Ni(OH)2及Co(OH)2片状纳米晶体的合成与表征

使用强碱氢氧化钾为沉淀剂,通过水热法成功合成了具有六角形貌的过渡金属氢氧化物Ni(OH)2及Co(OH)2片状纳米晶.利用X射线粉末衍射仪和透射电子显微镜对样品的结构和形貌进行了表征.透射电镜观察结果显示Ni(OH)2相为规则六角纳米片,Co(OH)2相为纳米片和纳米棒的混合物.选区衍射结果指出Ni(OH)2及Co(OH)2纳米晶体均为单晶体.Ni(OH)2及Co(OH)2纳米片的产率分别达到了70%和90%.将实验结果同前人的过渡族金属氢氧化物纳米片报道进行了比较,提出了一个新的片状纳米晶的形成机制,指出在正常的沉淀条件下,Ni(OH)2及Co(OH)2纳米晶的稳定形貌总为六角片状.     

纳米复合β-Ni(OH)2电极材料的制备与电化学性能

氢氧化镍(Ni(OH)2)是碱性二次电池的正极材料,本文采用化学沉淀法制备了纳米Ni(OH)2超微粉体,XRD检测证实晶型为β相，用TEM对粉体进行形貌分析，结果表明所得产物是颗粒状纳米晶，粒径20nm左右．将纳米Ni(OH)2粉以10％的比例掺杂到常规球镍中制得纳米复合β-Ni(OH)2电极材料，其电化学容量和放电平台较常规球镍有很大提高，大电流放电时，纳米复合β—Ni(OH)2电极材料的电化学容量比常规球镍提高达40．9％。     

纳米β-Ni(OH)2与球型Ni(OH)2的热性能比较研究

用配位沉淀法合成出纳米级Ni（OH）2，并对其进行XRD，TEM，DSC分析，分析结果表明，所得纳米β-Ni（OH）2为可用作电极材料的β-Ni（OH）2，粒径为30－40nm，且热分解温度比普通球镍低10℃左右，摩尔分解热比普通球镍低4－7kJ，从理论上分析了产生此现象的原因。     

β-Ni(OH)2和NiO单晶纳米结构的水热合成与TEM表征

用水热法合成了β-Ni(OH)2单晶纳米薄片,并用透射电子显微镜观察其显微结构.发现这些纳米薄片呈六边形,横向尺寸45 nm～140 nm,厚度20 nm～50 nm.六边形纳米片的上下表面是(001),六个侧面可确定为(100),((1)10)或(0(1)0),紧邻侧面夹角120°.六角结构的β-Ni(OH)2呈六边形时系统能量最低.β-Ni(OH)2纳米薄片经500 ℃热分解即转化为NiO单晶纳米卷、纳米槽和纳米片.NiO纳米结构的外缘尺寸为25 nm～120 nm,纳米卷内空尺寸10 nm～24 nm,纳米槽凹坑尺寸10 nm～20 nm.β-Ni(OH)2纳米薄片中可能存在缺陷、微孔或结晶较差的区域,这些区域的热分解速率快,有利于形成NiO纳米卷.     

FeCo2S4/Ni(OH)2的合成及超电容性能研究

将多组分活性材料组合成新的结构用作电极材料是提高超级电容器性能的一种有效措施。采用典型的两步水热法与电沉积法制备了FeCo2S4/Ni(OH)2复合纳米材料,并表征其物理及电化学性能。结果表明,FeCo2S4纳米花被电沉积上的Ni(OH)2纳米片包围,形成三维互连网状结构,有利于电极材料与电解液的充分接触。所得的FeCo2S4/Ni(OH)2复合电极材料显示出极高的比电容(当电流密度为1 A·g^-1时,比电容达1588.2 F·g^-1)、优异的倍率性能及循环稳定性。此外,以FeCo2S4/Ni(OH)2为正极、活性炭为负极组装了非对称超级电容器。结果显示,非对称超级电容器具有高能量密度及良好的循环稳定性。     

Zn_5(OH)_8Cl_2·H_2O微纳米片的超声合成与热解以及光致发光性能研究

运用超声化学法,以细化后的Zn、CCl_4和H_2O为原料合成了Zn_5(OH)_8Cl_2·H_2O微纳米片,将Zn_5(OH)_8Cl_2·H_2O微纳米片在500℃下高温裂解,收集并表征了所得固相产物的结构形貌和光致发光性能,同时重点分析了所得固相产物的形成过程和生长机理。结果表明:该制备方法反应迅速,合成的Zn_5(OH)_8Cl_2·H_2O纳米片径向尺寸分布在400 nm到3μm;所得到的固相产物为形貌不同的ZnO微纳米晶体,形成过程经历了高温裂解和置换反应;晶体生长符合VS生长机理。Si基底和Al_2O_3基底ZnO晶体在约515 nm处均出现了较宽绿峰,前者带边发光峰与深能级发光峰强度比相对较大,表明其缺陷较少结晶较好,该结果可指导Zn_5(OH)_8Cl_2·H_2O和多形貌ZnO微纳米晶体的可控制备与应用。     

Ni（OH）1.4（SO4）0.3纳米带和相关的结构演变

氢氧化镍作为碱性蓄电池的正极活性物质，广泛应用于镍氢、镍镉和镍锌等电池。＋2价氢氧化镍主要有α和β两种晶型。β-Ni（OH）2属于六角晶系（单胞参数为：a=0．313nm，c=0．463nm），其中OH^-为六角密积形成等间距层状结构，氢氧键平行于c轴，Ni^2＋处于层间八面体位置。α-Ni（OH）2晶化程度相对较差，其结构仍属于六角晶系（单胞参数为：a=0．31nm，c=2．268nm），β-Ni（OH）2的层状结构在此仍然保留，但层间却无序的插有水分子及酸根离子，插入酸根离子的种类取决于母溶液。     

纳米级β-Ni(OH)2电极材料的制备

采用均相沉淀法使ＮｉＣｌ_2溶液与沉淀剂ＮａＯＨ反应,制备出纳米级Ｎｉ（ＯＨ）_2超微粉末。用ＸＲＤ检测,证实其为电极用β－Ｎｉ（ＯＨ）_2,用ＴＥＭ对样品进行形貌分析,结果表明,所得产物为不规则的颗粒状的纳米晶,粒径为 ２０～４０ ｎｍ。研究还初步探讨了沉淀剂浓度、反应温度、配合剂用量等实验参数对纳米粉组成和结构的影响。并应用正交实验法,对工艺条件进行了优化。将制备出的纳米级Ｎｉ（ＯＨ）_２按一定比例掺入普通的球型微米级Ｎｉ（ＯＨ）_２中,充放电测试结果表明,比容量可增加约１０％。     

激光熔覆Zr65Al7.5Ni10Cu17.5复合涂层组织结构

在Ti基体上激光熔覆Zr65Al7.5Ni10Cu17.5合金粉末,得到含非晶、纳米晶复合涂层。涂层由金属间化合物和非晶、纳米晶构成。涂层按组织形貌分为3层:表面枝晶区、中部细晶区和结合区枝晶区。金属间化合物为Al2Zr3,CuZr2和Zr2Ni,纳米晶为简单四方Al2Zr3相,晶格常数为:a=b=76.18nm,c=69.85nm。     

Co掺杂ZnO纳米棒的电沉积法制备及其光学性能

在Zn（NO3）2和Co（NO3）2溶液中,以柠檬酸作为络合剂,采用阴极恒电位沉积法直接在ITO衬底上制备出纯ZnO和Co掺杂ZnO（ZnO∶Co）纳米棒阵列膜。采用X射线衍射、扫描电镜和能量色散谱对所制备ZnO纳米棒的晶体结构和表面形貌进行了表征,利用光致发光光谱研究了样品的发光性质。结果表明：所制备的ZnO纳米棒呈六角纤锌矿结构,具有沿（002）面择优生长特性,Co掺杂使ZnO纳米棒的直径变细。部分Co^2＋取代了Zn^2＋进入ZnO的晶格,掺入量为2.2at%左右。Co掺杂使ZnO的禁带宽度变窄,紫外发射峰产生显著红移。     

离线热处理和原位电子辐照下羟基硫酸镍纳米带结构演变的TEM研究

利用透射电子显微术,主要包括亮场像形貌观察、选区电子衍射结合运动学模拟计算和高分辨电子显微像,对水热法制备的结晶良好的Nj(SO4)0.3(OH)1.4纳米带结构和生长形态进行了表征,并结合利用在不同温度的离线热处理及原位电子辐照,对从结晶良好的Nj(SO4)0.3(OH)1.4纳米带到疏松多孔的NiO纳米带,最后到NiO纳米颗粒的结构演变进行了系统研究,得到了Nj(SO4)0.3(OH)1.4和NiO的取向关系,揭示了这一系列过程的结构演变并给出了Nj(SO4)0.3(OH)1.4的初步结构模型.     

Layered α‐Co(OH)2 Nanocones as Electrode Materials for Pseudocapacitors: Understanding the Effect of Interlayer Space on Electrochemical Activity

The effect of space accessible to electrolyte ions on the electrochemical activity is studied for a system of transition‐metal hydroxide‐based pseudocapacitors. Layered α‐Co(OH)₂ with various intercalated anions is used as a model material. Three types of layered α‐Co(OH)₂ with intercalated anions of dodecyl sulfate, benzoate, or nitrate, are prepared by a simple reflux and an anion‐exchange process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations and X‐ray diffraction (XRD) data show the formation of layered α‐Co(OH)₂ nanocones with interlayer spacing between adjacent Co(OH)₂ single sheets of 1.6, 0.7, and 0.09 nm, corresponding to the anions as listed above. Electrochemical characterization reveals that interlayer space has a great effect on the electrochemical activity of α‐Co(OH)₂ nanocones as an electrode material. For the interlayer spacing of 1.6 nm, in the case of dodecyl sulfate‐intercalated α‐Co(OH)₂, the Faradaic reaction takes place more adequately than for benzoate‐ and nitrate‐intercalated α‐Co(OH)₂. As a result, a higher specific capacitance and better cycling stability is obtained for the dodecyl sulfate‐intercalated α‐Co(OH)₂. The electrochemical activity obviously reduces when the interlayer space decreases to 0.7 nm. Our results suggest the importance of rational designing the interlayer space of layered transition metal hydroxides for high‐performance pseudocapacitors.     

Synthesis and optical properties of nanostructured Ce(OH)_4

Nanocrystalline cerium hydroxide (NCs-Ce(OH)_4) is a intermediate product of CeO_2, synthesized success-fully using a novel and simple wet chemical rout at an ambient temperature for the preparation of NCs CeO_2 powder and film on mass scale for various purposes. The synthesized NCs-Ce(OH)_4 was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), Fourier transform infrared (FTIR),UV-visible and photoluminescence (PL) spectroscopy. The average crystallite size of NCs-Ce(OH)_4 has been estimated by the Scherrer equation to be 3-4 nm. The SEM examinations show that the surface texture was uniformly agglom-erated and homogeneous. Thermal analysis suggests that cerium (IV) ion is in the tetra hydrated form. Absorption and luminescence spectroscopic studies have been examined for future application in the development of optical devices.     

Synthesis and optical properties of nanostructured Ce(OH)4

Nanocrystalline cerium hydroxide (NCs-Ce(OH)4) is a intermediate product of CeO2, synthesized successfully using by a novel and simple wet chemical rout at ambient temperature for the preparation of NCs CeO2 powder and film on mass scale for various purposes. The synthesized NCs-Ce(OH)4 was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), Fourier transform infrared (FTIR), UV-Visible and photoluminescence (PL) spectroscopy. The average crystallite size of NCs-Ce(OH)4 has been estimated by Scherrer equation was to be 3-4 nm. The SEM examinations show that the surface texture was very uniformly agglomerated and homogeneous. Thermal analysis suggests that cerium (IV) ion is in the tetra hydrated form. Absorption and luminescence spectroscopic studies have been examined for future application in the development of optical devices.     

Manganese Oxide Octahedral Molecular Sieves (OMS‐2) Multiple Framework Substitutions: A New Route to OMS‐2 Particle Size and Morphology Control

Self‐assembled multidoped cryptomelane hollow microspheres with ultrafine particles in the size range of 4–6 nm, and with a very high surface area of 380 m² g^?1 have been synthesized. The particle size, morphology, and the surface area of these materials are readily controlled via multiple framework substitutions. The X‐ray diffraction and transmission electron microscopy (TEM) results indicate that the as‐synthesized multidoped OMS‐2 materials are pristine and crystalline, with no segregated metal oxide impurities. These results are corroborated by infrared (IR) and Raman spectroscopy data, which show no segregated amorphous and/or crystalline metal impurities. The field‐emission scanning electron microscopy (FESEM) studies confirm the homogeneous morphology consisting of microspheres that are hollow and constructed by the self‐assembly of pseudo‐flakes, whereas energy‐dispersive X‐ray (EDX) analyses imply that all four metal cations are incorporated into the OMS‐2 structure. On the other hand, thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) demonstrate that the as‐synthesized multidoped OMS‐2 hollow microspheres are more thermally unstable than their single‐doped and undoped counterparts. However, the in‐situ XRD studies show that the cryptomelane phase of the multidoped OMS‐2 hollow microspheres is stable up to about 450°C in air. The catalytic activity of these microspheres towards the oxidation of diphenylmethanol is excellent compared to that of undoped OMS‐2 materials.     

不同元素掺杂对复合晶体Sr_(14)(Cu_(1-y)M_y)_(24)O_(41)(M=Zn,Ni,Co)结构的影响

用常规的固相反应法制备了Zn2 ,Ni2 ,Co3 掺杂的3组复合晶体Sr14(Cu1-yMy)24O41(M=Zn,Ni,Co)系列样品.选区电子衍射研究表明,这些样品的自旋链亚结构的衍射点都出现了在a*和b*方向上扩展成衍射线的现象,而仅由自旋梯子亚结构产生的衍射斑点仍保持明锐.随着掺入离子的电子总自旋的增大,自旋链亚结构的衍射斑点扩展成衍射线的现象加重.掺入Co3 离子的复合晶体Sr14(Cu1-yMy)24O41中对应于自旋链亚结构的衍射斑点已完全扩展成垂直于c*的漫散射条纹.掺Co样品[001]带轴高分辨像显示,两套亚系统沿[001]方向的投影在口和b方向上的周期非常完整.这表明,Sr14(Cu1-yMy)24O41的自旋链亚结构仅在沿着c发生了初始相位无序.而掺入离子的电子总自旋的不同使这种初始相位无序的程度不同.     

Formation of GaN Nanowires by Ammoniating Ga2O3 Films Deposited on Oxidized Al Layers on Si Substrate

Large quantities of gallium nitride（GaN） nanowires have been prepared via ammoniating the Ga2O3 films deposited on the oxidized aluminum layer at 950℃ in a quartz tube. The nanowires have been confirmed as crystalline wurtzite GaN by X-ray diffraction, X-ray photoelectron spectrometry scanning electron microscope and selected-area electron diffraction. Transmission electron microscope （TEM） and scanning electron microscopy（SEM） reveal that the nanowires are amorphous and irregular, with diameters ranging from 30 nm to 80 nm and lengths up to tens of microns. Selected-area electron diffraction indicates that the nanowire with the hexagonal wurtzite structure is the single crystalline. The growth mechanism is discussed briefly.     

Fabrication of Mg（OH）2 Powders by Decomposition of Mg3N2 Powders

Mg（OH）2 powders were formed by the decomposition of Mg3N2 powders synthesized by a simple reaction of Mg with N Ha. X-ray diffraction（XRD）, Fourier transform infrared spectroscopy （FTIR）, and scanning electron microscopy（SEM） were used to study the structure, composition and morphology of the products. Mg （OH）2 nanowires with an average diameter about 300 nm-500 nm were found in these Mg（OH）2 powders.     

Morphology and growth mechanism of aligned ZnO nanorods grown by catalyst-free MOCVD

We report on ZnO nanorods grown by catalyst-free metal-organic chemical vapour deposition (MOCVD) in a commercial Epigress reactor using diethylzinc and N₂O as precursors. Well-aligned ZnO nanorods with uniform diameter, length and density have been grown perpendicularly to the sapphire (0 0 0 1) surface. Scanning electron microscopy (SEM) has been used to observe the morphology of the ZnO nanorods and X-ray diffraction and transmission electron microscopy (TEM) to investigate the crystalline structure of the nanorods. TEM observation as well as photoluminescence measurements confirm the very good crystalline quality of the nanorods. SEM observation on samples that have been prepared with various deposition times has been used in order to investigate the growth mechanism. Three types of ZnO morphologies have been identified: a thin two-dimensional ZnO layer formed at the sapphire surface, covered by three-dimensional hexagonal-shaped islands and hexagonal nanorods on top of them.     

Epitaxial growth and electrical conductance of metal(CoSi2)/insulator(CaF2) nanometer-thick layered structures on Si (111)

Epitaxial growth of a metal (CoSi₂) /insulator (CaF2) nanometer-thick layered structure on Si(111) was demonstrated and the resistivity of CoSi₂ epilayer in this structure was investigated. An epitaxial CoSi₂ layer on CaF₂ was obtained by the two-step growth technique,i.e. solid phase epitaxy with the epitaxial Si layer grown in the first step and Co deposited in the second step. This technique was shown to be effective to avoid the Co agglomeration on CaF₂ layer observed in the co-evaporation of Si and Co. An epitaxial CaF₂ layer was formed on CoSi₂/CaF₂ at low substrate temperature (450°C) with partially ionized and accelerated CaF₂ beam, to avoid Co agglomeration in the CoSi₂/CaF₂ underlayer as well. Obtained results showed a single-crystalline nature in reflection high-energy electron diffraction (RHEED) and transmission electron microscopy (TEM) observations. The resistivity of a few nm-thick CoSi₂ epilayers embedded by CaF₂ has been investigated. We studied thickness and annealing temperature dependence of resistivity and showed that a minimum resistivity of 30 μΩ cm was obtained in a 2 nm-thick CoSi₂ sample annealed at 860°C.