Ion-exchange synthesis of α-modification of nickel hydroxide

An anion-exchange method for synthesizing nickel hydroxide using industrial strongly basic AV-17-8 anionite has been proposed. The influence of conditions (concentration and nature of starting salt, amount of the anionite, process duration, etc.) on the precipitate yield has been established. The product has been investigated by scanning electron microscopy, IR and Raman spectroscopy, X-ray phase analysis, and thermal and chemical analyses. It has been established that the product is a disordered layered modification of nickel hydroxide α-Ni(OH)₂, which contains anions and water molecules in the interlayer spacing. Nickel hydroxide particles are needle crystals (40–80 nm) that form agglomerates 0.3–0.5 μm in size.     

Sonochemical intercalation synthesis of nano γ-nickel oxyhydroxide: Structure and electrochemical properties

Nano γ-nickel oxyhydroxide (nano γ-NiOOH), intended as a new positive electrode material for alkaline Zn/Ni batteries, was synthesized by a sonochemical intercalation method. Using NaClO as oxidant, 5 M NiCl₂ solution was added dropwise to a concentrated alkaline solution of NaClO + NaOH, which allows all four elementary reactions (precipitation, oxidation, cation exchange, and water molecule intercalation) to proceed simultaneously under low-frequency ultrasonic irradiation. XRD, SAXS, TEM, SEM, AAS, IR, TG, CT (complexometric titration), cyclic voltammetry (CV), and a charge-discharge test of imitative cell have been used to characterize the microstructural characteristics, composition and electrochemical properties of the synthesized material. The results showed that the lattice parameters of nano γ-NiOOH are a = 2.8256 Å and c = 20.7938 Å. The average oxidation state of Ni in the sample is 3.65 as measured by an indirect iodine method. The alkali metallic Na⁺ ions and water molecules have been inserted into sites between NiO₂ layers. The cyclic voltammogram of nano γ-NiOOH exhibited two cathodic peaks and two anodic peaks, which is in accord with the redox reaction between the various phases of Ni(OH)₂ and NiOOH. The charge-discharge test of imitative cells revealed that nano γ-NiOOH exhibited a higher discharge capacity than spherical β-NiOOH.     

Suppression of the α → β-nickel hydroxide transformation in concentrated alkali: Role of dissolved cations

The presence of dissolved cations such as Al and Zn in alkaline electrolyte (6 M KOH) suppresses the -nickel hydroxide transformation. The uptake of Al (10 mol%) and Zn (30 mol%) exhibited by the active material likely stabilizes the -phase. Dissolved Al is deleterious to the performance of the nickel hydroxide electrode, whereas, dissolved Zn enhances the specific discharge capacity of nickel hydroxide by approximately 25% showing that the mode of metal uptake is different in the two cases.     

The effect of the catalyst on the synthesis of 2,2′-dichlorohydrazobenzene during the electrochemical reduction of o-chloronitrobenzene

In this paper, 2,2′-dichlorohydrazobenzene was synthesized by the electrochemical reduction of o-chloronitrobenzene using the ion-exchange membrane method. The effects of different catalysts (litharge, lead tetroxide, and lead nitrate) on the synthesis were investigated. The influence of different catalyst loading approaches on the electrochemical reduction were also examined. The structure and surface morphology of the catalysts were characterized by X-ray diffraction and scanning electron microscopy. Catalyst activity was examined by dynamic potential analyses and cyclic voltammetry. Litharge was found to induce the greatest improvement in the electrolysis reaction rate and also decreases the reaction time. Coating the catalyst on the cathode helps enhance the product yield. The possible reaction mechanism was studied, and the catalyst was found to play a key role in transforming raw substances into intermediates. However, there is little effect on intermediate product transformation into the desired product.     

Application of nickel(II) complexes to the efficient synthesis of α- or β-amino acids

Nonproteinogenic α- or β-amino acids have attracted tremendous attention, as they are widely utilized for biological, biochemical, pharmaceutical, and asymmetric chemical investigations. Recently, we developed a series of new strategies for preparing achiral and chiral nickel(ii) complexes for the synthesis of amino acids. We applied these new methods utilizing chiral nickel(ii) complexes for the asymmetric Mannich reaction to synthesize enantiopure α,β-diamino acids, the enantioselective tandem conjugate addition-elimination reaction to prepare glutamic acid derivatives, the Suzuki coupling reaction to yield β(2)-amino acid derivatives, the asymmetric Mannich reaction to synthesize 3-aminoaspartate, the asymmetric Michael addition reaction to give β-substituted-α,γ-diaminobutyric acid derivatives, the asymmetric alkylation reaction to prepare linear ω-trifluoromethyl containing amino acids, and the asymmetric Michael addition reaction to synthesize syn-β-substituted tryptophans.     

Microreactor-assisted synthesis of α-alumina nanoparticles

In this paper, nanosized α-Al₂O₃ powders were synthesized with the aid of a high throughput impinging stream microreactor. It was demonstrated that the as-prepared powders exhibited better dispersity and more homogeneous distribution of particle size than that prepared by conventional parallel flow precipitation method due to the drastic collisions and homogeneous explosive nucleation in microchannel during the precipitation process. The effects of calcinating temperature and time on the morphology, phase composition and particle size of α-Al₂O₃ were systematically studied. Comparatively well dispersed and crystallized α-Al₂O₃ powders with higher sintering activity were obtained by calcinating the as-prepared precursors at 1200 °C for 2 h in air. The specific surface area of α-Al₂O₃ powders was above 20 m² g⁻¹ and average particle size was about 110 nm with higher sintering behavior. From room temperature to 1520 °C, the green compact exhibited shrinkage of 19.34%. This work opens a door for developing ultrafine α-Al₂O₃ powders with uniform size distribution, high crystallinity, and excellent thermal expansion property.     

Investigations on electrochemical α-methoxylation of selected dipeptides

Voltamperometric studies on the indirect electrochemical α-methoxylation of Boc-Pro-Gly-OMe and Boc-Val-Gly-OMe in MeOH in the presence of NaCl or NaBr as the mediator suggested that the first reaction step was a direct N-halogenation of the dipeptide by active chlorine or bromine adsorbed on the electrode surface. The kind of mediator (NaCl or NaBr), its concentration, the current density, and the applied electric charge had a significant influence on the reaction course. In the case of Boc-Pro-Gly-OMe, the use of sodium bromide was necessary to obtain a relatively high ratio of α-monomethoxylation to α,α-dimethoxylation. For Boc-Val-Gly-OMe, the selectivity for α-monomethoxylation was close to 100%, independently of the mediator. Optimisation of the selected electrolysis parameters allowed us to significantly improve the yield and selectivity of the α-methoxylation of Boc-Pro-Gly-OMe (Kardassis et al. Tetrahedron 54:3471, 1998) and to obtain good results in the α-methoxylation of Boc-Val-Gly-OMe.     

Insights into the electrochemical activity of nanosized α-LiFeO2

In recent work [J. Morales, J. Santos-Peña, Electrochem. Commun. 9 (2007) 2116], we prepared nanosized α-LiFeO₂ with increased electrochemical activity in lithium cells relative to various lithium ferrite polymorphs. In this work, we studied the previous electrodes in different charge states in order to obtain a more accurate picture of the phenomena occurring during cycling. Exsitu X-ray photoelectron spectroscopy (XPS) measurements confirmed the oxidation/reduction of iron atoms during the charge/discharge process. The electrochemical impedance spectroscopy results suggested that the electrolyte is not oxidised during the first charge, but rather than a solid electrolyte interface is formed after one cycle. Also, thermal tests revealed that Fe(IV) present in the electrodes reacted with the electrolyte to form oxidised carbon species. Finally, α-LiFeO₂ was tested as a positive electrode material in a lithium battery under different regimes. Stabilised capacities up to 150 mAh g⁻¹ were obtained under a C/4 regime. This lithium ferrite is therefore an attractive alternative to LiCoO₂.     

Characterization of N,N′-dimethyl-3,4,9,10- perylenetetracarboxylic acid diimide and phthalocyaninatozinc(ii) in electrochemical photovoltaic cells

As a direct comparison to all-solid state photovoltaic cells, photoelectrochemical cells consisting of n-type N,N-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (MePTCDI) and p-type phthalocyaninatozinc(ii) (PcZn) thin film electrodes vapour-deposited onto ITO have been investigated in aqueous ferri/ferrocyanide, p-benzoquinone/hydroquinone or I3–/I– electrolytes. The ferri/ferrocyanide cell has been studied in more detail, and the results are discussed with regard to the HOMO-, LUMO- and Fermi-energies of the materials used. A setup of the electrodes in a tandem cell could increase the efficiency of the cell due to improved light harvesting. Saturation of the photocurrent with increasing ferri/ferrocyanide electrolyte concentration at single PcZn or MePTCDI electrodes is discussed using a model of reactant adsorption prior to the charge transfer step. In addition, a decrease observed for the open-circuit voltage of the entire cell with increasing ferri/ferrocyanide concentration leads to an optimum concentration of 10–3 moldm–3.     

Study on the chemical synthesis and the performance of V(Ⅲ)-V(Ⅳ) electrolyte

钒电池是一种高效储能装置,钒电池电解液直接影响电池性能。本文以V2O3、V2O5和H2SO4为原料,化学合成了用于钒电池的V(Ⅲ)-V(Ⅳ)电解液,研究了无水乙醇与焦磷酸钠作为添加剂对电解液稳定性和电化学活性的影响。实验结果表明,当V2O3/V2O5质量比为7.2∶1时,可以得到V(Ⅲ)/V(Ⅳ)离子浓度比为1.0的电解液;添加剂的加入能提高电解液的稳定性和电化学反应活性。     

Isomerization of α-pinene oxide in the presence of methyltrioxorhenium(VII)

The catalytic performance of methyltrioxorhenium(VII) (MTO) has been investigated for the first time in the isomerization of α-pinene oxide (PinOx) into campholenic aldehyde (CPA). The high isomerization activity of MTO is coupled with high selectivity to CPA: CPA yield of up to 87% (100% conversion) was obtained by using α,α,α-trifluorotoluene as solvent at 15 °C. Catalyst recycling is possible in a relatively simple fashion by using MTO coupled to an appropriate ionic liquid. The catalytic application of MTO in the isomerization of PinOx versus the integrated epoxidation–isomerization process of the conversion of α-pinene into CPA is discussed.     

An electrochemical alternative strategy to the synthesis of β-lactams via NC4 bond formation

A simple electrochemical synthesis of β-lactams has been developed using constant current electrolysis in a suitable solvent-supporting electrolyte solutions, with subsequent addition of bromoamides. The regio- and stereo-selectivity of the electrochemically-induced cyclization of bromoamides to β-lactams, via NC4 bond formation, has been evidenced. This synthesis avoids any addition of bases and probases and gives β-lactams in high yields.     

Formation of porous α-alumina from ammonium aluminum carbonate hydroxide whiskers

Ammonium aluminum carbonate hydroxide (AACH) whiskers prepared by hydrothermal technique were employed as precursor material for development of porous alumina. After compaction of AACH whiskers at 8 bars, calcination was performed at 650?°C followed by sintering at different temperatures. The sintered samples were characterized by XRD, FTIR, SEM and mercury intrusion porosimetry. Mechanical strength was determined by compression testing. At sintering temperatures of 1200?°C to 1400?°C, the % age porosity was around 80%. At 1500?°C, the percentage porosity decreased to 71%. The as-prepared AACH consisted of bundles of whiskers with diameters as thick as 0.7?µm, while an individual whisker had a diameter of about 100?nm with an aspect ratio of about 33. A two-phase mixture consisting of θ- and α-alumina was obtained at 1100?°C, while at 1200?°C and above, single phase α-alumina was formed. θ-alumina retained the bundle-like morphology. However, transformation to α-alumina was accompanied by formation of bead-like morphology. These beads were joined together through necks/stems within the whiskers as well as across the parallel-lying whiskers. These necks grew at 1300?°C to form aggregates with smooth surfaces. At 1400?°C, these aggregates started joining with each other by neck formation and at 1500?°C, a three-dimensional network was formed. For sintering temperatures of up to 1400?°C, pores with sizes around 260?nm were very stable. At 1500?°C, significant pore growth took place along with an overall densification. Therefore, number of pores with sizes of around 260?nm decreased and those with sizes around 10?µm, 1?µm and 5?nm increased. The compression strength of samples sintered at 1100?°C to 1300?°C was in the range of 3.4–4.3?MPa. At 1400?°C, the strength increased to 5.2?MPa, while at 1500?°C, it jumped to 10.8?MPa due to the formation of three-dimensional network.     

Interaction of calcium phosphates with calcium oxide or calcium hydroxide during the “soft” mechanochemical synthesis of hydroxyapatite

In the present work, the formation kinetics of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ during ball milling of mixtures of calcium phosphates with calcium oxide or calcium hydroxide was studied. The conversion degrees of reaction mixtures containing calcium dihydrogenphosphate/dicalcium phosphate/tricalcium phosphate/calcium pyrophosphate and calcium oxide/calcium hydroxide were determined for different milling times. The formation kinetic data were analyzed together with the Gibbs free energies of the corresponding reactions. It was found that the kinetic factors dominate at the initial formation stage of hydroxyapatite due to the acid-base interactions during the “soft” mechanochemical synthesis. A technologically attractive synthesis route of Ca₁₀(PO₄)₆(OH)₂ was suggested based on the “soft” mechanochemical synthesis via reactions between СаНРО₄ and СаО or Са(ОН)₂.     

Hydrothermal synthesis of single-crystal α-tristrontium phosphate particles

Anisotropic ceramic bodies can be fabricated by a reactive template grain growth method; however, template particles with suitable powder properties are required to create the ceramics with well controlled anisotropy. Therefore, we synthesized well-isolated α-tristrontium phosphate (α-TSP) particles with a hexagonal plate-like shape as template particles for anisotropic strontium apatite ceramics using α-strontium hydrogen phosphate (α-SrHPO₄) precursor particles. Three synthetic parameters were varied: (i) precursor particle size, (ii) stirring rate, and (iii) hydrothermal temperature. Well-isolated hexagonal plate-like α-TSP single-crystal particles were successfully synthesized by hydrothermal treatment at 150 °C for 3 h at a stirring rate of 150 rpm using fine α-SrHPO₄ precursor particles. The developed plane of the hexagonal plate-like α-TSP particles was determined to be the {00l} plane, and the side planes were revealed to be not {h00} planes, but inclined {h0l} planes. The resulting α-TSP particles may provide a promising template for the development of anisotropic apatite-based ceramics.     

Size-controlled synthesis of nano α-alumina particles through the sol–gel method

Nano α-alumina particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 M aluminum nitrate. 1/3-benzened disoulfonic acid disodium salt (SDBS) and sodium bis-2-ethylhexyl sulfosuccinate (Na(AOT)) were used as surfactant stabilizing agents. Solution was stirred for different periods (24, 36, 48 and 60 h) at 60 °C. The samples were then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Introduction of surfactant stabilizing agents and different stirring times will affect the size and shape of particle formed and also the degree of aggregation. SDBS, however, produced better dispersion, finer particles and spherical shape nanoparticles, compared to Na(AOT). The finest particle size (20–30 nm) was obtained at 48 h stirring time with SDBS surfactant.