Thermodynamics, crystal structure, and characterization of a bio-based nylon 54 monomer

We investigated the crystallization of bio-nylon 54 monomer salt in terms of the solid–liquid equilibrium, crystal structure, thermal behaviors and crystallization mode.

Relation between Medium-Range Order and Crystallization in Al-Ni Based Glass-Former Alloys

The structure evolutions of Al83Ni10Ce5Si2, Al83Ni10Ce7, Al85Ni10Ce5, Al87Ni7Nd6 and Al87Ni5Co2Nd6 metallic glasses have been studied in detail. The studies establish a relation between the amount of medium range order (MRO) and crystallization mode. An increased amount of MRO suppresses the precipitation of primary fcc-Al and transforms the crystallization mode from a primary crystallization (Al87Ni7Nd6) to a eutectic crystallization (Al87Ni5Co2Nd6); while a decreasing amount of MRO promotes the precipitation of primary fcc-Al and transforms the crystallization mode from a eutectic crystallization (Al83Ni10Ce7 and Al85Ni10Ce5) to a primary crystallization (Al83Ni10Ce5Si2).

A novel analytical approach to estimate isothermal and dynamic crystallization Avrami kinetic parameters

The Avrami equation has been extensively used to describe the polymer crystallization kinetics. Evaluation of kinetic parameters of this equation is quite troublesome, calling for properly predetermining induction time. To avoid this problem, an analytical approach in terms of differential scanning calorimetry exotherm maximum point was adopted here so as to conveniently estimate the Avrami equation kinetic parameters both in isothermal and dynamic crystallization mode. In the case of dynamic crystallization under isokinetic conditions, a modified version of the Avrami model by Nakamura was employed and adequate predictions based on the derived formulas were obtained. However, due to the simplified assumptions of the Avrami theory, our adopted relations are only applicable to earlier stages of crystallization process and do not account for secondary crystallization.

Quasicrystallization of (Zr65Al7.5Cu27.5)95Ti5 Glassy Alloy

Phase transformation in the melt-spun (Zr65Al7.5Cu27.5)95Ti5 glassy alloy was investigated by a combined use of X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). It was found that the crystallization mode of the Zr65Al7.5Cu27.5 glassy alloy was altered by the addition of Ti, and nanometer scaled icosahedral phase (I-phase) formation was observed in the primary crystallization stage of the (Zr65Al7.5Cu27.5)95Ti5 quaternary glass, which transformed to the stable Zr2Cu-type phase upon further annealing. The crystallization behavior of (Zr65Al7.5Cu27.5)95Ti5 glass was further discussed in terms of the activation energy as compared to that of Zr65Al7.5Cu27.5 alloy.

The Synthesis and Crystallization of Poly(vinylidene fluoride) in Supercritical CO2

A series of poly(vinylidene fluoride)s (PVDFs) is synthesized in supercritical carbon dioxide (sc-CO2). The influences of polymerization pressure, molecular weight distribution and H-H defect concentration on the crystallization of PVDF have been studied in combination with differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXRD) and Fourier transform infrared spectroscopy (FT-IR) measurements. The result shows that the morphology, molecular weights, polydispersity and head-to-head (H-H) defect concentrations of the PVDFs are affected by the reaction pressure and good solubility generated from sc-CO2. Especially, the sc-CO2 polymerization has greatly improved the crystallization mode of the obtained PVDFs such as the complete degree of crystallinity, crystallinity and the crystal phase. This will create more comprehensive application fields for PVDF.

RETRACTED – Formation and properties of Zr-based bulk quasicrystalline alloys with high strength and good ductility

The crystallization mode of the Zr–Al–Ni–Cu amorphous alloys changed from a single stage to become two stages by the addition of Ag or Pd, and the first-stage exothermic reaction was found to result from the precipitation of nanoscale icosahedral particles with a size of 20 to 50 nm. The precipitation took place by high nucleation and low growth rates in a polymorphous mode for the Ag-containing alloys, and a diffusioncontrolled mode for the Pd-containing alloys. The nanoscale mixed structure alloys exhibited improved strength and ductility as compared with the corresponding amorphous single-phase alloys. The findings of the dispersion strengthening as well as the dispersion ductilization gave a future opportunity to fabricate a new bulk nonequilibrium phase alloy by use of the new phenomenon.