Vinča Institute of Nuclear Sciences
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描述金属氢化物反应器中反应-传热耦合现象的理论模型构建
No full textIn order to improve the theoretical model of metal hydride reactors and achievc an accurate description of the reaction process of the rcactor, the classical Stefan problem is utilizcd to describe the hydrogen-thermal coupling phenomenon inside the metal hydride reactor, simplifying it into a reaction front advancc problem. By combining the thermal potential theory and the caloric theory proposed by Guo Zengyuan et al, a ncw modified method based on the "thermal potential" theory is introduced. In this method, whcn solving for the dissipation function, instead of differentiating the thermal displacement field into two parts based on its relationship with the internal heat source, the entire thermal displacement field is diffcrcntiatcd as a whole. As a rcsult, it was found that compared with the literature results, the approximate solution obtained by the modified method of thermal potential theory encompassed the existing theoretical models structurally and exhibited high accuracy* with an average error of 0. 6% compared to the simulation results. Research has shown that utilizing the reaction front advance model to describe hydrogen-heat coupling phenomena in the reactor is reasonable, and the proposed theoretical model can provide reasonable and accurate predictions for the reaction process under different operating conditions. © 2025 Xi'an Jiaotong University. All rights reserved.为了完善金属氢化物反应器理论模型，实现精确描述反应器内部反应过程，利用经典的Stefan问题，描述金属氢化物反应器内部的氢热耦合现象，将之简化为反应锋面推进问题。通过结合热势理论和过増元等的热质理论，提出了一套新的基于热势理论的修正求解方法。该方法在求解耗散函数过程中，不再依照热位移场与内热源的关系将热位移场区分为两个部分分别求导，而是对热位移场整体进行求导。结果发现，与文献结果对比，热势理论修正方法求得的近似解在结构上涵盖了现有的理论模型，且具有较高的精度，与模拟结果的平均误差为0.6%。研究表明，利用反应锋面推进模型描述反应器中氢热耦合现象是合理的，所构建的理论模型可以对不同工况下的反应过程进行合理及精确的预测
Discovery of a new zinc oxide semiconductor: 21R polytype
No full textZinc oxide (ZnO) is a notable semiconductor with a range of interesting electronic and optical properties. Polytypic behavior of crystal structures can strongly affect the properties of materials, especially in ZnO. We report the first prediction of a new 21R polytype in zinc oxide with advanced properties. Ab initio calculations were carried out using two-hybrid functionals: HSE06 and PBE0. Structural properties of different ZnO polytypes were investigated, and theoretical data concurred with experimental results. This can be further exploited for various applications based on their unique properties. Electronic properties were studied using band structures and density of states (DOS). Present DFT calculations agree very well with previous calculations and measurements of known ZnO polytypes, and the new 21R polytype is found as a direct band gap semiconductor. The size of the band gap in the case of the hybrid HSE06 functional is calculated to be 2.79 eV and with PBE0 is 3.42 eV. Understanding the structure–property relationship helps in tailoring ZnO for specific applications and optimizing its performance in various technological contexts, especially as an advanced semiconductor material, with possible applications such as 0D, 1D, 2D, and 3D materials
Antimicrobial properties of hydroxyapatite material obtained by green technology pathway
No full textDue to increasingly intense problems in terms of resistance to various types of infections, including bacterial resistance to antibiotics, new materials with effective contact antimicrobial action are intensely being researched. Hydroxyapatite (HAp) represents the leading material from the calcium-phosphate group, which can be used as a biocompatible material, in environmental protection as an adsorbent for heavy metal removal from polluted waters, and also as an antimicrobial agent. The wide specturm of use of this material lies in its structural and functional properties. The main goal of this work was to obtain pure nanocrystalline hydroxyapatite material, using green technologies, i.e. precursors that are ecologically acceptable for the environment such as hydrogen phosphates as a source of PO4 and hydroxide as a source of Ca. Synthesized HAp nanocrystalline material was structurally investigated by X- ray diffraction method and morphological properties are investigated by scanning electron microscopy method. Based on obtained results pure nanocrystalline material was obtained with average crystallite sizes about 10 nm and hexagonal symmetry. The microstructural results confirms proper crystal grains small in sizes agglomerated in larger forms. The antibacterial activity of the obtained HAp was tested against Gram-positive bacteria Staphylococcus aureus, Listeria monocytogenes, and Gram-negative bacteria Pseudomonas aeruginosa and Acinetobacter baumanii by total plate count assay. Results shows that obtained material posses the best antimicrobial properties against Staphylococcus aureus with 50% and Acinetobacter baumanii with 45% of efficiency while for Pseudomonas aeruginosa and Lysteria monocytogenes shows 20% and 8% of efficiency compared to the control. Obtained HAp material at a concentration of 50 mg/mL showed a reducing property towards the bacteria.EEM2025 - 9th International Congress Engineering, Environment and Materials in Process Industry; 2-4 april 2025; Bijeljina, Republic of Srpska, Bosnia and Herzegovina
Swelling Behavior, Biocompatibility, and Controlled Delivery of Sodium–Diclofenac in New Temperature-Responsive P(OEGMA/OPGMA) Copolymeric Hydrogels
No full textThis study investigates the synthesis and properties of innovative poly(oligo(alkylene glycol)) methacrylate hydrogels synthesized via gamma radiation-induced copolymerization and the crosslinking of oligo(ethylene glycol) methacrylate (OEGMA) and oligo(propylene glycol) methacrylate (OPGMA) at varying mole fractions. Our primary objective is to investigate the impact of copolymerization on the swelling properties of P(OEGMA/OPGMA) hydrogels compared to their homopolymeric counterparts, namely, POEGMA and POPGMA, which exhibit distinct volume phase transition temperatures (VPTTs) of around 70 and 13 °C, respectively, under physiological conditions. To this end, a comprehensive library of smart methacrylate-based hydrogel biomaterials was developed, featuring detailed data on their swelling behavior across different copolymer molar ratios and physiological temperature ranges. To achieve these objectives, we conducted swelling behavior analysis across a wide range of temperatures, assessed the pH sensitivity of hydrogels, utilized scanning electron microscopy for morphological characterization, performed in vitro biocompatibility assessment through cell viability and hemolysis assays, and employed diclofenac sodium as a model drug to control drug delivery testing. Our findings demonstrate that the newly synthesized P(OEGMA40/OPGMA60) copolymeric hydrogel exhibits desirable characteristics, with VPTT close to the physiological temperatures required for controlled drug delivery applications
Temperature tunable biopolymer photonic structure
No full textTunable biopolymer photonic structures responsive to temperature changes are investigated. Two types of biopolymers are employed: pullulan, characterized by a linear polysaccharide structure, and dextran, which has a branched configuration. The photonic structures are fabricated by holographic recording in dichromate-doped pullulan and dextran. Properties of pululan [1,2] and dextran [3] films as holographic material - surface gratings, its diffraction efficiency, copying and environmental stability, were previously investigated. Photonic structures, fabricated using a simple counter-propagating beam holographic setup, consist of multilayered biopolymer configurations, separated and supported by nanopillars. This complex morphology is formed through the combined action of holographic recording and nonsolvent-induced phase separation. The optical properties of the resulting biopolymer photonic structures were analyzed during heating and cooling cycles. A Peltier element was used to control the sample temperature, while reflection spectra from white halogen light were recorded using a fiber-optic spectrometer. During heating, the reflectance peaks shifted toward shorter wavelengths (blue-shifted), showing a negative spectral shift of 60 nm for pullulan and 27 nm for dextran with a temperature increase of +50 K. Upon cooling, the spectral peaks nearly returned to its original position.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia
Effects of high heat flux obtained by pulsed laser irradiation on PM 316L alloy
No full text316L alloy, known for its excellent mechanical properties up to 600 °C and massive application in various industries, is considered as one of the important candidates for fusion reactor construction materials, as well as matrix for other potential materials with this purpose. It belongs to the class of austenitic steels, which are only lately considered as a basis for the so-called oxide dispersion strengthened (ODS) steels, where ceramic nanoparticles ensure endurance of the material at temperatures over 700 °C, under high pressure and neutron irradiation. Austenitic ODS steels, including 316L-based, are still being developed and, although ferritic steels are studied as well, they are expected to perform better in regards to certain high temperature properties [1]. 316L steel can be synthesized through different routes – aside from conventional casting, it can be obtained from powders by novel method of selective laser method (SLM), as well as contemporary techniques of powder metallurgy (PM) used in this work. Samples were then subjected to laser irradiation in vacuum which, in one approximation, could simulate high heat fluxes present in the reactor. Since materials are also exposed to the effects of light species, preliminary results of conventionally obtained 316L irradiated by ultrashort laser pulses in He atmosphere are also given. Synthesis of 316L alloy comprised hot pressing of powders, using following process parameters: temperature 1150 °C, holding time 2 h, pressure 40 MPa, argon atmosphere. Density of the obtained samples, determined by Archimedes method, was about 90% of the theoretical value. Laser irradiation was done using picosecond Nd:YAG laser with energies up to 30 mJ at different number of delivered pulses (up to 500). XRD analysis has identified austenite as dominant phase with FCC crystal structure. Microstructural characterization was performed using SEM-EDS. Based on the obtained SEM images of the surface damages in vacuum, damage threshold for 500 pulses was estimated to be about ~0.9 J/cm2.X International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; 25 - 29 August 2025 Belgrade, Serbia
Novel multiphase composite electrode decorated with Pd nanoparticles for electrochemical determination of herbicides
No full textThis study investigates the electrochemical determination of dicamba (3,6-dichloro-2-methoxybenzoic acid, DIC) and 2,4-D-dichlorophenoxyacetic acid (2,4-D) using a palladium (Pd)-decorated multiphase composite electrode (TiN/Ti1.886O3/MgTiO3/Mg2TiO4) denoted as Pd@MPC. The synergistic coexistence and contact between these phases improved the electrochemical performance of the material and provided complementary properties such as electrical conductivity (from TiN and Pd), chemical stability (of MgTiO3), and surface reactivity (of Ti1.86O3 and Pd), which are crucial for efficient electroanalytical applications. The electrode material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM), which confirmed the successful incorporation of Pd nanoparticles and significantly improved the catalytic properties. Pd, which is known for its excellent electrocatalytic activity, especially in oxidation reactions, facilitates the electrochemical detection of pesticides such as DIC and 2,4-D. The Pd nanoparticles likely serve as active sites for the oxidation of pesticides and improve the sensitivity and selectivity of the sensor. Voltammetric analyses showed that the Pd@MPC/GC electrode exhibited significantly better electrocatalytic activity compared to a commercially available glassy carbon electrode. The results showed that pH strongly influenced the signal-to-noise ratio, with optimal analytical performance achieved at pH 2.0. The developed method showed linearity within a concentration range of 4.99 to 53.82 ng/mL, with correlation coefficients of r = 0.998 for DIC and r = 0.990 for 2,4-D, and a detection limit of 3.03 ng/mL. Recovery tests in river water samples showed a recovery rate of 101%, which is consistent with the results of the HPLC/DAD method used as a comparative method. These results underline the effectiveness of the Pd@MPC/GC electrode for environmental monitoring applications
Active Packaging Based on Hydroxypropyl Methyl Cellulose/Fungal Chitin Nanofibers Films for Controlled Release of Ferulic Acid
No full textIn recent years, active packaging has become a focal point of research and development in the food industry, driven by increasing consumer demand for safe, high-quality, and sustainable food products. In this work, solvent casting processed an active antibacterial multicomponent film based on hydroxypropyl methylcellulose incorporated with ferulic acid and chitin nanofibers. The influences of ferulic acid and different content of chitin nanofibers on the structure, thermal, mechanical, and water vapor stability and antioxidant and antibacterial efficiency of films were studied. It was shown that the inclusion of only ferulic acid did not significantly influence the mechanical, water vapor, and thermal stability of films. In addition, films containing only ferulic acid did not display antibacterial activity. The optimal concentration of chitin nanofibers in hydroxypropyl methylcellulose–ferulic acid films was 5 wt%, providing a tensile strength of 15 MPa, plasticity of 52%, and water vapor permeability of 0.94 × 10−9 g/m s Pa. With further increase of chitin nanofibers content, films with layered and discontinuous phases are obtained, which negatively influence tensile strength and water vapor permeability. Moreover, only films containing both ferulic acid and chitin nanofibers demonstrated antibacterial activity toward E. coli and S. aureus, suggesting that the presence of fibers allows easier release of ferulic acid from the matrix. These results imply that the investigated three-component systems have potential applicability as sustainable active food packaging materials
Rubber-based rubber blends, composites, and nanocomposites
No full textBlending two or more rubbers or rubbers with polymers has been a novel technique to obtain the desired properties from blends at low cost. Composites are engineered or naturally occurring solid materials that result when two or more different constituent materials, each having its significant characteristic (physical or chemical properties), are combined to create a new substance with superior properties to original materials in a specific finished structure. Nanocomposites are those composites in which one phase has nanoscale morphology such as nanoparticles, nanotubes, or lamellar nanostructure. Rubber-based rubber blends, composites, and nanocomposites have been considered suitable for several essential applications such as electro-catalysts in batteries for energy saving; low-weight materials for less fuel consumption; in artificial joints, economically beneficial; carbon nanotubes most widely speaking nanomaterial, which can be made as nanocomposite fibers; abrasion and wear; marine application; food packaging; fuel tanks; films; environmental protection; flame ability reaction; erosion and corrosion
Eu3+- activated Sr2GdF7 colloid and nano-powder for horticulture LED applications
No full textA series of multifunctional Sr2Gd1-xEuxF7 (x = 0, 0.05, 0.10, 0.40, 0.60. 0.80, and 1.00) phosphors in stable colloidal form and as nanopowders have been prepared using a hydrothermal method. Powder X-ray diffraction analysis confirmed that the materials crystallize in a cubic crystal structure. Transmission electron microscopy shows quasi-spherical nanoparticles with an average particle size of ∼24 nm. Photoluminescence measurements show highly efficient red emission in both colloids and nanopowders, with intensity continually increasing up to 80 mol% of Eu3+ content without concentration quenching. The most prominent emission peaks are around 600 nm (orange/red) and 700 nm (deep red), with the latter more pronounced. Quantum efficiency follows a similar trend, and reaches 60 % for the sample with 80 mol% of Eu3+ content. In addition, similar asymmetry ratio values and CIE coordinates show that there is not a big change in the local symmetry around Eu3+ ions or emission color across the series. This confirms that Eu3+ resides in the same crystalline environment in samples. The observed 5D0-level lifetimes gradually decrease from 12.0 ms to 6.9 ms as the Eu3+ concentration increases. Judd-Ofelt parameters show slight variation with Eu3+ concentration with Ω4 always larger than Ω2. The temperature-dependent steady-state and time-resolved photoluminescence measurements demonstrate high stability of nanopowders’ emission up to 100 °C. The combination of temperature stability and high efficiency of emission, as well as the untypical dominant deep-red emission at 700 nm labels these nanoparticles as potential nanophosphors for various applications. © 2024 The Author