Letteratura scientifica selezionata sul tema "Mg-Dopant"

We investigated atomic structures and chemical states of active and inactive dopant sites for Mg- and Si- doped in GaN using photoelectron holography and X-ray absorption near edge structure. In the case of Mg-doped GaN, we found that a Mg atom substituting a Ga atom (MgGa) is an active dopant site in GaN whereas MgGa with two H atoms is an inactive dopant site in GaN. We found that a Si atom substituting a Ga atom is an active dopant site in Si-doped GaN whereas Si3N4 is an inactive dopant site in GaN.

A systematic approach was used to develop the empirical model for optimizing the preparation process parameters for the synthesis of LiFe[Formula: see text]MgxTiyPO4/C composite cathode material. For optimizing the production parameters, response surface methodology (RSM) was applied to develop a linear regression model and maximize the discharge capacity. Analysis of the variance (ANOVA) showed that the three variables (Mg-dopant, Ti-dopant and sintering temperature) and the interactions among them were significant factors. Response surfaces formed by RSM illustrated that the doping of Mg and Ti on Fe site had obviously synergistic effect on the discharge capacity. In the process optimization, the parameters were 2.9% of Mg-dopant, 3.0% of Ti-dopant and sintering temperature of 678.5[Formula: see text]C, corresponding to a discharge capacity of 136.7[Formula: see text]mAh/g predicted by the model. This predicted value was in good agreement with the actual value (136.4[Formula: see text]mAh/g) by confirmatory experiment. The optimized LiFe[Formula: see text]Mg[Formula: see text]Ti[Formula: see text]PO4/C composite exhibits a good rate performance and cycling stability due to the enhancement of electronic conductivity and lithium diffusion coefficient ([Formula: see text][Formula: see text]cm2/s) by the co-doping of Mg and Ti ions.

Titanium dioxide (TiO2) with magnesium (Mg) doping for dye-sensitized solar cell (DSSC) photoanode application has been synthesized. DSSC components used in this study were photosensitizer (bixin), electrolyte (), cathode (platinum), and photoanode (Mg-TiO2). This research aims to determine the characteristics of Mg-doped TiO2 photoanode with variations in dopant concentration based on the results of XRD and DR/UV-Vis analysis, as well as to determine the maximum efficiency conversion energy of DSSC using Mg-doped TiO2 and undoped TiO2 as photoanodes. The synthesis of TiO2 and Mg-TiO2 was carried out using the hydrothermal method with variations in the concentration of Mg dopant of 0, 0.5, 1, and 2% based on the molar ratio. The presenceof 2% of Mg in anatase TiO2 paste decreased the TiO2 band gap from 3.15 to 2.60 eV. Analysis results show that adding Mg dopant decreased the crystal size. Mg dopants on TiO2 could also form new energy levels, which reduced the band gap energy of TiO2. In addition, the increased concentration of Mg dopants also shifted the absorption capacity of TiO2 from the ultra-violet (UV) wavelengths region to the visible light area. The maximum energy conversion efficiency of the DSSCs with Mg-doped TiO2 photoanode of 0.5, 1, and 2% are 0.045; 0.070, and 0.172%, respectively, where these three efficiency values are higher than undoped TiO2 (0.017%). The results proved that the presence of Mg dopants on the TiO2 photoanode can increase the efficiency of DSSC.

In this investigation, pure aluminum (Al) powders were cryomilled with and without magnesium dopants to study (a) the effect of cryomilling time on the crystallite size and (b) the effect of magnesium dopant on Al to achieve grain boundary stability. The cryomilling process was carried out using liquid nitrogen for different durations. The characterization of the cryomilled powders was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to understand the particle morphology, crystallite size, and elemental composition. The results demonstrated that the size of the crystallites in both Al and Mg-doped Al powders reduces as the cryomilling duration increases. The results also indicated that the preferential segregation of Mg dopant at the grain boundaries of Al provides stability to the cryomilled powders at elevated temperatures. This article discusses the mechanism for the changes in crystallite size and the effect of the Mg dopant on the grain boundary stability in Al powders.

Abstract In this paper, we reported the synthesis of NiO NPs and Mg doped-NiO NPs using the facile sol-gel method. Besides, the influence of the variation of Mg dopant on the structural, morphological and optical properties of the prepared Mg-NiO NPs was studied. The synthesized Mg-NiO NPs nanoparticles were characterized by X-Ray Diffraction Analysis (XRD), Energy Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared Spectroscopy (FTIR), Field-Emission Scanning Electron Microscopy (FE-SEM), and UV-Vis spectrophotometer. The X-ray diffraction confirmed the formation of the cubic structure of Mg doped-NiO NPs after doping with the magnesium. The increase in the crystal size was observed with the increase in the concentration of the Mg dopant element. The FESEM images reveal the formation of nickel oxide through the appearance of spherical clusters, while the hybrids appear as wrinkled surface covered with spherical particles of magnesium. The UV-Vis spectrum showed a shift towards shorter wavelengths with an increase in the concentration of the Mg dopant element due to the quantum confinement effect. The hemolysis activity study showed that NiO NPs had a low hemolysis percentage of 1.47% and increased with increasing concentration. While, increasing of the RBC hemolysis (5.9%) after NiO doped with Mg. The antibacterial activity was studied against S. aureus and P. aeruginosa bacteria, and indicated the highest growth inhibition zones of Mg-doped NiO NPs as compared with NiO NPs against of Staphylococcus aureus and Pseudomonas aeruginosa, respectively.

Les détecteurs de neutrons jouent un rôle crucial dans plusieurs domaines telles que la sécurité (aéroports, frontières) pour contrôler les activités illicites des matériaux nucléaires, les centrales nucléaires pour la sécurité et la surveillance des rayonnements neutroniques, la physique des hautes énergies et la science nucléaire. En outre, des événements récents tels que l'explosion de Fukushima et l'empoisonnement au polonium ont stimulé l'intérêt pour le développement de petits détecteurs de neutrons à base semi-conducteurs (DNS), portables et peu coûteux. Pour atteindre une efficacité élevée dans les DNS, des facteurs tels que l'absorption des neutrons et la collecte des charges (électrons et trous) sont essentiels. L'objectif général de ce travail est de développer des détecteurs de neutrons thermiques efficaces à partir des nitrure d’éléments III contenant du bore tels que le nitrure de bore (BN) et les alliages de BGaN. Ces matériaux sont très prometteurs pour les applications de détection des neutrons en raison de la section efficace de capture des neutrons de l'isotope 10 du bore (10B) et de leur faible sensibilité aux rayons gamma. Cependant, le principal défi que pose le III-N contenant du bore pour la détection des neutrons est la qualité des matériaux eux-mêmes. Par exemple, la synthèse de BGaN monocristallin épais avec une teneur importante en bore, nécessaire pour les détecteurs de neutrons, est très difficile avec la méthode MOVPE en raison des dégradations induites par la déformation, telles que la séparation de phase et la formation d’une morphologie 3D en colonne. Nous avons donc développé une approche innovante consistant en des super-réseaux (SLs) BGaN/GaN avec une teneur en bore de 3% dans la couche BGaN. Ces matériaux BGaN/GaN SLs ont été utilisés pour fabriquer des dispositifs MSM et PIN, qui ont montré un signal significatif induit par les neutrons. Même avec cette approche, on constate qu'il y a toujours plusieurs limites concernant la teneur en bore, la qualité du matériau et l'épaisseur globale, qui sont des facteurs importants pour la réalisation de détecteurs de neutrons à haute efficacité. L'utilisation de couches épitaxiales de BN (100 % de bore) devrait permettre d'améliorer l'absorption des neutrons thermiques et les performances des détecteurs de neutrons. Notre groupe est le premier à publier des films de h-BN en couches 2D de grande surface et de haute qualité cristalline sur un substrat de saphir par la méthode MOVPE. Ces films de BN ont été utilisés pour démontrer des photodétecteurs UV. Dans ce travail, nous avons synthétisé des échantillons de BN naturel et enrichi en 10B d'une épaisseur allant jusqu'à 2.5µm et les avons utilisés pour fabriquer des détecteurs MSM. Les avantages des structures MSM sont la possibilité de réaliser un fonctionnement autonome, similaire à celui démontré pour les photodétecteurs UV, et de bénéficier d'un gain interne afin d'augmenter le signal neutronique. Ce travail vise également à étudier le dopage du BN en utilisant Mg comme dopant dans l’objectif de réaliser dans le future de détecteurs de neutrons BN à base de junction p-n. Comme une teneur élevée en bore est hautement souhaitable pour les détecteurs de neutrons, nous avons aussi exploré expérimentalement un nouveau matériau : les alliages BAlN riches en bore
Neutron detectors play a crucial role in various applications such as homeland security (airports, borders and ports) to control illegal activities involving nuclear materials, nuclear power plants for neutron radiation safety and monitoring, high energy physics and nuclear science. In addition, recent events such as the Fukushima explosion and the polonium poisoning have stimulated interest in the development of small, portable and low-cost solid-state neutron detectors (SSND). To achieve high efficiency in SSND factors such as neutron absorption and charge collection are critical.The general objective of this work is to develop efficient solid-state thermal neutron detectors based on boron containing III-nitride materials such as boron nitride (BN) and boron-gallium nitride (BGaN). Boron in these materials is very important for the detection of thermal neutrons due to the high neutron capture cross section of the isotope boron-10 (10B) and its low sensitivity to gamma radiation. However, the main challenge with boron containing III-N for neutron detection is the quality of the materials. For instance, growth of thick, high quality single crystalline boron-rich BGaN needed for neutron detectors is difficult due to strain-induced degradations such as phase separation and columnar 3D growth. Therefore, we developed an innovative approach consisting of BGaN/GaN superlattices (SLs) with a nominal boron content of 3% in the BGaN layer. These BGaN/GaN SLs materials were used to fabricate metal-semiconductor-metal (MSM) and p-i-n heterojunction devices, which showed significant neutron-induced signal. Even with this approach, it is found that there are several constraints on the boron content, the quality of the material, and the overall thickness, which are key factors for the realization of high-efficiency neutron detectors.By using binary BN (100% boron) epitaxial layers, higher thermal neutron absorption and performance of neutron detectors are expected. Our group has reported for the first time large area 2D layered h-BN films with high crystalline quality on sapphire substrate by metal organic vapor phase epitaxy (MOVPE). These BN films were used to demonstrate high efficiency deep UV photodetectors. In this work, we have grown up to 2.5µm thick natural and 10B enriched BN samples and used them to fabricate MSM based detectors. The advantages of MSM structures are the ability to achieve self-powered operation, similar to that demonstrated for UV photodetectors, and to benefit from internal gain in order to increase the neutron signal.This work also aims to investigate the control of the electrical conductivity of h-BN by in-situ Mg doping for the future realization of p-n based BN neutron detectors. Since a high boron content is highly desirable for neutron detectors, we have further explored experimentally for the first time a new material: boron-rich BAlN alloys

This chapter aims to show significant progress that our group has been developing and the applications of several doped semiconductor nanocrystals (NCs), as nanopowders or embedded in glass systems. Depending on the type of dopant incorporated in the nanocrystals, the physical, chemical, and biological properties can be intensified. However, it can also generate undesired toxic effects that can potentially compromise its use. Here we present the potential of zinc oxide NCs doped with silver (Ag), gold (Au), and magnesium (Mg) ions to control bacterial diseases in agriculture. We have also performed biocompatibility analysis of the pure and Ag-doped sodium titanate (Na2Ti3O7) NCs in Drosophila. The doped nanocrystals embedded in glassy systems are chrome (Cr) or copper (Cu) in ZnTe and Bi2Te3 NCs for spintronic development nanodevices. Therefore, we will show several advantages that doped nanocrystals may present in the technological and biotechnological areas.

The autonomy of next generation Electric Vehicles relies on the development of high energy density automotive batteries. LiMn1.5Ni0.5O4 (spinel structure) is a promising active cathode material in terms of charge rate capability, theoretical capacity, cost and sustainability being a cobalt-free material. In the current study pristine and doped (Fe, Al, Mg) LiMn1.5Ni0.5O4 particles were synthesized by an Aerosol Spray Pyrolysis pilot scale unit in a production rate of 100 gr. h−1 and were evaluated for their electrochemical activity in Half Coin Cell form. The doped particles were characterized in terms of their surface area, particle size distribution, crystallite size, morphology and ion insertion of the doping element into the LiNi0.5Mn1.5O4 lattice by Raman spectroscopy. The mixed oxide particles had homogeneous composition which is an inert characteristic of aerosol spray pyrolysis synthesis. The electrochemical activity of the material is attributed both to the nanoscale structure, by successful dopant ion insertion into the spinel lattice as well as to optimization of carbon and spinel particle interface contact in the microscale for increase of electrode conductivity.

In this study, magnesium (Mg) disks were coated with β-tricalcium phosphate (β-TCP) doped with different mass percent of silver (Ag) (0 wt%, 1 wt%, 5 wt% and 10 wt%) in an effort to modulate the detrimental osteoimmunomodulatory properties and colonization of bacteria on Mg disk, due to the reported favorable osteoimmunomodulatory properties of β-TCP and antibacterial properties of Ag. This paper describes the growth, characterization and corrosion analyses of β-TCP doped with different compositions of Ag thin film coatings. The phase composition and microstructure analyses were performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The SEM images showed that varying the percentage of Ag dopant affects the surface morphology of the β-TCP coatings. The corrosion protection behavior of the coated samples were evaluated using electrochemical measurement techniques, such as potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). The corrosion tests were performed in Hank’s Balanced salt solution using a three-electrode electrochemical cell. The results showed that the β-TCP coating and β-TCP doped with Ag coatings on the Mg disks exhibit a much superior stability and lower corrosion rate compared to bare Mg. It was observed that increasing the mass of the Ag dopant increases the corrosion protection, but 10 wt% Ag doping in β-TCP reduces the corrosion protection behavior. The SEM images of the samples after corrosion show that the β-TCP and β-TCP doped with 10 wt% Ag suffered the most corrosion attack compare to β-TCP doped with 1 wt% and 5 wt% Ag. In conclusion, we have developed β-TCP and β-TCP doped with 1 wt%, 5 wt% and 10 wt% Ag coating with tunable corrosion protection efficiency above 88%.

Abstract This work reviews the capabilities of cathodoluminescence spectroscopy to monitor several key performance indicators in GaN-based High Electron Mobility Transistors (HEMTs) manufacturing. In particular, high throughput threading dislocation (TD) density measurements in the 108-109 cm-2 range are presented, together with dislocation type discrimination capabilities. Beyond these applications, other relevant topics such as buried AlGaN layers composition and Mg dopant concentration for normally off devices are introduced.

Ferroelectrics with periodically arranged antiparallel domains are very attractive for applications in nonlinear optics,1 the major difficulty being the fabrication of perfect periodic structures. To produce bulk crystals we used Czochralski growth of lithium niobate crystals doped with Y, Dy, and with Mg as a second dopant, and barium-sodium niobate. Both crystals were grown along the ferroelectric z-axis, and lithium niobate along [ 01 1 ¯ 2 ] -direction as well (at 57° to z-axis in YZ-plane).