National Institute Of Materials Physics - Romania

Mo matrix composites (MMC) with Mo-9Si-8B inclusions were fabricated by pressure-less sintering (PLS) and spark plasma sintering (SPS) techniques at temperatures between 1200-1500 degrees C using 1 wt.% Ni sinter additive. The positive impact of the addition Ni addition on the sinterability and formation of a continuous Mo matrix of MMC with randomly distributed Mo3Si and Mo5SiB2 inclusions was determined. The Ni addition increased the shrinkage of MMC during PLS by almost a third. The continuous Mo matrix of MMC and a relative density of more than 98% was obtained after SPS at 1400-1500 degrees C. The composite with the maximum relative density of 98% showed a Vickers hardness of 482 +/- 9 (HV20). The potential of using Ni-activated PLS and SPS to produce high-density MMC is shown.

In recent years, significant progress has been made in the surface functionalization of magnetic nanoparticles (MNPs), revolutionizing their utility in multimodal imaging, drug delivery, and catalysis. This progression, spanning over the last decade, has unfolded in discernible phases, each marked by distinct advancements and paradigm shifts. In the nascent stage, emphasis was placed on foundational techniques, such as ligand exchange and organic coatings, establishing the groundwork for subsequent innovations. This review navigates through the cutting-edge developments in tailoring MNP surfaces, illuminating their pivotal role in advancing these diverse applications. The exploration encompasses an array of innovative strategies such as organic coatings, inorganic encapsulation, ligand engineering, self-assembly, and bioconjugation, elucidating how each approach impacts or augments MNP performance. Notably, surface-functionalized MNPs exhibit increased efficacy in multimodal imaging, demonstrating improved MRI contrast and targeted imaging. The current review underscores the transformative impact of surface modifications on drug delivery systems, enabling controlled release, targeted therapy, and enhanced biocompatibility. With a comprehensive analysis of characterization techniques and future prospects, this review surveys the dynamic landscape of MNP surface functionalization over the past three years (2021-2023). By dissecting the underlying principles and applications, the review provides not only a retrospective analysis but also a forward-looking perspective on the potential of surface-engineered MNPs in shaping the future of science, technology, and medicine.

In this work, applications of nanohybrid composites based on titanium dioxide (TiO2) with anatase crystallin phase and single-walled carbon nanohorns (SWCNHs) as promising catalysts for the photodegradation of amoxicillin (AMOX) are reported. In this order, TiO2/SWCNH composites were prepared by the solid-state interaction of the two chemical compounds. The increase in the SWCNH concentration in the TiO2/SWCNH composite mass, from 1 wt.% to 5 wt.% and 10 wt.% induces (i) a change in the relative intensity ratio of the Raman lines located at 145 and 1595 cm(-1), which are attributed to the E-g(1) vibrational mode of TiO2 and the graphitic structure of SWCNHs; and (ii) a gradual increase in the IR band absorbance at 1735 cm(-1) because of the formation of new carboxylic groups on the SWCNHs' surface. The best photocatalytic properties were obtained for the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.%, when approx. 92.4% of AMOX removal was achieved after 90 min of UV irradiation. The TiO2/SWCNH composite is a more efficient catalyst in AMOX photodegradation than TiO2 as a consequence of the SWCNHs' presence, which acts as a capture agent for the photogenerated electrons of TiO2 hindering the electron-hole recombination. The high stability of the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.% is proved by the reusing of the catalyst in six photodegradation cycles of the 98.5 mu M AMOX solution, when the efficiency decreases from 92.4% up to 78%.

Thick tungsten oxide layers were prepared electrophoretically in order to be used as photoanodes in photoelectrochemical water oxidation applications. The highest photocurrent density was obtained for a WO3 layer with thickness of similar to 900 nm. Additionally, WO3/BiVO4 and WO3/BiVO4/MIL-101(Fe) heterojunctions have been fabricated using WO3 layer as substrate. WO3/BiVO4 shows an increased value of the electrochemical active surface area indicating that more sites of this photoanode are activated through the formation of the heterojunction. The small V5+ signals observed in the V 2p XPS spectra of these heterojunctions were attributed to the substitution of V5+ atoms with W6+ atoms on the surface of BiVO4. Excessive W doping of the BiVO4 film determined the decrease of the photoelectrochemical performance of WO3/BiVO4 photoanode. The significant improvement of the photoconversion efficiency of the sample decorated with MIL-101(Fe) indicated that this cocatalyst provides sites more efficiently in the photoelectrochemical process. This performance was correlated with the reduced value of the charge transfer resistance at electrode/electrolyte interface obtained from electrochemical impedance spectroscopy investigation.

Titanium dioxide nanobelts were prepared via the alkali-hydrothermal method for application in chemical gas sensing. The formation process of TiO2-(B) nanobelts and their sensing properties were investigated in detail. FE-SEM was used to study the surface of the obtained structures. The TEM and XRD analyses show that the prepared TiO2 nanobelts are in the monoclinic phase. Furthermore, TEM shows the formation of porous-like morphology due to crystal defects in the TiO2-(B) nanobelts. The gas-sensing performance of the structure toward various concentrations of hydrogen, ethanol, acetone, nitrogen dioxide, and methane gases was studied at a temperature range between 100 and 500 C-degrees. The fabricated sensor shows a high response toward acetone at a relatively low working temperature (150 C-degrees), which is important for the development of low-power-consumption functional devices. Moreover, the obtained results indicate that monoclinic TiO2-B is a promising material for applications in chemo-resistive gas detectors.

We present a breakthrough in the development of novel nanocomposites based on reduced graphene oxide (RGO)-functionalized zinc oxide (ZnO) nanorods that hold exceptional promise for their use in white light emitting diodes (LEDs) and reliable UV photodetection. The nanorods had a pristine hexagonal wurtzite struc-ture, as confirmed by XRD analysis. SEM images revealed sandwich-like nanocomposites with ZnO nanorods coated in reduced graphene oxide and embedded between two layers of RGO. The study also confirmed the hybridization and interactions between the layers using Raman measurements. The resulting nanocomposites displayed a lower band gap energy than ZnO and exhibited unique photoluminescence spectra with a white PL light. The photodetector based on RGO/ZnO/RGO sandwich structures demonstrated exceptional photoresponse, with higher photocurrent under UV illumination, making it highly promising for a wide range of optoelectronic applications. Overall, this study offers a novel and powerful approach to create nanocomposite structures with enhanced optical characteristics.

Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H-2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), approximate to 5 x 7 & Aring;(2) in cross-section, that generate H-2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H-2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H-2 photochemically for a long time.

The response of nickel oxide gas sensors towards CO and H2 and the underlying gas sensing mechanisms were investigated with special focus on the influence of ambient humidity interference. Surface reactions were tracked by using diffuse reflectance infrared Fourier transformation spectroscopy with simultaneous resistance measurements. The sensor response to both gases is barely influenced by the background humidity. Spectroscopic results reveal that the underlying processes at the surface are almost identical for CO and H2 reception and similar to the effect of the removal of oxygen. Accordingly, the detection of the analytes is based purely on the reduction and oxidation of the oxide material instead of the formation of analyte specific surface species.

This work evaluates the effects of manganese (Mn) doping on the morpho-structural features, mechanical performance, and in vitro biological response of beta-tricalcium phosphate (beta-TCP) derived bioceramics for bone tissue engineering applications. Five different Mn doping levels (i.e., 0.01%, 0.05%, 0.1%, 0.5%, and 1 wt.%) were investigated, with the beta-TCP-based bioceramics being sintered at four temperatures (i.e., 1000, 1100, 1200, and 1300 degrees C). A densification improvement was induced when using Mn in excess of 0.05 wt.%; the densification remained stationary in the sintering temperature range of 1200 - 1300 degrees C. The structural analyses evidenced that all samples sintered at 1000 and 1100 degrees C were composed of beta-TCP as major phase and hydroxyapatite (HA) as a minor constituent (similar to 4-6 wt.%). At the higher temperatures (1200 and 1300 degrees C), the formation of alpha-TCP was signalled at the expense of both beta-TCP and HA. The Mn doping was evidenced by lattice parameters changes. The evolution of the phase weights is linked to a complex inter-play between the capacity of the compounds to incorporate Mn and the thermal decomposition kinetics. The Mn doping induced a reduction in the mechanical performance (in terms of compressive strength, Vickers hardness and elastic modulus) of the beta-TCP-based ceramics. The metabolic activity and viability of osteoblastic cells (MC3T3-E1) for the ceramics were studied in both powder and compacted pellet form. Ceramics with Mn doping levels lower than 0.1 wt.% yielded a more favorable microenvironment for the osteoblast cells with respect to the undoped beta-TCP. No cytotoxic effects were recorded up to 21 days. The Mn-doped beta-TCPs showed a significant increase (p < 0.01) in alkaline phosphatase activity with respect to pure beta-TCP.

A testing methodology and a new "anchor"geometry for tensile samples were developed for evaluation of the W/Cu joint strength between the W monoblock and the CuCrZr cooling pipe joined via the Cu interlayer in the ITER-specification monoblock. The proposed samples can be machined from the ITER-specification monoblock. These monoblock tensile samples are designed for uniaxial tests allowing their remote manipulation for testing in hot cells after neutron irradiation, which is crucial for the assessment of the effect of this irradiation. For validation purposes, tensile tests with standard miniaturised dog-bone samples were performed using prototype block-to-block joints (W/CuCrZr) produced with the field-assisted sintering technique. The results are obtained from the conventional and the new tensile samples. Conventional samples were machined from the W/CuCrZr block-to-block joints, while the new "anchor"tensile samples were machined from the W/CuCrZr block-toblock joints and ITER monoblock containing the W block and Cu interlayer. A good agreement in the evaluation of the joint strength was obtained. The fracture surfaces and the joint interface were investigated with scanning electron microscopy. Micro-hardness was characterised across the joint interface.