Properties of copper-detonation nanodiamond composites obtained by spray drying

Nanostructural copper-detonation nanodiamond (DND) composites have been obtained by the method of spray drying. The technological process consists in spraying and drying a mixture of an aqueous copper salt solution and DND suspension, followed by thermal treatment in a reductive atmosphere. The DND content in copper powder was varied from 0.5 to 5.0 mass %. The average DND particle size in suspension was 4–6 nm. Copper-DND nanocomposite powders consist of nearly spherical particles with average size within 20–30 μm. Composition and structure of obtained materials have been studied.     

Hollow spherical nanoparticulate aggregates as potential ultrasound contrast agent: shell thickness characterization

Objective: The objective of this work is to manufacture hollow spherical nanoparticulate aggregates for use as an ultrasound contrast agent by means of spray drying of nanoparticulate suspension at a fast drying rate. Methodology: Biocompatible PMMA-MeOPEGMA and silica nanoparticles are used as the model nanoparticles. The impacts of changing the nanoparticle concentration, pH, and spray drying operating condition on the size and shell thickness-to-particle radius (S/R) ratio, which governs the shell mechanical stability, are investigated. Results and conclusion: The results indicate that the hollow microspheres size varies between 2 and 10 μm having S/R ratio between 2% and 4%, where the smaller size particles exhibit a higher S/R ratio. The resultant S/R ratio is found to be more influenced by process parameters acting at the nanoparticle scale (e.g., suspension pH) than by the spray drying operating condition.     

Porous Silica Particles Modified in a NH3 + H2O + H2O2 Mixture: Structure,Filling with Cobalt Oxide,and Catalytic Activity for CO Conversion

Inorganic Materials - Silica particles containing large mesopores (5–25 nm in size) and micropores (0.6–2 nm in size) have been prepared by chemical etching of spherical micro- and...     

Synthesis of mesoporous CaCO3 particles by a spray drying method from the stable suspensions achieved in a beads mill

Dispersion of nanoparticles in liquids is an important issue on various applications. CaCO₃ agglomerates were disintegrated into its nanoparticles by a beads mill. The dynamic light scattering (DLS) method showed the size of dispersed particles of 22 nm reduced from the initial size of 130 nm. The effectiveness of smaller beads on the dispersion was explained by their enough impact energy and their high collision frequency. No further grinding of nanoparticles by the beads was explained by the short relaxation time of nanoparticles. The mesoporous CaCO₃ particles were synthesized from the stable suspensions by the spray drying method. As the dispersion air flowrate increased, the particle size decreased due to the smaller droplet size. Non-spherical particles were explained with the velocity difference between the colloidal solution and the dispersion air, with the longer momentum transfer time and with the faster evaporation rate. The pores originated from the spaces between the beads-milled particles, which was also created by the shear force.     

Comparison of zinc oxide nanoparticles and its nano-crystalline particles on the photocatalytic degradation of methylene blue

Comparison of ZnO nanoparticles and its nano-crystalline particles on the photocatalytic degradation of methylene blue was investigated. ZnO nanoparticles and its nano-crystalline particles were synthesized from sprayed droplets of an aqueous zinc nitrate solution by flame spray pyrolysis and spray pyrolysis assisted with an electrical furnace, respectively. ZnO nanoparticles of 20 nm in average diameter and ZnO nano-crystalline particles of 20 nm in the grain size were prepared to compare the photocatalytic activity. The photocatalytic activity of those ZnO particles was evaluated by measuring the degradation of methylene blue in water under the illumination of ultraviolet rays. Effect of the particle morphology, initial concentration of methylene blue, and photocatalyst loading on the degradation of the methylene blue was investigated under the illumination of ultraviolet rays. The photocatalytic degradation capacity of the ZnO nanoparticles was higher than that of the ZnO nano-crystalline particles. The efficiency of photocatalytic degradation of methylene blue increased with increase in photocatalyst loading and decrease in initial concentration regardless of particle morphology.     

超细球形空心磷铵灭火粉的制备与应用

采用气流和离心两种喷雾干燥方法制备超细球形空心磷酸二氢铵灭火粉,并添加甲基含氢硅油乳液、氟碳表面活性剂FK-510、羧甲基纤维素钠对粉体进行原位改性。结果表明:气流喷雾制备出的颗粒较细但不均匀,而离心喷雾制备出的颗粒均匀却较粗;表面活性剂甲基含氢硅油、FK-510的添加使粉体疏水性得到了很大提高;羧甲基纤维素钠的添加能使提高颗粒的球形度以及表面光滑度;喷雾干燥过程选择温度较低以及空气相对湿度较小的大气条件有利于制备高品质灭火粉。另外灭火实验结果表明:喷雾干燥制备的超细球形空心磷酸二氢铵灭火粉灭火效果明显优于某些市售灭火粉。     

Synthesis and characterization of iron aluminide nanoparticles by DC thermal plasma jet

Intermetallic iron aluminide alloy nanoparticles were synthesized by non-transferred DC plasma spray torch at atmospheric pressure. These powder particles were characterized by vibrating sample magnetometer (VSM), X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), laser scattering particle size distribution analyzer, energy dispersive X-ray spectra (EDX) and thermo gravimetric-differential thermal analysis (TG/DTA) studies and the results are discussed. Commercially available iron and aluminium powders in the size range between 40 and 100 μm were ball milled with suitable ratio (Fe-85% and Al-15%) by weight to form a iron-aluminium blende; this was used as feed stock to synthesize iron aluminide nanoparticles. These nanoparticles particles were spherical in shape and black in colour, with the size range between 30 and 70 nm observed by ESEM. It is seen that the powders processed at higher power levels (15.3 kW) have more number of single spherical nanoparticles than powders processed at lower power levels (9.8 kW). The formation of iron aluminide nanoparticles is confirmed by XRD analysis and an exothermic reaction by DTA studies.     

Observation on growth process of gold Y- and phi-shaped nanoparticles in solutions

The morphological evolution of gold (Au) nanoparticles is demonstrated via TEM and UV-vis spectroscopy in a real-time basis. Y-shaped and phi-shaped Au nanoparticles were prepared by a seed mediated method at 0 degrees C. The evolution of shape ranging from spheres to Y- and phi-shapes was characterized by UV-vis spectroscopy. For the spherical particles, the corresponding transverse plasmon absorption (540 nm) was observed at the initial growth stage. As further growth proceeded, new peaks appeared at ca. 620 nm and ca. 700-1000 nm, which was to the characteristic peak of Y-shaped and phi-shaped nanoparticles, respectively. In addition, all intermediate steps were observed in the morphology change by TEM. At the initial step, spherical particles with 20 nm size were generated and the particles were gradually evolved from tiny triangular shape or I-shape to Y- and phi-shape. In this study, the growth mechanism of Au nanoparticles was investigated by the characterization of optical properties as well as morphologies with respect to reaction time.     

Sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor in a heated flow

The sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor into a heated flow was investigated both experimentally and theoretically. Spherical micrometer-sized particles consisting of compactly aggregated nanoparticles were formed, due to solvent evaporation and the drying process of the colloidal precursor. The degree of sintering of aggregated nanoparticles depended on the furnace temperature profile, residence time and primary particle size of the aggregated nanoparticles. Spherical monodispersed colloidal silica, in sizes ranging from 22 to 100 nm was selected as the primary particles. The sintering rate increased with temperature and residence time, and decreased with increasing primary particle size. The aggregated nanoparticles sintered completely, resulting in particles with smooth surfaces that were synthesized at 1400 °C, residence time 31.7 s that was obtained by using a carrier gas flow rate of 1.5 L/min and 0.1 M colloidal silica nanoparticles 100 nm in size. An appropriate model of sintering in the system was proposed to explain the shrinkage and the neck growth of the aggregated nanoparticles. The sintering analysis suggested that solid-state volume diffusion suitably described the sintering mechanism of spherical aggregated silica nanoparticles in a heated flow.     

Core‐Cone Structured Monodispersed Mesoporous Silica Nanoparticles with Ultra‐large Cavity for Protein Delivery

A new type of monodispersed mesoporous silica nanoparticles with a core–cone structure (MSN‐CC) has been synthesized. The large cone‐shaped pores are formed by silica lamellae closely packed encircling a spherical core, showing a structure similar to the flower dahlia. MSN‐CC has a large pore size of 45 nm and a high pore volume of 2.59 cm³ g⁻¹. MSN‐CC demonstrates a high loading capacity of large proteins and successfully delivers active β‐galactosidase into cells, showing their potential as efficient nanocarriers for the cellular delivery of proteins with large molecular weights.     

Tuning of magnetite nanoparticles to hyperthermic thermoseed by controlled spray method

Magnetite nanoparticles with super-paramagnetic properties have great potential to achieve advances in fields such as hyperthermia, magnetic resonance imaging and magnetic drug targeting. In particular, magnetic particles less than 50 nm are easily incorporated into cells and generate heat under an alternating magnetic field by hysteresis loss. Various methods of preparing magnetic particles have attracted attention, such as spray pyrolysis, microwave irradiation of ferrous hydroxide, microemulsion technique and hydrothermial preparation technique. In this study, magnetite nanoparticles were synthesized with various molar ratio of Fe²⁺ and Fe³⁺ by coprecipitation using spray-guns and dropping syringe. Experiments at different molar concentrations of Fe ions were conducted, which shows the ideal molar concentration of Fe²⁺ to be 0.5 M for pure magnetite. Both in the spray and drop method, pure magnetite nanoparticles could be synthesized when the molar concentration of Fe²⁺ was 0.5 M. With increasing the molar ratio of Fe²⁺, the particle size of the magnetite nanoparticles was increased. The smallest size could be reduced to approximately 7 nm by the spray method. The shape of the synthesized nanoparticles was nearly spherical. The calculated highest loss power by hysteresis losses was 597 W/g, generated with a molar concentration ratio of 0.5:1 (Fe²⁺:Fe³⁺).     

Synthesis and characterization of nanocrystalline mesoporous zirconia using supercritical drying

Synthesis of nano-crystalline zirconia aerogel was done by sol-gel technique and supercritical drying using n-propanol solvent at and above supercritical temperature (235-280 degrees C) and pressure (48-52 bar) of n-propanol. Zirconia xerogel samples have also been prepared by conventional thermal drying method to compare with the super critically dried samples. Crystalline phase, crystallite size, surface area, pore volume, and pore size distribution were determined for all the samples in detail to understand the effect of gel drying methods on these properties. Supercritical drying of zirconia gel was observed to give thermally stable, nano-crystalline, tetragonal zirconia aerogels having high specific surface area and porosity with narrow and uniform pore size distribution as compared to thermally dried zirconia. With supercritical drying, zirconia samples show the formation of only mesopores whereas in thermally dried samples, substantial amount of micropores are observed along with mesopores. The samples prepared using supercritical drying yield nano-crystalline zirconia with smaller crystallite size (4-6 nm) as compared to higher crystallite size (13-20 nm) observed with thermally dried zirconia.     

Size-controlled synthesis of alumina nanoparticles from aluminum alkoxides

Aluminum oxide nanoparticles were prepared by the hydrolysis of aluminum oxide alkoxides followed by calcinations, in the presence of surface stabilizing agents, such as Na(AOT) molecules. The size of alumina precursors (bohemite) was 20-30 nm, yielding aluminum oxide particles with an average size of 80 nm after calcinations at 1200 °C. The shape of the α-alumina nanoparticles was mainly spherical and the high temperature inhibited the formation of the hexagonal crystals. The introduction of Na(AOT) during the appropriate processing step, had the effect of controlling the size of the particles, the degree of aggregation and the particles shapes.     

Fabrication of size-controlled polyimide nanoparticles

Polyimide particles were fabricated through the two-steps imidization of poly(amic acid) particles prepared by using reprecipitation method. PAA and PI nanoparticles were all spherical, and the changes of particle size, its distribution, and morphology were not observed before and after the imidization. The preparation of PI nanoparticles size-controlled between ca. 20-500 nm was also achieved by changing the experimental conditions, temperature of the poor solvent, the composition of two kind of poor solvent, and PAA-NMP solution concentration.     

From Meso to Macro: Controlling Hierarchical Porosity in Supraparticle Powders

A drying droplet containing colloidal particles can consolidate into a spherical assembly called a supraparticle. Such supraparticles are inherently porous due to the spaces between the constituent primary particles. Here, the emergent, hierarchical porosity in spray-dried supraparticles is tailored via three distinct strategies acting at different length scales. First, mesopores (<10 nm) are introduced via the primary particles. Second, the interstitial pores are tuned from the meso- (35 nm) to the macro scale (250 nm) by controlling the primary particle size. Third, defined macropores (>100 nm) are introduced via templating polymer particles, which can be selectively removed by calcination. Combining all three strategies creates hierarchical supraparticles with fully tailored pore size distributions. Moreover, another level of the hierarchy is added by fabricating supra-supraparticles, using the supraparticles themselves as building blocks, which provide additional pores with micrometer dimensions. The interconnectivity of the pore networks within all supraparticle types is investigated via detailed textural and tomographic analysis. This work provides a versatile toolbox for designing porous materials with precisely tunable, hierarchical porosity from the meso- (3 nm) to the macroscale (≈10 µm) that can be utilized for applications in catalysis, chromatography, or adsorption.     

Preparation of drug nanocrystals embedded in mannitol microcrystals via liquid antisolvent precipitation followed by immediate (on-line) spray drying

The aim of this study is to investigate the feasibility of producing pharmaceutical nanoformulations for enhanced oral or pulmonary delivery of poorly water-soluble drugs via liquid antisolvent precipitation followed by immediate (on-line) spray drying. A poorly water-soluble corticosteroid, budesonide, was chosen as the model drug. Budesonide nanoparticles were prepared through liquid antisolvent precipitation, and then processed into a powdered nanoformulation which consists of budesonide nanoparticles embedded in mannitol microcrystals by immediate (on-line) spray drying. The size of the freshly precipitated and the reconstituted budesonide particles was analyzed by dynamic light scattering (DLS). The spray-dried nanoformulation, together with budesonide and mannitol raw materials, their physical mixture and the spray-dried mannitol, were characterized by field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). In vitro dissolution test and aerosol deposition study were conducted on the spray-dried nanoformulation and the physical mixture of budesonide and mannitol raw materials. It was found that the spray-dried nanoformulation, consisting of mannitol microcrystals comprising budesonide nanocrystals with z-average mean size of 520?±?11.4?nm, exhibited enhanced drug dissolution rate and higher fine particle fraction (FPF). The results of this study indicated the potential of the combined process of liquid antisolvent precipitation followed by immediate (on-line) spray drying to be used as a direct and continuous formulation process to produce powdered nanoformulations to achieve enhanced oral or pulmonary delivery of poorly water-soluble drugs.     

Efficient optical trapping and visualization of silver nanoparticles

We performed efficient optical trapping combined with sensitive optical detection of individual silver nanoparticles. The particles ranging in size from 20 to 275 nm in diameter were trapped in three dimensions using low laser power by minimizing spherical aberrations at the focus. The optical forces were quantified, and we found that the larger the particle, the stronger the optical force. The particles were imaged by an additional strongly scattered laser.     

Synthesis of nanophase alumina, and spheroidization of alumina particles, and phase transition studies through DC thermal plasma processing

Using a non-transferred DC plasma spray torch, nanosized alumina particles were synthesized from micron-sized aluminium particles. Irregular-shaped micron-sized alumina particles were spheroidized using the plasma spray torch. The synthesized powder particles were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, Fourier transform infra-red (FT-IR) spectroscopy and photoluminescence (PL) spectroscopy. The synthesized alumina nanoparticles appear spherical in shape, but mostly agglomerated in the size range 30-75 nm. It was identified that the main phase is γ-alumina with a small amount of δ-alumina. In the spheroidized alumina particles, the main phase is α-alumina with a small amount of γ-alumina. The mechanism of formation of alumina and its phase change are explained in detail.     

Preparation of size-controlled tungsten oxide nanoparticles and evaluation of their adsorption performance

The present study investigated the effects of particle size on the adsorption performance of tungsten oxide nanoparticles. Nanoparticles 18-73 nm in diameter were prepared by evaporation of bulk tungsten oxide particles using a flame spray process. Annealing plasma-made tungsten oxide nanoparticles produced particles with diameters of 7-19 nm. The mechanism of nanoparticle formation for each synthetic route was examined. The low-cost, solid-fed flame process readily produced highly crystalline tungsten oxide nanoparticles with controllable size and a remarkably high adsorption capability. These nanoparticles are comparable to those prepared using the more expensive plasma process.     

Analysis of dispersion and aggregation behavior of carbon black particles in aqueous suspension by colloid probe AFM method

To clarify the role of polymer dispersants at the carbon black (CB) nanoparticle/liquid interface, the adsorbed structure of the dispersants and the interactions between particle surfaces was evaluated using colloid probe AFM. As it is difficult to prepare stable spherical granules consisting of CB nanoparticles with diameters on the scale of several microns, for a colloidal probe by spray drying and sintering, CB nanoparticles were uniformly coated on the surface of spherical resin particles using a physical composing process. In order to establish the mechanism of action of the CB polymer dispersant by using the prepared colloid probe, polyethyleneimine (PEI) and PEI functionalized with a hydrophobic toluoyl group (T-PEI) were compared. It was found that on the adsorption of T-PEI, the viscosity of the aqueous CB suspension and the size of the aggregates were remarkably decreased in acidic conditions. Although the amounts of PEI and T-PEI adsorbed onto the CB were almost the same, a larger repulsive interaction was observed in the case of the T-PEI. CB nanoparticle dispersion was promoted by the increase in steric repulsion due to the structure of the adsorbed T-PEI.