Cheng Hai Hong

Effect of surface treatment on magnetorheological characteristics of core-shell structured soft magnetic carbonyl iron particles

Core-shell structured soft magnetic carbonyl iron (CI) particles coated with poly(glycidyl methacrylate) were fabricated using a dispersion polymerization method. The surface of the CI particles was pretreated with 4-aminobenzoic acid to enhance the affinity between CI and poly(glycidyl methacrylate) (PGMA). The synthesized CI/PGMA core-shell particles were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The CI/PGMA particles were dispersed into a non-magnetic liquid for applications as a magnetorheological (MR) fluid, in which the rheological properties can be altered significantly by an external magnetic field. The MR suspension was analyzed using a rotational rheometer at various magnetic field strengths. Although the fabricated CI particles exhibited lower MR properties than pure CI particles, they showed improved dispersion stability according to the Turbiscan apparatus.

Effect of salt on turbulent drag reduction of xanthan gum

The turbulent flow of an aqueous KCl solution driven by a rotating disc in a closed chamber showed significant drag reduction (DR) when a small amount of xanthan gum (XG) was added. The effects of the experimental parameters (XG and KCl concentrations, and time) on the drag reduction efficiency were examined. While the DR efficiency of XG decreased with increasing salt (KCl) concentration, the time-dependent DR efficiency was found to be fitted well using Brostow model equation.

Polymeric colloidal magnetic composite microspheres and their magneto-responsive characteristics

AbstractThis feature article reviews recent research on the fabrication of magnetic polymeric composite particles as well as their special applications as magnetorheological (MR) fluids. MR materials are a class of smart particles that can form chain-like structures when dispersed in a non-magnetic medium under an applied magnetic field. A range of methodologies for their fabrication, such as in situ polymerization and solvent casting, have been introduced to prepare micron-sized magnetic composite particles with polymers followed by a demonstration of their corresponding morphologies as well as their magnetic and MR properties. Both the magnetic properties of the particle and the MR performance of the MR fluid are strongly influenced by the incorporation of polymers including the synthesis method and mass ratio.

Shear Stress and Dielectric Analysis of H3PO4 Doped Polyaniline Based Electrorheological Fluid

We synthesized phosphoric acid (PA) doped polyaniline (PANI) particles (PANI‐PA) and investigated their electrorheological (ER) and dielectric characteristics when they were dispersed in silicone oil. Flow curves of the PANI‐PA based ER fluid under several applied electric field strengths were analyzed using a shear stress model. We also examined ER characteristics based on the relaxation time obtained from the dielectric spectrum.

Fabrication of smart magnetite/reduced graphene oxide composite nanoparticles and their magnetic stimuli-response.

Novel Fe3O4/reduced graphene oxide (RGO) composite nanoparticles were synthesized and confirmed by FT-IR spectra as good candidates for magnetic stimuli-responsive magnetorheological (MR) materials. The morphology of Fe3O4/RGO was observed by both scanning and transmission electron microscopy and their sedimentation stability improved due to a decreased density of the synthesized composites. The MR performance of the Fe3O4/RGO-based fluid was investigated with a rotational rheometer, and the Cho-Choi-Jhon model of the rheological equation of state was adopted to explain their performances for the entire shear rate region.

Preparation and electrorheological property of conducting copolyaniline/MCM-41 nanocomposite

Nanocomposite materials of silica-based mesoporous molecular sieve, MCM-41, with conducting polyaniline (PANI) and copolyaniline of poly(methyl aniline) (MEPA) inside the channels (PANI/MCM-41 and MEPA/MCM-41, respectively) were prepared and their nanocomposite formations were confirmed through N 2 -adsorption isotherm and TEM measurement. These nanocomposite particles were adopted for a dispersed phase in electrorheological (ER) fluids, and the ER property was measured using a rotational rheometer equipped with a high voltage generator. Suspension of PANI/MCM-41 showed enhanced ER properties than those of MEPA/MCM-41 or PANI alone, due to the anisotropic polarization of PANI/MCM-41 having higher conductive PANI located inside the aligned channels of MCM-41 host.

Effect of Halloysite Clay on Magnetic Carbonyl Iron-Based Magnetorheological Fluid

Soft magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids with different loadings of halloysite nanoclay were prepared, in which the MR fluid is a complex colloidal suspension consisting of magnetic particles dispersed in a liquid, showing its rapid, reversible, and tunable change between a liquid-like and solid-like state with an applied external magnetic field. The MR characteristics were measured via rotational tests, in which the flow curves exhibited a non-Newtonian behavior for all investigated samples under applied magnetic fields. Flow curves showed not only the dynamic yield stress change measured as a function of magnetic field strength using a power law fit, but also the existence of a solid-like character. Sedimentation of the MR fluid with and without an additive was also examined.

Rheological Characteristics of Solvent-Cast Poly(e-Caprolactone)/Organoclay Nanocomposite

As an effective way to enhance various properties of polymer, polymer/clay nanocompoiste is being adopted since it can hybrid the properties of the two components, showing superior physical and mechanical properties. In this study, poly(ε-caprolactone) (PCL) nanocomposites using an organoclay were prepared by a solution intercalation method, and their unique internal structures and rheological properties induced by the presence of organoclay at nano level were studied using WAXD and a rotational rheometer.