查看完整版本: 纳米复合材料的强度越来越强，Nanocomposite goes from strength to strength

纳米复合材料的强度越来越强，Nanocomposite goes from strength to strength

[size=5][b]纳米复合材料的强度越来越强，Nanocomposite goes from strength to strength[/b][/size]
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zZ$o-Z} [b]【纳米科技世界快讯】A new high-strength material consisting of ultrafine nanograins of aluminium has been made by researchers in Australia. The material has a strength of up to 740 MPa and a Vickers microhardness of 2285 MPa and might find use in automobile and aerospace applications in the future.[/b]
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Ultrafine-grained and nanocrystalline metallic materials have good mechanical properties compared to conventional-grained materials. One efficient way of producing such materials is with a technique called ECAP (equal channel angular processing). This involves severely deforming ultrafine metal powders to consolidate them and refine their microstructure.
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6Pwtj s{w [i](a) and (b) HRTEM images of a nanocomposite showing that it contains both amorphous and crystalline Al[/i]2[i]O[/i]3[i] and Al (c) XRDpatterns of different samples. Credit:[/i]
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ECAP has been recently used to consolidate micron-sized Al powder into fully dense material that has a refined grain structure and good mechanical strength. However, ultrafine and nanosized aluminium powder is significantly more difficult to consolidate because the material contains a much higher proportion of surface oxide layer. This layer and the subsequent oxidation that occurs during processing interferes with the consolidation process.
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Kenong Xia of the University of Melbourne and colleagues have now tackled this problem by applying a back pressure of 200 MPa while processing the metal powder at a relatively high temperature of 400 °C. The technique produces large shear strains that break up the oxide layer and mix it into the rest of the powder. "This has turned the perceived disadvantage of the surface oxide layer on Al particles and oxidation during processing into an advantage," Xia told nanotechweb.org.N:Bl(g;T9a$n:`c

X Yc%O6E+R,@4N The final material is truly nanocrystalline because it contains grains about 5 to 10 nm in size. Until now, the smallest grains achieved using ECAP were around 100 nm. It is a composite containing aluminium and aluminium oxide in both crystalline (gamma Al2O3) and amorphous forms, which gives the material its exceptional hardness of 2285 MPa and high strength of 740 MPa. In contrast, the strongest commercially available Al alloys have strengths between 600 and 650 MPa.
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The nanostructure formed is also very stable at temperatures of up to 400 °C, which means high-temperature structural automobile and aerospace applications might be possible.
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The researchers are not stopping here. They would now like to improve the fracture properties of the material and also plan to control the amount and distribution of various structures in the nanocomposite to improve its ductility.
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The work was published in [url=http://scitation.aip.org/journals/doc/APPLAB-ft/vol_91/iss_3/031901_1.html][i]Appl. Phys. Lett.[/i] [b]91[/b] 031901[/url]。
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g0a0?4Sr Source:  nanotechweb.org

:victory: :victory: :victory: :victory: 好东西！

受教了:lol :handshake

:victory: :victory: :victory: 不错，看看

回复 1# 的帖子

:victory: :victory:  不知这种工艺能否工业化生产

:handshake :handshake :handshake