Multilayer insulation technique

Large vessels for the storage of cryogenic fluids are field-erected, rather than assembled in a factory, because it is difficult to ship parts much larger than 12 ft in diameter. It is impractical to insulate these field-erected tanks with high-efficiency multilayer insulations by conventional methods, so a new technique has been devised to apply superinsulations to vessels which cannot be moved or rotated. 

Since it is necessary to construct tanks of this type by field-erected techniques rather than to shop-fabricate and ship to the field, it was obvious that standard methods of applying multilayer insulation could not be used. The inner vessel could not be rotated around its axis to spirally wind these materials. In addition, the construction schedule required installation of the superinsulation within a seven-day time period. To meet these stringent requirements, quilted superinsulation, a new technique of applying multilayer insulations, covered by U.S. patents 3,007,596 3,009,600 3,009,601 and patents pending was developed. 

Application of multilayer insulation to a cryogenic vessel is accomplished either by spiral wrapping or, when this is not practical, by suspension of insulation layers on the vessel. The object of the development work was to provide a technique to install a number... 

Mach-Zehnder interferometer, 144 Medical applications, 153 Metal-insulator transitions, 52 Monte Carlo procedure, 135 Multi-energy X-ray imaging, 131 Multilayer targets, 131 Multiphoton absorption, 85 Multiphoton ionization, 82 Multiple filamentation, 91, 92 Multipulse techniques, 152... 

Mono- and multilayer films of polyimides were successfully prepared using Langmuir-Blodgett technique. Monolayer films of polyamic acid long alkylamine salts were prepared at the air-water interface. The mono-layer films were deposited on appropriate plates to produce multilayer films of the precursor to polyimide films. Finaly, the polyimide multilayer films were obtained by treatment of the multilayer films of the polyamic acid amine salts with acetic anhydride and pyridine. The polyimide multilayer films had excellent coating ability giving a very smooth surface. They also exhibited insulating characteristics as reliable as polyimide thick films. 

Chemical and physical processing techniques for ferroelectric thin films have undergone explosive advancement in the past few years (see Ref. 1, for example). The use of PZT (PbZri- cTi c03) family ferroelectrics in the nonvolatile and dynamic random access memory applications present potentially large markets [2]. Other thin-film devices based on a wide variety of ferroelectrics have also been explored. These include multilayer thin-film capacitors [3], piezoelectric or electroacoustic transducer and piezoelectric actuators [4-6], piezoelectric ultrasonic micromotors [7], high-frequency surface acoustic devices [8,9], pyroelectric intrared (IR) detectors [10-12], ferroelectric/photoconduc-tive displays [13], electrooptic waveguide devices or optical modulators [14], and ferroelectric gate and metal/insulator/semiconductor transistor (MIST) devices [15,16]. 

As demonstrated by Heath et al., application of the LB technique in conjunction with semiconductor nanoparticies may lead to the generation of tunnel diodes [60]. These devices consist of a monolayer of 3.8 nm CdSe nanocrystals and an insulating bilayer of eicosanoic acid, sandwiched between an Au and an Al electrode. Advanced spectroscopic techniques such as attenuated low-energy photoelectron spectroscopy were also applied to LB-derived multilayered nanostructured assemblies of differently sized CdS particles [61]. Recent examples of applications of the LB technique... 

Along with the multilayered ceramic capacitors, there are many other categories of electronic ceramic materials that are active by nature— that is, they perform a function other than that of a simple insulator in the electronic circuitry. Some are conductors or semiconductors, while others act as resistors, sensors, electrooptics, or magnetic components. In this section we will describe some of the electronic devices that depend upon tape casting as a forming technique. 

A fabric-based capacitor was made using a novel 3D-weaving technique [56]. As shown in Fig. 28.30, the multilayer woven stmcture is made of live layers the conductive layers (A and D), the insulating and stabilizing layers (B and E), and the middle layer (C), which acts as the distancing and insulating layer. 

A similar family of polyimides has been described by other workers [38]. The polyamic acid alkylamine salt (23) was used to form a surface monolayer, and this was then deposited into multilayers by the LB technique. By treating the deposited films with acetic acid, a highly stable polyimide multilayer (24) was produced. The major difference between these polyimides and those of structure (22) is the mode of preparation. In this case a chemical method is used, whereas thermal cyclization was used for (22). LB polyimide films of structure (24) have been found to be very stable in various organic solvents and exhibit insulating behaviour (electrical and thermal) comparable to conventional polyimide films. 

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