Influence Of Mechanical Milling Research Articles

Advance processing of cluster-free CNT reinforced 6082 Al matrix nanocomposites: influence of mechanical milling and cryomilling

ABSTRACT In the present study, lightweight high-strength carbon nanotubes (CNTs) reinforced aluminium-based composite was fabricated through powder metallurgical processing. The effect of planetary milling and cryogenic assisted milling on the structure, morphology, mechanical properties, phase composition, and thermal stability of CNTs reinforced Al6082 Al nanocomposites powders was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM)- Energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and indentation techniques. The CNTs in the Aluminium (AL) matrix were distributed uniformly after 50 h of milling. Further, the cryomilling of 50 h milled Aluminium matrix composites (AMC) decreases agglomeration even more and was successful in cleaving the nanotubes as well as minimising entanglements. The broadening of diffraction peaks suggests a reduction in the crystallite size (from ~36 to ~20 nm) and an increase in induced strain. Milled powders were consolidated through the hot-press and spark plasma sintering technique. The mechanical properties of these AMCs were evaluated through indentation for hardness (>250 HV) and compressive testing techniques. SPSed samples reported better properties in comparison to hot-pressed samples. It is discovered that post-CM of Mechanical Milling (MM) powder aids in overcoming issues related to the agglomeration of Al/CNT composites, and the goal to fabricate tangle-free CNT reinforced composite was achieved. Moreover, it showed enhanced mechanical properties with a maximum yield strength of 210 MPa and good synergy between strength and ductility.

Al-Fe-Ni Metallic Glasses via Mechanical Alloying and Its Consolidation

In this paper, the influence of mechanical milling on the microstructural evolution and magnetic properties of Al82Fe14Ni4 alloys prepared by mechanical alloying is investigated. The elemental powder mixture was processed under argon gas at 250 rpm and 350 rpm using a planetary ball mill. The powder particles experienced severe deformation, fragmentation and mutually cold-welding during the collisions of the balls. The diffraction peaks of the Al, Fe and Ni phases gradually disappeared during the milling process, and a halo peak corresponding to the amorphous phase formed. The amorphization of powders milled at 250 rpm was slower than that of 350 rpm. These alloys achieved a fully amorphous structure after milling for 60 h. The amorphous powder alloy milled at 350 rpm exhibited higher thermal stability compared with that of an alloy milled at 250 rpm. The saturation magnetization and coercive of the milled Al82Fe14Ni4 alloy powder were decreased following the formation of a para-magnetic amorphous phase. The highest compressive strength, about 710 MPa, was obtained for the Al82Fe14Ni4 alloy sintered at 600 °C by SPS.

Influence of Mechanical Milling and Heat Treatment on the Properties of Bronze Powder

We have studied the influence of high-energy treatments on changes in the morphology, structure, phase composition, and (as a consequence) hardness of BrA 10 (DIN CuAl10Fe3Mn2) bronze powder particles. It has been shown for the first time that, independent of energy delivery rate during mechanical treatment of the powder, after the delivery of a given amount of energy the particles are similar in size, phase composition, and internal structure. Mechanical milling of the material leads to changes in particle shape, cleaning and activation of the particle surface, changes in the internal structure of the particles, and an increase in their hardness from 248 to 322 HV0.025. Unlike mechanical milling, heat treatment of the material leads to stress relieve, accompanied by a decrease in its hardness from 248 to 104 HV0.025.

Influence of mechanical milling on the hydrogen absorption properties of TiCrV – based alloys

The hydrogen economy is a concept focused on this element as a carrier of clean and cheap energy, one of the keys is the storage of this gas safely. In this sense, TiCrV-based alloys have great capacity to store hydrogen. In the present working studied the influence of the process of mechanical milling of high energy in the storage capacity of hydrogen of TiCr1.1 V0.9 alloy. The alloy was synthesized by arc fusion and manually crushed. The effects of mechanical milling were studied for periods of time of 1 hour and 3 hours at 300 revolutions per minute with a weight/weight ratio of the sample 10: 1. The x-ray diffraction analyzes revealed solid phase formation of body center cubic phase, characteristic of TiCrV base alloys, and formation of TiCr1.8H5.3 hydrides and TiH2 hydrides with orthorhombic structure and body center cubic, respectively. The hydrogen storage capacity of the TiCr1.1 V0.9 alloy decreased with the increase in grinding time. The reasons for the drop in hydrogen storage capacity are mainly two: contamination of the surface of the alloy powder and changes in the microstructure generated by the plastic deformation in the grinding process. However, an increase in absorption kinetics was observed at longer milling times because the surface area increases since the crystallite size decreases. This phenomenon can be explained by the catalytic effect produced by the decrease in the particle size of the samples. The differential scanning calorimetry analysis was able to determine that the TiCr1.8H5.3 hydride stored a greater amount of hydrogen and has a lower desorption temperature compared to the TiH2 hydride.

Synthesis and characterization of Sn reinforced Al-Cu-Fe quasicrystalline matrix nanocomposite by mechanical milling

The influence of mechanical milling (MM), primarily on microstructure and phase evolution in Al62.5Cu25Fe12.5 (at%) quasicrystalline (IQC) matrix reinforced with varying volume fraction of Sn has been investigated by means of X-ray diffraction (XRD), scanning & transmission electron microscopy (SEM and TEM) and differential scanning calorimetry (DSC) methods. It was observed that with increasing the milling duration, the IQC phase transforms to crystalline B2 phase [Al (Cu, Fe) and Pm3 m, a = 0.29 nm]. In SEM and TEM analysis, it was found that both IQC and Sn particles are refined during MM. The XRD and TEM results confirm the formation nanostructured matrix consisting of nanocrystalline B2 phase along with minor IQC phase reinforced with ultrafine grained Sn particles after 40 h of MM. The STEM-EDS results show a homogenous distribution of elements (Al, Cu, Fe). The Sn particles were immiscible in a matrix consisting of B2 and IQC phase as indicated by XRD and TEM investigations.

Exploring the suitability of milled fly ash for brake friction composites: characterization and tribo-performance

The present work investigates the usefulness of milled fly ash, prepared by 60 h mechanical milling of raw fly ash, for the application of brake friction composites. Two specimens were prepared by reinforcing 80 wt% of the raw and milled fly ash with 20 wt% of the phenolic resin. The influence of mechanical milling on the friction and wear performance of the developed raw fly ash composite (RFC) and the milled fly ash composite (MFC) specimens were investigated at varying sliding velocity from 2.6–10.4 ms−1 under 50 N and 150 N using wear and friction monitoring apparatus. It was revealed from the surface morphology of the milled fly ash powder that the large size spherically shaped particles turned in to small size rough shaped particles after ball milling. The average particle size of the raw fly ash reduced from 85.69 μm to 14.61 μm and the specific surface area of the milled fly ash increased by 7.3 times that of the raw fly ash. The tribo-study showed that the average friction coefficient of MFC was found to be noticeably higher than the RFC at all the sliding conditions except at 7.8 ms−1 and 150 N. The increase in sliding velocity increased the weight loss of RFC and MFC specimens at low and high loads. The friction performance of MFC was found encouraging but attention is needed towards decreasing the wear rate when using the milled fly ash for the development of brake friction composites.

Distribution control of AlN particles in Mg-Al/AlN composites

A new process for the preparation of ultrafine AlN particles reinforced Mg-Al matrix composites was proposed to control the agglomeration of ultrafine AlN particles. The influence of mechanical milling on the modification of reinforcement particles and the refinement of matrix alloy particles was also investigated. Particles barriers for uniform distribution into matrix grain interiors in P/M process were analyzed. For AlN-Mg mixture, AlN particles were separately cladded in Mg coating and homogeneously distributed in the mixture after milling for 15 h. Mg-Al matrix alloy particles were significantly refined after milling for 20 h, and the strip-type Al was fragmented and uniformly distributed in Mg matrix. There are three critical factors controlling the agglomeration of ultrafine AlN reinforcement in Mg-Al matrix. Finally a fully homogeneous intragranular distribution of AlN particles in Mg-Al matrix was obtained.

Influence of mechanical milling on structure, particle size, morphology and magnetic properties of rare earth free permanent magnetic Zr2Co11 alloy

In an effort to explore finding rare earth free permanent magnet material for device applications, the Co based Zr2Co11 compound has been selected for investigation. A detailed study was carried out on the effect of mechanical milling on structure, particle size, morphology and magnetic properties. The alloy of nominal composition Zr18Co82 exhibited co-existence of minor Zr6Co23 phase along with main phase Zr2Co11. When subjected to long duration mechanical milling, the alloy has undergone structural disorder leading to partial amorphization. The particle size has decreased from 200 μm to 120 μm up on milling for 6 h in a planetary milling process. Further milling caused less influence on particle size reduction. However, it had an effect on particle size distribution. The size reduction is not very high due to ductile nature of Zr2Co11 phase and the morphology of the particles too showed coarse plate shape. The coercivity variation against particle size reduction is less than appreciable, given that the crystal structure being rhombohedral with significant magnetocrystalline anisotropy. The defects induced during milling and the presence of deleterious minor phases are considered the main cause for reduction in the coercivity.

Syntesis of Niobium Nitride Using Cryogenic Milling

In the present paper a preliminary study was performed on the influence of mechanical milling on the synthesis of niobium nitrade. The niobium metal powder sample, passing # 635 mesh sieve, was processed by mechanical milling in SPEX mill for 8 hours using a ball-to-powder ratio of 7:1 and a nitrogen atmosphere. The powder was annealed at different temperatures, 900 °C, 1000 °C, 1100 °C and 1200 °C for 1 hour in a hydrogen and argon atmosphere to study their crystallization, which then were formed into blanks for analysis of the compressibility curves. These samples were also subjected to X-ray diffraction and the data were compared between the annealing temperatures. The compressibility curves of niobium samples with and without grinding were also evaluated, showing high compacting capacity. These samples were subjected to X-ray diffraction and X-ray fluorescence. As the formation of nitrides (Nb2N) was observed in SPEX type mill, the interest in studying the synthesis of nitrides came up, using mechanical milling in Attritor type mill. Same previous results of Attritor processing indicate a Nb2N and NbN synthesis after annealing treatments.

Effect of mechanical milling on nanocrystalline grain stability and properties of Cu–Al2O3 composite prepared by thermo-chemical technique and hot extrusion

In this study, an influence of mechanical milling on the structural characteristics, mechanical properties and electrical conductivity of the ultrafine Cu–3vol.% Al2O3 composite is analyzed. The initial Cu–Al2O3 powder was prepared by in situ thermo-chemical technique. Compared are two samples prepared by compacting of the non-milled and the intensively milled powder. The milling process ensured additional powder refinement and uniform distribution of secondary nano-particles in the Cu matrix. In the process of hot extrusion and annealing of the compact at elevated temperatures, the particles effectively strengthened crystallite/grain boundaries. Therefore, the composite has a homogeneous, thermal stable nanostructure up to 900°C, good hardness of 130HB and yield strength of 235MPa. The composite prepared from the non-milled powder is characterized by a bimodal grain size microstructure, low hardness of 80HB, lower yield strength of 185MPa and it is structurally stable only up to 200°C as a consequence of recrystallization processes and grain growth. The electrical conductivity of both materials is sufficient for electrotechnical applications.

Phase transformation of ZrO2 nanoparticles produced from zircon

This article focuses on the phase transformation of zirconia (ZrO2) nanoparticles produced from zircon using a bottom-up approach. The influence of mechanical milling and thermal annealing on crystalline phase transformation of ZrO2 nanoparticles was explored. It was found that the iron oxide, as an inherent impurity present in ZrO2 nanoparticles, produced from zircon stabilises the cubic phase after calcination at 600°C. The stabilised cubic phase of ZrO2 nanoparticles was disappeared and transformed into partial tetragonal and monoclinic phases after mechanical milling. The phase transformation occurred on account of the crystal defect induced by high-energy mechanical milling. The destabilisation of cubic phase into monoclinic phase was observed after the thermal annealing of ZrO2 nanoparticles at 1000°C. The phase transitions observed are correlated to the exclusion of iron oxide from the zirconia crystal structure.

Influence of mechanical milling on photocatalytic activity of g-C3N4 prepared by heating melamine

Using X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, ultraviolet-visible diffuse reflection spectra, and photoluminescence spectroscopy, the effect of mechanical milling on the photocatalytic activity of g-C3N4 photocatalyst was investigated. The rhodamine B, as a photodegrading goal, was used to evaluate the photocatalytic activity of g-C3N4. The experimental results indicate that the milling treatment is an effective method to improve the photocatalytic activity of g-C3N4. The enhanced photocatalytic activity was attributed to the improvement in catalyst’s surface area and dye adsorption on catalyst surface. Moreover, checking the luminescence properties of g-C3N4, it is found that the photocatalytic active sites on g-C3N4 are likely the same as luminescence sites.

The Formation of Nanocrystalline SrFeO<SUB>3−<I>δ</I></SUB> Using Mechano-Synthesis and Subsequent Sintering: Structural and Mössbauer Studies

The influence of mechanical milling and subsequent sintering of a 2:1 molar mixture of SrCO3 and alpha-Fe2O3 on the formation of SrFeO(3-delta) pervoskite-related nanocrystalline particles is investigated. The structural evolution during the formation process is systematically investigated using X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Pre-milling the mixture in air for 120 h leads to the incorporation of Sr2+ in the alpha-Fe2O3 crystal structure thus facilitating the formation of a 2:1 nanocrystalline mixture of SrFeO3 and SrFeO2.875 by sintering the pre-milled mixture in air at 800 degrees C (12 h). This temperature is approximately 300 degrees C lower than those at which SrFeO(3-delta) phases are synthesized by the conventional ceramic techniques. Pre-milling the precursors was found to result in a smaller oxygen deficiency (delta) relative to conventional ceramic synthesis of SrFeO(3-delta). Rietveld refinement of the X-ray diffraction shows the interatomic distances in the resulting SrFeO2.875 nanocrystalline phase to be slightly different from those of the conventionally prepared bulk leading, in turn, to a crystal structure with tilted polyhedral cationic sites. This structural distortion is related to both small-size and surface effects in the nanoparticles that have no counterparts in the corresponding bulk material. The surface structure of the attained SrFeO(3-delta) nanocrystalline particles shows a significant partial reduction of Fe4+ to Fe3+ due to ambient conditions and the presence of an appreciable amount of SrCO3 as well.

Influence of mechanical milling and thermal annealing on electrical and magnetic properties of nanostructured Ni-Zn and cobalt ferrites

The present article reports some of the interesting and important electrical and magnetic properties of nanostructured spinel ferrites such as Ni0.5Zn0.5Fe2O4 and CoFe2O4. In the case of Ni0.5Zn0.5Fe2O4, d.c. electrical conductivity increases upon milling, and it is attributed to oxygen vacancies created by high energy mechanical milling. The real part of dielectric constant (ɛ′) for the milled sample is found to be about an order of magnitude smaller than that of the bulk nickel zinc ferrite. The increase in Néel temperature from 538 K in the bulk state to 611 K on the reduction of grain size upon milling has been explained based on the change in the cation distribution. The dielectric constant is smaller by an order of magnitude and the dielectric loss is three orders of magnitude smaller for the milled sample compared to that of the bulk. In the case of cobalt ferrite, the observed decrease in conductivity, when the grain size is increased from 8–92 nm upon thermal annealing is clearly due to the predominant effect of migration of some of the Fe3+ ions from octahedral to tetra-hedral sites, as is evident from in-field Mössbauer and EXAFS measurements. The dielectric loss (tan δ) is an order of magnitude smaller for the nano sized particles compared to that of the bulk counterpart.

The influence of mechanical milling on the properties of W–40wt.%Cu composite produced by hot extrusion

Abstract In this paper, W–40 wt.%Cu composites with high density, fine microstructure, and good properties have been obtained by hot extrusion from the powders milled for different times. The experimental results show that a homogenous structure containing very fine tungsten phases embedded in copper is formed after milling. After extrusion, the density and specific conductance of the composites decrease and the hardness increases with the increase of milling time. After annealing at 800 °C for 2 h, the specific conductance of the composites decreases from 61% IACS to 44% IACS and the hardness increases from 215 to 255 HV with the milling time increases from 0 to 10 h.

The influence of mechanical milling on structure and soft magnetic properties of NiFe and NiFeMo alloys

Ni–Fe-based alloys (permalloys) are commonly used as soft magnetic materials, exhibiting high permeability, low coercivity, low magnetostriction and high-saturation magnetization. In particular, Ni–Fe–Mo alloys have high relative permeability and low eddy current losses. We have investigated the structure and magnetic properties of powders prepared by mechanical milling of NiFe (81 wt% of Ni) microcrystalline ribbon and NiFeMo (79 wt% of Ni, 16 wt% of Fe) swarfs in a high-energy planetary ball mill. The coercivity of NiFe rapidly increases up to 1600 A/m for 35 h and the coercivity of NiFeMo increases gradually up 1800 A/m for all time of milling (500 h). The XRD analysis revealed that there is major phase FeNi 3 (with Curie temperature of 550 °C) as well as minor phases NiO and Fe 3O 4 for milled NiFe alloy. The milled NiFeMo alloy consists of FeNi 3 phase and other phase, whose Curie temperature was detected by thermomagnetic analysis to be about 650 °C.

Influence of Mechanical Milling on the SiC Particulate Size in an Al-SiC Composite

Particle reinforced aluminum-matrix composites are particularly attractive for the automobile and air-craft industries, due to their light weight, high strength, and good wear resistance. In the present work, silicon carbide (SiC) particulates have been incorporated into a pure Al matrix with the help of mechanical milling in a planetary ball-mill. Composite powders were prepared using both raw as well as premilled SiC powders. The effect of milling time on the SiC particulate size was investigated. Systematic analysis of x-ray diffraction data revealed a reinforcement particle size of about 30 nm in a composite containing 50 vol.% SiC. It has been observed that the size reduction occurs at a faster rate when indirect milling is used.

Effect of Mechanical Alloying on the Structural and Magnetic Properties of DyNi4Al Compounds

We have investigated the influence of mechanical milling on structural changes and magnetic properties of DyNi4Al compound. The decrease of intensity and broadening of the diffraction lines have been detected after milling as a consequence of amorphisation of the samples. The size of grains evenly decreased in process of milling. The Curie temperature of the DyNi4Al decreases with milling time as a consequence of the reduction of grain size and decrease of magnetic interaction. On the other hand the coercivity increases in process of milling and its saturated value appears after milling for 20 h.

Influence of thermal annealing on the hydrogenation properties of mechanically milled AB 5-type alloys

The influence of mechanical milling and posterior annealing treatment on kinetic and thermodynamic H-properties of AB 5-based alloys are here reported. Short milling process yields non-homogeneous microstructural (wide distribution of nano-crystallite sizes and amorphous phase) and morphological alloy powders. Annealing treatment of long-milled alloy produces a homogeneous microstructural alloy. Annealed alloy exhibits a unique nano-crystallite size without presence of amorphous structure. H-capacity in short-milled alloy is higher than for annealed alloy due to the contribution of both amorphous and well crystallised domains. The short-milled alloy exhibits extra H-trapping sites in amorphous domains as detected by thermal desorption. Absorption hydrogen kinetic in short-milled alloy is faster than for annealed alloy mainly due to fast H-transport through amorphous domains.

The Influence of Mechanical Milling and Subsequent Calcination on the Formation of Lithium Ferrites

The influence of ball milling and subsequent calcination of a 2.5:1 molar mixture of α-Fe2O3 and Li2CO3 on the formation of lithium ferrites has been investigated. Premilling was found to considerably lower the temperature at which the lithium ferrites LiFeO2 and LiFe5O8 are formed. A β-to-α phase transition in LiFe5O8 was found to take place on cooling from ca. 1000°C depending on the milling history and cooling regime.