Wet Mechanical Milling Research Articles

Effects of ball milling medium on Cu-Al spinel sustained release catalyst for H2 generation from methanol steam reforming

Using pseudo-boehmite and ultrafine copper hydroxide as the raw materials with n(Cu/Al) = 1:3, the effects of ball milling medium on the Cu-Al spinel sustained release catalysts prepared via the solid-state reaction method are explored. The obtained catalysts are characterized by XRD, BET, and H2-TPR techniques, and their catalytic properties in methanol steam reforming (MSR) are evaluated. The results demonstrate that Cu-Al spinel solid solution can be synthesized by both dry and wet mechanical ball milling methods, and more Cu2+ ions are found to be incorporated into the spinel lattice through the latter method. The crystalline sizes of as-synthesized spinels are similar; however, the specific surface areas and pore volumes are different as well as their reduction properties. Compared with the dry milling method, the wet ball milling method can facilitate the solid phase reaction, generating catalysts with solely spinel crystalline phase, higher specific surface area, and larger pore volume. Furthermore, catalysts derived from the wet milling method demonstrate improved catalytic activity and stability, and lower CO selectivity in MSR. The highest activity is obtained over CuHAl-Ac-950 prepared using ethanol (95%) as the ball milling medium.

Study of the effect of lanthanum and cerium doping combination on magnetic properties of M-type hexaferrite oxide permanent magnets

A study has been carried out on the effect of combination of Lanthanum and Cerium doping on the magnetic properties of M-Type hexaferrite permanent magnet oxide. The research was conducted using the wet mechanical milling method. The research materials used were Fe2O3, BaCO3, La2O3, and CeO2, all of which were of high purity 99.9%. This research also uses technical materials such as Ethanol and Nitrogen. Stoichiometric calculations were carried out to calculate the composition of the mixture of each ingredient. The combination of Lanthanum and Cerium substitution was varied with the composition of the doping ion concentration (x = 0 – 0.5 and y = 0 – 0.1). Permagraph characterization was carried out to determine the magnetic properties of each test sample. Results based on the permagraph characterization, the properties of M-type hexaferrite permanent magnets increased with the increase in the doping ion concentration in the sample. The presence of doping ions that have a magnetic moment is strongly suspected to contribute to the interaction of the type and the total moment in the M- type hexaferrite structure.

Influence of multi‐walled carbon nanotube content on electromagnetic wave absorption and mechanical properties of carbon nanotube/polyamide 12 composite

AbstractThree‐dimensional printing has proven to be a convenient and effective method for manufacturing structured electromagnetic wave (EMW) absorbers with adjustable EMW absorption characteristics. In this study, composites of multi‐walled carbon nanotube (MWCNT) and polyamide 12 (PA12) were prepared via wet dispersion and mechanical ball milling followed by melt extrusion. The effects of different levels of MWCNT content on the EMW absorption and mechanical properties of the MWCNT/PA12 composite were examined. Within the MWCNT content from 7 to 12 wt%, the flexural strength of the composite increases with the addition of MWCNT, and the impact strength, tensile strength, and volume resistivity of the composite decrease with the addition MWCNT. With regard to the best impedance matching, when sodium dodecylbenzene sulfonate was used as the dispersant, the lowest reflection loss observed herein for the MWCNT/PA12 composite was −20 dB, which was achieved with an MWCNT content of 10 wt%. Furthermore, the composite exhibited superior mechanical properties. The tensile and flexural moduli of the composite were 18.85% and 33.97% higher than those of pure PA12, respectively. Moreover, the MWCNT/PA12 composite was proven to be a high performance modeling material suitable for fused deposition modeling. And the tensile strength, flexural modulus, and impact strength of the printed samples can reach 94.45%, 92.94%, and 85.51% of those of the injection‐molded samples, respectively.

Wet Mechanical Milling Induced Phase Transition to Cubic Anti-Perovskite Li2OHCl

Anti-perovskite solid-state electrolyte Li2OHCl usually exhibits orthorhombic phase and low ionic conductivity at room temperature. However, its ionic conductivity increases greatly when the temperature is up to 40 °C, while it goes through an orthorhombic-to-cubic phase transition. The cubic Li2OHCl with high ionic conductivity is stabilized at room temperature and even lower temperature about 10 °C by a simple synthesis method of wet mechanical milling. The cubic Li2OHCl prepared by this method performs an ionic conductivity of 4.27 × 10−6 S/cm at room temperature, about one order of magnitude higher than that of the orthorhombic Li2OHCl. The phase-transition temperature is decreased to around 10 °C. Moreover, it can still remain cubic phase after heat treatment at 210 °C. This work delivers a huge potential of fabricating high ionic conductivity phase anti-perovskite solid-state electrolyte materials by wet mechanical milling.

Soft Magnetic Nanocrystalline Ni-Fe-X-Y and MeFe2O4 Powders Obtained by Mechanosynthesis

"The soft magnetic nanocrystalline powders, alloys (Ni3Fe, 79Ni16Fe5Mo, 77Ni14Fe5Cu4Mo, wt. %) and zinc ferrite, were obtained by dry and wet mechanical alloying and reactive milling, followed by different heat treatments. The powders were characterised by X-ray diffraction, scanning electron microscopy, X-ray microanalysis, differential scanning calorimetry, thermomagnetic and magnetic measurements. The X-ray diffraction shown the progressive new phases formation. The crystallite size is between 18-7 nm depending on materials and milling conditions. The particle size is smaller for wet-mechanical alloying comparing with dry-milling. The thermomagnetic measurement shown the Curie temperature of the alloys. The spontaneous magnetisation of the wet-milled and annealed samples is higher than of the molten alloys. Keywords: mechanical alloying; Ni-Fe-X-Y alloys; soft ferrite; magnetisation; XRD; DSC. "

Synthesis and characterization of permanent magnetic oxide system Ba1-x-yLaxCeyFe12O19 system doped with La-Ce metal using wet mechanical milling method

The development of permanent magnet-based rare earth metals becomes a serious problem if the raw materials are difficult to find. The solution chosen is to utilize an oxide-based permanent magnet with little substitution of rare earth metals. In this study presented a permanent magnetic synthesis of barium hexaferrite-based oxides that were doped with La and Ce atoms. The synthesis of this material uses the wet mechanical milling technique to obtain the single phase permanent magnet system Ba1-x-yLaxCeyFe12O19 (x = 0, 0.02, 0.04 and y = 0. 0.05, 0.1). The precursor is weighed according to stoichiometric composition and is milled for 5 hours then compressed at a pressure of 7000 Psi. Sintering temperature for the formation of the barium hexaferrite phase at 1200oC for 2 hours. All samples after sintering were characterized using XRD and EDS. A single phase is obtained on all sample compositions with a hexagonal P63/mmc structure and is supported by elemental analysis data that each substituted sample contains elements La and Ce. Lattice parameters a, b, and c appear to decrease with increasing concentrations of La and Ce doping ions with a ratio of c/a in the range of 3.93-3.94.

Effect of powder manufacturing process on characteristics of nanostructured MCrAlY coatings: dry vs. wet ball milling

Metallic MCrAlY coatings have been widely utilized to protect the high-temperature materials operating in aggressive conditions of gas turbines. However, with more demands on the turbine inlet temperature rise for efficiency gains, there is a need to further improve the high-temperature performance of the MCrAlY coatings. A possible way to meet this challenge is by microstructure modification. The aim of this study is to produce nanocrystalline MCrAlY powders via wet and dry mechanical milling techniques and deposit the obtained feedstock powders by high-velocity oxygen fuel (HVOF) spraying method. A comprehensive characterization and comparison of the different powder processing techniques and the corresponding coatings were studied. It was established that the nano-scaled MCrAlY feedstock powder with low contamination levels could be achieved by mechanical milling. Moreover, the powder samples were well-deposited by the HVOF process and the correlation between powder properties and coating characteristics was investigated.

Production of aluminum nanoparticles by wet mechanical milling

AbstractOne of the great challenges in the use of nanomaterials is their production at low costs and high yields. In this work aluminum nanoparticles, from aluminum powder, were produced by wet mechanical milling through a combination of different attrition milling conditions such as ball-powder ratio (BPR) and the amount of solvent used. It was observed that at 600 rpm with a BPR of 500/30 g for 12 h, it was possible to produce nanoparticles with a size close to 20 nm, while at 750 rpm with a BPR of 380/12.6 g for 12 h, nanoparticles of approximately 10 nm were obtained. Scanning and transmission electron microscopy confirmed that the milling product is an agglomeration of nanoparticles with different sizes. These results show the feasibility of obtaining aluminum nanoparticles by mechanical milling using only ethanol as solvent, avoiding hazardous by-products obtained from chemical routes, and the use of complicated methods such as laser ablation and arc discharge.

Irregularly Shaped Iron Nitride Nanoparticles as a Potential Candidate for Biomedical Applications: From Synthesis to Characterization.

Magnetic nanoparticles (MNPs) have been extensively used in drug/gene delivery, hyperthermia therapy, magnetic particle imaging (MPI), magnetic resonance imaging (MRI), magnetic bioassays, and so forth. With proper surface chemical modifications, physicochemically stable and nontoxic MNPs are emerging contrast agents and tracers for in vivo MRI and MPI applications. Herein, we report the high magnetic moment, irregularly shaped γ′-Fe4N nanoparticles for enhanced hyperthermia therapy and T2 contrast agent for MRI application. The static and dynamic magnetic properties of γ′-Fe4N nanoparticles are characterized by a vibrating sample magnetometer (VSM) and a magnetic particle spectroscopy (MPS) system, respectively. Compared to the γ-Fe2O3 nanoparticles, γ′-Fe4N nanoparticles show at least three times higher saturation magnetization, which, as a result, gives rise to the stronger dynamic magnetic responses as proved in the MPS measurement results. In addition, γ′-Fe4N nanoparticles are functionalized with an oleic acid layer by a wet mechanical milling process. The morphologies of as-milled nanoparticles are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), and nanoparticle tracking analyzer (NTA). We report that with proper surface chemical modification and tuning on morphologies, γ′-Fe4N nanoparticles could be used as tiny heating sources for hyperthermia and contrast agents for MRI applications with minimum dose.

Effects of wet and dry ball milling on the physicochemical properties of sawdust derived-biochar

Ball milling has been used as a green method for the modification of biochars in recent years. Therefore, the effects of physicochemical properties of biochars derived from sawdust via dry and wet mechanical ball milling and hand lapping were integrally compared in this study. Elemental analyses show the significant reduction of the C content and increase in the ash content for the resulting 12 h-wet-ball-milled biochar. The specific surface areas of the dry- and wet-ball-milled biochars were significantly larger than those of the pristine and hand-lapping biochars. Scanning electron microscopy (SEM) images of the biochars show that 12 h of wet ball milling produced smaller and better-distributed particles. Good thermal stability of the resulting biochars (less than 5% of mass losses) was confirmed by thermogravimetric (TG) analysis. Fourier transform infrared (FT-IR) spectra show that long-term wet ball milling (12 h) increased the functional groups of the resulting biochars. The various ball milling processes have no obvious impact on the phase in the biochars characterized by the x-ray diffraction (XRD) pattern. Overall, long-term wet ball milling (12 h) is a simple method for the preparation of smaller and better-distributed biochar composites.

Facile preparation of Cr2O3 nanoparticles and their use as an active catalyst on the thermal decomposition of ammonium perchlorate

ABSTRACTCr2O3 nanoparticles were prepared by repeated wet mechanical milling technique. Three drying methods, oven drying, vacuum drying, and vacuum freeze-drying were comparatively used to dry Cr2O3 nanoparticles. These processes can be easily scaled up to 10-kg quantities. It took only 2–3 h to cut bulk size to nanometer by milling. The obtained Cr2O3 nanoparticles are semi-spherical and homogeneous with an average size of 30 nm measured by SEM and TEM and show similar diffraction peak positions to bulk one investigated by XRD. The TG/DSC study indicated that, compared with bulk Cr2O3, Cr2O3 nanoparticles obtained by oven drying and vacuum drying, the catalytic performance of Cr2O3 nanoparticles obtained by vacuum freeze-drying is the best in lowering the peak temperature of high temperature decomposition and the activation energy, while increasing the apparent decomposition heat and the reaction rate constant of ammonium perchlorate (AP) due to their good dispersion and large specific surface area. The possible catalytic mechanism of Cr2O3 on the thermal decomposition of AP was proposed by TG-MS analysis. These findings showed that wet mechanical milling technique combined with vacuum freeze-drying technology is suitable for efficient preparation of Cr2O3 nanoparticles, which could be a promising additive for accelerating the thermal decomposition of AP.

Anhydrous proton conduction of 0.6CsHSO4-0.4H4SiW12O40 (CHS-WSiA) composite materials fabricated by dry and wet mechanical ball milling

Abstract Anhydrous proton conductive 0.6CsHSO4-0.4H4SiW12O40(CHS-WSiA) composites (in molar ratio) were fabricated by dry and wet mechanical milling. From X-ray diffraction (XRD), the diffraction peak with the highest intensity of WSiA shifted to higher angle from 25.5° to 26.2° in the composites synthesized via dry and wet mechanical ball milling, which indicated that H+ ions in WSiA were partly substituted with Cs+ ions in CHS via ion-exchange reaction to form CHS-WSiA composites. The structural characterizations and conductivity of CHS-WSiA composites fabricated by CHS and WSiA were studied by XRD, thermogravimetry analysis, field emission scanning electron microscopy, and electrochemical impedance analysis (EIS), respectively. The proton conductivities of the composites were largely increased via high chemical interaction between CHS and WSiA, particularly in the low temperature region under a superprotonic phase-transition of CHS. The highest proton conductivity of 9.41 ×10-4 S cm-1 was achieved at 170°C under dry nitrogen atmosphere for 0.6CHS-0.4WSiA composites obtained by wet milling process.

Effects of cesium-substituted silicotungstic acid doped with polybenzimidazole membrane for the application of medium temperature polymer electrolyte fuel cells

Inorganic-organic composite membranes were prepared by using partly cesium-substituted silicotungstic acid (CHS-WSiA) and polybenzimidazole (PBI, MRS0810H) for medium temperature polymer electrolyte fuel cells (MT-PEFCs). Cesium hydrogen sulfate (CsHSO4, CHS) and silicotungstic acid (H4SiW12O40, WSiA) were milled to obtain 0.5CHS-0.5WSiA composites by dry and wet mechanical millings. N,Ndimethylacetamide (DMAc) was used as a disperse medium in the preparation of the inorganic solid acids by wet mechanical milling and also a casting agent for fabrication of membrane. Finally, flexible and homogeneous composite membranes with several phosphoric acid doping levels (PADLs) were obtained. The wet mechanical milling using DMAc was found to effectively promote good substitution of H+ ion in WSiA by Cs+ ion of CHS and promoted the formation of smaller grain sizes of composites, compared with dry milling. A high maximum power density of 378 mWcm-2 and a good constant current stability test were obtained from a single cell test using the PBI composite membrane containing 20 wt% of 0.5CHS-0.5WSiA from wet milling and phosphoric acid doping level (PADL) of 8 mol, at 150 °C under an anhydrous condition. Wet milling CHS-WSiA crystallites were highly dispersed in PBI to give homogenized membranes and played a significant role in the enhancemance of acidity by increasing the number of proton sites in the electrolyte membrane. After the addition of CHS-WSiA into PBI membrane, the acid and water retention properties were improved and incorporated as new proton conduction path by adsorbing phosphoric acid in these composite electrolyte membranes. These observations suggest that composite membranes with 8 mol of PADL are good promising PA dopedmembranes with effective electrochemical properties for the medium temperature fuel cells.

Synthesis and structural properties of xLi2MnO3⋅(1-x)LiNi0.5Mn0.5O2 single crystals towards enhancing reversibility for lithium-ion battery/pouch cells

A series of xLi2MnO3·(1-x)LiNi0.5Mn0.5O2 (x = 0.3, 0.4, 0.5 and 0.6) single crystals is successfully synthesized via wet mechanical ball milling. Considering the components of Li2MnO3 and LiNi0.5Mn0.5O2 in xLi2MnO3·(1-x)LiNi0.5Mn0.5O2, the Mn 2p X-ray photoelectron spectra are successfully refined to Mn3+ and Mn4+ states in each component. Through GITT evaluation of the dynamic DLi+, the minimum DLi+ value is observed for the initial charging, which is attributed to the irreversible process of Li2O being removed from the layered Li2MnO3 structure. The DLi+ values in the 1st charge process are lower than those in the 3rd charge process. The 0.4Li2MnO3·0.6LiNi0.5Mn0.5O2 sample exhibits the best electrochemical properties compared to the other samples. At a 0.1 C current rate, it delivers 212 mAh g−1 without capacity loss for 100 cycles. At current rates of 1 and 2 C, it delivers 158.5 and 102.1 mAh g−1, respectively. In the full cell state (pouch cell), the 0.4Li2MnO3·0.6LiNi0.5Mn0.5O2 sample presents practical electrochemical properties that deliver 180 mAh g−1 for 100 cycles at a 0.1 C rate.

Effect of F-doping on the properties of LiFePO4-x/3Fx/C cathode materials via wet mechanical agitation-assisted high-temperature ball milling method

LiFePO4-x/3Fx/C (x = 0, 0.03, 0.06, 0.09) were obtained via wet mechanical agitation-assisted high-temperature ball milling method. XRD, SEM, TEM, galvanostatic testing, EIS, and CV were applied to study the effects of the amount of F-doping on the structure and electrochemical performance of LiFePO4/C. The results showed that LiFePO3.98F0.06/C displayed the best electrochemical performance: its initial discharge capacities were 162.6 (0.1 C), 156.6 (0.5 C), 150.2 (1.0 C), 144.5 (2.0 C), 131.6 (5.0 C), and 115.8 mAhg−1 (10 C), respectively. Moreover, its discharge capacity was 110.5 mAhg−1 over 100 cycles with a capacity retention rate of 95.4% at 10 C-rate. F-doping is suggested to be an effective approach to enhance the electrochemical performance of LiFePO4.

Morphological and Thermophysical Behavior of Hidroxyapatite Powders Processed by Mechanical Milling

The current research represents one section of our studies concerning the improvement of the biocompatibility related to the biocomposite materials for bone grafts application. The submicronic/nanometric hydroxyapatite stands for the progress in biocompatibility. This study highlights the wet mechanical milling process and its effects on the morphological and thermophysical properties of the hydroxyapatite powder particles (30-50µm as raw material) obtained by this method (500 nm average). The scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) facility point out the morphological and chemical compositional features of the processed powders during 10 hours in dry argon atmosphere. The thermal analysis (TA) in argon atmosphere, too, reveals the influence of the milling parameters on the thermal effects generated by the processed hydroxyapatite powders. The experimental results of our research validate some milling mechanisms reported by the literature for wet/dry mechanochemical process conditions.

Improved dehydriding property of polyvinylpyrrolidone coated Mg-Ni hydrogen storage nano-composite prepared by hydriding combustion synthesis and wet mechanical milling

In this work, polyvinylpyrrolidone (PVP) coated Mg95Ni5 nano-composites were prepared by hydriding combustion synthesis (HCS) plus wet mechanical milling (WM) with tetrahydrofuran (THF) and donated as WM-x wt% PVP (x = 1, 3, 5 and 7) respectively. The phase compositions, microstructures and dehydriding property, as well as the co-effect of PVP and THF were investigated in detail. XRD results showed that the average crystal size of MgH2 in the milled Mg95Ni5 decreased from 23 nm without PVP to 18 nm with 1 wt% PVP. The peak temperature of dehydrogenation of MgH2 in the milled Mg95Ni5 decreased from 293.0 °C without THF to 250.4 °C with THF. The apparent activation energy for decomposition of MgH2 in WM-7 wt% PVP was estimated to be 66.94 kJ/mol, which is 37.70 kJ/mol lower than that of milled Mg95Ni5 without THF and PVP. PVP and THF can facilitate the refinement of particle size during mechanical milling process. Attributed to small particle sizes and synergistic effect of PVP and THF, the composites exhibit markedly improved dehydriding properties.

Synthesis and Electrochemical Characterization of a Glass-Ceramic Li7P2S8I Solid Electrolyte for All-Solid-State Li-Ion Batteries

Development of a tangible solid state battery has received great attention but there are various engineering challenges to overcome, especially for the scalable processing and the use of Li metal anode. In order to tackle these issues, we first evaluated the electrochemical stability of thio-LISICON solid electrolytes, i.e., Li10GeP2S12 (LGPS), Li7P3S11 (LPS), and Li7P2S8I (LPSI), where the glass-ceramic LPSI electrolyte showed a superior compatibility with Li metal. Moreover, a superionic conductivity of 1.35 × 10−3 S/cm could be achieved by optimizing the wet mechanical milling and the low-temperature annealing processes. Using this superior LPSI solid electrolyte, we evaluated the electrochemical performance of pellet-type and slurry-type all-solid-state cells with LiNbO3-coated LiNi0.6Co0.2Mn0.2O2 (LNO-NCM622)/LPSI composite cathode and Li metal anode. The initial discharge capacity of ∼150 mAh/g was achieved for the pellet-type test cell and ∼120 mAh/g for the slurry-type cell. Comparing the interfacial resistances of the two types of cells, strategies to enhance the performance and realize a scale-up fabrication of all-solid state Li-ion batteries are discussed.

Sinthesis and Characterization of Nd<sub>2</sub>Fe<sub>14</sub>B Powder from Nd-Fe-B Flakes by Wet Mechanical Milling and Heat Treatment

The Nyodimium-Iron-Boron (Nd-Fe-B) based materials are known as the best type of magnetic materials and it contains a magnetic phase Nd2Fe14B. The Nd-Fe-B alloy Flakes is one of the main raw material for producing of NdFeB-based permanent magnets and the size of Nd-Fe-B flakes are still coarse. Synthesis of Nd2Fe14B powder has been done by a wet mechanical milling method using the High Energy Milling (HEM) for 10 hrs and continued by heating at 600°C in vacuum condition (10-4 Pa). This process is used to produce a fine powder Nd2Fe14B for making of permanent magnets. The milling medium was used a toluene (pa-Emerck)) to protect of particle from oxidation during the milling process. After milling processes, the samples were measured distribution particle size by using Particle Size Analyzer (PSA). Microstructure analysis has been conducted by using X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM/EDX) for samples before milling and sample after heating. The characterization results show that after milling 10 hours, it was obtained fine powder with average size about 1.35 μm. According to SEM/EDX and XRD analysis show that the crystal structure of the sample before milling was different compared to the sample after heating. It is found new magnetic phase with formula Nd2Fe14B.

Mechanosynthesis, structural, thermal and magnetic characteristics of oleic acid coated Fe3O4 nanoparticles

Oleic acid coated iron ferrite-magnetite nanoparticles (Fe3O4) have been synthesized via a new combined route, ceramic method and subsequent wet mechanical milling, starting from a stoichiometric mixture of the easily accessible Fe and Fe2O3 precursors. In the first step, the magnetite has been obtained in well crystallised state by heat treatment of precursor's mixture. In the second step, the as obtained magnetite powder has been wet milled in a high energy planetary ball mill using oleic acid as process control agent. Using the same conditions dry milled magnetite samples have been obtained for comparison. The as obtained powders have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), magnetic measurements M = f(H), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). According to XRD analysis two different processing mechanisms are observed for dry and wet milling modes. The magnetite mean crystallite size is 19 nm according to XRD after 240 min of wet mechanical milling. The High Resolution SEM confirmed that the powder consists in nanoparticles that have particles with the size up to 30 nm. The bond of the oleic acid to the magnetite nanoparticles has been observed by FTIR and DSC investigations. The presence of free and bonded oleic acid is revealed and the free oleic acid can be removed controlled by heat treatment. The magnetisation of the milled samples is lower as compared to the magnetisation of the un-milled sample due to several causes such as disordered structure, finite size effect and powder contamination. A powder contamination with iron occurs during milling and this leads to the formation of a wüstite-FeO phase for the dry milled samples. In the case of the wet milled samples, due to an oleic acid layer the FeO phase formation is prevented.