Jožef Stefan Institute
  • Ljubljana, Slovenia
Recent publications
The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
The ATLAS experiment at the Large Hadron Collider has a broad physics programme ranging from precision measurements to direct searches for new particles and new interactions, requiring ever larger and ever more accurate datasets of simulated Monte Carlo events. Detector simulation with Geant4 is accurate but requires significant CPU resources. Over the past decade, ATLAS has developed and utilized tools that replace the most CPU-intensive component of the simulation—the calorimeter shower simulation—with faster simulation methods. Here, AtlFast3, the next generation of high-accuracy fast simulation in ATLAS, is introduced. AtlFast3 combines parameterized approaches with machine-learning techniques and is deployed to meet current and future computing challenges, and simulation needs of the ATLAS experiment. With highly accurate performance and significantly improved modelling of substructure within jets, AtlFast3 can simulate large numbers of events for a wide range of physics processes.
Low-temperature solid-state reactions between Ni and Si were studied using in situ transmission electron microscopy (TEM). In the experiments thin amorphous silicon (a-Si) films were laid on Ni micro-grids and heated up to 973 K. In our approach the supporting Ni-grid serves as an unlimited source of nickel to successively form the whole range of Ni-silicide phases while diffusing into amorphous silicon. Unlike other thin film experiments where Ni and Si are layered on top of each other, our arrangement enables lateral diffusion of Ni along the Si layer and therefore enables the formation and study of successive Ni-Si phases side by side. That allowed us to observe in situ α-NiSi2 as the first reaction product, in contrast to most studies that had reported either δ-Ni2Si or θ-Ni2Si as the first phase to form. α-NiSi2 was continuously present at the reaction front propagating into the a-Si film. The phase sequence followed the increasing Ni concentration from a-Si towards the Ni-grid: α-NiSi2, NiSi, Ni3Si2, δ-Ni2Si, γ-Ni31Si12 and Ni3Si. Almost all known Ni-silicide phases were found to form at relatively low temperatures except the θ-Ni2Si, β-NiSi2 and β3-Ni3Si. The dominant phase was γ-Ni31Si12 which appeared in three structural modifications, differing in lattice periodicity along the c-axis. The periodicity of the basic γ-Ni31Si12 structure along the c-axis is ~12 Å (c0 = 12.288 Å) and that of the other two modifications were ~18 Å and ~36 Å, denoted by S12, S18 and S36 respectively. Of the three, only S12 has a structural model, S18 had been previously observed by Chen, but S36 had not been documented in previous works. During our in situ heating experiments, in addition to the Ni-silicide layer formation a new phenomenon was observed, namely the appearance, growth and transformation of Ni-silicide whiskers which was attributed to the accumulation of compressive stress in the thin layer.
An extensive study on using plant waste aqueous extracts as natural chemicals for in-situ synthesis of zinc oxide (ZnO) on cotton is presented. Reducing agents were prepared from green tea leaves (GT), pomegranate peels (PG), and staghorn sumac leaves (SsL) and drupes (SsD), and the alkaline medium from discarded wood ash. Zinc acetate was found to be more appropriate precursor than zinc nitrate. Formation of ZnO on cotton was confirmed by energy dispersive spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction analysis (XRD). The inductively coupled plasma mass spectrometry and X-ray fluorescence results showed the highest amount of ZnO on cotton was formed using PG and SsL extracts, which was also confirmed with scanning electron microscopy and UV/visible spectroscopy. The ZnO-functionalised samples exhibited excellent UV-blocking ability and different wetting properties (hydrophilic or hydrophobic) depending on the reducing agent used due to their different total phenolic content. This study shows that by choosing the plant waste source as a reducing agent for ZnO formation directly on cotton, the properties of cotton can be designed to be hydrophilic or hydrophobic with excellent UV-blocking properties. The XRD results of ex-situ synthesis prove that the short reaction time enables the formation of ZnO.
Layered double oxide (LDO) photocatalyst microparticles were synthetized with special radial lamellar orientation. We presented that the 25.31 ± 2.34 μm LDO particles with rough surface can incorporated in fluoropolymer solution and resulted a composite layer with dual superhydrophobic and photocatalytic properties with high bacterial adhesion and inactivation ability. Next the LDO content in the composite layers were systematically increased (0, 20, 40, 60, 80 and 100 wt% LDO) which facilitated the surface adhesion of bacteria by electrostatic interactions. The structure of the initial LDO and LDO/fluoropolymer composites was verified by small angle X-ray scattering (SAXS), XRD and SEM measurements. We showed that the surface roughness and hydrophobicity increase with increasing LDO loading. At 80/20 wt% LDO/fluoropolymer ratio the apparent surface energy was low enough to obtain a superhydrophobic surface (θw= 156.3° and γstot= 2.7 mJ/m²). The bacterial adhesion extent on LDO/fluoropolymer composite layers increases with increasing LDO content because the adhesion takes place preferentially to LDO lamellae. The reason for this pronounced adhesion of negatively charged and hydrophilic bacteria onto positively charged and hydrophilic LDO surfaces is the electrostatic attraction between oppositely charged surfaces. The bacterial adhesion was detected by scanning electron and fluorescence microscopy and crystal violet staining assay. Finally, the adhered bacteria were inactivated by the LED-light illumination due to photoreactivity of LDO particles containing 12 wt% of ZnO phase.
The increasing use of Liquefied Natural Gas (LNG) in shipping has led to an increased interest in marine bunkering safety in ports. The main tool for risk management and siting of bunkering facilities is quantitative risk assessment. This paper addresses the uncertainties in the available data on bunker equipment (loading and unloading arms and hoses), safety system failure rates, and ignition probabilities required for risk assessment. Using the search engines Scopus and Google, a literature search was conducted for studies and papers on the risk assessment of LPG bunkering. Analysis of the relevant studies revealed that different sources of data were used for equipment failure rates and ignition probabilities. The analysis of failure rates for leaks and ruptures of arms and hoses revealed that there are several problems with comparability, but also that there is a high degree of uncertainty, with data ranging from two to four orders of magnitude. The analysis of ignition probabilities showed that the uncertainty is about two orders of magnitude for small releases and within one order of magnitude for large releases. The failure rates of the emergency shutdown systems are within one order of magnitude. A wide range of arm and hose failure rates represents a large uncertainty for a reliable risk assessment. The way forward appears to be a transparent data collection system that describes the scope and the various assumptions.
Construction and demolition waste are one of the largest waste streams generated in the EU by volume. They consist of materials such as concrete, bricks, gypsum, wood, glass, metals, foams, plastics, solvents, asbestos, asphalt, and excavated soil. Nowadays, many of them can be recycled, some even endlessly. This research attempts to contribute to the non-destructive characterization of such a waste with a novel method using terahertz radiation. By combining terahertz imaging and spectroscopy, we performed analytical characterization of selected building materials. The results demonstrate that terahertz technology allows an inside view into some of the non-conducting building materials. THz imaging can detect and visualize the organic solvents in the insulation material, which are often disposed of together with construction and demolition waste. It can also visualize the content of foreign objects or hazardous and toxic substances, which is important for their separation in the recyclate according to the type of the material. Furthermore, THz spectra reveal some spectral lines that can differentiate between different plastics and polymers within the frequency range of 1.0–4.5 THz due to different material structures and chemical compositions. Such results significantly contribute to the decision of which product meets all the standards, which can be returned to the production process due to irregularities or may be disposed of as waste. The only way to reduce construction and demolition waste in the future is to encourage the adoption of innovative technologies like terahertz spectroscopy in combination with traditional methods. This approach can bring some changes also to the construction design philosophy toward more sustainable buildings with minimum end-of-life demolition.
Coupled antiferromagnetic–ferromagnetic bilayers have been intensively investigated as low-dimensional memory materials. However, the connection between their architecture and emergent hysteresis loop phenomena remains elusive. Here, we revealed this relation through low-temperature simulations of the field-driven Ising spin reversal dynamics in heterostructures of coupled ferromagnetic and antiferromagnetic layers of varied thicknesses and a weak random-field disorder. The hysteresis loop exhibits the fractional-magnetisation plateaus, where their number, the height of the central loop, and the structure of side sub-loops strictly depend on the antiferromagnetic layer thickness. Meanwhile, the interlayer coupling chiefly determines the coercive field values, modified by the magnetic disorder, the thickness of the ferromagnetic layer and the system size, in agreement with the derived theoretical formula. The magnetisation fluctuations are modulated with peaks at the transitions between successive plateaus, reflecting the active groups of spins with different levels of (anti)ferromagnetic couplings arising at the interplay of antiferromagnetic sublattices and disorder. The cyclic trend drives the magnetisation fluctuations within limited time intervals; multifractal fluctuations occur on larger time scales. These findings shed new light on the tuneable hysteresis loop properties and the related magnetisation fluctuations in thin antiferromagnetic–ferromagnetic bilayers. The described hysteresis-loop phenomena are not limited to these model systems but should be present in different antiferromagnetic materials with complex morphology.
The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the past decade. With predictions on further electrification growing exponentially the demand for these materials will even increase. This implies that efforts in assuring sustainability must involve recycling from secondary resources. In recent years the electrochemical approaches in recycling have been extensively investigated and applied owing to their advantages of high efficiency and selectivity, easy operation, low energy consumption, and environmental friendliness. In this paper, we investigate the Sm 2 (Co,Fe,Cu,Zr) 17 permanent magnet leaching process using the anodic oxidation to be paired with the metal deposition on the cathode. Linear sweep voltammetry was performed from − 0.15 to 1 V versus Pt quasi reference electrode that indicated current peaks that would correspond to some preferential leaching of the crystal phases contained in the magnet. The latter was confirmed using the SEM/EDXS analysis. The continuous leaching of the Sm 2 (Co,Fe,Cu,Zr) 17 magnet was performed at a direct current density of 2, 4 and 8 mA cm ⁻² at the time period of 0–240, 240–480 and 480–720 min, respectively. The ICP-MS results confirmed the leaching of all the metals from the original Sm 2 (Co,Fe,Cu,Zr) 17 permanent magnet. The concentration of Sm ³⁺ , Cu ²⁺ , Fe ²⁺ and Zr ²⁺ increases linearly along with the leaching time. Reversely the concentration of Co ²⁺ decreases linearly due to its consumption by electrodeposition of Co, Fe and Cu on the cathode. The presented paired electrochemical process could serve as a starting point for the recycling and recovery of critical raw materials without any acid usage and waste generation. Graphical abstract
Atmospheric gases and particulate matter (PM) in contact with the material’s surface lead to chemical and physical changes, which in most cases cause degradation of the cultural heritage material. Atmospheric damage and soiling are recognized as two pivotal forms of deterioration of cultural heritage materials caused by air pollution. However, the atmospheric damage effect of PM is rather complicated; its variable composition accelerates the deterioration process. Considering this, one of the important contributions of this work is to review the existing knowledge on PM influence on atmospheric damage, further recognize, and critically evaluate the main gaps in current understanding. The second phenomenon related to cultural heritage material and PM pollution is soiling. Even if soiling was recognized long ago, its definition and knowledge have not changed much for several decades. In the past, it was believed that black carbon (BC) was the primary soiling agent and that the change of the lightness could effectively measure the soiling. With the change of pollution situation, the lightness measurements do not represent the degree of soiling correctly. The additional contribution of this work is thus, the critical evaluation of soiling measurements, and accordingly, due to the change of pollution situation, redefinition of soiling is proposed. Even though numerous studies have treated soiling and atmospheric damage separately, there is an overlap between these two processes. No systematic studies exist on the synergy between soiling and atmospheric damage caused by atmospheric PM.
Brain hubs are best connected central nodes in the human connectome that play a critical role in integrated brain dynamics. How the hubs perform their function vs different dynamical processes and the role of their higher-order connections involving different brain regions remains elusive. Here we simulate the phase synchronisation processes on the human connectome core network consisting of the eight brain hubs and all attached simplexes of different sizes. The leading pairwise interactions among neighbouring nodes are assumed, taking into account the natural weights of edges. Our results reveal that increasing the positive pairwise couplings promotes a continuous synchronisation while a weak partial synchronisation occurs for a wide range of negative couplings. The weights of edges stabilise the synchronisation process supporting the absence of hysteresis. Furthermore, the time evolution of the order parameter shows cyclic fluctuations induced by the concurrent evolution of phases associated with different groups of nodes. We show that these oscillations exhibit long-range temporal correlations and multifractality. The asymmetrical singularity spectra are determined, which vary with the time scale and depend on the weights of edges. These findings suggest a possible way that the brain functional geometry maintains a desirable low-level synchrony through complex patterns of phase fluctuations.
Distribution studies of ²³⁸U, ²²⁶Ra, ²³²Th, and ⁴⁰ K in soil, statistical analysis of activity concentrations, and radiological safety assessment were carried out in the phosphate ore site of Dagbati, southern region of Togo. The measurements were done using high purity germanium (HPGe) detector gamma‑ray spectrometer. High values of activity concentrations of ²³⁸U and ²²⁶Ra measured were partially attributed to the nature of rocks and the geological structure of the studied area. Twenty-two out of 30 (73.33%) of soil samples presented values above the recommended limit for gamma-ray absorbed dose rate. Although the annual effective dose equivalent mean value of 0.68 mSv year⁻¹ (0.54 for indoor and 0.14 for outdoor) was below the recommended limit, more than 73% of soil samples were above. Similarly, external and internal hazard’s indices, gamma level index, and excess lifetime cancer risk vary from 0.06 to 1.69, 0.09 to 3.20, 0.15 to 4.19, and 0.00004 to 0.00123, respectively, with more than 73% soil samples having values above the recommended limit. These are indications that long-term exposure to natural radiation may lead to cancer risk. However, considering the level of uranium in soil samples, the mass exhalation rate of radon was investigated and the mean value of 1450 mBq kg⁻¹ h⁻¹ obtained is lower than the safe value of 57,600 mBq kg⁻¹ h⁻¹. Therefore, using phosphate mining soil as building material is safe in terms of radon exposition but might lead to radiation exposure and further an increase of cancer incidence for the population.
Crystal growth from anhydrous HF solutions of M2+ (M = Ca, Sr, Ba) and [AuF6]- (molar ratio 1:2) gave [Ca(HF)2](AuF6)2, [Sr(HF)](AuF6)2, and Ba[Ba(HF)]6(AuF6)14. [Ca(HF)2](AuF6)2 exhibits a layered structure in which [Ca(HF)2]2+ cations are connected by AuF6 units, while the crystal structure of Ba[Ba(HF)]6(AuF6)14 exhibits a complex three-dimensional (3-D) network consisting of Ba2+ and [Ba(HF)2]2+ cations bridged by AuF6 groups. These results indicate that the previously reported M(AuF6)2 (M = Ca, Sr, Ba) compounds, prepared in the anhydrous HF, do not in fact correspond to this chemical formula. When the initial M2+/[AuF6]- ratio was 1:1, single crystals of [M(HF)](H3F4)(AuF6) were grown for M = Sr. The crystal structure consists of a 3-D framework formed by [Sr(HF)]2+ cations associated with [AuF6]- and [H3F4]- anions. The latter exhibits a Z-shaped conformation, which has not been observed before. Single crystals of M(BF4)(AuF6) (M = Sr, Ba) were grown when a small amount of BF3 was present during crystallization. Sr(BF4)(AuF6) crystallizes in two modifications. A high-temperature α-phase (293 K) crystallized in an orthorhombic unit cell, and a low-temperature β-phase (150 K) crystallized in a monoclinic unit cell. For Ba(BF4)(AuF6), only an orthorhombic modification was observed in the range 80-230 K. An attempt to grow crystals of Ca(BF4)(AuF6) failed. Instead, crystals of [Ca(HF)](BF4)2 were grown and the crystal structure was determined. During prolonged crystallization of [AuF]6- salts, moisture can penetrate through the walls of the crystallization vessel. This can lead to partial reduction of Au(V) to A(III) and the formation of [AuF4]- byproducts, as shown by the single-crystal growth of [Ba(HF)]4(AuF4)(AuF6)7. Its crystal structure consists of [Ba(HF)]2+ cations connected by AuF6 octahedra and square-planar AuF4 units. The crystal structure of the minor product [O2]2[Sr(HF)]5[AuF6]12·HF was also determined.
There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross-sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements.
Piezoelectric resonance impedance spectroscopy is a standardized measurement technique for determining the electromechanical, elastic, and dielectric parameters of piezoceramics. However, commercial measurement setups are designed for small-signal measurements and encounter difficulties when constant driving voltages/currents are required at resonances, higher fields, or combined AC and DC loading. The latter is particularly important to evaluate the DC bias-hardening effect of piezoelectrics. Here, we propose a novel measurement system for piezoelectric resonance impedance spectroscopy under combined AC and high-voltage DC loading that complies with established standards. The system is based on two separate output amplifier stages and includes voltage/current probes, a laser vibrometer, custom protection components, and control software with optimization algorithm. In its current form, the measurement setup allows the application of AC frequencies up to 500 kHz and DC signals up to +/-10 kV on samples with impedance between 10-1 and 106 Ω. The operation of the proposed setup was benchmarked against commercial impedance analyzers in the small-signal range and reference equivalent circuits. Test measurements under combined AC and DC loading were performed on a soft Pb(Zr,Ti)O3 piezoceramic. The results revealed that a DC bias voltage applied along the polarization direction ferroelectrically hardens the material, while the material softens and eventually depolarizes when the DC bias voltage is applied in the opposite direction. The results confirm the suitability of the designed measurement system and open new exciting possibilities for tuning the piezoelectric properties by DC bias fields.
4-Aryl-3-thiocyanatobutan-2-ones were prepared by Meerwein reactions from methyl vinyl ketone and aryldiazonium salts under copper(II) catalysis in 35-75% yields. α-Thiocyanato ketones regioselectively react with 1-methyl-3-aminopyrazole forming N-(3-pyrazolyl)-substituted 2-aminothiazoles in 80-91% yields. An ester group in position 3 of the pyrazole induced a regioselective ring-closure reaction followed by an intramolecular cyclization, which gave first representatives of a new heterocyclic system, pyrazolo[4,3-e]thiazolo[3,2-a]pyrimidine, in 74-93% yields. In addition, the preparations of 5-benzyl-4-methylthiazol-2-ones in 84-93% yields are described.
The data used for analysis are becoming increasingly complex along several directions: high dimensionality, number of examples and availability of labels for the examples. This poses a variety of challenges for the existing machine learning methods, related to analyzing datasets with a large number of examples that are described in a high-dimensional space, where not all examples have labels provided. For example, when investigating the toxicity of chemical compounds, there are many compounds available that can be described with information-rich high-dimensional representations, but not all of the compounds have information on their toxicity. To address these challenges, we propose methods for semi-supervised learning (SSL) of feature rankings. The feature rankings are learned in the context of classification and regression, as well as in the context of structured output prediction (multi-label classification, MLC, hierarchical multi-label classification, HMLC and multi-target regression, MTR) tasks. This is the first work that treats the task of feature ranking uniformly across various tasks of semi-supervised structured output prediction. To the best of our knowledge, it is also the first work on SSL of feature rankings for the tasks of HMLC and MTR. More specifically, we propose two approaches—based on predictive clustering tree ensembles and the Relief family of algorithms—and evaluate their performance across 38 benchmark datasets. The extensive evaluation reveals that rankings based on Random Forest ensembles perform the best for classification tasks (incl. MLC and HMLC tasks) and are the fastest for all tasks, while ensembles based on extremely randomized trees work best for the regression tasks. Semi-supervised feature rankings outperform their supervised counterparts across the majority of datasets for all of the different tasks, showing the benefit of using unlabeled in addition to labeled data.
Yttrium manganite, YMnO3, was doped with different concentrations of titanium (x = 0, 0.04, 0.08, 0.10, 0.15, 0.20) in order to improve the microstructural and multiferroic properties. The powders were prepared using sol-gel polymerization complex method from citrate precursors. Depending on the titanium concentration, the hexagonal structure and/or the rhombohedral superstructure are present in the sintered samples. The YMn1–xTixO3+δ (x = 0.10, 0.15, 0.20) ceramic samples showed significantly reduced density of microcracks, and of inter- and intragranular pores, and relative densities greater than 90%. The structural parameters for YMn1–xTixO3+δ (x = 0, 0.10, 0.15) were correlated with the results of magnetic and ferroelectric measurements. The most of titanium-doped samples showed a reduction of the leakage current density in comparison with undoped YMnO3, and their ferroelectric responses were slightly improved. The modifications in structural arrangement resulted in partial suppression of ideal antiferromagnetic ordering visible through decrease of the Néel temperature and Weiss parameter, as well as the appearance of weak ferromagnetism and increase of magnetization (especially, in samples x = 0.08, 0.10, 0.15). These changes in physical quantities most likely originated from incorporation of the uncompensated magnetic moments and possible spin canting induced by enhanced symmetry break of the superexchange bridges. Graphical abstract
Purpose of Review The ability to autonomously manipulate the physical world is the key capability needed to fulfill the potential of cognitive robots. Humanoid robots, which offer very rich sensorimotor capabilities, have made giant leaps in their manipulation capabilities in recent years. Due to their similarity to humans, the progress can be partially attributed to the learning by demonstration paradigm. Supplemented by the autonomous learning methods to refine the demonstrated manipulation actions, humanoid robots can effectively learn new manipulation skills. In this paper we present continuous effort by our research group to advance the manipulation capabilities of humanoid robots and bring them to autonomously act in an unstructured world. Recent Findings The paper details progress in the area of humanoid robot learning, ranging from trajectory imitation, motion adaptation in order to maintain feasibility and stability, and learning of dynamics to statistical generalization of actions, autonomous learning, and end-to-end vision-to-action learning that exploits deep neural networks. Summary With the focus on manipulation, the presented research provides the means to overcome the complexity behind the problem of engineering manipulation skills on robots, especially humanoid robots where programming by demonstration is most effective.
Magnetic nanoplatelets (NPLs) based on barium hexaferrite (BaFe12O19) are suitable for many applications because of their uniaxial magneto-crystalline anisotropy. Novel materials, such as ferroic liquids, magneto-optic composites, and contrast agents for medical diagnostics, were developed by specific surface functionalization of the barium hexaferrite NPLs. Our aim was to amino-functionalize the NPLs' surfaces towards new materials and applications. The amino-functionaliza-tion of oxide surfaces is challenging and has not yet been reported for barium hexaferrite NPLs. We selected two amine ligands with two different anchoring groups: an amino-silane and an amino-phosphonate. We studied the effect of the anchoring group, backbone structure, and processing conditions on the formation of the respective surface coatings. The core and coated NPLs were examined with transmission electron microscopy, and their room-temperature magnetic properties were measured. The formation of coatings was followed by electrokinetic measurements, infrared and mass spectroscopies, and thermogravimetric analysis. The most efficient amino-functionaliza-tion was enabled by (i) amino-silanization of the NPLs precoated with amorphous silica with (3-aminopropyl)triethoxysilane and (ii) slow addition of amino-phosphonate (i.e., sodium alendro-nate) to the acidified NPL suspension at 80 °C.
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913 members
Boris Turk
  • Department of Biochemistry, Molecular and Structural Biology
Eva Zerovnik
  • Department of Biochemistry, Molecular and Structural Biology
Matjaz Gams
  • Department of Intelligent Systems
Jamova 39, 1000, Ljubljana, Slovenia
Head of institution
Prof. dr. Boštjan Zalar