Silver zinc oxide

The reaction is of the acceptor type (28). Consistent with this and the views presented above, the data of Table VI suggest that contact with silver has bent the bands in zinc oxide and thus lowered the activation energy and the start temperature. However, a bifunctional catalytic action of the silver-zinc oxide system canot be excluded with certainty. 

Activation Energies and Starting Temperatures of Methanol Reactions over Silver, Zinc Oxide, and their Mixture (1 1 by wt)... 

More specialized materials also may be used. Adsorption on copper/aluminum oxide or silver/zinc oxide reduces the mercury level to less than 1 p,g m [119]. 

A useful classification of sensitizing dyes is the one adopted to describe patents in image technology. In Table 1, the Image Technology Patent Information System (ITPAIS), dye classes and representative patent citations from the ITPAIS file are Hsted as a function of significant dye class. From these citations it is clear that preferred sensitizers for silver haUdes are polymethine dyes (cyanine, merocyanine, etc), whereas other semiconductors have more evenly distributed citations. Zinc oxide, for example, is frequendy sensitized by xanthene dyes (qv) or triarylmethane dyes (see Triphenylmethane and related dyes) as well as cyanines and merocyanines (see Cyanine dyes). 

Dry cells (batteries) and fuel cells are the main chemical electricity sources. Diy cells consist of two electrodes, made of different metals, placed into a solid electrolyte. The latter facilitates an oxidation process and a flow of electrons between electrodes, directly converting chemical energy into electricity. Various metal combinations in electrodes determine different characteristics of the dry cells. For example, nickel-cadmium cells have low output but can work for several years. On the other hand, silver-zinc cells are more powerful but with a much shorter life span. Therefore, the use of a particular type of dry cell is determined by the spacecraft mission profile. Usually these are the short missions with low electricity consumption. Diy cells are simple and reliable, since they lack moving parts. Their major drawbacks are... 

By the half-cell potentials, we conclude the Zn-Zn+2 half-reaction has the greater tendency to release electrons. It will tend to transfer an electron to silver ion, forcing (54) in the reverse direction. Hence we obtain the net reaction by subtracting (54) from (52). But remember that this subtraction must be in the proportion that causes no net gain or loss of electrons. If two electrons are lost per atom of zinc oxidized in (52), then we must double half-reaction (54) so that two electrons will be consumed. 

Often, the oxides of certain metals are used as the oxidizer. In the names of systems and batteries, though, often only the metal is stated, so that the example reported above is called a silver-zinc, rather than silver oxide-zinc battery (or system). 

To resolve the problem applying methods of collimated atom beams, equilibrium vapour as well as radioactive isotopes, the Hall effect and measurement of conductivity in thin layers of semiconductor-adsorbents using adsorption of atoms of silver and sodium as an example the relationship between the number of Ag-atoms adsorbed on a film of zinc oxide and the increase in concentration of current carriers in the film caused by a partial ionization of atoms in adsorbed layer were examined. 

The above rate equations confirm the suggested explanation of dynamics of silver particles on the surface of zinc oxide. They account for their relatively fast migration and recombination, as well as formation of larger particles (clusters) not interacting with electronic subsystem of the semiconductor. Note, however, that at longer time intervals, the appearance of a new phase (formation of silver crystals on the surface) results in phase interactions, which are accompanied by the appearance of potential jumps influencing the electronic subsystem of a zinc oxide film. Such an interaction also modifies the adsorption capability of the areas of zinc oxide surface in the vicinity of electrodes [43]. 

The above results put forward the question, whether or not one can directly compare in experiment the influence produced by adsorbed atomic and molecular silver particles on electric conductivity of a zinc oxide film. 

The procedures of experiments were the following [15, 26]. After deposition of a specific quantity of silver on substrate the heating of a tray with silver was turned off, the shutter 7 was opened and the sensor was positioned opposite to the substrate in such a manner that the surface of the sensor was parallel to the surface of substrate. In these experiments we detected an irreversible donor signal of the sensor which can be related to adsorption silver atoms on the sensor made of a zinc oxide film. It is known [27] that silver atoms are donors of electrons. Note that the signals of the sensor were observed only when the sensor was positioned in front of a substrate. There were no signals detected in any other arrangement between sensor and substrate. 

We heated the substrate of zinc oxide containing 10 cm 2 of silver atoms (in this case there was already no emission after completion of deposition) at 300 C. Such thermal treatment results in formation of microcrystals, rather than evaporation adatoms on the surface of the substrate made of zinc oxide. In paper [34] it was shown that microcrystals with diameter 100 A deposited on the zinc oxide surface are acceptors of electrons, therefore the formation of microcrystals results in increase of resistivity of a sensor substrate above the initial value (prior to silver deposition). In this case the initial value of the resistance of sensor-substrate was 2.1 MOhm, after adsorption of silver atoms it became 700 kOhm, and as a result of heating at 300°C and formation of microcrystals - acceptors of electrons it in increased up to 12 MOhm. If such a substrate is subject to deposition of 3-10 5 cjjj-2 silver again, then emission of silver atoms gets detected. From the change of resistivity of sensor-detector due to deposition of silver atoms one can conclude that in this case the emission of atoms is 4 times as low than in experiment with pure substrate made of zinc oxide, which confirms the supposition made on the mechanism of emission of adatoms. 

Finally, if we heat the sensor-substrate with deposited silver atoms using internal heater (platinum film attached to the back side of the sensor-substrate) up to 700 C then the surface of zinc oxide gets completely cleaned of silver. This can be confirmed by the value of resistivity of sensor-substrate which comes back to the initial value of 2.1 MOhm (the silver during such treatment partially evaporates, partially migrates to the contacts). The experiment showed that as a result... 

These studies were carried out on industrially manufactured piezoquartz resonators with an AT-cut featuring silver thin-film electrodes. Oscillations with a frequency of 10 MHz (resonant frequency) were generated by generator of the TKG-3 type. The sensor of silver atoms (films of zinc oxide) were positioned in the same vial with resonator, the sensor was positioned parallel to the resonator plane the distance between them was about 5 mm. Prior to the experiment the vial containing resonator and sensor was heated up to 473 K and kept at above... 

Interaction of the 3 2 complex with iron(III) chloride and calcium oxide, mercury oxide or silver oxide was usually too violent for preparative purposes, but zinc oxide was satisfactory. Reaction with water was violent. 

The shift in the C=C frequency, vi, for adsorbed ethylene relative to that in the gas phase is 23 cm-1. This is much greater than the 2 cm-1 shift that is observed on liquefaction (42) but is less than that found for complexes of silver salts (44) (about 40 cm-1) or platinum complexes (48) (105 cm-1). Often there is a correlation of the enthalpy of formation of complexes of ethylene to this frequency shift (44, 45). If we use the curve showing this correlation for heat of adsorption of ethylene on various molecular sieves (45), we find that a shift of 23 cm-1 should correspond to a heat of adsorption of 13.8 kcal. This value is in excellent agreement with the value of 14 kcal obtained for isosteric heats at low coverage. Thus, this comparison reinforces the conclusion that ethylene adsorbed on zinc oxide is best characterized as an olefin w-bonded to the surface, i.e., a surface w-complex. 

O The reaction products in a silver button battery are solid zinc oxide and solid silver. 

Other commonly employed redox electrodes are metals such as copper, cobalt, silver, zinc, nickel, and other transition metals. Some p-block metals such as tin, lead and indium can also function as redox electrodes. However, s-block metals such as magnesium do not make good redox electrodes since the elemental metal is reactive and forms a layer of oxide coating, which leads to poor reproducibility, poor electronic conductivity and electrode potentials that are difficult to interpret, (see Section 3.3.1). 

The separator used in silver—zinc cells should be permeable to water and hydroxyl ions, stable in strong alkaline solutions, and not oxidized by the solid silver oxide or dissolved silver ions and should retard the migration of dissolved ions to the anode. 

Silver(II) oxide is used to make silver oxide-zinc alkali batteries. Also, it is an oxidizing agent. 

The reactions which will be discussed here are basic in the application of dyes as sensitizer for photographic materials like silver halides, zinc oxide and others. Model experiments can be performed at electrodes of such materials which help to understand the mechanism of spectral sensitization in photography. 

---