二氧化锰/普鲁士蓝纳米复合薄膜的制备及其电致变色性能

采用两步电沉积法在导电玻璃表面成功制备了二氧化锰/普鲁士蓝纳米复合薄膜。首先,以四水乙酸锰和无水硫酸钠为原料配制电解质溶液,通过电沉积法直接在导电玻璃表面沉积纳米二氧化锰薄膜。其次,以铁氰化钾、氯化钾和无水氯化铁为原料配制电解质溶液,沉积普鲁士蓝薄膜,表征了复合薄膜的结构,分析了复合薄膜的电致变色特性。结果表明,电沉积得到的二氧化锰为片状结构,且片的厚度小于10 nm,沉积在二氧化锰纳米片上的普鲁士蓝呈球状结构,直径约200 nm,形成了致密的、有裂纹的膜层。所制备的复合薄膜具有良好的电致变色性能。在400～800 nm的可见光范围平均光调制幅度达到52%,着色时间和褪色时间分别为4.3 s和3.6 s,着色效率达到68.4 cm2/C。     

纳米氧化钼薄膜的水热生长、器件制备及其电致变色性能

以金属钼粉为原料制备的过氧钼酸为前驱体溶液,直接在导电玻璃表面水热生长纳米氧化钼薄膜,并组装成电致变色器件,研究了器件的电致变色性能。研究表明:180?C下以过氧钼酸为前驱体溶液水热反应12 h可以得到均匀的薄膜,薄膜由厚约100～150 nm的纳米块组成;在波长720 nm处透过率调制幅度最大,达到13.3%;器件变色较快,其着色时间为3.5 s,褪色时间为2.9 s。     

氧化钼/聚吡咯复合膜的制备及变色性能研究

为了弥补无机变色材料的不足,引入有机聚合物进行复合,组装成互补型电致变色器件.本文以七钼酸铵为原料,采用水热法合成六方相氧化钼(h-MoO_3),通过浆料法制备氧化钼变色薄膜并组装成变色器件.利用恒电压聚合法制得聚吡咯薄膜,并与氧化钼薄膜复合组装纳米氧化钼/聚吡咯复合变色器件.采用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、紫外-可见分光光度计和电化学工作站对样品的结构以及器件的变色性能进行表征.结果表明:氧化钼的晶型为h-MoO_3;随反应时间的延长,不规则颗粒状的MoO_3逐渐生长并形成六角棒状,其直径为3μm,长度为20μm;氧化钼/聚吡咯复合变色器件的着色与褪色时间分别为35s和22s;在481nm处吸收峰的强度从0.62减小到0.55,光学对比度变化大.     

琼脂基凝胶电解质的制备及其在电致变色器件中的应用

为制备基于琼脂凝胶电解质的电致变色器件,以琼脂作为基体,双三氟甲烷磺酰亚胺锂(LiTFSI)为电解质盐,碳酸丙烯酯(PC)为增塑剂,去离子水为溶剂,加热搅拌先制得电解质溶液。采用电沉积法制备普鲁士蓝(PB)薄膜并组装电致变色器件。将配制好的电解质溶液注入电致变色器件中,电解质溶液在冷却后直接在器件中变为凝胶,得到基于琼脂凝胶电解质的电致变色器件。研究了器件的电致变色性能,结果表明,器件在波长580 nm处透过率调制幅度达39.9%,器件的着色响应时间为16.2 s,褪色响应时间为15.2 s,表现出较快的响应速度。     

铁氰化镍电致变色器件的制备与性能研究

由于具备氧化还原的可逆性及氧化还原过程中伴随不同的颜色变化,普鲁士蓝及其类似物在电致变色领域引起了广泛的关注。因此,采用一种简单高效的直接沉淀法制备出纳米铁氰化镍粉体,并通过旋涂法制备了铁氰化镍薄膜。为了得到更均匀牢固的薄膜,在悬涂液中加入3,4-乙烯二氧噻吩单体的聚合物(PEDOT:PSS)或聚乙烯吡咯烷酮(PVP),研究了不同聚合物对成膜均匀性及其电致变色性能的影响。将薄膜组装成器件,考察了透过率和响应时间等电致变色性能。结果表明:所制备的铁氰化镍粉末达到了纳米级别,在400nm波长时,基于铁氰化镍PEDOT:PSS复合材料薄膜和基于铁氰化镍PVP复合材料薄膜两种器件的调制幅度达到最大值,分别为15%和12%,前者的着色时间和褪色时间分别为4和21s;后者的着色时间和褪色时间分别为51和36s。     

氧化钨片状结构的制备及其电致变色器件的性能

报道了一种不需要晶种层直接在导电玻璃表面生长氧化钨薄膜的简易方法,这比需要晶种层生长薄膜的方法所用时间少、成本低、操作简便。研究了不同溶剂和表面活性剂对氧化钨形貌的影响,用X-射线衍射(XRD)、扫描电镜(SEM)及透射电镜(TEM)表征了所制备的氧化钨纳米片和纳米块的晶相和微观结构。结果表明:由酒石酸钠作表面活性剂制得的纳米片尺寸较小。对组装成的器件进行了透过率和响应时间等电致变色性能测试,结果表明:由比表面积大和结构稳定的纳米薄膜组成的电致变色器件表现出较好的电致变色性能。     

三氧化钼纳米带自组装柔性薄膜超级电容器的制备及其性能研究

采用单质钼为钼源,水热合成了具有高长径比的三氧化钼(MoO_3)纳米带,并通过减压抽滤制备了MoO_3纳米带自组装柔性薄膜。对MoO_3纳米带的形貌和结构进行了表征,采用三电极体系研究了MoO_3纳米带的电化学电容行为,考察了MoO_3纳米带自组装柔性薄膜直接作为电极组装柔性薄膜电容的性能。实验结果表明,MoO_3纳米带的长度为6～10μm,宽度为100～300 nm,厚度为7～10 nm,MoO_3纳米带自组装薄膜显示了很高的柔性,在100 mV/s的扫描速率下面积比电容为340 mF/cm~2。以此组装的柔性薄膜电容在5 mA/cm~2的电流密度下,2 000圈循环后电容保持率可达80%。     

钒取代磷钨酸盐/刚果红电致变色膜的制备及性能研究

基于Layer-by-Layer技术,将有机染料刚果红和钒取代磷钨酸盐(K7P2W16V2O62·18H2O)复合,制备了一种复合电致变色材料:[PEI/P2W16V2/PEI/刚果红]20.紫外-可见吸收光谱监测显示复合材料的合成均一、稳定.紫外可见分光光度计与电化学工作站联机表明:染料刚果红的加入使复合材料实现了由红色到栗色、再到红色的可逆颜色变化,增加了磷钨酸盐电致变色材料的变色种类.并且此复合材料展现了良好的电致变色性能,复合材料在650 nm处的光反差可以达到20.11%,复合膜的着色效率可以提高到33 cm2C-1,着色时间和褪色时间分别缩短到4.74 s和8.16 s.     

多孔Co3O4纳米片的制备及其电化学性能研究

采用溶剂热法制备片状Co(CO3)0.5(OH).0.11H2O前驱物,经400℃煅烧2 h即可得到多孔Co3O4纳米片.通过场发射扫描电镜(FESEM)和透射电镜(HRTEM)观测了纳米片的形貌,利用X射线衍射(XRD)分析了纳米片的结构,通过循环伏安、恒流充放电和交流阻抗测试了材料的电化学电容性能.结果表明:多孔Co3O4纳米片厚度约为50 nm,孔径主要分布在10 nm左右;0.5 A/g恒流充放电情况下,比容量高达707 F/g,当电流密度高达8 A/g时比容量依然高达547 F/g;同时,该材料循环1 000次后,容量保持率为97.4%.     

全固态电致变色玻璃的光透过率研究

用sol-gel方法,以钨粉和H2O2为主要原料,通过聚乙二醇和碳酸丙烯酯掺杂,制备出WO3电致变色薄膜.用此种薄膜组装成全固态电致变色玻璃器件,对玻璃器件进行着色-褪色过程的光透过率测试.结果表明：掺杂制备的WO3电致变色薄膜性能要优于未掺杂的薄膜,碳酸丙烯酯掺杂制备的薄膜变色性能较好;此外,还从WO3电致变色薄膜的变色机理和离子传输过程对玻璃的光透过率进行了一定的讨论.     

N掺杂Co3O4纳米片的制备以及活化过一硫酸盐的性能研究

采用牺牲模板法合成N掺杂Co₃O₄纳米片（N-Co NS）,通过透射电子显微镜（TEM）、原子力显微镜（AFM）和光电子能谱（XPS）对制备材料的形貌结构、化学组成进行分析,并通过催化活化过一硫酸盐（PMS）降解水中双酚A （BPA）来探究催化剂的催化性能.实验结果表明与Co₃O₄纳米颗粒（Co NP）、Co₃O₄纳米片（Co NS）相比,N-Co NS表现出了较高的催化性能.在PMS浓度为2 mmol·L^-1、BPA初始质量浓度为50 mg·L^-1的反应条件下,N-Co NS在10 min内完全降解水中的BPA,表明N掺杂和二维纳米片结构有利于催化剂性能的提升.通过pH及离子影响实验证实N-Co NS在复杂水化学环境中仍具有较高的活性.此外结合自由基捕获实验和电子顺磁共振（EPR）测试证实反应体系中产生了高氧化活性的羟基自由基和硫酸根自由基.     

Self-cleaning glass coated with Fe^3＋ -TiO2 thin film

The self-cleaning glass coated with Fe^3 -TiO2 photocatalytic thin film was prepared by sol-gel process from the system Ti(OC4H9),-NH(C2H4OH)2-C2H5OH-H2O containing FeCl3. The microstructure and properties of the film were studied using differential thermal analysis-thermogravimetry(DTA-TG), X-ray diffration (XRD) and scanning electron microscope(SEM). The transmittance of the self-cleaning glass was measured by using UV-Vis spectrometer. The effects of content of Fe^3 and the thickness of Fe^3 -TiO2 thin film on the photocatalytic ac-tivity were examined. The results show that the photocatalytic thin films are mainly composed of Fe3O4 and TiO2 particles within 10-100 nm. The appropriate amount of Fe^3 is effective for improving the photocatalytic activities of TiO2. The best photocatalytic activity is obtained when the molar ratio of Fe^3 to TiO2 is 0. 005 and the glass is coated with 9 layers.     

Study of GaN MOS-HEMT using ultrathin Al2O3 dielectric grown by atomic layer deposition

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic-layer deposited (ALD) Al₂O₃ as the gate dielectric. Through further decreasing the thickness of the gate oxide to 3.5 nm and optimizing the device fabrication process, a device with maximum transconductance of 150 mS/mm was produced. The drain current of this 0.8 μm gate-length MOS-HEMT could reach 800 mA/mm at +3.0 V gate bias. Compared to a conventional AlGaN/GaN HEMT of similar design, better interface property, lower leakage current, and smaller capacitance-voltage (C-V) hysteresis were obtained, and the superiority of this MOS-HEMT device structure with ALD Al₂O₃ gate dielectric was exhibited. Supported by the National Natural Science Foundation of China (Grant No. 60736033) and the National Basic Research Program of China (“973“) (Grant No. 51327020301)     

Ferroelectric properties of Bi3.4Ho0.6Ti3O12 thin films prepared by sol-gel method

We have prepared the Ho-substituted bismuth titanate (Bi_3.4Ho_0.6Ti₃O₁₂, BHT) thin films on Pt/Ti/SiO₂/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm² and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×10⁹ switching cycles at 1 MHz frenquency, and the BHT film shows good insulating behavior according to the test of leakage current. Supported by the Hubei Province Natural Science Foundation (Grant No. 2007ABA309)     

Modification of nano-TiO2 by Al2O3 in-situ coating

A novel technology of in-situ coating Al₂O₃ on the surface of H₄TiO₄ was developed to prevent the aggregation of nano-TiO₂ powders and improve the dispersibility and thermal stability in the way of forming a uniform coating layer. The heterogeneous nucleation was conducted to prepare the precursor of nano-TiO₂ and then Al₂O₃ was coated on the surface of precursor. The effects of Al₂O₃ in-situ coating on the properties of nano-TiO₂ were investigated. The results show that H₄TiO₄ can be dispersed well under alkaline condition (pH 8.5) and the heterogeneous nucleation can be controlled easily. The optimized uniform coating layer is obtained by adding 5% (mass fraction) and 10% of Al₂O₃ and the aggregation of nano-TiO₂ powders is effectively inhibited and the dispersibility is obviously improved. The crystal sizes of TiO₂ powders are 12.3, 11.4 and 8.7 nm after coating 0,5% and 10% of Al₂O₃ respectively. Al₂O₃ on the surface of particulates in amorphous phase could increase the thermal stability of nano-particles after calcined at 550 °C. Foundation item: Project(04GK2007) supported by Hunan Industrial Key Project of Science and Technology     

Mechanism and behaviors of Cr3+-doped TiO2

TiO₂ powder and TiO₂ thin film on the surface of glazed ceramic tile were prepared by sol-gel method. The influences of different doping Cr³⁺ concentration on the photocatalytic activity of TiO₂ were discussed, UV-visible and X-ray diffraction analysis were used to test the performance of TiO₂ powder and film. The results indicate that photocatalytic activity of doping Cr³⁺-TiO₂ thin film is higher than that of powder, and the interaction between Cr³⁺-doped and substrate can greatly enhance the photocatalytic activity. The results of X-ray diffraction and photoabsorption show that the Cr³⁺-doped energy level in TiO₂ is 0.62 eV high from the top of valence band, which belongs to the type of deep energy level doping. On the basis of the semiconductor energy level theory and Cr³⁺ dopant energy level, the semiconductor energy level model of Cr³⁺ in TiO₂ powder and thin film were established, and the doping mechanisms of Cr³⁺-doped in TiO₂ powder and thin film were analyzed. Foundation item: Project (20466001) supported by the National Natural Science Foundation of China     

Pressureless sintered 3Y-TZP/20%Al2O3 composite ceramic

Nanometer 3Y-TZP/20%Al₂O₃ (mass fraction) composite powders prepared by the chemical coprecipitation method were pressureless sintered at 1550 °C for 2 h. Effects of calcining temperatures at 800 °C, 1 000 °C, and 1 200 °C on phase structure, relative density, and Vicker’s hardness of the sintered bodies were studied. The results show that 1 000 °C was the optimal calcining temperature, and the powder calcined was composed of tetragonal zirconia with the Scherrer crystalline size of 6.3nm. The relative density was up to 98.5% under pressureless sintering, and the sintered body was t-ZrO₂ (without m-ZrO₂)+α-Al₂O₃ with the average size of 0.4 μm. Foundation item: State Key Laboratory for Powder Metallurgy(No.9706-36) Biography of the first author: YIN Bang-yao, born in 1966, majoring in advanced ceramic materials.     

Luminescent properties of BaO-La2O3-B2O3 glasses with dopant

The luminescent properties of glasses synthesized in air atmosphere by conventional high temperature process were stud{ed. The emissions spectra of Eu^2 and Eu^3 were observed in BaO-La2O3-B2O3-Eu2O3 glasses.The results show that the broad emission peaks at 430 nm correspond to 5d→4f emission transition of Eu^2 , the sharp emission peaks at 592, 616, 650 and 250 nm correspond to 5^D0→1Fj(j=1--4) emission transition of Eu^3 ,respectively, which indicates that the BaO-La2O3a-B2O3-Eu2O3 glass can convert ultraviolet and green omponents of sunlight into blue and red light so as to increase the intensity of blue and red light, respectively. The luminescent in--tensity of Eu^2 increases with increasing the molar ratio of Tb^3 in BaO-La2O3-B2O3-Eu2O3a-Tb4O3 glasses, whereas the luminescent intensity of Eua^3 decreases. So the luminescent intensity of Eu(Ⅲ,Ⅱ) is influenced by Tb^3 .These phenomena can be explained by electron transfer mechanism; Eu^3 (4f6) Tb^3 (4f^8)→Eu^2 (4f′) Tb^4 (4f′). Taking advantage of the luminescent properties of BaO-La2O3-B2O3-Eu2O3 glasses, light-conversion glass for agriculture can be produced.     

Characteristics of LiCoO2, LiMn2O4 and LiNi0.45Co0.1Mn0.45O2 as cathodes of lithium ion batteries

LiNi_0.45Co_0.10Mn_0.45O₂ was synthesized from Li₂CO₃ and a triple oxide of nickel, cobalt and manganese at 950 °C in air. The structures and characteristics of LiNi_0.45Co_0.10Mn_0.45O₂, LiCoO₂ and LiMn₂O₄ were investigated by XRD, SEM and electrochemical measurements. The results show that LiNi_0.45Co_0.10Mn_0.45O₂ has a layered structure with hexagonal lattice. The commercial LiCoO₂ has sphere-like appearance and smooth surfaces, while the LiMn₂O₄ and LiNi_0.45Co_0.10Mn_0.45O₂ consist of cornered and uneven particles. LiNi_0.45Co_0.10Mn_0.45O₂ has a large discharge capacity of 140.9 mA · h/g in practical lithium ion battery, which is 33.4% and 2.8% above that of LiMn₂O₄ and LiCoO₂, respectively. LiCoO₂ and LiMn₂O₄ have higher discharge voltage and better rate-capability than LiNi_0.45Co_0.10Mn_0.45O₂. All the three cathodes have excellent cycling performance with capacity retention of above 89.3% at the 250th cycle. Batteries with LiMn₂O₄ or LiNi_0.45Co_0.10Mn_0.45O₂ cathodes show better safety performance under abusive conditions than those with LiCoO₂ cathodes. Foundation item: Project(50302016) supported by the National Natural Science Foundation of China; Project(2005037698) supported by the Postdoctoral Science Foundation of China