Papers by Keyword: Electron Microscopy

Abstract: All over the world the investigations of nanophotonic structures called photonic crystals (PCs) are performed. These crystals have potential applications in optoelectronics, e.g. optical filters, antireflective surface coatings, lossless frequency selective mirrors. In Institute of Physics at Silesian Technical University the opal photonic crystals consisting of monodisperse spherical particles, that have diameters of several hundred nanometers, are produced using colloidal self-assembly technics. The main aim of this work is the comparison between pieces of information on morphology of photonic crystals that can be obtained from electron microscopy and from the angular characteristics of optical transmittance and reflectance. The morphology of the samples is characterized by scanning electron microscopy (SEM). Nanosphere diameters are established from statistical analysis of SEM images. The optical properties, which are determined by the photonic band structure, are studied by means of light transmission and reflection measurements. There is a relationship between the wavelength position of transmittance minimum or reflectance maximum and the diameter of the nanospheres. The size of nanospheres obtained from optical measurement results were compared with data obtained from SEM images.

Abstract: Carbon nanospheres of uniform diameter around 40 nm have been achieved in the absence of catalyst by microwave pyrolysis chemical vapor deposition. The products have been characterized by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The results show that the nanospheres with high purity, which are solid by their cross-sections, consisting of concentric incompletely closed graphitic layers. Their thermal stability in dynamic air atmosphere is also discussed.

Abstract: As a novel Cu-IUD material, it is necessary for copper/low-density polyethylene (Cu/LDPE) porous composite to have some suitable mechanical properties if it is used to prepare a clinical Cu-IUD with frame. However, it is not clear how the porosity of the porous structure affects the mechanical properties of Cu/LDPE porous composites. Therefore, the influence of the porosity of porous structure on the mechanical properties of Cu/LDPE porous composites is investigated in the present paper. The results show that the porosity has significant effects on the mechanical properties of Cu/LDPE porous composites. The mechanical properties of the Cu/LDPE porous composites decrease with the increasing of porosity, for the effective load area decreases, the chance for occurrence of cracks increases and the crystallinity degree of LDPE matrix increases with the increasing of porosity. These results are very important and they can be applied to guide the design of Cu/LDPE porous composite IUD for use in the future clinical application.

Abstract: The aim of this paper is to evaluate the structure of wastes from non-ferrous metals. Wastes from the production of metals were selected namely waste from the production of aluminum - red mud and the waste from the production of nickel - black nickel mud. Morphology of samples was documented by scanning electron microscope, phase analysis using diffraction techniques and the content of elements was determined by EDX analysis. The influence of pretreatment of these wastes on the structure was also investigated.

Abstract: Triangular shaped defects with obtuse-angles at tops and long bases are often observed in surfaces of epitaxial films. We have investigated the origins of them, and it became clear that these defects without clear origins were formed by contaminations of tantalum carbide particles. Formations of micro-order pipes at the origin points of these defects were also observed. These micro-order pipes did not accompany strain and dislocations around them, though their appearances were very similar to the ones so-called micro-pipes.

Abstract: Dependence of the coating carbon layer configuration of cordierite monolith on reaction conditions in methane decomposition was investigated using N2 physisorption, SEM and TEM. The monolith surface area was increased after coating CNFs/CNTs. The microstructure of the coating layers in the coated monolith is dependent on the coating reaction conditions and the entanglement among CNFs/CNTs. High coating temperature and the presence of hydrogen in reaction gas for coating are advantageous to formation of CNTs. By comparison, coating layers of CNFs have better stability than that of CNTs in ultrasonic treatment.

Abstract: The peculiarities of martensitic transformations and formation of nanostructured states in metastable austenitic steel (Fe-18Cr-8Ni-Ti) after severe plastic deformation by high pressure torsion are investigated. It is shown that during severe plastic deformation with increased strain rate not only direct (γ→α΄) but also reverse (α΄→γ) martensitic transformations occur, which is revealed by the changes in the volume content of α΄ - martensite during deformation. The fragments thought to be formed by direct and reverse martensitic transformations and those of dynamic recrystallization of austenite are observed.

Abstract: The influence of thermomechanical processing on the Ti-21.8Nb-6Zr (TNZ) and Ti-19.7Nb-5.8Ta (TNT) (at%) alloys’ structure, phase composition, mechanical and functional properties is studied. Both alloys possess polygonized dislocation substructure (average subgrain size  100 nm), and manifest superelastic behavior at room temperature and recovery stress generation during constant-strain temperature scanning experiments. After aging treatment, both alloys were -phase precipitation hardened, but their mechanical behavior was impacted differently -- it was detrimental for TNZ and beneficial for TNT. The different impact of aging heat treatment on the mechanical behavior of these alloys is explained by the differences in the -phase nucleation rate, precipitates’ size, shape, volume fraction and distribution, and by their effect on the alloys’ critical stresses and transformation temperatures.

Abstract: Advances in the development of new high strength steels have resulted in microstructures containing significant volume fractions of retained austenite. The transformation of retained austenite to martensite upon straining contributes towards improving the ductility. However, in order to gain from the above beneficial effect, the volume fraction, size, morphology and distribution of the retained austenite need to be controlled. In this regard, it is well known that carbon concentration in the retained austenite is responsible for its chemical stability, whereas its size and morphology determines its mechanical stability. Thus, to achieve the required mechanical properties, control of the processing parameters affecting the microstructure development is essential.

Abstract: In this paper, we have synt hesized exotic carbon fibers with branched spurs by a chemical vapor deposition method using nickel catalyst precursor at 600 °C. No catalyst particles were found at the base of the carbon spurs, suggesting that the ni ckel catalyst particles, which were decomposed from the nickel catalyst precursor, facilitated the growth of the carbon fibers but not the spurs. The formation of the spurs resulted from the fluctuation of the carbon source gas acetylene flow. The samples were characterized by field emission sc anning electron microscopy, transmission electron microscopy, and X-ray powder diffraction.