Ultrafine Particle Size Research Articles

Preparation of α‐Si3N4 by direct nitridation using polysilicon waste by diamond wire cutting

AbstractWith the rapid development of the semiconductor industry and solar photovoltaic industry, a large number of polysilicon wastes from diamond wire cutting are accumulated, which not only pollute the environment, but also cause safety problems due to the ultrafine particle size and high reactivity. The diamond wire cutting polysilicon waste was used to prepare α‐Si3N4 by direct nitridation method. This method could not only fully recycle the waste and reduce environmental pollution, but also could reduce the production cost of α‐Si3N4. Furthermore, the effects of FeCl3, NaCl, and metal Cu on the nitridation of polysilicon waste are investigated in detail, respectively. It is found that FeCl3 and NaCl are not ideal additives for the preparation of α‐Si3N4. However, α‐Si3N4‐dominated Si3N4 can be obtained via adding 5 wt% Cu after nitridation at 1250°C for 8 hours, and the relative content of α‐Si3N4 reaches 92.37%.

Ultrafine Prussian Blue as a High‐Rate and Long‐Life Sodium‐Ion Battery Cathode

Prussian blue analogs (PBAs) have attracted much attention as cathodes in sodium‐ion batteries due to their stable crystalline structure, high theoretical capacities, and facile synthesis. However, PBAs synthesized by the conventional precipitation method usually have the drawbacks of poor rate performance and cycling stability. Herein, the ball‐milling method is developed to prepare the ultrafine high‐quality Prussian blue. Benefited from its good crystallinity and ultrafine particle size of 40 nm, the obtained Na0.9Fe[Fe(CN)6]0.96 exhibits an outstanding cycling stability and rate capability, which can deliver a specific capacity of 106 mAh g−1 at 30 °C, maintaining 80% capacity after 500 cycles at 10 °C. The results show that a size effect can contribute to the enhancement of electrochemical kinetics of PBAs, and the scalable production of high‐performance PBAs can be anticipated based on the ball‐milling method.

In Situ Synthesis of MoC1- x Nanodot@Carbon Hybrids for Capacitive Lithium-Ion Storage.

In this study, in situ synthesis of carbon-coated MoC1- x nanodots anchored on nitrogen-doped carbon (MoC1- x@C) for lithium storage is reported. The obtained MoC1- x@C hybrids exhibit intriguing structural characteristics including ultrafine particle size (ca. 1.2 nm) of MoC1- x nanodots, porous structure of nitrogen-doped carbon matrix, and good robustness. When evaluated as anodes for lithium-ion batteries, the optimized MoC1- x@C sample demonstrates a superior specific capacity (1099.2 mA h g-1 at 0.1 A g-1) and good rate capability (369.1 mA h g-1 at 5 A g-1). The MoC1- x@C anode also presents remarkable cycling stability with a much higher specific capacity (657.9 mA h g-1) than that of commercial bulk MoC (91.4 mA h g-1) after 500 cycles at 1 A g-1. Kinetics analysis of the anodes reveals the charge storage mechanism, which demonstrates the existence of capacitive redox reactions occurring at the shallow surface of the MoC1- x nanodots and closely relating to the particle size. The outstanding electrochemical performance results from the synergistic effect of the elastic carbonaceous encapsulation to accommodate the huge volume expansion and the ultrafine MoC1- x nanodots to provide more reactive sites for capacitive lithium storage.

New method for increase in product fineness in stirred mills

Nowadays, ultrafine product particles size (<20μm) is more demanded for various industries. However, the problem in achieving the target product fineness in the stirred milling exists.To solve this problem, new method of the grinding process in stirred mills is proposed and investigated in this paper. The method implies increase in grinding balls collision energy in the radial and axial directions by introducing the ellipsoidal stirrer and the unbalanced drive with the spring elements, respectively, to the typical design of stirred mill. Description of the collision forces and collision energies calculation in the radial and axial directions is presented.Efficiency of the new method has been investigated and approved by mathematical modeling and experimental studies. It has been proved that joint increase in collision energy in the radial and axial directions allows to obtain finer product particles size with spending less processing time.

A new route for preparing Mo-10wt.%Cu composite compacts

In this work, high pure Mo-10 wt% Cu composite powders with a ultrafine particle size are prepared by a two-step reduction process (first carbothermal reduction and then hydrogen reduction). Ammonium heptamolybdate and copper nitrate trihydrate powders are used as molybdenum and copper source, respectively. The mixtures of raw materials are calcined at 400 °C firstly to form the composite oxides which are then reacted with insufficient carbon black at 1050 °C for 2 h. The as-prepared powders are further reduced by hydrogen at 750 °C for 2 h to obtain the ultrafine Mo-10 wt% Cu composite powders. The experimental results show that the residual carbon of the Mo-10 wt% Cu powders can be decreased to 0.015 wt%, and the composite powders have an average particle size of 200 nm. The sintering behavior of ultrafine MoCu powders and the properties (vickers hardness and thermal conductivity) of samples after sintering are investigated. High sintering temperature is beneficial to increase the density of the compact. At 1200 °C, the relative density of the MoCu compacts is 98.8%. The vickers hardness and thermal conductivity of the Mo-10 wt% Cu composites sintered at 1200 °C for 3 h are 233 HV and 130 (W/m·k), respectively.

Effect of electronic cigarette (EC) aerosols on particle size distribution in indoor air and in a radon chamber

Abstract Particle size distribution is an important factor governing whether aerosols can be deposited in various respiratory tract regions in humans. Recently, electronic cigarette (EC), as the alternative of tobacco cigarette, has become increasingly popular all over the world. However, emissions from ECs may contribute to both indoor and outdoor air pollution; moreover, comments about their safety remain controversial, and the number of users is increasing rapidly. In this investigation, aerosols were generated from ECs and studied in the indoor air and in a chamber under controlled conditions of radon concentration. The generated aerosols were characterized in terms of particle number concentrations, size, and activity distributions by using aerosol diffusion spectrometer (ADS), diffusion battery, and cascade impactor. The range of ADS assessment was from 10−3 μm to 10 μm. The number concentration of the injected aerosol particles was between 40 000 and 100 000 particles/cm3. The distribution of these particles was the most within the ultrafine particle size range (0–0.2 μm), and the other particle were in the size range from 0.3 μm to 1 μm. The surface area distribution and the mass size distribution are presented and compared with bimodal distribution. In the radon chamber, all distributions were clearly bimodal, as the free radon decay product was approximately 1 nm in diameter, with a fraction of ~0.7 for a clean chamber (without any additional source of aerosols). The attached fraction with the aerosol particles from the ECs had a size not exceeding 1.0 μm.

Vehicle interior air quality conditions when travelling by taxi

Vehicle interior air quality (VIAQ) was investigated inside 14 diesel/non-diesel taxi pairs operating simultaneously and under normal working conditions over six weekday hours (10.00–16.00) in the city of Barcelona, Spain. Parameters measured included PM10 mass and inorganic chemistry, ultrafine particle number (N) and size, lung surface deposited area (LDSA), black carbon (BC), CO2, CO, and a range of volatile organic compounds (VOCs). Most taxi drivers elected to drive with windows open, thus keeping levels of CO2 and internally-generated VOCs low but exposing them to high levels of traffic-related air pollutants entering from outside and confirming that air exchange rates are the dominant influence on VIAQ. Median values of N and LDSA (both sensitive markers of VIAQ fluctuations and likely health effects) were reduced to around 104 #/cm3 and < 20 µm2/cm3 respectively under closed conditions, but more than doubled with windows open and sometimes approached 105 #/cm3 and 240 µm2/cm3. In exceptional traffic conditions, transient pollution peaks caused by outside infiltration exceeded N = 106 #/cm3 and LDSA= 1000 µm2/cm3. Indications of self-pollution were implicated by higher BC and CO levels, and larger UFP sizes, measured inside diesel taxis as compared to their non-diesel pair, and the highest concentrations of CO (>2 ppm) were commonly associated with older, high-km diesel taxis. Median PM10 concentrations (67 µg/m3) were treble those of urban background, mainly due to increased levels of organic and elemental carbon, with source apportionment calculations identifying the main pollutants as vehicle exhaust and non-exhaust particles. Enhancements in PM10 concentrations of Cr, Cu, Sn, Sb, and a “High Field Strength Element” zircon-related group characterised by Zr, Hf, Nb, Y and U, are attributed mainly to the presence of brake-derived PM. Volatile organic compounds display a mixture which reflects the complexity of traffic-related organic carbon emissions infiltrating the taxi interior, with 2-methylbutane and n-pentane being the most abundant VOCs, followed by toluene, m-xylene, o-xylene, 1,2,4-trimethylbenzene, ethylbenzene, p-xylene, benzene, and 1,3,5-trimethylbenzene. Internally sourced VOCs included high monoterpene concentrations from an air freshener, and interior off-gassing may explain why the youngest taxi registered the highest content of alkanes and aromatic compounds. Carbon dioxide concentrations quickly climbed to undesirable levels (>2500 ppm) under closed ventilation conditions and could stay high for much of the working day. Taxi drivers face daily occupational exposure to traffic-related air pollutants and would benefit from a greater awareness of VIAQ issues, notably the use of ventilation, to encourage them to minimise possible health effects caused by their working environment.

Temporal variations of ultrafine particle concentrations in aircraft cabin: A field study

Characterization of indoor aerosols in aircraft cabin has been of great interest. However, few studies have presented investigations of ultrafine particle (UFP) concentrations in actual aircraft cabin environment. In this study, we presented the characteristics of UFP number concentration levels, size distributions and temporal variations in fourteen randomly selected domestic commercial flights in China. The results showed that the concentration levels of UFPs in cabin air were 417 ± 1089 counts cm−3, with the lowest values occurred during cruising phase, and the dominant peak at the size channel of 72–100 nm in general. Some of the peak values were observed at the moments of turbulence of air stream or passing through cloud. To further identify contributions of UFPs from interior and outside cabin, CO2 in return air was simultaneously observed as a ventilation tracer to calculate the total airflow rates in those flights. A simplified model was developed to estimate the contribution rates of UFPs from bleed air and cabin interior at cruising phase in selected flights, combing with mass conservation equation under some assumptions. It indicated that, UFPs were commonly derived from unfiltered bleed air system in most of those flights at cruising phase. However, some exceptions were found in some flights, possibly due to unfiltered bleed air system and in-cabin ozonation. This study could be a reference for further understanding the status quo and control strategies of ultrafine particulate pollution in commercial aircraft cabins.

Investigation on grinding impact of fly ash particles and its characterization analysis in cement mortar composites

Abstract The extensive usage of cement in almost all infrastructure projects will affect the health of construction industry around the world. At present, the entire globe is marching towards sustainable, eco-friendly and energy efficient infrastructure development with economic viabilities. The research elucidates the effect of grinding of Fly Ash (FA) and Ground Fly Ash (GFA) was studied. The fly ash particles are ground from 727 cm2/g to 3526 cm2/g specific surface area Ground fly ash were analyzed from the Blaine’s fineness test and particle size and optimized with 120 min of grinding to achieve the ultra-fine particle size. The Cement replacement by 15% FA and 30% GFA were determined from the mechanical strength of blended mortar specimens. The investigation is aimed to increase the consumption of fly ash and enable to reduce the usage of natural resources for the cement production with ultrafine fly ash as an efficient replacement material.

Sn-SnO2 hybrid nanoclusters embedded in carbon nanotubes with enhanced electrochemical performance for advanced lithium ion batteries

Sn-based materials are one promising high-capacity anode material for lithium-ion batteries. The practical application of Sn-based materials is generally restricted by their significant capacity fading due to the volume expansion and structural changes during Sn alloying/dealloying process. In this work, Sn-SnO2 hybrid nanoclusters are embedded into carbon nanotube network, forming a Sn-SnO2@CNT composite. The Sn-SnO2 nanoclusters are consisted of interconnected Sn and SnO2 nanocrystals, in which SnO2 forms a beneficial environment for the alloying/dealloying of Sn. The ultrafine particle size of SnO2 (<10 nm) also allows a highly reversible conversion reaction, contributing to high overall capacities. The Sn-SnO2 nanoclusters are uniformly dispersed in CNT matrix, therefore providing abundant active sites for Li-ion storage. The CNT matrix functions in improving electrical conductivity, preventing Sn aggregation, and accommodating Sn volume change in prolonged cycles. As a result, the hybrid Sn-SnO2@CNT electrode shows excellent rate capability (1059 mAh g−1 at 1 A g−1 and 960 mAh g−1 at 5 A g−1, corresponding to 0.53 mAh cm−2 at 0.5 mA cm−2 and 0.48 mAh cm−2 at 2.5 mA cm−2) and outstanding cycling stability (86% capacity retention after 1000 cycles at 0.5 A g−1), making it an promising anode material for high-performance lithium-ion batteries.

General Immobilization of Ultrafine Alloyed Nanoparticles within Metal-Organic Frameworks with High Loadings for Advanced Synergetic Catalysis.

The development of a general synthesis approach for creating fine alloyed nanoparticles (NPs) in the pores of metal–organic frameworks (MOFs) shows great promise for advanced synergetic catalysis but has not been realized so far. Herein, for the first time we proposed a facile and general strategy to immobilize ultrafine alloyed NPs within the pores of an MOF by the galvanic replacement of transition-metal NPs (e.g., Cu, Co, and Ni) with noble-metal ions (e.g., Pd, Ru, and Pt) under high-intensity ultrasound irradiation. Nine types of bimetallic alloyed NPs of base and noble metals were successfully prepared and immobilized in the pores of MIL-101 as a model host, which showed highly dispersed and well-alloyed properties with average particle sizes ranging from 1.1 to 2.2 nm and high loadings of up to 10.4 wt %. Benefiting from the ultrafine particle size and high dispersity of Cu–Pd NPs and especially the positive synergy between Cu and Pd metals, the optimized Cu–Pd@MIL-101 exhibited an extremely high activity for the homocoupling reaction of phenylacetylene under unprecedented base- and additive-free conditions and room temperature, affording at least 19 times higher yield (98%) of 1,4-diphenylbuta-1,3-diyne than its monometallic counterparts. This general strategy for preparing various MOF-immobilized alloyed NPs potentially paves the way for the development of highly active metal catalysts for a variety of reactions.

Chemically monodisperse tin nanoparticles on monolithic 3D nanoporous copper for lithium ion battery anodes with ultralong cycle life and stable lithium storage properties.

In this report, a simple and effective low-temperature synthesis route has been proposed to smoothly achieve monodisperse tin nanoparticles upon monolithic 3D nanoporous copper (3D-NPC@MTNPs) from chemical dealloying of as-cast Al-45 at% Cu alloy sheets in HCl solution; they exhibit superior Li storage properties and ultralong cycle life as the anode for lithium ion batteries (LIBs). The results show that the 3D-NPC@MTNPs composite can be fabricated on a large scale by electroless plating of Sn on a uniform NPC matrix with a pore size of ca. 200 nm in an acidic plating bath below room temperature. Compared to two dimensional copper foil supported tin thin films (2D-CF@TTFs), the 3D-NPC@MTNPs electrode displays a markedly higher first reversible capacity of 0.485 mA h cm-2 as well as superior cycling stability with 52.4% capacity retention and over 96.7% coulombic efficiency after 500 cycles. This can be largely ascribed to the synergistic effect between the favorable monodispersity of Sn nanoparticles with ultrafine particle size and single crystal nature and the unique 3D nanoporous electrode architecture with a large specific surface area and a good mass transfer channel, which facilitates the accommodation of mechanical strain, improvement of structural stability, enhancement of bonding force, and acceleration of mass transfer, which are indicative of a quite promising candidate as a high-performance anode for LIBs.

Novel LiV(PO4)0.9F1.3 with ultrahigh rate capability and prolonged cycle life.

Novel triclinic LiV(PO4)0.9F1.3, characterized through its crystal lattice expansion, ultrafine primary particle size and uniform carbon coating, was designed and fabricated through regulating the PO4/F ratio. It exhibited excellent electrochemical performance, maintaining 105 mA h g-1 at 50C and 92.9% capacity retention after 500 cycles at 10C due to its superior structural stability, greater charge transfer properties, enhanced electronic conductivity and fast Li+ diffusion kinetics.

Impact of various blends of linseed oil-derived biodiesel on combustion and particle emissions of a compression ignition engine – A comparison with diesel and soybean fuels

This study reports on a comparative analysis of the influence of linseed oil-derived biodiesel on a compression ignition engine combustion and performance. New findings on particle emission and size distribution are presented and discussed. A low-sulfur commercial diesel fuel and soybean biodiesel were used as a reference. Engine feeding with biodiesel blends leads to slight increase (5–15%) in the maximal pressure rise rate compared to the diesel fuel accompanied by a minor rise in coefficient of variation at low loads. Combustion duration of all studied biodiesel blends is longer compared to the diesel fuel under all operating modes. At low-load operating modes, reduction in particle number concentrations under feeding with blends of the diesel fuel with soybean and linseed-derived biofuels (in 1:1 ratio by volume) is observed in the entire range of measured particle sizes. At high loads, the opposite trend is revealed: in the ultrafine particles size range (<90 nm), the measured particle number concentration for the biodiesel blends is substantially higher compared to diesel fuel. In contrast to soybean biodiesel, the linseed-derived blends demonstrated a trend of reduction in nitrogen oxides emission as compared to diesel at higher engine loads.

Simulation of the size-composition distribution of atmospheric nanoparticles over Europe

Abstract. PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile organic vapors on particle number concentrations. The model predictions were evaluated against field observations collected during the PEGASOS 2012 campaign. The measurements included both ground and airborne measurements, from stations across Europe and a zeppelin measuring above Po Valley. The ground level concentrations of particles with a diameter larger than 100 nm (N100) were reproduced with a daily normalized mean error of 40 % and a daily normalized mean bias of −20 %. PMCAMx-UF tended to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily normalized mean bias of 75 %. The model was able to reproduce, within a factor of 2, 85 % of the N10 and 75 % of the N100 zeppelin measurements above ground. The condensation of organics led to an increase (50 %–120 %) in the N100 concentration mainly in central and northern Europe, while the N10 concentration decreased by 10 %–30 %. Including the VBS in PMCAMx-UF improved its ability to simulate aerosol number concentration compared to simulations neglecting organic condensation on ultrafine particles.

Sensor Selection and Scaling Up Mobile Monitoring for High-Resolution Mapping of Community Air Quality: Design Considerations in the MOV-UP Airport Ultrafine Particle Study

As novel environmental monitoring and exposure sensing approaches evolve, there is still the need to match the air quality concerns of communities with appropriate measurements. Designing an appropriate measurement approach for exposure studies requires identifying the sources of greatest concern, the set of pollutants that best characterize these sources, and sampling in manner that quantifies variations in concentrations in space and time. Recently, for the new Mobile Observations of Ultrafine Particles (MOV-UP) study, a sampling plan was designed to characterize ultrafine particle levels in communities near the SeaTac International Airport in Seattle, WA.Because of the need to cover a large area of approximately 250 km2 with a limited instrument and staffing budget within the timeframe of a year, a mobile monitoring approach was chosen, in which two instrumented vehicles would collect ultrafine particle measurements along local roads that transect the flight paths of the airport. Mobile monitoring would allow coverage of the large area with a relatively small number of high-end ultrafine particle counters.In addition to measuring ultrafine particle concentrations for the MOV-UP study, there was also a need to distinguish between ultrafines sourced from roadway traffic versus those from aircraft. GPS data were used to identify driving on major roadways, and were supplemented by additional measurements of ultrafine particle size and black carbon levels to help discriminate between roadway and aircraft sources. A principal component analysis (PCA) yielded multivariate eigenvalues representative of the different sources of concern. Also, relating flight patterns with wind patterns may also help to identify ultrafine particle levels attributable to aircraft.

Role of anthropogenic emissions and meteorology on ultrafine particle bursts over a high altitude site in Western Ghats during pre-monsoon

The ultrafine particle number concentration and size distribution during pre-monsoon (spring) over a high altitude location, Ooty (11.3 °N, 74.4 °E, 2240 m amsl) in Western Ghats, the highest peak in South India, are examined using campaign based ground observations. The total number concentrations are in the range ∼1000–3000 cm−3 with significant increase (2–4 folds) during the periods of ultrafine particle (UFP) (diameter < 100 nm) bursts. The UFP burst happens mostly during afternoon/evening with significant enhancement in number concentrations of nucleation (Nnuc) and Aitken (NAitk) mode particles. Examination of the association of these events with prevailing meteorology and trace gas concentrations revealed weaker dependence in general. However, the association between NOX and the UFP concentration indicates the possibility of common source for both. During the high concentrations of UFP, local winds originated predominantly from south/south west directions of the study location where the valley region with significant anthropogenic activities is located. Time of occurrence of the UFP bursts, trace gas concentrations and direction of the winds points towards the role of valley winds in transporting plume of pollutants to the mountain top observatory during the daytime.

Numerical and experimental studies on nozzle two-phase flow characteristics of nanometer-scale iron powder metal fuel motor

Metal iron powder is a promising new type of energy source that is of enormous practical and research interest for future automotive power systems. To better optimize engine design, this study was devoted to the characteristic investigation of a two-phase flow. Experimental studies involving nanometer iron powder particle combustion and engine thrust measurement were conducted to confirm the results obtained from numerical calculations that were performed using a fourth-order Runge–Kutta–Gill method. Governing equations for nozzle two-phase flow were established to perform a theoretical study to analyze the combustion properties of iron oxide particles and flow in the nozzle. The results indicate that variations in the size and coagulation content of particles play a significant role in the loss of two-phase flow. Significant emphasis was placed on the effect of particle size (0.4–1.0 μm) and condensate content (10–40%) of ultrafine particles on the specific impulse. To further validate the theoretical results, the burning rates of particles of three different sizes were experimentally measured. In addition, the motor thrust and the specific impulse with the particle size of 50 nm were tested through combustion experiment, and the results show excellent agreement.

Fabrication of ultrafine ZnFe2O4 nanoparticles for efficient photocatalytic reduction CO2 under visible light illumination

A one-pot, solvent-thermal process was used to create the ultrafine ZnFe2O4 nanoparticles photocatalyst. During the solvent-thermal process, the in situ self-forming NaCl not only served as a “cage” to confine the ion diffusion, but also acted as a microreactor for nanocrystallite growth. An average particle size of ∼10nm and a high-specific surface area of ∼112.9m2/g were observed for the ultrafine ZnFe2O4 nanoparticles Owing to the synergistic effect of ultrafine particle size, the full utilization of the visible light region and high conduction band (CB) position, ultrafine ZnFe2O4 photocatalyst displayed an efficient photocatalytic CO2 reduction under visible light illumination. Besides, the ultrafine ZnFe2O4 photocatalyst showed high production selectivity for CH3CHO and C2H5OH generation in aqueous CO2/NaHCO3 solution. This work may provide a new idea for the synthesis of new high-efficiency photocatalysts.

Composition of Metallic Elements and Size Distribution of Fine and Ultrafine Particles in a Steelmaking Factory.

Background: The characteristics of aerosol, in particular particle size and chemical composition, can have an impact on human health. Particle size distribution and chemical composition is a necessary parameter in occupational exposure assessment conducted in order to understand possible health effects. The aim of this study was to characterize workplace airborne particulate matter in a metallurgical setting by synergistically using two different approaches; Methodology: Analysis of inhalable fraction concentrations through traditional sampling equipment and ultrafine particles (UFP) concentrations and size distribution was conducted by an Electric Low-Pressure Impactor (ELPI+™). The determination of metallic elements (ME) in particles was carried out by inductively coupled plasma mass spectrometry; Results: Inhalable fraction and ME concentrations were below the limits set by Italian legislation and the American Conference of Governmental Industrial Hygienists (ACGIH, 2017). The median of UFP was between 4.00 × 104 and 2.92 × 105 particles/cm3. ME concentrations determined in the particles collected by ELPI show differences in size range distribution; Conclusions: The adopted synergistic approach enabled a qualitative and quantitative assessment of the particles in steelmaking factories. The results could lead to a better knowledge of occupational exposure characterization, in turn affording a better understanding of occupational health issues due to metal fumes exposure.