1,720,969 research outputs found
PRORA USV - TECH sharp hot structures: Advanced ceramic materials and related technology for slender-shaped hot structures
No full textIn the framework of the Italian National Space Research Program (PRO.RA), supported by the Italian Ministry of Education and Research (M.I.U.R), a dedicated technology project, managed by the Italian Aerospace Research Centre (C.I.R.A. S.c.p.A.) and aimed to assess the use of ultra high temperature ceramics in the manufacturing of future RLV hot structures, is now running. A multi-material structure, which couple diborides (addressed as the sole materials that can be conveniently employed at temperatures above 2200K) to a C/SiC frame, is under investigation with the aim to demonstrate an innovative concept of nose cap. The current state of the research work is presented and the to-date results are described. Experimental data related to plasma sprayed coatings and self-standing components as well as to hot isostatically pressed samples are reported and discussed
Effects of Processing Conditions on Exfoliation and Rheological Behaviour of PBT-Clay Nanocomposites
No full textCurrent status of the development of Ultra High Temperature Ceramic materials for hot structures within the PRORA-USV SHS project
No full textThe role of chemical affinity in exfoliation and rheological response of PBT-organosilicate nanocomposites
No full textEffect of organoclay structure on morphology and rheological response of PBT nanocomposites
No full textIn this paper the effect of different organoclays on the structure and the rheological properties of poly(butyleneterephtalate)-clay nanocomposites produced by melt compounding was investigated. The study was carried out using as nanometric fillers four commercial montmorillonites, treated with different organic modifiers and having similar interlayer spacing and organo-modifier concentration. Each organoclay was melt compounded with PBT (at 3%, 6% and 9% by weight of clay) using a twin screw extruder. Using the same processing conditions, hybrid samples containing the unmodified silicate were also prepared for comparison purposes. All the obtained nanocomposite samples were submitted to physico-chemical (XRD, TEM and FT-IR), and rheological measurements in order to evidence the role of polymer-clay affinity on the morphology and on the viscoelastic response of the materials. The results have pointed out that, with the used processing conditions, all nanocomposites exhibit a mixed intercalated/exfoliated structure; nevertheless, the clay dispersion homogeneity and the exfoliation level reached in the samples are higher for Nanofil 919. and Dellite 43B fillers, the organic modifiers of which may favorably interact with PBT matrix
PRORA USV SHS: Development of sharp hot structures based on ultra high temperature metal diborides
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Surface properties and oxidation behaviour of ultra high temperature ceramics for sharp leading edges
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