Spherical Composite Particles Research Articles

Preparation of spherical NiO-8YSZ composite powder through spray drying

Homogeneous sphere NiO-8YSZ composite powder with a narrow size distribution is significant for the fabrication of high-quality solid oxide fuel cell (SOFC) anodes. In this study, spray drying was used to prepare evenly distributed and spherical NiO-8YSZ composite particles used for the fabrication of SOFC anodes. The result showed that the particles prepared with a solid content of 65 wt %, atomizing pressure of 60 kPa, drying temperature of 180 °C, and sintering at 1200 °C for 2 h exhibited the best holistic quality with high sphericity (90 % over 0.84), narrow size distribution (D10 = 27.78 μm, D90 = 45.49 μm), high collection rate (70 %), and low content of unstable phases. The influence of these main parameters on the quality of the prepared particles was investigated and discussed as well. It was found that the solid content and the atomizing pressure demonstrated opposite effects on the particle size, with the former showing a positive correlation and the latter showing a negative correlation. The drying temperature decided the agglomeration degree of the prepared powder, which was involved in the presence of grape-like particles. In addition, the collection rate appeared to be positively correlated with the solid content and the atomizing pressure. The atmospheric plasma sprayed coating fabricated using the sprayed-dried powder prepared with the optimal parameters demonstrated significantly improved micromorphology and structure when compared with the coating fabricated using the mechanical mixed composite powder, which proved the prominent advantage of the powder produced through this spray drying method. All these progresses were considered good instructions for the studies on powder granulation and its applications in manufacturing high-quality coating materials.

Fabrication and evaluation of stable amorphous polymer-drug composite particles via a nozzle-free ultrasonic nebulizer

We present a promising method for producing amorphous drug particles using a nozzle-free ultrasonic nebulizer with polymers, specifically polyvinylpyrrolidone (PVP), poly(acrylic acid) (PAA), and Eudragit® S 100 (EUD). Model crystalline phase drugs–Empagliflozin, Furosemide, and Ilaprazole–are selected. This technique efficiently produces spherical polymer-drug composite particles and demonstrates enhanced stability against humidity and thermal conditions, compared to the drug-only amorphous particles. The composite particles exhibit improved water dissolution compared to the original crystalline drugs, indicating potential bioavailability enhancements. While there are challenges, including the need for continuous water supply for ultrasonic component cooling, dependency on the solubility of polymers and drugs in volatile organic solvents, and mildly elevated temperatures for solvent evaporation, our method offers significant advantages over traditional approaches. It provides a straightforward, flexible process adaptable to various drug-polymer combinations and consistently yields spherical amorphous solid dispersion (ASD) particles with a narrow size distribution. These attributes make our method a valuable advancement in pharmaceutical drug formulation and delivery.

Self‐templated magnesiothermic reduction of ORMOSIL particles to monodisperse hollow spherical SiC composite particles

AbstractHollow silicon carbide (SiC) particles have attracted attention due to their well‐defined morphology, low density, and large surface area that can be leveraged for a wide variety of applications. Here, we report the self‐templated synthesis of monodisperse hollow spherical SiC composite particles with controllable shell thicknesses using magnesiothermic reduction of organically modified silica (ORMOSIL) particles. Monodisperse ORMOSIL particles containing three organic groups of methyl, vinyl, and mercaptopropyl were produced by a simple one‐pot sol–gel process and then converted to hollow spherical SiC composite particles via a magnesiothermic reduction at 700°C under an inert atmosphere. The spherical morphologies of the original ORMOSIL particles were well maintained through this self‐templated conversion process, but the sizes of the hollow SiC particles were slightly reduced by the thermal treatment. Field emission transmission electron microscopy studies revealed that the shell of hollow particles mainly consists of primary β‐SiC particles with nanometer‐scale sizes. The physical and chemical properties of the hollow SiC composite particles were investigated by scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller, X‐ray diffraction, Fourier transform infrared spectroscopy, Raman, and solid‐state nuclear magnetic resonance analyses. The shell thickness of hollow spherical SiC composite particles can be controlled by simply changing the duration of the thermal conversion process. This study not only provides a simple and easy approach for the preparation of hollow spherical SiC particles but also opens the possibility of large‐scale manufacturing of such particles for commercial applications.

A two-step strategy for production of spherical non-aggregated multi-component particles by suspension-fed spray flame

For applications in optics, energy storage, and semiconductors etc., spherical non-aggregated particles are desired for better flowability, molding capability and homogeneous densification. Spray flame synthesis has attracted widespread attention with its excellent ability for atomic-level mixing/doping and good potential for scale-up production. However, spray flame synthesis usually produces aggregates due to the known collision-coalescence growth. In this paper, we propose a two-step strategy of suspension-fed spray-flame synthesis. The first step involves the synthesis of aggregated nanoparticles, followed by a second step where these aggregates are reconstructed into spherical non-aggregated particles while retaining the advantage of atomic-level homogeneous mixing. It is found that for aggregated Y2O3 nanoparticles, the critical point for reconstructing into spherical particles occurs when the flame temperature exceeds the melting point. The spherical particle size increases with the solid concentration of the suspension by a power of about 0.28. Assuming that droplets do not undergo micro-explosions and instead follow a one droplet to one particle route results in an overestimation of particle size by a factor of 6 to 8. This discrepancy suggests that micro-explosions may play certain role in the new suspension-fed flame synthesis, and largely reduces the final particle size. Furthermore, the Al2O3-Y2O3 and MgO-Y2O3 particles are selected for the multicomponent suspension-fed synthesis, representing the miscible and immiscible systems, respectively. The results show that for the Al2O3-Y2O3 system, uniformly mixed spherical non-aggregated particles are obtained. For the MgO-Y2O3 system, both composite spherical particles with pinning structure and MgO nanoparticles are identified, indicating that for obtaining spherical multi-component non-aggregated particles, the flame temperature needs to be higher than not only the eutectic component's melting point but also any single component's melting point. Overall, suspension-fed spray flame synthesis opens up a new pathway for the low-cost industrial-scale production of spherical non-aggregated multi-component particles.

Preparation of porous CoNi/N-doped carbon microspheres based on magnetoelectric coupling strategy: A new choice against electromagnetic pollution

Magnetoelectric coupling is a key strategy to obtain high-performance microwave absorption materials. Especially for carbon matrix composites, the absorbing capacity can be optimized via the tuning of the graphitization degree and the content ratio of the magnetic and dielectric components. Based on this theory, a simple strategy, consisting of the solvothermal method and annealing in an inert atmosphere, is adopted in this study to combine CoNi magnetic alloys with graphitized carbon into micron-scale composite spherical particles. Additionally, special attention is paid to the correlation among the graphitization degree of carbon matrix, component proportion, and dielectric response ability, so as to achieve a flexible micromorphology design and a tunable microwave absorption performance. When the pyrolysis temperature is offset to the best of 700 ℃, a broadband absorption of 6.61 GHz (reflection loss < − 10 dB) is achieved at an ultrathin matching thickness of 1.9 mm. Adjusting the carbon content can further optimize the impedance matching and realize a high-intensity absorption with a reflection loss of − 72.7 dB. Our work proposes a useful strategy to realize the effective combination of the magnetic and dielectric loss mechanisms and boost the microwave absorption capacity toward achieving the desired broadband and a high-efficiency absorption performance.

Investigating the role of filler shape on the dynamic mechanical properties of glass‐filled epoxy composites

AbstractThe influence of filler shape and volume fraction on the dynamic mechanical characteristics of rigid glass filler epoxy composites is investigated. Two variants of glass fillers, spherical particle and slender (milled) fibers, are doped into the epoxy matrix till 10% volume fraction. The composites are room temperature cured and tested to measure their viscoelastic properties. The dynamic mechanical analyses performed in the temperature range of 20–180°C at 10 Hz suggest that the milled fiber composites display consistently higher storage and loss moduli, whereas the higher loss factor peaks were noted for the spherical particle composites. The C‐factor, filler reinforcement efficiency of the composites and entanglement density, evaluated from the storage modulus values, indicate that the milled fibers composites are more effective in transferring the loads in both glassy and rubbery zones when compared against the spherical particle case. Also, the filler/matrix adhesion factor (A factor) and the interphase adhesion factor, calculated from the loss factor curves reveal stronger filler/matrix interactions in the case of milled fiber epoxy composites. Interestingly, the filler geometry or volume fraction has only marginal influence on the glass transition temperature of the composites.

A facile method to prepare layered solid fillers-based polymer composites with isotropic thermal conductivity

Layered solid particles such as hexagonal boron nitride (h-BN) and graphite have been employed as anisotropic thermo-conductive fillers in polymer composites. To meet the recent requisite capability of thermal interface materials (TIMs), facile methods to prepare polymer composites with isotropic thermal conductivity utilizing the layered solid fillers have been desired. We accomplished to prepare composites of epoxy and the layered solid fillers with isotropic thermal conductivity. Production of spherical composite particles followed by compression forming of them yielded the polymer composites with isotropic thermal conductivity. The solids loading of the obtained polymer composites surpassed 60 vol%. The thermal conductivity values of the prepared specimens were ∼ 8 Wm−1K−1 for the h-BN/epoxy composite and 28 ∼ 29 Wm−1K−1 for the graphite/epoxy one. The internal solid fillers configuration achieved by integration of the spheres was studied by X-ray diffraction analysis.

A novel approach of fabricating monodispersed spherical MoSiBTiC particles for additive manufacturing

It is very challenging to fabricate spherical refractory material powders for additive manufacturing (AM) because of their high melting points and complex compositions. In this study, a novel technique, freeze-dry pulsated orifice ejection method (FD-POEM), was developed to fabricate spherical MoSiBTiC particles without a melting process. Elemental nanopowders were dispersed in water to prepare a high-concentration slurry, which was subsequently extruded from an orifice by diaphragm vibration and frozen instantly in liquid nitrogen. After a freeze-drying process, spherical composite particles with arbitrary composition ratios were obtained. The FD-POEM particles had a narrow size range and uniform elemental distribution. Mesh structures were formed within the FD-POEM particles, which was attributed to the sublimation of ice crystals. Furthermore, owing to their spherical morphology, the FD-POEM particles had a low avalanche angle of 42.6°, exhibiting good flowability. Consequently, the combination of FD-POEM and additive manufacturing has great potential for developing complex refractory components used in industrial applications.

Elastic equilibrium of spherical particle composites with transversely isotropic interphase and incoherent material interface

The rigorous analytical solution to the unit cell model of spherical particle composite with transversely isotropic interphase and incoherent material interface has been obtained by the multipole expansion method. To this end, a general expression of the displacement vector in spherical transversely isotropic solid in terms of the vector spherical harmonics has been derived. By accurate fulfillment of the contact conditions, the model boundary value problem is reduced to the linear algebraic system. The anisotropic interface model has been developed as the first order approximation of the transversely isotropic interphase. Relevance of this model to the theory of material interfaces and its applicability in the nanomechanics context is discussed. The developed model expands the theory of curved deformable interfaces of Gurtin et al. [Phil. Mag. A 78 (1998) 1093] on the incoherent interfaces between the dissimilar elastic materials and provides a certain insight into the interface elastic moduli. Taking incoherency of the nano level interfaces into account enables more realistic models and thus increases the predictive power the homogenization theory of nanostructured solids. The obtained accurate numerical data discover a significant effect of the interphase/interface anisotropy on the local stress and effective stiffness of spherical particle composite.

Conductivity and elastic stiffness of spherical particle composite with partially disordered microstructure

The spherical particle composite with the microstructure varying from perfectly ordered to completely disordered is considered. The partially disordered periodic packings of spheres are generated in the framework of the reprehensive unit cell model with aid of the Metropolis algorithm. The orientation order invariants Qi introduced by Steinhardt et al. [Phys. Rev. B 28 (1983) 784] in the molecular physics context are taken as the structural parameters providing a quantitative measure of disorder. Variation of these parameters due to gradual disordering of the cubic symmetry packings has been studied by means of computer simulation. The effective conductivity and elastic moduli of the spherical particle composites with partially disordered periodic microstructure is found by the multipole expansion method. Numerical study discovers a close relationship between the order metrics and macroscopic properties of composite. The micromechanics-prompted approximation of this relationship is suggested and tested on the numerical data obtained by computer simulation.

Mesoporous silicate/alginate composites as a carrier for amitriptyline hydrochloride and in vitro release

The objective of this research is to prepare mesoporous silica (M41) based nanomaterials and encapsulate in the solid polymeric matrix for controlled drug release application. Amitriptyline (AT) -loaded M41/sodium alginate (AL) composite microparticles were prepared by the ion exchanged gelation techniques. Composite microparticles were characterized by FT-IR spectroscopy; surface area analysis and scanning electron microscopy. Here we propose mesoporous silica (M41) for loading of hydrophilic drug, amitriptyline (AT) and further constructed drug loaded M41 into a pH-responsive alginate microparticles. The resulting drug loaded composites microparticles was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), particle size and zeta potential analyzer. Drug loading was confirmed by the decrease of specific surface area and pore volume in the drug loaded composites as well microparticles. The morphology of drug loaded hybrid nanomaterials and composite micro spherical particles were evaluated by scanning and transmission electron microscopy (SEM and TEM, respectively) measurements. The AT release from microspheres composites was pH dependent, and the release rate was much lesser in gastric pH than that in intestinal pH media. Thus, the biocompatible composite spherical particles hold the substantial potential to be further developed as effective and safe drug-delivery carriers. Drug release kinetics ( in vitro in simulated gastric and intestinal fluids) showed that both of them were affected by the properties of materials. The release profile of AT from composites was best fitted in Higuchi kinetic model while the Korsmeyer–Peppas model suggested a non fickian diffusion release mechanism. Such formulations show potential as an efficient controlled drug delivery system.

Preparation of cylinder-like polystyrene-silica composite particles

The cylinder-like shape is one of the most common shapes in geometry and polymer-silica composite particles have been one of the most commonly reported organic-inorganic composite particles, while cylinder-like polymer-silica composite particles are seldom reported in literature. In this work, we report a facile method to prepare cylinder-like polystyrene-silica (PS–SiO2) composite particles by judicious combination of PVP-involved dispersion polymerization and magnetic stirring. First, spherical PS-SiO2 composite particles were synthesized by dispersion polymerization of styrene in an ethanol/water mixture. Second, cylinder-like PS-SiO2 composite particles were prepared by stirring the spherical PS-SiO2 particles in a water medium in the presence of PVP. The effects of PVP molecular weight, PVP concentration, stirring rate, stirring time and stirring temperature on the morphology of the composite particles were investigated. Optimization of the stirring conditions allowed relatively high percentage (up to ~73%) of cylindrical particles to be achieved. This method is expected to expand the morphology library of polymer-silica composite particles.

The synthesis and water-swelling performances of magnetic composite microspheres with multi-shell structures via a combination method

Magnetic composite polymeric microspheres have several technical advantages in improving oil recovery applications. Swelling and stability are key properties that are a direct result of water shutoff efficacy. However, the important aspect of swelling and stability is the materials of the microspheres. In this paper, multiple–shell structures of magnetic hybrid composite spherical particles with different materials which were Fe3O4@SiO2@PAM, Fe3O4@TiO2@PAM, Fe3O4@SiO2@PAM-MBAAm were synthesized via a combination method and theirs physical properties including morphology, particle size distribution, and water swelling property were thoroughly examined. Meanwhile, the plugging performances were studied. The main goal of this paper was to investigate effect of materials of constituents on swelling properties of microspheres. The results demonstrate that both inorganic and organic constituents can affect the swelling properties of microspheres. Moreover, plugging properties of microspheres with different components are different at different salt concentrations, temperatures and pH values. Meanwhile, the results also open up possibilities for studying on the system of heat-resistant, salt-resistant, and pH-resistant oil displacement agent.

Preparation of submicron-sized Sm2Fe17N3 fine powder by ultrasonic spray pyrolysis-hydrogen reduction (USP-HR) and subsequent reduction–diffusion process

A new reduction–diffusion method for preparing submicron-sized Sm2Fe17N3 was developed. First, submicron-sized α-Fe/Sm2O3 composite precursors with good dispersibility were prepared directly by ultrasonic spray pyrolysis and hydrogen reduction (USP-HR). Then, the precursor was successfully converted into Sm2Fe17N3 powder by Ca reduction–diffusion and nitridation. The results displayed that the precursor prepared by USP-HR was a monodisperse homogeneous composite of spherical particles of α-Fe and Sm2O3. α-Fe and Sm2O3 exist in an intercalated structure in the composite spherical particles. This creates conditions for the preparation of ultrafine Sm2Fe17N3 particles with uniform sizes and dispersity. The results show that Sm2Fe17N3 is a single-phase, composed of submicron-sized particles with no other impurity phases. The physical property measurement system shows that the coercivity of 0.616 ± 0.347 µm particles reaches 14.7 kOe.

Fabrication of Magnetic α-Fe2O3/Fe3O4 Composite Particles by Nanosecond Laser Irradiation of α-Fe2O3 Powder in Water

Magnetic α-Fe2O3/Fe3O4 composite spherical particles were synthesized by nanosecond pulsed laser irradiation to α-Fe2O3 nanoparticle powder suspended in pure water and acetone. It was shown that the laser-induced reduction efficiencies in two solvents were comparable. The obtained submicrometer spheres exhibited a ferromagnetic property having a higher coercivity than that of commercial Fe3O4.

Compaction of a two-dimensional system of composite spherical particles under the influence of self-gravitation: Between lock-and-key model and Tetris-structure

A self-gravity ofspherical granular particles in the two-dimensional system is simulated. Some of the spherical particles are bonded through a spring force to form composite particles. These spherical and composite particles are attracted to each other due to gravitational force and prevented from collapse into a single point by the normal force. A previous study reported that a two-dimensional monodispersed system will form a hexagonal close-packed (HCP) configuration. In this work, it will be perturbed by some of the composite particles that could have HCP form, simple cubic (SC) form, or a mix of SC-HCP (MSH) form. These forms can be categorized into SC family (□, I, L, T, F, H, E), HCP family (Δ, □, V, X), and MSH family (⌂, K, M, W, N, Z), that can be compacted to maximum contactopy through lock-and-key mechanism (KL). The compaction of some forms from the SC family is similar to the Tetris game, where the structure should be compacted before it could be eliminated in the game. In this work, not all forms from the three families are simulated. The particles in general tend to form a final configuration with the most compact form and the composite particles seems also to influence their surrounding particles to construct the configuration.

Custom particle morphology in energetic nanocomposites prepared by arrested reactive milling in immiscible liquids

The effect of polar and nonpolar liquid process control agents (PCA) on properties of metal rich Al/CuO thermites prepared by Arrested Reactive Milling was studied. Acetonitrile and hexane, and their mixtures were used as PCA. Milling in nonpolar hexane results in fully dense, micron-sized composite particles of 100nm-scale CuO inclusions in an Al matrix. Using polar acetonitrile results in a mixture of nano-sized, largely unagglomerated Al and CuO particles. Porous composites, agglomerated to different degrees, formed in hexane-acetonitrile mixtures. In particular, micron-sized porous spherical composite particles formed in a mixture with 25% acetonitrile. Such spherical composites may result from interaction of suspended powder particles with stressed droplets of a Pickering emulsion forming when immiscible liquids serve as PCA. Despite dramatic changes in the powder morphology, all composites were reactive. Systematic differences, discussed in the text, were observed in their ignition temperatures and oxidation kinetics.

Effective viscosity of a concentrated suspension of composite porous spherical particles

We present an analytical study of the effective viscosity of concentrated suspension of porous spherical particles with a rigid core, under the creeping flow conditions. It is assumed that the individual particle is surrounded by a hypothetical fluid envelope. This model is popularly known as cell model, which takes into account the interaction of neighboring particles. The flow fields inside the free flow region and porous region are governed by Stokes equation and Brinkman equation together with mass conservation, respectively. The effective viscosity of the suspension depends on various parameters such as, radii of the fluid envelope and porous particle, permeability of the porous particle and further on the type of boundary condition at the outer cell, volume fraction etc. Various limiting cases are obtained and compared with earlier existing results in literature both theoretical and experimental.

Dynamic compression behavior of glass filled epoxy composites: Influence of filler shape and exposure to high temperature

The effect of filler shape, volume fraction and high temperature cycle on the dynamic compression behavior of rigid particle filled polymer composite is demonstrated by performing experiments using split-Hopkinson pressure bar (SHPB) setup. Two glass filler variants, spherical particles and milled fibers, are reinforced into epoxy matrix upto 10% volume fraction. Two sets of test specimens are prepared; room temperature cured (RTC) and high temperature exposed (HTE) - the ones prepared by subjecting RTC composites to a temperature cycle beyond their glass transition temperature (Tg). The yield stress of milled fiber composites which are consistently higher in HTE cases increases with increasing filler volume fraction whereas it remains nearly constant in all spherical particle composites. While RTC materials exhibit strain softening characteristics, the post-yield strain hardening behavior of HTE composites is attributed to the increased cross-link density of epoxy matrix. Debonded fillers and their foot-prints on the crushed surfaces of HTE composites indicate the relaxation of residual stresses, developed at the filler/matrix interface during curing process. Computational analyses suggest that the average matrix stress in composites remains unaffected by the shape of the inclusions whereas comparatively higher inclusion stresses indicate that slender fillers provide better resistance to deformation when compared to the circular ones. Near constant stresses in circular inclusions at low volume fractions is attributed to the large inter-particle separation. Computational results complement experimental observations where the milled fiber composites consistently exhibited higher yield stress when compared the spherical particle counterparts.

A 3D network structured reduced graphene oxide/PtRu alloyed composite catalyst in-situ assembled via particle-constructing method

Polystyrene (PS) microspheres are wrapped by reduced graphene oxide (rGO) nanosheets based on the thermodynamically driven heterocoagulation method, and in order to acquire PS/rGO@PtRuNPs composite particles, the resultant PS/rGO composite particles should be used as matrix to deposit Pt-Ru alloyed nanoparticles (PtRuNPs), taking unique advantages of both alloying effect and the 3D structure. A distinct 3D graphene/PtRu alloyed composite catalyst is fabricated by in-situ stacking of the ternary composite particles, which has double network channels for both electrons and reaction solution. The rGO sheets on the surface of the PS microspheres are interconnected interrelated with each other to construct a 3D network structure, while a interconnected gap among the spherical composite particles forms the other network for the reaction solution to spread into the composite catalyst. The influence of different Pt/Ru ratio on the catalytic activity for methanol oxidation is investigated, and under the obtained optimal Pt/Ru ratio, the most effective and economical noble metal consumption is further explored through changing the ratio of metal to graphene. As a result, the PS/rGO@PtRuNPs ternary composite catalyst has better catalytic activity than close-stacked rGO/PtRuNPs catalyst.