Subjects: Physics >> Nuclear Physics submitted time 2024-03-18
Abstract： By including octupole correlations in the Nilsson potential, the ground-state rotational bands in the
reflection-asymmetric (RA) nuclei are investigated by using the cranked shell model (CSM) with the monopole and
quadrupole pairing correlations treated by a particle-number-conserving (PNC) method. The experimental kinematic
moments of inertia (MoIs) of alternating-parity bands in the even-even nuclei 236,238U and 238,240Pu, and parity-doublet
bands in the odd-𝐴 nuclei 237U and 239Pu are well reproduced by the PNC-CSM calculations. Compared to the neighboring even-even nuclei 236,238U and 238,240Pu, 50% ∼ 60% increase of 𝐽(1) can be seen for the intrinsic 𝑠 = −𝑖 bands in 237U
and 239Pu. Those mainly attribute to the pairing reduction due to the Pauli blocking of the unpaired neutron occupying
the neutron orbitals near the Fermi surface. The gradual increase of 𝐽(1) versus rotational frequency can be explained
by the pairing reduction due to the rotation. The present calculation shows that the MoIs of the reflection-asymmetric
nuclei are higher than those of the reflection-symmetric (RS) nuclei at the low rotational frequency. Furthermore, compared with the RS nuclei, the pairing reduction of the RA nuclei increase when a larger octupole deformation 𝜀3 is
included in the calculation.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： The effect of grain size on the susceptibility to intergranular corrosion of 316LN stainless steel was investigated by means of electrochemical potentiokinetic reactivation test and electronic work function measurement, as well as microstructure characterization. Steel samples of various grain sizes were produced by heat treating the steel at 1100 ℃ for different duration. The result showed that the degree of sensitization decreases with increasing grain size; corrosion pits occur at grain boundaries and thereby form a network-like pits-chain for samples of fine grains. In the contrast, no obvious corrosion occurred on samples of coarse grain. The results of electronic work function measurement imply that the surface electronic density of states and charge density distributions for steel of coarse grains are much stable than that of fine grains.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： The corrosion behavior of 2A12-T4 Al-alloy in salt-spray environment was studied by means of mass loss method, electrochemical test, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that the relationship between the corrosion induced mass loss and corrosion time was in accordance with power rule. At the initial corrosion stage, pitting corrosion occurred under the action of Cl-, then pitting corrosion turned to be overall corrosion, and the scale of corrosion products composed of Al(OH)3 was loose and thickened with time. During the middle and later corrosion stages, the outer portion of corrosion product spalled off, while the residual portion of corrosion product scale became compact. With the increasing corrosion time, Icorr decreased firstly, then increased and finally decreased again. In the meantime, capacitive reactance arc shrunk firstly, then expanded, and finally shrunk slightly.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Surface aluminized layer was prepared on a Ti2AlNb alloy by double- glow discharge plasma surface technique. The kinetic data of oxidation mass gain were measured for the alloys with and without aluminized layer at 650, 750 and 850 ℃ respectively, and the oxidation rate constants at different temperatures were determined by the relevant linear fitting. The microstructure and phase composition of the formed oxide scale were analyzed by XRD and SEM. It was found that aluminized layer consisted of compact deposited layer and Al-Ti-Nb diffusion layer. At each temperature, the aluminized alloy exhibited parabolic oxidation kinetics and the oxidation rate constant was lower than that of the blank ones. The aluminized layer significantly improved oxidation resistance of Ti2AlNb alloy due to the formation of a dense and continuous Al2O3-rich scale. The inter-diffusion layer provided protection for the substrate from high temperature oxidation and intergranular embrittlement.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： FEM calculation for the preparation process of SiC fiber and SiC/Ti-6Al-4V composite was carried out to investigate the effect of different processing parameters on the residual stress of the SiC fiber as well as the densification behavior and residual stress of the composite. The results show that, for the fabrication process of fibers, the axial thermal stress of the WC layer decreases with the decrease of deposition temperature and thickness of C layer. For the densification of composites, HIP temperature and sheath thickness have greater impact on the density, but HIP time and fiber volume fraction have smaller impact; with the increasing HIP temperature and decreasing sheath thickness, the density of the composite could be enhanced; the radial residual stress on the matrix greatly increases with the increase of HIP temperature and fiber volume fraction and decrease of sheath thickness appropriately; the hoop residual stress on the matrix greatly decreases with the increase of HIP temperature and sheath thickness, while decrease of HIP time appropriately. Finally the following processing parameters were recommended for preparation of SiC/Ti-6Al-4V composite with good quality: HIP temperature 950-960℃, HIP time 9 h and sheath thickness 70-80 mm and fiber volume fraction 45%-50%. FEM calculation results show some differences with those measured in the experiment for the residual stress of the composite, but with similar variation tendency.
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