Vibratory Ball Mill Research Articles

Synthesis of core-functionalised naphthalene diimides from naphthalenetetracarboxylic dianhydride using a vibratory ball mill: bromination, imidization and Heck-type reactions.

The synthesis of 9 core-functionalised naphthalene diimide (c-NDI) residues is reported via a 3-step solvent free synthesis from naphthalenetetracarboxylic dianhydride using only mechanochemical activation. Selective dibromination and subsequent dimidiation were achieved for the first time in a vibratory ball mill, resulting in the key structural intermediate, 2,6-dibromonaphthalenediimide (DBND), which is the basis for elaboration into a multitude of organic electronic materials. Our new synthesis of DBND is achieved in just 5 hours' reaction time over two steps compared to typical solution state times of 24 hours. Subsequent Heck-type cross coupling reactions, with a range of styrene residues, produced a series of c-NDIs in good yields. The Heck-type reactions are rapid (1.5 hours), require no additional heating or solvent and are tolerant of atmospheric moisture and air.

Preparation of C-S-H gels by mechanochemistry and its influences on properties of super-retarded cement-based materials with sucrose

In this paper, low-cost dihydrate gypsum (CaSO4⋅2H2O) was used as calcium source together with sodium metasilicate solution to prepare calcium silicate hydrate (C-S-H) gels through a mechanochemical activation strategy by using planetary and vibrational ball-milling. The influences of the prepared C-S-H gels on hydrating and hardening properties of super-retarded cement-based materials with sucrose were investigated. The results showed that CaSO4⋅2H2O reacted with sodium metasilicate solution under mechanochemical effect during both planetary and vibrational ball-milling, although CaSO4⋅2H2O was just slightly dissolved in water. It was also interestingly found that the C-S-H gels can continuously form while resting for a certain time after ball-milling. Under the mechanochemical activation, the prepared C-S-H gels had complete characteristic diffusion peaks and were composed of layered, flocculent and fibrous structures. While incorporating the prepared C-S-H gels into the super-retarded cement paste with sucrose, the cement hydration was greatly accelerated and the compressive strength of the hardened cement-based materials was also effectively improved at early age as expected. Through X-ray diffraction (XRD) analysis, it was found that C-S-H gels can effectively promote the growth of CH crystals along the (001) and (101) crystal planes. The scanning electron microscopy (SEM) results supported that the C-S-H gels inhibited the refinement of ettringite (AFt) crystals in super-retarded HCP with sucrose, which was more obvious at 28 d.

Evaluation of dry sliding wear characteristics of hybrid a356 composite

As advancements in lightweight and synthetic materials have evolved, our ability to tailor materials to meet societal demands has expanded. Aluminium alloys, known for their high strength-to-weight ratio and cost-effectiveness, are extensively utilized in engineering applications, including structural casting and automotive components. This study employed the stir casting method to investigate the impact of silicon carbide (SiC) and graphite (Gr) on a hybrid A356 composite, aiming to enhance its tribological applicability. SiC and Gr particles were processed using a vibratory ball milling machine for two hours, followed by composite fabrication with varying particle sizes. Microstructural investigation using optical microscopy revealed maximum hardness values of 127 BHN and 125 BHN for A356 composites reinforced with 12.50% SiC, 15.50% Gr, and 11.43% SiC, 15.86% Gr, respectively. Wear rate analysis demonstrated that reinforced A356 composites exhibited higher wear resistance compared to unreinforced alloys. Notably, the sample reinforced with 11.43% SiC and 15.86% Gr displayed exceptional wear resistance. Photo micrographs of A356-SiC-Gr samples at different sliding distances, velocities, and loads revealed minimal plastic deformation during wear testing, resulting in abrasive and cohesive wear. Overall, this study underscores the effectiveness of graphite (Gr) and silicon carbide (SiC) as reinforcement materials for enhancing the tribological properties of A356 composites.

Milling amorphous FeSiB ribbons with vibratory ball and disc mills

Fe, Si and B powders, mixed with atomic composition Fe78Si9B13, are subjected after arc melting to a melt spinning process, which is optimized to obtain the greatest amount of amorphous ribbon. The amorphous ribbons are milled to powder form in a vibratory ball mill and a vibratory disc mill, taking care of maintaining the amorphous character. Ribbons and powders have been characterized by X-ray diffraction (XRD), laser diffraction, SEM and TEM microscopy, and differential scanning calorimetry (DSC). The amorphous character and particle size of the powders are characterized as a function of the mill charge and the milling time. It is shown that the use of the ball mill is appropriate for obtaining small quantities of amorphous or nanocrystalline powder, while the disc mill can process larger quantities of powder in a shorter time. The particle sizes obtained for milling times between 10 and 150 min range between 26 and 412 μm, ready for use in powder metallurgy processes.

High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites: Synthesis, mechanical, microstructural and thermal characterization

This study aims to introduce a novel type of particulate reinforced Al matrix composite. High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites were produced via a combined process of different powder metallurgy methods. Firstly, boride compounds (HfB2, TiB2, ZrB2, VB2, NbB2) were synthesized in the laboratory scale using the related metal oxide, boron oxide, and magnesium by mechanochemical synthesis (MCS) and leaching processes under optimum conditions. Secondly, the synthesized and purified boride powders were mixed in equimolar ratios using a planetary ball mill for 72 h, and they were sintered at 2000 °C under 30 MPa via spark plasma sintering (SPS). Thirdly, equimolar high entropy (HfTiZrVNb)B2 bulks were crushed, converted into powder forms, and added into Al powders at different amounts as 1, 2, 5, 10, and 15 wt %. Lastly, these powder blends were mechanically alloyed in a vibratory ball mill for 6 h, cold pressed and pressureless sintered at 630 °C for 2 h. For characterization techniques, X-ray diffractometry (XRD), thermal analysis, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), density measurements using pycnometer and Archimedes' methods, microhardness and dry sliding wear tests were conducted on the sintered composites. The highest hardness (∼1.5 GPa) and the lowest wear rate (∼0.0012 mm3/Nm) were obtained in the Al-15 wt % (HfTiZrVNb)B2 sample.

Investigating the effect of polyvinylpyrrolidone matrix on surface characteristics and dissolution rate of anticancer drug dasatinib

AbstractDasatinib (DAS) is a second‐generation tyrosine kinase inhibitor used in the treatment of Philadelphia chromosome‐positive chronic myeloid leukemia and acute lymphoblastic leukemia. Nevertheless, this drug is hindered by poor gastrointestinal absorption and limited bioavailability, primarily attributable to its low aqueous solubility. To improve its properties, solid dispersions of DAS within a matrix of the hydrophilic polymer polyvinylpyrrolidone (PVP) are prepared by cogrinding in a vibrational ball mill at various drug‐to‐polymer ratios. The prepared solid dispersions are thoroughly characterized by several methods to verify the drug's amorphization and enhanced wettability as a result of successful mechanochemical activation. Fluidized bed melt granulation and traditional tableting are used to prepare tablets of 8 mm diameter with strictly defined aimed properties. Characterization of tablets includes testing their hardness, disintegration, and in vitro dissolution. The in vitro release profiles reveal a significant improvement in the release rate of DAS from tablets containing solid dispersion with the highest polymer ratio when compared with those containing untreated DAS or solid dispersions with a low polymer ratio. The results confirm the significant effect of the PVP ratio in solid dispersions on the surface characteristics and dissolution rate of DAS.

Convenient and efficient N-methylation of secondary amines under solvent-free ball milling conditions

In the present work, we report the development of a rapid, efficient, and solvent-free procedure for the N-methylation of secondary amines under mechanochemical conditions. After optimization of the milling parameters, a vibrational ball mill was used to synthesize 26 tertiary N-methylated amine derivatives in a short time of 20 min (30 Hz frequency) and high yields ranging from 78 to 95%. An exception was compounds having a hydroxyl group in their structure, for which a decrease in reaction efficiency was observed. During our research, we investigated alternate reaction selectivity occurring in compounds able to form ring closure products that are 3,4-dihydro-2H-1,3-benzoxazine derivatives instead of N-methylated products. The liquid-assisted grinding technique has been applied using formalin as a methylating agent and sodium triacetoxyborohydride as a reducing agent in a reductive amination reaction.

Thermodynamic limits of the depolymerization of poly(olefin)s using mechanochemistry.

Mechanochemistry is a promising approach for chemical recycling of commodity plastics, and in some cases depolymerization to the monomer(s) has been reported. However, while poly(olefin)s comprise the largest share of global commodity plastics, mechanochemical depolymerization of these polymers in standard laboratory-scale ball mill reactors suffers from slow rates. In this work, the observed reactivities of poly(styrene), poly(ethylene) and poly(propylene) are rationalized on the basis of thermodynamic limitations of their depolymerization by depropagation of free radical intermediates. In addition, subsequent phase partitioning equilibria for the removal of monomers from the reactor via a purge gas stream are discussed for these polymers. For poly(styrene), a typical vibratory ball mill supplies just enough energy for its depolymerization to be driven by either thermal hotspots or adiabatic compression of the impact site, but the same energy supply is far from sufficient for poly(propylene) and poly(ethylene). Meanwhile, removal of styrene from the reactor is thermodynamically hindered by its lower volatility, but this is not an issue for either propylene or ethylene. The implications of these thermodynamic limitations for mechanochemical reactor design and potential for mechanocatalytic processes are highlighted.

(HfTiZrMnCr)B2 high entropy diboride ceramics: Synthesis mechanism, microstructural, mechanical and thermal characterization

This study explains the synthesis mechanism of (HfTiZrMnCr)B2 high entropy diboride ceramics prepared via a combined route consisting of ball milling and spark plasma sintering. Firstly, metal borides were in-house synthesized using mechanochemical synthesis and leaching processes under optimum conditions from metal oxides, B2O3 and Mg precursors. The (HfTiZr)B2 composition, chosen as the main composition, was hybridized with two different methods: planetary and vibratory ball milling. As a result of milling experiments, 6 h vibratory milling was determined as the optimum duration, and all compositions were produced by spark plasma sintering method (2000 °C, 30 MPa) following this optimum condition. Different compositions were used to see which one of the HfB2, TiB2, ZrB2 compounds acted as a host material. Based on the phase analyses, single-phase HEB structures, Ti-rich phases and Hf, Ti, Zr-oxides were observed in the microstructure. Detailed physical, microstructural, mechanical and termal characterizations were performed: the highest hardness values were observed in the (HfTiMnCr)B2 and (HfTiZrMnCr)B2 samples as ∼ 27 GPa, the lowest wear rate was recorded for the (HfTiZrMnCr)B2 sample as ∼2 × 10−6 Nm/mm3, and the highest oxidation resistance was achieved at the (HfZrMnCr)B2 and (HfTiMnCr)B2 samples as weight gains ∼ 1.90%.

A general one-pot, solvent-free solid-state synthesis of biocompatible metal nanoparticles using dextran as a tool: Evaluation of their catalytic and anti-cancer activities

We propose a general green method coupled with a solid-state vibration ball milling strategy for the synthesis of various metal nanoparticles (MNPs), employing a polymeric carbohydrate dextran (Dx) as a reducing and stabilizing molecule. The synthesis of size-controlled Dx-based MNPs (Dx@MNPs), featuring comparatively narrow size distributions, was achieved by controlling the mass ratio of the reactants, reaction time, frequency of the vibration ball mill, and molecular weight of Dx. Notably, this process was conducted at ambient temperatures, without the aid of solvents and accelerating agents, such as NaOH, and conventional reductants as well as stabilizers. Thermal properties of the resulting Dx@MNPs nanocomposites were extensively investigated, highlighting the influence of metal precursors and reaction conditions. Furthermore, the catalytic activity of synthesized nanocomposites was evaluated through the reduction reaction of 4-nitrophenol, exhibiting great catalytic performance. In addition, we demonstrated the excellent biocompatibility of the as-prepared Dx@MNPs toward human embryonic kidney (HEK-293) cells, revealing their potential for anticancer activities. This novel green method for synthesizing biocompatible MNPs with Dx expands the horizons of carbohydrate-based materials as well as MNP nanocomposites for large-scale synthesis and controlled size distribution for various industrial and biomedical applications.

β-MnO2/three-dimensional graphene-carbon nanotube hybrids as cathode for aqueous zinc-ion battery

Aqueous zinc-ion batteries (RZIBs) are one of the favorable complementary candidates for lithium-ion batteries. The cathode material determines the whole performance. Herein, β-MnO2/3D GPE-CNTs hybrid cathode materials were fabricated by intermittent high-energy vibratory ball milling method. It delivered a higher specific discharge capacity of 313.31 mAh·g−1 and excellent cycling stability compared to the bare β-MnO2 sample. Morphological characterizations revealed that the enhanced electrochemical performance of the β-MnO2/3D GPE-CNTs hybrid was mainly attributed to the three-dimensional framework structure, large specific surface area, and good conductivity of GPE-CNT, as well as its resulting particle refinement with uniform dispersion and partial suppression of grain amorphization. This article provided a new sight of fabricating Mn-based materials/conducting carbon material hybrid for good performance cathode in RZIBs.

Mechanochemical Organic Synthesis - Powerful Tool in Greener Chemistry

Organic chemical reactions are usually promoted by heating of reactants in various organic solvents. Amongst emerging synthetic methods mechanochemistry is recognized as being promissing in the reduction of the environmental impact by conducting chemical reactions in solid state. Energy required to promote transformation is obtained by mechanical force commonly by vibrational ball milling. Greener aspects of the mechanochemistry are in the reduction of solvent use, shorter reaction times, room temperature and better reactions yields in comparison to classical thermal solution conditions. This mini-review gives selected examples of eco-sustainable mechanochemical organic reactions.

Mechanically Stimulated Solid-State Interaction of Platinum Tetrachloride with Sodium β-Diketonates.

A new mechanically stimulated solid-state reaction of PtCl4 with sodium β-diketonates has been discovered. Platinum (II) β-diketonates were obtained by grinding excess sodium trifluoroacetylacetonate Na(tfac) or hexafluoroacetylacetonate Na(hfac) in a vibration ball mill, followed by subsequent heating of the resulting mixture. The reactions occur under much milder conditions (at about 170 °C) compared to similar reactions of PtCl2 or K2PtCl6 (at about 240 °C). Excess diketonate salt plays the role of a reducing agent in the conversion of Pt (IV) salt to Pt (II) compounds. The effect of grinding on properties of the ground mixtures was studied by XRD, IR, and thermal analysis methods. The difference in the course of the interaction of PtCl4 with Na(hfac) or Na(tfac) indicates the dependence of the reaction on the ligand properties. The probable reaction mechanisms were discussed. This method of synthesis of platinum (II) β-diketonates makes it possible to substantially reduce the variety of reagents used, the number of reaction steps, the reaction time, the use of solvents, and waste generation compared to conventional solution-based methods.

Fabrication of porous pure magnesium by MgH<sub>2</sub> produced by mechanical milling and spark plasma sintering (MM-SPS) process

Pure magnesium (Mg) powders with stearic acid added as process control agent (PCA) were mechanically milled (MMed) using a vibration ball mill. The MMed powders were consolidated into bulk materials by the spark plasma sintering (SPS). Changes in hardness, thickness and solid-state reactions of the SPS materials have been examined by hardness measurements, vernier caliper and an X-ray diffraction (XRD), respectively. The Vickers hardness of the SPS material decreased with increasing sintering temperature. Minimum value of Vickers hardness was 17 HV. The thickness of the SPS material increased with increasing sintering temperature. However, little effect of sintering time on the thickness was observed. In the SPS materials, the formation of MgH2 by solid phase reaction was observed during sintering. During sintering, MgH2 was decomposed to produce hydrogen gas; and it contributed to expand the SPS materials. Porous pure magnesium could be formed using only the MM-SPS process without the addition of a foaming aid.

Engineering Multiple Microstructural Defects for Record-Breaking Thermoelectric Properties of Chalcopyrite Cu1- x Agx GaTe2.

Defect engineering for vacancies, holes, nano precipitates, dislocations, and strain are efficient means of suppressing lattice thermal conductivity. Multiple microstructural defects are successfully designed in Cu1- x Agx GaTe2 (0≤x≤ 0.5) solid solutions through high-ratio alloying and vibratory ball milling, to achieve ultra-low thermal conductivity and record-breaking thermoelectric performance. Extremely low total thermal conductivities of 1.28W m-1 K-1 at 300 K and 0.40Wm-1 K-1 at 873 K for the Cu0.5 Ag0.5 GaTe2 are observed, which are ≈79% and ≈58% lower than that of the CuGaTe2 matrix. Multiple phonon scattering mechanisms are collectively responsible for the reduction of thermal conductivity in this work. On one hand, large amounts of nano precipitates and dislocations are formed via vibrating ball milling followed by the low-temperature hot press, which can enhance phonon scattering. On the other hand, the difference in atomic sizes, distorted chemical bonds, elements fluctuation, and strained domains are caused by the high substitution ratio of Ag and also function as a center for the strong phonon scattering. As a result, the Cu0.7 Ag0.3 GaTe2 exhibits a record high ZTmax of ≈1.73 at 873K and ZTave of ≈0.69 between 300-873K, which are the highest values of CuGaTe2 -based thermoelectric materials.

Development of multicomponent hybrid powders based on titanium and niobium carbides as a promising material for laser cladding

Multicomponent hybrid TiC-NbC(Zr, Si) powder was developed and manufactured by mechanosynthesis in a high-energy vibratory ball mill. High-purity fragmented TiC, NbC, Zr and Si powders were selected and mixed in a ratio of 60:15:10:15 at.%, respectively, to manufacture the above powder. Several modes of mechanosynthesis were chosen for the experiment: 3, 6, 9 and 12 hours. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) analyzes were used to study the morphology, chemical and phase compositions of the obtained TiC-NbC(Zr, Si) powder. The SEM analysis confirmed the presence of all TiC, NbC, Zr and Si components in the final powder regardless of the mechanosynthesis time. However, the XRD analysis showed that after 9 and 12 hours of mechanosynthesis, the Zr and Si diffraction lines are completely absent. This occurs due to the dissolution of the Zr and Si elements in titanium and niobium carbides. In addition, it has been established that more than 6 hours are required to synthesize finely dispersed TiC-NbC(Zr, Si) powder. The study results can be useful for optimization of the mechanosynthesis process.

Electrochemical and electrical characteristics of ball milled Cs2Ti6O13 modified by the surface-to-bulk migration of hydroxyl groups.

Ball milling of solids under benign conditions leads to surface functionalization without altering the crystal structure and morphology. However, these additional surface functional groups are rarely fixed but instead mobilized across such ball milled solids. This phenomenon, including its effects on electrochemical and electrical properties, has received limited attention. We report herein that dry vibratory ball milling of lepidocrocite-type Cs2Ti6O13 generated hydroxyl groups which subsequently migrated from surfaces to bulk. The increased number of bulk hydroxyl groups is deduced from Raman, IR, and solid state 1H nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. In contrast, the decrease in the relative proportion of surface hydroxyl groups/water and carbon-oxygen species was deduced from X-ray photoelectron spectroscopy. The inaccessible hydroxyl groups in ball milled Cs2Ti6O13 lead to a smaller amount of stored charge and increased charge transfer resistance, according to galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy studies in 1 M Na2SO4. The alternating current electrical properties were also measured, revealing fundamental insights such as the one-dimensional conduction pathway and the relaxation time in microseconds. A model has been proposed for this surface-to-bulk migration of the hydroxyl groups, which competes with surface dangling bonds leading to particle agglomeration.

Mechanoactivated TiNbZrSi powder for strong and wear-resistant biomedical coatings

The paper presents a study of morphology and chemical composition of the TiNbZrSi powder customized by mechanoactivation in an experimental high-energy vibration ball mill equipped with steel mortars and balls of different diameters. The initially synthesized as-cast TiNbZrSi tablet was preliminarily ground into a powder with fraction of about 400 µm using a conventional bench hammer. After that, the above powder was subjected to mechanoactivation within 4 hours in an Ar atmosphere at room temperature. In addition, the synthesized TiNbZrSi powder was deposited onto additively manufactured Ti-6Al-4V ELI substrates through their co-mechanoactivation followed by annealing for 1 hour at a temperature of 800 °C to ensure better adhesion. The characterization of the TiNbZrSi powder before and after co-mechanoactivation with the specified substrate was carried out by scanning electron microscopy.

Enhancing the ignitability of the Al–TiO2–B2O3 powder mixture through intensive vibratory ball milling (C:P12)

Alumina-TiB2 is a hard ceramic composite with applications in aviation, aerospace and wear resistant tools. It can be manufactured in-situ through a highly exothermic aluminothermic self-sustaining reaction from the starting materials of Al, TiO2 and B2O3. In this paper, the effect of vibration ball milling on the particle size reduction and the reactivity enhancement of the Al–TiO2–B2O3 powder mixture is examined by XRD, SEM, EDS, DTA and particle analysis techniques. Measures for combating the stoichiometric inconsistencies deriving from the tendency of B2O3 to absorb atmospheric water, giving boric acid H3BO3, are implemented. Characterisation of the milled samples display Al microparticles with d(0.9) below 64 μm, coated with nano-particles of TiO2 and B2O3, with particle sizes up to 600 nm. Differential thermal analysis reveals that ignition is feasible for all of the milled mixtures, unlike the un-milled one. It also presents that extensive milling results in a reduction in the ignition temperature of the reactant mixture to 925 °C for the 5 h-30Hz milled sample, from the previous 982 °C recorded for the 1 h–20Hz milled sample. The in-situ synthesised Al2O3–TiB2 matrix deriving from the 5 h-30Hz milled sample, gives less of the unwanted Al5BO9 phase and improved skeletal and bulk densities, by 0.15 g/cc and 0.1 g/cc respectively, compared to the respective composite deriving from un-milled reactants powder mixture.

5′-Chalcogen-Substituted Nucleoside Pyrophosphate and Phosphate Monoester Analogues: Preparation and Hydrolysis Studies

Novel sulfur and selenium substituted 5',5'-linked dinucleoside pyrophate analogues were prepared in a vibration ball mill from the corresponding persilylated monophosphate. The chemical hydrolysis of pyrophosphorochalcogenolate-linked dimers was studied over a wide pH-range. The effect of the chalcogeno-substitution on the reactivity of dinucleoside pyrophosphates was surprisingly modest, and the chemical stability is promising considering the potential therapeutic or diagnostic applications. The chemical stability of the precursor phosphorochalcogenolate monoesters was also investigated. Hydrolytic desilylation of these materials was effected in aqueous buffer at pH 3, 7 or 11 and resulted in phosphorus-chalcogen bond scission which was monitored using 31P NMR. The rate of dephosphorylation was dependent upon both the nature of the chalcogen and the pH. The integrity of the P-S bond in the corresponding phosphorothiolate was maintained at high pH but rapidly degraded at pH 3. In contrast, P-Se bond cleavage of the phosphoroselenolate monoester was rapid and the rate increased with alkalinity. The results obtained in kinetic experiments provide insight on the reactivity of the novel pyrophosphates studied as well as of other types of thiosubstituted biological phosphates. At the same time, these results also provide evidence for possible formation of unexpectedly reactive intermediates as the chalcogen-substituted analogues are metabolised.