Function Of Ball Milling Time Research Articles

Synthesis and Characterization of Gadolinium Oxide-Hematite Magnetic Ceramic Nanostructures

Mixed-oxide nanostructures of the type xGd2O3-(1-x)α-Fe2O3 (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO3 after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.

Effects of mechanochemical activation on the structural, magnetic and optical properties of yttrium iron garnet-graphene nanoparticles

Yttrium iron garnet nanoparticles were exposed to mechanochemical activation by high-energy ball milling for 0, 2, 4, 8 and 12 h, with and without graphene nanoparticles. The samples were subsequently characterized by Mössbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. Examination of the quadrupole doublet's abundance as function of ball milling time indicated that graphene slowed down the precipitation of the yttrium iron perovskite (yttrium orthoferrite) phase. The increased linewidth of the doublet showed that the carbon from graphene preferentially entered the lattice of the yttrium orthoferrite. The saturation magnetization decreased with decreasing particle size for prolonged milling due to the occurrence of the antiferromagnetic hematite phase. The enhanced absorption in the infrared region could be associated with the incorporation of carbon from graphene in the lattice of the yttrium orthoferrite. The results are interesting for sensing and microwave applications.

Influence of graphene on the magnetic properties of nickel ferrite nanoparticles

Nickel ferrite nanoparticles were subjected to mechanochemical activation for ball milling times ranging from 0 to 12 h. The milling was performed with and without the addition of equimolar concentrations of graphene nanoparticles. Characterization of resulting nano-powders was undertaken by Mӧssbauer spectroscopy and magnetic measurements. The hyperfine magnetic field was studied as function of milling time for octahedral and tetrahedral sites. An additional quadrupole split doublet represented the occurrence of superparamagnetic particles in the as-obtained and milled specimens. A new phase was obtained in the graphene-milled set of samples, which could be assigned to carbon-rich particles. The degree of inversion and canting angle were derived from the Mӧssbauer measurements and studied as function of ball milling time. The degree of inversion was found to decrease with milling time, especially for the set without graphene and evidenced a transition from inverse to normal spinels. The canting angle decreased with time for the graphene milled nanoparticles. The recoilless fraction was determined as function of milling time and was consistent with the observation – for the first time in literature – of a distribution of recoilless fractions in the studied specimens. The saturation magnetization, remanence magnetization and coercive field were derived from the hysteresis loops, recorded at 5 K and 5 T. The zero-field-cooling-field-cooling measurements were obtained in a magnetic field of 200 Oe and the blocking temperature was determined. Our results show new features of the behavior of nickel ferrite nanoparticles under mechanochemical activation with and without graphene.

Mechanical milling: a sustainable route to induce structural transformations in MoS2 for applications in the treatment of contaminated water

Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene, a new 2D material, molybdenum disulfide (MoS2), has attracted immense interest in various applications. On the other hand, ball-milling process provides an original strategy to modify materials at the nanometer scale. This methodology represents a smart solution for the fabrication of MoS2 nanopowders extremely-efficient in adsorbing water contaminants in aqueous solution. This work reports a comprehensive morphological, structural, and physicochemical investigation of MoS2 nanopowders treated with dry ball-milling. The adsorption performances of the produced nanopowders were tested using methylene blue (MB) dye and phenol in aqueous solution. The adsorption capacity as a function of ball-milling time was deeply studied and explained. Importantly, the ball-milled MoS2 nanopowders can be easily and efficiently regenerated without compromising their adsorption capacity, so to be reusable for dye adsorption. The eventual toxic effects of the prepared materials on microcrustacean Artemia salina were also studied. The present results demonstrate that ball-milling of MoS2 offers a valid method for large-scale production of extremely efficient adsorbent for the decontamination of wastewaters from several pollutants.

Behavior of Graphite and Graphene under Mechanochemical Activation with Hematite and Magnetite Nanoparticles

ABSTRACTEquimolar mixtures of graphene and iron oxide nanoparticles were subjected to mechanochemical activation. The phase sequence was investigated using Mӧssbauer spectroscopy as function of ball milling time. For low milling times (2-4 hours) the series with hematite (Fe2O3) nanoparticles was fitted with 2 sextets, corresponding to hematite with carbon introduced in the lattice. At high milling times (8-12 hours) the same series exhibited an additional sextet with hyperfine parameters characteristic to iron carbides and a quadrupole-split doublet, which could be assigned to carbon clusters with small amounts of iron in them. The series with magnetite nanoparticles (Fe3O4) at low milling times was analyzed considering 2 sextets, corresponding to the tetrahedral and octahedral sites of magnetite. At high milling times, the magnetite series also exhibited a broad sextet representing iron carbides and the doublet associated with iron-containing carbon clusters. Supporting information was obtained by determinations of the recoilless fraction. The results were compared with those obtained by ball milling graphite with hematite and magnetite nanoparticles.

The Key Role of Ball Milling Time in the Microstructure and Mechanical Property of Ni-TiCNP Composites

Titanium carbide nanoparticle-reinforced nickel-based alloys (Ni-TiCNP composites) with ball milling time ranging from 8 to 72 h were prepared by ball milling and spark plasma sintering. Transmission electron microscopy (TEM) and scanning electron microscopy equipped with electron backscatter diffraction were used to characterize the microstructures. Their hardness and tensile properties were measured using the Vickers pyramid method and tensile tests. TEM results showed that a slight coarsening of TiCNP occurred during the ball milling process. The grain sizes of the Ni-TiCNP composites with various ball milling times were different, but they were all much smaller than those of the pure Ni. In all cases, the Ni-TiCNP composites showed higher strengths and hardness values than the unreinforced pure nickel. Furthermore, the strength of the Ni-TiCNP composites increased initially and then decreased as a function of ball milling time. The maximum strengths occurred in the 24-h ball milling sample, which presented the lowest average grain size. The Hall-Petch strengthening was suggested to be the main reason responsible for such variations in mechanical properties. Additionally, the elongation percentage of the Ni-TiCNP composites decreased gradually with ball milling time. This may be caused by the change of microvoids in the composite as the ball milling time varies, which is also related to their fracture behavior.

The Effect of Porosity and Milling Induced Defects on the Thermoelectric Properties of p‐Type Bi2Te3‐Based Bulks

The p‐type (Bi,Sb)2Te3 bulks are prepared from ball‐milling powders by resistance pressure sintering method and their thermoelectric properties are investigated as a function of ball milling time. Prolonging milling time would introduce more anti‐site defects, interaction of vacancies and antisite defect, grain‐boundaries and interface defects, leading to lower carrier concentration and mobility. The peak value of ZT = 1.0 is achieved at 300 K for the 5 h sample. When the testing temperature is over 323 K, the ZT value of the 0 h sample is higher than that of the 5 h sample. The effect of porosity on the thermoelectric properties is also investigated by effective medium theory. As the porosity increased, the electrical resistivity increases and the thermal conductivity decrease.

Carbon-Substituted Hematite and Magnetite Nanoparticles

ABSTRACTGraphite-doped hematite and magnetite nanoparticles systems (∼50 nm) were prepared by mechanochemical activation for milling times ranging from 2 to 12 hours. Their structural and magnetic properties were studied by 57Fe Mössbauer spectroscopy. The spectra corresponding to the hematite milled samples were analyzed by considering two sextets, corresponding to the incorporation of carbon atoms into the iron oxide structure. For ball milling time of 12 hours a quadrupole split doublet has been added, representing the contribution of ultrafine particles. The Mössbauer spectra of graphite-doped magnetite were resolved considering a sextet and a magnetic hyperfine field distribution, corresponding to the tetrahedral and octahedral sublattices of magnetite, respectively. A quadrupole split doublet was incorporated in the fitting of the 12-hour milled sample. The recoilless fraction for all samples was determined using our previously developed dual absorber method. It was found that the recoilless fraction of the graphite-doped hematite nanoparticles decreases as function of ball milling time. The f factor of graphite-containing magnetite nanoparticles for the tetrahedral sites stays constant, while that of the octahedral sublattice decreases as function of ball milling time. These findings reinforce the idea that carbon atoms exhibit preference for the octahedral sites of magnetite.

Mössbauer Study of Graphite-Containing Iron Oxide Nanoparticles

Graphite-doped hematite and magnetite nanoparticles systems (~50 nm) were prepared by mechanochemical activation for milling times ranging from 2 to 12 hours. Their structural and magnetic properties were studied by 57Fe Mossbauer spectroscopy. The spectra corresponding to the hematite milled samples were analyzed by considering two sextets, corresponding to the incorporation of carbon atoms into the iron oxide structure. For ball-milling time of 12 hours a quadrupole split doublet has been added, representing the contribution of ultrafine particles. The Mossbauer spectra of graphite-doped magnetite were resolved considering a sextet and a magnetic hyperfine field distribution, corresponding to the tetrahedral and octahedral sublattices of magnetite, respectively. A quadrupole split doublet was incorporated in the fitting of the 12-hour milled sample. The recoilless fraction for all samples was determined using our previously developed dual absorber method. It was found that the recoilless fraction of the graphite-doped hematite nanoparticles decreases as function of ball-milling time. The f factor of graphite-containing magnetite nanoparticles for the tetrahedral sites stays constant, while that of the octahedral sublattice decreases as function of ball-milling time. These findings reinforce the idea that carbon atoms exhibit preference for the octahedral sites of magnetite.

Evaluation of Material Characteristics with Sintering Temperature in Ti2AlC MAX Phase Material using Spark Plasma Sintering Method

In this study, ternary compound Max Phase Ti2AlC material was mixed by 3D ball milling as a function of ball milling time. More than 99.5 wt% pure Ti2AlC was synthesized by using spark plasma sintering method at 1000, 1100, 1200, and 1300oC for 60 min. The material characteristics of synthesized samples were examined with relative density, hardness, and electrical conductivity as a function of sintering temperature. The phase composition of bulk was identified by X-ray diffraction. On the basis of FE-SEM result, a terraced structures which consists of several laminated layers were observed. And Ti2AlC bulk material obtained a vickers hardness of 5.1 GPa at the sintering temperature of 1100oC.

The influence of ball-milling time on the dehydrogenation properties of the NaAlH4–MgH2 composite

The recently developed NaAlH4–MgH2 composite shows improved hydrogen-storage properties compared to MgH2 and NaAlH4. However, the dehydrogenation reaction rates are still too limited, hampering practical applications. Mechanical ball milling is broadly used to improve the dehydrogenation reaction rates of hydrides. Therefore, the hydrogen-storage properties of the NaAlH4–MgH2 (1:1) composite have been investigated as a function of ball-milling time. Expectedly, elongated milling led to a faster dehydrogenation rates. New insights of the structural transformation pathways of the decomposition reaction are provided. A number of Al–Mg alloys, including the only reported Al12Mg17, seem to participate in the dehydrogenation. Thereby, complex alloying process of Al with Mg or MgH2 has been proposed. Our data indicate the possibility that hydrides Na3AlH6 and NaMgH3, which are the intermediate products of the dehydrogenation, coexist. The study shed a light on the complexity of the decomposition pathways of hydride mixtures in which the key role play alloys.

아연-공기전지용 페롭스카이트 산화물 촉매의 산소환원반응 특성

Abstract >> LaCoO 3 powders synthesized by Pechini process were pulverized by planetary ball-milling to decreaseparticle size and characterized as a catalyst in alkaline solution for oxygen reduction and evolution reaction (ORR& OER). The changes of physical properties, such as particle size distribution, surface area and electric conductivity,were analyzed as a function of ball-milling time. Also, the variations of the crystal structure and surface morphologyof ball-milled powders were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrochemically catalytic activities of the intrinsic LaCoO 3 powders decreased with increasing ball-milling time, but their electrochemical performance as an electrode improved by the increase of the surfacearea of the powder. Key words : Zn-air battery(아연공기전지), Cathode(양극), Perovskite(페롭스카이트), LaCoO 3 , Oxygen reduction(산소환원), Oxygen evolution(산소발생) † Corresponding author : jpshim@kunsan.ac.kr [ 접수일 : 2014.06.27 수정일 : 2014.07.10 게재확정일 : 2014.08.31 ]Copyright ⓒ 2014 KHNES

Structural and magnetic properties of Li2O–Fe2O3 ceramic nanostructures

xLi2O–(1−x)α-Fe2O3 (x=0.1, 0.3, 0.5, and 0.7) nanoparticle systems were successfully synthesized by mechanochemical activation of Li2O and α-Fe2O3 mixtures for 0–12h of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale, which is of crucial importance for catalysis, sensing and electrochemical applications. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of xLi2O–(1−x)α-Fe2O3 nanoparticle systems under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the particle size as function of composition and milling times and indicated the presence of Li-substituted hematite and tetra lithium iron oxide LiFeO2, along with the formation of multiple phases for large x values and long milling times. The Mössbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with lithium oxide. Magnetic measurements recorded at 5K to room temperature (RT) in an applied magnetic field of 50,000Oe showed that the magnetization of the milled samples is larger at low temperatures than at RT and increases with decreasing particle size. Zero field cooling measurements made possible the determination of the blocking temperatures of the specimens as function of ball milling time and evidenced the occurrence of superparamagnetism in the studied samples. This result correlates well with the observed presence of a quadrupole-split doublet in the Mössbauer spectra.

Synthesis and Characterization of Indium Oxide Doped Hematite xIn2O3·(1-x)α-Fe2O3 Solid Solution

ABSTRACTIndium oxide-doped hematite xIn2O3·(1-x)α-Fe2O3 (x = 0.1-0.7) solid solution systems were synthesized using mechanochemical activation. The microstructures, magnetic and thermal properties of the system were dependent on In2O3 molar concentration x and ball milling time. XRD results showed that the completion of In3+ substitution of Fe3+ in hematite lattice occurs after 12 h ball milling for x = 0.1. For x = 0.3, 0.5 and 0.7, the substitutions between In3+ and Fe3+ into hematite and In2O3 lattices occur simultaneously. The lattice parameters of hematite and In2O3 vary as a function of ball milling time. The change in these parameters was due to ions substitution between In3+and Fe3+ and the decrease in grain sizes. Mössbauer spectra of the system with x = 0.3 were fitted with three sextets and two quadrupole-split doublets after milling, representing In3+ substitution of Fe3+ in hematite lattice and Fe3+ substitution of In3+ in two different sites of In2O3 lattice. TGA results showed that the hematite decomposition is enhanced due to the smaller hematite grain size. The crystallization of hematite and In2O3 was suppressed with the drops of enthalpy values due to the stronger solid-solid interactions after ball milling. These caused gradual In3+-Fe3+ substitution in hematite/In2O3 lattices.

Mechanochemical synthesis and characterization of xIn2O3·(1 − x)α-Fe2O3 nanostructure system

Indium oxide-doped hematite xIn2O3·(1 − x)α-Fe2O3 (x = 0.1–0.7) nanostructure system was synthesized using mechanochemical activation by ball milling and characterized by XRD, simultaneous DSC–TGA, and UV/Vis/NIR. The microstructure and thermal behavior of as obtained system were dependent on the starting In2O3 molar concentration x and ball milling time. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. After 12 h of ball milling, the completion of In3+ substitution of Fe3+ in hematite lattice occurs for x = 0.1, indicating that the solid solubility of In2O3 in hematite lattice is extended. For x = 0.3, 0.5, and 0.7, the substitutions between In3+ and Fe3+ into hematite and In2O3 lattice occur simultaneously. The lattice parameters a and c of hematite and lattice parameter a of indium oxide vary as a function of ball milling time. The changes of these parameters are due to ion substitutions between In3+ and Fe3+ and the decrease in the grain sizes. Ball milling has a strong effect on the thermal behavior and band gap energy of the as-obtained system. The hematite decomposition is enhanced due to the smaller hematite grain size. The crystallization of hematite and In2O3 was suppressed, with drops of enthalpy values due to the stronger solid–solid interactions after ball milling, which caused gradual In3+–Fe3+ substitution in hematite/In2O3 lattices. The band gap for hematite shifts to higher energy value, while that of indium oxide shifts to lower energy value after ball milling.

Synthesis and characterization of xTiO 2[rad](1 − x)α-Fe 2O 3 magnetic ceramic nanostructure system

Rutile-doped hematite xTiO 2 (1 − x)α-Fe 2O 3 (x = 0.0–1.0) nanostructures were synthesized using mechanochemical activation by ball milling. Their complex structural, magnetic and thermal properties were characterized by X-ray diffraction, Mössbauer spectroscopy and simultaneous DSC–TGA. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. For the molar concentrations x = 0.1 and 0.3, the Mössbauer spectra were fitted with one, two, three or four sextets, corresponding to the degree of Ti ion substitution of Fe ions in hematite lattice. After 12 h of ball milling, the completion of Ti ion substitution of Fe ions in hematite lattice occurs for x = 0.1 and 0.3. For x = 0.5 and 0.7, Mössbauer spectra fitting required sextets and a quadrupole-split doublet, representing Fe ions substituting Ti ions in the rutile lattice. The completion of Fe ion substitution of Ti ions in rutile lattice was not observed, as indicated by XRD patterns and Mössbauer spectra for these two molar concentrations. Simultaneous DSC–TGA measurements revealed that the mechanochemical activation by ball milling has a strong effect on the thermal behavior of this nanostructure system. The enthalpy dropped dramatically after 2 h of milling time, indicating the strong solid–solid interactions between TiO 2 and α-Fe 2O 3 after ball milling. The change in weight loss of hematite was caused by the decrease of grain size and ion substitutions between Fe and Ti after mechanochemical activation.

Mössbauer spectroscopy study of the synthesis of SnFe2O4 by high energy ball milling (HEBM) of SnO and α-Fe2O3

The formation of single phase nanoparticles of spinel structured ferrite, SnFe2O4, by mechanochemical syntheses using HEBM of stoichiometric amounts of solid SnO and α-Fe2O3 with acetone as surfactant was achieved progressively as function of ball milling time. Single phase SnFe2O4 formation commenced from five hours of continuous ball milling, and reached completion after 22 hours, thereby yielding a material with a lattice parameter of 8.543 Å, and particle size of 10.91 nm. The coercivity was 4.44 mT, magnetic saturation value of 17.75 Am2/kg, and remanent magnetizations of 1.50 Am2/kg, correspondingly. The nanosized particles exhibited superparamagnetic behavior phenomenon based on Mössbauer spectroscopy measurements. The kinetic analyses based on the modified Kissinger method yielded four characteristic stages during the thermal evolution of the 22 hours milled state with activation energies of 0.23 kJ/mol, 2.52 kJ/mol, 0.024 kJ/mol, and 1.57 kJ/mol respectively.

Effects of ball-milling on the hydrogen sorption properties of LaNi 5

Pressure–composition isotherms of LaNi 5 alloys were studied as function of ball-milling time. Results indicate that ball-milling convert a part of the LaNi 5 to a non-absorbing state—a state which does not absorb hydrogen under conditions where un-milled LaNi 5 powders absorb and transform to LaNi 5H 6, in addition to particle size reduction and creation of defects. The non-absorbing fraction in the milled sample is found to grow with increase in the ball-milling time. The resistance to the hydride formation of the long-time ball-milled LaNi 5 samples is found to continue even after a 1-h high vacuum annealing at around 1000 K. This indicates that the hydrogen-absorption-resist-anomalous state formed during the long-time ball-milling is rather stable.

Mechanochemical Synthesis of Novel Sensor Materials

AbstractThe xZnO-(1-x)alpha-Fe2O3 and xZrO2-(1-x)alpha-Fe2O3 nanoparticles systems have been obtained by mechanochemical activation for x=0.1, 0.3 and 0.5 and for ball milling times ranging from 2 to 24 hours. Structural and magnetic characteristics of the zinc and zirconium-doped hematite systems were investigated by X-ray diffraction (XRD), Mössbauer spectroscopy and conductivity measurements. Using the dual absorber method, the recoilless fraction was derived as function of ball milling time for each value of the molar concentration involved. As ZnO is not soluble in hematite in the bulk form, the present study clearly illustrates that the solubility limits of an immiscible system can be extended beyond the limits in the solid state by mechanochemical activation. Moreover, this synthetic route allowed us to reach nanometric particle dimensions, which makes these materials very important for gas sensing applications.

Structure and characterization of cerium-doped hematite nanoparticles

Cerium-doped hematite particles of the type x CeO 2 -(1− x )α-Fe 2 O 3 ( x =0.1, 0.5) were synthesized using mechanochemical activation and characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). XRD patterns yielded the dependence of lattice parameters and particle size as a function of ball milling time for each value of the molar concentration x . For x =0.1, the Mössbauer spectra were fitted with one or alternatively, two sextets, corresponding to Ce ions substituting Fe ions in the hematite structure. For x =0.5, Mössbauer spectra fitting required the addition of a quadrupole-split doublet, representing Fe substituting Ce in the CeO 2 lattice. We evidenced this transition using our recently developed method for precise determination of the recoilless fraction in a single room-temperature transmission Mössbauer measurement of a two-absorber sample. We observed the occurrence of a minimum in the values of the recoilless fraction for t =4 h of milling, followed by a further decrease of the f factor due to the appearance of nanoparticles in the system. This system was also obtained by magnetomechanical activation in an applied magnetic field of 0.4 T. It was concluded that magnetic ball milling is a useful technique for obtaining magnetic systems with dilute impurities. TEM and high-resolution TEM were performed on the milled samples to examine the morphology of the nanoparticles obtained.