Search

In this work, o-phenylenediamine (o-PD) and ethanol are used as raw materials, and a simple solvothermal method is used to prepare yellow emissive nitrogen-doped CDs (YNCDs) (with yellow emission λex/λem = 410/555 nm).

Carbon-based magnetic composites with enhanced electromagnetic (EM) wave absorption ability have received intensive attention. Herein, a composite of N-graphene and small size magnetic Co nanoparticles (NPs) with advantages of excellent dielectric ability was synthesized through an in situ grown method. Under optimized conditions, Co NPs decorated on NGN (Co/NGN-2) have the best EM wave absorption performance, of which a minimum reflection loss of − 45.8 dB can be achieved at 13.48 GHz with a thin coating of 2 mm at 15 wt% filler loading in paraffin wax. The effective absorption bandwidth is about 4.6 GHz in Ku-band (12.4–18 GHz). Importantly, the effective absorption bandwidth can be extended by changing the thickness of the absorber. In fact, the coupling of NGN with Co NPs can form an effective impedance match, and thus the small size Co NPs with low density and good performance decorated on NGN material make the present method promising for EM applications.

Rational microstructure design of carbon based composites is becoming a promising method to reinforce their electromagnetic (EM) wave absorption performance, but their synthesis remains a challenge. Herein, we have reported a design of small-size Ni2P grown on carbon nanotubes (CNTs) as lightweight and high efficiency EM wave absorber. The Ni2P NPs can be uniformly grown on CNTs by controlling the nucleation and growth rate of Ni2P during the synthesis. The size and coverage of Ni2P on CNTs can be tuned by adjusting the reaction conditions with a high yield, which is large favorable for adjusting their application performance. The Ni2P/CNTs sample with low filler loading (30 wt%) in the paraffin wax exhibits a good wave absorption performance with the minimum reflection loss (RL mini) value of −51.8 dB at 5.28 GHz. Moreover, it shows a good EM wave absorption ability even at the thinnest thickness of 2 mm (−46.1 dB), and an effective absorption bandwidth of 11.68 GHz is achieved when the absorber thickness is in the range of 1.5–5 mm. The excellent EM wave absorbing performance makes the Ni2P/CNTs as a promising new microwave absorbing material in sustainable filed.

The results of experimental studies of strain kinetics of composite magnetically controlled materials in the creep mode with preliminary exposure and without exposure are described by the Burgers model with two elastic and two viscous parameters, which is a combination of viscoelastic Kelvin–Voigt and Maxwell models connected in series. The dependence of the model parameters on the magnetic field induction is determined. The values of elastic and viscous parameters increase with increasing magnetic field induction in the range up to 500 mT by one or two orders of magnitude. It was determined that the value of the viscous Maxwell parameter does not change after preliminary exposure in the field. The values of the other two elastic and viscous Kelvin–Voigt parameters increase with exposure in a magnetic field.

The “Panda”-type polarization-maintaining quartz optical fiber was respectively annealed at 25℃ and 90℃ after electron irradiation with energy of 160 keV and fluence of 5 × 1015 electrons/cm2. It is found that the attenuation coefficient shows an exponential decrease with increasing annealing duration, while the attenuation coefficient has sharper change and lower maximum value under higher annealing temperature. Based on the theory of defects generating and annihilating, an annealing model of the irradiated quartz fiber was established to describe the evolution of defects and attenuation coefficient during annealing. The proposed model can be used to calculate the annealing process of the irradiated fiber under different temperature.

To achieve a satisfactory photovoltaic performance in dye-sensitized solar cells (DSSCs), counter electrode (CE) catalysts with low cost, superior catalytic activity, and excellent conductivity sho...

Based on the improved performance by interface construction, poly-lactic acid (PLA)/biomass composites have attracted much attention and received wide application as a completely degradable material. This work aims to study the effect of biomass components and the designed interface on the photo-degradation behavior of PLA/biomass composites exposed to the simulated sunlight irradiation, which could further alleviate the restriction caused by the poor ultraviolet (UV) stability of PLA. The biomass shows a significant delay effect in the degradation rate of the PLA matrix by the absorption of visible and UV ranges, acting as a photo-oxidative stabilizer during the irradiation. The investigation of the surface chemical changes reveals a dual mechanism for the degradation of the composites, consisting of a typical Norrish II photochemical and photo-oxidation mechanism. The interface in the composites is constructed by the surface treatment of biomass through the in situ polymerization of lactic acid, which could effectively alleviate the shielding effect of biomass. In our view, this work provides a novel strategy to prepare the PLA/biomass composites that possessed excellent photo-oxidative stabilization provided by biomass, adjustable degradation cycle offered by the interface construction, and potential application in more advanced packaging and agriculture fields.

Cu2ZnSnS4 (CZTS) and Cu2ZnSn(S,Se)4 (CZTSSe) as promising photovoltaic materials have drawn much attention because they are environmentally benign and earth-abundant elements. In this work, the monodispersed, low-cost Cu2ZnSnS4 nanocrystals with small size have been controllably synthesized via a wet chemical routine. And CZTSSe could be easily prepared after selenization of CZTS. When they are employed as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), the power conversion efficiency (PCE) has been improved from 3.54% to 7.13% as CZTS is converted to CZTSSe, which is also compared to that of Pt (7.62%). The exact reason for the enhanced catalytic activity of I3– is discussed with the work function and density functional theory (DFT) when CZTSSe converted from CZTS. The results of a Kelvin probe suggest that the work function of CZTSSe (5.61 eV) is closer to that of Pt (5.65 eV) and higher than that of CZTS, which matched the redox shuttle potential better. According to the theory calcula...

Composites with good dispersion and excellent microwave absorption properties have important applications. Therefore, an easily dispersible NiFe2O4/reduced graphene oxide (RGO) composite has been prepared conveniently through a simple hydrothermal method. Highly crystalline, small size (about 7 nm) monodispersed NiFe2O4 nanoparticles (NPs) are evenly distributed on the surface of RGO. The microwave absorbability revealed that the NiFe2O4/RGO composite exhibits excellent microwave absorption properties in the X-band (8–12 GHz), and the minimum reflection loss of the NiFe2O4/RGO composite is −27.7 dB at 9.2 GHz. The NiFe2O4/RGO composite has good dispersibility in nonpolar solvent, which facilitates the preparation of stable commercial microwave absorbing coatings. It can be a promising candidate for lightweight microwave absorption materials in many application fields.

The catalytic activity of materials is highly dependent on their composition and surface structure, especially the density of low-coordinated surface atoms. In this work, we have prepared two-dimensional hexagonal FeS with high-energy (001) facets (FeS-HE-001) via a solution-phase chemical method. Nanosheets (NSs) with exposed high-energy planes usually possess better reaction activity, so FeS-HE-001 was used as a counter electrode (CE) material for dye-sensitized solar cells (DSSCs). FeS-HE-001 achieved an average power conversion efficiency (PCE) of 8.88% (with the PCE of champion cells being 9.10%), which was almost 1.15 times higher than that of the Pt-based DSSCs (7.73%) measured in parallel. Cyclic voltammetry and Tafel polarization measurements revealed the excellent electrocatalytic activities of FeS-HE-001 towards the I 3 – /I– redox reaction. This can be attributed to the promotion of photoelectron transfer, which was measured by electrochemical impedance spectroscopy and scanning Kelvin probe, and the strong I 3 – adsorption and reduction activities, which were investigated using first-principles calculations. The presence of high-energy (001) facets in the NSs was an important factor for improving the catalytic reduction of I 3 – . We believe that our method is a promising way for the design and synthesis of advanced CE materials for energy harvesting.

An electromagnetic (EM) wave absorber with characteristic absorption in the millimeter wave range is very important for the EM industry. Especially, absorption properties in the microwave frequency range C-band (4–8 GHz) are necessary in the field of military aircraft. Herein, a Fe3C/graphitic carbon (Fe3C/GC) composite has been synthesized through a low-cost and facile ion-exchange route. The Fe3C/GC could exhibit excellent EM wave absorption properties in the C-band with the frequency range of 4–8 GHz and also exhibits good dielectric loss, which could be attributed to the existence of lightweight GC in the composite. The reflection loss value of the Fe3C/GC composite exceeds −10 dB in the frequency range of 4–8 GHz with an absorber thickness of 2–4 mm, implying its potential application as a lightweight EM wave absorber in the C-band region. Moreover, the Fe3C/GC composite shows better electromagnetic wave absorption properties than other iron compound GC-based composites, such as Fe2N/GC and Fe/GC.

Cu

Magnetic fluids based on superparamagnetic, well-crystalline and mono-dispersed Fe3O4 nanoparticles are synthesized by a facile thermal decomposition method. Low-cost Fe(oleate)3 is used as ferrous resource, and paraffin oil is introduced as solvent and carrier simultaneously. Fe3O4 nanoparticles with three kinds of different size (12, 16 and 20 nm), exhibiting different saturation magnetization of 65.51, 68.03 and 74.48 emu/g, respectively, are prepared easily by controlling the thermal decomposition time. Magnetic performance and viscosity-temperature characteristics of the magnetic fluid are also studied. It is found that the saturation magnetization of the magnetic fluid with 5% Fe3O4 mass percentage is 2.94 emu/g, which exhibits a good viscosity temperature characteristics compared with paraffin carrier.

A stable poly-alpha olefin oil based magnetic fluid of bilayer surfactant coated (oleic acid and succinimide) Fe 3 O 4 nanoparticles was prepared by a using phase transfer method. The bilayer surfactant-coated magnetic particles are characterized by Fourier-transform infrared spectroscopy, the result shows that the Fe 3 O 4 nanoparticles are coated by oleic acid, and the bilayer surfactant succinimide wraps the oleic acid coated Fe 3 O 4 nanoparticles. Transmission electron microscopy images indicate that the dispersibility of the bilayer coated Fe 3 O 4 nanoparticles is better than that of the uncoated ones. Vibrating sample magnetometer measurement confirms that both the coated and uncoated Fe 3 O 4 nanoparticles are super-paramagnetic. Stability measurements show the magnetic fluids prepared by bilayer coated Fe 3 O 4 nanoparticles is nearly constant for 360 days at room temperature.

Size controllable MnFe2O4 superparamagnetic nanoparticles (NPs) were prepared by a solvothermal method using low-cost metal oleate as the source. The particle size, chemical composition and magnetic properties were investigated. The MnFe2O4 nanomaterials exhibit high colloidal stabilities and superparamagnetic properties, with an average particle size in the range of 2 to 10 nm by modifying the reaction condition, such as surfactant, reaction temperature and reaction time. By changing Mn(2+) to different cations, CoFe2O4, NiFe2O4, and ZnFe2O4 with different magnetic properties could be obtained. The hydrophobic MnFe2O4 NPs could also be modified with many surfactants, such as cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS) and sodium dodecylsulfate (SDS), with the aim of achieving high zeta-potential hydrophilic bilayer-coated MnFe2O4 NPs. In addition, the water soluble MnFe2O4 magnetic NPs can be applied to the removal of Pb(ii) from waste water with good recovery under external magnetic field.

The work presented a practical and low-cost strategy for the preparation of Mo2C/graphitic carbon nanocomposite (Mo2C/GC). This synthesis has been conducted by a single-step heat treatment of resin–MoO42−–[Fe(CN)6]4− precursor in N2 atmosphere. The final material consists of well-dispersed Mo2C nanoparticles (typically 10–15 nm) on graphitic carbon. The formation process of Mo2C/GC has been investigated. The resultant material exhibits good supporting effect on Pt and Pd catalysts toward electro-oxidation of methanol, ethanol and formyl acid. This method is very simple and enables a systematic design of new, predictable catalysts.

We have reported a facile solution-based strategy for shape-controllable synthesis of Fe3O4 nanocrystals (NCs) with high yield, uniform shape and good stability. The low-cost polyisobutene succimide (PIBSI), Fe(oleate)3 and paraffin oil, are separately used as surfactant, iron precursor and solvent. By controlling the heating rate and growth time, the Fe3O4 NCs with cubic, cuboctahedral and octahedral morphology can be successfully prepared with narrow size-distribution and high crystallinity via the thermal decomposition method. The key to realizing shape control of small size (≤15 nm) Fe3O4 nanocrystals is choosing PIBSI as the surfactant. It played an important role in tuning the morphology of Fe3O4 NCs. Also, its characteristics of a long chain with plentiful non-polar groups can dramatically improve the stability and dispersibility of the Fe3O4 NCs in the reaction solvent (paraffin oil). The paraffin oil, in which Fe3O4 NCs are dispersed, becomes a magnetic fluid with high stability.