Solid-state Mechanochemical Reaction Research Articles

Annealing Effect of Ce-Doped CaGa2S4Synthesized by Mechanochemical Solid-State Reaction

Annealing Effect of Ce-Doped CaGa₂S₄Synthesized by Mechanochemical Solid-State Reaction

Annealing Effect of Ce-Doped CaGa2S4 Synthesized by Mechanochemical Solid-State Reaction

The effect of annealing on samples prepared by ball milling of a mixture of CaS, Ga2S3, and Ce2S3 powders was investigated. When the mixture of powders was ball-milled for 1 h, no crystalline CaGa2S4:Ce was formed, and by subsequent annealing at 400 °C, CaGa2S4:Ce crystallites were formed. When the mixture powder was ball-milled for 5 h, nanometer-sized CaGa2S4:Ce crystallites were mechanochemically synthesized without heat treatment. By subsequent annealing of the crystallites at several temperatures from 300 to 800 °C, the strain on the mechanochemically synthesized Ce-doped CaGa2S4 nanometer-sized crystallites was removed and crystallites of about dozens of nanometer size were retained by 500 to 600 °C annealing.

Preparation of Ce-Doped CaGa2S4 by Mechanochemical Solid-State Reaction

CaGa2S4:Ce crystallites were synthesized by the mechanochemical reaction of CaS, Ga2S3, and Ce2S3 source powders. The growth process was studied by observing X-ray diffraction (XRD) patterns and Raman scattering spectra of the synthesized powder as a parameter of reaction time. Ce doping of CaGa2S4 was studied in terms of its photoluminescence (PL). The approximate crystallite size calculated by a Williamson–Hall plot was 59 (+5, -3) nm.

Preparation of carboxylate-functionalized cellulose via solvent-free mechanochemistry and its characterization as a biosorbent for removal of Pb 2+ from aqueous solution

Carboxylate-functionalized cellulose can be used as a low cost but effective biosorbent for heavy metals remediation. In this study, it was simply fabricated from wood cellulose and succinic anhydride via solvent-free mechanochemistry in the absence of catalyst at ambient temperature through pan-milling. Fourier transform infrared spectra (FT-IR) confirmed the realization of mechanochemical esterification of cellulose. Reaction kinetics study showed that this solid-state mechanochemical reaction was governed by “slow followed by fast” kinetics model. The reaction sites were mainly at the new surface of cellulose powder where hydrogen bondings in cellulose were broken up and hydroxyl groups were activated due to the fairly strong forces imposed by the pan-mill. X-ray photoelectron spectroscopy (XPS) indicated that the mechanochemical succinylation of cellulose occurred even in a short milling time. The exponential increment of surface area of cellulose during pan-milling was correlated to the increasing substitution degree. Preliminary adsorption studies showed that the modified cellulose possessed excellent adsorption capacity towards Pb 2+, with lead ion uptake value of 422 mg/g and 84.4% metal removal from a 500 mg/g Pb 2+ solution, significantly higher than those values for unmodified cellulose.

Synthesizing AlN powder by mechanochemical reaction between aluminum and melamine

A solid state mechanochemical reaction (MCR) method for synthesizing AlN powder with aluminum and melamine powders as the reactants was proposed and put into practice. It was found that the solid state MCR between aluminum and melamine is an instantaneous and exothermic reaction. For a certain charge ratio, a critical ball milling time is needed for the MCR to occur. The higher the charge ratio, the faster the MCR. Cryogenic environments help to accelerate the MCR between Al and melamine. In addition to the direct one-step MCR synthesis approach mentioned above, AlN powder can also be synthesized by pre-ball-milling Al and melamine powders followed by heat treatment. Using this two-step approach, the heat treatment temperature is only about 638 °C, which is much lower than that used in other ways for synthesizing AlN powder. The lower heat treatment temperature can be attributed to the combined effect of both the adoption of melamine and the high reactivity of powders caused by ball milling. Comparatively, the present solid state MCR method for synthesizing AlN powder may be more cost-effective and hence more promising to be used to industrially produce both AlN powder and in situ AlNP reinforced aluminum matrix composites.

Preparation of MoS2 by a novel mechanochemical method

A novel simple process for preparing MoS 2 by a mechanochemical route under the normal temperature and pressure has been developed. In this method, the mechanochemical solid-state reaction was completed in a high-energy planetary ball mill filled with pure argon. The effects of milling time and speed were discussed and the product was characterized by XRD, DSC and TEM. It is found that the as-obtained samples are MoS 2 with short low stacked layers less than 10 nm, which have potential application in the highly active catalysts.

Solid phase mechanochemical synthesis of polyaniline branched nanofibers

A polyaniline supramolecular structure composed of polyaniline nanofibers, has been prepared by a simple solid-state mechanochemical reaction and template-free method. XRD analysis confirmed the good crystallinity of the product, and FTIR and UV–vis analysis indicated that the product was a highly doped emeraldine salt. Electrochemical cyclic voltammetry confirmed the electrocatalytic effect of the branched nanofiber to dopamine and hydroquinone. The growth mechanism of the unique supramolecular structure in mechanochemical reaction was discussed, together with the effect of the crystalline water of the oxidant.

Mechanochemical synthesis of nanocrystalline titanium monoxide

Nanocrystalline cubic titanium monoxide, TiO x (0.92 < x < 1.19), with mean crystallite size of ≈ 6 nm, was synthesized by mechanochemical treatment of Ti and TiO 2 (rutile) powder mixtures with molar ratios of 1:1, 1.10:1 and 1.25:1. The mechanochemical solid state reaction in a high-energy planetary ball mill was completed for 2 h in either air or argon atmosphere. During heating in vacuum at 900 and 1000 °C for 24 h, nanocrystalline TiO x transforms to a well-crystallized, cubic or monoclinic TiO x . The materials prepared were characterized by XRPD, TGA/DSC and SEM/EDS analysis.

Synthesis of ZnO and ZrO&lt;sub&gt;2&lt;/sub&gt; Powders by Mechanochemical Processing

The ZnO and ZrO2 powders were prepared by mechanochemical processing and subsequent heat treatment of the starting powder of precursors mixture of ZnCl2 and Ca(OH)2, and ZrOCl2·8H2O and NaOH, respectively. Inert salt matrix, ether CaCl2 or NaCl, which prevents particle agglomeration was formed during mechanochemical solid state reaction. After mechanochemical treatment, samples were calcined at various temperatures. Selective removal of the matrix phase by washing the resulting powder with appropriate solvent yields almost pure ZnO and ZrO2 powders. Characterization of the powders was performed by X-ray diffraction (XRD), differential thermal and thermo gravimetric analysis (DTA−TG) and scanning electron microscopy (SEM).

Supramolecular Conjugates of Carbon Nanotubes and DNA by a Solid-State Reaction

DNA-wrapped nanotubes of both multiwalled and single-walled carbon nanotubes were obtained by a solid-state mechanochemical reaction. Scanning electron microscopic images show that the nanotubes were cut into shorter lengths and were fully covered with DNA, which was further confirmed by fluorescence microscopy. This resulted in a high aqueous solubility of the products with a stability of >6 months. The results show that nanotubes were cut also with uniform distribution where >90% of the multiwalled products were 500 nm to 3 microm and 80% of the single-walled products were 250 nm to 1 microm in length, respectively. UV-vis spectra and gel electrophorosis show that the DNA in the product is intact. This facile technique for obtaining supramolecularly masked, water-soluble carbon nanotubes by a solid-state reaction has a great potential for both biological and nonbiological applications of nanotubes.

Synthesis of Fullerene Derivatives with Novel Structures. Liquid—Phase versus Solid—State Reactions

AbstractFor Abstract see ChemInform Abstract in Full Text.

Riboflavin-radical formation by mechanochemical solid-state reaction using stainless steel vessel

The mechanochemical reaction of free riboflavin (FR) due to vibratory ball milling was carried out in a stainless steel vessel at room temperature under anaerobic conditions. The ESR of the fractured sample showed a broad single-line spectrum. It is suggested that the solid-state single-electron transfer (SSET) reaction from the surface of the stainless steel vessel to FR proceeded during the vibratory milling, resulting in the formation of the corresponding anion radicals. When the mechanochemical reaction of FR in the presence of calcium pantothenate (PC) was carried out, the radical concentration increased with the increasing PC content. It was shown that the anion radical in the metal complex was stable for a lengthy period of time even in highly humid air.

Synthesis of Fullerene Derivatives with Novel Structures-Liquid-Phase versus Solid-State Reactions-

Reactions of C60 with various carbon nucleophiles, particularly those with substituted acetylide and fluorenide ions in the liquid phase, give various C60 derivatives. While the reaction with cyanide salts only affords the cyanated C60 in liquid phase, the solid-state mechanochemical reaction selectively gives the dumbbell-shaped dimer. As typically shown by this example, the solid-state reaction was found to be quite advantageous for the formation of various types of fullerene dimers. The reaction of C60 with phthalazine also results in formation of entirely different products depending on the reaction phase. While the solid-state reaction gives a fullerene dimer incorporated in a bicyclic framework, the liquid-phase thermal reaction affords a derivative of an open-cage fullerene. Utilizing this reaction, an attempt has been made for organic synthesis of endohedral fullerene encapsulating molecular hydrogen through a series of procedures, i.e., opening a hole on the fullerene cage, insertion of molecular hydrogen, and reduction of the size of the opening.

Mechanochemical synthesis of a novel C 60 dimer connected by a germanium bridge and a single bond

A novel C 60 dimer connected by a germanium bridge and a single bond was synthesized by the mechanochemical solid-state reaction using a high-speed vibration milling technique. The structural characterization was made by the 1H and 13C NMR, APCI mass, and UV-vis spectroscopy, and the presence of the electronic interaction between the two C 60 cages was demonstrated by the electrochemical method.

Mechanochemical Synthesis of a Novel C60 Dimer Connected by a Silicon Bridge and a Single Bond.

Abstract A novel C60 dimer connected by a germanium bridge and a single bond was synthesized by the mechanochemical solid-state reaction using a high-speed vibration milling technique. The structural characterization was made by the 1H and 13C NMR, APCI mass, and UV-vis spectroscopy, and the presence of the electronic interaction between the two C60 cages was demonstrated by the electrochemical method.

Mechanochemical synthesis of a novel C(60) dimer connected by a silicon bridge and a single bond.

[reaction: see text] A novel C(60) dimer connected by a silicon bridge and a single bond was synthesized by the mechanochemical solid-state reaction employing a high-speed vibration milling technique and fully characterized by the (1)H and (13)C NMR, APCI mass, and UV-vis spectroscopy. The presence of the electronic interaction between the two C(60) cages was demonstrated by the electrochemical method.

The reaction of fullerene C(60) with phthalazine: the mechanochemical solid-state reaction yielding a new C(60) dimer versus the liquid-phase reaction affording an open-cage fullerene.

The reaction of fullerene C(60) with phthalazine was studied both in solution and in the solid state using the high-speed vibration-milling technique. The reaction in solution gave open-cage fullerene derivative 1 in 44% yield by a one-pot reaction. In contrast, the solid-state reaction afforded dimeric derivative 2 as the sole product. Dimeric derivative 2 was found to undergo intramolecular [2 + 2] cycloaddtion between the two C(60) cages located in close proximity to give a new C(60) dimer 6 in quantitative yield. The structures of these new derivatives of C(60) were determined by spectroscopic methods, and the electrochemical behavior of 2 and 6 was also studied.

The fullerene cross-dimer C130: synthesis and properties

The fullerene C60–C70 cross-dimer C130 was synthesized by the mechanochemical solid-state reaction using a high-speed vibration milling technique, and was characterized by UV-vis and 13C NMR spectroscopy as well as electrochemical methods.

The fullerene dimer C 120 and related carbon allotropes

Dimerization of C 60 under the solid-state mechanochemical reaction conditions to give C 120 was found to occur in the presence of potassium salts such as KCN, KOH, and KOAc, or of a small amount of alkali metals, or even of organic solid amines such as 4-aminopyridine. The reaction is presumed to involve the formation of the C 60 radical anion, and an equilibrium state is attained between C 60 and C 120. When the solid-state reaction was conducted under the catalysis of 4-aminopyridine, the formation of a small amount (∼4% yield) of fullerene trimer C 180 was also observed. The trimer C 180 was confirmed as its cyanated derivative by APCI MS spectroscopy, and was characterized by IR and UV–Vis spectroscopies. Based on the results of HPLC analyses, there are at least four isomers of C 180. The solid-state reaction of C 60 with C 70 in the presence of 4-aminopyridine afforded the cross-dimer C 130 in a low yield (∼2%) in addition to C 120 (6%). The dimer C 130 was also confirmed as the cyanated derivative by APCI MS spectroscopy, and was characterized by UV–vis and 13C NMR spectroscopies.

Mechanochemically induced formation of La2SiO5

A mechanochemical technique was applied to prepare La2SiO5 under conditions where the conventional solid-state synthesis shows unsatisfactory results. The effects of the mechanochemical treatment of a mixture of lanthana and silica gel (in molar ratio La2O3/SiO2 = 4:3 has been studied by X-ray diffractometry (XRD), infrared spectroscopy (IR) and using a scanning electron microscope (SEM). Differential thermal analysis (DTA) and thermogravimetry (TG) have been used to follow the thermal behaviour of initial and milled samples. It was found that the amorphous silicate precursor of La4.67(SiO4)3O is formed as a result of a mechanochemical solid-state reaction. The crystallization of the latter silicate occurs at 880°C during the subsequent heat treatment of the milled samples. The formation of La2SiO5 without any XRD—detectable traces of La4.67(SiO4)3O takes place after heating at 1100°C for 2 h. The rate of conversion increases with increasing the milling time, reaching 96% after mechanochemical treatment for 3 h and subsequent heating at 1100°C.