Copper in air

Copper and silver combined with refractory metals, such as tungsten, tungsten carbide, and molybdenum, are the principal materials for electrical contacts. A mixture of the powders is pressed and sintered, or a previously pressed and sintered refractory matrix is infiltrated with molten copper or silver in a separate heating operation. The composition is controlled by the porosity of the refractory matrix. Copper—tungsten contacts are used primarily in power-circuit breakers and transformer-tap charges. They are confined to an oil bath because of the rapid oxidation of copper in air. Copper—tungsten carbide compositions are used where greater mechanical wear resistance is necessary. 

Ultramodern techniques are being applied to the study of corrosion thus a very recent initiative at Sandia Laboratories in America studied the corrosion of copper in air spiked with hydrogen sulphide by a form of combinatorial test, in which a protective coat of copper oxide was varied in thickness, and in parallel, the density of defects in the copper provoked by irradiation was also varied. Defects proved to be more influential than the thickness of the protective layer. This conclusion is valuable in preventing corrosion of copper conductors in advanced microcircuits. This set of experiments is typical of modern materials science, in that quite diverse themes... combinatorial methods, corrosion kinetics and irradiation damage... are simultaneously exploited. 

P. Wenger and C. Urfer. N. Smith found that in the oxidation of tin or copper in air, ammonia is simultaneously oxidized—induced reactions zinc has no action, but in glass dishes positive results were sometimes obtained—while only a slight action -was observed in the oxidation of ferrous and manganous hydroxides. 

How much cupric oxide is formed by heating 1467 gm. of copper in air ... 

Figure 6. Corrosion of copper in air containing SO2 and/or NO at 90% relative humidity (19).

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. 

Figure 7.9. Series of IRRAS spectra on copper in air containing 80% reiative humidity (RH) and 8.7 ppm SO2. Exposure time (a) 1, (fa) 4, (c) 8, (d) 12, and (e) 16 h. Reprinted, by permission, from J. Itoh, T. Sasaki, T. Ohtsuka, and M. Osawa, J. Electroanal. Chem. 473,256-264 (1999), p. 259, Fig. 3. Copyright 1999 Eisevier Science SA...

The first published attempt at the synthesis of any CPP was reported in 1934 by Parekh et al. [3]. Having synthesized the parent macrocycle, p,p-diphenylenete-trasulfide, 38, the thermal liberation of 4 equiv. of sulfur (as copper sulfides and sulfur oxides) upon heating with copper in air was attempted (Fig. 19). Only partial desulfination was observed, however, probably owing to the extreme strain associated with the resulting [2]cycloparaphenylene. 

The reader might wonder why a reaction such as (6.3), which does not involve oxygen, is called an oxidation-reduction reaction. The reason is as follows. Originally the term oxidation" was applied to reactions in which a substance combines with oxygen, for example, the oxidation of copper in air... 

Description of the problem Yellow brass tubes (65% copper) in air compressor showed leaking in cooling water after 17 years of service. 

Itoh J, Sasaki T and Ohtsuka T (2000), The influence of oxide layers on initial corrosion behavior of copper in air containing water vapor and sulfur dioxide , Corros. Sci. 42, 1539-1551. 

The complexes of copper(I) like those of silver(I) (p. 430), but unlike those of preceding transitions metals, tend to prefer a linear coordination of two ligands, i.e. X—Cu—X thus copper(I) chloride in aqueous ammonia gives the colourless [Cu(NH3)2] (readily oxidised in air to give blue [Cu (NH3)4(H20)2] copper(I) chloride in hydrochloric acid gives [CuClj], although [CuCl3] is also known. 

Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. In air, tellurium burns with a greenish-blue flames, forming the dioxide. Molten tellurium corrodes iron, copper, and stainless steel. 

Copper Sulfide—Cadmium Sulfide. This thin-film solar cell was used in early aerospace experiments dating back to 1955. The Cu S band gap is ca 1.2 eV. Various methods of fabricating thin-film solar cells from Cu S/CdS materials exist. The most common method is based on a simple process of serially overcoating a metal substrate, eg, copper (16). The substrate first is coated with zinc which serves as an ohmic contact between the copper and a 30-p.m thick, vapor-deposited layer of polycrystaUine CdS. A layer is then formed on the CdS base by dipping the unit into hot cuprous chloride, followed by heat-treating it in air. A heterojunction then exists between the CdS and Cu S layers. 

There are explosion hazards with phthahc anhydride, both as a dust or vapor in air and as a reactant. Table 11 presents explosion hazards resulting from phthahc anhydride dust or vapor (40,41). Preventative safeguards in handling sohd phthahc anhydride have been reported (15). Water, carbon dioxide, dry chemical, or foam may be used to extinguish the burning anhydride. Mixtures of phthahc anhydride with copper oxide, sodium nitrite, or nitric acid plus sulfuric acid above 80°C explode or react violently (39). 

When heated with pyrocatechol [720-80-9] copper powder, and alcohoHc sodium hydroxide, carbon tetrachloride gives a blue color that changes to red on addition of hydrochloric acid. This color reaction is not produced by chloroform. Quantitative analysis of carbon tetrachloride may be done by first decomposing the sample free of organic and inorganic chlorides, heating in a sealed tube with alcohoHc potash, and subsequently determining the potassium chloride formed as the silver haHde. The Zeiss interference refractometer has been used to determine the concentration of carbon tetrachloride vapor in air (36). 

Although in the dry state carbon tetrachloride may be stored indefinitely in contact with some metal surfaces, its decomposition upon contact with water or on heating in air makes it desirable, if not always necessary, to add a smaH quantity of stabHizer to the commercial product. A number of compounds have been claimed to be effective stabHizers for carbon tetrachloride, eg, alkyl cyanamides such as diethyl cyanamide (39), 0.34—1% diphenylamine (40), ethyl acetate to protect copper (41), up to 1% ethyl cyanide (42), fatty acid derivatives to protect aluminum (43), hexamethylenetetramine (44), resins and amines (45), thiocarbamide (46), and a ureide, ie, guanidine (47). 

Copper(I) chloride is insoluble to slightly soluble in water. SolubiUty values between 0.001 and 0.1 g/L have been reported. Hot water hydrolyzes the material to copper(I) oxide. CuCl is insoluble in dilute sulfuric and nitric acids, but forms solutions of complex compounds with hydrochloric acid, ammonia, and alkaU haUde. Copper(I) chloride is fairly stable in air at relative humidities of less than 50%, but quickly decomposes in the presence of air and moisture. 

Copper Oxides. Coppet(I) oxide [1317-39-17 is a cubic or octahedral naturally occurring mineral known as cuprite [1308-76-5]. It is ted or reddish brown in color. Commercially prepared coppet(I) oxides vary in color from yellow to orange to ted to purple as particle size increases. Usually coppet(I) oxide is prepared by pytometaHutgical methods. It is prepared by heating copper powder in air above 1030°C or by blending coppet(II) oxide with carbon and heating to 750°C in an inert atmosphere. A particularly air-stable coppet(I) oxide is produced when a stoichiometric blend of coppet(II) oxide and copper powder ate heated to 800—900°C in the absence of oxygen. Lower temperatures can be used if ammonia is added to the gas stream (27-29). 

Copper(II) oxide is less often prepared by pyrometaHurgical means. Copper metal heated in air to 800°C produces the copper(II) oxide. Decomposition of nitrates, carbonates, and hydroxides at various temperatures also occurs. 

---