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Ti2AlC/TiAl composites with different volume fractions were prepared by hot pressing technology, and their reinforced structural characteristics and mechanical properties were evaluated. The results showed that when the reinforced phase volume fraction of Ti2AlC was 20%, three-dimensional interpenetrating network structures were formed in the composites. Above 20%, Ti2AlC phase in the composites accumulated and grew to form thick skeletal networks. The microplastic deformation behavior of Ti2AlC phase, such as kink band and delamination, improved the fracture toughness of the composites. Comparative analysis indicated that the uniform and small interconnecting network structures could further reinforce the composites. The bending strengths of composites prepared with 20 vol.% Ti2AlC reached (900.9±45.0) MPa, which was 25.5% higher than that of TiAl matrix. In general, the co-continuous Ti2AlC/TiAl composite with excellent mechanical properties can be prepared by powder metallurgy method.

Stimulated emission has been observed from oxide structure of silicon when optically excited by 514 nm laser. The photoluminescence (PL) pulse has a Lorentzian shape with a full width at half maximum (FWHM) of 0.5–0.6 nm. The twin peaks at 694 nm and 692 nm are dominated by stimulated emission which can be demonstrated by its threshold behavior and transition from sub-threshold to linear evolution in light emission. The gain coefficient from the evolution of the peak-emission intensity as a function of the optically pumped sample length has been measured. The oxide structure was fabricated by laser irradiation and annealing treatment on silicon. A model for explaining the stimulated emission has been proposed in which the trap states of the interface between oxide of silicon and porous nanocrystal play an important role.

Relativistic comparison theorems are established for discrete eigenvalues of Klein–Gordon equation with vector and scalar potentials in d -dimensions. Theorem 1 : If V ( λ ) and S ( λ ) depend on a parameter λ , ∂ S / ∂ λ ⩾ 0 , S ⩾ 0 , ∂ V / ∂ λ ⩾ 0 , V ⩽ 0 , E > 0 , then it follows that ∂ E n / ∂ λ ⩾ 0 . Theorem 2 : If S 2 ⩾ S 1 ⩾ 0 , 0 ⩾ V 2 ⩾ V 1 , E > 0 , then the corresponding eigenvalues are ordered as E n ( 2 ) ⩾ E n ( 1 ) . Theorem 3 : If 0 ⩾ V 2 ⩾ V 1 , S 2 ⩾ | S 1 | , E n ( 1 ) > 0 , E n ( 2 ) > 0 , then E n ( 2 ) ⩾ E n ( 1 ) . Some illustrative examples are given.