Xuliang Lv

Growing 3D ZnO nano-crystals on 1D SiC nanowires: enhancement of dielectric properties and excellent electromagnetic absorption performance

Nowadays, only by balancing the relationship of electromagnetic applications and electromagnetic pollution management can human health and quality of life be guaranteed. SiC nanowires have long-term thermodynamic stability and they are widely used in special applications. However, their poor dielectric properties hindered the improvement of electromagnetic absorption (EA) performance. Light weight and high efficiency are two key factors for EA materials. In this study ZnO nano-crystals were grown on SiC nanowires through an easy scale-up double hydrolysis reaction method. With significant increments in complex permittivity, a composite loaded with 30 wt% of as-prepared sample can achieve an effective EA bandwidth (≤−10 dB) of 6.60 GHz at the thickness of 2.5 mm (11.08–17.68 GHz). The outstanding properties of the as-prepared sample imply that it is a promising nano-material in the world of EA.

One-pot synthesis of biomass-derived carbonaceous spheres for excellent microwave absorption at the Ku band

Micro carbonaceous spheres have been successfully synthesized from watermelon via a one-pot hydrothermal reaction. After a quick annealing process to remove the surface oxygen groups, the as-prepared spheres presented an excellent microwave absorption performance at the Ku band (12–18 GHz), with a loading ratio of 25 wt% in a paraffin-based composite at 2.0 mm thickness.

Natural biological template for ZnO nanoparticle growth and photocatalytic dye degradation under visible light

Luffa sponge was used as a biotemplate for the growth of ZnO nanoparticles. This new structure of ZnO displayed a unique photocatalytic performance for dye degradation under visible light.

Constructing semi-fluorinated PDEAEMA-b-PBTFVBP-b-PDEAEMA amphiphilic triblock copolymer via successive thermal step-growth cycloaddition polymerization and ATRP

A series of amphiphilic perfluorocyclobutyl-containing ABA triblock copolymers, PDEAEMA-b-PBTFVBP-b-PDEAEMA (DEAEMA: 2-(diethylamino)ethyl methacrylate; BTFVBP: 4,4′-bis(1,2,2-trifluorovinyloxy)biphenyl), was synthesized through the site transformation strategy, combining thermal step-growth cycloaddition polymerization of BTFVBP and atom transfer radical polymerization (ATRP) of DEAEMA. A BTFVBP trifluorovinyl aryl ether monomer was first thermally polymerized to form a semi-fluorinated perfluorocyclobutyl aryl ether-based segment, followed by end functionalization for preparing a Br-PBTFVBP-Br macroinitiator bearing one ATRP initiating group at each end. ATRP of DEAEMA was initiated by Br-PBTFVBP-Br to afford four PDEAEMA-b-PBTFVBP-b-PDEAEMA triblock copolymers with relatively narrow molecular weight distributions (Mw/Mn ≤ 1.42) via varying the feeding ratio of DEAEMA to the macroinitiator. The critical micelle concentration (cmc) of the obtained amphiphilic triblock copolymers was determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as a probe. Micellar morphologies were investigated by transmission electron microscopy. It was shown that such triblock copolymers could self-assemble into large compound micelles, vesicles, and bowl-shaped micelles in aqueous solution with different initial water contents and compositions.

Synthesis and self-assembly of PMBTFVB-g-PNIPAM fluorine-containing amphiphilic graft copolymer

Two well-defined perfluorocyclobutyl aryl ether-based amphiphilic graft copolymers containing a hydrophobic poly(2-methyl-1,4-bistrifluorovinyloxybenzene) (PMBTFVB) backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAM) side chains were synthesized via sequential thermal step-growth [2π + 2π] cycloaddition polymerization of 2-methyl-1,4-bistrifluorovinyloxybenzene and atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAM). PMBTFVB homopolymer was converted to PMBTFVB–Cl macroinitiator by monochlorination of the pendant methyls with N-chlorosuccinimide and benzoyl peroxide. A grafting-from strategy was then adopted for preparing well-defined PMBTFVB-g-PNIPAM graft copolymers with narrow molecular weight distributions (Mw/Mn < 1.30) via ATRP of NIPAM, which was initiated by the Cl-containing macroinitiator. The critical micelle concentration (cmc) was determined by a fluorescence probe technique and the effects of salinity on the cmc of PMBTFVB-g-PNIPAM graft copolymer were also investigated.

Controllable Fabrication of Fe3O4/ZnO Core–Shell Nanocomposites and Their Electromagnetic Wave Absorption Performance in the 2–18 GHz Frequency Range

In this study, Fe3O4/ZnO core–shell nanocomposites were synthesized through a chemical method of coating the magnetic core (Fe3O4) with ZnO by co-precipitation of Fe3O4 with zinc acetate in a basic medium of ammonium hydroxide. The phase structure, morphology and electromagnetic parameters of the Fe3O4/ZnO core–shell nanocomposites were investigated. The results indicated that the concentration of the solvent was responsible for controlling the morphology of the composites, which further influenced their impedance matching and microwave absorption properties. Moreover, Fe3O4/ZnO nanocomposites exhibited an enhanced absorption capacity in comparison with the naked Fe3O4 nanospheres. Specifically, the minimum reflection loss value reached −50.79 dB at 4.38 GHz when the thickness was 4.5 mm. It is expected that the Fe3O4/ZnO core–shell structured nanocomposites could be a promising candidate as high-performance microwave absorbers.

The research of spectrophotometric color matching based on multi-peaks Gaussian fit

Spectrophotometric color matching is an important method for computer color matching, which is more accurate but difficult than tri-stimulus values color matching, because which will result in metamerism. The fundamental theory of computer color matching is the linear relationship between Kubelka-Munk function and concentration of dye. In fact, the spectral reflectivity of every pixel in hyperspectral image composed of subpixel mixing in instantaneous field of view. According to the Glassman laws of color mixing, the mixed pixel’s spectral reflectivity equals to the algebra sum of each reflectivity of subpixel multiply its area percentage. In this case, spectrophotometric color matching match the spectral reflectivity curve by adjusting the combined form of subpixel which constitute the pixel. According to numerical methods for Multi-peaks Guassian fitting, the spectral reflectivity curve can be fit as the sum of several characteristic peak, which accord with Normal Distribution. Then the spectrophotometric color matching can simplify the solution with infinite wavelength into solving the linear equations with finite known peak intensity. By using Imaging Spectrometer measure the color samples in standard color cards from different distance, the spectral reflectivity curve of each single color sample and the mixed color samples can be gotten, and the experiments results show that the spectrophotometric color matching based on Multi-peaks Gaussian fitting is superior to the tri-stimulus values color matching, and which is easy to operate.

Fe3O4 nanoparticles decorated on a CuS platelet-based sphere: a popcorn chicken-like heterostructure as an ideal material against electromagnetic pollution

Electromagnetic irradiation has caused environmental pollution and harmful effects on human health. The use of effective materials to attenuate electromagnetic energy is urgently required. In this study, Fe3O4 nanoparticles (NPs) decorated on a CuS platelet-based sphere (CuS/Fe3O4) with popcorn chicken-like micromorphology were synthesized through a solvothermal deposition method. The effects of reaction temperature and quantity of Fe3O4 NPs on the heterostructures, morphologies and electromagnetic absorption (EA) properties of the heterostructures were investigated. CuS/Fe3O4 heterostructures exhibited remarkable enhancement in comparison with pure Fe3O4 NPs and the CuS platelet-based sphere. With the contribution from dielectric and magnetic losses, a CuS/Fe3O4 heterostructure-loaded composite could achieve a minimum reflection loss (RL) of −61.32 dB at 14.00 GHz and an effective EA bandwidth (≤−10 dB) of 4.15 GHz at a thickness of only 1.5 mm simultaneously. The current study indicates that the CuS/Fe3O4 heterostructures can potentially be applied as advanced electromagnetic absorbers.

Hollow cube-like CuS derived from Cu2O crystals for the highly efficient elimination of electromagnetic pollution

In this study, hollow cube-like CuS composites derived from Cu2O crystals were synthesized via a simple one-step reaction. The formation of hollow cavities can be explained through the Kirkendall-based process. The morphologies and electromagnetic absorption (EA) properties of the CuS were measured and investigated. A sample with 35 wt% hollow CuS loading paraffin-composite achieves an optimal reflection loss (RL) of −63.99 dB at 12.09 GHz under the thickness of 2.25 mm. Simultaneously, the effective EA bandwidth (RL ≤ −10 dB) can be tuned between 4.63 and 18.00 GHz by changing the thickness of the absorber from 1.5 mm to 4.0 mm. The excellent EA performance is attributed to the high dielectric loss, appropriate impedance matching and multiple reflections induced by the unique hollow cube-like structure. Thus the hollow cube-like CuS is expected to be a promising material in approaching for microwave absorption against the electromagnetic pollution.

Decorating MOF-Derived Nanoporous Co/C in Chain-Like Polypyrrole (PPy) Aerogel: A Lightweight Material with Excellent Electromagnetic Absorption

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared by a self-assembled polymerization method. With a filler loading ratio of 10 wt %, the composite of Co/C@PPy could achieve a promising electromagnetic absorption performance both in intensity and bandwidth. An optimal reflection loss value of −44.76 dB is achieved, and the effective bandwidth (reflection loss lower than −10 dB) is as large as 6.56 GHz. Furthermore, a composite only loaded with 5 wt % Co/C@PPy also achieves an effective bandwidth of 5.20 GHz, which is even better than numerous reported electromagnetic absorption (EA) materials. The result reveals that the as-fabricated Co/C@PPy—with high absorption intensity, broad bandwidth, and light weight properties—can be utilized as a competitive absorber.