Anaerobic vs. aerobic preparation of silicon nanoparticles by stirred media milling. The effects of dioxygen, milling solvent, and milling time on particle size, surface area, crystallinity, surface/near-surface composition, and reactivity

RSC Advances ◽  
2016 ◽  
Vol 6 (113) ◽  
pp. 112370-112380
Author(s):  
Eric V. Bukovsky ◽  
Karlee P. Castro ◽  
Brent M. Wyatt ◽  
Olga V. Boltalina ◽  
Steven H. Strauss
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Silicon Nanoparticles ◽  
Milling Time ◽  
Surface Composition ◽  
Near Surface ◽  
Media Milling ◽  
Attritor Milling

Silicon nanoparticles milled anaerobically in heptane or mesitylene are smaller and much more reactive than SiNPs milled aerobically in the same solvents for equal attritor milling times.

Changes in Particle Size and Crystallinity in Ground Nickel Powder

2008 ◽  
Vol 587-588 ◽  
pp. 468-472
Author(s):  
J.M. González ◽  
José A. Rodríguez ◽  
Enrique J. Herrera
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Crystallite Size ◽  
Surface Area ◽  
Specific Surface Area ◽  
Nickel Powder ◽  
Milling Time ◽  
High Energy ◽  
Published Data ◽  
Average Particle

Nickel powder was dry-milled using a high-energy disc-oscillating mill. The average particle size increases and the specific surface area diminishes with milling time. Crystallite size decreases and microstrains increase, under the same conditions, as shown by X-ray analysis. At 120 min milling time, the crystallite size has a value of 17 nm, i.e., a nanostructured powder, with a perturbed lattice, is obtained. The above results have been compared with published data about the effects of milling on a ceramic powder. There is, in both cases, a general agreement concerning the changes produced in crystallite size. Nevertheless, opposite results are reached regarding particle size and specific surface area.

scholarly journals PEMANFAATAN TEKNIK HEM UNTUK PENUMBUHAN CNT DARI GRAFIT MENGGUNAKAN Ni SEBAGAI KATALIS = UTILIZATION OF HEM TECHNIQUE FOR GROWTH OF CNT FROM GRAPHITE POWDERS BY USING Ni AS CATALYST

2016 ◽  
Vol 10 (1) ◽  
pp. 35-40
Author(s):  
Yunasfi . ◽  
P. Purwanto ◽  
Mashadi .
Keyword(s):  
Particle Size ◽  
Raman Spectroscopy ◽  
Electron Microscope ◽  
Carbon Nanotube ◽  
Surface Area ◽  
Transmission Electron Microscope ◽  
Milling Time ◽  
High Energy ◽  
Milling Process ◽  
Transmission Electron

Utilization of HEM (high energy milling) technique for growth of CNT (carbon nanotube) from graphite powders by using Ni as catalyst was carried out. Milling process performed on a mixture of graphite powder and nickel powder (Ni-C powders) with the ratio of weight percent of 98%: 2%, with a variation of milling time between 25 up to 75 hours. Characterization using PSA (Powder Size Analyzer), SAA (Surface Area Analyzer), TEM (Transmission Electron Microscope) and Raman Spectroscopy performed to obtain information about particle size, surface area, morphology and the structure bonding of the milled powder respectively. The analysis results of Ni-C powders using PSA and SAA showed the smallest particle size and biggest surface area obtained after milling process for 50 hours, i.e. 80 nm and 705 m2/g, respectively. TEM observations revealed formation of flat fibers which quantity increased with increasing milling time. This flattened fiber behave as an initiator for the growth of CNTs. Ni-C powder milling for 50 hours results more clearly show the growth of CNTs. Analysis by Raman Spectroscopy showed two bands at 1582 cm−1 as a peak of G band and at 1350 cm-1 as a peak of D band. These spectra are typical for sp2 structure. The position of G band peak is close to 1600 cm-1 as the evidence of a change to nano-crystalline graphite. The highest intensity of D band shown in the milling process for 50 hours, which indicates that this milling time produces more graphite-like structure compared to other conditions, and is predicted good for growing CNTs. AbstrakPemanfaatan teknik HEM (High Energy Milling) untuk penumbuhan CNT (carbon nanotube) dari serbuk grafit dengan menggunakan Ni sebagai katalis. Proses milling dilakukan terhadap campuran serbuk grafit dan serbuk nikel (serbuk Ni-C) dengan perbandingan berat 98% : 2%, dengan variasi waktu milling antara 25-75 jam. Karakterisasi menggunakan fasilitas PSA (Particle Size Analyzer), SAA (Surface Area Analyzer), dan TEM (Transmission Electron Microscope) serta Raman Spektroscopy yang masing-masingnya untuk mendapatkan informasi tentang ukuran partikel, luas permukaan dan morfologi serta struktur ikatan serbuk hasil milling. Hasil analisis serbuk Ni-C dengan PSA dan SAA menunjukkan ukuran partikel paling kecil dan luas permukaan paling besar diperoleh setelah proses milling selama 50 jam, masing-masing 80 nm dan 705 m2/g. Pengamatan TEM menunjukkan serbuk-serbuk berbentuk serat pipih dengan kuantitas yang meningkat dengan bertambahnya waktu milling. Serat pipih ini perupakan cikal bakal penumbuhan CNT. Serbuk Ni-C hasil milling menunjukkan penumbuhan CNT terlihat lebih jelas setelah milling selama 50 jam. Hasil analisis dengan Raman Spectroscopy memperlihatkan puncak G band pada bilangan gelombang 1582 cm−1 yang merupakan spektrum untuk struktur sp2 dari grafit dan puncak D band pada bilangan gelombang 1350 cm-1 yang mungkin merupakan deformasi struktur grafit. Posisi puncak G band mendekati 1600 cm-1 menjadi bukti perubahan ke grafit nano kristal. Intensitas D band tertinggi ditunjukkan oleh sistem komposit Ni-C hasil proses milling selama 50 jam dan hal ini sebagai indikasi bahwa proses milling selama 50 jam terhadap sistem komposit Ni-C lebih berstruktur mirip grafit (graphitic-like material) dibanding kondisi lainnya dan diprediksi bagus untuk menumbuhkan CNT. Dengan demikian, waktu milling yang optimal untuk penumbuhan CNT dari serbuk grafit dengan menggunakan Ni sebagai katalis adalah adalah 50 jam.  

Quality by Design-based Optimization of Formulation and Process Variables for Controlling Particle Size and Zeta Potential of Spray Dried Incinerated Copper Nanosuspension

2019 ◽  
Vol 12 (3) ◽  
pp. 248-260
Author(s):  
Saurabh Singh ◽  
Sachin Kumar Singh ◽  
Malti G. Chauhan ◽  
Bimlesh Kumar ◽  
Narendra Kumar Pandey ◽  
...  
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Spray Drying ◽  
Milling Time ◽  
Drug Loading ◽  
Optimization Procedure ◽  
Process Variables ◽  
Media Milling ◽  
Predicted Values ◽  
Spray Dried

Background: In the present study copper nanosuspension was prepared from Incinerated Copper Powder (ICP) by top down media milling. Glycyrrhiza glabra (GG) and Gum Acacia (GA) were used as stabilizers in the formulation. Methods: Box Behnken Design was used to investigate the effect of formulation and process variables on particle size and zeta potential and optimize their ratio to get target product profile. The ratio of GA and GG to ICP was varied along with milling time and its speed. Further the prepared nanosuspensions were solidified using spray drying. Results: The particle size was found to be decreased with the increase in GG to ICP ratio, milling time and milling speed, whereas, reverse effect on particle size was observed with an increase in GA to ICP ratio. The zeta potential was found to be increased with the increase in GG to CB ratio and milling speed and it decreased with the increase in GA to ICP ratio and milling time. The obtained value for particle size was 117.9 nm and zeta potential were -9.46 mV which was in close agreement with the predicted values by the design which was, 121.86 nm for particle size and -8.07 mV for zeta potential respectively. This indicated the reliability of optimization procedure. The percentage drug loading of copper in the nanosuspension was 88.26%. The micromeritic evaluation of obtained spray dried nanoparticles revealed that the particles were having good flow and compactibility. Conclusion: It can be concluded that application of media milling, design of experiment and spray drying have offered very good copper nanosuspension that has the potential to be scaled up on industrial scale.

scholarly journals Gradually Fe-doped Co3O4 nanoparticles in 2-propanol and water oxidation catalysis with single laser pulse resolution.

2022 ◽  
Author(s):  
Swen Zerebecki ◽  
Kai Schott ◽  
Soma Salamon ◽  
Joachim Landers ◽  
Eko Budiyanto ◽  
...  
Keyword(s):  
Particle Size ◽  
Laser Pulse ◽  
Surface Area ◽  
Active Sites ◽  
Surface Composition ◽  
Oxidation Catalysis ◽  
Colloidal Nanoparticles ◽  
Co3o4 Nanoparticles ◽  
X Ray ◽  
Cation Doping

Controlling the surface composition of colloidal nanoparticles is still a challenging yet mandatory prerequisite in catalytic studies to investigate composition-activity trends, active sites, and reaction mechanisms without superposition of particle size- or morphology-effects. Laser post-processing of colloidal nanoparticles has been employed previously to create defects in oxide nanoparticles, while the possibility of laser-based cation doping of colloidal nanoparticles without affecting their size, remains mostly unaccounted for. Consequently, at the example of doping iron into colloidal Co3O4 spinel nanoparticles, we developed a pulse-by-pulse laser cation doping method to provide catalyst series with gradual surface composition but maintained extrinsic properties such as phase, size, and surface area for catalytic studies. Laser pulse number-resolved doping series were prepared at laser intensity chosen to selectively heat the Co3O4-NPs to roughly 1000 K and enable cation diffusion of surface-adsorbed Fe3+ into the Co3O4 lattice while maintaining the spinel phase, particle size, and surface area. The combination of bulk-sensitive X-ray fluorescence (XRF) and surface-sensitive X-ray photoelectron spectroscopy (XPS) was used to confirm a surface enrichment of the Fe-dopant. XRD, Magnetometry, and Mössbauer spectroscopy revealed an increasing interaction between Fe and the antiferromagnetic Co3O4 with an increasing number of pulses, in line with a proposed laser-induced surface doping of colloidal Co3O4 with Fe. Using Fick’s second law the thermal diffusion-related doping depth was estimated to be roughly 2 nm after 4 laser pulses. At the example of gas-phase 2-propanol oxidation and liquid-phase oxygen evolution reaction, the activity of the laser-doped catalysts is in good agreement with previous observations on binary iron-cobalt oxides. The catalytic activity was found to linearly increases with the calculated doping depth in both reactions, while only catalysts processed with at least one laser pulse were catalytically stable, highlighting the presented method in providing comparable, active, and stable gradual catalyst doping series for future catalytic studies.

scholarly journals Study of homogenization on media milling time in preparation of irbesartan nanosuspension and optimization using design of experiments (DoE)

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Chetan Borkhataria ◽  
Dhavalkumar Patel ◽  
Swati Bhagora ◽  
Nilesh Patel ◽  
Kalpesh Patel ◽  
...  
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Zirconium Dioxide ◽  
Milling Time ◽  
Stability Study ◽  
Combination Method ◽  
Poloxamer 407 ◽  
Potential Value ◽  
Media Milling ◽  
Accelerated Stability

Abstract Background The present investigation aimed at preparing nanosuspension of irbesartan to improve its dissolution. Dissolution enhancement of irbesartan can improve the oral bioavailability. Here, it was also studied how media milling time can be reduced by subjecting irbesartan to prior homogenization and then media milling. Results First, homogenization of irbesartan was carried out in the presence of poloxamer 407 at 6000 rpm for 2 h. Final nanosuspension preparation was done by media milling with zirconium dioxide beads. Here, the amount of poloxamer 407 and zirconium dioxide beads was studied as statistical independent variables. Response surface plot analysis and desirability function were applied to the selected optimized batch. The prepared batches were subjected to evaluation for zeta potential value, mean particle size, PDI, dissolution study, and stability study. Target particle size was less than 500 nm, and in vitro dissolution in 10 min was more than 80%. Zeta potential value was ~ 27 mV for optimized nanosuspension. Desirability of 0.941 was achieved. Checkpoint batch was prepared and evaluated to confirm the validity of mathematical model. Accelerated stability study was performed on the optimized batch at 40 ± 2 °C/75 ± 5% RH for 6 months. Conclusion The results confirmed the stability of formulation at accelerated stability conditions. Using presuspension prepared by homogenization, media milling time primarily reduced from 24–28 h to 18 h. Future perspective is to study other factors in combination method in discrete.

Particle size, leaf pubescence and condition of humidity at leaf surfaces are key factors determining the retention of volcanic ash on crop foliage.

2021 ◽  
Author(s):  
Noa Ligot ◽  
Benoît Pereira ◽  
Patrick Bogaert ◽  
Guillaume Lobet ◽  
Pierre Delmelle
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Leaf Surface ◽  
Volcanic Risk ◽  
Chilli Pepper ◽  
Leaf Pubescence ◽  
Leaf Surfaces ◽  
Plant Foliage ◽  
Leaf Surface Area ◽  
Ash Deposit

<p>Volcanic ashfall negatively affects crops, causing major economic losses and jeopardising the livelihood of farmers in developing countries where agriculture is at volcanic risk. Ash on plant foliage reduces the amount of incident light, thereby limiting photosynthesis and plant yield. An excessive ash load may also result in mechanical plant damages, such as defoliation and breakage of the stem and twigs. Characterising crop vulnerability to ashfall is critical to conduct a comprehensive volcanic risk analysis. This is normally done by describing the relationship between the ash deposit thickness and the corresponding reduction in crop yield, i.e. a fragility function. However, ash depth measured on the ground surface is a crude proxy of ash retention on plant foliage as this metrics neglects other factors, such as ash particle size, leaf pubescence and condition of humidity at leaf surfaces, which are likely to influence the amount of ash that stays on leaves.</p><p>Here we report the results of greenhouse experiments in which we measured the percentage of leaf surface area covered by ash particles for one hairy leaf plant (tomato, Solanum lycopersicum L.) and one hairless leaf plant (chilli pepper, Capsicum annuum L.) exposed to simulated ashfalls. We tested six particle size ranges (≤ 90, 90-125, 125-250, 250-500, 500-1000, 1000-2000 µm) and two conditions of humidity at leaf surfaces, i.e. dry and wet. Each treatment consisted of 15 replicates. The tomato and chilli pepper plants exposed to ash were at the seven- and eight-leaf stage, respectively. An ash load of ~570 g m<sup>-2 </sup>was applied to each plant using a homemade ashfall simulator. We estimated the leaf surface area covered by ash from pictures taken before and immediately after the simulated ashfall. The ImageJ software was used for image processing and analysis.</p><p>Our results show that leaf coverage by ash increases with decreasing particle size. Exposure of tomato and chilli pepper to ash ≤ 90 μm always led to ~90% coverage of the leaf surface area. For coarser particles sizes (i.e. between 125 and 500 µm) and dry condition at leaf surfaces, a significantly higher percentage (on average 29 and 16%) of the leaf surface area was covered by ash in the case of tomato compared to chilli pepper, highlighting the influence of leaf pubescence on ash retention. In addition, for particle sizes between 90 and 500 µm, wetting of the leaf surfaces prior to ashfall enhanced the ash cover by 19 ± 5% and 34 ± 11% for tomato and chilli pepper, respectively.</p><p>These findings highlight that ash deposit thickness alone cannot describe the hazard intensity accurately. A thin deposit of fine ash (≤ 90 µm) will likely cover the entire leaf surface area, thereby eliciting a disproportionate effect on plant foliage compared to a thicker but coarser deposit. Similarly, for a same ash depth, leaf pubescence and humid conditions at the leaf surfaces will enhance ash retention, thereby increasing the likelihood of damage. Our study will contribute to improve the reliability of crop fragility functions used in volcanic risk assessment.</p>

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