Treatment temperature

Above the solution treatment temperature (ca 1250°C), the alloy is single phase with a bcc crystal stmcture. During cooling to ca 750—850°C, the sohd solution decomposes spinodally into two other bcc phases a and lattice parameter composition. The matrix a-phase is rich in Ni and Al and weakly magnetic as compared with which is rich in Fe and Co. The a -phase tends to be rod-like in the (100) dkection and ca 10 nm in diameter and ca 100 nm long. As the temperature is decreased, segregation of the elements becomes mote pronounced and the difference between the saturation polarizations of the two phases increases. 

Other Continuous Processes. Various pasteurization heat treatments ate identified by names such as quick time, vacuum treatment (vacreator), modified tubular (Roswell), small-diameter tube (MaHotizer), and steam injection. The last three methods are ultrahigh temperature (UHT) processes (see Fig. 3). Higher treatment temperatures with shorter times, approaching two seconds, are preferred because the product has to be cooled quickly to prevent deleterious heat effects. 

Temperature Range" refers to the range of operating temperatures, heat treatment temperatures, or temperatures developed in welding which can produce the type of embrittlement shown. 

Fig. 13. Increase in stack width parameter, L with heat treatment temperature, HTT, for some graphitising cokes, [Adapted from 1 12],...

Recently, Dinwiddie et al. [14] reported the effects of short-time, high-temperatme exposures on the temperature dependence of the thermal conductivity of CBCF. Samples were exposed to temperatures ranging from 2673 to 3273 K, for periods of 10, 15, and 20 seconds, to examine the time dependent effects of graphitization on thermal conductivity measured over the temperature range from 673 to 2373 K. Typical experimental data are shown in Figs. 7 and 8 for exposure times of 10 and 20 seconds, respectively. The thermal conductivity was observed to increase with both heat treatment temperature and exposure time. 

Z varies from -0.23 to - 0.64 over the heat treatment temperature range 2673 to 3273 K, and the term (e +Z) in Eq. (5) therefore varies from 0 to -0.4 over the same temperature range. Equation (6) was then substituted back into eq. (5) which was used to refit the data to determine the relationship between X and the heat treatment conditions (time and temperature, Eqs. 7 and 8). The empirical parameter X in Eq. (5) was found to be given by... 

Figures 7 and 8 show thermal conductivity data for CBCF after exposure to temperatures of 2673, 2873, 3073, and 3273 K, for 5.7 and 15 7 seconds, respectively. The symbols in the Figs. 7 and 8 represent measured thermal conductivity values, and the solid lines are the predicted behavior from Eqs. (5) through (8) The model clearly accounts for the effects of measurement temperature, exposure tune, and exposure temperature The fit to the data is good (typically within 10%). However, the fit to the as fabricated CBCF data (Fig 6) was less good (-20%), although the scatter in the data was larger because of the much lower heat treatment temperature (1873 K) in that case.

Fig. 2. The master graph of reversible capacity for lithium plotted versus heat treatment temperature for a variety of carbon samples. The three regions of commereial relevance are marked. Solid symbols are data for soft carbons, open symbols are data for hard carbons.

Graphitic carbon normally refers to soft carbon heated above about 2100°C. The probability of finding turbostratie disorder begins to decrease as the heat-treatment temperature increases to above 2100°C. When the heating temperature reaehes above 3000°C, graphite forms. Coneeptually, graphite is a graphitic carbon with no or very little turbostratic disorder. 

P decreases as the heat-treatment temperature increases above 2200°C. The parameters which describe the size of the crj stallite, and L, also increase with the heat-treatment temperature. The capacity parameter in Table 1 will be described and carefully discussed later in this chapter. 

Fig. 15. The H/C atomic ratio versus heat-treatment temperature for samples as indicated...

Austenitic steels of the 304S15 type are normally heat treated at 1 050°C and cooled at a fairly rapid rate to remove the effects of cold or hot working, and in this state much of the carbon is in supersaturated solid solution. Reheating to temperatures below the solution treatment temperature leads to the formation of chromium-rich MjjCj precipitates predominantly at the grain boundaries with the production of chromium gradients and reduced corrosion resistance as is the case with the martensitic steels. Any attack is... 

Al-Mg-Si alloys are strengthened by precipitation hardening in which MgjSi is formed. They are not very susceptible to stress-corrosion cracking which only occurs in specimens subjected to a high solution-treatment temperature followed by a slow quench Ageing such material eliminates susceptibility . 

Different procedures for the precipitation, washing and thermal treatment of hydroxides result in different fluorine contamination levels in the final products - tantalum and niobium oxides. Laboratory and industrial experience confirms some correlation between the initial concentration of fluorine in the dried hydroxides and the fluorine content in the final oxides obtained after appropriate thermal treatment. For instance, it is reported in [499] that if the initial concentration of fluorine in niobium hydroxide equals A%, then the fluorine content in the final niobium oxide can be estimated according to the thermal treatment temperature as follows ... 

Figure 27. Relation of Mn02 heat treatment temperature and residual capacity ratio after 11 months at 60 °C.

Figure 28 shows the discharge characteristics at a current density of 1.2 mA cm-2 of electrolytic MnOz heat-treated at various temperatures. From the characteristics shown, it may be concluded that the optimum heat-treatment temperature range for stable discharge is between 375 and 400 °C, which agrees with the data of Fig. 27. 

The crystallinity of artificial graphite can generally be controlled by the heat-treatment temperature, but it is lower than that of natural graphite. The Lc of artificial graphite is less than 1000 A and the d value is more than 3.36 A. 

Polyacene is classified as a material which does not belong to either soft or hard carbons [84], It is also made by heat-treatment of phenol resin. As the heat-treatment temperature is lower than about 1000 °C, polyacene contains hydrogen and oxygen atoms. It has a conjugated plane into which lithium ions are doped. It was reported that the discharge capacity of polyacene is more than 1000 mAhg. However, there are no practical lithium-ion batteries using polyacene. 

Depending on the precursor and the heat-treatment temperature, the carbonaceous materials discussed so far contain heteroatoms in addition to the prevailing carbon atoms. Even highly crystalline graphite is saturated with heteroatoms at dislocations in the crystallites and at the edges... 

Fig. 15. Microhardness of lamellar PE with different crystallinities as a function of chlorosulfona-tion time. The effect of treatment temperature on the hardening level reached is shown 22)...

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