Melt crystallization pulsed crystallizers

One of the early column crystallizers was that iatroduced for the separation of xylene isomers (see Xylene and Ethylbenzene). In this unit, shown schematically ia Eigure 25, -xylene crystals are formed ia a scraped-surface chiller above the column and fed to the column. The crystals move downward counter-currenfly to impure Hquid ia the upper portion of the column and melted -xylene ia the lower part of the column. Impure Hquor is withdrawn from an appropriate poiat near the top of the column of crystals while pure product, xylene, is removed from the bottom of the column. The pulse unit drives melt up the column as reflux and iato a product receiver. 

The laser system consisted of a home-built Ti sapphire fs laser oscillator and regenerative amplifier (RGA). The pulse duration was 50 fs at 800 nm and 1 kHz repetition rate. The output of the RGA was split into two parts. One part was used as pump pulse. The other part served as a source for the generation of probe pulses with the help of a non-collinear optical parametric amplifier (NOPA, Clark). The sample preparation was explained elsewhere [7]. Briefly, sodium (Alfa Aesar) was used as received and sodium bromide (Alfa Aesar) was dried and re-crystallized under vacuum. The preparation of the samples was carried out in a glovebox under argon atmosphere. Localized electrons were generated by heating the metal-salt mixture to 800 °C, i.e. well above the melting point of the salt. 

Using laser-induced X-ray pulses from solid targets, ultrafast time-resolved X-ray diffraction experiments have been performed extensively and new phenomena such as ultrafast melting have been demonstrated [26,27]. In the present study, in order to demonstrate the practical capabilities of the X-rays thus produced, the pulse X-ray diffraction obtained from a Si crystal with this source is examined [28]. 

Tc 600°C), at which crystallization occurs. The released latent heat raises the local temperature further, and thermal conduction maintains self-sustaining explosive transformation until the crystallization front has propagated down the thermal gradient to a point below Tc. Pulsed electron beam heating experiments indicate that a-Si melts at 1170°K (Baeri et al., 1980). 

If the fat is cooled to some point below the melting point of the highest melting component and allowed to fully equilibrate (crystalhze to the maximum extent in the most stable polymorph), there will be some ratio of sohd to liquid fat dependent on the nature of the TAG mixture in the natural fat. This solid fat content (SFC) is often measured by a pulsed nuclear magnetic resonance (NMR) technique. A plot of the maximum amount of fat crystallized (SFC) at sequentially higher temperatures... 

The only heat capacity study for the 6-crystal is that of Cezairliyand McClure (1 ). Using a pulse heating technique, they studied the heat capacity of a sample containing 3.12% (wt) Zr in the range 2054 to 2400 K. These results were corrected by Cezairliyan and McClure (JL) to represent pure B-Hf and are extrapolated linearly to the melting point, 2500 K, and to 298.15 K. The entropy at 298.15 is calculated in a manner similar to that for the enthalpy of formation. 

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