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Estonian Nanotechnology Competence Center and University of Tartu | Date: 2010-03-25

Method of preparation of surface coating of variable transmittance and an electro-optical layered appliance including the same comprises dispersing of liquid crystal microdroplets in hydrolyzable and polymerizable precursors and applying obtained mixture on a surface by spraying. Applying the material to the surface by spraying is intrinsically related to the synthesis processes because the properties of the surrounding environment (i.e. content of water and acidity, UV radiation) and the chemical reactions that take place during spraying have considerable influence on the properties (i.e. driving voltage, thickness of obtained layer). Obtained layered appliance comprises of a matrix material with dispersed microdroplets of liquid crystal obtained by the described method, electrically conductive transparent electrodes with contacts, a dielectric material, substrate and covering layers.

Polyakov B.,University of Tartu | Polyakov B.,University of Latvia | Dorogin L.M.,University of Tartu | Vlassov S.,University of Tartu | And 5 more authors.
Micron | Year: 2012

A novel method for in situ measurement of the static and kinetic friction is developed and demonstrated for zinc oxide nanowires (NWs) on oxidised silicon wafers. The experiments are performed inside a scanning electron microscope (SEM) equipped with a nanomanipulator with an atomic force microscope tip as a probe. NWs are pushed by the tip from one end until complete displacement is achieved, while NW bending is monitored by the SEM. The elastic bending profile of a NW during the manipulation process is used to calculate the static and kinetic friction forces. © 2012 Elsevier Ltd.

Tonurist K.,University of Tartu | Thomberg T.,University of Tartu | Janes A.,University of Tartu | Kink I.,Estonian Nanotechnology Competence Center | Lust E.,University of Tartu
Electrochemistry Communications | Year: 2012

Influence of the separator material characteristics on the performance of electrical double layer capacitors (EDLCs), based on the two identical ideally polarizable microporous titanium carbide-derived carbon electrodes in room temperature ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate), has been tested by cyclic voltammetry, constant power and electrochemical impedance spectroscopy methods. Self-made separator materials have been prepared from poly(vinylidene fluoride) solutions in N,N-dimethylacetamide or N,N-dimethylformamide and acetone mixture (8:2 mass ratio) by using the electrospinning method. Noticeable influence of the separator porosity and chemical composition on the limits of ideal polarizability, specific capacitance, equivalent series resistance, phase angle, specific energy and power of the EDLCs has been obtained and discussed. © 2012 Elsevier B.V.

Obraztsov A.N.,Moscow State University | Kopylov P.G.,Moscow State University | Loginov B.A.,Moscow Institute of Electronic Technology | Dolganov M.A.,Moscow State University | And 2 more authors.
Review of Scientific Instruments | Year: 2010

Single crystal diamond tips with perfect pyramidal geometry were obtained by a combination of chemical vapor deposition and selective oxidation of polycrystalline films. The parameters of the deposition process were chosen to provide growth of a textured film consisting of micrometer sized diamond crystallites embedded into nanodiamond ballas-like material. The heating of the film in an air environment was used for selective oxidation of the nanodiamond component. The films obtained contain free standing pyramidal single crystal diamond tips oriented by their apexes to the substrate surface. The tips were used for the fabrication of atomic force microscopy probes and their evaluation in comparison to common silicon probes. © 2010 American Institute of Physics.

Sutka A.,Riga Technical University | Parna R.,University of Tartu | Mezinskis G.,Riga Technical University | Kisand V.,University of Tartu | Kisand V.,Estonian Nanotechnology Competence Center
Sensors and Actuators, B: Chemical | Year: 2014

Pure and cobalt-ion-containing nickel ferrite samples Ni 1-xCoxFe2O4 (x = 0, x = 0.01, x = 0.05 and x = 0.1) were prepared by using the sol-gel auto-combustion method. To form the desired structure after the auto-combustion process, the samples were annealed in air at 800 C for 1 h, followed by slow cooling in air (2.5 C/min) or rapid cooling by quenching in water. The influences of cobalt ion addition and the cooling rate on the electronic structure, morphology and electrical properties of Ni-Co ferrite were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The gas-sensing properties of pure and cobalt-ion-containing nickel ferrites were studied by using acetone as a test gas. The gas-response of nickel ferrite samples was strongly influenced by the cooling rate and cobalt addition. The effect was attributed to a change in the Ni3+ concentration and a restriction of the transduction of the chemical signal into an output electrical signal. It was demonstrated that the gas response of Ni1-xCo xFe2O4 tends to increase with decreasing cobalt ion content and with decreasing concentration of the point defects such as cation vacancies and Ni3+ ions. © 2013 Elsevier B.V.

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