Comparative study on sintering behavior of Al86Ni6Y4.5Co2La1.5 mechanically alloyed amorphous powder and melt-spun ribbon

In this research work, the sintering characteristics of Al₈₆Ni₆Y_4.5Co₂La_1.5 mechanically alloyed amorphous powders and milled melt spun ribbon have been compared. Mechanically alloyed amorphous powders were synthesized via 200?h high energy ball milling. Melt spun ribbons were synthesized by single roller melt spinning technique and grounded to powder form by ball milling. Mechanically induced partial crystallization occurred in the ribbons during milling. Significantly higher amount of contaminations such as carbon, oxygen and iron were observed in the mechanically alloyed amorphous powders compared to the milled ribbons. Both powders were consolidated via spark plasma sintering. Superior particle bonding was found in the sample consolidated from milled ribbons, ascribed to the lower amount of contamination that could not effectively restrict the viscous flow and diffusion of atoms. Various complex crystalline phases evolved in the sample consolidated from milled ribbon particles due to the presence of crystalline phases in the powders which acted as nucleation sites, whereas the amorphous phase was mostly retained in its counterpart. Vickers microhardness of the consolidated alloys from milled ribbon and mechanically alloyed amorphous powders were 3.60?±?0.13?GPa and 2.53?±?0.09?GPa, respectively. The higher hardness in the former case was attributed to the superior particle bonding and distribution of hard intermetallic phases in the amorphous matrix.     

Synthesis of LiMn2O4 via high-temperature ball milling process

Spinel LiMn₂O₄ powder was prepared by a novel process of high-temperature ball milling. For comparison, the spinel LiMn₂O₄ powder was also synthesized by the traditional method of solid state reaction. It was found that high-temperature ball milling significantly decreased the synthesis temperature and time. LiMn₂O₄ with pure spinel phase could be successfully synthesized only by 2?h high-temperature ball milling at 500°C and 600°C. However, pure spinel LiMn₂O₄ could not be completely synthesized by 2?h solid state reaction at 800°C. The LiMn₂O₄ particles prepared by high-temperature ball milling are nano-sized (<100?nm) and much smaller than that prepared using solid state reaction. The electrochemical tests results indicated that the as-synthesized LiMn₂O₄ by 2?h high-temperature ball milling at 600°C showed a favorable initial discharge capacity of 124.2 mAh g^?1 at current rate of 0.1 C and still retained a capacity of 119.8 mAh g^?1 at 0.1 C after 80 continuous cycles from 0.1 to 2.0 C.     

Oscillatory combustion of propene during in situ mechanical activation of solid catalysts

Mechanochemical activation of solids can lead to a strong increase in their activity as catalysts in heterogeneously catalyzed reactions. In the following, we report on the effects of solid catalyst activation during ball milling that lead to oscillatory behavior in CO and CO₂ formation during propene oxidation. The oscillations arise under in situ ball milling conditions over chromium(III) oxide (Cr₂O₃) and cerium(IV) oxide (CeO₂), respectively. The experiments were conducted under continuous gas flow at ambient pressure and temperature, using both a modified steel and a tungsten carbide milling vessel. Abrasion of particles from the steel milling vessel could be eliminated as the sole cause for the oscillations through substitution by a tungsten carbide milling vessel. The intensity and frequency of oscillations are shown to be dependent on the propene-to-oxygen ratio, the milling frequency, milling ball size and metal oxide used. Overall, Cr₂O₃ shows higher activity for oscillatory propene combustion under in situ mechanical activation than CeO₂.     

Direct fabrication of anatase/activated carbon nano-hybrid materials by hydrothermal with ball milling method at low temperature

Nano-hybrid materials of anatase and activated carbon were fabricated in a single step by a hydrothermal with ball milling method (H with B) using a conventional autoclave and SiC balls at 180°C. To investigate the influence of ball milling and activated carbon, a hydrothermal method without ball milling (H without B) and a carbonless hydrothermal method with ball milling (Carbonless H with B) were performed. By comparing the three samples based on Transmission Electron Microscopy (TEM) observation and Selected Area Electron Diffraction (SAED) analysis, it was revealed that TiO₂ particles in the hybrid materials heterogeneously nucleate on the activated carbon and have a tendency of crystal growth along the c axis under the given experimental condition. The crystal growth direction was controlled isotropically by assisting the ball milling during reaction. The balls seem to act as a stirrer rather than a grinder for the sample containing the activated carbon.     

On the mechanism of mechanochemical synthesis of Ti2SC from Ti/FeS2/C mixture

In this study, the synthesis of Ti₂SC MAX phase by high energy ball milling, and the effects of heat treatment on ball milled powder was investigated. To this aim, a mixture of Ti, FeS₂ (as sulfur source), and C according to Ti₂SC stoichiometry, were ball milled by a planetary ball mill for different milling periods up to 10 h. The structural evolution, and the morphology of the products was studied by x-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), respectively. The results showed that after 10 h of ball milling, the raw materials reacted together and resulted in the formation of Ti₂SiC and TiC phases. The ball milled powder was then compacted and heat treated at 1000 and 1200 °C. Heat treatment caused the progressing of synthesis reactions, and led to increasing the purity of Ti₂SC phase. The heat-treated powder was leached in 1 M HCl for 2 h to remove iron from the product. The XRD results confirmed successful iron removal by leaching. SEM micrographs of the final product revealed the specific lamellar structure of MAX phases. Elemental mapping confirmed the homogeneous distribution of Ti, S and C elements.     

Effects of dispersant addition on the synthesis of indium-doped calcium zirconate by co-precipitation techniques

The synthesis of In₂O₃-doped CaZrO₃ by solid oxide and oxalate co-precipitation routes has been studied. The effects of using polymeric surfactants (PEG) and ball milling on the synthesis were determined by characterizing the materials at various stages using SEM, XRD, FTIR and particle size analysis. PEG addition and ball milling led to the formation of smaller particles which reduces the time and temperature needed for perovskite formation.     

Mechanochemical synthesis and characterization of xIn2O3��(1???x)��-Fe2O3 nanostructure system

Indium oxide-doped hematite xIn₂O₃·(1 ? x)??-Fe₂O₃ (x = 0.1?C0.7) nanostructure system was synthesized using mechanochemical activation by ball milling and characterized by XRD, simultaneous DSC?CTGA, 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?Csolid interactions after ball milling, which caused gradual In³⁺?CFe³⁺ 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.     

The Effect of Silver Inclusion on Superconducting Properties of YBa2Cu3O y Prepared Using Planetary Ball Milling

The effect of Ag inclusion on the structure microstructure and the critical current density of the YBa₂Cu₃O_7?δ sample prepared using the planetary ball milling process has been investigated. YBa₂Cu₃O_7?δ ceramics have been synthesized in air by a solid state reaction method from an oxide precursor powder, which was prepared from the starting powders of Y₂O₃, Ba₂CO₃, and CuO via a one-step annealing process in air at 950 ^°C. After planetary ball milling for 4 h of the oxide precursor powders, it was mixed with an AgNO₃ solution, and then was dried and uniaxially pressed, and subsequently annealed at 950 ^°C in air. Phase analysis by X-ray diffraction (XRD), granular structure examination by scanning electron microscopy (SEM), microstructure investigation by transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDXS) were carried out. To understand the effects of the ball milling on the pinning behavior, magnetic field and temperature dependences on a critical current density have been studied. Analyses show that Ag-milled YBCO samples exhibit higher values of critical current density in applied magnetic field compared to Ag-unmilled one. The better pinning properties of the Ag-milled samples are believed to be due to the microstructure of more fine and uniform distribution of silver and Y-deficient nanosized generated by ball milling.     

Formation kinetics of Ni–15% Fe–5% Mo during ball milling

Systematic study on Ni–15% Fe–5% Mo by high energy ball milling of elemental Mo powder and pre-alloyed intermetallic FeNi₃ has been done to understand the formation kinetics during ball milling. X-ray powder diffraction (XRPD) has been employed to study the structure evolution. Mo atoms were found to dissolve into FeNi₃ within 40 h of milling. The speed of the diffusion of Mo atoms into FeNi₃ alloy was very slow as analyzed using the Johnson–Mehl–Avrami (JMA) equation. The substitution process destroyed the long-range FeNi₃ and NiMo bonds were formed. This change caused a decrease in magnetization.     

The Structure and Magnetic Properties of Fe-Si-Cu-Nb-B Powder Prepared by Mechanochemical Way

We have studied the influence of the long-term (1700 h) milling on the structure and magnetic properties of Fe_73.5Si_13.5Cu₁Nb₃B₉ powder prepared in a vibratory mill. Three samples (in amorphous state, partially crystallized state, and mixed of pure elements) of the same chemical content were prepared. We found that the structure and magnetic properties significantly depend on the milling time. The coercivity of the sample prepared from pure elements monotonously increases with increased milling time. The coercivity of the samples milled from the ribbon increases to its maximum for milling time of 800 h and then decreases.     

Enhanced photocatalytic performance of Cu2O nano-photocatalyst powder modified by ball milling and ZnO

In this paper, a ball milled Cu₂O-ZnO nano-photocatalyst with good photocatalytic performance in visible light range was prepared. Effect of ZnO presence and ball milling of Cu₂O on the structure, microstructure, optical properties and photocatalytic performance were studied. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) analysis and UV–Vis spectrophotometer were used as characterization techniques. FESEM results indicated that ball milling of Cu₂O changed the morphology of Cu₂O-ZnO composite. The uniform formation of ZnO particles with average size of 30 nm over the Cu₂O surface was observed. The formation of p-n heterostructure with good contact between Cu₂O and ZnO nanoparticles was found by HRTEM image. Ball milling of Cu₂O promotes visible light absorption and reduction band gap to 1.9 eV in Cu₂O-ZnO photocatalyst. Intensity of PL spectra for the ball milled Cu₂O-ZnO photocatalyst was obviously lower. Ball milled Cu₂O-ZnO photocatalyst shows the highest photocatalytic activity and degradation efficiency of 98% was obtained for 2 mg/L methylene blue (MB) solution after 240 min. The kinetics of the photodegradation was followed the Langmuir-Hinshelwood (L-H) model and degradation rates were decreased by increase of MB concentration. In the case of ball milled Cu₂O and presence of ZnO, the MB degradation kinetics was two times faster.     

Effect of preliminary high-energy ball milling on the structural-phase state and microhardness of Ni3Al samples obtained by spark plasma sintering

The study of the influence of the duration of preliminary high-energy ball milling on the features of the structural-phase state and the level of microhardness of consolidated Ni₃Al samples obtained by the method of spark plasma sintering has been carried out. It was found that the inhomogeneous state of the precursor from the 3Ni-Al powder mixture in the case of preliminary ball milling of a short duration (1 min) is a cause of the formation of an inhomogeneous structural-phase state of the consolidated Ni₃Al sample. An increase in the duration of high-energy ball milling provides a homogeneous phase composition, promotes the refinement of the grain structure and an increase in the microhardness values of the obtained Ni₃Al samples. The main factors determining the processes of structural-phase transformation during the formation of Ni₃Al under the conditions of spark plasma sintering, depending on the preliminary high-energy ball milling, are revealed. It is shown that grain boundary strengthening is the one of the effective mechanisms for increasing the strength of the material under study.     

Synthesis of TiC by controlled ball milling of titanium and carbon

Titanium and carbon powder mixtures with compositions of Ti_100−x C _x (x = 50, 40, 30) were milled under a helium atmosphere using a magneto ball mill. Controlled ball milling was performed in a higher energy impact mode and a lower energy shearing mode. For Ti₅₀C₅₀ and Ti₆₀C₄₀ powder mixtures milled in impact mode, TiC was formed via a mechanically-induced self-propagating reaction (MSR). When milling Ti₇₀C₃₀ in impact mode, the reaction to form TiC proceeded gradually as milling progressed; indicating that, for milling conditions that lead to the formation of TiC via MSR, a minimum carbon content is required to sustain the self-propagating reaction to form TiC. Milling in shearing mode resulted in the gradual formation of TiC during milling. This study found that increasing the carbon content of the starting powder mixture slowed the milling process. Replacing the activated carbon starting powder with high purity graphite was found to have little effect on the ignition time; indicating that the slowing of the milling process is not due to graphite acting as a lubricant during milling. Rather, this slowing of the milling process is most likely due to an increased carbon content resulting in an increase in the volume of the powder mixture. This would have a similar effect during milling to decreasing the ball:powder weight ratio (BPR), which is known to slow the milling process.     

Excess Conductivity Investigation of Y<Subscript>3</Subscript>Ba<Subscript>5</Subscript>Cu<Subscript>8</Subscript>O<Subscript>18±<Emphasis Type="Italic">δ</Emphasis></Subscript> Superconductors Prepared by Various Parameters of Planetary Ball Milling Technique

Superconducting samples of type Y₃Ba₅Cu₈O_18±δ were elaborated by using a planetary high-energy ball milling (HEBM) technique with various parameters. Phases, microstructure, and superconductivity have been examined using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and electrical resistivity measurements. SEM investigation shows the occurrence of nanoentities embedded into the superconducting matrix for samples prepared by a ball milling technique. The main objective of this study is to investigate the influence of ball milling parameters on the fluctuation-induced conductivity (FIC). The electrical resistivity versus temperature, ρ(T), above T _c was analyzed using Lawrence–Doniach (LD) and Aslamazov–Larkin (AL) models. Different fluctuation regimes indicated by short-wave fluctuation (SWF) and three-dimensional (3D), two-dimensional (2D), one-dimensional (1D), and critical region (CR) fluctuations were identified. The coherence length at zero temperature, the effective layer thickness, the critical magnetic fields, and the critical current densities are determined. The superconducting parameters strongly depend on the planetary ball milling technique, and the results are explained in relevancy to the microstructure. It was found that the achievement of a microstructure with well-dispersed nanoentities is an effective way for introducing pinning centers for enhancing critical current density and flux pinning capability of bulk Y-358.     

Investigation of LaFeO3 perovskite growth mechanism through mechanical ball milling of lanthanum and iron oxides

LaFeO₃ perovskite was synthesized mechanochemically through ball milling of La₂O₃ and Fe₂O₃ in stoichiometric ratio. X-ray powder diffraction (XRPD), simultaneous differential scanning calorimetry and thermogravimetry analysis (DSC–TGA), M?ssbauer spectroscopy, scanning electron microscopy (SEM), and optical diffuse reflectance spectroscopy were combined for a detailed study of the growth mechanism of LaFeO₃ perovskite during the ball milling process. The XRPD results showed that La₂O₃ is unstable when exposed to air. Both La₂O₃ and La(OH)₃ phases coexist under the ball milling process, indicating that La₂O₃ or La(OH)₃ can be used to produce LaFeO₃. The formation of LaFeO₃ perovskite was evident after only 2 h of milling and the amount of LaFeO₃ gradually increased with the increase of ball milling time. After 12 h of ball milling, single phase LaFeO₃ was formed. The M?ssbauer spectroscopy studies show that the spectrum of the formed LaFeO₃ phase consists of three sextets and one doublet, indicating the wide distribution of LaFeO₃ particle sizes and some of the smaller particles having superparamagnetic properties. This is in good agreement with the SEM images, which show that the formed LaFeO₃ phase consists of nanometer-sized particles and micrometer-sized agglomerates. The formation of LaFeO₃ phase was mainly caused by the La³⁺ substitution of Fe³⁺ in Fe₂O₃ lattice. Optical diffuse reflectance spectroscopy studies show that the formed LaFeO₃ phase has semiconductor properties, with the band gap energy ~2.67 eV.     

Preparation of Al2O3–TiB2 nanocomposite powder by mechanochemical reaction between Al,B2O3 and Ti

Mechanochemical processing is a novel technique for the synthesis of nano-sized materials. This research is based on the production of Al₂O₃–TiB₂ nanocomposite powder using mechanochemical processing. For this purpose, a mixture of aluminum, titanium and boron oxide powders was subjected to high energy ball milling. The structural evaluation of powder particles after different milling times was conducted by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that during ball milling the Al/B₂O₃/Ti reacted with a combustion mode producing Al₂O₃–TiB₂ nanocomposite. In the final stage of milling, the crystallite sizes of Al₂O₃ and TiB₂ were estimated to be less than 50 nm.     

Synthesis and characterization of V8C7 nanocrystalline powder by heating milled mixture of V2O5, C and Ca via mechanochemical activation

In this study, nano-crystalline vanadium carbide was synthesized through reduction of V₂O₅ by carbon and Ca using high energy ball milling and subsequent heat treatment. Vanadium pentoxide, calcium and carbon black were placed in a planetary ball mill and sampled after different milling times. The activated powders were synthesized by microwave heating at temperatures 800 °C. XRD and FESEM were used for characterization of synthesized powder. On the basis of obtained results, the synthesized V₈C₇ crystallites were in the scale of nanometers and the lattice parameter had some deviation from the standard value. Furthermore, investigations showed that at higher milling time, the amorphization degree of V₄C₃ phase increased, while the degree of crystallite decreased.     

Longitudinal and transverse strength of glass ribbon for plastic reinforcement

The strength measurements for Corning Code 8871 glass ribbon with a rectangular crosssection measuring 0.22 in.×0.002 in. are presented. Owing to the narrow width of the ribbon, tensile strength measurements were carried out only in the longitudinal direction. To establish the isotropy of ribbon strength, flexure tests were conducted in both the longitudinal and transverse directions. It was found that in the as-manufactured condition, the transverse strength is lower than the longitudinal strength, indicating preferred orientation of flaws introduced during manufacturing. After etching in 10% HF/15% HNO₃ solution for different lengths of time, the longitudinal and transverse flexural strengths increased with etch time, reaching an asymptotic value after 20 sec. The transverse strength value, after etching, was generally higher than the longitudinal strength, partly due to the considerably smaller surface area exposed to tension and partly due to the uncertainties in measurement of chord length. The anisotropy of ribbon strength in the as-manufactured condition could partly account for the anisotropic strength of ribbonreinforced composites as reported in the literature [4, 5].     

Hydrogen sorption enhancement in cold-rolled and ball-milled CaNi<Subscript>5</Subscript>

The effect of cold rolling and ball milling on the hydrogen sorption properties of CaNi₅ was investigated with a special emphasis on the first hydrogenation. We compared cold rolling for 5, 12, and 25 rolling passes in the air with ball milling in argon for 30 and 60 min. Results show that 15 min of ball milling had a positive effect on the first hydrogen absorption, but further milling to 60 min made the sample almost impermeable to hydrogen. Cold rolling had a positive effect on first hydrogenation. We found that cold rolling greatly reduces the particle size as well as the crystallite size. We also found that dehydrogenation under 5 kPa of hydrogen at 323 K was not complete. Two partially hydride phases remained: CaNi₅H and Ca₂Ni₇H _x .