Strengthening mechanisms in carbon nanotube-reinforced aluminum composites

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=6128&context=eispapers

Stir casting process for manufacture of Al–SiC composites

The metal-matrix composites/nano-composites (MMCs/MMNCs) reinforced with hard ceramic particulates have received a tremendous attention due to their potential improvements in physical and mechanical performances. In the present work, we have comprehensively collected currently available experimental data sets of Al-based MMCs/MMNCs and have carried out thorough analyses to quantitatively address the impacts of the reinforcement volume fractions, reinforcement particle sizes, and metal-matrix grain sizes on their mechanical properties including the yield strength, ultimate strength, and strain to failure of composites. We also performed a quantitative analysis on the strengthening mechanisms of Al MMNCs to reveal that the grain refinement can play a major role in increasing the strength of composites. Al-based MMC or MMNC materials generally exhibited an indirect relationship between the strength increase and strain-to-failure increase. The results include a critical comparison for the mechanical performance of particulate-reinforced composites for both pure and alloyed Al matrices to elucidate the contemporary status of Al MMC and MMNC materials.

Mechanical performance of particulate-reinforced Al metal-matrix composites (MMCs) and Al metal-matrix nano-composites (MMNCs)

Hydrogen peroxide (H2O2) is an effective green oxidant, which has been widely applied for environmental remediation. Here, we prepared a novel aluminum-graphite (Al-Gr) composite, which was capable of high-efficient production of H2O2 through selective O2 reduction via a two-electron pathway. We discovered the production of H2O2 at a wide pH range, which could be enhanced by optimizing Al-Gr synthesis conditions. Poly(ethylene glycol) (PEG) addition could promote the formation of a welding interface and porous structure between Al and Gr in the Al-Gr composite, which enhanced the galvanic corrosion of Al0, the selectivity of oxygen reduction via the two-electron pathway, and the mass transfer of O2 in the Al-Gr/O2 system. The formation of Al4C3 could be regulated by sintering temperature and sintering time, which could promote the intergranular corrosion of Al0 and enhance the mass transfer of O2 by reaction with water to generate the porous structure in the Al-Gr composite. The concentration of H2O2 reached 777.5 mg/L at an initial pH of 9.0, an Al-Gr dosage of 8 g/L, and an O2 gas flow rate of 400 mL/min. The possible mechanisms of Al-Gr synthesis and H2O2 production in the Al-Gr/O2 system were proposed. The Al-Gr composite was effective for the in situ production of H2O2, which could be further decomposed into a hydroxyl radical (•OH) by Al0 in the Al-Gr composite. This composite could be used not only to decolorize the Rhodamine B dye but also to degrade various organic contaminants in different water matrices, indicating its environmental significance.

High-Efficient Generation of H2O2 by Aluminum-Graphite Composite through Selective Oxygen Reduction for Degradation of Organic Contaminants.

Wetting of polycrystalline SiC by molten Al and Al−Si alloys

http://www.ysxbcn.com/down/upfile/soft/20120904/21-p1930.pdf

Wetting of pure aluminium on graphite, SiC and Al2O3 in aluminium filtration

The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10−8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Wettability of Aluminum on Alumina

An analytical model regarding the ceramic foam filter (CFF) as a network of branches (cylinders) has been developed to describe inclusion removal in CFFs used for aluminium filtration. The model based on measurements of filters with 30 pores per inch, should also predict behaviour of commercial filters with finer pores. Filtration efficiency is a function of particle size, metal velocity, particle settling velocity, and filter properties—the branch diameter, filter thickness, porosity, and specific surface area. The model takes into account interception with cylinders and settling on branch surfaces. The velocities are calculated from the Forchheimer and Ergun’s equation. There is good agreement between the model and plant experiments. Removal by interception increases strongly with decreasing cylinder diameter. There is indication that Al2O3 and SiC filters differ in their capture of inclusions.

Inclusion (particle) removal by interception and gravity in ceramic foam filters

http://www.ysxbcn.com/down/2014/12_en/25-p3922.pdf

Wetting behavior of aluminium and filtration with Al2O3 and SiC ceramic foam filters

In this work, a systematic study on the interactions between aluminum oxide films and TiB2 grain refiner particles and their effect on grain refinement behavior have been conducted. Oxide films were introduced into a commercial purity aluminum melt by adding AA 6061 alloy chips while the grain refiner particles were introduced by adding Al-3T-1B master alloy. Strong sedimentation of TiB2 grain refiner particles was observed in aluminum melt without chip addition during long-time settling. Most of the TiB2 particles were settled and accumulated at the bottom of crucible. In contrast, the sedimentation of TiB2 particles is much less in the melt with the addition of oxide films. A large fraction of TiB2 particles were found to be adhered to the oxide films located at the top part of the crucible, which inhibited the sedimentation of grain refiner particles. TP-1 type tests were also done to study the grain refinement efficiency of Al-3Ti-1B master alloy under different melt cleanliness and settling time. It is found that sedimentation of TiB2 particles greatly reduces the grain refinement efficiency. The introduction of oxide films seems to slightly alleviate the fading effect. This is owing to the strong adherence between the oxide films and TiB2 particles, which leads to a retardation of particle sedimentation.

/pdf/the-interactions-between-oxide-film-inclusions-and-4xmxxs89j2.pdf

Sarina Bao

Papers

Wetting of pure aluminium on graphite, SiC and Al2O3 in aluminium filtration

Wettability of Aluminum on Alumina

Inclusion (particle) removal by interception and gravity in ceramic foam filters

Wetting behavior of aluminium and filtration with Al2O3 and SiC ceramic foam filters

The Interactions Between Oxide Film Inclusions and Inoculation Particles TiB2 in Aluminum Melt