Dry Ball Milling Process Research Articles

Preparation of Metal-Oxide-Doped Li7P2S8Br0.25I0.75 Solid Electrolytes for All-Solid-State Lithium Batteries.

The all-solid-state lithium battery (ASSB) has received great attention due to its greater safety than the conventional lithium-ion battery (LIB). Sulfide-based inorganic solid electrolytes are an important component to fabricate the ASSB. But to attain a better performance, the ionic conductivity and electrochemical stability of the sulfide-based solid electrolytes need to be improved. In this work, we prepared the metal-oxide-doped/mixed Li7P2S8I0.75Br0.25 lithium superionic conductors by a dry ball-milling process. The high ionic conductivity was achieved by a low-temperature (200 °C) heat-treatment process. The metal-oxide-doped Li7P2S8I0.75Br0.25 solid electrolyte exhibited a higher ionic conductivity value of 7.3 mS cm-1 at room temperature than the bare Li7P2S8I0.75Br0.25 solid electrolyte. The structural characteristics of the prepared solid electrolytes were studied by solid NMR and laser Raman analysis. The electrochemical stability of the prepared solid electrolyte was studied by cyclic voltammetry and DC charge-discharge analysis. The addition of metal oxide increased the electrochemical stability and dry-air stability of the Li7P2S8I0.75Br0.25 solid electrolyte. The Ta2O5-doped Li7P2S8I0.75Br0.25 solid electrolyte was stable even after 300 charge-discharge DC cycles and also 100 h of dry-air exposure. Further, the Ta2O5-doped Li7P2S8I0.75Br0.25 solid electrolyte-based ASSB exhibited a high discharge capacity value of 184 mA h g-1 at 0.1 C rate with 66% initial cycle Coulombic efficiency.

Synthesis of glass–ceramic Li7−2xZnxP2S8–xOxI oxysulfide solid electrolyte with high chemical stability for all-solid-state lithium batteries

All-solid-state batteries remain problems to be overcome due to the high-temperature heat-treatment process, and the compatibility problem with Li metal as an anode. In this work, Li7P2S8I (LPSI) solid electrolyte with high ionic conductivity is prepared using a high-energy dry ball milling process with a low-temperature (200 °C) heat-treatment process. Then, ZnO are doped with LPSI solid electrolyte, particularly Zn2+ at the Li site and O2− at the S site, by our optimized synthesis process. The ZnO co-doping is confirmed by powder X-ray diffraction, Laser–Raman, field emission scanning electron microscopy, and nuclear magnetic resonance spectroscopy analysis. The ionic conductivity value of the prepared solid electrolytes is measured by electrochemical impedance spectroscopy analysis, and the prepared LPSI and Li6.9Zn0.05P2S7.95O0.05I solid electrolytes exhibit an ionic conductivity of (4.4 and 4.2) mS·cm−1, respectively, at room temperature. To evaluate the electrochemical stability of the prepared solid electrolyte, we perform cyclic voltammetry and galvanostatic discharge/charge voltage profiles analysis. In addition, the fabricated all-solid-state battery exhibits a high specific capacity of 165.4 mAh·g−1 (0.1 C), and a high-capacity retention rate of 95.2 %. Interestingly, ZnO co-doped LPSI solid electrolyte exhibits longer air-stability than the undoped LPSI solid electrolyte in dry air with 10 % humidity.

Preparation of Li-Excess and Li-Deficient Antiperovskite Structured Li2+xOH1-xBr and Their Effects on Total Ionic Conductivity.

This paper describes about the effect of Li-H exchange amount on total lithium-ion (Li+) conductivity of Li2+xOH1-xBr (x = -0.5 to +0.4). These samples are systematically prepared at room temperature by a dry ball-milling process using LiOH, LiOH·H2O, Li2O, and LiBr as starting materials. Synchrotron X-ray diffraction analysis reveals that single-phase Li2+xOH1-xBr samples are formed within x = -0.5 to +0.35. For improving total Li+ conductivity (σt), a larger x value increases both the Li carrier density and lattice constant as positive factors, while that decreases both the crystallite size and OH rotational unit possibly assisting Li+ conduction as negative factors. This trade-off provides an optimized σt of 3.6 × 10-6 S cm-1 at the Li-excess Li2.2OH0.8Br composition, which is ca. 3 times higher than pristine Li2OHBr (1.1 × 10-6 S cm-1). The hydrogen incorporation into the lattice is confirmed by neutron diffraction analysis, and the refined composition is almost consistent with the prepared composition.

Effects of grinding time on morphology and collectorless flotation of coal particles

The impact of particle shape and surface properties has been mainly overlooked in the literature for different mineral systems. In this study, to investigate the effects of morphological variations, samples of clean coal particles (−0.212 + 0.075 mm) were used and the flotation experimental in a batch condition (2 L Denver cell) were conducted in the absence of collectors by keeping the particle size constant. Binocular microscopic images were used to determine the shape factors of coal particles. A dry ball milling process was carried out as a function of grinding time (60–960 s) and representative samples were taken for determining both shape and floatability of particles. Further, particle-bubble attachment, zeta potential, roundness, surface roughness values and flotation kinetics were measured. It was indicated that by increasing milling duration from 60 s to 960 s, the roundness and roughness increased from 0.792 to 0.809 and 23 nm to 57 nm, respectively. This led to increasing flotation rate constant from 0.4482 ± 0.02 to 0.4856 ± 0.03 1/min. In addition, the theoretical calculations for energy barrier showed that upon increasing the roughness degree from 0 to 57 nm, the energy barrier significantly decreased from 2.79E-16 to 6.51E-17 J/m2, which also proved our findings from a theoretical point of view. Thus, it was finally concluded that the more the roughness, the higher the flotation kinetics and the lower the energy barrier.

Preparation of Graphene Nanosheets from Graphite Flakes via Shear Assisted Exfoliation

Graphene is one of the most important forms of carbon. Due to its exceptional physical, chemical, and mechanical properties, it’s used in different fields such as electronic, energy storage, and medical applications. Therefore, the production of graphene in large quantities, at a low cost, and high quality, has become critical. Using graphite powder, a few layers of graphene sheets were prepared via a series of mechanical exfoliation methods. the dry ball milling process by the planetary mill was used. Thereafter, the milling was followed by shear force and then supported by ultra-sonication to reach the lowest level of the graphene layers. Morphological properties were examined using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Also, structural characterizations were investigated using Raman spectra and X-ray diffraction measurements (XRD) and (FTIR). Findings presented in this research highlighted that the synthesis method followed was found to have several advantages, including low cost and the ease of producing a few layers of graphene nanosheets. Subsequently, the promising efficiency of the used methodology is important.

Production of multifunctional bamboo-based phase change encapsulating material by straightforward dry ball milling

Phase change materials (PCMs) have attracted much attention due to their high energy storage density and thermal efficiency. In this paper, bio-based bamboo flour (BF) and polyethylene glycol (PEG) were compounded together as a shape stable phase change material (SSPCM). A novel bamboo-based matrix for packaging organic PCMs was prepared by a simple dry ball milling process. Using the reinforcement of bamboo fiber and the porous characteristics of parenchyma cells, PEG / BF not only has high encapsulation rate, but also has high thermal conductivity. The leakage test results showed that the BF adsorption capacity with longer milling time was improved. The packaging ability of BF on PEG tended to be unchanged after 12 h of milling. The maximum loading of both PEG 4000 and 2000 in SSPCMs was 50 wt%, while PEG 10,000 was 70 wt%. The composites had good shape stability and no leakage defects. FTIR results showed that there was no new diffraction peak in composites appeared indicating that limited chemical reaction happened between BF and PEG. The results of XRD showed that the crystallinity of PEG decreased with the employ of BF. The phase transition temperature of SSPCMs measured by DSC did not depend on the content of BF. The highest melting latent heat of SSPCM was 113 J/g by PEG 10,000/30% BF and the enthalpy efficiency reached 61.08%. Continuous network structure of bamboo fiber in composites improved the thermal conductivity of the PEG/BF. The highest thermal conductivity of PEG 10,000/BF products can reach 0.64 W/m•K. The results of thermal cycle tests and TG also showed that PEG/BF had good thermal and chemical stability. The study proved that the composite had potential application value in solar energy storage combined with other materials such as polymer bamboo composites, bamboo based composites and other bamboo fiber reinforced materials.

Tuning of Li-argyrodites ionic conductivity through silicon substitution (Li6+xP1-xSixS5Cl0.5Br0.5) and their electrochemical performance in lithium solid state batteries

Lithium solid state batteries are one of the state of the art energy storage systems due to their high safety. However, ionic conductivity in solid electrolytes is a concern, because at present it does not match the ionic conductivity of non-aqueous Li-ion batteries, thus resulting in sluggish electrochemical kinetics. In this report, we enhance the ionic conductivity of Li-argyrodites (Li6PS5Cl0.5Br0.5) through Si substitution at the P-site using a dry ball milling process. Among the silicon substitutions, Li6.2Si0.2P0.8S5Cl0.5Br0.5 exhibited the high ionic conductivity of 5.12 mS cm−1 compared to pristine Li6PS5Cl0.5Br0.5 at 4.02 mS cm−1. The Rietveld refinement analysis revealed that after silicon substitution, volume of the unit cell gets increased that allows the lithium at T2-site, that promotes the fast Li-ion transport. Moreover, the optimized solid electrolyte was utilized in a solid state battery system, and demonstrated a high initial capacity of 148.1 mAh g−1 at 0.1 C rate compared to pristine argyrodite (135.1 mAh g−1). Further, we demonstrated the interface phenomena between electrode and solid electrolyte using ex-situ XPS analysis. This confirmed the formation of interface products such as LiCl, Li2S, lithium polysulfides and P2Sx, which influence the cycling stability of the ASSLBs.

A Polymer-in-Salt Electrolyte with Enhanced Oxidative Stability for Lithium Metal Polymer Batteries.

The lithium (Li) metal polymer battery (LMPB) is a promising candidate for solid-state batteries with high safety. However, high voltage stability of such a battery has been hindered by the use of polyethylene oxide (PEO), which oxidizes at a potential lower than 4 V versus Li. Herein, we adopt the polymer-in-salt electrolyte (PISE) strategy to circumvent the disadvantage of the PEO-lithium bis(fluorosulfonyl)imide (LiFSI) system with EO/Li ≤ 8 through a dry ball-milling process to avoid the contamination of the residual solvent. The obtained solid-state PISEs exhibit distinctly different morphologies and coordination structures which lead to significant improvement in oxidative stability. P(EO)1LiFSI has a low melting temperature, a high ionic conductivity at 60 °C, and an oxidative stability of ∼4.5 V versus Li/Li+. With an effective interphase rich in inorganic species and a good stability of the hybrid polymer electrolyte toward Li metal, the LMPB constructed with Li||LiNi1/3Co1/3Mn1/3O2 can retain 74.4% of capacity after 186 cycles at 60 °C under the cutoff charge voltage of 4.3 V. The findings offer a promising pathway toward high-voltage stable polymer electrolytes for high-energy-density and safe LMPBs.

Lattice dynamics of Li2FeSiO4/C from 57Fe Mössbauer spectroscopy

Lithium Iron (II) Silicate, Li2FeSiO4, is a promising cathode material for Li-ion battery applications. Its carbon composite Li2FeSiO4/C was synthesized by a simple dry ball-milling process combined with high- temperature treatment, using citric acid as carbon source, and characterized by temperature-dependence. Powder X-ray diffraction shows that it crystallizes in a monoclinic structure with (P21/n) symmetry. 57Fe Mossbauer effect studies in the temperature range 16.5–298 K were carried out. The temperature dependence of the isomer shifts was used to estimate the effective vibrating mass, Meff, yielding a value of ~87 g mol−1 for Fe in the FeO42-- moiety. This is due to the significant covalency of the Fe-0 bond in the orthosilicate composite. The temperature dependence of the recoil-free fraction (spectral areas), when combined with the effective vibrating mass calculation, yields the “Mossbauer lattice temperature” of θM = 165 K Low temperatures reveals that paramagnetic Li2FeSiO4/C becomes antiferromagnetic at 16.5 K.

Multifunctional boron nitride nanosheet/polymer composite nanofiber membranes

In this work, we successfully prepared multifunctional boron nitride nanosheets (BNNS)/polyvinyl alcohol (PVA) nanofiber membranes. Using sulfanilic acid (SA) as a medium, hexagonal boron nitride (h-BN) were exfoliated into SA-functionalized BNNS through dry ball-milling process followed with liquid-phase exfoliation based on Lewis acid-base interaction. The f-BNNS/PVA composite nanofiber membranes with different loading amounts of f-BNNS were prepared through electrospinning. The results demonstrated the electrospun f-BNNS/PVA composite nanofiber membranes show high mechanical properties and thermal conductivities. The yield and ultimate tensile strengths of f-BNNS/PVA composite nanofiber membrane at 5 wt% loading amount can reach ∼8.56 and ∼11.37 MPa. Meantime, the thermal conductivity of f-BNNS/PVA composite nanofiber membrane with 10 wt% loading amounts of f-BNNS is ∼0.7328 W/(m•K), almost 6.47 times higher than that of neat PVA membrane. Besides, the f-BNNS/PVA composite nanofiber membrane can also be used as a filtration membrane for fast malachite green (MG) absorption and separation of MG and rhodamine B dyes.

Effect of Synthesis on Performance of MXene/Iron Oxide Anode Material for Lithium-Ion Batteries.

Two-dimensional heterostructures, such as Fe2O3/MXene nanoparticles, can be attractive anode materials for lithium-ion batteries (LIBs) due to the synergy between high lithium-storage capacity of Fe2O3 and stable cyclability and high conductivity provided by MXene. Here, we improved the storage performance of Ti3C2T x (MXene)/Fe2O3 nanocomposite by confining Fe2O3 nanoparticles into Ti3C2T x nanosheets with different mixing ratios using a facile and scalable dry ball-milling process. Composites of Ti3C2T x-25 wt % Fe2O3 and Ti3C2T x-50 wt % Fe2O3 synthesized by ball-milling resulted in uniform distribution of Fe2O3 nanoparticles on Ti3C2T x nanosheets with minimum oxidation of MXene as compared to composites prepared by hydrothermal or wet sonication. Moreover, the composites demonstrated minimum restacking of the nanosheets and higher specific surface area. Among all studied composites, the Ti3C2T x-50 wt % Fe2O3 showed the highest reversible specific capacity of ∼270 mAh g-1 at 1C (∼203 mAh g-1 based on the composite) and rate performance of 100 mAh g-1 at 10C. This can open the door for synthesizing stable and high-performance MXene/transition metal oxide composites with significantly enhanced electrochemical performance for LIB applications.

Nickel Nanoparticles Decorating Graphite Flake Surface Using Planetary Ball Milling: Physical Characterization and Methanol Electrooxidation Investigation

In recent years, several researches have been conducted in order to investigate the physical and chemical method for obtain the metallic nanoparticles, such as co-precipitation, hydrothermal, thermal decomposition of organometallic compounds, electrochemical, and ball milling method [1-4]. The particle size, shape and crystallinity depend on the selected synthesis method. In this sense the ball milling technique is one of the widely used to produce metallic nanoparticles, being the method feasible for large production [4]. A simple approach was proposed to obtain graphite surface decorated with nickel nanoparticles (Ni NPs) from dry ball milling process. Ni NPs were obtained after 40 h of high energy milling and 100, 200, 300 and 400 rpm ball rotation speeds. Both Ni NPs and graphite decorated samples were characterized by Scanning Transmission (STEM), Raman Spectroscopy, Scanning Electron Microscopy, X-ray diffraction pattern (XRD). The electrocatalytic activity of Ni/Graphite samples were evaluated from methanol oxidation in alkaline medium using electrochemical techniques. Good agreement between STEM and XRD results can be found, reporting average diameter size of 4.9 nm and average crystallite size of 5.50 nm for Ni NPs. The methanol electrooxidation electrocatalytic activity was more efficient for Ni/Graphite with 100 rpm compared to Ni/Graphite others. REFERENCES M. Freire, T.S. Ribeiro, I.F. Vasconcelos, J.C. Denardin, E.B. Barros, M. Giuseppe, L. Carbone, S.E. Mazzetto, P.B.A. Fechine, MZnFe2O4 (M = Ni, Mn) cubic superparamagnetic nanoparticles obtained by hydrothermal synthesis, J. Nanopart. Res. 15 (2013) 1-12.Alonso, P. Riente, J.A. Sirvent, M. Yus, Nickel nanoparticles in hydrogen-transfer reductions: Characterisation and nature of the catalyst, Appl. Catal. A 378 (2010) 42–51.Aghazadeh, A.N. Golikand, M. Ghaemi, Synthesis, characterization, and electrochemical properties of ultrafine b-Ni(OH)2 nanoparticles, Int. J. Hydrogen Energy 36 (2011) 8674-8679.F. de Carvalho, S.N. de Medeiros, M.A. Morales, A.L. Dantas, A.S. Carriço, Synthesis of magnetite nanoparticles by high energy ball milling Appl. Surf. Sci. 275 (2013) 84-87.

The efficiency of copper ore comminution: A thermodynamic exergy analysis

This study analyzes the exergy efficiency of comminution using a laboratory sized dry ball mill and a copper mineral ore from central Chile. In this research, we develop a minimum work index from uniaxial compression tests results on the ore fitted to Morrell’s comminution energy equation using Hukki’s constant mineral parameter. An exergy analysis is then performed on a laboratory sized dry ball mill by considering the surface energy variation for different ore sizes, the obtained Hukki-Morrell fitted relationship from the compression tests of the ore and the minimum inertial energy required during a dry-ball milling process. The theoretical minimum work needed to crush the rock is first calculated by comparing the difference in surface energy between the incoming ore and the outgoing crushed rock. However, this analysis (based on the creation of new surfaces) suggests an impractical low minimum work of little use as a benchmark. Instead, use of the Hukki-Morrell relationship evaluated at the resulting ore particle sizes suggests a practical benchmark. Using this benchmark for the laboratory’s dry ball mill process renders an efficiency of approximately 3%. One could use the heat from the outgoing crushed ore to, theoretically perform work, but the heat flows through at a low temperature that this change would only increase the efficiency to 3.1%. We also consider the inertial energy needed to drive the ball mill employing it as a new benchmark for our efficiency calculation. The latter raises the efficiency of the dry ball milling to an average 23%. Finally, electrical energy measurements and inertial calculations on operating an empty versus loaded ball mill suggest that the efficiency could be increased by ensuring correct machinery scaling (diameter of the drum shell), ball load and a properly maintained transmission system.

Preparation and characterization of SiO2/C nanocomposites by a combination of mechanochemical-assisted sol–gel and dry ball milling processes

A novel preparation route was developed for synthesizing SiO2/C nanocomposites through a mechanochemical-assisted sol–gel process combined with a high-energy dry ball milling process. The effect of process parameters, such as milling time, rotation speed and carbon content, on the structure and morphology of SiO2/C nanocomposites was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and transmission electron microscopy with energy-dispersive spectroscopy. It was demonstrated from the physical characterization that the proposed preparation route might be an effective synthesis route for SiO2/C nanocomposites consisting of highly dispersed carbon nanoparticles on fine amorphous SiO2 particles. The electrochemical performance was characterized using Li|1M LiPF6 in EC:DMC=1:1| SiO2/C cells in the potential range from 0.01 to 3.0V versus Li/Li+. The SiO2/C nanocomposite prepared under optimized process conditions exhibited a highly stable reversible capacity of 663mAhg−1(872mAhg-SiO2−1) at a current density of 46mAg−1 after 30 cycles with no capacity fading.

Phase Transformation and Magnetic Property of Ni-Mn-Ga Powders Prepared by Dry Ball Milling

This study investigated the phase transformations and magnetic properties of Ni-Mn-Ga alloy powders prepared by dry ball milling in argon atmosphere. The Fe and Cr elements were found to be introduced in the alloy after ball milling, which should result from the severe collision and friction among the particles, balls, and vial. The x-ray diffraction result indicated that the Fe and Cr elements should have alloyed with the Ni-Mn-Ga matrix. The martensitic transformation temperature and Curie temperature of the 800 °C annealed powders decreased by ~33 °C and increased by ~28 °C, respectively, as compared to that of the bulk alloy. The comprehensive effect of the changing of valence electron concentration of the alloy due to the introduction of Fe and Cr and the grain refinement of the alloy caused by ball milling should be responsible for the reduction of martensitic transformation temperature. The saturation magnetization of the 800 °C annealed powders became larger (~5 emu/g) than that of the bulk alloy. The enhancement of magnetic properties, such as the increase of Curie temperature and enhancement of saturation magnetization of the annealed Ni-Mn-Ga powders, should be attributed to the increase of magnetic exchange caused by introduction of Fe in the alloy. The contaminations of Fe and Cr elements emerging from the dry ball milling process changed the phase transformation and magnetic properties of the Ni-Mn-Ga alloy. Therefore, the dry ball milling process is difficult to control the contamination from the milling medium and not suitable to prepare Ni-Mn-Ga powders. On the contrary, the wet ball milling method under liquid medium should be a better method to prevent the contamination and fabricate pure Ni-Mn-Ga ferromagnetic shape memory alloy powders.

A multitechnique approach to assess the effect of ball milling on cellulose.

This paper presents a detailed analysis of effect induced by a dry ball milling process on cellulose structure, morphology and properties. The partial amorphization of cellulose was qualitatively estimated by ATR-FTIR analysis. Through WAXD analysis the crystallinity index and the mean size of the cellulose crystallite domains were calculated, both these parameters showing a progressive decrease as a function of the milling time. In particular, crystallinity index decreased from 0.53 to 0.15 after 60min ball milling, whereas the mean size of the cellulose crystallite domains showed a reduction from the original value of about 4.0nm up to about 3.4nm after 30min. These quantitative results were confirmed by 13C CP-MAS NMR analysis and measurements of the proton spin-lattice relaxation time in the rotating frame (T1ρ1H). Moreover, the increasing of the amount of water absorbed by cellulose samples (from 7.3wt% for untreated cellulose up to 11.6wt% for the cellulose sample ball milled for 60min) and the reduction of the thermal stability were evaluated by TGA. Finally, SEM analysis revealed that the original fibrous structure almost disappeared and was modified to a quasi-circular shape.

The Influence of Milling on the Dissolution Performance of Simvastatin.

Particle size reduction is a simple means to enhance the dissolution rate of poorly water soluble BCS-class II and IV drugs. However, the major drawback of this process is the possible introduction of process induced disorder. Drugs with different molecular arrangements may exhibit altered properties such as solubility and dissolution rate and, therefore, process induced solid state modifications need to be monitored. The aim of this study was two-fold: firstly, to investigate the dissolution rates of milled and unmilled simvastatin; and secondly, to screen for the main milling factors, as well as factor interactions in a dry ball milling process using simvastatin as model drug, and to optimize the milling procedure with regard to the opposing responses particle size and process induced disorder by application of a central composite face centered design. Particle size was assessed by scanning electron microscopy (SEM) and image analysis. Process induced disorder was determined by partial least squares (PLS) regression modeling of respective X-ray powder diffractograms (XRPD) and Raman spectra. Valid and significant quadratic models were built. The investigated milling factors were milling frequency, milling time and ball quantity at a set drug load, out of which milling frequency was found to be the most important factor for particle size as well as process induced disorder. Milling frequency and milling time exhibited an interaction effect on the responses. The optimum milling settings using the maximum number of milling balls (60 balls with 4 mm diameter) was determined to be at a milling frequency of 21 Hz and a milling time of 36 min with a resulting primary particle size of 1.4 μm and a process induced disorder of 6.1% (assessed by Raman spectroscopy) and 8.4% (assessed by XRPD), at a set optimization limit of < 2 μm for particle size and < 10% for process induced disorder. This optimum was tested experimentally and the process induced disorder was determined to be 6.9% (± 2.2) by Raman spectroscopy and 7.8% (± 2.3) by XRPD. Subsequent intrinsic dissolution testing revealed that the process induced disorder was negligible with regard to the dissolution rate. The predicted primary particle size of 1.4 μm could be confirmed experimentally, but due to agglomeration of the primary particles a dissolution rate advantage was not shown, highlighting the importance of dissolution testing at an early stage of drug development.

Sinterability and ionic conductivity of coprecipitated Ce0.8Gd0.2O2−δ powders treated via a high-energy ball-milling process

Abstract Ceria-based solid solutions are promising electrolytes for intermediate-temperature, solid oxide fuel cells. The effect of a dry, high-energy, ball-milling process on the sintering and densification behaviour of coprecipitated ceria-based powders is investigated by means of X-ray diffraction, Brunauer–Emmett–Teller (BET) surface-area measurements, density measurements, and electron microscopy. The dry ball-milling process leads to (i) a larger specific surface-area with weak agglomeration; (ii) rearrangement of grains into dense granules; (iii) a higher green density. These effects significantly reduce sintering temperatures and promote densification of ceria-based ceramics. Moreover, a comparison is made of the sintering behaviour and ionic conductivity of the milled samples with and without cobalt oxide doping. Cobalt oxide is a very effective sintering aid, but usually results in an enlarged grain-boundary effect for Si-containing samples. Thus, since SiO 2 is a ubiquitous background impurity in both raw materials and ceramic processing, the dry ball-milling process is a more feasible method for improving the sinterability of coprecipitated ceria-based powders.

Formation of titanium nitrides via wet reaction ball milling

A new mechanochemical route to synthesize TiN has been developed by ball milling elemental titanium powders with the organic compound pyrazine in a benzene solution for periods of up to 336 h. The structures of the milled powders were examined by means of X-ray diffractometry. Titanium nitrides were formed directly during the milling. Unlike the dry ball-milling process, the present wet milling resulted in the formation of an intermediate titanium nitride Ti 2N which has never been found in previous studies using dry milling. With increasing milling time, Ti 2N was observed to gradually transform into the stoichiometric compound TiN. Upon heating, the Ti 2N formed during milling was completely transformed to TiN. The intrinsic mechanisms of the solid–liquid reactions are discussed.

Manufacturing of aluminum flake powder from foil scrap by dry ball milling process

A feasibility study for producing aluminum flake powder from aluminum foil scrap by dry ball milling under an inert argon with a few % of oxygen was carried out. It was found that the pieces of aluminum foil scrap were laminated to each other, elongated by micro-forging of the falling balls, fragmented into small pieces of foil and finally formed into flake powder, during the ball milling. A larger ball is more beneficial to the milling of aluminum foil into the flake powder due to the large impact energy during the falling of the ball. Intermediate stops during the ball milling produced a finer aluminum flake powder than non-stop milling for up to 25 h due to cooling of the vial. A larger amount of stearic acid reduces friction between the foil or the balls and vial wall, thus give less milling efficiency, 3 wt.% of stearic acid as additive being verified as the optimum content. The aluminum flake powder produced by the dry ball milling of aluminum foil scrap can be applied to fingerprint detection or to aerate light-weight concrete.