High temperature behavior testing

Two different thermal methods were used for the analysis of the high-temperature behavior of the various ash san5>Ies, i.e., simultaneous DTA/TGA using a NETSCH STA 429 friermal analysis instrument, and sintering tests performed in a simple muffle furnace, both in combination with a SEM/EDX technique for the elemental analysis of the thermally treated ash samples, using a JEOL 6300 scaiming microscope. 

S. Ueta, J. Sumita, K. Emori, M. Takahashi, K. Sawa, Fuel and fission gas behavior during rise-to-power test of the High Temperature Engineering Test Reactor (HTTR) , J. Nucl. Sci. Technol., 40[9], 679, (2003). 

The effects of temperature on the aging behavior of polymeric materials became especially clear when materials for the interior equipment of motor vehicles were tested. Since these are often exposed to solar radiation at high temperatures, the test conditions for artificial weathering must be selected accordingly. A specific black panel temperature is set in the weathering devices. 

Figure 3.1-126 shows some typical results of stress rupture tests characterising the time-dependent high temperature behavior dominated by creep deformation. A compilation of creep data may be found in [1.101]. 

The high temperature behavior of the polyimide separator is also demonstrated in Fig. 11.10 with shrinkage test. The polyimide separator and the polyolefin based separators were exposed to 110 and 150°C for 3 h. The polyimide separators maintained their dimensional stability, while the polyolefin-based separators demonstrated higher shrinkage and poor high temperature stability. 

Mechanical strength of the assemblies was first tested on X10CrMoVNb9-l (Fig. 10.36) non-ODS martensitic steel welds (this steel presents a similar behavior under welding as 9% Cr ODS steel). Internal pressure burst tests were carried out at room temperature and showed a good mechanical strength of the welded joints (failure occurring each time out of the weld zones). The same tests are about to be done on ODS steel welds and some high-temperature mechanical tests will also be performed. 

In the present study, a current-activated pressure-assisted densification method was used to fabricate a dense zirconia - spinel ceramic. High temperature mechanical testing as well as microstructural examinations were conducted to investigate the deformation behavior of the nanocomposite produced by this method. 

A good summary of the behavior of steels in high temperature steam is available (45). Calculated scale thickness for 10 years of exposure of ferritic steels in 593°C and 13.8 MPa (2000 psi) superheated steam is about 0.64 mm for 5 Cr—0.5 Mo steels, and 1 mm for 2.25 Cr—1 Mo steels. Steam pressure does not seem to have much influence. The steels form duplex layer scales of a uniform thickness. Scales on austenitic steels in the same test also form two layers but were irregular. Generally, the higher the alloy content, the thinner the oxide scale. Excessively thick oxide scale can exfoHate and be prone to under-the-scale concentration of corrodents and corrosion. ExfoHated scale can cause soHd particle erosion of the downstream equipment and clogging. Thick scale on boiler tubes impairs heat transfer and causes an increase in metal temperature. 

At high temperature, the behavior is different. A stmcture designed according to the principles employed for room temperature service continues to deform with time after load apphcation, even though the design data may have been based on tension tests at the temperature of interest. This deformation with time is called creep because the design stresses at which it was first recognized occurred at a relatively low rate. 

These findings clearly illustrate how the results of so-called "accelerated-aging" tests can be affected by the high temperatures in ordinary xenon- and carbon-arc equipment and can, therefore, lead to erroneous conclusions regarding the photochemical behavior of materials at near-normal temperatures (23). 

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