Short Milling Research Articles

Coupling rare-earth metal introduction and alkali oxide addition to achieve efficient regeneration of LiBH4 by reacting hydrous LiBO2 with Al

The lack of cost-effective regeneration techniques for LiBH4 limits its large-scale applications for supplying hydrogen via hydrolysis. Now, we report a facile method to regenerate LiBH4 by ball milling its real hydrolytic byproduct (LiBO2·xH2O) with cheap Al based reducing agents, instead of traditional Mg. Effective strategies are developed to promote the formation of LiBH4 by introducing Li2O to enable the dense Al2O3 to convert into LiAlO2 on Al surface and break up passivation layers, and by partially replacing Al with Al-RE alloy to improve grinding and contacting efficiency of raw materials and facilitate the conversion from initial H+ in LiBO2·2H2O to final H¯ in LiBH4. A yield of 10.4 % can be obtained for a relatively short ball milling time (10 h) for the Al-Al2Ce-Li2O-LiBO2·2H2O system. Another advantage of this method is that the utilization of H+ source in LiBO2·2H2O improves energy efficiency and reduces the cost. This work broadens the species of reducing agents for borohydride regeneration and enriches its regeneration methods.

Research on the ultrasonic vibration-assisted short electric arc milling process of Inconel 718

Research on the ultrasonic vibration-assisted short electric arc milling process of Inconel 718

Role of short germination and milling on physical properties, amino acid and metabolomic profiles of high amylose rice fractions

Short germination is a process that can improve bioactive compounds in rice. This work aimed investigate the physical properties, phenolic compounds (PC), antioxidant activity and amino acids composition of husk + bran, brown and milled rice with high amylose content after short germination (16 h). α-amylase activity (Falling Number, FN) and enthalpy (ΔH) were unchanged (p < 0.05). RVA curve profiles were similar, even though after short germination and milling. Globally, metabolomics analysis identified 117 PC, in which 111 (bound), 104 (free) and 21 revealed in both extracts. p-Coumaric, trans-ferulic and ferulic acids were the most abundant PC revealed in all fractions. The portion husk + bran showed the highest level of total antioxidant activity (709.90 µmol TE) in both free and bound fractions. In terms of total amino acids, there was no statistical difference (p < 0.05) among non-germinated and germinated samples, contrary to free amino acids content. Glutamic acid (Glu) presented the highest values combining short germination and milling (1725–1900 mg/100 g) consequently, leads to higher value of GABA (12.21 mg/100 g). The combination of short germination and milling demonstrated a good strategy to improve the nutritional quality of rice, unless the thermal and pasting properties have been altered, contribute to potential health benefits on human nutrition.

Effects of non-electrical parameters on the characteristics of discharge craters and machining performance in short electrical arc milling

During electrical discharge machining (EDM), the process parameters greatly influence the discharge characteristics and machining performance, including electrical and non-electrical parameters. As a new EDM method, short electrical arc milling (SEAM) is plagued by frequent short circuits, poor debris removal, and low energy-transfer efficiency. Therefore, this paper investigated the influence of non-electrical parameters (electrode material, working medium, and electrode rotation) on the crater characteristics, machining efficiency, and electrode wear. The micromorphological characteristics of the workpiece were explored. The results suggested that non-electrical parameters compressed and fractured the plasma channels, thus changing the effect of EDM. The air-tap water medium and electrode rotation promoted debris removal and arc breaking, which prevented the arc from ablating the workpiece. When GH4099 alloy was machined with a copper electrode, the workpiece surface quality and machining efficiency were high, and the thickness of the heat-affected zone was small. This work reveals the characteristics of short electric arc discharge and provided a theoretical basis for the efficient and high-quality machining of difficult-to-cut materials by SEAM.

Fast Hydrogen Sorption Kinetics in Mg-VCl3 Produced by Cryogenic Ball-Milling.

Hydrogen storage in Mg/MgH2 materials is still an active research topic. In this work, a mixture of Mg-15wt.% VCl3 was produced by cryogenic ball milling and tested for hydrogen storage. Short milling time (1 h), liquid N2 cooling, and the use of VCl3 as an additive produced micro-flaked particles approximately 2.5-5.0 µm thick. The Mg-15wt.% VCl3 mixture demonstrated hydrogen uptake even at near room-temperature (50 °C). Mg-15wt.% VCl3 achieved ~5 wt.% hydrogen in 1 min at 300 °C/26 bar. The fast hydriding kinetics is attributed to a reduction of the activation energy of the hydriding reaction (Ea hydriding = 63.8 ± 5.6 kJ/mol). The dehydriding reaction occurred at high temperatures (300-350 °C) and 0.8-1 bar hydrogen pressure. The activation energy of the dehydriding reaction is 123.11 ± 0.6 kJ/mol. Cryomilling and VCl3 drastically improved the hydriding/dehydriding of Mg/MgH2.

Experimental research on short electric arc milling machining based on the mechanical-fluid coupling effect

Short electric arc milling (SEAM) involves the complex coupling between the high-density heat output of the arc, the high-speed rotation of the tool electrode, and the high-pressure flushing fluid inside the tubular electrode. To improve the arc discharge utilization, this study investigates the effects of mechanical action, fluid action, and mechanical-fluid coupling action on the arc breakage of short arcs via experiments. It is found that the high-speed rotation of the electrode reduces the adsorption of the working fluid to the electrode surface, which can help to reduce the recast of molten metal on the workpiece surface and improve the surface quality. The coupling of the two makes a greater contribution to arc breaking and molten metal removal, while also improving the spatial continuity of the arc discharge. Moreover, after SEAM based on the mechanical-fluid coupling effect, the nickel-based alloy GH4169 is found to have lower surface roughness, lower tool electrode wear, a higher material removal rate, and a thinner recast layer.

Experimental research on short electric arc milling of Ti6Al4V with different electrode polarities

Experimental research on short electric arc milling of Ti6Al4V with different electrode polarities

Experimental study on high-efficiency DC short electric arc milling of titanium alloy Ti6Al4V

Short electric arc milling (SEAM) is an efficient electrical discharge machining method, especially for the efficient removal of difficult-to-machine conductive materials with high hardness, high toughness, and wear resistance. In this study, titanium alloy Ti–6Al–4V is used as the research object to conduct machining experiments. The material removal mechanism of SEAM technology is studied using a DC power supply and different tool electrode materials (copper, graphite, Q235 steel, and titanium). The energy distribution of the discharge gap is analyzed using a data acquisition system and a high-speed camera. The arc is found to move with the spindle rotation in the process of arc discharge, and multi-point discharge occurs in the process of single-arc discharge. The voltage and current waveforms and the radius of the etched particles during the experiment are measured; the material removal rate (MRR) and relative tool wear rate (RTWR) are calculated; and the surface and cross-section micromorphology and hardness are analyzed. The experimental results show that when the electrode material is graphite, the maximum feed rate is 650 mm/min; the MRR can reach 17268 mm3/min; the ideal maximum MRR is more than 65,000 mm3/min; and the RTWR is only 1.27%. When the electrode material is Q235 steel, the minimum surface roughness is 35.04 μm, and this material has good stability under different input voltages. When the electrode material is copper, the hardness of the resolidified layer is close to that of the base material, which is beneficial for further processing. The lowest specific energy consumption is 18.26 kJ/cm3 when titanium is used as the electrode material.

Experiment investigation on machining characteristics of 7075 aluminium alloy with short electric arc milling

Experiment investigation on machining characteristics of 7075 aluminium alloy with short electric arc milling

Labeling and Probing the Silica Surface Using Mechanochemistry and 17 O NMR Spectroscopy*.

In recent years, there has been increasing interest in developing cost‐efficient, fast, and user‐friendly 17O enrichment protocols to help to understand the structure and reactivity of materials by using 17O NMR spectroscopy. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca. 5 %) without significantly changing the nature of the material. High‐precision 17O compositions were measured at different milling times by using large‐geometry secondary‐ion mass spectrometry (LG‐SIMS). High‐resolution 17O NMR analyses (including at 35.2 T) allowed clear identification of the signals from siloxane (Si−O−Si) and silanols (Si−OH), while DNP analyses, performed by using direct 17O polarization and indirect 17O{1H} CP excitation, agreed with selective labeling of the surface. Information on the distribution of Si−OH environments at the surface was obtained from 2D 1H−17O D‐HMQC correlations. Finally, the surface‐labeled silica was reacted with titania and using 17O DNP, their common interface was probed and Si−O−Ti bonds identified.

Investigating the pulse short electric arc milling of Ti6Al4V alloy

In this study, the machining characteristics of pulse short arc milling (SEAM) Ti6Al4V alloy were studied. In this regard, the influence of SEAM parameters on the material removal rate (MRR), relative electrode wear ratio (REWR), and surface integrity of Ti6Al4V is studied. A wide variety of processing parameters, including different voltages, frequencies, duty cycles, flushing pressures, electrode rotation speeds, and electrode feed rates, are considered in the investigation. Scanning electron microscope (SEM), energy dispersive spectrograph (EDS), and micro-hardness analysis are applied to analyze results. Moreover, a multichannel data acquisition system is used to measure gap voltage and gap current. Obtained results cover the variation of MRR, REWR, surface roughness (Ra), average resolidified layer thickness, and average heat-affected zone thickness with different processing parameters. Furthermore, the electrode surface morphology and chemical composition of the negative growth of REWR are studied. Based on the obtained results, the microstructure of the resolidified layer and heat-affected zone of the workpiece cross-section is confirmed. This study provides a basis for the high-quality pulse SEAM technology of difficult-to-machine (DTM) materials to enter the semi-finishing field.

Mechanosynthesis and Thermoelectric Properties of Fe, Zn, and Cd-Doped P-Type Tetrahedrite: Cu12-xMxSb4S13.

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350–400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites’ thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies.

Mechanochemical Activation and Spark Plasma Sintering of the Lead-Free Ba(Fe1/2Nb1/2)O3 Ceramics.

This paper investigates the impact of the technological process (Mechanochemical Activation (MA) of the powder in combination with the Spark Plasma Sintering (SPS) method) on the final properties of lead-free Ba(Fe1/2Nb1/2)O3 (BFN) ceramic materials. The BFN powders were obtained for different MA duration times (x from 10 to 100 h). The mechanically activated BFN powders were used in the technological process of the BFN ceramics by the SPS method. The measurements of the BFNxMA ceramic samples included the following analysis: Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), DC electrical conductivity, and dielectric properties. X-ray diffractions (XRD) tests showed the appearance of the perovskite phase of BFN powders after 10 h of milling time. The longer milling time (up 20 h) causes the amount of the perovskite phase to gradually increase, and the diffraction peaks are more clearly visible. Short high energy milling times favor a large heterogeneity of the grain shape and size. Increasing the MA milling time to 40 h significantly improves the microstructure of BFN ceramics sintered in the SPS technology. The microstructure becomes fine-grained with clearly visible grain boundaries and higher grain size uniformity. Temperature measurements of the BFN ceramics show a number of interesting dielectric properties, i.e., high values of electric permittivity, relaxation properties with a diffusion phase transition, as well as negative values of dielectric properties occurring at high temperatures. The high electric permittivity values predestines the BFNxMA materials for energy storage applications e.g., high energy density batteries, while the negative values of dielectric properties can be used for shield elements against the electromagnetic radiation.

The effect of ball milling on birch, pine, reed, walnut shell enzymatic hydrolysis recalcitrance and the structure of the isolated residual enzyme lignin

Methodologies for the high-yield recovery of lignin with retention of its native CO bonded structure is an essential prerequisite for many novel high-end lignin applications. Enzymatic residual lignin isolation is such a methodology that leaves the lignin untouched by using enzymatic desaccharification. Thus, a series of representative lignocellulose substrates (birch, pine, walnut shell and reed) were evaluated for effective native lignin isolation, with emphasis on the effect on the lignin structure and purity. The effect of enzyme loading and ball milling severity were studied by tracking residual saccharides and the structural integrity of the isolated lignin. Prolongation of ball milling time could achieve a higher carbohydrate removal and avoid the loading of extra enzyme. However, the application of two or more steps of enzymatic hydrolysis with higher enzyme loading and short ball milling time was shown as an alternative to long ball milling time to achieve similar carbohydrate removal and avoid extensive decrease of the lignin molecular weight (MW). This MW decrease was caused by breaking of some linkages, but not too a large enough extent to cause significant differences in the 2D HSQC NMR spectra. The recalcitrance towards increased enzyme hydrolysis activity by ball milling was different for the four representative biomasses and followed an order of walnut shell > reed ≈ pine > birch by comprehensive analysis the obtained data. Overall, the results showed a clear two-way synergy between enzymatic treatment and ball milling efficiency to isolate lignin with high yield, high native linkage content, purity and minimal MW reduction.

Rotating short arc EDM milling method under composite energy field

• A new EDM milling method with rotating short arcs under composite energy field was proposed. • A mathematical model to describe the trajectory of particles in the composite field was established. • Rotating short arc was generated by the Lorentz force, the electrical force and the high-speed rotation of electrode. • The MRR of rotating short arc machining is increased by 46 % compared with traditional EDM. • An increase in the strength of the magnetic field increases the MRR and decreases the TEWR. Electrical discharge machining (EDM) is a rapidly developing technique amongst nontraditional techniques. However, low processing efficiency significantly hinders its application in industry. This study proposes a new high-speed EDM milling method using rotating short arcs under a composite energy field. By the combined effect of the Lorentz force, electric field force, and high-speed rotation of the tool electrode, rotating short arcs are generated between the tool electrode and the workpiece, which in turn provide constant erosion of materials. The proposed method can increase the discharge energy density by converging the electric arcs through the composite energy field, and increase the energy obtained by the workpiece. By this means, it improves the material removal rate. During processing, a portion of debris is attracted by the magnetic field and adheres to the end surface of the electrode, which can protect the electrode and reduce the electrode wear rate. Compared with traditional EDM, the material removal rate of the rotating short arc milling was increased by 46 %, while the tool electrode wear rate decreased by 62 %. Furthermore, an increase in the strength of the magnetic field increases the material removal rate of the rotating short arc milling and decreases the tool electrode wear rate and surface roughness. Therefore, high-efficiency and high-quality EDM milling can be achieved by using the proposed method.

Effect of Short Attritor-Milling of Magnesium Alloy Powder Prior to Spark Plasma Sintering.

The spark plasma sintering (SPS) technique was employed to prepare compacts from (i) gas-atomized and (ii) attritor-milled AE42 magnesium powder. Short attritor-milling was used mainly to disrupt the MgO shell covering the powder particles and, in turn, to enhance consolidation during sintering. Compacts prepared by SPS from the milled powder featured finer microstructures than compacts consolidated from gas-atomized powder (i.e., without milling), regardless of the sintering temperatures in the range of 400–550 °C. Furthermore, the grain growth associated with the increase in the sintering temperature in these samples was less pronounced than in the samples prepared from gas-atomized particles. Consequently, the mechanical properties were significantly enhanced in the material made of milled powder. Apart from grain refinement, the improvements in mechanical performance were attributed to the synergic effect of the irregular shape of the milled particles and better consolidation due to effectively disrupted MgO shells, thus suppressing the crack formation and propagation during loading. These results suggest that relatively short milling of magnesium alloy powder can be effectively used to achieve superior mechanical properties during consolidation by SPS even at relatively low temperatures.

Machining performance of titanium alloy in short electric arc milling

In order to solve the high-efficiency removal of difficult-to-cut materials such as titanium alloys, this paper conducts a in-depth research on the process characteristics of short electric arc milling machining (SEAM). The effects of processing conditions on material removal rate (MRR), tool wear ratio (TWR) and surface roughness (Ra) are studied. DeWesoft high-speed acquisition system, scanning electron microscope (SEM) and energy spectrometer (EDS) are used to characterize the machining performance of Ti-6Al-4V in SEAM. The results show that the surface of the machined Ti-6Al-4V has an obvious central depressions, surrounded by edge bumps and wrinkles caused by the melt. The effective number of short electric arc discharge is high, and the discharge rate can be maintained at a high level, increasing utilization rate of electric energy. The peak current of normal discharge reaches more than 900 A, which can generate a higher MRR. In addition, the surface morphology, re-solidified layer, and particle morphology of Ti-6Al-4V used for SEAM are also studied. These results lay a theoretical and technical foundation for the industrial application of SEAM.

Comparison of short and long milling flows on yield and physicochemical properties of brans from biofortified and nonbiofortified hull‐less oats

AbstractBackgroundThe aim of this study was to compare bran yields of short‐ and long‐flow roller mill from biofortified (+) and nonbiofortified (−) hull‐less oats cv. Haskara and determine effect of biofortification (Zn, I, Se) on composition and physicochemical properties of fractions.FindingsZn, I, and Se contents were significantly increased by biofortification. Yields of coarse bran (CB) obtained by short flow were 42.6% for both Haskara samples, while those of fine bran (FB) obtained by long flow were 46.6% and 47.4% for Haskara (+) and Haskara (−). Beta‐glucan (BG) contents of CB were 8.42% and 8.31%, while those of FB were 8.68% and 8.65% for respective samples. There were no significant differences between CB of Haskara (+) and Haskara (−) samples in terms of mass median diameter, dispersion, particle density, porosity, BG solubility, and RVA viscosity. The differences between FB of the same samples were also not significant in terms of those parameters. However, long flow significantly increased dispersion, porosity, BG solubility, and RVA viscosity and significantly decreased mass median diameter and bulk density compared to short flow.ConclusionsBiofortified oats can be used to obtain β‐glucan‐enriched milling fractions.Significance and noveltyThis is the first study on bran fractions obtained by different milling flows from biofortified hull‐less oats.

Arc characteristics in short electrical arc high-efficiency milling for GH4169

To solve core problems of slow arc response and unstable combustion, arc movement characteristics and arc action rules in short electrical arc milling are studied using a high-speed acquisition system and the Phantom high-speed camera in this article. To improve arc reignition, the characteristic parameters of arc discharge are determined as a discharge gap of 0.053 mm and discharge time of 2180 μs. A short electrical arc milling experiment with nickel-based superalloy GH4169 is carried out, confirming that the continuous stable discharge of the arc can easily produce a material removal rate of 40 g/min and a tool wear ratio of 0.8%. An SU8010 scanning electron microscope and energy spectrum analyzer are then used to study the erosion mechanism of GH4169 in short electrical arc milling. This article aims to expand the processing range of short electrical arc machining in the field of special material processing to provide experimental and theoretical bases for the development of short electrical arc milling technology theory and methods.

A study on machining characteristics of nickel-based alloy with short electric arc milling

Short electric arc milling (SEAM) is an electrical discharge machining method characterized by low voltage and high current. This method has high machining efficiency, and the eroded material is quickly discharged from the discharge gap by a high-speed rotating tool electrode and a certain pressure of the gas-liquid mixed medium. In this paper, the effects of tool polarity, working medium, voltage, duty cycle, frequency, and flushing pressure on the performance of short electric arc milling were investigated by using the material removal rate (MRR), tool mass wear ratio (θ), and surface roughness (SR) as technical indicators. Moreover, the surface morphology, cross-section morphology, chemical composition, and micro-hardness of GH4169 after machining were also studied, and the machine mechanism was further revealed. This work lays a foundation for more efficient and high-precision short electric arc milling.