Cooling speed

Bonding temp. Holding time Heating speed Cooling speed Load Vacum... 

The growing of crystals is determined by the diffusion of molecules to the surface of the nucleus, the finding of a proper place, and the distribution of the freed energy to the surroundings. Under normal conditions (cooling speed vf < 102 °C/s and subcooling T. < 10 °C) Eq. (8) can be used ... 

Talsma shows that peak 2 changes only from -39.8 °C to —40.4 °C (liposomes, liposomes concentration, buffer and cooling speed as in (I), but no mannitol) if the liposomes size is decreased from 0.87 pm to 0.14 pm. With small liposomes, the start of the homogeneous crystallization is delayed. This can also be deduced from the weakly performed crystallization (Fig. 3.19 (d), peak 3), if mannitol is only within the liposome. 

Tg is the so-called glass temperature and this varies according to the cooling speed. Ts (Tolid) is the temperature at which the solid is formed. 

A decrease in thermal diffusivity, with increasing temperature, is also observed in semicrystalline thermoplastics. These materials show a minimum at the melting temperature as demonstrated in Fig. 2.18 [24] for a selected number of semi-crystalline thermoplastics. It has also been observed that the thermal diffusivity increases with increasing degree of crystallinity and that it depends on the rate of crystalline growth, hence, on the cooling speed. 

Fig, 2. Keroplast crystallization kinetics ( p = 0.3 (vol.) share) at cooling speed 20.0°C/min. Points-experimental values curve — calculations results [13]... 

Table 3 shows the average cooling speed for different freezing methods. 

Figure 1 Freezing process. Above Vials with product are cooled together with the shelves, cooling speed approx. 0.6°C/min. Below Vials with product are loaded on precooled shelves at -50°C, cooling speed approx. l°C/min. Subcooling is more pronounced. 7, 7pr measured by Th 8, measured with RTD 9, temperatures by RTD are 5-7°C higher than by Th. [From H. Willemer, Measurements of temperature, ice evaporation rates and residual moisture content in freeze-drying. Dev. Biol. Standard. 74 123-136 (1992).]...

The cooling speed during the crystallization is much smaller than the average speed and varies with the thickness of the product much more than the average value. 

Time from Cooling Time from Cooling Cooling speed... 

Figure lOa-e tries to give an impression of the accuracy of such measurements of the freezing speed, summarized in Table 3. From the data of Table 3 one can draw the conclusion that freezing and cooling speeds can be measured, and corrections for variations in AT" calculated with an average error of 10-15% if some experimental data are available as per example... 

Table 3 Comparison of Cooling Speeds Measured in the Same Installation with Comparable Vials...

The study of hydrate and ice formation in gas saturated samples was carried out under conditions of cyclic temperature changes. At the beginning the temperature in a sample was lowered from room to low positive values ( +l +3 C) (cooling speed about 0.02 C/min), causing a hydrate accumulation in the pore space of soil, detected by a sharp pressure drop in the pressure chamber. Then, after the hydrate accumulation process, the chamber with the sample was cooled to sub-zero temperatures (-7 -8 C). In this step the... 

Thermal cycle resistance of Tic, TiC-Mo andTiC/Mo FGM coatings were investigated by the thermal cycling test of temperature range between room temperature and 1223K in 5 times ( heating, cooling speeds were 100 K/s ) in air. ... 

A CPC 600 calorimeter (15) has been used with heating or cooling speeds between 0.5 and 4°/mn. Acid Nafions 120 containing different water percentages have been studied. 

The influence of the cooling speed is shown in fig. 8 for the same sample run at a constant heating speed of 2°C/mn. No change is observed between samples quenched in liquid nitrogen or rapidly cooled with He gas. In this case some exothermic contribution is apparent. 

Figure 8. Influence of the cooling speed on the same specimen as in Figure 7. Cooling speeds 1 °/mn ----, He gas -------, liquid nitrogen quenching.

Formation of crystalline cyclohepta-amylose inclusion complexes has been followed by recording continuously the turbidity of the aqueous solution of cyclohepta-amylose and the guest molecule (solvent, drug, or aromatic compound) from 60 C downwards. The concentrations of the guest molecules were such that they could not form crystals above the crystallization temperature of pure cyclohepta-amylose. The appearance of turbidity caused by crystal formation before the characteristic temperature of cyclohepta-amylose crystallization is therefore considered to be evidence for inclusion complex formation. The influence of parameters such as concentration, pH, cooling speed, presence of inorganic salts, and inoculating crystals was studied. 

It was decided to try to keep the skelp in the furnace overnight at 1550 F (843 C) to save the rethreading time. At 2345 hr, the fuel was shut off, but the air for combustion was increased to maximum flow to increase the cooling speed of the skelp and furnace. With the very high velocity air flowing over the skelp, it scaled so rapidly that it disappeared within a minute—oxidized by the high velocity air. 

The second basic structural constituent of carbon steel, cementite (iron carbide, FesC), has completely different properties in contrast to ferrite. It is hard and brittle and thus cannot be cut. Cementite can occur either by itself or as a structural constituent of perlite or bainite, depending on carbon content and cooling speed. 

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