Mechanism Of Particle Formation Research Articles

Potential human exposure and risks of incidental nanoparticles released during rotary dry cutting of ceramic tiles

Rotary dry cutting and rectifying of ceramic tiles are sources of fine particulate matter (PM2.5) and nanoparticles (NPs). These activities are typically carried out inside industrial facilities during the manufacturing process, as well as outdoors and in residential indoor spaces during the installation phase, where mitigation measures are seldom implemented. This work aimed to understand the particle formation and release mechanisms, as well as particle properties (physical, chemical, and toxicological) and potential impacts on human health and the environment, for particles generated during ceramic tile rotary dry cutting operations. Aerosols were characterised in terms of particle number and mass concentrations, chemical composition, morphology and in vitro cytotoxicity. Two types of commercially available and representative tiles were tested in controlled chamber experiments: porous and non-porous ceramic body tiles (referred to in this work as A and B types, respectively). Results evidenced the release of fine particles and NPs during dry cutting of both materials, in comparable concentrations (20.000-45.000/cm3, 1-min average). However, the particle size distribution was significantly finer from A tiles (70% of the particle number concentration was nanosized (<100 nm)) in comparison to B tiles (<20%). While airborne particle chemical profiles were similar for both types of materials in the coarser size fractions (>0.6μm), in the smaller size fractions (<0.6μm) larger differences were observed. The chemical composition of airborne aerosols was consistent with that of the deposited dust. In vitro cytotoxicity responses evidenced statistically significant differences between exposure to aerosols from both types of tiles: cell viability was lower after exposure to aerosols from A tiles (50% at the original concentration) compared to those from B tiles, which exhibited high cell viability regardless of the aerosol concentration. Overall, results evidenced NP formation and release during rotary dry cutting of ceramic tiles, varying physical-chemical and cytotoxic profiles as a function of the material being processed, and highlight this activity as a potential health hazard in scenarios where prevention and mitigation measures are not implemented.

Effect of Zr dopant on in vitro cytotoxicity and neurogenic property of spray-dried bioactive glass microspheres

Bioactive glasses (BGs) have been extensively applied in dental and tissue engineering fields due to their bioactivity, biocompatibility, and degradability. Despite the advantages, the material itself lacks functionalities such as angiogenesis and antibacterial properties which could limit its applications. To address this, trace elements like copper (Cu), manganese (Mn), boron (B), and zinc (Zn) have been incorporated to enhance their therapeutic applications. Further, to explore the potential of neurogenic applications, this study fabricated both spray-dried undoped and Zr-doped BG specimens, which were then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The in vitro bioactivity was assessed with simulated body fluid (SBF), cytotoxicity with L929 fibroblast cells, and neurogenic properties via the neuronal marker Tuj1+. Finally, the study discusses the particle formation mechanism and their in vitro biological properties, aiming to enhance the understanding of BGs in neurogenesis.

Pentagonal Symmetry in Aperiodic Cyclic Multiply Twinned Nano- and Mesodiamonds.

This Review provides the first comprehensive overview of the structure and properties of exotic sp3-crystalline aperiodic cyclic multiply twinned nano- (10-100 nm) and meso- (up to 1 mm) diamond particles (MTPs) exhibiting pentagonal symmetry. It spans their independent experimental discoveries (1963, 1964, 1972, and 1983) and theoretical structural insights (1993) to recent advancements. The Review focuses on high-symmetry MTPs formed by the fusion of multiple cubic diamond fragments through [111] facets. The sp3 diamond lattice of individual fragments offers a vast range of MTP varieties. These particles are shown to be a special case of aperiodic crystalline solids with limited dimensions and rotational symmetry, leading to a breakdown of translational invariance. Detailed mathematical analysis of the MTPs' lattices highlights the crucial role of central cores in determining the symmetry and effective dimensions of these structures. Both structural and kinetic aspects of the formation mechanisms of pentagonal diamond particles are considered, revealing the main role of embryo seeds (low fullerenes, polyhexacyclo[5.5.1.12,6.18,12.03,11.05,9]pentadecane (C15), and polyheptacyclo[5.5.1.12,7.19,14.03,13.06,11]octadecane (C18)) in determining the MTPs' symmetry and structure. The effective dimensions of multiply twinned diamonds are shown to be limited by structural stress caused by the mismatch of perfect pentagonal and tetrahedral dihedral angles. The extraordinary mechanical and electronic properties of multiply twinned diamonds are discussed, highlighting that hexagonal interfaces between cubic diamond fragments may determine exceptional ultrahard and quantum characteristics. The MTP X-ray diffraction spectra reveal clear pentagonal patterns with single (diamond decahedrons or dodecahedrons) or ten (diamond icosahedra) central 5-fold axes. A comparative analysis of experimental structural data and simulations at different theoretical levels demonstrates a perfect correspondence of theoretical models with crystalline lattices.

Cluster-dynamics-based parameterization for sulfuric acid–dimethylamine nucleation: comparison and selection through box and three-dimensional modeling

Abstract. Clustering of gaseous sulfuric acid (SA) enhanced by dimethylamine (DMA) is a major mechanism for new particle formation (NPF) in polluted atmospheres. However, uncertainty remains regarding the SA–DMA nucleation parameterization that reasonably represents cluster dynamics and is applicable across various atmospheric conditions. This uncertainty hinders accurate three-dimensional (3-D) modeling of NPF and the subsequent assessment of its environmental and climatic impacts. Here we extensively compare different cluster-dynamics-based parameterizations for SA–DMA nucleation and identify the most reliable one through a combination of box model simulations, 3-D modeling, and in situ observations. Results show that the parameterization derived from Atmospheric Cluster Dynamic Code (ACDC) simulations, incorporating the latest theoretical insights (DLPNO-CCSD(T)/aug-cc-pVTZ//ωB97X-D/6-311++G(3df,3pd) level of theory) and adequate representation of cluster dynamics, exhibits dependable performance in 3-D NPF simulation for both winter and summer conditions in Beijing and shows promise for application in diverse atmospheric conditions. Another ACDC-derived parameterization, replacing the level of theory with RI-CC2/aug-cc-pV(T+d)Z//M06-2X/6–311++G(3df,3pd), also performs well in NPF modeling at relatively low temperatures around 280 K but exhibits limitations at higher temperatures due to inappropriate representation of SA–DMA cluster thermodynamics. Additionally, a previously reported parameterization incorporating simplifications is applicable for simulating NPF in polluted atmospheres but tends to overestimate particle formation rates under conditions of elevated temperature (&gt;∼300 K) and low-condensation sink (&lt;∼3×10-3 s−1). Our findings highlight the applicability of the new ACDC-derived parameterization, which couples the latest SA–DMA nucleation theory and holistic cluster dynamics, in 3-D NPF modeling. The ACDC-derived parameterization framework provides a valuable reference for developing parameterizations for other nucleation systems.

A New Approach to Single‐Step Fabrication of TiOx‐CeOx Nanoparticles

Mixed metal oxide (MMO) nanoparticles (NPs) are hybrids consisting of two or more nanoscale metal oxides. Advantages of MMO NPs over single metal oxides include improved catalytic activity, enhanced electrical and magnetic properties, and increased thermal stability due to the synergy of the different oxide components. This study presents a novel fabrication route for TiO2‐CeO2 NPs enriched with oxygen vacancies using a Haberland‐type gas aggregation cluster source. The NPs, deposited from different segmented Ti/Ce targets under varying O2 addition, were examined with respect to final composition, morphology, and Ti, Ce surface oxidation states. Particle formation mechanisms are proposed for the observed morphologies. Additionally, available O2 during deposition and its impact on the formation of defective sites were investigated. Defective sites in TiO2‐CeO2 NPs were analyzed using transfer to X‐ray photoelectron spectroscopy and transmission electron microscopy without contact to ambient oxygen. The incorporation of Ce to the target exhibits synergistic effects on the synthesis process. Segmented Ti/Ce targets enable the deposition of a broad range of mixed oxide NPs with diverse compositions and morphologies at considerably enhanced deposition rates, which is vital for practical applications. The presented fabrication approach is expected to be applicable for a broad variety of MMO NPs.

Effects of raw materials on microstructure and mechanical properties of second phase particles reinforced W[sbnd]Re composites

Combined strengthening of micron and nanoscale second phase particles is of great significance for improving the comprehensive properties of tungsten (W) based refractory alloys. In this work, with the addition of raw HfC, HfH2 and carbon powders, three types of W-3 wt%Re-0.3 wt%HfC (WRH) composites were fabricated by powder metallurgy and rotary swaging. The microstructure and mechanical properties of three WRH samples were investigated comparatively. Results show that three WRH samples are constituted by W matrix, HfO2 and HfC second phase particles. When HfH2 powder is served as the raw material, the obtained two kinds of composites show the microstructure configuration with a micro-nano combined second phase particles. That is, some larger HfO2 particles are located at the matrix grain boundaries and fine nanoscale HfC particles are inside W matrix grains. Based on it, both composites exhibit the better overall performance. When the carbon powder ratio reaches 0.03 wt%, WRH composite shows the smallest average matrix grain size and a smaller size of second phase particles inside the matrix grains, and thereby gaining the better ultimate tensile strength and hardness. As carbon powder ratio rises to 0.07 wt%, WRH sample presents an excellent elongation. Besides, the formation mechanisms of HfO2 and HfC particles, as well as the correlation between microstructure and mechanical properties, were discussed particularly.

Quantitative Visualization of Lipid Nanoparticle Fusion as a Function of Formulation and Process Parameters.

Lipid nanoparticles (LNPs) have proven to be promising delivery vehicles for RNA-based vaccines and therapeutics, particularly in LNP formulations containing ionizable cationic lipids that undergo protonation/deprotonation in response to buffer pH changes. These nanoparticles are typically formulated using a rapid mixing technique at low pH, followed by a return to physiological pH that triggers LNP-LNP fusion. A detailed understanding of these dynamic processes is crucial to optimize the overall performance and efficiency of LNPs. However, knowledge gaps persist regarding how particle formation mechanisms impact drug loading and delivery functions. In this work, we employ single-molecule Convex Lens-induced Confinement (CLiC) microscopy in combination with Förster resonance energy transfer (FRET) measurements to study LNP fusion dynamics in relation to various formulation parameters, including lipid concentration, buffer conditions, drug loading ratio, PEG-lipid concentrations, and ionizable lipid selection. Our results reveal a strong correlation between the measured fusion dynamics and the formulation parameters used; these findings are consistent with DLS and Cryo-TEM-based assays. These measurements offer a cost-effective method for characterizing and screening potential drug candidates and can provide additional insights into their design, with opportunities for optimization.

Global variability in atmospheric new particle formation mechanisms

A key challenge in aerosol pollution studies and climate change assessment is to understand how atmospheric aerosol particles are initially formed1,2. Although new particle formation (NPF) mechanisms have been described at specific sites3–6, in most regions, such mechanisms remain uncertain to a large extent because of the limited ability of atmospheric models to simulate critical NPF processes1,7. Here we synthesize molecular-level experiments to develop comprehensive representations of 11 NPF mechanisms and the complex chemical transformation of precursor gases in a fully coupled global climate model. Combined simulations and observations show that the dominant NPF mechanisms are distinct worldwide and vary with region and altitude. Previously neglected or underrepresented mechanisms involving organics, amines, iodine oxoacids and HNO3 probably dominate NPF in most regions with high concentrations of aerosols or large aerosol radiative forcing; such regions include oceanic and human-polluted continental boundary layers, as well as the upper troposphere over rainforests and Asian monsoon regions. These underrepresented mechanisms also play notable roles in other areas, such as the upper troposphere of the Pacific and Atlantic oceans. Accordingly, NPF accounts for different fractions (10–80%) of the nuclei on which cloud forms at 0.5% supersaturation over various regions in the lower troposphere. The comprehensive simulation of global NPF mechanisms can help improve estimation and source attribution of the climate effects of aerosols.

Kinetic evaluation of the uranyl peroxide synthetic route on morphology

Abstract An important challenge in utilizing particle morphology in nuclear forensic or fuel fabrication applications is understanding why differences in morphologies are observed following varying processing conditions. This is often due to competition and interplay between thermodynamic and kinetic influences. To that end, some of the kinetic influences in the uranyl peroxide precipitation reaction were evaluated and compared to thermodynamic influences studied previously. Metastudtite (UO2O2·2H2O) was synthesized from solutions of uranyl nitrate or chloride, and the reaction time was varied from 100 s to 230 min enabling an evaluation of kinetic and thermodynamic influences. The metastudtite was then calcined to U3O8, and all materials were analyzed by powder X-ray diffraction (p-XRD) and scanning electron microscopy (SEM). Analysis by p-XRD confirmed the sample purity of metastudtite and U3O8. SEM images were analyzed using the Morphological Analysis for Materials (MAMA) software to measure the size and shape of the nanoparticles for a statistical comparison between materials. Metastudtite produced at shorter reaction times exhibited a kinetically controlled shape by forming smaller and rounder particles than metastudtite produced at longer reaction times. Metastudtite produced at the longer reaction times exhibited differences between the uranyl nitrate and uranyl chloride routes with the nitrate exhibiting a more angular and faceted morphology than the chloride. Overall, the control of the supersaturation ratio (S) played a significant role in determining the morphology of the metastudtite. Morphological differences between the U3O8 confirmed the role of nanoparticle agglomeration in forming larger sintered particles. The results help demonstrate the importance of understanding particle formation mechanisms in the long-term development of morphology in nuclear forensics or in developing advanced fuels with specific characteristics.

Instant green synthesis: obtaining stable nanoparticles and understanding the extract's behavior in the particle formation mechanism

Numerous plant extracts are abundant in biomolecules that can be employed in the biogenic synthesis of metallic nanoparticles owing to their potent reducing capabilities. The mechanism by which biomolecules act as reducers and expedite the reduction of silver ions remains poorly understood. This study presents an instantaneous and environmentally friendly synthesis of silver nanoparticles (AgNPs) using varying concentrations of commercially available green tea and concentrations of a dextrose-reducing solution. The AgNPs formed instantaneously, likely due to the competitive reaction between the polyphenols present in green tea and the dextrose. The best AgNPs produced using a diluted green tea solution at a concentration of 0.05 g of tea/ml and 100 μl of dextrose solution exhibited high stability over a period of 90 days, as confirmed by UV–vis spectroscopy and dynamic light scattering. The results of antioxidant properties from diluited tea showed 2,2-diphenyl-1-picrylhydrazyl (DPPH) 0.013 ± (0.1) μmol Trolox Equivalent Anyioxidant Capacity (TEAC) TEAC/g, Ferric Reducing Antioxidant Power (FRAP) 10.3 ± (0.1) μmol TEAC/g and Total Polyphenol Content (TPC) 0.12 ± (.001) μgGAE(Galic Acid Equivalent)/g). The resulting nanoparticles are extremely small, measuring approximately 30 to 50 nm in size, and exhibit a spherical morphology as evidenced by SEM imaging. The plasmon bandwidth is better in more diluted tea and higher proportions of dextrose added than the others condition of synthesis. Probably, the results of 2nd extraction of green tea diluted can be evidence that phenolic compounds, mainly, caffeine and gallic acid, are contributing to forming and stabilizing the silver nanoparticles. This fundamental knowledge showed the method employed is ecologically sound and adheres to green principles.

Study on the mechanism of second phase formation in high-purity fused silica materials for semiconductor application

Gas bubble is a common defect in high-purity fused silica materials, but the formation of the second phase particles related to gas bubble and its mechanism remain unclear till now. In this work, we have presented a method for characterization of colored gas bubbles in high-purity fused silica crucibles for Czochralski silicon by the means of TEM and EDX. Based on it, the origin of the coloring of the gas bubbles is demonstrated to be induced by the gathering of Fe impurity and then, the formation of high-density second phase—ferric oxide (Fe2O3) crystals around the gas bubbles. Moreover, our results provide insight into the formation mechanism of second phase crystals which can be induced by stress field variations around gas bubbles during the cooling process that probably promoted by volume shrinkage effect and increasing solubility of gas from gas bubbles into fused silica substrate. The understanding of the second phase particle formation mechanism in high-purity fused silica materials is valuable for its further controlling.

Mechanism behind the Controlled Generation of Liquid Metal Nanoparticles by Mechanical Agitation.

The size-controlled synthesis of liquid metal nanoparticles is necessary in a variety of applications. Sonication is a common method for breaking down bulk liquid metals into small particles, yet the influence of critical factors such as liquid metal composition has remained elusive. Our study employs high-speed imaging to unravel the mechanism of liquid metal particle formation during mechanical agitation. Gallium-based liquid metals, with and without secondary metals of bismuth, indium, and tin, are analyzed to observe the effect of cavitation and surface eruption during sonication and particle release. The impact of the secondary metal inclusion is investigated on liquid metals' surface tension, solution turbidity, and size distribution of the generated particles. Our work evidences that there is an inverse relationship between the surface tension and the ability of liquid metals to be broken down by sonication. We show that even for 0.22 at. % of bismuth in gallium, the surface tension is significantly decreased from 558 to 417 mN/m (measured in Milli-Q water), resulting in an enhanced particle generation rate: 3.6 times increase in turbidity and ∼43% reduction in the size of particles for bismuth in gallium liquid alloy compared to liquid gallium for the same sonication duration. The effect of particles' size on the photocatalysis of the annealed particles is also presented to show the applicability of the process in a proof-of-concept demonstration. This work contributes to a broader understanding of the synthesis of nanoparticles, with controlled size and characteristics, via mechanical agitation of liquid metals for diverse applications.

Application of fluidized bed homogeneous crystallization for simultaneous recovery of Fe(II) and Cu(II) as particles from wastewater

The mixture of copper and iron often results in materials with favorable properties. The material production processes involving these metals including electroplating produce hazardous wastewater. In this study, the Fluidized Bed Homogeneous Crystallization (FBHC) process was applied to treat iron and copper-containing wastewater. The initial iron copper particles were successfully recovered from synthetic wastewater with [Fe]0:[Cu]0 of 2:1, the total metal concentration of 3 mM, at effluent pH = 7.75 ± 0.75, with the upflow velocity (U) of 1.76 m/h. The agglomerates hardening process is a crucial step for initial particle synthesis. The SEM analysis reveals the spherical particle's densified crust and porous core. The particle formation mechanism which includes the formation of the nucleus, attachment of precipitate flakes, and densification of particles was proposed after microscopic observation. The initial particles synthesized were used to initiate the treatment of synthetic wastewater at the operating condition pH = 7.75 ± 0.5, [Fe]0:[Cu]0 of 2:1, the total metal concentration of 3 mM, [CO32−]0:[M]0 = 1.2:1, and U of 28.66 m/h which results in the total metal removal of 99% and crystallization ratio of 90% and 88% for iron and copper respectively. The conditions were then applied to treat electroplating wastewater and resulted in the total metal removal of 99% for both iron and copper and a crystallization ratio of 83% and 79% for iron and copper, respectively. The treatment provided advantages in terms of treating larger amounts of sludge while eliminating the need to provide seed thus yielding a higher purity of product.

The Processing Space of the Spray-Dried Mannitol-Leucine System for Pulmonary Drug Delivery.

Designing spray-dried particles for inhalation aims at specific physicochemical properties including a respirable aerodynamic diameter and adequate powder dispersibility. Leucine, an amphiphilic amino acid, has been shown to aid in optimizing bulk powder properties. Mannitol, a model crystalline active and common bulking agent, was co-sprayed with leucine at several excipient ratios, ethanol/water ratios, and spray dryer outlet temperatures in order to experimentally probe the underlying particle formation mechanisms in this binary crystalline system. During the droplet drying of two crystallizing components, the material that nucleates first will preferentially enrich the surface. It is desired to have a completely crystalline leucine shell to improve powder properties, however, mannitol competes with leucine for the surface depending on excipient concentration and manufacturing parameters. The resulting particles were studied initially and at a two-month timepoint via solid state characterization, visual analysis, and particle size analysis in order to detect changes in bulk powder properties. It was determined that, similar to systems where only leucine can crystallize, initial leucine saturation in the formulation dictates powder characteristics.

Elucidating the mechanisms of atmospheric new particle formation in the highly polluted Po Valley, Italy

Abstract. New particle formation (NPF) is a major source of aerosol particles and cloud condensation nuclei in the troposphere, playing an important role in both air quality and climate. Frequent NPF events have been observed in heavily polluted urban environments, contributing to the aerosol number concentration by a significant amount. The Po Valley region in northern Italy has been characterized as a hotspot for high aerosol loadings and frequent NPF events in southern Europe. However, the mechanisms of NPF and growth in this region are not completely understood. In this study, we conducted a continuous 2-month measurement campaign with state-of-the-art instruments to elucidate the NPF and growth mechanisms in northern Italy. Our results demonstrate that frequent NPF events (66 % of all days during the measurement campaign) are primarily driven by abundant sulfuric acid (8.5×106 cm−3) and basic molecules in this area. In contrast, oxygenated organic molecules from the atmospheric oxidation of volatile organic compounds (VOCs) appear to play a minor role in the initial cluster formation but contribute significantly to the consecutive growth process. Regarding alkaline molecules, amines are insufficient to stabilize all sulfuric acid clusters in the Po Valley. Ion cluster measurements and kinetic models suggest that ammonia (10 ppb) must therefore also play a role in the nucleation process. Generally, the high formation rates of sub-2 nm particles (87 cm−3 s−1) and nucleation-mode growth rates (5.1 nm h−1) as well as the relatively low condensational sink (8.9×10-3 s−1) will result in a high survival probability for newly formed particles, making NPF crucial for the springtime aerosol number budget. Our results also indicate that reducing key pollutants, such as SO2, amine and NH3, could help to substantially decrease the particle number concentrations in the Po Valley region.

Spray freeze dried uniform mannitol microspheres

Spray freeze drying is an attractive technology for fabricating pharmaceutical powder, but it is still challenging to tailor the microparticle physical and chemical structure. Herein, a series of uniform mannitol microparticles with controllable morphology and crystal properties were successfully fabricated via a self-developed micro-fluidic jet spray freeze tower. The effects of feed solution composition and freezing temperature on microparticle size, morphology, surface architecture and crystal property were investigated to propose the particle formation mechanism. Freezing temperature showed more apparent effect on the microparticle characteristics with higher solid content (10 and 15 w/w%) in aqueous solution; Whereas the addition of ethanol as a co-solvent had a notable impact on microparticle morphology, concurrently perturbing the crystallization tendencies of mannitol. These results provide new insights for producing spray freeze dried pharmaceutical microparticles.

New Insights on the Formation of Nucleation Mode Particles in a Coastal City Based on a Machine Learning Approach.

Atmospheric particles have profound implications for the global climate and human health. Among them, ultrafine particles dominate in terms of the number concentration and exhibit enhanced toxic effects as a result of their large total surface area. Therefore, understanding the driving factors behind ultrafine particle behavior is crucial. Machine learning (ML) provides a promising approach for handling complex relationships. In this study, three ML models were constructed on the basis of field observations to simulate the particle number concentration of nucleation mode (PNCN). All three models exhibited robust PNCN reproduction (R2 > 0.80), with the random forest (RF) model excelling on the test data (R2 = 0.89). Multiple methods of feature importance analysis revealed that ultraviolet (UV), H2SO4, low-volatility oxygenated organic molecules (LOOMs), temperature, and O3 were the primary factors influencing PNCN. Bivariate partial dependency plots (PDPs) indicated that during nighttime and overcast conditions, the presence of H2SO4 and LOOMs may play a crucial role in influencing PNCN. Additionally, integrating additional detailed information related to emissions or meteorology would further enhance the model performance. This pilot study shows that ML can be a novel approach for simulating atmospheric pollutants and contributes to a better understanding of the formation and growth mechanisms of nucleation mode particles.

Root cause analysis of indentation mark defect on Zn coated steel sheet in continuous galvanizing line

The coated steel industry is growing as demand of corrosion resistant steels are ever increasing in automotive, construction, appliances, and general engineering segments. The surface requirement of the coated steel is becoming more stringent that demands coated surfaces within specified roughness, waviness, reflectance and free from surface defects. The continuous galvanising line number 2 of Tata Steel Limited, Jamshedpur suffers from a chronic surface defect that appears like a scratch mark in the coated steel. The present study deals with the root cause analysis of the defect focussing on the rolls within annealing furnace in CGL#2, Jamshedpur. The roll profile, roll and strip slippage, roll surface compositions (using profilometer, XRF) are studied in detail. Similarly, the steel strip collected from inside the furnace was also studied for the defect orientation, surface composition (using SEM & EDS), trapped particles etc. The mathematical calculation of slippage along with the characterization evidence confirm the formation of defect through a complex mechanism of particle formation due to non-uniform roll profile, followed by particle coagulation and finally formation of the defect on the strip under tension by those particles. Possible operational strategies to eliminate the defect is also outlined.

In situ Investigations of the Formation Mechanism of Metastable γ-BiPd Nanoparticles in Polyol Reductions.

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

Particle Formation Mechanism of TiCl4 Hydrolysis to Prepare Nano TiO2

This study utilizes Aspen Plus chemical process simulation software (V11), applies uniform nucleation theory and growth kinetics equations, and explores the particle formation mechanism of TiCl4 hydrolysis to prepare nano TiO2. In the water/ethanol system, the effects of the reaction time, reaction temperature, water addition, pH value, and ethanol amount on the crystal nucleation rate and TiO2 particle distribution (PSD) were studied in detail by adding triethanolamine dropwise and using the Aspen Plus chemical process software simulation calculation method. The calculation results indicate that at room temperature, the formation of TiO2 crystal nuclei mainly occurs in the first 300 s and then enters the growth stage. The reaction was carried out under neutral conditions at room temperature for 4 h in 1 mL TiCl4, 6 mL C6H15NO3, 15 mL H2O, and 30 mL C2H5OH. The maximum number of particles reached 195 mesh per cubic micrometer, and the particle size after crystal nucleus growth was smaller, with a D50 of 6.15 nm. The distribution curve shows a normal distribution, which is basically consistent with the experimental results. When studying various factors, it was found that controlling the reaction time within 60 min and maintaining the reaction temperature at room temperature can reduce the particle size D50 to 2.44 nm. Continuing to adjust the amount of water added, it was found that at 1 mL, D50 decreased again to 0.19 nm. Adjusting the pH value found that maintaining the neutrality did not change the particle size. Continuing to adjust ethanol, it was found that adding an appropriate amount of ethanol promoted nucleation and growth. At 4 mL, the maximum number of particles reached 199 mesh per cubic micrometer, but D50 slightly increased to 0.24 nm.