Small-volume aluminum alloys with native oxide shell deliver unprecedented strength and toughness

2017 ◽  
Vol 126 ◽  
pp. 202-209 ◽  
Author(s):  
Shi-Hao Li ◽  
Wei-Zhong Han ◽  
Ju Li ◽  
Evan Ma ◽  
Zhi-Wei Shan
Keyword(s):  
Aluminum Alloys ◽  
Small Volume ◽  
Native Oxide ◽  
Oxide Shell ◽  
Strength And Toughness

Research on Fatigue Life Prediction and Reliability of High Strength and Toughness Aluminum Alloys

2020 ◽  
Vol 20 (4) ◽  
pp. 1399-1407
Author(s):  
Haigen Jian ◽  
Xiaomei Yang ◽  
Yedong Wang ◽  
Xinlei Lei ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aluminum Alloys ◽  
Life Prediction ◽  
High Strength ◽  
Fatigue Life Prediction ◽  
Strength And Toughness

scholarly journals Bimetallic Nanoparticles as a Model System for an Industrial NiMo Catalyst

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3727
Author(s):  
Sara Blomberg ◽  
Niclas Johansson ◽  
Esko Kokkonen ◽  
Jenny Rissler ◽  
Linnéa Kollberg ◽  
...  
Keyword(s):  
Bimetallic Nanoparticles ◽  
Model System ◽  
Native Oxide ◽  
Oxide Shell ◽  
Industrial System ◽  
Narrow Size Distribution ◽  
Nimo Catalysts ◽  
Further Development ◽  
Industrial Relevance

An in-depth understanding of the reaction mechanism is required for the further development of Mo-based catalysts for biobased feedstocks. However, fundamental studies of industrial catalysts are challenging, and simplified systems are often used without direct comparison to their industrial counterparts. Here, we report on size-selected bimetallic NiMo nanoparticles as a candidate for a model catalyst that is directly compared to the industrial system to evaluate their industrial relevance. Both the nanoparticles and industrial supported NiMo catalysts were characterized using surface- and bulk-sensitive techniques. We found that the active Ni and Mo metals in the industrial catalyst are well dispersed and well mixed on the support, and that the interaction between Ni and Mo promotes the reduction of the Mo oxide. We successfully produced 25 nm NiMo alloyed nanoparticles with a narrow size distribution. Characterization of the nanoparticles showed that they have a metallic core with a native oxide shell with a high potential for use as a model system for fundamental studies of hydrotreating catalysts for biobased feedstocks.

Toughness after Interrupted Quench

2006 ◽  
Vol 519-521 ◽  
pp. 1017-1022 ◽  
Author(s):  
R.T. Shuey ◽  
Murat Tiryakioğlu ◽  
Gary H. Bray ◽  
James T. Staley
Keyword(s):  
Fracture Toughness ◽  
Aluminum Alloys ◽  
Yield Strength ◽  
Hold Time ◽  
Age Hardening ◽  
Quantitative Modeling ◽  
Nonlinear Relation ◽  
Strength And Toughness

We discuss data from a range of heat-treatable aluminum alloys, showing both yield strength and fracture toughness vs time at temperature of interrupted quench. Drop in toughness occurs at much shorter hold time than drop in strength. Concurrently the fracture becomes more intergranular. When later the yield strength falls, fracture becomes more transgranular, and toughness may rise. We attribute this pattern to two mechanisms: 1) Early quench precipitates nucleated on grain and/or subgrain boundaries grow to size sufficient to initiate fracture under tension, long before they withdraw significant solute from subsequent age-hardening. 2) Later quench precipitates nucleated on dispersoids and/or dislocations withdraw solute relatively uniformly, reducing matrix yield strength while increasing matrix ductility. We propose that quantitative modeling of change in strength and toughness with change in quench, requires multiple C-curves for multiple types of quench precipitates, and nonlinear relation of toughness to amount of boundary quench precipitate.

Magnetic and Morphological Properties of Nanophase Metallic Particles of Fe, Co, and Ni

1990 ◽  
Vol 206 ◽  
Author(s):  
S. Gangopadhyay ◽  
G. C. Hadjipanayis ◽  
C. M. Sorensen ◽  
K. J. Klabunde
Keyword(s):  
Vapor Deposition ◽  
Room Temperature ◽  
Small Volume ◽  
Morphological Properties ◽  
Oxide Shell ◽  
Deposition Technique ◽  
Argon Gas ◽  
Metallic Particles ◽  
Vapor Deposition Technique ◽  
Nano Size

ABSTRACTA vapor deposition technique has been used to prepare nano-size particles of Fe, Co and Ni using argon gas. The particles were passivated from further oxidation using a small volume of air. The range of particle size obtained in these systems was 47–200 Å. The saturation magnetization of Fe particles varied between 25–200 emu/g with the higher values corresponding to larger particles and the highest coercivity achieved at room temperature was 1050 Oe. In the case of Co and Ni, the magnetization varied in the range 35–100 emu/g and 14–45 emu/g, respectively. The highest room temperature coercivity was 1200 and 41 Oe for Co and Ni, respectively. A shell-type structure consisting of a metallic core surrounded by an oxide shell has been proposed for the particles.

scholarly journals Photo-oxidation of Ge Nanocrystals: Kinetic Measurements by In Situ Raman Spectroscopy

2006 ◽  
Vol 958 ◽  
Author(s):  
I. D. Sharp ◽  
Q. Xu ◽  
C. W. Yuan ◽  
J. W. Beeman ◽  
J. W. Ager ◽  
...  
Keyword(s):  
Oxidation Rate ◽  
Laser Intensity ◽  
Ion Beam ◽  
Oxidation Mechanism ◽  
Native Oxide ◽  
Stokes Line ◽  
Oxide Shell ◽  
Kinetic Measurements ◽  
Ge Nanocrystals

ABSTRACTGe nanocrystals are formed in silica by ion beam synthesis and are subsequently exposed by selective HF etching of the silica. Under ambient conditions, the exposed nanocrystals are stable after formation of a protective native oxide shell of no more than a few monolayers. However, under visible laser illumination at room temperature and in the presence of O2, the nanocrystals rapidly oxidize. The oxidation rate was monitored by measuring the Raman spectra of the Ge nanocrystals in-situ. The intensity ratio of the anti-Stokes to the Stokes line indicated that no significant laser-induced heating of illuminated nanocrystals occurs. Therefore, the oxidation reaction rate enhancement is due to a photo-chemical process. The oxidation rate varies nearly linearly with the logarithm of the laser intensity, and at constant laser intensity the rate increases with increasing photon energy. These kinetic measurements, along with the power dependencies, are described quantitatively by an electron active oxidation mechanism involving tunneling of optically excited electrons through the forming oxide skin and subsequent transport of oxygen ions to the Ge nanocrystal surface.

scholarly journals Light, strong, and stable nanoporous aluminum with native oxide shell

2021 ◽  
Vol 7 (28) ◽  
pp. eabb9471
Author(s):  
Wei Yang ◽  
Zhao-Ping Luo ◽  
Wei-Kang Bao ◽  
Hui Xie ◽  
Ze-Sheng You ◽  
...  
Keyword(s):  
High Strength ◽  
Native Oxide ◽  
Oxide Shell ◽  
Galvanic Replacement ◽  
Self Healing ◽  
Ambient Conditions ◽  
Structural Applications ◽  
Nanoporous Metals ◽  
Scalable Synthesis ◽  
Similar Density

Aluminum (Al) metal is highly reactive but has excellent corrosion resistance because of the formation of a self-healing passive oxide layer on the surface. Here, we report that this native aluminum oxide shell can also stabilize and strengthen porous Al when the ligament (strut) size is decreased to the submicron or nanometer scale. The nanoporous Al with native oxide shell, which is a nanoporous Al-Al2O3 core-shell composite self-organized in a galvanic replacement reaction, is nonflammable under ambient conditions and stable against coarsening near melting temperatures. This material is stronger than conventional foams of similar density consisting of pure Al or Al-based composites, and also lighter and stronger than most nanoporous metals reported previously. Its light weight, high strength, and excellent stability warrant the explorations of functional and structural applications of this material, if more efficient and scalable synthesis processes are developed in the future.

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