A new Mg98.3Y1.3Ni0.4 alloy containing long period stacking ordered (LPSO) phases with good strength-ductility synergy was prepared by high temperature homogenization and rolling, which possesses a ...high ultimate tensile strength of 320 MPa and elongation of 17.0% and low work hardening rate during tensile deformation. Bulk LPSO phases with lamellar morphology exist in original grains after homogenization. Refined grains, broken LPSO phases and high-density geometrically necessary dislocations provide a good strength for as-rolled alloy with the strength increment of 146.3 MPa, 51.7 MPa and 68.3 MPa, respectively. Good ductility and low work hardening rate are attributed to weak basal texture, activation of non-basal slips with high Schmid factors and annihilation of high-density dislocations. In situ tensile testing result shows deformation coordination by non-basal slips, deformation twinning, grain rotation and absorption of plastic deformation energy by LPSO phases, which suggests a good ductility as well.
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More than 4000 papers in the field of Mg and Mg alloys were published and indexed in Web of Science (WoS) Core Collection database in 2021. The bibliometric analyses indicate that the microstructure, ...mechanical properties, and corrosion of Mg alloys still are the main research focus. Mg ion batteries and hydrogen storage Mg materials have attracted much attention. Significant contributions to the research and development of magnesium alloys were made by Chongqing University, Shanghai Jiaotong University, and Chinese Academy of Sciences in China, Helmholtz Zentrum Hereon in Germany, Ohio State University in the United States, the University of Queensland in Australia, Kumanto University in Japan, and Seoul National University in Korea, University of Tehran in Iran, etc.. This review is aimed to summarize the progress in the development of structural and functional Mg and Mg alloys in 2021. Based on the issues and challenges identified here, some future research directions are suggested.
Grain refinement of cast magnesium alloys, particularly in magnesium–aluminium (Mg–Al) based alloys, has been an active research topic in the past two decades, because it has been considered as one ...of the most effective approaches to simultaneously increase the strength, ductility and formability. The development of new grain refiners was normally based on the theories/models that were established through comprehensive and considerable studies of grain refinement in cast Al alloys. Generally, grain refinement in cast Al can be achieved through either inoculation treatment, which is a process of adding, or in situ forming, foreign particles to promote heterogeneous nucleation rate, or restricting grain growth by controlling the constitutional supercooling or both. But, the concrete and tangible grain refinement mechanism in cast metals is still not fully understood and there are a number of controversies. Therefore, most of the new developed grain refiners for Mg–Al based alloys are not as efficient as the commercially available ones, such as zirconium in non-Al containing Mg alloys. To facilitate the research in grain refinement of cast magnesium alloys, this review starts with highlighting the theoretical aspects of grain refinement in cast metals, followed by reviewing the latest research progress in grain refinement of magnesium alloys in terms of the solute effect and potent nucleants.
Graphene nanoplatelets (few layer graphene) and carbon nanotubes were used as reinforcement fillers to enhance the mechanical properties of AZ31 magnesium alloy through high energy ball milling, ...sintering, and hot extrusion techniques. Experimental results revealed that tensile fracture strain of AZ31 magnesium alloy was enhanced by +49.6% with 0.3 wt.% graphene nanoplatelets compared to −8.3% regression for 0.3 wt.% carbon nanotubes. The tensile strength of AZ31 magnesium alloy was decreased (−11.2%) with graphene nanoplatelets addition, while increased (+7.7%) with carbon nanotubes addition. Unlike tensile test, compression tests showed different trend. The compression strength of carbon nanotubes-AZ31 composite was +51.2% greater than AZ31 magnesium alloy as compared to +0.6% increase for graphene nanoplatelets. The compressive fracture strain of carbon nanotubes-AZ31 composite was decreased (−14.1%) while no significant change in fracture strain of graphene nanoplatelets-AZ31 composite was observed. The X-ray diffraction results revealed that addition of reinforcement particles weaken the basal textures which affect the composite's yield asymmetry. Microstructure evaluation revealed the absence of intermetallic phase formation between reinforcements and matrix. The carbon reinforcements in AZ31 magnesium alloy dissolve and isolate β phases throughout the matrix. The increased fracture strain and mechanical strength of graphene nanoplatelets and carbon nanotubes-AZ31 composites are attributed to large specific surface area of graphene nanoplatelets and stiffer nature of carbon nanotubes respectively.
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•Powder metallurgy method was used to fabricate magnesium composites.•The AZ31-carbon materials composite were blended using ball milling.•The reinforcement particles weaken the basal texture which affects yield asymmetry of composites.•AZ31-graphene nanoplatelets composite exhibited impressive increase in tensile elongation.•AZ31-carbon nanotube composite revealed impressive increase in compression strength.•The structure of reinforcement particles influences the mechanical behavior of composite.
•The strength and ductility of the AZ31 alloy are simultaneously enhanced after the introducing of a high fraction of twin-matrix pairs.•Without significantly changing the global SFs, many more ...non-basal slip systems are activated in the AZ31 alloy due to the deformation compatibility requirements of the twin-matrix interaction.•The uniformity of the strain distribution at the grain-size scale is enhanced as result of the extra activated non-basal slip.
Pre-twinning was used to tailor the strength and ductility of AZ31 magnesium alloy. Simultaneous enhancements in both ductility and strength were achieved in the AZ31 after the introducing of a high fraction of twin-matrix pairs. The slip trace analysis indicated that although the area-weighted average global Schmid factors (SFs) were not significantly changed, much more non-basal slip was activated in the pre-twinned sample compared with that in the as-received sample, which was beneficial to achieving higher work hardening and obtaining higher uniform elongation. The high-resolution digital image correlation (DIC) combined with ex-situ electron backscatter diffraction (EBSD) characterization revealed that the uniformity of the grain-size scale strain distribution was improved and the local strain concentration at the boundary was reduced during the loading as result of the extra activated non-basal slip, which delayed intergranular crack initiation and increased ductility. The activation of much non-basal slip with high critical resolved shear stress, the hetero-deformation, and the fine equivalent grain size caused the strengthening of the AZ31 sample with a high fraction of twin-matrix pair interfaces. These results imply that tailoring the twin-matrix interface density is an effective strategy to achieve excellent strength-ductility combinations in HCP metals.
Electromagnetic waves generated by electronic equipment are widely present in all living and working spaces because of the rapid development of electronic products and frequent use of digital ...systems. Electromagnetic shielding is an effective method of protection against these waves. Therefore, the demand for materials with high electromagnetic shielding properties has remarkably increased. Magnesium (Mg) alloys, as potential electromagnetic shielding materials, have sparked great interest worldwide. This review highlights the effects of grain size, texture, alloying elements and second phase on the shielding properties of Mg alloys. Recent progress on the shielding properties of Mg–Zn, Mg–Al, Mg–RE and other new shielding Mg alloys is then summarised, and the successful design of Mg alloys with superior electromagnetic shielding properties, such as Mg–Zn–Y–Ce–Zr, Mg–Sn–Zn–Ca–Ce, Mg–Gd–Y–Zn–Zr and Mg-based composite materials, is described. Finally, this review provides insights into the future development and applications of Mg alloys with superior shielding properties.
A MOF Glass Membrane for Gas Separation Wang, Yuhan; Jin, Hua; Ma, Qiang ...
Angewandte Chemie International Edition,
March 9, 2020, Letnik:
59, Številka:
11
Journal Article
Recenzirano
Metal–organic framework (MOF) glasses are promising candidates for membrane fabrication due to their significant porosity, the ease of processing, and most notably, the potential to eliminate the ...grain boundary that is unavoidable for polycrystalline MOF membranes. Herein, we developed a ZIF‐62 MOF glass membrane and exploited its intrinsic gas‐separation properties. The MOF glass membrane was fabricated by melt‐quenching treatment of an in situ solvothermally synthesized polycrystalline ZIF‐62 MOF membrane on a porous ceramic alumina support. The molten ZIF‐62 phase penetrated into the nanopores of the support and eliminated the formation of intercrystalline defects in the resultant glass membrane. The molecular sieving ability of the MOF membrane is remarkably enhanced via vitrification. The separation factors of the MOF glass membrane for H2/CH4, CO2/N2 and CO2/CH4 mixtures are 50.7, 34.5, and 36.6, respectively, far exceeding the Robeson upper bounds.
Retained properties: A MOF glass membrane was synthesized by melt‐quenching a solvothermally synthesized ZIF‐62 polycrystalline membrane on an alumina support. The glass membrane is free of intercrystalline defects and acts as a molecular sieve for the separation of light gases. The separation performance for H2/CH4, CO2/N2, and CO2/CH4 far exceeds the respective Robeson upper bounds.
In present study,the microstructure,mechanical and electrochemical properties of aluminum-graphene nanoplatelets(GNPs) composites were investigated before and after extrusion.The contents of graphene ...nanoplatelets(GNPs) were varied from 0.25 to 1.0 wt.%in aluminum matrix.The composites were fabricated thorough powder metallurgy method,and the experimental results revealed that Al-0.25%GNPs composite showed better mechanical properties compared with pure Al,Al-0.50%GNPs and Al-0.1.0%GNPs composites.Before extrusion,the Al-0.25%GNPs composite showed ~13.5%improvement in ultimate tensile strength(UTS) and ~50%enhancement in failure strain over monolithic matrix.On the other hand,Al-0.50%GNPs and Al-0.1.0%GNPs composites showed the tensile strength lower than monolithic matrix.No significant change was observed in 0.2%yield strength(YS) of the composites.However,the extruded materials showed different trends.The0.2%YS of composites increased with increase in GNPs filler weight fractions.Surprisingly,UTS of composites with 0.25 and 0.50%GNPs was lower than monolithic matrix.The failure strain of the baseline matrix was enhanced by ~46%with 0.25%graphene nanoplatelets.The superior mechanical properties(in terms of failure strain) of the Al-0.25%GNPs composite maybe attributed to 2-D structure,high surface area and curled nature of graphene.In addition,the corrosion resistance of pure Al and its composites reinforced with 0.5 and 1.0 wt%GNPs was also investigated.It was found that the corrosion rate increased considerably by the presence of GNPs.
Magnesium (Mg) alloys show great potential to be extensively applied in practice owing to their superior properties, while the poor corrosion resistance does undoubtedly restrict their applications. ...Superhydrophobic coatings with good repellency to corrosive solutions can significantly decrease the interaction between the corrosive species and the substrate, so that they are receiving a lot of attention to improve the corrosion resistance of Mg alloys. Various strategies have been introduced to develop a superhydrophobic coating on Mg alloys, which were reviewed to elucidate the current research status to provide a clue or thinking for beginning researchers. Further, the existing issues of superhydrophobic coating were discussed, especially for their real applications in practice, mainly owing to their poor mechanical stability. Based on the existing issues, the future study was discussed to improve the stability of hierarchical structures and entrapped air pockets, impart the superhydrophobic coating self-healing property to repair the damaged area during service, provide double protection by incorporation of corrosion inhibitors, or even introduce slippery liquid-infused porous surfaces with lubricant layer to provide better corrosion protection for Mg alloys.
Scheme of the preparation process of the TpPa-1/HPAN membrane.
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•A continuous COFs membrane was fabricated by direct growth method.•The TpPa-1/HPAN membrane exhibited high water flux ...and dyes rejection.•The TpPa-1/HPAN membrane possessed superior stability.
Covalent organic frameworks (COFs) are emerging as crystalline porous materials for advanced membranes, due to their regular pore structures and high porosity. The fabrication of defect-free ultrathin COFs membranes is still very challenging, since the poor COF-substrate affinity hampers the nucleation of COF crystallites. In this work, a facile direct growth method was developed to deposit continuous imine-based COF layer (TpPa-1, synthesized by the Schiff-base reactions of 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1)). Aldehydes groups were firstly immobilized on polyacrylonitrile (PAN) porous substrate as the nucleation sites to promote the growth of continuous TpPa-1 layer via a good COF-to-substrate adhesion. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffractometer (XRD) confirmed the formation of COF layer. The TpPa-1/HPAN membrane exhibited high water flux of 418.5 L/(m2 h MPa) under the operation pressure of 0.1 MPa and excellent dyes rejection (93.91% for Orange GII and over 99% for Methyl blue, Congo red and Alcian blue). The high separation performance, coupled with its facile fabrication and remarkable stability, may render imine-based COFs membrane promising for wastewater treatment.
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