Ceramic/resin composite film

Almost every type of material used in spacecraft construction was on board glasses for optical instruments, solar arrays, thermal control coatings, ceramics, metals, plastic films, bulk resins, composites, paints, adhesives, lubricants and rubbers. Their examination will provide designers with a rich harvest of data which could not be obtained from any simulation test on Earth. This data will be extremely useful for selecting materials for spacecraft intended to spend 30 or more years in orbit, such as the Freedom Space Station. 

Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanofibre reinforced HOPE [52], carbon black filled LDPE-ethylene methyl acrylate composites [28], carbon black filled HDPE [53], carbon black reinforced PP [27], talc filled PP [54], copper particle modified epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon fibre/PC composites [58], PC/MnCli composite films [59], titanocene polyester derivatives of terephthalic acid [60], lithium trifluoromethane sulfonamide doped PS-block-polyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetrafluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon fibre conductive composites [66], carbon nanofibre modified thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon fibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon fibre EVA composites [66], HDPE carbon fibre nanocomposites [52] and PPS [73]. 

The effect of k on d is most clearly demonstrated in the experiment by Fukada and Date (1970) on the polyester resin film, filled with powdered barium titanate and polarized under a d.c. field. The strong piezoelectricity, as shown in Fig. 29, is ascribed to the polarization charge of the ceramic filler and heterogeneous strain due to the composite structure. The real part d exhibits a maximum at 90° C and d" has a peak and a succeeding dip at this temperature where the primary relaxation of polyester resin occurs. The behavior of d and d" is quite similar to that of k and k" in Fig. 16, respectively, in which decreasing X = an corresponds to increasing temperature. 

Polymer thick films also perform conductor, resistor, and dielectric functions, but here the polymeric resins remain an integral part after curing. Owing to the relatively low (120—165°C) processing temperatures, both plastic and ceramic substrates can be used, leading to overall low costs in materials and fabrication. A common conductive composition for flexible membrane switches in touch keyboards uses fine silver particles in a thermoplastic or thermoset polymeric binder. 

Since no rise in temperature is observed in the vicinity of the substrate, film production on the surface of resinous materials such as plastic is possible. As the fine raw material particles are not broken down to the molecular level in the film production process, even multicomponent complex compounds do not undergo composition shifts, so that the method has the merit of being able to produce films with a complicated composition. So far, this method has been used to produce films of PZT piezoelectric ceramics and alumina. 

Figure 10-6 (a) is a cross sectional photograph of the BaTi03 composition of AD film formed on a resin substrate. A dense structure packed with ceramic particles of several dozen nm can be observed. The dielectric characteristics ( 100 kHz) that can currently be obtained are dielectric constant 400, tan 8 2% or so (dielectric constant of bulk BaTiO. around 3,000). Figure 10-6 (b) is the microstructure of the microwave dielectric structure of Ba(Zni/3Ta2/3)03-Al203 AD film. This exhibits a microstructure of alumina particles distributed uniformly in a BZT matrix. The Q value (1/tan 8) of the film is 500 (Q value of bulk Ba(Zni/3Ta2/3)03 around 5,000). 

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