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In this work, the microstructure evolution and corrosion performance of additively manufactured GH4099 superalloy were investigated. The alloy samples were prepared by selective laser melting (SLM) technology with different laser power and scanning speed. The results showed that the GH4099 prepared by SLM had a fine grain structure, and the average grain size of all samples is below 18 μm. The relative density of SLMed samples first rose and then fell as the volume density increased. Under the process conditions of P = 170 W and V = 800 mm/s, sample N2 possessed the highest relative density and the minimum pores. In addition, the electrochemical test results indicated that sample N2 exhibited the best corrosion resistance, and its corrosion potential (ECorr) and corrosion current density (ICorr) were − 0.287 V and 0.149 μA·cm−2, respectively. The relative density and pores of the alloys were the main reason for the difference in corrosion properties. In particular, the irregular pores caused by lack of fusion were regarded as the initiation site of pitting and crack expansion, which has a greater effect on corrosion resistance than spherical pores. According to XPS results, the passivation film mainly consists of oxides and hydroxides of Ni, Cr, Co, and Al. The hydroxides of Ni, Cr, Co, and Al constituted the outer layer of the passivation film. After the dehydration reaction of hydroxides, their oxides formed the inner layer of the passivation film. In addition, the evolution of the passivation film including the formation and breakdown of the passivation film was also discussed. [ABSTRACT FROM AUTHOR]

In this work, the thermal stability of nanocrystalline (NC) AZ31/TiB2 magnesium matrix composites was investigated, while the microstructure evolution and mechanical properties were analyzed. The results indicated the AZ31/TiB2 still maintained NC structure after annealing at 350 °C for 180 min. Even at the high annealing temperature of 400 °C and 450 °C for 180 min, their average grain size just reached about 124 nm and 155 nm, indicating excellent thermal stability. The TiB2 particles with sub-micron size uniformly distributed in Mg matrix had no change in size and no reaction with matrix during the annealing treatment. Due to the strong Zener pinning effect of TiB2 particles, the grain growth of Mg matrix at high temperature was effectively inhibited. Meanwhile, the solution and precipitation behavior of Al atoms were completed in a short time, due to the existence of many grain boundaries and structural defects. By calculation, the grain growth kinetics was described by the kinetics equation D 8 - D 0 8 = k t and the activation energy Eg for grain growth was 131.6 kJ/mol, which was much higher than that of pure Mg (92 kJ/mol). Due to their excellent thermal stability, the decrease in both compressive yield strength and ultimate compressive strength was no more than 12.2% after annealing treatment. Even annealing at 450 °C for 180 min, the CYS and UCS of the samples were still above 283 MPa and 295 MPa, respectively. [ABSTRACT FROM AUTHOR]

Two kinds of Fe/amorphous carbon (a-C) submicron fibers were prepared by electrospinning using polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) as precursor polymer, followed by carbonization under the same conditions. Contributed to the different reaction mechanisms during the annealing process, different phases namely graphite carbon (g-C) and Fe4N formed at the interface between the Fe nanoparticles and the a-C matrix. Electromagnetic absorption properties have shown that the Fe@Fe4N submicron fibers have superior absorption performance than the Fe@g-C ones. The minimal reflection loss (RL) value of the former is − 39.8 dB at 5.4 GHz with the absorber thickness of 5.0 mm, and the effective absorption bandwidth (RL ≤ − 10 dB) can reach 5.0 GHz when the absorber thickness is 2.5 mm. By contrast, the Fe@g-C submicron fibers have little absorption. The attenuation constant, impedance matching coefficient, complex permittivity and complex permeability were investigated in detail. The microstructure and composition were explored various superior tools. The results revealed that the interface Fe4N has a critical role in affecting the magnetic loss and dielectric loss, which brings better impedance matching and relatively low dielectric loss. Therefore, the Fe@Fe4N submicron fibers have excellent microwave absorbing properties. [ABSTRACT FROM AUTHOR]

DP antagonists are claimed to be useful in the treatment of allergic disorders. Laropiprant is a potent and selective DP antagonist to reduce the allergic disorders, especially niacin-induced flushing. In our study, a series of novel laropiprant derivatives (I-1- I-18) were synthesized and characterized by IR, H-NMR, C-NMR and HRMS spectrum. The potency of these compounds was evaluated in a murine model of niacin-induced flushing. The results indicated that most compounds exhibited faster-acting effect of suppressing vasodilation than laropiprant. Among them, I-1, I-2, I-3, I-9, I-13, I-15 and I-16 exhibited substantial flushing inhibitory effect. Especially, I-1 and I-2 showed higher potency than laropiprant and would be valuable for further investigation. [ABSTRACT FROM AUTHOR]

An efficient synthetic method for 2, 3-dihydro-1 H-indene-1-methanamine and its derivatives is described. Six compounds of 2, 3-dihydro-1 H-indene-1-methanamines were synthesized from corresponding 4-nitro-3-phenylbutanoic acid in satisfactory yields (50.9-57.9 % in 4 steps), and three compounds ( 1c, 1e, 1f) were newly reported. This procedure has the advantages of mild conditions, less pollution, and simple manipulation. [ABSTRACT FROM AUTHOR]

It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU) - cetyltrimethylammonium bromide (CTAB) – nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0 × 10−8–1.0 × 10−6 g mL−1 for fish sperm DNA (fsDNA), 2.0 × 10−8–1.0 × 10−6 g mL−1 for calf thymus DNA (ctDNA), 1.0 × 10−8–1.0 × 10−6 g mL−1 for yeast RNA (yRNA), and their detection limits (S/ N = 3) are 8.0 ng mL−1, 10.5 ng mL−1 and 5.8 ng mL−1, respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The interaction mechanism is also studied. [ABSTRACT FROM AUTHOR]

Hydrogenation of transition metal oxides offers a powerful platform to tailor physical functionalities as well as for potential applications in modern electronic technologies. An ideal nondestructive and efficient hydrogen incorporation approach is important for the realistic technological applications. We demonstrate the proton injection on SrCrO3 thin films via an efficient low-energy hydrogen plasma implantation experiments, without destroying the original lattice framework. Hydrogen ions accumulate largely at the interfacial regions with amorphous character which extend about one-third of the total thickness. The HxSrCrO3 (HSCO) thin films appear like exfoliated layers which however retain the fully strained state with distorted perovskite structure. Proton doping induces the change of Cr oxidation state from Cr4+ to Cr3+ in HSCO thin films and a transition from metallic to insulating phase. Our investigations suggest an attractive platform in manipulating the electronic phases in proton-based approaches and may offer a potential peeling off strategy for nanoscale devices through low-energy hydrogen plasma implantation approaches. [ABSTRACT FROM AUTHOR]