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Nuclear Science User Facilities 58 grains at 1000C Figure 1c. From Fig. 1c alone it is clear that the Si present inTi3SiC2 provides significant irradia- tion resistance compared to its binary counterpartTiC.TEM micrographs of theTi3AlC2 samples revealed stacking faults and possible dislocation loops at both 100 Figure 2a and 500C Figure 2b. More extensiveTEM work is necessary for these samples to collect high-resolutionTEM micrographs of the defect microstructures and confirm the presence of loops. Resistivity measurements were collected using a 4-pt probe technique while applying a constant current of 100 mA.Voltages were collected every 5 seconds for 10 minutes to reach steady state.The resistivity values show more than an order of magnitude increase after irradiation at 100C but epoxy to limit worker exposure and the resistivity jig was redesigned. During three-week trips in June and September Darin collected prelimi- naryTEM results Figures 1 and 2 and resistivity measurements Figure 3 forTi3SiC2 andTi3AlC2 from these three capsules.Ti3AlC2 irradiated at 1000C did not survive extraction and is absent from these results. FIB prep for these initial samples was poorly executed and Darin has since been improving on his techniques. TEM micrographs ofTi3SiC2 reveal 1 black spots within the basal plane at 100C Fig. 1a 2 dislocation arrays and stacking faults at 500C Fig 1b and 3 highly damaged preexisting TiC grains next to mostly cleanTi3SiC2 Figure 2. a Brightfield TEM image near the 11-20 zone axis of ATR-Ti3AlC2 sample irradiated to 0.1 dpa at 100C reveals basal dislocations throughout the sample some of which may possibly be short dislocation loops. b TEM micrograph of same sample irradiated to 0.1 dpa at 500C taken in 2 beam condition tilted away from the 11-20 zone axis shows dislocation arrays parallel to the basal planes as well as stacking faults. Several of the dislocations do not appear straight due to the tilt of the sample they are most likely curved within the basal planes. Further TEM investigation is needed to confirm the presence of dislocation loops or other irradiation induced defects within these materials. The MAX phases a class of machinable layered ternary carbides and nitrides have great promise for use in the next-generation of nuclear reactors. This is the first time the MAX phases have been neutron irradiated at temperatures as high as those carried out here.