National Institute Of Materials Physics - Romania

Publications

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444 articles found

1. Magnetoelectric properties of CoFe2O4/BNT-BT0.08 biphasic nanocomposites, with 0-3 connectivity, prepared by sol-gel method

Authors: Cernea, M; Radu, R; Amorin, H; Vasile, BS; Surdu, VA; Trusca, R; Gavrila, R; Galassi, C

Published: AUG 15 2023, JOURNAL OF ALLOYS AND COMPOUNDS, 952, 170041, DOI: 10.1016/j.jallcom.2023.170041

Motivated by the goal of developing ultralow power, smart and multifunctional nano (micro) electronic devices, research has shown unwavering interest in synthesis methods, architectures and interphase connectivity of composites containing magnetostrictive and piezoelectric phases, known as magnetoelectric (ME) materials. Herein we report on CoFe2O4/0.92Bi0.5Na0.5TiO3-0.08BaTiO3 biphasic ME composites, obtained by sol-gel chemistry, by mixing the precursor sols of the two phases into one precursor sol and further transforming it into gel, with the goal of obtaining homogeneous nanocomposites with magnetoelectric properties. The structural properties, the temperature dependance of dielectric properties, the magnetic and magnetoelectric properties of these biphasic mixtures, with various molar ratios CoFe2O4/ BNT-BT0.08 = 0.5:1, 1:1 and 1.5:1, are investigated. It is observed that the amount of CoFe2O4 and the synthesis in situ of these composites influences their macroscopic properties showing a high difficulty of carrying out an efficient poling resulting in small piezoelectric and magnetoelectric response. It was concluded that the synthesis procedure, the type of architecture and the interphase connectivity are of outmost importance for magnetoelectric properties based on lead-free materials. (c) 2023 Published by Elsevier B.V.

2. Nanostructured Al2O3/graphene additive in bio-based lubricant: A novel approach to improve engine performance

Authors: Hettiarachchi, SJ; Bowen, J; Kershaw, M; Baragau, IA; Nicolaev, A; Kellici, S

Published: AUG 2023, TRIBOLOGY INTERNATIONAL, 186, 108619, DOI: 10.1016/j.triboint.2023.108619

Personal and industrial use of internal combustion engines (ICEs) is projected to continue until 2050 and beyond. Yet demands to reduce global dependence on petrochemicals and fossil fuel-derived lubricants are increasing and environmentally necessary. New strategies for maintaining and enhancing ICE performance by reducing friction, wear, fuel consumption, and exhaust emissions will reduce the depletion of mineral and fossil fuel reserves and environmental pollution. This paper reports the tribological enhancement of nano-bio lubricants formulated using 2D nanocomposites of Al2O3/graphene as novel additives in coconut oil, whose performance as a lubricant compares favorably with the mineral-based engine oil 15W40. Structural, compositional, and morphological characterization of the Al2O3/graphene nanocomposite revealed an ultra-fine particle size (< 10 nm) with spherical/laminar morphology and a rich sp2 domain, exhibiting a consistent colloidal stability when formulated as nanofluid. Through the use of various characterization techniques, including friction and wear analysis we gained valuable insight into the tribological mechanism. Our optimization of this 2D tribological system using coconut oil formulation resulted significant reductions in the coefficient of friction (28 %), specific fuel con-sumption (8 %), and exhaust pollutant emissions (CO, SO2, and NOx). This work demonstrates the benefits of using nano-bio lubricant formulated using coconut oil and 2D-based hybrids as base stock and additives, delivering solutions to global challenges such as improving fuel consumption while reducing environmental pollution; solutions that can be transferred to other areas where lubricants are a necessity.

3. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe-0@Ni-0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

Authors: Borhan, AI; Ghemes, IA; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUL 1 2023, APPLIED SURFACE SCIENCE, 624, 157067, DOI: 10.1016/j.apsusc.2023.157067

4. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics

Authors: Borhan, AI; Ghemes, AI; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUN 15 2023, APPLIED SURFACE SCIENCE, 622, 156987, DOI: 10.1016/j.apsusc.2023.156987

We reported on the sequential development of a high-operative photocatalyst with penta-component inorganic bulk heterojunction for improved charge trapping characteristics at particle-particle interfaces for enhanced solar light-driven photocatalytic degradation of active tetracycline antibiotic. Structural, morphological, optical, and electronic properties of the synthesized samples were investigated using a series of complementary char-acterization techniques, such as XRD, FE-SEM, HR-TEM, XPS, as well as hard and soft XAS in both total electron yield (TEY) and fluorescence yield (TFY). For the case of the carbon composite material, SrTiO3@NiFe2O4@-Fe0@Ni0@CNTs, a reduced crystallinity when compared to the starting support material was noticed, although this translated into a significant improvement of the morphology and the photocatalytic performance. The SrTiO3@NiFe2O4@Fe0@Ni0@CNTs fibrous photocatalyst can efficiently achieve a high-to-total degradation of tetracycline antibiotic under visible light irradiation in less than two hours, following a non-linear PFO kinetic model with an apparent reaction rate of about 0.0606 min-1 and an 98% photodegradation activity. The XPS and XAS analysis demonstrated unequivocally the appearance of nanoscale zero-valent iron (Fe0) and zero-valent nickel (Ni0) on the photocatalyst surface, which facilitates the separation of photogenerated e+ and h+ pairs, and the appearance of more active sites.

5. Photocatalytic Activity of the Blends Based on TiO2 Nanoparticles and Reduced Graphene Oxide for Degradation of Acetaminophen

Authors: Daescu, M; Chivu, M; Matei, E; Negrila, C; Cramariuc, O; Baibarac, M

Published: JUN 4 2023, MOLECULES, 28, 4546, DOI: 10.3390/molecules28114546

The aim of this work is to highlight the influence of blends based on TiO2 nanoparticles and reduced graphene oxide (RGO) on the photodegradation of acetaminophen (AC). To this end, the catalysts of TiO2/RGO blends with RGO sheet concentrations equal 5, 10, and 20 wt. % were prepared by the solid-state interaction of the two constituents. The preferential adsorption of TiO2 particles onto the RGO sheets' surfaces via the water molecules on the TiO2 particle surface was demonstrated by FTIR spectroscopy. This adsorption process induced an increase in the disordered state of the RGO sheets in the presence of the TiO2 particles, as highlighted by Raman scattering and scanning electron microscopy (SEM). The novelty of this work lies in the demonstration that TiO2/RGO mixtures, obtained by the solid-phase interaction of the two constituents, allow an acetaminophen removal of up to 95.18% after 100 min of UV irradiation. This TiO2/RGO catalyst induced a higher photodegradation efficiency of AC than TiO2 due to the presence of RGO sheets, which acted as a capture agent for the photogenerated electrons of TiO2, hindering the electron-hole recombination. The reaction kinetics of AC aqueous solutions containing TiO2/RGO blends followed a complex first-order kinetic model. Another novelty of this work is the demonstration of the ability of PVC membranes modified with Au nanoparticles to act both as filters for the removal of TiO2/RGO blends after AC photodegradation and as potential SERS supports, which illustrate the vibrational properties of the reused catalyst. The reuse of the TiO2/RGO blends after the first cycle of AC photodegradation indicated their suitable stability during the five cycles of pharmaceutical compound photodegradation.

6. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

Authors: Mighri, Z; Souiwa, K; Rostas, AM; Patru, RE; Bocirnea, AE; Iacob, N; Kuncser, V; El Khouja, O; Leonat, LN; Hidouri, M; Nasri, H; Galca, AC

Published: MAY 24 2023, INORGANIC CHEMISTRY, 62, DOI: 10.1021/acs.inorgchem.2c04389

The phosphate KCoCr-(PO4)(2) and iron-substitutedvariants KCoCr1-x Fe x (PO4)(2) (x =0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route,while a high substitution level of Fe was achieved. Their structureswere refined using powder X-ray diffraction and indexed in a monoclinicsystem with a P2(1)/n spacegroup. A 3D framework with six-sided tunnels parallel to the [101]direction was formed in which the K atoms are located. Mo''ssbauerspectroscopy confirms the exclusive presence of octahedral paramagneticFe(3+) ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopyconfirmed the presence of paramagnetic Cr3+ ions. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present higher ionic activity. Relative to the electrochemicalactivity of K, these materials could be good candidates for positiveand/or negative electrode materials for energy storage applications. The synthesized phosphate KCoCr-(PO4)(2) and Fe-substituted variants KCoCr1-x Fe x (PO4)(2) (x = 0.25, 0.5, and 0.75) present a 3D frameworkwith six-sided tunnels in which the K atoms are located. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present improved ionic activity, making these materials goodcandidates for positive and/or negative electrode materials for energystorage applications.

7. Outstanding visible light photocatalysis using nano-TiO2 hybrids with nitrogen-doped carbon quantum dots and/or reduced graphene oxide

Authors: Baragau, IA; Buckeridge, J; Nguyen, KG; Heil, T; Sajjad, MT; Thomson, SAJ; Rennie, A; Morgan, DJ; Power, NP; Nicolae, SA; Titirici, MM; Dunn, S; Kellici, S

Published: MAY 9 2023, JOURNAL OF MATERIALS CHEMISTRY A, 11, DOI: 10.1039/d2ta09586f

Historically, titanium dioxide (TiO2) has been one of the most extensively studied metal oxide photocatalysts; however, it suffers from a large bandgap and fast charge recombination. We report the use of green, rapid, single-step continuous hydrothermal flow synthesis for the preparation of TiO2, and TiO2 hybrids with reduced graphene oxide (rGO) and/or N-doped carbon quantum dots (NCQDs) with significant enhancement in photocatalytic activity. Using a solar light generator under ambient conditions with no extra oxygen gas added, we observed the evolution reaction of the model pollutant (methylene blue) in real time. Tailoring of the light absorption to match that of the solar spectrum was achieved by a combination of materials of nano-TiO2 hybrids of nitrogen-doped carbon quantum dots and graphene in its reduced form with a photocatalytic rate constant of ca. 25 x 10(-5) s(-1). Using a diversity of state-of-the-art techniques including high-resolution transmission electron microscopy, transient photoluminescence, X-ray photoelectron spectroscopy and high accuracy, sophisticated hybrid density functional theory calculations we have gained substantial insight into the charge transfer and modulation of the energy band edges of anatase due to the presence of graphene or carbon dots, parameters which play a key role in improving drastically the photocatalytic efficiencies when compared to pristine titania. More importantly, we prove that a combination of features and materials displays the best photocatalytic behaviour. This performance is delivered in a greener synthetic process that not only produces photocatalytic materials with optimised properties and tailored visible light absorption and efficiency but also provides a path to industrialization.

8. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

Authors: Mighri, Z; Souiwa, K; Rostas, AM; Patru, RE; Bocirnea, AE; Iacob, N; Kuncser, V; El Khouja, O; Leonat, LN; Hidouri, M; Nasri, H; Galca, AC

Published: 2023 MAY 24 2023, INORGANIC CHEMISTRY, DOI: 10.1021/acs.inorgchem.2c04389

9. Copper-/Zinc-Doped TiO2 Nanopowders Synthesized by Microwave-Assisted Sol-Gel Method

Authors: Predoana, L; Petcu, G; Preda, S; Pandele-Cusu, J; Petrescu, SV; Baran, A; Apostol, NG; Costescu, RM; Surdu, VA; Vasile, BS; Ianculescu, AC

Published: APR 2023, GELS, 9, 267, DOI: 10.3390/gels9040267

Using the microwave-assisted sol-gel method, Zn- and Cu-doped TiO2 nanoparticles with an anatase crystalline structure were prepared. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent and ammonia water as a catalyst. Based on the TG/DTA results, the powders were thermally treated at 500 degrees C. XRD and XRF revealed the presence of a single-phase anatase and dopants in the thermally treated nanoparticles. The surface of the nanoparticles and the oxidation states of the elements were studied using XPS, which confirmed the presence of Ti, O, Zn, and Cu. The photocatalytic activity of the doped TiO2 nanopowders was tested for the degradation of methyl-orange (MO) dye. The results indicate that Cu doping increases the photoactivity of TiO2 in the visible-light range by narrowing the band-gap energy.

10. Polymeric Carbon Nitrides for Photoelectrochemical Applications: Ring Opening-Induced Degradation

Authors: Maxim, FI; Tanasa, E; Mitrea, B; Diac, C; Skala, T; Tanase, LC; Ianasi, C; Ciocanea, A; Antohe, S; Vasile, E; Fagadar-Cosma, E; Stamatin, SN

Published: APR 2023, NANOMATERIALS, 13, 1248, DOI: 10.3390/nano13071248

Active and stable materials that utilize solar radiation for promoting different reactions are critical for emerging technologies. Two of the most common polymeric carbon nitrides were prepared by the thermal polycondensation of melamine. The scope of this work is to investigate possible structural degradation before and after photoelectrochemical testing. The materials were characterized using synchrotron radiation and lab-based techniques, and subsequently degraded photoelectrochemically, followed by post-mortem analysis. Post-mortem investigations reveal: (1) carbon atoms bonded to three nitrogen atoms change into carbon atoms bonded to two nitrogen atoms and (2) the presence of methylene terminals in post-mortem materials. The study concludes that polymeric carbon nitrides are susceptible to photoelectrochemical degradation via ring opening.