Due to the large thermal neutron absorption cross section of ¹⁰B, B₄C-Al composites have been used as neutron absorbing materials in nuclear industries, which can offer not only good neutron shielding performance but also excellent mechanical properties. The distribution of B₄C particles affects the mechanical performance and efficiency of the thermal neutron absorption of the composite materials. In this study, 15 wt % B₄C-Al and 20 wt % B₄C-Al composites were prepared using a powder metallurgy process, i.e., ball milling followed by pressing, sintering, hot-extrusion, and hot-rolling. The yield and tensile strengths of the composites were markedly increased with an increase in the milling energy and the percentages of B₄C particles. Microstructure analysis and neutron radiography revealed that the high-energy ball milling induced the homogeneous distribution of B₄C particles in the Al matrix and good bonding between the Al matrix and the B₄C particles. The load transfer ability and mechanical properties of the composites were consequently improved. The results showed the high-energy ball milling process is an appropriate fabrication procedure to prevent the agglomeration of the reinforcement particles even if the matrix to reinforcement particle size ratio was nearly 10.

Ab initio calculations based on the density functional theory have been performed to investigate the migrations of hydrogen(H) and helium(He) atoms in β-phase scandium(Sc),yttrium(Y),and erbium(Er) hydrides with three different ratios of H to metal.The results show that the migration mechanisms of H and He atoms mainly depend on the crystal structures of hydrides,but their energy barriers are affected by the host-lattice in metal hydrides.The formation energies of octahedral-occupancy H(H oct) and tetrahedral vacancy(V tet) pairs are almost the same(about 1.2 eV).It is of interest to note that the migration barriers of H increase with increasing host-lattice atomic number.In addition,the results show that the favorable migration mechanism of He depends slightly on the V tet in the Sc hydride,but strongly on that in the Y and Er hydrides,which may account for different behaviours of initial He release from ScT2 and ErT2.

The fast and in-line multigas detection is critical for a variety of industrial applications. In the present work, we demonstrate the utility of multiple-pass-enhanced Raman spectroscopy as a unique tool for sensitive industrial multigas detection. Instead of using spherical mirrors, D-shaped mirrors are chosen as cavity mirrors in our design, and 26 total passes are achieved in a simple and compact multiple-pass optical system. Due to the large number of passes achieved inside the multiple-pass cavity, experiments with ambient air show that the noise equivalent detection limit (3σ) of 7.6 Pa (N₂), 8.4 Pa (O₂) and 2.8 Pa (H₂O), which correspond to relative abundance by volume at 1 bar total pressure of 76 ppm, 84 ppm and 28 ppm, can be achieved in one second with a 1.5 W red laser. Moreover, this multiple-pass Raman system can be easily upgraded to a multiple-channel detection system, and a two-channel detection system is demonstrated and characterized. High utilization ratio of laser energy (defined as the ratio of laser energy at sampling point to the laser output energy) is realized in this design, and high sensitivity is achieved in every sampling position. Compared with single-point sampling system, the back-to-back experiments show that LODs of 8.0 Pa, 8.9 Pa and 3.0 Pa can be achieved for N₂, O₂ and H₂O in one second. Methods to further improve the system performance are also briefly discussed, and the analysis shows that similar or even better sensitivity can be achieved in both sampling positions for practical industrial applications.