Publications

Recently, perovskites have become a hotspot for researchers attempting to exploit metal and oxygen vacancies in structures of the form MTiO3, facilitating the convenient electron/hole migration, thus displaying interesting properties. Magnesium Titanate (MgTiO3) is a prominent part of the perovskite class, exhibiting remarkable electrical, thermal, and chemical properties. Undoped and Mn-doped MgTiO3 samples were obtained using a solid-state reaction starting from previously synthesized MgO and TiO2 powders, which were separately doped with different Mn ion concentrations. The resulting multiphase materials with a major MgTiO3 phase were thoroughly morpho-structurally analyzed employing XRD, STEM, Raman, PL, XPS, and EPR spectroscopy. The electrochemical results indicate that they show superior performance when used as electrode materials for supercapacitor application due to the high defect concentration as shown in EPR and PL spectroscopy and the ferroelectric behavior observed in XPS and XRD. When used in symmetric and asymmetric supercapacitor devices, they show promising results, with specific capacity values reaching up to 109 F/g for the symmetric and 609 F/g for the asymmetric devices, while energy and power density values reached 84.7 Wh/kg and 90.8 kW/kg respectively, proving a great potential in the energy storage field.

This study investigates the effects of neutron irradiation on tungsten (W) and copper-chromium-zirconium (CuCrZr) joints under conditions mimicking the high neutron flux environment of a tokamak fusion reactor. Samples of W/CuCrZr joints were subjected to irradiation in the Belgian Reactor 2 (BR2) nuclear reactor at SCK CEN (Belgian Nuclear Research Centre) to simulate the intense neutron exposure characteristic for International Thermonuclear Experimental Reactor (ITER) and DEMOnstration power plant reactor (DEMO) operations. The primary objective was to evaluate changes in the mechanical properties and microstructure of these materials, which are critical for their potential use in plasma-facing components. It is revealed that a significant reduction in tensile elongation of the joint, indicating some degree of embrittlement, is observed after the irradiation. Importantly, this effect is independent of the irradiation temperature. Possible physical reasons for the observed phenomenon are discussed.

Laser thin layer deposition technologies were applied to develop organic heterostructures on flexible transparent conductive electrode (TCE). Flexible substrates such as flexible glass (FG), polyethersulfone (PES), amorphous polyethylene terephthalate (PET-A) and biaxially-oriented polyethylene terephthalate (PET-B) were employed to assess the influence of the substrate type on the optical and electrical characteristics of the organic devices. For comparison reason, the organic heterostructures were fabricated on rigid glass substrate and commercially available indium tin oxide (ITO)-coated PET. Hence, flexible and rigid glass substrates were coated with ITO film by pulsed laser deposition (PLD) at low fluence, subsequently a blend layer based on zinc phthalocyanine (ZnPc) and N, N '-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14) being deposited by matrix assisted pulsed laser evaporation (MAPLE) on the TCE film. The investigations evidenced that the roughness and the substrate type can strongly influence the properties of the ITO layer deposited by PLD as well as the optical and electrical characteristics of the organic heterostructures based on the blend layer deposited by MAPLE. Thus, the lowest roughness (0.8 nm) and the best Hall mobility (41.9 cm2/V center dot s) were achieved for ITO coatings deposited on flexible glass substrate. Also, the highest current density value (9.3 x 10- 4 A/cm2 at 0.5 V) was reached for the organic heterostructures fabricated on this type of flexible substrate.

Featured Application Optoelectronic devices in space missions.Abstract Transparent conductive oxides are essential materials for many optoelectronic applications. For new devices for aerospace and space applications, it is crucial to know how they respond to the space environment. The most important issue in commonly used low-Earth orbits is proton radiation. This study examines the effects of high-energy proton irradiation (226.5 MeV) on thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO). We use X-ray diffraction and electron microscopy observations to see the changes in the structure and microstructure of the films. The optical properties and homogeneity of the materials are determined by spectrophotometry and spectroscopic ellipsometry (SE). Analysis of the chemical states of the elements with X-ray photoelectron spectroscopy (XPS) gives insight into what proton irradiation changes at the surface of the oxides. All measurements show that ITO is less influenced than AZO. The proton energy and fluence used in this study simulate about a hundred years in low Earth orbit. This research demonstrates that both transparent conductive oxide thin films can function under simulated space conditions, with ITO showing superior resilience. The ITO film was more homogenous in terms of the total thickness measured with SE, had fewer defects and adsorbates present on the surface, as XPS analysis proved, and did not show a difference after irradiation regarding its optical properties, transmission, refractive index, or extinction coefficient.

Lithium-ion batteries (LIBs) are fundamental to modern technology, powering everything from portable electronics to electric vehicles and large-scale energy storage systems. As their use expands across various industries, ensuring the reliability and safety of these batteries becomes paramount. This review explores the multifaceted aspects of LIB reliability, highlighting recent advancements and ongoing challenges. The importance of safety has been underscored by numerous incidents, such as the well-known smartphone battery explosions and more than 10,000 fires a year at facilities throughout Australia, both linked to LIB failures. These events emphasize the need for robust reliability and safety measures to ensure consistent performance and longevity. Factors like battery chemistry, design, manufacturing, and operating conditions can all influence the reliability of LIBs. Despite their widespread use, the mechanisms of failure, failure rates, and consequences of LIB failures are still not well understood, raising significant safety concerns. Current reliability assessment techniques include experimental methods, computational models, and data-driven approaches. Emerging trends, such as advanced characterization techniques and standardized testing protocols, advocate for improved practices to enhance the reliability and safety of LIBs across all applications.

Hydroxyapatite (HAp), resembling human bone tissue, is a promising biomaterial for dental and hip prosthetics. Incorporating fluorine ions enhances HAp properties, particularly in dental restoration. This new study examines the physicochemical and biological properties of fluorine substituted hydroxyapatite (FHAp) coatings. Structural and morphological properties of the coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition of the FHAp coatings was studied using energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy. Fourier Transform Infrared spectroscopy (FTIR) investigations were also conducted. The typical peaks identified in XRD patterns of the FHAp were associated with pure hydroxyapatite with hexagonal structure. The general XPS spectrum of FHAp coatings shows peaks corresponding to the constituent elements of stoichiometric HAp as well as the presence of F that was used as a substituent. Consequently, the FTIR studies results underlined the presence of hydroxyapatite in the FHAp coatings. The SEM images reveal the presence of a uniform and continuous layer of particle conglomerates evenly distributed across the FHAp surface. Valuable information about the FHAp coating's wettability, adhesion and coating thickness were also obtained. Also, the AFM images suggest the absence of the significant irregularities from the surface of the FHAp coatings. Investigations of FHAp coatings reveal promising outcomes for cell viability and proliferation. Detailed analysis of FHAp's 3D surface characteristics and roughness, following ISO 25178-2:2012 standards, highlights their favorable biocompatibility, supporting MG63 cell proliferation. The surface roughness parameters of FHAp coatings were found to vary, with Sa values spanning from 0.029 +/- 0.004 mu m to 0.778 +/- 0.007 mu m, while Sq ranged from 0.035 +/- 0.005 mu m to 0.907 +/- 0.011 mu m. Furthermore, FHAp exhibits skewness (Ssk) from -0.048 +/- 0.006 to 0.195 +/- 0.009, kurtosis (Sku) from -0.600 +/- 0.011 to -1.050 +/- 0.021, and fractal dimension from 2.14 +/- 0.01 to 2.19 +/- 0.01, indicating consistent surface complexity and favorable properties. The Minkowski Functionals mirror the morphological observations from AFM images, emphasizing their dynamic influence on the samples' surfaces.

Ruthenium-based catalysts were prepared through a deposition-precipitation approach, taking beta zeolites with Si/Al ratios of 12.5, 18.5, and 150, respectively, as supports, and 1-3 wt% loadings of metal. Their activation was performed in the presence of either H2 or NaBH4. The dispersion of the Ru species and the acid-base properties were influenced by both the preparation method and the activation protocol. The catalysts reduced under H2 flow presented well-dispersed Ru(0) and RuOx nanoparticles, while the reduction with NaBH4 led to larger RuOx crystallites and highly dispersed Ru(0). These characteristics exerted an important role in the hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). The H2 dissociation occurred via a heterolytic mechanism involving Lewis acid-base pairs associated with RuOx and the framework oxygen (Si-O-Al) located near the zeolite pore edge. The Ru(0) nanoparticles activated the -C=O bond of the LA substrate, while the presence of the carrier zeolite Br & oslash;nsted acid sites promoted the ring-closure esterification of the 4-hydroxyvaleric acid (4-HVA) intermediate to GVL. An optimal combination of these features was achieved for the catalyst with 3 wt% Ru and a Si/Al ratio of 150, which selectively converted LA (XLA = 96.5%) to GVL (SGVL = 97.8%) at 130 degrees C and 10 bars of H2.

In this work, three methods for the synthesis of composites based on poly(ortho-toluidine) (POT) and WS2 are reported: (a) the solid-state interaction (SSI) of POT with WS2 nanoparticles (NPs); (b) the in situ chemical polymerization (ICP) of ortho-toluidine (OT); and (c) the electrochemical polymerization (ECP) of OT. The preparation of WS2 sheets was performed by the ball milling of the WS2 NPs followed by ultrasonication in the solvent N,N'-dimethyl formamide. During the synthesis of the POT/WS2 composites by SSI and ICP, an additional exfoliation of the WS2 NPs was reported. In this work, we demonstrated the following: (a) the ICP method leads to POT/WS2 composites, which contain repeating units of POT in the leucoemeraldine salt (LS) state, while (b) the ECP method leads to POT/WS2 composites, which contain repeating units of POT in the emeraldine salt (ES) state. Capacitances equal to 123.5, 465.76, and 751.6 mF cm-2 in the cases of POT-ES/WS2 composites, synthesized by SSI, ICP, and ECP, respectively, were reported.

This study examined the gradual replacement of Ca2+ with a small amount of Mg2+ ions (0-1 wt%) in selected calcium phosphates commonly used in regenerative medicine: hydroxyapatite Ca10(PO4)6(OH)2, brushite CaHPO4 center dot 2H2O, and (3-tricalcium phosphate ((3TCP) Ca3(PO4)2. These compounds were obtained using precipitation reactions from aqueous solutions, followed by appropriate thermal treatment (drying or furnace heating). The microstructure and physicochemical properties of the materials were thoroughly analysed using powder X-ray diffraction (PXRD), scanning and transmission electron microscopy (SEM and TEM), and mid-infrared spectroscopy (FT-IR). Additionally, the release of Mg2+ ions from the selected materials was investigated, and a preliminary in vitro toxicity assessment was performed. The results showed that the introduction of magnesium ions up to 1 wt% was achieved with relatively high efficiency (63-82 % for brushite, 77-97 % for hydroxyapatite, and 88-100 % for (3-tricalcium phosphate). The entire series of hydroxyapatites was phase-homogeneous, but monetite was observed as an additional phase in the case of brushite samples. In contrast, several (3TCP samples were contaminated with a small amount of calcium oxide and hydroxide. The incorporation of Mg2+ ions significantly impacted the unit cell parameters of each type of calcium phosphate and the ultrastructure of the obtained powders. With an increase in the amount of introduced magnesium, the resulting crystals became smaller and showed a greater tendency to form aggregates. The obtained results indicate that it is possible to obtain calcium phosphate materials containing Mg2+ ions with a gradual release of ions. The fastest ions release occurred from the brushite sample, while the slowest was from the apatitic powder, which is in great accordance with the solubility of the materials. All samples, except for Mg0.5-Bru, were non-cytotoxic.

The purpose of this work is to obtain different kinds of advanced nanostructures with four materials of interest: carbon, titanium, aluminum and silicon, deposited by Thermionic Vacuum Arc (TVA) technology on the Si substrate, in two cases: C/Ti/C/Al/C/Si multilayer film and C+Ti/C+Al/C+Si composite film with inclusion of nitrogen. Also, for each type of samples some parameters varied: substrates temperature (Room Temperature, 200 degrees C, 300 degrees C, 400 degrees C) and the bias voltage applied on the substrates, i.e. - 400 V. Thermal Desorption Spectroscopy (TDS) analyses revealed the presence of nitrogen in all cases. The Raman spectra reveal that the film nitrogen treatments leads to the formation of nitrides for each compound. The infrared absorption spectra are dominated by the formation of C-N bonds, which are the same as in the Raman spectra. EDX and Elemental composition show the values of atomic percentage depending on the substrate deposition temperature. TEM and XPS depth profiles are studied. Based on nanoindentation studies, the Young modulus and hardness are measured. The tribology measurements are also performed.