#solubility

Intermediate Compounds and the Nickel-Uranium Binary System

Phase Poll #11 concluded yesterday with a fairly even split between nickel (53%) and uranium (47%). We also got one vote for a temperature of 1000K, thanks to @grimmtaupe. The Ni-U diagram is really only considered in the space of nuclear alloys, and isn’t very popular even then, so we’re going to spend some time on this post talking about intermediate compounds.

I’ve already briefly discussed congruently melting compounds vs. incongruently melting compounds, after the conclusion of phase poll #7. These definitions focus on phase transitions, while defining intermediate compounds starts to delve into the realm of solid solubility. Uranium and nickel have very low solid solubility below ~600°C (or ~873K). This can be seen from the numerous vertical lines on the phase diagram, each of which represents a specific intermediate compound, defined as simply phases with compositions that fall between two neighboring phases. Intermediate compounds almost always have a different crystal structure than the neighboring phases as well.

Solid solutions, on the other hand, can be continuous (like in the Ni-Cu phase diagram), primary/terminal (the fcc Ni phase and the bcc U phase at either side of the Ni-U phase diagram), or intermediate (like the hcp phase in the Ag-Al phase diagram). The primarily vertical lines on a phase diagram can thus give a visual indication of the solid-solubility of two elements across their compositional space.

Back to the chosen composition, our alloy would be primarily Ni9U7. Not much is known about this compound, but the thing about phase diagrams is that they’re difficult to create, even if computational tools have accelerated the process in modern times. Some research (ref. 3 below) into nickel-uranium alloys suggests that the phase is actually U10Ni13, and crystalizes in a monoclinic crystal structure. If we consider the temperature as well, we can see from our previous definitions that Ni9U7 is an incongruently melting compound. For the nickel uranium system in general, small additions of nickel have been shown to promote sintering of uranium carbides.

Sources/Further reading: ( Ni-U: 1/image 2 ) ( Ni-U: 2 ) ( Ni-U: 3 ) ( Phase diagrams: 1 ) ( Phase diagrams: 2 ) ( Phase diagrams: 3 )

- Me, an innocent Year 11 who had not yet suffered the horror that is a 65 page and 15,000 word depth study on the solubility of potassium nitrate.

Hey guys! A lot of people seemed to love my last video on chemical reactions, so I decided to make one on salts and solubility! 

High-thermoresistant biopolyimides become water-soluble like starch

This is the first ever report on the syntheses of water-soluble polyimides which are derived from bio-based resources, showing high transparency, tunable mechanical strength and the highest thermoresistance in water-soluble polymers.

Water-soluble polymers are of great interest in many areas of soft materials. These soft materials have been widely used in applications related to aqueous solutions, such as dispersants, aggregation agents, thickeners, moisturizers, binders, and hydrogels. With the increase in global awareness about environmental concerns, the importance of water-soluble materials has been highlighted and thereby researchers have expanded their application windows to electronics, functional coatings, advanced adhesives and biomedical materials. Most natural polymers such as polysaccharides, polypeptides, or their derivatives are water-soluble while synthetic water-soluble polymers are also available such as poly(ethylene oxide), poly(vinyl alcohol), polyacrylates, polyacrylamide, and their derivatives. However, conventional water-soluble polymers have limited applications due to their low thermal distortion temperatures (ca. 200 °C).