Q Series DSCs

Modules 910,2910, and2920 The TA Instruments Q series DSCs evolved from their 910,2910, and 2920 modules. The DSC 910,2910, and 2920 cells use a thermoelectric heat leak made of constantan (a copper/nickel alloy) as noted in Hg. 2.2. The sample and reference pans sit on raised platforms or pods with the constantan disk at their base. The temperature sensors are disk-shaped chromel/constantan area thermocouples and chromel/alumel thermocouples. The thermocouple disk sensors sit on the underside of each platform. The AT output from the sample and reference thermocouples is fed into an amplifier to increase their signal strength. The heating block is made of silver for good thermal conductivity and also provides some reflectivity for any emissive heat. 

In most cases the AT=Ts T, is displayed as a function of block temperature Tbi, or temperature of the Tzero sensor for the Q series DSCs. Thus, when heating starts, the DSC signal (AT = Tj - T() will shift from zero (at the starting isothermal) to a steady state value of T, - T. This shift is proportional to the heating rate and the sample heat capacity. Essentially, this phenomenon is used to measure the heat capacity of the sample (see Section 2.6, on heat capacity). 

Q Series Modules The TA Instruments cell for the Q series DSC utilizes three thermocouples (see Fig. 2.2) and the associated Tzero technology... 

A.2. Other Calibrations In addition to the calibrations described above, special calibration procedures may exist in various commercial instruments, such as the Tzero calibration in the Q series DSCs of TA Instruments. The reader should consult the instruction manuals for understanding and carrying out these calibrations. 

An easy way to balance the intensity of the light beam is to use a carbon disk as both sample and reference and irradiate both cells simultaneously. The carbon disk is skipped in the TA Instruments Q-series DSC, where intensity... 

TABLE 2.14. Performance Characteristics of Q Series DSCs of TA Instruments... 

TABLE 2.15. Controlled Cooling Rates for Q Series DSCs of TA Instmments... 

The heat capacities of series of ammonium bromides ([(Ci)2C3HOC2N]Br, [(Cj)2C4HOC2N]Br, and [(Q)2QHOC2N]Br) were measured for the solid and liquid phase, and the difference in the solute heat capacity between the liquid and solid phase at the melting temperature, j has been determined by the DSC analysis [79]. Negative values of were observed for these... 

Here, q is called the Ozawa index. Corresponding to one-dimensional growth, q = 2 two-dimensional growth, q = 3 and three-dimensional growth, = 4. In practical measurements, one may determine the values of crystallinity XJa) at a constant temperature from a series of DSC crystallization curve with various cooling rates a, and then plot lg[—ln(l—X )] versus lg(a), to obtain the Ozawa index directly from the slope, as illustrated in Fig. 10.31a-c. 

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