NaCl Particles Research Articles

A humidity-controlled fast integrated mobility spectrometer (HFIMS) for rapid measurements of particle hygroscopic growth

Abstract. We present a humidity-controlled fast integrated mobility spectrometer (HFIMS) for rapid particle hygroscopicity measurements. The HFIMS consists of a differential mobility analyzer (DMA), a relative humidity (RH) control unit and a water-based FIMS (WFIMS) coupled in series. The WFIMS (Pinterich et al., 2017) combines the fast integrated mobility spectrometer (Kulkarni and Wang, 2006a, b) with laminar flow water condensation methodologies (Hering and Stolzenburg, 2005; Spielman et al., 2017). Inside the WFIMS, particles of different electrical mobilities are spatially separated in an electric field, condensationally enlarged and imaged to provide 1 Hz measurements of size distribution spanning a factor of ∼ 3 in particle diameter, which is sufficient to cover the entire range of growth factor (GF) for atmospheric aerosol particles at 90 % RH. By replacing the second DMA of a traditional hygroscopicity tandem DMA (HTDMA) system with the WFIMS, the HFIMS greatly increases the speed of particle growth factor measurement. The performance of the HFIMS was evaluated using NaCl particles with well-known hygroscopic growth behavior and further through measurements of ambient aerosols. Results show that the HFIMS can reproduce, within 2 %, the literature values for hygroscopic growth of NaCl particles. NaCl deliquescence was observed between 76 and 77 % RH in agreement with the theoretical value of 76.5 % (Ming and Russell, 2001), and efflorescence relative humidity (43 %) was found to lie within the RH range of 41 to 56 % reported in the literature. Ambient data indicate that the HFIMS can measure the hygroscopic growth of five standard dry particle sizes ranging from 35 to 165 nm within less than 3 min, which makes it about 1 order of magnitude faster than traditional HTDMA systems.

Functional properties of foamed and/or stretched polypropylene-films containing sodium chloride particles for humidity regulation

The relative humidity level in the immediate vicinity of objects such as foods and technical items has an influence on transpiration and undesired relative humidity dependent reactions on their surfaces such as water vapour condensation, chemical reactions and microbial growth. Desirable are therefore materials that regulate the relative humidity to predefined levels in closed spaces such as in packagings and also in housing spaces. Such materials should be able to adjust the surface humidity of objects via water vapour diffusion in the gas phase without being in direct contact. A strategy to create such humidity regulating materials is the use of substances that absorb and desorb high amounts of water vapour, such as sodium chloride. Sodium chloride (NaCl) particles absorb water vapour at a relative humidity above 75% at 23 °C and then they form NaCl solution. NaCl solution desorbs water vapour when the relative humidity in the immediate vicinity decreases below the equilibrium relative humidity of that salt solution. Therefore, this system is able to regulate the relative humidity in its immediate vicinity. A strategy to provide free space in polymeric structures for the NaCl solution is the creation of cavities by foaming and stretching. However, only little knowledge exists about the influence of the combination of both processes on the functional properties of humidity regulating films with salt as active substance. Hence, the aim of this study was to investigate how and to which extend foaming and/or stretching affects the functional properties, i.e. water vapour sorption and mechanical properties, of polypropylene (PP) films containing NaCl particles. For this study, foamed and non-foamed PP with 3 and 6 weight-% NaCl were extruded into films. In the next step, some of these samples were biaxially stretched and their structures, water vapour absorption, porosities and mechanical strengths were analysed. The only-foamed films had a porosity of 0.3, the porosity of only-biaxially stretched films was between 0.1 and 0.2. The porosity increased to 0.7 when the films were first foamed and stretched afterward. Foamed and then stretched films with 6 wt.-% NaCl absorbed a high amount of water vapour from air with a value of 0.8 g H2O/g film at 97% relative humidity. Stretching of filled and non-filled foamed films also resulted in higher mechanical strength of the pure matrix polymer in comparison to the pure matrix polymer of non-stretched films. By the results of this study is shown that humidity regulating films with high water vapour sorption capacity can be produced via extrusion, foaming and stretching processes which are established processes in the polymer industry.

Flow characteristics of coarse particles in horizontal hydraulic conveying

In hydraulic conveying of solid particles, the flow characteristics play a significant rule on choosing the optimal operating conditions for a desired conveying rate. The main goal of this study is to investigate the flow characteristics in terms of essential operating conditions. For this target 3D CFD-DEM simulations were held to provide information on the hydraulic conveying of coarse particles in a fully developed horizontal flow in a pipe. The simulation was done in a periodic pipeline which was validated with experimental data and showed good agreements for the pressure and concentration profile. Therefore, the modeling and the simulation setup, which are given in this study, can be used as a basis for further investigating this phenomenon. To examine the effects of the operating conditions on the flow, a parametric study was done using NaCl particles and brine as the carrier. This investigation included running several simulations and changing the operating conditions: mean fluid velocity, particle concentration, particle size and pipe size. The results were analyzed to retrieve the pressure drop, the velocity profiles of the phases, the concentration profiles, the turbulent intensity, the delivered concentration and the dominant forces. By analyzing these results, we found how the flow pattern is governed by the operating conditions. In particular, an interesting aspect that found is that in the mean velocity range of 0.6–4m/s two regimes dominated the flow, below (moving bed) and above the velocity of 1.5m/s (heterogeneous flow). Furthermore, it is found that the inter-particle collisions are the most dominant effect that support the suspended particles above the bed, which suggest that flow eddies have less significance in that manner.

Precise fabrication of open porous Mg scaffolds using NaCl templates: Relationship between space holder particles, pore characteristics and mechanical behavior

Mg-based scaffolds have great potential of application for bone defect repair due to their biodegradability and the excellent osteoinductivity, yet currently the fabrication of Mg-based porous materials is still a challenge. In this study, a new fabrication method was proposed to produce porous Mg scaffolds, which could be achieved by three steps: (1) defectless NaCl open porous template with enhanced relative density was prepared with NaCl particles by hot press sintering (HPS) process; (2) green compact of Mg and the NaCl template was produced by infiltration casting; (3) open porous Mg scaffold was achieved after leaching out the template. By using spherical NaCl particles and irregular polyhedral NaCl particles, respectively, two different types of templates were prepared, and correspondingly Mg scaffolds with spherical and irregular pores were respectively fabricated. The irregular-pore scaffold (I-scaffold) exhibited higher yield strength, while the spherical-pore scaffold (S-scaffold) showed superior interconnectivity and more stable compressive deformability due to the uniform spatial structure.

Filtration efficiency and loading characteristics of PM2.5 through commercial electret filter media

Abstract Atmospheric PM2.5 pollution has been attracting much public attention for decades because of its adverse health effects. China and other Asian countries are frequently exposed to high PM2.5 concentrations, and filtration techniques through HVAC systems and indoor air cleaners are often used to mitigate PM2.5 in indoor environments, e.g. commercial and residential buildings, schools, and hospitals. Electret filter media provide lower pressure resistance and are frequently used in air purification systems. However, existing test standards, e.g. ASHRAE 52.2-2012, only challenge filters with particles larger than 300 nm which makes it impossible to assess filter performance at the most penetrating particle size (MPPS) since the inherent MPPS of electret media is smaller than 100 nm. In this study for investigating the performance of the electret filter media against PM2.5, the filter media were first challenged with monodisperse particles of 3–500 nm (the majority of PM2.5 number concentration resides in this range) at face velocities of 0.05, 0.25 and 0.5 m s−1 to obtain initial efficiency curves. Then the time-dependent efficiencies during the loading process were investigated using polydisperse NaCl particles which mimicked the size distribution of typical atmospheric PM2.5. Additionally, the effects of fiber charge and particle charge on initial efficiency and loading characteristics were evaluated by intentionally removing the fiber charges and charging the particles bipolarly (neutralized) or unipolarly. Results showed that the effects of fiber and particle charges on initial efficiency enhancement depended on particle sizes. The polarization force enhanced the collection of particles larger than ∼20 nm particles, the image force enhanced the collection of particles smaller than ∼100 nm, and the Columbic force enhanced the collection of particles smaller than ∼300 nm. Charging the particles unipolarly can slow down the reduction of electrical efficiency during loading and enhance the minimum efficiency by 10–30% for 50–500 nm particles, compared to that of bipolarly charged particles. A model using an electric degradation parameter and mechanical collection efficiency raising factor was applied to explain the performance of electret media in loading processes.

Enhancement of filtration efficiency by electrical charges on nebulized particles

There have been few investigations of effects of electrical charge, carried by lab-generated particles, on filtration efficiency testing. Here, we measured the elementary charge on particles and the fraction of particles carrying that charge with a combined electrometer, differential mobility analyzer, and scanning mobility particle sizer. A typical solid NaCl aerosol and liquid diethylhexyl sebacate (DEHS) aerosol were generated with Collison and Laskin nebulizers, respectively. Our experimental results showed that NaCl aerosols carried more charge after aerosol generation. The average net elementary charge per particle was approximately 0.07. The NaCl aerosol was overall positively charged but contained a mixture of neutral and charged particles. Individual particles could carry at most four elementary charges. According to constant theorem, we speculated that original NaCl aerosol contained 17% neutral, 45% positive-, and 38% negative-charged particles in the diameter range from 30 to 300nm. A Kr-85 neutralizer was used to decrease the charge on the NaCl particles. Our results indicated that the DEHS aerosol was electrically neutral. The effects of electric charge on particle collection by electret and electroneutral high efficiency particulate air (HEPA) filters were analyzed. Theoretical calculations suggested that charges on original NaCl aerosol particles enhanced the filtration efficiency of HEPA filters.

Preparation of super-hydrophobic micro-needle CuO surface as a barrier against marine atmospheric corrosion

A super-hydrophobic (SH) CuO surface was prepared on copper using chemical etching followed by fluorination treatment. The relationship between surface morphology and hydrophobicity was investigated. When the etching time varied from 5 to 120min, morphology changed from sparse sharp needles to dense sharp needles, and then to a stamen-like structure with flower-like clusters. All these surfaces were SH with the dense micro-needle surface (10min etching) the best. This SH surface made salt (NaCl) particles deliquesce and roll away. Electrochemical tests showed that it reduced corrosion in a 3.5% (w/w) NaCl solution by more than 102 times.

The electrical resistivity and relative permittivity of binary powder mixtures

Effective electrical resistivities and static relative permittivities of binary powder mixtures were measured and compared to theoretical equations given by Generalized Mixture Rule (GMR). The measured values for mixtures were influenced by the resistivity and permittivity of the pure component materials, the particle sizes and by the sticking between the different particles. According to the Random Model (RM), the effective resistivity and relative permittivity of any randomly packed mixture material can be calculated from the component resistivities and relative permittivities, respectively, and their concentrations. It was shown that RM gave good predictions for both quantities for powders if the particle sizes of the component materials were almost the same. However, this was not the case when large NaCl particles were mixed with fine sugar particles. When these mixtures were prepared, finer, more numerous sugar particles coated the larger NaCl particles, and the mixtures were not random but closer to the series configuration. Effect of particle size was studied briefly by mixing very fine NaCl particles with sugar of similar size. With these mixtures, results predicted by RM were obtained.

The effect of sodium chloride on the nanoparticles observed in a laminar methane diffusion flame

The occurrence of nano-particles along the centerline of a laminar co-flow diffusion flame with a fuel jet diameter of 10 mm was investigated under two conditions: a methane diffusion flame with and without the addition of NaCl particles of the order of 100 nm in diameter in the fuel flow. Samples of nano-particles from different heights above the burner (HAB) were extracted through a small pinhole in a tubular probe and were immediately diluted several thousand times. Subsequent to sampling, particles were directed to a scanning mobility particle sizer (SMPS) to measure the particle size distribution. A rapid thermocouple insertion method was used to measure the temperature of the flow at different axial and radial positions. Extracted nano-particles from different HABs were collected on grids and their structure was studied using transmission electron microscopy (TEM). The spatial temperature field in the flow was not significantly changed with the addition of NaCl particles to the fuel flow. Particle size distributions for the methane-only flame showed different stages of nano-particle evolution, from inception and surface growth to coagulation and oxidation. TEM images showed that primary soot particles had core–shell structures. Particle size distributions for the methane–NaCl flame showed that considerable concentrations of sub-10 nm particles appeared at heights above the burner where soot inception is typically not expected in a methane flame. The TEM images showed that the structure of these nano-particles was similar to cubical NaCl particles. For higher HABs the particle size distribution followed a similar trend as the methane-only flame, except for regions of the flame where coagulation is the dominant process. The addition of NaCl reduced the mobility diameter of soot particles and increased their number concentration. These results indicate that the addition of NaCl to the flame reduces the coagulation between soot primary particles.

Low-density microcellular carbon foams from sucrose by NaCl particle templating using glycerol as a plasticizing additive

Carbon-NaCl composites with high NaCl loading (83.3 to 92.2wt%) were prepared by setting molten sucrose-NaCl-glycerol pastes in a stainless steel mold at 160°C. The carbonization of the composites followed by NaCl removal by washing with water produced low-density microcellular carbon foams. The setting of the paste was due to the caramelization of molten sucrose as well as the slow evaporation of glycerol. The carbon-NaCl composites had the adequate compressive strength (6.9 to 17.8MPa) and ductility for machining using conventional machine tools. Machining of the carbon-NaCl composites followed by NaCl removal was used as a strategy to produce low-density carbon foams with desired contours. The glycerol not only decreased the density of carbon foams produced from the sucrose-NaCl system but also produced a remarkable change in the foam microstructure from a combination of macropores and microcells to only microcells of sizes predominantly in the range of 3 to 6μm. Carbon foams prepared at NaCl to sucrose weight ratios in the range of 1.5 to 3 show density, compressive strength, thermal conductivity and EMI shielding effectiveness in the ranges of 0.096 to 0.214g/cm3, 0.60 to 4.83MPa, 0.087 to 0.235Wm−1K−1 and 24.7 to 41.7dB, respectively.

Scalable synthesis of Sb/MoS2/C composite as high performance anode material for lithium ion batteries

Metal Sb is considered as alternative candidate anode material for lithium-ion batteries (LIBs) due to its high capacity, but the significant volume expansion during the charge and discharge process cause poor stability seriously influencing on the practical application in batteries. Herein, a facile and scalable method is developed for preparation of Sb/MoS2/C composite using the cubic NaCl particles as template. The Sb nanoparticles embedded deeply in carbon nanosheets buffer the internal stress caused by the volume expansion of Sb and avoid the direct exposure of electrolyte to the Sb nanoparticles. The MoS2 nanoparticles can provide more active sites to store more Li+ and speed up the migration rate of Li+. Tested as an anode material, the Sb/MoS2/C composite shows outstanding rate capability (763 mA h g−1 at 0.2 A g−1, 642.2 mA h g−1 at 0.5 A g−1, 544 mA h g−1 at 1.0 A g−1, 459 mA h g−1 at 2.0 A g−1 and 353 mA h g−1 at 5.0 A g−1) and long cycling stability (a high capacity of 679.5 mA h g−1 is achieved at 0.2 A g−1 after 250 cycles).

Performance Degradation of PEMFC by Sea Salt Aerosol Contamination

In this study, performance degradation of proton exchange membrane fuel cells (PEMFCs) by 1 μm scale sea salt aerosol was investigated. The regulations of NOx emission control on ships are strengthened year by year. Installation of PEMFCs as electrical power source is one of important choice. In order to investigate the influence of seawater contamination, several studies focus on the effects of sodium chloride (NaCl) [1, 2]. The fuel cell performance degradation by NaCl was investigated by injecting NaCl solution into the cathode side gas inlet, however, fuel cell has a filter and there is no such a situation. On the other hand, conventional filter cannot remove extreme small sea salt particles (1 μm scale sea salt aerosol). Effects of the invaded sea salt aerosol for the fuel cell performance were not elucidated. In this study, artificial sea salt aerosol generator was developed and the effects of sea salt aerosol contamination in the cathode side were investigated. Figure 1 shows experimental setup. Sea salt aerosol generator was consisted by ultrasonic vibrator, NaCl solution tank, and heated pipe. Ultrasonic vibration generates fine droplets of NaCl solution. Water evaporates from the droplet while flowing through the heated pipe and finally, fine NaCl crystals remain in the gas as aerosol. The diameter of sea salt aerosol can be controlled by varying concentration of NaCl solution. Figure 2 shows SEM image of collected sea salt aerosols at the end of cathode gas supply line. With using 3 mol/L NaCl solution, approximately 1 μm scale sea salt particles were stably produced. The cell has an active area of 4 cm2 (2 × 2 cm) with serpentine channels. The channel width and depth were 1.0 and 1.0 mm, respectively, and the rib-to-channel ratio was 1. Fuel cell temperature and relative humidity of anode/cathode gas were set 60°C and 70%, relatively. Flow rate of sea salt aerosol was 1.2 mg/h. Fuel cell was operated with constant current density condition (0.5 A/cm2). Figure 3 shows time variation of cell voltage. When the sea salt aerosol injection was started, the cell voltage clearly dropped, and it suggested cell performance degradation. The cell was disassembled after completing the power generation test. NaCl deposition was not observed in the channel. On the other hand, it was found that NaCl particles existed in the GDL by polarizing microscope imaging. A large number of NaCl particles were present under the channel, whereas almost no particles presented under the rib. The NaCl particles not only adhered to the channel side of the GDL but also invaded into the region close to the catalyst layer and the particle diameter has increased compare to initial one (Figure 4). Similar distribution was observed from inlet to outlet in the serpentine channels. However, NaCl particles did not block the pore in the GDL, and there were still enough gas flow path. Figure 5 shows result of cyclic voltammetry (CV) measurement. Comparing the effective surface area of the platinum catalyst before and after adding the sea salt aerosol, decrease of 22.6% has been occurred. It is considered that poisoning of platinum catalyst was caused by adsorption of chloride ion (Cl-) [1]. These results suggest that 1 μm scale fine sea salt aerosol reaches catalyst layer in the cathode with passing the GDL easily, and finally, cell performance degradation will be caused. Present experiment has been performed under accelerated condition, investigation of degradation process with different flow rate of sea salt aerosol is future task. Investigation of performance recovery by generated liquid water is also important issues. There is a possibility that high humidity cell operation prevent the poisoning.

Prediction of Electrochemical Performance of Lower Temperature Operating Na-NiCl2 Battery

Sodium nickel chloride (Na-NiCl2) batteries are gaining growing attentions as a strong potential contender for advanced electric vehicle (EV) and stationary energy storage system (ESS) applications. The cathode compartment of a Na-NiCl2 battery features by a mixture of solid NaCl and Ni granules impregnated with a liquid NaAlCl4 catholyte. During charge-discharge cycles, complicated electrochemical reactions take place, including transportation of Na+ ions through NaAlCl4 catholyte, the dissolution/coarsening of NaCl particles, formation/decomposition of NiCl2 layers on the active Ni surface, and electron transport through the Ni granules. We are developing advanced Na-NiCl2 batteries that operate at relatively lower temperatures of below 200 °C to minimize its cell degradation typically observed at high operation temperature (over ~270 °C) and to enable application of simple and cheaper polymer seals for cell manufacturing. However, the diffusion and the ionic migration kinetics of active Na+ ions are restricted at the lower temperatures that may limit cell performance. In this presentation, we introduce a multi-physics continuum computational model to capture the electrochemical behaviors of planar lower temperature Na-NiCl2 batteries. The computational results will elucidate impacts of (i) cell operation temperatures, (ii) current densities, and (iii) cathode dimensions on the electrochemical performance of prototype planar Na-NiCl2 cells. The developed prediction model is expected to provide a useful guideline for the experimental fabrication of advanced Na-NiCl2 batteries with maximized cell performance at relatively lower temperatures.

Water-soluble-template-derived nanoscale silicon nanoflake and nano-rod morphologies: Stable architectures for lithium-ion battery anodes

Earth abundant and economical rock salt (NaCl) particles of different sizes (<3 μm and 5–20 μm) prepared by high energy mechanical milling were used as water-soluble templates for generation of Si with novel nanoscale architectures via low pressure chemical vapor deposition (LPCVD). Si nanoflakes (SiNF) comprising largely amorphous Si (a-Si) with a small volume fraction of nanocrystalline Si (nc-Si), and Si nanorods (SiNR) composed of a larger volume fraction of crystalline Si (c-Si) and a small volume fraction of a-Si resulted from modification of the NaCl crystals. SiNF yielded first-cycle discharge and charge capacities of ∼2,830 and 2,175 mAh·g−1, respectively, at a current rate of 50 mA·g−1 with a first-cycle irreversible loss (FIR loss) of ∼15%–20%. SiNR displayed first-cycle discharge and charge capacities of ∼2,980 and ∼2,500 mAh·g−1, respectively, at a current rate of 50 mA·g−1 with an FIR loss of ∼12%–15%. However, at a current rate of 1 A·g−1, SiNF exhibited a stable discharge capacity of ∼810 mAh·g−1 at the end of 250 cycles with a fade rate of ∼0.11% loss per cycle, while SiNR showed a stable specific discharge capacity of ∼740 mAh·g−1 with a fade rate of ∼0.23% loss per cycle. The morphology of the nanostructures and compositions of the different phases/phase of Si influence the performance of SiNF and SiNR, making them attractive anodes for lithium-ion batteries.

Resistance of Type 5 chemical protective clothing against nanometric airborne particles: Behavior of seams and zipper

ABSTRACTIn the field of dermal protection, the use of chemical protective clothing (CPC) (including coveralls) are considered as the last barrier against airborne engineered nanomaterials (ENM). In the majority of cases, Type 5 CPC, used against solid particles (ISO 13982-1), perform well against ENM. But in a recent study, a penetration level (PL) of up to 8.5% of polydisperse sodium chloride airborne nanoparticles has been measured. Moreover, in all the previous studies, tests were performed on a sample of protective clothing material without seams or zippers. Thus, the potential for permeation through a zipper or seams has not yet been determined, even though these areas would be privileged entry points for airborne ENM.This work was designed to evaluate the PL of airborne ENM through coveralls and specifically the PL through the seams on different parts of the CPC and the zipper.Eight current models of CPC (Type 5) were selected. The samples were taken from places with and without seams and with a zipper. In some cases, a cover strip can be added to the zipper to enhance its sealing. Polydisperse nanoparticles were generated by nebulization of a sodium chloride solution. A penetration cell was developed to expose the sample to airborne nanometric particles. The NaCl particle concentration in number was measured with an ultrafine particle counter and the PL was defined as the downstream concentration divided by the upstream concentration.The results obtained show that the PL increased significantly in the presence of seams and could reach up to 90% depending on the seam's design. Moreover, this study classifies the different types of seams by their resistance against airborne ENM. As for the penetration of airborne NaCl particles through the zipper, the PL was greatly attenuated by the presence of a cover strip, but only for certain models of coveralls. Finally, the values of the pressure drop were directly linked to the type of seam. All of these conclusions provide recommendations to both manufacturers and users.

Aerosol dynamics model for the simulation of hygroscopic growth and deposition of inhaled NaCl particles in the human respiratory tract

The purpose of the present work is the implementation of the aerosol dynamics model ADiC, specifically its heat/vapor transport and phase transition components, into the stochastic lung deposition model IDEAL. The combined ADiC/IDEAL model allows the simultaneous calculation of relative humidity, hygroscopic growth and deposition of inhaled NaCl aerosols in individual airways of the human lung along randomly selected particle paths and randomly selected times during the inhalation phase. Hygroscopic growth decreases deposition of submicron particles compared to hydrophobic particles with equivalent diameters due to a less efficient diffusion mechanism, while the more efficient impaction and sedimentation mechanisms increase total deposition for micrometer particles. Due to the variability and asymmetry of the human airway system, individual trajectories of inhaled particles are associated with individual growth factors. For a realistic breathing scenario, particles are inhaled at different times during the inspiratory phase and hence experience individual growth factors, thereby further enhancing the variability of individual growth factors and resulting deposition patterns. While nanometer particles adopt their equilibrium growth factor value already within the mouth and pharynx/larynx during the inspiratory phase, micrometer particles approach this value at the end of inspiration, thus further increasing in size during the exhalation phase. In summary, individual hygroscopic growth factors vary for different paths and different inhalation times. For model validation purposes, theoretical predictions were compared with human experimental deposition data and previous hygroscopic growth model simulations for total deposition of ultrafine and micrometer-sized NaCl particles.

Evolution and interaction of corrosive species during the initial NaCl particle induced corrosion on zinc coated skin-passed steel

Within this work, NaCl particle induced corrosion of electrolytically zinc coated, skin-passed steel and especially the influence of the skin-pass texture was investigated. Skin-passing is a wet-rolling procedure that applies a texture on the sample surface to improve the mechanical properties and to enhance the optical appearance of applied coatings.Samples were studied in-situ and ex-situ using Raman spectroscopy and optical microscopy in a self-designed 3D-printed weathering cell. Raman imaging and spectral correlation function were applied ex-situ to obtain more detailed information about the product distribution after drying the sample. Complementary information was obtained using SEM and EDX mapping.

Synthesis of graphene nanoflakes by grinding natural graphite together with NaCl in a planetary ball mill

Natural graphite is a soft material that conventional milling methods fail to grind into nanoparticles. We found that adding NaCl into graphite during milling allows obtaining graphene nanoflakes of about 50[Formula: see text][Formula: see text][Formula: see text]200[Formula: see text]nm2 as evidenced by Transmission Electron Microscope (TEM). NaCl particles are substantially brittle and harder than graphite, serving as milling agents by both helping to chop graphite into smaller pieces and preventing graphite particles from agglomeration. After milling, NaCl can be easily washed away by water. Probable mechanism for exfoliation of graphene during the modified ball milling may be explained by NaCl and graphene slipping or sliding against and over each other, exfoliating the graphene particles into thin layers.

Fabrication and electrochemical properties of a graphene-enhanced hierarchical porous network of Fe3O4/carbon nanobelts

A novel, facile and scalable process of simultaneous activation and templating is developed for in situ synthesis of graphene-enhanced 3D hierarchical porous carbon nanobelt networks uniformly anchored with polycrystalline Fe3O4 nanoparticles (5–45nm) (Fe3O4–rGO/poly(vinyl alcohol) (PVA)-derived carbon) as a high-performance supercapacitor electrode. During the synthesis, 3D self-assembled NaCl particles are adopted as a structural template to direct the growth of 3D carbon nanobelt networks with interconnected macropores, KOH is used as an activating reagent to generate porous nanobelts with masses of micro-, meso- and macropores, and graphene sheets behave as a chemical activator to promote the growth of hierarchical porous thin nanobelts. The resulting Fe3O4–rGO/PVA-derived carbon electrode leads to a combination of the redox pseudo-capacitance of Fe3O4 and the electric double-layer capacitance of the carbon species with a remarkably high capacitivity (538.8Fg−1 at 5Ag−1) and outstanding cycle performance (∼590Fg−1 after 5000 cycles at 5Ag−1). This work offers a new strategy for preparation of 3D hierarchical porous carbon networks for future applications.

Note: Electric field assisted megasonic atomization for size-controlled nanoparticles.

In this study, we report the use of megasonic atomization along with an electric field to reduce the aerosol particle size. The electric field assisted megasonic atomization (EMA) was achieved by implementing mesh and an induction charging ring at the output of a megasonic atomizer. The aim was to increase the number of particles generated and reduce the size of the particles to the nanoscale regime. In the present study, the megasonically generated NaCl and TiO2 aerosols were charged by applying an electric supply voltage up to +20 kV through the induction ring. The generated nanoparticles were evaluated by an electrical low-pressure impactor and scanning electron microscopy. It is observed that, for +15 kV, the number concentration of NaCl and TiO2 particles was found to have increased by up to five times, and the peak size of the particles was shifted from 40 nm to 15 nm. The particle size reduction and increase in the number concentration might be due to Coulomb fission. Hence, the developed EMA system is suitable for many industrial applications where a large number of uniform-sized nanoparticles are required.