Study of the texture of polycrystalline FCC materials using one incomplete direct pole figure

The article deals with the algorithm for texture analysis of polycrystalline materials using one direct pole figure (DPF). It is shown that the incomplete direct polar figure {111} for fcc materials contains the necessary information about the material texture. The algorithm provides identification of the preferred texture components in a multicomponent texture material and determination of their properties. The proposed algorithm is as follows. The upper hemisphere of the digital representation of the DPF is scanned by a polar complex of vectors that are normal to the reflection planes. Then the reliability parameters for each orientation are calculated and a set of the most reliable orientations is formed. The chosen orientations are recalculated to the Rodrigues space wherein the preferred texture components are formed by clustering. At the same time, an iterative algorithm with symmetry operators is used to avoid the umklapp effect. Each texture component is represented by the following parameters: Rodrigues mean vector, Miller indices, and Euler angles. The share and scattering of the texture component are also calculated. A method for selecting the optimal number of clusters providing presentation of the texture with the desired degree of detail is proposed. This is achieved by comparing two incomplete direct pole figures taken for {111} and {200} to select the maximum cluster scattering value on which the number of formed predominant texture components depend. The developed algorithm seems promising for rapid texture analysis, in analysis of sharp and weak textures and when there are less than three DPFs.

High Quality Single Crystal 3C-SiC(111) Films Grown on Si(111)

We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the ultimate goal to demonstrate high quality and yield electronic and MEMS devices. A single-side polished 50 mm (111)Si wafer was loaded into a hot-wall SiC CVD reactor for growth. The 3C-SiC process was performed in two stages: carbonization in propane and hydrogen at 1135°C and 400 Torr followed by growth at 1380°C and 100 Torr. X-ray diffraction rocking curve analysis of the 3C-SiC(222) peak indicates a FWHM value of 219 arcsec. This is a very interesting result given that the film thickness was only 2 µm, thus indicating that the grown film is of very high quality compared with published literature values. X-ray polar figure mapping was performed and it was observed that the micro twin content was below the detection limit. Therefore TEM characterization was performed in plan view to allow assessment of the stacking fault density as well as confirmation of the very low micro twin concentration in this film. TEM analysis indicates a low concentration of stacking faults in the range of 104 cm-1.

3C-SiC Hetero-Epitaxial Films for Sensors Fabrication

Silicon Carbide (SiC) is a very promising material for the fabrication of a new category of sensors and devices, to be used in very hostile environments (high temperature, corrosive ambient, presence of radiation, etc.). The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on bulk material or on the SiC surface. The hetero-epitaxial growth of 3CSiC on silicon substrates allows one to overcome the traditional limitations of SiC microfabrication. This approach puts together the standard silicon bulk microfabrication methodologies with the robust mechanical properties of 3C-SiC. Using this approach we were able to fabricate SiC cantilevers for a new class of pressure sensor. The geometries studied were selected in order to study the internal residual stress of the SiC film. X-Ray Diffraction polar figure and Bragg- Brentano scan analysis were used to check to crystal structure and the orientations of the film. SEM analysis was performed to analyze the morphology of the released MEMS structures.

Investigation on Residual Stress and Crystallographic Texture of YSZ Films Prepared by EB-PVD

Yttria Stabilized Zirconia (YSZ) films were prepared by electron beam physical vapor deposition (EB-PVD) technique with a high deposition rate up to 1μm/min. An improved sin2ψ method was employed to analyze the residual stress of films by means of grazing incidence X-ray diffraction (GIXRD). The result of residual stress measurement reveals that residual stress of YSZ film is compressive stress and keeps a linear relationship with the deposition temperature, which is induced mainly by the thermal expansion mismatch between the film and substrate. The XRD result of films, prepared with different incident angles, demonstrates that the films show preferred orientation evidently. Furthermore, a parameter ωhkl was introduced from the inverse polar figure measurement theory to reveal the degree of preferred orientation clearly. The calculating result of ωhkl value indicates that the preferred orientation of different specimens changes with the incident angles, which is due to columnar growth pattern of films prepared by EB-PVD. In order to characterize the crystallographic texture visually, XRD with 2D detector system was used to analyze the texture of films. The result shows that Debye rings appear asymmetric intensively, which denotes the existence of preferred orientation directly and agrees with the calculating result of ωhkl value.

Les héritières. Les écrivaines d’aujourd’hui et les féminismes

À partir de l’analyse des dossiers du Matricule des Anges, magazine littéraire français dédié à la littérature contemporaine, Audrey Lasserre propose d’interroger l’héritage et le positionnement féministes des écrivaines d’aujourd’hui. Envisagée par l’examen précis des lectures convoquées, la part affirmée des féminismes littéraires, tout comme celle d’ailleurs des féminismes en général, révèle leur peu d’autorité dans le champ littéraire actuel. De fait, les romancières, loin de revendiquer un héritage féministe, fût-il pluriel, semblent avoir intégré, en matière de scénario auctorial du moins, une règle du jeu littéraire : le féminin est une figure polaire répulsive disqualifiant la littérarité.AbstractBased on the analysis of documents from Matricule des Anges, a French literary magazine dedicated to contemporary literature, Audrey Lasserre proposes to question the feminist heritage and the positioning of women writers today. Envisioned by the precise examination of the mentioned readings, the asserted part of literary feminisms, as well as that of other feminisms in general, reveals how little authority they have within the current literary field. In fact, far from claiming a feminist heritage, be it plural, novelists seem to have integrated, in terms of auctorial scripts, a rule of the literary game: the feminine is a repulsive polar figure disqualifying literarity.

The Reciprocal Polar of a Circle

The reciprocal polar figure of a circle s, with regard to another circle c, is a conic, one of whose foci is the centre of the reciprocating circle. The polar reciprocal of a with regard to c is obtained by taking the polars of points on s with regard to c, and then constructing the envelope of these lines.