Zinc oxide, deposition

Zinc oxide deposited in paper provides an "alkaline reserve (which is more nearly neutral in pH than the more commonly used calcium and magnesium reserves) by reacting with any strong or weak acids introduced into the paper subsequent to the deacidification process ... 

In other cases, the carbon acts as a promoter and increases the rate of the reaction, or enables it to proceed at lower temperatures. Working with zinc oxide deposited on charcoal, Adadurov39 observed that the carrier may alter the course of the reaction. 

In the processes under consideration, the adhesive forces of the developer powder have been increased principally by charging the contiguous bodies, i.e., as a result of electrical forces. The same sort of effect can be achieved by adjusting the wettability of the surface (see Chapter II). For this purpose, panchromat-ically sensitized zinc oxide deposited on aluminum foil is used as the photocon-... 

Electrode surface chemistries affect and determine the kinetics and mechanisms of redox couples, namely Zn VZn and Br2/Br, in the Zn/Br RFB system. Across the spread of zinc-related catalysis literature reviewed in this book, a significant proportion of publications are concerned with zinc oxide deposition rather than pure zinc. It is possible, however, to adapt relevant methods to introduce potentially suitable functional additives into the system in order to improve electrolyte properties in different areas of the ZBB. Such methods include catalysis of reactions occurring at the EEI, boosting bulk electrolyte properties and controlling diffusion processes across the membrane separator region. 

The active layer of the DSSCs consists of a mesoporous nanocrystalline metal oxide (typically titanium dioxide or zinc oxide) deposited on fluorine-doped tin oxide (FTO) electrode and covered with some organic or organometaUic dye. The dye molecules (D) absorb light while populating... 

New developments relating to the manufacture of thin film transistors (TFT) are being reported from Japan where the Tokyo Institute of Technology has developed a flexible, transparent device on a PETP substrate. This TFT comprises an amorphous oxide semiconductor, which serves as the active layer, and which is made from indium, gallium and zinc oxide deposited by laser ablation to a thickness of 30-60 nm. The TFT, with its transparent electrodes and circuitry, is manufactured in a vacuum at a temperature of 150 "C or less. Because of this low processing temperature it is possible to use low cost PET film, with a thickness of 200 pm, as a substrate thereby enabling transistors to be manufactured at a relatively low cost. 

Flame spray metallising is widely used for the protection of metal against corrosion, especially for in situ protection of stmctural members. The principal metal used for spraying of plastics is sine. Aluminum and copper are also used. If the distance from the part is too great, the zinc solidifies before it touches the part and adhesion is extremely poor. If the molten zinc oxidizes, conductivity and adhesion are poor. If the distance is too short, the zinc is too hot and the plastic warps or degrades. These coatings are not as dense as electrically deposited coatings because of numerous pores, oxide inclusions, and discontinuities where particles have incompletely coalesced. 

Tsai et al. have also used RAIR to investigate reactions occurring between rubber compounds and plasma polymerized acetylene primers deposited onto steel substrates [12J. Because of the complexities involved in using actual rubber formulations, RAIR was used to examine primed steel substrates after reaction with a model rubber compound consisting of squalene (100 parts per hundred or phr), zinc oxide (10 phr), carbon black (10 phr), sulfur (5 phr), stearic acid (2 phr). 

Where particulate matter (in the form of corrosion products of iron oxide) is present in returning condensate, it often contains copper, nickel, and zinc oxides as well. This debris can initiate foaming (through steam bubble nucleation mechanisms) leading to carryover. It certainly contributes to boiler surface deposits, and the Cu usually also leads to copper-induced corrosion of steel. 

Chaparro AM (2005) Thermodynamic analysis of the deposition of zinc oxide and chalco-genides from aqueous solutions. Chem Mater 17 4118-4124... 

Semiconductor films of ZnO used as operational elements are obtained by oxidation at - 500 - 600°C in the jet of purified oxygen of zinc film deposited at vacuum iP 10 Torr) on substrates made of fused quartz with subsequent sintering at - 350°C at high vacuum conditions [34]. As it was concluded in paper [17] the sintered polycrystalline sample obtained in such a manner should not be considered as a set of various separate crystallites touching each other but rather as a monolithic pattern in which microcrystals with diameter of 1-10 pm are linked with each other by bridges with length and thickness of the order of 0,1 pm (see Fig. 2.4). 

In order to develop more informative and direct method of studying the spillover effect of active particles, the authors of [37] suggested to use the sensor method of detecting migrating particles based on separation of sensor and emitter (donor) of active particles. The latter consists of small metal globules, or clusters (with a diameter of about 20-30 A) of Pt, Pd, Ni, etc. (activator) deposited on quartz or sapphire (AI2O3) plate in the form of a strip less than 1 cm wide. The sensor for detection of hydrogen atoms consisted of a zinc oxide strip (with a width of about 0.1 cm and thickness wlOO nm) deposited on the same plate at a distance of 0.03 or 0.6 cm (two versions) from the inner boundaries of activator strips [38]. 

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... 

An occasional batch of zinc dust failed to effect the desired reduction, possibly because of excessive oxide deposition on the surface of the zinc. It is suggested, therefore, that the surface of the zinc dust be cleaned with dilute hydrochloric acid just before amalgamation. 

Fouad, O.A., Ismail, A.A., Zaki, Z.I. and Mohamed, R.M. (2006) Zinc oxide thin films prepared by thermal evaporation deposition and its photocatalytic activity. Applied Catalysis B Environmental, 62, 144-149. 

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