Phosphors for plasma display panels

Excitation and emission characteristics were reviewed for phosphors which were reported, applied, or suggested for the plasma display panel (PDP). Correlation of luminescence characteristics to the host crystal structure and the activator of the phosphor was explained. Improvements of the PDP phosphor for practicality were considered. (C) 2000 Elsevier Science S.A. All rights reserved.

Vibration analysis of laminated shells using a refined shear deformation theory

A previously published refined shear deformation theory is used to analyse free vibration of laminated shells. The theory includes the assumption that the transverse shear strains across any two layers are linearly dependent on each other. The theory has the same dependent variables as first-order shear deformation theory, hut the set of governing differential equations is of twelfth order. No shear correction factors are required. Free vibration of symmetric cross-ply laminated cylindrical shells, symmetric and antisymmetric cross-ply cylindrical panels is calculated. The numerical results are in good agreement with those from three-dimensional elasticity theory.

整体壁板激光辅助预应力成形

整体壁板成形是大飞机制造的关键难题之一.本文探索了激光辅助预应力成形方法应用于整体壁板这一类筋条加强结构工件的可行性.该方法的原理是:首先对整体壁板施加弹性载荷,然后用激光束扫描并加热其弹性变形能集中区域,通过降低该区域材料的屈服极限促使弹性变形能转化为塑性功,实现整体壁板的塑性成形.对网格筋条加强结构试件进行了激光辅助预应力成形试验和有限元分析以及时效成形试验,验证了激光辅助预应力成形方法的可行性,并讨论了激光扫描道次与工件成形效率的关系.

MODIFIED DIRECT TWOS-COMPLEMENT PARALLEL ARRAY MULTIPLICATION ALGORITHM FOR COMPLEX MATRIX OPERATION

A direct twos-complement parallel array multiplication algorithm is introduced and modified for digital optical numerical computation. The modified version overcomes the problems encountered in the conventional optical twos-complement algorithm. In the array, all the summands are generated in parallel, and the relevant summands having the same weights are added simultaneously without carries, resulting in the product expressed in a mixed twos-complement system. In a two-stage array, complex multiplication is possible with using four real subarrays. Furthermore, with a three-stage array architecture, complex matrix operation is straightforwardly accomplished. In the experiment, parallel two-stage array complex multiplication with liquid-crystal panels is demonstrated.

二元振幅型面板用于光束空间整形

为了提高高功率激光系统的整体效率和充分利用光能,需要对前端注入的高斯光束进行空间整形,实现驱动器终端激光的均匀化输出。采用振幅型二元面板对激光光束进行空间强度整形,利用误差扩散法进行了理论设计,数值摸拟了整形效果,同时讨论了面板加工误差以及空间滤波器的小孔大小等因素带来的影响。根据理论设计,分别加工了反高斯透射率分布和抛物线透射率分布的二元面板,并进行了整形实验,实现了各自的整形功能,并做了误差分析。实验证明二元面板能对激光光束的空间强度分布实现了精确的整形。

等离子体平板显示（PDP）用荧光粉的合成及其光谱性质

等离子体平板显示（PDP）是目前高清晰度、大屏幕平板显示中的佼佼者，使挂壁彩电成为现实，但其关键部分之一-PDP荧光粉的发展却存在着相当滞后的问题，因此急需开发出性能更好的PDP荧光粉或对现有荧光粉的性能进行改善。改善PDP荧光粉性能的重要手段之一是选择合适的合成路径，因此本文探索了软化学合成方法-水热法在合成 PDP荧光粉合成中的应用，同时也采用高温固相法、共沉淀法对PDP荧光粉进行了合成，通过对比分析探索合成方法对PDP荧光粉光谱性质的影响。分别采用水热法、高温固相法、共沉淀法对掺杂稀土发光离子的稀土正硼酸盐（Y，Gd）BO_3、正磷酸盐（La，Gd）PO4、矾酸盐（Y，Gd）VO4、矾磷酸盐Y（P，V）O_4和硼硅酸盐LoBSIOS进行了合成，并用XRD、IR、SEM、XPS、TG-DTA等手段对其结构进行了表征，对上述PDP荧光粉的真空紫外（VUV）光谱、紫外可见光谱及发射光谱性质进行了研究，得到了一些新的、有意义的结果。（1）首次采用水热法以稀土氧化物、氢氧化物或硝酸盐与硼酸为原料合成了（Y,Gd）BO_3：RE~(3+)（RE＝Eu，Th）系列荧光粉，并对其VUV光谱特性进行了研究。sEM分析发现水热法以氢氧化物、硝酸盐合成的荧光粉粒度在100-200nm之间。XPS揭示不同基质中带结构具有一定的差异。光谱分析发现（Y,Gd）BO_3：RE~(3+)的VUV光谱中110-175nm范围内存在着基质硼酸根（B3场）的吸收带，该吸收带随基质中G矛"浓度的增大而增强并发生了红移，认为红移是由于基质中B-O反键轨道能量的变化引起的。对能量传递过程进行分析认为G矛十起到能量传递中间体的作用，使基质对激活剂的敏化效率随G矛十浓度的增大而提高。（Y,Gd）BO3:RE3＋中基质敏化效率的提高也可能是由于基质敏化带的红移使Gd3十或RE3＋更容易从基质中获得能量。我们认为作为PDP荧光粉Eu3＋或Th3＋在GdB03基质中的发光性能更好。对水热合成的（Y,Gd）BO3：Eu~(3+)荧光粉进行热处理发现，荧光粉的亮度随热处理温度的提高而明显增强，说明一定温度下热处理有利于提高荧光粉的发光性能，这可能是由于热处理后荧光粉的结晶度提高，内部缺陷减少。比较水热法、高温固相法和共沉淀法对荧光粉性质的影响时发现三种方法制备的荧光粉光谱特性基本一致，但高温固相法和共沉淀法制备的荧光粉粒度较大，形貌不规则。（2）采用水热法制备了不同G矛十浓度的PDP荧光粉（L a，Gd）Po4：RE3＋（RE＝Eu，Tb），发现以稀土硝酸盐溶液和伽玩）2HPO4为原料，在pH值为5·240oC下反应3天可以合成出结晶度较高的纯相。从SEM照片中观察到水热法制备的荧光粉为晶化很好的棒状晶体。对水热法制备的LaP04：Eu3+和GdPO4：Eu3+进行热处理后发现热处理后晶体的尺寸变小，但形貌没有发生明显的变化，发光性能效果稍有提高。首次对共沉淀法合成的不同Gd3＋浓度的（La，Gd）PO4：KE3＋（RE=Eu，Tb）荧光粉的VUV光谱进行了分析，并研究了Gd3＋在能量传递过程中的作用，发现随基质中Gd3十浓度的增大，基质对发光离子的敏化效率提高，认为Gd3＋起着能量传递中间体的作用。同时观察到（La，Gd）PO4：Eu3+中电荷迁移带随着Gd3＋浓度的增大而发生红移，这也可能会导致基质对Eu3+敏化效率的提高。首次利于xPs分析了LaPO4和GdP04的价带结构，发现LaP04的价带由O2的2P能级构成，而GdPo4的价带则是由O2-的2p能级和Gd3＋的4f能级共同构成，这种价带结构的差异可能对（La，Gd）PO4：RE3＋在VUV区的吸收产生影响。（3）首次对水热法合成的（Y,Gd）VO4：Eu3+的VUV光谱进行了研究，观察到120-170nm范围内存在着vO43一离子团的弱吸收带，200nm处存在着来自2P（O）→4f（Y）或5d（均跃迁的激发带，20onm以后的激发宽带是由Eu3＋的电荷迁移带与VO43-的吸收带重叠而成的。对不同Gd3＋浓度的（Y，Gd）VO4：E矿"的vLJ'v光谱进行研究发现，在一定G矛＋浓度范围内Gd3＋的加入使基质vo43+对Eu3+的敏化效率提高。对（Y,Gd）VO4：Eu3+中的能量传递过程进行分析认为，（Y,Gd）vo4：Eus＋中可能存在着VO_4~(3-)→Eu~(3+)和VO_4~(3-)（vuv）→Gd~(3+)→VO_4~(3-)（UV）→Eu~(3+)等几种能量传递方式，Gd3＋起着能量传递中间体的作用。（4）首次采用水热法合成了Y（P，v）O4：Eu3"红色荧光粉，发现初始体系pH为12.5、在240℃下反应6天可以得到Y（P，V）o4：Eu3＋纯相。结合XRD和SEM分析发现Y（P，V）O4：Eu3＋荧光粉的粒径随VO3-4浓度的增大而增大，YPO4：Eu3+的粒径为100-150nm，而YVO4：Eu3+的粒径则为400-450nm。对水热法合成的Y（P， V）O4:Eu3+的VUV光谱进行研究发现基质对Eu3+的敏化效率随VO3-4户含量的增多而提高。通过比较发射光谱中~5D_0→~7F_2与~5D_0→~7F_1跃迁的强度发现二者强度之比随VO_4~(3-_浓度的增大而增大，说明荧光粉的色纯度随VO4含量的增多而更好。比较水热法和高温固相法合成的Y（P，V）O4：Eus"的VUV光谱发现水热法制备的荧光粉在真空紫外区的吸收较弱，说明水热法制备的荧光粉虽然粒度较小，形貌规则，但发光性能不如高温固相法制备的Y（P,V）O4：Eu3＋荧光粉。（5）分别采用水热法和高温固相法制备了单掺稀土发光离子的LaBSIOS，并对它们的光谱性质进行了研究。通过比较产物的SEM照片发现水热法可以制备出粒度为2-3μm，形状近似于球形的产物，而高温固相法制备的样品形貌不规则，粒度分布范围广。对水热法制备的LaBSiO_5：Eu~(3+)进行红外光谱分析发现1300-400cm~(-1)范围内为BO_4基团和SiO_4基团的振动峰。首次对高温固相法制备的LaBSiO_5:Re~(3+)（RE=Eu，Sm，Th）的vuv光谱性质进行了分析，认为其VUV光谱中125-200nm范围内存在着BO_4基团的吸收带（125-165nm）和SiO4四面体的吸收带（165-183nm）。比较两种方法制备的荧光粉的光谱性质和亮度发现两种方法制备的荧光粉光谱性质基本一致，而水热法制备的LaBSiO_5：RE~(3+)（RE＝Eu，Sm，Tb）在254nm紫外光激发下亮度相对较低。

Luminescent properties of Mn2+ in hexagonal aluminates under ultraviolet and vacuum ultraviolet excitation

Mn2+-doped xBaO center dot 6Al(2)O(3) and BaMgAl10O17 phosphors were prepared by solid-state reaction. The investigation of vacuum ultraviolet (VUV) excitation spectra of these phosphors exhibits that 0.82BaO center dot 6Al(2)O(3):Mn2+ and BaMgAl10O17:Mn2+ have a stronger absorption than BaO center dot 6Al(2)O(3):Mn2+ at about 147 nm. The emission spectra under VUV excitation demonstrated that 0.82BaOBa center dot 6Al(2)O(3):Mn2+ and BaMgAl10O17:Mn2+ have a higher luminescent intensity than BaO center dot 6Al(2)O(3):Mn2+. The lifetime analysis indicates that they have similar decay times, indicating that 0.82BaOBa center dot 6Al(2)O(3):Mn2+ and BaMgAl10O17:Mn2+ can be used as luminescent materials for plasma display panels. We observed that the critical concentration of the Mn2+ ions by host excitation is different from that of Mn2+ direct excitation, revealing a different mechanism of energy transfer. The critical distance was calculated. A model was suggested to explain the process of the energy transfer from the host to the Mn2+ ions.

Application of rare earths in thermal barrier coating materials

Rare earths are a series of minerals with special properties that make them essential for applications including miniaturized electronics, computer hard disks, display panels, missile guidance, pollution controlling catalysts, H-2-storage and other advanced materials. The use of thermal barrier coatings (TBCs) has the potential to extend the working temperature and the life of a gas turbine by providing a layer of thermal insulation between the metallic substrate and the hot gas. Yttria (Y2O3), as one of the most important rare earth oxides, has already been used in the typical TBC material YSZ (yttria stabilized zirconia). In the development of the TBC materials, especially in the latest ten years, rare earths have been found to be more and more important. All the new candidates of TBC materials contain a large quantity of rare earths, such as R2Zr2O7 (R=La, Ce, Nd, Gd), CeO2-YSZ, RMeAl11O19 (R=La, Nd; Me=Mg, Ca, Sr) and LaPO4. The concept of double-ceramic-layer coatings based on the rare earth materials and YSZ is effective for the improvement of the thermal shock life of TBCs at high temperature.