Nanocrystalline Phase Formation inside Shear Bands of Pd-Cu-Si Metallic Glass

Pd77.5Cu6Si16.5 metallic glass was prepared by fluxing treatment and water quenching method. To avoid possible artifacts, shear bands were created by indentation after TEM sample preparation. Bright field image, diffraction pattern, and the dark field image of TEM that covered the shear band region were presented. A few nanocrystalline phases were noticed inside the shear bands, which favored the plastic deformation ability and supported the explanation of mechanical deformation-induced crystallization

The Composition, Diversity and Predictive Metabolic Profiles of Bacteria Associated With the Gut Digesta of Five Sea Urchins in Luhuitou Fringing Reef (Northern South China Sea)

Sea urchins strongly affect reef ecology, and the bacteria associated with their gut digesta have not been well studied in coral reefs. In the current study, we analyze the bacterial composition of five sea urchin species collected from Luhuitou fringing reef, namely Stomopneustes variolaris, Diadema setosum, Echinothrix calamaris, Diadema savignyi, and Tripneustes gratilla, using high-throughput 16S rRNA gene-based pyrosequencing. Propionigenium, Prolixibacter, and Photobacterium were found to be the dominant bacterial genera in all five species. Interestingly, four sea urchin species, including S. variolaris, D. setosum, E. calamaris, and D. savignyi, displayed a higher mean total abundance of the three bacterial genera (69.72 ± 6.49%) than T. gratilla (43.37 ± 13.47%). Diversity analysis indicated that the gut digesta of sea urchin T. gratilla displayed a higher bacterial α-diversity compared with the other four species. PCoA showed that the four groups representing D. setosum, D. savignyi, E. calamaris, and S. variolaris were overlapping, but distant from the group representing T. gratilla. Predictive metagenomics performed by PICRUSt revealed that the abundances of genes involved in amino acid metabolism and metabolism of terpenoid and polyketide were higher in T. gratilla, while those involved in carbohydrate metabolism were higher in the other four sea urchin species. Therefore, our results indicated that the composition, diversity and predictive metabolic profiles of bacteria associated with the gut digesta of T. gratilla were significantly different from those of the other four sea urchin species in Luhuitou fringing reef

Room Temperature Synthesis of Branched ZnO Nanowires Array with Tunable Morphology

Herein, a novel method is proposed to synthesize B-ZnO NWA by simply immersing the Zn NWA in NaOH solution at room temperature (25 °C). Based on the systematic investigation of various factors that affect the growth of B-ZnO NWA, the growth mechanism of B-ZnO NWA is clarified. Guided by the growth mechanism, the control of the morphology of B-ZnO NWA is achieved by adjusting the pore structure of anodized aluminum oxide templates, hot-pressing parameters, NaOH concentration, solution temperature, and immersion time. In contrast to previous reports, the prepared B-ZnO NWA has hollow trunks, which can further increase the specific area of B-ZnO NWA. Considering the facile, environmental, and low-cost synthesis, the prepared B-ZnO NWA with tunable morphology has great prospects in a wide range of applications, especially those related to the conversion and utilization of solar energy, which are gaining increasing interest nowadays

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability, magnetization and low core loss. In this paper, Fe73.5Cu1Nb3Si15.5B7 (at%) nanocrystalline alloy ribbons, with ultra-thin thickness of 14 µm, and also 18 and 22 µm, were prepared by a planar flow casting method with a single roller device. Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing. The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10â100 kHz, at induction amplitudes of 100â500 mT, at room temperature. It was found that the excess eddy current loss Pex was the dominant factor in the overall core loss above 10 kHz. The toroidal samples made of the 14 µm thickness ribbon exhibit very low total core loss of 48 W/kg at a frequency of 100 kHz and magnetic flux density of 300  mT. The ratio of the Pex was up to 89% at 100 kHz. The ribbon with lower thickness exhibits lower Pex and therefore lower total core loss. The domain structure evidences were found. It indicates that the ribbons with small thickness are preferable for application in high frequency condition. Keywords: Nanocrystalline, Ribbon thickness, Core loss, Domain structur

Designing High Entropy Bulk Metallic Glass (HE-BMG) by Similar Element Substitution/Addition

In this paper, we report that two newly designed high entropy bulk metallic glasses (HE-BMGs), Ti20Hf20Cu20Ni20Be20 with a critical diameter of 2 mm, and Ti16.7Zr16.7Nb16.7Cu16.7Ni16.7Be16.7 with a critical diameter of 1.5 mm, can be fabricated by copper mold casting method. These newly developed HE-BMGs exhibited a high fracture strength over 2300 MPa. The glass forming ability and atomic size distribution characteristics of the HE-BMGs are discussed in detail. Moreover, a parameter δ′ was proposed to evaluate the atomic size distribution characteristics in different HEAs. It showed that this new parameter is closely related to the degree of lattice distortion and phase selection of high-entropy alloys. Adjusting the value of δ′ parameter by similar element substitution/addition would be beneficial for designing high entropy bulk metallic glasses

Microstructure, phase stability and mechanical properties of Nb–Ni–Ti–Co–Zr and Nb–Ni–Ti–Co–Zr–Hf high entropy alloys

Owning to their excellent thermal stability and high strength at elevated temperature, high entropy alloys (HEAs) possess great potential for the application in aviation and aerospace fields. In present work, two novel Nb–Ni–Ti–Co–Zr and Nb–Ni–Ti–Co–Zr–Hf HEAs were prepared by arc melting and copper mold suction-casting method. The microstructure, phase stability, mechanical properties at room temperature and elevated temperature of the two HEAs were studied. Both of the HEAs possess high yield stress at room temperature, especially for the Nb–Ni–Ti–Co–Zr (with 2331 Mpa). In addition, the Nb–Ni–Ti–Co–Zr HEA exhibited high yield stress of 564 Mpa at elevated temperature of 800 °C and large compressive plastic strain (more than 50% at 800 °C). Nb–Ni–Ti–Co–Zr–Hf alloy showed new phase precipitation at 800 °C, whereas the structure of Nb–Ni–Ti–Co–Zr was more stable, which is one of the reason why it possesses high strength at room temperature and elevated temperature. The high temperature properties of the Nb–Ni–Ti–Co–Zr HEA make it promising for high temperature application

Review on the Research and Development of Ti-Based Bulk Metallic Glasses

Ti-based bulk metallic glasses (BMGs) are very attractive for applications because of their excellent properties such as high specific strength and high corrosion resistance. In this paper, we briefly review the current status of the research and development of Ti-based bulk metallic glasses. Emphasis is laid on glass-forming ability, mechanical properties, corrosion resistance, and biocompatibility

Phase transformations in the rapidly solidified Ti40Zr20Hf20Pd20 alloy

We report that an approximant phase was initially obtained in amorphous Ti40Zr20Hf20Pd20 alloy. In the initial stage of the devitrification process, the approximant phase transforms into an icosahedral (1) phase with a high thermal stability while the cF96 Zr2Ni-type (space group Fd (3) over barm with a = 1.25 nm and 96 atoms cell(-1)) particles precipitate from the amorphous matrix. Eventually the I phase grows to several hundred nanometers when annealed at about 1000 K and then transforms into the Zr2Ni-type phase with an endothermic reaction. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved