Combined Optical Microscopy Research Articles

Quantifying the influence of heating and resting on the bitumen microstructure

The investigation of the bitumen microstructure can provide an alternative approach to characterise the material. However, various factors prior to its analysis need to be considered, before being able to come to a meaningful conclusion. This involves the identification of factors like heating time and temperature as well as resting time and how it can affect the resulting microstructure. Furthermore, the need for quantifying the microstructure is sought after. Thus, the goal of this study is to address these parameters and quantify their respective influence via optical inverse dark- and brightfield microscopy, subsequent particle analysis of the darkfield images and partial link to infrared spectroscopy. The results show that optical microscopy in combination with particle analysis from dark field images can be used for quantification of the microstructure and even differentiate binders from different crude oil sources. However, small binder quantities, typically used for microscopy, can oxidize rapidly. Thus, a heating time of 30 – 60 s at a temperature of 150 °C was deemed sufficient for these unmodified binders. In addition to that the microstructure becomes stable after 30 min of resting, making binder characterisation via microscopy much more convenient. For imaging analysis an overall area covered by bee structure enables universal characterisation and comparison, while providing good differentiation between binder A (10%), B (2%) and C (16%). These findings should set the basis for future research, where microscopy can be used to identify and tackle important questions related to changes caused by ageing, modification with polymers, additives, filler or rejuvenators.

Investigation of failure mechanisms and remaining life prediction of firewater pipelines used in industrial applications

Firewater (FW) pipelines network maintenance and monitoring are of utmost importance since they are not easily accessible for inspection. Failure and corrosion of carbon steel FW pipes, particularly localized corrosion, can propagate leaks and bursts of pipelines, which leads to expensive repairs or replacement, or even uncontrolled situations during an emergency. Therefore, being aware of the pipeline conditions, predicting their failure mechanisms, their remaining life, planning to manage emergencies, and evaluating their conditions are essential. In this study, visual inspection, metallurgical examinations using optical microscopy in combination with scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and corrosion test using a three-electrode system were employed to determine the cause of failure. Also, the water samples were subjected to various chemical and bacterial analyses. Corrosion and scale-forming potential, Physico-chemical properties, sulfate-reducing bacteria, Iron-reducingbacteria, and total bacterial count were investigated on water samples to evaluate the corrosion conditions of FW pipes. Furthermore, the remaining life prediction and monitoring of the pipelines have been studied based on laboratory simulation experiments and advanced non-destructive tests (NDT) by using Long Range Ultrasonic Testing (LRUT) and Phased Array Ultrasonic Testing (PAUT). The results indicate that the oxygen corrosion attack especially the accumulation of air bubbles (dissolved oxygen), forming tubercles, and aggressive anions (Cl- and SO42-) that are the root causes of the pipeline's failure. It can happen in general and localized forms such as localized pitting corrosion, tuberculation, top-of-the water line corrosion (TWLC), and cavitation damage. Also, by comparing NDT tests and laboratory experiments results, the remaining life results in state 2 are in good agreement. Thus, the laboratory simulation experiments are verified and can be used as a desirable indicator for the remaining life of FW pipelines and strategies for improved durability design and maintenance.

Effect of spray angle onto the microstructure of EB-PVD enabled 8YSZ thermal barrier coatings

Abstract The microstructure plays an important role in the durability and performance of the Thermal Barrier Coatings (TBCs). The TBCs were deposited on Ti-6Al-4 V substrate with NiCrAlY bond coat using APS and 8YSZ using in-house EB-PVD. The paper presents the effect of spray angle onto the microstructural and mechanical properties of 8YSZ in detail. The surface microstructural and elemental composition are examined using SEM with EDS. The coating porosity was examined by SEM and ImageJ using the grayscale threshold technique. Also, the mechanical properties like hardness, surface roughness, and thickness were measured by indentation, surface profilometer, and optical microscopy in combination with ImageJ. The results show 90° TBC with the uniform structure in the presence of a few pores and cracks compared to 60° TBC. In 60° TBC, the dissimilar grain growth and elongated grains with average size 300 nm compared to 90° TBC grain size 150 nm was observed. In 60° TBC, porosity with 20.65% more was present which contributes to large shadow region leading to high porosity. Also, the decrease in coating hardness with 5% was observed with an inclined spray angle. In 60° TBC, the rough and non-uniform surface was obtained, but the overall coating thickness was almost similar for both the spray angle condition.

Microstructural Characterization of Quenched and Partitioned commercial Medium Carbon Steel

In order to achieve the desired properties, the microstructure of metals is often modified by heat treatments. A suitable combination of high strength and good ductility can be achieved by adjusting the amounts of martensite and retained austenite through a Quenching and Partitioning (Q&P) process. Controlling these material properties offers new potentials in the production of light weight steel parts. This paper presents a basic study of heat treatment conditions with subsequent microstructural characterization of quenched and partitioned commercial 0.54C-1.45Si-0.71Mn spring steel. Beginning from full austenitization, different quenching and partitioning parameters were applied. Microstructural characterization was performed using optical microscopy in combination with different etching methods as well as Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD). It is shown that the intended dual phase microstructure with a specific phase fraction of austenite can be produced. Those results and consideration of hardness measurements show that the investigated commercial spring steel is a promising candidate for improving mechanical properties by a Q&P process.

An investigation of corrosion and sedimentation in the air cooler tubes of benzene drying column in linear alkyl benzene production plant

In this study the corrosion, sedimentation and subsequently choking in the air cooler tubes of benzene drying section in Bistoun Petrochemical Company, at Iran were investigated. The main reasons of failure were analyzed using standard failure analysis techniques such as visual checking, chemical and mechanical characterizations, metallurgical examinations employing optical microscopy in combination with scanning electron microscopy, X-ray fluorescence and X-ray diffraction analysis. The chemical analysis was used to determine the corrosion products. The accumulation of sediment and under-deposit corrosion has resulted in localized corrosion and perforation in the inner surface of the tubes. In addition, the erosion–corrosion accelerated the destruction of tubes. The microbial corrosion can happen because of high water content. The results showed that a combination of corrosion types has occurred. A new idea was proposed for the separation mechanism of low concentration of water from benzene in the process. Finally, the suggestions have been proposed for trouble shooting, preventing corrosion and clogging in the tubes of air cooler and subsequently avoiding production stop.

Analysis of a failed pipe elbow in geothermal production facility

Failure of a pipe elbow used in geothermal production facility was reported to occur after 2 months in service. A leak was found to form at the bottom of elbow of horizontal pipe. The main cause of failure was investigated through conducting standard failure analysis including visual examination, chemical analysis, mechanical characterization, metallurgical examinations using optical microscopy in combination with scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analysis and corrosion test using a three-electrode potential technique. Results of this investigation indicated that the failure of elbow was caused by an erosion-corrosion with the presence of wall thinning in leak area. The failure mechanism was discussed in this paper.

Reduction of Dislocation Density in Bulk Silicon Carbide Crystals Grown by PVT on Profiled Seeds

The distribution of extended defects in silicon carbide (SiC) crystals grown on profiled seeds by the sublimation (physical vapor transport) method has been studied by optical microscopy in combination with chemical etching. It is established that free lateral growth on protruding relief elements (mesas) is accompanied by a sharp decrease in the density of threading dislocations and micropipes. The decreased density of dislocations is retained after growing a thick layer that involves the overgrowth of grooves that separated individual mesas.

Structural Perfection of Silicon Carbide Crystals Grown on Profiled Seeds by Sublimation Method

— The distribution of extended defects in silicon carbide (SiC) crystals grown on profiled seeds by the sublimation (physical vapor transport) method has been studied by optical microscopy in combination with chemical etching and AFM. It is established that free lateral growth on protruding relief elements (mesas) is accompanied by a sharp decrease in the density of threading dislocations and micropipes. The decreased density of dislocations is retained after growing a thick layer that involves the overgrowth of grooves that separated individual mesas.

Hot spot dynamics in carbon nanotube array devices.

We report on the dynamics of spatial temperature distributions in aligned semiconducting carbon nanotube array devices with submicrometer channel lengths. By using high-resolution optical microscopy in combination with electrical transport measurements, we observe under steady state bias conditions the emergence of time-variable, local temperature maxima with dimensions below 300 nm, and temperatures above 400 K. On the basis of time domain cross-correlation analysis, we investigate how the intensity fluctuations of the thermal radiation patterns are correlated with the overall device current. The analysis reveals the interdependence of electrical current fluctuations and time-variable hot spot formation that limits the overall device performance and, ultimately, may cause device degradation. The findings have implications for the future development of carbon nanotube-based technologies.

Experimental Study on the Formation of Non-Metallic Inclusions Acting as Nuclei for Acicular Ferrite in HSLA Steels through Specific Deoxidation Practice and Defined Cooling Conditions

Specific types of non-metallic inclusions are known to act as heterogeneous nuclei for the formation of acicular ferrite, which provides excellent toughness. By increasing the amount of acicular ferrite in the microstructure, the properties of HSLA steels can be optimized significantly.Although the formation of acicular ferrite caused by heat treatments (thermomechanical treatments or welding) is quite well described in literature, there is less information to find about the formation of acicular ferrite immediately out of the liquid melt. Within the present study experiments on laboratory scale are carried out simulating the influence of cooling conditions and Ti-content on size, chemical composition and morphology of non-metallic inclusions and consequently on the amount of acicular ferrite. All experiments were carried out with a dipping test simulator enabling very well controllable cooling conditions. Optical microscopy in combination with special etching methods as well as SEM/EDS-analysis was used for microstructure and inclusion characterization.

Analysis of internal corrosion in subsea oil pipeline

Failure of a subsea crude oil API 5L X52 steel pipeline which led to oil leakage has been reported to occur after 27 years in service. Some leaks were found to form at the bottom of the horizontal API 5L X52 steel pipeline near an elbow section which connected the pipeline to a riser. The present investigation aims to analyze the main cause of failure by conducting standard failure analysis methods including visual examination, chemical and mechanical characterizations, metallurgical examinations using optical microscopy in combination with scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analysis and corrosion test using a three-electrode potential technique. Results of this investigation suggest that the cause of failure is electrochemical corrosion combined with mechanical process known as flow-induced corrosion. The failure mechanism is discussed with specific attentions are paid to fluid flow rate and chloride-containing water phase.

Alignment of a Columnar Hexagonal Discotic Liquid Crystal on Self-Assembled Monolayers

The alignment of the columnar hexagonal (Colh) phase of the discotic liquid crystal 2,3,6,7,10,11-hexakis(undecyloxy)triphenylene on well-characterized surfaces comprised of thiol-on-gold self-assembled monolayers (SAMs) has been studied using polarizing optical microscopy in combination with evanescent wave ellipsometry. Homeotropic alignment is preferred for both COOH- and CH3-functionalized SAMs (both high and low energy surfaces). Even when the SAM layer is comprised of edge-on oriented triphenylene units, evanescent wave ellipsometry shows that the liquid crystal aligns predominantly in a homeotropic (face-on) manner. These results confirm the view that the surface acts primarily as a mechanical barrier and although the chemical nature of the surface can enhance the ease or quality of the alignment of the Colh phase, it is of secondary importance.

Structural Perfection of Silicon Carbide Crystals Grown on Profiled Seeds by Sublimation Method

The distribution of extended defects in silicon carbide (SiC) crystals grown on profiled seeds by the sublimation (physical vapor transport) method has been studied by optical microscopy in combination with chemical etching. It is established that free lateral growth on protruding relief elements (mesas) is accompanied by a sharp decrease in the density of threading dislocations and micropipes. The decreased density of dislocations is retained after growing a thick layer that involves the overgrowth of grooves that separated individual mesas.

Study of the organic matter in the rocks of the crystalline basement and weathering mantle of Tatarstan

This paper is dedicated to study of the rocks of crystalline basement and weathering mantle taken from several parametric boreholes at the territory of Tatarstan Republic. Optical-microscopy in combination with methods of organic geochemistry, including isotope analysis, revealed a migration nature of the organic matter of the studied rocks from oil-source beds of the Devonian domanikoid-facies deposits.

Multimodal optical microscopy in combination with gold nanorods for cancer cell imaging

The multimodal optical imaging technique, which utilizes nonlinear and linear optical processes, plays an important role in biological and biomedical research. As second-order nonlinear phenomenon, the two-photon luminescence (TPL) results from the nonlinear excitation of fluorescent molecules, while the second harmonic generation (SHG) depends on the second order nonlinear polarization, orientation, and noncentrosymmetric properties of molecules. In contrast, the linear resonance light scattering (RLS) occurs when the molecules are excited by a light beam with a wavelength close to their absorption bands. Since SHG, TPL, and RLS involve different kinds of optical processes, they might be used in parallel to provide complementary information about the structure and function of cells and tissues. Herein, we develop for the first time a multimodal optical microscopy with the capability of simultaneous SHG, TPL, and RLS imaging. We analyze theoretically and demonstrate experimentally the near-infrared irradiation-induced SHG, TPL, and RLS from the gold nanorods with nanometer spatial resolution. With the gold nanorods as the contrast agents, we further demonstrate the simultaneous SHG, TPL, and RLS imaging of A431 human epithelial skin cancer cells. This multimodal optical microscopy might provide a reliable and complementary approach for biological and biomedical research.

Three-dimensional morphology of cementite in steel studied by X-ray phase-contrast tomography

We show that non-destructive, in-line X-ray phase-contrast tomography (PCT) can be used to study the three-dimensional morphology of individual cementite particles in steel with a spatial resolution of approximately 1.5 μm in a sample volume of 600 × 400 × 250 μm 3 . The smallest detectable cementite grains are 5 μm in size. The PCT results correspond very well to optical microscopy in combination with serial sectioning. We estimate the temporal resolution of PCT for in situ studies of cementite to be 30 min.

Structural perfection of silicon carbide crystals grown on profiled seeds by sublimation method

The distribution of extended defects in silicon carbide (SiC) crystals grown on profiled seeds by the sublimation sandwich method (physical vapor transport) has been studied by optical microscopy in combination with chemical etching. It is established that free lateral overgrowth of protruding relief elements (mesas) is accompanied by a sharp decrease in the density of threading dislocations and micropores. The decreased density of dislocations is retained after growing a thick layer that involves the overgrowth of grooves that separated individual mesas.

Magneto-optical near-field microscopy of ultrathin films in ultrahigh vacuum.

We demonstrate that magnetic domains of ultrathin films can be imaged in situ in ultrahigh vacuum (UHV) by scanning near-field optical microscopy in combination with a Sagnac interferometer (Sagnac-SNOM). In the present set-up, the Sagnac interferometer is not only used for measuring the magneto-optical Kerr effect but also for tip-to-sample distance control. The high sensitivity of the instrument enabled us to study the magnetization reversal processes in externally applied magnetic fields in ultrathin films of Fe and Ni grown on Cu(100) single crystals.

Characterization of the α-Al(FeMn)Si nuclei on β-AlFeSi intermetallics by laser scanning confocal microscopy

As-cast billets of aluminum extrusion alloys of the 6xxx Al alloys family require a homogenization treatment to make the material suitable for hot extrusion [1]. During this homogenization treatment several processes take place such as the transformation of interconnected plate-like monoclinic β-Al5FeSi intermetallics into more rounded discrete cubic α-Al12(FeMn)3Si particles [2–4], the dissolution of Mg2Si [5–8] and Si precipitates [8] and the precipitation of elements still in supersaturated state [9, 10]. Of these processes the phase transformation of the intermetallics and the accompanying shape change is deemed to be the most important for obtaining a good extrudability and in particular a good surface quality in the extruded product. However, little microstructural and topological information is available concerning the details of this transformation process and in the absence of such information realistic modelling of the kinetics of this transformation on a physical basis is not possible [11]. To enable the construction of such physical models quantitative information concerning the position of the α particles on the β plates, their 3D shape during early and later stages of growth, and their site density is required. In principle such information can be obtained by standard optical microscopy in combination with stepwise (step size <0.2 μm) sectioning, scanning electron microscopy (SEM) on deep etched samples, or transmission electron microscopy (TEM). While the SEM offers the advantage of an extremely high depth of field which enables deep etched samples to be readily imaged, this technique does not allow quantitative data regarding 3D topography to be obtained. This paper describes the very first results of a 3D characterization of such α-Al(FeMn)Si particles on βAlFeSi plates in a partially homogenized 6005A Al alloy using laser scanning confocal microscopy (LSCM) in combination with a deep etching technique to isolate the intermetallics from the matrix. The advantage of LSCM over the methods mentioned earlier is that a sufficient lateral and vertical resolution (typically 190 nm lateral and 300 nm in the z direction) is possible and this yields the required accuracy of topological detail. This topology can be described quantitatively in 3 dimensions using commercial software. The material used in this work is a commercial DC cast 6005A series Al alloy the composition of which is given in Table I. The as-cast material contained interconected plate like β-AlFeSi intermetallics, with a typical length of a few tens of microns and a mean thickness of a few tenths of a micron. Using conventional optical microscopy on as-cast polished samples, no signs of α-Al(FeMn)Si particles on the β-AlFeSi plates were observed. The as-cast material was homogenized at 540 ◦C for 8 h followed by rapid quenching. From an extensive analysis of the kinetics of the β-AlFeSi to α-Al(FeMn)Si transformation [12] it is known that this annealing treatment transforms approximately half the volume of monoclinic β-Al5FeSi into cubic α-Al12(FeMn)3Si. The advantage of using a sample with such a degree of transformation is that the initial network of β-AlFeSi plates is more or less intact and the original position of the α particles with respect to the parent phase can be determined. The annealed samples were subsequently etched in an electrolytic solution of 78 ml percloric acid, 300 ml H2O, 730 ml ethanol, and 100 ml butylglycol at 10 volts for one minute. This etching procedure resulted in the removal of a layer of matrix material to a depth of approximately 10 μm below the original surface. No signs of attack of the surface of the β-AlFeSi intermetallics were observed. The deep etched samples

Correlation between defect structure and luminescence spectra in monocrystallineerbium-implanted silicon

The transformation of structural defects and photoluminescence (PL) spectra ofn- and p-type Cz-Si after implantation with erbium ions at 1 MeV energy to dosesof 1 × 1013 and 1 × 1014 cm−2 followed by annealing at 620–1100°C for 0.25–3.0 h inchlorine-containing atmosphere or oxygen have been studied by transmissionelectron microscopy, optical microscopy in combination with selective chemicaletching, and PL. For the doses used, annealing at a temperature lower than1100°C leads to the formation of different extended defects (partial Frank orperfect prismatic dislocation loops) of submicron sizes which do not prevent theappearance of Er-related lines and do not give rise to dislocation-related lines inthe PL spectrum. In contrast, high-temperature annealing at 1100°C resultsin the development of similar three-dimensional networks of pure edgedislocations with a density of ∼107 cm−2. These dislocations are responsible for theappearance of quite intensive dislocation-related luminescence (DRL).For high-dose implantation, when annealing at 1100°C is used, the samedislocation networks have been found to form in the n- and p-Si wafers withdifferent low-temperature annealing stages (if any). However, all theseparameters exert the peculiar influence upon the intensity of DRL lines.