Coiled fibre

Catalyst-assisted CVD processes can also be used to fabricate delicate microcomponents. Coiled fibres of carbon and refractory carbides are examples of such components which may be used in functional applications such as microsprings, microsensors and fillers of electromagnetic shielding materials. The microstructure of some coiled fibres is shown in Figure 3.39a. The device for the production of coiled fibre fabrication is shown in Figure 3.39b. A graphite plate substrate is placed at the central part of a horizontal CVD reaction chamber, and a metal... 

Figure 3.39. Microstructure of microcoiled fibres (a) Si3N4 coiled fibres [71] and (b) Experimental reactor [72]...

Table 3.9. Coiled fibres prepared by catalyst-assisted CVD processes [70]...

Whiskers/Platelets/Nano-Belts/Nano-Tubes/Coiled Fibres... 

Fig. 6. Scanning electron micrographs of the different stages of the interaction between Trichoderma harzianum and nylon fibers coated with purified ScleroUum rolfsii lectin. (A) A typical branching of the Trichoderma towards the fibers and contact of the branch tip with the fiber surface (bar=10pm) (B) subsequent elongation of the firmly attached tip along the fiber surface (bar= I pm) (C) Trichoderma hyphae coiled fibre, producing additional branches. The hyphal coils and branches adhere tightly to the fiber surface (bar = 10 pm). (From ref. [132], by permission from publisher.)...

Figure 13.4 (a) Optical images of a coiled fibre made by twist insertion into a 300 xm diameter nylon-6,6 fibre, a two-ply muscle made of the coiled fibres of (a), the braided structure made of 32 two-ply coiled nylon fibres made from a 100 pm diameter precuror fibre, and a 1.55 mm coil made from a 300 pm diameter precursor nylon fibre by twist insertion followed by mandrel coiling, (b) Optical images of coiled nylon-6,6 (300 pm) before and after heating, (c) Tensile actuation of coiled fibres as a function of the temperature. Inset shows the same data for untwisted fibres. 

Figure 13.7 Schematic illustration of a twisted then coiled fibre in which the change in fibre twist induces a length change in the coil for (a) heterochiral and (b) homochiral structures. c is the bias angle of the coil.

For fibres and filaments such orientation is desirable, but for solid objects where impact strength is often more important than tensile strength such orientation is usually unwelcome. It can also have further unwanted effects. This arises from the fact that oriented molecules are basically unstable and will at the first opportunity try to coil up. Thus on heating samples up to temperatures near severe distortion can occur leading to warped mouldings. 

New membranes have been developed with significantly enhanced mass-transfer characteristics. These membranes include rotating membrane systems that use a torsional oscillation to produce shear rates as high as 150,000 s. Coiled hollow fibres that exploit Dean vortices to increase solute transport and reduce fouling are receiving attention (Zydney, 2000). 

The coiling together of textile staple fibres, yams or threads to give the structure the required degree of strength, extensibility, flex resistance, etc. Twist is designated as so many turns per inch and either right hand (Z) or left hand (S). See S-Twist and Z-Twist. 

The wire beads used are produced from a combination of multi-strand copper, zinc or brass coated high-tensile steel wires. The required number of wires are formed into the required shape and then passed through a cross-head extruder to be coated with rubber compound. The coated wire layers are then formed into a coiled ring and the free wire ends secured together. For certain heavy duty applications use is made of either a light weight rubberised fabric or a small fibre filled rubber sheet to cover the joint area. In some cases the bead construction is also partially vulcanised. 

The structures of crystalline polymer-salt complexes provide insight into the structure of the more conducting amorphous materials. To date, large single crystals of polymer-salt complexes have not been prepared, but it has been possible to obtain structural information from single crystal X-ray diffraction applied to stretched oriented fibres in the PEO NaI and PEOiNaSCN systems (Chatani and Okamura, 1987 Chatani, Fujii, Takayanagi and Honma, 1990). One of the most detailed studies is of (PEO)3 NaI, Fig. 5.11(a). The sodium ion in this structure is coordinated to both the polymer and to the iodide ion and the polymer is coiled in the form of an extended helix. 

The coiled structure with entanglements does not allow eomplete crystallisation to occur. From very dilute solutions perfect crystals can be formed, in particular when the chain molecules are lying fully stretched and oriented. A technical example is the high-strength PE fibre Dyneema . 

Mrevlishvili189 gave the following enthalpy differences for the helix-coil transfer of collagen fibre - coils/solution (5 kcal/mole) coils/solution - helix/solution (—5.5 kcal/mole) helix/solution - helix/fibre (0.5 kcal/mole). The following table gives the differences between the hydration water of native and denaturated protein181,188> ... 

In nature, thread-like polymeric material fulfils an essential structural role. Plant life is built mainly from cellulose fibres. Animal life is built from linear protein material such as collagen in skin, sinew and bone, myosin in muscle and keratin in nails and hair. The coiled polypeptide chains of the so-called globular proteins which circulate in the body fluids are folded up to give corpuscular particles. 

Figure 7.25 One-dimensional imaging with the NMR-MOUSE (a) Single-point imaging sequence for phase-encoding of space, (b) drawing of the NMR-MOUSE with coils for pulsed field gradients, (c) sample of an elastomer sheet with parallel textile fibres and one-dimensional NMR image with the space direction perpendicular to the fiber direction...

We believe that the longitudinal and torsional mode are not critically damped for frequencies above one GHz. These absorptions may be of importance. Large scale motion of nucleosomes and of the fibres made of coils of nucleosomes (6) would certainly oscillate below one GHz and likely be overdamped. 

The proximate end of the tubing emerging from the flexible metal coil protector affixed to the harness was connected to a hollow fibre flow moderator with a rate of 50 plitre/hr at 48 kPa pressure. The Viaflex container was filled with 30 ml of... 

The electrolyte separated from the gases in gas channels 9 flows to central compartment 4, where it is cooled by means of inserted cooling coils. In the bottom part of the compartment the cooled electrolyte passes through filter 11 where the asbestos fibres from the diaphragm are removed and the electrolyte is then returned by the collecting side channel 10 to the electrolyzer compartments. 

The classic solution is the application of current and voltage transformers, usually as a cast resin embedded type. As a certain disadvantage of inductive transducers, their small frequency range may be considered. Other solutions for current sensors are Rogowski coils (with active or passive integrators) or the fibre-optic current sensor, based upon the Faraday effect [20]. 

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