Examination of temperature-induced shape memory of uranium--5. 3-to 6. 9 weight percent niobium alloys

AbstractThe goal of this study is to investigate the fundamental relationship between the extent of crosslinking and shape-memory behavior of amorphous, (meth)acrylate-based polymer networks. The polymer networks were produced by copolymerization of tert-butyl acrylate (tBA) and poly(ethylene glycol) dimethacrylates of differing molecular weights (PEGDMA). Polymer compositions were tailored via the amount (weight percent (wt%)) and molecular weight of the PEGDMA crosslinking agents added to produce four materials with varying levels of crosslinking (0, 2, 10, and 40 wt% crosslinking agent corresponding to 0, 0.6, 3.2, and 16.6 mole%) and nearly equal glass transition temperatures (Tg). The effect of crosslinking on deformation limits and free-strain recovery is evaluated. Near complete strain recovery was demonstrated by all materials; however, absolute recovery strain decreased with increasing crosslinking due to a corresponding decrease in strain-to-failure. The results provide insights regarding the link between polymer structure, deformation limits, and strain-recovery capabilities of this class of shape-memory polymers. An improved understanding of this relationship is pivotal for optimizing system response for a wide range of shape-memory applications.

Download Full-text

Direct Determination of Niobium in Uranium-Niobium Alloys

Advances in X-ray Analysis ◽

10.1154/s0376030800006285 ◽

1979 ◽

Vol 23 ◽

pp. 177-183

Author(s):

Jack L. Long

Keyword(s):

Standard Deviation ◽

Chemical Treatment ◽

Direct Determination ◽

Average Intensity ◽

Niobium Alloys ◽

Wet Chemistry ◽

Percent Niobium ◽

Wet Chemical ◽

Intensity Ratios

AbstractA procedure for determining niobium in uranium-niobium binary alloys was developed. The procedure requires only that a compact be made by pressing turnings, and wet chemical treatment is avoided entirely. By eliminating the wet chemistry, time is reduced by a factor of at least three compared with previous practice.Standardization was accomplished by separating each batch of machined turnings from specially cast uranium-niobium alloys into individual strands. A composite portion of each strand was analyzed for niobium by wet chemistry. The balance of the turnings from each batchy was pressed into a compact. Seven standard compacts resulted. The average Intensity ratio of niobium-to-uranium vs. the percent niobium for fourteen determinations on each standard compact was used to calculate a correlation coefficient of 0.999.The standard deviation of the Intensity ratios between duplicate compacts (average of 52 samples) was less than the standard deviation found between aqueous duplicates (average 125 samples) by a factor of 4.

Download Full-text