Novel Magnetorheological Suspensions Based on Co-Phthalocyanine/Fe Nanocomposite Particles

A novel magnetorheological (MR) suspension was based on methyl silicone oil and cobalt-phthalocyanine (Co-Pc)/Fe nanocomposite particles, which were synthesized by thermally decomposing liquid carbonyl Fe in the solution of Co-Pc in N, N-dimethyl formamide. The nanocomposite particles were fully characterized by XRD, SEM and HREM, and the thermal, magnetic and MR properties of nanocomposite particles were measured. Such factors as weight percent of particles (w), magnetic field strength (H), temperature (T) and shear rate (gamma) etc influencing on MR properties were investigated. The results indicated that Co-Pc/Fe nanocomposite with density of 3.66 g/cm(3) was almost micro-sized regular spheroids consisting of tens of Co-Pc coated alpha -Fe nanoparticles in inner and Co-Pc layers on surface of the spheroids. They showed good characteristics of anti-oxidation and soft magnetic. Increment of w increased field-induced shear stress (Delta tau) and zero-field viscosity (eta (0)) of MR suspensions monotonously, and improved anti-settlement stability, but eta (0) increased more markedly than Delta tau with increasing w. Delta tau was basically independent on T and gamma while increased obviously with increasing H. With increasing T, response time of the MR suspension to external magnetic field seemed to decrease. As a result, MR suspensions with satisfactory stability and rapid, completely reversible and significant MR effect can be obtained from Co-Pc/Fe nanocomposite particles.

MORPHOLOGY EVOLUTION OF POLY(St-co-BuA)/SILICA NANOCOMPOSITE PARTICLES SYNTHESIZED BY EMULSION POLYMERIZATION

Poly（St-co-BuA）/silica nanocomposite latexes were synthesized via conventional emulsion polymerization in the presence of 3-（trimethoxysilyl）propyl methacrylate modified colloidal nano-silica. The effects of surface property, particle size and content of colloidal nano-silica as well as the concentrations of monomer and surfactant on the morphology of nanocomposite latex particles were investigated by transmission electron microscope （TEM） and scanning electron microscope （SEM） in detail. Various interesting morphologies such as grape-like, Chinese gooseberry-like, pomegranate-like and normal core-shell structures were observed. Droplet nucleation mechanism competing with micelle nucleation mechanism was proposed to explain the morphological evolution of the nanocomposite particles.

Chemical synthesis and characterization of SmCo_(5)/Co magnetic nanocomposite particles

Magnetic nanocomposite material has been widely focused for the potential to become the next generation of magnetic material.In this paper,two kinds of chemical coating methods were used to prepare SmCo_(5)/Co nanocomposite particles which were further characterized and compared.The two methods were carried out by using different materials and at different temperatures.In Method I,oleylamine(OAm),oleic acid and Ca(acac)2 were used and the reaction was carried out at the temperature of 300℃.In MethodⅡ,anhydrous isopropanol,polyvinylpyrrolidone(PVP),N_(2)H_(4)·H_(2)O and CoCl_(2)·6 H_(2)O were used and the reaction temperature was~55℃.It was found that by using the two methods,the growth and the crystal structure of the Co nanoparticles(NPs)are different.In Method I,epitaxial growth on the surface of SmCo_(5) NPs was observed and the Co NPs were in a facecentered close packing crystal structure.While in Method II,the coated Co NPs were self-nucleated with a crystal structure of hexagonal close packing.Using MethodⅡwith the addition of surfactant,anisotropic nanocomposite particles were achieved with an enhanced saturated magnetization of 84.2 A·m^(2)·kg^(-1).And the coercivity change of the NPs illustrates that a nonmagnetic interlayer between the hard and soft magnetic phase is beneficial to maintain the coercivity.

Drug/polymer nanoparticles prepared using unique spray nozzles and recent progress of inhaled formulation

Inhaled formulations are promising for pulmonary and systemic non-pulmonary diseases.Functional engineered particles including drugs and drug-loaded nanocarriers have been anticipated because they can improve drug delivery efficacy against target sites in the lungs or blood.In this review,unique spray nozzles(e.g.,four-fluid spray nozzle and twosolution mixing type nozzle)for the preparation of nanocomposite particles which mean microparticles containing drug nanoparticles are described.These nozzles can produce nanocomposite particles in one-step and their spray drying system is suitable for scalingup.Nanocomposite particles are useful in improving drug absorption and delivery efficacy against alveolar macrophages.In addition,recent studies on several pulmonary diseases(tuberculosis,lung cancer,cystic fibrosis,pneumonia,vaccine and others)and related inhaled formulations were also reviewed.

NETWORK ENCAPSULATION OF NANOMETER CaCO_3

The encapsulation of stearic acid coated nanometer CaCO3 by a polystyrene (PS) network via emulsion polymerization is described, where gamma-methacryloxypropyltrimethoxysilane (MPS) was used as an efficient crosslinker. The important factors such as the type and amount of surfactant and initiator and the content of CaCO3 are investigated as well as the role of MPS. It has been shown that little PS was extractable with only 0.6 wt% of MPS (relative to styrene). The cationic surfactant cetyl trimethylammonium bromide (CTAB) proved more effective than the anionic surfactant sodium dodecyl sulfonate (SDS). The yield rises, particles become smaller and size distribution broadens with increased amount of CTAB. It is also found that either 2,2'-azobis(isobutyronitrile) (AIBN) or ammonium persulfate (APS) is suitable for attaining high monomer conversion. With increased amount of CaCO3, the encapsulation ratio can be varied from 17.9 to 3.6, while monomer conversion and yield decrease slightly. FT-IR spectra of the products after extraction indicate tight encapsulation between PS and CaCO3, and TEM photographs of composite particles with well-defined core-shell structure give direct evidence of encapsulation.

Scalable gas-phase processes to create nanostructured particles

The properties of nanoparticles are often different from those of larger grains of the same solid material because of their very large specific surface area. This enables many novel applications, but properties such as agglomeration can also hinder their potential use. By creating nanostructured particles one can take optimum benefit from the desired properties while minimizing the adverse effects. We aim at developing high-precision routes for scalable production of nanostructured particles. Two gas-phase synthesis routes are explored. The first one - covering nanoparticles with a continuous layer - is carried out using atomic layer deposition in a fluidized bed. Through fluidization, the full surface area of the nanoparticles becomes available. With this process, particles can be coated with an ultra-thin film of constant and well-tunable thickness. For the second route - attaching nanoparticles to larger particles - a novel approach using electrostatic forces is demonstrated. The micron-sized particles are charged with one polarity using tribocharging. Using electrospraying, a spray of charged nanoparticles with opposite polarity is generated. Their charge prevents agglomeration, while it enhances efficient deposition at the surface of the host particle. While the proposed processes offer good potential for scale-up, further work is needed to realize large-scale processes.