Aluminum microstructuring

Key words Dispersion strengthened materials, aluminum, microstructure, mechanical properties... 

Figure 2.14 Porous alumina layer inside microchannels in an aluminum microstructured device. The porous layer was obtained by anodic oxidation.

Materials at the 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Austin, Texas, Apr. 18-21, 2005. Multiscale Modeling for the Analysis of Grain-Scale Fracture within Aluminum Microstructures. 

The results of development work on processes indicate that the two main methods of preventing the duplex microstructure from forming appear to be fast-firing, or increasing the amount of / "-alumina at low temperatures. Based on these results, Duncan et al. [20] and Zyl et al. [21] have described production processes starting from aluminum oxy-hydroxides or aluminum hydroxides as precursors for the synthesis of the solid electrolyte "-alumina. Duncan et al. described an alumina precursor which substitutes in part or wholly for or-alumina in an established... 

Microfabrication of the parallel channels was performed by mechanical surface cutting of metal tapes [31]. In the case of aluminum alloys, ground-in monocrystalline diamonds were used [45]. In the case of iron alloys, ceramic micro tools have to be used owing to the incompatibility of diamonds with that material. Such a microstructured platelet stack is provided with top and cover plates, diffusion bonded and connected to suitable fittings for the inlet and withdrawal ducts by electron beam welding (Figure 3.9). 

The equilibrium, room temperature structure of pure cobalt is hep. The fee structure is stable at high temperatures (422 °C to 1495 °C) and has been retained at room temperature by rapid solidification techniques [101], X-ray diffraction analysis was used to probe the microstructure of bulk Co-Al alloy deposits containing up to 25 a/o Al and prepared from solutions of Co(II) in the 60.0 m/o AlCfi-EtMelmCl melt. Pure Co deposits had the hep structure no fee Co was observed in any of the deposits. The addition of aluminum to the deposit caused a decrease in the deposit grain size and an increase in the hep lattice volume. A further increase in the aluminum content resulted in amorphization of the deposit [44], Because the equilibrium... 

As can be seen from this figure, the heat-resistance was remarkably improved by the drastic changes in the microstructure from amorphous to polycrystalline structure. Another type of SiC-based fiber, SA fiber (2), has a sintered SiC polycrystalline structure and includes very small amounts of aluminum. This fiber exhibits outstanding high temperature strength, coupled with much improved thermal conductivity and thermal stability compared with the Nicalon and Hi-Nicalon fibers. The fabrication cost of the SA fiber is also reduced to near half of that of the Hi-Nicalon Type S [ 17]. The SA fiber makes SiC/SiC composites even more attractive to the many applications [18]. In the next section, the production process, microstructure and physical properties of the SA fiber are explained in detail. 

Independent of the ligand system, two different activation methods have been used in performing the propylene polymerization experiments. In both cases, the catalytic activities and molecular weights of the polymers are a sensitive function of the aluminum content provided by the activators. This dependence suggested an additional reversible chain transfer to aluminum when activating with MAO. As lower contents of A1 are provided in the polymerization system in the case of in situ activation with TIBA/borate, the only mechanism occurring is the chain back-skip. Furthermore, the differences in the polymer microstructures prepared with MAO and borate as cocatalysts are reflected. They sustain the proposed reversible chain transfer. 

Pavlovic, T. and A. Ignatiev. 1986. Optical and microstructural properties of anodically oxidized aluminum. Thin Solid Films 138 97-109. 

A characteristic of this type of reactor is the steel substrate, which is preferably used as the reaction chamber (it can also be titanium or aluminum). This allows the use of microstructures under robust experimental conditions such as high temperatures. 

A convenient method to produce porous surfaces is the anodic oxidation of aluminum plates. Such microstructured aluminum platelets have been coated by wet impregnation with Pt-, V- and Zr-precursors [35], and tested under catalytic methane combustion conditions. The conversion rate of oxygen followed directly the platinum content in the catalysts. These data were well reproducible even after five different runs. 

Padture, N.P., Bennison, S.J. and Chan, H.M. Flaw-tolerance and crack-resistance properties of alumina-aluminum titanate composites with tailored microstructures ,... 

Now that the top-down internal state variable theory was established, the bottom-up simulations and experiments were required. At the atomic scale (nanometers), simulations were performed using Modified Embedded Atom Method, (MEAM) Baskes [176], potentials based upon interfacial atomistics of Baskes et al. [177] to determine the conditions when silicon fracture would occur versus silicon-interface debonding [156]. Atomistic simulations showed that a material with a pristine interface would incur interface debonding before silicon fracture. However, if a sufficient number of defects were present within the silicon, it would fracture before the interface would debond. Microstructural analysis of larger scale interrupted strain tests under tension revealed that both silicon fracture and debonding of the silicon-aluminum interface in the eutectic region would occur [290, 291]. 

Y. Xue et al Microstructure-based multistage fatigue modeling of aluminum alloy 7,075-T651. Eng. Fract. Mech. 74, 2810-2823 (2007)... 

Variations of the amount of cocatalyst which are usually expressed by the molar ratio W Nd have a significant influence on polymerization rates, molar masses, MMDs and on the microstructures of the resulting polymers. These aspects are addressed in the following sections with a special emphasis on ternary catalyst systems. For ternary systems it has to be emphasized, however, that in many reports the ratio Ai/ Nd only accounts for the amount of aluminum alkyl cocatalyst and not for other Al-sources such as alkyl aluminum halides. Variations of the Ai/ Nd-ratios are also used for defined control of molar mass. This aspect is addressed in separate sections (Sects. 2.2.8 and 4.5). 

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