Sintering copper

Technology as we have witnessed over the years has been outpacing any other development. Some of the developments in technology such as co-extrusion in copper, sintered material objects of required shapes, use of thin-film techniques to produce a tape for electrical connections and the fabrication of tapes and wires of superconductor Nb3Sn lend hope for future technological developments in superconducting rare earth materials such as borocarbides and YBaaCujOy. 

So, the analysis show the possibility to transport along the copper heat pipe with water and copper sintered powder wiek a heat flow Q = 50 - 60 W at the saturated temperature neat 100 °C. 

Following the analysis of Qmax for different cylindrical mHPs, Figure 9 it is clear, that copper sintered powder as a wick has some advantages to compare with another wicks in the field of gravity, when the evaporator is disposed above the condenser. Advanced copper sintered powder wick (curve 1, Figure 9) has some advantages to compare with such wicks as mesh structure, grooves, fiber bundle. 

Figure 10. Cross section of flat copper niHP with a copper sintered powder (obtained by the cylindrical heat pipe flattening) (a), mesh structure (b) and wire bundle (c)...

Figure 11. Capillary limit for the flat mHP with a copper sintered powder as a wick...

Optimisation of copper sintered powder wick in miniature copper/water heat pipes with outer diameter 4 mm and length 200 mm is a good challenge to improve the mHP parameters. Analysis of the experimental data for such a new optimised miniature heat pipe with copper sintered powder wick proves the possibility to use mHPs independently of its orientation with the maximum heat transport capability near 50 W. 

Qlynick D L, Gibson J M and Averback R S 1998 Impurity-suppressed sintering in copper nanophase materials Phii. Mag. A 77 1205... 

If preferred, the reaction mixture may be cooled, and the crude furil filtered through a sintered gla.ss funnel. The filtrate (containing the copper sulphate-pyridine mixture) is re-oxidised by passing oxygen tlirough it for about 15 hours. An excellent alternative method of preparation is provided by suitable adaptation of Section IV,126, Method 2. 

Miscellaneous Methods. Powdered metals such as aluminum, chromium, nickel, and copper, along with various aHoys, can be appHed to parts by electrostatic deposition. The metal strip containing the attached powdered metal must be further processed by cold rolling and sintering to compact and bond the metal powder. 

The characteristics of a powder that determine its apparent density are rather complex, but some general statements with respect to powder variables and their effect on the density of the loose powder can be made. (/) The smaller the particles, the greater the specific surface area of the powder. This increases the friction between the particles and lowers the apparent density but enhances the rate of sintering. (2) Powders having very irregular-shaped particles are usually characterized by a lower apparent density than more regular or spherical ones. This is shown in Table 4 for three different types of copper powders having identical particle size distribution but different particle shape. These data illustrate the decisive influence of particle shape on apparent density. (J) In any mixture of coarse and fine powder particles, an optimum mixture results in maximum apparent density. This optimum mixture is reached when the fine particles fill the voids between the coarse particles. 

The process is used for ferrous P/M stmctural parts that have densities of at least 7.4 g/cm and mechanical properties superior than those of parts that have been only compacted and sintered. Depending on the appHcation, the porous matrix may be infiltrated only partially or almost completely. Copper-base alloy infiltrants have been developed to minimise erosion of the iron matrix. 

A sintered friction material is composed of a metal matrix, generally mainly copper, to which a number of other metals such as tin, zinc, lead, and iron are added. Important constituents include graphite and friction-producing components such as siHca, emery, or asbestos. 

Copper, with its high heat conductivity, resists frictional heat during service and is readily moldable. It is generally used as a base metal, at 60—75 wt %, whereas tin or zinc powders are present at 5—10 wt %. Tin and zinc are soluble in the copper, and strengthen the matrix through the formation of a soHd solution during sintering. 

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. 

The matte can be treated in different ways, depending on the copper content and on the desired product. In some cases, the copper content of the Bessemer matte is low enough to allow the material to be cast directly into sulfide anodes for electrolytic refining. Usually it is necessary first to separate the nickel and copper sulfides. The copper—nickel matte is cooled slowly for ca 4 d to faciUtate grain growth of mineral crystals of copper sulfide, nickel—sulfide, and a nickel—copper alloy. This matte is pulverized, the nickel and copper sulfides isolated by flotation, and the alloy extracted magnetically and refined electrolyticaHy. The nickel sulfide is cast into anodes for electrolysis or, more commonly, is roasted to nickel oxide and further reduced to metal for refining by electrolysis or by the carbonyl method. Alternatively, the nickel sulfide may be roasted to provide a nickel oxide sinter that is suitable for direct use by the steel industry. 

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. 

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