131. Univerza v Novi Gorici, Spremljanje, ugotavljanje in zagotavljanje kakovosti, Poročilo za študijsko leto 2016/2017Martina Bergant Marušič, Blaž Belec, Lorena Butinar, IMRE CIKAJLO, Saša Dobričič, Renata Kop, Martin Knez, Boštjan Potokar, Branka Mozetič Vodopivec, Egon Pavlica, Samo Stanič, Tea Stibilj Nemec, Arthur Stepanov, Veronika Piccinini, Anika Velišček, Peter Purg, Aljaž Rener, Nives Štefančič, Ana Toroš, Tanja Urbančič, Matjaž Valant, Aleš Vaupotič, Sabina Zelinšček, 2017, elaborat, predštudija, študija Ključne besede: zagotavljanje kakovosti, visoko šolstvo, univerza
Objavljeno v RUNG: 05.02.2018; Ogledov: 4219; Prenosov: 0
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132. Unusual magnetodielectric effects in La2CuMnO6 induced by a dynamic crossover in dielectric relaxation at TCJasnamol Pezhumkattil Palakkal, Cheriyedath Raj Sankar, Ajeesh Parayancheri Paulose, Matjaž Valant, Artem Badasyan, Manoj Raama Varma, 2018, izvirni znanstveni članek Opis: A series of fixed frequency dielectric measurements shows dielectric relaxation in La2CuMnO6, with a dynamic
(Arrhenius to Arrhenius) crossover at TC. The external magnetic field alters the relaxation parameters in the
vicinity of crossover and induces an unusual trend in the magnetodielectric coupling around TC. A large magnetodielectric
coupling of 55% (at 68 K, 4 kHz) and 61% (at 105 K, 285.8 kHz) under a small magnetic field of
5 kOe is discovered. Presence of ferromagnetic short-range correlations above TC and a sign reversal of magnetoresistance
around TC are observed. Specific heat analysis revealed the presence of ferromagnetic, variable
range hopping active charge localized state. The presence of ferromagnetic short-range correlations and the
influence of a core-grain dominated magnetoresistance on the Maxwell-Wagner interfacial polarization are responsible
for the observed large magnetodielectric effect. Both the magnetic ordering and external magnetic
field control the electric dipole relaxation in the material.
Ključne besede: Double perovskite
Griffiths-like phase
Dielectric
Magnetoresistance
Magnetodielectric
Objavljeno v RUNG: 03.01.2018; Ogledov: 3759; Prenosov: 0
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139. Photoelectrochemical Water Splitting Studies with nanostructured n and p-type semiconductor electrodesSaim Emin, Matjaž Valant, 2017, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje) Opis: Photoelectrochemical water splitting has been demonstrated as a promising way to efficiently split water. Currently, solar-to-hydrogen conversion efficiency using state-of-the-art material combinations in PEC system is in the order of 7%. Fabrication of nanostructured materials with unique morphologies and compositions is an important factor to fully utilize the possibilities in this field. We will present different strategies for the preparation of nanostructured metal oxide thin films by using electrodeposition and wet-chemistry techniques. Focus will be given on the preparation of ZnO and CuO thin films where intermediate phases like Zn(OH)8Cl2.H2O and CuX (X=Br, Cl) were electrodeposited. Wet-chemistry synthesis techniques will be also explored for the preparation of nanostructured WO3 and a-Fe2O3 thin films. Especially, the hot-pyrolysis technique for the preparation of colloidal W and Fe/Fe-oxide nanoparticles will be shown. Spin-coating of W and Fe/Fe-oxide NPs onto optically conductive substrates and subsequent heat treatment of the obtained films was found to be a convenient way for the preparation of nanostructured WO3 and a-Fe2O3 thin films.
Ključne besede: photoelectrochemical water splitting, colloidal nanoparticles, semiconductor
Objavljeno v RUNG: 24.10.2017; Ogledov: 4406; Prenosov: 0
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140. Tungsten carbide thin films for electrochemical water splitting studiesSaim Emin, Cesur Altinkaya, Ali Semerci, Matjaž Valant, Hasan Okuyucu, Abdullah Yildiz, 2017, objavljeni povzetek znanstvenega prispevka na konferenci Opis: We used wet-chemistry techniques to prepare colloidal tungsten (W) nanoparticles (NPs). The synthesis of W NPs was conducted using the so called hot-matrix method in 1-octadecene [1]. The sizes of obtained W NPs are in the order of 2 - 5 nm. These W NPs are coated with hydrophobic molecules which allow their dispersion in organic solvents like choloroform (CHCl3). It was found that the colloidal stability of the dispersions is exceptionally high exceeding several years. The stability of W NPs which prevents coagulation allows the preparation of thin films with uniform thicknesses by spin-coating, inkjet-printing and spray coating.
We have prepared tungsten carbide (W2C, WC) thin films. The preparation of W2C and WC was achieved by spin-coating of pre-synthesized W NPs on graphite substrate and following heat treatment under Ar atmosphere at 1000 and 1450°C.
The obtained W2C and WC films were used both in electrochemical water splitting studies. We also made a composite W2C-Pt films where we used only 5 at.% of Pt. The W2C-Pt composite has shown similar performance as pure Pt-C for hydrogen (H2) evolution. In conclusion, we have developed a procedure for the synthesis of W NPs which can be applied for the preparation of tungsten carbides films and their use for electrochemical water splitting.
Ključne besede: water splitting, nanoparticles, hot-matrix
Objavljeno v RUNG: 09.10.2017; Ogledov: 5960; Prenosov: 0
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