Search Results (41)

This article analyzes the reactive magnetron sputtering process, using a two-element Zn-Al target, for depositing aluminum-doped zinc oxide (AZO) layers, aimed at transparent electronics. AZO films were deposited on Corning 7059 glass, flexible Corning Willow^® glass and amorphous silica substrates. To optimize the process, the study examined the target surface state across varying argon/oxygen ratios. The gas mixture significantly influenced the Al/Zn atomic ratio in the films, affecting their structural, optical and electrical performance. Films deposited at 80/20 argon/oxygen ratio—near the dielectric mode—showed high light transmission (84%) but high resistivity (47.4·10⁻³ Ω·cm). Films deposited at ratio of 84/16—close to metallic mode—exhibited lower resistivity (1.9·10⁻³ Ω·cm) but reduced light transmission (65%). The best balance was achieved with an 82/18 ratio, yielding high light transmission (83%) and low resistivity (1.4·10⁻³ Ω·cm). These findings highlight the critical role of sputtering atmosphere in tailoring AZO layer properties for use in transparent electronics. Full article

In this work, a cylindrical gate-all-around junctionless field effect transistor (JLFET) was investigated. Junctions and doping concentration gradients are unavailable in JLFET. According to the results, the suggested device has a novel architecture that significantly enhances transistor performance while exhibiting a decreased vulnerability to short-channel effects (SCEs). The Atlas 3D device simulator has been used to analyze the proposed JLFET’s performance, especially for low-power applications for different channel lengths ranging from 10 nm to 60 nm with Al_0.30Ga_0.60As as III-V materials. The comparative simulated study has been based on various performance parameters, including subthreshold slope (SS), drain-induced barrier lowering (DIBL), transconductance, threshold voltage, and I_ON to I_OFF ratio. The results of the simulations demonstrated that the III-V JLFET exhibited a favorable SS and decreased DIBL compared to other circuit topologies. In the suggested study, gallium arsenide (GaAs) and its compound materials have demonstrated a strong correlation between the SS and DIBL values. The SS is approximately 63 mV/dec, extremely near the ideal 60 mV/dec value. Gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) exhibit DIBL of approximately 30 mV/V and an SS value of around 64 mV/dec. Full article

The alumina, in the form of α-Al₂O₃ tabular balls, considered in this study is a high-purity form of aluminum oxide that has been fired at high temperatures (well above 1900 °C), virtually removing porosity. However, the purity and inertness of the surface of the Al₂O₃ tabular balls minimize the catalytic activity, which is why lithium doping was tried. Thus, the target of this study was the effect of doping with lithium ions in some tabular balls of Al₂O₃ (the crystalline structure is corundum) on the improvement of the catalytic properties of alumina. This study examined the impact of a lithium catalyst on the combustion of various fuels within a porous inert medium (PIM) burner. This study specifically compared low calorific gaseous fuel (e.g., biogas) combustion in a PIM burner with and without the lithium catalyst. The experimental setup comprised a gas preparation unit for mixing CNG and CO₂ to simulate biogas and a PIM burner. The PIM burner comprised Al₂O₃ spheres (13 mm diameter, 45% porosity) in a random packing configuration. Three fuels, varying in composition and lower heating value (LHV ranging from 20.771 to 27.695 MJ/m³), were combusted at air ratios ranging from 1.67 to 1.79. The results indicated that the catalyst increased peak combustion temperatures by 23.2 °C to 51.4 °C, depending on the fuel type and air ratio. Significantly higher carbon monoxide (CO) concentrations were observed without the catalyst, particularly with fuel type F1, while nitrous oxide (NOx) levels remained consistently low. Upstream flame propagation was observed in the presence of the catalyst. These findings demonstrate the potential of lithium catalysts to enhance combustion stability and reduce emissions in porous media combustion burners. Following these studies, it can be stated that Li(I) has the role of promoter of the catalytic process. Full article

The influence of Mg doping in α-Al₂O₃ crystals is investigated in this article by first-principles calculations and formation energies, density of states, and computed absorption spectra. Three models related to Mg²⁺ substituting for Al³⁺ doping structures were constructed, as well as spinel structure models with varying aluminum-magnesium ratios. The formation energy calculations confirmed the rationality of the Mg_AlV_O model, which means that Mg substitutional doping incorporating oxygen vacancies is most likely to form in crystals. The combined action of magnesium and oxygen vacancies introduced new defect energy levels in the bandgap. The calculated absorption spectra of the Mg_AlV_O and Mg-rich spinel structures exhibited various color centers. The experimental absorption spectra and thermoluminescence characteristics of α-Al₂O₃:Mg and alumina-magnesium (Al-Mg) spinel crystal samples were tested. The thermoluminescence peak of the Al-Mg spinel was significantly stronger than that of the α-Al₂O₃:Mg crystal. The consistency between the model-calculated absorption spectra and the experimental results confirmed the theoretical predictions. Based on the experimental and computational results, the influence of Mg²⁺ substitutional doping in α-Al₂O₃ and the impact of the locally Mg-rich spinel on the optical and radiation performance of α-Al₂O₃:Mg crystals are elucidated. Full article

To reduce production costs and enhance the high-temperature resistance of SiO₂ aerogels, an aluminum-doped silica aerogel (ASA) was successfully prepared using the sol-gel method and atmospheric drying method. The composite silica sources included TEOS and inexpensive acidic silica sol, while the aluminum source was aluminum sol. The study investigated the influence of the molar ratio of acidic silica sol to TEOS, Al/Si, and calcination temperature on the composition, structure, and high-temperature resistance of the ASA. The results indicate that a sample with an acidic silica sol to TEOS molar ratio of 0.8 achieved a specific surface area of 683.204 m²·g⁻¹. The Al/Si molar ratio significantly impacted the high-temperature resistance of the ASA, with the sample having a molar ratio of 0.02 Al/Si displaying the highest specific surface area of 705.956 m²·g⁻¹ at 600 °C. Moreover, this surface area remained at 273.099 m²·g⁻¹ after calcination at 1000 °C, notably higher than the sample without aluminum sol (16.082 m²·g⁻¹). Mechanism analysis indicated that the addition of aluminum sol to the SiO₂ aerogel inhibited phase transitions, and both acidic silica sol and aluminum sol particles enhanced the aerogel structure, contributing to a marked improvement in high-temperature resistance. Full article

Precast ultra-high-performance concrete (UHPC) has emerged as indispensable in the engineering sector due to its cost-effectiveness and superior performance. Currently, precast UHPC grapples with challenges pertaining to slow setting times and insufficient early strength, largely attributed to its high water-reducing agent content. Effective utilization of early strength agents to augment UHPC’s early strength is pivotal in addressing this issue. This study investigates the efficacy of two distinct concrete early strength agents, namely calcium formate (Ca(HCO₂)₂) and aluminum sulfate (Al₂(SO₄)₃). A UHPC system with a water/cement ratio of 0.17 was used; both single and compound doping experiments were conducted using varied dosages of the aforementioned early strength agents. Our results show that both early strength agents significantly reduce setting time and enhance early strength at appropriate dosages. Specifically, the addition of 0.3% Ca(HCO₂)₂ led to a 33.07% decrease in setting time for UHPC. Moreover, the incorporation of 0.3% Ca(HCO₂)₂ and 0.5% Al₂(SO₄)₃ resulted in a strength of 81.9 MPa at 1.5 days, representing a remarkable increase of 118.4%. It is noteworthy that excessive use of Ca(HCO₂)₂ inhibits the hydration process, whereas an abundance of Al₂(SO₄)₃ diminishes the early strength effect. Simultaneously, this article provides recommendations regarding the dosage of two distinct early strength agents, offering a novel solution for expediting the production of prefabricated UHPC with a low water/cement ratio and high water-reducing agent content. Full article

Aluminum Nitride (AlN) is a promising piezoelectric material for microelectromechanical systems owing to its attractive physical and chemical properties and CMOS compatibility. It has a moderate piezo response compared to its rival material bound to its wide application. This obstacle can be overcome by doping or alloying. Sc alloying increases the piezo response of AlN up to four-fold; it also increases the electromechanical coupling coefficient, which is a prominent figure of merit for any MEMS device application. Sc doping induces elastic softening in wurtzite AlN, enhances polarization, and increases piezoelectric constants. However, the possibility of phase separation at higher Sc concentrations, and the wurtzite phase of AlN, which is responsible for piezoelectricity, becomes negligible. Therefore, knowing the optimum concentration of Sc for device applications is necessary. In this work, using density functional theory, we calculated the lattice parameter, band and density of states along with the physical properties such as Young’s modulus, the bulk modulus, Poisson’s ratio, and elastic constants of pristine AlN and Sc doped AlN. The DFT calculations show that the geometrical optimized lattice parameters agree with the literature. As a function of increased Sc concentration, the calculated Young’s modulus and elastic constants decrease, indicating a decrease in hardness and elastic softening, respectively. Meanwhile, the bulk modulus and Poisson’s ratio increase with an increase in Sc concentration, representing an increase in the crystal cell parameters and elastic deformation. AlN and AlScN thin films were grown on Si (111) substrate using magnetron sputtering to study the structural properties experimentally. The deposited films show the required c-axis (002) preferential crystallographic orientation. The XRD peaks of Sc doped AlN thin films have shifted to a lower angle than pristine AlN, indicating elastic softening/tensile stress in grown thin films. So, from our observation, we can conclude that Sc doping induces elastic softening in AlN and deposited films have a preferential crystallographic orientation that can be applied in MEMS devices. Full article

This article discusses an effective method for obtaining superconducting composites based on Y₁Ba₂Cu₃O_7-δ (YBCO) by optimizing the total preparation time in comparison with similar scientific works while searching for effective modifying micro-additives. YBCO-based composites were doped with microparticles of aluminum, nickel, and iron. It was established that the initial ratio of green components, heat treatment, and holding time directly affect the qualitative and quantitative formation of the useful superconducting phase Y₁₂₃, which in turn affects the basic superconducting properties of the final material. Full article

Methanol is a prospective hydrogen storage medium that holds the potential to address the challenges of hydrogen storage and transportation. However, hydrogen production via methanol steam reforming faces several key obstacles, including high reaction temperature (e.g., 250–300 °C) and low methanol conversion (at <200 °C), while the purification procedure of hydrogen is commonly required to obtain high-purity H₂. A novel method of H₂ absorption-enhanced steam reforming of methanol is proposed to overcome the challenges mentioned above. The method involves the absorption and separation of H₂ using an absorbent to facilitate the forward shift of the reaction equilibrium and enhance reaction performance. A thermodynamic analysis using the equilibrium constant method presents that the separation of H₂ can improve the methanol conversion rate and the total H₂ yield. The feasibility of the method is validated through experiments in a fixed-bed reactor (4 mm diameter, 194 mm length) under the conditions of 200 °C and 1 bar. In the experiments, 1 g of bulk catalyst (CuO/ZnO/Al₂O₃) and 150 g of bulk hydrogen absorbent (Aluminum-doped lanthanum penta-nickel alloy, LaNi_4.3Al_0.7 alloy) are sequentially loaded into the reactor. As a proof of concept, a CO₂ concentration of 84.10% is obtained in the reaction step of the first cycle, and a gas stream with an H₂ concentration of 81.66% is obtained in the corresponding regeneration step. A plug flow reactor model considering the kinetics is developed to analyze the effects of the number of cycles and H₂ separation ratio on the enhancement performance. The method indicates a high potential for commercialization given its low reaction temperature, high-purity H₂, and membrane-free design. Full article

Luminescent thermometers based on the luminescence intensity ratio between two thermally coupled levels have a strong appeal in the biomedical area due to the possibility of monitoring the temperature of deep tissues. In such procedures, it is necessary that the excitation and emission wavelengths are within the biological windows. Probes based on neodymium luminescence, with excitation and emission around 800 and 880 nm, are frequently proposed but have low relative sensitivity (0.2%.K⁻¹) due to the small energy separation between the explored Stark sublevels. By changing the excitation wavelength to around 750 nm, it is possible to explore the thermal coupling between the ⁴F_5/2 and ⁴F_3/2 levels. However, lasers in this wavelength range are not common. An alternative is to use LEDs as an excitation source. As a proof of concept, we investigated the thermometric performance of three distinct Nd-doped luminescent probes under 730 nm LED excitation and 532 nm laser excitation: nanocrystalline Y₂O₃, LiBaPO₄ microcrystals, and lithium-boron-aluminum (LBA) glass. The results indicated that the use of LEDs as an excitation source can be applied in nano-, micro- and macro-structured probes, as it does not compromise the thermometric performance of the systems, which exhibited relative sensitivities of approximately 2%.K⁻¹. Full article

Many scholars have focused on the workability and mechanical properties of fly ash (FA)- ground granulated blast furnace slag (GGBS) geopolymer. To enhance the compressive strength of geopolymer, zeolite powder was added in the present study. A series of experiments were carried out to investigate the effect of using zeolite powder as an external admixture on the per-formance of FA-GGBS geopolymer, 17 sets of experiments were designed and tested to deter-mine the unconfined compressive strength based on the response surface methodology, and then, the optimal parameters were obtained via modeling of 3 factors (zeolite powder dosage, alkali exciter dosage, and alkali exciter modulus) and 2 levels of compressive strength (3 d and 28 d). The experimental results showed that the strength of the geopolymer was the highest when the three factors were 13.3%, 40.3%, and 1.2. Finally, a combination of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and ²⁹Si nuclear magnetic resonance (NMR) analysis was used to conduct micromechanical analysis and explain the reaction mechanism from a microscopic perspective. The SEM and XRD analysis revealed that the microstructure of the geopolymer was the densest when the zeolite powder was doped at 13.3%, and the strength increased accordingly. The NMR and Fourier transform infrared spectroscopy analyses revealed that the absorption peak wave number band shifted toward the lower wave number band under the optimal ratio, and the silica–oxygen bond was replaced by an aluminum–oxygen bond, which generated more aluminosilicate structures. Full article

Nanocomposites formed by aluminum-doped zinc oxide nanoparticles (AZO–NP) and multiwall carbon nanotubes (CNT) are proposed here as a promising material for UV light sensing applications, with the great advantage of operating in air, at room temperature, and at low voltage. Nanocomposite layers were prepared with different AZO:CNT weight ratios by a simple methodology at room temperature. They were characterized by means of UV–Vis spectroscopy, scanning and transmission electron microscopies (SEM and TEM), and X-ray photoelectron spectroscopy (XPS). The interaction between the two nanomaterials was demonstrated by comparing the properties of the nanocomposite with the ones shown by the AZO–NPs. Dense AZO–CNT nanocomposite layers were deposited between two metal electrodes on a SiO₂/Si substrate, and the electrical properties were investigated in dark condition and under UV light irradiation. The electrical response to the UV light was a sudden current increase that reduced when the light was switched off. Several UV on/off cycles were performed, showing good repeatability and stability of the response. The mechanisms involved in the electrical response are discussed and compared to the ones previously reported for ZnO–CNT nanocomposites. Full article

Resistive random-access memory (RRAM) is a promising candidate for next-generation non-volatile memory. However, due to the random formation and rupture of conductive filaments, RRMS still has disadvantages, such as small storage windows and poor stability. Therefore, the performance of RRAM can be improved by optimizing the formation and rupture of conductive filaments. In this study, a hafnium oxide-/aluminum-doped zinc oxide/hafnium oxide (HfO₂/Al-ZnO/HfO₂) tri-layer structure device was prepared using the sol–gel method. The oxygen-rich vacancy Al-ZnO layer was inserted into the HfO₂ layers. The device had excellent RS properties, such as an excellent switch ratio of 10⁴, retention of 10⁴ s, and multi-level storage capability of six resistance states (one low-resistance state and five high-resistance states) and four resistance states (three low-resistance states and one high-resistance state) which were obtained by controlling stop voltage and compliance current, respectively. Mechanism analysis revealed that the device is dominated by ohmic conduction and space-charge-limited current (SCLC). We believe that the oxygen-rich vacancy concentration of the Al-ZnO insertion layer can improve the formation and rupture behaviors of conductive filaments, thereby enhancing the resistive switching (RS) performance of the device. Full article

This study proposed an effective method for optimizing laser drilling processing (LDP) by using grey relational analysis (GRA) for multiple performance requirements. First, we developed a system using a Quantel Brilliant Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser with a pulse width of 5–6 ns and F-theta lenses to deliver a focused laser beam with a diameter of 0.2 mm. The developed system was first employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate on a safe window with a high optical density and a grade of OD 7+ @ 950~1085 nm. To avoid errors in the experimental data due to unstable power, a laser power (energy) meter was used to measure the energy stability of the Quantel Brilliant Pulse Laser. Given the stability of 5.6%, this is an effective method for LDP. Four control factors were investigated, including laser pulse energy, repetition rate, focusing position offset, and drilling time. Then, nine experiments were performed using the Taguchi method with orthogonal arrays in L₉ (3⁴). The experimental results with multiple quality characteristics were measured and used to optimize the control factors by using GRA with equal weighting of the four qualities (roundness, Hillock ratio, taper, and HAZ). The results show that A1B3C1D1 is the optimal combination of the control factors, and the maximal variation of 0.406 is obtained from the control factor B (focusing position offset) which has the greatest contribution to the drilling time. We then performed confirmation experiment and obtained a better result from the combination of the control factors, A1B3C1D1. GRA helps us determine the best laser drilling parameters to meet the desired multiple drilling qualities. Full article

Complex composite films based on polyaniline (PANI) doped hydrochloric acid (HCl) incorporated with aluminum nitrate (Al(NO₃)₃) on Au-layer were designed and synthesized as a surface plasmon resonance (SPR) sensing device. The physicochemical properties of (PANI-HCl)/Al(NO₃)₃ complex composite films were studied for various Al(NO₃)₃ concentrations (0, 2, 4, 8, 16, and 32 wt.%). The refractive index of the (PANI-HCl)/Al(NO₃)₃ complex composite films increased continuously as Al(NO₃)₃ concentrations increased. The electrical conductivity values increased from 5.10 µS/cm to 10.00 µS/cm as Al(NO₃)₃ concentration increased to 32 wt.%. The sensitivity of the SPR sensing device was investigated using a theoretical approach and experimental measurements. The theoretical system of SPR measurement confirmed that increasing Al(NO₃)₃ in (PANI-HCl)/Al(NO₃)₃ complex composite films enhanced the sensitivity from about 114.5 [Deg/RIU] for Au-layer to 159.0 [Deg/RIU] for Au-((PANI-HCl)/Al(NO₃)₃ (32 wt.%)). In addition, the signal-to-noise ratio for Au-layer was 3.95, which increased after coating by (PANI-HCl)/Al(NO₃)₃ (32 wt.%) complex composite layer to 8.82. Finally, we conclude that coating Au-layer by (PANI-HCl)/Al(NO₃)₃ complex composite films enhances the sensitivity of the SPR sensing device. Full article