Iron-based microstructured or nanostructured materials, including Fe, γ-Fe2O3, and Fe3O4, are highly desirable for magnetic applications because of their high magnetization and a wide range of magnetic anisotropy. An important application of these materials is use as an electromagnetic wave absorber to absorb radar waves in the centimeter wave (2−18 GHz). Dendrite-like microstructures were achieved with the phase transformation from dendritic α-Fe2O3 to Fe3O4, Fe by partial and full reduction, and γ-Fe2O3 by a reduction−oxidation process, while still preserving the dendritic morphology. The investigation of the magnetic properties and microwave absorbability reveals that the three hierarchical microstructures are typical ferromagnets and exhibit excellent microwave absorbability. In addition, this also confirms that the microwave absorption properties are ascribed to the dielectric loss for Fe and the combination of dielectric loss and magnetic loss for Fe3O4 and γ-Fe2O3.

Hierarchical Dendrite-Like Magnetic Materials of Fe3O4, γ-Fe2O3, and Fe with High Performance of Microwave Absorption

MnFe2O4 nanoparticles have been synthesized on a large scale by a simple hydrothermal process in a wild condition, and the RGO/MnFe2O4 nanocomposites were also prepared under ultrasonic treatment based on the synthesized nanoparticles. The absorption properties of MnFe2O4/wax, RGO/MnFe2O4/wax and the RGO/MnFe2O4/PVDF (polyvinylidene fluoride) composites were studied; the results indicated that the RGO/MnFe2O4/PVDF composites show the most excellent wave absorption properties. The minimum reflection loss of RGO/MnFe2O4/PVDF composites with filler content of 5 wt % can reach −29.0 dB at 9.2 GHz, and the bandwidth of frequency less than −10 dB is from 8.00 to 12.88 GHz. The wave absorbing mechanism can be attributed to the dielectric loss, magnetic loss and the synergetic effect between RGO+MnFe2O4, RGO+PVDF and MnFe2O4+PVDF.

Enhanced microwave absorption property of reduced graphene oxide (RGO)-MnFe2O4 nanocomposites and polyvinylidene fluoride.

Here, we report, for the first time, hydrogenated TiO2 nanocrystals as a novel and exciting microwave absorbing material, based on an innovative collective-movement-of-interfacial-dipole mechanism which causes collective-interfacial-polarization-amplified microwave absorption at the crystalline/disordered and anatase/rutile interfaces. This mechanism is intriguing and upon further exploration may trigger other new concepts and applications.

Hydrogenated TiO(2) nanocrystals: a novel microwave absorbing material.

Titanium dioxide nanomaterials: self-structural modifications.

Core/shell nanoparticles were first reported in the early 1990s with a simple spherical core and shell structure, but the area is gradually diversifying in multiple directions such as different shapes, multishells, yolk/shell etc., because of the development of different new properties of the materials, which are useful for several advanced applications. Among different sub-areas of core/shell nanoparticles, yolk/shell nanoparticles (YS NPs) have drawn significant attention in recent years because of their unique properties such as low density, large surface area, ease of interior core functionalization, a good molecular loading capacity in the void space, tunable interstitial void space, and a hollow outer shell. The YS NPs have better properties over simple core/shell or hollow NPs in various fields including biomedical, catalysis, sensors, lithium batteries, adsorbents, DSSCs, microwave absorbers etc., mainly because of the presence of free void space, porous hollow shell, and free core surface. This review presents an extensive classification of YS NPs based on their structures and types of materials, along with synthesis strategies, properties, and applications with which one would be able to draw a complete picture of this area.

Yolk/shell nanoparticles: classifications, synthesis, properties, and applications

https://ir.nctu.edu.tw:443/bitstream/11536/25591/1/000225665600016.pdf

Microwave absorbing materials using Ag-NiZn ferrite core-shell nanopowders as fillers

Copper ions (Cu) grafted chitosan coating was prepared using the pneumatic spraying method on the silicone rubber surface. Coating's surface properties, morphology, composition, Cu releasing behavior, antibacterial, and anti-inflammatory activities are investigated and discussed. Surface properties, composition, and morphology were investigated by scanning electron microscopy (SEM) and contact angle measurements. The antibacterial activity has been tested with Escherichia coli and Staphylococcus aureus suspensions in vitro. Besides, the morphology of the biofilm was inspected with a field emission SEM. To evaluate the anti-inflammatory activity and biosafety of the coating in vivo, the optimized coating samples and control groups were implanted subcutaneously into the back of mice. The bacterial environment model was established by injection of the bacterial suspension. The morphology and bacterial adhered on the surface of catheters and the surrounding tissues were analyzed after 5 days of implantation. As in vitro results, the number of adhered bacterial on the surface of the silicon rubber surface was decreased, and the anti-inflammatory rate was increased by the intensify of the Cu content in chitosan coating. As for in vivo results, after 5 days of implantation, there was no evident inflammation in the surrounding tissues of all catheters in all without the S. aureus injected group. In the injected chitosan/Cu coated group; the inflammation, the number of the adhered bacteria were observed less than other injected samples without Cu; no inflammation were noticeable. Results indicate that the Cu-modified chitosan coating can confer excellent antibacterial and anti-inflammatory activity as applied on medical catheters.

Antibacterial and anti-inflammatory activities of chitosan/copper complex coating on medical catheters: In vitro and in vivo.

Mitigation of microbial corrosion by Cu addition to X65 pipeline steel by Pseudomonas aeruginosa MCCC 1A00099

Background: Catheters are polymeric materials frequently used in clinics and are associated with the risk of inflammation and coagulation. The development of bioactive catheter surfaces is worth applying because antibiotic resistance in bacterial infections is common. Copper (Cu) ion coordinated chitosan (Chitosan-Cu) coatings on medical catheters, and several studies have recently approved its application. Objective: It is crucial to investigate the possible cytotoxicity of Chitosan-Cu coatings on surrounding cells. Methods: The effect of the Chitosan-Cu complex coating, proven to have bioactive activities at different rates on L929 cells, was examined by the CCK-8 test kit. In 24 h, the cell viabilities of samples, with Chitosan: Cu ratios of 10:0, 10:1, 50:1, and 100:1, were measured as 105.14%, 89.90%, 91.91%, and 100.75%, respectively. In 72 h, they were measured at 119.45%, 109.33%, 110.24%, and 114.45%. The surface morphology of the coating was characterized by electron microscopy, and the entity of the Cu ions in the coating was characterized by x-ray photoelectron spectroscopy. Conclusion: Cytotoxicity assays showed that Cu, with a maximum concentration of 10% by volume, showed no toxic behavior.

Synthesis of chitosan-Cu based bioactive material for coating catheters: in vitro cytotoxicity evaluation


 In this study, we focused on the corrosion behavior of X65 pipeline steel and X65Cu pipeline steel in sterile and P. aeruginosa-containing media. The resistance of Cu-bearing X65 pipeline steel against (microbiologically influenced corrosion) MIC caused by P. aeruginosa was investigated. Results demonstrate that the corrosion rate of X65Cu pipeline steel was lower than that of X65 pipeline steel whether it was in a sterile or bacteria-containing media. It is noticeable that, in the presence of P. aeruginosa, X65Cu pipeline steel can prevent the formation of biofilm to a certain degree and reduce the corrosion rate of X65Cu pipeline steel to less than half as that of X65 pipeline steel. In addition, and the maximum pitting depth and average pitting depth of X65Cu pipeline steel were also much lower than that of X65 pipeline steel. The addition of Cu effectively reduced the corrosion of P. aeruginosa to X65 grade pipeline steel and improved the resistance to MIC pitting corrosion.

Ming Zong Shen

Papers

Microwave absorbing materials using Ag-NiZn ferrite core-shell nanopowders as fillers

Antibacterial and anti-inflammatory activities of chitosan/copper complex coating on medical catheters: In vitro and in vivo.

Mitigation of microbial corrosion by Cu addition to X65 pipeline steel by Pseudomonas aeruginosa MCCC 1A00099

Synthesis of chitosan-Cu based bioactive material for coating catheters: in vitro cytotoxicity evaluation

Mitigation of microbial corrosion by Cu addition in X65 pipeline steel in presence of Pseudomonas aeruginosa