Quenched melts

Melt Spun Ma.gnets, Melt spun magnets refer to those manufactured from rapidly quenched melts of Nd2Fe24B. The quenched material is in... 

It is amazingly stable. Apparently, S12 exists in liquid sulfur, because it can be found in quenched melts (91), and it is formed in solutions of Sfl in toluene during decomposition under the influence of light (92). The vapor is, however, unstable thus, mass spectroscopic identiflcation proves to be difficult (12). The molecules have 2/m-C2ft symmetry in the crystal, but are close to Sm-Dg. Table II shows that the bond properties lie between those of Sg and Sg ... 

SCjSj, and of molecules of even higher selenium content was seen in the mass spectra taken from the samples of both quenched melts and of crystals obtained by solvent extraction of them. It must be taken into account, however, that even gentle heating of the samples may initiate disproportionation reactions. Also the volatihty of different ring molecules may be quite different. Therefore the composition of the vapour does not necessarily reflect the composition of the solid phase in all details. 

Fig. 10.—F.t.-I.r. Spectra of Sucrose in Different Physical States. [Quenched melt (QM), freeze-dried (FD), and saturated aqueous solution (SS).]...

Te (solid, amorphous). Damiens1 found the heat of solution, in strong bromine water, of the quenched melt of tellurium and the amorphous or chemically precipitated tellurium to be zero and 2.7, respectively, greater than that of Te (c, II). 

There are convincing facts that in the melt at any given temperature there are also molecules other than S8 and multiples of S8. Some time ago we could isolate Si2 from molten sulfur. Only a few months ago Steudel (9) reported very interesting and promising new studies on quenched melts by Raman and IR spectroscopy. He found S0 and S7 in significant amounts. Other not-yet-identified lines indicate the probable presence of S5, S9, and/or Sn. 

Polymict aggregates of peridotite, eclogite and megacrysts, of variable grain size, some containing quenched melt. Mineral assemblages not in elemental or isotopic equilibrium. 

Figure 2.28. Infrared spectta of the LiF-NaF quenched melts with different contents of K2Nbp7.

The last two compounds were confirmed by both the X-ray analysis and IR spectroscopy of quenched melts. K2B4O7 is created preferentially with an increasing content of B2O3 in the mixture. The presence of metaborate anions, however, was not detected, most probably due to its low concentration in the melt. 

In the study of the structure, i.e. the ionic composition of the investigated molten electrolyte, the physico-chemical analysis, based on the results of measurements of phase equilibrium, density, surface tension, viscosity, and electric conductivity of melts, combined with X-ray phase analysis and IR, respectively, Raman spectroscopy of quenched melts, is used. In the last two measurements, it may be assumed that the high temperature composition is at least qualitatively conserved after quenching. In the investigation of the structure of the electrolytes, the so-called chemical approach is used. 

The amorphous poly(ethylene terephthalate) vas prepared by quenching melt-cast polymer of molecular vel t 2 x 10 to the... 

Liquid sulfur quenched in water from temperatures above 200 °C is plastic in the beginning and, if prepared in filaments, can be stretched to 3000% of its original length (fibrous sulfur, S ) [54]. After some time hardening through crystallization takes place. It also should be mentioned that the quenched melt, besides and Ss, contains other small rings like Se, S7, S9, Sio, etc. which will slowly decompose to and Ss at room temperature [49]. Thus, the polymer content of the quenched melt first increases by a few percent before it slowly decreases due to conversion to a-Ss on storage at room temperature [54]. 

Crystalline samples of fibrous sulfur can be prepared by stretching freshly quenched liquid sulfur or by drawing filaments directly from a hot sulfur melt. The quenched melt (plastic sulfur) is viscoelastic and transparent yellow but slowly transforms into an opaque crystalline material at room temperature. After several days the material contains besides the polymer a fraction of Ss rings and traces of S7 while all other rings have converted to either polymer or Ss [22]. The ring fraction can be extracted by washing the material with CS2. The insoluble fi action of polymeric sulfur is then allowed to crystallize (termed after Smith [109] or sometimes Sa, after Das [112]). 

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