Duration Of Ball Milling Research Articles

Metal carbonates-induced solution-free dehydrogenation of alkaline earth metal hydrides at room temperature

We report an efficient, convenient, solution-free method to achieve the room-temperature dehydrogenation of alkaline earth metal hydrides (MgH2 and CaH2). It is found, for the first time, that metal carbonates, which are readily available and cheap, can efficiently induce the hydrogen desorption of alkaline earth metal hydrides at room temperature under mechanical ball milling conditions. We demonstrate that the hydrogen yield and purity mainly depend on the nature of metal carbonates, rate and duration of ball milling, and reaction mixture composition. The best performances are obtained with the systems of MgCO3-MgH2 and MgCO3-CaH2 milled at 350 ​rpm for 12 ​h, with the COx-free hydrogen yield of 94% and 90%. This work opens a new way to achieve the efficient dehydrogenation of alkaline earth metal hydrides at room temperature.

Multicomponent bulk metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ synthesis via reaction flash sintering and characterizations

AbstractIn this research, near fully dense single phase bulk multicomponent transition metal nitride (Nb1/3Ta1/3Ti1/3)N1−δ has been successfully synthesized from mixed commercial powders of NbN, TaN and TiN via reaction flash sintering technique. This was performed with an applied pressure of ~ 35 MPa at 25°C under a constant DC electric field (~24‐32 V/cm). The flash event, which is the abrupt increase in current (up to ~ 25.2 A/mm2) and temperature, occurred without preheating. The threshold power dissipation on the sample right before the flash is ~ 0.7 W/mm3. The formation of single phase (Nb1/3Ta1/3Ti1/3)N1−δ random solid solution and its compositional uniformity were confirmed by XRD and EDS, respectively. The effects of ball milling duration and limiting current density on phase formation were studied. Simulation based on Joule heating provides an estimate of the ultimate sample temperature of ~ 1850°C. Vickers hardness of the obtained (Nb1/3Ta1/3Ti1/3)N1−δ is 17.6 ± 0.6 GPa, which is comparable to similarly flash sintered ingredient binary nitrides of TaN and NbN. TGA in air shows that the oxidation resistance of (Nb1/3Ta1/3Ti1/3)N1−δ is better than that of TaN and NbN but inferior to TiN. The study demonstrates that reaction flash sintering can be a highly efficient technique for synthesizing bulk multicomponent ceramics for both material fundamental investigations and application development.

Effect of Powder Morphology and Chemical Distribution on Properties of Multicomponent Alloys Produced Via Powder Metallurgy

In this study, effects of morphology and chemical distribution of powder on mechanical properties was investigated in Al0.5CoCrCuFeNi high-entropy alloys produced via powder metallurgy. At the early stages of ball-milling, Cr-deficient large powder is flattened, while Cr-rich powder is fractured to small particles because of the flattening of ductile particles and fragmentation of hard particles at initial milling stage. However, with an increase in the milling duration, the Cr atoms were more uniformly distributed throughout the powders and the powders exhibited spherical shape with smooth surface. Moreover, as the ball-milling duration increased from 36 to 96 h, the Vickers hardness and compressive yield strength also increased from 433 Hv0.5 and 1166 MPa to 525 Hv0.5 and 1739 MPa, respectively. This was attributed to the spherical powders reducing as well as forming fine and uniform microstructures in sintered alloys. Also, the elemental uniformity suppressed the formation of dendritic-unfavorable carbides.

Strain-induced partial phase transition in TiO2 nanoparticles manifesting frequency dispersive pseudo-inductive switching of capacitance

The appearance of ‘negative capacitance’ (NC) in dielectric spectroscopy not always demonstrates the true reverse charge accumulation between polarizable sites in the associated system. Nonlinear transport of charge-carriers might induce an inductive growth compromising the geometrical capacitance. This sort of dispersion is investigated in mixed phase polycrystalline TiO2 powder having an initial phase ratio of anatase and rutile ~80:20, obtained through mechanical grinding up to 16 h. A significant strain-induced phase transition from anatase to rutile was affirmed from XRD and Raman analysis; whereas reduction in size was nominal. From the Energy Dispersive Analysis of X-rays (EDAX); a remarkable oxygen vacancy formation with longer duration of ball-milling has been observed. In this study, the predominant effects of oxygen vacancy formation on nonlinear hopping conduction-driven inductive response at the higher frequencies are discussed. This genre of frequency-dependent switching can provide an electrical measure of defect-density and traps present in the system. The impacts of strain-induced phase transition on the optical and electrical properties of the material are highlighted in this regard.

Influence of ball milling duration of quarry dust on the properties of nickel-quarry dust composite coating

The main purpose of this research is to investigate the effect of various ball milling duration on the surface morphology, hardness and wear properties of nickel- quarry dust (Ni-QD) composite coating on aluminium alloy 6061 (AA6061) substrate. Ni-QD composite coatings were deposited on zincated AA6061 substrate by using electrodeposition technique. The quarry dust particles were prepared by ball milling process at 5, 10, 15 and 20 hours. Later, the quarry dust particles were added to nickel citrate bath at 50 g/l for electrodeposition of Ni-QD composite coating. The electrodeposition process was carried out for 1 hour at 40º C, under the current density of 3 A/dm2. X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and scanning electron microscope (SEM) analyses were carried out in order to investigate the influence of ball milling duration on the prepared quarry dust as well as the produced composite coating. In addition, microhardness and wear testing of Ni-QD composite coatings were also performed in this study. The microhardness values of the nickel composite coatings using ball milled quarry dust are higher than using crushed quarry dust. The microhardness values for all nickel composite coatings produced from crushed and ball milled quarry dust increases from 190.6 to 282.2. The increase in microhardness values is due to the high density of quarry dust in the electrolyte. The damage of the wear scar was improved, as the ball milling duration increases from 0 to 20 hours.

Influence of preparing conditions on the hot‐pressed sintering of transparent polycrystalline fluorite ceramics

AbstractTransparent polycrystalline fluorite ceramics were manufactured from naturally occurring fluorite mineral by a hot‐pressed sintering method. Naturally occurring fluorite minerals were ball milled by a planetary milling equipment. The phase structures of powders were single cubic fluorite phase, and diameters of fluorite powders were decreased from 100 to 20 μm with increasing ball milling duration. Influence of ball milling duration and sintering temperatures on optical properties of polycrystalline fluorite ceramics were studied systematically to obtain the optimum manufacturing process. For the mineral powders after 1 hours ball‐milling, the polycrystalline ceramic hot‐pressed at 1050°C exhibited the highest optical transmission. For a 2.5 mm thickness polycrystalline ceramic, the highest optical transmission at 500 and 1500 nm were about 60.1% and 75.7%, respectively.

Effect of Ni Addition on Catalytic Performance of Fe87Si5B2P3Nb2Cu1 Amorphous Alloys for Degrading Methylene Blue Dyes

Fe-based amorphous alloys have shown great potential in degrading azo dyes and other organic pollutants. It has been widely investigated as a kind of environmentally friendly material for wastewater remediation. In this paper, we studied the effect of Ni addition on the catalytic performance of Fe87Si5B2P3Nb2Cu1 amorphous alloy for degradation of methylene blue dyes and analyzed the reaction mechanism. (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous powder with desirable performance was produced by specific ball milling durations. Characterization of the Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys prepared by ball milling was performed by XRD and SEM. Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys were used as catalysts to catalyze the degradation of methylene blue dyes, which were detected by UV-VIS near-infrared spectrophotometer. By a series of comparative experiments, it was found that a catalyst dosage of 0.2 g and a reaction temperature of 80 °C were conditions that produced the best catalytic effect. The degradation rate of (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloy to methylene blue dyes prepared by ball milling increased from 67.76% to 99.99% compared with the Fe87Si5B2P3Nb2Cu1 amorphous alloy under the same conditions.

Highly Selective Room‐Temperature Catalyst‐Free Reduction of Alkaline Carbonates to Methane by Metal Hydrides

The realization of effective CO2 conversion into valuable hydrocarbons is a promising way of addressing the current environmental and energy issues. A convenient, highly selective, and efficient method of CO2 methanation and the synthesis of COx‐free hydrogen/methane fuel mixtures by ball milling‐induced reactions of alkaline carbonates with metal hydrides (MHs) is reported. The natural resources of MgCO3/CaCO3 and MgH2/CaH2 are used as carbon and hydrogen sources, respectively. Mechanochemical investigations of the room‐temperature reactions indicate that some alkaline carbonates can be reduced by MHs under catalyst‐free conditions to selectively afford CH4 as the sole hydrocarbon product in yields of up to 73%. Moreover, the contents of methane in the gaseous products and its yield are shown, which mainly depend on the nature of metal carbonates/hydrides, rate and duration of ball milling, and reaction mixture composition. Thus, this study opens new ways to achieve the CO2 utilization and synthesize of COx‐free hydrogen and methane fuel mixtures.

Effects of etching temperature and ball milling on the preparation and capacitance of Ti3C2 MXene

Two-dimensional Ti3C2 MXene is prepared by a combination of ball milling and HF etching of Ti3AlC2 powder. Effects of etching temperature and ball milling duration on the preparation and electrochemical performance of as-prepared Ti3C2 MXene are investigated in detail. It is found that higher etching temperature and longer ball milling duration lead to faster transformation from Ti3AlC2 to Ti3C2 MXene. The ball milling treatment can improve the capacitive of Ti3C2 MXene. This improvement in the performance is attributed to higher carbon content for better conductivity and faster transportation of electrons, and the larger surface area for more access of aqueous electrolyte to the electrode.

Synthesis of nickel boride by thermal explosion in ball-milled powder mixtures

In this work, a synthesis route of Ni3B, an attractive material for making heating elements and a promising component for catalysts, was developed using high-energy ball milling of nickel and boron powder mixtures. The milling duration was varied from 1 to 15 min. Ball milling led to partial dissolution of boron in the crystalline lattice of nickel and crystallite size refinement of nickel. Heating of the ball-milled mixtures at a constant rate led to thermal explosion, the indications of which were a rapid temperature rise and the formation of boride phases. The duration of ball milling was shown to influence the phase composition of the products of thermal explosion. The time of milling ensuring the formation of single-phase Ni3B was determined to be 7 min. The ignition temperature of thermal explosion decreased with the milling time: a decrease by more than 300 °C was observed for the mixture milled for 15 min relative to the non-milled mixture. The maximum temperature developed during thermal explosion increased in the mixture milled for 1 min relative to the non-milled mixture and then decreased with the milling time reaching the level of the non-milled mixture after 15 min of milling. The observed dependence of the maximum temperature on the milling time is related to the net effect of mixing uniformity improvement between the reactants and a partial transformation of the reaction mixtures into Ni(B) solid solutions and Ni3B during milling. The proposed synthesis route of a single-phase Ni3B powder has advantages of short processing time and low-energy consumption.

Stabilized CO2 capture performance of wet mechanically activated dolomite

The rapid loss-in-capacity in CO2 capture is the major barrier to the application of abundantly available CaO-based natural minerals in calcium looping process. In this work, the mechanically activated method of wet ball-milling was tried to prepare highly efficient CO2 sorbents from naturally occurring dolomite. Two major operation parameters, ball-milling duration and solid-to-liquid ratio, closely affecting the characteristics of wet ball-milled dolomites were investigated. It is found that the prolongation of ball-milling duration is beneficial to improve the cyclic CO2 capture capability of wet ball-milled dolomite. The solid-to-liquid ratio of 1:1 is optimum to control the aggregation of dolomite particles during ball-milling process. Therefore, the dolomite milled with a solid-to-liquid ratio of 1:1 for 120 min exhibits highly stable CO2 capture performance under severe calcination conditions, achieving a high carbonation conversion of 74.8% in the 25th cycle. The superior CO2 capture performance of wet ball-milled dolomite is mainly attributed to the appreciably reduced particle size and preserved porous microstructure, which promote the accessibility of CO2 to the interior, free CaO.

Preparation of presintered zirconia blocks for dental restorations through colloidal dispersion and cold isostatic pressing

This work proposes an effective method for dispersion of zirconia suspension for dental block preparation and optimizes the cold isostatic pressing (CIP) pressure to improve the densification of slip-casted zirconia blocks. Two batches of 44wt% zirconia suspension were prepared using distilled water in a pH 2 medium containing 0.5wt% polyethyleneimine as dispersant. The first batch was sonicated for different durations (from 5min to 30min), and the second batch was dispersed through ball milling at rotational speeds of 200, 300, and 400rpm for 60, 90, and 120min. All suspensions were subjected to sedimentation test and particle size measurement. Results revealed that the optimum ultrasonication duration was 10min, which yielded the smallest particle size of 133nm. Ball milling at 300rpm for 120min achieved the maximum dispersion of particles, with an average size of 75nm. Under the optimum conditions of ultrasonication duration, ball milling duration, and ball milling speed, the particle size decreased to 48nm, which is close to the primary particle size. These dispersion techniques and parameters were selected for preparing a suspension to be consolidated into blocks through slip casting and were enhanced through CIP at pressure ranging from 100MPa to 300MPa. CIP compaction at 250MPa significantly increased the shrinkage percentage of green zirconia blocks, with pore radius decreased to 18nm. The density of zirconia pressed at 250MPa and presintered at a low temperature of 950°C was 59% of the theoretical density and was higher than that of commercial presintered blocks. Thus, CIP should be conducted under a compaction pressure of 250MPa to produce dense and homogeneous zirconia blocks.

Anomalous fading in TL, OSL and TA – OSL signals of Durango apatite for various grain size fractions; from micro to nano scale

Anomalous fading (AF) of luminescence signals has been studied extensively both experimentally and by simulations. This paper reports a new type of study of anomalous fading in grains of Durango apatite, a naturally occurring luminescent material that yields very intense anomalous fading. Grains of Durango apatite were ball milled (BM) for various durations, up to 48h. Different ball milling durations resulted in different average grain size fractions as low as 200nm, as it was indicated by Scanning Electron Microscopy (SEM) measurements. The anomalous fading effect was studied for optically stimulated luminescence (OSL), thermoluminescence (TL), as well as thermally-assisted OSL signals (TA – OSL). Anomalous fading was found to be ubiquitous for all luminescence signals, and for all apatite grain size fractions. The anomalous fading rate is weakly affected by the grain size for the cases of OSL and TL, while the TA – OSL signals were found to fade in a much slower rate than either the TL or the conventional OSL signals. An important experimental result is that the fading rate of TA – OSL decreases as the grain size fraction is decreased. For average grain size fractions between 200 and 450nm, the TA – OSL signal is unaffected by the AF effect. A differential analysis on the TL glow curves showed that the AF rate decreases with increasing temperature along the glow curve, and also with increasing BM time. Finally, a component resolved de-convolution analysis was performed for both OSL and TA – OSL decay curves and recombination lifetimes are reported for both localized and delocalized components. FTIR analysis indicates that the ball milling procedure does not induce a new phase in this material.

Aqueous ball milling of nacre constituents facilitates directional self-assembly of aragonite nanoparticles of the gastropod Haliotis glabra

A ball-milling approach was developed to investigate the constituents of isolated nacre tablets of the gastropod Haliotis glabra in aqueous suspension without additional chemical additives. The obtained particle mixtures were characterized using X-ray crystallography as well as scanning and transmission electron microscopy. Aragonite nanoparticles retained their crystal structure even after 14 h of ball milling. The long-term stability of the particle mixtures varied as a function of the ball-milling duration. An increased milling time led to rod-like stable assemblies of aragonite nanoparticles. Selected area electron diffraction investigations revealed that the longitudinal axes in about one-third of these nanoparticle rods were oriented along the crystallographic c-axis of aragonite, indicating oriented attachment of the aragonite nanoparticles. These in vitro observations support the idea that a two-stage process, separated into crystallization of nanoparticles and oriented assembly of nanocrystals, could also occur in vivo.

Processing of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 Bulk Metallic Glass Alloy by Cu Mould Casting and Spark Plasma Sintering

The present investigation deals with the processing of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 bulk metallic glass (BMG) using different techniques. The maximum plate thickness for the amorphous phase formation has been found to be 1.25 mm using a conventional BMG casting technique (forced infiltration casting). For enhancing the dimension, an alternate processing route was employed to produce the BMG in the form of compacts. In this case, the dimensions are not restricted by the glass forming ability of the alloy. The process involved the preparation of amorphous ribbons using a melt spinner followed by high energy ball milling to crush the ribbons into very fine particles. The powder was then compacted in the form of pellets using spark plasma sintering technique. Density achieved was almost near to theoretical density (99%). The density was found to increase with a decrease in the particle size of glassy powder, which could be achieved by increasing the duration of high energy ball milling. The maximum densification occurred when the holding temperature was within undercooled liquid regime (∆Tx). Further increase of temperature beyond crystallization temperature (Tx) resulted in decreasing the compact density.

Mechanochemical synthesis of COx-free hydrogen and methane fuel mixtures at room temperature from light metal hydrides and carbon dioxide

In this work, we report a novel, simple and convenient method for CO2 methanation and synthesis of hydrogen and methane fuel mixtures at room temperature. COx-free hydrogen and methane fuel mixtures have been successfully generated for the first time in one pot at room temperature through the solid/gas mechanochemical reactions of selected light metal hydrides with CO2. It is noted that methane is the sole hydrocarbon product in the mechanochemical reactions of selected light metal hydrides with CO2, which suggests that the mechanochemical reduction of CO2 by light metal hydrides is highly selective. The yield and mole fraction of methane in the gas product depend mainly on the species of light metal hydride, rate and duration of ball milling, and CO2 pressure.

Effects of cation distribution on microwave dielectric properties of Mg1−xZnxAl2O4 ceramics

The effects of duration of ball-milling on cation distribution of calcined-MgAl2O4 and -ZnAl2O4 powders were investigated by 27Al solid-state nuclear magnetic resonance (NMR) measurement; the degree of inversion (λC), which corresponds to the fraction of Al3+ in tetrahedral site, of the MgAl2O4 powder increased from 0.33 to 0.42 when the duration of ball-milling varied from 0 to 24 h, though that of the ZnAl2O4 powders ranged from 0.04 to 0.07. Thus, the preferential occupation of Al3+ cation in tetrahedral site was obtained for the calcined-MgAl2O4 powders prepared by ball-milling for 24 h. As a result, the Q·f value of the MgAl2O4 ceramics extremely increased from 85,100 to 187,200 GHz with increasing the duration of ball-milling of the calcined powders, while that of the ZnAl2O4 ceramics was almost constant with a Q·f value of approximately 100,000 GHz. Moreover, the effects of Zn substitution for Mg on the microwave dielectric properties and cation distribution of the Mg1−xZnxAl2O4 ceramics were also investigated. 27Al NMR measurement revealed that the high λ0 values, implying the degree of the redistribution of the Al3+ cation in the octahedral site during firing, were observed in the composition range of 0–0.75 and the highest Q·f value of 222,600 GHz was obtained for the Mg1−xZnxAl2O4 ceramics at x = 0.75. Thus, it is considered that the preferential occupation of Al3+ cation at tetrahedral sites of the calcined-powders caused by the ball-milling is effective to enhance the Q·f value of the Mg1−xZnxAl2O4 ceramics.

Injectable chelate-setting hydroxyapatite cement prepared by using chitosan solution: Fabrication, material properties, biocompatibility, and osteoconductivity.

An injectable chelate-setting hydroxyapatite cement (IP6-HAp), formed by chelate-bonding capability of inositol phosphate (IP6), was developed. The effects of ball-milling duration of starting HAp powder and IP6 concentration on the material properties such as injectability and mechanical strength of the cement were examined. The cement powder was prepared by ball-milling the as-synthesized HAp powder for 5 min using ZrO2 beads with a diameter of 10 mm, followed by another 60 min with ZrO2 beads with a diameter of 2 mm, and thereafter surface-modified with 5000 ppm of IP6 solution. Injectable cement was then fabricated with this HAp powder and 2.5 mass% chitosan as a mixing solution, with a setting time of 36.3 ± 4.7 min and a compressive strength of 19.0 ± 2.1 MPa. The IP6-HAp cements prepared with chitosan showed favorable biocompatibility invitro using an osteoblast cell model, and osteoconductivity invivo using a pig tibia model.

Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

AbstractHigh-energy ball milling was used to synthesize Th1-xLaxO2-0.5x (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO2 powders. Dense La-doped ThO2 pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO2 pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C.

Highly ameliorated gaseous and electrochemical hydrogen storage dynamics of nanocrystalline and amorphous LaMg12-type alloys prepared by mechanical milling

Nanocrystalline and amorphous LaMg12-type alloy-Ni composites with a nominal composition of LaMg11 Ni + x wt. % Ni (x = 100, 200) were synthesized via ball milling. The influences of ball milling duration and Ni adding amount x on the gaseous and electrochemical hydrogen storage dynamics of the alloys were systematically studied. Gaseous hydrogen storage performances were studied by a differential scanning calorimeter and a Sievert apparatus. The dehydrogenation activation energy of the alloy hydrides was evaluated by Kissinger method. The electrochemical hydrogen storage dynamics of the alloys was investigated by an automatic galvanostatic system. The H atom diffusion and apparent activation enthalpy of the alloys were calculated. The results demonstrate that a variation in Ni content remarkably enhances the gaseous and electrochemical hydrogen storage dynamics performance of the alloys. The gaseous hydriding rate and high-rate discharge (HRD) ability of the alloys exhibit maximum values with varying milling duration. However, the dehydriding kinetics of the alloys is always accelerated by prolonging milling duration. Specifically, rising milling time from 5 to 60 h makes the hydrogen desorption ratio (a ratio of the dehydrogenation amount in 20 min to the saturated hydrogenation amount) increase from 57% to 66% for x=100 alloy and from 57% to 70% for x = 200. Moreover, the improvement of gaseous hydrogen storage kinetics is attributed to the descending of dehydrogenation activation energy caused by the prolonging of milling duration and growing of Ni content.