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Cracking of ferritic stainless steel tubes during production process
Majtás, Dušan ; Kreislová, K. ; Viani, Alberto ; Pérez-Estébanez, Marta ; Geiplová, H.
From the economic reasons many products originally made from austenite stainless steel are nowadays made from ferritic stainless steel. Ferritic steels have relatively low yield strength and the work hardening is limited. They cannot be hardened by heat treatment and only moderately hardened by cold working. Commercially made stainless steel tubes from ferritic steel, used for industrial plumbing was examined on presence of cracks. The cracking was present on the inner side of the convoluted tube shape. The tube manufacturing process consisted of continual bending of the sheet to tube shape, weld the tube, then of cold shaping by pulling through rib-forming frames, which is done in several steps. Then thermal treatment applies to the nearly finished product to remove stress remaining in the structure. Prime suspect was deformation beyond the ductility of used material. However the stress-strain tensile testing does not approved this hypothesis. Several samples of failed material were taken together with reference, and were examined by optical microscopy, and X-Ray Diffraction structure analysis. The structure of the cracked tubes does not show the signs of deformation over the limit, except the location near to the crack itself. Interestingly enough the failed material showed more homogenous structure than the original one. Needle like structures were found when the material is “overetched”, on these structures concentration of stress under bending occur. This structure was identified as δ-ferrite, however its presence in α-ferrite matrix is unclear.
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Zjištění materiálových vlastností vzorků přírodního kamene a umělého kamene z Mariánského sloupu na Hradčanském náměstí v Praze
Slížková, Zuzana ; Zeman, Antonín ; Petráňová, Veronika ; Viani, Alberto ; Pérez-Estébanez, Marta ; Frankeová, Dita ; Ševčík, Radek ; Mácová, Petra ; Janotová, Dana ; Hasníková, Hana ; Niedoba, Krzysztof ; Hauková, Petra
V rámci průzkumu před restaurátorským zásahem byly stanoveny materiálové charakteristiky přírodních i umělých kamenů, které jsou součástí Mariánského sloupu na Hradčanském náměstí v Praze. 15 vzorků bylo podrobeno rozsáhlým instrumentálním analýzám, jejichž výstupem je nejen chemicko-mineralogické složení vzorků, ale i stupeň jejich degradace včetně popisu porézního systému a úrovně zasolení.
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Characterization of by-products from the combustion of solid fuels with SEM/EDS and micro-Raman spectroscopy
Šašek, Petr ; Viani, Alberto ; Mácová, Petra ; Pérez-Estébanez, Marta ; Černá, M.
The solid residues from the combustion currently represent a problem that needs to be addressed. Quality products from combustion of solid biomass and coal is significantly different, may contain heavy metals and therefore their application difficult. Total used 4 samples of solid residues from the combustion of solid fuels, where two samples consisted of ash from the combustion of coal, respectively lignite and two samples were made with ash from the combustion of biomass, namely straw and hay. The microscopic analysis was used a scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) and Micro Raman. The qualitative analysis was used in addition X-ray diffraction. Within the microscopic analyses were tested superficially different types of materials.
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Mineralogical, chemical-physical characterization of mineral fibers and their interaction with the human body
Viani, Alberto ; Pérez-Estébanez, Marta ; Mácová, Petra
A standardized protocol of analysis of the mineral fibers with a preliminary full mineralogical characterization has never been applied so far. There are thousands of contributions in the literature on specific aspects of the problem but very few attempts to draw a general picture based on a multidisciplinary approach. To the eye of the proposers of the project, this seems to be the only way to reach a conclusive and shared general view at a molecular level of the bio-toxicity of mineral fibers at a structural level. In this first stage of a more vast project, the study of mineral fibers has been conducted using different experimental approaches. Eight samples of mineral fibers have been selected for their economic and social importance with the objective to systematically characterize their structural, physical-chemical characteristics and attain a direct comparison. X-rays diffraction data, micro-Raman and micro-Infrared spectra of some of them were collected at CET.
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Accuracy of internal and external standard method in quantitative analysis by X-ray powder diffraction
Pérez-Estébanez, Marta ; Viani, Alberto
The X-ray powder diffraction method is known to convey information on the phase composition of samples. Obtaining an accurate quantification of these phases has been long precluded. With the advent of the Rietveld method [1] this became possible. Hedemonstrated the possibility to extract accurate structural information from neutron powder diffraction data. Later, his approach has been extended to x-ray powder diffraction data with successful results. The basics of the Rietveld method lays on the complete exploitation of the whole powder profile without extracting the integrated intensities. The structural information are obtained by fitting the entire profile of the measured diffraction pattern to a calculated diffraction profile. The refinement procedure implements the least square regression and it requires a reasonable scheme of starting values that approximate the real datum.
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Characterisation of historic materials - the case of Tao-I-Kisra Palace (Iraq)
Slížková, Zuzana ; Pérez-Estébanez, Marta ; Viani, Alberto
The aim of this study is the characterization of bricks from the Taq-I-Kisra palace in southern Iraq (ancient Mesopotamian area). The palace is located in the plain of the Tigri river (see Fig. 1). The construction probably started around year 540 AD even if there is some uncertainty about its age. The arched hall on the facade is about 37 m high and is the largest vault ever constructed at the time (see Fig. 2). Originally conceived as an imperial palace, was later used as a mosque by the Arabs before being gradually abandoned. The historical constructions in this area are what remains of the capital of the empire. In accordance with geological data, in the area where the temple was built (and in general in the Mesopotamian area), the most available construction material was mud. Mud bricks were made mainly of clays. In ancient times there is evidence of mixes with sand, water, mud, and organic material, husks or straw.
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Reaction kinetics of magnesium phosphate cements
Viani, Alberto ; Pérez-Estébanez, Marta
Magnesium phosphate cements (MPCs), are a class of new binders developed to reduce the ecological impact of construction. When magnesium oxide reacts with potassium dihydrogen phosphate (KH2PO4) (KDP) in presence of water, crystallization of magnesium potassium phosphate hydrate (MKP) occurs, according to the reaction: MgO + KH2PO4 + 5H2O --> MgKPO4·6H2O. Despite the importance of MPC for a wide range of applications, including rapid concrete repair, recycling of hazardous wastes, waste encapsulation, bone repair, natural fibre composites, no data are available on hydration reaction kinetics.
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Průzkum vnějšího pláště márnice v Ostrovci u Velečína. Výzkumná zpráva k projektu MK NAKI DF11P01OVV008
Slížková, Zuzana ; Frankeová, Dita ; Petráňová, Veronika ; Zeman, Antonín ; Hauková, Petra ; Mácová, Petra ; Niedoba, Krzysztof ; Viani, Alberto ; Pérez-Estébanez, Marta ; Zíma, Pavel ; Janotová, Dana
Zpráva prezentuje výsledky průzkumu márnice v Ostrovci u Velečína. Tento objekt byl vybrán pro aplikování vzorků omítek vyvíjených v projektu MK NAKI DF11P01OVV008. Průzkum je zaměřen na soklovou část márnice, kde omítka opakovaně promrzá a po jedné zimě odpadává. Příčiny poruchy a materiálové složení byly zkoumány následujícími technikami: x-ray diffraction (XRD), thermal analysis (TG), optic and electron microscopy, FTIR and Raman spectroscopy.
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