Dubnium, production

Dual nickel, 9 820—821 Dual-pressure processes, in nitric acid production, 17 175, 177, 179 Dual-solvent fractional extraction, 10 760 Dual Ziegler catalysts, for LLDPE production, 20 191 Dubinin-Radushkevich adsorption isotherm, 1 626, 627 Dubnium (Db), l 492t Ductile (nodular) iron, 14 522 Ductile brittle transition temperature (DBTT), 13 487 Ductile cast iron, 22 518—519 Ductile fracture, as failure mechanism, 26 983 Ductile iron... 

Studies of the dubnium behavior. 930 experiments were conducted with 262Db produced at the Berkeley 88-Inch Cyclotron in the 249Bk(lsO,5n) reaction. Extractions were performed in the Aliquat336/Cl - HC1 system with a 50 s cyclic collection time of the KC1 aerosol on a Kel-F slider in ARCA II. The reaction products were fed onto the column in 10 M HC1 followed by the elution of a Ta fraction in 6 M HC1 and a Nb,Pa fraction in 6 M HNO3/O.OI5 M HF. The effluents were continuously sprayed through a 60 pm nozzle onto hot Ta discs on which they were evaporated to dryness by hot He gas and infrared light. Start of measurement of the activities was 60 s (Ta fraction) and 76 s (Nb, Pa fraction) after the end of collection, respectively. 

Pb( V,n) reaction [239]. The isotope Db Jy2 = 2.5 s) is produced in the Bi( Ti,2n) reaction with a cross section of 2 nb [251] and in the Pb( V,n) reaction [239]. An isomeric state, Db Tiri = 0.9 s), has also been observed in the Bi( i,2n) reaction [248, 252]. The isotope Db Ty2 = 1.6 s) is produced in the Bi( °Ti,3n) reaction with a cross section of 0.2 nb [248] and in the ° Bi(" Ti,2n) reaction [239]. Dubnium isotopes also result from the a decays of bohrium isotopes (see below), but with smaller cross sections than for their direct production. While some of the cold-fusion isotopes have half-lives in excess of one second, the production of longer lived nuclides in other reactions is of more interest to the radiochemisL... 

Dubnium (Z = 105) cannot be produced directly in " Ca-induced reactions, but long-lived isotopes occur in the decay chains of some of the heavier reaction products. The isotopes Db Ti/2 — 29 h) and Db Tia — 1.2 h) are the terminating SF activities of the decay chains derived from 115 and 115, respectively. These nuclides are produced in Am( Ca,xn) reactions with x = 3 and X = 4, respectively, with corresponding effective production cross sections of 8 pb and 2 pb, [8, 285, 286, 354]. Presently, it cannot be excluded that the SF... 

Research on the chemistry of transactinide elements was resumed in the mid 1980s at Berkeley by the first study of element 105 in aqueous solution [123]. The a-particle emitter, 35-s Db, produced by the " Bk( 0,5n) reaction, served as a probe. The investigated chemical topic was the adsorption on glass in very strong nitric acid, a characteristic property of tantalum and niobium. Dubnium was found to share this property. Due to the very low production rate of Db, some 800 manually performed experiments were required to obtain a statistically satisfying result based on 24 a-decay events altogether. This example showed that automated, computer-controlled online procedures were needed for a broad exploration of the open territory. 

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