基于液相掺杂的低损耗近等厚芯层掺稀土光纤

过高的纤芯损耗和纤芯折射率非均匀性严重制约了掺稀土光纤在高功率光纤激光器中的应用,提出一种基于液相掺杂的低损耗近等厚芯层掺稀土光纤的工艺方法.结合改良的化学气相沉积(MCVD)溶液掺杂法制备了含有多层疏松层的掺稀土光纤预制棒,理论分析了光纤预制棒缩棒前、后芯层差的变化原理,采用流量递减沉积工艺降低了缩棒后不同芯层之间的...     

钨掺杂M型二氧化钒粉体的水解法制备与结构分析

采用水解法制备不同W掺杂量的VO2(M)粉体。借助于X射线衍射仪、Fourier变换红外谱、差示扫描量热仪、X射线光电子谱仪和X射线精细结构谱对粉体的成分和结构进行表征。结果表明,W6+进入VO2晶格,形成固溶体V4+1-3xV3+2xWxO2。W掺杂降低了VO2(M)的相变温度,相变温度与W掺杂量在一定范围内成线性关系,掺杂效率约为18℃/1%(摩尔分数)。掺杂的大半径W原子部分替换了VO2(M)晶格中的V原子,晶格膨胀畸变产生的压应力通过共享顶点O,沿着W—O—V链传递到邻近的次晶格,造成V—O键键长变化,促使V周围的氧分布对称性随W掺杂量的增加而增大。当W掺杂量增大至2.5%时,单斜结构中的V—O1键和V—V1a键伸长,V—O2键和V—V1b键缩短,V—O1和V—O2峰合并成金红石结构的V—O峰,V—V1a峰和V—V1b峰合并成金红石结构的V—V1峰,即样品已转变为金红石结构。     

非金属掺杂改性二氧化钛光催化剂研究进展

采用掺杂金属离子或非金属离子可增强TiO2光催化材料可见光响应能力.金属离子掺杂往往牺牲其紫外光区催化能力,而采用非金属掺杂不仅能够增强其可见光响应能力,且保持紫外区光催化活性,非金属离子掺杂将是TiO2光催化改性的重要方法.综述了近年来采用非金属离子掺杂改性TiO2光催化剂的最新研究.     

Mg:Ce:Fe:LiNbO3晶体生长及其全息存储性能

在同成分LiNbO3(LN)中,掺入MgO的摩尔分数分别为0,2%,4%,6%,掺入(质量分数)0.1?O2和0.08?2O3,采用提拉法生长了优质的Mg:Ce:Fe:LN晶体.检测了Mg:Ce:Fe:LN晶体的红外透射光谱和光损伤阈值.结果表明:6%Mg:0.1?:0.08?:LN晶体的OH-振动吸收峰紫移到3 532cm-1,其光损伤阈值比Ce:Fe:LN晶体提高2个数量级以上.用二波耦合光路测试晶体的衍射效率,写入时间和擦除时间.计算了光折变灵敏度和动态范围.结果表明:Mg:Ce:Fe:LN晶体全息存储性能优于Fe:LN晶体和Ce:Fe:LN晶体.以4%Mg:0.1?:0.08?:LN晶体作为全息记录材料,实现了总存储页面为3 200幅图像的存储,再现图像清晰完整.     

Ce在负载Pd催化苯酚氧化羰基化合成碳酸二苯酯反应中的作用

采用微乳液法制备了Ce为助剂的Pd-Ce-O/SiO₂催化剂,用于苯酚氧化羰基化合成碳酸二苯酯（DPC）反应。活性评价结果显示,催化剂性能随着Ce用量的增加而提高,当Ce/Pd摩尔比为10/1时,苯酚转化率为64.4%,碳酸二苯酯选择性为83.4%。利用XRD表征发现,部分Ce⁴⁺进入到PdO晶格中,使得失活Pd原子中的电子更容易向Ce转移,从而易于再生,表现出更好的催化性能。根据上述结果,设计制备了Pd-O/CeO₂催化剂用于本反应,苯酚转化率和碳酸二苯酯选择性分别仅为24.0%和23.3%。表征发现,在Pd-Ce-O/SiO₂催化剂表面,Pd物种主要是PdO,而Pd-O/CeO₂表面的Pd物种则以PdO₂为主。由于苯酚氧化羰基化反应的活性中心为Pd(Ⅱ),所以Pd-O/CeO₂催化性能较差。并且,由于Pd与CeO₂之间存在强相互作用,催化剂表面Pd含量较低,这也是Pd-O/CeO₂催化活性较差的原因之一。     

Steam reforming on Ni-samaria-doped ceria cermet anode for practical size solid oxide fuel cell at intermediate temperatures

Direct internal and external reforming operations on Ni-samaria-doped ceria (SDC) anode with the practical size solid oxide fuel cell (SOFC) at intermediate temperatures from 600 to 750 °C are carried out to reveal the reforming activities and the electrochemical activities, being compared with the hydrogen-fueled power generation. The cell performance with direct internal and external steam reforming of methane and their limiting current densities were almost the same irrespective of the progress of reaction in the methane reformate at 700 and 750 °C. The durability test for 5.5 h at 750 °C with direct internal reforming operation confirmed that the cell performance did not deteriorate. The operation temperature of the cell controlled the reforming activities on the anode, and the large size electrode gave rise to high conversion due to the slow space velocity of the steam reforming. Direct internal steam reforming attained sufficient level of conversion for SOFC power generation with methane at 700 and 750 °C on the large Ni-SDC cermet anode.     

Linear discharge model,power losses and overall efficiency of the solid oxide fuel cell with thin film samarium doped ceria electrolyte. Part I: Linear discharge model

In this work, a solid oxide fuel cell with 60 μm samarium doped ceria film as the electrolyte is fabricated with a co-pressing technique. The performance of the cell is measured at 600, 650 and 700 °C. The corresponding maximum power outputs are 236, 331 and 401 mW cm^?2, respectively. The measured current–voltage (I–V) curves are straight lines. A linear discharge model is derived based on the Gorelov and Liu modified electromotive force (EMF) equations. The model fits the measured I–V curves with the maximum errors less than 1.5%. The overall activation overpotential of the cell is therefore postulated to be proportional to the polarization current.     

Microwave synthesis of mesoporous Cu-Ce0.8Sm0.2O2−δ composite anode for low-temperature ceramic fuel cells

In recent year, new nanocomposite electrolytes materials have been developed for low-temperature ceramic fuel cells (CFCs). To further improve the performance of CFCs based on the nanocomposite electrolyte, compatible active anode with sufficient low polarizations is needed. To improve the performance of anode, i.e. to enlarge tripe phase boundaries (TPB), anode materials with both porous structure and phase homogeneity of metal and ceramic are preferred. In the present study, we developed a novel microwave-assisted template-, surfactant-free synthesis route for mesoporous CuO–Ce_0.8Sm_0.2O_2−δ composite anode by homogeneous precipitation of microspherical precursor in aqueous solutions followed by calcination. The composite anode sample was characterized by thermogravimetry analysis, X-ray diffraction, SEM, EDX, etc. The characterization results indicated that CuO–SDC composite anode with mesoporous structure was prepared and both SDC and CuO phases were homogenously distributed. Fuel cells have been constructed using as-prepared composite as anodes and lithiated NiO as cathode based on the SDC–carbonate nanocomposite electrolyte. Fuel cell performance tests indicated that the cell with mesoporous Cu–SDC anode had better performance than conventional Cu–SDC anode prepared by solid-state method.     

高温闪烁晶体Ce:YAlO3开裂现象的分析

对提拉法生长的Ce;YAIO3(简称为Ce：YAP)晶体的开裂现象进行了研究,认为引起开裂的主要内在因素是YAP晶体热膨胀系数的各向异性。研究了Ce：YAP晶体的[010],[101],[121]等几个主要方向在30～800℃范围内的热膨胀系数曲线。结果表明：沿[010]和[101]方向的膨胀系数相差最大。通过对晶体中热应力分布的计算,得出晶棱显露处为应力集中点,指出晶体容易产生开裂的方向是[010]和[101]。通过对晶体的显微形貌观察发现,晶体中存在微裂纹。晶体的各向异性热膨胀系数,晶体生长过程中大的温度梯度以及快的降温速率等是Ce：YAP晶体产生开裂的主要原因。     

WLED用单基质硅酸盐荧光粉的制备及性能研究

采用溶液-燃烧法制备了Ca2MgSi2O7白光LED用荧光粉,探讨了溶液-燃烧法制备样品的工艺参数并分别对单掺Eu3+和三掺Eu3+,Ce3+,Tb3+在不同浓度下的荧光性能进行分析。通过同等条件下荧光光谱的对比分析发现单掺Eu3+离子,掺杂浓度为金属离子浓度的1%时荧光强度最强;三掺Eu3+,Ce3+,Tb3+的物质的量比为1∶1.5∶1时样品荧光强度最强。