Particle Size Dependence Research Articles

Advanced Anti-icing and Deicing Strategies for Overhead Power Transmission Lines Based on Giant Magnetocaloric Effect of La0.7Ca0.254Sr0.046MnO3.

Perovskite manganates (AMnO3) exhibit diverse structural, thermal, electrical, and magnetic properties. Their strong magnetocaloric effect (MCE) near the Curie temperature (TC) makes them ideal for magnetic-thermal anti-icing and deicing in power transmission lines. Below TC, ferromagnetic AMnO3 produces heat through multiple mechanisms, with the changing magnetic field induced by the strong AC current, causing heat through magnetic hysteresis and eddy currents, alongside the direct MCE. Above TC, no heating is generated, as MCE is unfavorable, thus preventing additional energy loss at elevated temperatures. In this work, La0.7Ca0.254Sr0.046MnO3 with TC close to 0 °C were synthesized by solid-state reaction. It is found that particle size >10 μm is beneficial for a large MCE, based on the results of particle size dependence of MCE. The resulting maximum magnetic entropy change at 277 K is 7.69 J·kg-1·K-1, and an adiabatic temperature change of 3.87 K at 277 K is achieved under 5 T. The prototype cable is fabricated using a well-established wire drawing process. A climate-simulation chamber is employed for the anti-icing and deicing experiments. The prototype cables demonstrated a strong capability for deicing and anti-icing. This simple and cost-effective prototype cable shows significant potential for mitigating the icing problem of overhead high-voltage power transmission lines.

Photoluminescence decay of mobile carriers influenced by imperfect quenching at particle surfaces with subdiffusive spread.

We recently presented a quantitative model to explain the particle-size dependence of photoluminescence (PL) quantum yields and revealed that exciton quenching is not diffusion controlled, but limited by surface reactions. However, the exciton decay kinetics has not been analyzed yet using our theoretical model. Here, we study kinetic aspects of the model and show that it should be extended to take into account subdiffusion rather than normal diffusion to maintain consistency with the observed complex decay kinetics; we also show that the PL decay kinetics is nonexponential even when the PL quenching is limited by surface reactions under subdiffusion. Our theoretical analysis of the PL quantum yield and the PL decay kinetics provides a comprehensive picture of mobile charge carriers, immobile polarons, and self-trapped excitons.

“Study of structural, optical, morphology and magnetic properties of samarium doped magnesium nanoferrites (MgSmxFe2-xO4) using sol-gel auto-combustion method”

The study presents a comprehensive report on Sm3+-doped magnesium ferrite (MgSmxFe2-xO4) and its properties across various x values (0.025, 0.075, 0.1, 0.125, and 0.150). The study utilized multiple characterization techniques, such as X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), UV–visible spectroscopy (UV–vis), Thermogravimetry Differential Thermal Analysis (TG-DTA), High-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM) to investigate the structural, magnetic, thermal, optical, and morphological properties of the material. The study determined various parameters, such as x-ray density, lattice constant, crystallite size, and radii on octahedral and tetrahedral sites. An increase in Sm3+ content resulted in an expansion of lattice parameters and a reduction in crystallite size, observed at 13.342 nm in single-phased samples. FT-IR spectroscopy confirmed Sm3+ ion substitution in octahedral sites, while transmission electron microscopy revealed spherical nanoparticles. The UV–vis spectroscopy observed an increase in Sm3+ leads to a corresponding rise in the energy band gap values transitioning from 2.0864, 2.1090, 2.1410, 2.1517, and 2.1850 eV of x = 0.025 to 0.150 respectively. Magnetic measurements indicated decreased magnetization with doping, attributed to particle size dependence. Overall, this study provides valuable insights into the magnetic properties and structural characteristics of Sm3+-doped magnesium ferrite nanomaterials, potentially advancing the development of advanced materials for diverse applications.

The role of chlorine promoters in mediating particle size effects in silver-catalyzed ethylene epoxidation

Measured chlorine coverages over Ag/α-Al2O3 catalysts with varying Ag weight loadings (1.3–35 wt%) and different Ag particle size distributions when parsed in terms of Cl coverages over particles of varying size constituted in the distribution reveal that Ag particles of size below ∼30 nm are covered in more than 1 monolayer (ML) of chlorine in presence of 3.5 ppm C2H5Cl. These assessments of Cl coverages were made possible by correlating the cumulative Cl coverage to the lognormal surface area distribution of 22 Ag/α-Al2O3 samples using a single exponential decay function. Fully chlorided small Ag particles exhibit low rates of epoxidation and only large Ag particles which exhibit sub-monolayer Cl coverages catalyze ethylene epoxidation with high ethylene oxide (EO) rates and selectivity. The Ag particle size dependence of Cl coverages plausibly explains why ≥ 100 nm Ag particles are typical in promoted Ag/α-Al2O3 ethylene epoxidation catalysts.

Complex quasi-brittle fracture modelling using lattice particle method coupled with a local isotropic damage model

In this paper, a local isotropic damage model is incorporated into the lattice particle method (LPM) to model complex quasi-brittle fracture problems. The issue of particle-size dependency is addressed using fracture energy in the damage model regularized with characteristic length that is particle-size dependent. The characteristic lengths are first estimated from mode-I fracture test by ensuring the prescribed and calculated fracture energies match well for both 2D and 3D cases. Extensive validation against experimental data in terms of crack path and structural response is then carried out to assess the accuracy of the proposed model in 2D and 3D settings. Positive outcomes, in line with the experimental findings, have been obtained for both 2D and 3D problems covering mode I and mixed-mode fractures. Furthermore, by employing a regular lattice network, the present model, when integrated with more sophisticated yield surfaces, can address intricate 3D fracture problems that entail the twisting of crack surfaces. Convergence of structural response and crack path is obtained when the particle spacing is refined.

Effect of diamond particle size on thermal conductivity and thermal stability of Zr-diamond/Cu composite

The diamond particle size plays a critical role in regulating the thermal conductivity of diamond/Cu composite. However, the dependence of diamond particle size on thermal conductivity is generally interfered with interface carbides, and the effect of diamond particle size on the thermal stability of diamond/Cu composite has not been addressed. In this study, we fixed the thickness of the ZrC interlayer between Cu and diamond at around 60 nm and varied diamond particle size from 54 to 272 μm to investigate the relationship between diamond particle size and composite thermal conductivity. The thermal conductivity of the Zr-diamond/Cu composite increases with increasing diamond size. A high thermal conductivity of 820 W/mK is obtained with a diamond particle size of 272 μm. The thermal conductivities of all composites are decreased after 100 thermal cycles, and the diamond/Cu composite with large diamond particle size shows better thermal stability during thermal cycling. The findings emphasize the importance of tailoring diamond particle size to attain high thermal conductivity in the diamond/Cu composites and provide useful guidelines for their thermal management applications.

Particle size effect on surface/interfacial tension and Tolman length of nanomaterials: A simple experimental method combining with theoretical.

Surface tension and interfacial tension are crucial to the study of nanomaterials. Herein, we report a solubility method using magnesium oxide nanoparticles of different radii (1.8-105.0nm, MgO NPs) dissolved in pure water as a targeted model; the surface tension and interfacial tension (and their temperature coefficients) were determined by measuring electrical conductivity and combined with the principle of the electrochemical equilibrium method, and the problem of particle size dependence is discussed. Encouragingly, this method can also be used to determine the ionic (atomic or molecular) radius and Tolman length of nanomaterials. This research results disclose that surface/interfacial tension and their temperature coefficients have a significant relationship with particle size. Surface/interfacial tension decreases rapidly with a radius <10nm (while the temperature coefficients are opposite), while for a radius >10nm, the effect is minimal. Especially, it is proven that the value of Tolman length is positive, the effect of particle size on Tolman length is consistent with the surface/interfacial tension, and the Tolman length of the bulk does not change much in the temperature range. This work initiates a new era for reliable determination of surface/interfacial tension, their temperature coefficients, ionic radius, and Tolman length of nanomaterials and provides an important theoretical basis for the development and application of various nanomaterials.

Effect of Ball Milling Conditions on the Microstructure and Dehydrogenation Behavior of TiH2 Powder

This study investigated the effects of revolution speed and ball size in planetary milling on the microstructure and dehydrogenation behavior of TiH2 powder. The particle size analysis showed that the large particles present in the raw powder were effectively refined as the revolution speed increased, and when milled at 500 rpm, the median particle size was 1.47 m. Milling with a mixture of balls of two or three sizes was more effective in refining the raw powder than milling with balls of a single size. A mixture of 3-mm and 5-mm-diameter balls was the optimal condition for particle refinement, and the measured median particle size was 0.71 m. The dependence of particle size on revolution speed and ball size was explained by changes in input energy and the number of contact points of the balls. In the milled powder, the endothermic peak measured using differential thermal analysis was observed at a relatively low temperature. This finding was interpreted as the activation of a dehydrogenation reaction, mainly due to the increase in the specific surface area and the concentration of lattice defects.

Static and dynamic atom displacements in nanocrystalline powders from diffraction analysis at finite temperature

We evaluate the accuracy of x-ray diffraction analysis performed by Rietveld refinement in extracting the static and dynamic atomic displacement parameters of spherical gold nanocrystals with sizes of 30 nm and below and within a temperature interval of 10–300 K. A self-consistent computational workflow composed of real- and reciprocal- space analyses is designed for this purpose. We obtain average lattice parameters, static and thermal atomic displacements as well as their temperature and particle size dependence in an ideally monodispersed and realistic nanocrystalline powder generated by molecular dynamics simulations. Then, we compare crystallographic parameters obtained from real- and reciprocal- space analyses to evaluate the accuracy of diffraction analysis. We also extend the comparison to local variations of crystallographic parameters in the nanocrystals and show how Rietveld refinement relates to the average parameters of the core and surface regions separately. We show that 1) average lattice parameters obtained from Rietveld refinement are greater than the mean lattice parameter of small nanocrystals and converge to the core lattice parameter with increasing particle size, 2) Rietveld refinement significantly underestimates static atom displacements of surface atoms in small nanocrystals, 3) dynamic atomic displacements in nanocrystalline gold powders are reliably obtained within 5 % error by Rietveld refinement, provided that thermal diffuse scattering is adequately removed from the diffraction data, 4) the discrepancy between real- and reciprocal-space analysis increases for the smallest gold nanocrystal.

Particle size dependence of nanoclustered ceria abrasives on surface activity and chemical mechanical planarization performance

The particle size of cerium oxide (ceria) abrasives plays a crucial role in the design and development of advanced self-stopping slurries for the chemical mechanical planarization (CMP) process in semiconductor device manufacturing. However, a lack of ceria nanoparticles (NPs) with a narrow size distribution and uniform shape poses challenges in investigating the fundamental principles of the relationship between abrasive size and CMP performance. In this study, we thoroughly investigated the effect of ceria NP size on the removal rate (RR) of silicon oxide using uniform-sized nanoclustered (NC) ceria NPs with three diameters: 51.4 nm (NC51), 68.6 nm (NC69), and 108.0 nm (NC108). While all three types of ceria NPs shared a crystallinity of ∼ 70.6 %, they exhibited distinct physicochemical characteristics. As the particle size decreased, the specific surface area and chemical activity (i.e., Ce3+/Ce4+) increased by 155 % and 69 %, respectively. In the CMP process, where direct contact between the abrasives and wafer occurs, the abrasive size influences CMP performance. Experimentally, NC51 achieved the highest RR among the three slurries, along with complex size-dependent contact properties and chemical activities. These experimental results offer significant insights into precise semiconductor manufacturing in a practical manner.

Particle-resolved hyperspectral pyrometry of metal particles

We present temperature histories of individual combusting metal particles using hyperspectral pyrometry. This method gives an increase in accuracy over traditionally used two- or three-color pyrometry, while maintaining temporal and spatial resolution. Temperatures can be determined between 1800 to >3000 K with a precision of typically <1%. It is shown that the maximum temperature of the burning iron particles increases from 2760 K to 2840 K with an increasing mean particle size from 32 to 54 μm in air with 21 % oxygen. The relatively high temperatures and its dependence on particle size are possibly related to flow field properties of the current experimental setup. Opportunities for this method, as well as future work, are discussed.Novelty and Significance Statement: In this article, a method to use a CCD camera and spectrograph as a hyperspectral detector, gaining a wavelength dimension while maintaining two spatial dimensions, is demonstrated and validated. This method is applied to measure the temperature of iron particles, a carbon free and circular energy carrier. This method is then used to prove that there is a particle size dependence on the maximum temperature, an open question which is often disputed in literature. This work will also add a dataset that can be used for the validation of numerical models. There are only two such datasets available for iron at this moment. Our analysis suggests that the heat release of iron is dependent on the slip velocity, possibly due to a circulating flow inside of the particle.

Particle Size-Dependent Electrophoresis in Polymer Solutions.

It has long been known that the electrophoretic velocity of a charged particle is independent of its size under the thin-Debye-layer limit. This so-called Smoluchowski velocity is, however, valid only for Newtonian fluids. A couple of recent theoretical studies predict the rheology-induced particle size dependence of electrophoresis in non-Newtonian fluids. This work presents the first experimental demonstration of such dependence in viscoelastic poly(ethylene oxide) (PEO) solutions. Three different-sized particles are observed to travel at the same electrophoretic velocity in a Newtonian buffer through a rectangular microchannel. In contrast, their measured electrophoretic velocities in the PEO solution exhibit an increasing trend for larger particles, which is consistent with theoretical prediction. This particle size dependence is found to grow with an increasing concentration or length of the PEO polymer. Both trends are attributed to enhanced fluid elasticity, as characterized by the increasing elasticity number.

Continuum modelling of a just-saturated inertial column collapse: capturing fluid-particle interaction

This work presents a simple two-phase flow model to analyse a series of axisymmetric granular column collapse tests conducted under elevated gravitational accelerations. These columns were prepared with a just-saturated condition, where the granular pores were filled with a Newtonian fluid up to the column’s free surface. In this configuration, unlike the fully submerged case, air-water-grain contact angles may be important to flow dynamics. The interaction between a Newtonian fluid phase and a monodispersed inertial particle phase was captured by an inter-phase interaction term that considers the drag between the two phases as a function of the particle phase porosity. While this experimental setup has broad applications in understanding various industrial processes and natural phenomena, the focus of this study is on its relevance to predicting the motion of debris flows. Debris flows are challenging to model due to their temporally evolving composition, which can lead to the development of complex numerical models that become intractable. The developed numerical scheme in this study reasonably reproduces the particle-size and gravitational acceleration dependencies observed within the experimental runout and basal fluid pressure dissipation data. However, discrepancies between the model and physical experiments primarily arise from the assumption of modelling the granular phase as a continuum, which becomes less appropriate as particle size increases.Graphical

Synthesis, structure, growth, characterization and quantum chemical studies on 2-amino-5-bromopyridinium trichloroacetate: A novel phasematchable organic NLO single crystal

Organic crystals have become excellent candidates towards nonlinear optical (NLO) applications as they possess superior second and third order optical nonlinearities and high electro-optic coefficients when compared with their inorganic counterparts. In this direction, 2-Amino-5-bromopyridinium trichloroacetate (2A5BPT), a new organic second-order nonlinear optical compound is synthesized and optical grade single crystals are formed utilizing a slow evaporation solution growth approach at room temperature while using methanol as the solvent. Single crystal X-ray diffraction study shows that the title compound is assigned to monoclinic crystal system having non-centrosymmetric space group Cc. The crystal is transparent ( ̴ 85%) throughout the whole visible spectrum, according to the Ultraviolet-Visble (UV–Vis) spectra, with a cutoff wavelength of 367 nm and an optical energy band gap Eg of 3.32 eV. The crystal possesses good thermal stability. The compound has a 1.6 times greater powder second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP). The phase matchability of the 2A5BPT is studied through particle size dependence of SHG. The intermolecular connection demonstrated by numerous inter contacts has been shown by a molecular Hirshfeld surface analysis of the crystal structure, and the related 2-dimensional finger print analysis further evaluates the individual contribution from each atom. In order to examine the first order hyperpolarizability, molecular electrostatic potential, and Highest occupied molecular orbital-Lowest unoccupied molecular orbital (HOMO-LUMO) energies, the quantum chemical calculations for the title molecule (2A5BPT) were carried out by density functional theory (DFT) utilizing the B3LYP/6–311++G(d,p) basis set. According to these results, the 2A5BPT crystal could be suitable for optoelectronic applications.

Nanocomposite Materials Based on Polylactide and Gold Complex Compounds for Absorbed Dose Diagnostics in BNCT.

In this study, approaches to the synthesis of complex compound of gold with cysteine [AuCys]n for measuring absorbed dose in boron neutron capture therapy (BNCT) were developed. The dependence of the complex particle size on pH were established. Nanocomposite materials based on polylactide containing [AuCys]n particles with an average size of about 20 nm were obtained using the crazing mechanism. The structure of obtained materials was studied by electron microscopy. The release kinetics of [AuCys]n from polymer matrix were investigated. Release of [AuCys]n from the volume of the polymeric matrix had a delayed start-this process began only after 24 h and was characterized by an effective rate constant of 1 μg/h from a 20 mg composite sample. At the same time, in vitro studies showed that the concentration of 6.25 μg/mL was reliably safe and did not reduce the survival of U251 and SW-620 cells.

Surface tension of metallic glass forming liquid nanoparticles

We report the surface tension γ of Cu64Zr36 metallic glass liquid nanoparticles calculated using molecular dynamics simulation. We carried out a systematic investigation to obtain the dependence of γ on particle size and temperature. The values of γ are between 0.85 and 1.25 N/m, with a negative coefficient of temperature dependence that covers both the liquid and (amorphous) solid state. The particle size dependence is extracted through the Tolman length δ, which takes the values between 0.53 and 0.83 Å. The surface tension is influenced by temperature, sphere size, and surface chemical segregation.

The second shear-thinning and strain-stiffening behaviors of bidisperse non-colloidal suspensions

Experimental research is done to determine the shear-thinning behavior of a bidisperse non-colloidal suspension under steady-state shear and the strain-stiffening behavior under oscillatory shear. The second shear-thinning behavior is displayed when the volume fraction of the bidisperse particle suspension is between medium and high. It exhibits with an increase in shear rate, the viscosity drops by approximately three orders of magnitude. At low shear rates, a strong particle size dependence of viscosity is observed, while at high shear rates, the particle size dependence is almost non-existent. To further understand the behavior of the second shear thinning, three sets of oscillatory shear tests and steady-state shear tests (constant shear rate) are carried out at three stopping points in parallel using a unique experimental technique we have developed. The values of modulus and viscosity at the third position are significantly smaller than those at the first and second positions. In the oscillatory shear test, the storage and loss moduli of the bidisperse suspension first decrease and then increase as the strain amplitude increases. The particle volume fraction, not the particle size, is closely related to the bidisperse critical strain amplitude. Compared with monodisperse suspension, bidisperse suspension has low viscosity and larger modulus well under steady-state shear and oscillatory shear operations, which is beneficial to the development of new materials and processes. Moreover, by adding a surfactant of a specific concentration to the bidisperse sample, it is proved that the change in the microstructure of the suspension particle is responsible for the rheological properties of the suspension.

Numerical study on the elucidation of powder mixing mechanism in a container blender

Numerical simulations by the discrete element method (DEM) and DEM-computational fluid dynamics (CFD) have greatly facilitated the investigation of mixing kinetics in various particle mixing systems, including the common container blender. Recently, airflow within the container blender has been found to remarkably improve the mixing efficiency of fine particles. Nevertheless, a wide range of particle sizes has not been examined regarding the airflow effect. Thus, to comprehensively understand the particle size dependence of the airflow impact on powder mixing, this study aims to investigate the relationship of various particle diameters and powder mixing in an industrial container blender. An advanced mathematical-statistical method, named proper orthogonal decomposition-analysis of variance (POD-ANOVA), is used to clarify the complex mixing mechanisms. Numerical results show that airflow has different impacts on the mixing efficiency determined by the particle size range. The mixing of coarse particles with diameters above 1.000 mm is not significantly influenced by airflow, whereas medium-sized particles, ranging from 0.5000 to 1.000 mm, display reduced mixing efficiency as particle size decreases. Conversely, for small particles (0.2000–0.5000 mm), the mixing efficiency improves when decreasing the particle size. The underlying variations of powder mixing mechanisms have been well elucidated, and the convection mixing mechanism is found to be crucial in determining the mixing efficiency via POD-ANOVA analysis. Consequently, this work provides critical insights into the airflow effect during powder mixing, which has been verified to be highly dependent on particle size and is dominated by the convection mechanism.

Influence of ash species on particle size dependence of water- and citric-acid-soluble potassium concentrations of woody biomass combustion ashes with low potassium content

The dependence of the concentrations of water- and citric-acid-soluble potassium on particle size was investigated for two types of low-potassium-content woody biomass combustion ash discharged from different biomass power plants. For both types of ash, the potassium concentration increased as the median diameter decreased; crystalline potassium, such as KCl and K2SO4, was identified more in fine combustion ash, whereas crystalline SiO2 and CaCO3 were abundant in coarse ash. The potassium components could be present as finer ash particles or as cover over coarser ash particles composed of crystalline SiO2 surfaces. Differences in the existence forms of the potassium components caused differences in the dependence of potassium concentration on the median diameter of the ash. Moreover, the methods used to calculate the particle size distributions of three ash particle components (water-soluble, citric-acid-soluble, and insoluble) in the ash residues can be used to evaluate the particle size dependence of both potassium concentrations to some extent. The potassium enrichment process demonstrated in this study could be successfully performed on a factory scale via the surface grinding of bottom ash. The collected fine grinding debris containing rich potassium, separated from the surface of the silica, was found to be possibly reusable as fertilizer.

(Invited) True Particle-Size Dependence of Photocatalytic Activity of Octahedral-Shaped Anatase Titania

Here, attempts to prepare octahedral-shaped anatase titanium(IV) oxide (titania) particles (OAPs) of uniform bulk structure (anatase with negligible non-crystalline components), surface structure (only exposing {101} facets) and particle size are reported as the first and sole example of a "pure" metal-oxide powder. The OAP samples were prepared by sonication-hydrothermal (HT) reaction of potassium-titanate nanowires through the process modified from the previous report [1]. Characterization of the samples by Rietveld analysis of XRD patterns (including non-crystalline phases using an internal standard) [2], reversed double-beam photoacoustic spectroscopy (RDB-PAS; a method measuring energy-resolved distribution of electron traps mainly located on the surface of metal-oxide and the other semiconducting samples) [3,4] and SEM observations revealed the homogeneousness of crystalline bulk, surface and particle size, respectively, to indicate the samples "pure". By controlling the preparation conditions, several OAP samples with different average size ranging of ca. 60–260 nm keeping the purity of the OAP shape. Roughly speaking, the particle-size distribution of those samples was the size of ca. 80% particles in the range of +20% of the average. Photocatalytic activities of those samples in (a) methanol dehydrogenation with in-situ deposited platinum to yield hydrogen, (b) oxidative decomposition of acetic acid under aerobic conditions to yield carbon dioxide and (c) oxygen evolution from deaerated aqueous silver sulfate were examined under ultraviolet-light (> 290 nm) irradiation to find that there seemed no particle-size dependence for the systems (a) hydrogen evolution and (b) carbon-dioxide evolution, while the activity in system (c) to liberate oxygen was almost linearly increased with the particle size [5]. These particle-size dependences of photocatalytic activity seem strange but could be "true" considering the purity of those samples, i.e., almost pure bulk crystal component exposing only anatase{101} facets. The previously reported particle-size dependence might be incorrectly derived due to the unknown effects by the other structural parameters.[1] Molecules 19, 19573 (2014). [2] Catal. Today 313, 218 (2018). [3] Chem. Commun. 52, 12096 (2016). [4] Electrochim. Acta 264, 83 (2018). [5] To be submitted.