Pins, metallic

DOWEL PINS - Metal pins that guarantee exact alignment of a flange joint on a horizontally split casing as found in turbine construction... 

Another ak pollutant that can have very serious effects is hydrogen sulfide, which is largely responsible for the tarnishing of silver, but also has played a destmctive role in the discoloration of the natural patinas on ancient bronzes through the formation of copper sulfide. Moreover, a special vulnerabihty is created when two metals are in contact. The electromotive force can result in an accelerated corrosion, eg, in bronzes having kon mounting pins. 

The most significant commercial product is barium titanate, BaTiO, used to produce the ceramic capacitors found in almost all electronic products. As electronic circuitry has been rniniaturized, demand has increased for capacitors that can store a high amount of charge in a relatively small volume. This demand led to the development of highly efficient multilayer ceramic capacitors. In these devices, several layers of ceramic, from 25—50 ]lni in thickness, are separated by even thinner layers of electrode metal. Each layer must be dense, free of pin-holes and flaws, and ideally consist of several uniform grains of fired ceramic. Manufacturers are trying to reduce the layer thickness to 10—12 ]lni. Conventionally prepared ceramic powders cannot meet the rigorous demands of these appHcations, therefore an emphasis has been placed on production of advanced powders by hydrothermal synthesis and other methods. 

Traction is typically used to align a bone by a gende, constant pulling action. The pulling force may be transmitted to the bone through skin tapes or a metal pin through a bone. Traction may be used as a preliminary treatment, before other forms of treatment or after cast immobilization. 

H, glass-to-metal seal (with center pin) I, anode tab J, cathode K, separator L, anode. Courtesy of MoH Energy Ltd. 

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). 

A popular connection system consists of square metal pins, usually 0.064 cm (0.025 in.) in size, that are pressed into holes drilled in a printed circuit board. The holes are copper (qv) plated on the insides and interconnect conductors on the top and bottom faces of the board. Multilayer boards have interior circuits that may also be interconnected in this way. The pias have either a soHd shank or a deformable (compHant) cross section where the pias joia the board (Fig. 2). Separable connectors or soldedess wraps (Fig. 3) engage the ends of the pias. One end of the pia can be the contact and spring of a separable connector. 

Base Metal Finishes. The low cost of base metal finishes obviates selective coating. Electro deposition is used for 0.5—5 p.m thick coatings of tin and tin—lead alloy, usually about 50 wt % Sn, 50 wt % Pb, on electronic connector contacts, on contacts at the edges of printed circuit boards, and on terminals. Sheet copper alloys that have been coated with tin—lead alloy are widely used for contacts that are stamped and then formed into the desired shapes, such as pins having a closed end and sockets. Aluminum connectors that have utility—industrial appHcations are more thickly coated, and hot-dipping in molten tin is common. 

Quite often problems arise when instruments for normal seiwice are subjected to low temperature use. Since some metals become brittle at low temperatures, the instrument hteraUy falls apart. Elastomeric gaskets and seals contract faster with decreasing temperatures than the surrounding metal parts, and the seal often is lost. Even hermetically sealed instruments can develop pin holes or small cracks to permit ciyogenic liqmds to enter these cases with time. Warming the instrument causes the trapped hquid to vaporize, sometimes generating excessive gas pressure and failure of the case. 

Close examination of the weld under a low-power stereoscopic microscope revealed small openings (Fig. 15.6). Probing these sites with a pin revealed a large pit that had been covered by a thin skin of weld metal. These sites contained fibrous, metallic remnants (Fig. 15.7). Examination under a scanning electron microscope further revealed the fibrous character of the material (Fig. 15.2) and also the convoluted shapes of the individual fibers (Fig. 15.21). Energy-dispersive spectrographic analysis of this material revealed the compositions in Table 15.1. 

Demonstrations (a) Balloons and safety pin (see Chapter 13, p. 121). Afterwards, put fractured edges of balloon rubber on overhead to show that wavy fracture path closely parallels that seen when metals have undergone fast fracture, (b) for Sellotape (see Chapter 13, p. 122). 

Metallurgy sleeve, shaft, set screws, gland, metallic parts, drive pins, clips, keyways, anti rotation pins, etc. 

The degree of surface cleanliness or even ordering can be determined by REELS, especially from the intense VEELS signals. The relative intensity of the surface and bulk plasmon peaks is often more sensitive to surface contamination than AES, especially for elements like Al, which have intense plasmon peaks. Semiconductor surfaces often have surface states due to dangling bonds that are unique to each crystal orientation, which have been used in the case of Si and GaAs to follow in situ the formation of metal contacts and to resolve such issues as Fermi-level pinning and its role in Schottky barrier heights. 

Dorn, m. thorn spine Mach.) pin, spike, plug, tongue, bolt, mandrel, etc. Metal.) slag (of copper), dornartig, a. thorn-like, spiked, domen, ddmen, v.t. Mach.) punch, drift indent. 

Leak resistance is obtained on makeup by interference of metal-io-meial seal between a long radius curved seal surface on the pin member engaging a conical metal seal surface of the box member (Figures 4-372 and 4-376). 

With the increased speed and horsepower capabilities of modem chain drives, the role of lubrication has increased in importance. The precision roller chain is actually a series of connected journal bearings and it is essential that lubrication minimizes the metal-to-metal contact of the pin/bushing joints of the chain. Many factors affect lubrication performance and chain life including heat, improper lubrication, windage, contamination, and oil viscosity. 

High-voltage coating-testing equipment When cathodic protection is applied to a structure which has a protective coating, the current required is proportional to the bare metal area on the structure. Thus whenever a protective coating is applied it should be of good quality, with very few failures or pin holes in it, so that the cathodic-protection system may be economic. 

Table 11-2 shows the built-in potential in metal/MEH-PPV/metal structures measured by either electroabsorption [15] or photocurrenl techniques [37] for a variety of contact metals. The uncertainty in both the work function differences and the built-in potential measurements is about 0.1 eV. For all of the structures except the Pt-Ca and Al-Sm devices there is good agreement between the metal work function difference, AW, and the built-in potential, Vhi. This indicates that for a wide range of metal contacts the Schottky energy barrier between the metal and MEH-PPV is well approximated by the ideal Schottky model and that state chaiging, which pins the Schottky energy barrier, is not significant. A built-in potential smaller than the difference between the contact work functions implies that... 

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