High-energy Milling Research Articles

Analysis of Structure, Morphology, Magnetic Properties, and Microwave Absorption of Lanthanum Orthoferrite (LaFeO3)

LaFeO3 has been prepared using the solid-state reaction method with High Energy Milling (HEM). The preparation of LaFeO3 was carried out using stoichiometric calculations. Based on the XRD measurement results, single-phase LaFeO3 with an orthorhombic crystal structure was obtained. From the SEM results, the morphology of LaFeO3 is uniform, and the EDS results show the weight percentage of La, Fe, and O elements are 49.74, 21.08, and 29.18 wt%, respectively. VSM LaFeO3 results show magnetic saturation, remanence, and coercivity are 0.24 emu/g, 0.02 emu/g, and 853.38 Oe, respectively, and the absorption of LaFeO3 is -7.40 dB at a frequency of 6.02 GHz with a LaFeO3 sample thickness of 1.5mm.

Mechanical Processing with Solid-State of Supercapacitor Materials: A Review of High Energy Milling and High Velocity Particle Methods

Supercapacitors have emerged as a crucial energy storage technology, bridging the gap between traditional capacitors and batteries. The performance of supercapacitors is heavily dependent on the properties of the electrode materials used. Mechanical processing methods, particularly High Energy Milling (HEM) and High-Velocity Particle (HVP) methods have shown great promise in enhancing the physical and electrochemical properties of supercapacitor materials. This review explores the fundamental principles, mechanisms, and recent advancements in HEM and HVP techniques for the synthesis and modification of supercapacitor materials. High energy milling, including ballmill and attritor milling, facilitates particle size reduction, increased surface area, and the creation of nanostructures, leading to improved capacitance and energy density. High velocity particle methods, such as cold spraying and thermal spraying, enable the deposition of uniform and dense coatings, enhancing conductivity and stability. The review also discusses the impact of process parameters on material properties, the challenges faced in scaling up these techniques, and the potential future directions for research. By providing a comprehensive overview of these mechanical processing methods, this paper aims to highlight their significance and potential in advancing supercapacitor technology.

Microstructure, Mechanical and Tribological Properties of Cu40Zn-Ti3AlC2 Composites by Powder Metallurgy

The exploration of unleaded free-cutting Cu40Zn brass with excellent mechanical and tribological properties has always drawn the attention of researchers. Due to its attractive properties combining metals and ceramics, Ti3AlC2 was added to Cu40Zn brass using high-energy milling and hot-pressing sintering. The effects of Ti3AlC2 on the microstructure, mechanical and tribological properties of Cu40Zn-Ti3AlC2 composites were studied. The results showed that Ti3AlC2 could suppress the formation of ZnO by adsorbing oxygen impurity and promote the formation of the β phase by releasing the β-forming element Al to the substrate. The hardness and wear resistance of Cu40Zn-Ti3AlC2 composites increased with increasing Ti3AlC2 content from 0 to 5 wt.%. The proper Ti3AlC2 additive was beneficial to both the strength and plasticity of the composites. The underlying mechanisms were discussed.

Demonstrating the Simplicity and In Situ Temperature Monitoring of the Mechanochemical Synthesis of Metal Chalcogenides Suitable for Thermoelectrics.

Mechanochemical synthesis is an extremely useful strategy to reach thermoelectric materials due to its solvent-free one-step character, as the targeted thermoelectricity (TE) materials in a nanocrystalline format can be prepared by mere high-energy milling of elemental precursors. Nevertheless, the subsequent densification method (e.g., spark plasma sintering or hot pressing) is required afterward, similarly to other synthetic methodologies. In this study, the simplicity of mechanochemical synthesis ispresented for two selected metal chalcogenides, namely copper sulfide (Cu1.8S, digenite) and tin selenide (SnSe, svetlanaite), which are known for high ZT values. These compounds can be prepared via a mechanically induced self-propagating reaction (MSR), which is a combustion-like process instantly yielding the products in a very short timeframe (within 1 min). The occurrence of MSR can be well-tracked by in situ temperature monitoring since an abrupt temperature increase occurs at the moment of MSR. We have developed a device which is capable of monitoring the temperature inside the milling jar every 80 ms during planetary ball milling, and it is therefore possible to very precisely track the moment of MSR ignition. The developed device presents an improvement in the monitoring capabilities in comparison with commercially available analogs. This contribution aims to provide a visual insight into all steps, with simple high-energy ball milling of elements to reach TE materials and in situ temperature monitoring being the central points.

Comparative study of microstructure and mechanical properties of Mg/B4C composites: Influence of sintering method and temperature

This present work compares the effect of heating methods including microwave and spark plasma sintering (SPS) process on the microstructure and mechanical properties of Mg–B4C. 5 wt%B4C mixed with Mg powders through high-energy mixer mill for 10 min at ethanol media. After mixing, the green bodies were prepared by uniaxially pressing the mixture. The microwave heating was done at sintering temperatures of 600, 650 and 700 °C without soaking time in graphite bed. While, in the case of SPS, the mixture of the powders was directly inserted into a graphite mold and sintering process was performed at 450 °C with initial and final pressures of 10 and 30 MPa at vacuum condition of 17 Pa, sequentially. The corresponding XRD patterns revealed Mg and B4C crystalline phase alongside the reaction product of MgB2 and also MgO byproduct. The FESEM investigations depict uniform distribution of B4C reinforcements at the Mg matrix. Moreover, increasing microwave sintering temperature led to decreasing pores at the microstructure of the prepared sample. The microstructure of SPSed sample revealed almost full densification compared to that of the microwave processed samples at all the sintering temperatures applied. Also, The XPS results show the presence of Mg, O, C and B elements on the surface of prepared composite, and HRTEM with HAADF-STEM images were obtained to study the interface of matrix and reinforcement. The highest bending strength and Vickers hardness of 116 ± 6 Hv and 231 ± 11 MPa were obtained for SPSed sample as well as for the highest relative density. Although the microwave sample was sintered at 700 °C at low pressure, sintering method demonstrated considerable mechanical properties in comparison to SPSed specimen, indicating a successful preparation method as a low-cost, energy- and time-saving process.

Exploring a New, Scalable Synthesis Route to Disordered Rock Salt (DRX) Cathode Materials

The global demand for lithium-ion batteries (LIBs) is ever-increasing as many nations seek to achieve a net carbon neutrality by the late 2030s. LiNi x Mn y Co1–x–y O2, (NMC) is one of the most widely-used Li-ion cathode active materials. Despite its excellent performance (e.g., reversible capacities up to ~220 mA h g–1 and 500+ cycles), NMC contains both Ni and Co, which are expensive and have vulnerable supply chains. Li-excess disordered rock salt (DRX) materials are promising new cathode materials that utilize earth-abundant transition metals such as Mn and Ti. Through a combination of cationic and anionic charge compensation, DRX materials can attain specific energies ≥700 Wh kg–1. Doping F– into the DRX structure (Li1+x Mn y Ti2–1–x–y O2–z F z ) has been reported to improve the material’s cycling stability. Despite their promising properties, most DRX cathodes are prepared through solid-state synthesis routes which require high-energy milling, provide little-to-no control over the particle morphology, and are difficult to scale.In this work, we developed a scalable combustion synthesis route (the glycine nitrate process) to produce high purity, high performance DRX cathodes. More specifically, we prepared two DRX precursors with nominal compositions of Li1.2Mn0.5Ti0.3O1.95 and Li1.2Mn0.7Ti0.1O1.85. When the precursors were heated under Ar to 1000 °C for 1 – 4 h, only 50% Li1.2Mn0.5Ti0.3O1.95 adopted a DRX structure, and no DRX formed for Li1.2Mn0.7Ti0.1O1.85. However, adding LiF to the precursors facilitates DRX phase formation during annealing and yields high purity DRX powders with the nominal compositions Li1.25Mn0.5Ti0.3O1.95F0.05 and Li1.35Mn0.7Ti0.1O1.85F0.15. In situ X-ray diffraction was employed to study the synthesis process, revealing DRX begins to form at just 600 °C, which is much lower than traditional solid-state routes. Furthermore, electrochemical tests on the Li1.35Mn0.7Ti0.1O1.85F0.15 cathode reveal these materials attain excellent performance with initial reversible capacities up to 215 mA h g–1 and stable cycling performance. These promising results demonstrate that combustion synthesis is a viable method for the scale-up of DRX materials.This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and was sponsored by the Vehicle Technologies Office (VTO) under the Office of Energy Efficiency and Renewable Energy (EERE). Some measurements were conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.

Neutron shielding performance of Cd/316L composite fabricated by arc plasma sintering

Ensuring subcriticality over storage duration, even in accident condition, is one of the important requirements for dry cask designed to store spent fuel from nuclear reactor. To comply this requirement, neutron absorbers are incorporated in the spent fuel basket to decrease the neutron multiplication factor and reactivity. The objectives of this study are to prepare Cd/316L composite for neutron absorber material by powder metallurgy and determine the neutron shielding performance of the obtained composite. Powder mixtures of SS316L with various Cd contents were milled using high energy milling, followed by pressing and sintering at 450 °C and 700 °C. The analyses of the samples were carried out using XRD, SEM-EDS, XRF, and neutron transmittance test. Additionally, the neutron transmittance was also calculated using MCNP5. The results show that transformation of austenite to α-ferrite occurred during powder milling process which remained in the sample after sintering at 450 °C. Transformation of α-ferrite in the milled sample to austenite occurred after sintering at 700 °C. Cd in the samples were predominantly oxidized to form CdO phase during sintering process at both temperature conditions. The loss of Cd content in the Cd/SS316L samples after milling process was approximately 10 %. The Cd content further decreased by approximately 10 and 50 % after sintering at 450 and 700 °C, respectively. Neutron transmittance test shows that the transmittance value for thermal neutron decreased with the increased of Cd in the Cd/316 sample. A good agreement has been obtained between the results from experiment and MCNP calculation.

The Influence of High-Energy Milling on the Phase Formation, Structural, and Photoluminescent Properties of CaWO4 Nanoparticles.

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet-visible (UV-Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method.

Study on Energy Transfer Mechanism of Grinding Balls in a Planetary Ball Milling System

Planetary ball milling systems (PBMSs) have become novel and high-energy milling equipment with wide applications. The present study explores the energy transfer mechanisms of grinding balls in these systems. A theoretical model has been developed by considering essential factors such as the diameter of the grinding balls and milling conditions, based on previous models and molecular dynamics simulations. To validate and improve the theoretical model, experimental data was collected by examining the impact of different grinding ball diameters on the change in copper powder particle size under controlled milling conditions. The mechanisms under particle size changes have been revealed, providing a deeper understanding of energy transfer in PBMSs and establishing a direct connection between the grinding ball diameter and the particle size of the resulting product. This research method makes it possible to predict the particle size and performance of the ball-milled product.

Characterization of the microstructural, magnetic, and thermal behaviors of boron-doped Fe–Co–Ni alloys produced via mechanical alloying

FeCoNi alloys, both doped and undoped, were synthesized into nanocrystalline forms using a high-energy mechanical milling technique. The study used the x-ray diffraction technique to examine the microstructure characteristics of powder materials. The identified patterns were examined using Maud software. It was found that mechanical alloying produced solid solutions with BCC and FCC structures and crystallite sizes in the range of 25 nm after 100h of milling. The BCC-Fe(Co,Ni,B) and orthorhombic-Fe3B phases were refined for the alloy doped with amorphous boron, while only the bcc-Fe(Co,Ni,B) phase was identified for the alloy doped with crystalline boron. Meanwhile, the FeCoNi alloy revealed a mixture of FCC-Co and BCC-FeCoNi phases. This sample has a soft ferromagnetic behavior, whereas the doped ones have hard ferromagnetic behaviors. The squareness ratios (Mr/Ms) are typically low. The microstructural variations were associated with magnetic characteristics. The thermal stability of the alloyed powder mixtures was investigated by the DSC technique from 25 to 700 °C for 2h. The alloyed samples were first annealed at selected temperatures and then analyzed using x-ray diffraction. The obtained x-ray diffraction results proved that at temperatures below 230 °C, the initial heavy deformed structure’s structural relaxation followed by the recrystallization of the fcc-Co phase and, at higher temperatures, the recrystallization of new phases, such as α-FeCo, fcc-FeNi, fcc-Ni3Fe, and borides of the (FeNi)23B6, -(FeCo)23B6 types. The stability of the crystalline phases that are formed and their magnetic characteristics can be regulated through a carefully calibrated annealing process.

Pozyskiwanie złota ze słowackiego koncentratu przy użyciu innowacyjnej metody

The complicated processing of concentrates with low gold content and the long-time use of non-ecological methods was the motion for finding a more efficient process for this noble metal obtaining. From this point of view, this research was focused on obtaining of nano gold from the concentrate White Hill (Detva, Slovakia) using mechanical activation and mechano-biological activation in a molecular hydrogen solution. Gold in this complex concentrate occurs physically enclosed in the intercrystalline space of minerals and is also isomorphic and fills defects in their structure. The exclusion of gold from such complex mineral matrixes of the concentrate can be achieved using a mechano-biological process. This innovative method for obtaining of nano gold with the application of a molecular hydrogen solution is an advantageous alternative to the non-environmental reagents used. Compared to the most used worldwide toxic cyanide reagent, a solution with molecular hydrogen represents a low-cost and above all completely harmless reagent with very good kinetics. Mechanical processes use high-energy milling, which has an effect on the more intensive formation of surface and bulk defects in solid substances. The main advantage of mechanical processes is a smaller number of technological operations, a shorter time required to obtain the desired product at favorable environmental temperatures, and also the formation of nanostructures. The use of a biological process with the application of limnetic algae showed that algae with siliceous structures make it possible to obtain gold from the White Hill concentrate with nanoscale size. Limnetic algae (diatoms, golden algae) are part of aquatic ecosystems and create the largest matter of biomass from all plants on the Earth. The mechano-biological process is a method that enabled to obtain of gold nanoparticles with an average size of 100 nm from the Slovak gold-bearing concentrate from the White Hill deposit (BV-1). Mechanical activation of this concentrate and siliceous shells of the specified limnetic algae (Dinobryon, Surirella) in a molecular hydrogen solution caused changes in the physical-chemical properties of gold minerals as well as in the constituents of algae minerals. These structural changes had a decisive influence on the exclusion of gold nanoparticles into the molecular hydrogen solution under the defined reaction conditions. The gold nanoparticles were subsequently fixed in the cellular matrix of mechanically activated algae shells. The explanation of this phenomenon was the action of biomolecules, which the algae cells secreted in the course of reactions with metal ions present in the molecular hydrogen solution. Gold nanoparticles from the investigated concentrate were obtained by a new mechano-biological procedure already for four hours. In the case of mechanical activation of the concentrate, but without activation of the used algae, gold nanoparticles were excluded after sixteen hours. It follows from this knowledge that the application of an absolutely ecologically harmless aqueous solution enriched by molecular hydrogen and the use of limnetic algae confirmed the suitability of the innovative method for obtaining of nano gold from the concentrate. From the achieved research results significantly more effective kinetics is evident in the case of activated algae. Nanoparticles of gold obtained by the mentioned procedure can have important practical utilization, such as accelerating of the decomposition of dangerous substances or neutralizing pollutants in contaminated water, soil, and air. Simultaneously, obtaining of gold nanoparticles would also be beneficial for removing algae from the aquatic environment, where they are very dangerous for all living organisms.

Insights into the mechanochemical synthesis of nanostructured PbTe: The role of structural defects

Mechanochemical synthesis of nanostructured PbTe, adding isopropyl alcohol during milling, is promoted by the presence of structural defects such as edge dislocations, amorphous zones, grain boundaries, among others. High-resolution transmission electron microscopy observations revealed that the nanostructured PbTe formation is fundamentally dependent upon crystalline imperfections during the high-energy milling process. Even though defect-dependent mechanisms rule the formation of nanostructured PbTe, oriented-attachment mechanism is also traced and contributes to the PbTe formation. Hence, experimentally, isopropyl alcohol is a key parameter for the mechanochemical synthesis of nanostructured PbTe.

Predicting the thermoelectric figure of merit in p-type BiSbTe-based alloys using artificial neural network modeling

The polycrystalline Bi0.5Sb1.5Te3 compound has drawn promising thermoelectric material over the decades with a figure of merit (zT) close to unity and numerous experiments have been conducted through a trial-and-error approach to further improve their zT by tuning the chemical composition and processing approaches. Despite a lot of studies available on BiSbTe alloys, choosing the right combination of alloy system with high zT is still a challenging task. Herein, we produced a p-type Bi0.5Sb1.5Te3 alloy through casting followed by high-energy milling to enhance the zT via reducing thermal conductivity. The experimental results revealed that a peak zT of 0.95 was achieved at 300 K due to a substantial reduction in thermal conductivity via enhanced carrier/phonon scattering at refined grain boundaries. In addition to the current scenario, the machine learning (ML) assisted artificial neural network (ANN) modeling was performed to predict the zT value by applying the composition, electrical conductivity, Seebeck coefficient, thermal conductivity, and temperature as the input parameters. The predicted zT by ANN modeling shows excellent accuracy with experimental findings about an average absolute error of 9.34 %. Therefore, the developed ANN modeling shows a protocol for composition-based prediction of zT with reduced experimental costs, time consumption, and excellent accuracy in terms of the theoretical and experimental databases.

Mechanical Alloying and Concentration Quenching of the Luminescence of Pr3+ Ions in Chalcogenide Glass

The disadvantage of chalcogenide glasses containing rare earth ions as luminescent materials for the IR optical range is the strong concentration quenching of luminescence due to the non-uniform distribution of rare earth ions in the glass matrix. This study investigates the effect of grinding chalcogenide glass containing Pr3+ ions in a planetary ball mill on its luminescent properties in the near-IR range, as well as its optical properties and structure. The results indicate that milling, under certain conditions, leads to a decrease in the concentration quenching of the luminescence of Pr3+ ions. This finding suggests that milling can be used in the development of glassy materials with the increased efficiency of luminescence of rare earth ions. However, it is essential to consider that high-energy milling may result in the formation of areas with increased pressure in the obtained material, leading to structural changes in the glass.

Structural and Magnetic Properties of Barium-Strontium-Hexaferrite Material Ba0.6Sr0.4Fe10-xCoxMnTiO19 (x = 0.5; 1.0; and 1.5) as Microwave Absorbers

We discuss the structure properties of Ba0.6Sr0.4Fe10-xCoxMnTiO19(BSFCMTO) for x = 0.5, 1.0, and 1.5 that influence its magnetic properties as a microwave absorber. A solid-state reaction method using high-energy milling was used to synthesize hexaferrite. There were no structural changes when the Co2+ ion was substituted for the Fe3+ ion; the structures of all samples were hexagonal and the space group was P63/mmc. The surface morphology had heterogeneous particles with a size of 300 to 600 nm. The magnetic properties tended to decrease with an increasing number of Co2+ ion substitutions. The reflection loss (RL) had a minimum value of -14.89 dB. This value was reached at a frequency of 10.96 GHz and had a bandwidth at 1.24 GHz with a sample thickness of 1 mm in the Ba0.6Sr0.4Fe9.9Co0.1MnTiO19 sample.

Temperature-dependent structural and magnetic properties of mechanically alloyed Ni80Co17Mo3 powder mixture

Nanostructured materials containing nickel improve the effectiveness of several applications. This study examines the preparation and characterization of nanostructured Ni80Co17Mo3 alloy powders using high-energy mechanical alloying and subsequent annealing. A 72 h milling process used pure elemental powders to synthesise nanocrystalline FCC-NiCo(Mo) solid solution. The milled powders were then subjected to annealing at different temperatures:300°C, 500°C, and 750°C. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and vibrating sample magnetometry indicated significant changes in the powdered alloy properties. The particles growth occurred as the annealing temperature increased, while the microstrain decreased significantly; 14.30±0.07 nm up to 56.30±0.28 nm and 0.680±0.003% up to 0.180±0.001%, at 25°C and 750°C respectively. SEM analysis revealed differences in particle size and shape as milling progressed. Surprisingly, the milled powdered alloy displayed improved magnetic properties, manifesting significant magnetic susceptibility and enhanced saturation magnetisation, remanent magnetisation, and coercivity within the temperature range of 300°C to 750°C. These findings indicate the development of a consistent and structured state, accompanied by significant crystal growth due to the annealing temperature. This study highlights the great importance of high-energy mechanical milling and subsequent annealing to tune / tailor the characteristics and subsequently investigate the potential utilization of nanostructured Ni-based alloys.

Transport properties of mechanochemically synthesized copper (I) selenide for potential applications in energy conversion and storage

This work studied the thermal stability, electrical, and thermoelectrical properties of copper(I) selenide, Cu2Se synthesized by high-energy milling in a planetary ball mill. The phase composition was investigated by X-ray powder diffraction analysis and scanning electron microscopy. The conversion of the precursors during mechanochemical synthesis and the stability of the product was monitored by thermal analysis. The dependence of electrical properties on the product porosity was observed. For the densification of Cu2Se, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric characterization. High-temperature thermoelectric properties of synthetic Cu2Se were compared to its natural analogue-mineral berzelianite in terms of its potential application in energy conversion. Based on the results a relatively high figure-of-merit, ZT parameter (~ 1.15, T = 770 K) was obtained for undoped Cu2Se, prepared by rapid mechanochemical reaction (5 min). Cyclic voltammetry measurements of Na/NaClO4/Cu2Se cell implied that mechanochemically synthesized Cu2Se could be used as a promising intercalation electrode for sodium-ion batteries.

Advancing room temperature NO2 gas sensing performance through high-energy mechanical milling of Tin-dichalcogenides

Eco-friendly gas sensing devices with simple architecture, reduced cost, and high performance at room temperature are being sought to replace the traditional metallic oxide materials, aiming to address environmental concerns. Lamellae semiconducting materials have shown promising detection properties for this purpose. Here, we investigated the sensing response of SnS2, Sn(S0.5Se0.5)2, and SnSe2 tin-dichalcogenides prepared by high-energy mechanical milling. High RNO2/Rair response signals, from 102 to 106, for 2–100 ppm of NO2 were observed for temperatures between 30 °C and 300 °C. The materials were not sensitive to CO, while H2 detection could only be observed above 200 °C, implying high NO2 selectivity. Additionally, we investigated the influence of samples suspension in water and isopropanol on grain size and morphology. We found that isopropanol crystallizes amorphous selenium phase dispersed in the Sn-Se system and increase the agglomeration in the Sn(S0.5Se0.5)2 system. Deformed and defective particles were observed regardless the preparation methodology. This unique defect-rich morphology might increase surface reactivity for selective NO2 detection by physisorption, owing a high adsorption/desorption rate at room temperature.

Resilient Si@C architecture fabricated by mechanochemical conjugation and thermal reduction for lithium storage: Simulation on interfacial state evolution

Synchronal comminution via high-energy bead milling not only efficiently pulverizes Si particles and exfoliates graphene oxide (GO) sheets but also facilitates Si surface functionalization and intensify Si-C conjugation. After a thermal reduction, a well-wrapped Si@C anode material can be fabricated for lithium storage. The discharge specific capacities of this Si@C composite sustain at 1110.3 mAh g−1 after 300 cycles at 1 A g−1 and 316.4 mAh g−1 for 800 cycles at 5 A g−1, which are respectively 1.35 and 2.07 times that of its random blended Si/C counterpart. By employing molecular dynamics (MD) simulations with ReaxFF reactive force field to investigate the mechanochemical reactions between Si and GO amidst high-energy milling, an atomic scale portrayal of Si crystal fragmentation and Si-C bonding can be depicted. Analyses focusing on the differential forces exerted on various Si crystal planes, coupled with potential energy (PE) trends, reveal a higher propensity for cleavage in (111) plane, with (311) plane followed. Radial distribution function (RDF) outcomes indicate that ball milling leads to substantial disruption of crystalline order in Si particles, generating a plethora of Si dangling bonds. This disruption stimulates the formation of SiOOC, SiOC and SiC bonds at the Si/C interface, thus enhancing the integration of GO with Si substrate. Subsequent thermal reduction processes not only restore the structural order of Si and GO but also consolidate Si/C bonding.

Porous Si/Ca-Si-O nanocomposite lithium storage materials by calciothermic reduction of Si with CaH2

Silicon monoxide (SiO)-based anode materials are one of the most intensively investigated class of materials for use as high-capacity anodes in lithium-ion batteries. However, their low initial Coulombic efficiency (ICE), resulting from the irreversible electrochemical reaction of the amorphous SiO2 (a-SiO2) phase in the SiO, restricts the wide-spread adoption of SiO-based anode materials in lithium-ion batteries. Pre-emptive formation of an irreversible phase that converts a-SiO2 to a non-reactive state with lithium prior to cell assembly has received much attention for enhancing ICE. However, this process has the drawback of not ensuring long-term cycle performance. Herein, the pre-emptive formation of irreversible phase combined with the high-energy mechanical milling (HEMM) process is proposed to simultaneously improve both the ICE and long-term cycle performance. The resulting porous Si/Ca-Si-O nanocomposite electrode exhibits an impressive ICE of 86.4 % and maintains 55 % of its capacity over 200 cycles. The key factor in the significant ICE improvement is the irreversible Ca-Si-O phase, which is formed by the calciothermic reduction of Si with CaH2. In addition, the microstructural changes induced by the HEMM process effectively mitigate the volume expansion of Si during cycling, resulting in improved long-term cycle stability.