Annealing Effects in (Hg,Cr)Sr2CuO4+δ: Transport and X-Ray Absorption Studies

Superconducting (Hg_1–x Cr _x )Sr₂CuO₄₊, x 0.36, samples of 1201-type, synthesized in partial vacuum, show T _c ^onset of 58 K, T _c (R = 0) 52 K. It is found that T _c is not affected by the subsequent Ar or O₂ annealing treatment. Remarkably, the annealed samples show significant improvement in the diamagnetic signal. Hg L₃-edge measurements on 1201 samples show divalent state of mercury. The Cu K-edge spectra for the samples, after taking due account of the impurity phases, show noticeable modifications in the split main peak features on Ar or O₂ annealing, suggesting changes in the crystal field asymmetry. In the superconducting (SC) samples, a weak but distinct signature of Cu¹⁺ is seen. The Cu¹⁺ feature is absent in all the non-SC 1201 samples as well as in the impurity phase SrCuO₂ and Sr₂CuO₃ samples. An attempt is made to explain the observed Cu¹⁺ feature in SC (Hg,Cr)-1201 in the light of the available reports.     

Measurement and analysis of distribution coefficients in Fe-Ni alloys containing S and/or P: Part II. KIr,KGe, and KCu

Crystals of Fe-Ni-S-P alloys containing Ir, Ge, and Cu in small amounts were grown by plane front solidification. The electron microprobe was used to measure the compositions of these alloys. The Ir, Ge, and Cu distribution coefficients were determined by an analytical procedure from the composition data. The distribution coefficients of Ir, Ge, and Cu vary from 1.20 to 11.0, 0.75 to 2.1, and 0.06 to 0.84, respectively.K _Ir andK _Ge increase andK _Cu decreases with the S content of the liquid.K _Cu increases andK _Ir andK _Ge decrease with the P content of the liquid. Mathematical expressions have been formulated to relate the Ir, Ge, and Cu distribution coefficients to the S and P contents of the liquid. These distribution coefficients are important to the study of the solidification behavior of iron meteorites.     

Microstructural Characterization and Tensile Behavior of Rutile(TiO_2)-Reinforced AA6063 Aluminum Matrix Composites Prepared by Friction Stir Processing

Rutile(TiO_2) particle-reinforced aluminum matrix composites were prepared by friction stir processing. The microstructure was studied using conventional and advanced characterization techniques. TiO_2 particles were found to be dispersed uniformly in the composite. Clusters of TiO_2 particles were observed at a higher particle content of 18 vol%. The interface between the TiO_2 particle and the aluminum matrix was characterized by the absence of pores and reactive layer.Sub-grain boundaries, ultra-fine grains and dislocation density were observed in the composites. TiO_2 particles improved the mechanical properties of the composites. However, a drop in tensile strength was observed at a higher particle content due to cluster formation. All the prepared composites exhibited ductile mode of fracture.     

Palladium‐Catalyzed Selective Aryl Ring C–H Activation of N‐Acyl‐2‐aminobiaryls: Efficient Access to Multiaryl‐Substituted Naphthalenes

Palladium‐catalyzed cycloaromatization of N‐acyl‐2‐aminobiaryls, through a sequence of ortho C−H bond activation/alkyne insertion/meta C−H bond activation/alkyne insertion, was developed. An efficient synthesis of multiaryl‐substituted naphthalenes, N‐[2‐(5,6,7,8‐tetraarylnaphthalen‐1‐yl)aryl]acetamides, was demonstrated using molecular oxygen as the sole oxidant. Furthermore, through Buchwald's synthetic protocol, two compounds were converted into corresponding fluorescent carbazoles in 30–40% yield by intramolecular C−N bond formation.

     

Ionic liquid mediated green synthesis of Ag-Au/Y2O3 nanoparticles using leaves extracts of Justicia adhatoda: Structural characterization and its biological applications

In the present work, a facile synthesis was applied for the silver-gold decorated yttrium oxide nanoparticles with the use of Justicia adhatoda (leaves extract) and [BMIM] PF₆ (Ionic liquid) as a capping/stabilizing agent. The XRD analysis showed that Ag-Au/Y₂O₃ nanoparticles have a face-center cubic structure and crystallite size of 30 nm. The Y-O stretching bands were observed in the FT-IR spectrum at 464 to 495 cm^?1. The band gap of the silver-gold decorated Y₂O₃ nanoparticles was estimated as 5.75 eV from the UV-DRS spectrum. In the SEM and TEM images, the morphology of silver-gold/Y₂O₃ nanoparticles shows a nanoflake-like structure. The presence of silver, gold, yttrium and oxygen of elements has been confirmed by the EDX spectrum. The antibacterial activity of the nanoparticles was evaluated for the Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria. The anticancer activity was also studied by the human cervical cancer cell line. The silver-gold decorated yttrium oxide nanoparticles revealed an exceptional microbicidal and antitumor activity when compared with yttrium oxide, silver decorated yttrium oxide and gold decorated yttrium oxide.     

Sunlight-Assisted Photocatalytic Oxidation of Methane over Uranyl-Anchored MCM-41

Uranyl ions anchored within the mesopores of MCM-41 silicate host matrix served as highly efficient heterogeneous catalysts for sunlight-assisted room-temperature photooxidation of methane in the presence of air to selectively form carbon dioxide. The extent of conversion depended upon the methane content; lower the concentration, faster was the completion of reaction. It was also confirmed that no thermocatalytic reaction occurred below 200 °C in the absence of radiation, other test conditions remaining the same. These results are of relevance from the point of view of abatement of VOCs in the environment.     

Bioinspired Rattan-Derived SiSiC/Zeolite Monoliths: Preparation and Characterisation

In the present article, a three-step process for the preparation of SiSiC/zeolite composites is presented. Rattan-derived SiSiC composites were obtained via a two-step biotemplating liquid silicon infiltration process (LSI). The LSI process, consisting of pyrolysis of the biotemplates (Rattan stems) followed by reactive infiltration of the carbon preforms with liquid silicon at 1550 °C, led to the formation of SiSiC ceramic composites. The SiSiC replicas (59 wt.% of SiC, 40 wt.% of solidified Si, 1 wt.% carbon) faithfully reproduced the macrostructure of Rattan and exhibited an open porosity between 20 and 40 vol.%, with unidirectional parallel microchannels in the range of 100–300 μm in diameter. In a third stage MFI-type zeolite (Silicalite-1 and ZSM-5) coatings were developed on the SiSiC ceramic supports via a partial conversion of the substrate into zeolite (support self-transformation method). The metallic Si in the support was partially dissolved under hydrothermal conditions in a reaction mixture consisting of deionised water, template (TPABr) and NaOH, but without any external Si-source. The influence of different synthesis parameters in the development of the zeolite coating is discussed in detail. The resulting products were characterised by X-ray diffraction, TGA, N₂ adsorption/desorption and SEM-EDX. The filtrates were analysed by ICP-OES. SEM and adsorption measurements revealed that biomorphic cellular SiSiC/zeolite composites possess bimodal (micro-/macro-) porosity. In the final SiSiC/zeolite composite, a maximum zeolite loading up to 40 wt.% was calculated on the basis of TGA and XRD analyses. Thermal shock tests showed that a good coating adherence to the SiSiC substrate was obtained. In addition, a SiSiC/ZSM-5 monolith was also tested as structured catalyst for n-hexane cracking.