Degree Of Particle Agglomeration Research Articles

Effect of dual sintering with laser irradiation and thermal treatment on printed copper nanoparticle patterns

The dual sintering of copper (Cu) nanoparticles (NPs) was introduced to produce conductive patterns suitable for flexible electronics applications. In this method, laser irradiation using a Nd:YAG laser with a wavelength of 1064 nm was performed at laser powers of 400, 600 and 800 mJ. The laser irradiation time was 15 and 30 s for each laser power. After laser irradiation, all of the Cu NP patterns were thermally sintered under formic acid vapors. The temperature and time for thermal treatment were selected as 260 °C and 15 min, respectively. The resultant physical, chemical, electrical and mechanical properties were evaluated and compared considering the six different dual sintering conditions. The Cu NP patterns sintered using 800 mJ for 30 s showed increased necking and coalescence compared to the other patterns and featured a microstructure with increased density. Despite being oxidized, the Cu NP patterns sintered with 800 mJ for 30 s showed the lowest electrical resistivity of 11.25 μΩ cm. The surface of every sintered Cu pattern was oxidized, and mechanical hardness increased with increasing laser power. The Cu NP pattern sintered with 800 mJ for 30 s demonstrated the highest hardness of 48.64 N mm−2. After sintering using the six different conditions, the Cu NP patterns exhibited a weight loss of 0.02–3.87 wt%, and their roughness varied in the range of 26.15–74.08 nm. This can be attributed to the effective removal of organic residues and the degree of particle agglomeration. After performing folding tests up to 50 cycles, Cu NP patterns showed an upward trend in resistance with increasing laser power and time. The highest and lowest resistance ratios were observed as 3.97 and 17.24 for the patterns sintered at 400 mJ for 15 s and 800 mJ for 30 s, respectively.

Chloride-doped ZnO thin films prepared by spray pyrolysis: Effects on microstructural, optical, and photocatalytic properties

This study discusses the effects of chloride doping on the photocatalytic properties of ZnO thin films, evaluated under UV-A radiation (365 ± 5 nm) using acetaminophen as a model reactant. Zinc oxide (ZnO) thin films doped with chloride anions were prepared by spray pyrolysis. The films were homogeneous, stable to hydrodynamic forces, and photocatalytically active. The doping procedure affected the photoactivity of the semiconductor, its light absorption properties and the morphology of the surface, and promoted a redshift of the absorption edge. The microstructure of the films showed a positive correlation between the concentration and the degree of particle agglomeration; however, the higher content of chloride also promoted higher porosity. The undoped ZnO films exhibited the best photocatalytic performance under the investigated conditions. By comparing this work with the recent literature on the use of ZnO in the photocatalytic oxidation of acetaminophen, it was found that the synthesized ZnO films have better energetic efficiency (EE0,med = 9.91 kWh L−1) and provide similar quantum yields (φmed = 6.84 × 10−4 mol E−1). Finally, a segregation study indicates that grain-boundary segregation has a strong impact on photocatalytic efficiency, offering a sustainable and low cost alternative for designing ZnO-based photocatalysts.

Solvent-particles interactions during composite particles formation by pulsed laser melting of α-Fe2O3

This work thoroughly investigates chemical solvent-particles interactions during the formation of composite particles by pulsed laser melting of α-Fe2O3. Two solvents, with different dielectric constants, such as ethyl acetate (εr = 6) and ethanol (εr = 24.6), were examined in terms of their effect on the morphology, size, and phase composition of iron oxide composites. We calculated the laser fluence curves using the heating-melting-evaporation approach to identify the critical particle size that undergoes the phase changes first. We assessed the temperature of the particles irradiated with 390 mJ/pulse.cm2 in both solvents, including the heat dissipation between the particles and the liquid. The phase diagram of the Fe–O–C–H system was calculated to determine the temperature–pressure relationship of the system in equilibrium. We also employed an in situ GC–MS analysis to identify the volatile products during irradiation. Based on our experimental results, we concluded that the final diameter of the composites increases from 400 to 600 nm, along with the decreasing dielectric constant of the solvent, which is related to the different polarization of the organic liquid and the degree of particle agglomeration. The reduction of hematite in ethanol proceeded much faster, ending up with Fe/FeCx, while in ethyl acetate, it ended up with Fe3O4. Among all the particles, those with a diameter of 200 nm have the highest temperature and undergo the phase transition first. The temperature of a 200 nm composite particle in ethanol is slightly lower than in ethyl acetate, i.e. 1870 K as compared to 1902 K. Phase equilibrium diagrams proved the existence of Fe, FeO, and Fe3O4 as the preferred phases at about 1900 K. Our research provides a new insight into the process of submicron particle formation during pulsed laser irradiation and allows proposing a mechanism for the growth of particles of different size and phase composition depending on the solvent.

Review on the Synthesis Method of Nanocomposites and Approach to Making Semiconductors Visible Light Active

Many studies have been concentrated on the degradation of toxic organic compounds in waste water via photocatalysis of various semiconductors. It has attracted great attention in modern science because of its potential in solving many current environmental problems such as air and water pollution. The common photocatalysts are primarily nanocomposite metal oxides, are known to be good photocatalysts for the degradation of several environmental contaminants due to their high photosensitivity, stability and non-toxic nature. There are different approaches for the synthesis of nanomaterials: Top down and bottom up approaches. Top- down approach is best approach and refers to successive cutting of a bulk material to get nano sized particles. These applications have their interest in controlling particle size, particle shape, size distribution, particle composition and degree of particle agglomeration. Some nanoparticles have large band-gap which leads to high recombination rate of photogenerated electron–hole pairs limit their utilization for photocatalytic applications. More recently, significant efforts have also been made to develop new or modified semiconductor photocatalysts that are capable of using visible-light (λ = 400–700 nm) including semiconductor coupling, metal ion doping, nonmetallic element doping, and sensitization with organic dyes. Coupling of two semiconductor nanoparticles with different band gap widths has been demonstrated in many studies as one of the most effective ways to reduce the recombination of electron–hole pairs and consequently, achieving a higher photocatalytic activity. Moreover, the ternary nanocomposites have high visible light photocatalytic activity and organic dyes can be decomposed efficiently, implying the higher photocatalytic activity of the ternary nanocomposites.

Mechanism of Er inhibiting agglomeration of in situ ZrB2 particles in aluminum matrix composites

The improvement effect on distribution state of in situ ZrB2 nanoparticles induced by the addition of rare earth element erbium (Er) was investigated for the first time in this paper. An about two nanometers thick outer layer consisted of Er element was found to coat on the surface of ZrB2 particles. Aided by the introduction of Er, the degree of particle agglomeration was effectively reduced, which resulted in the superior and steady mechanical properties possessed by the final composites. The scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) were adopted here to observe the modification of particle distribution with the addition of Er. The morphology and composition of this ultrafine Er-layered structure on surface of in situ ZrB2 particles was detected and convinced by the spherical aberration corrected transmission electron microscope (AC-TEM).

Optimised Co-Precipitation synthesis condition for oxalate-derived zirconia nanoparticles

Zirconia (ZrO2) nanoparticles were successfully synthesised from zirconyl chloride and ammonium oxalate via co-precipitation (CP), followed by calcination of the resulting co-precipitated precursor. CP and calcination processing parameters showed considerable effects on the surface morphology, average crystallite size, and phase purity of the resulting ZrO2 particles. In this work, field emission scanning and transmission electron microscopy (FESEM and TEM) confirmed the existence of spherical and uniformly shaped ZrO2 particles, with crystallite size ranging between 6 and 35 nm. Pure ZrO2 nanoparticles synthesised through calcination at 650 °C had a strained monoclinic phase structure. On the other hand, ZrO2 particles prepared through calcination at 600 °C revealed presence of a transitional phase from tetragonal to monoclinic phase in its X-ray diffraction (XRD) patterns. The FESEM images and XRD results also revealed that the degree of particle agglomeration and average crystallite size had increased with increasing processing temperatures and durations. Henceforth, precursor was co-precipitated at 40 °C for 1 h, then calcined at 650 °C for 4 h for optimum production of ZrO2 nanoparticles with an average crystallite size of 12.85 nm and large Brunauer–Emmett–Teller (BET) surface area of 18.06 m2/g.

Effect of the PVA (polyvinyl alcohol) concentration on the optical properties of Eu-doped YAG phosphors

The influence of the polyvinyl alcohol (PVA) concentration on the synthesis and structural, morphological and optical properties of Y3Al5O13: Eu (Eu-doped YAG) was systematically investigated in this work. The final concentration of PVA in the preparation step influenced the crystallite size and also the degree of particle agglomeration in Eu-doped YAG phosphors. X-ray excited optical luminescence (XEOL) emission spectra results indicated typical Eu3+ emission lines and an abnormally intense 5D0 → 7F4. The intensity parameters Ω2 and Ω4 were calculated and indicated the PVA concentration affects the ratio Ω2:Ω4. X-ray absorption spectroscopy (XAS) results showed Eu valence did not change and the symmetry around the Eu3+ is influenced by the PVA concentration. XEOL-XAS showed the luminescence increases as a function of energy.

Performance of Agroindustrial Wastes for Removal of Disinfection By-products From Water

The aim of the present work was to use agroindustrial wastes as alternative adsorbents for the removal of trihalomethanes (THMs). SEM micrographs of sugar cane bagasse and coconut mesocarp samples showed a high degree of particle agglomeration, with particle sizes of 114.4 ± 74.0 μm, while the sugar cane bagasse particles were larger (557.3 ± 169.5 μm). The pyrogram obtained for sugar cane bagasse revealed the presence of many compounds with different functional groups containing oxygen atoms. In the case of the coconut mesocarp, the range of oxygenated functional groups was smaller. The adsorption processes showed fast kinetics, with equilibrium reached after around 240 min of contact. Adsorption tests revealed different selectivities of the biomass adsorption sites for the THMs. Adsorption percentages obtained with coconut mesocarp ranged from 49.2 ± 2.57 to 71.9 ± 1.88 %, while the values obtained for sugar cane bagasse were between 31.8 ± 1.08 and 67.4 ± 1.27 %. The orders of removal (significant at p CHBrCl2>CHBr2Cl>CHBr3 (using sugar cane bagasse) and CHBr2Cl>CHBrCl2>CHCl3>CHBr3 (using coconut mesocarp). Use of the sugar cane bagasse resulted in high removal percentages of chloroform (51.1 %) and dichlorobromoform (42.3 %) in the first 5 min of contact, showing that this biomass had greater affinity for trihalomethane compounds with more chlorine atoms in their structures. This finding has considerable environmental importance, given that these are the two commonest compounds found in water distribution networks.

Roll-to-Roll Coating by Liquid Flame Spray Nanoparticle Deposition

ABSTRACTNanostructured coatings have been prepared on a flexible, moving paperboard using deposition of ca. 10-50-nm-sized titanium dioxide and silicon dioxide nanoparticles generated by a liquid flame spray process, directly above the paperboard, to achieve improved functional properties for the material. With moderately high production rate (∼ g/min), the method is applicable for thin aerosol coating of large area surfaces. LFS-made nanocoating can be synthesized e.g. on paper, board or polymer film in roll-to-roll process. The degree of particle agglomeration is governed by both physicochemical properties of the particle material and residence time in aerosol phase prior to deposition. By adjusting the speed of the substrate, even heat sensitive materials can be coated. In this study, nanoparticles were deposited directly on a moving paperboard with line speeds 50-300 m/min. Functional properties of the nanocoating can be varied by changing nanoparticle material; e.g. TiO2and SiO2are used for changing the surface wetting properties. If the liquid precursors are dissolved in one solution, synthesis of multi component nanoparticle coatings is possible in a one phase process. Here, we present analysis of the properties of LFS-fabricated nanocoatings on paperboard. The thermophoretic flux of nanoparticles is estimated to be very high from the hot flame onto the cold substrate. A highly hydrophobic coating was obtained by a mass loading in the order of 50–100 mg/m2of titanium dioxide on the paperboard.

An Evaluation of Creep Behaviour in Friction Stir Welded MA754 Alloy

Effect of friction stir welding (FSW) on microstructure and creep properties of oxide dispersion strengthened (ODS) alloy MA754 were investigated. Fine-grained microstructure developed in the weld zone. TEM results showed some degree of particle agglomeration as a result of intense material flow. Creep tests of the FSW material were carried out at 973 and 1073 K. Power law creep behaviour was observed with stress exponent values of 6.9 and 6.3 at 973 and 1073 K, respectively. The results were compared to those of the as-received material. Creep resistance of FSW material was lower than that of as-received material associated with significantly reduced threshold stress. Post-weld annealing was carried out at 1598 K for 1 h. The heat treatment resulted in a coarse-grained microstructure and enhanced the creep resistance of the welded material. The creep data were compared with those of ODS Ni-Cr alloys in literature. The analysis shows the threshold stress of ODS alloys to be grain size- and temperature-dependent.

De-agglomeration of micronized benzodiazepines in dissolution media measured by laser diffraction particle sizing.

The objective of this research was to develop a method to characterize the degree of particle agglomeration using laser diffraction particle sizing, following the addition of benzodiazepine interactive mixtures to water. Interactive mixtures of diazepam, nitrazepam and oxazepam (up to 20% w/w) were prepared by mixing micronized benzodiazepines with lactose granules (250-355 microm). Micronized sodium lauryl sulfate and cetrimide (up to 5% w/w) were added to the benzodiazepine-lactose interactive mixes to produce ternary mixtures. Particle size distributions of benzodiazepines, after addition of the interactive mixtures to water, were determined using laser diffraction particle sizing. Bimodal distributions representing dispersed particles and agglomerates were observed initially after lactose carrier dissolution. Partial agglomerate to dispersed particle transition occurred during a 60-min observation period for all mixtures, reaching a constant level of agglomeration after this time. Interactive mixtures with higher benzodiazepine concentrations displayed transition profiles with higher levels of agglomeration. The presence of surfactant in interactive mixtures dramatically decreased agglomeration. Sodium lauryl sulfate was more effective than cetrimide in dispersing agglomerates. The shape of the transition curves during de-agglomeration demonstrated the presence of stable agglomerates that remained after the initial transition; these may be important in explaining dissolution and absorption rates.

Microstructure dependent performance of chemically deposited nanocrystalline metal oxide thin films

Nanostructured metal oxides with different morphologies have drawn considerable attention over the past few years due to their large surface area activated applications. Soft solution chemical methods allows bottom-up approach to tune morphology of nanocrystalline materials in thin film form with better control of particle size, shape, size distribution, particle composition, degree of particle agglomeration, etc. Here, we emphasize the deposition of some nanocrystalline metal oxide thin films using chemical methods and their morphology dependent performance in various applications. We explore the role of the experimental parameters on the developed structure and study the effect of growth parameters on the various properties of the nanocrystalline thin films. These thin films are suitable for application in photoelectrochemical cells, LPG sensors, supercapacitors and dye sensitized solar cells.

Effect of vibro-milling time and calcination condition on phase formation and particle size of nickel niobate nanopowders

Abstract The effect of milling time on the phase formation and particle size of nickel niobate, NiNb 2 O 6 , powder synthesized by a solid-state reaction via a vibro-milling technique was investigated. Powder samples were characterized using DTA, XRD, SEM and laser diffraction techniques. It was found that the smallest particle size of 32 nm was achieved at 25 h of vibro-milling after which a higher degree of particle agglomeration was observed on continuation of milling to 35 h. In addition, by employing an appropriate choice of the milling time, a narrow particle size distribution curve was also observed.

A comparison of dispersing media for various engineered carbon nanoparticles

BackgroundWith the increased manufacture and use of carbon nanoparticles (CNP) there has been increasing concern about the potential toxicity of fugitive CNP in the workplace and ambient environment. To address this matter a number of investigators have conducted in vitro and in vivo toxicity assessments. However, a variety of different approaches for suspension of these particles (culture media, Tween 80, dimethyl sulfoxide, phosphate-buffered saline, fetal calf serum, and others), and different sources of materials have generated potentially conflicting outcomes. The quality of the dispersion of nanoparticles is very dependent on the medium used to suspend them, and this then will most likely affect the biological outcomes.ResultsIn this work, the distributions of different CNP (sources and types) have been characterized in various media. Furthermore, the outcome of instilling the different agglomerates, or size distributions, was examined in mouse lungs after one and seven days. Our results demonstrated that CNP suspended in serum produced particle suspensions with the fewest large agglomerates, and the most uniform distribution in mouse lungs. In addition, no apparent clearance of instilled CNP took place from lungs even after seven days.ConclusionThis work demonstrates that CNP agglomerates are present in all dispersing vehicles to some degree. The vehicle that contains some protein, lipid or protein/lipid component disperses the CNP best, producing fewer large CNP agglomerates. In contrast, vehicles absent of lipid and protein produce the largest CNP agglomerates. The source of the CNP is also a factor in the degree of particle agglomeration within the same vehicle.

気固分散系における粉体のレオロジー評価

Design of particle handling processes requires the characteristics of powder on flowability. Although various indices exist, most were obtained from the static characteristics and cannot express the dynamic effect. In the case of liquid or gas, the characteristic of flowability is represented by viscosity. Especially in the case of liquid-solid suspension, it is well known that the viscosity changes by the degree of particle agglomeration, and the agglomeration of suspended particles is determined by “particle interaction”. However, the characteristics of powder layer have not been well understood. In this study, a method to measure the viscosity of a gas-solid suspension was developed. FT4 powder rheometer was used to measure the torque exerting on the blade, which rotated and descended into a powder layer. These data were used to calculate the viscosity of powder layer. We concluded that the well-known powder index for flowability may represent its dynamic characteristics and that the powder viscosity may provide more detailed information on powder flowability.

Effect of vibro-milling time on phase formation and particle size of lead zirconate nanopowders

Abstract A perovskite-like phase of lead titanate, PbTiO 3 , nanopowder was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of PbTiO 3 powder was investigated. Powder samples were characterized using TG-DTA, XRD, SEM and laser diffraction techniques. It was found that an average particle size of 17 nm was achieved at 25 h of vibro-milling after which a higher degree of particle agglomeration was observed on continuation of milling to 35 h. In addition, by employing an appropriate choice of the milling time, a narrow particle size distribution curve was also observed.

Preparation of hydroxyapatite nanoparticles by reverse microemulsion

Hydroxyapatite (HAP) nanoparticles have been successfully synthesized by reverse microemulsion (aqueous solution/mixed TX-100 and Tween 80/mixed n-butanol and n-hexanol/cyclohexane) at room temperature. In comparison with HAP particles, prepared by conventional direct precipitation method, the reverse microemulsion route led to a significant improvement in the particle size and the degree of particle agglomeration. The effect of different hydrophile–lipophile balance (HLB) values on the particle size was also discussed.

The Rheological Behaviour of Metallic Suspensions

The knowledge of the rheological behaviour of metallic suspensions is an important issue when simulating die filling in thixoforming processes. Therefore rheological experiments like step‐change in shear rate tests, shear stress ramps and oscillation experiments have been carried out to characterise the flow behaviour of semi‐solid alloys exemplarily for A356 and Sn‐15%Pb. The material exhibits a yield stress and shows shear‐thinning and thixotropic flow behaviour, which is strongly influenced by the solid fraction, the particle shape and size and the degree of particle agglomeration. The instantaneous response on a change in shear rate was observed and pretends shear‐thickening properties. All experiments were carried out in a Couette rheometer. The experimentally gained data are well fitted to a model approach, which consists of a modified Herschel‐Bulkley law and accounts for the time‐dependent effects by introducing a structural parameter κ.

Particle encapsulation with polymers via in situ polymerization in supercritical CO 2

Fine Dechlorane (DCR) particles with an average size of 12 μm were successfully encapsulated with poly(methyl methacrylate) (PMMA) and poly(1-vinyl-2-pyrrolidone) (PVP) polymers via in situ dispersion polymerization in supercritical carbon dioxide (scCO 2). Adjusting the process parameters can control the coating thickness, surface morphology, and degree of particle agglomeration. A uniform thin-film encapsulation of the host particles has been achieved under appropriate operating conditions, which is very difficult to obtain using other methods of supercritical fluid processing. SEM micrographs from our experiments show a variety of coating morphologies. It is found that dispersed polymer particles can deposit and aggregate on a thin layer of polymer coated on DCR and undergo plasticization, coagulation, and fusion into the encapsulating polymer. When the pressure is low or the concentration of stabilizer is high, a coexistence of smooth thin-film coating in contact with uncoagulated polymer particles was found. These observations suggest that polymerization occurs simultaneously through two parallel routes: reaction in dispersed polymer particles and reaction in the polymer domains nucleated on the surface of the host particles, which later develop into a uniform polymer layer. The latter resembles a precipitation polymerization as compared to conventional dispersion polymerization. It is also found that the stabilizer plays an important role in polymer growth and particle coarsening on the surface of the host particles. Without the stabilizer, PMMA could not be coated on the host particles and with a large amount of stabilizer, coagulated rough surface morphologies were observed due to steric repulsion. The effects of various process parameters, such as concentrations of monomer, surfactant stabilizer and initiator, and reaction pressure, are also discussed.

Spray-coating for biopharmaceutical powder formulations: beyond the conventional scale and its application.

Fluid-bed spray-coating process is widely used to prepare non-protein pharmaceutical solid dosage forms using macro-size seed particles (200-1000 microm) at kilogram batch sizes. In this study we developed a small-scale fluid-bed spray-coating process (20 g) to produce micro-sized vaccine powder formulations (40-60 microm) for epidermal powder immunization (EPI) METHODS: A bench-top spray coater was used to spray two vaccines, diphtheria toxoid (dT) and alum-adsorbed hepatitis-B surface antigen (Alum-HBsAg), onto crystalline lactose particles of 40-60 microm in diameter. Particle properties such as particle size, surface morphology, and degree of particle agglomeration were determined. Protein stability was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The immunogenicity of the vaccine was evaluated in vivo by needle injection and epidermal powder immunization (EPI) of mice or guinea pigs. Coating feasibility was demonstrated for both vaccine formulations containing different excipients. However, the nature of the vaccine antigen appeared to affect coating feasibility in terms of particle agglomeration considerably. Delivery of spray-coated dT and alum-HBsAg through EPI to mice and guinea pigs, respectively, generated significant antibody responses, at a level comparable to liquid formulation delivered subcutaneously through needle/syringe injection. The new spray-coating process represents an important technical advance and may provide a useful tool for developing high-valued biopharmaceutical powder formulations for novel applications. The strong in vivo performance of the coated dT and alum-HBsAg powders by EPI further demonstrated that spray-coating is a viable dry powder formulation process and the skin's epidermal layer presents an efficient vaccine delivery route.