Metals preparation

AH intrinsic germanium metal sold is specified to be N-type with a resistivity of at least 40 H-cm at 25°C or 50 H-cm at 20°C. Germanium metal prepared for use in infrared optics is usuaHy specified to be N-type with a resistivity of 4-40 Hem, to be stress-free and fine annealed, and to have certain minimum transmission (or maximum absorption) characteristics in the 3—5 or 8—12 pm wavelength ranges. Either polycrystaHine or single-crystal material is specified. 

Metal Preparation. Preparation of the metal surfaces to be bonded usually is required because most metals contain surface imperfections or contaminants that undesirably affect bond properties. The cladding faces usually are surface ground, using an abrasive machine, and then are degreased with a solvent to ensure consistent bond strength (26). In general, a surface finish that is >3.8 fim deep is needed to produce consistent, high quaUty bonds. 

Metalworking, such as swaging, drawing, rolling, etc, may also be performed on slabs or ingots of other metals prepared by any of the consoHdation and sintering techniques described. 

Measurement of Residual Stress and Strain. The displacement of the 2 -value of a particular line in a diffraction pattern from its nominal, nonstressed position gives a measure of the amount of stress retained in the crystaUites during the crystallization process. Thus metals prepared in certain ways (eg, cold rolling) have stress in their polycrystalline form. Strain is a function of peak width, but the peak shape is different than that due to crystaUite size. Usually the two properties, crystaUite size and strain, are deterrnined together by a computer program. 

Surfaces. Essentially any electrically conductive surface can be electroplated, although special techniques may be required to make the surface electrically conductive. Many techniques ate used to metalline nonconductive surfaces. These are weU-covered ia the Hterature (3) and can range from coating with metallic-loaded paints or reduced-silver spray, to autocatalytic processes on tin—palladium activated surfaces or vapor-deposited metals. Preparation steps must be optimized and closely controlled for each substrate being electroplated. 

Fig. 4. Process flow diagram for aluminum enameling showing (a) enamel preparation and application, and (b) metal preparation, where the cleaning processes A, B, and C represent primarily sheet D, primarily castings and E, aluminized steel (11).

Other Metals. Metals such as the austenitic series. Types 301—347, and the ferritic series. Types 409—446, of stainless steels may be enameled, as well as a number of other alloys (17). The metal preparation usually consists of degreasiag and grit blasting. Copper, gold, and silver are also enameled. These metals are usually prepared for appHcation by degreasiag. Copper is pickled usiag either a nitric acid [7697-37-2] or a sulfuric acid [7664-93-9] solution, followed by a dilute nitric acid dip. Silver may be pickled in hot dilute sulfuric acid followed by a dip in a nitric acid solution (18). 

Metal Preparation. Sheet-steel parts are formed by stamping, bending, and shearing. Many parts require welding (qv), which needs to be carried out in a uniform, smooth manner so that the welded joint can be enameled without defects. Cast-iron parts are formed by the usual cast-iron foundry methods however, additional care is given to prevent contamination of the surface. Surface contamination causes defects in the enamel, particularly bUsters and bubbles. Aluminum metal can be formed in sheets, extmsions, and as castings. 

First hydrido complex of a transition metal prepared by W. Hieber and F. Leutert. 

IR absorption spectra of several fluorotantalates of alkali and alkali earth metals prepared by hydrofluoride synthesis are presented in Fig. 17. 

Plutonium metal is prepared by two methods--direct reduction of the oxide by calcium (DOR)U,2J, and reduction of PuF by calcium in our metal preparation line (MPL)(3) (see Figure 1). In the DOR process, the plutonium contenF of the reduction slag is so low that the slag can be sent to retrievable storage without further processing. Metal buttons that are produced are no purer than the oxide feed and/or the calcium chloride salt. Los Alamos purifies the buttons by electrorefin-ing(4i,5 ), yielding metal rings that are > 99.96 percent plutonium. 

Recent process development efforts have been devoted to more expeditious and less costly pyrochemical reprocessing of residues created by the metal preparation and purification process. We intend to establish an internal recycle which yields either reusable or discardable residues and recovers all plutonium for feed to the electrorefining purification system. This internal recycle is to be performed in a more timely and less costly operation than in the present reprocessing mode. 

The goal of these two processes is to provide a closed loop on the plutonium streams in the metal preparation and purification sequence. 

MPL—See Metal preparation line Mulak model, PuF4.29-30... 

Catalyst Active Metal Preparation Method Loading amount of metal (wt%) Particle Size (nm)... 

Klabimde KJ, Cardenas-Trivino G (1996) In FurstnerA (ed) Active metals preparation, characterization, applications. VCH, Weinheim pp. 237-277... 

In many instances of commercial importance an alloy, rather than a metal, is obtained as the product of calciothermic reduction. The alloy may be an intermediate in metal preparation or even the end product of the process. 

When a metal contains both carbon and oxygen, as is invariably the case with metals prepared by carbothermic reduction under vacuum, deoxidation occurs by the following two processes at high temperatures and low pressures ... 

This plant produces 130 m2/h of enameled steel and operates 3500 h/yr. It uses 0.0036 m3 water/m2 of product to coat the steel. Average process water flow is 0.144 m3/h for coating operations and 0.734 m3/h for metal preparation. The primary treatment in-place for process wastewater is clarification and settling. Other water treatment practices employed are pH adjustment with lime or acid, sludge applied to landfill, polyelectrolyte coagulation, and inorganic coagulation. 

This facility produces 210 m2/h of enameled aluminum and uses 0.015 m3 water/m2 of product for coating operations. The average process flow rate is 1.33 m3/h for metal preparation operations and 0.716 m3/h for coating operations. The primary in-place treatment for process wastewater is chemical coagulation and clarification (i.e., settling). 

This plant produces 290 m2/h of enameled aluminum for 6400 h/yr. It uses 0.018 m3 water/m2 product for coating and ball milling purposes. The average process flow rate is 12.5 m3/h for metal preparation and 1.59 m3/h for coating and ball milling. In-place treatment consists primarily of chemical coagulation, clarification (settling), and final pH adjustment. 

Plant 36030 enamels both copper and steel. It uses 0.042 m3 water/m2 product in all coating operations. Process wastewater flow is 0.466 m3/h for metal preparation and 1.69 m3/h for coating... 

Pollutant Metal Preparation Coating Operation Metal Preparation Coating Operation... 

There shall be no discharge of process wastewater pollutants from any metal preparation operations in the cast iron basis material subcategory. The discharge of process wastewater pollutants... 

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