Getter system

FIGURE 41.17 Artist s concept of thermally insulated electric-vehicle battery module with cutaway showing biploar Li-Al/FeS stack, lightweight loosely wrapped multifoil insulation, and thermally activated getter system for controlling heat transfer from module. (Courtesy of Argonne National Laboratory.)... 

Titanium hydride is used as a source for Ti powder, alloys, and coatings as a getter in vacuum systems and electronic tubes as a sealer of metals and as a hydrogen source. 

Barium is prepared commercially by the thermal reduction of barium oxide with aluminum. Barium metal is highly reactive, a property which accounts for its principal uses as a getter for removing residual gases from vacuum systems and as a deoxidiser for steel and other metals. 

Table IV shows X-ray data (55) on the homogeneity of Pd-Ag films prepared by simultaneous evaporation from separate sources, either in conventional vacuum or in UHV, with the substrate maintained at 0°C. The second group of films was prepared using a stainless steel system incorporating a large (100 1/sec) getter-ion pump, sorption trap, etc., but deposited inside a glass vessel. By the tests of homogeneity adopted, alloy films evaporated in conventional vacuum were not satisfactory, i.e., the lattice constants were generally outside the limits of the experimental error, 0.004 A, and the X-ray line profiles were not always symmetrical. In contrast, alloy films evaporated in UHV were satisfactorily homogeneous. Further, electron micrographs showed that these latter films were reasonably unsintered and thus, this method provides clean Pd-Ag alloy films with the required characteristics for surface studies.

Cesium is used as a getter in electron tubes. Other applications are in photoelectric cells ion propulsion systems heat transfer fluid in power generators and atomic clocks. The radioactive Cs-37 has prospective applications in sterilization of wheat, flour, and potatoes. 

The pumping system is the most important part of the vacuum line, it is certainly the most expensive, and it should therefore be chosen with care. Because the pumping system on a chemist s vacuum line must be robust and capable of removing large quantities of gases, often in repeated cycles, sorption pumps, getter ion pumps, and sublimation pumps are generally unsuitable and are therefore not discussed in this book. 

The basic ECELL geometry consists of small apertures above and below the sample and the apertures are mounted inside the bores of the objective lens polepieces (figure 2.10(d)). The controlled environment ECELL volume is the normal sample chamber of the microscope. It is separated from the rest of the column by the apertures in each polepiece and by the addition of a gate valve, which is normally kept closed, in the line to the usual ion-getter pump (IGP) at the rear of the column. Differential pumping systems are connected between the... 

In attempting to assess the disposition of sulfur in the overall synfuels system, one must first examine the characteristics of the sulfur in the feedstock. Then, the feedstock is examined for sulfur "getter" materials. With evaluation of the operating parameters of the primary energy conversion reaction system, the fate of sulfur in the feedstock can be projected. 

Provision for gettering. A side bulb containing an electrically heatable tantalum filament serves this purpose. After initial heating of the tantalum to the evaporation temperature while the system is pumping, a film of tantalum is deposited on the walls of the gettering bulb after seal-off. 

---