阴极沉淀法制备纳米AlO3粉体及表征

采用阴极电化学沉淀方法制备氧化铝纳米粉体．对得到的纳米粉体进行了光吸收性能测试．并对其形成机理进行了初步的探讨。利用阴离子交换膜为隔膜的电解槽，在不添加分散剂的情况下。控制阴极的电流密度在150～500A／m^2范围．电解一定浓度的硝酸铝溶液，在阴极室内得到Al（OH）、沉淀，在500℃下焙烧2h．得到不同粒度的Al2O3颗粒。用TEM和XRD分析表明：当阴极的电流密度为300A／m^2时，得到的Al2O3粒度尺寸在30-40nm左右，晶型为γ-AlO3，对波长为370nm左右的紫外光有一定的吸收能力。     

Al_2O_3/SiO_2/介孔SiO_2包覆型复合磨料的制备及表征研究

先以纳米Al_2O_3为核,Na_2SiO_3和柠檬酸为原料,采用非均匀成核法制备出Al_2O_3/SiO_2包覆型复合纳米粉体;再以十六烷基三甲基溴化铵(CTAB)为介孔模板剂,通过自组装法制得Al_2O_3/SiO_2/介孔SiO_2包覆型复合磨料;并借助X射线衍射、红外光谱、透射电镜、能谱和N_2吸附-脱附等手段对样品进行表征。结果表明:SiO_2和介孔SiO_2依次包覆在Al_2O_3表面形成了Al_2O_3/SiO_2/介孔SiO_2包覆型复合磨料,其具有MCM-48型介孔孔道结构,平均孔径为2.3nm,比表面积为454m~2/g,孔体积为0.43cm~3/g。     

纳米纤维素/Fe3O4纳米球的原位合成及其电化学性能

利用实验室自制茶梗纳米纤维素原位合成纳米纤维素(CNC)/四氧化三铁(Fe_3O_4)纳米球,并对其粒径大小、结晶性质、磁性性能和电化学性能进行分析表征。结果表明,通过原位合成法所制得CNC/Fe_3O_4纳米球,粒子间分散性良好,直径约为10～30 nm;CNC/Fe_3O_4纳米球具有磁化强度34.9 A·m~2/kg的磁特性;CNC/Fe_3O_4纳米球表现出良好的电化学性能,CNC/Fe_3O_4电极的比电容主要是Fe_3O_4产生的赝电容,在电流密度0.03 A/g时,比容量可达30.14 F/g,在0.04 A/g电流密度下,经过500次充放电后容量保持率为78.76%。CNC/Fe_3O_4电极中离子的扩散为Warburg机理。     

Sc_2O_3掺杂对Y_2O_3-Gd_2O_3-HfO_2难熔稀土氧化物直热式阴极热发射性能的影响

Y_2O_3-Gd_2O_3-HfO_2难熔稀土氧化物直热式阴极具有制备工艺简单,热发射电流密度大,次级电子发射系数大,寿命长等优点,在大功率连续波磁控管中具有很好的应用潜力。为进一步提高Y_2O_3-Gd_2O_3-HfO_2阴极的热发射性能,本文对该阴极的发射物质进行了不同比例Sc_2O_3的掺杂,结果表明,Sc_2O_3的掺杂能有效提高Y_2O_3-Gd_2O_3-HfO_2阴极的热发射电流密度,其中,掺杂10%(质量比)Sc_2O_3的Y_2O_3-Gd_2O_3-HfO_2阴极热发射电流密度在1500℃下达到5.3 A/cm~2,比未掺杂时提升了35.5%。由于在阴极激活过程中Sc_2O_3与Y_2O_3形成了固溶体,合成氧化物中Sc得到电子并释放出游离Sc,增强了涂层的导电性,所以,Sc_2O_3掺杂Y_2O_3-Gd_2O_3-HfO_2难熔稀土氧化物直热式阴极热发射性能具有显著提高。     

基于BP神经网络的Ni-Al_2O_3镀层粒子复合量预测研究

采用超声波辅助电沉积法在A3钢表面制备了Ni-Al_2O_3镀层,通过BP神经网络对不同工艺参数下制备镀层的Al_2O_3粒子复合量进行预测,最后利用透射电镜(TEM)观察镀层结构组织。结果表明,该BP神经网络结构为3×8×1时,其预测值与真实值的拟合度R=0.9991,相对误差的最大值与最小值分别为1.71%与0.74%。TEM分析表明,当Al_2O_3粒子浓度9g/L,电流密度3A/dm2,温度40℃时,Ni-Al_2O_3镀层组织较为紧密,其平均粒径约为20nm。     

磁控溅射制备Er~(3+)掺杂Al_2O_3薄膜的上转换发光特性

Al_2O_3作为太阳能电池的钝化层,如果掺入稀土元素Er~(3+)通过吸收红外光并将其上转换为可见光被硅吸收,则可以提高太阳能的利用率。本文采用磁控溅射法制备得到厚度为500 nm左右的不同浓度Er~(3+)掺杂Al_2O_3薄膜。X射线衍射测试表明薄膜由θ-(Al,Er)_2O_3、Al_(10)Er_6O_(24)和ErAlO_3相构成。通过波长980nm的激光器激发产生光频上转换,获得了490 nm的绿光和670nm的红光发光,分别对应于Er~(3+)的~4F_(7/2)→~4I_(15/2)和~4F_(9/2)→~4I_(15/2)的能级跃迁。当Er~(3+)掺杂浓度为0.6%(摩尔比)时,上转换发光强度最强。上转换发光强度受到Al_(10)Er_6O_(24)和ErAlO_3晶体的生成以及Er~(3+)掺杂浓度的影响,并且对红光的影响要大于绿光。Er~(3+)掺杂Al_2O_3薄膜相比粉体材料具有较低的声子态密度,从而抑制了Er~(3+)无辐射跃迁,得到了不同于粉体材料的490nm绿光的发光。     

TMA脉冲和吹扫时间对原子层沉积的氧化铝薄膜的影响

采用原子层沉积技术(ALD)进行Al_2O_3薄膜工艺研究,获得85℃低温Al_2O_3薄膜ALD的最佳工艺条件。使用椭偏仪测试厚度,使用扫描探针显微镜对薄膜表面形貌进行分析,使用紫外-分光光度计对薄膜的透过率进行分析,所用水汽透过率测试仪器是自行开发的基于钙电学法的测试仪器。分析了在85℃低温下的生长工艺条件对薄膜性能的影响,从前驱体脉冲时间,吹扫时间等工艺条件,对Al_2O_3薄膜的工艺条件进行优化。以三甲基铝(TMA)和H_2O为前驱体制备的Al_2O_3薄膜:沉积速率为0.1nm/cycle,表面粗糙度为0.46nm,对550nm波长光透过率为99.2%,薄膜厚度不均匀性为1.89%,200 nm的Al_2O_3薄膜的水汽透过率为1.55×10~(-4) g/m~2/day。     

真空烧结制备电触头Cu-W/Al_2O_3合金组织和侵蚀性能分析

选择真空烧结方法制得组成为Cu-33.6W/Al_2O_3与Cu-26.8W/Al_2O_3的两种合金,并对电导率、组织致密度以及表面硬度进行分析,表征了经过电弧侵蚀得到的微观形貌及其熔焊性能。研究结果表明:以真空烧结方式制得的Cu-W/Al_2O_3触头达到了高于97%的致密度,随着W含量的提高,试样电阻率减小,硬度增加。在铜基体中出现了弥散态的Al_2O_3颗粒,实现弥散增强效果,显著提升合金耐高温能力。对阳极与阴极触头进行每次电接触测试时都发生了质量减小。采用DC(30 V,30 A)参数对触头阳极与阴极进行侵蚀,形成了长条状、液滴形以及凹凸变化的微观侵蚀形貌。施加10 A电流时,在最初测试阶段形成了大幅波动的熔焊力,随着合金内的W比例从26.8%提高到33.6%的过程中,材料获得了更强的抗熔焊性能。     

W80/Cu-Al_2O_3复合材料的耐电弧侵蚀性能

采用粉末冶金和熔渗法制备W80/Cu-Al_2O_3复合材料,测试其密度、硬度和导电率,探究Al_2O_3对W80/Cu复合材料耐电弧侵蚀性能的影响。结果表明,添加Al_2O_3对复合材料的致密度和导电率影响不大,硬度有所增加;W80/Cu和W80/Cu-Al_2O_3复合材料在不同电流条件下燃弧时间和燃弧能量基本相同,但W80/Cu-Al_2O_3复合材料的稳定性更高;在30 V、30 A条件下,W80/Cu复合材料在电弧侵蚀过程中发生材料从阴极向阳极转移,加入Al_2O_3增强相后,材料的转移方向为阳极向阴极转移,且材料损耗量降低,喷溅现象减少,电弧侵蚀后触头表面更加平整。     

超细晶镍钴合金的电铸工艺

为了进一步提高金属的硬度和强度,采用电铸工艺通过添加剂TN2提高阴极过电位,抑制晶粒生长,制备了超细晶镍钴合金层,研究了电流密度和添加剂TN2对铸层晶粒大小的影响.结果表明:提高电流密度可以细化晶粒,当电流密度从5 A/dm~2 增加到15 A/dm~2 时,晶粒大小从5μm 细化到500 nm;添加0.15 g/L TN2 时,铸层表面半光亮,晶粒进一步细化(小于500 nm),硬度高达60 HRC.     

Broadband Light Absorption and Efficient Charge Separation Using a Light Scattering Layer with Mixed Cavities for High‐Performance Perovskite Photovoltaic Cells with Stability

CH₃NH₃PbI₃ is one of the promising light sensitizers for perovskite photovoltaic cells, but a thick layer is required to enhance light absorption in the long‐wavelength regime ranging from PbI₂ absorption edge (500 nm) to its optical band‐gap edge (780 nm) in visible light. Meanwhile, the thick perovskite layer suppresses visible‐light absorption in the short wavelengths below 500 nm and charge extraction capability of electron–hole pairs produced upon light absorption. Herein, we find that a new light scattering layer with the mixed cavities of sizes in 100 and 200 nm between transparent fluorine‐doped tin oxide and mesoporous titanium dioxide electron transport layer enables full absorption of short‐wavelength photons (λ < 500 nm) to the perovskite along with enhanced absorption of long‐wavelength photons (500 nm < λ < 780 nm). Moreover, the light‐driven electric field is proven to allow efficient charge extraction upon light absorption, thereby leading to the increased photocurrent density as well as the fill factor prompted by the slow recombination rate. Additionally, the photocurrent density of the cell with a light scattering layer of mixed cavities is stabilized due to suppressed charge accumulation. Consequently, this work provides a new route to realize broadband light harvesting of visible light for high‐performance perovskite photovoltaic cells.     

Synthesis and enhanced light absorption of alumina matrix nanocomposites containing multilayer oxide nanorods and silver nanoparticles

In this paper, multilayer oxide nanorods were deposited in the nanopores of anodic aluminum oxide (AAO) via solution infiltration followed by heat treatment. The nanorods have a core–shell structure. First, the shell (nanotube) with the thickness of about 40 nm was made of TiO₂ through the hydrolysis of (NH₄)₂TiF₆. Second, silver nanoparticles with the diameter of about 3 nm were added into the TiO₂ layer through thermal decomposition of AgNO₃ at elevated temperatures. Then, cylindrical cores (nanorods) of CoO and ZnO with 200 nm diameter were prepared, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and composition of the nanorods. UV–vis light absorption measurements in the wavelength range from 350 to 1000 nm were performed to study the effect of nanorod and nanoparticle addition on the light absorption property of the alumina nanocomposites. It is found that CoO nanorods increase the light absorption of the alumina matrix composite in the wavelength range from 500 nm to 800 nm, but the TiO₂ shell does not increase the light absorption much. The ZnO nanorods do not change the light absorption either. However, the addition of silver nanoparticles significantly enhances light absorption of both AAO/TiO₂/Ag/CoO and AAO/TiO₂/Ag/ZnO nanocomposites. This increase in the visible light absorption reveals that there exists surface plasmon around the fine silver nanoparticles in the nanorods.     

Study of chromium modified TiO2 nano catalyst under visible light irradiation

Visible light active photocatalysts were successfully prepared by incorporating chromium into anatase TiO2 at two Cr/Ti atomic ratios (0.03% and 0.11%) by the use of a modified sol-gel process. Results show that the size of the chromium modified TiO2 particles is approximately 14-25 nm. As indicated by diffuse reflectance ultra violet/visible absorption spectra, heavier chromium dosage tends to result in greater absorption in both ultra violet and visible light. The simulation results from Cr K-edge X-ray absorption spectra suggest that Cr(0) and Cr(III), accounting for approximately 25% and 75% of total Cr, respectively, coexist in the TiO2 catalyst doped with 0.11% Cr. Cr dopant is suggested to be responsible for the phenomenon of enhanced light absorption in both ultra violet and visible regions. Further, Cr(0) can act as an electron remover because of the formation of the Schottky barrier between Cr(0) and TiO2, thus reducing the possibility of electron hole recombination. Photo-catalytic degradation of methylene blue under irradiation of blue light (with peak flux at 460 nm wavelength and a small flux near 367 nm) was considerably enhanced under appropriate reaction time (12 and 24 h) as small amount of Cr was doped into anatase titanium dioxide catalyst. After prolonged reaction time, Cr(0) was suggested to be poisoned and/or oxidized by SO4(2-), one of the final products of mineralizing methylene blue, thus loosing the capability of the electron hole separation.     

基材含微粒的空腔结构吸声器吸声性能预报的研究

采用一种近似方法计算含球形微粒和空腔结构吸声器的吸声系数,即首先用自洽理论,计算掺入微粒的复合材料的等效力学参数,再用求空腔结构吸声器的等效力学参数方法,计算这种复合材料具有空腔结构的该参数,最后用声波在分层吸收媒质中传播模型来计算能量吸收系数。所得数值模拟结果表明:基材掺入微粒形成的复合材料其吸声性能有不同程度的变化,性能的提高与否与基材和微粒的种类、孔隙率及粒子分布概率密度等因素有关;对于某些含微粒的复合材料若开空腔则可进一步提高吸声器的低频吸声性能。总之,基材含微粒的空腔结构吸声器的吸声系数是以不同程度的灵敏度受控于表征微粒的参数以及空腔结构。     

椰壳活性炭基超级电容器的研制与开发

为了开发体积小巧、大功率放电性能优良的超级电容器,选用比表面积1 660m2/g的椰壳活性炭,采用扣式电池结构,通过恒电流充放电、电化学阻抗谱、扫描电子显微镜等方法对其用于超级电容器的性能进行了考察。结果表明,选用椰壳活性炭的最大比容量为79F/g,大功率放电性能优良。继而采用该种椰壳活性炭为电极活性物质,以6m o l/L KOH为电解液,外包装采用涂覆防腐蚀尼龙层的铝箔袋软包装组装了1V、70F的超级电容器,外形尺寸为35mm×43mm×6mm。测试结果表明其比功率密度为170W/kg或330W/L,比能量密度1W h/kg,大功率放电特性较好。     

Facile one-step synthesis of Cu2O@Cu sub-microspheres composites as anode materials for lithium ion batteries

Cu_2O@Cu sub-microspheres composites with a narrow particle size distribution from 300 to 500 nm was successfully fabricated by one-step synthesis through the direct thermal decomposition of copper nitrate(Cu(NO_3)_2) in octadecylamine(ODA) solvent. As anode materials for lithium ion batteries, the Cu_2 O@Cu composites obviously possess high specific capacity, excellent cyclic stability and rate capability. The coulombic efficiency is about 84% in the 1 st cycle and increases significantly up to 97.8% during successive cycles at various current densities. Even under a high current density of 500 m A g~(-1), the discharge capacity of Cu_2 O@Cu composites remains up to 200 m Ah g~(-1). The excellent electrochemical properties are ascribed to the synergistic effect between high electronic conductivity and volume-buffering capacity of metallic copper composited with Cu_2 O.     

N、Fe共掺杂纳米TiO2的制备和性能

以钛酸丁酯为钛源,用醇热法制备了N、Fe单掺杂及共掺杂纳米TiO₂。对样品的晶型结构、表面形貌、比表面积、紫外可见吸收、光致发光和分解水制氢催化性能分别进行了表征。结果表明,在500℃退火的N、Fe共掺杂TiO₂样品均为锐钛矿相棱形纳米颗粒,分散性较好,平均粒径约20 nm;N、Fe共掺杂的摩尔分数分别为5.0%和2.0%时,样品具有良好的可见光吸收活性,对光的吸收从387 nm（未掺杂锐钛矿相TiO₂）红移至510 nm处。主要原因可能是,N和Fe共掺杂在其禁带中产生杂质能级,导致其禁带宽度减小;N、Fe单掺杂及共掺杂改性,有效抑制了电子-空穴的复合,提高了光生载流子的分离效率;在可见光下（λ>400 nm）N、Fe共掺杂TiO₂具有较高的光催化分解水制氢活性,氢气生成速率为299.2μmol·g^-1·h^-1。     

城市在役旧煤气管道的阴极保护研究及实践

城市管道地下环境复杂,拟采用牺牲阳极法对一条城市在役管道主线实施阴极保护,采用变频选频法和分段馈电试验法获得了管道的保护电流密度等重要参数,并探讨分析了影响城市旧煤气管道保护电流密度设计的某些因素.最终方案中阴极电流密度分别为0.65～1.00 mA/m2(武汉市中北路),1.50～3.00 mA/m2(武汉市徐东路),2.50～3.00 mA/m2(武汉市团结路至团结一路),影响电流密度的因素有管线腐蚀状况、土壤腐蚀性及阀门井数量.该方案成功地实施于工程中.     

利用膜气液接触器制备纳米材料的研究

利用膜气液接触器制备了纳米CaCO3、SrCO3、Al(OH)3和Al2O3粒子.根据气液反应理论预测了Ca(OH)2浓度、CO2分压等对CO2吸收速率的影响规律,并得到了实验验证.在实验条件下,Ca(OH)2浓度和CO2分压对CaCO3粒子的形貌影响较小,粒径约为70nm.添加PVP和PEG后,粒度降为48nm左右,分散性明显提高.所得SrCO3纳米粒子为球形,粒度均匀,Sr(OH)2浓度对粒子粒度具有明显影响.Al(OH)3粒子为球形,50nm左右,煅烧后得到Al2O3,粒子尺寸增加至70nm左右.反应后用稀盐酸清洗膜使之再生,膜重复使用9次,膜传质系数未见明显降低.