Particle Chemical Composition Research Articles

Heat Treatment of Nanostructured Powders Obtained by Spark Erosion of WC-8Co Cemented Carbide in Oil

Spark erosion of WC-8Co carbide pieces in oil resulted in a powder consisting of nanostructured spherical microparticles formed by rapid crystallization of the melt. These particles consist of rounded WC grains with an average diameter of about 0.18 μm, surrounded by cobalt. The process productivity, specific energy consumption, microstructure, particle size distribution, chemical and phase compositions of the obtained powder are determined. It was found that as a result of oil pyrolysis, free carbon is formed (3.4 %), which makes this powder unsuitable for the production of carbide products from it. A technique has been developed and the process of controlled removal of excess carbon by annealing the obtained powder in a CO2 atmosphere at a temperature of 1000 °C has been studied. As a result of annealing for 120 minutes, the carbon content decreases to the required value (5.6 %). Studies of the phase composition and microstructure showed that the obtained particles consist of elongated WC grains, the average diameter of which increased to 0.43 μm.

Effect of particle morphology on dust cloud dynamics

Dust explosions threaten the solids process industry. Parameters influencing dust explosions include particle size, chemical composition, and polydispersity; however, particle morphology is often overlooked. Studies show particle morphology impacts dust cloud minimum ignition energy (MIE) via heat transfer because higher specific surface results in lower conductive heat resistance. However, heat transfer is not the only factor impacting MIE; the effect of particle morphology on cloud dynamics is another important factor. This work focuses on the influence of particle morphology on cloud aerodynamics during MIE testing. A digital in-line holography method has been developed to measure aerodynamics of particles in an MIE apparatus. Results show higher cloud concentration and turbulence for irregularly shaped particles, and the implication on MIE is discussed. The present results aid understanding of particle morphology on cloud dynamics, which is crucial in determining the effect on explosion parameters such as MIE and the resulting risk assessment.

A case study on the soil-water characteristics of the vadose zone and the migration of intermediate-level nuclides in a planned spent-fuel reprocessing plant site

A flat arid unmanned Gobi in northwest Gansu, China, has been recognized as a good location for a planned spent-fuel reprocessing plant site. To better assess its applicability and safety as a proposed site, it is important to understand the composition and characteristics of the local vadose zone. Laboratory tests were carried out to analyze the basic properties of the soil in the unsaturated layer, such as particle size, structure, chemical composition and mineralogical characteristics. The permeability coefficients at different depths were measured by three methods, including the single ring, double ring, and inverse auger methods. Four groups of probes were buried at depths of 0.2–4 m in the vadose zone to detect changes in matrix suction with water content in the dehydration state and to determine the field soil-water characteristics curve. Based on the measured hydrological and geological parameters, the migration of intermediate-level nuclides H-3, Co-60, and Cs-137 from the vadose zone into groundwater was simulated by HYDRUS-1D under different rainfall intensities. The simulation results showed that the vadose zone in the study area has a strong retention effect, in which the Co-60 and Cs-137 nuclides were retained in the vadose zone during the 1000-year simulation period. The radioactivity and distribution coefficients of the nuclides were the main factors affecting the time to reach the pollution standard at the groundwater level on a short time scale. Rainfall significantly increased nuclide migration speed on a large time scale. Finally, two engineering protection measures derived from weakening the driving force and increasing the migration path were proposed and were effective in a numerical simulation.

Differences in fine particle chemical composition on clear and cloudy days.

Clouds are prevalent and alter PM2.5 mass and chemical composition. Cloud-affected satellite retrievals are often removed from data products, hindering estimates of tropospheric chemical composition during cloudy times. We examine surface fine particulate matter (PM2.5) chemical constituent concentrations in the Interagency Monitoring of PROtected Visual Environments network during Cloudy and Clear Sky times defined using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud flags from 2010-2014 with a focus on differences in particle hygroscopicity and aerosol liquid water (ALW). Cloudy and Clear Sky periods exhibit significant differences in PM2.5 and chemical composition that vary regionally and seasonally. In the eastern US, relative humidity alone cannot explain differences in ALW, suggesting emissions and in situ chemistry exert determining impacts. An implicit clear sky bias may hinder efforts to quantitatively to understand and improve model representation of aerosol-cloud interactions.

Source apportionment of PM2.5 and visibility in Jinan, China

Atmospheric extinction is impacted by the chemical composition of particles. To better understand the chemical composition of PM2.5 (particles with diameters of less than 2.5 μm) and its relationship with extinction, one-month sampling campaigns were carried out in four different seasons from 2013 to 2014 in Jinan, China. The seasonal average concentrations of PM2.5 were 120.9 (autumn), 156.6 (winter), 102.5 (spring), and 111.8 μg/m3 (summer). The reconstructed PM2.5 chemical composition showed that sulfate, nitrate, chlorine salt, organic matter (OM), mineral dust, elemental carbon (EC) and others accounted for 25%, 14%, 2%, 24%, 22%, 3% and 10%, respectively. The relationship between the chemical composition of PM2.5 and visibility was reconstructed by the IMPROVE method, and ammonium sulfate, ammonium nitrate, OM and EC dominated the visibility. Seven main sources were resolved for PM2.5, including secondary particles, coal combustion, biomass burning, industry, motor vehicle exhaust, soil dust and cooking, which accounted for 37%, 21%, 13%, 13%, 12%, 3% and 1%, respectively. The contributions of different sources to visibility were similar to those to PM2.5. With increasing severity of air pollution, the contributions of secondary particles and coal combustion increased, while the contribution of motor vehicle exhaust decreased. The results showed that coal combustion and biomass burning were still the main sources of air pollution in Jinan.

Formation of nano- or near-nanoparticles via oxidation in the Dabaoshan concealed deposit, Guangdong Province

Natural particles have always been abundantly present since the Earth’s origin. Over the years, researchers have focused on natural particles coming from the Earth’s surface. However, in this paper, we establish, via transmission electron microscopy (TEM), that many nano- or near-nanoparticles also can be produced in a concealed deposit. Particles collected from the oxidation zone in the Dabaoshan polymetallic concealed deposit were 50–700 nm in size and contained elements among the most abundant in the Earth’s crust, such as O, Mg, K, Ca, Si, Al, Ti, Fe and P, and concealed ore body-related elements. Nearly all particles were found to have O and S, indicating that these nano- or near-nanoparticles were formed via oxidation of primary minerals in the concealed deposit. According to their crystal form and chemical compositions, these particles were grouped into three main categories: (i) particle with low O content (O O > 10 wt.%) and (iii) particle with high O content (O > 30 wt.%). The crystal form and chemical compositions of particles can represent the degree of oxidation of primary minerals in the concealed deposit. Combining the close relationship with orebodies, nano- or near-nanoparticles can be used to be a useful prospecting method for deep-seated orebodies. Additionally, strong acids are also formed during the oxidation process that can destroy the ecosystem of the oxidation zone in the concealed deposit.

Residual intake and body weight gain on the performance, ingestive behavior, and characteristics of longissimus muscle of Dorper × Santa Inês lambs

• Residual intake and body weight gain (RIG) has positive impact on lambs finishing. • The increase in RIG efficiency improves the feed conversion ratio (FCR) by 16 %. • The better feed utilization by high-RIG lambs can be associated to lower rumination rates. • The characteristics of lambs longissimus muscle are not influenced by increase in RIG efficiency. The aim of this study was to evaluate the relationship between residual intake and body weight gain (RIG) and the performance, ingestive behavior, and characteristics of longissimus muscle of crossbred ½ Dorper × ½ Santa Inês lambs. Nineteen non-castrated male lambs, with a mean age of 4 months and a body weight (BW) of 23.04 ± 3.16 kg, were individually fed ad libitum in a feedlot for 90 days. The ration was composed of 640 g/kg Cynodon hay and 360 g/kg concentrate feed; it contained 158.6 g/kg crude protein and 2.12 Mcal/kg metabolizable energy on a dry matter (DM) basis. At the end of the trial, lambs were classified as efficient (n = 7), intermediate (n = 6), or inefficient (n = 6) for RIG based on ± 50 % of the standard deviation for this trait. The lowest and highest values for dry matter intake relative to BW (DMI BW ) were verified in the efficient and inefficient groups, respectively (3.13 vs. 3.43 % BW/day). The feed conversion ratio (FCR) decreased by 15.94 % (8.47 to 7.12 kg DM/kg gain) from the inefficient to the efficient group. The time spent feeding, in rumination, and in idleness, as well as the intake rate (IR), were similar among RIG groups, but the rumination rate (RR) was lower in the efficient group (1.61 g DM/min) compared with the intermediate and inefficient groups (1.82 g DM/min on average). Average particle size (APS) and chemical composition of the orts were not influenced by RIG and were similar among the efficiency groups. Backfat thickness, as measured by ultrasound (BFT US ) at the start and end of the trial, and backfat thickness and loin eye area, as measured directly from the longissimus muscle (BFT LE and LEA, respectively) after slaughter, were similar among RIG groups. Improving the efficiency for RIG leads to better feed utilization, without affecting the characteristics of longissimus muscle in lambs.

Characterization comparison of bottom ash and fly ash during gasification of agricultural residues at an industrial-scale gasification plant – Experiments and analysis

In this study, the characterization of the fly and bottom ashes from an industrial gasification plant for biomass syngas production were investigated and compared in terms of particle size distribution, chemical composition, fusibility, mineralogy and morphology. The experimental results indicated that the characteristic particle sizes of the bottom ashes from gasifier were larger than those of the fly ashes from cyclone or sprayer. By contrast, the fly ashes contained higher contents of potassium, sulphur and chlorine. The base-to-acid ratio (Rb/a) values for those fine fractions in the bottom residues and the fly particles from cyclone were in high deposition range (Rb/a > 1.0) while that for the slags in the bottom ash or the fly particles from sprayer was in medium deposition range (0.5–1.0). As regards the fouling index (Fu), the value of cyclone ash (Fu = 41.2) was higher than those of the other ashes, reflecting its relatively higher deposition tendency on heat transfer surfaces. Besides, the fusion temperatures of the fly ashes were lower than those of bottom ashes. The rounded forms of fly particles could be regarded as the indicative of ash melting. Comparison of thermograms indicated that the bottom ash contained more organics than fly ash, thus explaining its relatively higher weight loss during ash fusion. In practice, more attention should be paid on the rational control of operating temperature, which could relieve the occurrence of ash deposition/agglomeration to some extent.

Observation of Aerosol Optical Properties and New Particle Formation in the Yangtze River Delta

In a recent field campaign focused on air quality study, aerosol optical properties, particle number concentration, and PM2.5 components were monitored in Changzhou, Jiangsu Province, from May 27 to June 27, 2019. An array of instruments were deployed that included scanning mobility particle size spectrometer (SMPS), aethalometer (AE33), cavity attenuation phase shift single albedo monitor (CAPS-ALB), monitor for aerosols and gases in ambient air (MARGA) and RT-4 organic carbon/elemental carbon (OC/EC) carbon analyzer to study the ① changes in chemical composition and optical parameters of the new particles generated during the campaign period. ② comparison of the aerosol extinction coefficient recorded by these instruments and measured value in the reconstruction of IMPROVE (interagency monitoring of protected visual environment) and the calculated coefficient using MIE theory model were carried out. During the entire campaign, two new particle generation events were observed and also found that the particle size continued to increase from 4 nm to 64 nm. It was monitored that in the initial stage of new particle generation, sulfate contributed greatly. The measured average aerosol extinction coefficient during the period of particle generation, using these instruments was 95.40 Mm-1, while the average aerosol extinction reconstruction using the IMPROVE model was observed to be 140.20 Mm-1. The theoretical calculations based on Mie theory model yielded an average extinction coefficient of 93.54 Mm-1. It was found that the average aerosol extinction in Changzhou is lower than the average value of the urban aerosol extinction coefficient, which is measured to be 300 Mm-1 in China, during this period. The deployment of multiple instruments in a single campaign is more desirable because the combination of all observations helped in better characterization of the physicochemical properties of ambient aerosols from various aspects, including particle size spectrum and chemical composition.

Metal sorption onto nanoscale plastic debris and trojan horse effects in Daphnia magna: Role of dissolved organic matter

There is a debate on whether the Trojan horse principle is occurring for nanoscale plastic debris (NPD < 1 µm). It is realized that NPD have a high capacity to sorb environmental contaminants such as metals from the surrounding environment compared to their microplastic counterparts, which influences the sorbed contaminants’ uptake. Herein, we studied the influence of dissolved organic matter (DOM) on the time-resolved sorption of ionic silver (Ag+) onto polymeric nanomaterials, as models of NPD, as a function of particle size (300 and 600 nm) and chemical composition [polystyrene (PS) and polyethylene (PE)]. Subsequently, the toxicity of NPD and their co-occurring (adsorbed and absorbed) Ag+ on Daphnia magna was determined. Silver nitrate was mixed with 1.2 × 105 NPD particles/mL for 6 days. The extent of Ag+ sorption onto NPD after 6 days was as follows: 600 nm PS-NPD > 300 nm PS-NPD > 300 nm PE-NPD. The presence of DOM in the system increased the sorption of Ag+ onto 300 nm PS-NPD and PE-NPD, whereas DOM decreased the sorption onto 600 nm PS-NPD. Exposure to 1 mg/L NPD or 1 µg/L Ag+ was not toxic to daphnids. However, the mixture of these concentrations of PS-NPD and Ag+ induced toxicity for both sizes (300 and 600 nm). The addition of DOM (1, 10 and 50 mg/L) to the system inhibited the combined toxicity of Ag+ and NPD regardless of the size and chemical composition. Taken together, in natural conditions where the concentration of DOM is high e.g. in freshwater ecosystems, the sorption of metals onto NPD depends on the size and chemical composition of the NPD. Nevertheless, under realistic field conditions where the concentration of DOM is high, the uptake of contaminants in D. magna that is influenced by the Trojan horse principles could be negligible.

Cement dust from Balakliia cement plant (Ukraine): particle size distribution, chemical and radionuclide compositions and possible ways of reprocessing

Cement dust from Balakliia cement plant (Ukraine): particle size distribution, chemical and radionuclide compositions and possible ways of reprocessing

Production of ultrafine-grained spherical β-WC-W2C-Co microparticles by electro discharge erosion of WC-15Co alloy in glycerol and their solutions

The present work is devoted to the study of the production of ultrafine-grained (UFG) spherical microparticles by electro discharge erosion (EDE) of the WC-15Co cemented carbide in glycerol, distilled water, and their solutions. Energy costs, productivity, particle size distribution, and morphological and chemical compositions of the obtained powders were studied. It was found that energy cost is reduced by 2.2 times when glycerol was used instead of water. The use of water reduces carbon content from 5.2% to 1.4%. The use of glycerol and its aqueous solutions reduces carbon loss and increases its content in the obtained powders from 3.2% to 6.1%. During SE, cobalt, carbon, and tungsten evaporate from spherical particles and crystallize in the form of ultrafine particles, which subsequently remain in suspension after sedimentation of spherical particles. Mass fractions of sedimented spherical particle fractions ranged from 75% to 82%. Cobalt and carbon content in the spherical particles obtained in glycerol decrease from 15% to 10% and from 5.2% t to 3.1% respectively. The particles consist of rounded carbide grains (β-WC and W2C) with a diameter of up to 500 nm, the space between which is filled with cobalt. Microhardness of the particles increased from 12.1 GPa (initial alloy) to 15.6 (EDE in water)—23.7 GPa (EDE in glycerol).

Antitumor effect of copper nanoparticles on human breast and colon malignancies.

Breast and colon carcinomas are two types of common cancers which lead to cancer-related deaths. Due to their cytotoxic potential against cancer cells, recently many studies of copper nanoparticles (CuNPs) have been conducted. In the current work, we aim to evaluate the cytotoxic and apoptosis-inducing effects of CuNPs on the human breast (MCF-7) and colon (LoVo) cancer cells. CuNPs were prepared in starch-stabilizing aqueous solution by electroless deposition technique in alkaline tartrate bath using formaldehyde as the reducing agent of copper sulfate. The obtained CuNPs were characterized by SEM, TEM, and XRD to confirm the particle size, morphology, and chemical composition. Standard colorimetric MTT and LDH assays were used to estimate the cytotoxic effect of CuNPs on MCF-7 and LoVo cells. Furthermore, CuNP-treated cells undergoing apoptosis were assessed based on the expression of apoptosis-related genes using qRT-PCR. The results indicate that the mean particle size of the synthesized CuNPs was ~ 50-60nm, and they were spherical in shape with mainly the chemical structure of the copper metallic phase. MTT assay revealed that CuNPs induced cytotoxicity in tested cells with IC50 rates of 16.4 (in MCF-7) and 21.6μg/ml (in LoVo). Moreover, qRT-PCR analysis showed that CuNPs caused a significant increment of Bax, P53, and Caspases 9, 8, and 3 genes. Overall, the anticancer potential of prepared CuNPs were reported through apoptotic induction which highlight the potential use of CuNPs as an efficient anticancer agent.

Biomass-burning-derived particles from a wide variety of fuels – Part 2: Effects of photochemical aging on particle optical and chemical properties

Abstract. Particles in smoke emitted from biomass combustion have a large impact on global climate and urban air quality. There is limited understanding of how particle optical properties – especially the contributions of black carbon (BC) and brown carbon (BrC) – evolve with photochemical aging of smoke. We analyze the evolution of the optical properties and chemical composition of particles produced from combustion of a wide variety of biomass fuels, largely from the western United States. The smoke is photochemically aged in a reaction chamber over atmospheric-equivalent timescales ranging from 0.25 to 8 d. Various aerosol optical properties (e.g., the single-scatter albedo, the wavelength dependence of absorption, and the BC mass absorption coefficient, MACBC) evolved with photochemical aging, with the specific evolution dependent on the initial particle properties and conditions. The impact of coatings on BC absorption (the so-called lensing effect) was small, even after photochemical aging. The initial evolution of the BrC absorptivity (MACBrC) varied between individual burns but decreased consistently at longer aging times; the wavelength dependence of the BrC absorption generally increased with aging. The observed changes to BrC properties result from a combination of secondary organic aerosol (SOA) production and heterogeneous oxidation of primary and secondary OA mass, with SOA production being the major driver of the changes. The SOA properties varied with time, reflecting both formation from precursors having a range of lifetimes with respect to OH and the evolving photochemical environment within the chamber. Although the absorptivity of BrC generally decreases with aging, the dilution-corrected absorption may actually increase from the production of SOA. These experimental results provide context for the interpretation of ambient observations of the evolution of particle optical properties in biomass-combustion-derived smoke plumes.

Au nanoring arrays as surface enhanced Raman spectroscopy substrate for chemical component study of individual atmospheric aerosol particle

Monolayer-ordered gold nanoring arrays were prepared by ion-sputtering method and used as surface enhanced Raman spectroscopy (SERS) substrates to test the individual atmospheric aerosols particle. Compared to other methods used for testing atmospheric aerosols particles, the collection and subsequent detection in our work is performed directly on the gold nanoring SERS substrate without any treatment of the analyte. The SERS performance can be tuned by changing the depth of the gold nanoring cavity as originating from coupling of dipolar modes at the inner and outer surfaces of the nanorings. The electric field exhibits uniform enhancement and polarization in the ordered Au nanoring substrate, which can improve the accuracy for detecting atmospheric aerosol particles. Combined with Raman mapping, the information about chemical composition of individual atmospheric aerosols particle and distribution of specific components can be presented visually. The results show the potential of SERS in enabling improved analysis of aerosol particle chemical composition, mixing state, and other related physicochemical properties.

The role of turbulent fluctuations in aerosol activation and cloud formation

Aerosol indirect effects are one of the leading contributors to cloud radiative properties relevant to climate. Aerosol particles become cloud droplets when the ambient relative humidity (saturation ratio) exceeds a critical value, which depends on the particle size and chemical composition. In the traditional formulation of this problem, only average, uniform saturation ratios are considered. Using experiments and theory, we examine the effects of fluctuations, produced by turbulence. Our measurements, from a multiphase, turbulent cloud chamber, show a clear transition from a regime in which the mean saturation ratio dominates to one in which the fluctuations determine cloud properties. The laboratory measurements demonstrate cloud formation in mean-subsaturated conditions (i.e., relative humidity <100%) in the fluctuation-dominant activation regime. The theoretical framework developed to interpret these measurements predicts a transition from a mean- to a fluctuation-dominated regime, based on the relative values of the mean and standard deviation of the environmental saturation ratio and the critical saturation ratio at which aerosol particles activate or become droplets. The theory is similar to the concept of stochastic condensation and can be used in the context of the atmosphere to explore the conditions under which droplet activation is driven by fluctuations as opposed to mean supersaturation. It provides a basis for future development of cloud droplet activation parameterizations that go beyond the internally homogeneous parcel calculations that have been used in the past.

Particle Size Distribution and Chemical Composition of the Aerosolized Vitamin E Acetate.

Particle Size Distribution and Chemical Composition of the Aerosolized Vitamin E Acetate.

Continuous and comprehensive atmospheric observations in Beijing: a station to understand the complex urban atmospheric environment

ABSTRACT Due to profound impact on climate and human health, air quality has attracted attention from all levels of the civil society. The key step in the provision of required tools for the society to tackle the complex air quality problem is to characterize it in a comprehensive manner with a long-term perspective. Here, we describe a continuous and comprehensive observation station and its accompanying state-of-the-art instrumentation that was established to investigate the complex urban atmospheric environment in a rapidly developing Chinese Megacity. The station, located in downtown Beijing, aims to study air quality by identifying the major atmospheric pollutants and key processes determining their formation and loss mechanisms. A few hundreds of parameters are continuously measured with the state-of-the-art instruments, including trace gas concentrations, aerosol particle size distributions, and mass concentrations, covering aerosol particle chemical composition from molecules to micrometer-sized aerosol particles. This produced long-term, comprehensive big data with around bytes per year. In this paper, we provide an overview on the facilities of the station, the instrumentation used, the workflow of continuous observations and examples of results from 2018 to 2019 and a basis for establishing a modern long-term, comprehensive atmospheric urban observation station in other megacities.

Gamma-Ray Attenuation Study for the Soils of Bursa, Turkey, in the Energy Range 59.5–1332.5 keV

In this study, the gamma radiation attenuation was experimentally investigated for soil samples with different texture collected from Bursa Province, Turkey. Firstly, physical and chemical properties (e.g., density, particle size distribution, lime content, organic matter and chemical composition) of these soils were determined by several methods. The transmission measurements of soils performed by using Am-241, Cs-137, Co-60 and Na-22 sources and 2 × 2 inch NaI(Tl) scintillation detector were used to calculate shielding parameters, mass attenuation coefficient, half value layer and tenth value layer values, of these samples in form of pressed powder pellets. The values of these important parameters have been found to vary with gamma-ray energy and chemical composition of the studied soil samples. For instance, the mass attenuation coefficients were decreased with increasing gamma-ray energies and, with the increase in contribution of MgO and Na components, caused better absorption. The effect of compression pressure on attenuation coefficient was also investigated, and better absorption was observed for the sample pressed by high value of press force.

Synthesis of crosslinked poly(methacrylic acid) shell/lipid core colloidal nanoparticles via L-in-Lm interfacial polymerization and their pH responsiveness

In this present work, the synthesis of colloidal nanoparticles with crosslinked poly(methacrylic acid) (PMAA)-shell and lipid core via L-in-Lm interfacial polymerization was illustrated. The oil-in-water pre-emulsion of lipid (L) dispersed in an aqueous continuous phase containing monomer (Lm) was initially formed, and the polymerization took place at the oil/water interface. The oil phase contained sunflower oil (SF) as a model lipid and benzoyl peroxide (BPO) initiator, while an aqueous continuous phase consisted of methacrylic acid (MAA) as a model monomer, N,N’-methylenebis(acrylamide) (MBA) as cross-linker, and sodium dodecyl sulfate (SDS) as surfactant. After polymerization at elevated temperature, crosslinked PMAA was located on the surface of sunflower oil droplets as a shell layer, indicating that MAA monomer and MBA cross-linker were involved in the polymerization at the oil/water interface. The detailed investigation on the effects of polymerization parameters (e.g. polymerization temperature, initiator, monomer, surfactant, and cross-linker concentrations) was conducted. The physico-chemical properties, such as particle size, morphology, chemical composition, and pH-responsiveness were then determined. This synthetic route can provide PMAA-shell nanoparticles with accessibility and availability of carboxyl functional groups, and pH responsiveness that could be useful for various applications.