化学沉淀法制备电极用纳米β-Ni(OH)_2粉体材料

通过化学沉淀法成功制备了电极用纳米B-氢氧化镍粉体。用TEM及XRD时样品进行分析,结果表明,所得产物为球形或椭球形,粒径在2～20nm之间,平均粒径为10nm左右,晶型为β型的纳米晶粒。实验得出了制备纳米氢氧化镍粉体的温度、氨水浓度与pH值的最佳参数。     

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。     

阴离子（NO3－／Cl －／SO2－4）对 Ni（OH）2晶型及其结构稳定性的影响

采用超声波辅助沉淀法分别在单元掺杂、二元掺杂和不掺杂三种情况下制备了三种不同镍源的纳米氢氧化镍,研究三种阴离子（NO3－,Cl－,SO2－4）对产物晶相结构及稳定性的影响。结果表明：未掺杂时,半径较大的SO2－4离子有利于α‐Ni（OH）2的形成;在单掺杂Co（Ni2＋∶Co2＋＝1∶0．20）时,NO3－离子不仅有利于α‐Ni（OH）2的形成,而且可以使α‐Ni（OH）2在碱液中保持较高的稳定性;当复合掺杂Co／Cu（Ni2＋∶Co2＋∶Cu2＋＝1∶0．15∶0．05）时,三种镍源制得的样品均为纯α‐Ni（OH）2结构,但以Ni（NO3）2为镍源的α‐Ni（OH）2在碱液中结构稳定性较高,NiCl2次之,NiSO4较差。可见,α‐Ni（OH）2结构及稳定性既与掺杂情况有关,也与阴离子密切相关。     

A study on the effect of nanosized tin oxide on the electrochemical performance of nanosized nickel hydroxide in alkali solution

The nickel hydroxide nanopowders mixed with SnO₂ nanoparticles as an additive in different proportions were prepared and characterised by X-ray diffraction (XRD), transmission electron microscope (TEM) and electrochemical measurement by cyclic voltammetry. XRD examination suggests that the composite Ni(OH)₂/SnO₂ has both the phases of α-Ni(OH)₂ and β-Ni(OH)₂ with SnO₂ nanoparticles. TEM images show the nanostructures of nickel hydroxide, SnO₂ and dispersion of SnO₂ nanoparticles on nickel hydroxide particles in the composite. The electrochemical studies revealed that the composite electrode has better redox reversibility and specific capacitance values compared to the pure Ni(OH)₂, α-Ni(OH)₂ and usual β-Ni(OH)₂ electrodes and it can be applied as a promising positive active material for alkaline rechargeable batteries.     

电极活性物质球形氢氧化镍的结构特征研究

球形氢氧化镍的微结构对氢镍电池（MH—Ni）镍电极的电化学性能有重要的影响。本文通过扫描电镜（SEM）和透射电镜（TEM）研究了用控制沉淀-结晶法制备的球形氢氧化镍的结构特征,并与传统非球形氢氧化镍进行了比较,同时讨论了球形氢氧化镍活性物质的电化学行为。研究结果表明,球形氢氧化镍粉体由微球颗粒组成,每一个微球由片状氢氧化镍叠砌而成,这种片状氢氧化镍晶粒又由约0．5nm厚的40层晶片组成,因而球形氢氧化镍是一种纳米结构材料。片状氢氧化镍晶粒在微球内基本上沿径向排列,晶粒之间相互连接形成三维网络结构,晶粒解理面之间存在许多孔隙或缝隙。这种结构在电池的充放电过程中具有良好的力学稳定性,微球内存在的孔隙或缝隙可以用作质子传递的通道而有利于缩短质子在固相中扩散的距离,从而降低电极极化和提高电极的电化学性能及使用寿命。     

电池用正极材料纳米Ni(OH)2的研究进展

综述了电池正极材料Ni(OH)2的几种主要制备方法,介绍了各种制备方法的工艺条件及主要特点,描述了制备Ni(OH)2过程中的影响因素,指出氢氧化镍作为电池正极材料具有光明的前景,但对生产技术还需进一步研究.     

Aging of trivalent metal hydroxide/oxide gels in divalent metal salt solutions: Mechanism of formation of layered double hydroxides (LDHs)

While the aging of freshly precipitated Al(OH)₃ gels in solutions of Mg and Ni salts leads to LDH formation at high (> 12) pH, aging of ‘Fe(OH)₃“ leads to LDH formation in Mg salt solutions but not in Ni salt₃’ gels do not form LDHs on aging in any of the divalent metal salts. In general, conditions that promote the redissolution of the trivalent hydroxide also promote LDH formation showing that oxoanionic species such as AlO _- ² have a role in LDH formation.     

Thermogravimetric studies on nickel hydoxide electrode

Thermogravimetric analysis (TGA) has been used as a quick and accurate method for determining the content of Ni(OH)₂ for nickel hydroxide electrodes (NOE) prepared by the chemical precipitation of nickel hydroxide on sintered nickel plaque. The analysis can be carried out in a reducing atmosphere (Ar+4%H₂) or in air, and, while the final products differ, results for the two methods should be mutually consistant. The chemical reactions expected (in air vs. in hydrogen) are shown below:

From the weight loss of this reaction the loading of Ni(OH)₂ can be determined since the weight loss from the decomposition of pure Ni(OH)₂ is 19.4%.

Again the Ni(OH)₂ loading can be calculated since the theoretical weight loss for the above reaction (i) is 36.7% (for pure Ni(OH)₂).Portions of a commercial NOE were cut and used for the TGA experiments in air and in hydrogen atmospheres. These TGA experiments gave consistent results for the nickel hydroxide concentration of our NOE. X-ray diffraction (XRD) studies indicated the active material was crystalline nickel hydroxide. After TGA in air to 500°C, XRD showed only NiO (plus the Ni from the plaque), while after TGA in H₂ to 500°C XRD showed only Ni peaks. In addition to these two chemical reactions, a weight loss of 1–3% was observed between 80–180°C corresponding to the loss of adsorbed H₂O. The molar ratio of adsorbed water to the calculated Ni(OH)₂ loading was about 0.1M H₂O per mole of Ni(OH)₂. This water was adsorbed and not structural based on the X-ray results discussed in this paper.     

纳米级氢氧化镍和钴对镍电极性能的影响

通过充放电曲线和交流阻抗谱的测定探讨了纳米级氢氧化镍和氢氧化镍表面包复CoOOH以及镍箔上电镀钴层对氢氧化镍粉末压制的镍电极性能的影响。结果表明．纳米级氢氧化镍有较快的活化能力，CoOOH包Ni(OH)2则有较高的放电容量，而比例适当的纳米复合镍电极才有更好的电化学性能。氢氧化镍表面包复CoOOH可改善镍电极的充放电性能；镍箔上镀钴可大大降低电极过程的电荷转移电阻；钴含量大于3％后．虽然活化速度有所下降，但是大电流充放电时，镍电极活性物的利用率更高，放电容量更大。纳米级Ni(OH)2含量大于30%后，镍电极的活化速度不仅未能加快，反而略有减慢，而且容量也降低。     

Study on medium-temperature chemical heat storage using mixed hydroxides

It was demonstrated that chemical heat storage materials mixed with metal hydroxides were capable of storing heat at medium temperatures of approximately 200–300 °C. The performances of the developed materials were demonstrated in a thermo-balance and packed bed reactor. The mixed hydroxides can increase the operation heat storage temperature by changing the composition of mixed metal oxides in the material. Mg_αNi_1?α(OH)₂, which is a mixed hydroxide of magnesium hydroxide, Mg(OH)₂, and nickel hydroxide, Ni(OH)₂, is a candidate heat storage material. The mixed hydroxide was dehydrated, that is, it was capable of storing heats at 200–300 °C, at which pure Mg(OH)₂ could not be dehydrated and could not store heat. The heat output performance of the material was examined in a packed bed reactor. It was shown that the mixed hydroxide material was potentially useful for chemically storing medium-temperature heat such as waste heats emitted from internal combustion engines, solar energy system and high-temperature processes.     

The proton exchange chemistry of layered Ni(OH)2 for two types of high-capacity cathode materials in rechargeable batteries

Based on the studies of the first proton exchange/remove of layered Ni(OH)₂, super nickel oxide has been prepared with strongly alkaline concentrated sodium hypochlorite solution. The primary alkaline super nickel battery equipped with the prepared NiOOH cathode provides an energy capacity 2 times as large as that of the existing alkaline manganese batteries under high drain. In addition, according to the second proton exchange of Ni(OH)₂, the layered NiOOLi has also been synthesized by means of the proton/Li-ion exchange of super nickel oxide in LiOH solution, and then in molten lithium hydroxide. It provides higher discharge voltage and capacity than that of the widely adopted LiCoO₂ and LiMn₂O₄.     

Anomalous transient leaching behavior of metals solidified/stabilized by pozzolanic fly ash

This study presents observations on the transient leaching behavior of chromium, cadmium, and aluminum that were solidified/stabilized by pozzolanic fly ash. These three metals were selected since they were present in a simulated waste stream generated by an evaporator during plutonium purification and also because the minimum solubility of these metals occurs at significantly different pHs. The transient pH behavior of the toxicity characteristic leaching procedure (TCLP) leachate showed a monotonic increase for all cases, but the equilibrium value was affected by process conditions. The transient leachate concentration behavior showed curves with one or two local maxima for some cases and curves with a monotonic increase for other cases. Data from the leaching experiments was compared to the solubility curves for the hydroxides of each metal since it was assumed that the highly alkaline conditions inside the fly ash waste would cause the metals to precipitate as hydroxides after initially dissolving in the acidic leaching solution. It was found that of the three metals, only cadmium followed the solubility curve for pure hydroxide solutions or for fly ash systems currently reported in the literature.     

Solubility of mixed-valence U(IV–VI) and Np(IV–V) hydroxides in simulated groundwater and 0.1 M NaClO4 solutions

The kinetics of U(VI) accumulation in the phase of U(IV) hydroxide and of Np(V) in the phase of neptunium(IV) hydroxide, and also the solubility of the formed mixed-valence U(IV)-U(IV) and Np(IV)-Np(V) hydroxides in simulated groundwater (SGW, pH 8.5) and 0.1 M NaClO₄ (pH 6.9) solutions was studied. It was found that the structure of the mixed U(IV–VI) hydroxide obtained by both oxidation of U(IV) hydroxide with atmospheric oxygen and alkaline precipitation from aqueous solution containing simultaneously U(IV) and U(VI) did not affect its solubility at the U(VI) content in the system exceeding 16%. The solubility of mixed-valence U(IV–VI) hydroxides in SGW and 0.1 M NaClO₄ is (3.6±1.9) × 10^?4 and (4.3 ± 1.7) × 10^?4 M, respectively. The mixed Np(IV–V) hydroxide containing from 8 to 90% Np(V) has a peculiar structure controlling its properties. The solubility of the mixed-valence Np(IV–V) hydroxide in SGW [(6.5 ± 1.5) × 10^?6 M] and 0.1 M NaClO₄ [(6.1±2.4) × 10^?6 M] is virtually equal. Its solubility is about three orders of magnitude as high as that of pure Np(OH)₄ (10^?9–10^?8 M), but considerably smaller than that of NpO₂(OH) (～7 × 10^?4 M). The solubility is independent of the preparation procedure [oxidation of Np(OH)₄ with atmospheric oxygen or precipitation from Np(IV) + Np(V) solutions]. The solubility of the mixed-valence Np hydroxide does not increase and even somewhat decreases [to (1.4±0.7) × 10^?6 M] in the course of prolonged storage (for more than a year).     

Preparation and electrochemical performance of nano-scale nickel hydroxide with different shapes

Platelet-like, flake-like, and needle-like nano-scale β-Ni(OH)₂ particles were prepared by coordination homogeneous precipitation method in this paper. X-ray diffraction (XRD), transmission electron microscopy (TEM) and infrared absorption spectra (IR) were used to characterize the microstructure and morphology of the products. The nano-scale Ni(OH)₂ composite electrodes were prepared by mixing 10 wt.% samples with spherical Ni(OH)₂ to carry out charge-discharge test. The results show that the nano-scale Ni(OH)₂ composite electrodes have higher discharge specific capacity, and the nickel hydroxide nanoneedles show a better adulteration performance than the others.     

Study on the reduction behavior of CoOOH during the storage of nickel/metal-hydride battery

The storage of nickel/metal-hydride (Ni-MH) battery with co-precipitated cobalt hydroxide and post-added cobalt compound as the additives for pasted Ni(OH)₂ electrode is studied in this paper by using galvanostatic charge–discharge, cyclic voltammetry and X-ray diffraction (XRD). It is shown that (I) capacity loss occurs only on the battery with post-added cobalt compound during the storage; (II) CoOOH derived from co-precipitated cobalt hydroxide has a better stability than the one from post-added cobalt compound and an irreversible reduction of the latter is observed; and (III) an inactive Co + 3O(OH) is obtained from Ni(OH)₂ electrode with post-added cobalt compound after the storage and should be responsible for the property deterioration of Ni-MH battery. Thus, it is important to increase the stability of CoOOH derived from post-added cobalt compound when Ni-MH battery suffers a long-term storage.     

Construction of hierarchical three-dimensional interspersed flower-like nickel hydroxide for asymmetric supercapacitors

Low-cost and easily obtainable electrode materials are crucial for the application of supercapacitors.Nickel hydroxides have recently attracted intensive attention owning to their high theoretical specific capacitance,high redox activity,low cost,and eco-friendliness.In this study,novel three-dimensional (3D) interspersed flower-like nickel hydroxide was assembled under mild conditions.When ammonia was used as the precipitant and inhibitor and CTAB was used as an exfoliation agent,the obtained exfoliated ultrathin Ni(OH)2 nanosheets were assembled into 3D interspersed flower-like nickel hydroxide.In this novel 3D structure,the ultrathin Ni(OH)2 nanosheets not only provided a large contact area with the electrolyte,reducing the polarization of the electrochemical reaction and providing more active sites,but also reduced the concentration polarization in the electrode solution interface.Consequently,the utilization efficiency of the active material was improved,yielding a high capacitance.The electrochemical performance was improved via promoting the electrical conductivity by mixing the as-synthesized Ni(OH)2 with carbon tubes (N-4-CNT electrode),yielding excellent specific capacitances of 2,225.1 F·g-1 at 0.5 A·g-1 in a three-electrode system and 722.0 F·g-1 at 0.2 A·g-1 in a two-electrode system.The N-4-CNT//active carbon (AC) device exhibited long-term cycling performance (capacitance-retention ratio of 111.4％ after 10,000 cycles at 5 A·g-1) and a high specific capacitance of 180.5 F·g-1 with a high energy density of 33.5 W·h·kg-1 and a power density of 2,251.6 W·kg-1.     

镍氢电池掺钴镍正极的研究进展

对镍氢电池的镍正极覆钴改性的研究进展进行了综述,系统归纳了添加剂Co、CoO、Co(OH)2、CoOOH对电池镍正极性能的改善及覆钴工艺的研究进展,并对覆钴工艺的前景提出了新的展望.     

溶液pH对液相沉积氢氧化镍薄膜的影响

采用液相沉积法在不同pH值溶液中制备了多孔氢氧化镍(Ni(OH)₂)薄膜. 当溶液pH值在7.5～8.8之间变化时, 能在基片上形成均匀连续的由Ni(OH)₂纳米棒搭接组成的多孔薄膜, 主要晶型为β-Ni(OH)₂. 溶液pH值的微小变化会引起薄膜中棒状Ni(OH)₂尺寸的显著改变: 当pH=7.5时, Ni(OH)₂纳米棒的长度约为80nm, 直径约为50nm; 当pH=7.8时, Ni(OH)₂纳米棒的长度增大到180nm, 直径约为60nm; 当pH=8.0时, Ni(OH)₂纳米棒的长度显著增大约为300nm, 直径约为70nm. 然而, 当pH=8.3时, Ni(OH)₂纳米棒的长度减小约为230nm, 直径约为80nm; 当pH=8.8时, 纳米棒长度迅速减小约为110nm, 直径减小约为55nm. 结合Ni(OH)₂成核、生长过程和β-Ni(OH)₂晶体结构特点讨论了溶液pH值对Ni(OH)₂薄膜微观形态的影响机制.     

A High Performance of ENi–P Coatings on Mechanical and Tribological Properties with Influence of Bath pH on AZ91 Magnesium Alloy

Electroless nickel–phosphorus (ENi–P) coating was carried out on AZ91 magnesium alloy substrates by varying the bath solutions pH. The ENi–P coating process was carried out with sodium hydroxide as the pH adjuster. The effect of bath pH values on surface characteristics and wear resistance properties were investigated after deposition on AZ91 magnesium alloy substrates. Three suitable bath compositions with different pH were prepared for coating the substrates. Encouraging results for ENi–P deposit were obtained when the bath pH value was maintained at 6.5. A smooth and uniform microstructure was observed in the deposit obtained from bath B (6.5 pH). It also enhanced the microhardness and wettability, while the surface roughness of the ENi–P deposit reduced considerably, thereby resulting in better wear resistance and also preventing regular or early failures, and improving service life.     

Determination of lead and nickel in environmental samples by flame atomic absorption spectrometry after column solid-phase extraction on Ambersorb-572 with EDTA

Lead and nickel were preconcentrated as their ethylenediaminetetraacedic acid (EDTA) complexes from aqueous sample solutions using a column containing Ambersorb-572 and determined by flame atomic absorption spectrometry (FAAS). pH values, amount of solid phase, elution solution and flow rate of sample solution have been optimized in order to obtain quantitative recovery of the analytes. The effect of interfering ions on the recovery of the analytes has also been investigated. The recoveries of Pb and Ni under the optimum conditions were 99 +/- 2 and 97 +/- 3%, respectively, at 95% confidence level. Seventy-five-fold (using 750 mL of sample solution and 10 mL of eluent) and 50-fold (using 500 mL of sample solution and 10 mL of eluent) preconcentration was obtained for Pb and Ni, respectively. Time of analysis is about 4.5 h (for obtaining enrichment factor of 75). By applying these enrichment factors, the analytical detection limits of Pb and Ni were found as 3.65 and 1.42 ng mL(-1), respectively. The capacity of the sorbent was found as 0.17 and 0.21 mmol g(-1) for Pb and Ni, respectively. The interferences of some cations, such as Mn2+, Co2+, Fe3+, Al3+, Zn2+, Cd2+, Ca2+, Mg2+, K+ and Na+ usually present in water samples were also studied. This procedure was applied to the determination of lead and nickel in parsley, green onion, sea water and waste water samples. The accuracy of the procedure was checked by determining Pb and Ni in standard reference tea leaves sample (GBW-07605). The results demonstrated good agreement with the certified values.