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Zn${}_{0.7}$Mg${}_{0.3}$TiO₃ dielectric ceramic material has found widespread applications in the realm of communication technology, however, it is still a challenge to effectively regulate its performance characteristics. The dense Zn${}_{0.7}$Mg${}_{0.3}$TiO₃ ceramics were successfully prepared by a solid-state reaction method using micron- and nanometer-sized particles as raw materials. The results revealed that the grain sizes of the sintered ceramics increased with the increasing number of nanoparticles. Moreover, the lattice parameters gradually decreased with the increase in the number of nanoparticles. Especially, the cell volume decreased the dielectric constant (${\epsilon }_r$) and the resistance of the grain boundaries increased the quality factor ($Q\times f$). The study points to the effectiveness of tuning the structural and dielectric properties by adopting raw materials with different particle sizes.

The oxygen concentration of tantalum powder is critical for the fabrication of solid electrolyte tantalum capacitors. In the present paper an attempt has been made to study the influence of milling time, milling speed (rotations per minute (RPM)) of the vibratory disc mill and average particle size of tantalum powder on oxygen concentrations. It was observed that milling time is directly related to the oxygen content of the powder mass. However, the rotational speed of the mill also contributes to the particle size distribution and ambience gas content of the particles.

Zirconium diboride is widely applied to high-temperature materials, but it is easily oxidized at high temperature. To increase the oxidation resistance of zirconium diboride at high temperature, the A1(OH)₃–Y(OH)₃ is coated on the ZrB₂ surface to prepare A1(OH)₃–Y(OH)₃/ZrB₂ composite particles. In this paper, the effect of coating content on the properties of A1(OH)₃–Y(OH)₃/ZrB₂ composite particles is investigated. It is analyzed that the particle size and particle size distribution of A1(OH)₃–Y(OH)₃/ZrB₂ composite particles is increased with the coating content. The dispersion of ZrB₂ particles is largely increased with the coating content of 0%–20%; the dispersion of ZrB₂ particles is similar when the coating content is from 20% to 30%. The oxidation resistance ratio of the ZrB₂ particles with 30% coating content is the best than that of other conditions—it is about three times more than that of the original ZrB₂ particles.

Niobium powder was fabricated by metallothermic reduction process using K₂NbF₇ as the raw material, KCl and KF as the diluents and Na as the reducing agent. The apparatus for the experiment was designed and built specifically for the present study. Varying properties of niobium powder depending on reaction temperature and excess of reducing agent were analyzed. The niobium particle size increased significantly as the reduction temperature increased from 993 to 1093 K. The particle size was fairly uniform at a given reaction temperature, varying from 0.2 μ m to 50 nm depending on the reaction temperature. The yield of niobium powder increased from 58 to 83% with an increase in reaction temperature. The average particle size of niobium powder was improved from 70 nm to 0.2 μ m with the increase in the amount of Na excess. In addition, the yield rate of Nb powder was 82% in the 5% excess sodium.

Ni_0.65Zn_0.35Fe₂O₄ nanoparticles synthesized by sol–gel process have been subjected to various annealing temperatures with a view of obtaining size dependent properties and critical length. X-ray diffraction, transmission electron microscopy, VSM and ESR experiments were carried out as a function of crystallite size. From the ESR spectra it has been observed that the sample annealed at 1025°C has least magnetic anisotropy. The observed variations in saturation magnetization and coercive field have been explained in terms of magnetic anisotropy.

Zinc oxide nanoparticles (ZnO-NPs) are widely utilized in many applications due to distinct physical and chemical characteristics. There are growing concerns that abundant use of ZnO-NPs can cause harm to humans and the environment. There is a substantial problem with reproducibility in nanotoxicology research due to the inherent properties of nanoparticles. Dispersion media are used for the preparation of nanoparticles. However, the physical and biological behaviors of ZnO-NPs in aqueous dispersion media are poorly understood. In this study, we investigated the effect of ZnO-NPs on the viability of SH-SY5Y cells. Our results showed that ZnO-NPs diluted from water-dispersed stock solution caused significant cell death at a much lower dose compared to their counterpart diluted from the phosphate-buffered saline (PBS)-dispersed stock solution. Electron microscopic data indicated that ZnO-NPs from the PBS-dispersed stock solution form much larger agglomerates compared to the one from the water-dispersed stock solution. From these data, we can conclude that the types of media used for particle dispersion impact the change in the physical property and cytotoxicity of ZnO-NPs.

In the present study, aluminum alloy (Al/3.25Cu/8.5Si) composites reinforced with fly ash particles was fabricated using stir casting technique. Fly ash particles of three different size ranges 53–75, 75–103 and 103–125$\mu$m of 3, 6 and 9 weight percentages was reinforced in aluminum alloy. The effect of peak current, pulse on time, and pulse off time on surface roughness (SR), material removal rate (MRR) and tool wear rate (TWR) of electric discharge machining (EDM) was investigated. A central composite design using response surface methodology (RSM) was selected for conducting experiments, and mathematical models were developed using Design Expert V7.0.0 software. Analysis of variance (ANOVA) technique was used to check the significance of the models developed. Peak current was the major factor influencing the EDM of aluminum fly ash composites. The MRR, TWR, and SR of aluminum fly ash composites were also influenced by the size of the fly ash particles.

In this paper, perforations of 12mm thick Weldox 460E steel plates by 20mm diameter blunt projectiles are simulated based on Two-dimensional Smoothed Particle Hydrodynamics method (SPH), and the modified Johnson–Cook (MJC) material model is adopted. To describe the shear plugging process, the particle approximation between different materials is canceled, and only the particle contact model based on the principle of conservation of momentum is applied. Then the separation of projectile and plug is simulated successfully, which is consistent with the experimental observations. Furthermore, it can be found that the particle size has a great influence on the calculation by comparing the effects of the different SPH particle sizes on plugging calculations. In general, the smaller the particle size is, the greater the residual velocity of projectile is. The residual velocities are tending towards stability as the decrease of particle size. Taking computational efficiency and accuracy into consideration, 0.033 (size$=$0.4mm) is the most appropriate dimensionless particle size. Then, the effect of target thickness on perforation is conducted, which shows that the target thickness has certain influence on the global deformation of target. Moreover, the sensitivity of MJC material constants on the residual velocity of projectile is also analyzed and discussed using orthogonal experimental design method and the range analysis method. The results indicate that the most sensitivity parameter is yield strength $A$, followed by strain hardening modulus $n$ and strain hardening exponent $B$.

The unique characteristics of gas-solids two-phase flow and fluidization in terms of the flow structures and the apparent behavior of particles and fluid-particle interactions are closely linked to physical properties of the particles, operating conditions and bed configurations. Fluidized beds behave quite differently when solid properties, gas velocities or vessel geometries are varied. An understanding of hydrodynamic changes and how they, in turn, influence the transfer and reaction characteristics of chemical and thermal operations by variations in gas-solid contact, residence time, solid circulation and mixing and gas distribution is very important for the proper design and scale-up of fluidized bed reactors. In this paper, rather than attempting a comprehensive survey, we concentrate on examining some important positive and negative impacts of particle sizes, bubbles, clusters and column walls on the physical and chemical aspects of chemical reactor performance from the engineering application point of view with the aim of forming an adequate concept for guiding the design of multiphase fluidized bed chemical reactors.

One unique phenomenon associated with particle size is that fluidized bed behavior does not always vary monotonically with changing the average particle size. Different behaviors of particles with difference sizes can be well understood by analyzing the relationship between particle size and various forces. For both fine and coarse particles, too narrow a distribution is generally not favorable for smooth fluidization. A too wide size distribution, on the other hand, may lead to particle segregation and high particle elutriation. Good fluidization performance can be established with a proper size distribution in which inter-particle cohesive forces are reduced by the lubricating effect of fine particles on coarse particles for Type A, B and D particles or by the spacing effect of coarse particles or aggregates for Type C powders.

Much emphasis has been paid to the negative impacts of bubbles, such as gas bypassing through bubbles, poor bubble-to-dense phase heat & mass transfer, bubble-induced large pressure fluctuations, process instabilities, catalyst attrition and equipment erosion, and high entrainment of particles induced by erupting bubbles at the bed surface. However, it should be noted that bubble motion and gas circulation through bubbles, together with the motion of particles in bubble wakes and clouds, contribute to good gas and solids mixing. The formation of clusters can be attributed to the movement of trailing particles into the low-pressure wake region of leading particles or clusters. On one hand, the existence of down-flowing clusters induces strong solid back-mixing and non-uniform radial distributions of particle velocities and holdups, which is undesirable for chemical reactions. On the other hand, the formation of clusters creates high solids holdups in the riser by inducing internal solids circulations, which are usually beneficial for increasing concentrations of solid catalysts or solid reactants.

Wall effects have widely been blamed for complicating the scale-up and design of fluidized-bed reactors. The decrease in wall friction with increasing the column diameter can significantly change the flow patterns and other important characteristics even under identical operating conditions with the same gas and particles. However, internals, which can be considered as a special wall, have been used to improve the fluidized bed reactor performance.

Generally, desirable and undesirable dual characteristics of interaction between particles and fluid are one of the important natures of multiphase flow. It is shown that there exists a critical balance between those positive and negative impacts. Good fluidization quality can always be achieved with a proper choice of right combinations of particle size and size distribution, bubble size and wall design to alleviate the negative impacts.

Dissolution of nanoparticles is involved in the preparation, research and application of nanomaterials, but there is a surprising difference in dissolution thermodynamics between nanoparticles and the corresponding bulk materials. In the paper, the relations of dissolution thermodynamic properties, equilibrium constant of nanoparticles, respectively, and particle size were derived by introducing interface variables and the surface chemical potential. Experimentally, the solubility of nano-barium sulfate with different average particle sizes at different temperatures were determined by the method of electrical conductivity, obtaining the influencing regularities of particle size on the dissolution thermodynamic properties and the equilibrium constant. The regularities are in accordance with the theory. The results show that there are remarkable effects of particle size of nanoparticles on the dissolution thermodynamic properties and the equilibrium constant; with the decreasing of the size of nanoparticles, the dissolution equilibrium constant increases, while the standard dissolution Gibbs free energy, the standard dissolution enthalpy and the standard dissolution entropy decrease; and the logarithm of the dissolution equilibrium constant, the standard dissolution Gibbs free energy, the standard dissolution enthalpy and the standard dissolution entropy are linearly associated with the reciprocal of particle size, respectively. This new theory provides a quantitative description of nanoparticles dissolution behavior, and has important scientific significance for understanding and predicting of thermodynamic regularity of dissolution concerned in the preparation, researches and applications of nanomaterials.

The stability of 20wt.% Co/CNT catalyst was tested in the Fischer–Tropsch synthesis and the structural transformations both in the catalyst and support were analyzed. The catalyst showed high conversion and stable selectivity during three weeks of the test, which was attributed to the optimal and stable cobalt particle size of $\sim$13–14nm promoted by the support pre-oxidation. XPS, Raman, and nitrogen adsorption data revealed that the carefully chosen catalyst annealing and reduction conditions ensured the preservation of the support structure.

In this work, a facile ultrasonic method for the fabrication of AgCl quantum dots (AgCl QDs) with an average diameter of about 2.5nm was reported for the first time. The material was analyzed by various techniques. In addition, effects of material’s size on its photocatalytic activities were studied. Results suggested that the AgCl QDs exhibited excellent photocatalytic activity to degrade Rhodamine B (RhB) and tetracycline (TC) under visible light illumination, and the degradation rate of RhB (TC) had reached up to 96.6% (72.2%) in 20 min, which was higher than that of AgCl nanoparticles (23nm) and AgCl nanospheres (114nm), respectively. Besides, the band gap of the material was increased when the size of material decreased from 23nm to 2.5nm. The significantly improved photocatalytic performance and increased band gap of AgCl QDs were mainly related to the quantum size effects of AgCl, which results in the more electron fluctuation in quantized energy levels and the lower recombination of electrons and holes.

In this paper, carbon particles with micro- and nano-particle size were synthesized through a hydrothermal reaction of glucose, namely C-1(123.1 nm), C-2(229.2 nm), C-3(335.1 nm), C-4(456.2 nm) and C-5(534.0 nm) with distinct sizes. We utilized five size carbon particles as individual fillers into the EHS matrix materials to prepare composite eutectic phase change materials (C/EHS PCMs) by melt blending technique. The impact of carbon particle size on the dispersion stability and thermal properties of Na₂SO₄⋅10H₂O–Na₂HPO₄⋅12H₂O (EHS) phase change materials was investigated. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis were done to analyze the diameters of carbon particles. The cryogenic-scanning electron microscopy (Cryo-SEM) analysis indicated that the carbon particles resulted in modification in the morphology of the EHS. The results of in situ X-ray diffraction (XRD) and Fourier-transformed infrared (FTIR) analysis showed only simple physical mixing between carbon particles and EHS. It is shown that adding 0.2 wt.% C-2 can decrease the supercooling degree of EHS to 1.5${}^{\circ }$C. The cyclic stability of C/EHS varies significantly depending on the size of carbon particles. The thermal conductivity of EHS increased by 42.1%, 39.9%, 14.4%, 19.5%, and 18.8% with the addition of C-1, C-2, C-3, C-4, and C-5, respectively, at a mass fraction of 0.2%. The results of differential scanning calorimetry reveal that the incorporation of C-1, C-2, C-3, and C-4 into EHS leads to an enhancement of latent heat. The latent heat capacity of EHS with 0.2 wt.% C-2 is 243.4 J⋅g${}^{-1}$, and after undergoing 500 cycles of solid-liquid phase transition, the latent heat remained above 200 J⋅g${}^{-1}$. Through the comprehensive analysis, the C-2/EHS composite phase change material holds significant potential for advancing building insulation and solar energy storage technologies.

Nanofluid is a suspension of nanoparticles (solid particles with diameters below 100 nm) in a conventional base fluid with significantly improved heat transfer characteristics compared to the original fluid. The heat transfer coefficient is a quantitative characteristic of the convective heat transfer. The purpose of this paper is to study the effect of the nanoparticle size (diameter) on the heat transfer coefficient of forced convective heat transfer of nanofluid in the fully developed laminar region of a horizontal tube. Using thermal conductivity model which is a function of the nanoparticle size, flow of a nanofluid (water + Al₂O₃) in a circular tube submitted to a constant wall temperature is numerically investigated with two particle sizes of 11 nm and 47 nm. The calculated results show that the nanoparticle size does not significantly affect the heat transfer coefficient, however, the heat transfer coefficient decreases as the particle size increases.

Diffuse reflectivity in the longer wavelength region after the absorption edge was studied on the LaTiO₂N nitrided. It was discussed in the viewpoint of particle sizes by use of ball milling and bead milling technique. The diffuse reflectivity after absorption edge of the LaTiO₂N powders got lower in accordance with the reduction of particle sizes. In case of LaTiO₂N aqueous suspension after the bead-milling treatment in which the primary particles were well dispersed, remarkable enhancement of the diffuse reflectivity was observed with decreasing the average particle sizes.

A wear model is developed based on the discrete lattice spring–mass approach to study the effects of particle volume fraction, size, and stiffness on the wear resistance of particle reinforced composites. To study these effects, we have considered three volume fractions (10%, 20% and 30%), two sizes ($10\times 10$ and $4\times 4$ sites), and two different stiffness of particles embedded in the matrix in a regular pattern. In this model, we have discretized the composite system ($400\times 100$ sites) into the lumped masses connected with interaction spring elements in two dimensions. The interaction elements are assumed as linear elastic and ideal plastic under applied forces. Each mass is connected to its first and second nearest neighbors by springs. The matrix and particles sites are differentiated by choosing the different stiffness values. The counter surface is simulated as a rigid body that moves on the composite material at a constant sliding speed along the horizontal direction. The governing equations are formed by equating the spring force between the pair of sites given by Hooke’s law plus external contact forces and the force due to the motion of the site given by the equation of motion. The equations are solved for the plastic strain accumulated in the springs using an explicit time stepping procedure based on a finite difference form of the above equations. If the total strain accumulated in the spring elements connected to a lump mass site exceeds the failure strain, the springs are considered to be broken, and the mass site is removed or worn away from the lattice and accounts as a wear loss. The model predicts that (i) increasing volume fraction, reducing particle size and increasing particle stiffness enhance the wear resistance of the particle reinforced composites, (ii) the particle stiffness is the most significant factor affecting the wear resistance of the composites, and (iii) the wear resistance reduced above the critical volume fraction (${\mathrm{\text{V}}}_{\mathrm{\text{c}}}$), and ${\mathrm{\text{V}}}_{\mathrm{\text{c}}}$ increases with increasing particle size. Finally, we have qualitatively compared the model results with our previously published experimental results to prove the effectiveness of the model to analysis the complex wear systems.

To determine the optimal dispersion conditions of graphene flakes for ink, its heat dissipation properties were investigated by changing the particle size, dispersant, and binder types. In the case of particle size, the smaller the size of the graphene flakes, the better the dispersion, and regardless of the amount of dispersant and the type of binder, the greatest dispersion effect was exhibited by the mixed dispersant. Under these conditions, internal cohesion did not occur as in Newtonian flow over time, and for this reason, heat was released quickly, with a rapid cooling rate. It is clear that this process of determining the optimal dispersion conditions considering multiple factors will provide a good reference for determining dispersion conditions for various variables in the future.

Within the last 20 years, advances in characterization methods, particularly in the field of high-resolution electron microscopy, have made it possible to probe the surface and internal structure of sub-100 nm particles, or nanoparticles. Such studies have indicated conclusively that surface-energy considerations in metal nanoparticles cause these particles to adopt structures which only approximate to close packing but are terminated by close-packed faces. In oxides, where stoichiometry must be maintained, the adoption of low-index crystallographic faces almost invariably necessitates the introduction of cation or anion vacancies, and both have been observed. In such cases, the structure at the edges of the particles differs greatly from that of bulk phases, and it seems highly probable that the physical and chemical properties of these particles are also different. In certain cases it appears that new structural types, found only in nanoparticulate form, may exist. The significance of these findings, particularly as regards their relevance to particulate pollutants in the atmosphere, may be of great interest.

The use of by-products from fruit and vegetable processing plants as sources of dietary fiber and bioactive agents is currently of interest. This work was aimed at studying effect of the drying (60°-80°C) on the hydration properties of cabbage powder, i.e. water holding capacity (WHC) and swelling capacity (SWC). The moisture contents of high dietary fiber powder from cabbage were in the range of 6-8% (wet basis) or 6.4-8.7% (dry basis) which lowered than the desired moisture content (less than 9% (wet basis)) recommended for the commercial dietary fiber powder. Drying temperature did not have a significant effect on the total dietary fiber contents of cabbage outer leaves (40.50-43.15 %). Insoluble dietary fiber (IDF) contents were much higher than the soluble dietary fiber (SDF) contents leading to the SDF:IDF ratios of 1:7.5 to 1:7.8. The effect of particle size of fiber powder in the range of 63-450 μm, on the hydration properties was also evaluated. Decreasing the particle size of cabbage outer leaves resulted in decreasing of WHC and SWC. Comparing at similar particle size, WHC and SWC of outer leaves of cabbage fiber powder were not significantly different among 60°-80°C drying temperatures.

It is difficult for conventional polymer flooding to achieve a good profile control because most oilfields have been flooded with water for a long period of time and the long-term water injection erosion will lead to increase in heterogeneity of the reservoirs. Effective encapsulation of 3-(N,N-dimethylpalmitylammonio) propanesulfonate-cetyltrimethyl ammonium bromide-montmorillonite particles (SB-CTAB-MMT) with polyacrylamide (PAM) polymers was achieved by reactive potassium persulfate (KPS) initiator and methylene-bis-acrylamide (MBA) cross-linker system in an inverse phase suspension polymerization. The characterizations of electron microscopies, X-ray diffraction (XRD), and BZY-2 automatic surface tension apparatus showed that, in the encapsulation process, MMT layer exfoliations presented PAM/SB-CTAB-MMT nanocomposite microspheres, and tuned their particle size distribution. The nanocomposite microsphere samples had molecular mass over 5 × 10⁶, an average particle size from 10 μm to 15 μm with narrow size distribution, and smooth surface morphology. XRD patterns clearly proved MMT layer exfoliations in the polymer matrix, which was consistent with TEM analysis. These nanocomposite microspheres showed low interfacial tension, which may be the candidate materials for oil recovery in oil and gas engineering.