Rotating wheel technique

Figure 15 Two selected methods for metallic glass preparation (a) in the melt-spinning process the molten alloys are projected against a spinning wheel (b) in the twin-roUer quenching technique the melt is cooled between two rotating wheels. In both processes, the aim is to achieve ultrafast cooling...

The technique used, especially the rate of quenching, influences the catalytic activity of the alloy. A commonly used method is melt spinning or strip casting, in which a rotating wheel or disk is brought into contact with the molten alloy. The catalyst comes out in the form of ribbons no more than a few nanometers in thickness. Another technique that is likely to be increasingly practiced is ion sputtering, which has already been used to prepare Fe-Co-Si, Ni-Al-Cr, and Ni-Co (Otsuka Chemical Company, 1982). 

We start by discussing the surface penetration phenomenon. This can, for instance, be investigated by using what in paper science is known as the Bristow wheel, where absorption in a paper strip mounted on a rotating wheel is studied. The absorption time in such a set-up is controlled by simply varying the peripheral speed or the applicator box width. Figure 7.39 (59) shows some early absorption results obtained by using the Bristow wheel absorption technique. All curves show some measurable absorption volume, visible also for... 

A second, nonplethysmographic, technique for measuring airways resistance makes use of an airflow perturbation device (APD) (Fig. 21.18). In this approach, the patient breathes through a mouthpiece connected to a flow sensor. A pressure transducer measures the pressure at the mouth. At the outlet of the flow sensor is a rapidly rotating wheel that intermittently creates partial obstruction to airflow. During the time that there is no obstruction, the airflow is described by... 

In 1981, Herrmann summarized (Herrmann 1981) the results of searches for SHEs in damped collisions of with U carried out at the UNILAC at Darmstadt utilizing their unique high-energy uranium beams to bombard uranium targets. A wide variety of radiochemical separation techniques and a rotating-wheel system were used to search for elements 108 to 118 and even 126. These experiments were also to no avail and upper limits of 10 , 10 , and 10 cm were set on the cross sections for half-Kves of 1 to 100 ms, 100 ms to 1 day, and 1 day to 1 year, respectively. However, he predicted that the planned increases in fluence levels would permit reaching cross sections below these levels. Subsequently, the search for the production of SHEs in damped collisions (see Chap. 3 in Vol. 1) with (6.2—7.3 MeV/nucleon) at the... 

It is the preferred method where speed is not essential — but when the number of samples to be analyzed is large, multiple sample irradiation on the lucite wheel. with single-axis rotation is used. The precision of this latter technique for six plant samples of Octol is shown in Table 2a. 

Bucket elevators. The bucket elevators lift catalyst, at 900-1000°F., about 200 ft. Each elevator consists of two chains with a continuous line of alloy-steel buckets loosely supported between them (217). The upper shaft is fixed in position but the bottom shaft can move to offset thermal expansion and wear of the chain. Chain speeds are 90 to 125 ft./minute at catalyst-circulation rates of 100 to 150 tons/hour. Power requirement is 60 to 80 horsepower (241). Differential band brakes protect against reverse rotation in case of a power failure. Sprockets with renewable teeth were used at first (217), but a traction-wheel drive was later substituted because wear is more evenly distributed and life is longer (241). Repair techniques have been developed for extending chain life (316). Graphite is used to lubricate the chains (239). The upper shaft and main bearings are water-cooled and the bearings are lubricated with oil. 

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