纳米WO3块体材料的电致变色效应

WO3薄膜能够通过电、光、热变色.实验发现纳米WO3块材具有明显的常规块材不具有的电致变色特性，即当样品中有电流通过时，样品从负极到正极颜色由黄色变为深蓝色.变色前后样品的显微形貌和相结构都没有明显变化.x射线光电子能谱说明变色后的样品中出现了低价的钨离子(W5+).根据实验结果，变色过程被认为是一种电子注入效应.纳米样品中的高价钨离子(W6+)因为纳米材料的表面效应而具有足够大的活性，能与电子结合生成低价的离子，从而使样品变色. 关键词： WO3块材 纳米材料 电致变色     

液氮冷却法全无机智能窗器件的制备及其性能研究

为降低溅射过程中摹片温度的上升,进而成功制备非晶多孔、纳米微晶态电致变色薄膜和非晶态离子导电薄膜,介绍了一种配置于磁控溅射设备的液氮冷却装置.利用该装置制备了由WO3、NiOx和LiNbO3 薄膜组成的单基片全无机电致变色智能窗器件.采用分光光度计对该器件的电致变色性能进行了测试,并计算了它的漂白和着色态在400 nm到800 nm波长范围内的平均透射率.实验结果表明,经过50次循环后,该器件的漂白和着色态的平均透射率分别为61.5%和5.5%.X射线衍射和扫描电镜(SEM)图像显示,组成该器件的WO2、NiOx和LiNbO3薄膜分别为非晶多孔、纳米微晶和非晶态结构.     

中频孪生磁控溅射WO3薄膜及变色性能研究

采用先进的中频孪生非平衡磁控溅射技术,以金属钨为靶材,制备非晶态WO3电致变色薄膜。用X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外分光光度计等测试手段分析薄膜的结构、表面形貌、成分以及透射光谱特性。研究了氧气流量比及热处理温度对WO3薄膜变色性能的影响。结果表明,中频孪生非平衡磁控溅射技术是制备WO3变色薄膜的一种有效方法;室温条件下沉积获得的原始态薄膜为非晶态WO3;提高氧气流量比和适当热处理温度能有效改善薄膜的电致变色性能。实验中在较高氧气流量比,200℃热处理条件下制备的薄膜在380~780 nm的可见光范围内着色态和褪色态平均透光率差值高达50%以上,表现出较好的电致变色性能。     

非晶态WO3薄膜电致变色特性的研究

采用射频溅射三氧化钨粉末靶的技术，在不同的氧分压条件下沉积得到非晶态WO3电致变色薄膜，分析得知氧分压为1∶10的样品变色性能更好些.采用x射线衍射(XRD)，原子力显微镜(AFM)，伏安特性曲线和分光光度计分析所制备薄膜的特性.将薄膜在15mol/L的LiClO4的丙稀碳酸脂（PC）溶液进行电化学反应.发现氧分压在1∶10的情况下沉积得到的薄膜呈非晶态，薄膜有较多的孔隙，这有利于Li+的抽取，进而显示出很好的变色性能.x射线光电子能谱(XPS)成分分析表明WO3薄膜在原态中只有W和O两种原子电色反应后 关键词： 三氧化钨薄膜 非晶 射频溅射 电致变色     

染料敏化TiO2/WO3薄膜电池的光电变色

用光电化学方法研究了染料Ru(П) (4, 4′di COOEt 2, 2′bpy)2 (2, 2′bpy 4, 4′di CONH L tyrosineethylester) (PF6)2 (简写为Ru4)敏化TiO2 纳米结构电极的光电转换过程,同时,在导电玻璃上电沉积得到WO3 薄膜.结果表明,染料敏化的TiO2 多孔膜具有光电转换性能, WO3 薄膜具有良好的电致变色效应,将前者与电沉积得到的WO3 薄膜组成电池,在白光照射下可产生显著的颜色变化,有望用于自供电源的电色灵巧窗(Self poweredsmartwindow).     

WO3/Ag复合薄膜的制备及其电致变色性能

通过水热法在导电玻璃上合成WO_3纳米块,利用电沉积技术在WO_3纳米块上负载不同含量(20 s、50 s、80 s)的Ag纳米粒子,成功制备出WO_3/Ag复合薄膜.通过X射线衍射分析、扫描电子显微镜与能谱对WO_3/Ag复合薄膜进行表征,利用电化学测试与光谱测试,得到电致变色可逆性、响应时间、着色效率和光谱透过率等参数,并对其电致变色性能进行分析.结果表明,对比单一WO_3纳米块薄膜的电致变色性能,WO_3/Ag复合薄膜的电致变色性能显著增强.同时研究了不同Ag纳米粒子含量对WO_3/Ag复合薄膜电致变色性能的影响,研究表明沉积50 s的WO_3/Ag复合薄膜具有最优异的电致变色性能.     

Eu3+掺杂Gd2W2O9和Gd2（WO4）3纳米荧光粉发光性质研究

采用共沉淀法制备了不同Eu3+掺杂浓度的Gd2W2O9和Gd2(WO4)3纳米发光材料.通过对纳米材料样品的X射线衍射谱(XRD)和场发射扫描电镜(FE-SEM)照片的观察和分析,对样品的结构和形貌进行了表征.测量了各样品的发射光谱、激发光谱,计算了各样品的部分J-O参数和Eu3+5D0能级量子效率,绘制了不同基质中Eu3+发光的浓度猝灭曲线,对Eu3+掺杂的Gd2W2O9和Gd2(WO4)3纳米发光材料的光致发光性质进行了研究.实验结果证明,与较常见的Gd2(WO4)3:Eu一样,Gd2W2O9:Eu中Eu3+5D0→7F2跃迁的红色发光也能被395nm和465nm激发光有效激发,具有近紫外(蓝光)相对激发效率高,猝灭浓度大的优点,有潜力成为高效的近紫外(蓝光)激发白光LED用红色荧光粉材料.     

钾钨青铜K_xWO_3的晶体结构和电输运特性研究

以K2WO4、WO3和W粉为原料,用混合微波方法制备了钾钨青铜KxWO3样品.随着名义钾含量x的增加,KxWO3样品的晶体结构由六方(0.20≤x≤0.33)转变为四方(0.50≤x≤0.60).四方相样品均显示金属型导电特性.在六方相样品K0.2WO3中观测到了明显的电荷密度波(CDW)转变,转变温度为265K,其余六方相样品则为半导体型导电特性.在x=0.20不变的条件下,以Ca部分替代K制备了(K1-2 yCay)0.2WO3(名义钙含量y=0.1,0.2,0.3)样品,其主相仍为六方相.当0y≤0.2时,六方相的晶胞参数a和c随y的增加而增大.从电阻率-温度曲线上可以看出,名义钙含量的变化会影响样品中的CDW转变.     

聚合物前驱体法制备WO_3薄膜的电致变色性能

以偏钨酸铵为钨源,Pluronic F127为配位聚合物,在FTO导电玻璃上制备了WO3薄膜,研究了配位聚合物含量对WO3薄膜电致变色性能的影响。实验结果表明,制备的WO3薄膜属于立方晶相;随着Pluronic F127含量的增大,WO3薄膜表面粗糙度增大,电荷容量先增大后减小;当Pluronic F127的含量为26%时,WO3薄膜的电荷容量最大,电致变色性能最好,可见光区域的透光率光学调制范围达到62.68%,光学密度差达到0.864,且着色态的太阳能总透射率低于褪色态的,制备的薄膜具有较好的节能效果。     

Yb3+-Tm3+共掺钨钼酸盐纳米晶体的发光特性

以聚乙二醇为络合剂,采用水热法制备了发光性能优越的Yb3+-Tm3+共掺BaGd2(WO4)0.5(MoO4)0.5纳米晶体。改变稀土掺杂量并生产不同掺杂量的BaGd2(WO4)0.5(MoO4)0.5∶Yb3+/Tm3+。以X射线衍射仪(XRD)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)对样品进行表征。结果表明,BaGd2(WO4)0.5-(MoO4)0.5∶Yb3+/Tm3+纳米晶属四方晶系,粒径在25~40nm之间,使用Hitachif-4500分光光度计分析样品,发现当Yb3+/Tm3+为4∶1、Yb3+离子浓度为6.0%时,BaGd2(WO4)0.5(MoO4)0.5∶Yb3+/Tm3+的发光效率最高。当Tm3+离子发生1G4→3H6跃迁时会产生可见光发射,对应于光谱图中475nm处的蓝光;当Tm3+离子发生1G4→3F4跃迁时产生的可见光发射,对应于光谱图中650nm处的红光。光谱图像及泵浦功率的双对数曲线表明,其中蓝光发射是三光子发射过程,红光发射是双光子发射过程。样品的量子产率接近0.9%。Yb3+-Tm3+共掺BaGd2(WO4)0.5(MoO4)0.5纳米晶体的发光性能优异,具有很高的应用价值。     

非晶纳米过氧聚钨酸的Raman谱、热稳定性及UV-Vis光吸收特性

过氧聚钨酸是通过化学途径合成各种纳米结构氧化钨的重要前驱物之一。本文以双氧水(H₂O₂)、钨粉(W)和无水乙醇为原料合成了过氧聚钨酸溶胶,随后在常温下长时间放置,直至自然凝固,并在120 ℃干燥3 h后得到最终的深黄色胶状固体。利用XRD、SEM、Raman谱、TG/DSC分析和UV-Vis谱等分别考察了样品的成分结构、热稳定性和UV-Vis光吸收特性。宽的XRD峰表明样品是非晶结构,明显峰位的高斯型拟合表明样品是氧化钨与水合氧化钨的复合物。SEM表明样品呈纳米颗粒状(50～100 nm)和片层状形貌(厚约50 nm)。宽而明显的Raman峰的高斯型拟合进一步表明样品是非晶氧化钨和水合氧化钨的复合物,不仅拥有非常明显的O—W—O对称伸缩、非对称伸缩和WO振动,而且伴有O—W—O对称弯曲、非对称弯曲及吸附水的振动模式。TG/DSC分析表明过氧聚钨酸凝胶固体在120～500 ℃范围内存在四个不同的热力学过程：(Ⅰ)过氧聚钨酸凝胶固体的缓慢晶化(120～165 ℃);(Ⅱ)H₂O₂的分解和H₂O的去吸附(165～236 ℃);(Ⅲ)水合氧化钨的快速分解(236～287 ℃);(Ⅳ)最终产物WO₃的晶化和相变(287～500 ℃)。UV-Vis谱表明样品在350～600 nm范围存在一个明显的带边吸收,其光学带隙约2.25 eV,明显低于当前已报道的WO₃和H₂WO₄的带隙值(2.45～3.50 eV)。存留在复合物中的水分子、氧缺陷以及结构性畸变应该是导致其拥有较窄带隙的关键因素。     

大功率脉冲氙灯用稀土钨电极工作表面分析

为探讨电极表面发生变化的原因和烧蚀机理,为提升电极工作稳定性提供理论依据,分析了经过上万发次点灯测试的大功率脉冲氙灯稀土钨电极的表面形貌、元素深度分布及价态。结果表明:工作后的电极表面出现大量裂纹以及烧蚀坑;表面各元素主要由W, La, O三种元素组成,分布均匀;电极表面La以La3+形式存在,W存在原子态和+6价两种价态,占比分别为18.29%和81.71%;随刻蚀深度增加后,La的价态仍为+3价,W6+迅速减少直至W价态全部变为W0。     

蓝色氧化钨的光电子能谱研究

本文用光电子能潜技术对蓝色氧化钨的表面价态进行了一系列研究。结果表明:蓝色氧化钨并不是单一价态的氧化钨,而是由W⁺⁵和W⁺⁶两种价态组成。氩离子刻蚀,真空高温处理都是一个失氧还原过程,也是钨由高价态向低价态的转变过程。同时,费密能级附近的态密度随着价态变低而逐渐增加。 关键词：     

铝纳米晶的低温导电特性研究

采用真空热压技术将电磁感应加热-自悬浮定向流法制备的铝纳米粉末压制成块体样品.通过X射线衍射、透射电子显微镜、扫描电子显微镜及X射线能谱分析了铝纳米晶的微观结构,并用四探针法测量了不同温度下(8—300 K)样品的电阻率,研究了铝纳米晶的电阻率(ρ)随温度的变化规律.结果表明:由于晶界(非晶氧化铝)对电子的散射以及晶界声子对电子的散射效应,低温(40 K)下,铝纳米晶的本征电阻率随温度变化关系明显不同于粗晶铝,不仅呈现出T~4变化,还表现出显著的T3变化规律.因晶界等缺陷和非晶氧化铝杂质对电子的散射,铝纳米晶残余电阻率比粗晶铝电阻率大5—6个数量级.     

Synthesis and room-temperature NO_2 gas sensing properties of a WO_3 nanowires/porous silicon hybrid structure

We report on the fabrication and performance of a room-temperature NO2 gas sensor based on a WO3 nanowires/porous silicon hybrid structure. The W18O49 nanowires are synthesized directly from a sputtered tungsten film on a porous silicon （PS） layer under heating in an argon atmosphere. After a carefully controlled annealing treatment, WO3 nanowires are obtained on the PS layer without losing the morphology. The morphology, phase structure, and crystallinity of the nanowires are investigated by using field emission scanning electron microscopy （FESEM）, X-ray diffractometer （XRD）, and high-resolution transmission electron microscopy （HRTEM）. Comparative gas sensing results indicate that the sensor based on the WO3 nanowires exhibits a much higher sensitivity than that based on the PS and pure WO3 nanowires in detecting NO2 gas at room temperature. The mechanism of the WO3 nanowires/PS hybrid structure in the NO2 sensing is explained in detail.     

A comparison of electrochromic properties of sol–gel derived amorphous and nanocrystalline tungsten oxide films

A pristine acetylated peroxotungstate sol with and without 4 wt% of oxalic acid dihydrate (OAD) yielded nanocrystalline and amorphous tungsten oxide (WO₃) films respectively by dip coating technique. Contrary to the expected trend, whereby, the nanostructured 4% OAD film with a triclinic modification should have shown superior electrochromic efficiency, its amorphous 0% OAD counterpart exhibits higher optical modulation and coloration efficiency at photopic wavelengths. This anomalous behavior of the amorphous 0% OAD film was correlated to a higher W⁵⁺ content in its colored state. The colored nanocrystalline 4% OAD film contained a lower proportion of the W⁵⁺ color centers. Under the same level of lithiation, while the 4% OAD film was also constituted by W⁴⁺ states, its 0% OAD counterpart did not contain any 4+ states of tungsten. X-ray photoelectron spectroscopic (XPS) investigations also confirmed that the single peak at ∼1.4 eV in the absorption coefficient–wavelength spectrum of the colored 0% OAD film arises from the small polaronic transitions between the W⁶⁺ and W⁵⁺ states of tungsten whereas the W⁶⁺–W⁵⁺ and the W⁵⁺–W⁴⁺ charge transitions produce two distinct peaks at 1.2 and 1.6 eV in the α–λ spectrum of the colored 4% OAD film. The microstructure of the 4% OAD film, characterized by an interconnected network of nanocrystallites and pores promotes rapid ion insertion and extraction. Therefore, the larger magnitudes of NIR reflectance modulation, diffusion coefficient for lithium, electrochemical activity and faster color–bleach kinetics observed for the 4% OAD film, are a direct consequence of its structure. Band gap widening upon lithium insertion observed for both films, is a repercussion of Burstein–Moss effect and structural changes that occur upon coloration.     

Solid-gas reactions of complex oxides inside an environmental high-resolution transmission electron microscope

In a gas reaction cell (GRC), installed in a high-resolution transmission electron microscope (HRTEM) (JEOL 4000EX), samples can be manipulated in an ambient atmosphere (p<50mbar). This experimental setup permits not only the observation of solid-gas reactions in situ at close to the atomic level but also the induction of structural modifications under the influence of a plasma, generated by the ionization of gas particles by an intense electron beam. Solid state reactions of non-stoichiometric niobium oxides and niobium tungsten oxides with different gases (O2, H2 and He) have been carried out inside this controlled environment transmission electron microscope (CETEM), and this has led to reaction products with novel structures which are not accessible by conventional solid state synthesis methods.Monoclinic and orthorhombic Nb(12)O(29) crystallize in block structures comprising [3x4] blocks. The oxidation of the monoclinic phase occurs via a three step mechanism: firstly, a lamellar defect of composition Nb(11)O(27) is formed. Empty rectangular channels in this defect provide the diffusion paths in the subsequent oxidation. In the second step, microdomains of the Nb(22)O(54) phase are generated as an intermediate state of the oxidation process. The structure of the final product Nb(10)O(25), which consists of [3x3] blocks and tetrahedral coordinated sites, is isostructural to PNb(9)O(25). Microdomains of this apparently metastable phase appear as a product of the Nb(22)O(54) oxidation. The oxidation reaction of Nb(12)O(29) was found to be a reversible process: the reduction of the oxidation product with H(2) results in the formation of the starting Nb(12)O(29) structure. On the other hand, the block structure of Nb(12)O(29) has been destroyed by a direct treatment of the sample with H(2) while NbO in a cubic rock salt structure is produced.This in situ technique has also been applied to niobium tungsten oxides which constitute the solid solution series Nb(8-n)W9(+n)O47 with 0< or =n< or =4. All of these phases crystallize in the threefold tetragonal tungsten bronze (TTB) superstructure of Nb(8)W(9)O(47) (n=0). In the main reaction, these phases decompose in a gas plasma (O2, H2 or He, p=20mbar) into WO(3-x), which evaporates and solidifies again near the irradiated crystallite, and (Nb,W)(24)O(64), which crystallizes in a 2a superstructure of the TTB type observed here for the first time in the system Nb-W-O. Nb(8)W(9)O(47), Nb(7)W(10)O(47) and Nb(6)W(11)O(47) always react in this way, independent of the applied gas. On the other hand, the treatment of Nb(5)W(12)O(47) (n=3) and Nb(4)W(13)O(47) (n=4) in an oxygen atmosphere often caused a different reaction: these phases have been oxidized and a heavily disordered bronze-type structure has been formed. The oxygen excess in these products is largely accommodated in segregated domains of WO(3).     

High temperature coadsorption study of zirconium and oxygen on the W(100) crystal face

The coadsorption of zirconium and oxygen on W(100) has been studied by Auger electron spectroscopy, low energy electron diffraction, mass spectroscopy, ion sputtering, and work function measurement techniques. Adsorption of zirconium onto W(100) followed by heating in an oxygen partial pressure produces rapid diffusion of a ZrO complex into the bulk and the formation of a tungsten oxide layer. Heating in vacuum causes desorption of the tungsten oxide and segregation of the ZrO complex to the surface. The activation energy for the ZrO bulk-to-surface diffusion is 30 ± 2 kcal/mole. Upon heating in vacuum at 2000 K the composite surface exhibits predominantly a (1 × 1) LEED structure with a room temperature field emission retarding potential work function of 2.67 ± 0.05 eV. The Richardson work function for this unusually thermally stable surface is 2.56 ± 0.05 eV with a pre-exponential of 6 ± 2. The effects of carbon and nitrogen contamination on this low work function ZrOW composite surface are discussed and a structural model for the surface is presented.