Optical Pictures Research Articles

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.

Porous ceramic from particle-stabilised foams via gelcasting

In this paper, a new method to prepare particle-stabilised foams by using short chain amphiphile valeric acid was reported. Quantitative analysis of the optical microscope pictures taken at different time of particle-stabilised foams indicated that they were ultrastable and almost did not ripen and coalesce. Porous ceramic (porosity > 0.85) from particle-stabilised foams was fabricated by the gelcasting technique. With the ultrastable property, longer idle time can be reached. The morphology of this kind of porous ceramic was also investigated and compared to the conventional porous ceramic fabricated by using long chain surfactant Triton X-114 to foam the suspensions.

Optical microscopy versus scanning electron microscopy in urolithiasis

Stone analysis is incompletely done in many clinical centers. Identification of the stone component is essential for deciding future prophylaxis. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) still remains a distant dream for routine hospital work. It is in this context that optical microscopy is suggested as an alternate procedure. The objective of this article was to assess the utility of an optical microscope which gives magnification of up to 40x and gives clear picture of the surface of the stones. In order to authenticate the morphological analysis of urinary stones, SEM and elemental distribution analysis were performed. A total of 250 urinary stones of different compositions were collected from stone clinic, photographed, observed under an optical microscope, and optical photographs were taken at different angles. Twenty-five representative samples among these were gold sputtered to make them conductive and were fed into the SEM machine. Photographs of the samples were taken at different angles at magnifications up to 4,000. Elemental distribution analysis (EDAX) was done to confirm the composition. The observations of the two studies were compared. The different appearances of the stones under optical illuminated microscopy were mostly standardized appearances, namely bosselations of pure whewellite, spiculations of weddellite, bright yellow colored appearance of uric acid, and dirty white amorphous appearance of phosphates. SEM and EDAX gave clearer pictures and gave added confirmation of the stone composition. From the references thus obtained, it was possible to confirm the composition by studying the optical microscopic pictures. Higher magnification capacity of the SEM and the EDAX patterns are useful to give reference support for performing optical microscopy work. After standardization, routine analysis can be performed with optical microscopy. The advantage of the optical microscope is that, it is easy to use and samples can be analyzed in natural color.

Solidificação da zona de fusão na soldagem do AISI 304 com inconel 600 por laser de Nd: YAG

Neste trabalho estudou-se a morfologia de solidificação da zona de fusão, numa junta formada a partir de materiais dissimilares, composta por aço inoxidável austenítico AISI 304 e por liga de níquel Inconel 600, soldada com laser pulsado de Nd:YAG. Os parâmetros do feixe laser e do sistema óptico foram selecionados, visando obter uma solda com penetração total e bom acabamento superficial. A caracterização microestrutural foi realizada por microscopia ótica, onde se observou uma zona de fusão com penetração total do tipo keyhole, a presença de pequenos poros e a ausência de trincas. As juntas soldadas foram caracterizadas também, por meio de microscopia eletrônica de varredura (MEV). Medidas realizadas por espectrometria de raios X por dispersão de energia na zona de fusão indicaram uma distribuição levemente heterogênea de níquel e ferro. Observou-se que o início de solidificação da zona de fusão ocorreu por meio de crescimento epitaxial. A morfologia de solidificação da ZF foi basicamente dendrítica e celular sendo, influenciada pelo gradiente de temperatura, velocidade de solidificação e composição química. As variações de composição química e da morfologia de solidificação não alteraram significativamente os valores de microdureza Vickers na zona de fusão. Resultados obtidos nos ensaios de tração indicaram valores de eficiência de soldagem adequados.

Optical Near-Field Microscopy of Light Focusing through a Photonic Crystal Flat Lens

We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.

Effect of solvent on the chain conformation and cure behavior of phenolic resin

AbstractThe research indicates that in comparison with other solvents, such as ethanol, propanol, butyl alcohol and acetone, which are usually selected as the solvent in phenolic solution, methanol can increase curing rate and enhance crosslinking density of phenolic resins. Therefore, the chain conformations of resole dissolved in different solvents are investigated by using viscosity method. It shows that the chain conformation of resoles changes from loose coil to compact ball, as the strength of hydrogen bond between resole and solvent drops along with the decrease of polarity of solvents. The transition of the chain conformation causes the decrease of reaction probability and reaction rate between functional groups of resoles. The number of unreacted molecules increases, and the crosslinking density of cured resins decreases. The differential scanning calorimetric analysis shows that compared with the resins in methanol, ethanol, propanol, and butyl alcohol, exothermic peak of resole in acetone is obviously wider, and its peak exothermic temperature is lower. Both optical microscope pictures and atomic force microscope pictures demonstrate that the crosslinking density of resins in methanol is higher than those in other solvents. The research concludes that the type of solvent has a great influence on the curing rate and curing degree of resoles. © 2008 Wiley Periodicals, Inc. JAppl Polym Sci, 2008

Mixed Solvents for Morphology Control of Organic Solar Cell Blend Films

Poly(3-hexylthiophene) (P3HT) and fullerene derivative blend films formed by spin-coating from mixtures of ethanol and chloroform as solvent were studied. Compared with the blend films made from chloroform alone, films made with increasing ethanol concentration in the solvent showed greater degrees of P3HT crystallinity and increased phase segregation of the polymer and fullerene as observed by changes to the absorption spectra, photoluminescence spectra and optical microscope pictures.

Photoinduced Alignment and Multi-Processes of Refractive-Index Gratings in Pre-Irradiated Films of an Azobenzene-Containing Liquid-Crystalline Polymer

After being pre-treated upon irradiation of unpolarized light at 366 nm, an azobenzene-containing liquid-crystalline polymer film was photoinduced alignment by one linearly polarized laser beam at 488 nm, leading to a large birefringence of 0.21. Then holographic gratings were recorded in the pre-irradiated polymer films by interference of two coherent laser beams. Little surface relief was obtained by the holographic recording process, indicating that a refractive-index grating paid most of contributions to the diffraction efficiency. Because the cooperative motion of the azobenzene mesogens were eliminated in the cis-azobenzene-rich isotropic film by the pre-irradiation, multi-processes of the refractive-index gratings were successfully achieved. The obtained grating structures were clearly shown in the polarizing optical microscopic pictures, which were also verified by their diffraction patterns. The azobenzene-containing liquid-crystalline polymer used in this study has potential application in high-density information storage.

Polymer-Modified Bitumen Using Ethylene Terpolymers

Polymer modified bitumen (PMB) is used in various construction applications, especially in motorways. The aim of this study is to improve features of 60/70 penetration grade, modified bitumen used on highways. Increasing the sensitivity to temperature and oxidation resistance are very important points for the modified bitumen. This condition was provided by reacting the carboxylic acid groups in asphaltene with the reactive ethylene terpolymer to form ester. Reactive ethylene terpolymer (RETP) and ethylene terpolymer (ETP) manufactured by DuPont USA were used as additives in this study. Infrared Spectrophotometer (IR) graphics and optical pictures of the modified bitumen have been examined. It has been observed that the softening point has increased on the other hand, the penetration and ductility values have decreased according to the test results.

The Modification of Bitumen with Synthetic Reactive Ethylene Terpolymer and Ethylene Terpolymer

The aim of this study is to improve features of 60/70 penetration grade modified bitumen used on highways. A new asphalt compound has been formed by an additive to decrease sensitivity to temperature and to increase resistance of bitumen. As additives, synthetic reactive ethylene terpolymer (SRETP) and ethylene terpolymer (ETP), which were recommended by DuPont, have been added in bitumen and made some trials. Infrared (IR) graphics and optical pictures of the modified bitumen have been examined and after analysis of the tests, a clear increasing at softening point but decreasing in penetration and ductility values have been observed as a result.

Spatially resolved modeling of the combined effect of dislocations and grain boundaries on minority carrier lifetime in multicrystalline silicon

A model for the combined effect of dislocations and grain boundaries on minority carrier lifetime has been developed. Lifetime varies with dislocation density, grain boundary misorientation, and the coincidence site lattice (CSL) nature of the boundaries. Minority carrier lifetime was measured with high spatial resolution (50 μm) using the carrier density imaging (CDI) technique on a silicon nitride passivated multicrystalline sample. Dislocation density was measured on the same sample by image recognition of optical microscope pictures of a Secco etched surface. Grain boundaries were then mapped and characterized by electron backscatter diffraction (EBSD). Lifetime was simulated based on the dislocation and grain boundary measurements. Parameters were chosen to match closely the simulated and measured maps. Very good two-dimensional (2D) correlation was obtained by assigning roughly equal importance to recombination at dislocations and grain boundaries. The value for the capture cross section, which gives the best correlation, is 4×10−14 cm−3. This is in the range of values reported for interstitial transition metals like, for instance, iron. It appears necessary to include also the effect of grain boundaries to explain recombination in low lifetime areas. Sub grain boundaries were particularly recombination active and are dominating the number of active grain boundaries.

Integration of porous layers in ordered pillar arrays for liquid chromatography

The present paper describes a method for the production of partly porous micro-pillars in columns suitable for use in liquid chromatography. These layers increase the available surface at least two orders of magnitude without destroying the huge benefits of the ordered nature of the system. A process flow was developed that enabled us to create a 550 nm thick porous layer on the pillar array in a sealed channel configuration, withstanding pressures up to at least 70 bar. Measuring band broadening under non-retained conditions, only a modest increase in plate height was observed in the porous pillar array as compared to that in a non-porous pillar array. The homogeneity of the layers was demonstrated using an optical microscope and SEM pictures and by monitoring peak velocities at constant pressures. The internal porosity was determined using particles with a diameter larger than the mesopores in combination with a dye that could penetrate into the pores.

A supramolecular model of hydrophobic interactions in aqueous solutions of acenes

The optical spectra of aqueous suspensions of tetracene (obtained by heating crystals in water) and 9,10-bromoanthracene (obtained by mixing alcoholic solutions of the compound with water) were studied. Both optical pictures were turbidity spectra related to the formation of comparatively large colloidal light scatterers superimposed upon the absorption bands of light hydrophobic ensembles; the absorption bands of free acene molecules were absent. An analysis of the optical spectra and the construction of models with the use of molecular mechanics programs led us to conclude that light hydrophobic ensembles were molecular dimers comparatively stable in the aqueous phase because of the formation of hydration capsules around them. A model of spontaneous dispersion of crystalline tetracene in water under heating was suggested. The model included the stages of the emergence of tetracene molecules from the surface of crystals and their hydration in water layers adjacent to crystals, formation of molecular dimers on the surface of crystals, and diffusion of dimers into the bulk phase, where they experienced clusterization with the formation and sedimentation of fairly large light scattering colloidal particles.

Stabilization of solvent-impregnated resins (SIRs) by coating with water-soluble polymer and chemical cross-linking and its application in mercury removal

Stabilization of solvent impregnated resins was achieved by the formation of a surface coating with the absorptive layer of poly(vinyl alcohol) and cross-linking with the protective layer of vinyl sulphone (VS). Amberlite XAD-4 and vinyl sulphone proved to be effective matrix and cross-linking agents, respectively, in the preparation of a protective layer of SIRs containing Cyanex 923 as extractant. The stabilized SIRs were characterized by the amount of vinyl sulphone contributing to the N and S content in the stabilized resin as well as to its operational stability. Optical and single electron microscope pictures were used to examine the appearance and the morphology, respectively, of the external protective barrier of SIR. Batch and column mode of sorption/elution studies for the removal of mercury from aqueous solution at pH 4 were carried out with Cyanex 923 containing SIR coated with PVA cross-linked with VS. Stabilized SIR was found to be effective for the mercury removal and showed great stability during the batch recycle runs. Elution of mercury from SIR was quantitatively achieved with 3M HNO3. Kinetic and column performances were influenced by the degree of cross-linking of resin coating. Chemical stability and sorption capacity of stabilized SIR remained almost constant after several recycle runs whilst uncoated SIRs lose extractant with time as confirmed by efficiency studies.

Stress intensity factor measurements from digital image correlation: post-processing and integrated approaches

Digital image correlation is an appealing technique for studying crack propagation in brittle materials such as ceramics. A case study is discussed where the crack geometry, and the crack opening displacement are evaluated from image correlation by following two different measurement and identification routes. The displacement uncertainty can reach the nanometer range even though optical pictures are dealt with. The stress intensity factor is estimated with a 7% uncertainty in a complex loading set-up without having to resort to a numerical modelling of the experiment.

Photoacoustic and SEM analysis of fracture bone callus to different consolidation times

The Photoacoustic Spectroscopy (PA) and Scanning Electron Microscopy (SEM) were used to perform a study of fractured bone callus to different consolidation times. From these techniques we obtained optical absorption spectra and pictures of male rat fractured bones at different consolidation times. From these spectra it was possible to observe the presence of p-Nitrophenylphosphatase, characteristic phosphatase in rat fractured bones through their absorption peaks which were compared with characteristic reported peaks in the literature for this phosphatase. In this study we showed that p-Nitrophenylphosphatase could be considered as an indicator of the repair process of bone fractures. Through the complementary SEM analysis it was possible to obtain different pictures as the callus grows in the time.

High laser-fluence deposition of organic materials in water ice matrices by “MAPLE”

Matrix assisted pulsed laser evaporation (MAPLE) is a deposition technique for organic material. Water ice was used as a matrix for the biotechnologically important guest material, polyethylene glycol (PEG), for concentrations from 0.5 to 4 wt.%. The target was irradiated with 6 ns laser pulses at 355 nm at a fluence of 2.5–12 J/cm 2. Even at this high fluence, Fourier transform infrared spectroscopy (FTIR) indicates a chemical structure of the deposit close to that of the un-irradiated PEG. Matrix assisted laser desorption and ionization (MALDI) and gel permeation chromatography (GPC) show that the mass distribution of the deposited PEG is similar to that of the starting material. Optical pictures of the films show particle structures of PEG of a size up to 5–10 μm. The deposition rate measured with a quartz crystal microbalance is typically of the order of 1 ng/(cm 2 shot).

Evaluation of enamel dental restoration interface by optical coherence tomography

Evaluation of molar dental restorations on enamel is performed using optical coherence tomography (OCT) with 10 microm resolution. Images of approximately 50 microm failure gaps in the restorations are demonstrated and the OCT images are compared with x-ray and optical microscopy pictures. The results demonstrate the potential of the technique for clinical evaluation of dental restorations.

Tensile creep behaviour of polypropylene fibre reinforced polypropylene composites

Creep, the deformation over time of a material under stress, is one characteristic of composites that has resulted in poor performance in certain applications. This work was undertaken to investigate the advantages of using PP fibres in random poly(propylene- co-ethylene) (PPE) with different fibre concentrations. Addition of long polypropylene fibres into PPE greatly improved the creep resistance and modulus of elasticity of the composite compared with the matrix polymer. However, high concentrations of long fibres (>50%, w/w) resulted in fibre packing problems and an increase in void content, which lead to a reduction in creep resistance. The curves of creep modulus and relative creep versus time were shifted along the logarithmic time scale to develop a creep master curve, which allows for the prediction of very long and short time behaviour of the composite. To verify the experimental results, a four-parameter viscoelastic model was applied in order to quantify the viscoelastic behaviour of the composites. Morphology of the composites was investigated using optical and scanning electron microscopy (SEM). Optical microscopy pictures showed that trans-crystallization of the matrix polypropylene was observed in the PPE. SEM photographs displayed a thin layer of matrix on the reinforcement, which was attributed to good impregnation and wetting of the fibres.

Flicker Stereo: Digital 3D Viewing for PC & Presentation

Summary Flicker stereo alternates two pictures (∼ 1 frame/sec.) of the same structure with views tilted 6° ± 1° about a vertical axis—Natural appearing stereo visualization results. A flicker stereo program to be used for viewing with a personal computer (PC) was developed by the authors. The two images are installed, adjusted for superposition and then alternated on the computer monitor or computer projection system. Flicker stereo can be applied to micrographs from the optical microscope, SEM, TEM, pictures or line drawings. Flicker stereo provides simultaneous three dimensional viewing for several individuals without special viewers, projection systems and/or glasses. Different flicker images may be retrieved and viewed on a PC in rapid succession. Flicker stereo facilitates technical discussion between collaborators and provides a convenient approach for 3D visualization by audiences using a digital LCD projection. The program is available to readers.