Melt-and-quench

Beryl Melted and quenched An amorphous glassy product is produced. Dilute sulfuric acid leaching... 

The NC/PCL data present a different situation. Blends of 25 and 40% NC showed the opaqueness and a DSC endotherm, which indicate the presence of crystallinity. Consequently, melting and quenching produced lower Tgs as expected. Pure NC and 50% NC did not show either of these features. Yet, the Tg dropped from 338 to 328 K for NC and from 283 to 271 K for 50% NC after the heating-quenching cycle. Blends of 65 and 75% NC showed high initial Tgs but failed to show any transition after quenching. 

Fig. 8 Comparion of geometric structure of an ideal auxiliary phase (a) with those prepared by current techniques, such as in-situ formation (b), mechanically pressed discs (c), physical vapor deposition (d), and melting and quenching (e).

At the source side of the PEVD system, a counter electrode and a reference electrode were deposited on substrate areas of 1 cm and 0.1 cm, respectively. The thickness of both electrodes was about 3 pm. Because rapid equilibration must be established for the electrochemical reaction at the source side during the electrochemical studies, it is important to minimize polarization at the counter and reference electrodes. Thus, the source Na COj in this PEVD system wrapped both the counter and reference electrodes due to a melting and quenching technique. The Na COj powder was first heated in an alumina crucible above its melting point at 852°C. Then the source side of the PEVD system was quickly dipped into the melt. After cooling to room temperature, a layer... 

Olivine occurs mainly as inclusions in enstatite and is also found in albite, spinel, and troihte (Brearley, 1989). At least three kinds of poly-crystalline clusters appear to have formed separately (i) enstatite-rich units with forsterite inclusions, (ii) coarser versions with albite and olivine inclusions, and (iii) forsterite-anorthite units with no enstatite. Enstatite crystals are intergrowths of ortho- and clinopyroxene and their microstructures indicate cooling from >1,000 °C at -1,000 °Ch Brearley (1989) suggests that the Kakangari matrix formed from amorphous or partly crystalline particles <10 p,m in size that were annealed at 1,100-1,200 °C or possibly higher, and then rapidly cooled in an hour. The chondrules in Kakangari could have formed from similar material that was heated to higher temperatures, partly melted, and quenched at comparable rates, provided that the chondrules acquired lower concentrations when molten. 

The amorphous state, therefore, can be arrived at by methods other than melting and quenching and all such methods result in the loss of crystalline order. All these processes introduce additional enthalpy into the disordered material. Therefore amorphous materials crystallize irreversibly when heated to a temperature, below T of the parent crystalline material and the process is exothermic. The free energy of the amorphous state of a material is higher than that of its crystalline state. Thus the enthalpy addition (A//) during amorphization has to be generally... 

Chondrule Spherical millimeter-sized silicate droplet formed by melting and quenching prior to incorporation into undifferentiated meteorites. 

Figure 6.12 DMTA analysis of pure iPP, pure PB-1, and iPP/PB-l/HOCP 50/30/20 blends after iPP crystallization from the melt and quenching (a) and after iPP and PB-1 crystallization from the melt at room temperature (b). (From Reference 7 with permission from John Wiley Son, Inc.)...

Most samples were prepared by solvent casting, drying under vacuum at T, and molding under 1 kg/cm at Tg. The PVOH sample was prepared only by solvent casting, and the PE sample was prepared by melting and quenching. The samples... 

For the studies preformed by this group on the anthracene + pyrene system (Rice et al., 2010), mixtures were prepared at various compositions by using a melt and quench-cool technique (Fu et al., 2010). Generally, the melting points and enthalpaes of fusion of these PAH binary mixtures were found to often actually be independent of mixture preparation techniques. The hquidus and thaw points were determined according to the method proposed by Potmder an Masson (Pounder and Masson, 1934). The thaw temperature is the temperature at which the first droplet of liquid appears in a mixture-containing capillary. The liquidus temperature is the maximum temperature at which both solid crystals and liquid are observed to coexist. Above this temperature, there is only liquid phase present. 

Glasses of composition 5-25 wt% Si02, 50-80 wt% Nb205, 0-20 wt% Na20 and 0-31 wt% BaO, with the total amount of Na20 and BaO between 5% and 35% by weight, were melted and quenched into ribbon or thin (approximately 1-2 mm) patties. These were heat treated between 750 -950°C to achieve efficient nucleation and resulting transparency. 

Hydroxyapatite has been coated on metaUic dental and orthopedic implants by high-temperature plasma thermal spray since the 1980s [24,25]. In this process, HA powders are fed into a plasma flame (temperature 5,000 to 15,000°C). The powders are quickly melted and quenched on the metallic implant substrate to... 

Molecular Dynamics (MD) simulations are a well-established tool to obtain atomic-scale models of melt-derived amorphous materials, through a straightforward melt-and-quench computational procedure that mimics the experimental one [19-23], The main limitations that may limit the accuracy of any MD-derived model are ... 

Ab-initio MD (AIMD) can usually target systems of few hundreds atoms and time scales of few tens of picoseconds [26-31], In the case of glasses, this means that it is possible to perform an AIMD melt-and-quench simulation of a system around 100-200 atoms, using quenching rates around 20-100 K/ps [31-34]. The small system size in AIMD prevents to extract a full description of medium-range order features such as the network connectivity (NQ of a glass. However, the AIMD models provide the most accurate description of local structure, such as the coordination of key ions, unbiased from any potential bias introduced by an empirical force field. This could be particularly important in order to target the local stmcture... 

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