排序方式: 共有109条查询结果,搜索用时 31 毫秒
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利用AgNO3水溶液,通过严格控制TiO2薄膜的化学活性,系统研究了在TiO2表面光催化合成金属Ag纳米颗粒的生长行为。研究发现,光催化合成金属Ag纳米颗粒存在着两个完全不同的生长机制,分别对应着金属Ag纳米颗粒的各向同性和各向异性生长。当溶液浓度较低时,Ostwald熟化(OR)机制主导着金属Ag纳米颗粒的长大过程;当溶液浓度较高时,取向附生(OA)机制决定着金属Ag纳米颗粒长大成纳米片。原位消光光谱分析表明,OR机制和OA机制生长的前期具有相近消光特征,决定金属Ag纳米颗粒生长模式的关键是AgNO3溶液的浓度,更准确地说是金属Ag初级晶核的局域密度。在此基础上提出了有关光催化合成金属Ag纳米颗粒的生长模型。 相似文献
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近年来,石墨相氮化碳(g-C3N4)以其合适的带隙宽度、丰富的活性位点和成本低廉等优点,成为新兴的可见光响应非金属光催化剂,被广泛应用于光催化降解有机污染物领域。然而,纯g-C3N4对可见光的吸收效率较低且光生电子和空穴复合速率快,导致其光催化活性处于较低水平。基于g-C3N4的非金属特性,通过非金属掺杂可以有效提高g-C3N4的光催化性能,引起了学者们的广泛关注。本文介绍了目前非金属掺杂g-C3N4复合材料常见的制备方法,着重归纳了不同类型的非金属掺杂g-C3N4光催化降解水中有机污染物的相关研究进展,探讨其作为光催化剂在可见光条件下降解有机污染物的相关机理。最后,提出目前g-C3N4基复合材料在光催化降解水中有机污染物中所面临的挑战,旨在为非金属掺杂g-C3... 相似文献
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采用羰基合成-浸渍法制备了不同Pt/Sn摩尔比(3:1, 1:1, 1:2和1:3)的PtSn/Al2O3催化剂, 利用N2吸附-脱附实验、 X射线衍射(XRD)、 透射电子显微镜(TEM)、 吡啶吸附红外光谱(Py-IR)和热重-差热分析(TG-DTA)等手段对其进行了表征, 研究了Sn负载量对PtSn/Al2O3的结构性质及催化丙烷脱氢性能的影响. 结果表明, 制备的PtSn/Al2O3具有较高的丙烯选择性和稳定性. 当Pt/Sn摩尔比为3:1和1:1时, 铂和锡在催化剂上主要以Pt3Sn和PtSn合金形式存在, 合金的形成明显改善了催化剂的脱氢性能, 可抑制金属颗粒的高温烧结; 当Pt/Sn摩尔比为1:2和1:3时, 铂主要以金属形式存在. 随着Sn负载量的增加, 催化剂上L酸性位逐渐减少, 丙烷转化率降低, 丙烯选择性增加, 同时促使反应积炭从金属表面向载体迁移, 改善了催化剂的稳定性. 相似文献
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矿物组分快速定量提取模型及其应用 总被引:2,自引:0,他引:2
矿物成分快速鉴定是提高遥感矿产勘探、遥感矿物填图以及诸多地学研究等工作效率的关键。由于技术等各方面的限制,国内外针对矿物快速分析的模型和软件较少。20世纪90年代以来近红外光谱仪在技术上的突破和计算机的发展使得近红外光谱技术在矿物快速识别领域的应用变得可行,先后出现了基于吸收位置的反演模型(模型一)和基于波形匹配的反演模型(模型二)。文章提出了特征光谱线性反演模型。经美国地质调查局矿物光谱库(USGS)端元混合实验数据验证,该模型精度接近100%,远优于模型一和二。对新疆包古图地区地表随机所采23个样本分析,该模型平均精度为64.6%,另外两模型分别为:33.8%和8.1%,优于模型一和二。虽精度尚低于传统镜下鉴定方法,该模型具有高效、方便、工作量小、人为误差小等优点,已初步应用于新疆包古图地区遥感矿产勘探工作,有较好的推广前景。 相似文献
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Correlation between electronic structure and energy band in Eu-doped CuInTe_2 semiconductor compound with chalcopyrite structure 下载免费PDF全文
The Eu-doped Cu(In, Eu)Te_2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe_2. In this paper, the Eu-doped CuInTe_2(CuIn_(1-x)Eu_xTe_2, x = 0, 0.1, 0.2, 0.3) are studied systemically based on the empirical electron theory(EET). The studies cover crystal structures, bonding regularities, cohesive energies, energy levels,and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe_2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe_2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn_(1-x)Eu_xTe_2, the number of valence electrons changes regularly with increasing Eu content,and the calculated band gap E_g also increases, which implies that the optical properties of Eu-doped CuIn_(1-x)Eu_xTe_2 are improved. 相似文献
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利用物理光学相关知识及Collins衍射积分公式和硬边光阑的复高斯函数分解法,推导得到目标处干涉图样条纹间距与光学目标反射光时间分布关系的解析表达式.从原理分析、仿真计算和实验研究等方面研究了干涉场的条纹间距、光学目标口径参数和反射光时间分布包络的峰峰数、峰峰间距和峰峰比之间定量关系.结果表明,当条纹间距的大小约为目标的口径尺寸时,反射光时间分布包络的峰峰数由单峰向多峰过渡,峰峰间距和峰峰比曲线会出现极大值,根据这一变化规律可以估测出光学目标的口径参数,其估测精度受条纹间距可调节范围的影响. 相似文献
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The 10 kW Level High Brightness Face-Pumped Slab Nd:YAG Amplifier with a Hybrid Cooling System 下载免费PDF全文
We demonstrate a high power, high brightness, slab amplifier based on face-pumped Nd:YAG slab gain modules,having a high efficient hybrid cooling system of the conduction cooling and forced convection cooling. Using a single gain module, a laser output power up to 4.5 kW with a remarkable optical-optical conversion efficiency of 51% is realized, indicating an excellent lasing performance of the Nd:YAG slab module. The amplifier operates at a repetition rate of 700 Hz and delivers a maximum average output power exceeding 10.5 kW with pulse duration of 150us. A good beam quality factor is measured to be β = 1.9. To the best of our knowledge, this is the highest brightness for a 10 kW level Nd:YAG slab amplifier. 相似文献