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- Engkvist, Josefin
(författare)
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Characterization of oxide scales formed on FeCrAl alloys at high temperatures
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the characterization of oxide scales formed on FeCrAl alloys at high temperatures. The effect of water vapour on commercial FeCrAl alloys oxidized in both dry and humid O2 has been investigated. Also, the effect of varying Al concentrations in model FeCrAl alloys was studied as well as the effect of using surface coatings in order to increase the oxidation resistance of FeCrAl alloys. The formed oxide scales were characterized using analysis techniques such as SEM, EDX, TEM, XRD, XPS, AES and SIMS. The main part of the work concerns the SEM, EDX, AES and SIMS techniques. The commercial FeCrAl alloys investigated follow the same trend in oxide formation independent of whether the alloy was conventionally cast or manufactured by powder metallurgy. In the as-received cold rolled condition the surface of the FeCrAl material shows a few nm thin native oxide. This native oxide is a mixture of oxides from Fe, Cr and Al, with a relatively high concentration of Cr. The oxide formation at elevated temperatures can be separated in a low temperature and a high temperature mode. At relatively low temperatures (500-600°C) a mixed oxide similar to the pre-existing native oxide forms, while at higher temperatures a thicker two-layered alumina scale forms. The outer and inner alumina layers are separated by a Cr-rich zone which is believed to be a remnant of the pre-existing native oxide and hence represents the original alloy surface. Accordingly the inner alumina layer is formed by oxygen inward diffusion while the outer alumina layer grows by cation outward diffusion. The inner alumina is composed of a-Al2O3, while the outer layer, during early stages, is composed of rapidly growing metastable polymorphs of alumina which with time transform to a-Al2O3. This phase transformation starts at the Cr-rich zone and progress outward. In presence of water vapour this transformation is inhibited due to hydroxylation of the surface of the metastable phases. Hence, a higher oxidation rate was observed in presence of water vapour. Model FeCrAl alloys having Al concentrations in the range 1.2-5 wt.% were investigated. At 900°C a minimum of 3.2% Al is needed in order to form a continuous alumina scale. Higher Al concentrations (= 4.4%) result in a relatively pure alumina scale and a slower oxidation rate. In order to evaluate the possibility to improve the oxidation resistance of FeCrAl a PVD SiO2 coating was applied on a commercial FeCrAl foil prior to oxidation. Parallel exposures of coated and uncoated samples were made at 1000°C and revealed that the SiO2 coating significantly reduced the initial oxidation rate of the FeCrAl foil. Further, metal organic CVD of a ZrO2 film in situ on an RE free FeCrAl alloy at 400 and 800°C showed that at the lower temperature mainly ZrO2 was formed while at 800°C an oxide scale composed of both ZrO2 and Al2O3 was formed. The results obtained illuminate the importance of advanced electron microscopy and surface analysis techniques in order to increase the understanding of high temperature oxidation of FeCrAl alloys and the oxidation mechanisms of this group of materials.
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- Engström, Maria, 1968-
(författare)
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Cheroubika in the Russian Liturgical Tradition
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is a contribution to a growing field of studies on the reception of Byzantine culture in Russia. The object of investigation is the history of the Church Slavonic translation of the Cherubika, which constitute one of the most ancient and dogmatically important functional genres of Byzantine liturgical hymns. The chronological frame of this study is the 13th–17th century. Particular attention is focused on the last change in the liturgical texts in Muscovite Russia, in the mid-17th century. This liturgical reform, which led to the famous Schism in the Russian Church, is studied as part of the cultural reforms started by Tsar Alexis Romanov (1645-1676). The most characteristic feature of Orthodoxy is the principal unity of Scripture and Tradition, which in a hermeneutical perspective means the inseparability of text and context. The semiotic and interdisciplinary approach used in this study reflects this principle. The Slavic Cherubika are interpreted in a broad cultural perspective, and Church Slavonic translations are studied in the proper theological, rhetorical and linguistic contexts. Although the 17th-century translations made in Moscow were based on late Greek and South Slavic sources, they reconstruct the original dogmatic message of the Byzantine Cherubika and are hence closer to the Tradition than earlier Slavonic translations. This study offers a new interpretation of the nature of the Schism. It is shown that the main cause of the controversy between Reformists and Old Believers lies in their different understandings of the connection between Text and Ritual. The traditional medieval interpretation of the Cherubika is influenced by certain iconographical themes, other liturgical texts and the priest’s actions during the liturgy. The transition from a liturgocentric interpretation of sacral texts to a descriptive theological interpretation was a break from the characteristic Russian form of liturgocentrism and the beginning of a new cultural era.
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- Leon Vegas, Carolina
(författare)
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Ausencia, prohibición y carencia : Estudio de los personajes y el deseo frustrado en tres obras de García Lorca
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, the main male characters in three of the plays written by Federico García Lorca are analysed with the aim of seeing the role they play in the frustration of desire. After two chapters dedicated to a review of published critical studies on Lorca and to certain theoretical considerations, Chapter Three examines desire drawing on Ubersfeld's actancial model and observes that these male characters can be divided into two groups: those who are desired and those who are undesired. In Chapter Four this classification is linked to an analysis of absence, prohibition and lack. Absence is here defined not as related to their non-appearance on stage but rather to their non-presence in the lives of the desiring female protagonists. It is observed that a number of male characters are absent in the plays mainly due to death or a journey. As far as prohibition is concerned, in two of the works, there is a moral code associated with concepts such as "honour" and "decency", which blocks the female characters' access to the males they desire. Chapter Four also shows how several characters can be considered as lacking in the sense that they do not possess the ideal male qualities contained in the plays. This chapter reaches the conclusion that desired male characters are either absent or forbidden in the world of the desiring female, whereas undesired male characters are lacking in the sense that they fail to live up to the ideal highlighted in the plays. Chapter Five analyses the female characters' perception of the male figures, making use of René Girard's notion of "transfiguration", which alludes to a process of idealisation of the object of desire. Our analysis reveals a connection between desire, denied access to the object of desire and transfiguration in the main subjects of desire. The phenomenon of "transfiguration" has several functions in the play: firstly, the creation of hyperbolical male characters; secondly, that of transmitting the intensity of the desire experienced and, finally, the highlighting of the lack of certain qualities in several male characters. We thus observe that, in these three plays written by García Lorca, Girard's pessimistic view of desire is confirmed, since desire needs a series of obstacles, such as absence or prohibition, to survive. However, this is not the only explanation for the frustration of desire: other factors, like the actions of certain male characters or destiny, also play a decisive role.
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- Osipova, Anna
(författare)
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The Concept of ’Selling/Buying’ in the Russian Linguistic Picture of the World : from standard to sub-standard
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis belongs to the field of lexical semantics studies, associated with describing the Russian linguistic world-image. The research focuses on the universal situation of purchase and sale as reflected in the Russian lexical standard and sub-standard. The work deals also with subjects related to the sphere of social linguistics: the social stratification of the language, the structure of sub-standard, etc. The thesis is a contribution to the description of the Russian linguistic world-image as well as to the further elaboration of the conceptional analysis method. The results are applicable in teaching Russian as a foreign language, particularly in lexis and Russian culture and mentality studies.
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