Morphologies Controlled Synthesis of MnO2 Nanostructures

Spherical MnO₂ nanosheet aggregates have been synthesized by the reaction between MnSO₄ and KMnO₄ at room temperature. After the resulting products are treated under hydrothermal conditions, MnO₂ nanorods and tower‐like crystals have been prepared in the absence/presence of cetyltrimethylammonium bromide, respectively. The products are characterized by field‐emission scanning electron microscopy and x‐ray diffractometer, respectively.     

纳米结构MnO2的水热合成、晶型及形貌演化

以水热合成方法制备了具有不同微观形貌的纳米结构MnO2, 并以X射线衍射(XRD), 扫描电镜(SEM)和X射线光电子能谱(XPS)等方法对其进行了表征. 跟踪考察了二氧化锰的晶型及微观形貌随水热反应时间的演变过程, 在Ostwald ripening机理作用下, MnO2晶型转化过程为γ-MnO2, α-MnO2和β-MnO2, 同时形貌由微米球转变为海胆结构、空心海胆结构和纳米线.     

空心海胆状二氧化锰的制备及其在超级电容器中的应用

采用简单的一步水热法制备了空心海胆状二氧化锰,无需任何模板剂和表面活性剂。该材料具有3D的纳米结构,结构稳定,并由单个的二氧化锰空心管自组装而成。该纳米材料的特殊结构为其提供了高的比电容。在1mol·L-1硫酸钠电解液中,扫速为1mV·s-1的条件下,该材料的比电容值为254.6F·g-1。在电流密度为1.0A·g-1的条件下,充放电循环1000次后比电容值仍保持为初始值的97.5%。表明该材料具有良好的电容性能和稳定性,其具备用作高性能超级电容器的电极材料的潜能。     

空心海胆状二氧化锰的制备及其在超级电容器中的应用

采用简单的一步水热法制备了空心海胆状二氧化锰,无需任何模板剂和表面活性剂。该材料具有3D的纳米结构,结构稳定,并由单个的二氧化锰空心管自组装而成。该纳米材料的特殊结构为其提供了高的比电容。在1mol·L^-1硫酸钠电解液中,扫速为1mV·s^-1的条件下,该材料的比电容值为254.6F·g^-1。在电流密度为1.0A·g^-1的条件下,充放电循环1000次后比电容值仍保持为初始值的97.5%。表明该材料具有良好的电容性能和稳定性,其具备用作高性能超级电容器的电极材料的潜能。     

Application of thermo-electrochemistry to simultaneous leaching of sphalerite and MnO2

In order to enhance the electrogenerative leaching rate of sphalerite reasonably, the basic principle of generative process was applied to the simultaneous leaching of sphalerite in the presence of MnO₂. It was confirmed by experimental results that both mental ions and electric energy could be obtained in the simultaneous electrogenerative leaching process. The leaching cell had the open circuit potential about 1.0 V, about 2000 C of electric quantity was obtained, the optimal leaching ratio of Zn²⁺ and Mn²⁺ was 48.5, 39.6% respectively, after electrogenerative leaching for 11 h.     

矿化剂对水热法改性氢氧化镁晶体的影响

近几年来,氢氧化镁作为一种无机阻燃剂由于其具有制备条件相对温和,生产工艺简单且产品与自然环境友好等特点,在研究及生产活动方面备受关注且得到了长足的发展[1～4].目前采用氢氧化钠法进行反应一水热制备高分散阻燃级氢氧化镁的工艺路线已经比较成熟[5～8].然而,不利的是,氢氧化钠偏高的价格导致了产品的制造成本较高.而采用石灰法制备氢氧化镁阻燃剂具有价格低廉的特点,引起了人们的关注.     

Sonocatalyzed facile synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as oxidant agent under mild conditions

Nano MnO₂ was found to be an efficient oxidant agent for the synthesis of 2-substituted benzoxazoles through one-pot reaction of o-aminophenol and different aromatic aldehydes in acetonitrile under ultrasonic irradiation. This method was performed under mild conditions with high yields, inexpensive and readily available oxidant agent, facile and easy experimental procedure, simple purification of final products, and short reaction times. The prepared nano MnO₂ has been characterized by FTIR, XRD, and SEM techniques. The pure products were identified and characterized by physical and spectroscopic data such as; melting point, IR, ¹H NMR, and ¹³C NMR.     

Determination of heats of aluminothermic redox reaction of V2O5 and MnO2

Differential thermal analysis has been used for quantitative determination of heats of aluminothermic redox reaction of MnO₂ and V₂O₅ over a wide range of temperatures. Heat of reaction V₂O₅?Al and MnO₂?Al systems have been determined using the calibration plot established. The experimentally determined values compare well with those predicted from thermodynamic data available in the literature. It has been found that V₂O₅?Al system involves a higher heat of reaction in comparison to the MnO₂?Al system.     

SnS2纳米材料的水热合成及光催化性质

在不同的表面活性剂和硫源的条件下,采用水热法制备了多种形貌的SnS₂纳米材料,详细讨论了反应条件对其形貌和性质的影响,并采用X射线衍射(XRD)、扫描电镜(SEM)、和BET比表面积法对制备的样品的物相、形貌和组成进行了表征,通过光催化降解罗丹明B研究了所得样品的光催化性能。结果表明：表面活性剂和硫源对产物的结构和形貌起到了重要的作用。当Sn⁴⁺与表面活性剂的物质量的比为1：1时,样品均为纯的六方相SnS₂。采用柠檬酸三钠为表面活性剂、硫脲为硫源时制得的SnS₂纳米片具有最大的比表面积,同时表现出了最优的光催化性能。     

Ni2P@CoP3核壳纳米球的制备、表征及其用于超级电容器性能

利用水热技术先后获得Ni纳米球和Ni@Co(OH)_2海胆状核壳纳米球前驱体,通过高温煅烧法获得NiO@CoO核壳纳米球,再以次磷酸钠为原料,通过高温磷化法最终获得Ni_2P@CoP_3核壳纳米球。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高角度环形暗场像扫描透射电子显微镜(HAADF-STEM)、X射线粉末衍射仪(XRD)、能谱仪(EDS)及X射线光电子能谱(XPS)对产物的形貌、结构和组成进行表征。采用循环伏安(CV)、恒电流充放电(GCD)以及循环稳定性实验探索了电极材料的电化学性能。结果表明,Ni_2P@CoP_3核壳纳米球的直径约为400 nm,由六方系Ni_2P纳米核和立方相CoP_3纳米壳构成。相比单纯的Ni_2P或CoP_3纳米球,Ni_2P@CoP_3核壳纳米球发挥了复合结构的协同效应,更加有利于电解液的质子传递,促进了赝电容反应,表现出更高的比容量、稳定性和更长的循环寿命。     

MnO2 /聚苯胺复合材料的制备和性能

以δ-MnO₂为前驱体,通过酸处理后引入苯胺并聚合,得到了MnO₂ /聚苯胺复合材料。经XRD分析表明,在本研究条件下,经酸处理后的δ-MnO₂晶型由δ型转变为α型,而在随后的苯胺引入及其聚合步骤中MnO₂晶型均不再改变。以200 mA·g^-1的电流进行恒电流充放电性能测试,结果显示,MnO₂ /聚苯胺复合材料的充放电容量达到160.2 mA·g^-1,与     

MgFe2O4纳米粉体的水热合成及其表征(英)

MgFe₂O₄ nanoparticles were hydrothermally synthesized at 150 ℃ using iron nitrate [Fe(NO₃)₃·9H₂O], magnesium nitrate [Mg(NO₃)₂·6H₂O] and sodium hydroxide (NaOH) as starting materials by carefully controlling the reaction conditions. The influences of several factors such as presence or absence of Na⁺, molar ratio of Fe³⁺ / Mg²⁺, concentration of mental ions, temperature and reaction time on resultant products were investigated in the hydrothermal process. The sample was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and its magnetic properties were measured using vibrating sample magnetometer (VSM).     

二氧化铈八面体的水热合成与表征

本文选用硝酸铈和草酸利用水热合成方法合成出二氧化铈八面体。水热产物的形貌与物相可以通过改变反应温度和时间进行调控。基于实验结果,提出了形成二氧化铈八面体的自牺牲模板法机理。     

水热法制备Sb2S3纳米棒有序阵列

以Sb(S₂CNEt₂)₃为单源前驱体，通过改变时间、温度、表面活性剂等反应条件，用水热法成功合成了各种尺寸的Sb₂S₃纳米棒及其有序阵列。X-射线衍射(XRD)、能量分散光谱(EDS)以及选区电子衍射(SAED)研究表明纳米棒由正交晶系Sb₂S₃单晶构成。扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究显示Sb₂S     

异形复层结构TiO2纳米棒薄膜的水热合成及性能

本文采用水热反应法,通过改变合成条件,经XRD和FESEM表征,证实合成了四方金红石相异形复层(阵列-团簇)结构的TiO₂薄膜。合成薄膜的下层是TiO₂的阵列,上层是团簇状的TiO₂,并且构成阵列和团簇的每个方柱又由多根纳米棒(25～65 nm)组成。上层团簇的生成量和厚度可以通过改变反应物的初始浓度、反应时间和生长基片的角度进行调控。将这种异形复层结构薄膜试用于染料敏化太阳能电池(DSSC)光阳极,发现其光电转化效率比单层阵列TiO₂薄膜提高了2.6倍。由此表明TiO₂这种以纳米棒为单元结构的异形复层薄膜,上层团簇结构有利于产生采光作用以及吸附微粒的作用,下层阵列结构有利于载流子的定向快速传输,其复合结构的形成,致使光电转换效果明显提高。     

有双重固硫作用的PEDOT包覆MnO2纳米管阴极用于高性能的锂硫电池

制备了α-MnO₂纳米管作为硫的宿主材料,将硫填充到α-MnO₂管的中空部分,并通过原位聚合法在α-MnO₂外层包覆一层薄层聚（3,4-乙烯二氧噻吩）（PEDOT）进一步束缚硫。这样一种双重固硫的阴极材料S@α-MnO₂-PEDOT在锂硫电池中体现出了高的性能。在电流密度1 675 mA·g^-1（1C）下循环200圈,容量为774.4 mAh·g^-1,且在电流密度为3 350 mA·g^-1（2C）下容量达854.1 mAh·g^-1,体现出良好的循环稳定性和倍率性能。这些显著的性能得益于阴极材料新颖的结构。在这种结构中,α-MnO₂纳米管不仅能对硫起到物理限制作用,而且增强了硫宿主材料和多硫化物间的化学相互作用。同时,PEDOT的引入增强了含硫纳米复合材料的导电性,并进一步减少了由于体积变化和多硫化锂的过度溶解引起的硫的损失。     

水热处理氢氧化镁微晶性质研究

Shape apprearance and crystallite characterization of magnesium hydroxide at different hydrothermal tempera-tures have been investigated by SEM， XRD and DSC methods. The grain size， cell parameter and lattice distortion rate of powders under each condition were obtained. The results show that the grains had grown up， especially along the (001) surface as the hydrothermal temperature was raised， accompanying the shrinkage of lattice and the de-scending of distortion rate. These could be relate to the re-crystallization of Mg(OH)₂， as well as the thermal dif-fusion of OH^- with lower charges， resulting in good dispersion， high thermal decomposition temperature and en-thalpy of Mg(OH)₂. Moreover， it is helpful for the increase of the retardant behavior of Mg(OH)₂.     

异形复层结构TiO2纳米棒薄膜的水热合成及性能

本文采用水热反应法,通过改变合成条件,经XRD和FESEM表征,证实合成了四方金红石相异形复层(阵列-团簇)结构的TiO2薄膜。合成薄膜的下层是TiO2的阵列,上层是团簇状的TiO2,并且构成阵列和团簇的每个方柱又由多根纳米棒(25~65 nm)组成。上层团簇的生成量和厚度可以通过改变反应物的初始浓度、反应时间和生长基片的角度进行调控。将这种异形复层结构薄膜试用于染料敏化太阳能电池(DSSC)光阳极,发现其光电转化效率比单层阵列TiO2薄膜提高了2.6倍。由此表明TiO2这种以纳米棒为单元结构的异形复层薄膜,上层团簇结构有利于产生采光作用以及吸附微粒的作用,下层阵列结构有利于载流子的定向快速传输,其复合结构的形成,致使光电转换效果明显提高。     

Carbon Nanotube Fibers Decorated with MnO2 for Wire-Shaped Supercapacitor

Fibers made from CNTs (CNT fibers) have the potential to form high-strength, lightweight materials with superior electrical conductivity. CNT fibers have attracted great attention in relation to various applications, in particular as conductive electrodes in energy applications, such as capacitors, lithium-ion batteries, and solar cells. Among these, wire-shaped supercapacitors demonstrate various advantages for use in lightweight and wearable electronics. However, making electrodes with uniform structures and desirable electrochemical performances still remains a challenge. In this study, dry-spun CNT fibers from CNT carpets were homogeneously loaded with MnO₂ nanoflakes through the treatment of KMnO₄. These functionalized fibers were systematically characterized in terms of their morphology, surface and mechanical properties, and electrochemical performance. The resulting MnO₂–CNT fiber electrode showed high specific capacitance (231.3 F/g) in a Na₂SO₄ electrolyte, 23 times higher than the specific capacitance of the bare CNT fibers. The symmetric wire-shaped supercapacitor composed of CNT–MnO₂ fiber electrodes and a PVA/H₃PO₄ electrolyte possesses an energy density of 86 nWh/cm and good cycling performance. Combined with its light weight and high flexibility, this CNT-based wire-shaped supercapacitor shows promise for applications in flexible and wearable energy storage devices.