Smallest Particle Size Fraction Research Articles

Conversion of Natural Soil to Paddy Promotes Soil Organic Matter Degradation in Small-Particle Fractions: δ13C and Lipid Biomarker Evidence

The stabilization mechanism of soil organic matter (SOM) has received considerable attention. It is widely accepted that mineral sorption/protection is important for SOM stabilization. However, it remains unclear which organic carbon component is beneficial for mineral protection. We collected soil samples from a paddy field (TP) to compare with natural soil (NS). To illustrate the behavior of different SOM pools and their protection by particles, we separated the soils into different particle-size fractions and then removed the active minerals using an acid mixture (1 M HCl/10% HF). The different carbon pools were analyzed using stable carbon isotopes and lipid biomarkers. Our study showed that acid treatment evidently increased the extractability of free lipids, usually over 60%, which confirmed the predominant role of minerals in SOM protection. For NS, the δ13C values increased with decreasing soil particle sizes and soil depths, indicating that 13C-enriched SOM was selectively preserved. However, this trend disappeared after cultivation, which was mainly attributed to the combined effects of the input of 13C-depleted fresh SOM and decomposition of the preserved 13C-enriched SOM. Meanwhile, based on the degradation parameters of the overall lipid biomarkers, SOM showed higher degradation states in clay and silt fractions than in the sand fraction before cultivation. It is possible that the small particle-size fractions could selectively absorb highly degraded SOM. The clay-associated SOM showed a low degradation state, but its carbon content was low after cultivation. We propose that the previously protected SOM was degraded after cultivation and was replaced by relatively fresh SOM, which should be carefully monitored during SOM management.

Optimising Al2O3–water nanofluid

BackgroundThis study explores how nanofluids can be optimised to improve heat transfer in various applications. A genetic algorithm that finds the optimal parameter configuration to achieve the best performance is studied and applied. The research focuses on the critical factors of heat transfer coefficient and pressure drop, which determine the efficiency of nanofluid-based systems.The main body of the abstractThe methodology involves artificial intelligence and multi-objective optimisation techniques. Results show that pressure drop and heat transfer coefficient have an inverse relationship. The study provides a range of optimal values for nanofluid temperature, particle size, and volume fraction.ResultsThe results show that the temperature, particle size, and volume fraction should be high. Another variation will be small particle size and small volume fractions with fluid temperature around 80 °C. The analysis yielded the following configuration with the optimal PEC. Temperature (oC), particle size (nm), volume fraction (%), heat transfer coefficient (kW/m2K), pressure drop (Pas), and PEC were 82.6 °C, 175.26 nm, 4.75%, 792.49 kW/m2K, 29.94 Pas, and 5.01.ConclusionsThe research highlights the potential of Al2O3–water nanofluids to maintain pressure drop and enhance heat transfer. It contributes to understanding nanofluid optimisation and provides practical insights for designing and selecting nanofluid systems that enhance heat transfer.

Heavy Metals Pollution in Various Grain Sizes Under Different Land-Use Types in Urban Surface Dust in Shenyang City, China

ABSTRACT In this study, surface dust samples were collected within the second ring road of Shenyang City under different land-use types, and the concentration and chemical speciation of metals in different particle sizes under different land-use types were analyzed. Dust samples were separated into four particle size fractions (＜50, 50–100, 100–500, 500–2000 μm), and particles in the range of 100–500 µm were the highest representing one-third of the dust mass. The results revealed that metals were detected in order Zn > Cr > Pb > Cu > Ni > As > Cd in different particle sizes of dust under different land-use types. The relative contribution of individual particle-size fractions for seven metals was different, but the results showed preferential partitioning to small particle-size fractions. The relative contribution of metals in individual particle-size fractions and chemical speciation were significantly affected by the type of land use. Metals concentrated on the smaller particles in the traffic area, and the particles (<50 µm) contained the highest percentage of metals but Cr. The residual fractions (F5) of Ni, Cr, As and Cu overall represented the predominant portion in different particle size of fractions under different land-use types, Zn and Pb were mostly bound to the Fe–Mn oxides-bound fraction (F3), and the exchangeable fraction (F1) accounted for a relatively large proportion of Cd. The results of the risk assessment code (RAC) of Cd indicated that the risk of Zn was medium, and it was high for Cd in the dust of Shenyang City.

High-Temperature Behavior of Spent Li-Ion Battery Black Mass in Inert Atmosphere

The increased demand for Li-ion batteries has prompted the scientific community to improve recycling routes in order to reuse the valuable materials in batteries. After their end-of-life, the batteries are collected, discharged, and mechanically disintegrated, generating plastic and metallic streams that are recycled directly; this leaves behind a small particle size fraction known as black mass (BM). BM is composed mainly of graphite and Li-metal complex oxides. Pyrometallurgy is a route known for recycling of BM, in which identifying the BM’s behavior at high temperatures is essential. In this study, two types of BM are characterized in two fractions of 150–700 µm and smaller than 150 µm. The thermal behavior of the BM is studied with thermal analysis techniques. The analyses demonstrate that the mineralogical and morphological properties of the two fractions do not significantly differ, while the amounts of C and organic materials might vary. When the BM was thermally treated, the binders decomposed until a temperature of 500 ℃ was reached, where the volatilization of hydrocarbons was observed, although F mostly persisted in the BM. The Li-metal oxide was partially reduced to lower oxides and Li carbonate at ⁓ 600 ℃, and the main mass loss was caused by carbothermic reduction immediately thereafter. As the products of this process, metallic Co and Ni phases were formed, and part of the graphite remained unreacted. Regarding the Li behavior, it was observed that in the presence of Al, AlLiO2 is the most likely composition to form, and it changes to LiF by increasing the F concentration in the composition.Graphical

WC Decomposition Phenomena in ID-HVOF-Sprayed WC-CoCr Coatings Using Fine Powder Feedstock

Over the last few decades, the high velocity oxygen fuel (HVOF) spraying of WC-CoCr for internal diameter (ID) coating has attracted much interest for hard chrome replacement. Current demands for the ID coating of small cylindrical parts necessitates the use of specialized spray gun equipment and powder feedstocks with small particle size fractions. Due to the limited spray distance inside cylindrical parts with small IDs, the process control, spraying fine WC-CoCr powders, meets new challenges to avoid significant WC decomposition, which increases the risk of mechanical degradation. Within the scope of this study, ID-HVOF spraying using a fine-structured WC-CoCr (−15 + 5 μm) feedstock with a mean WC particle size of 400 nm is examined with respect to the WC decomposition phenomena using X-ray diffraction (XRD). Hence, a statistical design of experiments (DoE) is utilized to systematically analyze various spray parameter settings along with their interaction as part of the WC to W2C conversion.

Raman spectroscopic evaluation of crystallinity, chemical composition and stability of pharmaceutical powder aerosols

Raman spectroscopy was used to evaluate the effects of temperature and humidity on the physicochemical stability of inhalable spray-dried (SD) powders containing budesonide (BUD) and crystalline or amorphous lactose. Powders prepared by spray drying of BUD-lactose solution or suspension containing lactose crystals in BUD solution were stored for 0, 1 and 7 days at 25 °C/60 RH or 40 °C/75 RH. Bulk powders along with the large and small particle size fractions collected on stages 2 and 5, respectively, of the Next Generation Impactor (NGI) were chemically characterised. SD powder from solution contained BUD and lactose in amorphous form and both components were homogeneously distributed in bulk and in the particles collected from the two NGI stages. In contrast, SD powder from suspension showed heterogeneous distribution of lactose and drug in the particles containing crystalline lactose. After 1 day of storage at either condition, recrystallisation and changes in the chemical composition of the particles for the SD powder from solution occurred. The number of drug-only particles increased by 70 on stage 5, whereas most particles on stage 2 still contained both drug and lactose. These changes were not observed in the SD powder from suspension after storage, confirming superior stability of the SD powder obtained from suspension.

Process integration of sulphuric acid leach and particle size fractionation for cleaner copper concentrate production by enhancing the radionuclide mobility

• A process integration of selective H 2 SO 4 leach and particle size fractionation. • Mobility of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) in process. • The underlying mechanism of radionuclide mobility is unveiled. • A conceptual process is proposed for the cleaner Cu production from IOCGU ores. The growing demand of copper metal in the world continues to push the limit of utilization of complex copper resources, among which the iron oxide associated with copper–gold-uranium ore deposits (IOCG-U) contain economic copper and abundant gangues including uranium-bearing minerals that carry naturally occurring radionuclides and pose a challenge for public health and environment. To support the removal of radionuclides from copper flotation concentrate, the particle size fractionation method is integrated into the H 2 SO 4 leach process to illustrate the deportment of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) and other non-copper elements during the process. H 2 SO 4 leach treatment largely dissolved non-copper elements (Fe, Ca, Mg, Al, K, F, U, Th, etc) from the gangue minerals and promoting the further copper phase transformation from the primary chalcopyrite and bornite towards covellite and copper sulphates. In the leach process, over 98% of 238 U and 230 Th were dissolved into H 2 SO 4 leach solution due to the decomposition of uranium-bearing minerals, while the released 226 Ra, 210 Pb and 210 Po from uranium-bearing minerals were largely remobilized, precipitated as insoluble sulphate salts, and accumulated in the small particle size fractions of the H 2 SO 4 leach residue. The underlying mechanism of this deportment is attributed to the mineralogical changes as an increased amount of covellite, digenite and copper sulphate are associated with the small particle size fractions, and serve as preferential hosts for 226 Ra, 210 Pb and 210 Po. Therefore, a conceptual flowsheet which facilitates further removal of 226 Ra, 210 Pb and 210 Po from the H 2 SO 4 leach residue is discussed based on particle size fractionation of the copper concentrate leach residue where radionuclides have been selectively leached or re-distributed.

An experimental approach to assess the post-depositional mobility of 134Cs

The partitioning coefficient, Kd, which is defined by the reversible sorption processes between a solid and an aqueous phase at equilibrium, is one of the most important parameters to assess environmental transport and risk. In this study, a series of simple laboratory experiments were conducted to investigate sorption properties of 134Cs on a model sediment under two treatments (shaken vs non-shaken) and with three (small: <75 μm, large: > 75 μm and bulk i.e., composite) particle size fractions. Vertical transport of 134Cs across the water-sediment interface and into sediment was also evaluated. As expected, grain size had the strongest influence on 134Cs Kd values, with the small particle size fraction yielding significantly higher Kd values than the large and bulk fractions. The mean Kd values obtained from the various experiments ranged from 89 ± 13–130 ± 5 L kg−1 (small), 44 ± 10–91 ± 13 L kg−1 (large), 73 ± 3–112 ± 11 L kg−1 (bulk, shaken) and 73 ± 5–110 ± 4 L kg−1 (bulk, non-shaken). Most of the 134Cs partitioning processes occurred rapidly (<2 h) into the experiment. Physical mixing (shaken) did not appear to significantly affect the 134Cs Kd values. In complement, a separate experiment on the vertical penetration of 134Cs into a bulk sediment column showed that 134Cs was able to penetrate up to 5 cm into the sediment column after 88 days (∼0.6 mm d−1) and this flux rate is comparable to natural settings. Adsorption and contact time were found to be key for the 134Cs penetration process. Results from these experiments add to the literature on post-event radionuclide transport studies in marine settings and provide an experimental perspective that can be built upon to complement field observations.

Characterization of PM-Bound Heavy Metal at Road Environment in Tianjin: Size Distribution and Source Identification

To determine the size distribution and source identification of PM-bound heavy metals in roadside environments, four different particle size (&lt;0.2 μm, 0.2–0.5 μm, 0.5–1.0 μm and 1.0–2.5 μm) samples were collected and analyzed from four different types of roads during the summer of 2015 in Tianjin. The results showed that the concentrations of PM-bound heavy metal from the roadside environment sampling sites were 597 ± 251 ng/m3 (BD), 546 ± 316 ng/m3 (FK), 518 ± 310 ng/m3 (JY) and 640 ± 237 ng/m3 (WH). There were differences in the concentrations of the heavy metal elements in the four different particle size fractions. The concentrations of Cu, Zn, Cd, Sn and Pb were the highest in the larger particle size fraction (0.5–2.5 μm). Cd, Cu, Zn and Pb were the elements that indicated emissions from tire wear and brake pad wear. The concentrations of Cr, Co and Ni were the highest in the smallest particle size fraction (&lt;0.5 μm), indicating that motor vehicle exhaust was their main source. The correlation analysis results showed that there are differences in the concentration, distribution and correlation of different PM-bound heavy metals in different particle size fractions. The PCA results show that the accumulative interpretation variances of PM0.2, PM0.2–0.5, PM0.5–1.0 and PM1.0–2.5 reached 80.29%, 79.56%, 79.57% and 71.42%, respectively. Vehicle exhaust was the primary source of PM-bound heavy metal collected from the roadside sampling sites, while brake pad wear and tire wear were the second most common sources of the heavy metal.

Insight into the Composition of the Stabilized Residual from a Full-Scale Mechanical-Biological Treatment (MBT) Plant in Terms of the Potential Recycling and Recovery of Its Contaminants

There is a lack of knowledge about the composition and particle size distribution of the &lt;80 mm fraction mechanically separated from residual municipal solid waste (rMSW) and the stabilized residual (SR) after aerobic stabilization in a full-scale MBT plant. Therefore, the composition of the particle size fractions (&gt;60 mm, 60–40 mm, 40–10 mm) of the &lt;80 mm fraction and SR, collected in all seasons (summer (S), autumn (A), winter (W), spring (Sp)), was determined. Biodegradable waste (vegetable waste, other organic waste, paper, cardboard) constituted from 44.1% (A) to 54.3% (Sp) of the &lt;80 mm fraction and it decreased to 8.5% (W) to 17.1% (S) in the SR, after effective biodegradation. In SR, the smaller particle size fractions (up to 40 mm) predominated. The main contaminants in SR were plastic, glass, metal, and other waste. Hierarchical clustering indicated that the composition of the particle size fractions of SR was more similar across four seasons than that of the &lt;80 mm fraction. After stabilization and separation, the share of contaminants increased in the SR size fractions, which means that their recovery before landfilling may be profitable. This suggests a new direction in waste management that would be consistent with the principles of a circular economy, in which a waste product, like SR, which previously could only be landfilled, becomes a source of secondary materials.

Soil natural radioactivity of northern variant ravine biogeocenoses of Ukrainian steppe zone

Ravine biogeocenoses in the steppe zone of Ukraine are a unique natural phenomenon. Under these natural forests for many millennia formed a specific kind of soil – forest chernozems, which differ in a number of ways from the zonal chernozems. Today in the scientific literature you can find information about such properties of these soils as organic matter, structural and aggregate composition, lessivage, micromorphological features. However, the natural radioactivity of forest chernozems remains virtually unexplored. Our work is devoted to the establishment of the peculiarities of the natural radioactivity of the soils of ravine biogeocenoses. The soils of the Hlyboky ravine, which according to the classification of O.L. Belgard belongs to the northern version of the ravines of the steppe zone of Ukraine. As a result of the performed researches it is established that the surface horizons of chernozems of forest southern and northern exposures of the ravine differ in reduced values of ashing coefficient, which indicates an increased content of organic matter in them compared to other horizons of the studied soils. Eluvial horizons are characterized by reduced values of natural radioactivity compared to illuvial, which indicates increased sorption by small particle size fractions of radioactive elements compared to larger fractions. The maximum values of natural radioactivity were found in the lower genetic horizons of the studied soils. This indicates that the source of radioactive elements is the parent rock from which the soil was formed. Organic substances and their ability to bind radioactive elements are characterized by a smaller contribution to the natural radioactivity of soils compared to small particle size fractions and parent rock. The distribution of natural radioactivity values by soil profile is determined by the peculiarities of soil genesis of each individual soil type and to some extent can reflect them.

Determination of platinum group metals in dust, water, soil and sediments in the vicinity of a cement manufacturing plant

Global economic growth has led to an increase in cement production to meet the demand of infrastructural development over the past decades. This has resulted in cement factories being the major sources of dust pollution. Dust emanating from the cements plants deposits on buildings, roadways, on road pavements and plants. The purpose of this study was to determine the concentration of platinum group metals (PGMs) emitted with cement dust on a dust suppressed roadway next to a cement factory in Waterberg, South Africa. The concentrations of PGMs were determined using inductively coupled optical emission spectrometry. This region is well known for large reserves and mining of PGMs such as Pt, Rh, Ru and Pd. The highest concentration in the dust samples collected along the roadway was that of Pt followed by Ru, Rh and Pd. The concentrations of Pt, Ru, Rh and Pd in soil samples decreased with the increase of depth. Water concentration of PGMs decreased at each sampling point in the following order; Pt > Ru > Rh > Pd. Sediments samples were also sampled along the Crocodile River for characterisation of physico-chemical parameters. It was of great importance to also analyse PGMs in soils, water and sediments since, dust settles on them. Elevated concentrations of Pt were observed in all samples and the highest concentrations were partitioned to the small particle size fraction of 32 µm. The pH and electric conductivity (EC) of the sediments were measured and the pH values increased while EC values decreased moving along the river. The most common minerals identified in the dust samples were quartz and calcites. Vehicular emissions were also found to be the major contributor to suspended particulate matter and atmospheric deposition of dust dominantly result from emission from the cement plant. The cement plant was the major polluter through atmospheric deposition of dust particles. The result also revealed that the pH of the Crocodile River was slightly alkaline which was influenced by the effluent from the cement plant.

Effects of total suspended solids, particle size, and effluent temperature on the kinetics of peracetic acid decomposition in municipal wastewater.

In this study, the influence of total suspended solids (TSS) and particle size as well as effluent temperature on peracetic acid (PAA) decomposition kinetics in municipal wastewater was investigated. PAA decomposition was best described following second order kinetics in primary effluent (PE) and first order kinetics in secondary effluent (SE) samples. For synthetic samples prepared by varying TSS levels, PAA demand increased on average by about 0.042 mg/L in PE and 0.034 mg/L in SE for every 10 mg/L increase in TSS. Similarly, the PAA decay rate constant in these samples increased at a rate of 0.0014 L/mg.min and 0.00039 min-1, respectively, per 10 mg/L TSS. To examine the effect of particle size, synthetic samples with narrow size fractions (20-45, 45-75, and 75-90 μm) were prepared. It was found that samples with smaller particle size fractions had a greater PAA demand and decay rate constant. Effluent temperature also enhanced the PAA decomposition rate with the calculated activation energies for PE and SE samples being 29,980 J/mol and 34,860 J/mol, respectively.

Investigation of the dependence of the activity concentration of natural and artificial radionuclides on particle size in surface soil

Surface soil radioactivity is being studied at NED-NTUA since almost thirty years. The last few years this research has expanded to the study of soil particle size fractionation of radionuclides. The purpose of the present work was to study the tendency of many radionuclides to accumulate in the smaller particle size fractions. To this end, soil samples were collected from an area in the NTUA Campus where 241Am contamination, due to a failed 241Am-tipped lightning rod, had been previously detected. The samples were separated into size fractions using a sieving machine and analyzed by gamma spectrometry to determine 210Pb, 241Am, 234Th, 228Ra, 228Th, 226Ra, 7Be, 137Cs and 40K. The activity concentrations of these nuclides were found to significantly differ among the size fractions examined.

Evaluation of the strength, sorption and thermal properties of bamboo plastic composites

Natural fiber plastic composites were made from Nigerian grown bamboo (Bambusa vulgaris) and high density polyethylene (HDPE) by extrusion and evaluated for strength, sorption and thermal properties. Composites were manufactured using two different screened bamboo particle size fractions (<2 mm and < 0.5 mm). The composites were tested for flexural properties, water sorption, melt flow and thermal properties. The melt viscosities at 190oC were 22.3 ± 0.91 kPa·s (<2 mm) and 27.4 ± 1.2 kPa·s (<0.5 mm). The results obtained indicated that the composites made with the smaller particle size fraction had higher flexural strength (37.4 ± 1.0 MPa) and modulus of elasticity (2.0 ± 0.2 GPa) than those made with the larger particle size fraction (29.9 ± 1.1 MPa and 1.7 ± 0.1 GPa). Dynamic mechanical analysis (DMA) also showed higher dynamic storage modulus for the <0.5 mm particle-based composites than those made from the <2 mm particle size fraction due to higher density and better interfacial interaction between the fiber and matrix. Also, the composites made with the smaller particles and were more dimensionally stable (water absorption of 5.4% versus 18.5% at 61 d). The bamboo composites had thermal stablility range of 265 – 279oC (onset degradation temperature). The composites made with the smaller bamboo particles possessed the better properties in comparison with those made from the <2 mm. Particle size and density significantly affected the mechanical, physical, thermal and rheological properties of the composites evaluated. Keywords: Bambusa vulgaris, flexural properties, natural fiber plastic composites, particle size

Practical guidelines for the characterization and quality control of pure drug nanoparticles and nano-cocrystals in the pharmaceutical industry.

The number of poorly soluble drug candidates is increasing, and this is also seen in the research interest towards drug nanoparticles and (nano-)cocrystals; improved solubility is the most important application of these nanosystems. In order to confirm the functionality of these nanoparticles throughout their lifecycle, repeatability of the formulation processes, functional performance of the formed systems in pre-determined way and system stability, a thorough physicochemical understanding with the aid of necessary analytical techniques is needed. Even very minor deviations in for example particle size or size deviation in nanoscale can alter the product bioavailability, and the effect is even more dramatic with the smallest particle size fractions. Also, small particle size sets special requirements for the analytical techniques. In this review most important physicochemical properties of drug nanocrystals and nano-cocrystals are presented, suitable analytical techniques, their pros and cons, are described with the extra input on practical point of view.

The impact of wood-derived biochar on the survival of Trichoderma spp. and growth of Secale cereale L. in sandy soil

ABSTRACTThe interrelations between biochar (BC) and soil microbiota remain unclear. Addressing this will be important for understanding how BC affects soil properties and plant growth. Here, we tested the influence of wood-derived BC with immobilised Trichoderma viride on rye Secale cereale L. in sandy soil. We found that the addition of BC leads to a significant (P < .05) increase in the concentrations of Ca2+ and Mg2+, as well as a decrease in the concentration of Al3+, irrespective of BC particle size and the presence of T. viride. Plant growth was stimulated in the presence of small (<2 mm) particle-sized BC. Fungal diversity, as well as an absolute and relative abundance of Trichoderma spp., was tested by cultivation-dependent methods and qPCR. Both of these approaches revealed a positive effect of BC on the survival of Trichoderma spp. under the tested conditions, especially in the presence of a small particle size fraction.

Development of a novel fractal-like kinetic model for elucidating the effect of particle size on the mechanism of hydrolysis and biogas yield from ligno-cellulosic biomass

Abstract The effect of particle size on hydrolysis and biogas production kinetics from a typical ligno-cellulosic biomass was assessed by studying the anaerobic co-digestion of fixed amount of rice husk and cow dung mixture using a newly developed fractal-like kinetic model. British Standard (BS) sieves were used to obtain varying particles size fractions ranging from 0.150 to 0.212 mm, 0.212–0.300 mm, 0.300–0.600 mm, 0.600–1.000 mm and 1.000–1.700 mm from oven dried, milled rice husk and pulverized, dried cow dung respectively. These particle size fractions from both biomass were mixed in a ratio of 1:1 after which, they were loaded into batch reactors and digested anaerobically at ambient conditions for 75 days. Hydrolysis of ligno-cellulosic biomass was observed to depend on the fractal exponent (h), which indexed the presence of inaccessible regions in ligno-cellulosic biomass. Also, hydrolysis was observed to depend on two other intrinsic factors that comprised of the initial hydrolytic rate ( X o Y k o ′ ) and overall affinity constant ( k o ′ S o ) . Larger particle size fractions were associated with higher affinity but lower initial hydrolysis rate while, smaller particle size fractions were associated with lower affinity but higher initial hydrolysis rate. In addition, the fractal model compared favorably with the popular modified Gompertz equation.

A Comparative Study of Toluene Oxidation on Different Metal Oxides

This work reports the results of experimental and theoretical investigation of toluene oxidation on different metal oxide based catalysts (manganese oxide, MnOx, mixed manganese-iron oxide, MnFe, perovskite-type manganese oxide, LaMnO3 and commercial Pt-Al2O3 catalyst). Particular attention was devoted to single and mixed manganese based oxides and ceria based materials as alternatives to conventionally used noble metal containing catalysts. Toluene oxidation was performed under steady-state conditions in an integral fixed bed reactor operating over a wider range of reaction temperatures and at various space times. The influence of reaction variables on the rate of toluene oxidation was examined using the simple first-order kinetic model and the one-dimensional (1D) pseudo-homogeneous model to describe the reaction system. The proposed model was verified comparing the theoretical predictions with the experimental laboratory results. The results of catalytic tests indicated that the mixed manganese-iron oxide (MnFe) exhibited remarkable catalytic activity for the toluene oxidation, almost comparable with the activity of the commercial Pt-Al2O3. The reaction temperature T50 corresponding to 50% of the toluene conversion was observed at 419 K for the MnFe oxide and at 405 K for the Pt-Al2O3. A very good agreement of experimental data with the proposed 1D model was obtained. Based on the shape of the light-off curve and the values of the apparent activation energies, which decreased from 120.36 kJ/mol to 16.88 kJ/mol with reaction temperature increase, it was concluded that the reaction rate was probably limited by the mass transfer, no matter the relatively small catalyst particle size fraction employed in this study (315 - 400µm).

Effect of particle size, fraction and carbide banding on deformation and damage behavior of ferrite–cementite steel under tensile/shear loads

Deformation and damage behavior of ferrite–cementite steel was investigated using microstructure-based representative volume element (RVE) methodology. A series of automatically generated 2D RVEs with ferrite matrix and globular cementite particles were generated as representative of various microstructures. The geometrically necessary dislocation (GND) accumulation at the ferrite–cementite interphase was also studied by introducing an intermediate layer around the cementite particles. Damage mechanisms such as ductile fracture in ferrite matrix, brittle fracture in cementite, and decohesion at ferrite–cementite interphase were considered to study the fracture modes. The relationships between interface strength and particle size were estimated according to the modified Argon criterion and showed satisfactory agreement with related works. The influences of microstructural features, such as particle size, particle fraction and carbide banding, on deformation and damage evolution were investigated under tensile and shear loads. Simulation results indicated that small particle size and particle fraction could postpone the initial decohesion under both tensile and shear loads, while carbide banding can lead to early fracture due to local stress concentration, which has potential to cause the loss of ductility and premature failure. These adverse effects become more severe when more cementite particles remain in the band or the gather density of the cementite particles in the band becomes higher.