Bead Mill Research Articles

Effect of Selected Mechanical/Physical Pre-Treatments on Chlorella vulgaris Protein Solubility

Chlorella vulgaris has been recognized as an interesting alternative feeding source since it contains a good amount of high-quality protein. However, the presence of a recalcitrant cell wall strongly affects the nutrients’ digestibility, bioaccessibility, and bioavailability. The present study aimed to determine the influence of different pre-treatments (bead milling, extrusion, freeze-drying, heating, microwave, and sonication) on C. vulgaris’ protein solubility. For total protein content and solubility, the Bradford method and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) quantification were used, respectively, and protein degradation was assessed by SDS-PAGE through quantification of protein fractions (26 kDa, 32–40 kDa, 66–96 kDa, and others). The o-phthaldialdehyde assay was used for peptide formation. While there were no statistically significant differences for total soluble protein measurements in the supernatant fractions, the results showed an increase in larger proteins following bead milling and microwave pre-treatments, and sonication led to higher fractions of the remaining protein (mostly of low molecular weight). Nevertheless, extrusion significantly increased the release of peptides in the soluble fractions, and, considering industrial applicability, this method may be a better choice for improving C. vulgaris protein bioaccessibility in monogastric diets.

Extraction of soluble proteins by bead milling from Tetraselmis chui in two different physiological states

Tetraselmis is an interesting microalga for food products because of its high protein content and surface productivity as well as the possibility to scale up the culture easily. However, this specie is yet understudied compared to other algae such as Chlorella. Different batches of Tetraselmis chui were received from the same supplier, with different morphological properties, probably associated with a difference in physiological state: one batch contained circular and dividing cells and the other flagellated cells. The batches were characterized biochemically in terms of protein, carbohydrate and ash content and the rupturability was tested to characterize their behavior to cell disruption. One batch was found way more fragile than the other. The bead milling of the two batches showed also striking differences in terms of cell disruption kinetic, as well as dry matter repartition after centrifugation and protein recovery yields within the supernatant. Nearly no differences in protein yield were observed after bead milling in comparison to freeze-thawing for the resistant batch, with a final yield of 11 % of the initial proteins. However, a clear protein release was observed for the fragile batch along the milling residence time, with a final protein yield of 32 %. The protein released were characterized by SDS PAGE and zymography and differences were observed, confirming the difference in metabolism. Several physicochemical modifications were applied to the cell lysate to increase the yields using pH, temperature and dilution. This latest modification was the most promising. The results underlined that a difference in physiological state of Tetraselmis chui had a significant impact on the following biorefinery, affecting directly the cell disruption and the protein recovery yields. The valorization of the whole microalgae thus necessitates the finest coupling between upstream and downstream.

High-Conductive CsH2PO4 Membranes with PVDF-Based Polymers Additives.

The study is devoted to one of the important problems of hydrogen energy-the comparative analysis and creation of novel highly conductive and durable medium-temperature proton membranes based on cesium dihydrogen phosphate and fluoropolymers. The proton conductivity, structural characteristics and mechanical properties of (1 - x)CsH2PO4-x fluoropolymer electrolytes (x-mass fraction, x = 0-0.3) have been investigated and analyzed. UPTFE and PVDF-based polymers (F2M, F42, and SKF26) with high thermal stability and mechanical properties have been chosen as polymer additives. The used fluoropolymers are shown to be chemical inert matrices for CsH2PO4. According to the XRD data, a monoclinic CsH2PO4 (P21/m) phase was retained in all of the polymer electrolytes studied. Highly conductive and mechanically strong composite membranes with thicknesses of ~50-100 μm were obtained for the soluble fluoropolymers (F2M, F42, and SKF26). The size and shape of CsH2PO4 particles and their distribution have been shown to significantly affect proton conductivity and the mechanical properties of the membranes. The thin-film polymer systems with uniform distributions of salt particles (up to ~300 nm) were produced via the use of different methods. The best results were achieved via the pretreatment of the suspension in a bead mill. The ability of the membranes to resist plastic deformation increases with the growth of the polymer content in comparison with the pure CsH2PO4, and the values of the mechanical strength characteristics are comparable to the best low-temperature polymer membranes. The proton-conducting membranes (1 - x)CsH2PO4-x fluoropolymer with the optimal combination of the conductivity and mechanical and hydrophobic properties are promising for use in solid acid fuel cells and other medium-temperature electrochemical devices.

Investigation of the properties of composites goethite/polyvinyl alcohol

Goethite and composite films of polyvinyl alcohol (PVA)-goethite have been synthesized. The characteristics of the initial substances and the composite were carried out using the methods of scanning electron microscopy, optical microscopy, and X-ray phase analysis. It has been established that the mechanical characteristics of goetite/PVA composite obtained by processing in a bead mill are improved. Synthesized PVA-goethite composites containing 3 wt% goethite showed a 20% improvement in maximum tensile strength compared to PVA. X-ray phase analysis showed that the chemical structure of goethite, which contains hydroxyl groups, makes it possible to obtain a very strong bond with the polymer matrix. This effectively contributes to the mechanical strengthening of the polymer due to the chemical interaction of nanoparticles and the matrix with hydrophilic fragments on the polymer chains due to strong hydrogen bonding.

Skin absorption of felbinac solid nanoparticles in gel formulation containing l-menthol and carboxypolymethylene

BackgroundIt is important to design an effective formulation to enhance the skin penetration, and nanotechnologies have been used in dermal and transdermal drug delivery. In this study, we prepared formulations (gels) containing l-menthol and felbinac (FEL) solid nanoparticles (FEL-NP gel) for topical application, and investigated the local and systemic absorption of the prepared FEL-NP gel.MethodsFEL solid nanoparticles were obtained by bead milling of FEL powder (microparticles), and a topical formulation (FEL-NP gel) consisting of 1.5% FEL solid nanoparticles), 2% carboxypolymethylene, 2% l-menthol, 0.5% methylcellulose, and 5% 2-hydroxypropyl-β-cyclodextrin (w/w %) were prepared.ResultsThe particle size of FEL nanoparticles was 20–200 nm. The released FEL concentration from FEL-NP gel was significantly higher than that from FEL gel without bead mill treatment (carboxypolymethylene gel in which FEL microparticles (MPs) instead of FEL nanoparticles were incorporated, FEL-MP gel), and FEL was released as nanoparticles from the gel. Moreover, both transdermal penetration and percutaneous absorption of FEL-NP gel were significantly increased compared with those of FEL-MP gel, and the area under the FEL concentration-time curve (AUC) of FEL-NP gels was 1.52- and 1.38-fold of commercially available FEL ointment and FEL-MP gel, respectively. In addition, after 24 h of treatment, the FEL content in rat skin treated with FEL-NP gels was 1.38- and 2.54-fold higher than that when treated with commercially available FEL ointment and FEL-MP gel, respectively. Moreover, the enhanced skin penetration of FEL-NP gels was significantly attenuated by inhibition of energy-dependent endocytosis, such as clathrin-mediated endocytosis.ConclusionsWe successfully prepared a topically applied carboxypolymethylene gel containing FEL nanoparticles. In addition, we observed that the endocytosis pathway was mainly related to the high skin penetration of FEL nanoparticles, and FEL-NP gel application resulted in high local tissue concentration and systemic absorption of FEL. These findings provide useful information for the design of topically applied nanoformulations against inflammation by providing local and systemic effects.

From Micro to Nano: Grinding Natural Magnetite Ore for Microalgae Harvesting

Microalgae represent a promising feedstock for sustainable biomass and energy. The low cell concentration after cultivation, however, limits the current application fields. Magnetic microalgae harvesting is a recent approach to overcome the economic limitations of exploiting this natural resource. Accordingly, different particle types have been applied, mainly synthetically produced magnetic nanoparticles, though none on an industrial scale. Particle sizes between a few micrometers and a few nanometers have not been tested. We expected 200–500 nm to be advantageous for harvesting and as a compromise between the highly available surface and good separation properties. However, this intermediate magnetite particle size between the micro- and nano-scale cannot be reached via chemical synthesis. Therefore, we ground natural magnetite ore in a planetary ball mill and an agitator bead mill producing particles in the targeted size range. Applying ore particles ground from ~6 µm to 250 nm yields harvesting efficiencies comparable to synthetically produced nanoparticles (Ø ~ 10 nm), with only half the BET surface. Complete harvesting of saline microalgae Microchloropsis salina is possible with ground particles at alkaline pH. We demonstrate the feasibility of a harvesting process with natural, low-cost, easily separable, and readily available magnetite ore particles as a promising step towards exploiting valuable microalgal products in life sciences.

Scaled-up production and quality controlling techniques of energetic cocrystals: challenges and prospects

Cocrystallization techniques have become extremely important methods for obtaining novel high-energy insensitive energetic materials, and it has attracted great attention for the development of high-energy explosives and propellants, etc. in recent years. Several scale-up cocrystallization techniques including solvent-nonsolvent, semibatch reaction, bead milling, and spray drying methods et al. have been applied for obtaining the energetic cocrystals, and the preparation processes of these methods were also shown. The types and quality of raw materials and solvents, the synthetic times, morphology, and size of these cocrystals were described and compared by using different synthetic techniques in the review. Moreover, the principle, advantages and disadvantages of scale-up preparation methods were shown. More importantly, the preparation efficiency, the ratio between the quality of raw materials and the volume of solvent, and yield of different methods were also exhibited and discussed, which can provide key information and experiences for the future application of the materials. Finally, future research trends are suggested from different perspectives involving the formation mechanisms in the preparation process by using intermolecular interaction simulation, experimental study, and thermodynamic calculations, the optimization of traditional scale-up techniques, and the exploitation of novel methods for the energetic cocrystals.

Evaluation of efficiency of disruption methods for Coelastrella sp. in order to obtain high yields of biochemical compounds release

Downstream processes in microalgae, such as the extraction of high value-added compounds, are often hampered by the intrinsic rigidity of the cell wall. The toughness of this structure makes the intracellular compounds less available for extraction, which means that cell disruption methods are necessary to apply. Coelastrella sp. is a terrestrial microalga that reveals to be a promising source of bioactive compounds; however, due to its extremely resistant wall, few extraction and determination studies of these compounds have been performed. In order to maximize the extraction efficiency and be as energy-efficient as possible, five different cell disruption methods have been optimized: Freeze-Thaw cycles – ten freezing cycles at −80 °C and thawing at 40 °C; Bead Milling – 32 % (in volume) of beads (0.5 mm) and treatment time of 6 min; High-speed homogenization - 25,000 rpm for 80 min; Microwave – 800 W for 12 min; and Sonication – 40 kHz for 60 min.Sonication and bead milling proved to be the most efficient processes in cell disruption and intracellular organic matter release, with a value of 9.6 and 5.4, respectively. In addition to these two methods, which yielded rupture efficiencies above 90 % after the application of the treatment, High-speed homogenization also showed a disruption efficiency of around 90 %. On the other hand, microwave and freeze-thaw cycles had a low impact on Coelastrella sp. cells, allowing the surviving of about 39 % and 66 % of the initial sample, respectively. Sonication showed the highest efficiency in the release of proteins, carbohydrates and lipids, always followed by bead milling as the most efficient. Freeze-thaw cycles have shown to be the most efficient in releasing phenolic compounds, whereas microwave was the most inefficient in releasing biochemical compounds overall.Considering the results obtained and the energy consumption in each treatment, bead milling can be considered the most efficient method.

Mechanistic investigation of efficient cell disruption methods for lipid extraction from various macro and micro species of algae

Increased rate of use of conventional fossil fuels have caused its depletion and polluted the environment. Biodiesel is a promising fuel for compression ignition engine application. In this work, macroalgae namely Enteromorpha flexuosa is evaluated for the suitability for biodiesel production. Since the lipid yield of Enteromorpha flexuosa is low, cell disruption techniques were used, and results were compared to microalgae namely Spirulina platensis and Nannochloropsis oceanica. The results were investigated using proximity analysis, ultimate analysis, scanning electron microscopy, and fatty acid analysis. Cell disruption of algae was achieved using two methods, i.e., bead milling and acid treatment. Acid treatment resulted in a slightly higher lipid recovery than bead milling. The result showed high degree disruption was achieved with a lipid recovery of 97.05 %, 136.36 % and 65 % with acid treatment and 82.35 %, 50 % and 30 % with bead milling for Spirulina platensis, Nannochloropsis oceanica and Enteromorpha flexuosa, respectively. The fatty acid profile also revealed that Enteromoha flexuosa is a good candidate for quality biodiesel production with high saturated to unsaturated fatty acid and low linolenic fatty acid concentration.

Production of Hydrogel-Based Curcumin-Loaded O/W Suspoemulsions

Curcumin is a biopharmaceutical classification system (BCS) class IV substance with many potential therapeutic effects. However, like many other BCS IV active pharmaceutical ingredients, complex formulations are needed to guarantee a sufficiently high bioavailability. A not-so-well-known delivery system is a suspoemulsion (SE). SEs are emulsions with a crystalline API in continuous or dispersed phases. This study aimed to produce curcumin-loaded o/w suspoemulsions with the particle in the oil phase for, e.g., encapsulation or triggered release effects. The particles need to be smaller than the emulsion droplet size to attain high encapsulation efficiencies (EE) in the oil phase. Sonofragmentation and bead milling were tested for their ability to produce these nanocrystals in different dispersion media. It was discovered that production in miglyol was the best fit for the needed application of the crystals in SEs. Around 85% (by volume) of the particles produced with bead milling were smaller than the droplet size of about 5 µm. In contrast, only 23% of the sonofragmentated particles were below the diameter of those droplets. This oily suspension was then used to successfully produce hydrogel-based o/w suspoemulsions. In the second part of this study, we investigated different methods for determining encapsulation efficiency, but none of the methods accurately and satisfactorily resolved the encapsulation efficiency. Finally, the suspoemulsions could not be macroscopically distinguished from one another and were physically stable. In summary, we showed that stable hydrogel-based curcumin-loaded o/w suspoemulsions could be produced.

Effect of Graphite Nanoplatelet Size and Dispersion on the Thermal and Mechanical Properties of Epoxy-Based Nanocomposites.

This study investigated the effect of graphite nanoplatelet (GNP) size and dispersion on the thermal conductivities and tensile strengths of epoxy-based composites. GNPs of four different platelet sizes, ranging from 1.6 to 3 µm, were derived by mechanically exfoliating and breaking expanded graphite (EG) particles using high-energy bead milling and sonication. The GNPs were used as fillers at loadings of 0-10 wt%. As the GNP size and loading amount increased, the thermal conductivities of the GNP/epoxy composites increased, but their tensile strengths decreased. However, interestingly, the tensile strength reached a maximum value at the low GNP content of 0.3% and thereafter decreased, irrespective of the GNP size. Our observations of the morphologies and dispersions of the GNPs in the composites indicated that the thermal conductivity was more likely related to the size and loading number of fillers, whereas the tensile strength was more influenced by the dispersion of fillers in the matrix.

Population Balance Modeling and Mechanistic Analysis of Inorganic Pigment Dispersion in a High-Speed Disk Disperser and a Vertical Bead Mill

Population Balance Modeling and Mechanistic Analysis of Inorganic Pigment Dispersion in a High-Speed Disk Disperser and a Vertical Bead Mill

Insight into the mechanism behind oral bioavailability-enhancement by nanosuspensions through combined dissolution/permeation studies

As numerous new drug candidates are poorly water soluble, enabling formulations are needed to increase their bioavailability for oral administration. Nanoparticles are a conceptually simple, yet resource consuming strategy for increasing drug dissolution rate, as predicting in vivo oral absorption using in vitro dissolution remains difficult. The objective of this study was to obtain insight into nanoparticle characteristics and performance utilizing an in vitro combined dissolution/permeation setup. Two examples of poorly soluble drugs were examined (cinnarizine and fenofibrate). Nanosuspensions were produced by top-down wet bead milling using dual asymmetric centrifugation, obtaining particle diameters of approx. 300 nm. DSC and XRPD studies indicated that nanocrystals of both drugs were present with retained crystallinity, however with some disturbances. Equilibrium solubility studies showed no significant increase in drug solubility over the nanoparticles, as compared to the raw APIs. Combined dissolution/permeation experiments revealed significantly increased dissolution rates for both compounds compared to the raw APIs. However, there were substantial differences between the dissolution curves of the nanoparticles as fenofibrate exhibited supersaturation followed by precipitation, whereas cinnarizine did not exhibit any supersaturation, but instead a shift towards faster dissolution rate. Permeation rates were found significantly increased for both nanosuspensions when compared to the raw APIs, indicating a direct implication that formulation strategies are needed, be it stabilization of supersaturation by precipitation inhibition and/or dissolution rate enhancement. This study indicates that in vitro dissolution/permeation studies can be employed to better understand the oral absorption enhancement of nanocrystal formulations.

Synthesis and characterization of bismuth ferrite particles using a nano-agitator bead mill

Bismuth ferrite (BiFeO3) nanocomposites were synthesized using a novel nano-agitator bead milling method followed by calcination. Bismuth oxide and iron oxide nanoparticles were mixed in a stoichiometric ratio and milled for 3 h and calcined at 650 °C in air. X-ray diffraction with Rietveld refinement, scanning electron microscopy, and transmission electron microscopy techniques were used to elucidate the structure of BiFeO3. The particle diameter was found to be ∼17 nm. Magnetic and electrical measurements were performed, and these results were compared with those of similar methods. Mostly, BiFeO3 was obtained with minor secondary phase formation. The resulting powder was weakly ferromagnetic with a remnant magnetization of 0.078 emu/g. This can be attributed to residual strain and defects introduced during the milling process. Electrical testing revealed a high leakage current density that is typical of undoped bismuth ferrite.

Mechanical processing of Phaeodactylum tricornutum and Tetraselmis chui biomass affects phenolic and antioxidant compound availability, nutrient digestibility and deposition of carotenoids in Atlantic salmon

Cell walls of microalgae differ both in terms of chemical composition and architecture. Certain characteristics of cell walls limit both the effectiveness of extraction of valuable constituents and nutrient bioavailability and bioaccessibility in fish. We first investigated the potential of bead milling to disrupt cell walls to improve extractability of bioactive compounds from Phaeodactylum tricornutum and Tetraselmis chui. We also evaluated the effect of the mechanical treatment on i) digestibility of nutrients in the two microalgae and ii) fatty acid and pigment content of fillet of Atlantic salmon fed the algae diets.Cell wall disruption facilitated efficient release of total phenolic compounds (TPC), chlorophyll A, chlorophyll B and total carotenoids from both microalgae species, but increased only the total antioxidant capacity (TAC) of T. chuii. The polyphenol profile varied between the two species; we identified 2 and 6 polyphenols from P. tricornutum and T. chui, respectively.For the feeding experiment, microalgae biomass, intact or cell wall disrupted (90.7 and 76.4% disruption degree for T. chui and P. tricornutum, respectively), were mixed with the other feed ingredients. Atlantic salmon (315 g start weight / 55 fish per tank) were fed one of the five extruded experimental diets (a fishmeal-based reference diet and four feeds with 30% of the whole or broken microalgae biomass added to the reference diet). The digestibility of protein in the P. tricornutum was significantly higher compared to that of T. chui. Breaking the cell walls by bead milling caused a significant improvement in digestibility of protein in T. chui. The apparent digestibility coefficient of lipid was higher in P. tricornutum and bead milling improved the digestibility of the two algae. However, bead milling did not favourably change the fatty acid profile of Atlantic salmon. At the end of the feeding trial, P. tricornutum-fed fish had significantly improved pigmentation, probably due to the higher content of fucoxanthin and fucoxanthinol compared to the fish fed the reference diet. The main conclusion from the mechanical processing of the microalgae is that bead milling can increase i) the extractability of polyphenols and pigments, ii) the digestibility of lipid in both algae while the effect on protein was improved only for T. chui. Furthermore, P. tricornutum can be considered a natural pigment source in the feeds of Atlantic salmon.

Synthesis and Characterization of Zirconia-Silica PMMA Nanocomposite for Endodontic Implants.

This study aimed to enhance the mechanical properties of PMMA composites by introducing various types of fillers, including ZrO2, SiO2, and a mixture of ZrO2-SiO2 nanoparticles, which were prepared as prototypes for an endodontic implant. The ZrO2, SiO2, and mixed ZrO2-SiO2 nanoparticles were synthesized using the sol-gel method and the precursors Tetraethyl Orthosilicate, Zirconium Oxychloride, and a mixture of both precursors, respectively. Before polymerization, the as-synthesized powders were subjected to the bead milling process to obtain a well-dispersed suspension. Two scenarios for the fillers were implemented in the preparation of the PMMA composite: a mixture of ZrO2/SiO2 and ZrO2-SiO2 mixed with two different types of silane: (3-Mercaptopropyl) trimethoxysilane (MPTS) and 3-(Trimethoxysilyl) Propyl Methacrylate (TMSPMA). The observation of the characteristics of all of the investigated fillers included the use of a particle-size analyzer (PSA), a Zeta-potential analyzer, FTIR, XRF, XRD, and SEM. The mechanical properties of the MMA composites, as prepared under various scenarios, were observed in terms of their flexural strength, diametrical tensile strength (DTS), and modulus of elasticity (ME). These levels of performance were compared with a PMMA-only polymer. Each sample was measured five times for flexural strength, DTS, and ME. The results showed that the best PMMA composite was SiO2/ZrO2/TMSPMA, as revealed by measurements of the flexural strength, DTS, and ME corresponding to 152.7 ± 13.0 MPa, 51.2 ± 0.6 MPa, and 9272.8 ± 2481.4 MPa, which are close to the mechanical properties of dentin. The viability of these PMMA composites, as measured up to day 7, was 93.61%, indicating that they are nontoxic biomaterials. Therefore, it was concluded that the PMMA composite created with SiO2/ZrO2/TMSPMA can be considered to be an acceptable endodontic implant.

Advances in the Microbiological Diagnosis of Prosthetic Joint Infections

A significant number of prosthetic joint infections (PJI) are culture-negative and/or misinterpreted as aseptic failures in spite of the correct implementation of diagnostic culture techniques, such as tissue sample processing in a bead mill, prolonged incubation time, or sonication of removed implants. Misinterpretation may lead to unnecessary surgery and needless antimicrobial treatment. The diagnostic value of non-culture techniques has been investigated in synovial fluid, periprosthetic tissues, and sonication fluid. Different feasible improvements, such as real-time technology, automated systems and commercial kits are now available to support microbiologists. In this review, we describe non-culture techniques based on nucleic acid amplification and sequencing methods. Polymerase chain reaction (PCR) is a frequently used technique in most microbiology laboratories which allows the detection of a nucleic acid fragment by sequence amplification. Different PCR types can be used to diagnose PJI, each one requiring the selection of appropriate primers. Henceforward, thanks to the reduced cost of sequencing and the availability of next-generation sequencing (NGS), it will be possible to identify the whole pathogen genome sequence and, additionally, to detect all the pathogen sequences present in the joint. Although these new techniques have proved helpful, strict conditions need to be observed in order to detect fastidious microorganisms and rule out contaminants. Specialized microbiologists should assist clinicians in interpreting the result of the analyses at interdisciplinary meetings. New technologies will gradually be made available to improve the etiologic diagnoses of PJI, which will remain an important cornerstone of treatment. Strong collaboration among all specialists involved is essential for the correct diagnosis of PJI.

Development of Triamcinolone Acetonide Nanocrystals for Ocular Administration

Triamcinolone acetonide (TA) is a powerful anti-inflammatory drug used in the treatment of inflammatory ocular disorders; however, its poor aqueous solubility and ocular anatomical barriers hinder optimal treatment. The aim of this work was to obtain triamcinolone acetonide nanocrystals (TA-NC) to improve ocular corticosteroid therapy. Self-dispersible TA-NC were prepared by the bead milling technique followed by spray-drying, exhaustively characterized and then evaluated in vivo in an ocular model of endotoxin-induced uveitis (EIU). Self-dispersible TA-NC presented an average particle size of 257 ± 30 nm, a narrow size distribution and a zeta potential of -25 ± 3 mV, which remained unchanged for 120 days under storage conditions at 25 °C. In addition, SEM studies of the TA-NC showed uniform and spherical morphology, and FTIR and XRDP analyses indicated no apparent chemical and crystallinity changes. The subconjunctival administration of TA-NC in albino male white rabbits showed no clinical signs of ocular damage. In vivo studies proved that treatment with self-dispersible TA-NC alleviated the inflammatory response in the anterior chamber and iris in EUI rabbit eyes. Dispersible TA-NC are a promising approach to obtaining a novel nanometric TA formulation for ocular disorders.

部分酸化・反応焼結によるアルミナ/ムライト/炭化ケイ素配向ナノコンポジットの作製と特性

Nanocomposites with nanoparticles dispersed as the second phase have been reported to have improved mechanical properties. In spite of this potential processing methods to produce these nanocomposites are not well established. In this study, Al2O3/mullite/SiC nanocomposites were prepared by the reaction sintering of green compacts prepared by slip casting of a mixture of SiC and Al2O3 powders. Here, the surface of the SiC particles was first oxidized to produce SiO2 and to reduce the core of the SiC particles, and then the surface SiO2 was reacted with Al2O3 to produce mullite. By applying a strong magnetic field during slip casting, the Al2O3/mullite/SiC nanocomposites were fabricated with Al2O3 oriented, but not with mullite, Al2O3 was oriented so that the c-axis of the crystal was parallel to the direction of the strong magnetic field. The density was low due to the agglomeration of SiC raw powder. The bead mill using fine zirconia beads of 50 μm was effective to disperse the agglomerated particles and succeeded in obtaining high-density Al2O3/mullite/SiC with no agglomeration of SiC nanoparticles. The bending strength was greatly improved by dispersing the particles, but such improvement was not observed by texturing.

Mechanochemical Synthesis of Shape-Anisotropic Particles through Wet Milling Using High-Energy Mills

A high-energy ball mill, such as a planetary ball mill, is widely used for preparing a homogeneously mixed powder and reducing particle size. Because of the high impact energy generated by the collision of ball media, the planetary ball milling is expected to produce local high-temperature and high-pressure zones. In wet milling, the solubility of the material varies owing to the local and instantaneous changes caused by the collision. Consequently, mechanochemical reactions through a dissolution–precipitation mechanism can be attained without external heating. In this paper, we show the wet mechanochemical process in water to synthesize functional hydrous or hydrate materials with various shapes, including nanosheets, nanotubes, plates, flakes, rods, and nanoparticles. Morphology-controlled particles can be obtained by only adjusting the milling conditions, such as milling time, ball size, and centrifugal acceleration. Further, the products can be converted into electrode materials for Li-ion batteries, retaining the precursor morphologies. This wet mechanochemical synthesis can be also applied in a bead mill, where mass production and continuous processing are possible. The wet mechanochemical process is a new particle synthesis method that can achieve both grinding and crystal growth.