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Lead-free ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 stands out among environmentally friendly alternatives to commercial Pb(Zr,Ti)O3 piezoceramics for its large piezoelectric coefficients, and it is especially suitable for applications in which thermal depoling is not an issue like bio-implanted devices. However, ceramic processing by conventional means consistently results in exaggerated grain growth, which compromises reliability and has prevented its transfer to industry. We report here the application of high-energy milling for the mechanosynthesis of nanocrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 powders with enhanced reactivity, and to the control of grain growth during ceramic processing to obtain materials with tailored microstructures and decreasing grain sizes down to the sub-10 µm range. Characterization of the electrical and electromechanical properties was accomplished and uncovered triggering of a new mechanism for very large strain under electric field in fine-grained ceramics. Process optimization by precursor selection and preliminary up-scaling studies are also presented., Funded by the Spanish MINECO Project MAT2017-88788-R. M. Venet thanks financial support by São Paulo Research Foundation FAPESP (grant number 2017/17872-1).

Three efficient synthetic approaches towards new azomethine- and terpyridine-containing 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (diketopyrrolopyrrole, DPP) based polymers, such as P1 and P2, are reported. The first approach involves the Pd-catalyzed synthesis via two- or three-component Suzuki or Stille cross-coupling reaction in solution. The second approach involves Pd-catalyzed Suzuki cross-coupling reaction under ball-milling conditions. And, finally, the third approach involves Pd-free condensation reaction under ball-milling conditions. The newly obtained polymers exhibited absorbance around 700 nm and emission around 900 nm, and, thus, these polymers are considered to be NIR-fluorophores.

Dissertation, RWTH Aachen University, 2023; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, RWTH Aachen University, 2023, In recent decades, organic synthesis techniques have seen a crescent interest in the application of mechanochemical methods. In parallel with values of a reduced environmental impact, such methodologies have shown the possibility of developing reactivities otherwise unobtainable by other synthetic approaches. For this reason, ad-hoc monitoring techniques compatible with the mechanical needs of the mechanochemical reactors have been developed. This thesis entitled "Mechanochemistry of Small Organic Molecules: Synthetic Applications and Monitoring Protocols" aims to contribute to both the fields of mechanosynthetic applications and monitoring techniques for mechanically induced molecular interactions. A first part of the work reports the development and application of mechanochemical synthetic procedures, specifically being: the use of raw minerals as a source of catalytic species for metal-catalyzed reaction, the study of a mechanochemical cross dehydrogenative coupling reaction, and a mechanosynthetic bottom-up protocol for the synthesis of unsymmetric triarylamines from primary aryl amines. In a second part, the application of in-situ Raman monitoring techniques is used to discern the mechanism involved in the mechanosynthesis of the active pharmaceutical ingredient phenytoin, followed by the presentation of an NMR in-operando method for the analysis of mechanochemically accelerated sublimations., Published by RWTH Aachen University, Aachen

International audience; Hyper-crosslinked polymers (HCPs) are receiving great attention due to their high specific surface area, allowing them to offer high performance in many different applications. However, most of the time, their synthesis requires hazardous and time-consuming protocols, making their implementation and scaling up difficult. To overcome this problem, a relatively old technology such as mechanosynthesis (MS) has gained renewed interest as a greener and faster technology to produce HCPs, which involves much lower energy consumption during the reaction process. In this review, the latest advances on the performance of HCPs based on MS protocols are compiled and analysed, subdivided into those based on Friedel-Crafts alkylation, Scholl coupling reactions and other less common procedures. An analysis of MS versus solvent-based protocols regarding the twelve principles of green chemistry is also reported, as well as a section including a summary of the most recent applications of HCPs. Finally, the use of bio-based precursors for the formulation of HCPs is discussed, thus pooling knowledge for a greener, faster and more widely applicable future development of HCPs.

Low temperature magnetic properties of BiFeO₃ powders sintered by flash and spark plasma sintering were studied. An anomaly observed in the magnetic measurements at 250 K proves the clear existence of a phase transition. This transformation, which becomes less well-defined as the grain sizes are reduced to nanometer scale, was described with regard to a magneto-elastic coupling. Furthermore, the samples exhibited enhanced ferromagnetic properties as compared with those of a pellet prepared by the conventional solid-state technique, with both a higher coercivity field and remnant magnetization, reaching a maximum value of 1.17 kOe and 8.5 10₋₃ emu/g, respectively, for the specimen sintered by flash sintering, which possesses the smallest grains. The specimens also show more significant exchange bias, from 22 to 177 Oe for the specimen prepared by the solid-state method and flash sintering technique, respectively. The observed increase in this parameter is explained in terms of a stronger exchange interaction between ferromagnetic and antiferromagnetic grains in the case of the pellet sintered by flash sintering. MCIN/AEI/10.13039/501100011033 and ERDF A way of making Europe by the European Union CTQ2017-83602-C2-1-R Junta de Andalucía-Consejería de Conocimiento, Investigación y Universidad-Fondo Europeo de Desarrollo Regional Programa Operativo FEDER Andalucía 2014–2020 P18-FR-1087 INTRAMURAL-CSIC grant number 201960E092

For the first time, a spinel-type high entropy oxide (Zn0.25Cu0.25Mg0.25Co0.25)Al2O4 as well as its derivative lithiated high entropy oxyfluoride Li0.5(Zn0.25Cu0.25Mg0.25Co0.25)0.5Al2O3.5F0.5 and oxychloride Li0.5(Zn0.25Cu0.25Mg0.25Co0.25)0.5Al2O3.5Cl0.5 are prepared in the nanostructured state via high-energy co-milling of the simple oxide precursors and the halides (LiF or LiCl) as sources of lithium, fluorine and chlorine. Their nanostructure is investigated by XRD, HR-TEM, EDX and XPS spectroscopy. It is revealed that incorporation of lithium into the structure of spinel oxide together with the anionic substitution has significant effect on its short-range order, size and morphology of crystallites as well as on its oxidation/reduction processes. The charge capacity of the as-prepared nanomaterials tested by cyclic voltammetry is found to be rather poor despite lithiation of the samples in comparison to previously reported spinel-type high entropy oxides. Nevertheless, the present work offers the alternative one-step mechanochemical route to novel classes of high entropy oxides as well as to lithiated oxyfluorides and oxychlorides with the possibility to vary their cationic and anionic elemental composition.

International audience; The nanocrystalline hydroxyfluorapatite (HFA) was synthesized by mechanosynthesis with a planetary ball mill (PM200). The disc to jar speed ratio was constant (equal to 0.5). The effect of different milling parameters such as grinding duration, balls number's, initial powder mass and disc rotation speed were studied to apprehend their effects on both the process of grinding/mechanosynthesis and the synthesis of nanocrystalline HFA. Unlike previous studies in which milling parameters have been independently studied, the effects of these parameters on the phase contents were simultaneously studied. Abdellaoui's model was also introduced to analyse the physical milling parameters effect such as the injected shock power, the shock kinetic energy, the shock frequency and the cumulated kinetic energy on the microstructural properties and synthesized phases contents. The results predicted by the model were compared to experimental ones. This study showed that the optimal conditions for the synthesis of nanocrystalline HFA were reached when the mechanosynthesis was carried out with a speed of 450 rpm, 6 balls, 1.2 g of starting material and 24 h of grinding duration. X-ray diffraction characterization confirmed the purity phase of HFA nanocrystalline powders.

Nanostructured materials can show considerably different properties as compared to their coarse-grained counterparts. Especially prepared by high-energy ball milling they are to be characterized by a large fraction of point defects in the bulk and structurally disordered interfacial regions. Here, we explored how the overall conductivity of SmF3 can be enhanced by mechanical treatment and to which degree aliovalent substitution is able to further enhance anion transport. For this purpose nanocrystalline (hexagonal) SmF3 was prepared by high-energy ball milling; mechanosynthesis helped us to replace Sm3+ in SmF3 by Ba2+ and to create vacancies in the F anion sublattice. We observed a remarkable increase in total (direct current) conductivity when going from nano-SmF3 to Sm1−x Ba x F3−x for x = 0.1. Electrical modulus spectroscopy was used to further characterize the corresponding increase in electrical relaxation frequencies.

The mechanosynthesis route is a physical top–down strategy to produce different nanomaterials. Here, we report the formation of graphene nanoribbons (GNRs) through this route using carbon bars recovered from discarded alkaline batteries as raw material. The mechanosynthesis time (milling time) is shown to have an influence on different features of the GNRs such as their width and edges features. TEM revealed the presence of GNRs with widths of 15.26, 8.8, and 23.55 nm for the milling times of 6, 12, and 18 h, respectively. Additionally, the carbon bars evolved from poorly shaped GNRs for the shortest milling time (6 h) to well-shaped GNRs of oriented sheets forming for the longest milling time. Besides GNRs, graphene sheets (GNS) of different sizes were also observed. The Raman analysis of the 2D bands identified the GNS signal and confirmed the GNRs nature. ID/IG values of 0.21, 0.32, and 0.40 revealed the degree of disorder for each sample. The in-plane sp2 crystallite sizes (La) of graphite decreased to 91, 60, and 48 nm with increasing peeling time. The RBLM band at 288 cm−1 confirmed the formation of the GNRs. Mechanosynthesis is a complex process and the formation of the GNRs is discussed in terms of a mechanical exfoliation, formation of graphene sheets and its fragmentation to reach GNR-like shapes. It is shown that the synthesis of GNRs through the mechanosynthesis route, besides the use of recycled materials, is an alternative for obtaining self-sustaining materials.

The formation of phases in mechanically synthesized (Fe0.90−xMn0.10Nix)75C25 alloys, where х = 0.05 and 0.10, is studied via X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements. It is shown that certain products form during the mechanosynthesis of the initial powders in a planetary ball mill: cementite doped mainly with manganese, ferrite, and an amorphous phase doped mainly with nickel. Annealing at 500°C and higher temperatures leads to the formation of a composite consisting of cementite and austenite doped mainly with nickel. Cementite regions with two different Curie temperatures form as the alloys cool after high-temperature (700°C) annealing, due to differences in the manganese doping of cementite in these regions.

The paper proposes a method for preparing composite powders of the Ti/TiB2 system, studies the properties of the obtained composite powders, and also shows a series of experiments on its microplasma spraying. The properties of the sprayed coatings were investigated. On its basis the optimal ratio of the matrix and reinforcing components was established in order to increase significantly the hardness of the sprayed coatings.

International audience; Hyper-crosslinked polymers (HCPs), a relatively new type of polymers with inherent porosity and high specific surface area, are of great interest due to their excellent results in many different application areas. These HCPs are typically synthetised via solvent-based protocols such as Friedel-Crafts and Scholl coupling reactions, which are time-consuming and hazardous. In an effort to promote environmentally friendly synthesis routes, this presentation will focus on bringing together the most recent work that formulates HCPs through a greener and faster alternative, mechanosynthesis. An analysis in the light of green chemistry principles has been performed and so, the mechanosynthesis will be compared to current synthesis routes. The main applications of HCPs will also be presented and analyzed in order to give an overview of the potential of HCPs. Finally, the use of biosourced precursors to obtain HCPs will be discussed to provide an alternative route to obtain still more environmentally friendly HCPs. With this work, the authors aim to provide the necessary background for the development of greener alternatives for the synthesis of these remarkable HCPs.

Formation of phases in nanocomposites of composition of carbide steels alloyed with chromium and nickel obtained as a result of mechanosynthesis in a planetary ball mill and further annealing was studied. It was shown that the structure mainly consisting of nickel-alloyed austenite and chromium-alloyed cementite is realized in composite (Fe0.80Cr0.10Ni0.10)83C17 after annealing at temperatures of 700–800°C. The size of cementite grains is in the nanometer range.

Chemistry - a European journal 27(49), 12558 - 12565 (2021). doi:10.1002/chem.202101260, echanochemistry, as a synthesis tool for inorganic materials, became an ever-growing field in material chemistry. The direct energy transfer by collision of the educts with the milling media gives the possibility to design environmental-friendly reactions. Nevertheless, the underlying process of energy transfer and hence the kinetics of mechanosynthesis remain unclear. Herein, we present in situ synchrotron X-ray diffraction studies coupled with pressure measurements performed during the formation of ZnS and the subsequent phase transition (PT) from the hexagonal to the cubic modification. Milling Zn and S$_8$ results in the sublimation of S$_8$, observed by a sudden pressure increase. Simultaneously, the hexagonal metastable ZnS-modification (wurtzite) forms. Via detection of the pressure maximum, the exact start of the wurtzite formation can be determined. Immediately after the formation of wurtzite, the structural PT to the thermodynamic stable cubic modification sphalerite takes place. This PT can be described by the Prout-Tompkins equation for autocatalytic reactions, similar to thermally induced PT in sulfur vapor at high temperatures (T>1133 K). The increase in the reactivity of the wurtzite formation is explained by the reaction in sulfur vapor and the induction of defect structures by the collisions with the milling media., Published by Wiley-VCH, Weinheim

Comparative studies of the iron–75fullerite and iron–75graphite composites obtained by the mechanosynthesis method have been performed by X-ray diffraction and Mossbauer spectroscopy. It has been shown that a carbon polymorph and its deformation stability predetermine the kinetics of formation for the phase composition of composites. In the case of disordering in the crystal structure of fullerite with the further destruction of fullerene molecules, iron–75fullerite powders are characterized by the same phase composition as for the iron–75graphite composite: amorphous carbon, Fe3C, Fe7C3, and the P-phase.

Dysprosium hafnate Dy2HfO5 powders are prepared through mechanochemical synthesis from hafnium and dysprosium oxides. The structure and main physicochemical characteristics are studied using XRD, scanning electron spectroscopy, Raman spectroscopy (CS spectra), TEM, and chemical analysis. XRD and analysis of CS spectra shows that full transformation of initial oxides into single-phase nanodispersed dysprosium hafnate (Dy2HfO5) occurs during mechanical treatment of the mixture for 40 min. Raman spectrometry of the dysprosium hafnate powder prepared through mechanosynthesis shows the absence of unreacted hafnium and dysprosium oxides and the formation of single-phase dysprosium hafnate.

The ability to rationally design and predictably construct crystalline solids has been the hallmark of crystal engineering research. To date, numerous examples of multicomponent crystals comprising organic molecules have been reported. However, the crystal engineering of cocrystals comprising both organic and inorganic chemical units is still poorly understood and mostly unexplored. Here, we report a new diverse set of higher‐order cocrystals (HOCs) based on the structurally versatile—yet largely unexplored—phosph(V/V)azane heterosynthon building block. The novel ternary and quaternary cocrystals reported are held together by synergistic and orthogonal intermolecular interactions. Notably, the HOCs can be readily obtained either via sequential or one‐pot mechanochemical methods. Computational modelling methods reveal that the HOCs are thermodynamically driven to form and that their mechanical properties strongly depend on the composition and intermolecular forces in the crystal, offering untapped potential for optimizing material properties., Mechanosynthesis gives ternary and quaternary hybrid organic‐inorganic cocrystals held together via synergistic intermolecular interactions. Notably, higher‐order ternary and quaternary cocrystals can be readily obtained either via serial synthetic routes from the individual components or via one‐pot approaches.

Metal–organic frameworks (MOFs) have attracted a special attention due to outstanding porosity, adjustable pore sizes, and huge opportunities in varying organic–inorganic compositions. Enormous studies conducted so far on MOFs indicate their high potential in catalysis, gas adsorption, drug delivery, water treatment, energy storage, among others. However, mass production of MOFs is still limited mainly due to the non-economic, non-green and complex synthesis methods. Mechanochemistry is an alternative solution for efficient and environmentally friendly syntheses of various MOFs. Fast and solvent-free or solvent-less mechanosynthesis seems to be a very powerful versatile method for obtaining these advanced porous materials. The mechanochemical concept was used for the preparation of various MOFs including the most popular structures: MOF-5, ZIF-8, HKUST-1, MIL-101, UiO-66. These MOFs feature high specific surface areas, comparable to those prepared by conventional solvent-based methods. Furthermore, mechanochemistry was successfully used for the synthesis of non-conventional multimetallic MOFs and previously unreported solid phases. This review shows the recent developments, challenges and perspectives of green synthesis of diverse MOF structures using mechanochemistry. Besides describing the mechanochemical synthesis of MOFs, some achievements in green applications are also summarized. Importantly, current trends in research suggests for further development of these fields i.e., harmful gas adsorption, water treatment, and energy storage.

Composite materials based on ultrahigh molecular weight polyethylene (UHMWPE) and magnesium ferrite particles—precursors for future formation of light protective material against electromagnetic radiation—have been synthesized mechanochemically. By application of scanning electron microscopy, X‑ray diffraction, differential scanning calorimetry, and magnetic measurements, the influence of the methods of synthesizing ferrite particles (solid phase, coprecipitation, sol–gel, or mechanosynthesis) on the structural and morphological characteristics of UHMWPE/ferrite composite materials has been studied. It is shown that the mechanochemical method of composite formation contributes to as an increase in the dispersity ferrite particles, by their nonuniform distribution in the UHMWPE volume with the transformation of its supramolecular structure. The method of synthesizing ferrite particles has a different effect on the formation of the molecular structure of UHMWPE: the appearance of a larger number of molecular structures with low melting points was a sign of greater homogeneity of mixing using smaller and uniform particles of ferrite. The observed formation of low molecular weight polymer chains should increase the rate of mutual diffusion between the boundaries of the polymer particles, which in sintering processes will lead to better sintering of the particles.

Sugar amides, such as aldonamides, are interesting, sugar-based molecules used in various fields, from detergency to medicine. Nevertheless, their valorization, especially as alternatives to petroleum-based substances, can be slowed down by their synthetic pathway, which is generally not in accordance with green chemistry principles, and is also not economically competitive. We propose herein a fast procedure for the synthesis of aldonamide-derived glycoconjugates with mechanochemistry. The conditions were first optimized with galactonolactone, used as a model lactone, and dodecylamine. After only 5 min of grinding of stoechiometric amounts of amine and lactone, in the presence of water used as a Liquid Assisted Grinding (LAG) agent, the corresponding galactonamide was isolated with a high yield (90%) after a simple aqueous work-up. The optimized conditions were then applied to a wide variety of amines and sugar lactones, showing the versatility of the methodology. Gluco- and ribono-lactone exhibited similarly excellent reactivity, showing that the procedure is not sugar-dependent. Furthermore, the procedure was shown to be compatible with various functional groups such as alkene, alkyne, thiol, ester and hydroxyl.

'Microwave absorption by carbon-based materials and structures' special topic Editorial&nbsp

BaZrO3-based materials have been intensively researched due to their potential application as high-temperature proton conductors in devices such as proton ceramic fuel cells (PCFCs), separation membranes and electrolysers. Nonetheless, their implementation in these devices has often been constrained due to their processing difficulties, namely the formation of Ba-deficient compositions, coexistence of separate perovskite phases or the formation of segregated phases of the acceptor dopant. In this context, the current article shows mechanosynthesis to be an efficient preparation method for Ba(Zr,Y)O3-δ materials, producing pure powders, containing nanometric crystallites, that offer good densification and grain growth. The phase formation, microstructure and electrical properties of the most promising BaZr1-yYyO3-δ compositions, with yttrium contents of y = 0.15 (BZY15) and y = 0.20 (BZY20) are investigated and compared with literature data of materials made by other processing routes. Such a comparison highlights that phase separation of such compositions, commonly reported in the literature, does not occur for these mechanosynthesised materials of high homogeneity. Furthermore, high electrical performances can be obtained by this technique that can compete with some of the best reported in the literature. Electrical conductivity as a function of both oxygen and water partial pressure, in the temperature range of 550 °C − 850 °C, are measured for both compositions and the partial conductivities of protons, oxygen vacancies and electron holes are determined from the defect model. The electron-hole conductivity of BZY20 is observed to be higher than that of BZY15 under all conditions, while proton and oxide-ion conductivities are shown to be higher for the composition BZY15.

The mechanosynthesis process of composite powders for the preparation of a TiB2-20 wt pct MoSi2 composite material from reaction mixtures Ti + B + Mo + Si and Ti + B + MoSi2 in an argon atmosphere has been investigated. Synthesis proceeds according to mechanically stimulated reactions, and, in both cases, ultradisperse composite powders, along with the main phases, contain traces of lower silicides. The mathematical modeling of the distribution of interparticle contacts in the mixtures during solid-phase interaction has revealed a good agreement between the calculated and experimental data of mechanosynthesis. Spark plasma sintering in nonlinear regimes with a sequential increase in the sintering pressure from 6 MPa up to 50 MPa, accompanied by a decrease in the heating rate from 150 °C/min down to 50 °C/min, enables us to reduce the sintering temperature down to 1550 °C and obtain a dense composite with a mean size of TiB2 grains of about 200 nm. The TiB2-20 wt pct MoSi2 composite sintered at 1550 °C surpasses the composite sintered at 1750 °C in Vickers hardness (27.5 ± 3.2 GPa and 24.6 ± 2.2 GPa, respectively) but ranks below it in bending strength (480 ± 32 MPa and 571 ± 24 MPa, respectively).

This paper presents the results on the development of an alloy in the tellurium - copper - cerium system used for the manufacture of functional coatings using the technologies of supersonic cold gas-dynamic spraying. Coatings from the specified alloy are used for the manufacture of photocathodes of photoelectronic devices operating in the UV spectral region.

The paper reports on phase composition, microhardness and wear resistance of compacts and coatings based on η-carbides (Fe,W)6C and (Fe,W)12C produced by mechanical alloying of tungsten and iron powders in petroleum ether. The compacts have been prepared by magnetic-pulse compacting, and the coatings being formed on iron substrate by the selective laser sintering. The compacts exhibit microhardness up to 9.6 GPa and high abrasive wear resistance. Friction coefficients are 0.27-0.6 and 0.33-0.53 in frictional pairs with a steel disc and a ball made of WC-Co alloy, respectively, and wear not exceeding 10 µm in the tribo-pairs. The coatings have a microhardness of 16 GPa and friction coefficients of 0.28 and 0.2 for friction with balls made of steel and WC-Co, respectively, with no wear being practically observed in tribo-pairs. Combining the mechanosynthesis and selective laser sintering is shown to be very efficient to fabricate coatings based on η-carbides (Fe,W)6C and (Fe,W)12C possessing high values of hardness and wear resistance.

Aurivillius compounds with the general formula (Bi2O2)(An-1BnO3n+1) are a highly topical family of functional layered oxides currently under investigation for room-temperature multiferroism. A chemical design strategy is the incorporation of magnetically active BiMO3 units (M: Fe3+, Mn3+, Co3+ …) into the pseudo-perovskite layer of known ferroelectrics like Bi4Ti3O12, introducing additional oxygen octahedra. Alternatively, one can try to directly substitute magnetic species for Ti4+ in the perovskite slab. Previous reports explored the introduction of the M3+ species, which required the simultaneous incorporation of a 5+ cation, as for the Bi4Ti3-2xNbxFexO12 system. A larger magnetic fraction might be attained if Ti4+ is substituted with Mn4+, though it has been argued that the small ionic radius prevents its incorporation into the pseudo-perovskite layer. We report here the mechanosynthesis of Aurivillius Bi4Ti2-xMnxNb0.5Fe0.5O12 (n = 3) compounds with increasing Mn4+ content up to x = 0.5, which corresponds to a magnetic fraction of 1/3 at the B-site surpassing the threshold for percolation, and equal amounts of Mn4+ and Fe3+. The appearance of ferromagnetic superexchange interactions and magnetic ordering was anticipated and is shown for phases with x ≥ 0.3. Ceramic processing was accomplished by spark plasma sintering, which enabled electrical measurements that demonstrated ferroelectricity for all Mn4+-containing Aurivillius compounds. This is a new family of layered oxides and a promising alternative single-phase approach for multiferroism.

Ti-based composite materials with remarkable mechanical properties and good thermal stability were obtained and studied with the purpose of employment for producing resistant and versatile components in the automotive industry. The raw materials having the overall Ti80Mn8Al6Sn3Zr2C1 composition were prepared by mechanosynthesis from powders of comprising elements; after thermal processing and by following four different sintering pathways, both in the argon flow, the four samples (S1–S4) reached a specific composition of metallic and ceramic phases. Thermal analysis and calorimetry showed that the composite materials adsorb considerable amounts of argon, these being related to the obtained composition and microstructure. The results of the thermal study were used when choosing the thermal treatment conditions for sintering; in order to select the optimal processing conditions within the four different regimes of sintering for the raw materials and the final sample with the best functional properties, a comprehensive study for determining the composition, structure and morphological features was carried out by means of X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Two samples (S1 & S4) of the obtained composite materials have increased porosity due to the presence of titanium aluminium carbides (Ti3AlC & Ti3AlC2) that are known as highly porous ceramics, therefore absorbing more argon during the preparation process. The roughness and wear tests showed that the best results (smallest roughness: Ra = 1.11 μm and smallest wear: w = 2.472·10−4 mm3 N−1 m−1) belong to the S2 sample sintered in argon for 15 min at 1100 °C and further calcinated at 1050 °C for 75 min.

The application of polymers to replace oleylamine (OLA) and oleic acid (OA) as ligands for perovskite nanocrystals is an effective strategy to improve their stability and durability especially for the solution-based processing. Herein, we report a mechanosynthesis of lead bromide perovskite nanoparticles (NPs) stabilized by partially hydrolyzed poly(methyl methacrylate) (h-PMMA) and high-molecular-weight highly-branched poly(ethylenimine) (PEI-25K). The as-synthesized NP solutions exhibited green emission centered at 516 nm, possessing a narrow full-width at half-maximum of 17 nm and as high photoluminescence quantum yield (PL QY) as 85%, while showing excellent durability and resistance to polar solvents, e.g., methanol. The colloids of polymer-stabilized NPs were directly processable to form stable and strongly-emitting thin films and solids, making them attractive as gain media. Furthermore, the roles of h-PMMA and PEI-25K in the grinding process were studied in depth. The h-PMMA can form micelles in the grinding solvent of dichloromethane to act as size-regulating templates for the growth of NPs. The PEI-25K with large amounts of amino groups induced significant enrichment of PbBr2 in the reaction mixture, which in turn caused the formation of CsPb2Br5-mPbBr2 and CsPbBr3-Cs4PbBr6-nCsBr NPs. The presence of CsPbBr3-Cs4PbBr6-nCsBr NPs was responsible for the high PL QY, as the Cs4PbBr6 phase with a wide energy bandgap can passivate the surface defects of the CsPbBr3 phase. This work describes a direct and facile mechanosynthesis of polymer-coordinated perovskite NPs and promotes in-depth understanding of the formation and phase conversion for perovskite NPs in the grinding process.

Pb0.67Cd0.33F2 solid solution with a fluorite-type structure has been synthesized for the first time using high-energy grinding of the initial components, PbF2 and CdF2, taken in a ratio of 2 : 1, in an inert Ar atmosphere. The dynamics of this process is investigated by X-ray diffraction analysis. The lattice parameter of the mechanosynthesis product is а = 5.768(7) A, and the average particle size is ∼50 nm.

CdS nanoparticles were successfully synthesized using cadmium acetate and sodium sulfide as Cd and S precursors, respectively. The effect of using sodium thiosulfate as an additional sulfur precursor was also investigated (combined milling). The samples were characterized by XRD, Raman spectroscopy, XPS, UV-Vis spectroscopy, PL spectroscopy, DLS, and TEM. Photocatalytic activities of both CdS samples were compared. The photocatalytic activity of CdS, which is produced by combined milling, was superior to that of CdS, and was obtained by an acetate route in the degradation of Orange II under visible light irradiation. Better results for CdS prepared using a combined approach were also evidenced in photocatalytic experiments on hydrogen generation. The antibacterial potential of mechanochemically prepared CdS nanocrystals was also tested on reference strains of E. coli and S. aureus. Susceptibility tests included a 24-h toxicity test, a disk diffusion assay, and respiration monitoring. Bacterial growth was not completely inhibited by the presence of neither nanomaterial in the growth environment. However, the experiments have confirmed that the nanoparticles have some capability to inhibit bacterial growth during the logarithmic growth phase, with a more substantial effect coming from CdS nanoparticles prepared in the absence of sodium thiosulfate. The present research demonstrated the solvent-free, facile, and sustainable character of mechanochemical synthesis to produce semiconductor nanocrystals with multidisciplinary application.

Chemistry - a European journal 28(13), e202104409 (2022). doi:10.1002/chem.202104409, Published by Wiley-VCH, Weinheim

International audience; The mechanically assisted synthesis of organic compounds has recently focused considerable attention as it may be unique in features to selectively direct the reaction pathway. In the continuation of our work on the synthesis of modified cyclodextrins (CDs) via mechanochemical activation, we sought to discriminate the contribution of supramolecular effects and grinding during the course of a reaction in the solid state. As such, we recently investigated the influence of the particle size of β-CD in the synthesis of β-CD mesitylene sulfonate (β-CDMts) in the solid state using a vibrating ball-mill. We were particularly interested in the role of the particle size on the kinetics of the reaction. In this study, we show that grinding β-CD reduces the particles size over time down to a limit of 167 nm. The granulometric composition remains rather invariant for grinding times over 1 h. Each type of β-CD particles reacted with mesitylenesulfonyl chloride (MtsCl) to produce β-CDMts. Contrary to what could be intuitively anticipated, smaller particles did not lead to the highest conversions. The impact of grinding on the conversion was limited. Interestingly, the proportion of β-CDMts mono-substituted on the primary face significantly increased over time when the reaction was carried out in the presence of KOH as a base. The data series were confronted with kinetics models to get insight in the way the reactions proceeded. The diversity of possible models suggests that multiple mechanochemical processes can account for the formation of β-CDMts in the solid state. Throughout the study, we found that the reactivity depended more upon diffusion phenomena in the crystalline parts of the material than on the increase in the surface area of the CD particles resulting from grinding.

The formation of the cubic δ-Ta1−xN phase by high-energy ball-milling from tantalum and boron nitride (h-BN) is explored. Two different molar ratios Ta:BN, 1:1 and 2:1, were used. X-ray diffraction, scanning electron microscopy, surface area analysis by the Brunauer-Emmett-Teller method, and thermogravimetric analysis were used to characterize the products obtained. In both molar ratios and after a few minutes of milling, the mechanosynthesis of δ-Ta1−xN was observed. Increasing the entropy of the system by introducing vacancies and point defects by the high-energy ball-milling process seems to stabilize the cubic δ-Ta1−xN phase, as previous theoretical studies had reported. The phase obtained depends on the molar ratio used: in the molar ratio 1:1 a non-stoichiometric δ-Ta1−xN phase is obtained, while in the molar ratio 2:1 a stoichiometric δ-TaN phase and secondary phases are obtained. The amorphous boron remains dispersed in the material until the mechanical energy is high enough to trigger the formation of tantalum borides.

Mechanochemical synthesis of CsPbI3 , as a model system for ABX3 halides, was studied. Water was shown to strongly promote the kinetics of formation of CsPbI3 from the CsI+PbI2 mixture through increased mobility of the constituting ionic species. Since many binary and ternary halides are hygroscopic, it was concluded that the presence of small, uncontrollable and unintentional additions of water should often occur in both precursor mixtures and synthesized complex halides boosting the kinetics of formation of many, if not all, ternary organic-inorganic hybrid halides such as, for example, MAPbX3 (X=Cl, Br, I). In addition, trace amounts of water should influence the transport characteristics of complex halides. Thus, the presence of water explains, at least partially, the huge scatter in both the reported mechanochemical reaction times necessary for obtaining single-phase APbX3 perovskite halides and the activation energies of ionic diffusion in APbX3 .

The six possible equiatomic five-transition metal High Entropy Carbides (HECs) of the IVB (Ti, Zr, Hf) and VB (V, Nb, Ta) groups of the periodic table, i.e., TiZrHfVNbC5, TiZrHfVTaC5, TiZrHfNbTaC5, TiZrVNbTaC5, TiHfVNbTaC5 and ZrHfVNbTaC5, were successfully obtained via a powder metallurgy route at room temperature, specifically, by one-step diffusion mechanosynthesis starting from the elemental constituents (using graphite as the carbon source). Three of those HECs, TiZrHfVTaC5, TiZrVNbTaC5 and ZrHfVNbTaC5, were developed for the first time. Their development was possible without any subsequent thermal treatment, in contrast to the usual way (reactive sintering at 1800–2200 °C), and in a powder form, make them potential advanced raw ceramics for hard, refractory and oxidation resistance coatings or matrix phase composites.

Inspired by mechanic force induced S–S bridge activation in a protein context, we have developed the first mechanochemical electrophilic C–H sulfenylation of indoles in combination with iodine cata...

Designable porous materials have potential in a plethora of applications, but synthesis costs and strict reaction conditions limit their true commercialization. Herein, we show that hypercrosslinke...

A novel highly efficient photocatalyst composite BiFeO3/Fe3O4 has been synthesized by mechanosynthesis and applied to the degradation of Methylene Blue under visible light. Structural, optical and photocatalytic properties of the proposed photocatalyst composites are carefully investigated. The nanointerfaces, associated to ferrous Fe2+ ions of the Fe3O4 nanoparticles, improve the photocatalytic efficiency when compared with pure BiFeO3 or Fe3O4. The time required to the complete degradation of Methylene Blue solution is 40 min for the sample with 20% of Fe3O4 which is more than 7 times faster than the time required using BiFeO3 alone. Moreover, with the addition of H2O2 a complete degradation is achieved just after 10 min, which is faster than any other photocatalytic reaction reported for BiFeO3-based materials. This enhancement is assumed to be related to an electron drain process due to the difference between energy levels of the conduction bands of BiFeO3 and Fe3O4 combined with the direct Fenton-like process associated with the Fe2+ ions of the composites.

This review is a compilation of the green synthetic methods used in the synthesis of coumarin derivatives. Coumarins are a class of compounds with a pronounced wide range of biological activities, which have found their application in medicine, pharmacology, cosmetics and food industry. Their biological activity and potential application are highly dependent on their structure. Therefore, many researchers have been performing the synthesis of coumarin derivatives on a daily basis. High demands for their synthesis often result in an increased generation of different waste chemicals. In order to minimize the utilization and generation of toxic organic substances, green synthetic methods are applied in this manner. These methods are getting more attention in the last few decades. Green chemistry methods cover a wide range of methods, including the application of ultrasound and microwaves, ionic liquids and deep eutectic solvents, solvent-free synthesis, mechanosynthesis and multicomponent reactions. All typical condensation reactions for coumarin synthesis like Knoevenagel, Perkin, Kostanecki-Robinson, Pechmann and Reformansky reactions, have been successfully performed using these green synthetic methods. According to the authors mentioned in this review, not only these methods reduce the utilization and generation of toxic chemicals, but they can also enhance the reaction performance in terms of product yields, purity, energy consumption and post-synthetic procedures when compared to the conventional methods. Due to the significance of coumarins as biologically active systems and the recent demands of reducing toxic solvents, catalysts and energy consumption, this review provides a first full literature overview on the application of green synthetic methods in the coumarin synthesis. It covers a literature search over the period from 1995-2019. The importance of this work is its comprehensive literature survey on a specific class of heterocyclic compounds, and those researchers working on the coumarin synthesis can find very useful information on the green synthetic approaches to their synthesis. There are some reviews on the coumarin synthesis, but most of them cover only specific reactions on coumarin synthesis and none of them the whole range of green chemistry methods.

A method of low-temperature (up to 100°C) dry mechanosynthesis of calcium stearate has been developed by exposing the reaction of stearic acid and calcium hydroxide normal and tangential shear stresses in the apparatus of the satellite design of the working cavity. The efficiency of the mechanosynthesis of calcium stearate is calculated relative to a similar chemical reaction in a liquid medium. It was found that the rate of solid-phase synthesis of calcium stearate is an order of magnitude greater than the reaction rate in the liquid phase.

Chemical science 11(9), 2350 - 2355 (2020). doi:10.1039/C9SC06224F, Using the mechanosynthesis of the calcium urea phosphate fertilizer cocrystal as a model, we provide a quantitative investigation of chemical autocatalysis in a mechanochemical reaction. The application of in situ Raman spectroscopy and synchrotron X-ray powder diffraction to monitor the reaction of urea phosphate and either calcium hydroxide or carbonate enabled the first quantitative and in situ study of a mechanochemical system in which one of the products of a chemical reaction (water) mediates the rate of transformation and underpins positive feedback kinetics. The herein observed autocatalysis by water generated in the reaction enables reaction acceleration at amounts that are up to 3 orders of magnitude smaller than in a typical liquid-assisted mechanochemical reaction., Published by RSC, Cambridge

Control over the bottom up synthesis of metal nanoparticles (NP) depends on many experimental factors, including the choice of stabilising and reducing agents. By selectively manipulating these species, it is possible to control NP characteristics through solution-phase synthesis strategies. It is not known, however, whether NPs produced from mechanochemical syntheses are governed by the same rules. Using the Au NPs mechanosynthesis as a model system, we investigate how a series of common reducing agents affect both the reduction kinetics and size of Au NPs. It is shown that the relative effects of reducing agents on mechanochemical NP synthesis differ significantly from their role in analogous solution-phase reactions. Hence, strategies developed for control over NP growth in solution are not directly transferrable to environmentally benign mechanochemical approaches. This work demonstrates a clear need for dedicated, systematic studies on NP mechanosynthesis.

Current time-resolvedin situapproaches limit the scope of mechanochemical investigations possible. Here we develop a new, general approach to simultaneously follow the evolution of bulk atomic and electronic structure during a mechanochemical synthesis. This is achieved by coupling two complementary synchrotron-based X-ray methods: X-ray absorption spectroscopy (XAS) and X-ray diffraction. We apply this method to investigate the bottom-up mechanosynthesis of technologically important Au micro and nanoparticles in the presence of three different reducing agents, hydroquinone, sodium citrate, and NaBH4. Moreover, we show how XAS offers new insight into the early stage generation of growth species (e.g.monomers and clusters), which lead to the subsequent formation of nanoparticles. These processes are beyond the detection capabilities of diffraction methods. This combined X-ray approach paves the way to new directions in mechanochemical research of advanced electronic materials.