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The production of graphene–boron nitride nanosheet heterostructures via liquid phase exfoliation assisted by a milling process
摘要： Graphene–boron nitride (BN) nanosheet heterostructures have become one of the highly interesting matters in recent times owing to their advantages. In this study, the liquid phase exfoliation method was preferred for production of graphene–BN nanosheet heterostructures. However, a pre-milling process was applied to starting materials, instead of the classical liquid phase exfoliation method previously used in the literature. Hexagonal graphite (h-G) and h-BN mixtures were milled for 50 h and the milled powders were subjected to the liquid phase exfoliation process. As a result of the examinations, it was observed that graphene–BN nanosheet heterostructures were successfully synthesized. The widths of the synthesized nanosheets were 300–500 nm and nanosheets were multi-layers. It was seen that a large part of the powder mixture were occurred at high amorphization during the ball milling process. According to X-ray diffraction (XRD) peaks, the amorphization ratio was almost 90%. But, almost all of amorphous structures were removed during acid mixing and the thermal process. But, amorphous structures still existed in samples. In addition, the ball milling process damaged the sheets and defects formed. Despite all these disadvantages, the milling process carried out in this study provided formation of thinner and larger sheets compared with previous similar studies.
关键词： ball milling,BN nanosheets,exfoliation,heterostructures,Graphene
更新于2025-09-23 15:23:52
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Preparation method and underlying mechanism of MWCNTs/Ti6Al4V nanocomposite powder for selective laser melting additive manufacturing
摘要： The fabrication of high-performance metal matrix nanocomposites is a new development direction in laser additive manufacturing (AM); however, the unique localized line-by-line and layer-by-layer forming process of AM has special requirements on the applicable powder materials for AM. The feedstock powder preparation is an important factor in laser AM, especially the CNTs/metal nanocomposite powder for selective laser melting (SLM) due to the agglomeration of the CNTs. This work focused on the preparation of multi-walled carbon nanotubes/Ti6Al4V (MWCNTs/TC4) nanocomposite powder for laser AM by a planetary ball-milling (PBM). The effect of ball-milling time on the characteristics of nanocomposite powder was studied and the underlying physical mechanism for powder preparation was disclosed. Three nanocomposite powders with milling time of 2 h, 4 h and 16 h were used for SLM processing to determine the optimal nanocomposite powders. The results showed that although the MWCNTs were dispersed uniformly in the matrix powder at increased milling time, severely plastic deformation of nanocomposite powder occurred with loss of its spherical shape. It was concluded that a ball-milling time of 4 h at a speed of 300 rpm was determined to achieve optimal nanocomposite powder for SLM. SLM processing of the nanocomposite powder demonstrated a smooth laser-powder interaction, yielding good metallurgical bonding of scanning tracks with previous tracks and relatively flat surface of samples. This work provided the significant reference to prepare high quality CNTs/metal nanocomposite powder for SLM, which has great potentials to fabricate high-performance metal matrix nanocomposite.
关键词： Planetary ball milling,Selective laser melting,Ti6Al4V (TC4) powder,Multi-walled carbon nanotubes (MWCNTs),Powder characteristics
更新于2025-09-23 15:19:57
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Investigating Various Permutations of Copper Iodide/FeCu Tandem Materials as Electrodes for Dye-Sensitized Solar Cells with a Natural Dye
摘要： This work presents the synthesis and deposition of CuI and FeCu materials on copper substrates for dye-sensitized solar cell applications. FeCu is a metastable alloy of iron and copper powders and possesses good optical and intrinsic magnetic properties. Coupled with copper iodide as tandem layers, the deposition of these two materials was permutated over a pure copper substrate, characterized and then tested within a solar cell. The cell was sensitized with a natural dye extracted from a local desert plant (Calotropis Gigantea) and operated with an iodine/triiodide electrolyte. The results show that the best layer arrangement was Cu/FeCu/CuI, which gave an efficiency of around 0.763% (compared to 0.196% from reported cells in the literature using a natural sensitizer).
关键词： natural sensitizers,copper iodine,FeCu alloys,dye-sensitized solar cells,Calotropis Gigantea,ball milling
更新于2025-09-23 15:19:57
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Effect of tungsten doping on structural and optical properties of rutile TiO2 and band gap narrowing
摘要： Pure and W doped nanocrystalline rutile TiO2 samples were synthesized using high energy ball milling process. Rietveld refinement results of X-ray diffraction data confirmed that pure sample exhibited rutile TiO2 phase whereas doped samples contained both rutile TiO2 and a secondary Ti0.54W0.46O2 phase. Different models of Williamson–Hall method were employed to evaluate crystallite size and strain in the samples. The crystallite size was found to decrease from 50 to 47 nm with increase in the dopant concentration. The pure TiO2 exhibited tensile microstrain which became compressive and increased upon doping. A blue shift in A1g Raman mode with doping of W also indicated the increase in the compressive strain. The HR-TEM images also confirmed the presence of higher strain in doped samples compared to un-doped sample. The observed decrease in band gap from 3 to 2.83 eV with dopant concentration, as calculated from UV–vis spectroscopy data, may be attributed to the increased strain. The decrease in the intensity of photoluminescence emission indicated the increase in number of defects and oxygen vacancies with increasing dopant concentration. This is further, supported by the rise in Urbach energy, a signature of increased number of defects in doped samples. This study shows that the dopant induced strain plays significant role in band gap narrowing.
关键词： Strain,Peak profile analysis,Band gap narrowing,Rutile TiO2 nanoparticles,High energy ball milling
更新于2025-09-19 17:15:36
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A Non-Isolated Buck-Boost DC-DC Converter with Continuous Input Current for Photovoltaic Applications
摘要： High-power grinding mills are used in the cement and mining industries to crush clinker or copper ore and grind these materials to fine powder. The multi-megawatt speed-controlled mill drives operate at a very low angular speed. Synchronous motors with a high number of pole pairs are used as the prime movers. They are traditionally fed by load-commutated thyristorized cycloconverters. These are prone to failure modes that can lead to excessive torque pulsations and high overcurrents. The huge stator, which was built as a separate ring-shaped structure around the tubular mill, may then get mechanically displaced, and the operation of the plant is interrupted. A novel and reliable direct drive uses a voltage source inverter that operates at the unity power factor for increased efficiency. Synchronous optimal pulsewidth modulation ensures a low harmonic current distortion and reduced switching losses at a very low switching frequency. The optimization of the pulse patterns takes the anisotropic magnetic properties of a separately excited synchronous motor into account. The implementation in a 23-MW semiautonomous grinding mill installed in a Zambian copper mine is intended.
关键词： Alternators,pulse width modulation inverters,gradient methods,ball milling,software algorithms,variable speed drives,Fourier transform
更新于2025-09-19 17:13:59
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Size-controlled MoS<sub>2 </sub>nanosheet through ball milling exfoliation: parameter optimization, structural characterization and electrocatalytic application
摘要： Unique properties and potential applications of 2D materials draw much attention for mass production of thin-layer 2D materials. Ball milling exfoliation of 2D materials has been rarely used, in spite of a promising dry phase production method, because of the superficial information in the mechanism and the effect of the operating parameters on the yield, size and thickness. Here, we investigate systematically the ball milling operating parameters in the exfoliation of bulk MoS2 in the presence of sodium cholate (SC) as an exfoliant. The yield and dimensions of the exfoliated MoS2 nanosheet were monitored by changing the parameters such as the weight ratio of bulk MoS2 and SC (SC/MoS2), the filling ratio in the volume of milling ball and container (!), milling ball size (dB), milling revolution speed (nR), and initial mass of bulk MoS2 (mMoS2). The yield of exfoliation is found to be 95% at the optimum ball milling conditions (SC/MoS2 = 0.75, ! = 50%, mMoS2 = 0.20 g). In addition, yield and size of the exfoliated MoS2 were controlled by the conditions of the ball milling. As for the evaluation of size and thickness of the ball-milled MoS2 powder with less than 30% difference from those determined by the well-known absorption method. Finally, the size and thickness of the MoS2 nanosheets prepared by ball milling exfoliation were correlated with their electrocatalytic and photoelectrocatalytic activities.
关键词： electrocatalyst,sodium cholate,nanosheet,exfoliation,Ball milling,molybdenum disulfide,XRD
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Curve Correction of the Energy Yield by Flexible Photovoltaics for VIPV and BIPV Applications Using a Simple Correction Factor
摘要： High-power grinding mills are used in the cement and mining industries to crush clinker or copper ore and grind these materials to fine powder. The multi-megawatt speed-controlled mill drives operate at a very low angular speed. Synchronous motors with a high number of pole pairs are used as the prime movers. They are traditionally fed by load-commutated thyristorized cycloconverters. These are prone to failure modes that can lead to excessive torque pulsations and high overcurrents. The huge stator, which was built as a separate ring-shaped structure around the tubular mill, may then get mechanically displaced, and the operation of the plant is interrupted. A novel and reliable direct drive uses a voltage source inverter that operates at the unity power factor for increased efficiency. Synchronous optimal pulsewidth modulation ensures a low harmonic current distortion and reduced switching losses at a very low switching frequency. The optimization of the pulse patterns takes the anisotropic magnetic properties of a separately excited synchronous motor into account. The implementation in a 23-MW semiautonomous grinding mill installed in a Zambian copper mine is intended.
关键词： Alternators,ball milling,pulse width modulation inverters,gradient methods,software algorithms,variable speed drives,Fourier transform
更新于2025-09-19 17:13:59
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Nano-Scaled Lanthanum Hexaboride (LaB6) – Control of Properties in Dependence on Type of Manufacturing
摘要： This paper presents the influence of fabrication methods on the optical and photo-thermal properties of nano-LaB6. The nano particles (NPs) were manufactured via continuously operated ball milling or induction plasma technology. Whereas different grinding processes for LaB6 were also discussed using ethylene glycol (EG) and ZrO2 grinding media in previous works, the scaled-up plasma technology presents a new possibility to gain NPs with high yields and narrow size distribution. In our work, NPs < 100 nm are achieved by grinding experiments using ethanol, 1-methoxy-2-propanol and ethylene glycol. Furthermore, the change of grinding parameters was investigated intensively. Compared to milled NPs, nano-LaB6 in high purity are gained by plasma technology and shows differences in color, morphology (UHR-FESEM), absorption behavior and crystallite size (X-Ray). Acrylate terminated starPEG (poly ethylene glycol) was used as a high cross-linked network after in-situ UV polymerization to stabilize NPs homogenously. We also set the focus on photo-thermal conversion properties of LaB6 dispersions in ethylene glycol, i.e. transformation of the absorbed photon energy into heat, and temperature distribution around the laser spot which are characterized by an IR camera.
关键词： photo-thermal conversion,top-down,ball milling LaB6,LaB6 nano particles,SPR,plasma LaB6,LaB6 stabilization
更新于2025-09-16 10:30:52
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Optical and photoelectrochemical properties of Cu2SrSnS4 thin film fabricated by a facial ball-milling method
摘要： Earth-abundant and non-toxicity quaternary chalcogenide Cu2SrSnS4 is prepared by a facial ball-milling method. Its formation is revealed to be from the reaction between Cu2SnS3 and SrS at 600 oC. The bandgap of the prepared Cu2SrSnS4 film is speculated around 1.78 eV according to absorption test. The carrier lifetime of the prepared Cu2SrSnS4 film is about 2.06 ns. The photocurrent density of the Cu2SrSnS4 film is about 150 at -670 mV bias vs Ag/AgCl electrode and it repeats after 10 cycles of 1000 s. Its notable generation of photocurrent and photoelectrochemical stability indicates its potential for photoelectric conversion application.
关键词： Ball-milling,Thin films,Solar cell,Cu2SrSnS4,Optical,Solar energy materials
更新于2025-09-10 09:29:36
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Direct and Efficient Conversion from Low-Quality Graphite to High-Quality Graphene Nanoplatelets
摘要： Low-quality graphite (L-graphite), containing various impurities (e.g., metals and inorganics), can be directly and efficiently converted into high-quality iodine-doped graphene nanoplatelets (HIGnPs) via mechanochemical ball-milling in the presence of iodine (I2) with subsequent work-up procedures. Despite using L-graphite, the resultant HIGnPs show high-quality characteristics, including large specific surface area (969 m2 g?1), lower metallic residues, and well-maintained graphitic structure. In addition, HIGnPs display remarkable electrocatalytic performance for oxygen reduction reaction (ORR), involving benefits such as higher selectivity, longer-term stability, and better tolerance to methanol crossover/CO poisoning effects. Therefore, simple mechanochemical ball-milling in solid state can produce high-quality graphene nanoplatelets in large quantity at low-cost for commercialization, regardless of the initial quality of the graphite.
关键词： Oxygen reduction reaction,Mechanochemical reaction,High-quality graphene,ball-milling,Low-quality graphite
更新于2025-09-10 09:29:36