National Institute Of Materials Physics - Romania

This work examines the influence of milling parameters on the evolution of the microstructure of Ni50Ti50 alloy prepared by high-energy mechanical alloying (MA). The study unveils a particle-folding phenomenon observed through scanning electron microscopy, which diverges from the conventional welding and fracturing mechanisms previously associated with MA. It is found that milling duration is critical, with particle folding being predominant in the initial stages, subsequently becoming less pronounced in favor of traditional processes over extended milling times. The research underscores the importance of processing parameters in achieving desired microstructural characteristics and suggests the potential for better control of nanocrystalline material properties. The outcomes present new opportunities for material synthesis, offering insights into the fabrication of nanomaterials with enhanced and tailored properties for various technological applications.

In this study, porous polysiloxane (PS)/multi-walled carbon nanotube (MWCNT) nanocomposite films were developed as high-performance triboelectric layers for flexible triboelectric nanogenerators (TENGs). TENGs convert mechanical motion into electricity and offer a promising solution for self-powered electronic systems. The nanocomposites were fabricated using a doctor blading method, and porosity was introduced via a simple, scalable salt-leaching technique. Sieved salt particles of varying sizes produced films with fine, medium, and large pores. Raman spectroscopy confirmed uniform MWCNT dispersion and strong interfacial interaction within the PS matrix. SEM analysis verified controlled pore morphology. Dielectric measurements showed reduced permittivity with increasing pore size due to air void incorporation. Triboelectric performance improved significantly with porosity; the medium porosity sample exhibited the best output with an open-circuit voltage of 65 V, short-circuit current of 6.9 mu A, and a power density of 280.6 mW m-2. This enhancement is attributed to the optimized combination of surface roughness, contact area, and dielectric behavior, promoting efficient charge generation and transfer. These results highlight the potential of microstructural engineering in porous nanocomposites for next-generation energy harvesting applications.

The crystallization mechanism of Yb/Er-doped GdF3 nanocrystals in silica nano-glass ceramics was analyzed using model-free and model-fitting methods and thermal analysis data in correlation with structural data. The formation of GdF3 nanocrystals occurs at around 300 degrees C, and their size is temperature dependent, ranging from 14 to 40 nm, depending on the processing temperature. A similar trend is observed for cell volume, where a contraction of up to approximate to 2.3% (at 600 degrees C) was assigned to the gradual incorporation of Li and Yb,Er dopants. Model-free analysis showed an increase in activation energy (Ea) and the preexponential factor (log A) up to 175 kJ mol-1 and 14.8 s-1, respectively, until the completion of crystallization. Model-fitting analysis indicated a crystallization process controlled by an autocatalytic-type reaction where a second metastable phase (LiF) acts as a catalyst and facilitates a rapid and self-accelerated crystallization of the main GdF3 nanocrystalline phase. The ceramization process boosted UC luminescence up to values comparable to those of NaYF4:18Yb/2Er.

Due to the importance of buffer layers in interface engineering, the development of more variants and the rational design of materials have a significant influence on the performance of optoelectronic devices. This study provides a strategy to increase device performance by facilitating efficient charge transfer and defect passivation by combining the properties of eco-friendly materials (adenine, cytosine, guanine, thymine, and uracil) with the physicochemical properties of metal oxides. The aim of this paper was to investigate the interaction of zinc oxide (ZnO) nanostructures (seed, nanoparticles, and nanowires) with nucleobase layers and to discuss their potential applications as organic-inorganic interfacial bilayers. The impact is analyzed from structural, morphological, optical, and electrical points of view. Nucleobase-ZnO nanostructure layers present high optical transparency in the visible range. Electrical measurements confirmed that the high surface area of nanowires can enhance interactions with nucleobases, leading to better charge transfer. The results showed that these nucleobase-ZnO nanostructure layers are promising interface materials for enhancing optoelectronic device performance through interfacial charge transport and light management, while enabling the design of environmentally friendly devices.

Integrating two-dimensional transition-metal dichalcogenides with graphene is attractive for low-power memory and neuromorphic hardware, yet sequential wet transfer leaves polymer residues and high contact resistance. We demonstrate a complementary metal-oxide-semiconductor (CMOS)-compatible, transfer-free route in which an atomically thin amorphous MoS2 precursor is RF-sputtered directly onto chemical vapor-deposited few-layer graphene and crystallized by confined-space sulfurization at 800 degrees C. Grazing-incidence X-ray reflectivity, Raman spectroscopy, and X-ray photoelectron spectroscopy confirm the formation of residue-free, three-to-four-layer 2H-MoS2 (roughness: 0.8-0.9 nm) over 1.5 cm x 2 cm coupons. Lateral MoS2/graphene devices exhibit reproducible non-volatile resistive switching with a set transition (SET) near +6 V and an analogue ON/OFF approximate to 2.1, attributable to vacancy-induced Schottky-barrier modulation. The single-furnace magnetron sputtering + sulfurization sequence avoids toxic H2S, polymer transfer steps, and high-resistance contacts, offering a cost-effective pathway toward wafer-scale 2D memristors compatible with back-end CMOS temperatures.

This study explores the optimization of multi-walled carbon nanotube (MWCNT) concentration in nylon-based nanocomposites to enhance the performance of triboelectric nanogenerators (TENGs). Nylon/MWCNT nanocomposite films were fabricated using the spin-coating method, and their electrical output was systematically evaluated as a function of MWCNT concentration. Results show that the open-circuit voltage (Voc) and short-circuit current (Isc) increase with MWCNT loading up to 0.05 wt%, reaching a peak of 29.7 V and 3.0 mu A, respectively, compared to 17.5 V and 1.8 mu A for pristine nylon-based TENGs. However, a decline in output was observed at 0.1 wt% due to MWCNT agglomeration, which disrupts charge transfer and introduces charge leakage. The enhancement at optimal concentration is attributed to improved charge trapping and increased dielectric constant, while excessive CNT loading reduces the effective contact area and limits triboelectric charge generation. These findings underscore the crucial role of nanomaterial dispersion in optimizing TENG performance and offer valuable insights for the development of high-efficiency triboelectric energy harvesting systems.

This study aims to investigate the impact of clays on the quality of the Nubia reservoir in the Saqqara field, Gulf of Suez, Egypt. The research will contribute to a broader knowledge of reservoir characterization, offering valuable insights for similar geological settings in other regions, thereby aiding in the optimization of resource management in global petroleum industries. The shale evaluation procedure involves three primary steps: estimating shale volume, identifying clay minerals, and assessing shale distribution. The neutron-density (N-D) method was employed to estimate the shale volume in the Nubia reservoir, yielding an average of 0.6% across four wells, with a maximum recorded value of 2.2% in well GS323-3. These values represent that the Nubia reservoir contains a negligible amount of shale, indicating that the porosity and permeability are high. Clay mineral analysis, based on a Potassium-Thorium (K-Th) and Potassium-PEF cross-plots, identified the presence of chlorite, illite, montmorillonite, and heavy thorium-bearing minerals, where chlorite and illite enhance the mechanical stability of the reservoir, while montmorillonite may cause issues with swelling and pressure. Thorium-bearing heavy minerals are typically associated with reduced permeability due to their influence on chemical interactions. The shale distribution analysis, conducted using the Thomas and Stieber model, confirms the overall cleanliness of the Nubia reservoir. Most formation data points align with the 0% shale line, indicating high total porosity, while only a few points fall along the dispersed shale line. In conclusion, the findings indicate that the Nubia reservoir exhibits minimal shale content, predominantly clean lithology, and favorable porosity and permeability characteristics. Consequently, the reservoir is classified as high-quality, making it suitable for efficient hydrocarbon production.

This work reports the fabrication and optimization of nylon/multi-walled carbon nanotube (MWCNT) nanocomposite-based triboelectric nanogenerators (TENGs) using a spin coating method. By carefully tuning the MWCNT concentration, the device achieved a substantial enhancement in electrical output, with open-circuit voltage and short-circuit current peaking at 29.7 V and 3.0 mu A, respectively, at 0.05 wt% MWCNT loading on the surface of nylon. The corresponding power density reached approximately 13.9 mW/m2, representing a significant improvement over pure nylon-based TENGs. The enhanced performance is attributed to improved charge trapping and dielectric properties due to well-dispersed MWCNTs on the surface of nylon, while excessive loading caused agglomeration, reducing efficiency. This lightweight, flexible nanocomposite TENG offers a promising solution for efficient, sustainable energy harvesting in wearable electronics and self-powered sensor systems, highlighting its potential for practical energy applications.

Biodegradable polymers like poly(epsilon-caprolactone) (PCL) are widely studied for their potential applications in biomedical and environmental fields. To enhance PCL's thermal, and bioactive properties, researchers have explored composite formulations with other polymers or bioactive compounds. Oleic acid (OA), a naturally occurring fatty acid, has been identified as a promising modifier. This study investigates the modification of PCL with OA using an eco-friendly catalyst to improve its functional properties. PCL was grafted with OA using Maghnite-H+, a heterogeneous solid catalyst clay activated via sulfuric acid treatment. A response surface methodology with a central composite design was applied to optimize synthesis parameters, including reaction temperature, duration, and catalyst concentration. The resulting composite was characterized using FTIR and NMR to confirm structural modifications, while its thermal stability was evaluated. Antioxidant activity was assessed using the DPPH radical scavenging assay, and antimicrobial potential was tested against various microorganisms. The PCL-OA composite exhibited enhanced antioxidant activity, with increased radical scavenging efficiency compared to unmodified PCL. Antimicrobial tests revealed strain-dependent effects, with improved inhibition observed in specific combinations of caprolactone, OA, and PCL-OA. The findings suggest that OA incorporation enhances PCL's bioactivity, making it a promising material for biomedical and packaging applications.

The study of spectral gamma-ray logs plays a critical role in understanding the lithofacies and depositional environments of subsurface geologic formations. This research focuses on the Lam Member within the Habban oilfield, located in the Sab'atayn Basin, Yemen. By integrating spectral gamma-ray data with core analysis and other geological datasets, this study aims to provide insights into the stratigraphic distribution, mineral composition, and depositional processes of the Lam Member. Key parameters, such as thorium, uranium, and potassium concentrations, recorded from two wells were analyzed to infer sedimentary characteristics and environmental conditions. The results reveal significant lithologic heterogeneity and suggest a complex interplay of fluvial and marine depositional systems, enhancing the understanding of the basin petroleum potential. The Lam Member comprises interbedded carbonate (dolomite) and claystone with intercalated sandstone. Spectral gamma-ray results indicate that clay minerals primarily consist of mixed-layer clays, chlorite, kaolinite, and minor illite. Based on the Th/U ratio (less than 2), the depositional environment is identified as marine.