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A Cu-coated Al 2 O 3 substrates which can be used for power modules are prepared via sintering and reduction of CuO–SiO 2 film onto the surface of Al 2 O 3 ceramic without precious metal brazing filler or high-vacuum equipment. This method has a significant cost advantage over the existing technology. Effects of oxygen partial pressure from sintering atmosphere and SiO 2 content on microstructure and mechanical properties of Cu/Al 2 O 3 interface are systematically investigated. Phase compositions and morphologies of sintered Cu 2 O layer, reduced Cu layer and reactive layer are characterized via X-ray diffraction and scanning electron microscopy. In addition, physicochemical changes within CuO–SiO 2 during sintering are characterized by thermogravimetry-differential scanning calorimeter. It is found that oxygen and SiO 2 can promote the generation of Cu 2 O–CuO–SiO 2 eutectic phase with low melting point upon sintering, which increases the thickness of reaction layer and the densification of Cu layer. The shear strength between the Cu layer and the Al 2 O 3 substrate is enhanced with the increase in Cu layer densification degree, while varying in irregular manner with the thickness of reaction layer. In particular, the highest shear strength of 62.70 MPa is obtained at oxygen partial pressure of 0.02 atm and SiO 2 content of 1.5 wt%. [ABSTRACT FROM AUTHOR]

In this study, Ce 1−x Cu x O 2−x (x = 0, 0.01, 0.03, 0.05, 0.07) samples were prepared by hydrothermal method. The structure, microstructure, and elemental composition of the powders were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, whereas the electrical conductivity, ultraviolet–visible absorption spectroscopy, and infrared emissivity at 3–5 μm were measured as well. Moreover, the effects of Cu2+ doping concentration on the microstructure, morphology, bandgap, conductivity, and infrared emissivity of Cu-doped CeO 2 powders were systematically studied. The effects of Cu2+ doping on infrared reflection and absorption in a 3–5 μm band and their mechanisms were explained based on electromagnetic theory, lattice vibration absorption, and free carrier absorption. Our result indicated that the emissivity of 1% Cu-doped powder reached the lowest emissivity of 0.200 at 800 °C. When the doping concentration was above 1%, the curve of infrared emissivity versus temperature exhibited a "U" shape, with the minimum point shifting towards the low-temperature region with the increase of Cu doping amount. This phenomenon was attributed to the different enhancement amplitude of reflectivity and absorbance of CeO 2 powder by Cu2+ at different temperatures. [ABSTRACT FROM AUTHOR]

Stenotrophomonas maltophilia is a common conditional pathogen, and it is naturally resistant to most commonly used clinical antibiotics. The bacteriophage is considered to be a potential antibiotic alternative for treating multi-drug-resistant bacteria. In this study, a bacteriophage BUCT555 was isolated from hospital sewage for lysing the clinical multi-drug resistant Stenotrophomonas maltophilia. Electron microscopy studies revealed this phage belongs to the Podoviridae family. The double-stranded DNA genome of bacteriophage BUCT555 is composed of 39,440 bp with a GC content of 61.43%. The genome contains 57 open reading frames, 14 of which had assigned functions, while no virulence related genes, antibiotic resistance genes or tRNA were identified. The burst size of BUCT555 was 204 pfu per infected cell. Structure proteins of bacteriophage BUCT555 generated by SDS-PAGE and HPLC-MS revealed that it contains seven proteins with molecular weight ranging from 19 to 89 kDa. BLASTn analysis showed that phage BUCT555 has 2% homology with other phages in NCBI database, suggesting BUCT555 is a new phage genus of Podoviridae that infects Stenotrophomonas maltophilia. Characterization of the bacteriophage BUCT555 enriches our knowledge about the diversity of Stenotrophomonas maltophilia bacteriophages. • A novel bacteriophage BUCT555 was isolated for lysing the multi-drug resistant Stenotrophomonas maltophilia. • The BUCT555 is the third phage infecting Stenotrophomonas maltophilia in Podoviridae family, and the only has electron micrograph. • BUCT555 is classified as an unclassified Podoviridae. [ABSTRACT FROM AUTHOR]

Inspired by the double-helix structure of biological DNA, low-volume fraction and high-strength Al 2 O 3 twisted honeycomb structures with characteristics similar to those of helical structures in the z -axis were prepared by digital light processing 3D printing technology. As the twist angle increased, the compressive strength of the fabricated Al 2 O 3 structure decreased, and the deformation mechanism of the Al 2 O 3 structures gradually changed from stretching-dominated to bending-dominated, which can be predicted by the Gibson–Ashby model. The relationship between the effective elastic modulus and the volume fraction that can be modified by varying the wall thickness was described by the Pabst–Gregorova exponential relationship. The compressive strength of the Al 2 O 3 structure with a twist angle of 0° can reach 62.4 MPa at a volume fraction of 13.3%, providing guidance to optimize lightweight structures of ceramics. [ABSTRACT FROM AUTHOR]

Digital light processing 3D printing can be applied to fabricate complex silicon nitride (Si 3 N 4) components. However, because of the surface hydroxyl groups and large refractive index, it is still a foremost challenge to realize a stable photosensitive Si 3 N 4 slurry with combined benefits of low viscosity and large curing depth. In this study, we propose a new formulation strategy to prepare Si 3 N 4 slurry. Starting from the optimization of monomer ratio, we have systematically optimized powder particle size, dispersant and photoinitiator on the rheological properties and curing properties of Si 3 N 4 slurry. Specifically, we have fabricated a stable photosensitive Si 3 N 4 slurry (48 vol%) with a viscosity of 2.09 Pa s (30 s−1), a critical curing energy of 126.09 mJ/cm2 and a maximum curing depth of 80 µm. Finally, based on this optimized slurry, we have successfully obtained complex Si 3 N 4 green body with no defect, which demonstrates great potential to fabricate arbitrary complex ceramic components for various applications. [ABSTRACT FROM AUTHOR]

In this work, flake-shaped FeCo/BaFe 12 O 19 composites were successfully prepared via a facile two-step process involving ball milling and sol-gel treatment. Compared with commonly used FeCo alloys, FeCo/BaFe 12 O 19 composite material can achieve remarkable microwave absorption performance, and this is largely because of the flake-shaped structure and dielectric relaxation processes. Furthermore, changing mass fractions of BaFe 12 O 19 enable flexible control of applicable frequency ranges of FeCo/BaFe 12 O 19 composites. It was found that when the BaFe 12 O 19 mass fraction is as high as 20%, minimum reflection loss can reach −51.22 dB with effective loss of < –10 dB and effective bandwidth of 6.24 GHz even at a thin thickness of 1.45 mm. It is highly believed that these significant achievements will arouse interest from researchers for further practical exploration of microwave absorbers. [ABSTRACT FROM AUTHOR]

The combination of magnetic and dielectric materials is an effective and efficient approach to enhance microwave absorption performance. In this work, rGO/Zr4+-Ni2+ gradient-doped BaM composites were fabricated for broad microwave absorption bandwidth. The results show that the permittivity increases while the permeability reduces gradually with the rising of rGO content. With the mass ratio of rGO increasing up to 15%, the relatively high attenuation constant and good impedance matching condition lead to an outstanding microwave absorption performance with a broad bandwidth of 8.16 GHz and a minimum reflection loss of −57.07 dB at a thin matching thickness of 2.0 mm. Compared with the pure gradient-doped BaM sample, the bandwidth has been widened by 37.37% and the minimum reflection loss has been improved by 220.43%. The performance is also superior to most of the existing state-of-art absorbers. [ABSTRACT FROM AUTHOR]