多相氢氧化镍的合成及其性能研究

用液相共沉淀技术制备了具有α-Ni(OH)2和β-Ni(OH)2混合结构的多相氢氧化镍,并且扫描电镜研究了其形貌,用XRD研究了其多相氢氧化镍形成的过程,探讨了在陈化过程中和用0.2C率充放电过程中的结构稳定性,通过充放电测试讨论了其放电性能.结果发现,通过控制掺杂元素和工艺条件,多相氢氧化镍在碱性溶液中结构稳定,充放电过程中能交换1.3个电子,其放电比容量最大可达375mAh/g,放电电位平台比β-Ni(OH)2电极高100mV左右.     

掺锰球形氢氧化镍微结构表征

采用液相沉积法制备了掺锰球形氢氧化镍,进行了XRD和SEM表征,并对商品球形氢氧化镍的其他产品(掺杂锌、钴、镉)做了对比.结果表明,采用该方法制备的掺锰球形氢氧化镍结构与文献固相法制备的氢氧化镍不同,前者为β-Ni(OH)2,后者为α-Ni(OH)2,101峰半高宽为0.84°,与商品化的氢氧化镍接近,具有较好的电性能;粉末形貌与商品化的氢氧化镍相近,为球形和椭球形,粒度搭配合理;镍含量仅为40%左右,可大幅降低成本,具有较好的应用前景.     

钴掺杂纳米花瓣状氢氧化镍的制备及其电化学性能研究

采用水热法制备了钴掺杂的纳米花瓣状Ni(OH)2,讨论了钴掺杂量对产物形貌、结构和电化学性能的影响。结果表明,不同钴摩尔分数掺杂的样品都呈现α/β混合相花瓣微球,其比表面积均在280m2/g以上,远高于普通球形氢氧化镍(5~10m2/g)。电化学性能测试表明,钴添加剂显著提高了氢氧化镍高倍率放电容量和循环稳定性能,1.0C倍率时钴摩尔分数10%的样品放电容量可达430.1mAh/g(以纯氢氧化镍计),接近-αNi(OH)2的理论容量(480mAh/g),3.0C倍率时其放电容量(367.1mAh/g)仅比0.2C时的放电容量(406.9mAh/g)衰减9.8%。     

球形Ni(OH)2控制结晶过程中的陈化研究

利用控制结晶方法在连续搅拌反应器中制备了球形氢氧化镍,通过电子显微技术表征了球形氢氧化镍的内外结构并研究了其生长过程中的陈化现象.随着反应物过饱和度的下降,反应器内部按功能不同可分成成核区、生长区与熟化区等.在球形氢氧化镍控制结晶生长过程中存在Ostwald熟化,它在粒子之间及粒子表面发生;同时亦存在晶相转变α→β,表现为重结晶作用,在团聚粒子内部进行.Ostwald熟化与相转变构成的陈化作用在促使氢氧化镍粒子团聚密实、重结晶长大、形态向球形转变并使其表面光滑和内部结构呈放射状等微结构的形成过程中发挥重要作用.这一认识深化了球形工业结晶研究,并对反应器设计具有指导意义.     

Bi2O3—ZnO—Nb2O5系中焦绿石结构与相分布

根据焦绿石结晶化学原理，研究了Bi2O3－ZnO－Nb2O5（BZN）系中焦绿石的相结构与分布用淬冷技术保持样品的高温相结构，用粉末X-射线衍射技术（XRD）分析相组成与相结构得到了BZN系中两种焦绿名单相（立方相α和正交相β和α-β复相分布的等温相图，并探讨了该系统中焦绿石立方相和正交相之间的α-β位移式相变的机理     

超声波功率和pH值对Y掺杂纳米Ni(OH)2结构与性能的影响

采用超声波沉淀法制备了Y掺杂纳米Ni(OH)2,研究了超声波功率和溶液pH值对材料结构、粒径及电化学性能的影响.结果表明,不同超声波功率制备的样品均为α和β混合相结构,其中α-Ni(OH)2的比例随功率增大先增加后减少,粒径随功率增大先减小后增大.溶液pH值对Ni(OH)2晶相形成起重要作用,较低的pH值有利于α-Ni...     

Ti-4.4Al-3.8Mo合金的亚稳相变及其对硬度的影响

对锻态 Ti-4Al-3.8Mo合金分别进行了β单相区和α β两相区(相变点之下45℃)淬火处理,研究了亚稳相变对硬度的影响.结果表明,β单相区淬火处理的样品硬度比α β两相区处理的样品高约10%.β单相区淬火后的相组成为全α'马氏体,自910℃的α β两相区淬火后的相组成为等轴初生α相 α'马氏体 α"马氏体.硬度出现差异的主要原因是后者中存在硬度较低的初生α相和α"马氏体.本文修正了Ti-β稳定元素二元系亚稳相图(示意图),指出在α α'和α α"相区之间存在α α' α"相区,并使用修正后的相图解释了Ti-4.4Al-3.8Mo合金的相组成与硬度的关系.     

新型TC21钛合金相变行为和相组成研究

采用X射线衍射(XRD)对TC21钛合金β热处理后,经不同冷却速率冷却及双重退火后的相结构进行了分析,并用扫描电镜(SEM)和透射电镜(TEM)对显微组织和相的形貌特征进行了观察研究.结果得出,TC21钛合金在β处理时经炉冷和水冷后,合金由α和β两相组成.空冷状态下,合金主相为α+β,并有少量Nb3Si相析出.实验证明,冷却速率主要影响α和β相含量的比例,相的组成基本不受冷却速率的影响.合金经970.,30min,空冷+600℃,4h退火后,仍由α相和β相组成,没有发现新的析出相,但观察到转变β相中存在次生析出的细小针状α相.     

铝热还原氮化微晶白云母合成α-Al2O3/β-SiAlON的物相演变

以川西微晶白云母为主要原料,铝粉为还原剂,采用铝热还原氮化法合成了α-Al2O3/β-SiAlON材料,并利用X射线衍射仪(XRD)研究了不同温度下的物相变化及配铝量对反应产物的影响.结果表明:在1350℃和1450℃,所有样品的主要产物均为α-Al2O3和β-SiAlON相,但铝粉用量为35%(质量分数,下同)的样品经1350℃铝热还原氮化后的产物中含β-SiAlON相较多;当铝粉用量和加热温度分别为45%和1550℃时,反应产物中不含α-Al2O3和β-SiAlON相,却出现了AlON、AlN和Si3Al7O3N9相.     

添加有NiOOH的混合晶型Ni(OH)_2的电化学性能研究

采用络合沉淀法制备了具有特殊表面纳米片状结构的微米级混合晶型氢氧化镍,并研究了添加化学氧化NiOOH纳米颗粒对上述材料电化学性能的影响.采用SEM、XRD等手段表征了样品的形貌及物相特征,并考察了其作为镍氢电池正极活性材料的电化学性能.结果表明:添加的纳米片状β-NiOOH随机分布在氢氧化镍表面.以制备的样品为正极材料组装成镍氢模拟电池,在0.2C充放电条件下,制备材料的放电比容量可达306mAh/g;添加NiOOH能有效地改善镍电极的电化学性能,添加量为7wt%时,0.2C充放电条件下样品放电比容量为326mAh/g,在2C充放电条件下放电比容量可达311mAh/g.     

Structure and electrochemical performance of nickel hydroxide synthesized by rapid quench method

Nickel hydroxide with amorphous structure has been synthesized successfully by chemical precipitation method combined with rapid quench technique. The microstructure and morphology of the prepared samples were analyzed by XRD, Raman spectra, IR spectra, and SEM. The electrochemical performance of the sample was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge tests. The discharge capacity of the amorphous nickel hydroxide is 330.0 mAh g⁻¹ at 0.2C, much higher than that of the theoretical capacity of β-nickel hydroxide (289.0 mAh g⁻¹). Moreover, the amorphous nickel hydroxide exhibits higher electrochemical reaction reversibility, lower electrochemical impedance, and better cyclic stability compared with β-nickel hydroxide.     

混合氨-碱沉淀剂制备Ni(OH)_2/还原氧化石墨烯复合材料及其电化学性能

利用简单易行的化学沉淀-回流法制备了Ni(OH)_2/还原氧化石墨烯(RGO)复合材料,研究了不同混合氨-碱沉淀剂对复合材料电化学性能的影响。采用XRD、拉曼光谱(Raman)和SEM表征Ni(OH)_2/RGO复合材料的微观结构和形貌。当以NH_3·H_2O-NaOH作为沉淀剂时,Ni(OH)_2/RGO复合材料中β-Ni(OH)_2纳米片均匀分散在石墨烯片层之间,形成相互插层结构。利用循环伏安(CV)、恒电流充放电(GCD)和电化学交流阻抗(EIS)测试了复合电极材料的电化学性能。研究结果表明:放电倍率为0.2C时,Ni(OH)_2/RGO复合电极材料的放电比容量达到344.8mAh/g,比β-Ni(OH)2的放电比容量高出约29%;5C时放电比容量为274.5mAh/g,经过50个循环,容量保持率为98.8%,呈现出良好的倍率性能和循环性能。     

Synthesis,characterization, and electrochemical properties of Ni(OH)<Subscript>2</Subscript>/ultra-stable Y zeolite composite

A novel composite of Ni(OH)₂/ultra-stable Y zeolite materials was synthesized by an improved chemical precipitation method, which used the ultra-stable Y zeolite as the template. The Ni(OH)₂/ultra-stable Y zeolite composite and its microstructure were characterized by X-ray diffraction measurements and transmission electron microscopy. Electrochemical studies were carried out using cyclic voltammetry, chronopotentiometry technology and ac impedance spectroscopy, respectively. The result shows that the loose-packed whisker Ni(OH)₂ phase has profound impacts on electrode performance at very high power output. A maximum discharge capacity of 185.6 mA-h/g (1670 F/g), or 371 mA-h/g (3340 F/g) after correcting for weight percent of nickel hydroxide phase at the current density of 625 mA/g could be achieved in a half-cell setup configuration for the Ni(OH)₂/ultra-stable Y zeolite electrode, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effect of NH₄Cl concentration on the electrochemical properties characteristics has also been systemically explored.     

The influence of Na2CO3 content and Ni concentration on the physicochemical properties of nanometer Y-substituted nickel hydroxide

Nanometer Y-substituted nickel hydroxide was prepared by supersonic co-precipitation method with Na₂CO₃ as a buffer and NiCl₂ as a nickel source. The crystal structure, morphology, particle size distribution and electrochemical performance affected by the buffer (Na₂CO₃) content and Ni²⁺ concentration are characterized. The results indicate most of the samples are co-existence with α and β phases and the proportion of α-Ni(OH)₂ increases with the increase of Na₂CO₃, but decreases with the increase of Ni²⁺ concentration. The primary particles of samples are nanometer particles and the shape of primary particles transform from acicular to quasi-spherical with increasing Na₂CO₃ content, but converse process for the increase of Ni²⁺ concentration. The average particle size decreases initially and then increases. Complex electrodes were prepared by mixing 8 wt.% nickel hydroxides with commercial micro-size spherical nickel. The discharge capacities of samples increase initially and then decrease with increasing Na₂CO₃ content or decreasing Ni²⁺ concentration. When Na₂CO₃ content is 0.08 g and Ni²⁺ concentration is 0.2 mol/L, the sample has better electrochemical performance, such as larger discharge capacity (316.3 mAh/g at 0.2 C rate), lower charge voltage and higher discharge plateau, than those of other samples.     

Preparation and electrochemical performance of alpha-nickel hydroxide nanowire

Alpha-nickel hydroxide nanowire with diameter of 60 nm was successfully synthesized by conversely migrates technique. Structural and morphological characterizations were performed using power X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The capacitive properties were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy technique in 6 M KOH aqueous electrolyte. A maximum specific capacitance of 833 F g⁻¹ was obtained at constant current of 5 mA, indicating that the α-nickel hydroxide nanowire is a promising electrode material for electrochemical capacitors.     

氢氧化镍电极导电剂的研究

研究了镍粉，镍粉和石墨的混合物，石墨以及石墨和乙炔墨的混合物分别作为导电剂以机械混合的方式添加到电极活性物质中对氢氧化镍电极性能的影响，并用循环伏安法和交流阻抗法分析了实验结果。结果表明：在这四种导电剂中，镍粉作导电剂时氢氧化镍电极的性能最好，其次是以石墨或镍粉和石墨的混合物作导电剂的氧化镍电极，当石墨和乙炔黑的混合物作导电剂时氢氧化镍电极的性能最差。这是因为当镍作导电剂时氢氧化镍电极的电化学反应电阻最小，质子扩散最容易，电要的可逆性最好，且氧气析出最困难，而当石墨和乙黑和混合物作导电剂时氢氧化镍电极的电化学反应电阻最大，质子扩菜最困难，电极充电过程和析氧过程几乎同时进行，因而充电效率最低，活性物质的利用率最小，电极性能最差。     

Electrochemical properties of Super P carbon black as an anode active material for lithium-ion batteries

A new approach to investigate upon the electrochemical properties of Super P carbon black anode material is attempted and compared with conventional mesophase pitch-based carbon fibers (MPCFs) anode material for lithium-ion batteries. The prepared Super P carbon black electrodes are characterized using transmission electron microscope (TEM). The assembled 2032-type coin cells are electrochemically characterized by ac impedance spectroscopic and cyclic voltammetric methods. The electrochemical performance of charge and discharge was analyzed using a battery cycler at 0.1 C rate and cut-off potentials of 1.20 and 0.01 V vs. Li/Li⁺. The electrochemical test illustrates that the discharge capacity corresponding to Li intercalation into the Super P carbon black electrode is higher and coulombic efficiency is maintained approximately 84% at the end of the 20th cycling at room temperature.     

Effects of different particle sizes on electrochemical performance of spinel LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials

Spinel LiMn₂O₄ were prepared by adipic acid-assisted sol–gel method at 800 °C, and the cathode materials with different particle sizes were obtained through ball milling. The effects of different particle sizes on electrochemical performance of LiMn₂O₄ sample were investigated by X-ray diffraction (XRD), galvanostatic charge–discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. XRD data exhibits that all samples exhibit the same pure spinel phase; EIS and CV indicate that LiMn₂O₄ samples with smaller particle size have higher charge transfer resistance and oxidation potential than that of other samples corresponding to the extraction of Li⁺ ions, respectively; galvanostatic charge–discharge test shows that the particle size has significant effects on the electrochemical performance of spinel LiMn₂O₄ cathode materials.     

Electrochemical capacitance of polypyrrole nanowire prepared by using cetyltrimethylammonium bromide (CTAB) as soft template

Polypyrrole (PPy) nanowires were prepared in high yield by using cetyltrimethylammonium bromide (CTAB) as “soft template” in 0.2 M HCl aqueous solution. From the observation of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), PPy nanowires with a diameter in the range of 30–50 nm was obtained. The electrochemical capacitance of PPy nanowires was characterized by cyclic voltammetry, charge/discharge test and electrochemical impedance spectroscopy (EIS). Compared with conventional PPy, PPy nanowires had the higher specific capacitance and energy density. The capacitor also exhibited the good cycling performance with 1000 cycles.     

原位氧化法制备Zn-Ni氢氧化物纳米片及其电荷存储特性研究

通过简单、低成本的化学浴沉积法在泡沫镍上原位生成了Zn-Ni 氢氧化物(Zn-Ni double hydroxides)纳米片。SEM观察结果表明, Zn-Ni 氢氧化物纳米片均匀附着在泡沫镍表面, 形成均一的多孔纳米片阵列层。此外, 还有大量的Zn-Ni 氢氧化物纳米片聚集成多孔团聚体, 分布于泡沫镍骨架的空隙处, 从而获得较高的活性物质负载量(4.27 mg/cm²)。CV、CP和电化学阻抗测试表明, Zn-Ni 氢氧化物纳米片在2 mol/L KOH电解液中充放电电流密度1 A/g时, 比电容为746.2 F/g(面积电容为3.18 F/cm²); 3000次充放电循环后, 仍保持70.9%的初始比电容。