Li2O-B2O3-P2O5系统非晶态混合骨架效应的NMR研究

用核磁共振对非晶态中B³⁺离子的微观结构进行了测定,结合Raman光谱的研究,对Li₂O-B₂O₃-P₂O₅系统非晶态的性能(电导率、密度等)在P₂O₅/B₂O₃比约等于1时产生极值的原因从理论上作了阐明。     

Three-level all-fiber laser at 915 nm based on polarization-maintaining Nd~(3+)-doped silica fiber

Nd3+-doped fiber lasers at around 900 nm based on the 4F3/2→4I9/2 transition have obtained much research attention since they can be used as the laser sources for generating pure blue fiber lasers through the frequency doubling.Here,an all-fiber laser at 915 nm was realized by polarization-maintaining Nd3+-doped silica fiber.A net gain per unit length of up to 1.0 dB/cm at 915 nm was obtained from a 4.5 cm fiber,which to our best knowledge is the highest gain coefficient reported in this kind of silica fiber.The optical-to-optical conversion efficiency varies with the active fiber length and the reflectivity of the output fiber Bragg grating(FBG),presenting an optimal value of 5.3%at 5.1 cm fiber length and 70%reflectivity of the low reflection FBG.Additionally,the linear distributed Bragg reflector short cavity was constructed to explore its potential in realizing single-frequency 915 nm fiber laser.The measurement result of longitudinal-mode properties shows it is still multi-longitudinal mode laser operation with 40 mm laser cavity.These results indicate that the Nd3+-doped silica fiber could be used to realize all-fiber laser at 915 nm,which presents potential to be the seed source of high-power fiber laser.     

粉煤灰与复合添加剂的固相反应过程分析

煤灰分中主要矿物质之间的反应对灰分特性有着重要影响。本文在具有温控的小型高温反应器中对粉煤灰和复合添加剂所组成的混合灰样进行了静态煅烧试验，并对煅烧后的灰样进行了X射线衍射分析（XRD），着重讨论了温度和时间以及复合添加剂量对灰分矿相组成特性的影响。试验结果表明：当温度低于1200℃时，灰色中主要是游离态的氧化物和部分新生成的矿物如钙黄长石，硅酸二钙；当温度在1200℃-1300℃时，灰分中的主要矿物是钙黄长石，当温度在1320℃－1350℃时，灰分主要矿物是硅酸二钙，同时存在一定量的硅酸三钙、铝酸三钙、铁铝酸四钙以及硫铝酸钙。随着灰分中氧化钙的含量增加，高碱性矿物含量逐渐增大，同时高温下加热持续时间过长，部分新生成的矿物将发生分解。     

Structural Change in Au^3＋-Doped BK7 Glass Irradiated by Femtosecond Laser

We report on structural change in an Au^3＋-doped BK7 glass irradiated by an infrared femtosecond laser at 800 nm. A grating structure is inscribed in the glass sample. The glass sample is then annealed at various temperatures. Structural change of the grating is observed by an optical microscope. Absorption spectra indicate that colour centres are induced after the laser irradiation, and they decrease with increasing annealing temperature. Au nanoparticles are precipitated at high temperatures （≥ 600℃）. The mechanisms of the phenomena are discussed.     

氧燃烧方式下痕量元素形态转化的试验和模拟研究

结合热重试验及XRF测量,采用化学热平衡分析方法对煤中易挥发的有毒痕量元素砷、铬、锑和汞在不同燃烧方式下的化学形态及分布进行了研究。计算表明,在常规燃烧方式下,痕量元素在400-1800 K的温度范围内容易蒸发,生成气相单质或氧化物。富氧燃烧条件下,高浓度的CO2(g)以及碳颗粒温度的降低在一定程度上会抑制痕量元素的蒸发,同时CO2(g)也会抑制痕量元素向气相次氧化物及单质的转化。     

Sr4Al14O25:RE3+(RE=Eu,Ce,Tb)中稀土离子的发光性质

采用高温固相反应合成了Sr4Al14O25：RE^3 (RE＝Eu，Ce，Tb)样品，研究了其中Eu^3 ，Ce^3 和Tb^3 的光谱性质，以及Ce^3 与Tb^3 共掺时的能量传递现象；发现Eu^3 ，Ce^3 和Tb^3 占有两个格位，与Eu^2 在此基质中的情况相似；在Tb^3 的发射光谱中同时观察到了来自^5D3与^5D4的发射，表明两能级间无辐射跃迁过程不显著；Ce^3 对Tb^3 有敏化作用。     

混煤煤灰熔融特性及矿物质形态的研究

本文对混煤熔融特性温度进行测定，并利用X-射线衍射分析对混煤煤灰的矿物组成进行试验分析，结果表明：混煤可改变原煤的结渣程度；混煤灰熔点与混煤比不成线性关系变化是混煤煤灰的低温共熔现象所致；在变形温度T1下煤灰中矿物质莫来石对煤灰熔融特性温度影响较大，莫来石含量越高，灰熔点越高．     

Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3^＋-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm^3＋-doped BaO-TiO2-SiO2 glass by a focused 800hm, 250 kHz and 150fs femtosecond laser irradiation. No apparent blue and red emissions are observed at the beginning, while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm^3＋ are observed near the focal point of the laser beam after irradiation for 25s. Micro-Raman spectra confirm that Ba2 TiSi2O8 crystalline dots and lines are formed after laser irradiation. The mechanism of the phenomenon is discussed.     

Blue-to-Orange Tunable Luminescence from Europium Doped Yttrium--Silicon--Oxide--Nitride Phosphors

Europium-doped yttrium-silicon-oxide-nitride phosphors are synthesized by carbothermal reduction and nitridation method. The crystal structure of the phosphors changed gradually from oxide Y2Si2O7 to nitride YSi3N5 state with increasing dosage of Si3N4 and carbon powder. The Y2Si2O7：Eu phosphor shows a blue emission at 465 nm with 300 nm excitation and a characteristic red emission of Eu^3＋ at 612 nm with 230 nm excitation. The YSi3N5：EU phosphor shows a broad emission band centred at 595nm with some sharp peaks of Eu^3＋ with 325nm excitation. The absorption of the studied phosphors increases from 450 to 700hm with an increment in nitrogen content. Blue-to-orange tunable luminescence is observed with 390 nm excitation.     

γ辐照对掺Er硅酸盐玻璃吸收和发光特性的影响

用传统的高温熔融法熔制了一系列掺Er硅酸盐玻璃, 并测试了这些样品经5 kGy γ 射线辐照前后紫外至近红外的吸收和荧光光谱. 实验结果表明, 辐致暗化效应使得玻璃材料中形成了大量色心, 导致在400 nm附近出现强吸收带, 其尾端延伸至近红外区. 辐照产生的新能带增加了基质与Er³⁺ 特定能级(如²H_11/2, ⁴S_3/2及⁴F_9/2等) 之间的能量传递, 从而使辐照后的样品荧光寿命减小, 且在相同激发条件下荧光强度下降. 室温下辐照样品在荧光测试过程中出现了漂白现象.