The oxidation and decarburization behavior of 14.55 wt pct Cr-cast iron at 1273 K to 1423 K (1000 °C to 1150 °C) in a dry air atmosphere was studied. A gravimetric investigation showed that intensive ...oxidation of cast iron takes place at temperatures above 1273 K (1000 °C). It is found that oxidizing heating is accompanied by decarburization, which manifests itself in secondary and eutectic carbide dissolution. The volume fraction of carbides decreases with temperature and holding duration increasing. Decarburization results in the formation of a decarburized layer up to 4 mm in depth. A carbide-free layer in depth up to 100 μm appears in the free surface after 6 to 8 hours holding at 1373 K to 1423 K (1100 °C to 1150 °C). Preliminary activation energy calculations suggested that the eutectic carbide dissolution at the depths of 50 to 400 μm is controlled by carbon diffusion in austenite. The dissolution of eutectic carbides involves a capillarity-induced mechanism, which consists of formation and growth of capillary cavities inside carbides.
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This ...mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ̃ confidence level, using a low-background, 14.6-kilogram CsINa scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
P-type point contact (PPC) HPGe detectors are a leading technology for rare event searches due to their excellent energy resolution, low thresholds, and multi-site event rejection capabilities. We ...have characterized a PPC detector’s response to
α
particles incident on the sensitive passivated and p
+
surfaces, a previously poorly-understood source of background. The detector studied is identical to those in the
Majorana
Demonstrator
experiment, a search for neutrinoless double-beta decay (
0
ν
β
β
) in
76
Ge.
α
decays on most of the passivated surface exhibit significant energy loss due to charge trapping, with waveforms exhibiting a delayed charge recovery (DCR) signature caused by the slow collection of a fraction of the trapped charge. The DCR is found to be complementary to existing methods of
α
identification, reliably identifying
α
background events on the passivated surface of the detector. We demonstrate effective rejection of all surface
α
events (to within statistical uncertainty) with a loss of only 0.2% of bulk events by combining the DCR discriminator with previously-used methods. The DCR discriminator has been used to reduce the background rate in the
0
ν
β
β
region of interest window by an order of magnitude in the
Majorana
Demonstrator
and will be used in the upcoming LEGEND-200 experiment.
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