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A novel follow-up ultrasonic vibration assisted welding process was proposed to reduce the common defects in laser welding of dissimilar metals for nuclear reactor pump can end sealing, such as unmixed zone, precipitated phase, and uneven element distribution. The influences of ultrasonic vibration on morphology, microstructure and property of C-276/304 laser-welded joint was analyzed. The results indicated that, the most significant ultrasonic vibration at welding position was achieved at parameters of 25 N pressing force and 13 mm distance from ultrasonic action point to welding position. By the application of follow-up ultrasonic vibration, the width of unmixed zone was reduced and the macro element distribution was homogenized due to the enhancement of molten convection. The average grain radius was refined from 1.03 μm to 0.55 μm because acoustic pressure in the molten pool reduced critical nucleus size rk and caused grain fragmentation. The higher diffusion coefficient and cooling rate caused by ultrasonic vibration suppressed element segregation, and thus the amount of precipitated phase decreased from 2.15% to 0.62%, which finally improved the intergranular corrosion resistance of weld metal. The load capacity of weld joint was improved by 12.6%, and the micro-hardness of weld metal was also increased, attributing to the grain refinement strengthening. The follow-up ultrasonic vibration process proposed in this paper provided an efficient, convenient and widely applicable process for laser seal welding of dissimilar metals for nuclear reactor pump can end sealing with higher qualities.

Nd:YAG pulsed laser lap-welding of Hastelloy C-276 and 304 stainless steel was conducted. The effect of pulse energy on weld morphology, element distribution, microstructure, phase structure, tensile-shear property and corrosion property of weld joint was analyzed. The results indicated that, with the increase of pulse energy, both the penetration depth and bead width of weld metal (WM) and dilution level of 304 base metal (BM) were linearly increased. Unmixed zone between WM and 304 BM was reduced, however, the grains sizes in WM became coarser. The precipitated phase with higher content of Mo and W is mainly p phase, with the increase of pulse energy, segregation potential of Mo element was increased, however, the amount of precipitated phase was decreased due to a decline in Mo element in WM. The fracture mode of weld joint transferred from interfacial fracture to tensile fracture with the increase of bead width, and the maximum load capacity of which was achieved at a pulse energy of 4.0 J. The average micro-hardness value of WM was decreased with the increase of pulse energy due to the depletion of Mo and W strengthening elements and the coarser grain size in WM. The corrosion resistance of WM was weakened with the increase of pulse energy ascribed to the reduce of Ni and Mo elements.

The Ba2P2O7:Tb3+, Eu3+ phosphors were synthesized by a high temperature solid-state reaction method in air atmosphere and their crystal structures, lifetime, luminescence properties, and energy transfer mechanism were investigated in detail. A series of characteristic emissions of Ba2P2O7:Tb3+, Eu3+ phosphors were observed in the emission spectra at around 545 nm, 593 nm, and 613 nm when excited at 378 nm. The energy-transfer mechanism from Tb3+ to Eu3+ in Ba2P2O7 is determined by a dipole–dipole interaction. The emission intensity of Ba2−xP2O7:xEu3+ was enhanced by doping charge compensation Li+, Na+ and K+. The CIE coordinates of the phosphors can be tuned from blue-green through white, to yellow and finally to orange-red with changing the Eu3+/Tb3+ ratio. The average decay time of Eu3+ increases from 2.10 to 5.81 ms with the concentration of Tb3+ increasing from 2% to 8%, and reaches the maximum at 0.08, and is shortened when the concentration of Tb3+ goes beyond 8%.

Typical LED light sources have lower light utilization efficiency (LUE) in reflective directional illumination applications due to light pattern mismatch. Light patterns are generally controlled by secondary optical systems, which are heavy and large. Compared with the secondary optical system, the primary lens is smaller in size, lighter in weight, and more efficient in light extraction. This work is a preliminary study on the primary lens of LED in order to improve the LUE of LED in reflective directional illumination fields. Experimental result shows that the light extraction efficiency (LEE) of LED light source packaged by a primary optical lens is improved by a maximum proportion of 16.3%. The LUE of the LED packaged with the primary lens is up to 40.1% at 60°. After encapsulating the primary lens, the weighted mean angle of light intensity in the full space is at 57° which is bigger than that of LED without primary lens (46°).

In order to study the effect of joint clearance on the dynamic characteristics and chaos phenomena of the hybrid mechanism, 3-CPaRR Mechanism stability is related to the impact phenomenon between joint elements.

The novel red-emitting Na 3 Gd 2− x (BO 3 ) 3 : x Eu 3+ phosphors were synthesized by a solid-state method. Under near ultraviolet excitation, the phosphors exhibit dominant emission peak at 614 nm and generate bright red light, which is attributed to the electric-dipole transition 5 D 0 → 7 F 2 . The optimal doping amount of Eu 3+ in Na 3 Gd 2− x (BO 3 ) 3 : x Eu 3+ phosphors is x =0.3 for the maximum emission. The exchange interaction between Eu 3+ ions is identified to be the main mechanism in the concentration quenching process. The CIE color coordinates of the Na 3 Gd 2− x (BO 3 ) 3 : x Eu 3+ phosphors (x=0.650, y=0.350) are close to the NTSC standard values of red. With a relatively high quantum efficiency of 35.2%, Na 3 Gd 2 − x (BO 3 ) 3 : x Eu 3+ red-emitting phosphor is probably a promising candidate for near ultraviolet-based white LEDs application.