Control Of Particle Morphology Research Articles

Synthesis of metal powders via reduction of carbonates in self-stirred autoclave

Abstract Commercial carbonates were used as the metal sources for synthesis of metal powders, and a self-stirred autoclave device was proposed to accelerate the complete reduction of carbonates. Fluent software was employed to simulate the system and analyze the distribution of the solution and particles in the autoclave, Ni and Cu powders were synthesized to verify the experiment’s feasibility. Results indicate that sufficient mixing of reactants, solvents, and intermediate products is maintained in the improved self-stirred autoclave throughout the reaction process, facilitating the full reduction of carbonates and enhancing the uniformity of metal powders. Additionally, because basic carbonates can neutralize the hydrogen ions produced by the reduction reaction, and thus Ni powders can be synthesized without NaOH added, which is beneficial for controlling particle morphology and saving reaction time. Well-dispersed Ni and Cu powders were synthesized via the present route, which is possible to promote the reduction preparation of ultrafine metal powders for other insoluble and slightly soluble metal salts.

Enhanced electrochemical performance of the LiMn0.6Fe0.4PO4/C modified by secondary particle morphology control combined with primary particle size control

Enhanced electrochemical performance of the LiMn0.6Fe0.4PO4/C modified by secondary particle morphology control combined with primary particle size control

Reinforcement learning for the optimization and online control of emulsion polymerization reactors: Particle morphology

Online control of emulsion polymerization reactors is challenging due to the complex nature of the polymerization process, which causes difficulties not only for online measurement, but also for real-time prediction and optimization of future trajectories. In this work, the use of reinforcement learning (RL) to overcome these challenges is explored for the case of online control of particle morphology. It is shown in silico that assuming knowledge of the system dynamics in the form of a mathematical model, reinforcement learning can be used to train a neural network that can select optimal control actions in real-time to target a desired final polymer product. Moreover, it is shown that a second neural network model can be utilized as a state estimator to allow for full online control of particle morphology, which cannot be directly measured online. This work highlights the potential of machine learning for optimization and control in challenging polymerization systems.

Study on morphology and N-doping effects of carbon cathodes for zinc-ion hybrid supercapacitors

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) are spotlighted as next-generation energy storage devices; however, the carbon cathodes usually dictate their performance. Herein, we aim to optimize the electrochemical performance of the carbon cathodes through particle morphology control along with porosity and surface-active site control. N-doped spherical mesocelluler carbon foam (S-MCF-N) is synthesized using a mesoporous silica template, and spherical mesocelluler carbon foam (S-MCF) and irregularly shaped mesocellular carbon foam (MSUF-C) are synthesized as control samples. Consequently, S-MCF-N shows the best ion storage capability with its large surface area, with active sites that cause redox reactions and high electrical conductivity. In particular, the spherical morphology of S-MCF-N achieves a higher tap density and can reduce the electrode thickness, which decreases the diffusion length for electrolyte migration and electrode resistance. Therefore, S-MCF-N as the cathode materials deliver a specific capacitance of 208 F g−1 at 0.2 A g−1 and superb cycling stability of up to 7000 cycles at 5 A g−1 without capacity decay. Furthermore, benefiting from the reduced electrode thickness, S-MCF-N has a 112 % higher volumetric energy density than MSUF-C while showing a 42 % higher gravimetric energy density.

Quantitative Determination of the Compositional Inhomogeneity in NMC Cathode Materials by Williamson-Hall Analysis

Over the past decades, the co-precipitation synthesis technique has been used, particularly for making LiNixMnyCozO2 (NMC) cathode materials for lithium-ion batteries (LIBs), due to better control of particle morphology and higher compositional homogeneity in the final NMC product compared to other methods. However, the co-precipitation method introduces complexity and consumes large amounts of energy and water, which can increase cost. This has led researchers to investigate solid-state NMC synthesis techniques in order to improve sustainability and reduce LIB cost [1-3]. Obtaining homogeneous mixing of transition metals at the atomic scale by solid-state methods remains a challenge. Since compositional homogeneity has a vital effect on the electrochemical performance of the NMCs, it is essential to quantitatively estimate the degree of inhomogeneity in cathode materials for the development of new synthesis methods.In the present study, a quantitative X-ray diffraction (XRD) analysis technique using the Williamson-Hall (WH) method is used to determine the degree of inhomogeneity in NMC precursors and NMC cathode materials. In this regard, single-phase rock salt (RS) precursors with varying degrees of transition metal homogeneity were prepared by combining NiO, MnO and CoO by grinding for different times, followed by heating under an Ar flow. Then, NMC cathode materials were made by heating the RS-precursors with lithium carbonate in air. EDS elemental maps showed that transition metal inhomogeneity existed in the RS-precursors and final NMCs and that this inhomogeneity is primarily associated with the Mn distribution (Figure 1(a)). Furthermore, the compositional inhomogeneity became reduced with increasing precursor grinding time.Using a WH analysis method, composition variation in the NMC precursor and in the final NMC product could be quantitatively determined from conventional XRD powder patterns. Utilizing this analysis, it was found that inhomogeneity in the precursor is translated into the final NMC, so that a similar trend in the degree of inhomogeneity was observed for both synthesized precursors and their NMC products (Figure 1(b) and (c)). Additionally, NMCs with high compositional homogeneity showed much better electrochemical performance compared to the samples with higher degree of inhomogeneity. We believe the proposed method is highly useful in the development of new cathode precursors and in predicting the performance of the NMC cathode materials by quantitatively determining their degree of compositional inhomogeneity.

Particle morphology control for spherical powder fabrication using the ball milling process with DEM simulation

Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions, such as different ball diameters, high rotation speeds, and milling times, using a discrete element method (DEM) simulation. This experiment has investigated the characteristics of spherical particle morphology evolution involved in the mechanical alloying of copper powder. The morphological evolution of the copper particle was analyzed using scanning electron microscopy (SEM). A spherical copper particle was shown with a roundness value using imageJ software. The DEM was used to simulate the ball motion in a planetary ball mill, and the impact energy and shear energy generated during the collision were analyzed to estimate the contact number between the ball and the ball wall. Therefore, as the size of the ball decreased, the number of ball-to-ball and ball-to-wall contacts increased accordingly, and the spherical shape of the copper powder changed.

Silica-supported catalyst for the synthesis of low entangled UHMWPE suitable for solid-state processing

Different types of silica (mesoporous, spherical and nano-size particles), pre-activated with methylaluminoxane (MAO), are used to activate and support the bis[N-(3‑tert-butylsalicydene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride (FI) complex with the aim to synthesize low-entangled UHMWPE having controlled particle morphology. Through the porosity analysis, nitrogen adsorption and desorption isotherms, a decreased surfaced area of the chosen silica is observed when supported by MAO. From the bonding energy study by XPS, the bonding energy difference of Si and O, between the nano-size silica and in the MAO-nano silica, suggests the formation of Al-O-Si after chemical activation with MAO. Using elementary analysis, ICP-OES and XPS characterization, the aluminum content grafted on the silica surface is found to match with the anticipated amount of MAO on the MAO-Silica/FI catalytic system, indicating a stable grafting after catalyst supporting. From the rheological studies of the polymers, coupled with DSC results using an isothermal crystallization protocol, the resultant entangled state in the semi-crystalline polymers is estimated. The observations are that the entangled state achieved during polymerization from the investigated heterogeneous catalytic systems, is the lowest in PE-MAO-nano silica/FI, increases in PE-MAO-mesoporous silica/FI and is highest in PE-MAO-spherical silica/FI. Silica modification using two different silanes shows significant influence on the catalytic activity, giving lower polymer yield in MAO-modified-mesoporous silica and MAO-modified-nano silica compared to the unmodified MAO-silica. Whereas, no significant spatial effect is observed in the formation of chain entanglement, showing the increased entanglement density of the nascent polymers. By employing heterogeneous catalytic systems, reactor fouling and wall sheeting problems are resolved and the polymers show good morphology replication of the support. The UHMWPE synthesized using the nano silica as support, having the lowest entangled state and loosely packed crystals, can be uniaxially processed in the solid-state to a thin tape having thickness around 34 μm, showing maximum tensile strength of 3.26 N/tex and tensile modulus of 170 N/tex.

Film formation of high poly(vinyl chloride) content latex particles

Although poly(vinyl chloride) (PVC) is produced on a large scale industrially by emulsion and suspension polymerization, it is usually processed from the dry state and is seldom directly used as an aqueous polymer dispersion. In this work we demonstrate that by control of particle morphology and particle size distribution it is possible to produce latexes with high PVC content from which polymer films can be cast directly. A series of hybrid PVC/acrylic latexes with a core-shell structure are produced by semi-batch emulsion polymerization using a preformed PVC latex as a seed. Although monomodal particles of this type have a minimum film formation temperature in excess of 80 °C when the content of PVC is high, it is shown that through the use of a bimodal particle size distribution the packing efficiency of the spherical PVC domains is increased such that room temperature film formation is possible with PVC content up to 80 wt%.

Controllable synthesis of lignin nanoparticles with antibacterial activity and analysis of its antibacterial mechanism

As a kind of polyphenol substance, lignin is considered to have good biological activity and certain antibacterial properties. However, it is difficult to be applied because of its uneven molecular weight and difficulty in separation. In this study, by way of fractionation and antisolvent, we obtained lignin fractions with different molecular weight. Moreover, we increased the content of active functional groups and regulated microstructure of lignin, thereby increased lignin's antibacterial property. The classification of chemical components and the control of particle morphology also provided convenience for the exploration of lignin's antibacterial mechanism. The results showed that acetone with high hydrogen bonding ability could collect lignin with different molecular weights and increase the content of phenolic hydroxyl groups, up to 31.2 %. By adjusting the ratio of water/solvent (v/v) and stirring rate during the process of antisolvent, lignin nanoparticles (sphere 40–300 nm) with regular shape and uniform size can be obtained. Through observing the distribution of lignin nanoparticles in vivo and in vitro after co-incubation for different time, it could be found that lignin nanoparticles firstly damage structural integrity of bacterial cells externally, and then are swallowed into cells to affect their protein synthesis, which constitutes a dynamic antibacterial process.

Understanding ZIF particle chemical etching dynamics and morphology manipulation: in situ liquid phase electron microscopy and 3D electron tomography application.

In situ liquid phase transmission electron microscopy (TEM) and three-dimensional electron tomography are powerful tools for investigating the growth mechanism of MOFs and understanding the factors that influence their particle morphology. However, their combined application to the study of MOF etching dynamics is limited due to the challenges of the technique such as sample preparation, limited field of view, low electron density, and data analysis complexity. In this research, we present a study employing in situ liquid phase TEM to investigate the etching mechanism of colloidal zeolitic imidazolate framework (ZIF) nanoparticles. The etching process involves two distinct stages, resulting in the development of porous structures as well as partially and fully hollow morphologies. The etching process is induced by exposure to an acid solution, and both in situ and ex situ experiments demonstrate that the outer layer etches faster leading to overall volume shrinking (stage I) while the inner layer etches faster giving a hollow morphology (stage II), although both the outer layer and inner layer have been etched in the whole process. 3D electron tomography was used to quantify the properties of the hollow structures which show that the ZIF-67 crystal etching rate is larger than that of the ZIF-8 crystal at the same pH value. This study provides valuable insights into MOF particle morphology control and can lead to the development of novel MOF-based materials with tailored properties for various applications.

Elemental carbon and hydrogen concentrations as the main factors in gas-phase graphene synthesis: Quantitative fourier-transform infrared spectroscopy study

Gas-phase microwave plasma-assisted synthesis of freestanding graphene is a promising route to produce high-quality graphene flakes. However, a comprehensive understanding of the gas-phase kinetics that is required to advance production rates and yields is still lacking. Here, we use line-of-sight Fourier-transform infrared (FTIR) absorption spectroscopy as an in situ diagnostic to measure gaseous species formed during graphene synthesis, thereby elucidating the chemical kinetics mechanism. Different carbonaceous precursors that lead to the formation of either few-layer graphene flakes or soot-like particles are examined, and the results are compared with numerical simulations and mass spectrometry measurements. Quantitative FTIR measurements show a correlation between concentration of atomic carbon and hydrogen in the post-plasma region and particle morphology. Lower carbon and higher hydrogen concentrations lead to graphene formation, while higher carbon and lower hydrogen concentrations shift the reaction toward soot-like particles. We also investigate how the precursor chemical composition, precursor flowrate, and delivered microwave power affect the carbon concentration in the post-plasma region, thus enabling to control particle morphology.

Highly Active and Stable Large Mo-Doped Pt-Ni Octahedral Catalysts for ORR: Synthesis, Post-treatments, and Electrochemical Performance and Stability.

Over the past decade, advances in the colloidal syntheses of octahedral-shaped Pt-Ni alloy nanocatalysts for use in fuel cell cathodes have raised our atomic-scale control of particle morphology and surface composition, which, in turn, helped raise their catalytic activity far above that of benchmark Pt catalysts. Future fuel cell deployment in heavy-duty vehicles caused the scientific priorities to shift from alloy particle activity to stability. Larger particles generally offer enhanced thermodynamic stability, yet synthetic approaches toward larger octahedral Pt-Ni alloy nanoparticles have remained elusive. In this study, we show how a simple manipulation of solvothermal synthesis reaction kinetics involving depressurization of the gas phase at different stages of the reaction allows tuning the size of the resulting octahedral nanocatalysts to previously unachieved scales. We then link the underlying mechanism of our approach to the classical "LaMer" model of nucleation and growth. We focus on large, annealed Mo-doped Pt-Ni octahedra and investigate their synthesis, post-synthesis treatments, and elemental distribution using advanced electron microscopy. We evaluate the electrocatalytic ORR performance and stability and succeed to obtain a deeper understanding of the enhanced stability of a new class of relatively large, active, and long-lived Mo-doped Pt-Ni octahedral catalysts for the cathode of PEMFCs.

Control of particle morphology and size of yttria powder prepared by hydro(solvo)thermal synthesis

Control of particle morphology and size of yttria powder prepared by hydro(solvo)thermal synthesis

Mixed Solvent-Based Low Temperature Synthesis of Functionalized Cubic FeCo Theranostic Nanoparticles

FeCo alloy nanoparticles were rapidly synthesized by a salt-mediated mixed-polyol process without surfactants at a low reaction temperature (50 °C–100 °C) and its influence on particle size, shape, and composition were investigated. The presence of mixed polyols increase the viscosity of the solution, reducing the migration rate of cations, alter the diameter of FeCo nanoparticles and nucleation rate, and control particle morphology without the use of surfactants. Cubic FeCo nanoparticles were synthesized without surfactants even at a reaction temperature as low as 50 °C. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy showed that as-synthesized FeCo nanoparticles had a body-centered cubic (BCC) crystal structure with a particle size ranging from 25 to 75 nm in effective diameter, respectively. The maximum saturation magnetization of about 207 emu/g and a coercivity of ~100 Oe were achieved at room temperature for samples synthesized at 90 °C. These soft magnetic FeCo nanoparticles can be applied in preparing conjugated nanoparticles for both diagnostic and therapeutic biomedical applications.

A P123/benzyl alcohol/TEOS/HCl(aq.) templating system for preparation of KIT-6 type mesoporous silica with morphological and structural control.

A new P123 templating system is reported for preparing KIT-6s with a large synthesis domain and controllable particle morphology by using benzyl alcohol (Bz) as a co-solvent based on the partitioned cooperative self-assembly (PCSA) principle. As a result, spherical and rod-like KIT-6 can be obtained.

Particle morphology control of metal powder with various experimental conditions using ball milling

The morphology evolution of copper powder was studied under various ball-milling experimental conditions, such as low and high rotation speeds and a ball diameter of 1 mm and 10 mm. A scanning electron microscope and X-ray diffractometer were used to analyze the copper powder particle size, morphology, structure, and crystallite size. The effect of ball size on copper powder particle morphology in dry-type milling was studied using a planetary ball mill. Spherical copper powders were obtained by ball milling at a high rotation speed and with a ball diameter of 1 mm. The experimental results suggest that the particle size and morphology can be controlled by changing the milling conditions during the ball milling. Ball motion was simulated by using a three-dimensional discrete-element model to obtain the force, energy, and power of the ball motion in the ball mill for two different ball sizes and low and high rotation speeds.

X ray diffraction (XRD) analysis and evaluation of antioxidant activity of copper oxide nanoparticles synthesized from leaf extract of Cissus vitiginea

Nanoparticles have a diameter of up to 100 nm and a higher surface-to-volume ratio, enabling more active surface atoms to contribute to implementations and improve material properties. In nanoparticle preparation, the ability to control particle size, shape, and morphology is important. The most important tool for studying nanomaterials is XRD, it is a vital characterization tool in solid-state chemistry and materials science. For any compound, XRD is a simple method for determining the unit cell's size and shape. This study explains how copper oxide nanoparticles are formed in Cissus vitiginea leaves. The antioxidant function and XRD study of the synthesized CuONPs were also investigated. According to the XRD results, the copper oxide nanoparticles formed by reducing Cu2 + ions by Cissus vitiginea leaf extract are crystalline in nature. CuONPs have an average crystalline size of ~32.32 nm, according to the Debye-Scherrer formula. CuONPs have higher antioxidant activity than plant extract and are closest to ascorbic acid in terms of standard.

Thermoresponsive Polycation-Stabilized Nanoparticles through PISA. Control of Particle Morphology with a Salt

Poly[(vinylbenzyl) trimethylammonium chloride] (PVBTMAC) has been used as a stabilizer in the polymerization-induced self-assembly polymerizations of diacetone acrylamide (DAAM). A whole spectrum of particle morphologies was obtained simply by adjusting the ionic strength of the reaction mixtures; no dilution of the cationic charges with noncharged comonomers or with noncharged polymers was needed. In addition to the ionic strength, the effects of solid content and the length of the PDAAM block on the morphologies of the particles were studied in detail. The experiments are a continuation to previous studies on solution properties of PVBTMAC. It has been shown earlier that the solubility of the polycation may be tuned with counterions. Hydrophobic triflate ions induce an upper critical solution temperature behavior. In the present case, the chains bound to hydrophobic cores of the particles show either a one-step phase separation in aqueous triflate solutions or under certain conditions, a two-step transition. The step-wise transition is typical for responsive polymers with limited mobility.

Closed-loop in-silico control of a two-stage emulsion polymerization to obtain desired particle morphologies

Particle morphology strongly affects the performance of waterborne polymer dispersions, which are products-by-process materials produced by emulsion polymerization, a process prone to suffer run-to-run irreproducibility. Therefore, on-line control of particle morphology would be tremendously beneficial, but this is an unsolved issue because particle morphology is neither on-line measurable nor observable from available online monitoring techniques. This article explores in-silico the possibility to overcome this problem by using a mathematical model able to calculate the particle morphology from the monomer conversion and reactor temperature as a “soft sensor”. These estimates are used in combination with an economic nonlinear model predictive controller. It is shown that this controller is able to achieve a good control of the particle morphology even in the presence of serious disturbances such as the presence of a strong inhibition or the failure of the reactor cooling system. Under these circumstances, neither open-loop control nor tracking of off-line optimized reaction trajectories are able to control the particle morphology tightly. The limits of the soft sensor are investigated by considering non-detectable disturbances such as the use of a seed of unknown glass transition temperature and the benefits of a hypothetical online morphology measurement available for control is explored.

Solid State Ion Conductors to Enable Low Temperature Molten Sodium Batteries

Molten sodium batteries show clear promise for safe, long-lifetime grid-scale energy storage, and there is growing expectation that they may be able to impact a host of energy storage areas, ranging from vehicle electrification to industrial applications. Key to the successful development and implementation of these technologies, though, are 1) reducing the traditionally high operating temperature of these batteries and 2) identifying robust, zero-crossover solid state separators that will perform effectively at these reduced temperatures. Traditional molten sodium batteries, such as sodium-sulfur and sodium-nickel chloride (ZEBRA), operate near 300°C, where ceramic separators, such as β”-Al2O3 have high ionic conductivity, but these high temperature systems can be cost-prohibitive in large scale applications. Here, we discuss a significant deviation from these chemistries and materials in a sodium-iodide (NaI) battery that utilizes a molten sodium anode and a sodium iodide-based molten salt catholyte, operating at drastically reduced temperatures near 100°C. NaSICONs (Na Super Ion CONductors) show promise as effective ceramic separators in lab-scale demonstrations of this battery chemistry, but challenges to cost, widespread availability of the material, electrochemical compatibility, and mechanical stability of the ceramic have motivated the search for new sodium ion conducting separator materials and designs. We will describe not only critical synthetic considerations, but also important benefits and shortcomings of NaSICON separators for use in this specific battery chemistry. Importantly, we will describe recent efforts build on the promise of NaSICON materials, exploring new composite materials and hybrid structures that meet strenuous demands of ionic conductivity, chemical compatibility, and mechanical robustness for separators in low temperature sodium batteries. Innovative designs that take advantage of controlled particle morphology and organization in polymer-ceramic composites, for example, promise improved mechanical durability and effective ionic conductance in low cost, highly processable systems. Understanding the critical relationships between material composition, microstructure, and electrochemical performance of these emerging materials will be central to the successful development of a new generation of solid-state ion conductors and the realization of effective low temperature molten sodium batteries.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.