Increasing Deposition Time Research Articles

Nanoscale niobium coatings including superior conducting and corrosion resistance on titanium foil materials for PEMFC bipolar plates

In this work, the nanoscale Nb coating for titanium is fabricated by high power impulse magnetron sputtering technology to enhance its conductivity and corrosion resistance, which is utilized as bipolar plates material. The surface morphology, composition, corrosion resistance and conductivity of specimens with various deposition times were characterized. The results demonstrate that the thickness and roughness of nanoscale coatings increase with deposition time and all the Nb-coated titanium specimens exhibit superior corrosion resistance in 0.5 M H2SO4 solution with 5 ppm HF at 80 °C. The corrosion current density increases and then decreases with deposition time, reaching its smallest value at 600 s (3.07 μA cm−2), which is reduced by 3 orders of magnitude compared to the substrate (387.98 μA cm−2). After potentiostatic polarization experiment (PP) for 12 h, the polarization current density (ipp) of coatings reduces as deposition time increases, with values of 1.54, 0.58, 0.45 and 0.27 μA cm−2, respectively. Furthermore, a low ICR is obtained for fresh Nb-coated titanium specimens, with values of 8.45, 8.95, 3.62 and 3.04 mΩ cm2, respectively. After PP for 12 h, the ICR slightly increase to values of 9.83, 9.63, 6.76 and 6.15 mΩ cm2, which still satisfy the demand of 2025 DOE requirements (≤10 mΩ cm2).

Electrodeposition of Silicon in the Low-Temperature LiCl-KCl-CsCl-K2SiF6 Melt Under Direct and Pulse Current

In this work, the effect of electrolysis modes and their parameters on the morphology of the silicon deposits on glassy carbon were studied. In direct current mode it was found that an increase in current density and deposition time changes the morphology of the silicon from a coating to a deposit with a complex surface. Scanning electron microscopy showed that silicon films produced at low current densities and a short deposition time are represented by spherical particles with a diameter of less than 1 μm. The pulse current mode made it possible to increase the cathode density of the deposition current, and the pulse current density to an average of ≈250 mA cm−2 does not lead to the formation of a large amount of dendritic deposit. It was found that a low frequency makes it possible to obtain higher-quality silicon coatings, because when the frequency increases, the coating most often does not cover the entire electrode. The high value of the duty cycle, even at low pulse current densities, always leads to the formation of dendrites. An increase in the total deposition time also leads to an increase in the amount of deposit and the formation of dendrites.

Boiling heat transfer characteristics of Cu–Al2O3 nanocomposite coating surfaces in distributed jet array impingement

Nanocomposite coating surfaces were electrodeposited on copper substrate at various current densities, deposition times and Al2O3 concentration to experimentally investigate the enhancement of boiling heat transfer of HFE-7100 under atmospheric pressure in a distributed jet array impingement. The surface structure topography and wettability were analyzed to explore their relation to boiling heat transfer enhancement and critical heat flux (CHF). An increase in both current density and deposition time led to a decrease followed by an increase in the wettability of the Cu– Al2O3 surface. Conversely, an increase in Al2O3 concentration resulted in decreased surface wettability. However, unlike pool boiling, jet impingement attenuated the impact of enhanced surface wettability on boiling heat transfer and CHF; instead, the microstructure on the surface was found to be closely linked to boiling heat transfer performance. The nanocomposite coating surfaces exhibited a 70 % higher maximum boiling heat transfer coefficient and 50 % higher CHF than those of smooth surfaces. Excessive Al2O3 concentration weakened the enhancement of heat transfer performance due to the inhibitory effect of Al2O3 nanoparticles on copper growth, leading to reduced micro-nano structures.

Effect of Sb2S3 sacrificial layer thickness on structural, optical and electrical properties of CuSbS2 films and investigation of diode parameters of CuSbS2/CdS heterojunctions

The ternary copper chalcogenides CuSbS2 (CAS) is found to have appealing optical and photovoltaic properties to be used as absorber layer in thin film solar cells. However, the difficulty to grow good quality CuSbS2 layer of micrometer thickness by chemical bath deposition method holds a big challenge. In this work, we reported the effect of incorporating Sb2S3 sacrificial layer of different thickness on structural, optical and electrical properties of CAS films. The X-ray diffraction results and Raman spectroscopic analysis confirm the formation of single-phase orthorhombic crystal structure for CuSbS2. The increase of Sb content in CAS films with the increase in deposition time of Sb2S3 layer has been reflected in the change in relative intensity ratio of characteristic Raman peaks as well as in diffraction peak profiles. The magnitude of defect states in terms of Urbach energy is decreased drastically by increasing Sb percentage in the films. A clear improvement in electrical properties of CAS films is observed with the decrease in Cu/Sb ratio. The carrier density is increased by one order of magnitude from 1016 to 1017 cm−3 and hole mobility increases from 1.14 to 4.87 cm2/Vs. The impact of Sb concentration on Scottky diode parameters of CAS/CdS heterojunction was studied by using thermionic emission model. Both the ideality factor and series resistance are decreased with the increase in Sb content. The J-V measurements reveal that the integration of Sb2S3 sacrificial layer improves the PV parameters such as fill factor, open circuit voltage, photocurrent and efficiency. The overall improvement in diode parameters can be ascribed to decrease in defect states, better film quality, absorber layer thickness and improved stoichiometry of CAS films.

Construction of CdS/ZnO/TiO2 ternary heterojunction with hierarchical structure as photo-anode for enhancing photo-electrochemical performance

Composition and microstructure expert a significant impact on the photoelectric properties of the photo-anode. In this work, CdS/TiO2 and CdS/ZnO/TiO2 heterojunction materials were prepared using a simple and low-cost hydrothermal method. Their microstructure, crystallinity, elemental presence state and photoelectron-chemical performance of the heterojunction materials were investigated by SEM, XRD, XPS and Electrochemical workstation. The hydrothermal growth time of CdS has a significant impact on the structure and performance of heterojunctions. As the CdS deposition time increase, the photocurrent density of CdS/TiO2 shows a trend of first increasing and then decreasing. We optimized the process parameters of CdS/TiO2, and the optimal growth time for CdS is 6h. The transient photocurrent density value of CdS/TiO2 heterojunction is 0.15 mA/cm2. Depositing ZnO onto TiO2 to construct a hierarchical ZnO/TiO2 heterojunction can improve light absorption and accelerate carrier separation efficiency. The photoelectric performance of CdS/ZnO/TiO2 was compared with CdS/TiO2 and pure TiO2. The photocurrent density of CdS/ZnO/TiO2 is 1.5 mA/cm2, which is significantly larger than that of pure TiO2 and CdS/TiO2. This is due to the formation of a heterojunction between TiO2 and ZnO, which promotes the separation of carriers and ultimately improves the photoelectric performance of the CdS/ZnO/TiO2 ternary heterojunction. The fabricated CdS/ZnO/TiO2 heterojunction showed high photocurrent, which indicated a new candidate for photoelectric device.

Effect of Hydrophobic Dust Particles on the Evaporation Rate from Water Surface

In the paper, the effect of natural dust deposited from the air on the evaporation rate from the water surface is experimentally investigated. Experiments were conducted for stationary liquid without wind blowing across the surface and with mild wind that does not deform the surface, at a constant rate of particle deposition. It is shown that the evaporation rate is a linear function of the difference in the saturated vapor pressure at the water surface and the partial pressure of the air mixture at the temperature and relative humidity in the laboratory at the beginning of the deposition process, when the proportion of the surface covered with dust is small. With the increase in deposition time, hydrophobic particles gather into conglomerates, reducing the proportion of the exposed surface and the evaporation rate.

Surface Evaluation of Tricalcium Phosphate Bioceramic Coating on SS-316L by Electrophoretic Deposition

The development of orthopedic implant materials has become an important topic of discussion lately. The SS-316L alloy is widely used as an implant material due to its relatively low cost, corrosion resistance, and ease of production. However, metal alloys, especially SS-316L, are prone to ion release into the blood over time. Therefore, TCP or tricalcium phosphate [Ca3(PO4)2] is needed to coat the surface of SS-316L, preventing ion release into the blood and enhancing the biocompatibility of the implant material. In this study, TCP coating was applied to the SS-316L substrate using the electrophoretic deposition technique. The influence of deposition time on changes in microstructure and mechanical properties is the main focus of this study. The results of the coating technique indicate that the deposition yield increases with the deposition time. Morphological testing results show that increasing deposition time improves coating quality by increasing the thickness of the coating layer and preventing layer peeling. The coating process also reveals the accumulation of layers in certain areas and the formation of thin layers in other regions. A deposition time of 30 minutes results in a coating thickness ranging from 48.7 to 57.9 µm. Hardness testing, conducted with indentation loads of 50, 100, and 300 gf, indicates that longer deposition times and higher indentation loads during hardness testing result in reduced material hardness.

Deposition time dependent structural and optical properties of polycrystalline [formula omitted] films

Sputtering-derived InGaZnO4 (IGZO) thin films were grown on quartz substrates and undergone post-deposition annealing at 700 °C for 2hr in N2 ambient. The influence of deposition time or film thickness on the morphological, structural and optical properties of polycrystalline IGZO thin films has been systematically investigated by means of characterization from field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectrophotometer. Results of AFM have shown that the root-mean-square (RMS) surface roughness of the IGZO films increases from 0.888 to 2.640 nm as the deposition time is extended from 50 to 250min. Analysis of XRD indicates that all the films are in polycrystalline phase, with crystallites growing into larger size accordingly to increasing deposition time. Appealingly and scarcely ever reported, the XRD diffraction planes can be separated into three domains, such as (0 0 l), (1 0 l) and (1 1 l) with different growth thicknesses. Optical measurement suggests that the optical bandgap have redshifted from 3.55 to 3.31eV at longer deposition time. Related mechanics about the change in physical properties against deposition time have been elaborated in detail. The validity of Swanepoel method, 1983 in deriving the refractive index of thick IGZO films has also been discussed.

Chemical vapor deposition of silicon carbide on alumina ultrafiltration membranes for filtration of microemulsions

Worldwide, a considerable amount of oily wastewater is generated, with oil droplets from 2 to 200 nm that are difficult to separate because of their size and colloidal stability. This study presents a novel approach for effectively separating microemulsions via cubic silicon carbide (3C-SiC)-coated alumina (Al2O3) membranes fabricated based on low pressure chemical vapor deposition (LPCVD). SiC was deposited at a relatively low temperature at 860 °C on 100 nm Al2O3 membranes using two precursors: SiH2Cl2 and C2H2. With the increase in deposition time, up to 25 min, the pore size decreased from 41 nm to 33 nm, which is a smaller pore size of a SiC membrane than previously used for oil/water separation. The polycrystalline 3C-SiC-coated membranes showed improved hydrophilicity (water contact angle of 15°) and highly negatively charged surfaces (−65 mV). Microemulsion filtration experiments were carried out at a constant permeate flux (80 Lm−2 h−1) for six cycles with varying deposition time, pH, surfactant types, and pore sizes. The fouling of the SiC-coated membrane was, compared to the Al2O3 membrane, effectively mitigated due to the enhanced electrostatic repulsion and hydrophilicity. Surfactant adsorption mainly occurred when the surface charge of the microemulsion and the membranes were opposite. Therefore, the surface charge of the alumina membrane changed from positive to negative when soaked in negatively charged microemulsions, whereas SiC-coated membranes remained negatively charged regardless of surfactant type. The membrane fouling was alleviated when the membrane and oil droplets had the same charge. Lastly, the 62 nm SiC-coated membrane with 20 min coating time was the best choice for the filtration of the microemulsion, because of the high rejection of the oil droplets and low fouling tendency.

Highly flexible copper tape decorated with Ag nanoarrays as ultrasensitive SERS platforms for multi-hazardous pollutant sensing.

Ahighly flexible and cost-effective copper tape decorated with silver nanoparticles (Cu-TAg) has been developed for surface-enhanced Raman spectroscopy (SERS) sensing of multi-hazardous environmental pollutants. Highly ordered and spherical-shaped silver nanoarrays have been fabricated using a low-cost thermal evaporation method. The structural, morphological, and optical properties of Cu-TAg sensors have been studied and correlated to the corresponding SERS performances. The size of nanoparticles has been successively tuned by varying the deposition time from 5 to 25s. The nanoparticle sizes were enhanced with an increase in the evaporation time. SERS investigations have revealed that the sensing potential is subsequently improved with an increase in deposition time up to 10s and then deteriorates with further increase in Ag deposition. The highest SERS activity was acquired for an optimum size of ~ 37nm; further simulation studies confirmed this observation. Moreover, Cu-TAg sensors exhibited high sensitivity, reproducibility, and recycling characteristics to be used as excellent chemo-sensors. The lower detection limit estimation revealed that it can sense even in the pico-molar range for sensing of rhodamine 6G and methylene blue. The estimated enhancement factor of the sensor is found to be 9.4 × 107. Molecular-specific sensing of a wide range of pollutants such as rhodamine 6G, alizarin red, methylene blue, butylated hydroxy anisole, and penicillin-streptomycin is demonstrated with high efficiencies for micromolar spiked samples. Copper tape functionalized with Ag arrays thus demonstrated to be a promising candidate for low-cost and reusable chemo-sensors for environmental remediation applications.

Electrospun PCL Filtration Membranes Enhanced with an Electrosprayed Lignin Coating to Control Wettability and Anti-Bacterial Properties.

This study reports on the two-step manufacturing process of a filtration media obtained by first electrospinning a layer of polycaprolactone (PCL) non-woven fibers onto a paper filter backing and subsequently coating it by electrospraying with a second layer made of pure acidolysis lignin. The manufacturing of pure lignin coatings by solution electrospraying represents a novel development that requires fine control of the underlying electrodynamic processing. The effect of increasing deposition time on the lignin coating was investigated for electrospray time from 2.5 min to 120 min. Microstructural and physical characterization included SEM, surface roughness analysis, porosity tests, permeability tests by a Gurley densometer, ATR-FTIR analysis, and contact angle measurements vs. both water and oil. The results indicate that, from a functional viewpoint, such a natural coating endowed the membrane with an amphiphilic behavior that enabled modulating the nature of the bare PCL non-woven substrate. Accordingly, the intrinsic hydrophobic behavior of bare PCL electrospun fibers could be reduced, with a marked decrease already for a thin coating of less than 50 nm. Instead, the wettability of PCL vs. apolar liquids was altered in a less predictable manner, i.e., producing an initial increase of the oil contact angles (OCA) for thin lignin coating, followed by a steady decrease in OCA for higher densities of deposited lignin. To highlight the effect of the lignin type on the results, two grades of oak (AL-OA) of the Quercus cerris L. species and eucalyptus (AL-EU) of the Eucalyptus camaldulensis Dehnh species were compared throughout the investigation. All grades of lignin yielded coatings with measurable antibacterial properties, which were investigated against Staphylococcus aureus and Escherichia coli, yielding superior results for AL-EU. Remarkably, the lignin coatings did not change overall porosity but smoothed the surface roughness and allowed modulating air permeability, which is relevant for filtration applications. The findings are relevant for applications of this abundant biopolymer not only for filtration but also in biotechnology, health, packaging, and circular economy applications in general, where the reuse of such natural byproducts also brings a fundamental demanufacturing advantage.

Controlling Gold Morphology Using Electrodeposition for the Preparation of Electrochemical Aptamer-Based Sensors.

Nanostructuring of gold surfaces to enhance electroactive surface area has proven to significantly enhance the performance of electrochemical aptamer-based (E-AB) sensors, particularly for electrodes on the microscale. Unlike for sensors fabricated on polished gold surfaces, predicting the behavior of E-AB sensors on surfaces with varied gold morphologies becomes more intricate due to the effects of surface roughness and the shapes and sizes of surface features on supporting a self-assembled monolayer. In this study, we explored the impact of gold morphology characteristics on sensor performance, evaluating parameters such as signal change in response to the addition of the target analyte, aptamer probe packing density, and continuous sensing ability. Our findings reveal that surface area enhancement can either enhance or diminish sensor performance for gold nanostructured E-AB sensors, contingent upon the surface morphology. In particular, our results indicate that the aptamer packing density and target analyte signal change results are heavily dependent on gold nanostructure size and features. Sensing surfaces with larger nanoparticle diameters, which were prepared using electrodeposition at a constant potential, had a reduced aptamer packing density and exhibited diminished sensor performance. However, the equivalent packing density of polished electrodes did not yield the equivalent signal change. Other surfaces that were prepared using pulsed waveform electrodeposition achieved optimal signal change with a deposition time, tdep, of 120 s, and increased deposition time with enhanced electroactive surface area resulted in minimized signal changes and more rapid sensor degradation. By investigating sensing surfaces with varied morphologies, we have demonstrated that enhancing the electroactive surface does not always enhance the signal change of the sensor, and aptamer packing density alone does not dictate observed signal change trends. We anticipate that understanding how electrodeposition techniques enhance or diminish sensor performance will pave the way for further exploration of nanostructure-aptamer relationships, contributing to the future development of optimized, miniaturized electrochemical aptamer-based sensors for continuous, in vivo sensing.

Deposition time dependent physical properties of semiconductor CuO sprayed thin films as solar absorber

This study aims to develop copper oxide (CuO) films on standard glass substrates using the spray pyrolysis technique and investigate the effect of different deposition times on their structural, morphological, wettability, optical, and electrical properties to enhance their optoelectronic characteristics. CuO thin films were fabricated at different deposition times (5 to 20 min) with a substrate temperature of 400 °C. X-ray diffraction (XRD) analysis confirmed the crystalline structure of all deposited CuO films, showing a monoclinic phase with preferential orientation along the (111) direction, indicating a well-ordered atomic arrangement. Atomic force microscopy (AFM) examination revealed the influence of deposition time on the surface morphology, with a low roughness value of 13.315 nm observed for the 10 min film compared to 19.432 nm for the 20 min film. Contact angle (CA) analysis showed a transition from hydrophilic to hydrophobic behavior as the deposition time increased, indicating significant changes in surface properties. This transition to a hydrophobic nature (CA = 105°) for the 20 min sample is important for protecting photovoltaic devices from humidity-related degradation, ensuring long-term reliable operation even in challenging conditions. The transmittance of the film in the visible region was low, indicating high absorbance of CuO. The optical gap decreased from 1.98 to 1.61 eV with increasing deposition time, making films suitable as absorber layers in solar cells. Electrical analysis showed improved conductivity with increasing deposition time, leading to a decrease in electrical resistivity (3.77 Ω.cm) and high charge density (1.269 × 1016 cm−3) for the 20 min film. Therefore, the 20 min deposition film with a hydrophobic character exhibited good p-type electrical semiconductor properties and efficient absorption of solar light, making it promising for thin film solar cell applications.

Mechanical and Corrosion resistance behavior of Ultrasonication-assisted Electrodeposited Ni–SiC Nanocomposite coatings

Pure Ni/Ni–SiC composite coatings were electrodeposited onto stainless-steel substrate using ultrasonic-assisted electroco-deposition techniques by varying the deposition times. The investigations mainly focus on the structural, microstructural, mechanical, and corrosion properties of the composites coating deposited by varying deposition times in the presence of sodium dodecyl sulphate surfactant and Silicon carbide (SiC) nanoparticles (∼50 nm) reinforcement. The incorporation of filler and increasing deposition time decreases the surface roughness of the coating, making the composite Ni–SiC 2 h deposition smoother as (0.087 ± 0.005) μm compared to other coatings. X-Ray Diffraction results indicated that the coating exhibited an FCC Ni-type structure with the primary orientation along the (200) direction. Microstructural studies conducted with a scanning electron microscope revealed irregular shaped granules within the composite, along with fine grains, and their compaction increased with longer deposition times. Energy dispersive X-ray spectroscopy and elemental mapping confirmed that SiC was uniformly distributed in the 2 h composite coatings. This resulted in a considerable enhancement of the composite's mechanical properties, with a nano hardness of (3.12 ± 0.13) GPa and bulk microhardness of (213 ± 5) HV on both the top surface and cross-sectional surface of the composites, respectively. The corrosion study indicated that the Ni–SiC composite films deposited for 2 h provided better corrosion resistance when compared to pure Ni coating.

P-Type LaCuOS films grown by PLD using a quaternary target fabricated by a two-step solid-state reaction/sulfurization process

A LaCuOS target was obtained through a two-step route: first, the synthesis of the CuLaO2 compound by solid-state reaction, and subsequently its sulfurization under a sulfur atmosphere. The LaCuOS powder was used to deposition films by pulsed laser deposition at different growth times: 10, 15, 20, and 25 min. The films were deposited in vacuum at a substrate temperature of 400 °C and a wavelength of 266 nm. The structural characterization showed that the dislocation density and stress in LaCuOS films increase as the deposition time increases. The LaCuOS films exhibit optical transmittance of 52–81 % in the visible region. Electrical measurements indicate high values of hole mobility and carrier densities up to 1019 cm−3, with a p-type electrical conductivity of 0.74 S/cm; these properties suggest that LaCuOS films have the potential to be integrated as transparent material in devices.

Electrodeposition of crystalline germanium thin films by the electrochemical liquid-liquid-solid method

The direct electrodeposition of crystalline germanium thin films in aqueous solutions at low temperatures represents a promising and cost-effective method for synthesising semiconductor materials. This study investigates the influence of the deposition potential and time on the characteristics of crystalline germanium thin films derived from germanium oxide precursors in aqueous solution through electrochemical liquid–liquid-solid (ec-LLS) process at low temperature. Additionally, it establishes a Ge/Cu Schottky junction by heterogeneous growth of germanium films on copper (Cu) metal via electrochemical liquid–liquid-solid–solid (ec-LLSS) process.X-ray diffraction (XRD) analysis revealed that an increase in the deposition potential to −1.7 V resulted in a shift in the crystal orientation of the germanium film from (220) to (111), while excessive deposition potential (>−2.0 V) led to a reduction in the crystallinity of the deposited samples. At a deposition temperature of 70 °C and a deposition potential of −1.8 V, the crystal cluster size and the crystal quality increased with the increasing deposition time. However, at −2.0 V, the crystallinity of the germanium film reached an optimal state after 30 min and then gradually declined with time.Charactersation techniques such as EDS, XPS and Raman spectroscopy indicated that the use of liquid electrode Ga(l) as a doping source during the electrodeposition process allowed for heterogeneous growth of Ga-doped p-type germanium films on a Cu substrate.The I-V characteristic curves demonstrated that the Ge/Cu Schottky junctions exhibited significant rectification characteristics, rendering them suitable for potential applications in solar cells.

Electrical and thermal conductivity in graphene-enhanced carbon-fibre/PEEK: The effect of interlayer loading

Combining graphene at different loadings with composites offers the possibility of tailored electrical and thermal properties for the aerospace sector, including electrostatic dissipation, thermal management and lightning strike protection applications. The effects of interlaminar graphene loadings to impart property enhancement in fibre reinforced thermoplastic composites remains unknown. Spray deposition offers a highly scalable, and rapid method to embed graphene. This study investigates the application of spray-deposited graphene suspension synthesised via liquid phase exfoliation (LPE) to functionalise carbon fibre/polyether ether ketone (CF/PEEK) composites. LPE graphene suspensions were spray deposited onto CF/PEEK prepreg ply substrates to create smooth thin films. With increased deposition time the graphene thin film root mean squared roughness decreased from 3.51 μm to 2.52 μm. The addition of 0.25 wt%, 0.7 wt% and 1.1 wt% graphene to the interlaminar regions in consolidated CF/PEEK imparted enhanced electrical and thermal conductivity. Electrical conductivity enhancement of up to ∼252% transverse to the fibre direction and up to ∼204% through thickness was measured after the addition of 0.25 wt% graphene. Thermal diffusivity increased up to ∼183% through-thickness, while 61% in the transverse to the fibre direction with 0.7 wt% additions. However, increased graphene loading also increased the void content in the composite resulting in reduced shear strength. Excess surfactant vapourisation during high temperature processing likely created voids up to 2.8 vol% often located within the interply and interlaminar region hindering anisotropic conductivity enhancement. Nevertheless, graphene loadings within the interlaminar region show promise in imparting bulk property enhancement.

One-step spin-coating of methylammonium lead iodide on SILAR-deposited tin oxide, SnO2 films for effective electron transport

Tin oxide (SnO2) materials were prepared via successive ionic layer adsorption and reaction (SILAR) technique at varying deposition times. The synthesized tin oxide layer served as an electron transport layer for the deposition of a perovskite layer via spin coating method. The morphology, structure, elemental, optical features and vibration modes of the prepared samples have been studied using scanning electron microscopy (SEM), X-ray diffractometry (XRD), energy dispersive X-ray spectroscopy (EDX), UV–vis spectrophotometry, and Raman spectrophotometry, respectively. The films revealed granular-shaped nanograins with a maximum average grain size of 197.03 nm. XRD results showed a cassiterite pure-phase crystal structure with several prominent peaks. EDX studies confirmed the as-deposited elemental constituents with good optical properties obtained from the optical studies. The band gap energies ranged from 4.01 to 4.24 eV at increasing deposition times. The phonon modes and crystal structures were also revealed from the Raman studies. The materials find applications in solar cells and electronic devices.

Investigation of linear and non-linear optical features of crystalline and non-crystalline iron oxide thin films for optoelectronic purposes

Spray pyrolysis at various temperatures was employed to produce non-crystalline and crystalline iron oxide (α-Fe2O3) thin films on glass. The amorphous and crystalline characteristics of α-Fe2O3 thin films were affirmed via X-ray diffraction analysis. With low deposition times (5 min) and at various substrate temperatures, iron oxide seems almost in a non-crystalline structure. As for the increase in deposition time (40 min), the crystallinity’s degree was enhanced. According to Tauc’s law, the direct gap energy Ed for both the amorphous and the crystalline phases, were found to be 1.95 and 2.125 eV, respectively. Moreover, the indirect gap energy, Ein = 1.65 and 1.71 eV were obtained for the amorphous phases and the crystalline phases, respectively. The linear and non-linear optical features of amorphous and crystalline structure were meticulously and adaptably detailed. It is observed that the behavior of the refractive index n (λ) and extinction coefficient k (λ) of the crystalline state was lower than that of the amorphous state. The real and imaginary linear dielectric constant and also the thin film quality factor were estimated for both the amorphous and crystalline states as well as the volume and surface energy loss functions for the crystalline and amorphous states. In conclusion, amorphous and crystalline α-Fe2O3 nanocrystalline films improved their optical properties, making them potential candidates for multifunctional applications such as optoelectronics and spintronics electronics devices.

Numerical Evaluation of the Effect of Buoyancy-Driven Flow on the Migration of Respiratory Droplets

The understanding of the impact of buoyancy-driven flow on the migration of respiratory droplets remains limited. To investigate this phenomenon, the Lagrangian–Eulerian approach (k-ε turbulent model and discrete phase model) was employed to analyze the interaction between buoyancy-driven flow and coughing activity. The simulation approach was validated by simulating a jet problem in water. Although this problem describes the jet penetration in water, the governing equations for this problem are the same as those for coughing activity in the air. The results demonstrated that an umbrella-shaped airflow was generated above a person and a temperature stratification existed in the room. The buoyancy-driven flow significantly altered the dispersion pattern of the droplets. Notably, for large droplets with an initial diameter of 100 μm, the flow in the boundary layer led to an increased deposition time by about five times. Conversely, for small droplets with an initial diameter of 20 μm, the umbrella-shaped airflow resulted in a more rapid dispersion of droplets and subsequently facilitated their quicker removal by the room walls. After a duration of 300 s, the suspended droplet number of the case with buoyancy-driven flow was 33.4% smaller than that of the case without buoyancy-driven flow. Two or three persons being in the room resulted in a faster droplet removal.