Effect of ball milling time on the microstructure and compressive properties of the Fe–Mn–Al porous steel

In the present work,Fe–Mn–Al–C powder mixtures were manufactured by elemental powders with different ball milling time,and the porous high-Mn and high-Al steel was fabricated by powder sintering.The results indicated that the powder size significantly decreased,and the morphology of the Fe powder tended to be increasingly flat as the milling time increased.However,the prolonged milling duration had limited impact on the phase transition of the powder mixture.The main phases of all the samples sintered at 640℃ were α-Fe,α-Mn and Al,and a small amount of Fe2Al5 and Al8Mn5.When the sintering temperature increased to 1200℃,the phase composition was mainly comprised of γ-Fe and α-Fe.The weight loss fraction of the sintered sample decreased with milling time,i.e.,8.3wt% after 20 h milling compared to15.3wt% for 10 h.The Mn depletion region(MDR) for the 10,15,and 20 h milled samples was about 780,600,and 370 μm,respectively.The total porosity of samples sintered at 640℃ decreased from ~46.6vol% for the 10 h milled powder to ~44.2vol% for 20 h milled powder.After sintering at 1200℃,the total porosity of sintered samples prepared by 10 and 20 h milled powder was ~58.3vol% and ~51.3vol%,respectively.The compressive strength and ductility of the 1200℃ sintered porous steel increased as the milling time increased.

Low-Temperature Synthesis of Nano-AlN Based on Solid Nitrogen Source by Plasma-Assisted Ball Milling

Plasma-assisted ball milling was carried out on the Al+C3H6N6 system and Al+C_(4)H_(4)N_(4) system,respectively.The phase structure,functional groups and synthesis mechanism were analyzed by XRD and FT-IR,and the differences in the synthesis process of nano-AlN with different solid nitrogen sources were discussed.The results show that C3H6N6 has a stable triazine ring structure,and its chemical bond is firm and difficult to break,so AlN cannot be synthesized directly by solid-solid reaction at room temperature.However,there are a large number of nitrile groups(-CN)and amino groups(-NH_(2))in C_(4)H_(4)N_(4) molecules.Under the combined action of plasma bombardment and mechanical energy activation,C_(4)H_(4)N_(4) molecules undergo polycondensation and deamination,so that the ball milling tank is filled with a large number of active nitrogen-containing groups such as N=,≡N,etc.These groups and ball milling activated Al can synthesize nano-AlN at room temperature,with a conversion rate of 92%.SEM,DSC/TG analysis showed that the powder obtained by ball milling was formed by soft agglomeration of many fine primary particles about 50–80 nm.The surface morphology of the powder was loose and porous,and it had strong activity.After annealing at 800℃,the conversion rate of the Al+C_(4)H_(4)N_(4) system reached 99%.

COMPARISON ON REFINEMENT OF IRON POWDER BY BALL MILLING ASSISTED BY DIFFERENT EXTERNAL FIELDS

The cryogenic milling and milling in conjunction with dielectric barrier discharge plasma (DBDP) have been separately set up. The combined effect of low temperature and plasma on ball milling has been investigated by examining the refinement of particle size and grain size of iron powder using scanning electron microscopy, X-ray diffraction, and small angle X-ray scattering. It was found that the mean size of iron particles could reach 104nm only after 10 hours of ball milling in conjunction with DBDP, whereas a minimum average grain size of 8.4nm was obtained by cryomilling at -20℃; however, it is difficult to refine the particle size and grain size under the same milling condition in the absence of DBDP and cryogenic temperature.

Scalable and facile synthesis of V_(2)O_(5) nanoparticles via ball milling for improved aerobic oxidative desulfurization

In recent years, transition-metal oxides(TMOs) have been long employed for aerobic oxidative desulfurization. However, the inherent bottlenecks, such as the low explosion of active sites, limit the application of bulk TMOs catalyst. In this study, V_(2)O_(5) nanoparticles with oxygen vacancies were prepared in large-scale via facile ball milling strategy with adding oxalic acid as a reducing agent. The as-prepared catalysts exhibit remarkable sulfur removal for oils with different initial S-concentrations and different substrates. Sulfur removal could reach up to 99.7%(< 2 ppm) under the optimized reaction conditions. This work provides a feasible desulfurization strategy for fuel oils.

Optimization of Process Parameters for in High-Energy Ball Milling of CNTs/Al2024 Composites Through Response Surface Methodology

The mathematical models are developed to evaluate the ultimate tensile strength( UTS) and hardness of CNTs / Al2024 composites fabricated by high-energy ball milling. The effects of the preparation variables which are milling time,rotational speed,mass fraction of CNTs and ball to powder ratio on UST and hardness of CNTs / Al2024 composites are investigated. Based on the central composite design( CCD),a quadratic model is developed to correlate the fabrication variables to the UST and hardness. From the analysis of variance( ANOVA),the most influential factor on each experimental design response is identified. The optimum conditions for preparing CNTs / Al2024 composites are found as follows: 1. 53 h milling time,900 r / min rotational speed,mass fraction of CNTs 2. 87% and Ball to powder ratio 25 ∶ 1. The predicted maximum UST and hardness are 273.30 MPa and 261.36 HV,respectively. And the experimental values are 283.25 MPa and256.8 HV,respectively. It is indicated that the predicted UST and hardness after process optimization are found to agree satisfactory with the experimental values.

Characteristics of Cr and Al Powders by High Energy Ball Milling

The variation of microstucture and phase structure of metal Cr and Al powders prepared by high energy mechanical milling was analyzed and investigated.The results show that with the continuous balling the average grain sizes of the brittle Cr powders are gradually decreased,and the diffraction peaks are widened and the peak values lower owing to the interrelation caused by both cold welding and breaking;the tough Al powders exhibit intense cold welding,and most of powders lead to adhesion to ball surface and pot wall,meanwhile,the Al powders subjected to intense deformation have led to many dislocation rings with non dislocation wind up found in the microstructure.

Multirange Fractals in Materials: Applications to Fracture and Mechanical Alloying under Ball Milling

A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new expIanation to the WilIiford’s multifractal curve on the relationship of fractal dimension with fracture properties in materials has been given. It shows the importance of fractorizing out the effect of fractal structure from other physical causes and separating the appropriate range of scale from multirange fractals.Mechanical alloying process under ball milling as a non-equilibrium dynamical system has been also

Formation of a FCC Al_(54)Ti_(23)C_(23) Metastable Phase by Ball Milling

The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorphous phase is formed first at an early milling stage, then crystallization occurs during further milling, leading to formation of a nanocrystalline fcc metastable phase. In contrast, during annealing the amorphous phase is crystallized to the equilibrium phase instead of the fcc phase. This indicates that crystallization during ball milling is different from that induced by

Fabrication and microstructure of nanostructured Mg-3Ni-2MnO_(2) by ball milling in hydrogen atmosphere

Nanostructured Mg-3Ni-2MnO_(2) was synthesized by ball milling elemental powders of Mg,Ni and MnO_(2) in hydrogen atmosphere.The microstructures of the powder prepared at different milling time were analyzed by X-ray diffractometry(XRD), scanning electron microscopy(SEM)and high resolution electron microscopy(HREM).The milling time is the most key parameter impacting on the grain size and the microstructure of material.With prolonging the milling time,particle size becomes smaller and smaller.But after the ball milling time reaches about 20 h,reduction of grain size becomes slowly.When the milling time is more than 50 h,nanocrystalline fully forms.When the milling time is more than 80 h,there are more amorphous phases in materials.The average particle diameter of material is about 1μm and the grain size is 10-30 nm.

Structural Evolution of the Mn_(0.52)Sb_(0.48) Compound during High Energy Ball Milling

The structural transitions of the NiAs-type Mn0.52Sb0.48 magneto-ordered compound, ball milled to different periods, have been characterized by X-ray diffraction and DSC analysis. On the basis of lattice parameter results a structural evolution mode with three stages is proposed. In the first stage lattice parameters keep nearly unchanged with the refinement of grains and increase of lattice strain. In the second stage, microstrain shows a lowering tendency accompanying the successive decreases of grain size. The X-ray revealed internal strain is found to be strains inside the lattice, which can be relaxed with new grain formation. The change of Tc is shown to be affected by the dimension of c axis, however the overall magnetization is continuously decreased with milling, due to the disordering process occurred in milling. Correspondent disordering mechanisms have been tentatively postulated and discussed according to the changes of lattice para meters.

Synthesis of cathode material LiMn_(2)O_(4)for lithium-ion batteries by high-energy ball milling

Using electrolytic manganese dioxide and Li 2CO 3 as starting materials, the precursor of LiMn 2O 4 as cathode materials for lithium ion batteries was obtained by high energy ball milling. The LiMn 2O 4 powder was synthesized by calcinating the as milling powder at 750 ℃ for 24 h. X ray diffraction, SEM, cyclic voltammograms and charge discharge were carried out to investigate the property of LiMn 2O 4 cathode materials. Results show that the synthesized material, which is of standard spinel structure, possesses high reversibility of electrochemistry. The capacity in EC DMC(1∶1)+1 mol/L LiPF 6 electrolyte during first discharge is determined to be 125 mA·h/g.[

Modelling of the High-Energy Ball Milling Process

In this paper, the milling parameters of high energy ball mill (Fritsch Pulverisette 7) like vial geometry, number and size of balls and speed of the mill were modelled and discussed. Simulations through discrete element method (DEM) provide correlation between the milling parameters. A mathematical model is used to improve and develop this process. The results show that the loss of powder mass can remarkably improve the performance of milling. The balls made of stainless-steel have a positive effect on the milling efficiency. The simulation shows that the high ball milling velocities can contribute to faster particle size reduction.

Preparation of Bi_(4)Ti_(3)O_(12)(BIT)Ceramics via a High-Energy Ball Milling Process Doped with Multi-Walled Carbon Nanotubes(MWNTs)

We prepared the Nano-sized bismuth titanate Bi4Ti3O12 (BIT) powders, through a high-energy ball milling process from their oxides Bi2O3 and TiO2. This BIT phase can be formed after a milling process for 40 min. With an increasing milling time, this particle size of mixture is gradually reduced, thus, we have mostly an amorphous phase. The BIT ceramics were duly obtained by sintering the synthesized powders at temperatures ranging from 850°C to 1000°C. The BIT ceramics sintered at 1020°C for 1 h, exhibiting a density with 7.52 g/cm3 of a crystaline phase and a dielectric of K = 288.11 (100 Hz), as well as a dielectric loss of 0.05 (100 kHz). The High-energy ball milling process is a promising way to prepare BIT ceramics. After the preparation of the BIT, we doped it with the Multi-Walled Carbon Nanotubes which are properly obtained by a chemical vapour deposition (CVD), using nickel as a catalyst, as well as using acetilene at 720°C, and then proceeded with the dielectric and optical measurements.

Structural Evolution of an FeMoSiB Alloy during Ball Milling

Ball milling induced microstructure evolution in an FeMoSiB alloy with three kinds of different phase constitutions (bcc Fe solid solution and various borides) was investigated by means of X-ray diffraction and transmission electron microscopy. Experimental evidences indicate that a same final product of bcc Fe solid solution was formed upon miling for all samples. During the transformation, the XRD peaks of Fe phase shift to lower diffraction angIes; and those of borides disappear in turn, first the metastable Fe3B and Fe23B6 and then the stable Fe2B. The observed structure evolution might originate from the transformation of ordered Fe2B phase into disordered Fe solid solution.

Auxiliary ball milling to prepare WS_(2)/graphene nanosheets composite for lithium-ion battery anode materials

A novel nano-WS_(2)/graphene nanosheets(GNSs)composite is obtained by ball milling with xylitol as auxiliary agent and hightemperature sintering.Xylitol improves the shear force during ball milling and well overcomes the van der Waals interactions between the interlayer of graphite and WS_(2).Through high-temperature calcination,GNSs and WS_(2) nanosheets can form tight interface contact.The produced WS_(2)/GNSs composites can be used as anode materials for lithium-ion batteries,while maintaining a high reversible specific capacity of 705 mAh·g^(-1)with the capacity retention of 95%at a current density of 250 mA·g^(-1)after 200 cycles,mainly because WS_(2)/GNSs composites have a higher Li^(+)diffusion coefficient of 2.2×10^(-9)cm^(2)·s^(-1)and a higher specific surface area of 70.10 m^(2)·g^(-1).As a result,the xylitol-assisted ball milling method designed in this work is suitable for extended preparation of peeling of two-dimensional layer materials into nanosheets.

High-performance martensitic stainless steel nanocomposite powder for direct energy deposition prepared by ball milling

Direct energy deposition(DED)has great potential for the production of stainless steel matrix nanocomposite parts.However,the propensity of nanoparticle agglomeration leads to the difficulty in realizing homogenous dispersion of nanoparticles in the matrix.In this study,a series of agglomeration-free nanoWC-Co-reinforced 420 stainless steel matrix nanocomposite powders with high flowability were prepared by ball milling under the optimal parameters.The effect of ball milling time on the properties of the composite powders was investigated.Excellent powder properties ensure the DED processing performance.Furthermore,the corresponding composites were fabricated by DED,and the effects of nano-WC-Co content on the properties of the composites were comprehensively investigated.The contact angles between the single pass cladding layer and the substrate change with increasing nano-WC-Co content(decrease from 127.38°to 113.07°).The different contact angles will significantly influence the quality of the multipass cladding layer.Furthermore,the addition of nanoWC-Co leads not only to further grain refinement but also to more pronounced isotropy of the micros tructure.With the increase in nano-WC-Co content,the corrosion resistance is significantly improved(62.28%lower corrosion current for 420-15 wt%nano-WC-Co than for 420).

Reactive ball-milling synthesis of Co-Fe bimetallic catalyst for efficient hydrogenation of carbon dioxide to value-added hydrocarbons

Catalytic hydrogenation of CO_(2) using renewable hydrogen not only reduces greenhouse gas emissions,but also provides industrial chemicals.Herein,a Co-Fe bimetallic catalyst was developed by a facile reactive ball-milling method for highly active and selective hydrogenation of CO_(2) to value-added hydrocarbons.When reacted at 320℃,1.0 MPa and 9600 mL h^(-1) g_(cat)^(-1),the selectivity to light olefin(C_(2)^(=)-C_(4)^(=)) and C_(5)+ species achieves 57.3% and 22.3%,respectively,at a CO_(2) co nversion of 31.4%,which is superior to previous Fe-based catalysts.The CO_(2) activation can be promoted by the CoFe phase formed by reactive ball milling of the Fe-Co_(3)O_(4) mixture,and the in-situ Co_(2)C and Fe_(5)C_(2) formed during hydrogenation are beneficial for the C-C coupling reaction.The initial C-C coupling is related to the combination of CO species with the surface carbon of Fe/Co carbides,and the sustained C-C coupling is maintained by self-recovery of defective carbides.This new strategy contributes to the development of efficient catalysts for the hydrogenation of CO_(2) to value-added hydrocarbons.

Structural, Magnetic and Heating Efficiency of Ball Milled γ-Fe2O3/Gd2O3 Nanocomposite for Magnetic Hyperthermia

The preparation of γ-Fe2O3/Gd2O3 nanocomposite for possible use in magnetic hyperthermia application was done by ball milling technique. The nanocomposite was characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The heating efficiency and the effect of milling time (5 h and 30 h) on the structural and magnetic properties of the nanocomposite were reported. XRD analysis confirms the formation of the nanocomposite, while magnetization measurements show that the milled sample present hysteresis with low coercivity and remanence. The specific absorption rate (SAR) under an alternating magnetic field is investigated as a function of the milling time. A mean heating efficiency of 68 W/g and 28.7 W/g are obtained for 5 h and 30 h milling times respectively at 332 kHz and 170 Oe. The results showed that the obtained nanocomposite for 5 h milling time is a promising candidate for magnetic hyperthermia due to his properties which show an interesting magnetic behavior and high specific absorption rate.

Frequency and temperature dependent electrical characteristics of CaTiO_(3) nano-ceramic prepared by high-energy ball milling

Nanocrystalline calcium titanate(CT)ceramic has been synthesized by a combination of solid-state reaction and high-energy ball milling.This nano-ceramic is characterized by X-ray diffraction(XRD),dielectric study and impedance spectroscopy.The XRD pattern shows single phase ceramic of orthorhombic symmetry.The frequency-dependent dielectric study shows that the dielectric constant is maximized at low frequencies and decreases with an increase in frequency.Impedance spectroscopy analyses reveal a non-Debye type relaxation phenomenon.A significant shift in impedance loss peaks toward the higher-frequency side indicates conduction in the material favoring the long-range motion of mobile charge carriers.The grain conduction effect is observed from the complex impedance spectrum by the appearance of one semicircular arc in Nyquist plot.It is also observed that the resistance decreases with an increase in temperature showing a negative temperature coefficient of resistance(NTCR).Various thermistor parameters have been calculated by fitting with Steinhart-Hart equation.The modulus plots represent the presence of temperature-dependent electrical relaxation phenomenon with the material.The frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated.The activation energy has been calculated from an Arrhenius plot of DC conductivity and relaxation frequency.

A Comparison Study of Hydrogen Storage Thermodynamics and Kinetics of YMg11Ni Alloy Prepared by Melt Spinning and Ball Milling

Melt spinning(MS)and ball milling(BM)were employed to fabricate YMg_(11)Ni alloy,and their structures and hydrogen storage performances were examined.The results reveal that the as-spun and as-milled alloys both exhibit the nanocrystalline and amorphous structure.The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun alloy.More than that,the as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one,which are 549.8 and 560.9 K,respectively.Additionally,the as-milled alloy shows a superior hydrogen desorption property to the as-spun one.On the basis of the time needed by desorbing hydrogen of 3 wt%H_2,for the asmilled alloy,it needs 1106,456,343,and 180 s corresponding to hydrogen desorption temperatures of 593,613,633,and653 K.However,for the as-spun alloy,the time needed is greater than 2928,842,356,and 197 s corresponding to the same temperatures.Hydrogen desorption activation energies of as-milled and as-spun alloys are 98.01 and 105.49 k J/mol,respectively,which is responsible for that the as-milled alloy possesses a much faster dehydriding rate.By means of the measurement of pressure–composition–temperature(P–C–T)curves,the dehydrogenation enthalpy change of the alloys prepared by MS(DH_(de)(MS))and BM(DH_(de)(BM))is 81.84 and 79.46 k J/mol,respectively,viz.DH_(de)(MS)[DH_(de)(BM).