Changes In Particle Shape Research Articles

Valorization of brewer's spent grains (BSG) through alkaline hydrogen peroxide processing: Effect on composition, structure and rheological properties

This study investigated the impact of alkaline processing with hydrogen peroxide (AHP) on the chemical composition, structure, and rheological properties of brewer's spent grains (BSG). Suspensions with different concentrations of BSG (2–8 %) and AHP (1–8 %) were subjected to different processing times (0–12 h). The BSG chemical composition, morphology, crystallinity, modifications of functional groups, and rheological behavior were evaluated over processing. Increasing the concentration of AHP in the suspension and the processing time improved the removal of proteins, lignin, and extractives from BSG into the suspension and, consequently, increased the cellulose and hemicellulose content in the processed BSG. On the other hand, higher concentrations of BSG in the suspension slightly reduced the removal efficiency of these components. AHP processing also induced thinning of the cell wall and changes in particle shape. These changes together with the increase in crystallinity of the processed BSG indicated the material destructuring. FTIR spectra showed reduced intensity of lignin and protein post-processing, indicating their removal, while peaks related to cellulose and hemicellulose increased in processed BSG. The flow curves of the suspensions were adjusted to the Herschel-Bulkley model, exhibiting non-Newtonian behavior with flow yield stress (1.529 Pa < τ0 < 4.646 Pa) and pseudoplasticity (0.830 < n < 0.969) in all conditions. Flow resistance increased with increasing concentration of AHP, BSG, and processing time. Notably, the increase in processing time resulted in greater removal of BSG components, especially proteins, lignin, and extractives, which significantly contributed to the increase in both the flow yield stress and the consistency index of the suspensions. All this information is useful and will support the design of equipment and processes, especially those involving the extraction of proteins and the conversion of the BSG lignocellulose fraction into biofuels.

An Efficient Approach for Quantifying the Mechanical Degradation of Ni‐Rich NMC‐based Cathodes for Lithium‐Ion Batteries using Nano‐XCT Analysis

AbstractLiNi0.8Co0.1Mn0.1O2 has emerged as a promising electrode material for automotive lithium‐ion batteries due to its high specific discharge capacity, cost‐effectiveness, and reduced cobalt content. However, despite all mentioned beneficial attributes, the widespread adoption of this material class is impeded by active material degradation during cycling operation, which is linked to performance loss. This study compares scanning electron microscopy images and nano X‐ray computed tomography scans with a 3D reconstruction of pristine and cycle‐aged battery electrodes to determine structural changes over cycle life. Although a very moderate current rate was chosen for the cycle test, which suggests a homogeneous load across the entire electrode, particle fracture varied across electrode thickness and particle size. A quantitative analysis of the active material‘s gray scale value distribution reveals severe degradation near the separator interface with a reciprocal relationship to particle radius. Remarkably, particle shape and size remain relatively unchanged despite cracking, eliminating the need to adjust these parameters in aging simulations. Moreover, it underscores the practical significance of particle cracking, as it can significantly impact the electrode‘s performance. Thus, analyzing changes in particle shape and size alone is insufficient, and a comprehensive exploration of the particle interior using nano‐XCT is necessary.

Properties and Lightfastness of Natural and Artificial Azurite Used As Painting Pigment

Azurite is an inorganic pigment commonly used in traditional painting arts and even today. This pigment has two types: natural azurite and synthetic artificial azurite, called blue verditer or blue bice. Because they have the same structure and similar appearance they are difficult to distinguish. The purpose of this study is to compare these two types pigments, focusing on material properties and accelerated weathering behavior. Natural azurite consist of copper carbonate and mineral compounds like quartz, kaolinite. On the other hand, artificial azurites are synthesized using azurite and calcite. As a result of thermal analysis, unlike natural azurite, the calcite in artificial azurite resulted in weight loss at three temperatures, at approximately 350 ℃, 650 ℃, and 840 ℃. According to the microscope analysis results, natural azurites have clearly blue angular particles with sharp edges, produced by crushing. Artificial azurite showed spherules and aggregates with tiny rounded or fibrous particles. After accelerated weathering tests, the natural azurites had no change in color, particle shape or original components, but the artificial azurites noticeably changed color and shape. The color changes of artificial azurites occurred due to the growth of calcite crystallite, a slight new product formation, and change in particle shape. Even though natural azurites are more expensive pigments, they provide superior color durability and particle shape stability compared to artificial azurites.

The improved size distribution and NIR luminescence of ZGGO:Cr3+ nanoparticles induced by Y3+ doping

Zn2Ga2.98-xYxCr0.02Ge0.75O8 (ZGGO:Cr0.02,Yx) persistent luminescent nanoparticles (PLNPs) with different concentrations were synthesized by a hydrothermal method combined with a vacuum heat treatment. With increasing Y3+ concentration from 0 to 0.05, the average size reduces from 53 to 28 nm and the particle shape changes from irregular to nearly spherical due to Y3+ doping leading to the suppressed growth rate of nanocrystals via surface charge modification. On the basis of spectral analyses and the first-principles calculation, the near infrared (NIR) emission peaks at 703 and 743 nm originate from the 4T2→4A2 transition of Cr3+ occupying octahedral Ga3+ sites and the 4A2→4T1 transition of Cr3+ occupying tetrahedral Ga3+ sites, respectively. Meanwhile, it is found that Y3+ ions are more likely to occupy tetrahedral Ga3+ sites and it leads to not only the creation of more anti-site defect pairs and the enhanced afterglow intensity but also the increased rigidity and the improved dispersibility of PLNPs in different simulated body fluids induced by complete surface modification (i.e. SiO2 coating). The above results indicate that ZGGO: Cr0.02,Y0.03@SiO2 PLNPs have potential applications in bioimaging.

CO2 permeation through fusion-bonded epoxy coating in humid environments

The effects of water and CO2 exposure on the performance of epoxy-based coatings under conditions commonly found in pipeline applications are investigated. The permeability of fusion bonded epoxy (FBE) decreases as CO2 pressure increases and the presence of water facilitates gas transport through the coating. The latter is in conflict with theories of competitive transport in gas/vapor systems, in which water is the predominant permeant for its lower kinetic diameter and higher condensability. Our results show that this anomaly was due to the dynamic transformation of permeable channels in the coating structure. Microstructural characterization of FBE after exposure to CO2/H2O mixtures showed that carbonation of wollastonite fillers results in a change in shape and chemical composition of these filler particles. To verify these findings for the coating in the presence of adhesion forces, electrochemical impedance spectroscopy (EIS) was also used. Initially, the carbonation of fillers led to an increase in the pore resistance of the coating, which was attributed to the plugging of micropore channels on the coating surface. However, the subsequent decreasing trend of this parameter suggested that water infiltration into the coating had increased due to this degradation. This transformation facilitates the easier penetration of water and dissolved gas to the underlying substrate. Consequently, the accumulation of water inside the coating increases the dielectric constant, resulting in a higher capacitance of the coating. It appears that high concentrations of CO2 in wet conditions, even at low pressures, can have negative impacts on the barrier performance of the coating.

Microstructure response to shear strength deterioration in loess after freeze-thaw cycles

Shear strength deterioration owning to freeze-thaw (F-T) cycles affects loess slope stability in seasonal frozen region. The change in loess shear strength is closely related to particle microstructure. In this study, multiple F-t-tests (i.e., 0, 1, 3, 5, 10, 15, 20, and 30 cycles) were performed on natural loess from Jing'yang, China. Unconsolidated-undrained triaxial tests and scanning electron microscopy (SEM) were performed on the specimens after the predefined number of F-T cycles. Particle microstructure was quantitatively analyzed using fractal dimension theory. The relationship between shear strength index and particle microstructure characteristics parameters was evaluated using the grey correlation method. Changes in the loess microstructure involved two main processes: transformation and stabilization, and the particle shape, arrangement, and interparticle contact were transformed into different types. The particle shape changed from complex to round with debris detaching from the particle surface. The orderliness of particle arrangement increased and point-face intercontact was formed. The internal friction angle and cohesion decreased with an increasing number of F-T cycles, and the change pattern was similar to that of the particle microstructure characteristics, both of which changed significantly before 5 F-T cycles and stabilized after 15 F-T cycles. An evaluation of the correlation between shear strength index and particle microstructure characteristic parameters demonstrated that, the change in particle shape contributed the most to deterioration of shear strength during F-T cycles, followed by particle arrangement and particle distribution. These results provide insights into the mechanism of degradation of loess shear strength in seasonally frozen areas at the microstructural scale.

The Mechanism of Phase Transfer Synthesis of Silver Nanoparticles Using a Fatty Amine as Extractant/Phase Transfer Agent

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane &gt; cyclohexane &gt; toluene &gt; chloroform &gt; ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10−4 M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again.

상대습도 및 노후화에 따른 헤파필터 내 입자상 에어로졸 제거 효율 분석

With the recent increase in particulate matter across the country, demand for air purification devices including high-efficiency filters has increased. Still, there is a lack of research on the life and performance of filters. Therefore, the purpose of this study is to test the change in performance according to the relative humidity and aging of the filter. Considering the shape change of particles according to relative humidity, we tested the aerosol removal efficiency of the filter and took SEM analysis. Differential pressure and wind guage were also measured at the front and rear ends of the filter box. As a ventilation device, a device with 150 CMH was used that is distributed on the market, and HEPA filter (H13) was used alone. The result of the measurement confirmed that filter with high relative humidity condition in same aged condition shows a positive effect in terms of aerosol removal efficiency, differential pressure and wind guage have higher values. Comparing the aged filter with the new filter, the aged filter showed a low value in terms of aerosol removal efficiency and differential pressure. Therefore, this study confirmed significant performance variation of filter in difference with relative humidity and aging condition.

Bubble Trajectory Tracking Based on ORB Algorithm

The system of gas-liquid two-phase bubbly flows is widely found in many industrial fields, such as nuclear energy, chemical, petroleum, and refrigeration. Bubbly two-phase flows measuring including detection and tracking affects the specific engineering problem solving to a great extent. The particle tracking velocity (PTV) algorithm is generally used for the tracking of the particles in the flow field. However, it does not take the shape change of particles into account in the process of flow. In this paper, a kind of bubble feature matching method based on ORB algorithm is proposed, and the edge detection method of findContours in OpenCV is used to extract the bubble contour in the image. The proposed algorithm implements the trajectory tracking of the bubbles with shape change when moving up in liquid. The feasibility of bubble trajectory tracking is shown by displaying of different bubble tracks in the plan, 3D plots and contour changing plots.

Synthesis of Ag3PO4/Ag4P2O7 by microwave-hydrothermal method for enhanced UV–visible photocatalytic performance

Ag3PO4/Ag4P2O7 photocatalysts were successfully synthesized by microwave-hydrothermal method. Tuning the properties of photocatalysts was achieved using different amount of acetic acid (CH3COOH) and sodium hydroxide (NaOH) to adjust pH value of precursor solution (pH = 4, 7, 10 and 12). The crystal structure, morphology and optical property of samples were characterized and explained. The photocatalytic activity of sample was determined by degradation of rhodamine B (RhB) and methyl orange (MO) under a wavelength range of 350–700 nm irradiation. The results demonstrated that the change in shape of particles was not observed whereas the average particle size was decreased with increasing pH value because of the high hydroxide ions (OH−). The sample synthesized in the solution with the pH of 10 exhibited excellent photocatalytic performance and stability because of the highest surface area and the present of Ag4P2O7 on the surface of particles. The highest photodegradation efficiency was 99.34 and 96.12% by degrading RhB and MO, respectively. The enhancement of photocatalytic performance of Ag3PO4/Ag4P2O7 was discussed. The active species trapping experiments showed that the h+ was the main active species to decompose the dye molecules.

Effect of Milling Parameters on DEM Modeling of a Planetary Ball Mill

The effects of the milling parameters involving shape of powder particles, rotation speed, and ball-to-powder diameter (BPDR) on DEM modeling in the planetary ball mill were investigated. BPDR was varied from 1 to 10. The results revealed that the size and shape of the powder particles do not give a significant change in simulation results when BPDR attains maximum value of 10. The increasing of BPDR leads to the increase of simulation time and size. Hence, the effect of change of the powder particle shape on the calculated data size is not significant. The results also revealed that the increasing rotation speed increases impact energy between powder particles.

Strong increase the photoluminescence of Dy3+ doped germanate compounds by optimizing the synthesis conditions

The aim of the present study was to investigate the influence of synthesis conditions (temperature and synthesis time) and consequently the change in particle size and shape, their size distribution, degree of agglomeration and the degree of crystallinity on the emission intensity of three different germanates Li 2 CaGeO 4 , Ca 2 GeO 4 and Ca 5 Ge 3 O 11 doped by 1at% Dy 3+ . The analysis showed that the emission intensities of Li 2 CaGeO 4 , Ca 2 GeO 4 and Ca 5 Ge 3 O 11 doped by 1at% Dy 3+ increase 4, 10 and 3 times only as a result of optimizing the synthesis conditions. Studies have shown definitely that the dominant factor for this strong increase of the emission intensity is the increase of the degree of crystallinity. The presence of agglomeration in high temperature synthesis (in the case of Ca 2 GeO 4 ) strongly reduces the emission intensity. The sizes and shape of the particles, as well as their size distribution for the three investigated compounds are of secondary importance for the emission intensity. • Dysprosium doped powder Li 2 CaGeO 4 , Ca 2 GeO 4 and Ca 5 Ge 3 O 11 samples are prepared. • Different thermal treatment conditions are used. • XRD, SEM images and particle size distribution are presented. • Emission and excitation spectra of powder samples are presented. • Several relations between the synthesis regime and spectra intensity are obtained.

Factors determining the flowability and spreading quality of gas-atomized Ti-48Al-2Cr-2Nb powders in powder bed fusion additive manufacturing

A high-quality powder bed is necessary for obtaining high-quality products using powder bed fusion-based additive manufacturing. In this study, mechanical ball milling was suggested to improve the flowability and spreadability of gas-atomized (GA) Ti–48Al–2Cr–2Nb powder in the powder bed fusion additive manufacturing process. The deformation mechanism of the GA powder significantly differed depending on the ball milling media. Surface grinding mainly occurred during Al 2 O 3 ball milling, while the pulverization was dominant in WC ball milling because of the higher impact force. The flowability of the GA powder under dynamic conditions was improved after Al 2 O 3 and WC ball milling owing to the decreased cohesive force. The high cohesive force in the GA powder under dynamic conditions was attributed to the electrostatic force caused by charge accumulation on the oxide film. The packing density of GA powder was increased after WC ball milling despite the formation of numerous irregular particles owing to the synergetic effect of rapid energy dissipation, minimized wall effect, and void filling effect. Furthermore, the spreadability of the GA powder was improved by ball milling because of the decrease in the cohesive force. Therefore, it was demonstrated that the flowability and spreadability of the GA powder can be improved via ball milling because of changes in particle size, shape, and surface properties. • Flowability of GA powder under the dynamic condition was improved after ball milling owing to the decreased cohesion force. • High cohesive force in GA powder was mainly attributed to the electrostatic force caused by charge accumulation on the oxide film. • Spreadability of GA powder was improved after ball milling due to the decreased cohesion force.

Systematic evaluation and effect of different treatments (HMT, QESD, OSA) on flow properties of Chenopodium album starch

AbstractThis study investigate the changes in the flow properties of Chenopodium album starch (CAS) after modification through quasi‐emulsion solvent diffusion (QESD), octenyl succinic anhydride (OSA), and heat moisture treatment (HMT). The native starch's Carr's index (36.92%) and Hausner ratio (1.55) indicates poor flowability as compared to modified starch that shows fair flowability. The caking strength and cohesion index after modification decreased from 1072.67 to 222.00 g.mm and 15.37 to 8.48 g.mm, respectively. Shear properties assessed at three different pressures (3, 6 and 9 kPa) showed that native CAS was less flowable (COF 22.8 at 6 kPa) than modified (COF 26.9 at 6 kPa), making bulk handling harder. The surface roughness value of the powder as measured by atomic force microscopy was found to be lesser in modified starch (92.49 μm) in comparison to native starch (117.60 μm). Scanning electron microscopy revealed the formation of spherical, smooth oval, and regular shaped starch particles after modification. X‐ray diffraction analysis showed an improvement in crystallinity from 20.01 to 29.86% after modification. Conclusively, QESD treatment significantly improved the flow properties of Chenopodium album starch in comparison of HMT and OSA treatment.Novelty impact statementDifferent treatments (HMT, QESD, and OSA) improved the flow properties by developing regular‐shaped, smooth surface, and larger starch particles with increased crystallinity. The changes in particle size distribution, particle shape, and surface roughness had a substantial impact on all flow parameters throughout a wide range of stress situations. The present research would be valuable in determining the impact of various climatic conditions on material flowability, which is an essential consideration when building processing equipment, hoppers, and silos for the bulk handling of starch.

Image histogram decomposition method for particle sizing – A numerical simulation study

Scanning probe microscopy is a useful tool in nanoscience. The effective application of nanotechnologies in various fields requires a knowledge of the characteristic attributes of nanoparticles such as shape, dimensions and statistical distribution, and a wide spectrum of experimental and theoretical methods based on various principles have been developed to determine these characteristics. Image histograms offer a global overview of the characteristics of an image. Their shape can encode specific statistical properties of displayed objects such as the distribution function in the case of similar and scalable objects. The model of height histogram presented here proposes a method which solves the long-term problem of processing images of extremely dense particle distributions. The method is based on the principle of the superposition of histograms of individual particles whose topographic surface is described by a parametric model. The resulting height histogram is defined by a convolution of the model of the particle histogram with the distribution function of particle size, with this construction forming the basis of the regression model. The parameters of the distribution function can be obtained via the optimization of the model. The method has been tested on artificially generated configurations of particles of various shapes and size distributions. Each of these configurations creates a topographic surface which is transformed into an image, and the heights obtained from the image allow a histogram to be calculated. Firstly, various configurations of particles are simulated without the presence of any disruptive influences. Next, several experimental effects are evaluated separately (for example, the background, particle shape irregularity and particle overlap). The decomposition of the histogram by the regression model on artificially generated images shows the robustness of the method with respect to particle density, partial horizontal overlap, randomly generated backgrounds and random fluctuations in particle shape. However, the method is sensitive to uniform changes in particle shape, a factor which limits its use to particles with known parametric models of their shape which allow the means of their parameters to be estimated.

Modification of DSSC Based on Polymer Composite Gel Electrolyte with Copper Oxide Nanochain by Shape Effect.

Solvent evaporation and leakage of liquid electrolytes that restrict the practicality of dye-sensitized solar cells (DSSCs) motivate the quest for the development of stable and ionic conductive electrolyte. Gel polymer electrolyte (GPE) fits the criteria, but it still suffers from low efficiency due to insufficient segmental motion within the electrolytes. Therefore, incorporating metal oxide nanofiller is one of the approaches to enhance the performance of electrolytes due to the presence of cross-linking centers that can be coordinated with the polymer segments. In this research, polymer composite gel electrolytes (PCGEs) employing poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (P(VB-co-VA-co-VAc)) terpolymer as host polymer, tetrapropylammonium iodide (TPAI) as dopant salt, and copper oxide (CuO) nanoparticles as the nanofillers were produced. The CuO nanofillers were synthesized by sonochemical method and subsequently calcined at different temperatures (i.e., 200, 350, and 500 °C), denoted as CuO-200, CuO-350, and CuO-500, respectively. All CuO nanoparticles have different shapes and sizes that are connected in a chain which impact the amorphous phase and the roughness of the surface, proven by the structural and the morphological analyses. It was found that the PCGE consisting of CuO-350 exhibited the highest ionic conductivity of 2.54 mS cm−1 and apparent diffusion coefficient of triiodide of 1.537 10−4 cm2 s−1. The enhancement in the electrochemical performance of the PCGEs is correlated with the change in shape (rod to sphere) and size of CuO particles which disrupted the structural order of the polymer chain, facilitating the redox couple transportation. Additionally, a DSSC was fabricated and achieved the highest power conversion efficiency of 7.05% with JSC of 22.1 mA cm−2, VOC of 0.61 V, and FF of 52.4%.

A new approach to quantify powder's bed surface roughness in additive manufacturing

The powder bed surface roughness plays an important role in the quality of the final parts fabricated using powder bed Additive Manufacturing processes. This paper reports the development and application of a new technique and prototype instrument which can be used to simulate the creation of a powder bed and reveal the surface properties of that bed. The tester was successfully used to study powder bed surface roughness, but can also be used to evaluate powder bed relative packing fraction, change in particle size and shape over the build plate and electrostatic charges over the powder bed. The focus of this paper is on the developments of metrics to define powder bed surface roughness. In this investigation, six plastic and two metal powders, as well as two recoater blade shape, were used. Two gap sizes of the recoaters were tested, namely two and five times higher than the powder D90. A novel shadowgraphy technique based on illuminating the surface with low-angle collimated light and analysing the image was employed to quantify powder bed surface roughness. Two main metrics to quantify the surface roughness of the powder bed were found to be useful. The first metric is amplitude of variation in surface height which is defined as the difference between surface height at each data point and the average height over 100 points. The second metric is wavelength of roughness which is calculated as the average horizontal distance between positive peaks, averaged over 100 data points. The surface roughness results showed that the shadowgraphy technique as well as the metrics developed by this method to quantify powder bed surface roughness, are capable of quantifying and distinguishing various powder bed features (and therefore potential quality failures in the bed). These metrics successfully captured the impact of different spreading variables; i.e. recoater shape, gap size and particularly the powder flow functions on the powder bed surface roughness.

Rigid body motion of multiple particles in solid-state sintering

The deep understanding of rigid body motion and shape change of multiple particles is required to predict the complicated microstructural evolution during sintering for manufacturing products with tailored properties. Although large-scale simulations of sintering, such as the phase field method, the kinetic Monte Carlo method, and the discrete element method, have been developed recently, it is still a challenge to incorporate the rigid body motion of particles correctly. Here we present a rigorous simulation of sintering by coupled grain boundary and surface diffusion to show how rigid body motion accelerates the fundamental processes in complex evolution of microstructure, e.g., the growth of contact area, the pinch-off of a pore channel, and the shrinkage and elimination of a closed pore. We propose that this result will be used as a benchmark for checking to what extent large-scale multi-particles simulations can approximate the rigid body motion of particles in sintering accurately.

Generation of Local Diffusioosmotic Flow by Light Responsive Microgels.

Here we show that microgels trapped at a solid wall can issue liquid flow and transport over distances several times larger than the particle size. The microgel consists of cross-linked poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-AA) polymer chains loaded with cationic azobenzene-containing surfactant, which can assume either a trans- or a cis-state depending on the wavelength of the applied irradiation. The microgel, being a selective absorber of trans-isomers, responds by changing its volume under irradiation with light of appropriate wavelength at which the cis-isomers of the surfactant molecules diffuse out of the particle interior. Together with the change in particle size, the expelled cis-isomers form an excess of the concentration and subsequent gradient in osmotic pressure generating a halo of local light-driven diffusioosmotic (l-LDDO) flow. The direction and the strength of the l-LDDO depends on the intensity and irradiation wavelength, as well as on the amount of surfactant absorbed by the microgel. The flow pattern around a microgel is directed radially outward and can be maintained quasi-indefinitely under exposure to blue light when the trans-/cis-ratio is 2/1, establishing a photostationary state. Irradiation with UV light, on the other hand, generates a radially transient flow pattern, which inverts from inward to outward over time at low intensities. By measuring the displacement of tracer particles around neutral microgels during a temperature-induced collapse, we can exclude that a change in particle shape itself causes the flow, i.e., just by expulsion or uptake of water. Ultimately, it is its ability to selectively absorb two isomers of photosensitive surfactant under different irradiation conditions that leads to an effective pumping caused by a self-induced diffusioosmotic flow.

Shape dependent multiferroic behavior in Bi2Fe4O9 nanoparticles

Ferroelectric and magnetic properties are investigated for Bi2Fe4O9 nanoparticles with different shapes (cuboid and sphere-like) synthesized by hydrothermal and sol-gel method. The magnetic study reveals that coercivity, Neel temperature and remanent magnetization strongly depend on shape of the particle. The nanoparticle with sphere-like shape exhibits magnetization curve of antiferromagnetic (AFM) ordering with ferromagnetic (FM) component. As the particle shape changes from sphere-like to cuboid, the AFM component is dominating over the ferromagnetic component. A small exchange bias is also observed at low temperature in both the sphere-like and cuboid nanoparticle. The coercivity, remanent magnetization and Neel temperature of sphere-like nanoparticle is greater than cuboid nanoparticle. Ferroelectric measurement shows the remanent polarization of cuboid is greater than sphere-like nanoparticle but the coercivity is almost same. This Bi2Fe4O9 nanoparticle shows a small change in polarization under magnetic field. The polarization value decreases with magnetic field increases. The magnetoelectric coupling-measured by change of remanent polarization under magnetic field are found to be greater in Bi2Fe4O9 sphere-like nanoparticles. These shape dependent magnetic and ferroelectric properties are coming because of shape anisotropy.