Duration Of Ball Milling Research Articles

Synthesis and investigation of Al<SUB align="right">2O<SUB align="right">3/SiO<SUB align="right">2/ZrO<SUB align="right">2 powders for biological and medical application

This research focused on the synthesis and investigation of the thermal properties and microstructure and phase structures of the Al2O3/SiO2/ZrO2 system applied in the dental field. The ball-milling duration influence on the transformation from the alumina and silica into the mullite is also studied. Detailed investigations of the different proportions of materials on the preparation and microstructural phases of ternary eutectic were presented. Furthermore, the crystallisation process was investigated by using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results indicate that sintering microstructure of the ternary eutectic composite is greatly influenced by the materials proportions. The synthetically thermal analysis shows that the eutectic temperature of ternary Al2O3/SiO2/ZrO2 composite is 1,040°C, is well matching the phase diagram of Al2Oi3/SiO2/ZrO2. The formation of the mullite phase can be determined due to the ball-milling time 6h that could be interesting laser sintering biological and medical materials.

Preparation of Y2Ti2O7 pyrochlore using high-energy ball milling and their structural, thermal and conducting properties

Pyrochlore-structured materials are very important materials due to their structural and conducting properties. These properties can be further modified by changing processing conditions. In the present study, pyrochlore (Y2Ti2O7) is synthesized using high-energy ball milling. During various stages of ball milling, the ball-milled powder is taken for investigating the structural and thermal properties. The replacement of Ti2O3 by TiO2 in nominal composition leads to lower ball milling duration to form Y2Ti2O7. Differential thermal analysis showed the single exothermic peak below 800 °C, which indicates formation of disordered pyrochlore phase. The as prepared powders (40-h ball milled) were compacted and heat treated at 1,450 °C for 12 h. The conductivity of sintered sample is found to be one order higher than earlier reported pure Y2Ti2O7 pyrochlore.

온도 유지시간 제어를 적용한 하이브리드 분말 압출 공정을 통한 요구 특성의 스퍼기어 제조

본 연구는 압출 시 성형온도를 유지하여 Zn-22Al 합금분말의 성형성을 향상시키는 하이브리드 분말 압출 공정의 개발 및 온도 유지시간이 압출된 스퍼기어의 기계적 특성에 미치는 영향을 조사하기 위해 수행되었다. 피치원 지름 1.8mm 의 소형 스퍼기어는 압출온도 290, 300, 310℃에서 성형되었다. 볼밀시간 32h 의 Zn-22Al 합금분말을 압출온도 310℃에서 압출 시 표면 결함이 없는 소형 기어가 제조되었다. 경도분포는 기어 중심부와 치형부에서 불균일하였고 소결공정 후 내부 변형에너지의 차이로 인해 내부균열이 발생하였다. 위와 같은 문제를 해결하기 위해 온도 유지시간 제어를 이용한 하이브리드 압출 연구를 수행하였다. 압출된 스퍼기어의 평가는 압출하중, 비커스 경도 및 치수정밀도 측정을 통해 이루어졌다. 온도 유지시간 15min 에서 압출된 스퍼기어의 기계적 성질이 가장 우수하였다.

Effect of Particle Size and Sintering Procedure on Microstructure, Dielectric, Ferroelectric and Mechanical Properties of SrBi4Ti4O15

Bismuth layered-perovskite compounds such as SrBi4Ti4O15 (SBTi) ceramics are prepared by solid state reaction. The SBTi ceramics are sintered by microwave and conventional sintering techniques. In this study, the effect of ball milling on different sintering processes, microstructure as well as on dielectric, ferroelectric and mechanical properties of SBTi ceramics is emphasized. The powder has been milled to produce nanocrystalline powders using a planetary ball mill. Different samples have been prepared by varying the milling time from 5 to 20 h, keeping the milling speed fixed at 300 rpm. The X-ray diffraction results show that crystalline powders with a single perovskite structure can be obtained when calcined at 700°C for 4 h. It has been observed that the average grain size, dielectric and ferroelectric properties are dependent on the duration of ball milling. The dielectric constant and loss tangent of the conventional sintered samples range between (140 and 165), and (0.05 and 0.07) respectively and those of the microwave sintered samples range between (155 and 175), and (0.04 and 0.06) respectively when measured at 1 MHz frequency. The microwave sintering process has been found to improve the homogeneity of the grains and morphology. The microwave sintering of the SBTi ceramics leads to higher densification (98% of the theoretical density), fine microstructure and good mechanical and ferroelectric properties in much shorter duration of time than that of conventional sintering process.

Electrochemical Hydrogen Storage Characteristics of (Mg<sub>1-X</sub>Zr<sub>X</sub>)<sub>2</sub>Ni (x = 0 - 0.3) Alloys Prepared by Mechanical Alloying

The electrode alloys (Mg1-xZrx)2Ni (x = 0, 0.3) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted by Zr in order to improve the electrochemical hydrogen storage characteristics of the Mg2Ni-type alloy. The effects of substituting Mg with Zr as well as milling duration on the microstructures and electrochemical performances of the alloys were investigated in detail. The results showed that the substitution of Zr facilitates the formation of amorphous Mg2Ni-type phase. The electrochemical measurement indicated that the substitution of Zr significantly enhances the discharge capacity and cycle stability of the alloys, and it markedly improved the discharge potential characteristic of the alloys. For a fixed alloy, the electrochemical performances, including the cycle stability and the discharge voltage characteristic as well as discharge capacity, of the alloys were markedly improved with prolonging of the ball-milling duration.

Facile Synthesis of Co3O4/CoO Nanoparticles by Thermal Treatment of Ball-Milled Precursors

Co3O4/CoO nanoparticles have been synthesized by a simple method which is based on the ball-milling and calcination of cobalt acetate and citric acid. The samples were characterized using X-ray diffraction, transmission electron microscope, and Fourier transform infrared spectroscopy. The results show that Co3O4 nanoparticles with an average particle size of ∼40 nm can be obtained by calcination of ball-milled precursors at relatively low temperature (350 °C) for 3 hours. It should be noted that it is possible to control the size of Co3O4 particles by calcination temperature, calcination time and also by ball-milling duration using this method. Meanwhile, the pure CoO nanoparticles were obtained successfully by thermal decomposition of Co3O4 at 950 °C and quickly quenching to liquid nitrogen.

Preparation, Characterization of Sulfur-Doped Nanosized TiO2 and Photocatalytic Degradation of Methylene Blue Under Visible Light

Sulfur-doped TiO2 catalysts were prepared by a mechanochemical method. The prepared catalysts exhibited photocatalytic activity in methylene blue degradation under visible light. The catalyst structure has been characterized using UV–visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) as well as Fourier transform infrared spectroscopy (FT-IR). UV–visible spectroscopy revealed that the absorption edge of the doped TiO2 was red-shifted compared with bare TiO2. XRD patterns suggested that the brookite phase became more prevalent with increasing ball milling duration. In addition, surface sulfate species were detected by FT-IR, XPS and TGA. We deduce the rise of catalytic activity is due to the synergetic effect between the brookite phase and the anatase phase that would probably retard the electron–hole recombination. On the other hand, methylene blue was found to be N-demethylated during the irradiation thus giving rise to blue-shifting of peak at 664 nm in UV–visible spectroscopy.

Preparation of strontium hexaferrite magnets from celestite and iron ore fines by mechanochemical route

In the present investigation celestite and iron ore fines have been used for the preparation of strontium hexaferrite powder. The mechanical alloying process has been adopted to prepare strontium hexaferrite powder. The mixture of celestite after chemical upgradation and physically upgraded iron ore fines along with sodium carbonate was milled for different duration in a high energy planetary ball mill with tungsten carbide jar and ball to prepare strontium hexaferrite powder. A long duration of ball milling for different duration has led to solid-state displacement reaction. At the end of each experiment the product was washed thoroughly and dried. The X-ray diffraction study of milled powder after annealing shows the development of single phase strontium hexaferrite. The resultant powder was compacted under magnetic field and sintered to prepare the magnet after annealing the ferrite powder. The moderate value of coercivity, remanence and energy product were observed in this sintered magnet. The work illustrates the feasibility to prepare strontium hexaferrite magnetic powders directly from natural ores.

Electrochemical hydrogen storage performance of Mg–Ti–Zr–Ni alloys

Mg 1.5Ti 0.5− x Zr x Ni ( x = 0, 0.1, 0.2, 0.3, 0.4), Mg 1.5Ti 0.3Zr 0.1Pd 0.1Ni and Mg 1.5Ti 0.3Zr 0.1Co 0.1Ni alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. X-ray diffraction studies showed that all the replacement elements (Ti, Zr, Pd and Co) perfectly dissolved in the amorphous phase and Zr facilitated the amorphization of the alloys. When the Zr/Ti ratio was kept at 1/4 (Mg 1.5Ti 0.4Zr 0.1Ni alloy), the initial discharge capacity of the alloy increased slightly at all the ball milling durations. The further increase in the Zr/Ti ratio resulted in reduction in the initial discharge capacity of the alloys. The presence of Zr in the Ti-including Mg-based alloys improved the cyclic stability of the alloys. This action of Zr was attributed to the less stable and more porous characteristics of the barrier hydroxide layer in the presence of Zr due to the selective dissolution of the disseminated Zr-oxides throughout the hydroxide layer on the alloy surface. Unlike Co, the addition of Pd into the Mg–Ti–Zr–Ni type alloy improved the alloy performance significantly. The positive contribution of Pd was assumed to arise from the facilitated hydrogen diffusion on the electrode surface in the presence of Pd. As the Zr/Ti atomic ratio increased, the charge transfer resistance of the alloy decreased at all the depths of discharges. Co and Pd were observed to increase the charge transfer resistance of the Mg–Ti–Zr–Ni alloys slightly.

Electrochemical hydrogen storage characteristics of Mg1.5Al0.5−xZrxNi (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) alloys synthesized by mechanical alloying

Abstract Mg 1.5 Al 0.5− x Zr x Ni ( x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) type alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. X-ray diffraction studies showed that Zr facilitated the amorphization of Mg 2 Ni phase, while Al retarded the amorphization of this phase. The increase in the Zr content was observed to bring about significant improvement in the discharge capacities at all the ball milling durations. The stepwise replacement of Al with Zr, however, caused considerable reduction in the initial discharge capacities of the alloys. Despite the adverse effect of Al on the initial discharge capacity, it prevented the rapid degradation of Mg 2 Ni phase with the charge/discharge cycles. When the beneficial effects of Zr and Al were combined by designing Mg 1.5 Al 0.5− x Zr x Ni type alloys, Mg 1.5 Al 0.2 Zr 0.3 Ni alloy was found to have the highest discharge capacity at almost all the charge/discharge cycle steps. Among the obtained capacity retaining rates, Mg 1.5 Al 0.4 Zr 0.1 Ni alloy had the best performance. This alloy has kept at least 50% of its initial discharge capacity at 20th cycle. The analysis by the electrochemical impedance spectroscopy revealed that the charge transfer resistances of Al-rich alloys were low at high depth of discharges. This observation was attributed to the formation of the porous unstable Mg(OH) 2 layer due to the intercalation of Al 2 O 3 layers, which have the high rate of solubility in strongly basic solutions, and thus the exposition of the underlying electrocatalytically active Ni sites.

Regeneration of spent-NaBH 4 back to NaBH 4 by using high-energy ball milling

High-energy ball milling was employed to regenerate spent-sodium borohydride, i.e., mainly the sodium metaborate (NaBO 2), back to sodium borohydride (NaBH 4) by a reaction with magnesium hydride (MgH 2). The samples were characterized using scanning electron microscopy (SEM), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy. In general, as the ball-milling duration increases, the yield of NaBH 4 increases accordingly and leads to an extreme value of 76%, when MgH 2 in stoichiometric excess by 40% was initially present in ball mills.

Effects of Ball-Milling Duration on Microstructure and Electrochemical Characteristics of Mg2-xZrxNi(x=0–0.6) Electrode Alloys

Abstract The Mg2Ni-type electrode alloys Mg2-xZrxNi (x=0, 0.15, 0.3, 0.45 and 0.6) were prepared by mechanical alloying (MA) with different ball-milling duration. The microstructures and the electrochemical characteristics of the experimental alloys were tested and measured systemically. The effects of ball-milling duration on the microstructures and electrochemical performances of the alloys were investigated in detail. The results obtained by XRD and TEM show that the amorphous phase in the alloy increases with prolonging of ball-milling duration. The electrochemical measurements indicate that the cycle stability and the discharge potential characteristics of the alloys are markedly improved with prolonging of ball-milling duration. The effect of the ball-milling duration on the discharge capacity of the alloys is dependent on their composition. For x≤0.3, the discharge capacity of the alloys mono-tonically increases with prolonging of milling duration. But for x>0.3, it has a maximum value with the change of milling duration.

Preparation and Characterization of Nano structured Materials from Fly Ash: A Waste from Thermal Power Stations, by High Energy Ball Milling

The Class F fly ash has been subjected to high energy ball milling and has been converted into nanostructured material. The nano structured fly ash has been characterized for its particle size by using particle size analyzer, specific surface area with the help of BET surface area apparatus, structure by X-ray diffraction studies and FTIR, SEM and TEM have been used to study particle aggregation and shape of the particles. On ball milling, the particle size got reduced from 60 μm to 148 nm by 405 times and the surface area increased from 0.249 m2/gm to 25.53 m2/gm i.e. by more than 100%. Measurement of surface free energy as well as work of adhesion found that it increased with increased duration of ball milling. The crystallite was reduced from 36.22 nm to 23.01 nm for quartz and from 33.72 nm to 16.38 nm for mullite during ball milling to 60 h. % crystallinity reduced from 35% to 16% during 60 h of ball milling because of destruction of quartz and hematite crystals and the nano structured fly ash is found to be more amorphous. Surface of the nano structured fly ash has become more active as is evident from the FTIR studies. Morphological studies revealed that the surface of the nano structured fly ash is more uneven and rough and shape is irregular, as compared to fresh fly ash which are mostly spherical in shape.

Hydriding Properties of MgH2-Mg2Ni0.8Co0.2 Composites Obtained by Ball Milling

Abstract The hydrogen absorption-desorption characteristics of composites consisting of 90 wt.% MgH2- 10 wt.% Mg2Ni0.8Co0.2 prepared by ball milling for 30 and 180 min under argon have been investigated. The results obtained have been compared with those for the 90 wt.% Mg-10 wt.% Mg2Ni0.8Co0.2 composite synthesized in the same medium after 30 min of milling. The presence of the Mg2Ni0.8Co0.2 phase has been found to improve the hydriding kinetics of magnesium, the absorption capacity remaining high at temperatures below 573 K. The use of magnesium hydride instead of magnesium has proved to have a favorable effect on the properties of the composites after prolonged activation in an inert medium. It has been established that the absorption-desorption characteristics of the composite 90 wt.% MgH2-10 wt.% Mg2Ni0.8Co0.2 activated mechanically for 180 min are comparable with those of the composite 90 wt.% Mg-10 wt.% Mg2Ni0.8Co0.2 after mechanical activation for only 30 min. The favorable absorption-desorption characteristics of the composites have been explained with the catalytic effect of the additive, the presence of magnesium hydride and the duration of ball milling.

Electrochemical characteristics of mechanical alloyed [formula omitted][formula omitted] electrode alloys

The electrode alloys ( Mg 1 - x Zr x ) 2 Ni ( x = 0 , 0.1 ) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted with Zr in order to improve the electrochemical characteristics of the Mg 2 Ni -type alloy. The microstructures and the electrochemical characteristics of the experimental alloys were measured systemically. The effects of substituting Mg with Zr as well as the relevant MA technique on the microstructures and electrochemical performances of the alloys were investigated in detail. The results show that the substitution of Zr is favourable for the formation of an amorphous phase. The electrochemical measurement indicated that the substitution of Zr can dramatically enhance the discharge capacity and cycle stability, and it markedly improves the discharge voltage characteristic of the alloys. For a fixed alloy, the electrochemical performances, including the cycle stability, the discharge voltage characteristic and discharge capacity, of the alloys were significantly improved with the increase of the ball-milling duration.

Mechanochemical synthesis of nano-sized Bi2V0.9Cu0.1O5.35 powders

Nano-sized Bi2V0.9Cu0.1O5.35 powders were synthesized via a mechanochemical route from the component oxide mixture. However, a ball-milling duration of over 30 h was needed to ensure a high phase purity. Otherwise, the milled samples had poor sinterability and low sintered density since expansion occurred during sintering.

Wear of Mg-5%Al-5%Nd Alloy with Nanocrystalline Grain Size

This paper explores the wear characteristics of nanocrystalline Mg-5%Al-5%Nd, synthesized by mechanical alloying. Pin-on-disc unlubricated sliding wear tests were conducted against a hardened tool-steel counterface under loads of 10 and 30 N, and within a velocity range of 0.2-5.0 m/s. Despite its appreciably superior mechanical properties, the nanostructured alloy did not exhibit the expected improvement in wear resistance when compared to its conventional microngrain- sized counterpart; in fact, the former performed worse when testing conditions became more severe. Scanning electron microscopy (SEM) suggested that extensive delamination in the nanocrystalline alloy was the primary reason for its high wear rates. This wear mechanism was promoted by the presence of MgxNd dispersiods, which were found only within the nanocrystalline material. These compounds likely resulted from the long duration (20 hrs) of ball-milling, which was the mechanical alloying technique employed to reduce the grain size of the final alloy.

Microstructure characterization of ball milled prepared nanocrystalline perovskite CaTiO 3 by Rietveld method

Perovskite CaTiO 3 has three polymorphic phases: cubic, tetragonal and orthorhombic. The present article deals with the first time preparation of nanocrystalline orthorhombic polymorphs of CaTiO 3 by high energy ball milling the equimolar mixture of CaO and anatase (a)-TiO 2 powders. It has been observed that a small amount of CaTiO 3 is formed just after 1 h of ball milling and the wt.% of the phase increases with increasing milling time. The starting mixture is transformed almost completely to nanocrystalline CaTiO 3 within 6 h of ball milling. To verify the stability of the phase at high temperature, the 6 h milled powder has been post-annealed at 773 and 1273 K for 2 h. Phase transition kinetic study, quantitative phase estimation and microstructure characterization of CaTiO 3 and other secondary phases evolved at different duration of ball milling in ball milled samples have been critically analyzed by Rietveld’s powder structure refinement method using X-ray powder diffraction data. Nanocrystalline (∼6 nm) CaTiO 3 powder has been obtained within 1 h of milling but in the course of milling up to 6 h of duration, crystallite size is seen to increase gradually with increasing milling time due to agglomeration of nanosized crystallites. It has been observed that the a-TiO 2 has been transformed to polymorphic srilankite(s)-TiO 2 phase and nanosized CaTiO 3 crystallites are formed by the solid state diffusion of nanosized s-TiO 2 and CaO crystallites. Post-annealing study reveals that the orthorhombic CaTiO 3 phase is stable up to 1273 K with larger and strain free crystallites of ∼125 nm.

The microstructure of mechanically alloyed Al–Mg determined by X-ray diffraction peak profile analysis

The effect of the nominal Mg content and the milling time on the microstructure and the hardness of mechanically alloyed Al-rich Al-Mg solid solutions is studied. The crystallite size distribution and the dislocation structure are characterized by X-ray diffraction (XRD) peak profile analysis and the hardness is obtained from depth-sensing indentation tests. Magnesium gradually goes into solid solution during ball milling and after 3 h an almost complete solid solution is attained. With increasing milling time, the Mg concentration in solid solution, the dislocation density and the hardness increase, whereas the crystallite size decreases. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing nominal Mg content. After 3 h milling there are no changes in both the microstructure and the hardness.

The Microstructure of Mechanically Alloyed Nanocrystalline Aluminium-Magnesium

The effect of the nominal Mg content and the milling time on the microstructure of mechanically alloyed Al(Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all of the Mg atoms are soluted into the Al matrix. With increasing milling time the Mg content in solid solution, the dislocation density as well as the hardness are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for a long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.