Bridgman

The rates of several chemical reactions accelerate by factors of 10 or more between 0.1 and 100 MPa at ambient temperature, so much interesting chemistry occurs at these lower pressures. At such Tow pressures, Bridgman [26] even showed how to cook eggs at room temperature. 

All static studies at pressures beyond 25 GPa are done with diamond-anvil cells conceived independently by Jamieson [32] and by Weir etal [33]. In these variants of Bridgman s design, the anvils are single-crystal gem-quality diamonds, the hardest known material, truncated with small flat faces (culets) usually less than 0.5 nun in diameter. Diamond anvils with 50 pm diameter or smaller culets can generate pressures to about 500 GPa, the highest static laboratory pressures equivalent to the pressure at the centre of the Earth. 

Bridgman P W 1941 Explorations towards the limit of utilizable pressures J. Appi. Phys. 12 461... 

Asay J R and Shahinpour M (eds) 1993 High-Pressure Shock Compression of Solids (New York Springer) Bridgman P W 1958 The Physics of High Pressure (London G Beii and Sons)... 

Brooks H, Birch F, Hoiton G and Paui W (eds) 1964 Collected Experimental Papers of PW Bridgman voi i-Vii (Cambridge Harvard University Press)... 

TJItrahigh (99.999 + %) purity tellurium is prepared by zone refining in a hydrogen or inert-gas atmosphere. Single crystals of tellurium, tellurium alloys, and metal teUurides are grown by the Bridgman and Czochralski methods (see Semiconductors). 

Research. A significant impact on research at high pressure has come about with the use of gem quaHty diamonds as Bridgman-type anvils in a smaU compact high pressure device (40—42). With this type of apparatus, pressures greater than those at the center of the earth (360 GPa = 3.6 Mbars) have been reached, and phase transformations of many materials have been studied. Because of the x-ray transparency of diamond, it is possible to determine the stmcture of the phases under pressure. Because of the strenuous environment, crystals selected for this appHcation have to be of very high quaHty. 

P. W. Bridgman, DimensionalA.naljsis Yale University Press, New Haven, Coim., 1922. 

Many data on the compressibility of solids obtained prior to 1926 are contained in Gnmeisen, Handhuch der Physik, vol. 10, Springer, Berlin, 1926, pp. 1-52 also avadahle as translation, NASA RE 2-18-59W, 1959. See also Tables 271, 273, 276, 278, and other material in Smithsonian Physical Tables, 9th ed., 1954. For a review of high-pressure work to 1946, see Bridgman, Reo. Mod. Ph /5., 18, 1 (1946). 

Bridgman [Froc. Am. Acad. Aits Sci., 59, 141 (1923)] showed that the thermal condrrctivity of liquids is increased by only a few percent rrnder a pressrrre of 100,330 kPa (1000 atm). The thermal condrrctivity of some liqrrids varies with temperatrrre throrrgh a maximrrm. It is often necessary for the engineer to estimate thermal condrrctivities methods are indicated in Sec. 2. 

But at the present it (Bridgman s work) increases the presumption that the discontinuity in the shock wave is to be explained by something else. The whole question of what causes such discontinuities seems to be somewhat obscure. It is apparently recognized that such a phenomena as reaching the plastic limit may explain the discontinuity at 10,(X)0 (kg/cm ) mentioned above, but the precise mechanism by which reaching the plastic flow point may induce the discontinuity seems not to have been worked out. 

Shortly after this time, it was discovered that Bridgman s static high-pressure scale was in error due to calibration problems, and the shock-induced 13 GPa transition became the new calibration standard. 

The present book, with contributions from a group of very knowledgable scientists in the field, is an attempt to provide a basis for addressing Bridgman s concerns. The response requires multidisciplinary contributions from solid mechanics, solid-state physics, materials science, and solid-state chemistry. Certainly, advances in theory, experimentation, and numerical simulation are impressive, and many aspects of shock-compressed solids have been studied in detail. At the fundamental level, however, it is certainly appropriate to question how well shock-compression processes are understood. 

Figure 4.5. P.W. Bridgman (courtesy of G. Holton. Harvard University).

Bridgman had strong views on the importance of empirical research, influenced as little as possible by theory, and this helped him test the influence of numerous variables that lesser mortals failed to heed. He kept clear of quantum mechanics and dislocation theory, for instance. He became deeply ensconced in the philosophy of physics research for instance, he published a famous book on dimensional analysis, and another on the logic of modern physics . When he sought to extrapolate his ideas into the domain of social science, he found himself embroiled in harsh disputes this has happened to a number of eminent scientists, for instance, J.D. Bernal. Walter s book goes into this aspect of Bridgman s life in detail. 

Simple terms can be a trap and a delusion. In the study of materials, we must be prepared to face complexity and we must distrust elaborate theoretical systems advanced too early, as Bridgman did. As White (1970) remarked with regard to Descartes Regarding the celebrated vorticist physics which took the 1600s by storm... it had all the qualities of a perfect work of art. Everything was accounted for. It left no loose ends. It answered all the questions. Its only defect was that it was not true . 

Bridgman, P.W. (1925) Proe. Amer. Acad. Arts Sci. 60, 305 also (1928) ibid63, 351 Most easily accessible, in Collected Experimental Papers, 1964, ed. Bridgman, P.W. (Harvard University Press, Cambridge, MA). 

Bridgman, P.W. (1931, 1949) The Physics of High Pressure, 1st and 2nd editions (Bell and Sons. London). 

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