Aluminium cathodes

The isolation of zinc, over 90% of which is from sulfide ores, depends on conventional physical concentration of the ore by sedimentation or flotation techniques. This is followed by roasting to produce the oxides the SO2 which is generated is used to produce sulfuric acid. The ZnO is then either treated electrolytically or smelted with coke. In the former case the zinc is leached from the crude ZnO with dil H2SO4, at which point cadmium is precipitated by the addition of zinc dust. The ZnS04 solution is then electrolysed and the metal deposited — in a state of 99.95% purity — on to aluminium cathodes. 

Z. Liu, O.V. Salata, and N. Male, Improved electron injection in organic LED with lithium quinolate/aluminium cathode, Synth. Met., 128 211-214 (2002). 

A later method proposed by Oehman [26] produces glycol nitrate and diethylene glycol from ethylene by electrolysis. A platinum wire mesh submerged in an acetone solution of calcium nitrate acts as anode, ethylene being blown through the solution continuously. The cathode space behind the aluminium cathode is filled with a solution of calcium nitrate in nitric acid. At the anode the nitrate ion forms a free radical N03 which combines partially with ethylene to produce nitroglycol (6) ... 

Cadmium electrolysis on a rotary aluminium cathode. The cadmium is then converted into cadmium oxide in their plant and used for the production of new batteries. 

Fig. 11.17 The energy-level diagram for the two-layer system CuPc/Cgo (left) between an ITO anode and an aluminium cathode and for the mixed system CuPciCgo between an ITO anode with a PEDOT PSS buffer layer, and an aluminium cathode (right). The level scheme is shown for the case that the layers are not yet in contact. After making contact, the Fermi levels equalise, so that the HOMOs and the LUMOs are bent in such a way that the electrons drift...

The dimerisation reaction is favoured by aluminium cathodes at whose partially insulated surfaces high cathodic potentials exist. Simple tetraalkylammonium cations reduce reversibly at mercury to form insoluble compounds of mercury with quaternary ammonium radicals. These compounds, stable only at sub-ambient temperatures, decompose on warming with the formation of hydrocarbon and amine products. ... 

Yang and Pei reported the use of PPOPH as the electron injection layer in MEH-PPV based LEDs (i5). They found that the device performance and quantum efficiency were improved by a factor of 40 when using PPOPH as an electron injection layer between an emissive MEH-PPV layer and an aluminium cathode. 

Hwang DH, Kim ST, Shim HK, Holmes AB, Moratti SC, Friend RH. Highly efficient green light-emitting diodes with aluminium cathode. Synth Met 1997 84(l-3) 615-8. 

A cell for the Hall—H roult process is shown in Fig. 4.1, and a block diagram of the whole process is shown in Fig. 4.2. Cell design is determined largely by the need to contain molten cryolite at high temperatures and to withstand attack by molten aluminium and also by sodium and fluorine formed as minor products at the cathode and anode respectively. Hence the cell is a strong steel box lined first with alumina to act as a refractory, thermal insulator and then with carbon. In fact the base of the tank is lined with prebaked carbon blocks which are inlaid with steel bars to reduce their electrical resistance and which act as current carriers to the molten aluminium cathode. The sides are lined with partially graphitized anthracite in coal tar pitch. The process is then run so that there remains a layer of solid cryolite and alumina at the sides of the cell and a soHd crust on the surface. This acts as a further barrier to corrosion and also to reduce the heat loss from the cell. The cell also has facilities for the periodic addition of alumina through the crust and for the removal of aluminium metal by suction. It is hooded with an extractor... 

A copolymer 84 (Scheme 38) containing dialkyl PPP, ladder-type PPP, and electron-transporting diaryloxadiazole segments (m w p = 4 3 3) has been prepared by a similar copolymerisation with 2,5-bis(4-bromophenyl)-l,3>4-oxadiazole added as a comonomer [160]. It emits blue light (A.max = 410, 480 nm) with an efficiency of 0.4% when aluminium cathodes are used [161]. This is twice the efficiency obtained for similar devices using the copolymers 83 without the oxadiazole units. 

Figure 3.4 (a) WLI 3D surface profile from the edge of screen printed aluminium cathode, and (b) image of aluminium cathode (after Size)... 

Kulmala S, Ala-Kleme T, Hakanen A, Haapakka K (1997) F-centre luminescence from oxide-covered aluminium cathode induced by two step reduction of peroxydisulfate anions. J Chem Soc Faraday Trans 93 165-168... 

A) When magnesium corrodes in sea-water or certain other electrolytes, alkali formed at the aluminium cathode may attack the aluminium. 

Electron injection has been improved by inserting an inorganic insulating layer such as AlO [10], Si02 [11] or LiF [12] between the cathode and the emissive material. Recently, we have demonstrated how insulating Langmuir-Blodgett (LB) films may be used to improve the efficiency of LEDs based on poly-(2-methoxy,5-(2 ethylhexyloxy)-/i-phenylenevinylene (MEH-PPV) [13]. In this work, we describe the use of multilayer LB films of arachidic acid (AA), sandwiched between the emissive layer and the aluminium cathode, to enhance the... 

We have studied the effects of incorporating fatty acid Langmuir-Blodgett films into dual layer organic light emitting structures based on 8-hydroxyquinoline aluminium (Alq) and N,N -diphenyl-N,N -(3-methylphenyl)-l,r-biphenyl-4,4 -diamine (TPD). The insertion of arachidic acid layers between the Alq emissive layer and an aluminium cathode was found to produce a threefold increase in the quantum efficiency. The precise mechanism for this enhancement is currently subject to further study. 

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