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A powdered PVA/CaCO3 nanocomposite carrier was successfully fabricated for effective loading of small bioactive molecules, such as vitamin D3 (VD3). Generation of, namely, VD3/PVA/CaCO3 nanocomposite scaffold was carried out through an adsorption mechanism as a loading route of an active compound onto a powder carrier. Developed composites were characterized by structural, morphological and thermal analyses techniques, such as X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, MALDI (matrix-assisted laser desorption/ionization) – mass spectrometry (MS), Brunauer–Emmett–Teller (BET) – NLDFT (Non-local Density Functional Theory) method, scanning electron microscopy (SEM), simultaneous TG-DTG and coupled TG-MS. XRD results showed that the average crystallite size of synthesized VD3/PVA/CaCO3 amounts 32.93 nm exhibiting microstrain presence, where PVA incorporation causes non-uniform calcite lattice distortion. SEM analysis showed that VD3/PVA/CaCO3 nanocomposite scaffold contains agglomerated rhomboidal calcite particles with VD3 particles of irregular shapes attached. Fabricated VD3/PVA/CaCO3 clearly showed the existence of calcite “staircase” dendrites as the aftermath of inhibiting the effect of impurities on the growth of crystals in normal directions. It was determined that the decomposition of PVA additionally enhances the thermal stability of VD3, through the stabilization effect by acting on van der Waal’s forces during polyene formation, confirmed by MALDI-TOF MS results.

The challenges of modern society and the requirements for high-tech materials have led to a new stage in the development of chemical synthesis methods. This stage is demanding a reliable, controllable, and green approach to the production of necessary materials. One of the recently developed approaches for metal oxide nanoparticles synthesis is the solvent deficient method. A cutting edge of this synthetic method is a synthesis with increased control throughout chemical transformation resulting in optimal conditions for materials production. As a result, oxide nanoparticles are produced fast, environmentally friendly, cost-effective, and with low energy consumption. On the other hand, a complex reaction mechanism is presenting a challenge for reliable kinetic studies. The present review follows the recent trends in the development of the solvent deficient method concerning the binary, ternary, and complex metal oxides. Special attention is given to considering approaches responsible for desirable mechanisms of catalytic applications. In future development, the reported synthesis method is expected to be employed in a high entropy oxides formation. Due to simple preparation steps, it will be possible to automatize the reaction procedure and investigate a large number of possible compositions which is imperative for new complex materials. Finally, precursors heating could be transformed from conventional to microwave. Solvent-deficient method deals with precursors sensitive to microwave irradiation which could ensure rapid heating and transformation to desirable oxide nanomaterials.

This study presents the results of the iron oxide content determination in bauxite by means of inductively coupled plasma optical emission spectrometry (ICP-OES), volumetry, and UV–VIS spectrophotometry. Nine certified bauxite reference samples with Fe2O3 content from 7.14 to 28.20% were analyzed. Two methods of bauxite sample preparation were applied: melting with a mixture of Na2CO3:Na2B4O7 (3:1) and dissolving with a combination of acids (HCl, HNO3, and H2SO4). The recovery value for all the methods used in relation to the certified values was in the range from 92.41% to 113.87%. By using statistical tests, it has been confirmed that the results of ICP-OES analysis generally agree with other methods, which supports its adoption as an alternative for Fe2O3 determination in bauxite. Due to a shorter preparation time and complete dissolution, it is recommended to prepare the samples by melting.

Bismuth ferrite (BiFeO 3 , BFO) powders were synthesized by a simple and cost-effective solvent-deficient method using bismuth nitrate, iron nitrate, and ammonium bicarbonate as the only precursors. Single phase BiFeO 3 powder was fabricated after the Bi:Fe ratio was adjusted and after the precursor mixture was calcined for one hour at 600 °C. We investigated the formation reactions, crystal structure, particle size distribution, magnetic and optical properties of synthesized BiFeO 3 . X-ray diffraction revealed the formation of well-crystallized BFO nanocrystallites starting at a temperature of 450 °C. BiFeO 3 powder calcined at 600 °C showed very weak ferromagnetism at room temperature which is different from the linear M – H relationship in bulk BiFeO 3 ceramics. The remnant magnetization value (Mr) was found to be 5 × 10 −3 emu g −1 and a coercive field value (Hc) nearly 500 Oe. The UV–visible spectra showed maximum adsorption at ∼464 nm with a derived bandgap value of 1.85 (1.8449 ± 0.0013) eV for BFO nanocrystallites supporting their potential application as visible light-response photocatalysts. Direct bandgap value obtained from reflectance measurement is determined to be 2.25 (2.2464 ± 0.0065) eV.

The reaction mechanism and kinetics of CeO2 synthesis using a solvent-deficient method are investigated by simultaneous thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The decomposition process of the cerium(III) nitrate hexahydrate and ammonium bicarbonate precursor mixture with four observed stages is monitored using TGA/DSC measurements in a nonisothermal regime with heating rates of 5, 10, 15 and 20 °C min−1. The proposed mechanism indicates a complex synthesis with several parallel reactions, some of which occur at room temperature. A detailed kinetic analysis is performed using isoconversional (expanded Friedman, modified Coats-Redfern and Kissinger) and model fitting (Nth order and nucleation and growth models) methods. The first three stages are best described by the Nth order model with activation energy values of 21, 53 and 90 kJ mol−1. The last stage, during which ammonium nitrate decomposition occurs, is best fit by the nucleation and growth model and has an activation energy of 129 kJ mol−1. The proposed mechanism, supported by the kinetic analysis in our study, indicates that CeO2 has already formed before the reaction reaches 200 °C. The average crystallite size of CeO2 synthesized at 300 °C, which was calculated from the XRD measurements and observed in the SEM and TEM data, is between 10 and 20 nm.

Lanthanum(III)-oxide (La2O3) powders were synthesized by a mechanochemically induced solvent-deficient method using lanthanum nitrate, and ammonium bicarbonate as precursors. The precursor mixture was calcined for one hour at either 600 or 800 °C. This study included an investigation of the formation reactions, crystal structure, specific surface area, and optical properties of synthesized La2O3. The proposed mechanism indicates a complex synthesis with several reactions, some of which are mechanochemically induced. The size of the La2O3 nanocrystallites, as determined by XRD, is 22.15±3.9 nm (by using the Williamson-Hall plot, it is determined that the strain is 1.4×10−3 and crystallite size 30.81 nm) while the specific surface is set to 7.04 m2g-1. The direct bandgap value obtained from reflectance measurement is determined to be 5.37 eV.

The oxide mixtures xCuO-(1-x) MoO3 were synthesized by gel-combustion procedure. The existence of phase mixture CuO + Cu3Mo2O9 and MoO3 + CuMoO4 in CuO-rich and MoO3 -rich composition region, respectively, were evidenced. The constant heating rate thermogravimetry in hydrogen atmosphere revealed that the reduction reactions proceed within the two clearly separated temperature regions. On the basis of mass changes, the mechanism of reduction processes was discussed. The measurements revealed considerable inhibition of CuO reduction by MoO3, and huge acceleration of MoO3 → MoO2 reduction step by copper. The particularities found in this system were commented in relation to our similar studies in NiO-MoO3 and CuO-WO3 systems. For particular composition, x = 0.5, existing preferably in form of a-CuMoO4, kinetic parameters of reduction were determined. The composition of oxide mixture influenced the particle size and morphology of resulting metallic Cu-Mo composites. This is the peer-reviewed manuscript of the article: Jelić, D., Zeljković, S., Jugović, D., Mentus, S., 2021. Thermogravimetric insight in the reduction of xCuO – (1-x)MoO3 oxide system (0.1 ≤ x ≤ 0.9) by hydrogen. International Journal of Refractory Metals and Hard Materials 96, 105480. [https://doi.org/10.1016/j.ijrmhm.2021.105480] Published version: [https://hdl.handle.net/21.15107/rcub_dais_10533]

Nano-sized alumina is prepared using a cost-effective solvent-free method with aluminum nitrate and ammonium bicarbonate precursors. Combined investigations by thermal analysis (TG/DTA), X-ray diffraction (XRD), specific surface area (BET), scanning electronic microscopy (SEM), infrared emission spectroscopy (FTIR), dynamic light scattering (DLS) and dilatometry were used to examine the effects of calcination temperature on the formation of Al2O3. XRD analysis shows that the γ-Al2O3 phase forms already at 300 °C and slowly continues to form with increasing temperature indicating a diffusion-controlled reaction as shown by FTIR. The size of the γ-Al2O3 nanocrystalline, as determined by XRD, is between 1.5 and 1.9 nm and slowly increased with the reaction temperature. DLS results revealed that a particle size of γ-Al2O3 dispersed in water grows with increasing reaction temperature due to nanocrystalline particle aggregation, which was additionally confirmed by SEM. The densification behavior of the boehmite and γ-Al2O3 phases was investigated using dilatometry.

Nanocrystalline Ba0.5Sr0.5Co0.8Fe0.2O3-? powders were prepared by a cost-effective solvent-deficient method using metal nitrates and ammonium bicarbonate as precursors. X-ray diffraction (XRD), specific surface determination (BET), thermal analyses (TG-DTA-DSC), dynamic light scattering (DLS) and scanning electron microscopy (SEM) were used to examine the effects of the calcination temperature on the Ba0.5Sr0.5Co0.8Fe0.2O3-? (BSCF) formation. XRD analysis showed that a cubic Ba0.5Sr0.5Co0.8Fe0.2O3-? was obtained after heating for 1 h at 1000?C. BSCF nanocrystals with a diameter of about 25 nm were obtained. On the other hand, the sample mass was stabilized at 915?C as recorded by thermogravimetric analysis (TG), indicating a formation of the complex BSCF oxide already at this temperature. The phase transformations during the synthesis of BSCF oxide are defined and confirmed with the note on the instability of the cubic phase. Using the four-point DC measurements between ?73?C and 127?C, the band gap of 0.84 eV was determined. The solvent-deficient method used in this study to synthesize Ba0.5Sr0.5Co0.8Fe0.2O3-? showed distinct advantages in comparison with other synthesis techniques considering simplicity, rapid synthesis, and quality of the produced nanocrystals.

The oxide mixtures CuO–WO3 of various compositions were synthesized by citrate–gel combustion process, starting with the aqueous solutions of copper nitrate, ammonium tungstate and citric acid. Cu–W nanocomposite powders were produced by reduction of oxide mixtures in hydrogen atmosphere under thermogravimetric control. Characterization of CuO–WO3 mixtures and their reduction products was performed by SEM and XRD methods. The morphology of both oxide and metal particles displayed notable dependence on composition. Copper displayed promoting action during reduction of CuO–WO3 mixtures. The mean reduction temperature shifted monotonously from that of CuO toward that of WO3. The reduction proceeded in three steps, first of which was mainly reduction of CuO and the other two originated mainly of the two-step reduction of WO3. The composition CuO–WO3 at a molar ratio 1:1 was shown to form the compound CuWO4. The reduction of this compound was subjected to a detailed thermokinetic study. For those purposes, model-free expanded Friedman, multiple heating rate Coats–Redfern and Kissinger methods and some model-fitting methods, incorporated in the software Kinetics2015, were used. Among model-fitting models, the nucleation and growth kinetic model enabled the best fit of experimental results for all three reduction stages.

In this work, by casting water-soluble ammonium anthracene on metal oxides, the organic surface modifier re-engineered the interface of the metal oxide to improve charge transport. The energy level of ammonium anthracene increased the work function of indium tin oxide (ITO), functioning as a hole-blocker (electron-transporter). Solar cells in which ITO was treated by the ammonium anthracene produced an average power conversion efficiency (PCE) of 5.8% without ZnO, the electron-transporting layer. When the ammonium anthracene was applied to ZnO, an average PCE of 8.1% was achieved, which is higher than the average PCE of 7.5% for nontreated ZnO-based devices.

In the first part of this study, the oxygen deficiency, ?, in Ba0.5Sr0.5Co0.8Fe0.2O3 - ? (BSCF) was measured by means of thermogravimetry as a function of oxygen partial pressure, p(O2), in the range of 1.1?10?6 < p(O2)/% < 41.67 at elevated temperatures ranging 873 ? T/K ? 1073. It was shown that ? becomes more pronounced with increasing T and with decreasing p(O2). The isotherms ? vs. p(O2) were determined. The second part of this study relates to the reaction of CO2 with Ba0.5Sr0.5Co0.8Fe0.8O3-? perovskite oxide in the absence and presence of O2 at temperatures ranging from 673 to 973 K also by thermogravimetry. The reactivity of CO2 with BSCF increased with increasing temperature and increasing exposure to CO2. Reaction of CO2 with BSCF was described by a equilibrium reaction isotherms. The results of X-ray diffractometry evidenced that the exposure to CO2 leads to the formation of carbonates.

Sinteza kalcijum feritnih pudera tipa perovskita je izvršena u kratkom vremenskom periodu putem dekompozicije karbonatnih i oksidnih prekursora korištenjem mikrovalne iradijacije (2.45 GHz, snage do 250 W). Na temperaturnim i energetskim dijagramima je kontinuirano bilježena apsorbovana, reflektirana i primjenjena snaga te temperatura uzorka. Karbonatni i oksidni prekursori su uspješno transformisani u kalcijum ferit. Početni materijali i produkti su karakterizirani difrakcijom X-zraka (XRD). Sinteza iz kalcijum oksida i magnetita se gledano po kristaliziranosti finalnog produkta pokazala uspješnijom. U poređenju sa dobro poznatim tradicionalnim putevima sinteze predstavljena metoda mikrovalno - potpomognute dekompozicije prekursora je brza, čista i energetski efikasna. Uz korištenje na mikrovalnu iradijaciju osjetljivih prekursora ovdje predstavljeni sintetski put zagrijavanjem mikrovalnm zračenjem može biti preporučen za proizvodnju kalcijum feritnih i drugih materijala tipa perovskita.