Microstructure,thermophysical properties and oxidation resistance of SiCf/SiC–YSi2–Si composite fabricated through reactive melt infiltration

As an ideal component material for advanced aeroengines, SiC composite faces severe challenges of high temperatures and oxidation. Here, a high-densification SiC_f/SiC–YSi₂–Si composite was prepared through combining PIP with RMI of Si–13 at% Y alloy to achieve enhanced performance at high temperatures. Based on the analysis of the microstructure and thermophysical properties, it found that the introduction of the highly crystalline Si–Y alloy can improve the high-temperature thermal conductivity of the composite through phonon and electron conduction. In addition, Y migrates to the surface and forms yttrium silicate with increasing oxidation temperature, which facilitates the excellent long-term oxidation resistance of the composite at 1200–1300 °C. Thus, the composite retained its high strength (89.15% and 86.84%) after oxidation at 1200 °C and 1300 °C for 100 h. The experimental results clearly demonstrate that the introduction of the Si–Y alloy is an effective way of preparing high-performance SiC composites.     

Nanostructured Silicon Matrix for Materials Engineering

Tin-containing layers with different degrees of oxidation are uniformly distributed along the length of silicon nanowires formed by a top-down method by applying metalorganic chemical vapor deposition. The electronic and atomic structure of the obtained layers is investigated by applying nondestructive surface-sensitive X-ray absorption near edge spectroscopy using synchrotron radiation. The results demonstrated, for the first time, a distribution effect of the tin-containing phases in the nanostructured silicon matrix compared to the results obtained for planar structures at the same deposition temperatures. The amount and distribution of tin-containing phases can be effectively varied and controlled by adjusting the geometric parameters (pore diameter and length) of the initial matrix of nanostructured silicon. Due to the occurrence of intense interactions between precursor molecules and decomposition by-products in the nanocapillary, as a consequence of random thermal motion of molecules in the nanocapillary, which leads to additional kinetic energy and formation of reducing agents, resulting in effective reduction of tin-based compounds to a metallic tin state for molecules with the highest penetration depth in the nanostructured silicon matrix. This effect will enable clear control of the phase distributions of functional materials in 3D matrices for a wide range of applications.     

Composite bioceramic scaffolds with controllable photothermal performance fabricated by digital light processing and vacuum infiltration

Photothermal scaffolds can help clear bone tumor cells after resection. In this work, hydroxyapatite-akermanite-Fe₃O₄ (HA-AK-FE) bioceramic scaffolds were fabricated by infiltrating digital light processing (DLP)-printed HA-AK scaffolds in nano-Fe₃O₄ solution. The prepared HA-AK-FE samples exhibited excellent and controllable photothermal performance under the irradiation of 808 nm near-infrared light. By controlling nano-Fe₃O₄ concentration, irradiation power and infiltration time, temperature of HA-AK-FE samples could be regulated in a wide range from room temperature to 150 °C within 15 s. Photothermal temperature remained stable after 4 times repeated irradiations. In SBF solution and under subcutaneous tissue, the heating rate and photothermal temperature decreased obviously compared with in air, but they could still meet the needs of killing tumors (41–48 °C). The Fe release concentration of wafers after immersing in SBF for 1 day was 0.037 mg/L and non-venomous. These results confirm the feasibility and controllability of fabricating photothermal scaffolds by coating nano-Fe₃O₄ with vacuum infiltration, and the prepared HA-AK-FE scaffolds are hopeful to be used in photothermal therapy of bone tumors.     

Cold sintering assisted processing of Mn-Zn ferrites

Typically, commercial Mn-Zn ferrites are sintered at high temperatures with prolong times. In this work, commercial Fe₂O₃-rich ferrite powders with the composition of 0.21Mn_0.8Zn_0.2Fe₂O₄-0.79Fe₂O₃ (wt%) are densified by cold sintering at 300 °C with the assistance of organic salts, including MnC₂O₄·2H₂O, FeC₂O₄·2H₂O, and Zn(C₂H₃O₂)₂·2H₂O. Excessive Fe₂O₃ enters into spinel structure forming a solid solution through annealing in low pO₂ at 1350 °C. The sintering behaviors, microstructures, magnetic properties and impedances are investigated. The dehydration of organic salts provides mediate liquid phase to trigger the dissolution-precipitation process, which assists the densification of ceramics. The grains grow from 0.15 µm to 0.52 µm and 7.67 µm after cold sintering at 300 °C and annealing at 1350 °C, respectively. The initial permeability of cold sintered sample is improved to 11000 with a Curie temperature of 125 °C. This work provides a feasible route for cold sintering assisted processing of commercial soft magnetic ferrites.     

La-doped WO3@gCN Nanocomposite for Efficient degradation of cationic dyes

In present investigation, gCN supported carbon coated Lanthanum doped tungsten oxide (C@LWO/gCN) composite were synthesized via hydrothermal approach. The photodegradation of different cationic dyes like malachite green (MG), crystal violet (CV) and methylene blue (MB) has been carried out under prepared C@LWO/gCN composite. Furthermore, the comparative photodegradation was also performed using pristine LWO and C@LWO nanowires. The synthesized samples were characterized via physiochemical techniques such as XRD, FESEM, EDX, FTIR, BET and UV/Vis spectroscopy. The results proved incorporation of La ions into WO₃ lattice and reduced band gap of doped sample which significantly boost up the capability of the material towards photodegradation. The maximum degradation was found out at pH = 6, 5 mg catalyst dose, 5 ppm dye concentration and 35 °C temperature. The achieved results proved that the trapping agents compete with prepared composite specie for the h⁺, e⁻, HO^● and O₂^●- radicals. The obtained experimental records of photodegradation of cationic dyes using C@LWO/gCN composite has correlation with pseudo first order kinetics, Langmuir-Hinshelwood model and t_1/2. The simplest facile synthetic approach, remarkable photodegradation performance against colored and colorless effluents suggest that C@LWO/gCN composite exhibit great potential for large-scale wastewater treatment.     

Biocompatible superhydrophobic surface on Zr-based bulk metallic glass: Fabrication,characterization, and biocompatibility investigations

Superhydrophobic metal materials are promising candidates for preparing the precision blood-contacting medical devices. Finding a metal material with excellent biocompatibility and superplastic forming ability to fabricate superhydrophobic surface is of great practical significance. Zr-based bulk metallic glass with high glass-forming ability was selected as the experimental sample. Micro-nano hierarchical structure was etched by electrochemical method in the ultrasonic environment, and the superhydrophobic surface with good biocompatibility was obtained after further modification. Electrochemical polarization tests show that the superhydrophobic surface can maintain long-term corrosion resistance in simulated body fluids. Blood and cell tests indicate that the superhydrophobic sample has an extremely rate of hemolysis and exhibits the ability to effectively inhibit the adhesion of platelets and smooth muscle cells. In addition, the superhydrophobic sample surface also exhibits good mechanical durability and chemical stability. This study offers a new perspective on the application of Zr-based bulk metallic glass in blood-contacting medical devices.     

Effect of cyclic loading on the microstructure of thin zirconia tapes

The effect of cyclic loading on the microstructure and the phase composition of thin zirconia tapes was studied. Zirconium oxide stabilized with 3 mol% of yttrium was used for preparing the tapes by the gel-tape casting method. The static and cyclic strengths of the samples with a thickness of approximately 0.2 mm were tested. The average static strength of 1233 MPa was determined in a three-point bend configuration. The maximal flexural stress during cyclic loading had to be kept below 900 MPa to ensure the failure-free performance of the tapes - (10⁷ cycles). No evidence of an excessive transformation of the tetragonal microstructure induced by cyclic loading was found. The transformation toughening mechanism of the tetragonal microstructure was not significantly affected by cyclic loading. Based on the results, thin flexible 3Y-TZP parts possess a low risk of mechanically induced excessive transformational microstructural changes during the service life of the part.     

Digital transformation of incumbent firms from the perspective of portfolios of innovation

Digital technology has created new elements of innovation types and given incumbent firms new portfolios of innovation. The portfolio of innovation used during a digital transformation allows it to be successfully implemented and gives a competitive advantage to incumbent firms. We present two propositions for the portfolio of innovation and its shift during the process of digital transformation. Based on an emergent innovation matrix, we conducted a multi-case study on three Chinese firms from different industries, in order to identify the novel innovation types that appear when these firms undergo digital transformation. The research suggests that incumbent firms innovate in various ways simultaneously to implement a digital transformation when faced with market and technology change, and the portfolio of innovation shifts during the digital transformation process.     

Enhancing hydrogen storage performance of MgH2 through the addition of BaMnO3 synthesized via solid-state method

Currently, magnesium hydride (MgH₂) as a solid-state hydrogen storage material has become the subject of major research owing to its good reversibility, large hydrogen storage capacity (7.6 wt%) and affordability. However, MgH₂ has a high decomposition temperature (>400 °C) and slow desorption and absorption kinetics. In this work, BaMnO₃ was synthesized using the solid-state method and was used as an additive to overcome the drawbacks of MgH₂. Interestingly, after adding 10 wt% of BaMnO₃, the initial desorption temperature of MgH₂ decreased to 282 °C, which was 138 °C lower than that of pure MgH₂ and 61 °C lower than that of milled MgH₂. For absorption kinetics, at 250 °C in 2 min, 10 wt% of BaMnO₃-doped MgH₂ absorbed 5.22 wt% of H₂ compared to milled MgH₂ (3.48 wt%). Conversely, the desorption kinetics also demonstrated that 10 wt% of BaMnO₃-doped MgH₂ samples desorbed 5.36 wt% of H₂ at 300 °C within 1 h whereas milled MgH₂ only released less than 0.32 wt% of H₂. The activation energy was lowered by 45 kJ/mol compared to that of MgH₂ after the addition of 10 wt% of BaMnO₃. Further analyzed by using XRD revealed that the formation of Mg_0·9Mn_0·1O, Mn₃O₄ and Ba or Ba-containing enhanced the performance of MgH₂.