Annealing crystallization

A simplified schematic of various available SSP systems is shown in Figure 4.18. The four main process stages of crystallization, annealing, reaction and cooling are present in all of the plant types. The processes differ from one another by the way in which the pellets are agitated in order to prevent agglomeration during heat-up. 

Fig. 12 (a) Experimental Patterson map derived from the in-plane scattering from a NiO(lll) single crystal annealed at 950 K under 10 mbar partial oxygen pressure (b) Calculated Patterson map for a spinel configuration including 7% of octopolar reconstruction (c) Experimental and calculated (left half circles) structure factors. 

Pronk, S., and Frenkel, D., Can stacking faults in hard-sphere crystals anneal out spontaneously J. Chem. Phys., 110, 4589, 1999. 

Conversion of the as-deposited film into the crystalline state has been carried out by a variety of methods. The most typical approach is a two-step heat treatment process involving separate low-temperature pyrolysis ( 300 to 350°C) and high-temperature ( 550 to 750°C) crystallization anneals. The times and temperatures utilized depend upon precursor chemistry, film composition, and layer thickness. At the laboratory scale, the pyrolysis step is most often carried out by simply placing the film on a hot plate that has been preset to the desired temperature. Nearly always, pyrolysis conditions are chosen based on the thermal decomposition behavior of powders derived from the same solution chemistry. Thermal gravimetric analysis (TGA) is normally employed for these studies, and while this approach seems less than ideal, it has proved reasonably effective. A few investigators have studied organic pyrolysis in thin films by Fourier transform infrared spectroscopy (FTIR) using reflectance techniques. - This approach allows for an in situ determination of film pyrolysis behavior. 

Amorphous tungsten oxide has been prepared by ultrasound irradiation of a solution of tungsten hexacarbonyl W(CO)6 in diphenylmethane (DPhM) in the presence of an Ar (80%) and O2 (20%) gaseous mixture at 90 °C [137]. Heating this amorphous powder at 550 °C under Ar yields snowflake-like dendritic particles consisting of a mixture of monodinic and orthorhombic WO2 crystals. Annealing... 

Many authors have reported on impurity accumulation during crystal annealing. Sulfur, in particular, has been observed to segregate on indium ), iron ), molybdenum ), silver ), titanium > > tungsten ), vanadium ), zinc ) and zirconium ), often with formation of an ordered structure, especially on iron ) and nickel ) and fixation at preferential sites ). 

Hydrogen evolution from single crystals has been studied. Salovey et al. [271] found a G value of 4.6 for bulk Marlex-50 polyethylene and thin films obtained from solutions of crystallized polyethylene. Values of 2.48 and 2.17 were obtained by Kawai et al. [278] for, respectively, bulk Marlex-50 and single crystals (annealed or not). 

Then, the amorphous regions crystallize. Annealed polymers, however, are more highly crystalline. In this case, the crystallites must be partially dissolved before the molecular axes can be oriented. 

Free Enthalpy Diagram Illustrating Crystal Annealing and Recrystallization... 

We investigated the structure formation during the isothermal crystallization (annealing) process from the oriented glassy states of PET using real-time X-ray scattering and thermal measurements. The results obtained are as follows ... 

Similarly, iV-doped SnOa nano-crystals annealed in an O2 atmosphere at different temperatures show two bands at 400 and 500-650 nm under 320-nm excitation [71]. The former consists of three sharp peaks, which are assigned to the band-acceptor and donor-acceptor pair transition as well as the phonon replica. For the latter, the intensity decreases, and the peak position shifts to low energy with the temperature increase. In addition, after annealing at 700 °C, the crystals also display excitation wavelength-dependent PL spectra. Based on the DFT calculation, three models are huilt (a) one shallow (relative to (110) surface) iV-dopant (Nq) and one shallow oxygen vacancy (Vq) (b) one deep Nq and one shallow Vq, and (c) one deep Nq and one deep Vq. Different defect depths successfully explain the excitation wavelength-dependent PL spectra. 

Wunderlich B (1976) Macromolecular physks, nudeation, crystallization, annealing. Academic Press, New Yoik... 

Wunderlich, B. Macromolecular Physics, II. Nucleation, Crystallization, Annealing Academic Press New York, NY, 1976. 

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