Copper evaporation

The carbon onions can be isolated from the metal substrate by thermal treatment The silver or copper evaporate in vacuo at temperatures above 850 °C to release the onions. EspedaUy when using a thin film of silver on a silica support, the nano-onions can easily be collected from the silica gel left after heating as there are virtually no interactions between them (Figure 4.12). If, on the other hand, sihcon or steel is employed as a support for the silver layer, a strong binding of... 

Under inert conditions, the conductive emeraldine salt of polyaniline does not react with copper. In air, it is transformed fast (within a minute) to the nonconductive blue emeraldine base and copper gets oxidized to Cu(I). In a slower process (within several hours), Cu(I) is then transformed to Cu(II). It was demonstrated that the presence of polyaniline changes the oxidation behavior of the copper. Copper evaporated onto polyaniline does not chemically react with the polyaniline or the tosylate anion and forms a dense layer of copper islands. 

IsA Copper (Evaporated) Coated onto Oven-Cured (380 c) PI-5878... 

The evaporation rate of Cu in molten C-Fe alloys were investigated under pressures of several hundred Pa in the temperature range from 1500 to 1600°C by [1995Che] and under pressure of 133 Pa at 1700°C by [20030no]. It was shown that the apparent rate constant of copper evaporation monotonically increases with increasing carbon content and with decreasing pressure. 

Figure 2. RAIRS spectra of C SH on Au as a function of the number of irradiation cycles. Each cycle is equivalent to the copper evaporation process. Scan parameters 300 scans at 84° incidence, 2 cm resolution. (A) C SH as deposited (B) C SH after one thermal cycle (C) C SH after two thermal cycles (D) C SH after three thermal cycles. The spectra have been offset for clarity. (Reprinted from reference 30. With permission]...

It was suprising to find that the copper evaporation process, (at least when carried out at high deposition rates) had a protective effect, trapping the SAM and perventing its desorption. As mentioned earlier in this section, consecutive thermal treatments inside the evaporation chamber led ultimately to the desorption of the SAM from the gold substrate. 

Figure 8. Cyclic voltammograms in ferricyanide solution, of a gold electrode passivated by a C SH SAM as deposited and after being subject to copper evaporation and stripping with 3 M nitric acid. The voltammogram of a bare gold electrode is reported for comparison. (A) C SH monolayer, (B) C SH monolayer after undergoing copper evaporation and stripping (O bare gold electrode. [Reprinted tom...

This was not observed when copper was deposited. In fact, multiple cycles of copper evaporation and removal yielded a fairly constant IR signature, indicating that desorption did not occur or that at least it occurred at a remarkably lower rate than for the bare SAM. Figure 7 shows how the spectra of C,jSH and C SH remain costant after two consecutive cycles of copper evaporation and subsequent removal with nitric acid. 

Cuprous bromide. The solid salt may be prepared by dissolving 150 g. of copper sulphate crystals and 87 5 g. of sodium bromide dihydrate in 500 ml. of warm water, and then adding 38 g. of powdered sodium sulphite over a period of 5-10 minutes to the stirred solution. If the blue colour is not completely discharged, a little more sodium sulphite should be added. The mixture is then cooled, the precipitate is collected in a Buchner funnel, washed twice with water containing a little dissolved sulphurous acid, pressed with a glass stopper to remove most of the liquid, and then dried in an evaporating dish or in an air oven at 100 120°. The yield is about 80 g. 

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Cadmium Sulfide Photoconductor. CdS photoconductive films are prepared by both evaporation of bulk CdS and settHng of fine CdS powder from aqueous or organic suspension foUowed by sintering (60,61). The evaporated CdS is deposited to a thickness from 100 to 600 nm on ceramic substates. The evaporated films are polycrystaUine and are heated to 250°C in oxygen at low pressure to increase photosensitivity. Copper or silver may be diffused into the films to lower the resistivity and reduce contact rectification and noise. The copper acceptor energy level is within 0.1 eV of the valence band edge. Sulfide vacancies produce donor levels and cadmium vacancies produce deep acceptor levels. 

GaUic acid is heated with about half its weight of water in a copper autoclave until the pressure reaches 1.2 MPa (12 atm) and the temperature is 175°C. Steam and carbon dioxide are released but sufficient water is retained to maintain the pyrogaHol as a Hquid. The cooled solution is decolorized with animal charcoal and is then evaporated until the volatile pyrogaHol distills into iron receivers. The sohdified material is purified by repeated distillation, sublimation, or vacuum distillation at 200°C in the presence of diaLkyl phthalates (8). 

Acid cleaners based on sulfamic acid are used in a large variety of appHcations, eg, air-conditioning systems marine equipment, including salt water stills wells (water, oil, and gas) household equipment, eg, copper-ware, steam irons, humidifiers, dishwashers, toilet bowls, and brick and other masonry tartar removal of false teeth (50) dairy equipment, eg, pasteurizers, evaporators, preheaters, and storage tanks industrial boilers, condensers, heat exchangers, and preheaters food-processing equipment brewery equipment (see Beer) sugar evaporators and paper-mill equipment (see also Evaporation Metal surface treati nts Pulp). 

Phosphorized deoxidized arsenical copper (alloy 142 (23)) is used for heat exchangers and condenser tubes. Copper-arsenical leaded Muntz metal (alloy 366), Admiralty brass (alloy 443), naval brass (alloy 465), and aluminum brass (alloy 687), all find use in condensers, evaporators, ferrules, and heat exchanger and distillation tubes. The composition of these alloys is Hsted in Table 5. 

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