Electrical conductivity initial characteristics

We used polycrystalline films of ZnO and Sn02 as adsorbents. The films were deposited from the water suspension of respective oxides on quartz substrates. These substrates contained initially sintered contacts made of platinum paste. The gap between contacts was of about lO" cm. All samples were initially heated in air during one hour at T 500 C. We used purified molecular oxygen an acceptor particle gas. H and Zn atoms as well as molecules of CO were used as donor particles. We monitored both the kinetics of the change of ohmic electric conductivity and the tangent of inclination angle of pre-relaxation VAC caused by adsorption of above gases and the dependence of stationary values of characteristics in question as functions of concentrations of active particles. 

Carbon fibers are made from many different feedstocks. The most important commercial fiber is made from polyacrylonitrile (PAN). It is four times stronger than steel, the same modulus or higher, and does not fail in creep or fatigue. These properties made the fiber attractive for aerospace applications initially, and later for sporting and industrial applications. Another important feedstock is pitch from refinery or steel-making operations, which leads to fibers with very high modulus and thermal and electrical conductivities. Properties of the fibers, and critical steps in their manufacture are described, together with structural characteristics and failure mechanisms. 

Percolation phenomena have also been observed in the case of drug-incorporated nonionic microemulsion system. Electric conductivity has been measured as a function of water content ca for the oleic acid (oil), surfactant (Tween 80/ cosurfactant(ethanol) mixture and variation of <7 as a function of (O has been observed (Figure 3.5A). The behavior exhibits profile characteristic of percolative conductivity [33-38]. The conductivity is initially low in an oil-surfactant nuxture but increases with increase in aqueous phase. The low conductivity below cd suggests that the reverse droplets are discrete (isolated droplets in a nonconducting oleic medium, forming w/o microemulsion) and have little interaction. When the water content is raised above the value of <7 increases linearly and steeply up... 

Lead azide is not readily dead-pressed, ie, pressed to a point where it can no longer be initiated. However, this condition is somewhat dependent on the output of the mixture used to ignite the lead azide and the degree of confinement of the system. Because lead azide is a nonconductor, it may be mixed with flaked graphite to form a conductive mix for use in low energy electric detonators. A number of different types of lead azide have been prepared to improve its handling characteristics and performance and to decrease sensitivity. In addition to the dextrinated lead azide commonly used in the United States, service lead azide, which contains a minimum of 97% lead azide and no protective colloid, is used in the United Kingdom. Other varieties include colloidal lead azide (3—4 pm), poly(vinyl alcohol)-coated lead azide, and British RE) 1333 and RE) 1343 lead azide which is precipitated in the presence of carboxymethyl cellulose (88—92). 

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