Onset crystallization temperature

Lee et al. (1996) applied step-wise crystallization fractionation to SME and reported similar results (Table 1.5). The liquid fraction had a total saturated FAME content = 5.5 wt% and crystallization onset temperature = -7.1 °C (determined by differential scanning calorimetry (DSC), compared to values of 15.6% and 3.7 °C before fractionation. Liquid product yield was also relatively low (25.5%). 

Lee et al. (1996) also investigated crystallization fractionation of SME from several solvents. Fractionation from hexane in three sequential steps with a final bath temperature of -28.4 °C resulted in a liquid product yield of 77% and total saturated FAME content of 6.0wt%. Crystallization onset temperature by DSC of the liquid fraction was -5.8 °C. Fractionation of SME from methanol solvent separated into two liquid layers as cooling temperatures approached -1.6°C. Acetone did not reduce crystallization onset temperature of the liquid fraction, and chloroform failed to form crystals at temperatures below -25 °C. Hanna et al. (1996) studied fractionation of TME... 

Critical cooling rate, Rc, can also be obtained on the basis of an empirical correlation between the crystallization onset temperature (7 ) obtained from the exothennic peaks in the DTA curves and the cooling rate, R, employed in the DTA experiment using the relation. 

The aim of this investigation is to examine the effect of nucleating agents on factors such as crystallization onset temperature and spherulite size. The nucleating potential of titanium dioxide based pigment and that of regranulated process waste is also examined since a knowledge of such effects is essential if process and product consistency is to be achieved. 

Fig. 27a-b represents the SEM micrographs taken from the surface and the cross-section of the 0.90Te02-0.10W03 sample heat-treated at 410 °C, above the first crystallization onset temperature, respectively. Fig. 27a exhibits the presence of dendritic leaf-like crystallites differently oriented on the surface. However, in the cross-sectional micrograph (see Fig. 27b), a typical amorphous structure without any crystallization on bulk structure can be clearly observed following the crystallites on the surface. Based on the SEM investigations, it was determined that the crystallites formed on the surface and did not diffuse into the bulk structure proving the surface crystallization mechanism (Qelikbilek et al., 2011). 

Figure 17 shows the onset of crystallization temperatures of NIE and CIE blends (60-100% butterfat in the blend). At the crystallization onset temperature, viscosity increased dramatically. All CIE samples had a higher crystallization onset temperature than their NIE counterparts. Both the proportion of butterfat and interesterification had significant effects on crystallization onset temperature... 

The higher crystallization onset temperatures of the CIE blends are not readily explainable. A plausible explanation is that the randomization of saturated fatty acids created a greater number of potential nucleation sites in the CIE blends than were present in the NIE blends. For example, dilution of butterfat with 10% canola oil led to a a drop in crystallization onset temperature. This was due to a lower proportion of TAGs containing saturated fatty acids, which reduced the number of nucleation sites. Interesterification of the 90 10 blend increased the onset temperature. Quite possibly, the UUU TAGs present in the canola oil were restructured and now contained a saturated fatty acid (SUU), thereby increasing the number of nucleation sites. Although not examined, the crystallization rate would have probably been slower for the CIE blends than for NIE blends. 

The addition of Pr to iron-boron melts, Pr (Feo.gBo.2)i- t5 was observed to stabilize the glassy structure. At x=0.1 and J = 899K a maximum appeared in the crystallization onset temperature, measured at a heating rate of 20 K/min (Kabacoff et al., 1982). 

The determination of the crystallization temperature of a sample is subject to many of the same considerations that apply to melting temperature determination. The crystallization temperature is normally reported as the temperature at which the exothermic peak maximum occurs but may also be reported as the temperature at which crystallization begins (the crystallization onset temperature). The observed crystallization peak temperature is always considerably lower (20°C or more) than the melting temperature observed subsequently for the same sample. The difference between the observed crystallization and melting peak temperatures increases as the rate of temperature ramp increases. 

The effect of physical aging on the crystallization state and water vapor sorption behavior of amorphous non-solvated trehalose was studied [91]. It was found that annealing the amorphous substance at temperatures below the glass transition temperature caused nucleation in the sample that served to decrease the onset temperature of crystallization upon subsequent heating. Physical aging caused a decrease in the rate and extent of water vapor adsorption at low relative humidities, but water sorption could serve to remove the effects of physical aging due to a volume expansion that took place in conjunction with the adsorption process. 

Single crystals of the 2223 phase were grown from a 2 2 3 4 (Tl Ba Ca Cu) starting composition that was heated at 920°C for 3 h and cooled to 300°C at 5°C/min (56) according to magnetic measurements the Tc values varied from 127 to 116 K in different preparations, with 125 K as a typically observed onset temperature. 

Measure the temperatures for the following Tf, Tm,Tc, and Te, where T is the extrapolated onset temperature, Tm is the melting peak temperature, Tc is the crystallization peak temperature, and Te is the extrapolated end temperature. Report two Tm values if observed. 

Figure 20 shows the thermal traces of (a) nonirradiated and 500 kGy-irradiated PTFE powder and (b) the corresponding PTFE0kGy-EPDM and PTFE500kGy-EPDM composites. The crystallization peak of 500 kGy-irradiated PTFE powder shifts to a lower temperature of about 303.5°C. Also, the crystallization onset occurred at lower temperature and continued down to approximately 290°C. These distinct variations in 500 kGy-irradiated in comparison to nonirradiated PTFE powder is due to the E-beam treatment process, which caused degradation of 500 kGy-irradiated PTFE powder. The molecular weight decreases due to chain scission and leads to PTFE macromolecules of different chain lengths. As a result, the crystallization peak occurs at lower temperatures and the crystallization process continues until much lower temperatures in comparison to nonirradiated PTFE powder. 

Fig. 44. Temperature dependence of the critical field Her (see Kawano-Funikawa 2001) in dependence on the magnetic prehistory of an ErNi2B2C single crystal. ( ) Virgin curve, ( ) H (perpendicular to c) decreasing, (o) H increasing Tc — critical temperature, Tn — magnetic ordering temperature, Twfm — onset temperature...

Form I obtained at a supersaturation x, temperature y, and time z at which crystals were harvested after crystallization onset Form II obtained at supersaturation x, etc. 

Results of the Discriminant Analysis. For each of the two set-ups, the following parameters were used peak maximum, onset temperature, heat necessary to melt the unstable, P and p crystals (absolute and relative values). This leads to eight parameters per storage time, which, multiplied by four storage times (0, 1, 4, and 24 h after production), leads to 32 parameters per individual. However, some parameters failed the tolerance test. This means that for that parameter the variance within a group was too big compared to the variance between the groups. These parameters were left out because they would not increase the prediction quality. 

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