1. Interface-governed electromechanical coupling in bioinspired hierarchical piezoelectric poly(l-lactide) architecturesMartina Žabčić, Lea Gazvoda, Masoumeh Sepideh Salehidashtbayaz, Ita Junkar, Selestina Gorgieva, Andraž Rešetič, Matjaž Spreitzer, Marija Vukomanović, 2026, original scientific article Keywords: piezoelectric materials, polyimide, bioinspired materials
Published in DiRROS: 21.04.2026; Views: 201; Downloads: 95
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2. Piezostimulation using ultrasound-active poly-L-lactide films : the effects of a ZnO filler and cold atmospheric plasma surface treatmentŠpela Štor, Martina Žabčić, Lea Gazvoda, Masoumeh Sepideh Salehidashtbayaz, Ita Junkar, Tina Radošević, Matejka Podlogar, Martin Šala, Matjaž Spreitzer, Marija Vukomanović, 2026, original scientific article Abstract: Piezostimulation has the potential to promote human cell growth while inhibiting bacterial growth. Antimicrobial action physically destroys the bacterial cell wall without providing bacteria with too many options for developing resistance. However, the mechanism is typically not fast enough to follow the rapid kinetics of microbial growth, and improvement of the efficacy is needed. Here, we show that the synergy of bulk modification with a ZnO filler and surface modification with cold atmospheric plasma leads to a highly functional organic piezoelectric biomaterial. Specifically, the ZnO filler strengthens the piezoelectric response of piezoelectric poly-L-lactide (piezo-PLLA) after its integration into the polymer bulk, whereas the plasma surface treatment changes the surface chemistry and partially reveals integrated ZnO particles on the surface. Both effects significantly affected piezostimulation and improved the interactions with two types of cells. Specifically, the increased content of ZnO NPs in the piezo-PLLA films increased the contact of both bacteria (E. coli) and human keratinocytes (HaCaT) with the film surface. Consequently, after activation with ultrasound (1 MHz), the surface very effectively transferred the signal to the adhered cells, which resulted in fast and effective antimicrobial activity. Moreover, for adhered HaCaT cells, stimulation promoted proliferation, cell mobility, intercellular connections and cytoskeleton formation. In combination, these two types of interactions are very important for promoting skin regeneration and wound healing.
Keywords: piezostimulation, antimicrobial surfaces, poly-L-lactide films
Published in DiRROS: 18.03.2026; Views: 332; Downloads: 196
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3. Steering the ▫$Bi_4Ti_3O_{12}-to-SrTiO_3$▫ hydrothermal transformation for controlling the functionality of two-dimensional (2D) ▫$SrTiO_3$▫ nanoplatelets for photocatalytic ▫$H_2$▫ evolutionMarjeta Maček, Nina Daneu, Kamal Khaja Mohaideen, Blaž Likozar, Alja Čontala, Matjaž Spreitzer, Jeffrey C. S. Wu, Suraj Gupta, 2026, original scientific article Keywords: hydrogen production, nanoplatelets, hydrothermal transformation
Published in DiRROS: 08.01.2026; Views: 648; Downloads: 352
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4. Strain-controlled superconductivity in epitaxially grown thin films of ▫$1T-TaS_2$▫Yelyzaveta Chernolevska, Anže Mraz, Rok Venturini, Bojan Ambrožič, Tomaž Mertelj, Goran Dražić, Damjan Svetin, Damjan Vengust, Hsin-Chia Ho, Matjaž Spreitzer, Dragan Mihailović, 2025, original scientific article Keywords: transition metal dichalcogenides, thin films, molecular beam epitaxy
Published in DiRROS: 26.11.2025; Views: 1082; Downloads: 305
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5. Effect of hydrothermal treatment on the structure and foaming of waste glassUroš Hribar, Matjaž Spreitzer, Jakob Koenig, 2026, original scientific article Abstract: This study explores the potential of hydrothermally treated waste glass for producing foamed glass using a carbonaceous foaming agent (glycerol) in an air atmosphere. The objective was to assess the feasibility of this alternative route for producing sustainable, lightweight materials with reduced energy and material inputs by repurposing cathode ray tube panels (CRT), flint glass (FG), and mixed-color container glass (MCG). Investigated glass powders were treated in a saturated steam atmosphere inside a pressure vessel and characterized using Xray diffraction and Fourier-transform spectroscopy to identify structural changes. The foaming behavior of hydrothermally treated waste was analyzed through heating stage microscopy and thermogravimetric analysis coupled with mass spectrometry. The foamed glass samples were further assessed for density and thermal conductivity. The results demonstrate that hydrothermal treatment significantly influences the foaming process. Glass powders with higher content of structurally bonded water exhibit lower sintering temperature and pronounced expansion after the hydrothermal treatment. A higher hydration level reduced the onset foaming temperature and facilitated higher expansion. Additionally, combining hydrothermally treated powders with glycerol as a foaming agent enabled effective expansion, even in an air atmosphere, achieving density as low as 108 kg m-3. The results of this study suggest that hydrothermal treatment of waste glasses enables the implementation of carbonaceous foaming agents in the air atmosphere and could thus offer an alternative route for the foaming of glass.
Keywords: foamed glass, waste glass, hydrothermal treatment
Published in DiRROS: 18.11.2025; Views: 593; Downloads: 296
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6. Optimizing foamed glass production with machine learningUroš Hribar, Sintija Stevanoska, Christian Leonardo Camacho Villalón, Matjaž Spreitzer, Jakob Koenig, Sašo Džeroski, 2025, original scientific article Abstract: Foamed glass is a lightweight material commonly used for insulation. However, optimizing its properties remains a challenge due to the large number of synthesis parameters involved in its production. While previous studies have investigated synthesis conditions, a comprehensive study applying machine learning approaches is lacking in the literature. In this paper, we apply machine learning methods, i.e., random forests of predictive clustering trees and a multilayer perceptron, training them on 124 experimental data points to accurately predict the apparent density and closed porosity of foamed glass. We then apply a multiobjective optimization algorithm together with the multilayer perceptron to find optimal values for the process parameters used in foamed glass production. Our results show that the combination of machine learning and multiobjective optimization is an effective proxy for the development of novel foamed glass materials.
Keywords: process optimization, machine learning, foamed glass
Published in DiRROS: 18.11.2025; Views: 744; Downloads: 279
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7. Enhancing densification of metakaolin-based geopolymers via the cold sintering processAbdullah Jabr, Srečo D. Škapin, Sara Tominc, Nina Daneu, Jakob Koenig, Vilma Ducman, Lidija Korat Bensa, Raúl Bermejo, Matjaž Spreitzer, 2025, original scientific article Abstract: Clay-based materials typically require high-temperature processing (>900 ◦C), resulting in high energy consumption. This study explores cold sintering of metakaolin (MK) powders to achieve high mechanical strength at significantly lower processing temperatures. By applying uniaxial pressure of 400 MPa and heating to only 240 ◦ C in the presence of 15 mol/L NaOH solution, successful densification of structurally sound and dense samples with an average density of 2.16 g/cm³ and a biaxial flexural strength of ~35 MPa was achieved. This strength surpasses that of conventionally sintered MK (1470 ◦C) by ~30 %. Densification was found to be governed by synergistic mechanisms involving MK exfoliation, conformal sintering around aggregates, and the precipitation of an amorphous sodium aluminosilicate hydrate phase. Crack formation was avoided through process optimization and verified using X-ray micro-computed tomography. These findings offer new insights into the chemo- mechanical mechanisms of cold sintering and demonstrate its potential as an efficient route for producing structural materials.
Keywords: cold sintering, metakaolin, geopolymer, delaminations, exfoliation
Published in DiRROS: 15.10.2025; Views: 576; Downloads: 305
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9. Unlocking high capacitive energy-density in Sm-doped ▫$Pb(Mg_{1/3}Nb_{2/3})O_3–PbTiO_3$▫ thin films via strain and domain engineeringZouhair Hanani, Jamal Belhadi, Nina Daneu, Urška Trstenjak, Nick A. Shepelin, Vid Bobnar, Thomas Lippert, Matjaž Spreitzer, 2025, original scientific article Keywords: relaxor ferroelectrics, thin films, strain analysis, electronic ceramics
Published in DiRROS: 17.04.2025; Views: 1170; Downloads: 528
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10. Characterization and Mechanical Properties of Sintered Clay MineralsSara Tominc, Vilma Ducman, Jakob Koenig, Srečo D. Škapin, Matjaž Spreitzer, 2024, published scientific conference contribution Abstract: The need to reduce energy consumption and the carbon footprint generated by firing ceramics has stimulated research to develop sintering processes carried out at lower temperatures(ideally not above 300 °C) and high pressures (up to 600 MPa), the so-called cold sintering process (CSP) (Grasso et al., 2020, Maria et al., 2017). To evaluate the applicability of CSP to clays, we focused on two representative clay minerals, kaolinite and illite, and on the natural clay material obtained from a Slovenian brick manufacturer. The selected clay materials were characterized on the basis of mineralogical-chemical composition (XRD, XRF) and particle size distribution (SEM analysis, PSD, BET). The powders of clay minerals and natural clay material were first sintered in a heating microscope to determine the sintering conditions and then in a laboratory furnace at 1100 °C for 2 hours and additionally at 1300 °C for kaolinites. The effect of compression of the initial powders on their final properties was also investigated.
Keywords: conventional sintering, cold sintering, clay minerals, characterization, mechanical properties
Published in DiRROS: 29.03.2024; Views: 2594; Downloads: 831
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