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Ambient vibration tests and analyses of a long-span rigid-frame bridge were conducted using distributed long-gauge fiber-optic sensors. The concept of a long-gauge fiber-optic sensor and it...

A BaMgAl 10 O 17 :Eu 2+ phosphor with fine particle size was synthesized by a chemical co-precipitation method. Co-precipitation of Ba 2+ , Al 3+ , Mg 2+ , and Eu 2+ was achieved under precisely controlled precipitation conditions. The Al 3+ ions were precipitated as ammonium aluminum carbonate hydroxide (AACH). Phase transition and particle growth processes of the precipitate mixture during calcining process were investigated, and the formation mechanism of the BaMgAl 10 O 17 phase was discussed. The results show that the formation temperature of the BaMgAl 10 O 17 phase in the co-precipitation mixture was significantly lower than that of a high temperature solid state reaction method. The BaMgAl 10 O 17 phase was formed from the reaction between the BaAl 2 O 4 phase and γ-Al 2 O 3 phase; no α-Al 2 O 3 phase appeared during the entire process. Well-dispersed BaMgAl 10 O 17 :Eu 2+ phosphor powder in the form of hexagonal flakes with small particle size (1–2 μm) could be prepared by this method.

Three typical types of precursors with obviously different morphology were synthesized when preparing α-Al2O3 powder from aluminum nitrate and ammonium acid carbonate solution using a precipitation method. The phases of the precursor samples were attributed to be an amorphous structure, ammonium aluminum carbonate hydroxide (AACH) and an undetermined phase. Two kinds of phase transition phenomenon were found among these three phases. The α-Al2O3 powder samples with different morphology and particle size were produced after baking the three types of precursors at 1200 °C for 1 h. The acicular α-Al2O3 with particle length of 1–2 μm and diameter of 100–200 nm was obtained by baking the AACH precipitate as precursor.

BAM (BaMgAl 10 O 17 :Eu 2+ ) is widely used in plasma display panel (PDP) as a blue-emitting phosphor. It is necessary to improve the grain size, morphology and dispersibility of BAM phosphor because of the development of high definition PDP. Moreover, the crystal growth mechanism during the synthesis process of BAM particle is not fully clarified. In this paper, we synthesize BAM phosphor by solid-state reaction method. The primary raw material α-Al 2 O 3 powder was prepared by precipitation method. The phase transitions and crystal growth process during the formation of BaMgAl 10 O 17 have been studied. The intermediate product BaAl 2 O 4 phase was synthesized at 1000 °C on the surface of α-Al 2 O 3 particles as coating. When temperature increased to 1300 °C, BaMgAl 10 O 17 phase was formed. The BaMgAl 10 O 17 particles keep the shape and dispersibility of α-Al 2 O 3 powder. The results show that BAM phosphor synthesized in this paper has a homogeneous grain size at around 2.5 μm, good dispersibility, regular morphology and good luminescence properties.

The thermal degradation mechanism of the BaMgAl 10 O 17 :Eu 2+ (BAM) phosphor used in plasma display panel (PDP) is not yet fully clarified. We studied the dependency of the luminance and chromaticity y -value of BAM phosphor on baking temperature, handling time, atmosphere and thermal treating process. The luminance and chromaticity y -value increased after baking at around 400 °C but decreased at 600 °C or higher temperatures. The thermal degradation was obviously aggravated in oxidative atmosphere. The shift of y -value was reversed when thermal treated in non-oxidative atmosphere. We considered that the mechanism of thermal degradation of BAM phosphor was firstly due to the migration of Eu 2+ ions and then due to the effect of oxygen. We also proposed a post-treatment for BAM phosphor to reduce the thermal degradation during panels’ fabrication.

The title phosphor is synthesized by addition of an aqueous solution of Al(NO3)3, Mg(NO3)2, Ba(NO3)2, and Eu2O3 into a NH4HCO3 solution containing NH4F (20—50 °C, pH 8—10) followed by calcination of the precipitate at 1200 °C (1 h) and reduction of the obtained fine powder (N2/H2, 1400—1500 °C, 2—3 h).