Machinable macor

The NPL (Figure 11.12) is based on the trap described by Schrama et al. [32] The outer electrodes (very fine hollow tubes of tantalum of 1 mm inner diameter and 2 mm outer diameter) are grounded, but they can receive a small DC potential. The inner electrodes, also in tantalum, are ca 0.5 mm diameter and separated from the outer electrodes by 0.56 mm. The amplitude of the RF potential is 260 Vp p at a frequency of 17.8 MHz, resulting in secular frequencies for strontium ion of 1.8 MHz (radial) and 3.0 MHz (axial). The electrodes are isolated from each other with a ceramic tube and the trap is mounted on a structure of machinable macor. Two compensation... 

MHz) for spin decoupling and H (61 MHz) for field locking. The container for liquid samples is shown in Figure 2.5. It consists of a normal high precision 5 mm NMR tube cut to a length of 60 mm and closed with a piston and a cap made from the machinable ceramic Macor. These probes were successfully used to study solvent exchange on solvated metal ions and metal ion complexes [14, 15]. 

The high-speed magic-angle spinner used has been described in detail elsewhere (5). The particular one we used is constructed of Macor, a machineable glass that gives no background in the 13C CP/MAS spectra. Additional experimental details and a discussion relating this procedure to solid coals and coal derived liquids have been previously published (8). 

The cell housings were machined from MACOR (machinable ceramic) blocks and type 316 stainless steel bar stock. The housings were 3" diameter and 1" deep cylinders. Gas flow chaimels were machined into the large surface faces with dimensions of 0.3 cm by 0.3 cm. Gas flow tubes were connected to supply process and sweep gases to the cell. Once the electrode and membrane materials... 

Brittle fracture is used for shaping and machining ceramics after they have been fired. Ceramics can be modified to make them machinable this is controlled fracture and is the approach we adopt with machinable glass-ceramics such as Macor (Chapter 26). Of course, many ceramics already are machinable and can be shaped into intricate and beautiful forms as illustrated in the carved marble sculpture shown in Figure 18.1. 

Final machining using Vycor (the cor is from Corning), Macor, or similar specially treated glasses. (Vycor contains built-in pores Macor contains small grains of mica.)... 

The material chosen as a test material is MACOR. MACOR is a machinable glass ceramic and is a fluorine rich glass with a composition approaching trisilicic fluorphlogopite mica (KMg3AlSi30ioF2) (6). The material was acquired in a rod form. 

For tile MACOR material, the material was machined into disks as was the case for the CMC as well as leaving a solid rod of material greater than 25 mm in height for testing in compression as a comparison (where the interfaces from stacking would not be present). 

All disks machined for this effort (CMC and MACOR) were machined with a center hole so that a centering rod of graphite could be used. The rod was machined shorter than the disk height so that it would not interfere or influence the measurement. This is shown in Figure 2. 

The MACOR differs from the CMC in that when it was machined into disks and then ground, there is not as much surface asperity to remove. This is clearly not the case for the CMC system studied. The surface is not uniform initially due to the 5 HS weave used in fabricating the ply. Once the plys are stacked (in this case all material was 8 ply thick), several CVI runs are done applying more material to the surface. As can be seen in Figure 4, as more material is removed, the initial compliance of the stack is reduced. This is due to removing the surface asperities. A balance must be struck between how much material is removed before the material is no longer representative of the CMC. 

Machinable glass-ceramics are based on internally nucleated fluoromica crystals in glass (Beall 1971a). One commercial material has been marketed for 20 years under the trademark MACOR and has found wide application in such diverse and speciality areas as precision electrical insulators, vacuum feedthroughs, windows for microwave-type parts, samples holders for field-ion microscopes, seismograph bobbins, gamma-ray telescope frames, and... 

Property Units MACOR machinable glass ceramic Boron nitride 96% BN Alumina nominally 94% AI2O3 Valox thermoplastic polyester... 

Other minor crystals present mullite (3AI2O3 2Si02) Tough, machinable (with conventional metalworking tools) House of cards structure, only local mechanical damage Apphcations precision dielectric components, electrical insulators, high-vacuum components, other electronic and mechanical parts Example Macor (Corning code 9658)... 

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