Cold-welding

Properties. Table 1 hsts many of the physical, thermal, mechanical, and electrical properties of indium. The highly plastic nature of indium, which is its most notable feature, results from deformation from mechanical twinning. Indium retains this plasticity at cryogenic temperatures. Indium does not work-harden, can endure considerable deformation through compression, cold-welds easily, and has a distinctive cry on bending as does tin. 

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

At no load, opening of contacts may lead to roughening of the surface, due to the breaking of the cold welding that takes place. 

High resistance-low kA alloy (low melting point) copper-chromium (CLR) w hich also has a good resistance to cold welding and a lower probability of current chopping, similar to in OCBs. Refer to curve 2 of Figure 17.8. 

Another mechanism of static friction suggests that when two surfaces are pressed together under a normal load, the atoms or molecules at the interface will rearrange themselves to minimize the energy and to form localized junctions called cold welding, which is often observed in contacts... 

Ferguson, G. S. Chaudhury, M. K. Sigal, G. B. Whitesides, G. M. 1991. Contact adhesion of thin gold-films on elastomeric supports—Cold welding under ambient conditions. Science 253 776-778. 

Kim, C. Burrows, P. E. Forrest, S. R. 2000. Micropatterning of organic electronic devices by cold-welding. Science 288 831-833. 

Kim, C. Forrest, S. R. 2003. Fabrication of organic light-emitting devices by low-pressure cold welding. Adv. Mater. 15 541-545. 

Fig. 1.10 Mechanical alloying through repetitive cold welding and fracturing...

Nevertheless, EDS analysis revealed that the levels of Na, Mg and A1 are similar in both the small particles and large aggregates. This indicates that NaAlH and MgH are blended well after 5 h of milling. Hence, it seems that the large aggregates are formed by cold welded small particles containing NaAlH and MgH. ... 

Formation of solid bridges by the fusion of adjacent crystals ( cold welding )... 

Metal powder can also be coated onto the workpiece. The 3M Company has developed a cold welding technique in which the workpiece, the metal powder, water, glass shot and additives are tumbled together in a barrel. Coatings are limited to ductile metals such as Cd, An, Sn, Pb, In, Ag, Cu, brass, and tin/lead solder the method is generally suitable only for small parts, and it doesn t produce a fine surfaced, cosmetic coating. Costs are comparable to those for electroplating with afterbake (Kirk-Othmer 1981). 

Excessive load, reduced fluid viscosity, and low speed can cause a breakdown of the lubrication layer to the point of a metal-metal contact. Direct adhesive contact can lead to molecular interaction strong enough to tear material out of the surface. This process is also known as cold welding . Metal surfaces under ambient conditions are usually covered with oxide layers that prevent cold welding at moderate loads. 

The indium studs 30 are used for connection of the n-type zones by cold welding with corresponding input studs 31 of a silicon integrated circuit formed in a silicon wafer 15. The two wafers 2 and 15 are disposed on a cooled surface 16 in a cryogenic enclosure 17. 

A p-type layer 18 and an n-type layer 20 of HgCdTe are grown epitaxially on a substrate 52 of cadmium zinc tellurium. A set of through holes are formed which extend through the layers 18 and 20 up to the surface of the substrate. A silicon dioxide layer is applied and at each detector a window is etched. A contact metal 24A is applied within each window. Contacts 24 and 26 are constructed on the detectors and on the read-out chip 14. The chip and the substrate 52 are pushed together to compress the contacts 24 and 26 against each other which cold welds them to each other. 

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