High-energy Milling Research Articles

Synthesis of NiLaxFe(2−x)O4 System as Microwave Absorber Materials by Milling Technique

The possibility that nickel ferrite doped with lanthanum could be used as a microwave absorbing material has been investigated. Microwave absorbing materials play a very important role in stealth technology, helping military equipment to avoid radar detection. Synthesis of the lanthanum-doped NiFe2O4 ferrite system (NiLaxFe2−xO4) as microwave absorbing materials was carried out. A series of NiLaxFe2−xO4 (x = 0.0025, 0.0050, 0.0075, and 0.01) were prepared using the solid-state reaction method. Each composition was milled using a high-energy milling (HEM) machine then finally sintered at 1000°C for 5 h. Rietveld refinement of x-ray diffraction (XRD) results showed that single-phase nickel ferrite doped with lanthanum in space group Fd-3m was formed for all compositions. The lattice parameter was found to decrease as the doping composition x was increased. Morphological observation by scanning electron microscopy (SEM) revealed that the largest particle size was obtained for the composition with x = 0.0025. Microwave absorption properties obtained by vector network analyzer (VNA) analysis showed that doping with lanthanum enhanced the ability to absorb microwaves from 90.01% to 96.61% (reflection loss −14.72 dB at 10.22 GHz). Thus, the composition with x = 0.01 (NiLa0.01Fe1.99O4) showed an excellent response and can be considered a candidate microwave absorbing material.

Magnetic properties and microwave absorption characteristic of MWNT filled with magnetite coated iron nanoparticles

In this study, the measurement of magnetic and microwave absorption characteristics of MWNT (multi-walled carbon nanotubes) filled with Fe3O4 coated α-Fe nanoparticles and synthesized by dry mill using high energy milling have been performed. The sample was prepared from mixing of Fe and MWNT with a ratio of 10:1, then milled for 0, 5, 10, 15, 20, and 25 h respectively. The refinement results of X-ray diffraction pattern show that the sample have be formed MWNT/α-Fe@Fe3O4 nanocomposite which consists of C, α-Fe and Fe3O4 phases. Increasing milling time would generate an increasingly large α-Fe@Fe3O4 composite due to oxidation effect on the α-Fe powders surface. The morphologies of α-Fe@Fe3O4 particles were observed by TEM (Transmission Electron Microscopy) measurements. The particles, with lengths of up to at least 20 nm, have easily penetrated the nanotube cavity. The magnetic properties measurements show that the MWNT/α-Fe@Fe3O4 nanoparticles have a low coercivity field and a high remanence magnetization. The reflection loss of MWNT/α-Fe@Fe3O4 nanoparticles increases with increasing milling time. The MWNT/α-Fe@Fe3O4 nanocomposite achieves a reflection loss below −10 dB (70% absorption) at 10–11 GHz, and below −15 dB (80% absorption) at 12–13 GHz. Meanwhile the microwave absorbing peaks of composites containing MWNT/α-Fe@Fe3O4 nanoparticles shift to lower frequencies with increasing milling time.

Cryogenic mechanical alloying of aluminum matrix composites for powder bed fusion additive manufacturing

Cryogenic mechanical alloying (cryomilling) was employed to fabricate aluminum matrix composite powder feedstock for additive manufacturing. The high energy milling of the powder system induces a homogenous distribution of reinforcement particles in the matrix powder by recurrent fracture and cold welding. In this study, aluminum matrix composite feedstock were produced via different cryomilling techniques at varying compositions, powder charges, and milling times. As-milled powders were characterized for particle size distribution, morphology, and homogeneity. Resultant powder demonstrated varying characteristics correlated to milling parameters. Powder metallurgy samples were also fabricated to understand as-sintered reinforcement distribution and the resultant strengthening. This research provides an indication of cryomilling capabilities to become an effective method for custom alloy powder production for powder bed fusion additive manufacturing.

Alternative method for generating hydrogen through high-energy mechanical milling using magnesium and methanol

This paper presents a new way to generate hydrogen through mechanical milling. Hydrogen was generated “in-situ” inside a stainless steel container where methanol and magnesium were utilized. The methanol atoms due to the high-impact process were broken to obtain hydrogen. In this same process, magnesium was selectively reacted with oxygen to form the corresponding oxide and hydrogen remain in gas form. Relatively short milling times were programmed. After the programmed times, hydrogen from the stainless steel container through liquid displacement was measured. Likewise, solids were analyzed before and after hydrogen production using XRD and SEM techniques. The volume of hydrogen was a function of the programmed milling time; the average values between 160 and 310 mL were obtained when the most appropriate amounts of magnesium and methanol were used. Only magnesium oxide was formed as by-product. XRD analyses demonstrated the transformation of magnesium and methanol to generate hydrogen.

The Effect of Mechanochemical on The Formation of Calcium Titanate (CaTiO3) Prepared by High Energy Milling

Single-phase calcium titanate (CaTiO3) was successfully synthesized by mechanical milling and the solid-state reaction of CaCO3 and TiO2. The speed of high energy ball milling was 700 rpm with the ball and jar were made from stainless steel. The milling time and ball to powder ratio was 10 h and 50 h, respectively. After milling for 10 h, the mixed powder of CaCO3 and TiO2 experienced heavy milling, which indicated by the average particle size before and after milling was > 1 µm and 85.56 ± 35.62 nm, respectively. Furthermore, the XRD pattern of milled powder revealed the disappearance of CaCO3 peaks and a considerable reduction of TiO2 peaks after milling for 10 h. Moreover, the presence of CaTiO3 peaks in the milled powder was noticeably detected in the XRD pattern, showing the mechanical alloying of CaCO3 and TiO2 was occurred. The milled powder was calcined at 800, 900 and 1000°C for 2 h. The results showed the formation of a single phase of CaTiO3 after calcination at any temperatures. However, the samples indicated the presence of Fe2O3, which from the milling media. The presence of impurities after milling is inevitable due to friction between ball and jar. Further study is needed to obtain the optimum condition of mechanical milling to minimize the contamination.

Synthesis and Characterization of p-n Junction Ternary Mixed Oxides for Photocatalytic Coprocessing of CO2 and H2O

In the present paper, we report the synthesis and characterization of both binary (Cu2O, Fe2O3, and In2O3) and ternary (Cu2O-Fe2O3 and Cu2O-In2O3) transition metal mixed-oxides that may find application as photocatalysts for solar driven CO2 conversion into energy rich species. Two different preparation techniques (High Energy Milling (HEM) and Co-Precipitation (CP)) are compared and materials properties are studied by means of a variety of characterization and analytical techniques UV-Visible Diffuse Reflectance Spectroscopy (UV-VIS DRS), X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Energy Dispersive X-Ray spectrometry (EDX). Appropriate data elaboration methods are used to extract materials bandgap for Cu2O@Fe2O3 and Cu2O@In2O3 prepared by HEM and CP, and foresee whether the newly prepared semiconductor mixed oxides pairs are useful for application in CO2-H2O coprocessing. The experimental results show that the synthetic technique influences the photoactivity of the materials that can correctly be foreseen on the basis of bandgap experimentally derived. Of the mixed oxides prepared and described in this work, only Cu2O@In2O3 shows positive results in CO2-H2O photo-co-processing. Preliminary results show that the composition and synthetic methodologies of mixed-oxides, the reactor geometry, the way of dispersing the photocatalyst sample, play a key role in the light driven reaction of CO2–H2O. This work is a rare case of full characterization of photo-materials, using UV-Visible DRS, XPS, XRD, TEM, EDX for the surface and bulk analytical characterization. Surface composition may not be the same of the bulk composition and plays a key role in photocatalysts behavior. We show that a full material knowledge is necessary for the correct forecast of their photocatalytic behavior, inferred from experimentally determined bandgaps.

Strengthening of Nanocrystalline Al with Al3Zr Core-Shell Structure

High-density Al-based composites reinforced with ten-wt.% recycled nanocrystalline CuZrAgAl particles have been fabricated by mechanical milling, cold- and hot-pressing. The microstructures, phase transformations, and mechanical properties of the mixed powder and sintered samples were investigated. After milling in a ball mill for 30 h, the microhardness of the mixed powder increases to 301 ± 31 HV0.01 and 222 ± 10 HV0.01 without and with ethanol milling, respectively. On account of the interdiffusion, the melting temperature of mixed powder reduces to 574 ± 5.0 °C and 627.5 ± 6.5 °C after 30 h milling. The study showed that the reinforcing particles are homogeneously distributed in the sintered nanocrystalline Al-based composites. During the hot-pressing, a shell zone forms at the interface of reinforcing particles during hot pressing after high energy milling with a minimum of ten hours milling time. This shell zone consists of Al3Zr (D023) phase. The coarsening resistant core-shell structure and grain refinement greatly improve mechanical properties. The compression strength at room temperature varies between 650 and 800 MPa at room temperature and is 380 MPa at 400 °C for the composite containing ten-wt.% of the Cu-Zr-based amorphous-nanocrystalline phases. The Brinell hardness of the sintered composite is 329 HB.

Chromium carbide micro-whiskers dataset: Morphologies with scanning and transmission electronic microscopy.

Chromium carbide exhibits a superior set of mechanical properties and chemical stabilities and is widely used in various engineering applications. Here, micro-whiskers of the Cr2O3 were successfully prepared using a carbothermal reduction method with high energy milling and liquid phase catalysis. The whiskers growth was observed with scanning electron microscopy and field emission gun transmission electron microscopy. This dataset shows all kinds of morphologies of the Cr2O3 whiskers during the growth stage, including agglomerated, pointed, and non-whiskered shapes, which are products of the mixture of Cr2O3:C = 1:5 or 1:8 or 1:10 under different temperatures and duration time. These data provide important additional information different from the source article but complement it with some negative but indicative and instructive data. Experimental scientists who want to investigate the growth and strengthening of whiskers of Cr2O3 or others can refer to and benefit from these data, such as possible combinations of the experimental conditions which may lead to certain outcomes and guide the predictive design of future relevant research with similar materials system.

Effect of high energy milling on microstructure and mechanical properties of Al2O3-10 wt% Co composites consolidated by spark plasma sintering (SPS)

Al2O3-10 wt% Co composites were prepared by high energy milling in the presence of ethyl alcohol and with subsequent spark plasma sintering (SPS). The powders milled for 5 and 30 h were sintered by SPS at 1350 °C for 5 min. The effect of milling time on the sinterability and mechanical properties was studied. The morphology and structure of milled powders were investigated by scanning electron microscopy, dynamic light scattering and X-ray diffraction. The Co phase forms plate-like particles of different sizes, while finely fragmented Al2O3 particles are incorporated in the Co phase, forming composite particles. The average size of the composite particles decreases with increasing milling time, achieving 1.33 μm after 30 h. Crystallite size and micro-strain are inversely proportional. Overall, all the samples display homogeneous microstructures, high density (85.29–91.60%) and microhardness in the range 11.41–14.37 GPa.

The influence of the rotation frequency of a planetary ball mill on the limiting value of the specific surface area of the WC and Co nanopowders

An increase in the hardness and wear resistance of WC-Co alloys with a decrease in the grain diameter of WC and Co makes it relevant to search for methods for producing powders with a maximum specific surface area (SSA). SSA growth is limited even when milling powders of WC and Co in the most high-energy mills. Effect of increasing the rotation speed of a planetary ball mill on the limiting value of the SSA of obtained nano sized WC and Co powders is studied. According to the developed model, an increase in the rotational speed of the mill leads to an increase in the limiting value of SSA if the cause is particle hardening. If the cause is coalescence, an increase in frequency leads to a decrease in the limiting value of the SSA. It was determined that the limiting value of SSA of WC particles increases from 1.0⋅108 m2/m3 to 2.2⋅108 m2/m3 (Sauter average diameter decreases from 60 to 27 nm) with increase of mill rotation frequencies from 2.5 to 4.2 rps due to a decrease in the volume of “indestructible” particles. And the limiting value of SSA of WC particles decreases from 2.2⋅108 m2/m3 to 1.1⋅108 m2/m3 (Sauter average diameter increases from 26 to 55 nm) with increase of mill rotation frequencies from 5 to 6.7 rps due to the increase of the coalescence rate. The experiment showed that the limiting value of SSA for Co powder decreases from 1.0⋅108 m2/m3 to 1.1⋅106 m2/m3 with increasing of the rotational speed of the mill from 2.5 rps to 6.7 rps (Sauter average diameter increases from 60 to 5450 nm) due to the increase of the coalescence rate. Studies have shown that the growth of SSA of WC grains is limited by a certain value (11.5 nm).

High-energy alkaline milling as a potential physical and chemical cornstarch ecofriendly treatment to produce nixtamalized flours

In this study, hard corn grains were nixtamalized (alkali-heat treatment) by a high-energy ball mill to investigate the effects on its physicochemical, textural, and microstructural properties. Ball milling modifies the structure and properties of cornstarch. The gelatinization peak of starch was evidenced and thermal and pasting properties were significantly affected. With regard to rheological properties, the viscosity peak increased from 2454 cP in traditional nixtamalized flour to 4294 cP in high-energy milling treatments with 1.4% of Ca(OH)2 and 20% moisture content, C1.4, while enthalpy ranged from 3.5 to 0.34 J/g, respectively. High-energy milling influenced the Fourier-Transform InfraRed Spectroscopic (FT-IR) patterns. All of the samples of the corn-grain starches presented the typical A-type X-ray diffraction pattern. The crystallinity of starch from CG showed a lower intensity in peaks 2θ ~ 15 and 23° compared with starch from WG and YG. The textural properties of the masas were influenced, adhesiveness was reduced, but cohesiveness was increased by the addition of Ca(OH)2. In the structural characterization by E-SEM, the control presented a greater amount of agglomerated starch granules, followed by the high-energy milling treatments. The results suggest that high-energy alkaline milling could be a potential physical and chemical method to modify corn-starch properties and obtain nixtamalized products.

Modification of pseudobrookite Fe1.7Mn0.3-xNixTiO5: Influence of Ni-substitution on the magnetic properties

In this study, the synthesis of pseudobrookite Fe1.7Mn0.3-xNixTiO5 with variations in composition (x = 0.01, 0.05, 0.1, and 0.15) using a mechanical milling technique has been performed. High purity powder of α-Fe2O3, TiO2, MnCO3, and NiO were prepared as raw materials. The mixture was milled for 5 hours using high energy milling equipment, and sintered at 1000 °C for 5 hours. The refinement result of X-ray diffraction profile shows that the all of pseudobrookite Fe1.7Mn0.3-xNixTiO5 samples have a single phase with particle size of less than 1 μm. The VSM result shows all the samples were ferromagnetic behavior. We concluded that the substitution Ni into Mn on the pseudobrookite Fe1.7Mn0.3-xNixTiO5 can change the magnetic properties of the material from paramagnetic to ferromagnetic through a mechanism of double exchange interaction.

Chromium carbide micro-whiskers: Preparation and strengthening effects in extreme conditions with experiments and molecular dynamics simulations

The rod-like Cr3C2 micro-whiskers were successfully synthesized from chromic oxide and blank carbon as reaction sources and halide salts and nickel as catalysts by using a carbothermal reduction method assisted with high energy milling and liquid phase catalysis. The optimal preparing condition was to calcine the mixture of Cr2O3:C:NaCl:KCl:Ni ​= ​1:8:0.4:0.4:0.3 (mole ratio) at 1300 ​°C for 2h without other post-treatments. The growth of Cr3C2 micro-whiskers was based on S-L-S mechanism that the brief reaction process of Cr2O3+C→Cr7C3→Cr3C2 occurred in molten catalyst liquids. Besides, the deficiency of carbon led to the generation of Cr7C3 particles, and its excess could induce the formation of coral clusters. The obtained Cr3C2 whiskers were not oxidized in air atmosphere at temperature lower than 1000 ​°C, and a thin Cr2O3 coating which prevented further oxidation gradually formed on the outside of whiskers from 1000 to 1200 ​°C. In addition, the bonding strength of heat resistant adhesive was increased by 16–28% from 500 to 1500 ​°C after adding Cr3C2 whiskers, which was mainly attributed to the pull-out mechanism, whereas the added carbon fibers were completely oxidized and left many sags in adhesive structure, thus severely decreasing the strength. Molecular dynamics simulations with the tersoff forcefield were carried out to facilitate fundamental understanding of the micro-whiskers growing in preferred directions. Combined with theoretical and experimental studies, this work significantly expands the design space and motivates future efforts in exploring the emerging applications of the mechanical properties of Cr3C2 whiskers in severe occasions.

Milling-driven nanonization of AsxS100-x alloys from second glass-forming region: The case of lower-crystalline arsenicals (56

Competitive intercrystalline phase-transformation and amorphization effects under high-energy mechanical milling are studied in AsxS100-x alloys from low-crystallinity domain (56<x<66) of the second glass-forming region (51<x<66), employing complementary X-ray powder diffraction analysis, micro-Raman scattering spectroscopy, heat flow differential scanning calorimetry and temperature-modulated multifrequency DSC TOPEM® methods. Milling is shown to activate preferential generation of nanosized monoclinic β-As4S4 phase in these AsxS100-x arsenicals at low As content (50<x<60) accompanied by appearance of isocompositional amorphous phase. Principal scenario of milling-driven interphase disproportionality in these arsenicals with high As content (58<x<66) is identified as plastic-crystalline rhombohedral β-As4S3 phase generation supplemented by extraction of As-rich amorphous substance probably of As4S2 composition. Appearance of amorphous a-As4S2 phase with relatively low glass-transition temperature of ~50 °C is supplemented to β-As4S4 polymorph stabilized along with nanostructured plastic-crystalline nc-β-As4S3 phase. Temperature-depressing effects of milling on calorimetric heat-transfer processes are revealed in whole compositional domain of the studied nanoarsenicals.

Effect of selective laser melting process parameters on microstructural and mechanical properties of TiC–NiCr cermet

TiC–NiCr cermet was in situ synthesized through selective laser melting (SLM) process using a Ti, C, and Ni80Cr20 powder mixture. Feedstock powder was prepared using high energy milling and mixing for a total time of 15 h. The effects of input energy density on the phase evolution and microstructure of SLM samples were investigated using X-ray diffractometery (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy dispersive spectrometer (EDS). The density of in situ fabricated cermets was measured using Archimedes’ principle, and microhardness and fracture toughness of the samples were determined through Vickers hardness test. Increasing the input energy density from 138.7 to 378.2 Jmm-3 resulted in an increase in relative density from 93.07% to 97.49% of theoretical density. Moreover, the microhardness and fracture toughness of the manufactured cermets increased to 1369.5 HV1 and 25.96 MPa m1/2, respectively. Further increasing of the energy density up to 416 J mm-3 resulted in lower density and increased porosities. Additionally, it resulted in a slight decrease in microhardness and fracture toughness.

Na2MgSnS4 – a new member of the A 2 I B II C IV X 4 family of compounds

Abstract A new member of the A 2 I B II C IV X 4 compound family, Na2MgSnS4, has been synthesized by ball milling of the binary sulfides SnS, Na2S, and MgS with elemental sulfur in a high-energy planetary mill, followed by annealing in an atmosphere of H2S (T = 600 °C/3 h). Na2MgSnS4 adopts the NaCrS2-type structure (rhombohedral, space group R 3 ¯ $\overline{3}$ m) with a = 3.7496(11) and c = 19.9130(6) Å. The Na atoms occupy Wyckoff position 3b, whereas the Mg and Sn atoms are statistically distributed on the cation sites 3a; all cations are surrounded by six sulfur atoms.

Microstructure and wear behavior of mechanically alloyed powder AlxMo0.5NbFeTiMn2 high entropy alloy coating formed by laser cladding

High entropy alloys (HEAs) is a newly wear-resistant material with multi-component structures of equal or near equal ratio. The tensile strength of pure Al is one fifth of the low carbon steel. After heat treatment and alloying, the strength will be greatly increased. Al alloys have good machining performance. The secondary and bending machining are also easier to obtain. To strengthen the wear resistance and hardness of normal steel tools, AlxMo0.5NbFeTiMn2 (x = 1, 1.5, 2) HEA coatings are experimentally manufactured in a systematic approach to complete existing results and prove an effective method of HEA coating preparation by laser cladding. The powders were first mechanically alloyed by a high-energy rod mill to ensure the homogenization of the structure. The structural characteristics were studied by XRD measurement, resulting in the crystal structure and its role in the HEA sample can be determined. Phase composition determined by electron microscope measurement (EDS, EBSD and TEM). It was found that their appearance, composition and contribution in the studied HEAs depended on the Al content. The phase composition of the coating consists of body-centered-cubic solid solution as well as (Nb, Ti)C carbides. As a result, the Al2Mo0.5NbFeTiMn2 HEA coating shows the highest microhardness and most excellent wear resistance of all tested coatings. Compared with the substrate, this indicates the smoother worn surface and lower volume wear rates can be concluded with Al addition in HEA coatings. It is assumed to be promising for a fusion alloy progress standpoint.

Evolution of intergranular microstructure and critical current properties of polycrystalline Co-doped BaFe2As2 through high-energy milling

The effect of microstructure control on intergranular critical current density (Jc) was evaluated using Co-doped Ba122 as a model material. Polycrystalline bulk samples were prepared by sintering mechanically alloyed powder prepared by planetary ball milling. Between low and intermediate milling energy, refinement of grain size, improvement in the uniformity of structure and composition, and a threefold improvement in Jc were observed with increasing milling energy. These indicate that the high-energy milling is an effective method for the synthesis of single-phase Ba122 samples and improvement of Jc by controlling the microstructure. At very high milling energy, the grain size of Ba122 reached as small as 30 nm, abnormal aggregates were formed, and the magnetic Tc and Jc decreased. Our results suggest that the suppression of the formation of large aggregates and control of grain boundary properties are necessary to achieve superior critical current properties.

Impact of grinding media on high-energy ball milling-driven amorphization in multiparticulate As4S4/ZnS/Fe3O4 nanocomposites

Amorphization scenarios in multiparticulate grinding media composed of As4S4/ZnS/Fe3O4 nanocomposites driven by high-energy ball mechanical milling are identified employing the X-ray powder diffraction analysis on intermediate-range ordering in the generated amorphous phase. This amorphous phase is supposed to be nucleated heterogeneously from grain boundaries of β-As4S4 crystallites followed by penetration deeply into grain interior, stabilizing the crystalline-amorphous core-shell structure of the fine-grained nanoparticles. Coexistence of nanocrystalline nc-β-As4S4 and amorphous arsenic monosulphide a-AsS phases is crucial feature of these nanocomposites, the amorphous substance being generated continuously due to re-amorphization of disordered phase initially existed in arsenic sulphide prepared by synthesis from elements and direct milling-driven vitrification of nc-β-As4S4. In monoparticulate β-As4S4-based and biparticulate As4S4/Fe3O4 nanocomposites, the amorphizing configurations are composed of single- and triple-broken chain-like network clusters. Under stronger conditions realized in the grinding medium composed by hard nanoparticles biased by their sizes in respect to 20:1 rule, as in triparticulate 1⋅As4S4-4⋅ZnS-1⋅Fe3O4 nanocomposite, the amorphization scenario differs being activated by double-breaking of intramolecular covalent bonds within As4S4 cage-like molecules. This effect is identified as nanocrystalline nc-ZnS-assisted milling-driven arsenic monosulphide amorphization in triparticulate 1⋅β-As4S4-4⋅ZnS-1⋅Fe3O4 nanocomposite solution.

PENGARUH MILLING TERHADAP KARAKTERISTIK MOLECULARLY IMPRINTED POLYMER KARBARIL (C12H11NO2)

Molecularly Imprinted Polymer (MIP) has been synthesized with carbaryl used as a template and forms complex bonds with Methacrylic Acid (MAA)through hydrogen bonds, followed by a cross-linking process using Ethylene Glycol Dimethacrylate (EGDMA) cross-linkers. The polymerization process begins with the thermal decomposition of Benzoyl Peroxide (BPO) as an initiator. Non-Imprinted Polymer (NIP) as a control polymer has also been synthesized using a similar procedure without using carbaryl templates. In this study, two variations of carbaryl are used, which are not milled carbamates, and carbaryl has been milled using High Energy Milling (HEM). The FTIR study was carried out to investigate the presence of carbaryl in polymers, MIP, and NIP. The spectrum shows that the concentration of carbaryl compound decreases after the extraction process. This result was also confirmed by the increase in the value of the percentage of transmittance in the MIP, especially the nano carbaryl MIP. This result is supported by the X-RD results, which showed a decrease in the size of the crystals in the carbaryl MIP from 10.07 Å while the nano carbaryl MIP was 9.16 Å.