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39 results on '"Timusk, Martin"'

16. Probing Contact Electrification: A Cohesively Sticky Problem

Author

Sherrell, Peter C., primary, Sutka, Andris, additional, Shepelin, Nick A., additional, Lapcinskis, Linards, additional, Verners, Osvalds, additional, Germane, Liva, additional, Timusk, Martin, additional, Fenati, Renzo A., additional, Malnieks, Kaspars, additional, and Ellis, Amanda V., additional

Published
2021
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27. Mechanical reinforcement of electrospun poly(vinyl alcohol) by α‐FeOOH nanowires.

Author

Šutka, Anna, Järvekülg, Martin, Šutka, Andris, Heinmaa, Ivo, Mäeorg, Uno, Smits, Krisjanis, and Timusk, Martin

Subjects
POLYVINYL alcohol, GOETHITE, NANOWIRES, NANOPARTICLES, ELASTIC modulus, GLASS transition temperature
Abstract

We report the mechanical performance of α‐FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α‐FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needle‐less electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5‐fold improvement of tensile strength compared to mats of neat PVA. The addition of α‐FeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% α‐FeOOH. POLYM. COMPOS., 39:2461–2468, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Published
2018
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34. Fabrication of Lead Titanate Pb Ti O3 Nanofiber Mats Via Electrospinning.

Author

Šutka, Andris, Timusk, Martin, Kisand, Vambola, Šutka, Anna, and Dauksta, Edvins

Subjects
*LEAD titanate, *MICROFABRICATION, *TITANIUM dioxide nanoparticles, *NANOFIBERS, *ELECTROSPINNING, *CRYSTAL morphology
Abstract

We report an electrospinning approach to producing Pb Ti O3 polycrystalline nanofibers. The influence of the polymer concentration in the solution on the obtainable Pb Ti O3 nanofiber morphology was investigated. Nanofibers were characterized by high-resolution scanning electron microscopy ( HR- SEM) and Raman spectroscopy. After annealing at 500°C for 3 h, the continuous structure of nanofibers remained intact. Only tetragonal Pb Ti O3 was identified by Raman spectroscopy. Piezoelectric behavior of Pb Ti O3 nanofiber mats was demonstrated by making a nanomat-based voltage generator with peak output voltage >1 V. [ABSTRACT FROM AUTHOR]

Published
2015
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35. The Adhesion‐Enhanced Contact Electrification and Efficiency of Triboelectric Nanogenerators.

Author

Lapčinskis, Linards, Mālnieks, Kaspars, Blūms, Juris, Knite, Māris, Oras, Sven, Käämbre, Tanel, Vlassov, Sergei, Antsov, Mikk, Timusk, Martin, and Šutka, Andris

Subjects
TRIBOELECTRICITY, ELECTRIFICATION, ATOMIC force microscopy, MECHANICAL energy, SURFACE charges, ENERGY conversion, SCISSION (Chemistry)
Abstract

In the present work, the contact electrification of polymers that differ in adhesion strength is studied. Electrical current is measured along with adhesion in macroscale contacting‐separation experiments. Additionally, local adhesion and roughness are studied with atomic force microscopy to get deeper insight into relations between surface properties and electrification. Measurements reveal that higher surface charge is formed on more adhesive surfaces, thus confirming covalent bond cleavage as a mechanism for contact electrification of polymers. Investigated materials possess enhanced contact electrification making them attractive candidates for the conversion of mechanical energy to electrical in triboelectric nanogenerator devices. [ABSTRACT FROM AUTHOR]

Published
2020
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36. Madala tihedusega polüdimetüülsiloksaanvahtude valmistamine

Author

Nigol, Ines Anett, Timusk, Martin, juhendaja, Tartu Ülikool. Loodus- ja täppisteaduste valdkond, and Tartu Ülikool. Füüsika instituut

Subjects
bakalaureusetööd, biopolümeerid, polüdimetüülsiloksaan, tiksotroopsed vedelikud
Published
2022

37. Alkogeel kütusetableti kütteväärtuse optimeerimine

Author

Timmusk, Paul Artur, Timusk, Martin, juhendaja, Tartu Ülikool. Loodus- ja täppisteaduste valdkond, and Tartu Ülikool. Füüsika instituut

Subjects
bakalaureusetööd, sool-geel protsessid, kütused, kütteväärtus
Abstract

https://www.ester.ee/record=b5379666*est

Published
2020

38. Polü(3,4-etüleendioksütiofeeni) õhukeste kilede valmistamine ja stabiilsus rakendusteks läbipaistva elektroodina

Author

Metsik, Jörgen, Mäeorg, Uno, juhendaja, Timusk, Martin, juhendaja, and Tartu Ülikool. Loodus- ja täppisteaduste valdkond

Subjects
polymer films, väitekirjad, dissertations, polymerization, dissertatsioonid, pinnakeemia, ETD, surface chemistry, polümeerkiled, polümerisatsioon
Abstract

Väitekirja elektrooniline versioon ei sisalda publikatsioone, Juhtivad polümeerid on sellised orgaanilised polümeerid, mis juhivad elektrit. See põnev materjalide klass on juba 20. sajandi lõpust pälvinud teadusmaailma suurt tähelepanu, sest võib osutuda kasulikuks paljudes erinevates rakendustes, alates sensoritest ja lõpetades päikesepatareidega. Näiteks on paljudes seadmetes vaja kasutada läbipaistvaid elektroode, mille materjaliks on tänapäeval harilikult indiumtinaoksiidi (ITO) kiled. Aga ITO kiled on kallid ja nendele oleks hea odavam asendus leida. Just siin võib juhtiv polümeer kasuks tulla. Erinevalt ITOst on juhtivad polümeerid ka hea painduvusega, mis võimaldaks valmistada painduvaid elektroonikaseadmeid. Polü(3,4-etüleendioksütiofeen) (PEDOT) on üks juhtiv polümeer, mis võiks läbipaistvaks elektroodimaterjaliks sobida. PEDOT on üsna kõrge juhtivuse, hea läbipaistvuse ning juhtivate omaduste küllaltki suure stabiilsusega. Paraku ei ole ükski neist omadustest siiski veel päris ideaalne, mistõttu tuleb otsida lahendusi nende omaduste parandamiseks. Antud doktoritöös uuriti kahte erinevat PEDOTi õhukeste kilede valmistamise meetodit. Ühe meetodi puhul pärineb polümeeri moodustav monomeer gaasifaasist ja teisel juhul lahusest. Määrati, millistes etappides kile kasv toimub ja kuidas saada paremate omadustega kilet. Uuriti ka PEDOTi kilede vananemist ja nende juhtivuse vastupidavust erinevates keskkondades. Selgus, et uuritud PEDOTi kiled ei juhi elektrit nii hästi kui ITO ja nende juhtivus ei ole ka nii stabiilne. Ent avastati siiski üks rakendus, milles PEDOT on ITOst parem. Triboelektriline nanogeneraator on energiatootmisseade, mis suudab toota elektrit ka väikeste igapäevaelu liikumiste mehaanilisest energiast, mis muidu raisku läheb. PEDOTi kile kasutamine sellise seadme elektroodimaterjalina võimaldab kolm korda suuremat võimsustihedust kui ITO ja PEDOTi kile on selleks ka piisavalt stabiilne., Conductive polymers are organic polymers, which conduct electricity. This fascinating class of materials has gained a lot of scientific attention starting already from the end of the 20th century, because it may become useful in numerous applications, from sensors to solar panels. For example, transparent electrodes consisting of indium tin oxide (ITO) films are used in a large number of devices. But ITO films are expensive and a cheaper solution would be greatly appreciated. For this purpose, a conductive polymer may be a better solution. Conductive polymers are also flexible while ITO is brittle, enabling preparation of flexible electronic devices. Poly(3,4-ethylenedioxythiphene) (PEDOT) is a conductive polymer, which could be used as a transparent electrode material. PEDOT has a relatively high conductivity, good transparency and quite stable conductive properties. However, none of these properties is perfect at the current level of development. Therefore, it is still necessary to find ways for improving these properties. Two different preparation methods for PEDOT thin films were studied in this thesis. For one method the source of polymerizing monomer is a gas phase, for another method a solution. During this work the stages of film growth were investigated and better film formation conditions were determined. Aging of PEDOT and stability of conductance were investigated in different conditions. It was found out that investigated PEDOT films are not so highly conductive and stable conductors as ITO. However, in one application PEDOT was better than ITO. A triboelectric nanogenerator is a device, which could produce electricity from the mechanical energy of small movements, which would be otherwise wasted. As an electrode material for this device, PEDOT film enables to have three times higher power densities than ITO film and it is sufficiently stable.

Published
2018

39. Makropoorse ränioksiidvahu valmistamine ja karakteriseerimine

Author

Kuus, Agnes, Timusk, Martin, juhendaja, Tartu Ülikool. Loodus- ja täppisteaduste valdkond, and Tartu Ülikool. Füüsika instituut

Subjects
aerogeelid, bakalaureusetööd, ränioksiid, sool-geel protsessid, soojusjuhtivus
Published
2016

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