Formation Of Spherical Particles Research Articles

Hydroxyapatite Microsphere Production by Plasma Spray

Hydroxyapatite is Ca5(PO4)3(OH) (HA) is a material used as a bone filler and dermal or therapeutic drug vehicles, due to their biocompatibility, bioactivity and relative reabsorption in hard or soft tissue. In particular, applications of facial fillers and cements formulated with HA require that this is available in the form of spheroidal particles, with size greater than 40 microns, with the purpose of reducing the in situ inflammation of connective tissue. Chemical synthesis techniques are limited to produce smaller particles, in micro or nanometric size. This paper proposes the reprocessing of the natural HA particles, obtained from fresh bovine bone, which is subjected to chemical and thermal treatments (pyrolysis in an oxidizing atmosphere at 900C for 2h), grinding and sieving (particles less than 200μm). These particles are atomized into plasma spray equipment that draws in a N2 flow, and projects them in distilled water. This material is observed by electron microscopy, which revealed the formation of spherical particles with smooth surfaces and with a size distribution of 20-70μm. X-ray diffraction analysis revealed the partial decomposition of the HA in other calcium phosphates: α-Ca3(PO4)2 and Ca4(PO4)2O, essential phases of the formulation of bone cements, which accelerate the absorption of the biological particles in the biological medium, requirement searched in facial fillers. The process would increase the size of the spherical particles.

Preparation, Characterization, Photocatalytic Activity of S and Ag co-Doped Mesoporous Titania Photocatalysts

In order to improve the photocatalytic performance of mesoporous titania under visible light, a series of photocatalysts of S and Ag co-doped mesoporous titania have been successfully prepared by template method using thiourea, AgNO3 and tetrabutyl titanate as precursors and Pluronic P123 (EO20PO70EO20) as template. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption measurements, and UV-visible spectroscopy were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The microcrystal of the photocatalysts consisted of anatase phase and was approximately present in the form of spherical particle. The photocatalytic performance was studied by photodegradation methyl orange in water under UV and visible light irradiation. The calcination temperature and the doping content influenced the photoactivity. In addition, the possibility of cyclic usage of co-doped mesoporous titania was also confirmed, the photocatalytic activity of mesoporous titania remained above 89% of the fresh sample after being used four times. It was shown that the co-doped mesoporous titania could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants. The synergistic effect of sulfur and silver co-doping played an important role in improving the photocatalytic activity.

Further studies on the effects of substituents at the Cp and salicyladiminato ligands of half-sandwich chromium(III) complexes on their catalytic properties for ethylene polymerization

A series of new half-sandwich chromium(III) complexes Cp′[2-R1-6-(CHNR2)C6H2O]CrCl [R1 = iPr (1), tBu (2, 3, 4, 5); R2 = iPr (2, 4, 5), tBu (1, 3); Cp′ = C5H5(1, 2, 3), C5H2Ph3 (4), C5Me4Ph(5)] were synthesized from the reactions of Cp′CrCl2(THF) with corresponding salicyladiminato lithium. All complexes were characterized by elemental analyses and the structures of complexes 1, 2, 3 and 5 were determined by X-ray diffraction analysis. These complexes show moderate catalytic activities for ethylene polymerization upon activation with a relatively small amounts of AlMe3 or AlEt3, producing high molecular weight polyethylene in the form of spherical particles. Under similar conditions, the catalytic activity of complexes carrying a same salicylaldiminato ligand changes with the cyclopentadienyl ligand in the order Me5Cp > Me4PhCp > 1,2,4-Ph3Cp > Cp. The catalytic activity of these catalysts is also affected significantly by the AlR3 cocatalyst in the order AlMe3 > AlEt3.

Facile synthesis of metastable Ni–P nanostructured materials by a novel bottom-up strategy

A novel bottom-up strategy combining chimie douce and non-conventional consolidation process to elaborate Ni–P metastable alloy is described here. The chimie douce method consists on the polyol process, modified by the addition of hypophosphite (strong reducing agent). It allows elaborating Ni–P nanopowder. The consolidation of the as-obtained nanoparticles is carried out by Spark Plasma Sintering (SPS). The microstructure of the powder and nanostructured dense sample was studied and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and FTIR spectroscopy. The nanopowder is formed of the metastable Ni–P alloy, with a composition of about 3.44% in phosphorus. Unlike Ni–P alloys prepared by electroless or electrodeposition, the nanoparticles developed show good crystallinity. They have spherical morphologies with a size of about 100 nm and are formed by aggregation of crystallites about 8 nm in diameter. Various analysis techniques showed that SPS treatment induced the transformation of the metastable Ni–P alloy in a two phases: almost pure nickel and a new phase with chemical formula Ni3P. This latter is in form of spherical particles with about 130 nm in diameter, while the nickel grains have a polygonal shape with 330 nm in diameter.

Polyvinylidene Fluoride/Acrylonitrile Butadiene Rubber Blends Prepared Via Dynamic Vulcanization

Dynamically vulcanized blends based on polyvinylidene fluoride (PVDF)/acrylonitrile butadiene rubber (NBR) were prepared and characterized. The mixing torque and dynamic rheology analyses showed that the NBR phase increased the viscosity of the blends. Scanning electron microscopy (SEM) results showed that the NBR phase was in the form of spherical particles dispersed in the PVDF phase during dynamic vulcanization. Comparing PVDF-rich and NBR-rich blends, the size of the rubber particles in the NBR-rich blends were larger than those in PVDF-rich blends. Differential scanning calorimetry (DSC) results showed that the addition of the NBR phase reduced the PVDF crystallinity and Tm. Thermal gravimetric analysis (TGA) results showed that the dynamically vulcanized PVDF/NBR blends had a higher residual char mass than the neat PVDF and NBR. For PVDF-rich blends, the PVDF can be highly toughened by NBR; the Izod impact strength of the PVDF/NBR (70/30) blend was 77.5 kJ/m2, which was about six times higher than that of pure PVDF. For rubber-rich blends, the PVDF component was beneficial to the mechanical properties of the blends, which can be used as thermoplastic elastomers.

Phase and structural conditions of low-temperature plasma interaction products with steel

Structural-phase research of low-temperature plasma interaction products with carbonaceous steel is conducted in the discharge between solid electrode and water. Such a discharge at a certain electric parameters leads to a powder formation of spherical particles with a diameter 10−6 - 10−3 m. A scale on surfaces of a steel electrode and the powder synthesized from it are subjected to a comparative analysis. Qualitative and quantitative phase characteristics of these products are different and depend on conditions of their formation. Their basic phase components are various ferric oxides: magnetite Fe3O4, wustite FeO, hematite α-Fe2O3. Magnetite is contained in the powder synthesized at normal atmospheric conditions in the greatest quantity. Atmospheric pressure reduction and discharge implementation in a nitrogenous aerosphere considerably reduce quantity of magnetite in a formed powder. Diffusion speed in oxide layers and reaction temperature also influence electrode iron oxidation process. The formation mechanism of ferritic powder from steel under the influence of discharge plasma with a liquid electrode is offered on the basis of the gained results.

Magnetic properties of Co 1−x Zn x Fe 2 O 4 spinel ferrite nanoparticles synthesized by starch-assisted sol–gel autocombustion method and its ball milling

In this article, Co1−xZnxFe2O4 (x=0.0 and 0.5) spinel ferrite nanoparticles were achieved at 800 °C by starch-assisted sol–gel autocombustion method. To further reduce the particle size, these synthesized ferrite nanoparticles were ball-milled for 2 h. X-ray diffraction patterns demonstrated single phase formation of Co1−xZnxFe2O4 (x=0.0 and 0.5) spinel ferrite nanoparticles. FE-SEM analysis indicated the nanosized spherical particles formation with spherical morphology. The change in Raman modes and relative intensity were observed due to ball milling and consequently decrease of particle size and cationic redistribution. An X-ray Photoelectron Spectroscopy (XPS) result indicated that Co2+, Zn2+ and Fe3+ exist in octahedral and tetrahedral sites. The cationic redistribution of Zn2+ and consequently Fe3+ occurred between octahedral and tetrahedral sites after ball-milling. The change in saturation magnetization (Ms) and coercivity (Hc) with decrease of nanocrystalline size and distribution of cations in spinel ferrite were observed.

Size- and shape-controlled synthesis and catalytic performance of iron–aluminum mixed oxide nanoparticles for NOX and SO2 removal with hydrogen peroxide

A novel, simple, reproducible and low-cost strategy is introduced for the size- and shape-controlled synthesis of iron–aluminum mixed oxide nanoparticles (NIAO(x/y)). The as-synthesized NIAO(x/y) catalyze decomposition of H2O2 yielding highly reactive hydroxyl radicals (OH) for NOX and SO2 removal. 100% SO2 removal is achieved. NIAO(x/y) with Fe/Al molar ratio of 7/3 (NIAO(7/3)) shows the highest NOX removal of nearly 80% at >170°C, whereas much lower NOX removal (<63%) is obtained for NIAO(3/7). The melting of aluminum oxides in NIAO(7/3) promotes the formation of lamellar products, thus improving the specific surface areas and mesoporous distribution, benefiting the production of OH radicals. Furthermore, the NIAO(7/3) leads to the minor increase of points of zero charges (PZC), apparent enhancement of FeOH content and high oxidizing ability of Fe(III), further improving the production of OH radicals. However, the NIAO(3/7) results in the formation of aluminum surface-enriched spherical particles, thus decreasing the surface atomic ratio of iron oxides, decreasing OH radical production. More importantly, the generation of FeOAl causes the decline of active sites. Finally, the catalytic decomposition of H2O2 on NIAO(x/y) is proposed. And the well catalytic stability of NIAO(7/3) is obtained for evaluation of 30h.

Microwave assisted synthesis of monodispersed Y2O3 and Y2O3:Eu3+ particles

Monodisperse spherical Y2O3 and Y2O3:Eu3+ nanocrystalline particles with particle size between 100nm and 350nm were successfully prepared by microwave assisted urea precipitation method followed by a thermochemical treatment. Fast microwave heating, controlled decomposition of urea and burst nucleation of metal ions in aqueous solution led to the formation of non-aggregated spherical particles with narrow size dispersion. The particle size and size dispersion was controlled by adjusting the urea/metal ions ratio, the metal ions concentration, the reaction time and the temperature. X-ray diffraction (XRD) analysis indicated that the as prepared particles have Y(OH)CO3 composition, which converted to highly crystalline cubic Y2O3 after calcination at temperatures above 600°C. The calcined Y2O3 particles preserved the spherical morphology of the as prepared particles and exhibited polycrystalline structure. The size of the crystallites increased from ~8nm to ~37nm with the increase of the calcination temperature from 500°C to 900°C. In order to transform these nanostructures to luminescent composition, Eu3+ doping has been performed. Y2O3:Eu3+ particles inherited the morphology and polycrystalline structure of the host Y2O3 particles. Photoluminescence (PL) analysis of Y2O3:Eu3+ particles showed a strong red emission peak at 613nm corresponding to 5D0–7F2 forced electric dipole transition of Eu3+ ions under UV excitation. All these critical characteristics, and being heavy-metal free, make these particles useful for bioimaging, and display devices.

Capillary assembly of microscale ellipsoidal, cuboidal, and spherical particles at interfaces.

Micron-sized anisotropic particles with homogeneous surface properties at a fluid interface can deform the interface due to their shape. The particles thereby create excess interfacial area and interact in order to minimize this area, which lowers the total interfacial energy. We present a systematic investigation of the interface deformations around single ellipsoidal particles and cuboidal particles with rounded edges in the near field for various contact angles and particle aspect ratios. The correlation of these deformations with capillary bond energies-the interaction energies of two particles at contact-quantifies the relation between the interactions and the near-field deformations. We characterize the interactions using effective power laws and investigate how anisotropic particles self-assemble by capillary forces. Interface deformations and particle interactions for cuboidal particles are weaker compared with those for ellipsoidal particles with the same aspect ratios. For both particle shapes, the bound state in side-by-side orientation is most stable, while the interaction in tip-to-side orientation is repulsive. Furthermore, we find capillary attraction between spherical and ellipsoidal particles. Our calculations therefore suggest cluster formation of spherical and ellipsoidal particles, which elucidates the role of spherical particles as stoppers for the growth of worm-like chains of ellipsoidal particles. The interaction between spherical and ellipsoidal particles might also explain the suppression of the "coffee-ring effect" that has been observed for evaporating droplets with mixtures of spherical and ellipsoidal particles. In general, our calculations of the near-field interactions complement previous calculations in the far field and help to predict colloidal assembly and rheological properties of particle-laden interfaces.

Growth mechanisms for spherical mixed hydroxide agglomerates prepared by co-precipitation method: A case of Ni1/3Co1/3Mn1/3(OH)2

Spherical Ni1/3Co1/3Mn1/3(OH)2 agglomerates were synthesized by the co-precipitation method in the presence of ammonia. The results show that the growth mechanism of spherical agglomerates follows three-stages, i.e. nucleation and anisotropic growth of single crystals; agglomeration of polycrystalline crystallites agglomerated by single crystal grains as primary particles to form embryonic agglomerates; formation, growth and consolidation of spherical agglomerates or particles by agglomeration of embryonic agglomerates, continued growth of individual crystals in the agglomerates and further attachment of primary particles. The first two stages are very fast while the last stage takes almost the entire process to complete. The main reason for the anisotropic growth of Ni1/3Co1/3Mn1/3(OH)2 crystal is that crystal surface energy of E(001), E(100), E(101) and E(102) is different with E(001) being the highest. The morphology of the final spherical agglomerates is explained by partial re-crystallization of contacting primary particles. The growth process of spherical agglomerates was examined by X-ray diffraction, scanning electron microscope, transmission electron microscope and calculation of crystal surface energy using density function theory.

Crystalline Submicrometer Spherical Particles with High Refractive Index for Optical Applications

Nanoparticles are generally aggregated in liquid to reduce surface energy, and therefore surface modification of the nanoparticles is important to obtain well dispersed nanoparticles in liquid. Thus the aggregation of nanoparticles should be avoided for practical use of nanoparticles as much as possible.Recently we found that B4C submicrometer spherical particles by irradiating low-fluence laser onto the B nanoparticles dispersed in organic solvent through the high-temperature carbonization reaction. Furthermore, we also found that similar submicrometer spherical particles were produced for various kinds of materials, such as metals (Au, Ag, etc.), oxides (ZnO, TiO2, etc.) and semiconductors (Si, GaP, etc.) using nanoparticles as raw materials and by unfocused laser beam irradiation.In these cases, raw nanoparticles are presumably not vaporized nor ablated but melted by nanosecond laser irradiation to form liquid droplets, resulting in spherical particle formation by quenching. Thus, this process “laser melting in liquid” is evidently different from the conventional technique, “laser ablation in liquid” for nanoparticle fabrication using high-fluence laser irradiation in liquid.More importantly, the particle size increased from nano-size to sub-micrometer size by laser melting in liquid. This is because aggregated nanoparticles melt together by optical absorption and subsequent temperature increase over melting temperature to form larger spherical particles. Thus the aggregation of nanoparticles plays an important role in submicrometer spherical particle formation.Here we present our recent results on the laser melting in liquid, such as the effect of processing parameters on the products. Especially we discuss the effect of raw particle size by dynamic light scattering and zeta potential on the product morphology and generated particle size. Physicochemical calculation of temperature estimation based on the particle heating-melting-quenching model by laser irradiation is compared with the experimental results. Optical and medical applications of submicrometer spheres is also demonstrated.

Structure investigations of nanocrystalline glass ceramics by ASAXS

Glass ceramics containing fluoride crystals such as BaF2 or CaF2 with crystallite sizes in the range from 5 to 100 nm are potential candidates for numerous photonic applications. Glass ceramics containing rare-earth-doped fluoride crystals are candidates for laser materials. The size distribution plays an important role and often a narrow size distribution is required for photonic applications. In the last years a hindered growth effect leading to a more narrow size distribution was observed during the crystallization of BaF2 as well as CaF2 nanocrystals in oxy-fluoride glasses. The aim of this study is a detailed quantitative structural and nano-chemical analysis of the formation of BaF2 or CaF2 in two glass ceramics by Anomalous Small-Angle X-ray Scattering (ASAXS) to reveal and understand the mechanism of hindered growth. Nanocrystals of BaF2 precipitate during heat treatment of a silicate glass of composition 69.6SiO2-7.52Al2O3-15.04K2O-1.88Na2O-4BaF2-2BaO. X-ray diffraction measurement proved the formation of BaF2 crystals in the glass matrix. High resolution TEM showed the formation of spherical particles of sizes in range from 10-40 nm surrounded by a layer enriched with SiO2. SAXS reveal the growth of nanocrystals with increasing annealing time and temperatures. ASAXS experiments are done at four energies close to the Ba-L3 X-ray absorption edge (5247eV). The ASAXS curves for the sample annealed at 5400C for 20h revealed a spherical core-shell model. It turned out that the layer surrounding the BaF2 crystals is enriched with SiO2. Sizes and compositions of these layers are analyzed quantitatively. Furthermore, the ASAXS analysis reveals the presence of very small nucleates of size of about 3 nm in the as melted glass sample already [1]. A precipitation of CaF2 nanoparticles takes place during heat treatment of glasses of composition 7.65Na2O–7.69K2O–10.58CaO–12.5CaF2–5.77Al2O3–55.8SiO2 up to 40 hours. SAXS experiments and especially ASAXS near the Ca-K edge proves the formation of CaF2 nanoparticle surrounded with SiO2 enriched layers, quantitatively. The ASAXS effect is very pronounced at this untypical low energy for ASAXS studies at the Ca-K edge. The ASAXS result reveals crystal sizes between 10-20 nm surrounded by a shell of lower electron density. Additional very small heterogeneities are found after long annealing with diameters of about 1.6 nm [2].

Photo-, cathodo- and thermoluminescent properties of dysprosium-doped HfO2 films deposited by ultrasonic spray pyrolysis

In this work, the photoluminescent (PL), cathodoluminescent (CL) and thermoluminescent (TL) properties of hafnium oxide films doped with trivalent dysprosium ions are reported. The films were deposited on glass substrates at temperatures ranging from 300 to 600°C, using chlorides as precursor reagents. The surface morphology of films showed a veins shaped microstructure at low deposition temperatures, while at higher temperatures the formation of spherical particles was observed on the surface. X-ray diffraction showed the presence of HfO2 monoclinic phase in the films deposited at temperatures greater than 400°C. The PL and CL spectra of the doped films showed the highest emission band centered at 575nm corresponding to the transitions 4F9/2→6H13/2, which is a characteristic transition of Dy3+ ion. The greatest emission intensities were observed in samples doped with 1 atomic percent (at%) of DyCl3 in the precursor solution. Regarding the TL behavior, the glow curve of HfO2:Dy+3 films exhibited spectrum with one broad band centered at about 150°C. The highest intensity TL response was observed on the films deposited at 500°C.

Influence of particle/solid surface zeta potential on particle adsorption kinetics

In this paper we attempt to understand monolayer formation of spherical particles on a solid surface immersed in a suspension and driven by electrostatic interaction force. The study focuses on the theoretical aspects of the particle adsorption and modeling work based on the random sequential adsorption (RSA) approach is done in order to describe the particle adsorption kinetics and the saturation coverage. The theoretical model is then compared with experimental data obtained under conditions similar to those of the modeling work. Studying the adsorption of polystyrene particles on a silicon wafer in an aqueous system was employed to experimentally validate the theoretical framework. It has been shown both theoretically and experimentally that the particle and solid surface zeta potential values do influence the adsorption kinetics but the effect is too negligible to be of any use in accelerating the kinetics. We have shown that the electrostatically driven particle adsorption is a transport limited process and the rate of transport is not a major function of the zeta potential values of the particle and the solid surface. The faster kinetics seen when the ionic concentration of the suspension is increased is because of the blocking effects and not due to faster approach of particles towards the solid surface. Finally, we have made an important addition to the existing models by incorporating the variation in the flux as a function of particle/solid surface zeta potentials, surface coverage and the randomized position of incidence of an incoming particle on the solid surface.

Optimization of the experimental conditions for the synthesis of micro-size monodisperse spherical silver powders using Box–Behnken design

Monodisperse and spherical micro-size silver powder, which has narrow size distribution and high purity, was prepared by using silver nitrate as metal source, L-ascorbic acid as reductant and sodium sulfate as dispersant. The aim of this paper was to study the simultaneous effects of pH (2–6), silver nitrate concentration [AgNO3] (0.25–0.75mol/L), dropping time td (5–15min) and their interactions on properties of silver particles. In order to detect factor interactions and optimize these parameters, Box–Behnken design of experiments (a response surface methodology) was used. Synthesized silver powders were characterized by a laser particle size analyzer (LPSA), a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). After surveying the experiment data and regression analysis of the data, a mathematical model was derived for optimizing particle size. The optimum condition was: [AgNO3], 0.75mol/L; pH, 6; and td, 5min. The predicted particle size was 1.39μm and the experimental particle size was 1.38μm at the optimum condition, which showed that the model agreed well with the experimental data. It is found that the [AgNO3] and dropping time have a positive effect and the pH value has a negative influence on the particle size. The possible mechanism for the formation of novel spherical silver particles is explored.

Abstract 584: ApoE3[K146N/R147W] Acts as a Dominant Negative ApoE Form that Prevents Remnant Clearance and Inhibits the Biogenesis of HDL

Introduction: The K146N/R147W substitutions in human apolipoproteinE3 (apoE3) have been associated with a dominant form of type III hyperlipoproteinemia which is expressed at an early age. Methods: The effects of the K146N,R147W substitutions on the lipid and lipoprotein profiles and the HDL phenotypes were studied by adenovirus mediated gene transfer of the full length and a truncated apoE3[K146N/R147W]-202 mutant using different mouse models. Results: A low dose of adenovirus expressing the apoE3[K146N/R147W] mutant in apoE deficient or in apoA-I x apoE double deficient mice exacerbated the hypercholesterolemia and increased greatly plasma apoE and triglycerides levels. In apoE deficient mice, the apoE3[K146N/R147W] mutant displaced apoA-I from the VLDL/LDL/HDL region and resulted in the accumulation of discoidal apoE containing HDL particles in plasma. Similar doses of WT apoE3 cleared the cholesterol of apoE deficient mice without induction of hypertriglyceridemia and promoted formation of spherical HDL particles. A unique feature of the truncated apoE3[K146N/R147W]-202 mutant is that it prevented the induction of hypertriglyceridemia but did not correct the hypercholesterolemia. Other apoE-202 truncated mutants tested did not induce hypertriglyceridemia but corrected hypercholesterolemia. Infection of apoE deficient mice with adenoviruses expressing the apoE3[K146N/R147W] and lipoprotein lipase corrected the hypertriglyceridemia but did not prevent the formation of discoidal HDL particles. Infection of apoE deficient mice with adenoviruses expressing the apoE3[K146N/R147W] and lecithin:cholesterol (LCAT) acyltransferase corrected hypertriglyceridemia, normalized the plasma cholesteryl ester to total cholesterol ratio and generated spherical HDL particles. The combined data indicate that the K146N/R147W substitutions in the full length and the truncated apoE3[K146N/R147W] mutant prevent receptor mediated remnant clearance. Conclusion: The lipid/lipoprotein and HDL abnormalities observed in the different mouse models suggest that the apoE3[K146N/R147W] mutant acts a dominant negative ligand that exacerbates the dyslipidemia and also affects the activity of LCAT and thus inhibits the maturation of HDL.

TiO2Microwave Synthesis, Electrophoretic Deposition of Thin Film, and Photocatalytic Properties for Methylene Blue and Methyl Red Dyes

Electrophoretic deposition (EPD) of TiO2thin film was carried out at room temperature on low cost steel substrate using microwave synthesized nanoparticles (NPs) of TiO2. Synthesized NPs and EPD thin film were characterized at different stages of synthesis for its crystal structure, morphology, elemental analysis, and surface area. Spherical particle morphology and formation of TiO2were confirmed by scanning electron micrograph (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). Synthesized NPs were formed in anatase phase having crystallite size of about 12.3 nm from Scherrer's formula using full width half maxima (FWHM). Surface area was found to be 43.52 m2/g by BET giving particle size of 33 nm. Photocatalytic (PC) behavior of TiO2NPs and EPD TiO2film on steel substrate was investigated under UV light for two commercial dyes and their photocatalysis efficiency was analyzed. NPs have shown better efficiency for methylene blue (MB) dye than EPD film whereas EPD film have shown higher PC activity for methyl red (MR) dye.

Novel calcium hexaluminate/spinel-alumina composites with graded microstructures and mechanical properties

Calcium hexaluminate (CA6) was incorporated into the matrix of magnesio aluminate spinel-alumina (MA-A) via infiltration of a porous preform fabricated from α-Al2O3 and MgO powders with a saturated calcium acetate solution and subsequent firing, forming CA6/(MA-A) functionally composites with graded fracture toughness. Actually, the porous preform was partially and perpendicularly immersed (1/4 of its length) in the solution. Owing to the capillary action, the calcium acetate solution was absorbed into the porous preform, and the different absorption distance led to the graded solution concentration in the height direction of the porous preform. The in-situ formation of CA6 conferred graded microstructures, as well as improved mechanical properties on the resultant composites. The CA6 content decreased gradually along the solution absorption direction, i.e., from one end [CA6/(MA-A) region] immersed in solution to the other end [MA-A region], reducing evidently the formation of layered structure along the direction, while increasing gradually the formation of spherical alumina particles. The CA6/(MA-A) region had a better toughness that could prevent the crack propagation and improve the spalling resistance. Meanwhile, the MA-A region could provide structural support, because of the higher Vickers hardness and density.

Detail study on ac-dc magnetic and dye absorption properties of Fe3O4 hollow spheres for biological and industrial application.

Here solvo-thermal technique has been used to synthesize hollow-nanospheres of magnetite. We have shown that PVP plays an important role to control the particle size and also helps the particles to take the shape of hollow spheres. Structural analysis was done by XRD measurement and morphological measurements like SEM and TEM were performed to confirm the hollow type spherical particles formation and their shape and sizes were also investigated. The detail ac-dc magnetic measurements give an idea about the application of these nano spheres for hyperthermia therapy and spontaneous dye adsorption properties (Gibbs free energy deltaG0 = -0.526 kJ/mol for Eosin and -1.832 kJ/mol for MB) of these particles indicate its use in dye manufacturing company. Being hollow in structure and magnetic in nature such materials will also be useful in other application fields like in drug delivery, arsenic and heavy metal removal by adsorption technique, magnetic separation etc.