Design techniques Aluminum

Techniques to handle the aluminum so that it can be continuously fed as chips or pellets into the electrochemical system have also been developed." One design uses aluminum particles having diameters of 1 to 5 mm." The electrode is a pocket whose walls are composed of cadmium-plated expanded steel screen. The electrode is fed by a system which keeps the cell maintained with an aluminum particulate at an optimum level. Figure 38.32 shows the performance of a cell operating at 50°C using SN KOH-containing stannate. The battery, with an electrode area of 360 cm, was able to deliver a current of 56 A at 1.35 V for 110 h, with the automatic addition of aluminum every 20 min. 

Aluminum, the most common material used for contacts, is easy to use, has low resistivity, and reduces surface Si02 to form interfacial metal-oxide bonds that promote adhesion to the substrate. However, as designs reach submicrometer dimensions, aluminum, Al, has been found to be a poor choice for metallization of contacts and via holes. Al has relatively poor step coverage, which is nonuniform layer thickness when deposited over right-angled geometric features. This leads to keyhole void formation when spaces between features are smaller than 0.7 p.m. New collimated sputtering techniques can extend the lower limit of Al use to 0.5-p.m appHcations. 

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Expander-compressor shafts are preferably designed to operate below the first lateral critical speed and torsional resonance. A flame-plated band of aluminum alloy or similarly suitable material is generally applied to the shaft in the area sensed by the vibration probes to preclude erroneous electrical runout readings. This technique has been used on hundreds of expanders, steam turbines, and other turbomachines with complete success. Unless integral with the shaft, expander wheels (disks) are often attached to the shaft on a special tapered profile, with dowel-type keys and keyways. The latter design attempts to avoid the stress concentrations occasionally associated with splines and conventional keyways. It also reduces the cost of manufacture. When used, wheels are sometimes secured to the tapered ends of the shaft by a common center stretch rod which is pre-stressed during assembly. This results in a constant preload on each wheel to ensure proper contact between wheels and shaft at the anticipated extremes of temperature and speed. 

Fabricating techniques can be used to reduce this problem in a product. However, the approach used in designing the product, particularly its mold (relocate gates), is most important to eliminate unwanted orientation or weld lines. This approach is no different from that of designing with other materials like steel, aluminum, or glass. 

This process, originally designated as RSR (rapid solidification rate), was developed by Pratt and Whitney Aircraft Group and first operated in the late 1975 for the production of rapidly solidified nickel-base superalloy powders.[185][186] The major objective of the process is to achieve extremely high cooling rates in the atomized droplets via convective cooling in helium gas jets (dynamic helium quenching effects). Over the past decade, this technique has also been applied to the production of specialty aluminum alloy, steel, copper alloy, beryllium alloy, molybdenum, titanium alloy and sili-cide powders. The reactive metals (molybdenum and titanium) and... 

Johnston, W.D. and Greenfield, I.G. (1991). Evaluation of techniques for interface modification in aluminum matrix composites. In Proc. ICCM-VIII. Composites Design. Manufacture and Application (S.W. Tsai and G.S. Springer, eds.), SAMPE Pub., Paper 19E. 

The object of this review is threefold (1) to discuss the various characterization techniques which have been applied to this catalyst system, (2) to relate what each technique reveals about the nature of the catalyst, and (3) to present an overall picture of the state of the catalyst as it now appears. We will not discuss the vast literature on catalyst activity testing, kinetics, or mechanisms here. These are subjects for review themselves. However, we will mention some selective catalyst activity tests which were designed to give some fundamental insight into the catalyst state or active sites present. Also, we will not discuss in detail the considerable work reported on pure compounds (unsupported) of molybdenum, cobalt, and/or aluminum but we will have occasion to compare some of their properties to our catalyst systems to assess to what degree they may be present in the catalyst. 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate information on the health effects of aluminum is available. Where adequate information is not available, ATSDR, in conjunction with the NTP, is required to assure the initiation of a program of research designed to determine the health effects (and techniques for developing methods to determine such health effects) of aluminum... 

The design of a cell that is compatible with more than one technique was illustrated by Couves et al. (1991). They briefly presented a cell design that allowed the collection of both XAFS spectra (in a dispersive geometry) and X-ray diffractograms. The cell operated at atmospheric pressure and included a pressed wafer of the catalyst. Little detail was provided, but the authors stated that the cell consisted of a custom-built Kanthal heating element embedded in a pyrophyllite block with a recess for the pressed sample. The sample could be heated to 1073 K in a flow of gas. More detail of the design was published by Dent et al. (1995). In essence, there is an outer container fabricated from aluminum that has the necessary Kapton windows and water-cooled end caps. A pyrophyllite heat shield fits inside the outer container, and a wire-wound heater, into which the sample holder fits, is placed inside this heat shield. The furnace was capable of operation from 373 to 1473 K. 

With more stringent requirements on alignment tolerances and planarization in multilevel designs, it is important to fill in the contact and via holes with metal to maintain acceptable step coverage. The step coverage by sputtered aluminum rapidly decreases with increasing aspect ratio. Instead of the sputtered aluminum, tungsten metal has been widely used to fill in the contacts and vias by the CVD technique. 

Stand both natural and anthropogenic sediments. Conventional soil analysis techniques include a mixture of subjective field designations combined with relatively simple quantitative laboratory tests for important major elements such as carbon, calcium, nitrogen, phosphorus, aluminum, and iron (J,2). 

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