介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

Heterostructured materials are an emerging class of materials with superior performances that are unattainable by their conventional homogeneous counterparts. They consist of heterogeneous zones wi...

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Heterostructured materials: superior properties from hetero-zone interaction

http://research.me.udel.edu/~dlburris/papers/JA27.pdf

A quantitative method for measuring nanocomposite dispersion

Potential and challenges of metal-matrix-composites reinforced with carbon nanofibers and carbon nanotubes

Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques

a b s t r a c t The rapidly solidified AlCr4.7Fe1.1Si0.3 (at.%) alloy produced at large scale by direct extrusion of gas atomised powders was investigated. Hot-extrusion yielded sound compacts and did not create any major structural changes compared to the as-atomised state. Microstructural characterisation of the as-extruded material revealed submicron scale -Al grains with an embedded Al7Cr crystalline phase and traces of a nano-scale quasicrystalline Al84.6Cr15.4 phase. The long-term thermal stability up to 300 ◦C of compacts was proven. The thermal stability of compacts was accompanied by high mechanical prop- erties, especially high strength and Young's modulus, and creep performance up to 300 ◦C. The same material was prepared by laboratory scale extrusion of cryo-chopped melt-spun ribbons as a reference material. No major differences in the structure or properties of the industrially prepared material were observed compared to the reference material.

Materials Science and Engineering A

Bulk Al materials with average grain sizes of 0.47 and 2.4 µm, were fabricated by quasi-isostatic forging consolidation of two types of Al powders with average particle sizes of 1.3 and 8.9 μm, respectively. By utilizing the native amorphous Al 2 O 3 (am-Al 2 O 3 ) film on the Al powders surfaces, a continuous, ∼7 nm thick, am-Al 2 O 3 network was formed in situ in the Al specimens. Systematic investigation of the changes to the am-Al 2 O 3 network embedded in the Al matrix upon heating and annealing up to 600 °C was performed by transmission electron microscopy (TEM). At the same time, the stability of the Al grain structure was studied by transmission Kikuchi diffraction (TKD), electron back-scatter diffraction (EBSD), and TEM. The am-Al 2 O 3 network remained stable after annealing at 400 °C for 24 h. In-situ TEM studies revealed that at temperatures ≥450 °C, phase transformation of the am-Al 2 O 3 network to crystalline γ-Al 2 O 3 particles occurred. After annealing at 600 °C for 24 h the transformation was completed, whereby only nanometric γ-Al 2 O 3 particles with an average size of 28 nm resided on the high angle grain boundaries of Al. Due to the pinning effect of γ-Al 2 O 3 , the Al grain and subgrain structures remained unchanged during annealing up to 600 °C for 24 h. The effect of the am-Al 2 O 3 →γ-Al 2 O 3 transformation on the mechanical properties of ultrafine- and fine-grained Al is discussed from the standpoint of the underlying mechanisms.

On the thermal stability of ultrafine-grained Al stabilized by in-situ amorphous Al2O3 network

Bulk Al–Al2O3 metal matrix composites (MMCs) named HITEMAL (high temperature aluminum) were fabricated in situ by forging compaction of five different types of gas-atomized commercial purity Al powders with a mean particle size in the range of 1–9 µm. As-forged HITEMAL consisted of (sub)micrometric Al grains (matrix) decorated with nanometric thick amorphous Al2O3 (a-Al2O3) skeleton. Low-angle grain boundaries (LAGBs) free of Al2O3 were located in the Al grain interior. The Al grain size and the portion of LAGBs increased with the increase in the relative powder surface area. As-forged HITEMAL shows excellent thermal stability up to 400 °C for 24 h. Annealing at temperatures ≥450 °C led to crystallization and morphological transformation from a-Al2O3 skeleton to nanometric γ-Al2O3 particles. Owing to the pinning effect of Al2O3 phase, no Al grain growth took place during annealing up to 500 °C. HITEMAL showed attractive mechanical properties especially when tested at 300 °C (yield strength up to 220 MPa, Young׳s modulus up to 58 GPa). Despite the presence of a nearly continuous a-Al2O3 skeleton along adjacent Al grains, forged HITEMAL materials had reasonable room temperature elongation of 7–26%. HITEMAL׳s elongation decreased as the Al grain size decreased and with increased testing temperature. The loss in elongation (uniform and total) was attributed to the inhomogeneous flow, which occurred due to high densities of high angle grain boundaries (dislocation sinks) and small content of LAGBs. The strength of HITEMAL stemmed from grain boundary mediated strengthening mechanisms. The results showed a positive deviation from the Hall–Petch plot, which is typical behavior of ultrafine-grained metals. Transformation of a-Al2O3 skeleton to γ-Al2O3 particles led to deterioration of the HITEMAL strength and Young׳s modulus.

Forged HITEMAL: Al-based MMCs strengthened with nanometric thick Al2O3 skeleton

The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

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Peter Krizik

Papers

Materials Science and Engineering A

On the thermal stability of ultrafine-grained Al stabilized by in-situ amorphous Al2O3 network

Forged HITEMAL: Al-based MMCs strengthened with nanometric thick Al2O3 skeleton

Reinforcement Size Dependence of Load Bearing Capacity in Ultrafine-Grained Metal Matrix Composites

Influence of grain boundaries with dispersed nanoscale Al2O3 particles on the strength of Al for a wide range of homologous temperatures