铁(Ⅱ)无机物热解制备γ-Fe2O3及其机理

用硫酸亚铁为原料,以氢氧化钠、氨水或碳酸钠水溶液作沉淀剂,得到相应的氢氧化物或碳酸盐沉淀物作前驱体,在存在SO42-或CO32-时,500℃下进行热解,即使原料中含有少量Fe(Ⅲ),热解产物仍为纯γ-Fe2O3.用X射线衍射、透射电镜对产物进行了表征.发现其转变机理为:Fe(Ⅱ)的无机物先经空气中的氧气氧化成Fe3O4,而后进一步被氧化成γ-Fe2O3.在无SO42-或CO32-时,在相同的条件下进行热解,产物却为α-Fe2O3.     

A Magnetic Composite for Cleaning of Oil Spills on Water

The production of magnetic polymer composites for cleaning of oil spills on water is investigated. The polymer matrix consists of a biopolymer material (alkyd resin), which is cured with TDI in the presence of a magnetic powder (maghemite, γ‐Fe₂O₃), which is incorporated into the final polymer material in situ. Obtained polymer resins were characterized through magnetic force, AFM and WAXS/SAXS, showing that the proposed preparation technique leads to production of magnetic nanocomposites. Additionally, oil removal tests performed with polymer beads showed that the polymer product can be used to remove considerable amounts of oil from the surface of aqueous environments. In the best case, one part of the polymer product could be used to remove more than eight parts of oil from water.

     

Thermally and Magnetically Programmable Hydrogel Microactuators

The rapid development in micro-machinery enabled the investigation of smart materials that can embody fast response, programmable actuation, and flexibility to perform mechanical work. Soft magnetic actuators represent an interesting platform toward combining those properties. This study focuses on the synthesis of micro-actuators that respond to thermal and magnetic stimuli using micro-molding with a soft template as a fabrication technique. These microsystems consist of a hydrogel matrix loaded with anisotropic magnetic nanospindles. When a homogeneous magnetic field is applied, the nanospindles initially dispersed in monomer solution, align and assemble into dipolar chains. The ensuing UV-polymerization creates a network and conveniently arrests these nanostructures. Consequently, the magnetic dipole moment is coplanar with the microgel. Varying the shape, volume, and composition of the micro-actuators during synthesis provides a temperature-dependent control over the magnetic response and the polarizability. Beyond isotropic swelling, shaping the hydrogel as long thin ribbons with a passive layer on one side allows for differential swelling leading to bending and twisting deformations, for example, 2D- or 3D-spiral. These deformations involve a reversible amplification of the magnetic response and orientation of the hydrogels under magnetic field. Temperature control herewith determines the conformation and simultaneously the magnetic response of the micro-actuators.