1. Alternative alkali activators based on waste bottle glass and waste cathode-ray tube glassKatja Koenig, Katja Traven, Vilma Ducman, 2021, published scientific conference contribution Abstract: Alkali-activated binders are an environmentally friendly alternative to Portland cement, particularly when locally-available raw materials are used. It is well known that alkali activation with a sodium silicate activator generates a hardened binder with higher compressive strength than a binder hardened with sodium hydroxide. As the alkali-silicate activators are produced through energy extensive processes, and their use can significantly increase the carbon footprint of the final products, it is of great significance to develop alternative alkaline activators based on locally-available waste materials. This article assesses the potential to apply waste bottle glass and waste cathode-ray tube (CRT) glass to synthesise alternative alkali activators by the hydrothermal method. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to determine silicon and aluminium content in the alternative activators. The influence of dissolution process parameters (time, temperature, particle size) on the concentrations of silicon and aluminium in the alternative activators was investigated. The alternative activators with silicon concentration up to 19 g/L and aluminium concentration up to 0.9 g/L were prepared at T = 120 °C and boiling time 24 h. The alternative alkali activators and, for comparison, also commercial sodium silicate were used in the alkali activation of fly ash powder. The formed pastes were cured at 70 °C for 72 h. Mechanical strength measurements indicated that alkali activation of fly ash with the optimal alternative activator yielded hardened paste with compressive strength of 33 MPa. However, the compressive strength of hardened paste prepared from fly ash and commercial sodium silicate reached 70 MPa. Part of this difference can be ascribed to the lower density of hardened pastes prepared with alternative activators.
Keywords: alkali -activated materials, alternative alkali activators, waste bottle glass, waste cathode -ray tube glass, fly ash, hydrothermal method
Published in DiRROS: 25.01.2024; Views: 149; Downloads: 101
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3. New insights into manganese local environment in MnS-1 nanocrystalsAlenka Ristić, Matjaž Mazaj, Iztok Arčon, Nina Daneu, Nataša Zabukovec Logar, Roger Gläser, Nataša Novak Tušar, 2019, original scientific article Keywords: MnS-1 nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis
Published in DiRROS: 23.11.2020; Views: 12008; Downloads: 845
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4. Structural and degradation studies of a biocompatible Zn-L-tartrate metal-organic frameworkAna Palčić, Andreas Puškarić, Matjaž Mazaj, Emanuela Žunkovič, Nataša Zabukovec Logar, Josip Bronić, 2015, original scientific article Abstract: New anhydrous Zn-l-tratrate was synthesized under hydrothermal conditions. Crystal structure which was solved by powder X-ray diffraction data from monoclinic unit cell (I2, a=11.7557(1), b=9.0319(1), c=5.0750(1), β=91.920(1)) consists of the three-dimensional framework where each Zn atom coordinates four tartrate ligands in distorted octahedral geometry. Due to its biocompatible components, the degradation of material was studied in aqueous media under different pH values (pH=1–7) and in the simulated body fluid (pH=7.4) performed by the measurement of the released Zn2+ concentrations at thermostatic conditions (37 °C). The results showed that under acidic conditions approximately 60% of Zn2+ is released from the investigated material after 6 h of degradation process. With the increase of the solution’s pH, the rate of degradation gradually decreases. XRD and SEM analyses indicate that in aqueous media the compound slowly disintegrates and does not undergo hydrolysis process regardless of pH. Biocompatibility of the compound and its controllable rate of degradation even in acid conditions open its potential use in the fields of bio-applications.
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The degradation kinetics of Zn-l-tar MOF material in aqueous media at different pH conditions.
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Keywords: Zn-tartrate, coordination polymers, hydrothermal synthesis, biomedical application, food supplement
Published in DiRROS: 26.01.2015; Views: 4983; Downloads: 465
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