Papers by Keyword: Microscopy

Abstract: The effect of long dwell time at elevated temperatures on two types of steels used for production of heavy forgings was evaluated. Microstructural changes and mechanical properties were monitored in temperature interval of 200 - 700 °C in order to avoid the possibility of grain boundary embrittlement during long dwell time at the processing temperature. Samples of the evaluated steels 26NiCrMoV14-5 and 22CrNiMoWV8-8 were being austenitized for 2 hours at temperature of 1200 °C and oil quenched. Subsequently the annealing at selected temperatures for 100 hours was applied. Tensile test, hardness and impact energy measurements were used for the evaluation. The results of mechanical testing, structural and fracture surface analyses indicate that for steels 26NiCrMoV145 and 22CrMoNiWV8-8 there exist a temperature interval of 300 - 400 °C and 500 600 °C respectively showing the toughness decrease.

Abstract: Austempered vermicular-graphite iron seem to be a perspective material because of its promising mechanical properties. These properties are strongly affected by parameters of applied heat treatment. Different heat treatment conditions (austenitizing dwell time, isothermal temperature and isothermal dwell) were varied and their effect on the structure and mechanical properties was evaluated and described. Properly selected heat treatment conditions lead to formation of ausferritic matrix with which is responsible for substantial increase in mechanical strength while maintaining sufficient ductility.

Abstract: The knowledge of magnetic and transport properties of construction steels for magnetic circuits plays an important role. Three different techniques: (i) flame spray, (ii) twin wire arc spray and (iii) powder mixture with halide activator were used to produce Si, CuSn6 and Si coatings, respectively, on the 41CrMo4 steel ring substrates. Immediately after the thermal spraying or inserting the steels into the powder mixture was used isothermal heat treatment at the temperatures of 800 °C / 6 hrs, 1000 °C / 4 hrs and 1250 °C / 2 hrs to produce the diffusion coatings. Several coating systems consisting of different phases and thicknesses were manufactured. Opto-digital microscope, scanning electron microscope and digital image analysis, second equipped with energy dispersive microanalyzer, were utilized to characterize the microstructure, chemical composition and thicknesses of the coatings. The influence of coatings on magnetic properties in the frequency range of 50-2000 Hz was also measured.

Abstract: This article is related to the unique application of fly ash-based stabilizer in the track bed of a railway line. In detail, it is focused on following analysis methods of samples structure and properties. The long-term observation of the stabilizer layer is based on the periodical sampling which is done once per year for the following compression strength test. Results collected over one decade showed the increasing tendency of the compression strength which is attributed to formatting the C-A-S-H gel. It is assumed it is done within structural conversion caused by the alkali activation of aluminosilicate components. This phenomenon was proved using electron microscopy. The statistical analysis of the compression strength resulted significant deviations the presence of which may be based on grains, poor stirring the mixture during placing, predisposed surfaces or micro cracks created during sampling in the railway track bed. The main outcomes of the paper are findings from non-destructive methods of Micro-CT and of electron microscopy, which were performed on specimens for the purpose of displaying their microstructure and identifying non-homogeneities of the specimens.

Abstract: We analyzed histological data statistically describing the distribution of orientations of vascular smooth muscle cells (VSMC) within porcine aorta. The data were correlated with the fractions of actin, desmin, vimentin, elastin and collagen within the same samples. In samples with more contractile VSMC and less elastin, the symmetrical helices of VSMC were arranged closely to each other and they were more concentrated than in samples with fewer actin-and desmin-positive VSMC and more elastin. The findings are suitable for microstructurally-motivated biomechanical modeling of porcine aorta under normal conditions.

Abstract: The effect of Ni or Zr addition to Ti-Cu alloy was studied on the microstructure evolution during mechanical milling regarding to dependence of the amorphous transformation on the various composition elements. The microstructure of initial crystalline alloys and the remained phases after few hours of milling were investigated. The milling process lasted to the full amorphization of the powders. The results show that amorphous Ti₄₈Cu₄₂Ni₁₀ and Ti₄₈Cu₄₂Zr₁₀ powders are obtained after 13 h and 14 h of milling.

Abstract: Chitosan is termed as one of the useful carbohydrate oligosaccharides derived from chitin, which can be used to improve film packaging by hybridizing with silver due to their advantages of flexibility, easy scale up and low cost methods. Design of packaging material with non-toxic property becomes key issue. The objective of this work is to synthesize and characterize chitosan-silver nanocomposite film for effective packaging. The nanocomposite was synthesized using in-situ, co-mixing chemical method and air drying method. The morphology integrity of the nanohybrid was confirmed using UV-Visible Spectrophotometer, Transmission Electron Microscope (TEM) and X-ray Diffraction (XRD). TEM analysis revealed the cap shaped spherical morphology with no agglomeration and uniform size distribution of the nanoparticles within the range of 20.00 nm. UV-visible analysis showed Plasmon resonance band at 275 nm and 435 nm indicating the presence of chitosan and silver with no observable peak and an increase in intensity of chitozan. XRD confirmed the order and crystalline peak located at 2θ = 35^ᵒ, 64^ᵒ and 77^ᵒ which have been keenly indexed as face centred cubic Silver nanocrystals. Thus, the nanocomposite film produced serves as an effective packaging material.

Abstract: Increase the life exploitation of implants has been the motor factor in the elaboration of the new biocompatible alloys based on cobalt. The paper aims the complete structural characterizations for CoCrMoSi6 alloy, based on modern investigation methods, like compositional analysis by EDX method, optical and electronic microscopy analysis, X-ray diffractrometric analysis, fracture analysis. The experiments aimed to establish all the structural aspects for CoCrMoSi6 alloy and his recommendation for using to manufacture the components for medical applications. The results obtained from the SEM microstructural analysis, for the original version allied with silicon in percentage of 6%, certify a dendritic structure specific to the cobalt base alloys. This paper established the structural aspects for a new variant of CoCrMoSi6 alloy and recommends their use successfully in the production of components for medical applications.

Abstract: The applications of stainless steels may be meeting in chemical industry, food industry, civil building, but present an increased interest also in machine constructions or household.This paper highlight the structural modifications obtained after temperature variations for AISI 321 stainless steel. The modifications of structure and proprieties can be induced by heat treatments applied to semi-products before or after the obtaining of final parts, but also by heating at regimes which respect the exploitation conditions of part. In the experiments, it is applied quenching to put into solution, with modification of final treatment temperature and maintaining time, aiming the dissolution of complex carbides and in this mode an easy processing. The treatment parameters were chosen, after the determination of alloying elements by AISI 321 samples, by optic spectrometry. The dilatometric analysis aimed to highlight the structural modifications, specific to thermal fatigue phenomenon, due to temperatures variations.

Abstract: The identification and measuring of geometrical dimensions of very small objects including textile is the biggest achievement of the image processing techniques. Not only the analysis of the basic structure of yarn like hairiness, thickness and number of twist but also the external structural analysis like twist parameters and linear density co-efficient is possible with outstanding approach of image analysis new techniques. Dyed polyester samples by using different dyestuffs were examined with the polarized light with the help of optical light microscopy. It was observed that the dyestuffs possess strong dichroism and the relationship between dichroism and the concentration of dyestuff was examined. Dark field and Bright field illuminations together with imaging polarimetry are compared in terms of depth of field tolerance and image quality. Experiments show that passive imaging polarimetry illumination is superior in terms of depth of field tolerance and contrast allowing significant improvement of textile structure investigation.