排序方式: 共有30条查询结果,搜索用时 15 毫秒
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用微乳液法合成出SiO2包覆的Er3+掺杂的Y2O3粉体.X射线衍射结果表明,所制备粉体为立方Y2O3结构.透射电镜照片显示,其颗粒形状近似为球形,粒径为20~50 nm.该粉体在波长为980 nm的半导体激光器激发下发射出中心波长为562 nm的绿色和660 nm的红色上转换荧光,分别对应于Er3+离子的4S3/2/2H11/2→4I15/2跃迁和4F9/2→4I15/2跃迁,发光强度和激发功率的关系揭示其均为双光子过程.Er3+掺杂的Y2O3粉体具有高效的上转换发光性能,而经过纳米复合后制成的Y2O3(核)/SiO2(壳)在水溶液中具有较好的悬浮性,这对于其在生物荧光标记的应用具有重要意义. 相似文献
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A new homemade apparatus, i.e. vibration assisted extrusion equipment, is employed to extrude polypropylene. Vibration assisted extrusion is based on the application of a specific macroscopic shear vibration field. Reduction of apparent melt viscosity as a function of vibration frequency is measured at different screw speeds and die temperatures. The effect of the process is investigated by performing mechanical tests, differential scanning calorimetry studies, polarized light microscopy and wide-angle X-ray diffraction. It is found that, compared with conventional extrusion, vibration assisted extrusion could effectively improve the rheological properties of PP melt by incorporating an extra shear vibration field. Both the tensile strength and elongation at break increased under the shear vibration field. For vibration assisted extrusion samples, both the melting temperature and crystallinity increased, accompanied by remarkable grain refinement. Vibration assisted extrusion induced a significantly enhanced bimodal orientation with a high fraction of a*-oriented α-crystallites, while only a limited improvement in the flow direction orientation. A structural model, i.e. bimodal c-axis and a*-axis orientation of PP macromolecular chains, was adopted to explain the experimental results. 相似文献
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高密度封装二极管激光器阵列 总被引:1,自引:1,他引:0
理论模拟了自制的高效冷却器的散热能力,分析了单元封装结构所需材料的导热特性,获得了高功率二极管激光器在高功率密度、高占空比条件下运行的可行性。改进了高密度封装的关键工艺,热沉金属化层达到了3~5 mm,焊料厚度为4~7 mm,封装间距0.6 mm,采用峰值功率1 kW的背冷式叠阵二极管激光器。实验测试结果表明:封装的二极管激光器叠阵单元的整体封装热阻为0.115 ℃/W,有良好的散热能力;该叠阵模块在电流为100 A、占空比15%时,输出峰值功率为986 W,峰值功率密度达到1.5 kW/cm2,平均每个板条的斜效率为1.25 W/A,激光器阈值电流为20 A左右。 相似文献
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提出了高效液相色谱法测定环境水中7种阴离子的方法.采用Asahipak ODP-50卡套柱(4.0 mm×150 mm,5 μm),柱温为40℃;流动相为邻苯二甲酸-乙腈-水(5:14:81);流速为1.5 mL·min-1;采用二极管阵列检测器(DAD),检测波长为266 nm;7种阴离子的峰面积与其浓度呈线性关系,相关系数在0.999 8~0.999 9之间.7种阴离子的回收率范围为95.3%~98.6%,F-、Cl-、NC-2、Br-、NO-3、PO3-4和SO2-4的检出限依次为8,14,34,59,37,30,80 μg·L-1;相对标准偏差(n=6)≤2.0%.该方法已用于地面水、地下水、矿泉水、饮用水及废水等样品的分析. 相似文献