Impact Mill Research Articles

Role of screen plate design in the performance of a rotor impact mill in fine grinding of biomass

The role of rotor impact mill screen plate design in biomass grinding has attracted limited interest. This study aimed to clarify the effect of operational parameters and various screen designs on the fine grinding of Sphagnum moss. Contoured screens having forward (rasp) and backward (inverse rasp) inclined trapezoidal apertures of nominal sizes 0.2, 0.3, 0.4, and 0.5 mm were studied. A smooth screen plate having circular perforations (0.5 mm) was used as a reference. Flow phenomena were modeled with Computational Fluid Dynamics (CFD) using 2D geometry for the screen apertures.Product particle size and capacity were mostly dependent on the equivalent diameter of the screen apertures together with rotor frequency and also on the screen design, while the aspect ratio was solely a function of particle size. Among the screens having nominal sizes of 0.3, 0.4, and 0.5 mm, the smooth screen produced the smallest particle size; followed by the rasp screens and the inverse rasp screens. The smooth screen had higher capacity than the rasp or inverse rasp screens, and a narrower operating range. In the case of 0.2 mm apertures, higher capacity was achieved with the inverse rasp than with the rasp screen. The net energy consumption (SEC) of grinding with the rasp screens was at a lower level than with the inverse rasp screens (or the smooth screen). No difference was seen in the case of the smallest size apertures, however.The results, supported by CFD modeling, indicate that the incidence angle of particles does not explain the passage of particles through screen apertures. The passage is affected by the flow patterns above and within the apertures, and the pressure difference over the screen plate. The eddies within the apertures reduce their effective open area, resulting in product particles much smaller than the aperture size. When the aperture inclination is toward the tangential flow (rasp), an eddy is also generated in front of the aperture that turns the flow perpendicular to the screen surface within the aperture. In contrast, when the aperture inclination is against the tangential flow (inverse rasp), an eddy is generated above the aperture that guides the flow smoothly into the aperture, although the flow has to make a U-turn first. A design of inverse rasps seems to be beneficial when very small apertures are used, as it appears that the eddies formed above the apertures prevent blocking by dislodging accumulated particles. The low SEC with rasp screens does not seem to make the passage of particles through apertures easier, but it does enable more efficient size reduction because of the ability of rasps to serve as a grinding track.

Microstructural properties and grinding of γ-Al2O3 and coal for environmental applications

ABSTRACTThe amphoteric characteristics of some metal oxides complemented by their chemical microstructures form the basis for their use for environmental engineering applications, e.g., alumina as catalyst and abrasive agents. This paper describes the microstructural properties and grinding behavior of γ-Al2O3 and coal particles in a batch impact mill. By grinding γ-Al2O3 and Hunan coal separately in an impact mill, a grinding process model of two dimensionless groups and is developed using Buckingham Pi theorem to obtain the desired particle morphologies. The properties established in this grinding model as key determinants of the grinding behavior are particle hardness, particle density and milling speed. The milling results confirm that γ-Al2O3 of the HBW 5/100 hardness 247 show higher resistance to grinding than coal of HBW hardness 28, because the final ground particle diameters d0.9 after 30 min milling were 136.6 and 33.4 µm for γ-Al2O3 and coal, respectively. This grinding model is pioneering as the particle hardness contained in the dimensionless group embodies an intrinsic material property which controls grinding and is confirmed to be in agreement with the fragmentation pattern.

Novel micronized woody biomass process for production of cost-effective clean fermentable sugars

Thermo-chemical pretreatments of biomass typically result in environmental impacts from water use and emission. The degradation byproducts in the resulting sugars can be inhibitory to the activities of enzymes and yeasts. The results of this study showed that combining existing commercial comminution technology can reduce total energy consumption with improved saccharification yield while eliminating chemical use. Impact mill was found to be the most efficient milling for size reduction of forest residual chips from ca. 2 mm to a specific value below 100 µm. The further micronization effectively disrupted the recalcitrance of the woody biomass and produced the highly saccharifiable substrates for downstream processing. In addition, extrusion can be integrated into a clean cellulosic sugar process for further fibrillation in place of the conventional mixing processing. The highest energy efficiency was observed on the impact-milled samples with 0.515 kg sugars kWh−1.

Energy consumption of two-stage fine grinding of Douglas-fir wood

Fine wood powders have advantages over traditional coarse wood particles for various emerging applications. However, an efficient system to produce fine wood powders has not been well established. We investigated the comminution capability and efficiency of a two-stage grinding system consisting of a hammer mill circuit and an rotor impact mill circuit to convert wood feedstocks into fine powders. Air-dried forest harvest residuals were comminuted by the hammer mill circuit to three intermediate product sizes with geometric mean particle sizes of 1618, 669, and 316 µm. These intermediate products were then pulverized into fine wood powders with median particle sizes ranging from 35 to 250 µm. The specific energy consumption increased with the decrease of median particle sizes, with a transition at around 100 µm after which the energy consumption increased exponentially. This large-scale grinding trial provides the reliable energy consumption data for design and process economic analysis of mechanical biomass preprocessing.

Impact of Milling on Rice Constituents (Oryza Sativa L.): A Metabolomic Approach

ABSTRACTMilling is an influential factor that affects the nutritional components in rice. However, the alteration of rice constituents by milling has not been thoroughly examined. In this study, rice with various degrees of milling was analyzed by gas chromatography–mass spectrometry and high-performance liquid chromatography–mass spectrometry. Principal component analysis and partial least square-discriminant analysis were performed to characterize the nutritional components that have significant changes during milling. The concentrations of sugars and sugar alcohols decreased while the phospholipids increased in accordance with the milling degree. These results provide a contrast to the common idea that brown rice is nutritionally superior to white rice. In conclusion, the knowledge of nutritional alterations related to milling may benefit rice production and consumption.

Analyzer for measuring gas contained in the pore space of rocks

In the present paper, the authors discussed the functioning of their own analyzer for measuring gas contained in the pore space of high strength rocks. A sample is placed inside a hermetic measuring chamber, and then undergoes impact milling as a result of colliding with the vibrating blade of a knife which is rotationally driven by a high-speed brushless electric motor. The measuring chamber is equipped with all the necessary sensors, i.e. gas, pressure, and temperature sensors. Trial tests involving the comminution of dolomite and anhydrite samples demonstrated that the constructed device is able to break up rocks into grains so fine that they are measured in single microns, and the sensors used in the construction ensure balancing of the released gas. The tests of the analyzer showed that the metrological concept behind it, together with the way it was built, make it fit for measurements of the content and composition of selected gases from the rock pore space. On the basis of the conducted tests of balancing the gases contained in the two samples, it was stated that the gas content of Sample no. 1 was (0.055 ± 0.002) cm3 g−1, and Sample no. 2 contained gas at atmospheric pressure, composed mostly of air.

A combined experimental and DEM approach to determine the breakage of particles in an impact mill

Population balance models (PBMs) are widely used to predict particle size variation in grinding. An accurate determination of particle breakage and selection functions in PBMs requires detailed knowledge on the stress causing particle breakage. This study proposed a combined experimental and numerical approach to determine the two functions. In the physical experiments, the breakage of individual iron ore particles in a Fritsch impact mill with different mill speeds was investigated and the product sizes were analysed. The simulations based on the discrete element method (DEM) were carried out under similar conditions to examine the dynamics of the particles inside the mill, such as number of impacts, impact velocity and impact angle. The simulation results showed that most of the particles experienced multiple impacts before they were ejected from the mill. The first impacts occurred at low impact energy which had no contribution to particle breakage. The second and third impacts, on the other hand, posed high impact energy on the particles and were the main cause of particle breakage. Based on the simulation results and the experimental data, two semi-empirical selection and breakage functions were determined. The accuracy of the equations was confirmed by applying them to predicting the size distribution of ground particles under different mill conditions.

Elastic properties of packing of granulated cork: Effect of particle size

Cork is a natural raw materials used in numerous traditional and innovative applications among which the most famous are cork stoppers, insulation boards, and wall and floor covering. Cork exhibits a relatively homogeneous honeycomb structure composed of polyhedron cells filled with gas, which gives its specific properties such as elasticity or hydrophobic behavior. Mechanical properties of cork have been studied from a long time. However, in many industrial applications cork is increasingly used as granulate (>200μm) or powder (<200μm) obtained by milling processes. By generating failure in the raw material, the comminution of cork could damage cells and induce modifications in the mechanical behavior of cork particles but the relation between the size of the particles and the mechanical properties of the packaging is still little known. In this study, we investigate the effect of cork particles size reduction on the mechanical properties of the packing. To this end, eighteen discrete size fractions of cork from 0 to 25μm to 2.5–3mm, generated by impact milling were characterized in term of shape, loaded density, and elastic recovery. Experiments show that impact milling mainly affects the elastic properties of particles less than 200μm. The mechanical behavior of cork particles was also described by model based on a mixing law taking in account the size and the shape of particles and the amount of damaged cells in the particles. The fitting of the model to the experimental data suggests that the elastic properties of the packing of cork particles have to be related to the content of damage cells more than to their size.

Production and characterization of cellulose nanoparticles from nopal waste by means of high impact milling

Apart from its dietary use, Opuntia ficus-indica (OFI), also known as nopal, is widely used in diverse non-food areas given its multiple properties and health benefits. In Mexico City, each year de-thorning process of nopal generates around 40,000 tons of waste. This waste contains a huge amount of hemicellulose and cellulose that can be used as a new biodegradable nanocomposite. Therefore, the aim of this work was to purify nopal thorns to obtain cellulose nanoparticles by high impact milling or high-energy ball milling. Confocal laser scanning microscopy (CLSM) showed that thorns have two main polysaccharides arranged in parallel fibers: cellulose and lignin. Size of the obtained cellulose nanoparticles were ranged from 24 to 122 nm. Crystallinity, as well as the type of cellulose obtained, were analyzed by means of XRD to evaluate its potential use as nanocomposite.

Encapsulation and Stabilization of β-Carotene in Amaranth Matrices Obtained by Dry and Wet Assisted Ball Milling

Amaranth starchy fractions have recently awakened interest from the industry, mainly due to its potential functional characteristics. The encapsulating efficiencies of starch-enriched fraction (SEF) and native starch (NS) obtained, respectively, by dry and wet assisted ball milling were studied. The effects of high impact milling, gelatin addition, and storage temperature (5–45 °C, 45 days) on the retention of β-carotene were investigated. Significant effects of both milling and amaranth protein present in SEF matrix on emulsification and subsequent retention of β-carotene were found. Ball milled SEF matrix showed the best encapsulation performance, with up to three times of total β-carotene content in comparison with the NS-containing matrices. Degradation of surface and encapsulated β-carotene followed a first-order kinetic model and was strongly influenced by storage temperature. The activation energy of surface β-carotene degradation doubled that of encapsulated β-carotene (86 vs. 48 kJ/mol, respectively). This difference indicates that encapsulated β-carotene is more stable to temperature changes than surface β-carotene and revealed the protective capability of the SEF matrix even at high temperatures. The color coordinates a* and L* for samples stored at 25 and 45 °C positively correlated with the remaining β-carotene, revealing the potentiality of color measurement as an adequate index of β-carotene retention. The starch-enriched amaranth fraction modified by high impact milling showed a high technological potential as an encapsulating agent and its own protein content served as a good emulsifier-stabilizer.

Torrefied Biomass Pellets—Comparing Grindability in Different Laboratory Mills

The firing and co-firing of biomass in pulverized coal fired power plants around the world is expected to increase in the coming years. Torrefaction may prove to be a suitable way of upgrading biomass for such an application. For transport and storage purposes, the torrefied biomass will tend to be in pellet form. Whilst standard methods for the assessment of the milling characteristics of coal exist, this is not the case for torrefied materials—whether in pellet form or not. The grindability of the fuel directly impacts the overall efficiency of the combustion process and as such it is an important parameter. In the present study, the grindability of different torrefied biomass pellets was tested in three different laboratory mill types; cutting mill (CM), hammer mill (HM) and impact mill (IM). The specific grinding energy (SGE) required for a defined mass throughput of pellets in each mill was measured and results were compared to other pellet characterization methods (e.g., durability, and hardness) as well as the modified Hardgrove Index. Seven different torrefied biomass pellets including willow, pine, beech, poplar, spruce, forest residue and straw were used as feedstock. On average, the particle-size distribution width (across all feedstock) was narrowest for the IM (0.41 mm), followed by the HM (0.51 mm) and widest for the CM (0.62 mm). Regarding the SGE, the IM consumed on average 8.23 Wh/kg while CM and HM consumed 5.15 and 5.24 Wh/kg, respectively. From the three mills compared in this study, the IM seems better fit for being used in a standardized method that could be developed in the future, e.g., as an ISO standard.

Spheroidization of Graphite As Anode Material for Li-Ion Batteries: Spheroidization Process and Material Texture and Morphology

Natural graphite (NG) is the dominant anode material for lithium ion batteries (LIBs) today, with a market share of approx. ~55%. With the continuous growth of portable, automotive, and other applications the total LIB market is expected to double within in the next decade. In view of this growth scenario, some prognoses predict supply bottlenecks of NG. Furthermore, the NG sources are geographically strongly concentrated today, which poses an immanent risk to supply security. In principle, the increasing demand for graphite as LIB anode material can be met by synthetic graphite, for which an upscaling of the production capacity is possible with economically justifiable effort within short time. Nonetheless, there are strong activities to develop new sources of NG. To benchmark the quality of these new materials, convenient and cost-effective characterization methods and facilities are required. Pristine flat flakes of NG are usually mechanically turned into spherical shapes (“spheroidization”) and coated with a thin film of amorphous carbon, in order to alleviate problems with exfoliation due to electrolyte solvent co-intercalation during lithium intercalation, to decrease the surface area and thus the irreversible capacity in the first charge/discharge cycle, as well as to increase density and thus the volumetric capacity. Recently, spheroidization is also more and more applied to synthetic graphite materials. Characteristic of the spheroidization procedure is that the yields are usually around 50% only. Any process improvement will therefore have a strong economic impact. The present work focuses on the lab-scale reconstruction of the industrial spheroidization and fractionation processes, using a rotor impact mill, an air jet sieve, and an air classifier. The aim is: to obtain a better understanding of the spheroidization process, by identifying critical process parameters and their influence on the resulting products (spherical graphite particles as well as by-products),to identify potentials for improving the process (especially in terms of yield), andto offer the opportunity to benchmark graphitic materials in lab-scale in comparison to industrially manufactured references. The obtained materials are analysed with regard to their electrochemical performance, as well as to their particle morphology (particle size distribution, particle shape, tap density and texture). The microstructure and texture is studied by SEM and FIB/SEM tomography, which provide information on the outer appearance in the nm scale and the open and closed porosity of the materials (Fig. 1). Acknowledgement: The authors are indebted to the German Federal Ministry of Education and Research (BMBF) for financial support (Project: Li-EcoSafe, contract no. 03X4636). Figure 1

Effect of particle size distribution on the self-hardening property of biomass-peat fly ash from a bubbling fluidized bed combustion

An increasing amount of biomass fly ash is produced because of the increased usage of renewable energy sources. Therefore, novel applications in which biomass fly ashes can be utilized efficiently are required. One interesting option is to use biomass fly ashes in hardening applications, such as earth construction. In this study, the self-hardening of ground fly ash from a Finnish power plant with a bubbling fluidized bed boiler that burns forest industry residuals and peat was investigated. Fly ash was ground with three different mills, namely, tumbling ball mill, impact mill, and jet mill, to different particle size distributions. Results showed that the amount of reactive components for ground fly ash samples was more or less the same with the original sample, but the particle size distribution was different. Moreover, the water requirement for self-hardening samples was completely different depending on the grinding mechanism. When particle size distribution was wider (after ball and impact milling), the water requirement was much lower due to the better packing of the particles. A smaller water requirement also led to greater compressive strength even the fly ash samples were chemically and mineralogically the same. After ball milling, obtaining four times higher self-hardening compressive strength, from 5MPa to 20MPa, was possible. For jet milled fly ash, the particle size distribution was narrow due to the classifier in the mill, and the water requirement was high. Therefore, the packing and self-hardening compressive strength of jet milled fly ash was lower than that of impact and ball milled samples.

Impact of milling, enzyme addition, and steam explosion on the solid waste biomethanation of an olive oil production plant.

Anaerobic digestion is a consolidated bioprocess which can be further enhanced by incorporating an upstream pretreatment unit. The olive oil production produces a large amount of solid waste which needs to be properly managed and disposed. Three different pretreatment techniques were evaluated in regard to their impact on the anaerobic biodegradability: manual milling of olive pomace (OP), enzyme maceration, direct enzyme addition, and thermal hydrolysis of two-phase olive mill waste. The Gompertz equation was used to obtain parameters for comparison purposes. A substrate/inoculum ratio 0.5 was found to be the best to be used in anaerobic batch test with olive pomace as substrate. Mechanical pretreatment of OP by milling increases the methane production rate while keeping the maximum methane yield. The enzymatic pretreatment showed different results depending on the chosen pretreatment strategies. After the enzymatic maceration pretreatment, a methane production of 274 ml CH4 g VS added (-1) was achieved, which represents an improvement of 32 and 71 % compared to the blank and control, respectively. The direct enzyme addition pretreatment showed no improvement in both the rate and the maximum methane production. Steam explosion showed no improvement on the anaerobic degradability of two-phase olive mill waste; however, thermal hydrolysis with no rapid depressurization enhanced notoriously both the maximum rate (50 %) and methane yield (70 %).

Evaluation and scale-up of miniaturized rotor–stator impact mills

Two recently marketed, miniaturized rotor–stator impact mills of 70mm and 35mm rotor diameter were evaluated and compared to a conventional small scale model of 110mm rotor diameter, in order to reduce the minimum batch size while maintaining adequate predictability. The minimum batch size of the conventional scale model is about 1 to 4kg and far too big to establish rotor–stator impact milling technology at the early-stage of drug development due to limited availability of drug compound, and rather inefficient for the technical processing of costly drug compounds during the drug development cycle. Both miniaturized equipment models show comparable behavior on product particle size by process parameters feed rate and rotor speed in relation to the conventional scale model. The minimum, predictable batch size could be considerably reduced to 400g and 10g for the rotor–stator impact mills of 70mm and 35mm rotor diameter, respectively. Scale-up could be established between the two miniaturized models and the conventional scale model for process parameter feed rate by a common power factor concept available in literature, and for process parameter rotor speed by the cumulative specific stress energy of the rotating pins. Finally, both miniaturized rotor–stator impact mills enable significant improvements for the application in drug development, with reduced dynamic working range of cumulative specific stress energy, compared to rotor–stator impact mills at pilot and manufacturing scales.

Anomalous size evolution of partially amorphized pharmaceutical particles during post-milling storage

Milling is simple and inexpensive method for particle size reduction. The micronization process such as fluid-energy impact mills (e.g. spiral jet mills and fluidized bed jet mills) is commonly used in the pharmaceutical industries to attain optimal/desire particle size distribution for pharmaceutical powders. However, this process may also cause several undesirable effects on active pharmaceutical ingredients (APIs) such as aggregation of fine particles, induction of electrostatic charges, mechanochemical transformation, defects on the surface of drug particles (amorphization) and changes in other physicochemical properties which may significantly affect the physical stability of API powders.In this study, the effect of milling-induced amorphization on the properties of APIs jet-milled at different energy-inputs (high (I), medium (II) and optimal (III)) provided from industry was investigated. Dynamic vapor sorption (DVS) technique has been established to quantify the amorphous content of industry milled APIs (I, II and III). A time-course study has been conducted to evaluate the physical stability of X-ray amorphous (generated by in-house cryo-milling as control) and three industrial samples I, II and III under accelerated stability test conditions (A=40°C/75%RH and B=25°C/55%RH) and any accompanying changes in key physicochemical properties such as crystallinity, agglomerate strength, particle size distribution (PSD) and morphology. In descending order, the amorphous content (%) of industrial API samples (milled different energy-inputs (high (I), medium (II) and optimal (III))) were ranked from I (50.9%), II (31.6%) to III (14.6%).Re-crystallization of X-ray amorphous and industrial samples was observed under both conditions A and B during storage of 13weeks. It was observed that there were changes in the particle size of APIs during post-micronization storage. There were reductions in particle size of all industrial samples under conditions A and B after 13weeks of storage. A possible explanation on the observation of anomalous particle size shift during post-milling storage was attributed to two different phenomena occurring at the same time and competing with each other. These two phenomena are called “surface re-crystallization” and “stress relaxation”. Re-crystallization of amorphous surface (observed from SEM) may lead to enlargement of particle size due to formation of solid bridges during storage. Microcompressor tester (MCT) analysis also suggested that the agglomerate strength increases during storage due to the surface re-crystallization. In case of particle size reduction, PSD analysis suggested that the milled agglomerates exhibited breakage pattern termed as localized disintegration whereby clusters of primary particles broke off from the outer surface of milled agglomerates. This was likely attributed to the energy-intensive micronization process that induces residual stresses, which propagate over time and lead to the breakage of particle agglomerates. Overall, the stress relaxation is more dominant than the re-crystallization and results in overall particle size reduction after storage.

Recycling of a fine, heavy fluff automobile shredder residue by density and differential fragmentation

A compilation of the physical properties of materials which might typically occur in automobile shredder residue and an analysis of their suitability for the separation of materials in fine (<15mm) heavy fluff ASR (fhf-ASR) is presented. Differences in density and resistance to crushing of fhf-ASR materials were identified as potentially the most suitable low cost, technologically simple means for the separating this waste into its three principal components – metals, minerals (glass/stones) and organics (plastics).Results presented of laboratory scale tests demonstrate that fhf-ASR can in large part be separated into three principal components. Tests were conducted with 0.63–2.0mm and 2–10mm fractions. Recovery of plastics by density separations were conducted with water only jigs for the 2–10mm fraction and shaker tables for the 0.63–2mm fraction. Comparisons are presented of the separations of glass and stones from metals obtained by linear screening and vibratory screening of roller mill and impact mill crushing products of the high density 2–10mm fraction. Equipment used for these tests are of a laboratory or demonstrative scale. It is reasonable to anticipate that industrial scale processing would produce significantly better results.The 2–15mm fraction was found to constitute 91.6% of the fhf-ASR sampled. The metals content of the 2–10mm portion of this fraction was upgraded from 2.5% to 31% and 76.9% with recoveries varying inversely with grade from 91.9% to 40.1%. From 63.6% to 17.1% with a recovery of 93.5% of the organic materials. A residual product of fine sand of crushed glass/stones of 99.4% purity recovered 71.3% of these.

The effect of milling additives on powder properties and sintered body microstructure of NiO

The evolution of powder particle size, crystal structure, and surface chemistry was evaluated for micron scale NiO powders subjected to impact milling with commonly employed milling additives: methanol, Vertrel XF, and amorphous carbon. The effect of the different comminution protocols on sintered body microstructure was evaluated for high temperature sintering in inert atmosphere (N2). X-ray photoelectron spectroscopy showed that NiO powder surface chemistry is surprisingly sensitive to milling additive choice. In particular, the proportion of powder surface defect sites varied with additive, and methanol left an alcohol or alkoxy residue even after drying. Upon sintering to intermediate temperatures (1100 °C), scanning electron microscopy (SEM) showed that slurry milled NiO powders exhibit hindered sintering behaviors. This effect was amplified for NiO milled with methanol, in which sub-500 nm grain sizes dominated even after sintering to 1100 °C. Upon heating to high temperatures (1500 °C), simultaneous differential scanning calorimetry/thermogravimetric analysis (DSC/TGA) showed that the powders containing carbon residues undergo carbothermal reduction, resulting in a melting transition between 1425 and 1454 °C. Taken together, the results demonstrated that when processing metal oxide powders for advanced ceramics, the choice of milling additive is crucial as it exerts significant control over sintered body microstructure.

Structure and Surface Chemistry Optimization of Graphite Electrodes for High-Voltage Dual-Intercalation Batteries

Existing standalone grid-level power systems rely on inefficient operation of diesel generators or expensive traditional battery technologies. Dual-intercalation batteries, which rely on high-voltage ion insertion into both cathodes and anodes, offer a promising electrical energy storage alternative. The respective 372 mAh/g and 90 mAh/g capacitances for cation and anion intercalation offer grid-level charge storage densities, implementation of affordable and available materials, and simpler disposal procedures for optimized and reliable energy storage systems[1]. Despite several expected advantages, the 5.2 V intercalation process currently exhibits low first-cycle efficiencies and limited charge/discharge rates. Possible causes can be likely attributed to a poor solid-electrolyte interface (SEI) and the large anion diameters, increasing inefficiencies from long intercalation pathways. Furthermore, theoretical predictions limit cathode stage 1 intercalation to one anion per 24 carbons (compared to one cation per 6 carbons for stage 1 anode intercalation), inherently limiting the system’s energy density. To maximize capacitance and long-term cyclabilities, the carbon structure and surface chemistry of both the cathode and anode materials must be optimized for the specific electrolyte and be appropriately matched with respective properties of the opposite electrode material. To accomplish this goal, we subjected spherical, core-shell, and stacked graphite structures to 1100 – 1800 °C vacuum annealing, impact milling, 570 °C air oxidation, C2F6 plasma discharge, and high-temperature treatments using melamine and H2. These procedures defunctionalized surfaces [2], altered defects in the sp2 lattice, or selectively grafted C=O, C-F, C-Nx, and C-H groups, respectively. Following electrochemical cycling between 4.0 and 5.2 V in 2.0 m LiPF6 in fluoroethylene carbonate (FEC), ethylmethycarbonate (EMC) electrolytes and a tris(hexafluoro-iso-propyl)phosphate (HFiP) additive, we observed different effects of specific surface chemistries on anode and cathode capacities and first-cycle efficiencies. In particular, we observe positive influences of hydrogenated anode surfaces and improved performances for oxidized cathodes. Similar modifications of spherical and layered graphite electrodes yielded asymmetric efficiencies and long-duration cyclabilities, indicating divergent influences of functionalities on specific intercalated ions. Matching the appropriate surface groups for anode and cathode dual-graphite batteries, we observe improvements in coulombic efficiencies and long-term cyclabilities. Our findings offer fundamental insights into the dual-intercalation process and provide pathways for optimization of these all-carbon, environmentally friendly energy storage systems [3] for grid-level applications. 1. Read, J. A.; Cresce, A. V.; Ervin, M. H.; Xu, K., Dual-graphite chemistry enabled by a high voltage electrolyte. Energy & Environmental Science 2014, 7(2), 617-620. 2. Dyatkin, B.; Gogotsi, Y., Effects of Structural Disorder and Surface Chemistry on Electric Conductivity and Capacitance of Porous Carbon Electrodes. Faraday Discussions 2014, 172. 3. Dyatkin, B.; Presser, V.; Heon, M.; Lukatskaya, M. R.; Beidaghi, M.; Gogotsi, Y., Development of a Green Supercapacitor Composed Entirely of Environmentally Friendly Materials. ChemSusChem 2013, 6 (12), 2269–2280. Figure 1

A Mastercurve to predict annual ryegrass (Lolium rigidum) seed devitalisation when exposed to multiple single sided impacts

A strategy to control herbicide resistant weeds is to use an impact mill to devitalise weed seeds as they exit a combine harvester. To model the impact milling of weed seeds, the milling response was split into material and machine functions separating the effect of seed properties from mill design and operational parameters. The material function was determined by subjecting annual ryegrass seeds ( Lolium rigidum ) to multiple single sided impacts using a rotational impact tester. The number of impacts, impact speed and seed moisture content were varied. Seed devitalisation was measured by germinating seeds in soil bins in a controlled environment room. Seed devitalisation increased with the number of impacts, the impact speed and decreasing moisture content. Seed devitalisation did not depend on the order of an impact sequence when exposed to multiple impacts at three different speeds. A threshold minimum energy per impact of 0.3991 kJ kg −1 (equivalent to ∼ 28 m s −1 ) was observed, below which almost zero devitalisation occurred. A material function Mastercurve for devitalisation was developed using this threshold energy level and one other material parameter which described a seed's resistance to fracture. The Mastercurve was able to accurately predict ( r 2 = 0.94) devitalisation of annual ryegrass seeds (11.3% m.c.) by the number of impacts above the threshold speed and impact speed in any impact sequence. The Mastercurve presented will be able to be used in future studies with a machine function to design impact mills to mechanically devitalise annual ryegrass seeds. • Seed devitalisation increased with impact speed and number of impacts. • Seed devitalisation reduced with moisture content. • Mastercurve fit based on impact energy above minimum impact energy. • Minimum impact energy for seed devitalisation was 0.3991 kJ kg −1 or 28 m s −1 .