Microstructure Evaluation and Impurities in La Containing Silicon Oxynitrides

Oxynitride glasses are not yet commercialised primarily due to the impurities present in the network of these glasses. In this work, we investigated the microstructure and instinctive defects in nitrogen rich La-Si-O-N glasses. Glasses were prepared by heating a powder mixture of pure La metal, Si3N4, and SiO2 in a nitrogen atmosphere at 1650-1800 °C. The microstructure and impurities in the glasses were examined by optical microscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy in conjunction with electron energy-loss spectroscopy. Analyses showed that the glasses contain a small amount of spherical metal silicide particles, mostly amorphous or poorly crystalline, and having sizes typically ranging from 1 µm and less. The amount of silicide was estimated to be less than 2 vol. %. There was no systematic relation between silicide formation and glass composition or preparation temperature. The microstructure examination revealed that the opacity of these nitrogen rich glasses is due to the elemental Si arise from the decomposition reaction of silicon nitride and silicon oxide, at a high temperature above ~1600 °C and from the metallic silicide particles formed by the reduction of silicon oxide and silicon nitride at an early stage of reaction to form a silicide intermetallic with the La metal

Polymer-Templated Durable and Hydrophobic Nanostructures for Hydrogen Gas Sensing Applications

A simple and hands-on one-step process has been implemented to fabricate polymer-templated hydrophobic nanostructures as hydrogen gas sensing platforms. Topographic measurements have confirmed irregular hills and dips of various dimensions that are responsible for creating air bubble pockets that satisfy the Cassie–Baxter state of hydrophobicity. High-resolution field-emission scanning electron microscopy (FESEM) has revealed double-layer structures consisting of fine microscopic flower-like structures of nanoscale petals on the top of base nanostructures. Wetting contact angle (WCA) measurements further revealed the contact angle to be ~142.0° ± 10.0°. Such hydrophobic nanostructures were expected to provide a platform for gas-sensing materials of a higher surface area. From this direction, a very thin layer of palladium, ca. 100 nm of thickness, was sputtered. Thereafter, further topographic and WCA measurements were carried out. FESEM micrographs revealed that microscopic flower-like structures of nanoscale petals remained intact. A sessile drop test reconfirmed a WCA of as high as ~130.0° ± 10.0°. Due to the inherent features of hydrophobic nanostructures, a wider surface area was expected that can be useful for higher target gas adsorption sites. In this context, a customized sensing facility was set up, and H2 gas sensing performance was carried out. The surface nanostructures were found to be very stable and durable over the course of a year and beyond. A polymer-based hydrophobic gas-sensing platform as investigated in this study will play a dual role in hydrophobicity as well as superior gas-sensing characteristics

X-Ray Photoelectron Spectroscopy Depth Profiling of As-Grown and Annealed Titanium Nitride Thin Films

Titanium nitride thin films were grown on Si(001) and fused silica substrates by radio frequency reactive magnetron sputtering. Post-growth annealing of the films was performed at different temperatures from 300 °C to 700 °C in nitrogen ambient. Films annealed at temperatures above 300 °C exhibit higher surface roughness, smaller grain size and better crystallinity compared to the as-grown film. Bandgap of the films decreased with the increase in the annealing temperature. Hall effect measurements revealed that all the films exhibit n-type conductivity and had high carrier concentration, which also increased slightly with the increase in the annealing temperature. A detailed depth profile study of the chemical composition of the film was performed by x-ray photoelectron spectroscopy confirming the formation of Ti-N bond and revealing the presence of chemisorbed oxygen in the films. Annealing in nitrogen ambient results in increased nitrogen vacancies and non-stoichiometric TiN films

X-Ray Photoelectron Spectroscopy Depth Profiling of As-Grown and Annealed Titanium Nitride Thin Films

Titanium nitride thin films were grown on Si(001) and fused silica substrates by radio frequency reactive magnetron sputtering. Post-growth annealing of the films was performed at different temperatures from 300 °C to 700 °C in nitrogen ambient. Films annealed at temperatures above 300 °C exhibit higher surface roughness, smaller grain size and better crystallinity compared to the as-grown film. Bandgap of the films decreased with the increase in the annealing temperature. Hall effect measurements revealed that all the films exhibit n-type conductivity and had high carrier concentration, which also increased slightly with the increase in the annealing temperature. A detailed depth profile study of the chemical composition of the film was performed by x-ray photoelectron spectroscopy confirming the formation of Ti-N bond and revealing the presence of chemisorbed oxygen in the films. Annealing in nitrogen ambient results in increased nitrogen vacancies and non-stoichiometric TiN films

Mechanical performance of date palm fiber-reinforced concrete modified with nano-activated carbon

Date palm fiber (DPF) is an easily processed, low cost, and accessible natural fiber. It has mostly been used in composites for non-structural applications. For DPF to be utilized in cementitious composites for structural applications, ways to reduce its harmful effect on compressive strength must be devised. Therefore, in this study, nano-activated carbon (NAC), due to its filler effects, was used as an additive to produce the DPF-reinforced concrete (DPFRC). To produce the DPFRC, 0, 1, 2, and 3% by cement weight of DPF and NAC were added. The fresh properties, strength, and microstructure of the concrete were examined. The findings revealed that DPF decreased the consistency, density, and compressive strength. Additionally, it increases the porosity in the concrete microstructure. The addition of up to 1% NAC significantly improved the compressive, flexural, and split tensile strengths of the concrete, while it decreased the harmful impact of up to 2% DPF on the DPFRC’s strength. The split tensile and flexural strengths of the concrete were enhanced with the addition of up to 2% DPF without any NAC. The addition of up to 2% NAC densified the DPFRC’s microstructure by refining and filling the pores generated by the DPF. The multivariable statistical models developed to estimate the mechanical properties of the DPFRC containing DPF and NAC were very significant with a very high degree of precision

Synthesis and Characterization of Silver Nanoparticles on ZnO thin films

<p>Metal nanoparticles, in particular noble metal nanoparticles with narrow size distribution, controlled scalability and purity, exhibit unprecedented and exciting properties strongly dependent on their size, shape and inherent electrons distribution with reference to those of macro-scaled counterpart. The challenge is how to fabricate these nanoparticles in cost-effective method as well as without hampering optical, electrical and topographical properties of other layers involved in device fabrication. In this study, a simple two-steps process was adopted to fabricate silver (Ag) nanoparticles on zinc oxide (ZnO) thin film followed by their topographic and optical characterizations. The underneath layer ZnO thin film, as an example, was also investigated thoroughly how the properties change during the nanoparticles fabrication. In the process, ZnO thin film was sputtered on standard glass substrate followed by further sputtering of an ultra-thin Ag layer. Subsequently the specimen was treated at high temperature.</p

One-Step Hydrothermal Synthesis of Anatase TiO2 Nanotubes for Efficient Photocatalytic CO2 Reduction

The hydrothermal dissolution-recrystallization process is a key step in the crystal structure of titania-based nanotubes and their composition. This work systematically studies the hydrothermal conditions for directly synthesizing anatase TiO2 nanotubes (ATNTs), which have not been deeply discussed elsewhere. It has been well-known that ATNTs can be synthesized by the calcination of titanate nanotubes. Herein, we found the ATNTs can be directly synthesized by optimizing the reaction temperature and time rather than calcination of titanate nanotubes, where at each temperature, there is a range of reaction times in which ATNTs can be prepared. The effect of NaOH/TiO2 ratio and starting materials was explored, and it was found that ATNTs can be prepared only if the precursor is anatase TiO2, using rutile TiO2 leads to forming titanate nanotubes. As a result, ATNTs produced directly without calcination have excellent photocatalytic CO2 reduction than titanate nanotubes and ATNTs prepared by titanate calcination

Construction of Bi2S3/TiO2/MoS2 S-Scheme Heterostructure with a Switchable Charge Migration Pathway for Selective CO2 Reduction

Switching between the redox potential of an appropriate semiconductor heterostructure could show critical applications in selective CO2 reduction. Designing a semiconductor photocatalyst with a wavelength-dependent response is an effective strategy for regulating the direction of electron flow and tuning the redox potential. Herein, the switching mechanism between two charge migration pathways and redox potentials in a Bi2S3/TiO2/MoS2 heterostructure by regulating the light wavelength is achieved. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS), electron spin resonance (ESR), photoluminescence (PL), and experimental scavenger analyses prove that the charge transport follows the S-scheme approach under UV–vis–NIR irradiation and the heterojunction approach under vis–NIR irradiation, confirming the switchable feature of the Bi2S3/TiO2/MoS2 heterostructure. This switchable feature leads to the reduction of CO2 molecules to CH3OH and C2H5OH under UV–vis–NIR irradiation, while CH4 and CO are produced under Vis–NIR irradiation. Interestingly, the apparent quantum efficiency of the optimal composite at λ = 600 nm is 4.23%. This research work presents an opportunity to develop photocatalysts with switchable charge transport and selective CO2 reduction.The authors are thankful to the DST National Single Crystal Diffractometer Facility Laboratory, DoS in Physics, UPE, IOE, and DST-PURSE, Vijnana Bhavana, University of Mysore, Mysuru, for providing the required facilities. The authors extend their appreciation to the Researchers Supporting Project number (RSP-2021/381), King Saud University, Riyadh, Saudi Arabia.Scopu