Atomic Ratio Research Articles

Development, process optimization and assessment of sustainable mobile biochar kiln for agricultural use

A novel and energy-efficient biochar kiln that can be operated in the field with few requirements has been developed. The generated syngas are recirculated into the combustion chamber to heat biomass. This study optimized the feedstock parameters, biochar yield, and economics of producing biochar from soybean straw using the Response Surface Methodology (RSM) based on Central Composite Design (CCD). The biochar kilns had an energy conversion efficiency of 47.02% and an overall kiln efficiency of 41.03% at steady-state operation over 500 °C. It produced an average of 29.43 ± 1.42% biochar with a minimal fuel-to-biochar ratio of 0.19 ± 0.02 and a payback period of 4.02 months. The statistical analysis confirmed that the characteristics of the feedstock affect the biochar output and economic aspects of the biochar production process. Based on the optimization studies, it was concluded that the feedstock's moisture content should be 8% and particle size should be 15 mm for higher biochar yield with maximum energy efficiency and benefit-cost ratio. Biochar produced at optimal conditions obtained from the optimization process was also characterized. Physical-chemical analysis reveals that biochar has a higher carbon content (79.38 ± 1.04 %) and a lower atomic ratio of H/C (0.696), O/C (0.14), and (N + O)/C (0.08), indicating higher carbon stability and aromaticity. The TGA analysis demonstrated the high thermal stability of biochar by showing a lower (2.15%) mass loss between the 343.8 and 407.1 °C temperature range. The SEM and TEM micrographs showed the microporous structure of the soybean straw biochar with a worm-like pattern and a cylindrical shape.

Plant-Mediated Synthesis of Zinc Oxide (ZnO) Nanoparticles Using Alnus nepalensis D. Don for Biological Applications

An aqueous bark extract of A. nepalensis D. Don was utilized to prepare zinc oxide (ZnO) nanoparticles through a green method, which is more economical, eco-friendly, and effective for exploring several biological applications and toxicity assessments against brine shrimp nauplii. The prepared ZnO nanoparticles were characterized using several characterizing techniques. The surface morphology and the elemental composition of the prepared ZnO NPs was analyzed by field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray (EDX) analysis. The colour of the solution was changed from reddish-brown to white indicating the formation of ZnO NPs which shows UV-vis absorption at 361 nm. The various functional groups of the organic compounds present in plant extract act as reducing and stabilizing agents in the formation of nanoparticles. The involvement of these functionalities in the formation of nanoparticles is indicated by the shifts and changes in the IR spectra of both the plant extract and the ZnO nanoparticles. The size of the nanoparticles was determined to be 15.31 nm with XRD analysis while the FE-SEM revealed the average grain size of 67.29 nm with irregular shape. The elemental composition of ZnO NPs shows a greater atomic percentage of zinc compared to other elements (C, N, Ni, O, and Ag), with an intense peak of zinc observed at approximately 1 keV. The trace amount of silver is due to the impurities present in the reagent used in the experiment. The antioxidant property of ZnO nanoparticles was evaluated with an IC₅₀ of 53.02 ± 3.43 μg/mL. The ZnO nanoparticles exhibited significant antibacterial activity against Klebsiella pneumoniae and Escherichia coli, with zones of inhibition (ZOI) of 18 mm and 23 mm, respectively as compared to the positive control neomycin of ZOI 28 mm against K. pneumoniae. The potential antibacterial activity of the ZnO NPS was revealed as the MIC and MBC against K. pneumoniae of 0.39 mg/mL and 0.78 mg/mL, respectively. In addition, the prepared ZnO nanoparticles showed toxicity against brine shrimp nauplii of LC₅₀ 16.59 μg/mL. The results of this study impart that plant-assisted synthesized ZnO nanoparticles possess significant antibacterial properties that reduce oxidative stress in human cells, ultimately contributing to cancer prevention.

Influence of Carbon Content on Element Diffusion in Silicon Carbide-Based TRISO Composite Fuel

The coating layers of Tri-structural Isotropic Particles (TRISO) serve to protect the kernel and act as barriers to fission products. Sintering aids in the silicon carbide matrix variably react with TRISO coating layers, leading to the destruction of the coating layers. Investigating how carbon content affects element diffusion in silicon carbide-based TRISO composite fuel is of great significance for predicting reactor safety. In this study, silicon carbide-based TRISO composite fuels with different carbon contents were prepared by adding varying amounts of phenolic resin to the silicon carbide matrix. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were employed to characterize the phase composition, morphology, and microstructure of the composite fuels. The elemental content in each coating layer of TRISO was quantified using Energy-Dispersive X-ray Spectroscopy (EDS). The results demonstrated that the addition of phenolic resin promoted the uniform distribution of sintering aids in the silicon carbide matrix. The atomic percentage (at.%) of aluminum (Al) in the pyrolytic carbon layer of the TRISO particles reached its lowest value of 0.55% when the phenolic resin addition was 1%. This is because the addition of phenolic resin caused the Al and silicon (Si) in the matrix to preferentially react with the carbon in the phenolic resin to form a metastable liquid phase, rather than preferentially consuming the pyrolytic carbon in the outer coating layer of the TRISO particles. The findings suggest that carbon addition through phenolic resin incorporation can effectively mitigate the deleterious reactions between the TRISO coating layers and sintering aids, thereby enhancing the durability and safety of silicon carbide-based TRISO composite fuels.

Correlation between the Mechanical Properties and Laser-Induced Breakdown Spectroscopy for Human Teeth

The present study investigates the correlation between mechanical properties and laser-induced breakdown spectroscopy (LIBS) for different tooth samples. A set of Fourteen samples collected from the Al-Kut Specialized Dental Centre in Wasit Governorate was analysed. Tooth samples were divided into groups depending on age and gender (men, women). The optical emission of the ionic-to- atomic intensity ratio of the Ca spectral line has been correlated with Leeb hardness test (LHT) values, compressive strength, and Young's modulus measured by standard tools. The ratio ionic line to atomic line CaII / CaI between the ionic calcium line at 396.84 nm and the atomic line at 558.87 nm for teeth is obtained using LIBS technique employing Nd: YAG laser with a wavelength of 1064 nm, an energy of 200 Mj, and a pulse duration of 10 ns. A linear relationship was observed between compressive strength, Young's modulus and hardness, and the concentrations of the elements (Ca). The small relative errors for hardness, compressive strength, and Young's modulus ranged from (1.44-5.57) %, (1.94-6.07) %, and (0.243-4.01) %, respectively. These findings validate applying LIBS to check out some important mechanical properties.

Enhanced Photocatalytic Paracetamol Degradation by NiCu-Modified TiO2 Nanotubes: Mechanistic Insights and Performance Evaluation.

Anodic TiO2 nanotube arrays decorated with Ni, Cu, and NiCu alloy thin films were investigated for the first time for the photocatalytic degradation of paracetamol in water solution under UV irradiation. Metallic co-catalysts were deposited on TiO2 nanotubes using magnetron sputtering. The influence of the metal layer composition and thickness on the photocatalytic activity was systematically studied. Photocatalytic experiments showed that only Cu-rich co-catalysts provide enhanced paracetamol degradation rates, whereas Ni-modified photocatalysts exhibit no improvement compared with unmodified TiO2. The best-performing material was obtained by sputtering a 20 nm thick film of 1:1 atomic ratio NiCu alloy: this material exhibits a reaction rate more than doubled compared with pristine TiO2, enabling the complete degradation of 10 mg L-1 of paracetamol in 8 h. The superior performance of NiCu-modified systems over pure Cu-based ones is ascribed to a Ni and Cu synergistic effect. Kinetic tests using selective holes and radical scavengers unveiled, unlike prior findings in the literature, that paracetamol undergoes direct oxidation at the photocatalyst surface via valence band holes. Finally, Chemical Oxygen Demand (COD) tests and High-Resolution Mass Spectrometry (HR-MS) analysis were conducted to assess the degree of mineralization and identify intermediates. In contrast with the existing literature, we demonstrated that the mechanistic pathway involves direct oxidation by valence band holes.

XPS study of the stability variations of [M(COD)Cl]<SUB>2</SUB> (M = Ir, Rh) complexes anchored on modified silica in reactions of spin-selective hydrogenation of unsaturated hydrocarbons by parahydrogen

Changes in the composition of anchored [M(COD)Cl]2–NH2–C3H6–SiO2 and [M(COD)Cl]2–P(Ph)2–C2H4–SiO2 (where M = Ir, Rh) catalysts in reactions of gas-phase selective hydrogenation of propene, propyne and 1,3-butadiene with parahydrogen (p-H2) were studied using XPS. The atomic ratio M/Cl has been proposed as an indicator of the stability of the structure of the anchored complex, both at the stage of sample preparation and in the reaction. Based on a comparison of XPS data and the results of catalytic testing using parahydrogen-induced polarization, it is shown that the stability of the anchored {[M(COD)Cl]2–Linker–SiO2} complex during hydrogen activation is a key factor in the catalytic behavior of systems. Such stability is influenced not only by the chosen metal and linker, but also by the nature of the hydrogenated substrate.

Hexagonal ZnTiO3 single-crystalline films on α-Al2O3 substrates: Structural and photoelectric properties

Hexagonal ZnTiO3 (h-ZnTiO3) films with stoichiometric were deposited on α-Al2O3 substrates using pulsed laser deposition (PLD) method and post annealing process. The effect of oxygen partial pressure on Zn/Ti atomic ratio, as well as the influence of annealing treatment on the structural and optical properties of the films were investigated in detail. The optimum h-ZnTiO3 film was deposited under 5 Pa oxygen partial pressure and annealed at 800°C, and it exhibited excellent crystalline quality and an optical band gap of 3.72 eV. A photodetector based on the film was fabricated, and its photoresponsivity was approximately 0.18 mA/W under 308 nm ultraviolet light irradiation. This demonstrates that as a wide bandgap semiconductor material, h-ZnTiO3 has potential applications in the field of devices.

High-Entropy Materials for Application: Electricity, Magnetism, and Optics.

High-entropy materials (HEMs) have recently emerged as a prominent research focus in materials science, gaining considerable attention because of their complex composition and exceptional properties. These materials typically comprise five or more elements mixed approximately in equal atomic ratios. The resultant high-entropy effects, lattice distortions, slow diffusion, and cocktail effects contribute to their unique physical, chemical, and optical properties. This study reviews the electrical, magnetic, and optical properties of HEMs and explores their potential applications. Additionally, it discusses the theoretical calculation methods and preparation techniques for HEMs, thereby offering insights and prospects for their future development.

Synthesis and field emission characterization of La-doped SiC nanowires using graphite powder as carbon source

Lanthanum (La)-doped SiC nanowires (NMs) were synthesized via a carbon thermal reduction process using different graphite powders, while milled Si-SiO2 mixed powders were employed as the silicon source. The identification of the products as β-SiC were supported by Select-area electron diffraction (SAED) and X-ray diffraction (XRD) analysis. The field emission results demonstrated that the turn-on field reached a minimum value of approximately 2.3 V/μm when the graphite content ranged from 2.5 g–3 g. The product exhibited higher density at this stage, accompanied by an increase in nanowire diameter and a tendency toward straightness. The energy spectrum analysis revealed a significant increase in the lanthanum content within the nanowires, with the atomic percentage rising from 0.05 to 0.26–0.27. The synergistic effect of morphology and La improved the field emission performance of the product. The findings may offer valuable insights for enhancing the field emission performance of one-dimensional nanomaterials.

Coarsening kinetics of alloy-doped nanoporous metals

Due to their high surface-to-volume ratios, nanoporous metals are being explored for a range of catalytic and structural applications. However, these materials have thermodynamically unstable morphologies and degrade via coarsening at elevated temperatures. One potential mitigation strategy is to introduce atomic species that inhibit diffusional transport, but there is limited mechanistic understanding. To begin addressing this knowledge gap, the impact of a slow-diffusing dopant on the coarsening behavior of a nanoporous metal is studied using kinetic Monte Carlo simulations. The simulations were analyzed using reaction models and isoconversional analyses to extract constitutive coarsening laws, which confirm a coarsening exponent associated with classical surface diffusion. In addition, a rate equation is derived for the role of alloying dopants. It is found that only a few atomic percent is needed to stymie coarsening over experimentally relevant timescales, which has broad implications for the future design and tailoring of these materials.

Renewable Diesel Production over Mo-Ni Catalysts Supported on Silica

Nickel catalysts promoted with Mo and supported on silica were studied for renewable diesel production from triglyceride biomass, through the selective deoxygenation process. The catalysts were prepared by wet co-impregnation of the SiO2 with different Ni/(Ni + Mo) atomic ratios (0/0.84/0.91/0.95/0.98/1) and a total metal content equal to 50%. They were characterized by XRD, XPS, N2 physisorption, H2-TPR, and NH3-TPD. Evaluation of the catalysts for the transformation of sunflower oil to renewable (green) diesel took place in a high-pressure semi-batch reactor, under solvent-free conditions. A very small addition of Mo, namely the synergistic Ni/(Ni + Mo) atomic ratio equal to 0.95, proved to be the optimum one for a significant enhancement of the catalytic performance of the metallic Ni/SiO2 catalyst, achieving 98 wt.% renewable diesel production. This promoting action of Mo has been attributed to the significant increase of the metallic Ni active phase surface area, the suitable regulation of surface acidity, the acceleration of the hydro-deoxygenation pathway (HDO), the creation of surface oxygen vacancies, and the diminution of coke formation provoked by Mo addition.

Revealing the fundamental relationship between the properties and microstructures of biomedical TiZrTaNbMo high entropy alloy

The body-centered cubic high-entropy alloys are a promising candidate as implanting materials for biomedical areas, but their severe strength-ductility trade-off limits their application. Herein, we designed and prepared the biomedical TiZrTaNbMo HEAs with different atomic ratios by adjusting their elemental composition based on the theoretical calculation of negative mixing enthalpy and valence electron concentration. It was found that the (TiZr)47(TaNbMo)2 alloy has BCC and HCP mixing structure, and the (TiZr)42.5(TaNbMo)5 and the (TiZr)45(TaNbMo)3.33 have simple BCC structure. the yield strength (YS) and total tensile elongation of the (TiZr)42.5(TaNbMo)5, (TiZr)45(TaNbMo)3.33, (TiZr)47(TaNbMo)2 are 866 ± 28 MPa and 16.5 ± 1.1 %, 929 ± 13 MPa and 17.8 ± 1.2 %, 899 ± 6 MPa and 5.5 ± 0.1 %, respectively. The theoretical calculation shows that the high YS strength mainly comes from the solid solution strengthening effect, the high ductility can be explained by the negative mixing enthalpy induced by Mo element. In addition, the (TiZr)45(TaNbMo)3.33 alloy has better wear resistance and corrosion resistance than the commercially available Ti6Al4V. This study shed light on synthesizing the high entropy alloy with the desired comprehensive properties as biomedical implant materials.

Comprehensive analysis of morphology, microstructure, and mechanical characterization of parameters in the Inconel 718 laser cladding process on AISI 1050

In this study, laser cladding of Inconel 718 powder was applied to AISI 1050 fabrication steel. In this process, an empirical study was conducted on 18 different samples produced to analyze the effects of laser power, scanning speed, and powder feeding rate, which are the most effective parameters in the laser cladding process, on morphology, microstructure, and mechanical characterization. The microstructures of these samples were investigated by a scanning electron microscope, and elemental distributions in the coating zone were investigated by energy dispersive spectrometry. In addition, their microhardness was measured throughout the coating. In light of the data obtained, the morphology of the three zones of the coating (clad zone, fusion zone, and heat-affected zone) was affected by the relevant parameters. The present work has given the optimum parameters: High powder feed rates (4.7, 5.2 rev/min), low scanning speeds (8 and 10 mm/s), and high laser power (with an increase from 1500 to 2100 W) all contributed to the maintenance of melt pool stability. A lower powder feed rate (3.8, 4.3 rev/mm) nevertheless assisted in encouraging the creation of a finer microstructure at lower laser powers (1500, 1800 W) and greater scanning speeds (12 mm/s). In all samples, the mean hardness in the fusion zone was higher than in the clad zone. It is stated that this phenomenon is caused by both the cooling rate and the Ni:Fe ratio. The hardness value increased with the increase in the percentage of Fe atoms in the fusion zone. The average hardness measurements were between 210 and 225 Vickers hardness, showing that the clad zone of all samples had a fairly consistent hardness level.

Compact vacuum transfer devices for highly air-sensitive materials in scanning electron microscopy

Surface analysis experiments on air-sensitive substances are challenging to avoid their contact with air, leading to inaccurate results due to oxidation or hygroscopicity. To address this issue, we designed a compact vacuum transfer device (VTD) and applied it to scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) experiments. Our VTD features a split structure that can be opened and separated in the SEM specimen exchange chamber via magnetic control. This design allows the SEM manufacturer's stub to be fed directly into the SEM specimen chamber, preventing damage to the instrument's internal components and avoiding restrictions on specimen height. Additionally, the compact design maximizes the utilization of sample accommodation space. Besides, it can be flexibly customized in different sizes and types of stubs to adapt electron microscopes from various manufacturers. To confirm the reliability of our device, we applied it to several highly air-sensitive samples for morphology and chemical composition analysis by SEM and EDS. The EDS results showed that the atomic percentage of Na reaches 94.55 % after 14 minutes and 93.44 % after 30 minutes of storage when transferring metallic sodium. Furthermore, our VTD enables airtight recycling and re-transfer of samples after the SEM (-EDS) experiments. These results demonstrate that our device has excellent practicality and airtightness, making it suitable for medium- and long-distance sample transfer between laboratories on the campus.

Coordination Environment and Distance Optimization of Dual Single Atoms on Fluorine‐Doped Carbon Nanotubes for Chlorine Evolution Reaction

AbstractThe chlorine evolution reaction (CER) is a crucial anode reaction in the chlor‐alkali industrial process. Precious metal‐based dimensionally stable anodes (DSA) are commonly used as catalysts for CER but are constrained by their high cost and low selectivity. Herein, a Pt dual singe‐atom catalyst (DSAC) dispersed on fluorine‐doped carbon nanotubes (F‐CNTs) is designed for an efficient and robust CER process. The prepared Pt DSAC demonstrates excellent CER activity with a low overpotential of 21 mV to achieve a current density of 10 mA cm−2 and a remarkable mass activity of 3802.6 A gpt−1 at an overpotential around 30 mV, outperforming those of commercial DSA and Pt single‐atom catalyst. The excellent CER performance of Pt DSAC is attributed to the high atomic utilization and improved intrinsic activity. Notably, introducing fluorine atoms on CNTs increases the oxidation and chlorination resistance of Pt DSAC, and reduces the demetalization ratio of Pt atoms, resulting in excellent long‐term CER stability. Theoretical calculations reveal that several Pt DSAC configurations with optimized first‐shell ligands and interatomic distance display lower energy barriers for Cl intermediates generation and weaker ionic Pt−Cl bond interaction, which are favorable for the CER process.

Photothermal effect enhanced antibacterial activity of CuAl-layered double hydroxides

CuAl-layered double hydroxides (CuAl-LDH) with Cu/Al atomic ratios of 2:1 and 3:1 are prepared by a facile coprecipitation method. The as-prepared CuAl-LDH have hexagonal crystalline structure and possess photothermal responsive ability. Upon 808 nm near-infrared laser irradiation for 10 min, CuAl-LDH-3 with a Cu/Al atomic ratio of 3:1 demonstrated rapid temperature elevation of 53 °C. Moreover, the dissolution rate of copper ions from CuAl-LDH increases with the increase of Cu/Al atomic ratio, and can be further promoted by irradiation. CuAl-LDHs are noncytotoxic to human umbilical vein endothelial cells and demonstrate excellent photothermal antibacterial performance against Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae), respectively. CuAl-LDH-3 displays the better antibacterial capacity attributed to the synergistic effects of the photothermal effect induced release of high concentration copper ions and the generation of reactive oxygen species (ROS). This work offers novel LDH-based antibacterial materials with photothermal and enzymatic effects.

Appropriate flame-spraying treatment exacerbates thermal oxidative degradation of residual polyethylene films

In dryland farming, plastic film mulching can significantly increase crop yields, but the resulting residues impair soil health. Heretofore, only few studies had examined how heat treatment facilitates the rapid degradation of polyethylene (PE) residual films. Herein, we characterized the variations in micro-morphology, functional groups, and crystallinity of PE residual films after moderate heat exposure using a self-made flame-spraying equipment. The results revealed that solid residues (SR) obtained from flame-spraying showed a gravimetric weight loss of 9.39 %–15.35 % compared with untreated PE residual films (UPF). Scanning electron microscope equipped with energy dispersive X-ray spectroscopy revealed considerable pits, cracks, and visible roughness in appearance and an increase in the oxygen-to‐carbon (O/C) atomic ratio. Fourier-transform infrared spectroscopy identified characteristic oxygen-containing functional groups and double bonds. X-ray diffraction showed that flame-spraying treatments did not alter the crystal form of polymer, but increased the crystallinity. Higher flame-spraying temperatures resulted in larger oxygen-containing bond indices and lower crystallinity, suggesting a more severe decomposition of PE residual film. The possible volatile gaseous products at different reaction temperatures were predicted using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR). Degradation of the PE residual film started at 220 °C, and concentrated release of major products such as long-chain aliphatic hydrocarbons, ketones, and CO2, occurred in the temperature range of 340 °C–440 °C. These results highlighted the effectiveness of the moderate flame-spraying method in accelerating rapid decomposition of residual films, and a flame-spraying temperature range of 220 °C–340 °C should be recommended to avoid potential environmental risks induced by the release of large quantities of degradation products. This study will contribute to enhance our understanding of the thermal oxidative degradation behavior of PE waste and provide a scientific basis for the rapid and clean establishment of PE residual films mitigation in agricultural fields.

Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H2-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co3O4 crystallites together with periclase-like and CeO2 phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H2-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T50, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed.

An innovative approach to control the Hf/Ti ratio in monolayers grown via atomic partial layer deposition

The Hf/Ti ratio was precisely controlled at monolayer thickness using atomic partial layer deposition (APLD). HfxTi1−xO2 films with varying Hf concentrations were deposited by adjusting the pulse time of Hf precursors within a single atomic layer. Characterization using x-ray reflectivity, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry confirmed the presence of Hf, Ti, and O in the films. Increasing the Hf content caused the binding energies of the O 1s peak to shift to higher values, indicating a chemical environment change from TiO2-like to HfO2-like. A higher Hf content also increased the relative atomic percentages of Hf, Ti, and O, altering the film properties. The mass density and optical properties were notably sensitive to changes in the Hf/Ti ratio at monolayer thickness. The potential of APLD to reduce dimensionality through precise control of both thickness and composition renders it especially appropriate for applications requiring highly specific material properties.

Low-energy argon ion beam irradiation for the surface modification and reduction of graphene oxide: Insights from XPS

Developing environmentally friendly methods for reducing graphene oxide (GO) is essential. This study investigates the surface modification and reduction of GO films using 200 eV argon ion (Ar+) beam irradiation. X-ray Photoelectron Spectroscopy (XPS) analysis reveals significant chemical changes on the GO surface. GO was irradiated with a 200 eV Ar+beam for varying times (0–80 s). XPS survey spectra showed the presence of carbon and oxygen, with an increasing carbon atomic percentage over time. High-resolution XPS spectra of C 1s revealed peaks corresponding to sp2, C–OH, O–C–O, CO, and O–CO bonds. In the O 1s spectra, CO, O–C–O, and C–OH groups were observed. Upon irradiation, the CO peak consistently decreased, the O–C–O peak fluctuated, and the C–OH peak increased, indicating effective reduction of CO groups, dynamic changes in O–C–O functionalities, and the formation of additional C–OH groups. The C/O ratio increased from ∼2.4 to 2.7, underscoring the reduction process and enhanced carbon content. This method proves to be an efficient approach for producing reduced graphene oxide (rGO) with improved properties for advanced applications.