High-energy Ball Milling Time Research Articles

Influence of milling time in solid-state synthesis on structure, morphology and electrochemical properties of Li4Ti5O12 of spinel structure

A high-energy ball-milling process was used for the solid-state synthesis of single phase powders of spinel-structured lithium-titanium oxide (Li4Ti5O12). The influence of the high-energy ball-milling time on the structure, morphology, and electrochemical performance of synthesized powders was investigated. Remarkably, the electrochemical tests performed at high rates showed significantly improved specific capacity of the powders obtained with extended synthesis times. In particular, after 50 charging/discharging cycles at the current rate of 1C, the samples retained more than 94% of their initial specific capacity.

Structure and magnetic properties of low-temperature phase Mn-Bi nanosheets with ultra-high coercivity and significant anisotropy

The microstructure, crystal structure, and magnetic properties of low-temperature phase (LTP) Mn-Bi nanosheets, prepared by surfactant assistant high-energy ball milling (SA-HEBM) with oleylamine and oleic acid as the surfactant, were examined with scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. Effect of ball-milling time on the coercivity of LTP Mn-Bi nanosheets was systematically investigated. Results show that the high energy ball milling time from tens of minutes to several hours results in the coercivity increase of Mn-Bi powders and peak values of 14.3 kOe around 10 h. LTP Mn-Bi nanosheets are characterized by an average thickness of tens of nanometers, an average diameter of ∼1.5 μm, and possess a relatively large aspect ratio, an ultra-high room temperature coercivity of 22.3 kOe, a significant geometrical and magnetic anisotropy, and a strong (00l) crystal texture. Magnetization and demagnetization behaviors reveal that wall pinning is the dominant coercivity mechanism in these LTP Mn-Bi nanosheets. The ultrafine grain refinement introduced by the SA-HEBM process contribute to the ultra-high coercivity of LTP Mn-Bi nanosheets and a large number of defects put a powerful pinning effect on the magnetic domain movement, simultaneously. Further magnetic measurement at 437 K shows that a high coercivity of 17.8 kOe and a strong positive temperature coefficient of coercivity existed in the bonded permanent magnet made by LTP Mn-Bi nanosheets.

Study on the Mechanical Alloying Process for Preparing Ag/LSCO Electrical Contact Material

The mechanical alloying process for preparing Ag/LSCO electrical contact materials were explored, and process parameters were optimized, such as reaction environment, process control agent types and dosage, high-energy ball milling time and the composition of Ag@LSCO intermediate composite particles. The results show that Ag/LSCO electrical contact sheet with compact structure were successfully achieved, when the reaction environment is air, 3wt% PEG6000 was employed as process control agent, the high energy ball milling time is 40h, and the Ag@LSCO intermediate composite particles were made of Ag and LSCO powders with mass ratio of 80:20. More importantly, the density, Vickers hardness and resistivity of Ag/LSCO electrical contact sheet all met or exceeded the requirements for practical application. Consequently, this study can provide a significant reference for industrial production of Ag/LSCO and other environmentally friendly silver-based electrical contact materials.

ZnO Nanopowders as Chemical Sensor to Malathion Vapor

Thick lms of zinc oxide (ZnO) nanopowders have been prepared by high energy ball-milling for various spans of mill time (3 18 h). The morphology and crystal structure of the prepared ZnO powder were characterized by scanning electron microscope and X-ray di raction. The ZnO thick lms were then used to construct a gas sensor for O,O-dimethyl dithiophosphate of diethyl mercaptosuccinate (malathion) at di erent operating temperatures. The sensor response at 100 ppm of malathion was found to reach a maximum as large as 80 at 6 h of high energy ball-milling, four times larger than that found for ethanol. Scanning electron microscope observation of the granular state and pore size distribution analyses indicated that increasing high energy ball-milling time gave rise especially to an increase in the volume of pores in the pore size range of 6 35 nm. It is suggested that such a change in nanostructure is responsible for the marked promotion of the response to malathion.

Effect of milling time on dual-nanoparticulate-reinforced aluminum alloy matrix composite materials

Carbon nanotubes (CNT) and nano-silicon carbide (nSiC)-reinforced aluminum (Al)-6061 alloy matrix composite materials were fabricated using high-energy ball milling and hot-pressing processes. The nSiC was used not only as a solid mixing agent to better disperse the CNTs in the Al powder, but also as a mean of inducing fine particle strengthening. The densification behavior of the dual-nanoparticulate-reinforced composites varied with the milling time. The crystallite sizes of Al in composites became significantly smaller when the milling time was increased. Moreover, the high-energy ball milling time significantly affected the microstructure and mechanical properties of the composites. We believe that the dual-nanoparticulate-reinforced composites can be used in a variety of applications as industrial component materials with precisely controlled properties.

Effect of high-energy ball milling time on structural and magnetic properties of nanocrystalline cobalt ferrite powders

Cobalt ferrite nanocrystals synthesized by conventional and size-controlled coprecipitation methods were treated by high-energy ball milling, HEBM, in order to study the effect of crystal size reduction and/or strain on the resulting magnetic properties. Processed nanocrystals were characterized by X-ray diffraction, Brunauer, Emmett, and Teller surface area analysis, transmission electron microscopy (TEM), and vibrating sample magnetometry. The cobalt ferrite nanocrystals exhibited crystal size reduction from initial values (average crystallite sizes of 12±1nm and 18±3nm, respectively) down to 10nm after HEBM for 10h. The specific surface area was decreased by milling (from 96.5 to 59.4m2/g; for the 12nm cobalt ferrite nanocrystals), due to particles aggregation. TEM analyses corroborated the aggregation of the nanoparticles at such long milling times. The same cobalt ferrite nanocrystals exhibited a rise in coercivity from 394 to 560Oe after 5h ball milling which was attributed to the introduction of strain anisotropy, namely point defects, as suggested by the systematic shift of the diffraction peaks towards higher angles. In turn, the magnetic characterization of the starting 18nm-nanocrystals reported a drop in coercivity from 4506Oe to 491Oe that was attributed predominantly to size reduction within the single domain region. A correlation between particle size, cationic distribution, and HEBM processing conditions became evident.

Preparation of fine-grained tungsten heavy alloys by spark plasma sintered W–7Ni–3Fe composite powders with different ball milling time

The fine-grained tungsten heavy alloys (WHAs) with grain size of about 1–3μm were successfully prepared by spark plasma sintered W–7Ni–3Fe composite powders with different high-energy ball milling (HEBM) time. This study analyzes the effects of HEBM time not only on the composite powders but on the microstructure and mechanical properties of WHAs. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the microstructure and phase evolution rules of powders and alloys, respectively. The γ-(Ni, Fe, W) is not observed in XRD patterns of the ball milled powders. With prolonging HEBM time, the W phase diffraction peak becomes increasingly wider, and its intensity continues to decline. However, the completely amorphous structures are not formed even after HEBM 40h. The relative density of the WHAs prepared by HEBM assisted SPS technique decreases gradually with increasing the ball milling time. For the WHAs sintered in 1150°C for 8min, the W grains grow finer and the content of the γ-(Ni, Fe, W) binding phase greatly increases with prolonging the HEBM time. Meanwhile, over 5h of HEBM time, the bending strength continuously decreases and the hardness slightly increases. The intergranular fracture of the W grains is the main bending fracture mode in all the WHAs. The microporous of different sizes are distributed on the bending fracture and progressively increased with prolonging the ball milling time.

Effect of high-energy ball milling time on superconducting properties of MgB2 with low purity boron powder

MgB2 bulks and tapes were fabricated using ball-milled precursor powders. The selected B powders have the β-rhombohedral crystalline structure as a main phase, with a small amount of MgO impurity. Milling time was tested from 0.5 to 120 h to get an optimized value. It is found that ball milling can facilitate MgB2 phase formation, refine the MgB2 grains and increase the defect density. Moreover, the active area, Bc2 and flux pinning are improved, which is of benefit to the enhancement of Jc performance. The 80 h milled MgB2 bulk sample has a Jc value of 2.8 × 104 A cm−2 at 5 K and 6 T, 41 times larger than that of the 0.5 h sample. At the same time, the transport Jc of the 80 h MgB2 tape reaches 2.3 × 103 A cm−2 at 4.2 K and 9 T, 32 times larger than that of the 0.5 h one. Due to the increase of impurities and the release of lattice deformation and strain, the Jc was decreased for the sample milled up to 120 h.

Influences of Ball-Milling Time on Gas-Sensing Properties of ZnO-WO<sub>3</sub> Nanocomposites

The relevance of sensor response to NO2 with the nanostructure of the sensing body was investigated for thick-film devices using ZnO(WO3) nanocomposites. When the nanocomposites was prepared from constituent oxides by milling in a high energy ball mill for various spans of time (1–21 h), the sensor response to 100 ppm NO2, defined as the ratio of the electrical resistance in air to that in the sample gas, was found to reach a maximum as large as about 80 at 21 h of high energy ball-milling (HEBM). XRD and SEM observations of the granular state and pore size distribution analyses indicated that increasing HEBM time gave rise especially to an increase in the volume of pores in the pore size range of 20–35 nm. It is suggested that such a change in nanostructure is responsible for the marked promotion of the response to NO2. For comparison, the response to NO2 of ZnO or WO3 nanoparticles prepared by an HEBM method was also presented. In this case, the response to NO2 can be 10 times larger at HEBM for 21 h.

The effect of ball milling on the microstructure of powder metallurgy aluminium matrix composites reinforced with MoSi 2 intermetallic particles

Six hot extruded Al–Mg–Si composites reinforced with 15 vol.% of MoSi 2 intermetallic particles were processed by powder metallurgy, varying reinforcement size and high energy ball milling time. The relation between these parameters and matrix microstructure, final reinforcement size and particle distribution has been investigated. Reinforcement distribution was quantified through the coefficient of variation of the mean near-neighbour distance, COV( λ m), which demonstrated to be the most sensitive method to characterize this feature. The results show that by increasing milling time homogeneity of MoSi 2 distribution significantly increased, achieving a COV( λ m) = 0.41, independently of initial reinforcement size. Increasing milling time, the submicrometric matrix grains and reinforcing particles together with the homogeneous reinforcement distribution gave rise to higher tensile properties without loss of ductility.

Preparing La 0.8Sr 0.2MnO 3 conductive perovskite via optimal processes: High-energy ball milling and calcinations

La 0.8Sr 0.2MnO 3 perovskite, characterized with high conductivity and temperature resistance, is potential material for solid oxide fuel cell (SOFC) interconnects or interconnect coating. Preparation processes of La 0.8Sr 0.2MnO 3 were optimized via high-energy ball milling (HEBM) and calcinations in order to synthesize efficiently a specimen with low electrical resistivity. The optimal process conditions were determined to be an HEBM time of 3 h, sintering temperature of 1200 °C, sintering time of 15 h and triple cycle. The lowest resistivity generated by the optimized process was 0.0039 Ω m, namely 0.10 Ω in the form of bulk electrical resistance. To summarize, La 0.8Sr 0.2MnO 3 perovskite characterized by low resistivity was produced with high preparation efficiency through the optimal process.

Piezoelectric and Dielectric Properties of PMN-PNN-PZT Ceramics with the Variation of High Energy Ball Milling Time

In this study, in order to develop the composition ceramics for low temperature sintering multilayer piezoelectric actuator, Pb(Mn1 / 3Nb2 / 3)O3−Pb(Ni1 / 3Nb2 / 3)O3− Pb(Zr0.48Ti0.51)O3 (abbreviated as PMN-PNN-PZT) ceramics were fabricated using Li2CO3, Na2CO3 and ZnO as sintering aids and according to the Ball milling time. And also, their dielectric and piezoelectric properties were investigated. At the High Energy Ball Milling (HEBM) time of 9 h and sintering temperature of 900°C, density, electromechanical coupling coefficient (kp), mechanical quality factor (Qm), dielectric constant (ϵr) and piezoelectric constant (d33) of PMN-PNN-PZT ceramics showed the excellent values of 7.978 g/cm3, 0.57, 1239, 1451 and 395 pC/N, respectively for low temperature sintering multilayer piezoelectric device application.

Electrical properties and microstructure of Y-doped BaTiO3 ceramics prepared by high-energy ball-milling

The effects of corn-starch content and high-energy ball-milling time on the microstructure and electrical properties of porous Y-doped (Ba, Sr)TiO3 samples were investigated. All the (Ba, Sr)TiO3 samples at room temperature crystallized in the tetragonal structure and the crystal structure was independent of the corn-starch content and ball-milling time. We found that the corn-starch additive and the ball-milling time affected the microstructure and the electrical properties. The (Ba, Sr)TiO3 samples exhibited a large PTCR jump (>105) due to the high porosity. The PTCR jump of the samples increased with increasing corn-starch content, while it decreased with increasing ball-milling time. In addition, the resistivity increased with increasing corn-starch content, while it decreased with increasing ball-milling time.

Preparation of porous BaTiO3-based ceramics by high-energy ball-milling process

Porous BaTiO3-based ceramics containing potato-starch (0–15 wt.%) were prepared by wet mixing and the effect of high-energy ball-milling time (1–20 h) on the electrical property and microstructure of the porous ceramics has been investigated. With increasing potato-starch content and ball-milling time, the porosity of the BaTiO3-based ceramics containing potato-starch increased and decreased, respectively. The grain size decreased and increased, with increasing potato-starch content and ball-milling time, respectively. The room-temperature electrical resistivity of the porous ceramics slightly increased with increasing potato-starch content, and decreased with increasing ball-milling time. PTCR jump of the porous ceramic was slightly increased with increasing potato-starch content, while it was slightly decreased with increasing ball-milling time.

Influence of mechanical activation of AL2O3 on synthesis of magnesium aluminate spinel

Magnesium aluminate (MA) spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.