from E L E C T R O M E T Metals Research
VANADIUM for the Age of Atomic Power V A N A D I U M M E T A L , due t o
low "neutron capture/* chemi cal stability, and corrosion re sistance, is already In test for nuclear r e a c t o r applications. Vanadium's o t h e r q u a l i t i e s purity, excellent heat conduc tivity, strength a t high tem peratures, good tensile proper ties—have led to its successful application a s a n addition to special alloys prepared by vac uum melting· and consideration for a variety of structural uses in the electronics field. E L E C T R O M E T ' S t e c h n i c a l staff i s available to assist you in ex ploring new applications. The coupon will bring additional data.
Elecfromet FERRO-ALLOYS AND METALS
UNION CARBIDE Thetcrnis"Electromet"and "Union Carbide"are> reg istered trade-marks of Union Carbide Corporation.
Electro Metallurgical Company Division of Union Carbide Corporation Box 268, Niagara Falls, Ν . Υ. Please send m e the Vanadium Technical Data Sheet NAME COMPA2STY POSITION ADDRESS CITY ZONE.
56
C&EN
SEPT.
2 2,
195 8
RE^EA«CH T e m p e r a t u r e h a d various effects o n liquids t o extremely high pressures a t room température a n d t h a t optical t h e profiles of t h e n e p t u n i u m b a n d s . measurements have b e e n m a d e o n Some bands experienced a r e d shift, Some b a n d s fused salt solutions of low vapor p r e s - others a b l u e shift. sures at temperatures u p to a red heat- broadened, while others showed a n u n However, the O R X L optical cell is t h e expected sharpening as t e m p e r a t u r e in W a g g e n e r attributes these first t o provide reliable containment o f creased. radioactive liquids under dual condi- variations to t h e differences in t h e in tions of elevated t e m p e r a t u r e and pres- teraction of the* electron states involved sure, such as those found in a q u e o u s with t h e solvate sphere of t h e solution. media above 100° C . h e told the Divi- H e plans further experiments t o e s t a b lish correlations between t h e effect of sion of Physical Chemistry. Waggener uses a standard G a r y t e m p e r a t u r e a n d solution environment Model 14 M recording spectrophotom- upon these spectra. Also in t h e works eter with t h e special cell assembly. a r e plans for a second, redesigned a s T h e cell, fabricated from annealed t i - sembly. T h e s e plans i n c l u d e : tanium, contains colorless, artificial • I n d e p e n d e n t thermostating of b o t h sapphire windows. Both titanium a n d s a m p l e a n d reference absorption cells sapphire w e r e selected because of their a t elevated temperatures and pressures. excellent corrosion resistance to w a t e r • Methods for rapidly equilibrating a n d aqueous solutions a t h i g h t e m p e r a a liquid sample with a vapor phase. tures. T h e window-mount design is unique, says W a g g e n e r . Spring-loaded, Waggener feels that speetrophotoTeflon ring seals make t h e w i n d o w metric studies of aqueous solutions leak-tight. T h e seals withstand 10ΘΟ a b o v e their boiling points will b e c o m e to 1600 p.s.i. of helium a t r e p e a t e d increasingly important. To support his temperature cycling b e t w e e n 3 0 ° a n d view, h e points to the growing tech 250° C. nology of "aqueous-homogeneous" Four fused-quartz legs with Inconel nuclear reactors, in which t h e fuel h X-trunnions cradle the sample cell arid a heavy w a t e r solution of a soluble reservoir assembly in a vacuum c h a m u r a n i u m c o m p o u n d . ber. These legs a r e fastened to a goldnlated metal base which is kinematically located on three pins. T h e h e i g h t Solid Proof of Solid of each pin is adjustable. T h e sample cell a t a n y o p e r a t i n g State Reactions temperature is optically c o m p a r e d w i t h N e w a p p r o a c h settles o l d a geometrically similar solvent cell thermostated at 25° C. Waggener argument on mechanism o f checked the cell's performance b y e x reactions between p o w d e r e d oeriments with water a n d aqueous s o solids lutions. T h e stability a n d reproduci bility of measurements over t h e entire It seems t h a t design r a n g e c o m p a r e favorably w i t h ACS reactions b e t w e e n those of room t e m p e r a t u r e operation. • N e p t u n y l Ion S t u d i e d . W i t h t h i s NATIONAL p o w d e r e d solids n e w analytical tool, W a g g e n e r m a d e _ _ Inorganic MEETING c a n proceed b y spectral measurements of neptunyl n i solid state dif trate i n 0.1 M d e u t e r a t e d nitric a c i d . Chemistry fusion process a t Deuterated solutions w e r e used to d e low temperatures. crease solvent background interference. Some 3 0 years T h e four ionic valence states of n e p t u ago t h e r e w a s nium (III, IV, V , V I ) all have charac teristic absorption b a n d s i n t h e visible h e a t e d controversy about w h e t h e r s u c h a n d near-infrared spectra, h e explained. "solid state" reactions really do occur Therefore, it was easy to follow the fate or whether mass transport t h r o u g h a of the N p ( V I ) ion speetrophotometri- gaseous or liquid phase is involved. cally a s a function of time a n d t e m Most scientists favored t h e solid state perature. Quantitative, irreversible r e mechanism, a n d the controversy d i e d down. duction of N p ( V I ) t o N p ( V ) o c c u r r e d Within t h e last few years, however, a at elevated temperatures. N p ( V ) r e group of Russian workers has reopened mained stable t h r o u g h o u t the rest of this controversy by reporting experi t h e heating and cooling cycle. mental evidence which indicates t h a t gas phase m a s s transfer is involved m
m
many of the so-called solid state reactions. These Russian Investigators believe further that solid state reactions between powdered solids are very unlikely except at high temperatures, since the small contact area between powder particles is too small for rapid gas diffusion. Hans J. Borchardt of GE told the Symposium on Solid State Chemistrx of the Division of Inorganic Chemistry tlmat he has developed a technique to tell without question when gas phase transfer cannot be the main mode of mass transport. And he has applied tliis to several reactions to show that they do proceed in the solid state below 500° C. under conditions such that vaporization or formation of liquid pbases is not possible. Borchardt made clear that he agrees with the Russians, though, that many of the "classical" solid state reactions are not solid state. The reactions which Borchardt investigated were those between U :i O^ and metal powders to give the metal oxides and UO^. Here no liquid phase can form, and the question is whether tlie reactions proceed directly between the solids or whether vaporization occurs as in the reactions, U 3 O s (solid) yielding U 0 2 (solid) plus oxygen (gas), and oxygen (gas) plus a metal yielding a metal oxide. If the reaction does rrvrvx#ajr9
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over-all reaction rate cannot exceed the rate of the dissociation step. Borchardt's work shows that at least some of rJhe reactions between U 3 O s and metals clo proceed at more than the calculated maximum dissociation rate and hence cannot involve only gas phase mass transfer. From thermodynamic considerations lie can calculate the "dissociation tem perature"—the minimum temperature a t which the dissociation reaction would have an initial rate of 1% conversion per minute. And then, by differential thermal analysis, he determines the temperature at which reactions be tween U 3 O s and metal powders have this same initial reaction rate. In the case of at least two metals, iron and niobium, he finds that this temperature is significantly lower than the "dissocia tion temperature" of U 3 O s . Hence these reactions must be proceeding pri marily by a mechanism other than one involving dissociation. And the only alternative seems to be a solid state diffusion process.
by IONIZING RADIATION —fromthe Van de
Graafi®
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• New improved properties in many materials — greater strength — better scuff and temperature resistance. • New fplastic^s with unique characteristics by polymerization, sur face grafting. Cold vulcanization of rubber. • New methods of initiating chemical reactions — Catalysis, elec tron-beam «racking of oil, isomerization, and oxidation. Nearly 200 H I G H X / O L F A G E ENGINEERING accelerators are in the field and a radiation facrility i s available for your use at our plant. Bring your product or problem to our technical sales department.
HIGH VOLTAGE ENGINEERING BUfclNS.TON
;
M*>
SEPT. 2 2,
1958
C&EN
57
