The Mo-Si-B, Mo-Zr-Si-B, and Mo-Hf-Si-B coatings were deposited by magnetron sputtering of the MoSi2-MoB, MoSi2-MoB-ZrB2 and MoSi2-MoB-HfB2 targets. The composition and structure of coatings were investigated by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Mechanical properties were measured by nanoindentation method. The short-time oxidation resistance of coatings was evaluated at temperatures of 1100, 1300, and 1500 °C. The results showed that all coatings deposited onto alumina substrates were characterized by a dense columnar structure. Mo-Si-B coatings contained phases of hexagonal h-MoSi2 and amorphous a-MoB. With the addition of Zr and Hf, an increase in the lattice parameter and a decrease in the grain size of h-MoSi2 by 50 and 25%, respectively, were observed. The base Mo-Si-B coating had a high hardness of 30 GPa. The introduction of Zr and Hf led to a decrease in hardness by 24 and 20%, respectively. The Mo-Si-B coating was characterized by a minimal oxidation depth (<10 nm) at 1100 °C and 1300 °C, but a network of cracks that penetrated to the substrate was formed. Cracks on the surface of the Mo-Zr-Si-B and Mo-Hf-Si-B coatings were not observed; the formation of oxide layers, 0.3–2.0 μm thick, was revealed. The oxidation resistance of coatings at temperature of 1500 °C increased in direction Mo-Si-B → Mo-Hf-Si-B → Mo-Zr-Si-B. The best results for the Mo-Zr-Si-B coating were associated with a smaller grain size, higher thermal stability, and the formation of a protective layer based on SiO2 with the inclusion of ZrO2 crystallites. 

Effects of doping with Zr and Hf on the structure and properties of Mo-Si-B coatings obtained by magnetron sputtering of composite targets

In this study, we have synthesized pristine and [0.5,1.5, and 2.5] M% samarium (Sm)-incorporating α-MoO3 2D-layered nanoplates utilizing a facile hydrothermal process, and investigated the physical properties along with antibacterial effectiveness. X-ray diffraction (XRD) patterns confirmed the single-phase, stable orthorhombic polycrystalline structure of the as-prepared samples. The crystallite size, lattice strain, and dislocation density were measured using both Debye–Scherrer (D–S) and Williamson-Hall (W-H) techniques. Both pristine and Sm-incorporating α-MoO3 samples showed two-dimensional (2D) layered nanoplate-type surface morphology, revealed by field emission scanning electron microscopy (FE-SEM) images. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Sm contents in the α-MoO3 matrix. After Sm incorporation in α-MoO3, the different functional groups as well as vibrational groups were observed by Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy analyses, respectively. The optical band gaps were measured from UV-vis diffuse reflectance spectroscopy (DRS) by employing the Kubelka–Munk formula and interestingly it is found that the bandgap energy (Eg) gradually decreased from 2.96 to 2.83 eV with the increment of Sm content. When compared to pristine α-MoO3, the Sm-incorporating samples experienced a steady improvement in room temperature ferromagnetic (RTFM) behavior as Sm content increased, as measured by hysteresis loops. The antibacterial activities of both samples were assessed against Gram-positive: Staphylococcus aureus (S. aureus), and Gram-negative: Escherichia coli (E. coli) and Salmonella enteritidis (S. enteritidis) bacteria by the agar well diffusion method and enhanced antibacterial activity was observed as the Sm concentration increased, compared to pristine nanoplates. The obtained results suggest that the synthesized Sm-incorporating α-MoO3 2D-layered nanoplate could be a potential antibacterial agent.

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Structural, optical, magnetic, and enhanced antibacterial properties of hydrothermally synthesized Sm-incorporating α-MoO3 2D-layered nanoplates

Deep eutectic solvents (DESs), a new class of ionic liquids have considered to be the attraction of researchers owing to their wide range of applications as green solvents. These solvents...

Deep Eutectic Solvent mediated synthesis and fabrication of WO3-MgO nanocomposite as an electrode material for energy storage applications

Nanoarchitectonics and Electrochemical Behavior of Cu Doped h-MoO3 as an Electrode Material for Energy Storage Applications

The effects of various parameter interactions on the textural structure of hydrochars produced via hydrothermal (HTC) and co-hydrothermal (Co-HTC) treatments of coal discards and sewage sludge (wastes), as well as the subsequent use of the hydrochars (HCs) synthesized for HIV drug (nevirapine and lamivudine) removal from wastewater, were investigated in this study. The HTC and Co-HTC process improved the carbon content of the raw material by 13.47%, 7.08%, and 30.65% for hydrochar coal tailing (HCT), hydrochar coal slurry (HCS), and hydrochar from coal–sewage blend (HCB), respectively. The Co-HTC-derived HCB had a high SBET of 20.35 m2/g and pore volume of 0.38 cm3/g, leading to significant adsorptive reductions of nevirapine (NEV) and lamivudine (LAM) (97.19% and 93.32%, respectively). HCT and HCS displayed high NEV and LAM adsorption capacities (50 mg g−1, 42 mg g−1 and 52 mg g−1, 41 mg g−1), respectively, despite being less effective than HCB (53.8 mg g−1, 42.8 mg g−1). In addition, the use of spent adsorption residues for energy storage applications was investigated further. The findings showed that spent adsorption residues are an effective carbonaceous material precursor to produce electrical double-layer capacitors (EDLCs).

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Coal Discards and Sewage Sludge Derived-Hydrochar for HIV Antiretroviral Pollutant Removal from Wastewater and Spent Adsorption Residue Evaluation for Sustainable Carbon Management

Systematic analysis and the effect of Mn doping on structural, optical and magnetic properties of MoO3 nanoparticles

Herein we report the hydrothermal synthesis, characterization and biological applications of h-MoO3 and silver doped MoO3 nanoparticles (NPs). The phase formations of the synthesized NPs were identified using X-Ray diffraction studies and vibrational spectral studies. The average crystallite size of the NPs tends to decrease with increase in doping concentration. The surface morphology and the elemental composition of the nanoparticles were observed from SEM and EDAX analysis. The crystallite nature was obtained from HRTEM images. The band gap energies obtained from UV-DRS spectra for h-MoO3 (3.26 eV) were found to decrease as the concentration of the dopant (Ag) increases (3.22–2.76 eV). The antibacterial activity of the prepared nanoparticles was tested against some gram positive and gram negative bacterial strains viz., Staphylococcus aureus and Bacillus cereus, Citrobacter koseri and Pseudomonas aeruginosa respectively. Also their seed germination properties were studied on foxtail and finger millet seeds for a period of seven days.

S. Hari Kengaram

Papers

Systematic analysis and the effect of Mn doping on structural, optical and magnetic properties of MoO3 nanoparticles

Nanoarchitectonics and Electrochemical Behavior of Cu Doped h-MoO3 as an Electrode Material for Energy Storage Applications

Influence of Ag Doped MoO3 Nanoparticles in the Seedling Growth and Inhibitory Action Against Microbial Organisms

Visible Light Driven Effective Photodegradation of Alizarin Red S Using Zirconium Doped Metastable Hexagonal MoO3 Nanorods