Filamentary conduction

The second characteristic of a memory device is filamentary conduction. Fig. 10.16 shows the on- and off-resistances as functions of the area of the device. The off-resistance scales inversely with area, as would be expected for a uniformly conducting material. The on-... 

Fig. 10.16. Dependence of the memory switch oif-resistance and on-resistance on device area, showing evidence of filamentary conduction in the on-state (LeComber et al. 1985).

Since the critical currents are reduced rather strongly in the filamentary conduction region, no additional filaments seem to be introduced by cold-working at liquid-hydrogen temperatures. Therefore it seems reasonable to assume, that the filaments, which are generally fixed in the sample p], break and cause the substance to become normal at lower critical currents. These results also appear to be useful for optimal operation of superconducting coils. 

The electrical response of a typical memory switch is shown in Figures 6.1(d) and 6.2(b). The switching process and filamentary conduction of a memory switch is essentially the same as tha of the threshold switch. In fact, when the voltage is removed immediately after switching, the memory switch reverts to the OFF state. On the other hand, the memory switch retains its conductive state after it has been kept in this state (5-10 mA current level) for about 10" sec, the lock-on time LO, to SET the memory state. Once in the ON-state, the device is turned off by the application of a short, intense RESET current pulse, typically of 5 /x sec duration and 120 mA current. The impedance of the device can be ascertained by a low level (0.5 V, 5 ju sec) read pulse as sketched in Figure 2(b). A typical SET — RESET sequence with interrogating READ pulses is shown in Figure 6.13 (Bunton and Quilliam (1972)). 18 traces are superimposed in this... 

DSC tests show a substantial reduction of the hydrogen desorption onset (red circles) (ToJ and peak (Tpeak) temperatures due to the catalytic effects of n-Ni as compared to the hydrogen desorption from pure MgH2 also milled for 15 min. (Fig. 2.57). It is interesting to note that there is no measurable difference between spherical (Fig. 2.57a) and filamentary (Fig. 2.57b) n-Ni, although there seems to be some effect of SSA. We also conducted desorption tests in a Sieverts apparatus for each SSA and obtained kinetic curves (Fig. 2.58), from which the rate constant, k, in the JMAK equation was calculated. The enhancement of desorption rate by n-Ni is clearly seen. At the temperature of 275°C, which is close to the equilibrium at atmospheric pressure (0.1 MPa), all samples desorb from 4 to 5.5 wt.% H2 within 2,000 s. 

Carbon fibers formed into filaments provide very compatible biomaterials. Carbon does not corrode in the body, nor does it generate a foreign body respon.se. Further, its high electrical conductivity suggests that a variety of electrode and conductor applications are possible. For example, filamentary carbon cathodes have been used to stimulate the growth of bone and soft tissues [136], when adjusting the level of current can be used to influence the growth. 

Conductive Nickel Flake Powder HCA-1 - product developed for conductive paints and adhesives which provides EMI shielding when used in surface coatings, inks, and adhesives. The flakes are treated in a controlled atmosphere to give cleaner surface which enhances conductivity Conductive Nickel Pigment 525 - dendritic filamentary shape similar to INCO products CNS - spherical shape and uniforms size for thick film inks... 

Nanocrystalline materials comprising sub-100 / metal particles, when compressed to 50% of their bulk density, show properties (specific heat, thermal conductivity, saturation magnetization and critical temperature for superconductivity) provocatively different from those of their crystalline or glassy counterparts.(48) It is well known that the interfaces of mechanically reduced composites are effective in interacting with dislocations and with flux lines in superconducting composites. Precursor materials for the preparation of ultrafine filamentary composites can also be imagined. Here the combinations of interphasial boundaries and dislocations can... 

In Fig. 5.20 one can see the rather rapid transition of the deterministic system from the slightly perturbed homogeneous fixed point (H) to the inhomogeneous filamentary one (I). This illustrates that for the given parameters the only stable solution, apart from a trivial, non-conducting fixed point, is an inhomogeneous steady state. 

The active material in the positive electrode is nickel hydroxide. Usually, the nickel hydroxide has a conductive network composed of cobalt oxides and a current collector which commonly is a nickel foam skeleton, but may alternately be a nickel fiber matrix or may be produced by sintering filamentary nickel fibers. ... 

Reduction of expensive inactive cell components is focused on the positive electrode, including the nickel foam substrate and cobalt metal and cobalt monoxide used to form the conductive network. Several approaches are being studied replacement of the cobalt compounds by metallic nickel fibers use of reduced quantity and less expensive cobalt compounds. An innovative approach being studied is the use of inherently more conductive nickel hydroxide accomplished by multielement modification, and by heterogeneous nickel hydroxide powder particles where filamentary metallic fibers have been embedded into the base nickel hydroxide to make contact with the overall conductive network. To reduce the cost of the foam substrate, development activities include less expensive nickel coating processes and elimination of the foam entirely by enhancing the conductivity of the nickel hydroxide and the conductive network. 

DBD can exist in two modes, that is, filamentary and homogenous mode. The latter is sometimes confusingly also called as APGD. In most cases, DBD plasma operates in the filamentary mode where the electrical conductivity is restricted to numerous successions of microdischarges. The plasma is... 

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