Tantalum-Titanium Oxynitride Thin Films Deposited by DC Reactive Magnetron Co-Sputtering: Mechanical, Optical, and Electrical Characterization

The possibility to tune the elemental composition and structure of binary Me oxynitride-type compounds (Me1Me2ON) could lead to attractive properties for several applications. For this work, tantalum-titanium oxynitride (TaTiON) thin films were deposited by DC reactive magnetron co-sputtering, with a –50 V bias voltage applied to the substrate holder and a constant substrate temperature of 100 °C. To increase or to decrease in a controlled manner, the Ti and Ta content in the co-sputtered films, the Ti and Ta target currents were varied between 0.00 and 1.00 A, in 0.25 A steps, while keeping the sum of the currents applied to the two targets at 1.00 A. The reactive gases flow, consisting of a nitrogen and oxygen gas mixture with a constant N2/O2 ratio (85%/15%), was also kept constant. The single-metal oxynitrides (TaON and TiON) showed a low degree of crystallinity, while all the other co-sputtered films revealed themselves to be essentially amorphous. These two films also exhibited higher adhesion to the metallic substrate. The TaON film showed the highest hardness value (14.8 GPa) and the TiON film a much lower one (8.8 GPa), while the co-sputtered coatings exhibited intermediary values. One of the most interesting findings was the significant increase in the O content when the Ti concentration surpassed the Ta one. This significantly influenced the optical characteristic of the films, but also their electrical properties. The sheet resistivity of the co-sputtered films is strongly dependent on the O/(Ta + Ti) atomic ratio.

Experimental Study on Stratification Morphology of the Molten Pool During Severe Accident

Stratification morphology of a molten pool under severe reactor accident was investigated by the CESEF experimental facility. The experimental scale was 5,000 g, the atomic ratio of U/Zr was 1.5, the content of stainless steel was 10%, and the oxidation degree of Zr was 40–100%. It was shown that the molten pool was obviously stratified within the range of experimental parameters; one was a metal layer, and the other was an oxide layer. The layered morphology of the molten pool was different with the composition of different corium. With the decrease in the Zr oxidation degree, the metal layer moved downward in the molten pool, and the molten pool would overturn. The main elements in the oxide layer were U, Zr, and O, and the content of stainless steel was low. The main element in the metal layer was stainless steel and contained a certain amount of U and Zr.

Solution-Processable Growth and Characterization of Dandelion-like ZnO:B Microflower Structures

Intrinsic and dandelion-like microflower nano-rod structures of boron-doped ZnO thin films were synthesized with an ecofriendly and cost-effective chemical bath deposition technique from an aqueous solution of zinc nitrate hexahdyrate [Zn(NO3)2.6H2O] as a precursor solution and boric acid as a doping solution. The boron concentrations were 0.1, 0.3, 0.5, 1.0, 3.0, 5.0, and 7.0 by volume. Scanning electron micrographs showed that doping with boron appears to hinder the vertical alignment of crystallites. Additionally, independent hexagonal nano-rod structures were observed to coalesce together to form dandelion-like structures on the film’s surface. The atomic ratio of the elements was determined via the X-ray photoemission spectrum technique. There were no substantial changes in the vibration structure of the film upon doping in terms of the Raman spectra. The optical band gap of ZnO (3.28 eV) decreased with B doping. The band gap of the ZnO:B film varied between 3.18 and 3.22 eV. The activation energy of the ZnO was calculated as 0.051 eV, whereas that of the ZnO:B film containing 1.0% B was calculated as 0.013 eV at low temperatures (273–348 K), versus 0.072 eV and 0.183 eV at high temperatures (348–523 K), respectively. Consequently, it can be interpreted that the 1% B-doped ZnO, which has the lowest activation energy at both low and high temperatures, may find some application areas such as in sensors for gases and in solar cells.

Natural vs. Synthetic Phosphate as Efficient Heterogeneous Compounds for Synthesis of Quinoxalines

Natural phosphate (NP) and synthetic fluorapatite phosphate (SFAP) were proposed as stable, inexpensive, readily available and recyclable catalysts for the condensation of 1,2-diamines with 1,2-dicarbonyls in methanol to afford quinoxaline at room temperature. NP provided as high as 92–99% yield for quinoxalines in short reaction times (i.e., 1–45 min), while SFAP created quinoxalines with 87–97% yield in 60–120 min. From the chemical analyses, X-ray fluoresecency, X-ray diffraction, energy dispersive X-ray and Fourier-transform infrared spectroscopy methods, two main phases (CaO, P2O5) appeared in NP together with other low content phases (SiO2, Fe2O3). Compared to other phases, apatite (CaO and P2O5 as Ca10(PO4)6) played a major role in the catalytic activity of NP. SFAP with similar Ca/P atomic ratio showed a relatively lower catalytic activity than NP for the condensation of 1,2-diamine with 1,2-dicarbonyl in methanol at ambient temperature. To investigate the recyclability of catalysts, the surface properties of NP and 6-recycled NP were investigated using scanning electron microscopy, energy dispersive X-ray and Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. Some differences were observed in NP and 6-recycled NP’s particle size, surface area, the volume and size of pores, and the content of elements; nevertheless, the use–reuse process did not noticeably change the catalytic property of NP.

Increasing Silicon Concentration and Doping Heteroatom to Successfully Realize High HER Catalytic Activity in 2D Metal-Free BSin (n = 1-4) Structures: A First-Principles Study

Under the DFT calculations, the graphene-like two-dimensional (2D) BSin (n = 1-4) nanostructures are stable in terms of energy, kinetics and thermal aspects, and can possess metallic conductivity, which are advantageous to their catalytic activities for hydrogen evolution reaction (HER). Our computed results reveal that they can uniformly exhibit high HER catalytic activity. With increasing the Si/B atomic ratio, higher HER activity can be achieved, due to the change from weak aromaticity to strong anti-aromaticity for the correlative BxSiy six-membered rings. Moreover, by doping P, S, Ge and C atoms with the different electronegativity, the HER activity of the studied systems can be further improved because the electron transfer induced by these dopants can effectively activates the relevant B and Si atoms. In addition, in view of more active sites, increasing the Si concentration can also generally increase the HER activity of doped systems. For all BSin systems studied, the Si-Si bridge sites or Si-sites can uniformly serve as the most active sites. This study not only represents the first application of 2D metal-free BSin in HER catalysis, but also provides new strategies for designing high-efficient and low-cost HER electrocatalysts based on Si/B or even other Si-containing materials.

Preparation and Characterization of Pt-Doped Bi2MoO6 Nanocomposites and Its High PDT Efficiency on HL60 Cells

In this study, Pt-doped Bi2MoO6 nanocomposites were prepared by solvothermal and in situ reduction method. We used XRD, UV-Vis spectroscopy, TEM, EDS, and XPS to characterize its chemical properties. Results showed that the Pt-doped Bi2MoO6 nanocomposites had advantages of small size, good dispersion, and wide spectral response range. Then, we tested its biological toxicity and PDT efficiency on HL60 cells. Both pure Bi2MoO6 and Pt-doped Bi2MoO6 nanocomposites showed great biocompatibility after coincubated with leukemia cells for 12 h in the dark. As to PDT efficiency, Pt-doped Bi2MoO6 had a better-inactivated effect than pure Bi2MoO6. Furthermore, the PDT efficiency went up when atomic ratios and concentration increased. While the atomic ratio was 5% and the concentration was 1000 μg/mL, it reached the highest value at 85.2%. At last, we briefly analyzed the photocatalysis mechanism, which demonstrated that it was a potential photosensitizer with high efficiency for treating leukemia.

Near-Ambient Pressure XPS and MS Study of CO Oxidation over Model Pd-Au/HOPG Catalysts: The Effect of the Metal Ratio

In this study, the dependence of the catalytic activity of highly oriented pyrolytic graphite (HOPG)-supported bimetallic Pd-Au catalysts towards the CO oxidation based on the Pd/Au atomic ratio was investigated. The activities of two model catalysts differing from each other in the initial Pd/Au atomic ratios appeared as distinctly different in terms of their ignition temperatures. More specifically, the PdAu-2 sample with a lower Pd/Au surface ratio (~0.75) was already active at temperatures less than 150 °C, while the PdAu-1 sample with a higher Pd/Au surface ratio (~1.0) became active only at temperatures above 200 °C. NAP XPS revealed that the exposure of the catalysts to a reaction mixture at RT induces the palladium surface segregation accompanied by an enrichment of the near-surface regions of the two-component Pd-Au alloy nanoparticles with Pd due to adsorption of CO on palladium atoms. The segregation extent depends on the initial Pd/Au surface ratio. The difference in activity between these two catalysts is determined by the presence or higher concentration of specific active Pd sites on the surface of bimetallic particles, i.e., by the ensemble effect. Upon cooling the sample down to room temperature, the reverse redistribution of the atomic composition within near-surface regions occurs, which switches the catalyst back into inactive state. This observation strongly suggests that the optimum active sites emerge under reaction conditions exclusively, involving both high temperature and a reactive atmosphere.

High Efficiency for Methanol Electrooxidation of Self-Supporting 3D Nanoporous PdAg Alloy Foams

The self-supporting three-dimensional (3D) nanoporous PdAg alloy (NP–PdAg) foams have been prepared by a simple one-step dealloying melt-spun Al–Pd–Ag ribbons in a 20[Formula: see text]wt.% NaOH aqueous solution at 90∘C for 1.5[Formula: see text]h. The structure is advantageous to the diffusion and removal of the intermediate products and the transmission of the methanol molecules. The NP–PdAg foams exhibit better electrocatalytic performance than the NP-Pd foam toward the methanol oxidation in potassium hydroxide (KOH) solution. The optimal atomic ratio of Pd to Ag in the NP–PdAg foams is 1:1, and its electrocatalytic activity is about 2.6 times that of the NP–Pd foam. The significant improvement in the electrocatalytic performance is attributed to the addition of a moderate amount of Ag. In the whole electrocatalytic process, Ag can provide OHads to oxidize the intermediate products on the surface of active Pd sites into carbon dioxide or other cleaning products. Also, the Ag can increase electrochemical active surface area and the adsorption energy of Pd to methanol molecules and OHads. These significantly prevent the accumulation of poisoning intermediates on the surface of Pd and quickly release more active Pd sites.