Narrow Particle Size Distribution Research Articles

Fabrication of spherical W–ZrC powder for additive manufacturing by spray granulation combined with plasma spheroidization

In this study, a W–1%ZrC spherical powder for additive manufacturing was successfully fabricated by spray granulation combined with radio frequency (RF) plasma spheroidization. 3 μm tungsten powder and the nano-sized ZrC powder were spray granulated into a porous agglomerated powder and then spheroidized to form a dense spherical powder by RF plasma. Spherical W–ZrC powder with a narrow particle size distribution and a uniform distribution of Zr element was obtained, whose flowability and apparent density was 7.5 s/50g and 9.36 g/cm3, respectively. Furthermore, ZrC enters the tungsten grains after plasma spheroidization, which causes dislocations in the tungsten grain. The spherical W–ZrC composite powder is expected to suppress the crack formation of W parts during the laser powder bed fusion process.

A Novel quality-by-design optimized spectrofluorimetric approach for estimation of the oral synthetic adiponectin receptor agonist AdipoRon in different biological matrices: Compliance with greenness metrics

The current study introduces the first analytical approach for the quantitative analysis of adipoRon, a synthetic adiponectin receptor agonist, using a facile, rapid, sensitive, and green spectrofluorimetric method. Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by adopting a fast microwave-assisted procedure using accessible and natural substrates (orange juice and urea). The suggested synthetic method produced CQDs with narrow particle size distribution (2–10 nm), high fluorescence stability, and good quantum yield (29.3%). The produced fluorescent QDs were used as fluorescent sensors and were quantitatively quenched by increasing adipoRon concentrations. A two-level full factorial design (22 FFD) was used to identify the most critical experimental factors affecting the relative fluorescence intensity of N-CQDs. The fluorescence quenching of N-CQDs by the drug was measured at 417 nm after excitation at 325 nm. Under the optimized conditions, the quenching of N-CQDs' fluorescent intensity displayed acceptable linearity with the adipoRon concentration range of 5.0–20.0 μg/mL with limits of quantitation and detection of 0.843 μg/mL and 0.278 μg/mL, respectively. Owing to the high sensitivity, the suggested method was efficiently applied for adipoRon estimation in different biological matrices, including spiked human plasma, real rat plasma, and liver homogenate samples with high % recoveries (87.41–103.17%) and low %RSD values (<2.87%). The method's greenness was evaluated using two metric tools, the complementary green analytical procedure index (ComplexGAPI) and the Analytical GREENNESS metric approach (AGREE), and the results showed that the method was excellent green. The proposed methodology was validated according to the ICHQ2 (R1) recommendations.

Preparation and properties of novel tungstate SrLa6W10O40: Eu3+ phosphors

Novel tungstate SrLa6-xW10O40: xEu3+ (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15, 0.18, 0.21) red phosphors were prepared by solid state method at 1150 ?C by using SrCO3, La2O3, WO3 and Eu2O3 as raw materials. The powders were agglomerated with particles having mostly spheroidal morphology, mean particle size D50 = 12.8 ?m and narrow particle size distribution. With the increase of doping amount x, there is no significant difference in the diffraction peak position of the phosphor, but the cell volume of SrLa6W10O40 slowly decreases. The relative strength of diffraction peaks decreases gradually and the half-peak width widens gradually, indicating that the inclusion of Eu3+ ions affects the crystallization of the SrLa6W10O40 matrix. Excitation and emission spectra of the prepared samples were obtained. The optimal doping content has the SrLa5.85W10O4: 0.15Eu3+ phosphor and is characterised with the colour coordinate of (0.652, 0.348), which is closer to the red standard colour (0.67, 0.33) than the near-ultraviolet red phosphor Y2O2S: Eu3+ (0.622, 0.351) used for commercial LED.

Pt/C catalysts synthesized in a commercial particle atomic layer deposition system enabling improved durability in fuel cells.

Particle atomic layer deposition (ALD) is an emerging method for engineering 3D materials, such as powders, for energy applications. In our study, we employ a commercially available and scalable particle ALD system to synthesize Pt/C electrocatalysts for fuel cells. Our method yields Pt/C catalysts characterized by highly dispersed platinum nanoparticles with a narrow particle size distribution of 2.2 ± 0.5 nm for 30 wt% Pt and 2.6 ± 0.6 nm for 40 wt% Pt, as verified through transmission electron microscopy and X-ray diffraction analysis. The performance of the ALD-synthesized catalysts is benchmarked against a state-of-the-art catalyst (TEC10V50E), with both catalysts exhibiting similar beginning-of-test performance (1.6 A cm-2 at 0.65 V) under application-relevant operation conditions (80 °C, 50% relative humidity). After 30 000 voltage cycles, conducted in accordance with the U.S. Department of Energy's accelerated catalyst degradation test, the ALD catalysts demonstrate up to 64% greater electrochemical active surface areas and superior retention of cell performance, with a 34% higher current density at 0.65 V, compared to the reference. Given the scalability of the commercial particle ALD system, these promising results encourage the use of particle ALD as a novel synthesis approach for fuel cell catalyst materials in the industry.

Highly Stable and Active Ru Clusters Supported on Boron Carbon Nitride for Acidic Water Oxidation

In recent years, metal oxides, such as IrO2, have been widely used in proton exchange membrane water electrolysis (PEMWE) because of their excellent catalytic activity and long-term stability [1]. However the high price and scarcity of these catalysts were not enough to meet the requirements of PEMWE [2]. Therefore, it is significant to explore novel electrochemically active, stable, and low-cost catalysts.In this paper, a uniformly dispersed Ru confined on boron carbon nitride support was synthesized and studied. The surface chemical states of Ru were tuned by the interaction between Ru and the active N in boron carbon nitrogen (BCN), forming a highly stable Ru-N bond. Benefiting from a graphene-like structure, the BCN-0.5Ru catalyst exhibited greater conductivity than RuO2. The strong interaction between Ru and the BCN support also allowed for accelerated charge transfer at the electrode interface.Transmission electron microscopy (TEM) investigations revealed that Ru clusters were uniformly dispersed on BCN (Figure 1a), and the particle size distributions (Figure 1b) showed that the Ru clusters possessed an average particle size of 4 nm. It suggests that the Ru nanoclusters on the BCN support had small particle sizes and a narrow particle size distribution. These results demonstrated that the BCN support helped disperse the Ru metal nanoclusters more homogeneously than what occurred when RuO2 was prepared via direct RuCl3 annealing. The electrochemical performance of oxygen evolution reaction (OER) for BCN-xRu catalysts in O2-saturated 0.5 M H2SO4 solution was evaluated. The BCN-0.5Ru catalyst demonstrates a low overpotential of 164 mV at a current density of 10 mA cm–2 and remains stable for 12 h in acidic electrolyte (Figure 1c). In contrast, RuO2 without any support fails in only 1 h (Figure 1c). We propose that the surface chemical states of Ru supported by BCN may play an important role in enhancing stability. This study provides insights into designing and synthesizing high-performance electrocatalysts for acidic OER.

(Digital Presentation) Direct Regeneration of NMC622 Cathode Material from Spent EV Li-Ion Batteries Via Hydrothermal Re-Lithiation

With the increasing demand for electric vehicles, there is a need to address the issues associated with the increasing number of waste or spent Li-ion batteries. A simpler and less expensive approach to recycle cathode materials from spent batteries, compared to hydrometallurgy and pyrometallurgy, is direct regeneration. In this study, a facile and cost-effective hydrothermal re-lithiation method, followed by post-annealing, was explored to repair the structure, morphology, and composition of spent NMC622. The effects of annealing temperature and purging gas on the physicochemical properties of the regenerated NMC622 were evaluated. The regenerated NMC622, annealed at 800°C under O2, exhibited an XRD profile that closely resembled that of the as-received spent NMC622, with peaks indexed to the planes of the α-NaFe2O4 structure and without any impurities. Additionally, it achieved the highest I(003)/I(104) ratio and the closest c/3a ratio to that of the as-received spent NMC, indicating that the original structure was successfully repaired after regeneration. It also exhibited less agglomeration, with a narrower particle size distribution than the as-received spent NMC622, indicating that the morphology was improved after regeneration. Elemental composition analyses further confirmed that the spent NMC622 was successfully regenerated using the employed method, as the Li content after regeneration increased from 6.99 to 7.20 wt%, a value close to the theoretical (7.16%). In general, this simple and inexpensive direct regeneration strategy provides a new perspective for lithium-ion battery regeneration, which can be extended to other battery systems in the future.

The Influence of Ammonia Concentration on the Precipitation of Ni(OH)2 Precursor in the Synthesis of LiNiO2 Cathode Materials for Lithium-Ion Batteries

Lithium-ion batteries have been implemented in the energy storage market for many decades, used as rechargeable batteries in portable devices, electric vehicles and a wide range of other applications. Ni-rich layered oxides as cathode materials in Li-ion batteries are of great interest due to their higher energy density and theoretical capacity of 274 mAh/g. [1] To improve fast lithium-ion diffusion in lithium-ion battery cathodes, enhance the limited capacity due to oxygen release and phase changes, reduce cost and toxicity and most importantly, inhibit unethical mining of cobalt. Alternative compounds to replace LiCoO2 are investigated by substituting different transition metals, such as Ni, Mn, or Al on the Co site in the structure. The increase of the Ni content and decrease of the Co content increases the capacity and lowers the costs in $/kWh, as Ni provides higher performance and a high energy-density. To cope with the higher demand of volume constrained applications [2], the volumetric energy-density is to be considered and is achieved by a high tap density of the active material, which is related to particle size, particle size distribution and morphology. [3] However, for high-nickel content cathodes, degradation processes like Li/Ni mixing [4], surface layer deconstruction [5], particle cracking[6], decomposition reactions with the electrolyte [7] and slow Li+ diffusion kinetics [8] occur, leading to lower capacity retention, a loss of capacity in the first cycle and thus an overall insufficient cycling stability.There are many research publications about optimising the calcination process of the Ni(OH)2 precursor and LiOH*H2O, [9][10][11], but currently, very little focus on the precursor material itself, it’s particle size and morphology, which affects the structural and electrochemical behaviour. The accumulation of mechanical strain due to repeated c-axis contraction and relaxation during charge/discharge processes lead to particle cracking, electrolyte infiltration, structural decay and results in a reduced electrochemical performance. To counter this, a large study regarding the morphology, particle size, and electrochemical behaviour of Ni(OH)2 precursor material produced in a highly controlled environment (batch stirred tank reactor BSTR) has been undertaken and the first results are presented here. A higher transition metal to ammonia ratio during synthesis leads to larger and more spherical secondary particles, a narrow particle size distribution, a higher tap density and also improved electrochemical cycling.[1] T. Ohzuku, A. Ueda and M. Nagayama, J. Electrochem. Soc., 1993, 140, 1862.[2] A. El Kharbachi, O. Zavorotynska, M. Latroche, F. Cuevas, V. Yartys and M. Fichtner, J. Alloys Compd., 2020, 817, 153261.[3] S. Yang, X. Wang, X. Yang, Z. Liu, Q. Wei, and H. Shu, Int. J. Electrochem., 2012, 9.[4] R. V. Chebiam, F. Prado and A. Manthiram, J. Electrochem. Soc., 2001, 148, A46-A53.[5] A. Gosh, J. M. Foster, G. Offer and M. Marinescu, J. Electrochem. Soc., 2021, 168, 020509.[6] R. Ruess, S. Schweidker, H. Hemmelmann, G. Conforto, A. Bielefeld, D. A. Weber, M. T. Elm and J. Janek, J. Electrochem. Soc., 2020, 167, 100532.[7] H. Rong, M. Xu, L. Xing and W. Li, J. Power Sources, 2014, 261, 148-155.[8] M. D. Radin, S. Hy, M. Sina, C. Fang, H. Liu, J. Vinckeviciute, N. Zhang, M. S. Wittingham, Y. S. Meng and A. Van der Ven, Adv. Energy Mater., 2017, 7, 1602888.[9] M. Bianchini, F. Fauth, P. Hartmann, T. Brezesinski and J. Janek, J. Mater. Chem. A, 2020, 8, 1808.[10] J. Välikangas, P. Laine, M. Hietaniemi, T. Hu, P. Tynjäla and U. Lassi, Appl. Sci., 2020, 10, 8988.[11] C. S. Yoon, M. H. Choi, B-B. Lim, E-J. Lee and Y-K. Sun, J. Electrochem. Soc., 2015, 162, A2483.

Towards enhancing ODS composites in laser powder bed fusion: Investigating the incorporation of laser-generated zirconia nanoparticles in a model iron–chromium alloy

Oxide dispersion-strengthened (ODS) steel is a sought-after composite material known for its high demand in high-temperature and corrosive environments. Achieving the desired ODS steel properties requires specific conditions for the size and nanoparticles (NP) distribution in the printed part. Laser ablation in liquid (LAL) enables precise NP size adjustment. At the same time, the dynamic melt pool solidification in the Laser Powder Bed Fusion (PBF-LB/M) process complements this by creating favorable conditions for successful ODS processing. In this study, ZrO2 NP with a small and narrow particle size distribution (d50 = 3.8 nm; d90 = 10 nm) is produced by LAL. Dielectrophoretic deposition achieves the homogeneous, deformation-free coating of the binary Fe20Cr (wt.-%) matrix powder with NP. PBF-LB/M printed parts out of the oxide-additivated powder exhibit a crack-free structure and a density of up to 98%. Expectedly, the metal matrix grain sizes and room temperature microhardness (~ 220 HV) are not affected by NP addition. NP tracing by 2D simulation indicates a homogeneous NP distribution and less than 10% NP to be agglomerated in the solidified part. Thus, a promising perspective for a complete laser-based process chain for generating and processing ODS alloys is outlined.Graphical abstractTable of Contents

Continuous gas-phase synthesis of iron nanoparticles at ambient conditions with controllable size and polydispersity

HypothesisBy altering aerosol growth dynamics with unipolar charges, one can obtain aerosols with narrow particles size distributions, a highly desirable feature in applications of functional nanoparticles. ExperimentsUnlike liquid colloid systems, aerosol particles in the free molecular regime undergo coarsening due to Brownian coagulation and will eventually attain a self-preserving size distribution with a typical geometric standard deviation of 1.46 - 1.48. We developed a novel continuous one-step aerosol synthesis reactor that produces iron nanoparticles from ferrocene at ambient conditions, which confines the site of precursor breakdown and particle formation in the downstream vicinity of a positive corona discharge. FindingsWe demonstrated that the particle size could be controlled within 3 - 10 nm with a suppressed geometric standard deviation (1.15 - 1.35). The as-produced iron nanoparticles were successfully used as catalyst for the growth of single-walled carbon nanotubes with a narrow diameter range. With a transient aerosol dynamics model, we showed that a fraction (as small as 0.1%) of unipolar-charged particles could have a significant impact on the aerosol growth dynamics, which eventually results in a narrower particle size distribution with smaller size and higher number concentrations.

Combined continuous nanoparticle synthesis with chromatographic size classification

In this paper, we report a combination of the continuous flow synthesis of gold nanoparticles (AuNPs) with subsequent purification and narrowing of the particle size distribution (PSD) by size-exclusion chromatography (SEC) by adapting the flow rates of synthesis and classification. First, we show scalability of chromatographic classification with respect to column dimension and the absence of irreversible nanoparticle adhesion on the column material. Two different syntheses lead to a large and widely distributed and a small and narrowly distributed AuNP dispersion, which are classified by a semipreparative column. The PSDs of individual fractions are characterized by analytical SEC. The broadly distributed AuNP dispersion was classified into three fractions with distinct PSDs. For the narrowly distributed AuNPs, the separation is almost independent of the mobile phase flow rate: coarse and fine fractions with almost identical PSDs and separation efficiency curves are observed irrespective of the flow rate. Even NP samples with narrow PSDs can be classified into multiple fractions with tailored PSDs while simultaneously removing dissolved impurities from the dispersion. With our study, we demonstrate the potential of a direct combination of continuous NP synthesis with chromatographic classification for the optimization of final PSDs and the simultaneous purification of nanoparticulate dispersions.

Preparation of flame-retardant HNS/DAAF energetic composite microspheres using droplet microfluidic technology

2,2′,4,4′,6,6′-Hexanitrostilbene (HNS) exhibits excellent detonation performance and has the potential to play a significant role in aerospace technology. However, its application is limited by the extreme space environment. In this study, glycidyl azide polymer/nitrocellulose (GAP/NC) was used as a binder to prepare HNS/DAAF energetic composite microspheres with different mass ratios using droplet microfluidic technology. The morphology, particle size, crystal structure, thermal decomposition, bulk density, mechanical sensitivity, and combustion behavior of the microspheres were characterized and tested. The results showed that the HNS/DAAF composite microspheres exhibited high sphericity and narrow particle size distribution while preserving the crystal structure of HNS. Compared to raw HNS, the HNS/DAAF composite microspheres demonstrated improved thermal stability and enhanced safety performance. Additionally, ignition experiments revealed that the addition of DAAF effectively suppressed the combustion of HNS. These findings provide valuable insights for the safe utilization of HNS in high-temperature environments.

Combustion synthesis and consolidation of Ti(C,N)–Si3N4–SiC heterophase ceramic with YAG sintering additives

In this comprehensive study, we investigated the macrokinetics of the filtration combustion process of reactive Ti–Si–C mixtures in a nitrogen environment. It was observed that an increase in nitrogen pressure resulted in a rise in combustion temperature (150–600 °C) and combustion rate (2–8 times) due to the improved availability of nitrogen in the combustion front. Combustion yielded Ti(C,N)–Si3N4–SiC ceramic powders with polyhedral-shaped composite particles and a narrow particle size distribution. The hot pressing (HP) of as-synthesized ceramics significantly altered their phase composition due to Si3N4 dissociation. Introduced as a counter-measure, the YAG sintering additives (5–10 %) not only facilitated the preservation of the phase composition during HP but also considerably reduced the porosity of consolidated ceramics from 25-28 % to 0.6–4.8 %. The samples consolidated using the optimized conditions had a dense and uniform microstructure, retained their initial phase composition, and exhibited hardness values up to 13.4 GPa, flexural strength up to 397 MPa, and fracture toughness up to 5.3 MPa × m1/2.

Intensifying levulinic acid hydrogenation using mechanochemically prepared copper on manganese oxide catalysts

A series of copper nanoparticles supported on manganese oxide octahedral molecular sieves (OMS-2) were prepared using mechanochemical (Ball-Mill) and conventional wet-impregnation (Wet-Imp) methods. All catalysts prepared were thoroughly characterized using ICP-OES elemental analysis, X-ray diffraction (XRD), N2 sorption, H2 temperature programmed reduction (TPR) and transmission electron microscopy (TEM) techniques. The catalyst preparation methods greatly affected the size of the Cu nanoparticles. TEM images showed that 5 wt% Cu/OMS-2 (Ball-Mill) catalyst had a narrow particle size distribution with an average Cu nanoparticle size of 2.1 nm, while the corresponding 5 wt% Cu/OMS-2 catalyst prepared using wet-impregnation method had an average Cu nanoparticle size of 19.2 nm. The structural features of the catalysts were corelated with the catalytic activity using the liquid phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), as an exemplar process. In LA hydrogenation at 190 °C and 20 bar H2 pressure, the ball milled catalysts achieved higher LA conversion, and greater GVL yield, as compared to the corresponding catalysts prepared by wet-impregnation method, reinforcing that Cu nanoparticle size and metal dispersion are important tool to intensify the catalytic activity. For instance, 5 wt% Cu/OMS-2 (Ball-Mill) catalyst achieved almost twice the turnover frequency (TOF), 24.7 h−1 as compared to the 5 wt% Cu/OMS-2 (Wet-Imp) catalyst, TOF 11.8 h−1, under identical reaction conditions. The results of this study demonstrate that ball milling is a superior method for Cu/OMS-2 catalyst preparation than wet impregnation.

Controlled synthesis of ZIFs by microemulsion method at high-throughput in a chaotic microreactor

The average size and particle size distribution (PSD) of zeolitic imidazolate frameworks (ZIFs) (such as ZIF-8, ZIF-67) are closely related to their physical and chemical properties. However, it is difficult to prepare small ZIFs with narrow PSD in traditional batch reactors owing to poor mixing efficiency. Here, a four-stage oscillating feedback microreactor (FOFM) was developed to prepare ZIFs by microemulsion method. CFD simulations and visualization experiments were conducted to investigate liquid-liquid two-phase flow patterns involved, demonstrating that chaotic advection can be effectively produced, thus dispersed phase is broken up into small droplets and homogeneous microemulsions are obtained. The proposed microemulsion method based on FOFM enables preparation of ZIF-8 with small average size (38.2 nm) and narrow PSD (σg = 1.24) without surfactant at a flow rate of 90 mL/min.

Characteristics of gasification chars – Results from a screening campaign

Despite several useful characteristics like high carbon content, large BET surface area and narrow particles size distribution, the solid residues from wood gasification, i.e. gasification chars, are rarely used and commonly considered as wastes. Furthermore, marketing of these materials is hampered by a limited knowledge base on their characteristics from different gasification technologies, an incomplete understanding on influencing factors and a lack of standardization both for the material itself and the analytical procedures that have to be employed for their characterization. To provide a basis for standardization and future utilization perspectives, a screening was performed covering a wide range of gasification technologies. The samples were analyzed for ash content, moisture, volatiles, fixed carbon and elemental composition as well as the content of polycyclic aromatic hydrocarbons (PAHs) and volatile aromatic hydrocarbons. In total, analysis data of 118 gasification char samples from plants of 17 different gasification plant manufacturers have been evaluated. The results indicate a wide variation in the characteristics of gasification chars both with respect to ash and carbon content, i.e. 3.9%–100% and 0.9–92.5%, respectively. Particularly high levels of organic contaminants are associated with samples originating from cold gas filtration with PAH contents of up to 130 g kg−1 and post-treatment would be necessary in most cases to qualify these materials for material applications. Hot gas filtration and thermal post-treatment was found to result in gasification chars with substantially lower levels of organic contaminants. For these materials, the PAH contents rarely exceeded 2 g kg−1.

Influence of tetraethyl orthosilicate coating on dielectric, impedance, and modulus properties of barium hexaferrite nanoparticles prepared by a modified sol–gel method

This work is devoted to study the comparison of the conduction mechanism in bare barium hexaferrite (BaFe12O19) nanoparticles and tetraethyl orthosilicate-coated (SiO2)x/BaFe12O19 (x = 5, 10, 15 and 20 wt. %) nanoparticles. The modified sol–gel method was adopted for the synthesis of these nanoparticles. The structures, morphologies, elemental composition, vibrational modes, and dielectric properties of these nanoparticles were studied by x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and dielectric measurements, respectively. The crystallite size and particle size of BaFe12O19 nanoparticles decreased with SiO2 coatings, which can be attributed to the confinement of crystal growth of these nanoparticles with the coating. It was found that these (SiO2)x/BaFe12O19 nanoparticles have a uniform spherical shape, are non-agglomerated, and have a narrow particle size distribution. At room temperature, these (SiO2)x/BaFe12O19 nanoparticles showed distinctive behavior with varying frequency and SiO2 coatings. The experimental results in this work may provide fundamental support to the research and development of materials for energy storage devices.

Development and Functionalization of a Novel Chitosan-Based Nanosystem for Enhanced Drug Delivery.

Nowadays, infection diseases are one of the most significant threats to humans all around the world. An encouraging strategy for solving this issue and fighting resistant microorganisms is to develop drug carriers for a prolonged release of the antibiotic to the target site. The purpose of this work was to obtain metronidazole-encapsulated chitosan nanoparticles using an ion gelation route and to evaluate their properties. Due to the advantages of the ionic gelation method, the synthesized polymeric nanoparticles can be applied in various fields, especially pharmaceutical and medical. Loading capacity and encapsulation efficiency varFied depending on the amount of antibiotic in each formulation. Physicochemical characterization using scanning electron microscopy revealed a narrow particle size distribution where 90% of chitosan particles were 163.7 nm in size and chitosan-loaded metronidazole nanoparticles were 201.3 nm in size, with a zeta potential value of 36.5 mV. IR spectra revealed characteristic peaks of the drug and polymer nanoparticles. Cell viability assessment revealed that samples have no significant impact on tested cells. Release analysis showed that metronidazole was released from the chitosan matrix for 24 h in a prolonged course, implying that antibiotic-encapsulated polymer nanostructures are a promising drug delivery system to prevent or to treat various diseases. It is desirable to obtain new formulations based on drugs encapsulated in nanoparticles through different preparation methods, with reduced cytotoxic potential, in order to improve the therapeutic effect through sustained and prolonged release mechanisms of the drug correlated with the reduction of adverse effects.

Dry reforming of methane over sub-stoichiometric NiAl2O4-mediated Ni/Al2O3 catalysts

A series of Ni/Al2O3 catalysts were prepared from substoichiometric NiAl2O4 precursors (Ni/Al molar ratio between 0.5 and 0.05) were examined for the dry reforming of methane. The calcined spinel precursors and the corresponding reduced catalysts were characterised by N2 physisorption, X-ray fluorescence, X-ray diffraction, Raman spectroscopy, electronic microscopy coupled to elemental mapping, X-ray photoelectron spectroscopy and temperature-programmed techniques. Compared with the stoichiometric counterpart, nickel species present in Ni-deficient precursors were mostly in the form of a spinelic phase. After high-temperature reduction, narrow particle size distributions centred at 10 nm were obtained. The largest available nickel surface area (18 m2g−1) was exhibited by the catalyst derived from the precursor with a Ni/Al of 0.15. The NiAl2O4-mediated catalysts, especially those with Ni/Al molar ratio in the 0.15–0.25 range, exhibited a notable performance at 90,000 h−1 and 650 °C. The optimal catalyst (14%wt.%Ni), with 93%CH4 and 80%CO2 conversions, was also able to operate for 200 h despite the significant formation of carbonaceous nanotubes (around 1gCgCAT-1) and were examined.

The potential of starch-chitosan blends with poloxamer for the preparation of microparticles by spray-drying

Using biopolymers as wall materials in spray drying poses challenges, particularly in attaining flowability and thermal stability among their physicochemical properties. This paper addresses these challenges by preparing microparticles using a blend of starch–chitosan and a poloxamer, commercially named Pluronic® F127. We aimed to elucidate the effects of varying poloxamer concentrations on the resulting particles through the spray drying technique. Blends with a poloxamer concentration of 3% (w/v) demonstrated a notably higher yield, especially when compared to those with 0% and 1% concentrations. Microparticles with 3% and 5% (w/v) poloxamer displayed a narrower particle size distribution, with the 3% blend showing a superior yield attributed to arrangements of blend components that improve flowability. X-ray diffraction analysis showcased the characteristic peaks of A-type starch form, with shifts suggesting enhanced interactions between components. Microparticles with increased poloxamer content showed elevated thermal degradation temperatures, with the 3% blend registering a significant rise, opening avenues for encapsulating heat-sensitive bioactive. This study primarily focuses on the preparation and basic characterization of microparticles. It underscores the potential of blends with optimal poloxamer concentrations in microencapsulation, emphasizing further research to harness their capabilities thoroughly.

Preparation and characterization of high solid content cationic waterborne polyurethane with core‐shell structures

AbstractIn this study, core‐shell structured cationic waterborne polyurethane (WPU) dispersions with high solid content were prepared. To this end, prepolymer A was synthesized from polytetramethylene ether glycol (PTMG), isophorone diisocyanate (IPDI), castor oil (CO) and 1,4‐butanediol (BDO) without integration of the hydrophilic groups. Prepolymer B with hydrophilic groups was prepared from PTMG, IPDI, CO, BDO and N‐methyldiethanol amine (MDEA). WPU dispersion with a core‐shell structure could be generated by mixing, neutralizing, and emulsifying of the prepolymer A and the prepolymer B. The results indicated that the generation of WPU dispersions through this technique exhibited a milky appearance while the pH values range from 5.30 to 5.60. The optimal combination of prepolymer A and prepolymer B (at a ratio of 5:5) resulted in a dispersion with the highest solid content (50.4%), lowest viscosity (69 mPa·s), and narrowest particle size distribution. As the proportion of prepolymer A to prepolymer B decreases, the tensile strength of WPU film reduces while the elongation at break and glass transition temperature increases. Moreover, initially the contact angle with water was decreased instead of increase. However, modifications in a ratio of prepolymer A and B was not showed any significant impact on the thermal stability performance of the WPU films.