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•Representative studies were given with emphasis on methods for preparation of metal organic framework nanosheets.•Crucial technologies for characterization of metal organic framework ...nanosheets were evaluated.•Series of promising applications by metal organic framework nanosheets were surveyed and discussed.
With infinite assembly and ultrathin nature, metal-organic frameworks nanosheets (MOFNs), as an emerging family of two-dimensional (2D) materials, have attracted extensive interest in fields of material science, chemistry and nanotechnology. Here, we aim to review the recent advances of MOFNs. The assortments of their synthetic methods of top-down, bottom-up and combined strategies are discussed at first, including the comparison of their advantages and limitations. Then, some crucial techniques towards the morphology and microstructure characterization of MOFNs were introduced. We have also discussed the wide ranges of potential applications, especially molecular separation, catalyst, energy conversion, conduction, photofunction, electrochromism and sensing. Finally, the challenges and outlooks for these multi-functional 2D materials were prospected based on current achievements, as well as their unique architectural features.
In this work, the tensile behavior and microhardness of 316L stainless steel fabricated by selective laser melting under different process parameters were investigated. The ultimate tensile strength ...decreased slightly with increasing energy input, while the opposite tendency was observed for the elongation to failure. Microstructure characterizations were performed to relate the pore morphology, melting pool geometry, solidification cell structure, and grain sizes to the mechanical performance of as-built samples. Fine grains with high fraction of low-angle grain boundaries and fine cellular structures with nano-inclusions are observed in the sample fabricated with a high scanning speed (1000 mm/s). As a result, the sample shows high ultimate tensile strength of up to 707 MPa, while maintaining a total elongation of 30%. The sample fabricated with a low scanning speed (800 mm/s) shows high ductility with total elongation to failure of 55%. The improved ductility is mainly attributed to the elimination of residual pores and melting pool boundaries, which result in brittle features in the as-built samples. The results indicate that selective laser melting may act as a physical metallurgy method to modify the microstructure, and thus improve the mechanical performance of metallic materials.
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•The scanning speed altered melting pool boundaries, residual pores, solidification cells, nano-inclusions and grain sizes.•High ultimate tensile strength was attributed to fine cellular structures and fine grains with low-angle grain boundaries.•Low scanning speed resulted in an enhanced ductility due to the minimization of residual defects and melting pool boundaries.
The main aim of this study was to apply high-energy longer mechanical milling and spark plasma sintering (SPS) techniques to produce in-situ α-Ti/TiO2/TiC hybrid composites from commercially pure-Ti ...(CP–Ti, HCP structure) powders. The CP-Ti powders were subjected to different milling times (0, 20, 40, 60, 80, 100, and 120 h). The results showed that the powder samples milled for 120 h produced Ti, Ti3O5, TiO, TiO2 phases, and dissolved C atoms from the process control agent (toluene) which were then converted to α-Ti, TiO2, and TiC phases (formed in-situ composites) through spark plasma sintering. This was expected due to more reactivity in the 120 h sample as longer milling introduces severe and robust structural refinements. Structural evaluations with increasing milling time were carried out using XRD, HRSEM, and HRTEM. The synthesized powders were then consolidated by SPS at pressures of 50 MPa and 1323 K for 6 min. The micro-hardness results have shown that the hardness was started to increase from 1.40 GPa to 5.56 GPa with increasing milling time due to more dislocation and pinning effect produced by grain refinement and formed TiO2/TiC intermetallic particles enhancing the strength of α-Ti matrix. The α-Ti/TiO2/TiC in-situ hybrid composite bulk sample yielded an ultimate compressive strength of 1.594 GPa.
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•Novel Ti-4Fe-3W/2TiC composite utilizing spark plasma sintering and hot extrusion.•Extruded composite at α+β exhibited yield strength of 1215 MPa at room temperature.•Extruded ...composite at β showed a consistent strength at high temperatures.•TiC dispersion was identical, while α morphology of the alloy matrixes was different.
Considering the high strength of titanium matrix composites (TMCs) at room and elevated temperatures, the aim of this study was to develop novel TMC Ti-4Fe-3W/2TiC (wt%) utilizing powder metallurgy and subsequent extrusion at different temperatures: the two-phase (α+β) and pure β phase regions. The TiC particle dispersion was almost identical in both composites with variation in the size distribution. However, there was a significant difference in the morphology of the α phase in the matrix. The α+β-extruded composite exhibited globular αp (grain size: 0.7 μm); in contrast, the β-extruded phase showed acicular αs (grain size: 1.5 μm). Additionally, α-Ti was the predominant phase in contact with TiC particles due to the semi-coherent relationship between these two phases. A remarkably high yield strength (1215 MPa) was achieved at room temperature in the α+β -extruded composite, while the β-extruded composite exhibited consistently improved strength at high temperatures. Morphological characterization using atomic force microscopy (AFM) revealed the β phase was slightly harder than the α phase, probably due to the solid solution of Fe and W that predominant in the β phase.
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•Wire and arc additive manufacturing of HSLA steel was performed.•Microstructure and mechanical properties were related to the thermal cycles.•No preferential texture was developed, ...leading to near-isotropic mechanical properties.•As-built parts exhibited excellent ductility and high mechanical strength.
Wire and arc additive manufacturing (WAAM) is a viable technique for the manufacture of large and complex dedicated parts used in structural applications. High-strength low-alloy (HSLA) steels are well-known for their applications in the tool and die industries and as power-plant components. The microstructure and mechanical properties of the as-built parts are investigated, and are correlated with the thermal cycles involved in the process. The heat input is found to affect the cooling rates, interlayer temperatures, and residence times in the 800–500 °C interval when measured using an infrared camera. The microstructural characterization performed by scanning electron microscopy reveals that the microstructural constituents of the sample remain unchanged. i.e., the same microstructural constituents—ferrite, bainite, martensite, and retained austenite are present for all heat inputs. Electron backscattered diffraction analysis shows that no preferential texture has been developed in the samples. Because of the homogeneity in the microstructural features of the as-built parts, the mechanical properties of the as-built parts are found to be nearly isotropic. Mechanical testing of samples shows excellent ductility and high mechanical strength. This is the first study elucidating on the effect of thermal cycles on the microstructure and mechanical properties during WAAM of HSLA steel.
To optimize nuclear waste repository performance, the destruction of minor actinide elements, particularly Np and Am, in a neutron fast spectrum reactor is possible by incorporating these elements ...into nuclear fuel. Evaluating the performance of minor actinide containing fuel is of paramount importance to enabling this technology. However, such a task is challenging without an available domestic fast spectrum test reactor. A comparison of fuel performance tested in an available domestic thermal reactor at the Idaho National Laboratory, the Advanced Test Reactor, and in a fast spectrum reactor in France (Phénix) is presented here in this study. This study evaluates the capability of using a cadmium shrouded test position to mimic the power profile along the fuel radius present in fast spectrum reactors so that thermally driven phenomenon (e.g., constituent redistribution) can be evaluated in a thermal reactor and determined to be prototypical of a fast reactor. Thus, optical microscopy and scanning electron microscopy has been performed on irradiated 35U-29Pu-4Am-2Np-30Zr fuel samples (where the number preceding the element is the weight percent concentration) from the two mentioned reactors that present similar irradiation temperatures and power conditions. The results indicate that fuel performance phenomena are reproducible in the two irradiation conditions. The redistribution of Zr occurred in the same manner for the two samples. Similar partitioning of U-Pu-Zr phases was observed, and the behavior of Am was similar in the analyzed specimens. Finally, the overall microstructure evolution seems not to be affected by minor actinides addition compared to expected behavior of conventional U-19Pu-10Zr ternary metal fuels for both specimens. Slight differences in fuel cladding chemical interaction were, however, observed. This difference is likely driven by difference in cladding composition rather than irradiation conditions.
Following many years of evolutionary development, first at the National Synchrotron Light Source, Brookhaven National Laboratory, and then at the Advanced Photon Source (APS), Argonne National ...Laboratory, the APS ultra‐small‐angle X‐ray scattering (USAXS) facility has been transformed by several new developments. These comprise a conversion to higher‐order crystal optics and higher X‐ray energies as the standard operating mode, rapid fly scan measurements also as a standard operational mode, automated contiguous pinhole small‐angle X‐ray scattering (SAXS) measurements at intermediate scattering vectors, and associated rapid wide‐angle X‐ray scattering (WAXS) measurements for X‐ray diffraction without disturbing the sample geometry. With each mode using the USAXS incident beam optics upstream of the sample, USAXS/SAXS/WAXS measurements can now be made within 5 min, allowing in situ and operando measurement capabilities with great flexibility under a wide range of sample conditions. These developments are described, together with examples of their application to investigate materials phenomena of technological importance. Developments of two novel USAXS applications, USAXS‐based X‐ray photon correlation spectroscopy and USAXS imaging, are also briefly reviewed.
The ultra‐small‐angle X‐ray scattering (USAXS) facility at the Advanced Photon Source has been significantly upgraded to provide rapid USAXS scanning at high X‐ray energies together with associated pinhole small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray scattering (WAXS) measurements. Complete USAXS/SAXS/WAXS data can be obtained within 5 min, allowing flexible in situ and operando measurement capabilities under a wide range of conditions.
•A novel deposition strategy integrating an oscillating arc and forced interlayer cooling was developed in WAAM of Inconel (IN) 718 components.•The geometric accuracy, defects, and microstructure ...were comprehensively improved with the novel deposition strategy.•A short process modified heat treatment was introduced to eliminate anisotropic mechanical properties and overcome the strength-plasticity trade-off of Inconel 718 alloy.
Nickel-based superalloys fabricated by wire-arc directed energy deposition, also known as wire arc additive manufacturing (WAAM), usually exhibit inherent columnar grain structure, micro-segregation, and rough surface. A novel deposition strategy, integrating an oscillating arc and forced interlayer cooling, was developed in WAAM of Inconel (IN) 718 components. The influences of deposition modes on geometrical characteristics, defects, microstructure, and mechanical properties were systematically evaluated. The results showed that the oscillation mode, compared to the standard parallel mode, can effectively promote the molten pool's spread and wettability, as well as prevent overflow, finally resulting in high geometric accuracy. In addition, the voids-like defects were reduced by 77.78%, while most common crack defects were not observed. Meanwhile, the forced interlayer cooling process further increased the cooling rate, leading to the reduction of the element segregation as well as the proportion of long-chain-like Laves phases. After a short-process modified heat treatment, the anisotropic mechanical behaviors of the as-deposited samples were almost eliminated. Compared with the parallel mode samples, the yield strength and ultimate tensile strength of the oscillation path samples increased by 5.75% and 9.25%, respectively, while the elongation increased significantly by 51.20%. This signifies that their strength and ductility were simultaneously improved. The strengthening mechanisms were further analyzed based on the distribution of the strengthening phases, as well as the residual Laves phases and porosity.
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•The effects of microwave sintering parameters on the densification, microstructure, and mechanical properties of a lunar soil simulant were examined.•Hybrid microwave sintering at ...950 W and frequency of 2.45 GHz can densify the simulant at a temperature range of 1075–1125 °C.•Hybrid microwave sintering in this study affected microstructural volumetric characteristics without major changes in the chemical–mechanical properties.•Microstructural evolution was predominantly affected by the sintering temperature.
Hybrid microwave sintering is considered a promising method to produce densified components using in-situ resources for lunar construction. This study aimed to examine the effects of primary microwave sintering parameters on the densification, microstructure evolution, and mechanical properties of a lunar soil simulant and analyzed the processing-microstructure-properties relationship. The experimental design was based on the Taguchi method, where temperature, dwell time, and heating rate were regarded as the primary design factors. Density measurements presented the porosity of microwave-sintered specimens ranging from 8.5 % to 11.5 %. Chemical and microstructural characterization was integrated and showed three identical mineral phases appeared at different sintering conditions. Nanoindentation was used to determine nanomechanical properties of microstructural components and subsequent effective stiffness via homogenization technique. Uniaxial compressive strength of sintered specimens was also measured. The sintering design parameters in the range attempted significantly affected microstructural characteristics, while no major changes in the chemical–mechanical properties of phases occurred. Taguchi analysis implied that microstructural evolution is predominantly affected by the sintering temperature, whereas the other two factors (i.e., dwell time and heating rate) were not significant. The fundamental understanding from this study can improve the design of hybrid microwave sintering to densify lunar soils for future lunar construction.
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