Vibratory Ball Mill Research Articles

Investigation of mechanically stimulated solid phase polymorphic transition of zirconia

The effect of mechanical treatment of monoclinic zirconia in a high-energy centrifugal planetary ball mill and in a vibrating ball mill, with much less mechanical impact, on its crystallographic characteristics and texture was investigated as a function of the applied mechanical load and the treatment medium. Mechanical treatment in a high-energy planetary ball mill was shown to result in particle desintegration into small crystallites of less than 20 nm in size, accumulation of strains, and fast solid phase transition to metastable nano-structured tetragonal form. The rate of the phase transition depended on the treatment medium. The transition completed during 15 min with dry-powdered ZrO 2. The presence of water retarded the phase transition. Mechanical treatment in a vibrating mill resulted in particle desintegration into crystallites of 38–42 nm in size, accumulation of strains, and gradual amorphization of the crystalline structure; however, the transformation to the tetragonal form did not occur. The factors favored the solid phase polymorphic transition of a stable form of ZrO 2 into metastable one are discussed. A high-temperature and a high pressure, which are developed in local sites of the solid under pulse mechanical impact of high-energy, provide thermodynamically favorable conditions and kinetic acceleration of the phase transition. The effect of the metastable form of ZrO 2 stabilization originates from the small size of the crystallites as a result of particle desintegration.

The structure and properties of PM composite materials based on EN AW-2124 aluminum alloy reinforced with the BN or Al 2O 3 ceramic particles

Investigations of composite materials based on EN AW-2124 aluminum alloy reinforced with the BN or Al 2O 3 particles with various weight ratios of 5, 10 and 15% are presented. Powders of the starting materials were mixed in the laboratory vibratory ball mill to acquire the uniform distribution of reinforcement particles in the matrix material. The components were initially compacted at cold state in a die with the diameter of Ø 26 mm in the laboratory vertical unidirectional press—with a capacity of 350 kN. The obtained P/M compacts were heated to a temperature of 480/500 °C and finally extruded—with the extrusion pressure of 500 kN. Bars with a diameter of 8 mm were obtained as the end product. Based on the microstructural examinations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminum matrix was revealed. Hardness tests, static tensile tests and the compressive tests made it possible to demonstrate that all these properties change along with the reinforcing particles concentration change. As an example, hardness increased from 89 HV1 for the material without the reinforcing phase to 123 HV1 for 15% of BN, and the ultimate compressive strength decreases along with the increase of the reinforcing phase fraction from 667 MPa for 5% to 472 MPa for 15% of BN.

Structure, properties and corrosion resistance of PM composite materials based on EN AW-2124 aluminum alloy reinforced with the Al 2O 3 ceramic particles

Investigations of composite materials based on EN AW-2124 aluminum alloy reinforced with the Al 2O 3 particles with various weight ratios of 5, 10, and 15% are presented. Powders of the starting materials were mixed in the laboratory vibratory ball mill to acquire the uniform distribution of reinforcement particles in the matrix material. The components were initially compacted at cold state in a die with the diameter of ∅26 mm in the laboratory vertical unidirectional press with a capacity of 350 kN. The obtained P/M compacts were heated to a temperature of 480–500 °C and finally extruded with the extrusion pressure of 500 kN. Bars with a diameter of 8 mm were obtained as the end product. Based on the microstructural examinations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminum matrix was revealed. Hardness tests and the ultimate compressive strength tests made it possible demonstrate that both these properties change along with the reinforcing particles concentration change. As an example, hardness increased from 89.27 HV1 for the material without the reinforcing phase to 123.4 HV1 for 15% Al 2O 3, and the ultimate compressive strength decreases along with the increase of the reinforcing phase fraction from 798 MPa for 5% to 663 MPa for 15% Al 2O 3. Results of the corrosion tests, determined using the potentiodynamic method in the 3% water solution of NaCl indicate that corrosion of the investigated composite materials depends on the volume fraction of the reinforcing particles. It was found out, based on the determined anode polarisation curves that the investigated materials are susceptible to pitting corrosion. Moreover, investigation results indicate that the composite materials reinforced with the ceramic particles with the portions of 5 and 10% are characteristic of a higher corrosion resistance in the selected environment, compared to the matrix material, whereas at the 15% portion this resistance it worse, the anode digestion current grows.

真空粉砕で生成したナノ構造化黒鉛の特性と水素放出特性

The natural graphite ground in vacuum atmosphere by a vibration ball mill is found to have porous nanostructure consisting of the agglomeration of primary particles of approximately 20nm in size. Such nanostructured graphite particles were used as a raw material to investigate the hydrogen desorption characteristics of the products ground in high pressure hydrogen atmospheres by 3 types of milling machines including a ball mill, a vibration ball mill and a planetary ball mill. We experimentally investigated the relationship between the nanostructures and the hydrogen desorption temperature from the products obtained by the grinding of the nanostructured graphite in hydrogen atmosphere. The micropores and mesopores in the nanostructured graphite prepared by a vibration ball milling in vacuum atmosphere almost remained during the further grinding by the ball milling in hydrogen atmosphere. The temperature at which hydrogen started to desorb from the ground products of the nanostrucutured graphite prepared by a vibration ball mill in vacuum atmosphere decreased to 470K from 600K, as reported previously.

Fabrication of ultrafine W – Cu powders by mechanical alloying

Ultrafine composite powders of W – 15 wt-%Cu, W – 25 wt-%Cu, and W – 35 wt-%Cu have been fabricated by mechanical alloying. The effects of type of mill, process control agent, temperature of milling, and ball/powder ratio on the final products have been evaluated. The results show that the planetary ball mill possesses a higher impact energy intensity than that of the vibratory ball mill. The optimum milling time is confirmed by the formation of a nanocrystalline microstructure in the planetary ball mill after optimisation of the milling parameters. A steady state between cold welding and fracture is attained with a milling time of up to 25 h in the planetary ball mill under optimised conditions. Crystallites with sizes of 7 – 8 nm for W – Cu composite powders have been obtained after 25 h of ball milling. The powders obtained after mechanical alloying have been characterised in terms of their size, shape, phase constitution, and microstructural features using X-ray diffraction and scanning electron microscopy.

Effects of short-time vibratory ball milling on the shape of FT-IR spectra of wood and cellulose

Vibratory ball milling is shown to have a strong influence on the shape of FT-IR spectra of wood and cellulose, even if the samples are milled for only a short time. The results show that neither temperature nor particle size or oxidation processes are the most important reason for the observed changes in the structure of the FT-IR spectra, but that the mechanical treatment itself is the main influencing factor. Studies of the effects of temperature, particle size, oxygen and mechanical treatment on chemical and structural changes are presented. The most conspicuous changes in the spectra of cellulose and wood were observed at wave numbers 1034, 1059, 1110, 1162, 1318, 1335, 2902 cm −1 and in the OH-stretching vibration region from 3200 to 3500 cm −1. It is suggested that these changes are mainly associated with a decrease in the degree of crystallinity and/or a decrease in the degree of polymerisation of the cellulose.

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.

メカノケミカル重合によるポリマー系ナノコンポジットの製造

Polymerization of styrene and methyl methacrylate were mechanochemically initiated by grinding montmorillonite particles in a vibrating ball mill. The effectiveness of mechanochemical polymerization was discussed through the characterizations of the polymer/particle composites and montmorillonite particles. As a result, it was shown that both monomers are polymerized by the grinding of montmorillonite. The products obtained were the composites of montmorillonite particles and polymer with size ranging from several tens nm to several hundreds nm. Relevant measurements suggested that the polymerization of styrene proceeds by cationic polymerization whereas that of methyl methacrylate occurs by radical polymerization. The large molecular weight of the resulting polymer could be explained by the lamellar structure of montmorillonite particles filled with monomers. Mechanochemical polymerization is expected to be one of the promising processes for polymeric nanocomposite production.

Characteristics of open- and closed-circuit grinding systems

The characteristic differences between open- and closed-circuit grinding systems were examined via the use of a continuous vibration ball mill and a blade type classifier. For the same median diameter of the product, the rate of powder production in the closed-circuit is about 5% higher than that of the open-circuit. The median diameter of classified coarse particles for the closed-circuit is smaller than that for the open-circuit. The power requirement per unit mass production increases with decreasing mean diameter of the product. For the same mean diameter of the product, the power requirement for the closed-circuit process is about 5% smaller than that of the open-circuit process. This value corresponds to the difference in the rate of powder production between the two systems.

Evaluation of Ti3SiC2 Prepared by Mechanical Alloying

The synthesis of Ti3SiC2 powder by mechanical alloying (MA) from elemental Ti, Si and C powders and evaluation of some properties of the sintered compacts of the MA powder were conducted. MA was carried out by vibratory ball milling and planetary ball milling. The influence of parameters, such as running time, ball size and rotation speed on MA powder were examined. The annealing of the MA powder was done at various temperatures and holding times. The MA powders could be sintered to dense Ti3SiC2-based ceramics which contained TiC as a secondary phase. Mechanical, thermal and electrical properties of sintered compacts were evaluated. The Ti3SiC2-based compact showed low hardness, high Young's modulus, and plastic behavior at high temperatures over 1373 K, And the compact showed high thermal expansion, high thermal conductivity, and higher electrical conductivity than other conventional ceramics.

ＣＯ２処理によるＣａＳｉＯ３の固化機構

The consolidation mechanism of calcium silicate with water under carbonation was investigated. CaSiO3 powder was activated by mechano-chemical treatment for 24h in air with a vibration ball-mill. The cakes of the vibration ball-milled CaSiO3 added with a fair amount of water were carbonated at 50°C in 0.33MPa CO2 for 0.5 to 6hrs. in order to obtain the specimens carbonated to different degrees. The microstructural development in this carbonation process was observed by transmission and scanning electron microscopy and 29Si-MAS NMR, and the pore size distributions of the consolidated bodies were evaluated by mercury intrusion and N2 gas adsorption methods. By this carbonation treatment, dense consolidated bodies were obtained which exhibited high compressive strength. In the carbonated specimen, needle like crystals of aragonite precipitated to fill up macro-pores, and particles coalesced to form continuous matrices. The results of 29Si-MAS NMR showed that Q2 structure of SiO2 component assignable to single silicate chains transformed into Q4 structure indicative of three-dimensional SiO2 networks. These experimental results suggest that carbonation-induced consolidation would be caused by poly-condensation of SiO2 component in CaSiO3.

Rietveld analysis of polymorphic transformations of ball milled anatase TiO 2

Rietveld’s whole powder profile fitting method based on crystal structure refinement is applied to extract the microstructure information of several polymorphic TiO 2 phases grown simultaneously during high energy vibratory ball milling of anatase phase. Warren–Averbach’s method of X-ray line profile analysis is also made for comparison of above results. The X-ray powder patterns of four TiO 2 phases along with α-Al 2O 3 (contamination) are simulated simultaneously for the first time to fit the experimental X-ray powder patterns of multiphase materials. The structural details of monoclinic TiO 2 (B) phase are also reported first time in this paper. The advantages of the present method of analysis over the other methods of X-ray line profile analysis are discussed in details.

Mechanochemical copolymerization of methyl methacrylate and styrene initiated by the grinding of quartz

AbstractThe copolymerization of methyl methacrylate and styrene mechanochemically initiated by the grinding of quartz in the monomer mixture was investigated by using a vibrating ball mill. The effect of the grinding of quartz on the copolymerization was investigated by characterizing both the polymer formed and the ground quartz. The copolymerization proceeds apparently from the quartz grindings and was closely related to the total surface area of the ground quartz. The molecular weight distributions of the copolymers formed were unimodal as found in a homopolymer of only methyl methacrylate. It was clear from the composition analysis of the copolymer that the mechanochemical copolymerization of methyl methacrylate and styrene proceeded with a radical polymerization mechanism because of radicals on the quartz surface produced by the grinding. The monomer reactivity ratios obtained by the Fineman‐Ross method suggested that the copolymers formed were alternating copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2011–2017, 2002; DOI 10.1002/app.10544

Mössbauer study of ball-milled Fe-Ge alloys

In this work the mechanical alloying of ${\mathrm{Fe}}_{100\ensuremath{-}x}{\mathrm{Ge}}_{x}$ was studied as a function of alloying composition $(9<~x<~40)$ processing time and annealing treatment. The alloys were prepared using a high-energy vibratory ball mill. For $9<~x<~27.5$ a single phase $A2$ solid solution was formed while for $x>~30$ besides the solid solution an increasing amount of disordered ${B8}_{1}$ (NiAs type) ${\mathrm{Fe}}_{3}{\mathrm{Ge}}_{2}$ was found. Thermally induced $A\stackrel{\ensuremath{\rightarrow}}{2}{D0}_{3}$ transition was investigated for $9<~x<~27.5.$ The detailed annealing temperature dependence of short- and long-range ordering into the ${D0}_{3}$ structure was studied for the case of ${\mathrm{Fe}}_{75}{\mathrm{Ge}}_{25}$ by means of M\"ossbauer-effect spectroscopy and x-ray diffraction. The solid solution orders gradually and homogenously into the ${D0}_{3}$ structure. To follow and quantify the evolution of short-range order a special fitting routine for M\"ossbauer spectra was used that takes into account local and nonlocal contributions to the hyperfine interactions experienced by a ${}^{57}\mathrm{Fe}$ probe, and that assumes nonlinearity dependences on the number of neighbors of a given class. By this means the short-range ${D0}_{3}$ order parameter S was determined for as milled steady states as well as annealed states for $9<~x<~27.5.$ In the case of ${\mathrm{Fe}}_{75}{\mathrm{Ge}}_{25}$ the evolution of mechanical alloying with time was investigated. It was found that alloying proceeds in two stages. In the first one, iron rich (with $A2$ structure) and disordered Ge-rich regions coexist along with an almost equiatomic $A2$ Fe-Ge solid solution, which was interpreted as an interphase physically located between the former two. The three phases collapse into just one bcc solid solution with $S\ensuremath{\approx}0.3$ for a critical time ${t}_{c},$ which was identified as the chemical mixing time reported by other authors. The second stage of mechanical alloying produces the complete homogenization of the solid solution. Plausible basic mechanisms of mechanical alloying of Fe-Ge mixtures are discussed on the basis of the results presented here.

Fibrillation of aramid fiber using a vibrating ball mill and evaluation of the degree of fibrillation

Methods of fibrillation of aramid fiber for a fiber-dispersion type of composite and evaluation of the degree of fibrillation were investigated. Continuous fibrillation of aramid fiber was carried out using a vibrating ball mill. The morphology of the fiber surface was controlled by adjusting the processing time of the fiber in the mill. An index based on image analysis was proposed to represent the morphological changes of treated fiber. The interaction between powder bed and fiber was determined by measuring the force required to pull a single fiber out of a compacted powder bed. The interaction between powder and fiber increased with the degree of fibrillation.

Effect of ball-charge fraction on mechanical alloying in vibratory ball mill

Effect of ball-charge fraction on mechanical alloying in vibratory ball mill

Study of fluorite phases in the system Bi2O3–Nb2O5–Ta2O5. Synthesis by mechanochemical activation assisted methods

Mechanochemical activation followed by annealing at moderate temperatures results in the stabilisation, at room temperature, of different fluorite-type phases, belonging to the Bi2O3–Nb2O5, Bi2O3–Ta2O5 and Bi2O3–Nb2O5–Ta2O5 systems. The results obtained from different starting compositions and mechanical activation devices (vibrating and planetary ball mills) were compared with those obtained by classical solid-state synthesis methods. Vibrating ball mill activation yields amorphous precursors, which permits one to obtain fluorites with increasing pentavalent cation content when the annealing temperature is further increased. Planetary ball milling leads to the apparent mechanosynthesis of a fluorite phase at room temperature. The products were studied by X-ray powder diffraction at room temperature and above, thermal analysis techniques and transmission electron microscopy. Moreover, impedance spectroscopy measurements carried out on Bi3MO7 (M = Nb, Ta) fluorites, obtained by a mechanochemically assisted method, showed that these materials are good ionic conductors, with conductivities at 600 °C of 5 × 10−4 S cm−1 or higher, the processing history of the materials having a great influence on their properties.

Studies on the effect of ball milling on lignin structure using a modified DFRC method.

The structures of milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and residual lignin (REL) from a loblolly pine were analyzed using a modified derivatization followed by reductive cleavage (DFRC) method developed to allow the quantitative determination of three different structural monomeric products originating in lignin: phenolic beta-O-4, alpha-O-4, and etherified beta-O-4 structures. Results show that MWL and CEL are structurally identical, with an increased phenolic beta-O-4 content compared to that of the original Wiley milled wood. These results indicate that the portion of lignin linked to carbohydrates and that not linked to carbohydrates are structurally the same. Modified DFRC analysis of the effect of ball milling on the structure of lignin in wood, MWL, CEL, and REL indicate that vibratory ball milling does not change the lignin structure provided certain precautions are taken. Specifically, dry vibratory ball milling under a nitrogen atmosphere causes substantial structural changes including condensation, whereas vibratory ball milling in toluene had little effect on the lignin structure. This indicates that the structural differences observed in MWL and CEL arise because of the extraction procedure, which preferentially extracts phenolic lignin structures. MWL and CEL are representative of the total lignin in wood; however, due primarily to the solvent extraction process, higher phenolic hydroxyl contents are observed. Nitrobenzene oxidation showed structural results similar to those from the modified DFRC method.

Mechanochemical polymerization of styrene initiated by the grinding of quartz

AbstractThe polymerization of styrene mechanochemically initiated by the wet grinding of quartz was attempted by using a vibrating ball mill with a laboratory scale. The effect of the grinding of quartz on the polymerization of the styrene was investigated by characterizing the polymer formed and the quartz ground. The results showed that styrene could also mechanochemically polymerize by the resulting active species of the grinding of quartz as well as methyl methacrylate. The polymerization was found closely related to the total surface area of the ground quartz. The molecular weight distributions of the polymer formed were not simply unimodal and remarkably broader than those of the methyl methacrylate. It was suggested that the polymerization of the styrene proceeded with a cationic active species from the experimental results and discussions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2849–2855, 2001

An X-ray diffraction study of nanocrystalline titanium prepared by high-energy vibrational ball milling

A detailed X-ray line-broadening study in ball-milled Ti sample is presented. It is observed that ball milling leads to the formation of nanocrystalline grains and transform partially to an f.c.c. Ti-phase after 10 h of milling. Using a Rietveld analysis, the volume fraction of f.c.c. phase was found to be ∼24% with a crystallite size of ∼20 Å. The origin of high strains is probably the dislocations present in the sample. Anisotropic line broadening of the fault-unaffected reflections is explained in terms of anisotropic dislocation contrast corresponding to 〈 a〉 and 〈 a+ c〉 dislocations. Both edge and screw dislocations were predicted with a significant basal slip. High dislocation density ∼10 11 cm/cm 3 has been found in the milled samples. A large increase in the isotropic thermal parameter was also observed for the h.c.p. Ti-phase after 10 h of milling.