Porous- and hollow-structured LiNb3O8 anode material was prepared by a hydrothermal-assisted sintering strategy for the first time. The phase evolution was studied, and the formation mechanism of the porous and hollow structure was proposed. The formation of the unique structure can be attributed to the local existence of liquid phase because of the volatilization of Li element. As the anode material, the initial discharge capacity is 285.1 mAhg−1 at 0.1 C, the largest discharge capacity reported so far for LiNb3O8. Even after 50 cycles, the reversible capacity can still maintain 77.6 mAhg−1 at 0.1 C, about 2.5 times of that of LiNb3O8 samples prepared by traditional solid-state methods. The significant improvement of Li storage capacity can be attributed to the special porous and hollow structure, which provides a high density of active sites and short parallel channels for fast intercalation of Li+ ions through the surface.
Low-temperature Bi-Nb-O system photocatalysts were prepared by a citrate method using homemade water-soluble niobium precursors. The structures, morphologies, and optical properties of Bi-Nb-O system photocatalysts with different compositions were investigated deeply. All the Bi-Nb-O powders exhibit appreciably much higher photocatalytic efficiency of photo-degradation of methyl violet (MV), especially for Bi-Nb-O photocatalysts sintered at 750 °C (BNO750), only 1.5 h to completely decompose MV, and the obtained first-order rate constant (k) is 1.94/h. A larger degradation rate of Bi-Nb-O photocatalysts sintered at 550 °C (BNO550) can be attributed to the synergistic effect between β-BiNbO4 and Bi5Nb3O15. Bi5Nb3O15 with small particle size on β-BiNbO4 surface can effectively short the diffuse length of electron. BNO750 exhibits the best photocatalytic properties under visible-light irradiation, which can be attributed to its better crystallinity and the synergistic effect between β-BiNbO4 and α-BiNbO4. The small amount of α-BiNbO4 loading on surface of β-BiNbO4 can effectively improve the electron and hole segregation and migration. Holes are the main active species of Bi-Nb-O system photocatalysts in aqueous solution under visible-light irradiation.
The effects of Li/Nb ratio on the preparation of Li-Nb-O compounds by a hydrothermal method were studied deeply. Li/Nb ratio has a great impact on the formation of LiNbO3; the ratio smaller than 3:1 is beneficial to the formation of LiNbO3, while larger than 3:1, forms no LiNbO3 at all and the morphology and chemical bond of Nb2O5 raw material are totally modified by Li ions. The reason can be attributed to the large content of LiOH, which is beneficial to form Li3NbO4 not LiNbO3, and also, even if LiNbO3 particle locally forms, it is easily dissolved in LiOH solution with strong alkalinity. Pure LiNb3O8 powders are obtained with two absolutely opposite Li/Nb ratios: 8:1 and 1:3; the former shows a unique porous and hollow structure, quite different from the particle aggregation (the latter shows). Compared with Li/Nb = 1:3, the 4.2 times higher photocatalytic performance of LiNb3O8 (Li/Nb = 8:1) are observed and it can be attributed to the unique porous and hollow structure, which provides a high density of active sites for the degradation of MB. Compared to LiNbO3, the improved photocatalytic performance of LiNb3O8 can be attributed to its layered structure type with the reduced symmetry enhancing the separation of electrons and holes.
Low-temperature b phase BiNbO 4 powders (denoted as Low-b) were prepared by a citrate method using home-made watersoluble niobium precursors. The stability of Low-b was systematically investigated from the aspects including calcination temperature, incubation time, and stress existing in pellets. Pure Low-b can be obtained between 700 and 750 8C and the crystal evolution of Low-b has not completed yet, compared with high-temperature b phase. Low-b is kinetically stable and no phase transition occurs when increasing the incubation time below 750 8C. Above 750 8C, both the calcination temperature and incubation time can induce the abnormal phase transition from Low-b to a phase; also, stress existing in pellets can effectively activate the phase transition of Low-b. We can conclude that the Low-b is thermodynamically unstable, while in kinetics, Low-b is stable. The dielectric properties of BiNbO 4 ceramics were investigated to analyze the influence of phase of BiNbO 4 powders precursors, especially the effect of phase transition of Low-b. It's found that BiNbO 4 powders firstly calcined at 700 8C is the best precursor to prepare dense ceramics with uniform grain size and the dielectric permittivity and dielectric loss of BiNbO 4 ceramics prepared at 1000 8C is 56.6 and 0.001 at 10 kHz, respectively.
With the development of integrated circuit manufacturing technology, low power test has become a focus of concern during testing fields. This paper proposes a new low power BIST built-in self test scheme based on block encoding which first exploit a block re-encoding method to optimize the test cube, and then a low power test based on LFSR (linear feedback shift register) reseeding is applied. According to the compatibility of flag, the scheme proposes a grouping algorithm based on flag to divide and reorder the test cubes in the test cube set. Experimental results show that the scheme not only obtain better test compression ratio and test data storage, but also reduce the test power consumption effectively.
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