Darko Hanzel

Darko Hanzel
Jožef Stefan Institute | IJS · Low and medium energy physics

PhD

About

91
Publications
7,852
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,774
Citations

Publications

Publications (91)
Article
Full-text available
The influence of Fe loading in Cu–Fe phases and its effect on carbon monoxide (CO) oxidation in H2-rich reactant streams were investigated with the catalyst material phases characterized by Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD) studies and Mossbauer Spectroscopy (MS). There was no change in the oxidation state...
Article
Bentonites are an important industrial resource and are also interesting from the mineralogical point of view. The main component of bentonites is a mineral from the smectite group in which chemical and structural variations, influencing bentonite properties, provide a great deal of interesting research topics. The aim of this study was to better d...
Article
A metastable ε-polymorph of iron(III) oxide (ε-Fe2O3) is a very attractive material from the technological, engineering, and scientific points of view. In comparison with other iron oxides, it is characterized by unusual magnetic properties and a giant coercivity of ~20 kOe, which is the largest value among metal oxides. The routine method of ε-Fe2...
Article
The magnetic anisotropy in pentagonal bipyramidal complexes of Co(II) (1 and 2), Fe(III) (3 and 4) and Ni(II) (5) with 2,2′-[2,6-pyridinediylbis(ethylidyne-1-hydrazinyl-2-ylidene)]bis[N,N,N-trimethyl-2-oxoethanaminium] equatorial ligand and isothiocyanato axial ligands has been investigated by magnetic susceptibility measurements, powder X-band EPR...
Article
Full-text available
The effect of the phase transformation of a FePO 4 catalyst material from the tridymite-like (tdm) FePO 4 to the α-domain (α-Fe 3 (P 2 O 7 ) 2 ) during the direct selective oxidation of methane to methanol was studied using oxidant species O 2 , H 2 O and N 2 O.
Article
Full-text available
Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. On an example of aluminum- and iron-containing MIL-100, we demonstrate that 27Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band EPR, Fe K-edge E...
Article
Full-text available
The effect of the FePO4 material phase transformation in the direct selective oxidation of methane to methanol was studied using various oxidants, i.e. O2, H2O and N2O. The phases of the heterogeneous catalyst applied, before and after the reactions, were characterized by M¨ossbauer spectroscopy. The main reaction products were methanol, carbon mon...
Article
The aim of this work is to present the magnetic properties of novel superparamagnetic iNANOvative™|silica nanoparticle clusters. A TEM analysis showed that these nanoparticle clusters, approximately 80 nm in size, contained an assembly of maghemite nanoparticles in the core and an amorphous silica shell. The maghemite nanoparticles in the core were...
Article
Full-text available
LiMBO 3 (M ¼ Fe, Co, Mn) has been identified as an interesting new cathode material for Li-ion batteries. It was shown to be difficult to synthesize the material as a pure phase and in a highly electrochemically active form. Here we report several methods for the successful preparation of LiFeBO 3 , including traditional ceramic and self-combustion...
Data
LiMBO 3 (M ¼ Fe, Co, Mn) has been identified as an interesting new cathode material for Li-ion batteries. It was shown to be difficult to synthesize the material as a pure phase and in a highly electrochemically active form. Here we report several methods for the successful preparation of LiFeBO 3 , including traditional ceramic and self-combustion...
Article
Full-text available
The effect of mild oxidation in air of LiFe1-yMnyPO4 (0 <= y <= 1) powders is studied via in situ and ex situ X-ray diffraction, thermogravimetric analysis and Mossbauer spectroscopy. Structural modifications involve an anisotropic change in the lattice parameters upon heat-treatment with conservation of the olivine-type structure up to similar to...
Article
Crystal structure of ultrafine Ba-hexaferrite (BaFe12O19) nanoparticles was studied using X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray absorption fine structure (XAFS), and Mossbauer spectroscopy (MS), ¨ to be compared to the structure of larger nanoparticles...
Article
Superparamagnetic Ba-hexaferrite nanoparticles were prepared using modified hydrothermal synthesis. The precursor and hydroxide [OH−] concentrations were optimized and the synthesis temperature and time were drastically reduced. The size and the morphology of synthesized nanoparticles was confirmed by transmission electron microscopy (TEM) images....
Article
Several samples of pure Li2FeSiO4 polymorphs, prepared by hydrothermal synthesis and then quenched from either 400 °C (Pmn21), 700 °C (P21/n), or 900 °C (Pmnb), were thoroughly investigated by Mössbauer and NMR spectroscopy. 57Fe Mössbauer spectroscopy showed that (i) iron in all the polymorphs existed in the divalent oxidation state, and (ii) chem...
Article
Full-text available
Solid solutions between iron and manganese cations in were successfully prepared by hydrothermal synthesis. The selected sample was electrochemically evaluated by the use of two in situ characterization techniques. Although the sample showed good reversibility with a large voltage polarization in the formation cycles, the observed electrochemic...
Article
We report on the crystal structure of a new polymorph of Li(2)FeSiO(4) (prepared by annealing under argon at 900 degrees C and quenching to 25 degrees C) characterized by electron microscopy and powder X-ray and neutron diffraction. The crystal structure of Li(2)FeSiO(4) quenched from 900 degrees C is isostructural with Li(2)CdSiO(4), described in...
Article
The local electronic and structural as well as the macroscopic magnetic properties of K <sub>3</sub> Cr <sub>2</sub> Fe <sub>3</sub> F <sub>15</sub> have been studied between room temperature and 4 K. The system has been found to be isostructural with ferroelectric and weakly ferrimagnetic K <sub>3</sub> Fe <sub>5</sub> F <sub>15</sub> above the fe...
Article
Full-text available
In the present study we aimed to show on selected sediments from Kupa drainage basin, the advantages of using combined multi-instrumental approach in physico-chemical assessment of sediment quality, with respect to inorganic pollutants. Mossbauer spectroscopy and solid-state magic angel spin nuclear magnetic resonance ((27)Al and (29)Si MAS NMR) me...
Article
The electron paramagnetic resonance (EPR) spectra of K3Cu3Fe2F15 consist above 85 K of a superposition of two Lorentzians with different intensities, T-dependences, linewidths, and g-factors. The broad line shows an antiferromagnetic (AFM) behavior and the narrow one shows a paramagneticlike behavior. The Mössbauer spectra consist at room temperatu...
Article
Li2FeSiO4/C and Li2MnSiO4/C cathode materials were a subject of in-situ characterisations during the first cycle of oxidation/reduction by complementary techniques of X-ray absorption spectroscopy and Mössbauer spectroscopy, whereby the changes in the local environment of Fe (and Mn) are monitored. Both techniques demonstrate the reversibility of m...
Article
The possible mechanism of lithium exchange from I.iFeTiO(4) is discussed on the basis of three different in situ structural characterization methods. The in situ X-ray diffraction (XRD) showed that the mechanism of lithium exchange was through a solid solution formation whereby the change in volume during the oxidation was 1.4%. The reversibility i...
Article
Full-text available
Ionic liquids, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide with 0.7 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or 0.5 M LiPF6, were successfully tested as electrolytes for Li2FeSiO4 cathodes operating at elevated temperatures of 60 degrees C. The...
Article
Nanoparticles of zinc-doped maghemite were prepared using ultrasonic radiation. As a precursor, a suspension of maghemite in an alkaline aqueous solution of zinc nitrate at pH 9 was sonicated. The zinc-doped maghemite nanoparticles were investigated by X-ray diffraction, Mössbauer spectroscopy, high-resolution electron microscopy (HREM) and SQUID m...
Article
The zinc-doped maghemite nanoparticles were prepared using ultrasonic radiation. As a precursor, a suspension of maghemite in an alkaline aqueous solution of zinc nitrate at pH = 9 was sonicated. They were investigated by x-ray diffraction, Mössbauer spectroscopy, high-resolution electron microscopy (HREM), and superconducting quantum interference...
Article
Here, we report on the observation of a weak ferromagnetic transition at TN = 122 K in a K3Fe5F15 system which is ferroelectric and ferroelastic below Tc = 490 K. The magnetization and the susceptibility continuously increase with decreasing T down to 2 K. The Mössbauer spectra show a spontaneous magnetic ordering and at least three sites correspon...
Article
The European water framework directive (WFD) has not come yet up with environmental quality standards for sediments. It is still open which sediment monitoring approaches will be used. The aim of the present work is to demonstrate on selected stream sediments what type of characterization can be obtained when using interdisciplinary approach.
Article
Barium hexaferrite BaFe12O19 nanoparticles with a single-domain size were synthesized using a controlled hydrothermal process involving the LaMer–Dinger principle and the Ostwald ripening mechanism. Nanocrystalline particles of BaFe12O19 were obtained when the molar ratio of the precursor composition Ba(OH)2·8H2O/γ-Fe2O3 was 0.3 and the concentrati...
Article
To increase the power density of battery materials, without significantly affecting their main advantage of a high energy density, novel material architectures need to be developed. Using the example of LiFePO4, we demonstrate a simple, sol−gel-based route that leads to large (up to 20 μm) primary LiFePO4 particles, each of which contains hierarchi...
Article
In this study, we investigate the feasibility and reliability of Fe K-edge XANES spectroscopy as a tool in determination of Fe2+/Fe3+ ratio in historic inks. We have measured Fe K-edge XANES spectra of several historic and model iron gall inks with different Fe2+/Fe3+ ratios, together with some standard reference Fe2+ and Fe3+ compounds with known...
Article
Full-text available
The present work was designed as an extension of a previous study of a barium anomaly observed in stream sediments of the Kupa River. In its upper part the Kupa River drains a region underlain by a trans-boundary aquifer. The river is a significant water resource in a region of tourism, sport, and fishing in both Croatia and Slovenia. The contamina...
Article
The Li1.746Nd4.494FeO9.493 (LNF) ternary phase, located in the Li2O-rich part of the Li2O–Nd2O3–Fe2O3 system, crystallizes with a cubic unit cell of dimension a=11.9763(3)Å and the space group Im3mIm3m. Refinement on F resulted in R=1.9%R=1.9%. The structure is comprised of a network of corners, edges and faces sharing the coordination polyhedra of...
Article
The Li{sub 1.746}Nd{sub 4.494}FeO{sub 9.493} (LNF) ternary phase, located in the LiâO-rich part of the LiâO-NdâOâ-FeâOâ system, crystallizes with a cubic unit cell of dimension a=11.9763(3)A and the space group Im3m. Refinement on F resulted in R=1.9%. The structure is comprised of a network of corners, edges and faces sharing the coordination poly...
Article
Full-text available
Porous LiMPO4/C composites (where M stands for Fe and/or Mn) with micro-sized particles were synthesised by sol–gel technique. Particles porosity is discussed in terms of qualitative results obtained from SEM micrographs and in terms of quantitative results obtained from N2 adsorption isotherms. Porous particles could be described as an inverse pic...
Article
Full-text available
Stream sediments from Savinja and its tributaries, Voglajna and Hudinja rivers, which drain an old metallurgic area of Slovenia, have been studied by detailed mineralogical, chemical, Mossbauer and geostatistical methods. It is a case study, which provides an example for a possible chemical threat to aquatic ecosystems, such as toxic contamination...
Article
In this paper we report on the influence that the deposition of an uppermost TiO2 layer on top of different sequences of Ti/TiN-based coatings has on the corrosion behaviour of these materials. The results show that this top TiO2 layer fails to block the pinholes or micropores existing in the nitride coatings when they are submitted to an accelerat...
Article
A new type of LiFePO4–carbon composite cathode material was prepared. The active component consists of micrometer-sized particles containing pores with wide distribution of sizes. When filled with electrolyte, the pores are responsible for supply of ions while the distance between the pores (30–150 nm) determines the solid-state diffusion kinetics....
Article
Full-text available
Porous, well crystalline LiFePO4 /C Composites with different amounts of carbon have been prepared by a sol-gel technique. The thickness of carbon coatings (paintings) has been determined by high-resolution transmission electron microscopy. It is shown that carbon coating thickness can be controlled by the amount of carbon and it has an impact on t...
Article
Fe(III) citrate was used as a source for synthesis of microsized porous LiFePO4/C particles. All samples, prepared either by solid-state or by sol-gel techniques, are phase-pure triphylite phases, which, however, have different morphology highly influenced by the type of synthesis and synthesis parameters. Their common feature is porosity due to th...
Article
Full-text available
1,3-Diaminopropane (DAP) was used as a structure-directing agent for the hydrothermal synthesis of an organically templated iron phosphate. During crystallization at 180 ºC, iron phosphate (FePO-DAP) with a layered structure was formed after one day. Longer crystallization yielded a mixture of FePO-DAP and leucophosphite, raising the question wheth...
Article
1,3-Diaminopropane (DAP) was used as a structure-directing agent for the hydrothermal synthesis of an organically templated iron phosphate. During crystallization at 180°C, iron phosphate (FePO-DAP) with a layered structure was formed after one day. Longer crystallization yielded a mixture of FePO-DAP and leucophosphite, raising the question whethe...
Article
Full-text available
Ore estuary (Northern Sweden) was chosen as a model for other anthropogenically unpolluted estuaries in the boreal region. Sediments were studied in detail in order to characterize the weathering products of silicate rocks. Primary rocks are mostly composed of granite and gneiss. Chemical analysis of total sediments was performed by the XRF method....
Article
We report on characterization and magnetic properties of very thin films of Fe-oxides formed by thermal desorption of iron stéarate Langmuir-Blodgett films using low temperature conversion electron Mössbauer spectroscopy (CEMS). Langmuir-Blodgett films of iron stéarate (23 and 27 monolayers) have been formed on silicon wafers and afterwards therma...
Article
Preliminary mineralogical, geochemical and Mössbauer studies of six surface sediments (fraction
Article
Triclinic ZnAPO-34 and triclinic FAPO-34 were synthesized by hydrothermal crystallization from zinc(II)- and iron(II)-containing gels. The products are thermally stable up to 900 °C. XANES and EXAFS analyses were applied to study the local environment of zinc in the ZnAPO-34 samples, while XANES analysis and Mössbauer spectroscopy were performed on...
Article
Full-text available
Brown layers have occurred just below the façade surface of some archaeological buildings. They are a consequence of chemical changes, which can give rise to further destruction. Brown layers and undamaged plaster underneath the brown layers consist of CaCO3, SiO2, Ca2SiO4, CaMg(CO3)2, silicate minerals containing Ca, Al, Mg, K, Fe, metal hydroxide...
Article
Iron(III) phosphate–oxalate (FePO–DAP) crystallizes from a clear solution containing 1,2-diaminopropane (DAP) and oxalic acid at 120 °C under hydrothermal conditions. Doubly protonated DAP is present inside a large one-dimensional 12-membered channel in a disordered manner, its presence creating different environments for the Fe atoms situated acro...
Article
We report studies of recently precipitated terrestrial Mn oxides from Pinal Creek (Arizona, U.S.A.) and from Yuno-Taki Falls (Hokkaido. Japan). In addition to chemical analysis [by energy dispersive X-ray spectroscopy (EDS) and proton induced X-ray emission spectroscopy (PIXE)], the following methods were used: X-ray diffraction (XRD), scanning ele...
Article
In this paper results are presented on the corrosion resistance against SO2-polluted atmospheres of ultrathin Fe layers (<2.5 nm) deposited on SiO2/Si wafers by two methods: vacuum evaporation and Langmuir–Blodgett (LB) technique. It is shown that the corrosion resistance of the evaporated films is similar to that shown by massive iron while the co...
Article
Full-text available
A most feasible tool in characterizing magnetic properties is Mössbauer spectroscopy. By a combination with electron spectroscopy, the depth profile of the Mössbauer excitation is experimentally accessible [Liljequist01, Stahl97]. Depth selective Mössbauer studies in the vicinity of the Néel temperatures of an antiferromagnetic FeBO3 single crystal...
Article
Samples of TiN hard coatings prepared by physical vapour deposition (PVD) were investigated by means of depth-sensitive positron annihilation spectroscopy. The results indicate that the samples are at the limits of the applicability of this method presumably due to the high defect concentration. Our findings also show that, though the samples are t...
Article
Hard nitride coatings deposited by plasma enhanced physical vapor deposition are very often used as wear protective coatings. The electrochemical properties of single layered TiN and CrN films have been compared to bi- and multilayered Ti/TiN coatings deposited on low carbon steel substrate. Cyclic voltammetry in acetate buffer has been applied to...
Article
The corrosion resistance of three different TiN coatings on iron (single TiN layer, Ti/TiN bilayer and Ti/TiN/Ti/TiN multilayer) subjected to a salt (ammonium sulphate and sodium chloride) fog spray (Prohesion) test has been investigated by means of x-ray photoelectron spectroscopy (XPS). The relative intensities of the Fe 2p and O 1s signals in th...
Article
The corrosion properties of single layered TiN and CrN films have been compared to bi-layered and multi-layered Ti/TiN films. XPS has showed that in humid SO2 atmosphere the best corrosion properties have been achieved by a multi-layered Ti/TiN coating. Cyclic voltammetry in acetate buffer has been applied to measure the porousity and corrosion res...
Article
Fe-Al intermetallic alloys have been considered as protective materials against corrosion. We have studied the properties of such intermetallic coatings Fe x Al1−x (x ≤ 0.5) on the aluminum-rich side and their oxidation behaviour. The samples were prepared using rf-magnetron sputtering. The composition and layer thickness were determined by Rutherf...
Article
In this work the behaviour of thin (30 nm), single-layer TiN coatings on iron in different humid SO2-aggressive environments [(i) [SO2] = 0.001% v/v, 80% relative humidity; (ii) [SO2] = 0.001% v/v, 98% relative humidity; (iii) [SO2] = 0.04% v/v, 80% relative humidity; (iv) [SO2] = 0.04% v/v, 98% relative humidity] has been studied by integral conve...
Article
In this paper, time, potential and pH dependence of SO42− and HSO3− accumulations measured by an in-situ radiotracer method on surface oxide layers of low carbon steel are presented and discussed. This work is a continuation of a research program[1–5] and deals with the characterization of the sorption behaviour of low carbon steel in solutions con...
Article
The corrosion behavior in humid SO2-polluted atmospheres of three different TiN coatings on iron [single layer TiN (1000 nm), bilayer Ti(100 nm)/TiN(1000 nm) and multilayer Ti(100 nm)/TiN(100 nm)/Ti(100 nm)/TiN(100 nm)] have been investigated by means of x-ray photoelectron spectroscopy. Only the single layer coating shows some degradation in low c...
Article
 Thin layers of 25 nm 57Fe have been evaporated on Si-wafers in high vacuum in order to enhance the sensitivity of Conversion Electron Mössbauer Spectroscopy (CEMS). On the 57Fe layer, 25 nm of TiN has been deposited using plasma activated reactive sputtering (Sputron). CEMS enables nondestructive characterisation and determination of physico-chemi...
Article
The microscopic nature of the Mössbauer phase analysis has been found as being particularly valuable in testing assumptions suggested by TEM results regarding the microdomain structure and the population of different lattice sites by iron ions in the perovskite system (1-y)La2/3 $A$ 1/3TiO3·yLaFeO3 with 0.04<y < 0.25 ( $A$ is an A-site vacancy)...
Article
Several polynuclear iron(III)-o-phthalates precipitated from acid and alkaline solutions were characterized by chemical and thermogravimetric analysis, and infrared, Mössbauer and magnetic measurements. Compounds prepared in acid solutions contain the trimer unit Fe3O and, although different in chemical composition and in thermal decomposition beha...
Article
Conversion electron Mössbauer (CEMS) and Auger electron spectroscopies (AES) were used to investigate the interfaces of Ti and TiN coatings on iron. The microstructure of the interface has been studied regarding the dependence on physical vapor deposition (PVD) parameters. In particular, the substrate temperature and the negative voltage (bias) app...
Article
The influence of heat treatment in ultrahigh vacuum (UHV) on Ti and TiN layers coated by physical vapour deposition (PVD) has been studied by AES, XPS and bremsstrahlung-induced AES. It could be concluded that up to 500° C (1 h) the Ti layer does not change significantly. At the TiN/steel substrate interface, however, a counterdiffusion of nitrogen...
Article
Titanium and titanium nitride-iron interfaces obtained by PVD coated thin films of Ti and TiN onto argon plasma etched iron substrates at various temperatures and negative bias were studied by use of CEMS. It was found that intermixing to Ti with Fe resulted in the appearance of an amorphous FeTi1−x phase. Furthermore, a comparison of CEM spectra...
Article
A new detector for CEMS has been built and optimized with respect to the statistical quality of spectra obtained. The optimization has been performed by measuring Mbauer and pulse height spectra at in- and off-resonance. Single channel analyzer settings were calculated by a new optimization routine. A comparison of different detector designs has be...
Article
Wear of cold forging tools, improved by TiN (PVD) hard coating and used in the production of alternator and starter components in the car industry, has been studied in detail. The most complicated case was the tool that produced a clutch housing of high precision. The 630 kN press process (50 pcs min−1) caused heavy adhesive and abrasive wear due t...
Article
The near surface diffusion and reaction processes in iron-silicon steel (3.1 wt.%Si) during 10 min decarburization in water vapour/hydrogen have been studied. The decarburization temperature has been varied between 506 and 714C for the fixed partial pressure ratio pH2O/pH2=0.017. An outer layer of SiO2 forms on the surface with its thickness increa...
Article
Mössbauer spectroscopy has been used to study the oxidation of vivianite crystals treated thermally in air and in vacuo. The rate of changes of the fractional ferrous content shows very complicated dehydration-oxidation processes depending on the duration of heating, on the surrounding atmosphere, and on the sample preparation procedure. The highes...
Article
Natural vivianite samples were studied by Mssbauer transmission and conversion electron spectroscopy. The intensities of ferrous doublets in vivianite and the widths of the resonance lines depend strongly on the origin of the samples, on their preparation history, and on exposures in vacuo as well as on thermal treatments. An additional ferrous dou...
Article
Mössbauer data as well as infrared and magnetic susceptibility results indicate that Fe(III)-phthalates are high spin ferric complexes with a combination of trinuclear oxo-bridged and monomer structures. Values obtained for the isomer shift and quadrupole splitting parameters suggest that different counter ions, such as OH, NO3, and Na, leave the F...