Milling Conditions Research Articles

High-Energy Ball Milling Enables an Ultra-Fast Wittig Olefination Under Ambient and Solvent-free Conditions.

30 Seconds to success!-The Wittig reaction, a fundamental and extensively utilized reaction in organic chemistry, enables the efficient conversion of carbonyl compounds to olefins using phosphonium salts. Traditionally, meticulous reaction setup, including the pre-formation of a reactive ylide species via deprotonation of a phosphonium salt, is crucial for achieving high-yielding reactions under classical solution-based conditions. In this report, we present an unprecedented protocol for an ultra-fast mechanically induced Wittig reaction under solvent-free and ambient conditions, often eliminating the need for tedious ylide pre-formation under strict air and moisture exclusion. A range of aldehydes and ketones were reacted with diverse phosphonium salts under high-energy ball milling conditions, frequently giving access to the respective olefins in only 30 seconds.

Effects of Roller Milling Parameters on Wheat-Flour Damaged Starch: A Comprehensive Passage Analysis and Response-Surface Methodology Optimization

Damaged starch typically arises from mechanical damage caused by the action of the roller mills during the wheat flour milling process. The content of resulting damaged starch in the flour significantly influences its characteristics, emphasizing the importance of understanding and controlling the formation of damaged starch for the production of specialized flours. A detailed passage analysis from three different commercial mills revealed that starch damage control is primarily achievable at front passages of the sizing and reduction system, which generate the majority of the flour release in the mill. Also, it revealed that damaged starch content increases progressively from the initial to the final passages during milling in the break, sizing and reduction system. To investigate the effects of milling parameters on damaged starch, flour yield, and energy consumption, a three-level and three-variable Box–Behnken experimental design with response surface methodology was applied. As independent variables roll gap (0.05–0.35 mm), feed rate (0.15–0.35 kg/cm min), and fast roll speed (400–800 rpm) were employed. The obtained models were utilized to optimize milling conditions for producing flours with special characteristics.

Preparation and Performance of PBAT/PLA/CaCO3 Composites via Solid-State Shear Milling Technology

Replacing traditional disposable, non-biodegradable plastic packaging with biodegradable plastic packaging is one of the key approaches to address the issue of “white pollution”. PBAT/PLA/inorganic filler composites are widely utilized as a biodegradable material, commonly employed in the field of packaging films. However, the poor dispersion of inorganic fillers in the polymer matrix and the limited compatibility between PBAT and PLA have led to inferior mechanical properties and elevated costs. In this work, we propose a simple and effective strategy to improve the dispersion of nano-CaCO3 in a PBAT/PLA matrix through solid-state shear- milling (S3M) technology, combined with mechanochemical modification and in situ compatibilization to enhance the compatibility between PBAT and PLA. The impact of varying milling conditions on the structure and performance of the PBAT/PLA/CaCO3 composites was investigated. During the milling process, PBAT and PLA undergo partial molecular chain fragmentation, generating more active functional groups. In the presence of the chain extender ADR during melt blending, more branched PBAT-g-PLA is formed, thereby enhancing matrix compatibility. The results indicate that the choice of milling materials significantly affects the structure and properties of the composite. The film obtained by milling only PBAT and CaCO3 exhibited the best performance, with its longitudinal tensile strength and fracture elongation reaching 22 MPa and 437%, respectively. This film holds great potential for application in the field of green packaging.

Metal-Free C-X Functionalization in Solid-State via Photochemistry in Ball Mills.

We report the first metal- and catalyst-free protocol for the facile cross-coupling of aryl halides towards C-B, C-P and C-S bonds under solid-state ball milling conditions via UV light irradiation. The reactions can be performed in the absence of bulk solvents at room temperature in a mixer mill, yielding up to 99% and being tolerant towards various functionalized aryl halides (X = I or Br). Furthermore, we developed a novel photoreactor design increasing the light intensity. With this we could demonstrate that our protocol surpasses classical solvent based as well as purely mechanochemical approaches in terms of green metrics and energy efficiency.

Ball milling of pyrite in air to significantly promote the Fenton reaction: A mechanistic study

Natural pyrite (FeS2) has been widely used as heterogenous Fenton catalyst due to the unique iron supplying and ferrous regeneration performance, however, natural pyrite has poor catalytic activity due to the low surface reactivity. Ball milling is commonly used to modify pyrite, but the mechanism has not been thoroughly studied. In our work, by optimizing the ball milling conditions, the catalytic efficiency of modified pyrite is increased by 60 times compared to natural pyrite, and the ball milled pyrite Fenton system was able to degrade dyes and a series of antibiotics within 30 min. Compared to ball milling in nitrogen and vacuum, ball milling in air increased the proportion of S2− and active iron sites on the surface of pyrite, which assisted and accelerated the regeneration of ferrous and enhanced the iron supplying performance. This work explored the mechanisms of ball milling to modify the properties of pyrite, reported a green and efficient ball milled pyrite Fenton system, and provided a new insight in regulating ball milling conditions for mechanochemical modification.

Impact of Ball Milling on the Microstructure of Polyethylene Terephthalate.

Polyethylene terephthalate (PET) is a semi-crystalline polymer that finds broad use. Consequently, it contributes to the accumulation of plastics in the environment, warranting PET recycling technologies. Ball milling is a commonly used technique for the micronization of plastics before transformation. It has also recently been reported as an efficient mixing strategy for the enzymatic hydrolysis of plastics in moist-solid mixtures. However, the effect of milling on the microstructure of PET has not been systematically investigated. Thus, the primary objective of this study is to characterize the changes to the PET microstructure caused by various ball milling conditions. PET of different forms was examined, including pre- and post-consumer PET, as well as textiles. The material was treated to a range of milling frequencies and duration, before analysis of particle size, crystallinity by differential scanning calorimetry and powder X-ray diffraction, and morphology by scanning electron microscopy. Interestingly, our results suggest the convergence of crystallinity to ~30% within 15 minutes of milling at 30 Hz. These results are consistent with an equilibrium between amorphous and crystalline regions of the polymer being established during ball milling. The combined data constitutes a reference guide for PET milling and recycling research.

Decorticated and non-decorticated BARI lentil varieties: An ample source of essential nutrients, minerals and bioactive compounds

BARI lentils play an important role in Bangladesh for providing essential nutrients to combat micronutrient malnutrition. Hence, the objective of the study was to explore the nutritional, mineral, and bioactive compounds analysis of the selected varieties under different milling conditions. Results exhibited that a significant number of bioactive compounds such as ascorbic acid (15.29 mg/100 g), ß-carotene (142.16 mg/100 g), total carotenoid (67.49 mg/100 g), anthocyanin (1.35 mg/100 g), and total phenolic compounds (20.72 mg GAE/100 g) were plentiful in non-decorticated lentil. In contrast, the non-significant amount of ascorbic acid (4.52 mg/100 g), ß-carotene (64.65 mg/100 g), total carotenoid (11.65 mg/100 g), anthocyanin (0.65 mg/100 g), and total phenolic compounds (11.68 mg GAE/100 g) was found in decorticated lentils. Non-decorticated lentils possessed the highest amount of crude protein (29.63 %), crude fiber (14.12 %), Ca (3.55 %), Mg (1.11 %), Fe (219.00 ppm), and Zn (32.62 ppm). A non-significant difference was noted between cooked decorticated and non-decorticated lentils during organoleptic taste by the sensory evaluators. Apart from this, the most instructive findings are, to utilize non-decorticated lentils that will contribute to minimizing the broken loss (cracked loss) and milling cost of the farmers without any presence of ochratoxin and patulin.

The influence of ball milling conditions on the powder characteristics and sintering densification of Mo[sbnd]Cu alloy

Mechanical alloying was utilized to produce Mo-30Cu(wt%) composite powder. The effects of milling conditions on the powder characteristics and sintering densification were investigated. The morphological evolution during the mechanical alloying process can be categorized into four stages: 1-individual Mo and Cu particles, 2-coexistence of Mo particles and blocky MoCu composite particles, 3-coarse irregular composite particles, and 4-refined near-spherical composite particles or lamellar MoCu composite particles, depending on whether process control agent (PCA) is added. The mechanical alloying degree of the MoCu composite powder was deepened gradually from stage 1 to 4, which is influenced by the ball milling parameters. As the milling speed and milling time increase, the lattice strain and the alloying degree of the MoCu composite powders increase while the grain size of molybdenum particles decreases, which is conducive to accelerating the sintering density. Among these ball milling parameters, an elevated milling speed notably accelerates the mechanical alloying process and the sintering density. Under the milling speed of 600 r/min, ball to powder ratio (BPR) of 10:1, and milling time of 4 h, the grain size, lattice strain, and average particle diameter of the composite powder were measured to be 48.4 nm, 0.247 %, and 21.04 μm, respectively, with the particle morphology being nearly spherical. The sintered density of the MoCu composite reached 98.1 %, larger than the other composites.

Hardness and Corrosion Behavior of CrMnFeCoNi Alloy Fabricated by Ball Milling and Spark Plasma Sintering.

The mechanical properties and electrochemical stability of high-entropy alloys are substantially affected by their composition distribution and crystal structure. However, the details concerning the conditions of milling and sintering for sintered alloys have rarely been reported. In this work, a series of CrMnFeCoNi alloys were fabricated by ball milling and spark plasm sintering for different periods. Their crystal structure, density, hardness, and corrosion resistance were investigated. As a result, a partial alloying of Cr, Mn, Fe, Co, and Ni was achieved by ball milling. However, Cr-rich particles, including Mn, were formed in the milled powders. The sintered alloys inherited the Cr-rich particles to form Cr-rich zones. The formation and change of chromium carbide were also confirmed in sintered alloys. Extended milling or sintering to 12 h achieved high hardness and corrosion resistance for the sintered alloys. The Cr-rich zones showed high hardness and Kelvin potential, which affect both the hardness and the corrosion resistance.

Experimental study of wet and dry milling effect on surface roughness of TC4 titanium alloy

Titanium alloys are important engineering materials used in various industry areas, such as aviation, aerospace and medical devices. The surface roughness is a significant parameter for assessing the machining quality of titanium alloys. In this study, in order to compare the effects of dry and wet milling conditions on the surface roughness of titanium alloys, we established a test system to obtain the surface roughness, three-dimensional milling vibration and three-dimensional milling force signals. The gray correlation theory was applied to investigate the correlation between surface roughness and milling vibration or milling force under dry and wet milling conditions. Using the least squares method, the prediction models of surface roughness corresponding to dry and wet milling conditions were developed according to the features of vibration or force signals. Furthermore, the combined prediction models of surface roughness that integrate multiple signal features and milling parameters were established. The comparison results revealed that there was a stronger correlation between roughness and milling force, milling vibration in wet milling. Wet milling exhibited significantly lower roughness compared to dry milling under the same machining parameters, with up to a 59% reduction. The correlation coefficient of the wet milling model is as high as 0.95.

The influence of mechanochemical activation on the rheological properties and strength development of geopolymer

To address the significant carbon emissions caused by the cement industry and its contribution to the greenhouse effect, there is an urgent need for new construction materials that can substantially reduce the use of traditional Portland cement. Alkali-activated binders, known for their excellent performance and lower carbon footprint, have emerged as a promising alternative. Despite the numerous advantages of geopolymers, their practical application is hindered by challenges in processability required for construction techniques, such as pumping, spreading, and forming. This study focuses on enhancing the rheological properties of geopolymers through mechanochemical activation and exploring the modification mechanisms involved. Slag and fly ash raw materials were processed under different ball milling conditions, specifically varying ball milling rotation speed (BR) and ball milling time (BT). The mechanical properties, workability, and rheological behavior of geopolymer specimens were evaluated to identify the optimal milling parameters affecting these properties. Detailed analysis using XRD, SEM, and heat of hydration tests elucidated the phase composition, microstructural evolution, and thermal characteristics of mechanochemically modified geopolymers, providing insights into the fundamental mechanisms of mechanochemical activation modification. The results indicate a significant correlation between ball milling parameters and the rheological properties of geopolymers. The optimal milling regime was identified as grinding at a speed of 70r/min for 50 min. This specific milling condition imparts ideal properties to the geopolymer, including moderate yield stress (34.353 Pa), low plastic viscosity (0.452 Pa s), good thixotropy, and high 28d strength (53.28 MPa), without any significant shear thickening behavior.

High-strength joining of WC-Si3N4 composite via spark plasma sintering and functionally graded material (FGM) bonding

Joining of large aspect ratio WC-based cemented carbide and Si3N4-based ceramic at 1650 °C was achieved via spark plasma sintering by using functionally graded material (FGM) as a bonding layer. The influence of FGM layer numbers on the bonding quality of the large aspect ratio WC-FGM-Si3N4 composite materials was assessed based on thermal expansion coefficient and residual stress data. The microstructure analysis of the interface between adjacent layers revealed the formation of a structure with grain bidirectional anchoring, which promoted the enhancement of the bonding strength. High-strength joining of the large aspect ratio WC-FGM-Si3N4 composite rods with the average shear strength of 210.5 MPa was successfully realised. Furthermore, the rod was ground into an end mill, and the obtained end mill connection strength fulfilled the stringent machining conditions for dry milling of nickel-based superalloys.

Mechanochemical Synthesis of Silylcyclopentenes via Ball Milling.

The development of innovative methods for synthesizing silylcyclopentene compounds is particularly important for enriching and improving the synthetical toolbox of organosilicon compounds. Herein, a facile approach has been developed for the synthesis of silylcyclopentenes promoted by mechanochemically generated organolithium species as silicon nucleophiles under ball milling conditions, avoiding the requirement of large amounts of bulk solvent. This operationally simple method demonstrates good functional group compatibility, which provides a great opportunity for further exploration of the synthetic applications of silylcyclopentenes. Density functional theory calculations indicated that the transient lithiosilole intermediates undergo a stepwise nucleophilic addition process, which governs this mechanic-force-promoted [4+1] cycloaddition reaction.

Experimentally Aided Operational Virtual Prototyping to Predict Best Clamping Conditions for Face Milling of Large-Size Structures

Vibrations occurring during milling operations are one of the main issues disturbing the pursuit of better efficiency of milling operations and product quality. Even in the case of a stable cutting process, vibration reduction is still an important goal. One of the possible solutions to obtain it is selection of the favorable conditions for clamping the workpiece to the machine table. In this paper, a method for predicting and selecting the clamping condition of a large-size workpiece for the reduction in vibrations during milling is presented. A modal test of the workpiece is performed first for a selected set of tightening screw settings. Next, one milling pass is performed to obtain reference data which are then used to tune the hybrid computational model. In the subsequent step, milling simulations are performed for a set of tightening variants, and the best one is selected, providing the lowest vibrations, assessed as the root mean square (RMS) of vibration displacements. In this paper, the description of the clamping selection procedure, key elements of the simulation model, and simulation and experimental results obtained for the milling of the test workpiece performed for a set of different clamping conditions are provided. The proposed method accurately predicts not only the best but also the worst clamping conditions.

Research on hammering characteristics of hammer mill based on discrete element method

In hammer mill crushing, the speed change of the rotor hammer head will have an effect on the efficiency of crushing, and so on. This paper takes the hammer mill rotor as the research object and carries out a simulation study, establishes the material particle crushing model, and verifies the validity of the model. The discrete element method (DEM) is used to simulate the movement of the material inside the hammer mill after crushing, revealing that the working principle of the hammer mill is based on the form of particle movement, and to study the law of the particle collision fracture bond energy, compressive stress and particle collision impact energy of the hammer mill. Through comparison, the final working condition of the hammer mill is that at the rotor speed of 1600 r min−1, the working efficiency of the whole equipment is the highest.

Energy-size relationship and starch modification in planetary ball milling of quinoa

The effects of speed (250–450 rpm) and time (10–50 min) on milling energy (E), particle size distribution (PSD), crystallinity degree (CD), damaged starch (DS), microstructure, hydration and pasting properties of flours obtained in a planetary ball mill (PBM) were investigated. As increasing milling severity quinoa flours showed polydispersed PSD (peaks at 417, 40 and 2 μm) with a shift towards smaller size and greater dispersion (Span: 3.0–5.2) as well as particles with rounded edges and polished surfaces (SEM images). The relationship E − D50 were satisfactorily predicted by the Walker's equation. The hydration tests as function of temperature and milling conditions revealed a complex flour behavior due to differences in PSD, composition, and DS content. The increasing milling energy caused a decrease in peak viscosity (PV), trough viscosity (TV) and final viscosity (FV) of up to 36%, 29%, and 25%, respectively. Significant correlations between flour attributes were found (DS-CD, r = −0.83, p < 0.01; PV-D50, r = 0.92, p < 0.01; TV-D50, r = 0.94, p < 0.01; FV-D50, r = 0.90, p < 0.01) denoted the increase of starch degradation as milling severity rises. These results can be used to improve the manufacture and the selection criteria of quinoa flour with specific functional attributes.

Eco-Friendly Mechanochemical Synthesis of Bifunctional Metal Oxide Electrocatalysts for Zn-Air Batteries.

The development of green and environmentally friendly synthesis methods of electrocatalysts is a crucial aspect in decarbonizing energy generation. In this study, eco-friendly mechanochemical synthesis of perovskite metal oxide-carbon black composites is proposed using different conditions and additives such as KOH. Furthermore, the optimization of ball milling conditions, including time and rotational speed, is studied. The mechanochemical synthesis in solid-state conditions without additives produces electrocatalysts that exhibit the highest bifunctional electrochemical activity towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, this synthesis demonstrates a lower Environmental Impact Factor (E-factor), indicating its greener nature, and due to its simplicity, it has a great potential for scalability. The obtained bifunctional electrocatalysts have been tested in a rechargeable zinc-air battery (ZAB) for 22 h with similar performance compared to the commercial catalyst (Pt/C) at significantly lower cost. These promising findings are attributed to the enhanced interaction between the perovskite metal oxide and carbon material and the improved dispersion of the perovskite metal oxide on the carbon materials.

Improving the Carbonation of Steel Slags Through Concurrent Wet Milling

This work studies mineral carbonation of steel slags with the aim to reduce the amount of slag that is landfilled. Besides permanently storing carbon dioxide (CO2), carbonating the slags can improve their quality for use in beneficial applications and reduces the leaching of harmful heavy metals. In order to intensify the mineral carbonation process, mechanical activation is used to improve both the carbonation kinetics and yield. The milling is performed in a planetary ball mill which allows for high-intensity grinding, resulting in a fast reduction of the particle size and quick amorphization and disturbance of the crystal structure, allowing high reaction rates to be achieved. The effects of the three main processing parameters of a planetary ball mill—bead-to-powder ratio R\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R$$\\end{document}, bead size D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D$$\\end{document} and milling speed S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S$$\\end{document}—are investigated. Under optimal conditions, more than 50% of the maximum CO2 uptake is achieved in only 6 min, representing a very significant improvement over regular slurry carbonation. Quantitative XRD allows to identify the reactivity of the different crystalline phases present in the slag under different milling conditions. With the help of a mass balance, the formation of an inert outer layer consisting of silica (SiO2) is confirmed. This explains both the shell diffusion mechanism controlling the carbonation reaction and the total conversion being limited to 50–60%.Graphical

Enhancing face-milling efficiency of wood–plastic composites through the application of genetic algorithm–back propagation neural network

ABSTRACT Wood–plastic composites (WPCs) have advanced physicochemical properties and are widely applied in various fields. How to achieve high-efficiency, high-quality machining of WPC is a pressing issue that WPC manufacturing enterprises need to address. To this end, this research focused primarily on improving the machinability of WPC with end milling experiments. In this work, a single-factor method was used to analyse the impact of axial milling depth, spindle speed, and tool rake angle on resultant forces and surface roughness. Main effects analysis was applied to explore the degree of influence of axial milling depth, spindle speed, and tool rake angle on cutting forces and surface roughness. Furthermore, three-dimensional characterisation techniques were utilised to analyse the surface morphology characteristics of WPC during end milling. Finally, a genetic algorithm–back propagation neural network was applied to develop prediction models for resultant force and surface roughness, and optimal milling conditions were identified as axial milling depth of 0.50 mm, spindle speed of 7841 r/min, and rake angle of 15°; these produced the lowest resultant force and surface roughness. The findings of this work are proposed as a guide for better cutting performance in the industrial production of WPC.

Low-frequency chatter suppression for robotic milling using a novel MRF absorber

Robotic milling has a unique advantage for large and complex parts. However, it is extremely prone to low-frequency chatter due to the robot structure mode. In robotic milling, low-frequency chatter has a huge impact on machining quality and efficiency. In this paper, a novel MRF (Magnetorheological fluid) absorber is used to suppress low-frequency chatter during robotic milling based on the proposed low-frequency chatter suppression strategy. First, the GPR (Gaussian process regression) model is used to predict the impulse response function based on a few measured impulse response functions. Next, a cutting force model is developed considering the tool runout and the robot structure mode. The parameters and coefficients of the cutting force model are optimized by the measured cutting forces. Then, the low-frequency chatter frequency is predicted considering the modal coupling effect based on the predicted impulse response function and the simulated cutting force. Finally, an MRF absorber is designed based on the chatter frequency range. The controlled storage modulus of the MRF in the pre-yield region enables a wider frequency shift characteristic of the designed MRF absorber. The MRF absorber controls the input current based on the predicted low-frequency chatter frequency to achieve chatter suppression during robotic milling. Robotic milling experiments verified that the MRF absorber can effectively suppress low-frequency chatter. The experimental results show that the Energy Ratio Chatter Indicator of the industrial robot with MRF absorber is less than 0.1 under different milling conditions.