Air-sandwich structure

In the air-sandwich structure, which consists of two disks bonded face to face and separated by a spacer-defined air gap, the substrate becomes the protective layer. Very high quality optical substrates are necessary because the write and read functions take place through the disk. The air gap is advantageous for ablative media. Other related structures have been disclosed in which a thin polymer film is supported physically or aerodynam-ically some distance above the recording surface (12). 

Air-sandwich structure, 340 Aldehyde reactions, 168 Aliphatic diol 4,5-disulfonate structure, 125/... 

Fig. 10.3. The air sandwich structure used with tellurium-based optical data...

Attempts have been made to increase the tellurium stability by using various polymers as overcoats and to form sandwich-type structures. The air sandwich structure utilises a substrate on which the tellurium metal is deposited. Annular spacers then provide the supports for the top polymer film and leave a cavity immediately above the metal, as shown in Fig. 10.3. 

Based upon a piezoelectric 1-3-composite material, air-bome ultrasonic probes for frequencies up to 2 MHz were developped. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to-noise ratio higher than 100 dB. Applications are the thickness measurement of thin powder layers, the inspection of sandwich structures, the detection of surface near cracks in metals or ceramics by generation/reception of Rayleigh waves and the inspection of plates by Lamb waves. 

Two polymers can be used in sequence to fill the mold, forming skin-core sandwich molded articles. Air can also be introduced in partially melt-filled molds, and pressurized to form a polymer skin-air core sandwich structure, through the gas-assist injectionmolding process. In all injection molding processes, the polymer is melted, mixed, and injected from the injection unit of the machine. 

Many investigations have been performed in order to elucidate the structure and bonding in cyclopentadienylthallium(I) compounds. Various bonding situations are found in this class. The parent compound, cyclopentadienyl-thallium (LHIa) is nearly unsoluble in polar solvents. It is rather stable to air and water and sublimable in a vacuum. The microwave spectrum (178) suggests a half-sandwich structure in the gas phase with a thallium to ring centroid distance of 2.41 A (see Fig. 11). The thallium-carbon distances of... 

Other unipositive, essentially spherical cations often behave like alkali ions of comparable size. For example, the very stable di (rj-cycl ope ntadienyl) co-balt(III) ion and its analogues with similar sandwich structures have precipitation reactions similar to those of Cs+, and [(tj-C5H5)2Co]OH is a strong base that absorbs COz from the air and forms insoluble salts with large anions. 

Well-defined arene complexes of Group 4 metals in various oxidation states have been isolated. The air- and moisture-sensitive complexes Ti(r -arene)2 (56) have a sandwich structure similar to that of the related chromium compounds [176-178]. They have been used for deoxygenation of propylene oxide and coupling reaction of organic carbonyl compounds [179]. The first synthesis of 56 was cocondensation of metal vapor with arene matrix [176]. Two more convenient methods are reduction of TiCl4 with K[BEt3H] in arene solvent [180] and reaction of TiCl4(THF)2 with arene anions followed by treatment with iodine [170,176]. The latter method involves the formation of an anionic titanate complex, [Ti(ri -arene)2] (57), which can also be formed from KH and 56 [181]. 

Aker Finnyards Oy used a foam sandwich structure, utilizing an epoxy resin infusion process with carbon fiber reinforcement to make the superstructure of a prototype air cushion vehicle. 

Due to the very demanding impact and stiffness properties required of the cab a single GRP skin construction could not be used and recourse had to be made to a sandwich structure. This type of construction would have the additional benefit that it would be used to accommodate air and cable... 

Bis(benzene)chromium has the 18-electron configuration and is thus iso-electronic with ferrocene. It forms brown-black crystals, m.p. 281°C and is thermally rather stable, although it is readily oxidized in air. In the crystal the molecule has a sandwich structure in which the rings are eclipsed symmetry)... 

In the Air Sandwich design, the active layer is coated onto a transparent substrate and is located within an air gap sandwich structure. Thus, no overcoat is needed. The laser beam is focused through the substrate onto the active layer and consequently the mechanical and optical properties of the substrate play an important part in optical disk construction. The substrate should be highly transparent ("85X) at the laser wavelength and optically uniform. Optical uniformity not only includes constant, standard path length, but low, uniform birefringence as well. The requirement of low birefringence arises from the use of... 

---