High-energy Milling Process Research Articles

Effects of Various Hybrid Carbon Matrices on the ZnSe Composite Anode for Lithium-Ion Batteries.

Zinc selenide-based hybrid carbon composites were synthesized by a high-energy mechanical milling process under an Ar atmosphere. The as-synthesized ZnSe-based carbon composites were characterized by X-ray diffraction and transmission electron microscopy. First, we examined the effect of single-component carbon matrices on the electrochemical performance of ZnSe. The results showed the best performance for graphite (G), followed by carbon nanotubes (CNTs), and amorphous carbon. Based on these results, in order to further enhance the performance of ZnSe, we introduced a binary-carbon matrix consisting of graphite and CNTs at various ratios of 1:1, 1:3, and 3:1, respectively. As a result, ZnSe©G/CNT (1:3) exhibited the best performance in terms of cyclic life and rate capability. Specifically, ZnSe©G/CNT (1:3) delivered a specific capacity of 1041 mAh g-1 at a current density of 100 mA g-1 after 300 cycles with a coulombic efficiency of over 99% with high rate performance.

Development of dense Al2O3–TiO2 ceramic composites by the glass-infiltration of porous substrates prepared from mechanical alloyed powders

In this work bio-composites were obtained by infiltrating porous alumina–titania (Al2O3–TiO2) substrates with a lanthania-rich (La2O3) glass. Al2O3–TiO2 substrates were fabricated using high-energy milled powder mixtures of two different compositions with molar ratios of 3:1 and 1:1, uniaxial compaction under 100 MPa and sintering at 1300 °C - 2 h or 1400 °C - 2 h. The high energy milling process of the powders resulted in homogeneous, extremely fine mixtures. For comparison, as-received Al2O3 and TiO2 powders were also mixed at a proportion of 3:1 and sintered at 1600 °C - 2 h. The sintered substrates presented α-Al2O3 and β-Al2TiO5 (aluminium titanate) as crystal phases and relative densities ranging between 65.5 ± 2% and 69.4 ± 1.2% of the theoretical density. These porous substrates were infiltrated with a lanthania containing glass at a temperature of 1140°C-2h. The resulting ceramic composites exhibited high density, varying between 94 to 99% of the theoretical density, Vickers hardness ranging between 895 ± 14 HV and 1036 ± 33 HV, fracture strength ranging between 218 ± 28 MPa and 254 ± 18 MPa and a fracture toughness (KC) higher than 2.6 MPam1/2. Phase analysis of the infiltrated substrates by X-ray diffraction indicated the decomposition of aluminium titanate into alumina and titania besides the formation of lanthanum borosilicate, LaBSiO5. In addition, all compositions studied presented non-cytotoxic behaviour and low chemical solubility, inferior to 75 μg/cm2.

Effect of Milling Speed and Time on Ultrafine ZnO Powder by High Energy Ball Milling Technique

The particle size of commercial zinc oxide (ZnO) powder has been found in micron scale. For the improvement of ZnO properties, size reduction in nanoscale is required. In this work, the particle size of ultrafine ZnO powder was reduced by high energy ball milling technique. commercial grade ZnO powder with average size 0.8 μm was used as starting material. Milling speed and time of high energy milling process are considered as crucial parameters affecting size reduction of ZnO particles. Crystalline structure, surface morphological and particle size of the milled samples were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and particle analyzer, respectively. The results suggested that ZnO patterns after milling process with various milling speed and time were identically in hexagonal crystalline phase affirmed by XRD result. SEM images indicate that size of ZnO products distinctly decrease according to the increase of milling time and speed. ZnO particle size after milling process was found in ultrafine power in range of 200-400 nm. These results suggest that particle size of the commercial ZnO powders can be effectively minimized to few hundred nanometer range depending on force attraction and suitable rotation during milling process with specific speed and time. Moreover, the significant milling parameters will be studied to find the optimum condition for the production of ZnO particles in nanoscale.

Application of Al2O3/AlNbO4 in the oxidation of aniline to azoxybenzene

Al2O3/AlNbO4 powder was fabricated by a facile high-energy milling process. The precursor materials, Al2O3 and Nb2O5, are readily available and have very attractive properties. Moreover, the catalytic activity of the sample in the liquid phase oxidation of aniline (OA) in the presence of hydrogen peroxide as oxidant was evaluated. The catalyst was found to be highly efficient and selective in the oxidation of aniline to azoxybenzene under mild conditions. When mixed with 28% AlNbO4 the alumina-based catalyst achieved high conversion and selectivity and very similar to the pure Nb2O5.

Recycling Chips of Stainless Steel Using a Full Factorial Design

The aim of this study was to provide an experimental investigation on the novel method for recycling chips of duplex stainless steel, with the addition of vanadium carbide, in order to produce metal/carbide composites from a high-energy mechanical milling process. Powders of duplex stainless steel with the addition of vanadium carbide were prepared by high-energy mechanical ball milling utilizing a planetary ball mill. For this proposal, experiments following a full factorial design with two replicates were planned, performed, and then analyzed. The four factors investigated in this study were rotation speed, milling time, powder to ball weight ratio and carbide percentage. For each factor, the experiments were conducted into two levels so that the internal behavior among them could be statistically estimated: 250 to 350 rpm for rotation speed, 10 to 50 h for milling time, 10:1 to 22:1 for powder to ball weight ratio, and 0 to 3% carbide percentage. In order to measure and characterize particle size, we utilized the analysis of particle size and a scanning electron microscopy. The results showed with the addition of carbide in the milling process cause an average of reduction in particle size when compared with the material without carbide added. All the four factors investigated in this study presented significant influence on the milling process of duplex stainless steel chips and the reduction of particle size. The statistical analysis showed that the addition of carbide in the process is the most influential factor, followed by the milling time, rotation speed and powder to ball weight ratio. Significant interaction effects among these factors were also identified.

Facile and scalable synthesis of SiOx materials for Li-ion negative electrodes

Amorphous SiO materials are considered to be alternative high-capacity anode materials for Li-ion batteries. However, the conventional preparation method is a high-temperature and energy-consuming vacuum process. In this study, a simple strategy to produce a SiOx material is proposed. Low-cost micron-sized Si and amorphous SiO2 powders are mechanochemically mixed using a high-energy mechanical milling process. As a result, SiOx materials are produced that have the potential to replace the current commercial SiO powders. The X-ray photoelectron spectra exhibit that the chemical bonding state of Si in the synthesized SiOx materials is similar to commercial SiO. The electron microscopic analyses demonstrate that the secondary particle sizes are reduced and Si crystallites with sizes of a few nanometers to a few tens of nanometers are embedded in the silicon oxide matrix. Due to the morphology and microstructure, the initial coulombic efficiency and cycling stability of the SiOx materials are greatly improved compared to the commercial SiO sample. To further enhance the electrochemical properties, carbon incorporations are carried out, which result in an excellent cycle performance being achieved for the Li-ion battery anodes. The ball-milled SiOx material has ample potential as an alternative to conventional SiO materials.

Effect of ball milling on the powder characteristics and welding mechanism of Mg2B2O5w/6061Al matrix composite

Mg2B2O5w/6061Al matrix composites were fabricated through the powder metallurgy (PM) technique. The morphology of the particles, particle size and the effect of powder characteristics on densification behavior of the compacted samples were investigated. It was found that milling way, milling time, milling speed and whisker content all had different effects on powders characteristics and densification. During the low-energy milling process, the particles morphology changed from spherical to flattened shape and the reinforcement accelerated the process to some extent; during the high-energy milling process, the particles experienced the welding-fracturing process, the Al particles morphology changed from spherical to flattened shape and then back to more equiaxed morphology, the reinforcement whisker apparently accelerated the milling process. During the uniaxial cold pressing process, the particles after high-energy milling achieved better densification, the reverse for the low-energy milled powders because of whiskers clusters. A good linear correlation coefficient was obtained when the experiential data were fitted by the Panelli and Ambrosio Filho equation.

Zn-induced synthesis of porous SiOx materials as negative electrodes for Li secondary batteries

Silicon oxide-based materials for Li-ion battery anodes have attracted extensive attention due to their higher capacity than graphite materials and better cycling performance compared to Si-based materials. However, the cycle performance needs to be further enhanced if they are to be widely used in commercial applications. In this study, we propose a simple strategy to prepare porous SiOx materials. Zn and SiO were combined by a high-energy mechanical milling process. The Zn/SiO composite was then heated to 900 °C and the Zn-based materials were removed by evaporation as Zn is a metal with a relatively low melting point (419.5 °C) and boiling point (907 °C). This process resulted in the production of porous SiOx materials with a large number of mesopores. Characterizations of the materials by X-ray diffraction analysis, X-ray photoelectron spectroscopy, and electron microscopy confirmed the synthesis of porous SiOx materials. The cycling performance of these materials was found to be improved. Carbon incorporation was performed in an effort to further enhance their performance, and the cycling performance of these porous SiOx/C composite materials was considerably enhanced, thus indicating that the strategy involving both a porous structure and carbon incorporation is very effective for improvement of the cycling stability of Li-alloy-based active materials.

The influence of mechanical activation process on the microstructure and mechanical properties of bulk Ti2AlN MAX phase obtained by reactive hot pressing

Abstract The effect of mechanical activation process on the microstructure and mechanical properties of bulk nanostructured Ti2AlN compound has been investigated in this work. The mixture of Ti and AlN powders was prepared in a 2:1 molar ratio, and a part of this powder was subjected to a high-energy milling process under argon atmosphere for 10 h using agate as grinding media. Finally, the densification and formation of the ternary Ti2AlN MAX phase through solid state reaction of both unmilled and milled powders were carried out by hot pressing under 15 or 30 MPa at 1200 °C for 2 h. The microstructure of precursor powder mixtures and the consolidated samples was characterized by using X-ray diffraction (XRD) and a scanning electron microscope equipped with an energy dispersive X-ray spectroscopy (SEM/EDS). The X-ray diffraction patterns were fitted using the Rietveld refinement for phase quantification and to determine their most important microstructural parameters. Microstructure and mechanical properties of the consolidated samples were correlated with the load used for the hot pressing process. The substantial increase of hardness, the higher densification and the lower grain sizes observed in the samples prepared from the activated powders were attributed to the formation of second phases like Ti5Si3 and Al2O3.

Effect of milling process on particle size, morphology and magnetization in non-stoichiometric Fe2O3-MnO2.

High-energy milling process on ceramic material was analyzed, it process generate modifications on morphology and particle size, the process showed the last one relation with the crystallite size, about of structural analysis Rietveld refinement let identify anisotropy with the variations on crystalline planes and deformations occasioned by milling process, the particle size decrease with the process, similar tendency was observed on the images obtained by Scanning Electronic Microscopy, an result in this study was the variation on magnetization without chemical reaction under non-stoichiometric conditions and the agglomerates sizes observed on samples it is by process.

Effect of different calcination techniques on the morphologyand powder flowability characteristics of Rare-earth Zirconates (Re2Zr2O7; Re = La, Gd, Nd, Y) synthesized by solid-state high-energy milling process

Effect of different calcination techniques on the morphologyand powder flowability characteristics of Rare-earth Zirconates (Re2Zr2O7; Re = La, Gd, Nd, Y) synthesized by solid-state high-energy milling process

Enhanced performance of carbon-free intermetallic zinc titanium alloy (Zn-ZnxTiy) anode for lithium-ion batteries

A carbon-free intermetallic zinc titanium alloy (carbon-free Zn/Ti) anode, comprising active Zn nanoparticles finely dispersed in ZnxTiy (Zn0.6Ti0.4 and Zn3Ti) intermetallic buffer, is prepared via a thermal-treatment followed by a high-energy mechanical milling process for a lithium-ion battery (LIB) anode. As a counter-intuitive phenomenon, without the need of a carbon matrix, the carbon-free Zn/Ti alloy exhibits superior cyclic performance (∼1064 mAh cm−3 of volumetric capacity after 350 cycles), a good rate capability (85% capacity retention at 3 A g−1 compared to its capacity at 0.1 A g−1), and a high initial coulombic efficiency (88%). Although the use of hybrid TiC-C matrix as a control sample still affords highly stable cyclic performance and good rate capability, it exhibits a relatively lower capacity than a carbon-free alloy electrode. The enhanced performance of carbon-free Zn/Ti anodes for LIBs is owing to the presence of stable and cohesive ZnxTiy intermetallic phases that provide high conductivity and mechanical stability, thereby mitigating the large volume changes of Zn particles during the lithiation/delithiation processes. High-performance Zn-ZnxTiy can be seen as a new promising anode for the next-generation energy storage technology.

Physico-chemical, thermal, and rheological properties of nixtamalized creole corn flours produced by high-energy milling

High-energy milling (HEM) was used to produce nixtamalized corn flours, the traditional nixtamalization process was used as a control. Four creole grains were stone-milled, adjusted to an appropriate moisture content and calcium hydroxide concentration and milled using HEM. The physicochemical, thermal, and rheological characteristics of the flours and corn masas were affected by the HEM process. Negritas and Ahualulco creole grains nixtamalized by HEM showed similar viscosity profiles as a control. HEM reduced the gelatinization enthalpy compared to control and raw flours. Diffractograms showed changes in the crystalline structures and FT-IR demonstrated different regions for lipids, proteins, and carbohydrates in all control and treated grains. The texture of corn masas revealed significant differences according to the grain type. ESEM analysis showed smaller particles of HEM flours compared to those of the control. HEM could be a faster, non-pollutant, energy-saving, alternative nixtamalization process.

Microwave Assisted Synthesis and Powder Flowability Characteristics of Rare-Earth Aluminate (ReAlO3, Re = La, Gd, Nd, Y) Powders

ABSTRACTRare-earth aluminate (ReAlO3, Re = La, Gd, Nd, Y) powders were successfully synthesized from a mixture of Re2O3 (Re = La, Gd, Nd, Y) and Al2O3 powders using microwave assisted synthesis which consists of two steps: microwave heat treatment and high-energy milling process. X-ray diffraction, laser particle size analyzer, nitrogen adsorption technique (BET) and scanning electron microscopy were employed to study the phase composition, particle size and distribution, specific surface area and powder morphology. The results suggest that microwave assisted method led to a very rapid synthesis of ReAlO3 compared to conventional solid-state reaction process. The crystals produced by microwave assisted synthesis have a perovskite structure and the particle size distribution ranges from 3.6-51.5 µm. The present work demonstrates that rare-earth aluminates (ReAlO3) produced via microwave assisted synthesis have good powder flowability and is an ideal material for thermal spray coating process.

Mechanical Behavior of Multiwalled Carbon Nanotube Reinforced 7075 Aluminum Alloy Composites Prepared by Mechanical Milling and Hot Extrusion

In this paper, multiwalled carbon nanotubes (MWCNTs) were synthesized by spray pyrolysis to be used later as material reinforcement in the production of MWCNTs/Al7075 aluminum composites. Both, MWCNTs and MWCNTs/Al7075 composites were microstructurally and mechanically characterized. Scanning electron microscopy (SEM) analysis shows MWCNTs formed by multiple layers rolled on themselves forming a tube shape with lengths up to 1300 µm and diameters ranging from 55 to 120 nm. MWCNTs were added to the aluminum matrix in different concentrations up to 3.0 wt%. Their dispersion in the aluminum matrix was carried out by ultrasonic/methanol method followed by high-energy mechanical milling process. The effect of MWCNTs on the morphology and mechanical behavior of composites were evaluated. Results indicate that a homogeneous dispersion of CNTs was obtained as a consequence of the dispersion routes used in the production of composites, observing no damage on their morphology. The mechanical behavior of the composites shows a noticeable improvement for MWCNTs concentrations above 2.0 wt%, with ductility similar to that found in the literature for the Al7075 commercial alloy.

Magnesium silicide-derived porous Sb-Si-C composite for stable lithium storage

Porous Sb-Si-C composite materials were synthesized through two-step high-energy mechanical milling (HEMM) and chemical etching processes as an anode material for lithium secondary batteries. Sb2O3 and Mg2Si as starting materials were transformed into Sb, Si, and MgO phases after the first step of HEMM. Activated carbon was then incorporated into the composites during the second step of the milling. Finally, porous composites were synthesized by removing MgO through chemical etching. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, electron microscopy, and Brunauer–Emmett–Teller (BET) surface area measurement. The electrochemical lithiation and delithiation mechanism of the porous Sb-Si-C nanocomposite electrode was examined by using ex situ XRD analysis. Electrochemical test results demonstrated that the reversible capacity of approximately 450 mAh g−1 was maintained well after 200 cycles. This performance can be attributed to the porous structure and the amorphous carbon matrix for alleviation of volume changes during repeated Li+ insertion and extraction cycling.

The role of NaOH and papaya latex bio-activator during production of carbon nanoparticle from rice husks

This research explains the role of NaOH and bio-activator from papaya latex in the synthesis of carbon nanoparticles from rice husks in a water medium to produce fullerene-like polytype of SiC. The process begins with the pyrolysis and then the high energy milling (HEM) process followed by dispersion of NaOH and coagulation of bio-activator. The HEM process creates residual stress which produces nanocrack. NaOH dissolved into ions which activate dipole force to create dipole moment on the tip of nanocrack and become the trigger of nanocrack dispersion. The crack dispersion breaks carbon into nanoparticles having polar electrical charge so that they are dispersed homogeneously inside the water. Bio-activator then continues to perform catalytic building molecular chain as a bridge connecting pole sides of carbon nanoparticles with the bonds of van der Walls. Catalytic performance causes the coagulation process of a nanoparticle to occur which resembles the morphological structure of fullerene-like polytype of SiC with the size of 20 up to 100 nm.

Nanocomposite of Si/C Anode Material Prepared by Hybrid Process of High-Energy Mechanical Milling and Carbonization for Li-Ion Secondary Batteries

Si/C nanocomposite was successfully prepared by a scalable approach through high-energy mechanical milling and carbonization process. The crystalline structure of the milled powders was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Morphology of the milled powders was investigated by Field-emission scanning electron microscopy (FE-SEM). The effects of milling time on crystalline size, crystal structure and microstructure, and the electrochemical properties of the nanocomposite powders were studied. The nanocomposite showed high reversible capacity of ~1658 mAh/g with an initial cycle coulombic efficiency of ~77.5%. The significant improvement in cyclability and the discharge capacity was mainly ascribed to the silicon particle size reduction and carbon layer formation over silicon for good electronic conductivity. As the prepared nanocomposite Si/C electrode exhibits remarkable electrochemical performance, it is potentially applied as a high capacity anode material in the lithium-ion secondary batteries.

Synthesis of Nanoporous ZrTiO<sub>4</sub>, Ti<sub>2</sub>ZrO<sub>6</sub> Containing Ceramic Materials

Sol-gel technology allows the synthesis of powders and nanoporous materials with a complicated structure and morphology, improving the reactivity of the synthesized material. Nanoparticles of ternary oxide ZrO2-SiO2-TiO2 system have properties ascendant to those of the pure components. In the present work, the powders of the ZrO2-SiO2-TiO2 system were obtained by a sol-gel technology. The powder particles were homogenized with a high energy milling process for 1 or 6 hours. The acquired particles and nanoporous ceramic materials, after sintering at 800 OC and 1000 OC, were characterized by X-ray diffraction, particle size distribution, compressive strength tests, BET specific surface area and porosity analysis.

The role of Carica papaya latex and aluminum oxide on the formation of carbon nanofibre made of coconut shell

This research examines the role of bio-activator, papaya latex in the synthesis of nanoporous carbon fibre made of the coal of coconut shell with aluminum oxide. The porous carbon was generated from coal activated by the papaya latex at the temperature of for 4 h. The high energy milling (HEM) process up to 600 thousand cycles was applied to the porous carbon added with a precursor of aluminum oxide. The size and morphology of the particle are analyzed using SEM and TEM while the molecular group and the particle crystallization are analyzed with FTIR and XRD. The results show that papaya latex plays an effective role in breaking down the oxygen atoms in carbonyl group on the surface of carbon particle and in aluminum oxide. The oxygen breakdown creates pores in carbon particle and active site on the aluminum oxide. When the HEM is applied, the porous carbon particle breaks into fullerene-like nanoparticle whose yield is high and spontaneously connects the aluminum oxide as intercalation of particle whose structure turns into dimer (bucky-ball) in the form of carbon nanofibre.