Tallinn University of Technology

About: Tallinn University of Technology is a education organization based out in Tallinn, Estonia. It is known for research contribution in the topics: European union & Computer science. The organization has 3688 authors who have published 10313 publications receiving 145058 citations. The organization is also known as: Tallinn Technical University & Tallinna Tehnikaülikool.

Li+ intercalation in isostructural Li2VO3 and Li2VO2F with O2− and mixed O2−/F− anions

Abstract: Mixed-anion materials for Li-ion batteries have been attracting attention in view of their tunable electrochemical properties. Herein, we compare two isostructural (Fmm) model intercalation materials Li2VO3 and Li2VO2F with O2− and mixed O2−/F− anions, respectively. Synchrotron X-ray diffraction and pair distribution function data confirm large structural similarity over long-range and at the atomic scale for these materials. However, they show distinct electrochemical properties and kinetic behaviour arising from the different anion environments and the consequent difference in cationic electrostatic repulsion. In comparison with Li2VO3 with an active V4+/5+ redox reaction, the material Li2VO2F with oxofluoro anions and the partial activity of V3+/5+ redox reaction favor higher theoretical capacity (460 mA h g−1vs. 230 mA h g−1), higher voltage (2.5 V vs. 2.2 V), lower polarization (0.1 V vs. 0.3 V) and faster Li+ chemical diffusion (∼10−9 cm2 s−1vs. ∼10−11 cm2 s−1). This work not only provides insights into the understanding of anion chemistry, but also suggests the rational design of new mixed-anion battery materials.

Nano-silicon carbide reinforced aluminium produced by high-energy milling and hot consolidation

Abstract: High-energy milling was studied for the ex situ strengthening of aluminium with silicon carbide (SiC) nanopowders. Heptane was used as a milling agent for both planetary- and attritor ball milling. Considering the different milling techniques and the differences in the resulting powders, effective dispersion of the nano SiC was achieved. Composite samples compacted by hot pressing showed an increase in hardness (HV 20 = 220) and a decrease in Al crystallite size from 220 to 55 nm with the nano-SiC content increasing from 1 up to 20 vol.%. The ultimate tensile strength was measured for extruded samples which resulted in 205 MPa (17% elongation) for 1 vol.% of nano-SiC and a strength of 420 MPa (4% elongation) for 10 vol.% of nano-SiC reinforcement. The mechanical properties were compared with what was predicted by the Hall–Petch relationship.

Competitive Binding of Natural Amphiphiles with Graphene Derivatives

Abstract: Understanding the transformation of graphene derivatives by natural amphiphiles is essential for elucidating the biological and environmental implications of this emerging class of engineered nanomaterials. Using rapid discrete-molecular-dynamics simulations, we examined the binding of graphene and graphene oxide with peptides, fatty acids, and cellulose, and complemented our simulations by experimental studies of Raman spectroscopy, FTIR, and UV-Vis spectrophotometry. Specifically, we established a connection between the differential binding and the conformational flexibility, molecular geometry, and hydrocarbon content of the amphiphiles. Importantly, our dynamics simulations revealed a Vroman-like competitive binding of the amphiphiles for the graphene oxide substrate. This study provides a mechanistic basis for addressing the transformation, evolution, transport, biocompatibility, and toxicity of graphene derivatives in living systems and the natural environment.

Politics of fiscal consolidation in Europe: a comparative analysis

Abstract: The aim of the article is to comparatively describe and explain consolidation measures and political decision-making processes in 14 European countries. The consolidation measures followed a similar pattern. Hiring and pay freeze occurred almost everywhere, whereas more radical cutback measures were introduced only in a limited number of countries. Cutback decision-making was not a one-off event, but consisted of a series of stages, beginning with temporary and small measures and gradually evolving into more serious cutbacks, sometimes arriving at targeted cuts and political priority-setting. The political decision-making was moderate and gradual rather than drastic and swift. Exceptions to this general pattern were the Baltic states as well as those European countries which received financial assistance on the condition of swift and severe cutbacks. Economic factors and supra-national influences primarily explained the size of consolidation measures, whereas domestic political factors turned out to have ...