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All-inorganic perovskites CsPbX3 (X = Cl, Br, I) have attracted worldwide interest due to their excellent luminescent performances. Meanwhile, Cs4PbBr6 have been studied because they can enhance the luminescent efficiency and stability of CsPbBr3. Herein, we introduced a microfluidic method based on room-temperature supersaturated recrystallization to synthesize blue-emitting CsPbBr3 nanocrystals (NCs) and green-emitting CsPbBr3/Cs4PbBr6 NCs. The ultrasmall CsPbBr3 NCs emitted at a deep blue wavelength of 461 nm with the full width at half maximum (FWHM) of 15 nm. transmission electron microscopy (TEM) results demonstrated that ultrasmall CsPbBr3 NCs with the average particle size of 3.8 nm were synthesized and the CsPbBr3 NCs were crystallized as monoclinic structure. X-ray photoelectron spectrometer (XPS) analysis suggested that ultrasmall CsPbBr3 suffered from VBr defect and the surface passivation of Cs4PbBr6 possessed a low level of VBr defect density. The lifetime of CsPbBr3/Cs4PbBr6 was much longer than that of CsPbBr3. The results showed that ultrasmall CsPbBr3 NCs can be regarded as a source of blue-emitting material and CsPbBr3/Cs4PbBr6 NCs had a better stability.

Ordered mesoporous carbon (OMC) has been regarded as a promising carbonaceous material for microwave absorption (MA) owing to its high specific surface area, sufficient ordered mesoporous nanostructures and easy decoration. However, its development in MA performance is seriously hampered by its shortcomings of lacking magnetic loss and poor impedance matching. Herein, a series of multi-dimensional ternary OMC/SiO2@Ni composites with hierarchical nanostructure (zero-dimensional (0D) Ni nanoparticles and three-dimensional (3D) OMC/SiO2 framework) is successfully prepared via a self-assembly method, an in situ synthesis, and followed by a calcination treatment. By adjusting the calcination temperature and Ni nanoparticle content, OMC/SiO2@Ni composites with different graphitization degree, Ni nanoparticle size and magnetic properties can be easily obtained. Remarkably, OMC/SiO2@Ni0.5-700 composite exhibits an exceedingly strong reflection loss (RL) value of −62.2 dB and a broad effective absorption bandwidth (RL ≤ −10 dB) of 8 GHz (almost covers X and Ku bands) with a layer thickness of only 2.5 mm. Such fabulous MA performance comes from a synergy between the well-designed hierarchical ternary nanostructure and improved impedance matching. This work provides an insight for rational structure design and multi-component loss mechanism of lightweight MA material, which shows great potential in practical applications.

Near-infrared (NIR) luminescent materials have unparalleled advantages in certain fields, such as anti-counterfeiting. Nd3+ ion doped Gd2O3 near-infrared phosphor was successfully prepared by co-precipitation method and high-temperature solid-phase reaction. The structure and morphology of Gd2O3:Nd3+ cubic phase phosphors were studied in detail. The prepared phosphor was optically analyzed by fluorescence spectrometer. The research results show that with the increase of the Nd3+ doping concentration, the luminous intensity of the near-infrared phosphor in the near-infrared region shows a trend of first increasing and then decreasing. When the Nd3+ ion doping concentration is 1.0 mol%, the obtained phosphors have the best luminous intensity in the near-infrared region under the excitation of 808 nm laser. Gd2O3:Nd3+ phosphor emits near-infrared light due to the intra-4f transitions of Nd3+ ions. The concentration quenching theory is used to prove that the concentration quenching of Gd2O3:Nd3+ belongs to the cross relaxation caused by electric multipole. Due to the unique optical properties of this near-infrared phosphor, it is expected to be further developed in the field of fluorescent materials.

Porous carbon has been expected to be a potential candidate as a lightweight and efficient microwave absorber. Nano-porous carbon carbonized directly from a walnut shell exhibits narrow microwave absorption frequency bandwidth, while the activation process can adjust the pore structure and optimize the microwave absorption performance. Herein, porous carbon materials were successfully prepared using walnut shells as precursors and ZnCl2 as the activating agent. The superior microwave absorption performances of the as-prepared samples could be attributed to the well-developed pore structures and the enhanced dielectric loss capacities of the samples. The interfacial polarization in the walls of the pores and the defects in the samples significantly contributed to the enhancement of the dielectric loss capacities of the samples. In this work, the broadband microwave absorbing porous carbon exhibited an effective absorption bandwidth (reflection loss ≤ −10 dB) of 7.2 GHz (ranging from 10.8 GHz to 18.0 GHz) when the absorber thickness was 2.5 mm. In addition, an effective absorption bandwidth of 6.0 GHz (ranging from 11.4 GHz to 17.4 GHz) could also be achieved when the absorber thickness was only 2.0 mm. The samples exhibited low densities, strong microwave absorption performances and wide effective absorption bandwidths with thin absorber thicknesses, due to which they have a great potential as lightweight and efficient microwave absorbers.

Ordered mesoporous carbon (OMC) is considered to be a prospective carbon-based material for microwave absorption because of its abundant well-ordered mesoporous structures, high specific surface area, numerous active sites, and facile preparation process. However, its development has been seriously hindered by its poor impedance-matching characteristic. Herein, silica-modified OMC composites with a designable impedance-matching transition layer are successfully fabricated via a self-assembly method and succeeding calcination treatment. In addition, the silica in OMC@SiO

Eu3+-activated BaLaMgNbO6 red-emitting phosphors were synthesized by a high-temperature solid-state reaction method. Phase analysis and luminescence were characterized by X-ray diffraction (XRD) and photoluminescence excitation and emission spectra. The XRD patterns showed that BaLaMgNbO6 had a monoclinic structure with space group P21/n. The excitation spectra consisted of a broad charge-transfer band and some sharp f-f absorption peaks characteristic of Eu3+. The intensity ratio of I615/I590 was used to detect the chemical environment of Eu3+. The chromaticity coordinates of BaLa0.7Eu0.3MgNbO6 were (0.67, 0.33), indicating that the BaLaMgNbO6:Eu3+ phosphors were excellent red-emitting phosphors. Under excitation by near-ultraviolet (UV) and blue light, the phosphor not only exhibited intense red emission but also showed high color quality. The Ozawa and Dexter energy-transfer theories were employed to calculate the theoretical quenching concentration and determine the concentration quenching mechanism. In addition, the activation energy of BaLa0.7Eu0.3MgNbO6 was calculated through the Arrhenius equation. A configurational coordinate diagram was used to explain the thermal quenching mechanism.

A series of Eu 3+ ions activated double perovskite CaLaMgSbO 6 phosphors were successfully synthesized. Crystal structure was investigated by XRD and the results showed that this double perovskite exhibited rock-salt ordering of B-site ions. High-resolution transmission electron microscopy was used to prove the existence of B-site ordering. Thereafter, luminescence properties of the as-prepared powders were discussed in detail. The phosphors could be well excited by ultraviolet, near ultraviolet, and blue light. The quenching concentration for the transition of 5 D 0 - 7 F 2 reached up to 50.0 mol%. The theoretical quenching concentration and quenching mechanism were discussed in detail. Excellent thermal stability of this double perovskite phosphor was obtained and the quenching mechanism was investigated based on the configurational coordinate diagram. The CIE coordinates showed that this double perovskite phosphor had great potential in solid state lighting.

Crystal structures of Sr 1- x Ca x LaMgSbO 6 :Eu 3+ phosphors were studied in detail. Both the SrLaMgSbO 6 and the CaLaMgSbO 6 have a monoclinic ( P 2 1 / n ) structure. With increasing the Ca 2+ concentration, the peaks gradually divided and the phase changed from SrLaMgSbO 6 to CaLaMgSbO 6 . The symmetry of La 3+ in SrLaMgSbO 6 is lower than that in CaLaMgSbO 6 . Eu 3+ ions, as the structural probes, were selected to study the structure. Lifetimes and intensity ratio were used to study the symmetry in the structure. Thermal quenching of the phosphors was discussed from 323 K to 473 K. The emission intensities of 5 D 1 → 7 F J and 5 D 0 → 7 F J damped in different ratios while increasing temperature. The configurational coordinate diagram was used to explain this interesting phenomenon.

Heavy rare-earth oxysufide Er2O2S was successfully synthesized by using Na2CO3 as flux. The assumed phase evolution processes were verified by the calculation of thermodynamics and the analysis of TG/DSC, XRD, UV–vis, EDS and XPS. The role of Na2CO3 in reaction was proved to be attributed to enhance the chemical potential of S via reacting to form Na2S2O3 and Na2S. The reaction processes were proved to be possible in thermodynamics. The flux Na2CO3 could generate oxygen vacancy due to the formation of $$Na_{{Er}}^{{ \times \times }}$$ . The band gap, lattice volume and oxygen 1s XPS spectra were investigated to explore the existence of oxygen vacancy. The oxygen vacancy enhanced the stability of Er2O2S crystal structure and could realize the synthesis at a higher temperature. Thus, Na2CO3 not only promoted the preferential formation of Er2O2S but also could effectively stabilize the hexagonal structure of Er2O2S. Meanwhile, compared with K2CO3, Er2O2S/ polymethyl methacrylate (PMMA) coating exhibited a better absorbing property with Na2CO3 as flux.

A series of ferrite/Co/porous carbon materials were prepared by the situ-thermal carbonization of ferrite/ZIF-67 under N 2 atmosphere, and the microwave absorption properties have also been investigated. The magnetoelectric synergistic microwave absorbing material is promising as an efficient microwave absorbing material. The component absorbers with unique porous carbon structure make great contribution to the impedance match, interface polarization, magnetoelectric synergistic effect, and multiple reflection and scattering loss. The carbonization temperature indicates a crucial effect on the porous structure, and too high temperature will result in the collapse of the porous structure. The ferrite/Co/porous carbon fabricated at 500 °C (FC500) exhibits the most enhanced microwave absorbing performance. The maximum reflection loss (RL) of FC500 reaches −31.05 dB at 14.32 GHz, and the effective absorption bandwidth (RL ≤ −10 dB) is 4.8 GHz (12.24 GHz–17.04 GHz) corresponding to a thickness of 1.5 mm. The maximum reflection loss (RL) can reach −47.31 dB at 8.4 GHz, and absorption bandwidth (RL ≤ −10 dB) is 2.72 GHz (6.80 GHz–9.52 GHz) with a thickness of 2.5 mm. Thus, the component absorption materials can significantly decrease the weight of ferrite absorbers, ascribing to the thinner optimum thickness.

Eu 3+ -doped double perovskite (Ba, Sr)LaMgSbO 6 phosphors were synthesized by the traditional solid-state reaction method. Structure evolution was investigated by X-ray diffraction and Rietveld structure refinement. The crystallographic data of powders were given in detail. Also, the photoluminescence properties, including excitation spectra, emission spectra, intensity ratios of I ( 5 D 0 - 7 F 2 )/I ( 5 D 0 - 7 F 1 ), Commission International de L'Eclairage (CIE) chromaticity coordinates, UV–vis diffuse reflectance spectra, lifetimes, and the thermal quenching properties were thoroughly discussed. With the increase of Sr 2+ concentration, the emission intensities increased and the decay times decreased. Band gap was calculated to explain the phenomenon of the increased emission intensity. The phosphors showed temperature-sensitive luminescent properties based on the thermal quenching performance. The configurational coordinate diagram was used to explain the thermal quenching mechanism.

Sm2(C2O4)3∙10H2O was prepared by coprecipitation method with Na3Cit as chelating agent. The microstructures were studied using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). The 1060 nm laser absorption properties were characterized by spectrophotometer. The results showed that the composition and morphology of Sm2(C2O4)3∙10H2O could be tuned by varying the molar ratio of Na3Cit to Sm3+ and the aging time. Then, the 1060 nm laser absorption properties were optimized. The spectral reflectivity at 1060 nm was low to 0.831 when the molar ratio of Na3Cit to Sm3+ was 1.2 and the aging time was 24 h. The as-prepared Sm2(C2O4)3∙10H2O can be applied as an effective laser absorber.

Graphene is a promising lightweight microwave absorption (MA) absorber, but the limited dielectric loss and nonmagnetic characteristic have impeded its further applications. Through the structure modification, porous (1–2.5 μm) graphene was successfully prepared via a simple pyrolysis process, and the minimum reflection loss (RL) value reached −48 dB at 9.8 GHz, which demonstrated that porous graphene (PG) showed outstanding MA performance than the ordinary graphene (OG). In order to strengthen the magnetic loss, and then boost the impedance matching, Fe3O4 nanoparticles (∼10 nm) were deposited uniformly on the surface of PG via in situ precipitation to synthesize porous graphene-Fe3O4 (PG-Fe3O4) composites. It was found that the as-prepared PG-Fe3O4 composites showed especially high MA performance, and the minimum RL of −53.0 dB was achieved at 5.4 GHz with the thickness of 6.1 mm. The absorption bandwidth of RL less than −10 dB was from 12.6 to 18.0 GHz (5.4 GHz) with a thin thickness of 2.7 mm. The excellent MA properties of PG-Fe3O4 composites were the consequence of the perfect impedance matching, porous structure as well as the multi-polarization. These results demonstrated that the PG-Fe3O4 composites with excellent MA properties and lightweight should be promising absorbers for practical applications.

To obtain excellent microwave absorption (MA) performance, elaborately designing dielectric-magnetic hierarchical C@NiCo 2 O 4 @Fe 3 O 4 composites were successfully synthesized by a two-step route. Both the sea urchin-like structure generated by NiCo 2 O 4 and the void space in the core originated from the decomposition of carbon spheres were beneficial structural characteristics for the attenuation of electromagnetic waves. The impedance matching as a result of the addition of uniformly Fe 3 O 4 nanoparticles was a strong contributor to the excellent MA property of C@NiCo 2 O 4 @Fe 3 O 4 composites. The minimum reflection loss (RL) value of it reached −43.0 dB at 13.4 GHz with a thickness of 3.4 mm, which was much higher than that of C@NiCo 2 O 4 or pure NiCo 2 O 4 .

Eu3+ ions activated BaLaMgSbO6 phosphors were successfully synthesized by the solid-state reaction method using NH4Cl as the flux. The BaCl2 was selected to substitute BaCO3 as the starting material to attest that NH4Cl not only reacted with BaCO3 but also reacted with other starting materials. The analysis of TG/DSC was used to probe the role of NH4Cl flux in the process of synthesizing BaLaMgSbO6 powders. The crystal structure was investigated by XRD and Rietveld refinement, and the morphology by SEM. The phosphors had monoclinic double perovskite structure with the space group P21, as well as the rock-salt ordering of B-site. The luminescence properties, including the photoluminescence excitation and emission spectra, and the color coordinates were investigated. Also, the relationship between the crystalline size and the emission intensity were discussed. With increasing the calcination temperature, both the crystalline size and the emission intensity monotonously increased. The relative intensity ratio of red/orange emission was used to measure the degree of distortion from the inversion symmetry of the local environment of the Eu3+ ions in BaLaMgSbO6.

Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor.

ZnO nanofibers (NixZn(1 − x)O with x = 0.03, 0.05, 0.07, 0.09) have been prepared by electrospinning method. The structural, morphological, static magnetic properties and microwave absorption properties are investigated in detail. The as-prepared samples show hexagonal wurtzite structure. However, the lattice constants decrease with the increase of Ni doping cotent, which result in the shrunk of the diameter of nanofibers. The static magnetic properties and microwave absorption properties can be tuned by varying the Ni content. The maximum saturation magnetization is obtained when x = 0.07 due to cation percolation threshold. The dielectric loss properties could be attributed to the dipole polarizations and interface polarization. The magnetic loss properties are mainly caused by natural resonance and exchange resonance. In addition, the networks of NixZn(1 − x)O nanofibers also benefit dissipating electromagnetic energy. The refelection loss (RL) of Ni0.07Zn0.93O nanofibers reaches −2.7 dB at 7.6 GHz and the electromagnetic wave absorption less than −2 dB is found to reach 3.1 GHz for an absorber thickness of 4.5 mm.

1064 nm laser stealth absorbent Sm2O2S was prepared by solid state flux method. The effects of doping Er3+ and Tm3+ on the powder’s phase compositions and reflecting property were investigated. The phase composition, morphology and reflectivity of powders were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet visible spectrophotometer (UV-3600PC). The results exhibited that doping Er3+ and Tm3+ cause no significant changes on crystal structure. However, the morphology of powders changed a lot after doping Er3+/Tm3+, which influenced on the reflecting property. Because of the characteristic absorption of Er3+ and Tm3+, the reflectivity of Sm2O2S powders decreased in different degrees. The doping amount of Er3+ was 15 mol%, the lowest reflectivity 0.7450 % was obtained. The optimized doping amount of Tm3+ was 10 mol% and the reflectivity was 0.7403 %.

ZnO nanofibers were fabricated by electrospinning method. The morphology and microstructure of the as-prepared ZnO nanofibers were studied in details. The ZnO nanofibers showed pure polycrystalline phase with the hexagonal wurtzite structure. The average diameter of the ZnO nanofibers, calcined at 550 °C, was around 140 nm. Moreover, the electromagnetic loss properties of the as-prepared ZnO nanofibers were investigated. The mechanism of dielectric loss could be attributed to the electric dipolar polarization and interface polarization. The mechanism of magnetic loss properties were mainly caused by natural resonance and exchange resonance. The networks of ZnO nanofibers also facilitated dissipating electromagnetic energy. The dielectric loss factor tanδe was around 0.06085 and the magnetic loss factor tanδμ was approximate 0.04095. The as-prepared ZnO nanofiber exhibited excellent electromagnetic loss properties and it could be usd as a potential candidate for lightweight microwave absorption material.

A novel 1.54 μm laser absorbent of Er2O2S was prepared by solid state flux method. The effects of different calcining temperatures and preservation time on the synthesis and reflecting property of Er2O2S were investigated. The mechanism of fluxing agent was assumed and proved. The phase composition, morphology, and reflectivity of the powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet visible spectrophotometer (UV-3600PC). The results showed that pure phase of Er2O2S could be obtained with Na2CO3 as fluxing agent at 800–1200 °C, too high temperature and too long preservation time were bad for synthesizing Er2O2S. Na2CO3 played an important role during the reaction, the elemental sulfur in Er2O2S came from Na2S2O3 indeed. Different calcination conditions had a great impact on particle morphology, which had influence on the reflectivity of the products. The reflectivity was the lowest (0.39 %) when the calcining temperature was 1200 °C.

In this paper, the aluminum/polymer composite coating was prepared and the infrared emitting properties and environmental stability performance of the as-prepared coating were studied. The factors, such as polymer binders, pigment/binder ratios, preparation technology and coating thickness were investigated in detail. Firstly, the study of the polymer binders indicated that modified fluorocarbon resin was the best candidate due to its low infrared emissivity and well-performed physical and chemical properties. Secondly, the optimal pigment/binder ratio was 1.25:1. Thirdly, the optimum coating thickness was 75 μm and the scrape coating method was suitable to prepare the coating. Finally, the optimized aluminum/polymer composite coating showed low infrared emissivity of 0.31. The adhesive force of the coating was first grade and the impact resistance was more than 50 kg cm. In addition, it exhibited excellent salt, acid and alkali resistance. The as-prepared aluminum/polymer composite coating can be used as infrared stealth coating in the wavelength of 8–14 μm.

Increasing attention has been focused on microwave absorption (MA) performance in the Ku band (12.4–18.0 GHz) due to the rapid development of radar, military aircraft and satellite communications. In this work, 2D heterostructure MoS2/graphene composites were proven to be promising full Ku band MA materials due to their superb characteristics of high dielectric loss, low density, large surface area and good thermal stability. By a simple one step solvothermal method, MoS2/graphene composites were successfully obtained, and the matched 2D structure between MoS2 and graphene could generate synergistic effects and maximize the MA properties. Only with 30 wt% of the as-prepared MoS2/graphene composites, excellent MA properties in wide frequency bands were obtained. An optimal reflection loss (RL) value of −41.9 dB was obtained at 16.1 GHz with a thickness of 2.4 mm and the RL values exceeding −10 dB were achieved in the whole Ku band (12.2–18.0 GHz) with a thickness of 2.6–3.0 mm.

Hierarchical hybrid nanostructures are desirable materials for microwave absorption (MA) capacity. However, how to obtain this kind of versatile structural materials still remains a great challenge. In this work, a novel MA composite of MnO2@NiMoO4 was synthesized via two-step hydrothermal processes combined with a simple annealing process. As confirmed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy analysis, the well-defined NiMoO4 nanosheets could uniformly cover the surface of the MnO2 nanorods. Compared with pure MnO2 nanorods, these hierarchical composite structures could provide a higher superficial area, and more effective components, which will favor the penetration of microwaves into the absorber effectively instead of reflecting it, and then translate it into thermal energy. The minimum reflection loss (RL) value of MnO2@NiMoO4 composites was −31.4 dB at 11.2 GHz with a thickness of 3 mm, and the band of reflection loss was below −10 dB when frequency was in the range from 9.6 to 14.1 GHz. However, the minimum RL value of MnO2 was only −12.5 dB at 10.4 GHz with a thickness of 3 mm. The significantly enhanced microwave absorption of MnO2@NiMoO4 composites is mainly attributed to the hierarchical hybrid nanostructures, multi-effective components, good impedance matching, and interfacial polarization between MnO2 and NiMoO4. Meanwhile, the surface attached NiMoO4 is useful to increase the multiple reflection of electromagneticwaves. It is believed that these MnO2@NiMoO4 composites could serve as an excellent microwave absorber in practical applications.

A series of double perovskite (Gd0.85-xLux)2MgTiO6: 0.3Eu3+ red phosphors were prepared via a typical high temperature solid-state reaction. XRD and HRTEM exhibits that the phosphors well crystallized as a double perovskite with the space group of P21/n symmetry. The luminescent properties of samples were investigated via excitation and emission spectra. The phosphors emit strong red light and weak orange red light under ultraviolet (UV) and near-UV excitation suggesting that Eu3+ ions situated in the sites without inversion symmetry. The UV–vis spectra included a broad host absorption band assigned to O2--Eu3+ and some peaks at 395 nm, 465 nm and 533 nm attributed to the typical f-f transition of Eu3+. The CIE chromaticity coordinates of all samples were near to the standard red light, indicating that the (Gd0.85-xLux)2MgTiO6: 0.3Eu3+ was a potential candidate material for red emitting phosphors. The decay curves matched with the lines fitted by a one exponential decay formula and the decay time increased with increasing Lu3+-dopant concentration within x

Porous carbon has been expected to be a potential candidate as a lightweight and efficient microwave absorber. Nano-porous carbon carbonized directly from a walnut shell exhibits narrow microwave absorption frequency bandwidth, while the activation process can adjust the pore structure and optimize the microwave absorption performance. Herein, porous carbon materials were successfully prepared using walnut shells as precursors and ZnCl

Double perovskite KLaMgWO6:Eu3+ phosphors were successfully synthesized by an improved sol–gel method using citric acid and polyethylene glycol as complexing agents. The structure evolution and photoluminescence were systematically invested by X-ray diffraction, Rietveld refinement and fluorescence spectra. The structure of Eu3+ doped samples was double-perovskite with space group C2/m. Enhanced luminescence properties were gotten by adding 5.0 wt% PEG. Na+ with smaller radius was selected to substitute K+ in this novel host. With increasing the concentration of Na+, the tolerance factors decreased and the structure of BO6 tilted gradually and lowered structure symmetry. Then the emission intensity ratio of 5D0–7F2/5D0–7F1 transition increased and the red emission played the dominate role. Also the emission intensity was enhanced by increasing the concentration of Na+. The phosphors showed better color purity with better CIE chromaticity coordinates. Therefore the synthesized phosphors is a potential light conversion red material for light emitting diode.

In this work, metal oxide (MnO2, SnO2 and Co3O4)–graphene composite materials were successfully prepared via different synthesis methods. Uniform metal oxide nanoparticles were well dispersed on graphene sheets, and transmission electron microscopy characterizations showed that the average sizes of MnO2, SnO2, and Co3O4 particles were about 60, 5, and 10 nm, respectively. Reflection losses of graphene composites and pure graphene were systematically evaluated between 2 and 18 GHz, which revealed that all composites exhibited enhanced microwave absorption properties compared to pure graphene. The minimum reflection losses of MnO2-graphene, SnO2–graphene, and Co3O4–graphene composites with a thickness of 2.0 mm were −20.9, −15.28, and −7.3 dB at the frequency of 14.8, 15.94, and 9.6 GHz, respectively, whereas −4.5 dB for pure graphene. The enhanced absorption ability probably originated from the combined advantage of metal oxide particles and graphene, which proved beneficial to improve the impedance matching of permittivity and permeability. Besides, the intrinsic characteristics of MnO2, SnO2, and Co3O4 nanoparticles, the interface between nanostructured metal oxides and graphene sheets, and the multi-dielectric relaxation processes are all influence factors to improve the properties of microwave absorption.

Graphene oxide (GO) was rarely used as microwave absorption (MA) material due to its lower dielectric loss compared with reduced GO (RGO). However, the characteristics of low conductivity, light weight, and large surface area were beneficial to the impedance matching for absorbers already containing highly conductive metal materials. Cu@Ni nanowires are promising MA materials due to the desired dielectric loss from copper and excellent magnetic loss from nickel. However, the high density was an impediment to its further application. Combining Cu@Ni nanowires with GO should be an effective solution to decrease the absorber’s density and improve its MA properties. Herein, we demonstrated that Cu@Ni nanowires/GO composites exhibited enhanced MA capacities compared with Cu@Ni nanowires or GO alone, and the minimum reflection loss reached −42.8 dB at 16.9 GHz with a thickness of 2.1 mm. The enhanced MA performance mainly originated from good impedance matching, as a result of the addition of low conductivity of GO. To confirm this point, the MA performance of Cu@Ni nanowires/RGO was studied, and unsurprisingly, weak MA performance was obtained. Our work provides a new strategy to decrease the density, broaden the frequency band and tune MA performance of composites.

Graphene/nickel composite materials were successfully prepared via a one-step in situ reduction from nickel chloride, graphene oxide, and hydrazine at 80 °C for 3 h. Face-centered cubic Ni nanostructures with uniform size and high dispersion assembled on graphene sheets. Through the measurement of complex relative permittivity and permeability, their microwave absorption properties were evaluated. In comparison with pure Ni nanoparticles and graphene, the composite materials demonstrated much better characteristics of microwave absorption. The lowest reflection loss value of the composites with a thickness of 3 mm can reach −23.3 dB at 7.5 GHz. Our research reveals that graphene/Ni composites are promising microwave absorption materials with desirable absorption properties and reduced material weight.

Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu(2+) and Ni(2+), the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased.

Carbonyl iron fibers were fabricated by magnetic-field-induced thermally decomposition of polymetallic carbonyl. Their fibrous morphology and magnetic properties were investigated by scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) at room temperature respectively. The microwave characterizations of carbonyl iron fiber-filled foam composites were evaluated through arch test based on a network analyzer. The diameter and aspect ratio of the fibers have great influence on reflection loss. It was also found that carbonyl iron fiber-filled foam composites with small thinness and lightweight exhibit good microwave absorbing properties in the frequency of 8–18 GHz, 26–40 GHz and 75–110 GHz.

Green emission ZnO quantum dots were synthesized by an ultrasonic sol-gel method. The ZnO quantum dots were synthesized in various ultrasonic temperature and time. Photoluminescence properties of these ZnO quantum dots were measured. Time-resolved photoluminescence decay spectra were also taken to discover the change of defects amount during the reaction. Both ultrasonic temperature and time could affect the type and amount of defects in ZnO quantum dots. Total defects of ZnO quantum dots decreased with the increasing of ultrasonic temperature and time. The dangling bonds defects disappeared faster than the optical defects. Types of optical defects first changed from oxygen interstitial defects to oxygen vacancy and zinc interstitial defects. Then transformed back to oxygen interstitial defects again. The sizes of ZnO quantum dots would be controlled by both ultrasonic temperature and time as well. That is, with the increasing of ultrasonic temperature and time, the sizes of ZnO quantum dots first decreased then increased. Moreover, concentrated raw materials solution brought larger sizes and more optical defects of ZnO quantum dots.

Ho(AcAc)3 modified ZnO quantum dots (QDs) were successfully prepared via a conventional method. The FTIR spectra were taken to explore the combination of Ho(AcAc)3 and ZnO QDs. The addition of Ho(AcAc)3 could lower the emission intensity of ZnO QDs by modifying the defects of ZnO QDs. Three types of ZnO QDs with different optical defects were used to composite with Ho(AcAc)3. The effect of Ho(AcAc)3 on different optical defects in ZnO QDs was distinctive. Ho(AcAc)3 modified ZnO QDs were successfully composited with the epoxy resin. With the addition of ZnO QDs, the emission intensity and UV absorption increased. Samples with Ho(AcAc)3 had higher visible light transmittance than those without Ho(AcAc)3. As such, Ho(AcAc)3 could improve the dispersity of ZnO QDs in epoxy. Thus, Ho(AcAc)3 could act as a compatibilizer between ZnO QDs and epoxy resin.