Soft mechanochemical synthesis: Preparation of cathode materials for rechargeable lithium batteries

To prepare intercalation lithium — transition metal oxide cathode materials for rechargeable lithium batteries, the reactions in the mixtures of the correspondent hydroxides in highly energetic planetary activators, so called ‘soft mechanochemical synthesis’ were studied. The method can be used for direct preparation of final products in a high dispersed and disordered state, as well as for obtaining high reactive precursors yielding final products by the subsequent brief heating at considerably lower temperatures as compared to conventional ceramic method. The as prepared products were analyzed using X-ray diffraction, TG, IRS, XPS, ⁷Li NMR, EPR, diffuse reflectance spectroscopy, electron microscopy, BET, and electrochemical measurements. The peculiarities of crystal structure, electronic state of transition metal ions and cycling behaviour of materials are discussed. The method as proposed is concluded to be economically effective and ecologically clean.     

Solid-state mechanochemical synthesis of ferrocene

Solid-state mechanochemical reactions of iron(II) chloride with cyclopentadienides of alkaline metals or thallium, which lead to the formation of ferrocene, were studied. The dependence of the yield of the product on the parameters of mechanical loading for the reaction with cyclopentadienylthallium was determined.     

Solvent-free mechanochemical synthesis of diacylfuroxans

Acetophenones with a variety of substituents could be converted to diacylfuroxans in a solvent-free reaction by combining the reagents Fe(NO₃)₃·9H₂O and P₂O₅ under high-speed ball milling. This reaction was facile and eco-friendly, and exhibits advantages in terms of better toleration, safety, and easier operation. The nitrate acid and nitrogen dioxide generated in situ should play a major role in this mechanochemical reaction.     

Oxidation of metallic iron with oxygen via mechanochemical activation

The X-ray phase analysis and X-ray diffraction, as well as IR and Mössbauer spectroscopic techniques were employed to study mechanochemical oxidation of iron metal powder with oxygen. The phase composition of the products of mechanochemical activation of iron in a vibrating mill was determined. The extent of oxidation of iron was examined in relation to the particle-size distribution of the starting iron powder.     

Rational design of ordered mesoporous carbon with controlled bimodal porosity via dual silica templating route

Combining both nano-replication and nano-imprinting techniques using dual silica templates provides a simple way to synthesize ordered mesoporous carbons with bimodal pore size distributions ( approximately 1.5 nm and approximately 3.5 nm).     

Solvent-assisted mechanochemical synthesis of metal complexes

The application of solvent-assisted mechanochemical synthesis to the study of metal complex formation is illustrated by examples involving complexes of silver halides with ethylenethiourea.     

Solvent-free mechanochemical synthesis of phosphonium salts

Phosphonium salts have been prepared during high-energy ball-milling of triphenylphosphine with solid organic bromides; the reactions occur at ambient conditions without a solvent; in the case of 2-bromo-2-phenylacetophenone the reaction in a solution usually produces a mixture containing both the C-phosphorylated and O-phosphorylated compounds, while the solvent-free mechanically induced transformation results in the thermodynamically favorable C-phosphorylated product; the occurrence of the observed transformations during mechanical processing of solid reactants is confirmed by the solid-state 31P NMR spectroscopy and X-ray powder diffraction.     

Solid-phase mechanochemical synthesis of zirconium tetracarboxylates

The solid-phase synthesis of zirconium carboxylates Zr(OOCR)₄ (R = Alk) by reactions of zirconium tetrachloride with metal carboxylates (isobutyrate, pivalate, and palmitate) (the molar ratio ZrCl₄: RCOOM is 1: (4–5)) under mechanical activation is developed. Further thermal treatment of the reaction mixture and extraction with an organic solvent afford zirconium carboxylates.     

Polymer-mediated synthesis of highly dispersed Pt nanoparticles on carbon black

A new method was developed to prepare highly dispersed Pt nanoparticles on carbon black to use as proton exchange membrane (PEM) fuel cell catalysts. This method involves using a polymer, poly(vinylpyrrolidone) (PVP), to prevent particle aggregation and thereby reduce nanoparticle sizes to achieve high dispersion. It was found that Pt nanoparticles mediated by PVP are smaller than those obtained without PVP and have a narrower size distribution. Well-dispersed Pt nanoparticles with metal loadings from 5 to 35 wt % were obtained on carbon black (Vulcan XC-72R). It was found that well-dispersed Pt nanoparticles on carbon black could be synthesized at a PVP monomers-to-Pt atoms ratio of 0.1 under our experimental conditions. Larger amounts of PVP did not produce smaller nanoparticles, but rather reduced the Pt mass loading on carbon black. The morphology of the Pt nanoparticles that were supported on carbon black was characterized with transmission electron microscopy and X-ray diffraction. Their active surface areas were determined using cyclic voltammetry in a sulfuric acid solution. High Pt dispersion was obtained for the catalysts synthesized with PVP mediation, even at Pt loadings up to 35 wt %. The catalysts prepared with PVP mediation generally showed larger active specific areas than did those prepared without PVP.     

Low-temperature mechanochemical synthesis of nanosized silicon carbide

The methods of X-ray diffraction analysis, scanning electron microscopy, synchronous thermal analysis, and adsorption are used to study the mechanochemical synthesis of silicon carbide through the reaction Si + C → β-SiC. The reaction is found to take place in several stages. At the first stage, i.e., at activation doses below approximately 5 kJ/g, the powders of the components are independently ground to increase the specific surface area of the mixture to 145 m²/g, graphite is amorphized, and the sizes of the coherent-scattering regions of silicon drastically diminish. At the second stage (doses of 5–15 kJ/g), dense Si/C aggregates are formed and two fractions (coarse and fine) with different particle sizes arise in silicon crystallites. As the activation dose is enhanced, the amount of the fine fraction rises, while the sizes of coherent-scattering regions decrease to 2–3 nm. When samples are heated at 800°C, the fine fraction of silicon interacts with carbon to yield silicon carbide with crystallite sizes of 3–4 nm, whereas the coarse fraction of silicon recrystallizes. At the third stage, i.e., at doses of higher than 15 kJ/g, the mechanochemical synthesis of SiC occurs through the following scheme: fine fraction Si + C → amorphous SiC → crystallization of SiC.     

Grafting of maleic anhydride onto carbon black surface via ultrasonic irradiation

The grafting of maleic anhydride onto carbon black surface based on the Diels–Alder addition via ultrasonic irradiation was investigated. Fourier transform infrared spectroscopy (FT‐IR) and thermogravimetric analysis (TGA) were used to determine the chemical structure of the resulting products. The anhydride ring in the modified products can be opened into two carboxylic groups. Accordingly, the carboxylated carbon black was analyzed quantitatively through acid‐based titration to determine the concentration of anhydride ring on the modified carbon black's surface. The grafted molecules amount calculated from the concentration of the anhydride ring was consistent with the results of TGA data. Comparison of zeta potential measurement demonstrated that there were more negative charges attached to the surface of carbon black after ultrasonic modification. TEM observations showed that the conglomeration degree of modified carbon black decreased more than that of initial carbon black. Copyright © 2008 John Wiley & Sons, Ltd.     

Grafting onto carbon black by the reaction of reactive carbon black having epoxide groups with several polymers

The grafting of functional polymers onto carbon black surface by the reaction of epoxide groups introduced onto the surface was investigated. The introduction of epoxide groups was achieved by the reaction of the phenolic hydroxyl and carboxyl groups on carbon black with chloromethyloxirane in the presence of sodium hydroxide. The amount of epoxide groups introduced onto the channel black Neospectra II was equal to 0.40 meq/g. The epoxide groups were reacted with polypropylene glycol, silicone diol (SDO), silicone diamine (SDA), and polyethyleneimine to give polymer-grafted carbon blacks. For example, the percentage of grafting of SDO (M_n = 1.0 × 10³) and SDA (M_n = 3.9 × 10³) reached to 23.6 and 67.2%, respectively. The percentage of grafting increased with the molecular weight (M_n) of the polymers, while the number of grafted chain (G_n) decreased. In the case of SDO, the relationship between M_n and G_n was found to be G_n = 4.68 × 10^?2 M. The carbon black obtained from the reaction gave stable colloidal dispersions in tetrahydrofuran and the stability of dispersion increased with an increase in the percentage of grafting.     

LiVPO4F/Li3V2(PO4)3 nanostructured composite cathode materials prepared via mechanochemical way

Single-phase LiVPO₄F and LiVPO₄F/Li₃V₂(PO₄)₃ nanostructured composite cathode materials were prepared by heating of the VPO₄?+?LiF mechanochemically activated mixture to 700 °C and subsequent quick or slow cooling to room temperature, respectively. The formation of the composites was proved by a combination of different physico-chemical methods, including XRD, FTIR, ⁶Li and ³¹P NMR, SEM, TEM, and HRTEM. It has been shown that in the composites LiVPO₄F and Li₃V₂(PO₄)₃ nanocrystals well inset into each other resulting in the nanodomain composite formation. Charge–discharge curves of the composites have a sloping profile both in the high-voltage (3.0–4.5 V) and in the low-voltage (1.3–2.5 V) ranges, noticeably different from plateaus for a phase-pure LiVPO₄F, thus indicating a probable change of a two-phase regime of lithium intercalation for a single-phase one. Enhanced rate capability of the LiVPO₄F/Li₃V₂(PO₄)₃ composites is associated with their microstructure and high ionic conductivity of Li₃V₂(PO₄)₃.     

Solid-phase mechanochemical synthesis of arabinogalactan and chlorsulfuron complexes

Possibility of mechanochemical synthesis of water-soluble complexes from Siberian-larch arabinogalactan and poorly soluble herbicide chlorsulfuron was examined, their molecular dynamics was analyzed by the NMR method, and their stability and herbicide activity were compared with those of the starting substances.     

Inhibition of organic mechanochemical synthesis by water vapor

The effect of water on the mechanochemical synthesis in the glycine–malonic acid system has been studied in different types of devices. Comparative studies of the hygroscopicity of the reagents and products made it possible to rationalize the inhibiting effect of water vapor and the difference in the reaction course in impact and shear devices and in devices providing both action modes. The importance of control of ambient humidity for mechanochemical reactions on the laboratory and industrial scales has been illustrated.     

One-step synthesis of novel biacidic carbon via hydrothermal carbonization

The novel biacidic carbon has been synthesized via one-step hydrothermal carbonization of glucose, citric acid, and hydroxyethylsulfonic acid at 180 °C for only 4 h. The novel carbon had an acidity of 1.7 mmol/g with the carbonyl to sulfonic acid groups molar ratio of 1:3, which was confirmed by IR, XPS, TPD, SEM, and BET analyses. The catalytic activities of the carbon were investigated through esterification and oxathioketalization. The results showed that the carbon owned the comparable activities to sulfuric acid, which indicated that the carbon holds great potential for the green processes.     

Optimization of the process variables in the microwave-induced synthesis of carbon xerogels

Carbon xerogels (CX) can be synthesized by microwave-assisted heating. The transfer of this technology to an industrial scale passes through the optimization of the variables that affect the process. The effect of the main operational variables, i.e., initial volume of the precursor, gelation and ageing time and temperature of the synthesis, on the final porous properties of CX has been evaluated. It was found that the development of porosity in the CX synthesised in the microwave oven is hardly influenced by the increase in the initial volume of the precursor solution. This suggests that it is feasible to scale up the production of these materials by means of microwave heating. Furthermore, the consumption of energy does not increase in proportion to the volume of xerogel synthesized. Thus, the process is energy efficient, saves a considerable amount of time and requires only a single device to carry it out. These advantages, along with the fact that a temperature variation of 10 °C is not determinative in the xerogels’ final properties, indicate that CX could be produced on a large scale in a cost effective way .