Subject thermal treatment time

Experiments with CPGs subjected to progressive thermal treatment leading to partial dehydroxylation of the surface and its enrichment in boron atoms showed specific adsorption properties of these materials differentiating them from silica gels [30,31,73]. It was found that depending on the type of adsorbate two trends in the adsorption behaviour of heated CPG can be observed [30,31]. The increase of thermal treatment time leads to the increase of CPG adsorption properties in relation to water, chloroform or hexane [30] (e.g. see Fig. 13). 

We heated the substrate of zinc oxide containing 10 cm 2 of silver atoms (in this case there was already no emission after completion of deposition) at 300 C. Such thermal treatment results in formation of microcrystals, rather than evaporation adatoms on the surface of the substrate made of zinc oxide. In paper [34] it was shown that microcrystals with diameter 100 A deposited on the zinc oxide surface are acceptors of electrons, therefore the formation of microcrystals results in increase of resistivity of a sensor substrate above the initial value (prior to silver deposition). In this case the initial value of the resistance of sensor-substrate was 2.1 MOhm, after adsorption of silver atoms it became 700 kOhm, and as a result of heating at 300°C and formation of microcrystals - acceptors of electrons it in increased up to 12 MOhm. If such a substrate is subject to deposition of 3-10 5 cjjj-2 silver again, then emission of silver atoms gets detected. From the change of resistivity of sensor-detector due to deposition of silver atoms one can conclude that in this case the emission of atoms is 4 times as low than in experiment with pure substrate made of zinc oxide, which confirms the supposition made on the mechanism of emission of adatoms. 

A physical approach was also applied to reduce the allergenicity of psyllium and psyllium-containing food products (Wullschleger, 1993). Psyllium was subjected to a thermal treatment imder certain pressure and moisture content for a predetermined time period to destroy the allergenic proteins. The preferred treatment conditions included a temperature of 245-265 °F, pressure range of 14—20 psi, and a time period between 55 and 75 min. This procedure may eliminate up to 100% of the allergenicity of psyllium. 

Unlike MOE, there does not appear to be any increase in MOR when wood is subjected to thermal treatment, even for short time periods (Figure 5.7). This is because MOR is actually the equivalent stress in fibres at the point of failure and, as such, is related to the ultimate bending strength of the wood (Dinwoodie, 2000). 

Precursor Techniques A homogeneous sample containing all of the non-volatile constituents is prepared first. Stoichiometry is easily maintained in the precursor and reasonable reaction times and temperatures can be employed. Generally, the precursor will be a mixture of phases, however. Then, the precursor and volatile constituents are formed into an intimate mixture and are subjected to a brief thermal treatment to form the desired phase. 

Thus, the catalytic cracking of PET has been recently a subject of interest [26], Several acid solids (zeolites 4A and 13X and alumina) as well as metal salts (CuCh, MgCE and Zn, Sn, Mg, Mn acetates) have been tested as catalysts at 400-500°C. Copper chloride has been found as the most effective catalyst, reducing the degradation time by almost 3.5 times in regard to the thermal treatment and minimizing the amount of carbonaceous residues. 

The solubility of the powdered MgO in molten KC1 was 140-420 times as high as that for the oxide which had been subjected to pressing and preliminary thermal treatment. This was explained by the formation of suspensions in the solutions contacting with the powdered oxide. The slope of the dependence of the solubility of MgO pressed in pills, against the inverse temperature, is three times as large as that for the powdered oxide, in molten... 

The same results were obtained by Ghorab and Kisher [158]. Also Sylla [159] found the reduction of ettringite content in cement pastes after 3 h of thermal treatment at temperature of 60 °C this phase disappears almost entirely after this period when the temperature of curing rises to 80 °C. The same results were found by Odler et al. [160]. It found also good relation with the composition of solution, which in the pastes subjected to thermal treatment at temperature of 90 °C have a diSerent sulphate ions concentration (Fig. 6.38). The concentration of these ions is maintained on the high level after 28 days of paste matured in water and is quicker reduced after this period [151]. However, even after 90 days it is four times higher than in the paste cured all the time in water at ambient temperature. 

Fig. 6.38 Composition of the liquid phase in Portland cement paste subjected to thermal treatment at 90 °C and then cured in water at 20 °C, plotted as afunetion of time. (According to [151])...

The adhesion of specimens subjected to environmental exposure tests was evaluated prior to and subsequent to the contact. Wet thermal shock testing consisted of five cycles each for IS minutes in boiling water and 2 minutes in ice water. The maximum transfer time between the two baths was 30 seconds. Thermal and temperature/humidity exposures were performed in controlled atmosphere chambers for 200 hours. Simulated solder tests comprised immersing the test. specimen in a silicone oil followed by solder flotation. The solder temperature varied from 232 to 288 C and the contact time was S or 10 seconds. In some cases, two flotations were performed on the same sample. The effect of a heat treatment at 135 C prior to solder testing was examined the heat treatment time varied from 0 to 16 hours. ... 

The repeat unit of the PET molecule, the product of a condensation reaetion of terephthalic acid and ethylene glycol, was shown in Fig. 2.3 and is repeated here in Fig. 5.20. For their study, Illers and Breuer chose a commercial product with no detectable initial crystallinity, and removed all traces of residual stress as well as any previously existing water by appropriate prolonged thermal treatments above the glass-transition temperature of 67 °C. Different levels of crystallinity in samples were then obtained by nine separate isothermal crystallization protocols at temperatures ranging from 70 to 245 °C for pre-selected times until equilibrium crystallinities ranging from 0 to 46% were achieved in each case. Only samples subjected to temperatures above 86 °C showed X-ray evidence of crystallinity. 

Gas chromatography was a,lso, applied to polybutene-1 [189] which after cooling from the melt, turns into an vmstable crystalline state modification II with = 120° this passes in time into a stable modification I with Tm = 130°C [190, 191]. Because the difference between the density of the two crystalline forms is significant it was found that it increases in time but X-ray diffraction studies show no modification of crystallinity [190]. Gas chromatography allows the determination of the proportion of crystalline phase in both modifications. The column loaded with stationary phase was subjected to a ballistic thermal treatment starting from temperatures higher than Tm and then maintained at room temperature for several weeks. Eetention data were determitted for... 

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