Metal electrodes aluminum

The use of reactive metal electrodes are also effective for the silylation of various organic halides and simple arenes [75]. For instance, Dunogues et al. reported that electrolysis of aryl chlorides in the presence of excess Me3SiCl in a one-compartment cell equipped with a sacrificial aluminum anode in 80 20 THF/HMPA gave the corresponding aryltrimethylsilanes (Scheme 36). When... 

For the dielectric loss measurement by a bridge (Ando Co. TR-10C),metal-PPE-metal sandwich specimens were prepared on the silicon dioxide substrate (Corning 7059). Evaporated aluminum was used as a metal electrode. The PPE film for the use of dielectric measurement was formed with the discharge electrode whose surface area was 26 cm2 and the remainder of the electrode was covered by the Teflon plate. Two kinds of samples were prepared for this experiment. One of them was formed at 5 KHz, 0.5 torr, 20 cm3STP/min and 5 watts. The other was formed at 13.56 MHz, 0.5 torr, 40 cm3STP/min and 25 watts. 

Let us assume that the total surface of an electrode is in an active state, which supports dissolution, prior to anodization. The application of a constant anodic current density may now lead to formation of a passive film at certain spots of the surface. This increases the local current density across the remaining unpassivated regions. If a certain value of current density or bias exists at which dissolution occurs continuously without passivation the passivated regions will grow until this value is reached at the unpassivated spots. These remaining spots now become pore tips. This is a hypothetical scenario that illustrates how the initial, homogeneously unpassivated electrode develops pore nucleation sites. Passive film formation is crucial for pore nucleation and pore growth in metal electrodes like aluminum [Wi3, He7], but it is not relevant for the formation of PS. 

Aluminum, a highly electropositive metal similar to the aUcaline earth metals, can be useful in deposition of low work function cathode metal electrodes in OLEDs and OELDs, and is preferred for many electronics applications because of its low cost and high conductivity, although it is somewhat prone to electro migration [8, 65]. Since A1 is an important metal for device applications its deposition on SAMs has been extensively studied [20, 21, 23, 32, 33,41, 50, 65-69]. The critical problem for Al, however, is its facility in penetration along with filament growth. 

Fig. 5.37. (a) I/V characteristics of typical MDMO-PPV/PCBM solar cells with a LiF/A1 electrode of various LiF thicknesses ( 3 A, 6 A, 12 A) compared to the performance of a MDMO-PPV/PCBM solar cell with a pristine A1 electrode ( ). (b) and (c) are box plots with the statistics of the FF and Voc from 6 separate solar cells. LiF or SiOx were thermally deposited at a rate of 1-2 A/min from a tungsten boat in a vacuum system with a base pressure of 10-4 Pa. We emphasize that, for thickness values of the order of 1 nm, LiF/SiOx does not form a continuous, fully covering layer, but instead consists of island clusters on the surface of the photoactive layer. Slow evaporation conditions are essential for more homogenous distribution of the LiF on the organic surface. The nominal thickness values given here represent an average value across the surface of the substrate. The metal electrode (either aluminum or gold) was thermally deposited with a thickness of 80 nm... 

Alkaline, alkaline earth metals and aluminum are naturally covered with anodic films. The removal of these native films, even in the best glove box atmosphere, exposes the fresh metal to reactive atmospheric contaminants at a high enough concentration and quickly cover the metal with new surface films. As discussed above, even the glove box atmosphere of an inert gas containing atmospheric components at the ppm level should be considered as being quite reactive to active metals such as lithium. Therefore, anyone intending to study the intrinsic behavior of active metal electrodes in solution must prepare a fresh electrode surface in solution. 

There are studies in which the fact that active metal electrodes are covered with surface films is not so important, e.g., when these metals are used as counterelectrodes, or when they are studied as practical anodes in batteries. However, even in these cases, the native active metals as received may be covered with two thick films. It is therefore, necessary to remove the initial native film covering the active metal under an inert atmosphere. The passivating films of lithium and calcium can be scraped off with a stainless steel knife. In the case of harder active metals such as magnesium and aluminum, an abrasive cloth or... 

The most common active metal electrodes in nonaqueous systems are indeed the surface film controlled ones described above. However, there are some exceptional cases in which surface film free active electrodes in nonaqueous solutions can be obtained. Three types of such systems are blue solutions, aluminum nonaqueous-aprotic plating systems, and magnesium electrodes in Grignard reagent solutions. 

Note Many other metals can be used to replace the lead anode electrode. Such metals include, aluminum, zinc, iron, nickel, copper, and various other metals forming the corresponding metal chromates. 

Additional work on dielectrics includes deposition of silica, PABS (lead aluminum boron silicates), PLZT (lead lanthanum zirconium titanate) and BST (barium strontium titanate) on Si-Ti-Pt wafers (Figure 2). The wafer specimens were patterned with metal electrodes and electronic properties were characterized. 

An electrochemical cell consists of a nickel metal electrode immersed in a solution with [Ni2+] = 1.0 M separated by a porous disk from an aluminum metal electrode immersed in a solution with [Al3+] = 1.0 M. Sodium hydroxide is added to the aluminum compartment, causing AI(OH)3(s) to precipitate. After precipitation of Al(OH)3 has ceased, the concentration of OH- is 1.0 X 10-4 M and the measured cell potential is 1.82 V. Calculate the Ksp value for Al(OH)3. 

Because the metal electrodes make ohmic contacts with the p- and n-doped regions, both electrons and holes can be efficiently injected and the carrier densities are approximately balanced. Thus, higher quantum efficiencies are often observed in LECs than in LEDs made with the same semiconducting polymer. Moreover, the same stable electrodes can be used with any semiconducting polymer. By contrast, recall that for polymer LEDs, the anode and cathode metals must be matched to the rr- and Tr -bands, respectively. Thus, for polymer LEDs, different electrodes must be developed to optimize emission from each new polymer (and for each new color ). Red, green and blue (and broad-band white) emission from polymer LECs have been demonstrated with external efficiencies of 2-4% using air stable electrodes (aluminum). 

Other components of the battery are the current collectors. Figure 1 shows the current collectors for the positive and negative electrodes in the lithium-ion cell. The active materials for the positive and negative electrodes (in this case) consist of thick layers of porous materials coated onto the current collectors. The current collector works as a support for the active material and provides a conducting path for the active material paste reducing the resistance of the battery [4]. Current collectors are used only in porous electrodes metal electrodes do not require current collectors. The current collectors should be chemically stable and resistant to corrosion. They should also have a high electronic conductivity to reduce the internal resistance of the battery. Copper and aluminum are the current collectors used in lithium-ion batteries for the negative and positive electrodes, respectively. 

Haak and Nolta (141, 14%) have observed rectifying phenomena when polycrystalline samples of metal-free or metal phthalocyanines are compressed between different metal electrodes. A small amount of a liquid polar impurity was found to be essential for rectification to occur. The rectification ratio (ratio of conductance in forward and reverse directions, the forward direction being movement of electrons from the least noble electrode to the sample) varies from 25 to 500. The latter value is obtained when copper phthalocyanine is sandwiched between either platinum and silver, or silver and aluminum, electrodes. Kleitman (188) has also demonstrated that metal-free phthalocyanine can act as a rectifier. 

The most commonly used crystals in BAW devices are 5, 9, or 10 MHz quartz in the form of 10-16 mm disks that are approximately 0.15 mm thick. Metals are often evaporated directly onto the quartz plates to serve as electrodes. The metal electrodes are 3000-10000 A thick and 3-8 mm in diameter and can be made of gold, silver, aluminum, or nickel (figure 19.2). SAW devices, however, are capable of operating at much higher frequencies than the bulk devices and normally crystals of more than 100 MHz resonant frequency are used. Therefore,... 

Films of oxides can be produced by anodization of metal electrodes. For example, AI2O3 forms on an aluminum anode immersed in a solution of H3PO4. The thickness of the film can be controlled by the applied potential and the time of anodization. Such a film can be used as a support for other materials, such as poly(vinylpyridine) (PVP). Oxide films of other metals, such as Ti, W, and Ta, can be produced in a similar way. Oxide films can also be produced by CVD, vacuum evaporation and sputtering, and deposition from colloidal solution. Related inorganic films are those of polyoxometallates (iso- and heteropolyacids and their salts) (20). For example, the heteropolyanion P2W17M0O62K6 shows a number of reduction waves at a glassy carbon electrode. A wide variety of metallic polyanionic species (e.g., of W, Mo, V) exist and have a rich chemistry. Films of such materials are interesting for their electrocatalytic possibilities. 

The TVD curves of selected amino acids were determined by Contarini and Wendlandt (121). A comparison of the TVD and DSC peak temperature is shown in Table 11.8. The TVD peak temperatures are somewhat higher than those obtained by DSC. Obviously, the kinetics of the electrodedecomposition produces) reaction are different from those of the decomposition reaction. These electrode reactions probably involve one or more diffusion steps between the electrode surface and the amino acid or amino acid decomposition produces), which would be different from the decomposition kinetics themselves. The leading edge of the TVD curve peaks is reproducible to within +1-2%. However, after the peak maximum temperature is attained, the reproducibility falls to within +20% in some cases. This is related to the electrode-amino acid decomposition products interface, which, due to the nature of the reaction, would not be expected to be reproducible. The trailing edge portion of the curve also consists of several shoulder peaks that may be related to the consecutive and/or concurrent reactions previously described in the DSC curves. These reactions could produce decomposition products that would react with the aluminum metal electrode surface. 

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