Ultra Fine Research Articles

Assessment of indoor air quality in health clubs: insights into (ultra)fine and coarse particles and gaseous pollutants.

Exercising on regular basis provides countless health benefits. To ensure the health, well-being and performance of athletes, optimal indoor air quality, regular maintenance and ventilation in sport facilities are essential. This study assessed the levels of particulate, down to the ultrafine range (PM10, PM2.5, and particle number concentration in size range of 20-1,000 nm, i.e., - PNC20-1000 nm), gaseous pollutants (total volatile organic compounds - TVOCs, CO2, and O3) and comfort parameters (temperature - T, relative humidity - RH) in different functional spaces of health clubs (n = 8), under specific occupancy and ventilation restrictions. In all HCs human occupancy resulted in elevated particles (up to 2-3 times than those previously reported), considering mass concentrations (PM10: 1.9-988.5 μg/m3 PM2.5: 1.6-479.3 μg/m3) and number (PNC 1.23 × 103 - 9.14 × 104 #/cm3). Coarse and fine PM indicated a common origin (rs = 0.888-0.909), while PNC showed low-moderate associations with particle mass (rs = 0.264-0.629). In addition, up to twice-higher PM and PNC were detected in cardiofitness & bodybuilding (C&B) areas as these spaces were the most frequented, reinforcing the impacts of occupational activities. In all HCs, TVOCs (0.01-39.67 mg/m3) highly exceeded the existent protection thresholds (1.6-8.9 times) due to the frequent use of cleaning products and disinfectants (2-28 times higher than in previous works). On contrary to PM and PNC, TVOCs were higher (1.1-4.2 times) in studios than in C&B areas, due to the limited ventilations combined with the smaller room areas/volumes. The occupancy restrictions also led to reduced CO2 (122-6,914 mg/m3) than previously observed, with the lowest values in HCs with natural airing. Finally, the specific recommendations for RH and T in sport facilities were largely unmet thus emphasizing the need of proper ventilation procedures in these spaces.

Development of microstructure and properties within oxide dispersion strengthened steel directly consolidated by hot rotary swaging

Steels strengthened with fine oxides maintain favourable mechanical properties at high temperatures. This unique study evaluates the effects of direct consolidation of mechanically alloyed powders of ferritic steel and Y2O3 nanooxides by hot rotary swaging (multiple swaging ratios) on microstrutcures and mechancial properties of final rods. Direct consolidation of the steel powder by the proposed method was successful at the swaging ratio 1.0. However, the quality of consolidation improved with increasing the swaging ratio to 1.4, and finally to 1.8 (no visible pores). The microstructure of the rod processed with swaging ratio 1.8 exhibited homogeneous dispersion of oxide particles and featured ultra-fine (UF) grains, its average Vickers microhardness exceeded 700 HV1.

Performance evaluation of Falcon fluidized bowl and ultrafine (UF) bowl concentrators for the recovery of ultrafine scheelite particles

The recent developments in enhanced gravity concentrators, such as Falcon centrifugal separators, are proven beneficial in treating fine and ultrafine mineral particles. This concentrator is classified into a fluidized bowl concentrator and an ultrafine (UF) bowl concentrator based on the bowl design, which has considerable significance in facilitating the separation process. The present investigation concerns the recovery of ultrafine scheelite particles present in the gold mine tailing with an average WO3 content of 0.08%. The separation behaviour and application of different bowls concerning various particle sizes have been investigated. It is found that the Falcon UF concentrator can achieve a high recovery while the Falcon fluidized bowl can obtain a higher grade. Further, the fluidized bowl was found more effective at eliminating entrapped calcite mineral particles than the UF bowl. The effectiveness of both bowls is assessed in recovering heavy particles of various sizes, and the results show that the fluidized bowl performs better in recovering coarser heavy particles, while the UF bowl performs better in recovering fine heavy particles. Based on these findings, an integrated circuit (fluidized and UF bowls) has been designed, which resulted in achieving a higher (85%) recovery of WO3 values compared to individual bowls.

Electrodeposited from Ion-Organic Melt Ti-B Protective Coatings on Al-Foil

The great demand for advanced batteries in applications such as mobile devices, the transportation sector, and stationary storage has spurred intensive research and development on rechargeable lithium batteries. The corrosion behavior of Al-foil, as material for theirs current collectors, has long been a concern due to uniform or localized pitting corrosion occurs in contact with an organic electrolyte. Pitting corrosion is attributed to inhomogeneous current flow through the aluminum / electrode interface and results in local breakdown of the passive film on Al-foil. Particular attention among different protective coatings of Al-foil excites Ti-B coatings as conductive and electrochemically inactive protective layers.The main objectives of the present work are investigation of regimes for electrodeposition of Ti-B protective coatings onto Al-foil and examination of the corrosion behavior of Al-foil with such electrodeposited Ti-B protective coatings in contact with an organic electrolyte under various electrodes charging conditions.Low melting point of aluminium (tm = 6600C) made impossible electrodeposition of Ti-B coatings from chloride-fluoride melts (tel = 7000C). But it is possible from ion-organic melts at 70−2000C. In this work was investigated electrodeposition of Ti-B coatings from carbamide melt contains titanium and boron oxides. Cyclic voltammetry has shown the limit current density and potential of electrochemical synthesis. Ultra fine Ti-B coatings were electrodeposited onto Al-foil at 1300C. Figure shows the surface morphologies of an obtained Ti-B coating. Such cost-effective method of obtaining Ti-B protective coatings on Al-foils gives excellent results under theirs using as current collectors in rechargeable lithium batteries. Figure 1

Pearlite formation via martensite

When the coarsening of a second–phase particle in a solid–phase matrix is discussed, the microstructural evolution of the corresponding matrix phase is often unconsciously ignored. Present electron microscope observations have revealed that as–quenched high–carbon Fe–C martensite with a high density of twins first transforms into a pearlite structure upon tempering, followed by shrinkage of the cementite layers, in which ultra–fine θ–Fe3C particles are connected from a two–dimensional view. Two cementite layers form a loop or necklace–like morphology. Loop shrinkage or aggregation of the ultra–fine carbide particles results in carbide coarsening and pearlite structure development. The driving force for the aggregation of the fine carbide particles or the shrinkage of the cementite layers is believed to be the recrystallization of numerous α–Fe crystallites formed during the martensitic transformation. The thicker cementite layer in the pearlite structure is formed via a similar process (two or more cementite layers merging together) of detwinning behavior. The present experimental observations have revealed a new coarsening mechanism of cementite particles in carbon steels. A new mechanism for pearlite structure formation (twinned martensite can be treated as a precursor of pearlite) and coarsening has also been discussed.

A cycling-insensitive recycling method for producing lithium transition metal oxide from Li-ion batteries using centrifugal gravity separation

The separation and recovery of electrode active materials from Li-ion batteries is a requisite step prior to any downstream hydrometallurgical and direct recycling processes. Prior research efforts into the separation between the two electrode active materials from Li-ion batteries was limited to the froth flotation process; however, any changes to the surface properties of the active materials resulted in an inferior separation performance. In this work, a novel separation method, namely the Falcon Ultra-Fine (UF) centrifugal gravity concentration, is developed to separate electrode active materials from Li-ion batteries. Results obtained with a mixture of pristine lithium transition metal oxides (LTMOs) and graphite showed that the separation between the two materials perform well with over 90% of LTMOs in the concentrate product after one pass in the UF concentrator. Multiple stages of the separation processes enabled a concentration of LTMOs with 99% purity. Results obtained with aged electrode active materials from spent Li-ion batteries showed that the concentrate product consisted of at least 98% by weight of LTMOs. It was observed that there was a misplacement of LTMOs in the overflow product, which was attributed to the presence of ultrafine LTMOs as well as PVDF-binded cathode agglomerates in the feed. Results of this work demonstrate a viable method for separating mixed electrode active materials and producing high-purity LTMOs, which can be potentially used for the direct recycling of cathode active materials in the manufacturing of new Li-ion batteries.

Recovery of Rare Earth Oxides from Flotation Concentrates of Bastnaesite Ore by Ultra-Fine Centrifugal Concentration

Historically, the ability to effectively separate carbonate gangue from bastnaesite via flotation has frequently proven to be challenging without sacrificing significant rare earth oxide (REO) grade or recovery. However, in light of the fact that the rare earth bearing minerals often exhibit higher specific gravities than the carbonate gangue, the possibility exists that the use of gravity separation could be used to achieve such a selective separation. This however is complicated by the fact that, in cases such as this study when the liberation size is finer than 50 microns, most traditional gravity separation methods become increasingly challenging. The aim of this study is to determine the applicability of centrifugal concentrators to beneficiate ultra-fine (UF) bastnaesite and calcite bearing flotation concentrates. By using a UF Falcon, it was possible to achieve initial gravity REO recoveries exceeding 90% while rejecting on the order of 25% to 35% of the total calcium from an assortment of rougher and cleaner flotation concentrates. Additionally, when additional stages of cleaner UF Falcon gravity separation were operated in an open circuit configuration, it was possible, from an original fine feed of 35 microns containing 50.5% REO and 5.5% Ca, to upgrade up to approximately 59% REO and 2.0% calcium. While not the goal of this study, these results also support previous limited data to suggest that UF Falcons are potentially capable of treating a wider range of materials than they were originally designed for, including feeds rich in heavy mineral content.

Formation of Fe, Pt and (Pt/Fe) ultra-fine metal nanoparticles in different solution polarity prepared by Nd-YAG pulsed laser

Iron(Fe/FeO), Platium (Pt) and (Pt/Fe) ultra Fine(UF) nanoparticles (NPs) were synthesized by pulsed (Q-switched, 1064 doubled frequency-Nd: YAG). The laser ablation of Fe and Pt metal plates has been performed by immersing these metal plates in deionised water (DDW) and ethanol alcohol solvent. The pulsed laser ablation in liquids (PLAL) process preformed with 100 pulse energy of 700 mJ and liquid depth is 5 mm. The formation efficiency of PLAL process was quantified in term of the absorption spectrum peaks and TEM images anlaysis. The absorption spectra of Iron (Fe/FeO, Pt) in DDW reveal a sharp and single peak around (292/363 and 234)nm, respectively, indicates the production of pure and spherical shape of Fe/FeO, Pt UF NPs with an average size in the range of 2-5 nm. While, it was notice absorbance peaks wavelength shifted to the shorter wavelength in ethanol alcohol due to high polarity of alcohol in both bimetalic nanoparticles (Fe and Pt). By changing the solution polarty it can open an easy way to control the size and shape of Fe and Pt and Bimetals (Pt/Fe ) colloidal nanoparticles.

Cover Image

The cover image is based on the Original Article Effect of Nozzle Temperature on the Emission Rate of Ultrafi ne Particles During 3D Printing by Chungsik Yoon, Sunju Kim, Jihoon Park et al., https://doi.org/10.1111/ina.12624.

Chemical and Physical Characterization of McIntyre Powder using Inductively Coupled Plasma Mass Spectroscopy and Electron Microscopy

Aim: The objective of this study was to determine the chemical and physical characteristics of McIntyre powder, which was stated to be a mixture of aluminum oxide and elemental aluminum. The aim was to (i) confirm this with current techniques and to see if there were any toxic metals present, which could contribute to health effects including neurological disorders, Parkinson’s and (ii) obtain a precise particle size distribution. McIntyre Powder was inhaled by at least 27,500 gold and uranium miners of Ontario as a prophylaxis to prevent silicosis during 1944-1979. Materials and Methods: The chemical characterization involved analysis by inductively coupled plasma mass spectroscopy (ICP-MS) and by scanning electron microscopy. The physical characterization was carried out using transmission electron microscopy. Results: The chemical analysis results confirm that the McIntyre Powder contains mainly aluminum and only trace amounts of other metals. The physical characterization shows that it is about 12% ultra fine (also referred to as nano particles) and 88% fine particles. Approximate aerodynamic diameters of the particles are mean 321.5 nm (0.32 im), median 273.8 nm (0.27 im) with a range of 9.5 nm (0.01 im) to 1314 nm (1.31 im). Conclusion: There are no metallic impurities in McIntyre Powder in quantities that could make a significant contribution to health effects. There is a 12% ultrafine particle content which could be important because of the apparent ability to translocate to the brain.

Study of structure, phase composition and physicomechanical properties of modifi ed castings from heat-temperature ZhS3DK alloy

The structure and properties of castings obtained using various modifi ers are studied. It is shown that the introduction of multicomponent modifi er containing ultrafi ne powders of titanium carbide, titanium carbonitride leads to decrease in grain, uniform distribution of carbide precipitates and increase in mechanical properties. The critical temperatures of phase transformations in the cast ZhS3DK alloy and its analogue with modifi ers are determined by the differential thermal analysis method. The heat treatment condition of modifi ed cast heattemperature alloys of the ZhS3DK type is corrected.

Obtaining of doped composite material Al—Cu—Mn—TiC with enhanced tribological properties

The results of tribological characteristics of alumomatric composite material Al — 5 % Cu — 2 % Mn — 10 % TiC obtained by the self-propagating high-temperature synthesis method are presented. It is shown that in comparison with technical aluminum and matrix alloy, signifi cantly lower indicators of the coeffi cient of friction, wear and heating temperature characterize composite material, reinforced with nano- and ultrafi ne particles of titanium carbide.

Cyclic deformation behavior and related micro-mechanisms of a special CVD Ni processed with bimodal grain structures: Ultrafine (UF) grains and large grains with UF/nano twins

Stress-controlled cyclic tests were conducted on bulk sheet Ni-carbonyl Chemical Vapor Deposited material (CVD Ni) with bimodal grain structures: ultrafine (UF) grains and large grains with UF/nano twins. The tests were run with the cyclic stress ratio R = 0.05 and peak stress level of 0.9–1.5 times of the material's yield strength. Results show that within the applied peak stress ratio of 0.9–1.1, the material demonstrated cyclic hardening behavior first, followed by stress–strain saturation till fracture; upon increasing the ratio to 1.4–1.5, an additional softening stage was activated and continued till fracture. By transmission electron microscope (TEM) examination, it was found that such cyclic deformation responses were associated with the stability of the ultrafine- and nano-twin structures. Initial hardening was found mainly due to the increase in dislocation density and the activities of dislocations especially with their strong interactions with the dense twin boundaries (TBs). The saturation was contributed by the simultaneous operations of the softening effect due to massive detwinning and the hardening behavior due to dislocation interactions with existing TBs. Newly formed dislocation walls and cell structures were further found in samples with stress ratio of 1.4 at fracture, corresponding to the softening stage. Furthermore, such microstructural evolution, which were observed also through annealing and monotonic deformation of the same material, is identified as a consistent energy reduction path for the material. Thus, an energy criterion is further established to predict the massive detwinning events that cause the major softening phenomena under cyclic deformation.

Cyclic Deformation Behavior and Related Micro-Mechanisms of Ni-Carbonyl Chemical Vapor Deposited (CVD) Material with Bimodal Grain Structures: Ultrafine (UF) Grains and Large Grains with UF/Nano Twins

Stress-controlled cyclic tests were conducted on bulk sheet Ni-carbonyl Chemical Vapor Deposited material (CVD Ni) with bimodal grain structures: ultrafine (UF) grains and large grains with UF/nano twins. The tests were run with the cyclic stress ratio R=0.05 and peak stress level of 0.9 to 1.5 times of the material's yield strength. Results show that within the applied peak stress ratio of 0.9-1.1, the material demonstrated cyclic hardening behavior first, followed by stress-strain saturation till fracture; upon increasing the ratio to 1.4-1.5, an additional softening stage was activated and continued till fracture. By transmission electron microscope (TEM) examination, it was found that such cyclic deformation responses were associated with the stability of the ultrafine- and nano-twin structures. Initial hardening was found mainly due to the increase in dislocation density and the activities of dislocations especially with their strong interactions with the dense Twin Boundaries (TBs). The saturation was contributed by the simultaneous operations of the softening effect due to massive detwinning and the hardening behavior due to dislocation interactions with existing TBs. Newly formed dislocation walls and cell structures were further found in samples with stress ratio of 1.4 at fracture, corresponding to the softening stage. Furthermore, such microstructural evolution, which were observed also through annealing and monotonic deformation of the same material, is identified as a consistent energy reduction path for the material. Thus, an energy criterion is further established to predict the massive detwinning events that cause the major softening phenomena under cyclic deformation.

Application of Falcon Centrifuge as a Cleaner Alternative for Complex Tungsten Ore Processing

Scheelite (CaWO4) is one of the main raw material for the production of tungsten. It is usually encountered in skarn deposits where it is commonly associated with other calcium minerals as fluorite, apatite, and calcium silicates. Worldwide, scheelite is upgraded to the chemical grades by direct flotation, but the separation efficiency remains limited due to similar flotation behaviors of scheelite and gangue minerals with fatty acid. The only solutions used to overcome this issue involve high energy consumption or ecotoxic reagents. In the present study, a novel method based on the use of a centrifugal Falcon concentrator was investigated to perform an efficient elimination of gangue minerals and fine particles as well as an acceptable scheelite recovery enabling a decrease of the flotation reagents consumption. The performances of the two types of laboratory Falcon bowls, Falcon UltraFine (UF) and Falcon Semi-Batch (SB), were modeled using the design of experiments (DoE) methodology, which allowed to determine the best operating parameters for each bowl. The separation performances were mainly affected by the rotary speed and the pulp density for the Falcon UF and by the rotary speed and the fluidization pressure for the Falcon SB. Due to the fluidization pressure, the Falcon SB exhibited higher gangue minerals rejection with slightly lower recoveries than the Falcon UF. Overall, the optimized Falcon SB test allowed to reach 71.6%, 22.6%, 17.2%, and 12.6% for scheelite, calcium salts, dense calcium silicates, and light non-calcic silicates respectively while the desliming efficiency reached 98.8%. For comparison purposes, a classical hydrocyclone allowed to attain 89.1%, 89.3%, 79.5%, and 76.5% for scheelite, calcium salts, dense calcium silicates, and light non-calcic silicates respectively while the desliming efficiency reached 52.0%. Theses results can be used reliably to assess the separation performances of an industrial Falcon C which can be regarded, along with Falcon SB, as a sustainable and efficient gangue rejection method for complex W skarn ore, which allows the use of environmentally friendly reagents during downstream flotation stages.

Synthesized and Characterizing of (Au@Pt) Ultra Fine Nanoparticles Prepared by Pulsed Laser Ablation in Liquids

Gold(Au), Platium (Pt) and Gold –Coated Platinum (Au@Pt) ultra Fine(UF) nanoparticles (NPs) were preperd by Pulsed Laser Ablation in Liquids method with (Q-switched, 1064 doubled frequency-Nd: YAG). The laser ablation of Au ,Pt metal plates and (Au@Pt) has been performed by immersing these metal plates in two different liquid deionised water (DIW) and ethanol alcohol . (PLAL) process preformed with 100 pulse energy of 700 mJ and liquid depth is 2cm. The nanoparticles of the gold element were coated with platinum(Au@Pt) in two steps. The nanotubes of the gold element were first examined and the platinum metal was then immersed in the liquid from the first step. The formation efficiency of PLAL process was quantified in terms of the absorption spectrum peaks. The absorption spectra ( Pt) in DIW shows a sharp and single peak around 234nm, and (Au@Pt) shows a sharp and single peak for Au at 516nm and for Pt 221nm. The TEM images show that the nanoparticles are rather spherical in shape. While the average size for all the samples was in rang from(2-5)nm. There was an increase in size when using ethanol alcohol. Changing the way of the fluid environment is a simple and flexible way to control the size and strength of Au and Pt and (Au@Pt) colloidal nanoparticles.

Strain hardening behavior of Ni-carbonyl Chemical Vapor Deposited (CVD) material with bimodal grain structures: Ultrafine (UF) grains and large grains with UF/nano twins

Through Ni-carbonyl CVD process, bulk Ni material (hereafter referred as CVD Ni) with bimodal grain structures, i.e. UF grains and large grains with UF/nano twins, can be produced. In tensile test, this material demonstrated a very good combination of strength and ductility as well as a special strain hardening behavior. Upon investigating the material's hardening behavior, a critical threshold strain, εc, of 0.02 was identified for the distinct change in the strain hardening behavior. Prior to this strain level, the strain hardening rate of the CVD Ni was found always higher than that of its counterpart coarse-grained (CG) Ni; but it dropped, after this strain, to the same level as the CG material. Furthermore, through the analysis of results from Tension Unloading Reloading-in-Tension (TURT) tests, this specific strain value was also found to be significant in the change of the hysteresis loop width as well as the back stress strain hardening responsible for the material's Bauschinger behavior. Microstructural evolution examination suggests that most of the twin boundaries (TBs) initially acted as obstacles to dislocation movement providing strong dislocation back stress and hence contributing to the strong hardening behavior. From the strain level of 0.02 and onwards, however, massive detwinning was detected which is responsible for the drop in the hardening rate. Finally, dislocation cell structures, that were typically evolved from entanglements of dislocation inside CG Ni, were also found inside the detwinned large grains of CVD Ni in the high strain regime, which yielded similar strain hardening behavior as in the CG Ni material.

Experimental investigation into the kinetics of Falcon UF concentration: Implications for fluid dynamic-based modelling

Centrifugal gravity separators, such as the Falcon UltraFine (UF) concentrator, are the most common gravity concentration techniques used for fine particles processing. Hence, understanding the kinetics and separation mechanisms at play within these separators is of paramount interest. Recent research yielded a predictive physical model for the Falcon UF which however does not explain some results obtained with industrial ores. The Falcon UF kinetics have been investigated through the processing of fine-grained ores from the Altenberg tin deposit (Germany), the Tabuaço tungsten deposit (Portugal), a synthetic iron ore as well as results from previous studies on kaolin residues. Results have shown an evolution of Falcon UF performance with time/feed mass in contradiction with the stationary separation hypothesis on which the physical model was based. In terms of Falcon UF separation timing, four phases can be distinguished. First, upon initial feeding of the bowl, particles are trapped or rejected depending on their settling velocity. It yields a relatively ineffective selection according to density so that only ultrafine particles are ejected from the bowl, resulting in the quick growth of the concentrate bed. When the bed reaches a critical size, recovery and enrichment continue to increase through selective resuspension phenomenon that favours the concentration of dense particles and the ejection of larger particles. This way, the bed builds up while the content of concentrate bed surface evolves until resuspension balances the stream of dense material reaching the bed and recovery drops. The evolution of partition curves over time confirmed the low recovery of ultrafine particles during the whole operation but also showed a decrease of coarse particles recovery with time. It suggests that the second separation mechanism is less sensible to particle size compared to the first one and that size even has a negative impact on recovery. Furthermore, erosion figures in furrows are observed in the concentrate bed which may play locally an active role in the separation. These observations suggest that two separation mechanisms are at play. Firstly, differential particles settling within the flowing film which is already accounted for in the existing physical model. Secondly, resuspension of particles from the concentrate bed by the action of a lift force acting preferentially on coarse particles deposited at the surface of the bed and resulting in the rejection of coarser and lower-density particles. The addition of a lift force component to the existing model is discussed and a resuspension criterion is proposed as a guidance of the physics involved in this second separation mechanism. Future developments will require a dynamic model which would need to integrate the evolution of the concentrate bed content over time.

Dynamic froth stability of copper flotation tailings

In this work, dynamic froth stability is used for the first time to investigate the flotation behaviour of copper tailings. Reprocessing of material from tailings dams is not only environmentally desirable, but also increasingly economically feasible as head grades can be high compared to new deposits. Flotation tailings, however, usually contain a large proportion of fine (10–50 μm) and ultra fine (<10μm) material and the effect of these particle sizes on froth stability is not yet fully understood.For this study, samples were obtained from the overflow and underflow streams of the primary hydrocyclone at a concentrator that reprocesses copper flotation tailings. These samples were combined in different ratios to assess the dynamic froth stabilities at a wide range of particle size distributions and superficial gas velocities. The findings have shown that the effect of particle size on dynamic froth stability can be more complex than previously thought, with a local maximum in dynamic froth stability found at each air rate. Moreover, batch tests suggest that a local maximum in stability can be linked to improvements in flotation performance. Thus this work demonstrates that the dynamic froth stability can be used to find an optimum particle size distribution required to enhance flotation. This also has important implications for the reprocessing of copper tailings as it could inform the selection of the cut size for the hydrocyclones.

Comparison of atmospheric new particle formation events in three Central European cities

Simultaneous particle number size distribution measurements were performed in the urban environment of Budapest, Vienna, and Prague, three Central European cities located within 450 km of each other. The measurement days from the continuous, 2-year long campaign were classified for new particle formation (NPF) events using an adapted classification scheme for urban sites. The total numbers of NPF event days were 152 for Budapest, 69 for Vienna, and 143 for Prague. There were 12 days when new particle formation took place at all three sites; 11 out of these 12 days were in spring and in summer. There were only 2 (Budapest-Vienna), 19 (Budapest-Prague), and 19 (Vienna-Prague) nucleation days, when NPF did not occur on the third site. The main difference was related to source and sink terms of gas-phase sulphuric acid. Air mass origin and back-trajectories did not show any substantial influence on the atmospheric nucleation phenomena. The relative contribution of particles from NPF with respect to regional aerosol to the particles originating from all sources was expressed as nucleation strength factor. The overall mean nucleation strength factors were 1.58, 1.54, and 2.01 for Budapest, Vienna, and Prague, respectively, and showed diurnal and seasonal variations. The monthly mean NSF varied from 1.2 to 3.2 in Budapest, from 0.7 to 1.9 in Vienna, and from 1.0 to 2.3 in Prague. This implies that the new particle formation in cities is a significant source of ultrafine (UF) particles, and the amount of them is comparable to the directly emitted UF particles.