width on material formulation.