Mean Particle Size Research Articles

Mesoscale self-organization of polydisperse magnetic nanoparticles at the water surface.

In this study, we investigated the self-ordering process in Langmuir films of polydisperse iron oxide nanoparticles on a water surface, employing in situ x-ray scattering, surface pressure-area isotherm analysis, and Brewster angle microscopy. X-ray reflectometry confirmed the formation of a monolayer, while grazing incidence small-angle x-ray scattering revealed short-range lateral correlations with a characteristic length equal to the mean particle size. Remarkably, our findings indicated that at zero surface pressure, the particles organized into submicrometer clusters, merging upon compression to form a homogeneous layer. These layers were subsequently transferred to a solid substrate using the Langmuir-Schaefer technique and further characterized via scanning electron microscopy and polarized neutron reflectometry. Notably, our measurements revealed a second characteristic length in the lateral correlations, orders of magnitude longer than the mean particle diameter, with polydisperse particles forming circular clusters densely packed in a hexagonal lattice. Furthermore, our evidence suggests that the lattice constant of this mesocrystal depends on the characteristics of the particle size distribution, specifically the mean particle size and the width of the size distribution. In addition, we observed internal size separation within these clusters, where larger particles were positioned closer to the center of the cluster. Finally, polarized neutron reflectometry measurements provided valuable insights into the magnetization profile across the layer.

Application of Green Synthesized Silver Nanoparticles for Dye Wastewater Treatment

A facile one-pot synthesis of silver nanoparticles (AgNPs) was achieved using the ethanolic extract of Cavendish banana florets as source of reducing agents for the conversion of Ag+ to Ag. The appearance of surface plasmon resonance peak between 410–435 nm in the UV Vis spectra confirmed the formation of AgNPs. The effects of different reaction conditions on the size and concentration of AgNPs were evaluated. The optimum conditions identified were pH 7 at 80 °C. Transmission electron microscopy (TEM) revealed spherical AgNPs with a mean particle size of 13.55 nm. On the other hand, energy-dispersive X-ray (EDX) analysis confirmed the presence of silver (Ag) as the bulk element (87.25%). Other elements such as carbon (C) and oxygen (O) are attributed to the capping agents of AgNPs which agrees with the results in the Fourier-transform infrared spectroscopy (FTIR) analysis. The optimized AgNPs were used for dye degradation using methyl orange (MO) as the model dye under acidified conditions. The maximum MO dye degradation of 96.07% and 77.32% at pH 1.5 and 2 were achieved after 10 min and 1320 min, respectively. This highlights the potential use of green-synthesized AgNPs for dye wastewater treatment.

Synthesis, characterization, and anticancer properties of Ag nanoparticles derived from walnut leaves tested on cells of L929, MCF-7 and H1299

In this study, Ag nanoparticles (Ag NPs) were synthesized using walnut leaves according to a straightforward method. The synthesized Ag NPs were characterized by advanced analytical techniques such as XRD, TEM, UV–Vis, FESEM, EDS and FTIR. The synthesized Ag NPs tested on some cells to detect its antiproliferative effects. The antiproliferative effects of Ag NPs derived from walnut leaves were investigated on L929, MCF-7 and H1299 cells. The characterization studies showed that Ag NPs were well formed and the cell studies revealed that the synthesized Ag NPs have considerable anticancer effects. The mean particle size of Ag NPs was found to be 18.76 nm by TEM analyses. FESEM analyses revealed that Ag NPs contained Ag, C, and O elements and FTIR analyses revealed these elements bound to each other with C–O bounds. The amount composition of Ag NPs was detected to be 85 % by EDS analyses. The antiproliferative effect of AgNPs obtained from walnut leaf extract on human breast cancer cell line (MCF-7), human lung cancer cell line (H1299) and mouse fibroblast cell line (L929) was determined by MTT cell viability assay method. While the silver nanoparticles synthesized within the scope of the study did not show any toxic effect on the mouse fibroblast cell line (L929) that we used for control purposes, it was observed that it was highly effective against MCF-7 and H1299 cells. Apoptosis and necrosis index studies were calculated by cell counting from randomly selected areas and these studies revealed that the synthesized silver nanoparticles suppressed cell viability by inducing apoptosis in cells. Significantly suppressing the viability of cancer cells proves that silver nanoparticles obtained from walnut leaves can be a new treatment approach for cancer treat.

Development of favipiravir dry powders for intranasal delivery: An integrated cocrystal and particle engineering approach via spray freeze drying

The therapeutic potential of pharmaceutical cocrystals in intranasal applications remains largely unexplored despite progressive advancements in cocrystal research. We present the application of spray freeze drying (SFD) in successful fabrication of a favipiravir-pyridinecarboxamide cocrystal nasal powder formulation for potential treatment of broad-spectrum antiviral infections. Preliminary screening via mechanochemistry revealed that favipiravir (FAV) can cocrystallize with isonicotinamide (INA), but not nicotinamide (NCT) and picolinamide (PIC) notwithstanding their structural similarity. The cocrystal formation was characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and unit cell determination through Rietveld refinement of powder X-ray analysis. FAV-INA crystalized in a monoclinic space group P21/c with a unit cell volume of 1223.54(3) Å3, accommodating one FAV molecule and one INA molecule in the asymmetric unit. The cocrystal was further reproduced as intranasal dry powders by SFD, of which the morphology, particle size, in vitro drug release, and nasal deposition were assessed. The non-porous flake shaped FAV-INA powders exhibited a mean particle size of 19.79 ± 2.61 μm, rendering its suitability for intranasal delivery. Compared with raw FAV, FAV-INA displayed a 3-fold higher cumulative fraction of drug permeated in Franz diffusion cells at 45 min (p = 0.001). Dose fraction of FAV-INA deposited in the nasal fraction of a customized 3D-printed nasal cast reached over 80 %, whereas the fine particle fraction remained below 6 % at a flow rate of 15 L/min, suggesting high nasal deposition whilst minimal lung deposition. FAV-INA was safe in RPMI 2650 nasal and SH-SY5Y neuroblastoma cells without any in vitro cytotoxicity observed. This study demonstrated that combining the merits of cocrystallization and particle engineering via SFD can propel the development of advanced dry powder formulations for intranasal drug delivery.

Experimental study on the aluminum aggregate property during the treatment of lightweight oil spills using electrocoagulation

ABSTRACT The properties of aggregates significantly affect the demulsification efficiency within the electrocoagulation reactor. This paper aims to explore aggregate properties including the particle size, strength factor (Fs), and recovery factor (Fr). The experiments were carried out using aluminum-aluminum electrodes. The experimental results indicate that breakage time did not change Fs much but was positively correlated with Fr. When the current was increased from 0.75 A to 1.0 A, Fs experienced a decrease of 12.42%, while Fr exhibited an increase of 19.38%. In comparison to pH 9.0, both Fs and Fr demonstrated an increase at pH levels of 2.0 and 10.0. The size of aggregates significantly decreases under rocking conditions simulating offshore environments, while the oil removal rate does not change much. This phenomenon can be attributed to the fact that different initial mean particle sizes have different Fs and Fr. The aggregates |Fs-Fr| were positively correlated with the initial average particle size of the electroflocculated aggregates. The present study offers a crucial theoretical foundation for the growth and regulation of aggregates formed during electrocoagulation treatment of oil spills on the sea surface. Synopsis: This paper is of great theoretical value for understanding the growth and control of EC aggregates to treat offshore light oil spills using the electrocoagulation process.

Physiological and antimicrobial properties of a novel nanoemulsion formulation containing mixed surfactant and essential oils: Optimization modeling by response surface methodology

This research aims to optimize the parameters for the production of a stable nanoemulsion containing a mixture of essential oils (EOs) with a surfactant blend (Tween and Span 80) and assess its antimicrobial potency against spoilage bacteria and foodborne pathogens. The impact of a surfactant blend’s hydrophilic-lipophilic balance (HLB) as well as surfactant:oil ratio was investigated based on the mean particle size (z-average) and polydispersity index (PDI). Results showed HLB value of 12 and a ratio of surfactant to oil at 0.75:1 exhibited an emulsion with the smallest z-average and PDI. Following this, a response surface methodology (RSM) employing central composite design (CCD) was utilized to formulate an optimal nanoemulsion using the microfluidization (MF) technique. The RSM revealed that the microfluidizer pressure of 15,000 psi and 4 cycles produces a z-average of 38.11 nm, PDI of 0.27, ζ-potential of 37.8 mV, and encapsulation efficiency (EE) of 83.8%. The comparison between the experimental and anticipated results of the optimized nanoemulsion revealed no significant differences (p > 0.05). The optimal nanoemulsion displayed excellent stability during 30 days of storage at both 4 and 30 °C compared to 5 days for coarse emulsion. The nanoemulsion exhibited potent antimicrobial activity, showing minimum inhibitory concentration (MIC) values in the range of 0.019 to 0.156 μL/mL, surpassing the antimicrobial efficacy of the coarse emulsion, which had MIC values between 0.039 to 0.312 μL/mL. Thus, this study emphasized the efficacy of RSM design in developing an optimal nanoemulsion with enhanced antimicrobial properties using EOs, making it a promising natural food preservative.

Comparative Analysis of Mechanical In-Field Corn Residue Shredding Methods: Evaluating Particle Size Distribution and Rating of Structural Integrity of Corn Stalk Segments

The European corn borer is a major pest of corn that overwinters in corn stubble and stalks. Shredding these residues disrupts the larvae’s habitat or directly harms them. A corn header has been engineered with a new type of cutting tool on its horizontal choppers, featuring sharp edges and dulled flails, to shred corn stubble near the soil surface. This study investigated the effect of the dulled flails on the shredding intensity of corn stover. Field trials compared flail knives with standard knives for particle size distribution of corn stover and structural integrity of corn stalk segments. Additionally, a common two-step method, which involved a standard knives-equipped corn header followed by tractor-driven flail mowers, was tested. The flail knives reduced the mean particle size by 3.6 mm compared to the standard knives. Subsequent processing with tractor-driven flail mowers, following the corn header using standard knives, led to a reduction in mean particle size by 11.8 mm. It also further reduced the number of incompletely destroyed stalk segments. However, completely intact internodes were scarce in all methods. Given that flail knives enhance shredding intensity without a second processing step, this concept is concluded to be effective for corn stover shredding.

Quercetin-Loaded Nanostructured Lipid Carrier In Situ Gel for Brain Targeting Through Intranasal Route: Formulation, In Vivo Pharmacokinetic and Pharmacodynamic Studies.

Quercetin (QT) shows potential for protecting against neurodegenerative diseases like Alzheimer's. However, its limited bioavailability and instability in physiological pH hinder its clinical use. The purpose of this work is to construct QT-filled nanostructured lipid carriers (QT-NLC) intranasal in situ gel to enhance pharmacokinetic and pharmacodynamic performance. NLCs were developed using a melt emulsification-high-pressure homogenization and were optimized using design expert software with the Box-Behnken design. NLCs were then incorporated into an in situ gel based on Lutrol F127 and further characterized. The pharmacodynamics of the formulation was evaluated in neurodegeneration induced by trimethyl tin (TMT) Wistar rats. The optimized QT in situ gel had spherical shape, entrapment efficiency of 96.1 ± 4.40%, and in vitro drug release of 83.74 ± 1.40%. The mean particle size was 123.3 ± 5.46nm. After intranasal administration, in vivo single-dose pharmacokinetic studies demonstrated a significant therapeutic concentration of drug in CNS, having Cmax 183.41 ± 11.76ng/mL and Tmax of 2h. The more brain targeting efficiency of NLCs was proved by the developed QT in situ gel, which had a higher drug targeting efficiency (DTE) of 117.47% and drug targeting potential (DTP) of 88.9%. As compared to the neurodegeneration control group, the QT in situ gel-treated group had significantly decreased escape latency and pathlength. Biochemical analysis and histological investigations demonstrated that QT in situ gel exhibited superior anti-Alzheimer's potential compared to standard drug, donepezil. The promising results of the developed and optimized intranasal QT in situ gel suggest its potential and can be used in Alzheimer's disease management.

Propolis-loaded liposomes: characterization and evaluation of the in vitro bioaccessibility of phenolic compounds.

Propolis has low water solubility, poor stability, and limited bioaccessibility of phenolic constituents when subjected to in vitro digestion. To overcome these drawbacks, the liposomal encapsulation method can be employed. Soybean phosphatidylcholine lecithin mixed with Tween 80 (T80) and ammonium phosphatides (AMP) was used to produce propolis extract (PE)-loaded liposomes. The mean particle size, zeta potential, encapsulation efficiency values, and transmission electron microscopy analysis were used to characterize liposomes. Individual phenolics were determined for digested and nondigested propolis-loaded liposomes and propolis extract. Tween 80 incorporation reduced the size of unloaded liposomes, whereas AMP inclusion yielded larger liposomes. In both formulations, PE loading significantly increased the size and reduced the zeta potential values and homogeneity of the size distribution. In free PE, the most bioaccessible polyphenols were phenolic acids (3.20 to 5.63 %), and flavonoids such as caffeic acid phenethyl ester, galangin, pinobanksin, and pinocembrin (0.03 to 2.12 %) were the least bioaccessible. Both liposomal propolis provided significantly higher bioaccessibility of phenolic compounds. The liposomes with T80 and AMP in their compositions recovered 52.43 and 185.90 % of the total amount of phenolic compounds in the nondigested samples, respectively. The liposomes containing AMP not only exhibited high solubility for PE but also provided protection to the phenolic compounds during in vitro digestion. Liposomal encapsulation could be a promising approach to improving the solubility and stability of PE in digestive fluids, making it suitable for the delivery of propolis in oral formulations.

Chemometrics Assisted Formulation of Glimepiride Nanosuspension for Solubility Enhancement in Diabetic Therapy—A Systematic Approach

AbstractGlimepiride (GLM), a third‐generation sulfonylurea oral hypoglycemic medication, is used to treat type II diabetes. Admittedly, it has a low bioavailability, a relatively short half‐life (t1/2), and high toxicity. To address the issue, a nanosuspension of poorly soluble GLM is designed using a Quality‐by‐Design (QbD) method, to enhance its solubility. Prospective risk factors are identified and assessed using Critical Material Attribute (CMAs) and Critical Processing Parameter (CPPs) to evaluate the targets by Taguchi orthogonal array (OA) design and to study the effects of formulation and process variables on dependent variables. The amount of Polyvinylpyrrolidone (PVP) (X2), agitation time (X5), and concentration of Poloxamer (X7) are found as significant parameters (p < 0.05), and are further optimized using the Box Behnken Design as response surface methodology model. The optimized GLM nanosuspension 1) has mean particle size (PS), zeta potential, viscosity (VS), and percentage cumulative drug release (CDR%) of 258.17 nm, −25.2 mV, 1.087cPs, and 98.52%, respectively. The pattern of drug release is fitted to Non‐Fickian kinetics. The study results in an economic and efficient nano formulation with enhanced solubility.

Wall-resolved large eddy simulation of mixed-size sand-laden flow

Most of the existing numerical studies on wind-blown sand flow simplify sands into single-size particles, whereas natural wind-blown sand flow is a two-phase flow with mixed-size particles, thus, the simulation of mixed-size sand-laden flow is necessary. In the present work, wall-resolved large eddy simulations of mixed-size sand-laden flows are realized. Each sand in the wind field is tracked using the Lagrangian point-particle model. The transport characteristics of sand particles in mixed-size sand-laden flow are investigated under the premise of considering bed erosion. Considering the significant influence of sand-bed collision on simulation, the splash function is modified in the present simulation according to the previous experimental results. It reveals that in mixed-size sand-laden flow, the fraction of rebound sand particles in all the saltation particles is approximately 0.6, which is twice times of the ejected sand particles, and the modification of the sand rebound angle greatly affects the simulation results of mixed-size sand-laden flow. Meanwhile, the mean size of the saltation sand particles decreases with height and is 20% lower at the top of the saltation layer than that near the sand bed in the present simulation. Further analysis by grouping of sands with their size shows that the sand transport intensity of small sands decreased more rapidly with increasing height. The volume fraction and sand transport intensity of small sand particles exceed those of medium and large sand particles at heights y/δ = 0.05 and y/δ = 0.1.

Remifentanil and Propofol Co-loaded Nanoemulsion: Formulation Development and In vivo Pharmacodynamic Evaluation

Background: The present work is an effort to develop novel propofol (PPF) and remifentanil (RFT) co-loaded nanoemulsion (NME) for the treatment of anesthetic effects. Methods: The PPF/RFT NME was prepared via the high-pressure homogenization method. Its physicochemical properties were assessed to ensure good quality and suitability for i.v. administration. We also studied the in vivo pharmacokinetics and pharmacodynamics of PPF/RFT NME in dogs with an optimized formulation. Results: This study showed that the mean particle size of PPF/RFT NME was 124.2 nm and the zeta potential was −20.6 mV. In the stability test, the NME maintained a good round shape and did not demonstrate any significant changes in physicochemical characteristics. In terms of the in vitro release, the early burst release of the NME preparations containing PPF or RFT was ideal in clinical practice, where a loading dose or a rapid onset of the drug was required. Based on histopathological observations, no histological change occurred to the rat organs after the administration of PPF/RFT NME. Regarding pharmacodynamics, compared with the combination group at the same dose, PPF/RFT NME could make animals enter the anesthetic state faster and the anesthetic effects last longer. In addition, vital signs of PPF/RFT NME could be maintained in a good state while better effects were delivered. Conclusions: This study used PPF and RFT to prepare a compound NME. This could reduce the anesthesiologist's administration time and make the anesthesia process more efficient.

Small Interference RNA Encapsulated in Liposomes: An Effective Strategy for In vitro Inhibition of Sars-CoV-2 Load

Background: The pressing need for effective SARS-CoV-2 antiviral medicines has driven research into innovative therapeutic techniques. RNA interference with small interfering RNAs (siRNAs) has shown promise as an antiviral treatment. Objective: We evaluated the effectiveness of lipid-based nanoparticles as a viable delivery platform for siRNA-based approach against SARS-CoV-2 in vitro infection. Methods: Liposomes were fabricated by microfluidics to incorporate SARS-CoV-2-specific siRNAs based on conserved sections of the Spike protein coding sequence. Nanoparticle tracking analysis was used to evaluate the nanoparticles' physicochemical features. VERO cell lines infected with SARS-CoV-2 were used to test the efficiency of siRNA-loaded liposomes. RT-PCR was used to determine the viral load by quantifying the SARS-CoV-2 genome. Results: The results showed that liposomes efficiently decreased viral load in infected cells with good physicochemical features, such as a mean particle size of about 180 nm, zeta potential of +2.5 mV and encapsulation efficiency (53.6%). Conclusion: These findings imply that lipid-based nanoparticles might be a targeted delivery strategy for siRNA-based approaches.

Mechanical Activation of CaSO4 Enriched Petroleum Coke Fly Ash for Development of Green Pellets

Mechanical Activation of calcium sulphate enriched petroleum coke fly ash (PCFA) generated from circulation fluidized bed combustion (CFBC) boiler was investigated to improve the surface reactivity of PCFA. The physico- chemical, mineralogical (XRD), morphological (SEM) characteristics of PCFA, activated PCFA and developed green pellets were studied in detail. It was found that the milling time of 45 minutes is efficient for the activation of PCFA and results in fragmentation of coarse particle into fine porous particles. Mechanical activation results in enhancing physical properties and reactivity of PCFA without any further chemical treatment. The mean particle size of activated PCFA with 45 min milling time was 12.51-12.60µm and the porous morphology were seen through SEM. The hydration phases like ettringite, portlandite and calcium silicate hydrate mainly contribute to the development of mechanical strength in activated PCFA pellets which were also confirmed through morphology of needle-shaped crystallites. The study recommends that mechanically activated PCFA could be used as an adsorbent material for heavy metals removal from waste waters.

Preparation, characterization, and stability of nano-emulsions loaded with the Moringa oleifera seed hypoglycemic peptide MoHpP-2

In a previous study, we successfully isolated and identified novel hypoglycemic peptide MoHpP-2 from Moringa oleifera seed protein hydrolysates. However, the peptide exhibited activity instability. To increase its stability, we employed a high-speed homogeneous emulsification method to prepare a MoHpP-2-loaded nano-emulsion. The optimal conditions for preparing MoHpP-2-loaded nano-emulsions were as follows: 5 % soy lecithin as emulsifier; medium-chain triglycerides as oil phase; water phase to oil phase ratio of 9:1; 0.05 % MoHpP-2 addition; and rotational speed of 19,000 rpm. The encapsulation efficiency of the nano-emulsion was 74.00 % and reached the nano-meter level with mean particle size of 162.05 nm. The resulting nano-emulsion was considered an oil-in-water type, and FTIR analysis confirmed effective embedding of MoHpP-2, and rheological analysis further indicated shear thinning behavior of the nano-emulsion. Moreover, the prepared nano-emulsion had good Na+ and pH stability, and significantly enhanced thermal stability of MoHpP-2 at 80–100 °C. Furthermore, the nano-emulsion had good stability when stored at 4 °C for 36 days. In addition, in vitro gastrointestinal simulation experiments revealed that the release mechanism of MoHpP-2 was found to conform to the Super Case II transport model. Overall, this study provides a theoretical support for the application of high-stability nano-emulsion loaded with MoHpP-2 in functional foods.

Anti-CD64 Antibody-Conjugated PLGA Nanoparticles Containing Methotrexate and Gold for Theranostics Application in Rheumatoid Arthritis.

Rheumatoid arthritis, an autoimmune disorder, exerts a considerable effect on quality of life. The inflammatory mechanism involved in rheumatoid arthritis is not clearly known, and therefore the need to develop effective medicines as well as new methods for early detection is a challenge. In this study, we developed PLGA nanoparticles containing gold and methotrexate in core and anti-CD64 antibody conjugated to nanoparticle surface via coupling process. The nanoparticles were examined for their surface morphology using SEM and TEM. The mean particle size, zeta potential, and PDI values of nanoparticles were 413.6 ± 2.89 nm, -10.12 ± 2.12 mV, and 0.23 ± 0.04, respectively, indicating good stability and particle homogeneity. In vitro drug release revealed a controlled release pattern with 93.44 ± 1.60% up to 72 h of release in the presence of pH 5.8, indicating the influence of pH and NIR on drug release. In vivo results on adjuvant-induced arthritis on Wistar rats indicated that animals receiving antibody-conjugated nanoparticles showed improvement in clinical indices and arthritic score as compared to non-conjugated nanoparticles and free drugs. This innovative drug delivery system will be an excellent strategy to maximize therapeutic effectiveness by limiting dosage-related side effects.

Statistically developed stable Camptothecin-loaded Soluplus/TPGS mixed micelles for improved ovarian cancer treatment

In this research, Camptothecin-loaded mixed micelles (CPT-MMs) were formulated by combining Soluplus®, a novel amphiphilic excipient, with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS). The use of appropriate excipients is crucial in stabilizing micellar structures and improving drug entrapment efficiency. TPGS, with its ability to self-assemble into micelles, was an ideal candidate, and incorporating Soluplus further enhanced micelle stability and drug-loading capacity. A 32 full factorial design was employed to investigate the influence of key factors on particle size and %entrapment efficiency (%EE). The statistical analysis using Design Expert® VR software provided meaningful conclusions on the significance of each factor and their interactions, facilitating the successful optimization of CPT-MMs dispersion with improved drug delivery capabilities. The mean particle size, zeta potential, %drug loading capacity (%DLC), and (%EE) of CPT-MMs were 77.8 ± 2.67 nm, −23.4 ± 0.36 mV, 45.6 ± 1.78%, and 68.61 ± 1.8% respectively. CPT-MMs demonstrated sustained-release characteristics, preventing premature drug release and enhancing drug accumulation in tumor tissues, potentially optimizing CPT delivery for cancer treatment. Importantly, CPT-MMs dispersion exhibited lower hemolysis compared to plain CPT, indicating excellent biocompatibility and safety for intravenous administration. The sustained release of CPT from CPT-MMs dispersion may lead to reduced cytotoxicity and improved therapeutic efficacy. Additionally, the lyophilized formulation showed superior stability compared to the liquid micelles. In conclusion, the development of CPT-MMs presents a promising strategy for enhancing drug delivery and optimizing therapeutic outcomes in cancer treatment. The sustained-release feature, along with enhanced biocompatibility and stability, holds great potential for the clinical translation of these MMs as efficient drug delivery systems for ovarian cancer treatment.

Synthesis and characterization of microencapsulated paraffin with melamine-urea-formaldehyde shell modified with lignin

The study aims to fabricate MUF/paraffin microcapsules with lignin nanoparticles (LNPs)/ melamine-urea-formaldehyde (MUF) resin as hybrid shell material with different LNPs addition were synthesized in oil-in-water emulsion stabilized synergistically by styrene/maleic anhydride (SMA) and LNPs. The morphological characterization of LNPs was observed by transmission electron microscopy (TEM). The particle size of LNPs, the mean particle size and ξ potentials of SMA/LNPs mixture at pH =4.5 were investigated by zeta potential measurement. Field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), and differential scanning calorimetry (DSC) were characterized the morphologies, crystallography, chemical component, thermal stability and phase change properties of MUF/paraffin microcapsules with different LNPs addition. The results showed that MUF/paraffin microcapsules were spherical. The LNPs did not influence the chemical structure or crystal type of MUF/paraffin microcapsules. When the LNPs addition was 0.15 g, the melting enthalpy and crystallization enthalpy is respectively 130.03 and 121.92 J/g and the encapsulation efficiency of MicroC-15 is 61.04 %.

Evaluation of a Partector Pro for atmospheric particle number size distribution and number concentration measurements at an urban background site

Abstract. Particle number size distributions, total number concentrations and mean particle sizes have been measured for 70 d at an urban background site in Mülheim-Styrum, Germany, with a handheld Partector Pro of the first generation and a TSI mobility particle size spectrometer (MPSS). The aim of the study was to evaluate the performance of the Partector Pro against the MPSS. The results show that the size distributions, measured with the Partector Pro, agree with the MPSS mostly within ± 25 % for particle sizes between 10 and 113.5 nm, whereas higher, systematic differences were observed for larger particles. The measurement accuracy was shown to be dependent on the geometric mean diameter and the geometric standard deviation of the aerosol. Best results were found for the most abundant size distributions with geometric mean particle diameters ≥ 30 nm and geometric standard deviations larger than 1.8. The total number concentration, measured by the Partector Pro, was found to be in excellent agreement with the MPSS with a slope of the linear fit of 0.9977 and a regression coefficient of R2=0.9956. The agreement of the geometric mean particle diameter, determined with the Partector Pro and the MPSS was good but moderately dependent on the particle size distribution. For mean particle sizes between 20 and 50 nm, the bias was within ±15 %. Higher deviations of up to 30 % were observed when the geometric mean particle sizes exceeded 70 nm and when the geometric standard deviations exceeded approximately 2.7.

Synthesis of highly disperse NbSi2–Si3N4 and Si3N4–NbN composite powders

AbstractThe behavior of reaction powder mixtures of stoichiometric compositions calculated for the synthesis of higher niobium nitride and silicide in the temperature range 800–1400°С in vacuum according to the reactions 4Nb + Si3N4 and 3Nb + 2Si3N4, respectively, has been investigated. The decomposition of Si3N4 is accompanied by the formation of lower nitride and lower silicide phases of niobium. The content of the silicide phase increases with heat treatment temperature, and, at 1400°С, NbSi2 forms. The nitride phase remains practically unchanged up to 1300°С and disappears at 1400°С. On the basis of the established regularities, we have developed synthesis methods for Si3N4–NbN and Si3N4–NbSi2 powders, which include the introduction of excess Si3N4 with respect to the stoichiometric composition. The combined two‐stage technological cycle of synthesis of Si3N4–NbN involves vacuum annealing at 1000°С and subsequent nitriding at 1300°С. The synthesis method for NbSi2–Si3N4 assumes the in situ successive formation of niobium silicide phases up to 1400°С. The synthesized Si3N4–15NbN and NbSi2–14Si3N4 powders consist of multiphase agglomerates with a mean size of 5.5 and 8.8 µm, respectively, and a nanodisperse fraction with a mean particle size of 200 nm.