Temperatur rise time

This measurement highlights two important features of the thermo-magnetic write scheme. First, excellent selectivity as only heated junctions can be magnetically written and second, that the temperature-rise time can be only a few nanoseconds. The use of extra heating layers in the junction... 

Fig. 4.7.1. Temperature-time profile of a Pyroprobe instrument A ideal pyrolysis with the ribbon probe B coil probe with quartz boat and 200°C interface temperature. Explanation of terms Py-T pyrolysis temperature Py-t pyrolysis time T rise t temperature-rise time...

Flash pyrolysis A pyrolysis that is carried out with a fast temperature rise time (to a constant final temperature). 

Temperature rise time (TRT) The time required for a pyrolyser to go from its initial temperature to the final temperature. 

Once a Teq is chosen, a second problem must be solved. A given elevated temperature cannot be reached instantly even for a small mass of material. It always requires a short interval of time. This interval is referred to as temperature rise time (TRT). Pyrolysis units capable of generating isothermal conditions in a very short TRT (flash pyrolysis) are commonly available. 

During the temperature rise time (TRT), the kinetic constant k will vary. Assuming a linear temperature increase with the rate q and starting at To, the temperature is given at a certain moment t by the formula ... 

The yield of different pyrolysis products depends on the cellulose quality such as the average value for DP. the proportion of low molecular weight polymer, crystallinity, as well as the water content and the acidity of the sample. The experimental conditions influencing the chemistry of the pyrolysate include the equilibrium temperature Teq, temperature rise time (TRT), total heating time (THT) (see Section 4.1), and pyrolysis experimental setup [25,26]. A variation in pyrolysis products depending on cellulose type is exemplified in Table 7.2.1. This table gives the yield of gases, tar, char, and water for two commercially available celluloses [13]. 

Another parameter selected for analytical pyrolysis experiments is the temperature rise time (TRT). This parameter measures the time necessary for the heating element of the pyrolyzer to reach Teq. The goal in flash pyrolysis is to have a very short TRT, such that the decomposition of the sample takes place, virtually, in isothermal conditions. 

Temperature rise time TRT and total heating time THT... 

ECAE processing was done according to the specifications given in Table 2. Refer to Table 1 for clarification of ECAE route descriptions. In all cases, ECAE processing was done at slow speed in order to minimize the heat of deformation and associated temperature rise. Time-temperature data were recorded for the Zr-based materials by type K thermocouples embedded in the front and back regions of the extrusion cans. 

Heating should be instantaneous to prevent drawn out transfer of the pyrolyzates through the injection port. Heated filament and Curie-point pyrolysis result in less secondary pyrolysis products compared to furnace pyrolysis. Curie-point pyrolyzers accurately reproduce pyrolysis conditions with a rapid temperature rise time, yet the choice of different pyrolysis temperatures is limited. Very little sample preparation or pretreatment is required for laser pyrolysis however, a specific laser wavelength may not be appropriate for aU types of samples. 

Mean equivalence ratio Time at 50% temperature rise Time at 95% temperature rise Combustion duration Ignition delay of hot flame Collision frequency... 

The system applied in the study mentioned above consisted of a CDS model 122 Pyroprobe with a ribbon filament as the heating surface (see Chapter 3 and Appendix 1). This pyrolyser heats by varying the resistance of the platinum element. Temperature rise times for flash pyrolysis are typically of the order of milliseconds. IR spectra were obtained with an FT-IR bench system equipped with a CDS pyrolysis/FT-IR interface. The data were collected at 8 cm" with a deuterated triglycine sulfate (DTGS) detector. The interface is cylindrical in shape with two potassium bromide windows for the IR beam to pass through. 

Solid samples are either dissolved or introduced by means of solid-injection syringes. Care must be taken to introduce the sample for pyrolysis into the furnace without admitting air, since the pyrolysis zone is already hot and degradation starts immediately. The pyrolysis products are then swept into the analytical device by the carrier gas [508]. In furnace pyrolysis problems include long temperature rise times and lack of control over the duration of the pyrolysis. 

The nature and distribution of pyrolysis products from a particular sample critically depend largely on the pyrolysis temperature and the specific set of pyrolysis conditions (i.e. temperature rise time, sample size, pyrolyser geometry). Laser pyrolysers are practically the only type of radiative heating pyrolyser with certain applicability. A laser pyrolyser consists of five components (i) laser (ii) fibre optics (Hi) probe for sample introduction (iv) pyrolyser body, containing the pyrolysis chamber and (v) heater of the pyrolysis chamber with dedicated control unit. The laser beam can be focused onto a small spot of a sample to deliver the radiative energy. This provides a special way to pyrolyse only a small portion of a sample. Only the sample itself is... 

Table 3.28 lists the main features of laser pyrolysis techniques. Laser pyrolysis is characterised by rapid non-linear heating, and a large AT. Temperature rise times and cooling times are very short, usually in the range of 100 to 300 /us [360], and quite different from conventional pyrolysis cfr. Ta-... 

Very short temperature rise times/cooling times... 

Time-resolved LIBS Time-resolved ESR Temperature-rise time Total-reflection X-ray fluorescence (c/r. TXRF)... 

TRT Temperature-rise time diffusivity (5) Attenuation (ultrasonics) ... 

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