Papers by Author: Li Min Dong

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Authors: Yan Long Sun, Li Min Dong, Tao Jiang, Cao Guo, Xiao Qi Zhang
Abstract: An method for making AlN(aluminum nitride) nanowires by double decomposition, and the effection of additives was described. Future more, the growth mechanism of AlN nanowire synthesis with addictive were analyzed. AlN nanowire were synthesis by he AlCl3 and NaN3 in stainless steel cauldron without solvent and using Mg and Zn as additive. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study characters of the AlN nanowire. It is shown that the process can produce AlN nanowire with mean diameters ranging from 50 to 100 nm at 450°C. The additive has effective facilitated on the synthesis of aluminum nitride nanowires, can improve the properties of aluminum nitride nanowire, minish the average diameter of aluminum nitride nanowires.
Authors: Li Min Dong, Fei Lv, Qin Li, Zhi Dong Han, Xian You Zhang
Abstract: A series of Eu3+, Dy3+ actived Ca1-xBaxSnO3 phosphors were synthesized by coprecipitation method. The structure, morphology and fluorescence property of phosphors were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectroscopy. SEM results showed that the as-prepared phosphors are smooth and uniform with the cubic morphology. The incorporation of a small amount of Ba to CaBaSnO3 improved the emission characteristics. Fluorescence spectrum showed the emission intensity is the best with the incorporation of Ba2+ (x = 0.3), when calcination temperature is 900°C.
Authors: Zhi Dong Han, Qing Rui Zhao, Li Min Dong, Ze Wu, Xian You Zhang
Abstract: Nano-size BaM hexaferrites (BaLa0.5Fe11.5O19) were synthesized in the presence of SiO2 nano- particles by sol-gel method. The X-ray diffraction (XRD) patterns of ferrites annealed at above 900°C manifested that all the species had hexagonal crystal structure and no diffraction peaks of SiO2 found. Compared with BaLa0.5Fe11.5O19 powders, those synthesized in the presence of SiO2 nano-particles presented in smaller powder size, as proved by scanning electron microscopy (SEM). As a result, SiO2 nanoparticles promoted the formation of more homogeneous and finer ferrite crystal while the structure of hexaferrites consisted with that synthesized without SiO2 nano-particles. Microwave absorbing properties were evaluated. As a result, BaLa0.5Fe11.5O19/SiO2 showed good microwave absorbing properties with the maximum absorption more than 20dB.
Authors: Li Min Dong, Zhi Dong Han, Ze Wu, Xian You Zhang
Abstract: A novel ceramic synthesis technique, microwave-assisted process was investigated for the production of Barium Hexagonal ferrite (BaFe12O19) powders with improved physical properties. Compared to conventional syntheticroute, the new method significantly shortened synthetic steps and reaction time. This technique involves the reaction of stoichiometric amount of metal nitrates and appropriate dosage of citric acid at microwave oven and the whole process took only 15 min. The powders of BaFe12O19 were further investigated by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The results showed that the formation temperature of M-type Ba hexaferrite is significant low, compared to conventional furnace heating. The X-ray diffraction analysis demonstrates that the phase purity of the microwave-processed samples were determined and compared with a conventionally processed material. SEM observations indicate that the size of the synthesized BaFe12O19 powders is small and uniform distribution. Thus, microwave irradiation is proved to be a novel, extremely facile, timesaving and energy-efficient route to the synthesis of BaFe12O19 powders.
Authors: Yan Long Sun, Yin Chan Liang, Ming Le Zhi, Zhao Fen Zeng, Li Min Dong
Abstract: Aluminum nitride (AlN) nano-wire was synthesized by double decomposition with AlCl3 and NaN3 in stainless steel cauldron without solvent and using Mg as promoter. The effect of reaction temperature, holding time and promoter to the structure, surface morphology and particle size are analyzed. The synthesized AlN was characterized using X-ray diffraction (XRD) and scanning electronic microscopy (SEM). A series of electron microscopy characterization results show that the optimum reaction conditions are as follows: reaction temperature is 450°C and holding time is 8h. The average diameter of AlN nano-wire is 100nm.
Authors: Ya Nan Ye, Li Min Dong, Hou Zhao Che, Shuai Ying Mao, Zi Yi Chen, Xian You Zhang
Abstract: Chemical precipitation method was used to prepare phosphors ZnO: Eu2+ and Mn2+ (urea as a precipitating agent, ZnO as a substrate and Eu, Mn as doping elements). A series of preparations with different composition and sintering temperature were characterized by scanning electron microscope (SEM), thermal gravimetric analysis (TG-DTA), x-ray powder diffraction (XRD) and fluorescence spectrophotometer respectively, and the nano-particle characteristics and luminescence properties of the product were studied in detail. The results showed that the size of the nano-particle was uniform (with a narrow distribution), and the fluorescence mechanism would not change when Eu and Mn were doped in the ZnO matrix to prepare luminescence material, it was a feasible way to reduce the damage to the environment and further to explore the ZnO phosphor technology and the application of light-emitting.change when Eu and Mn were doped in the ZnO matrix to prepare luminescence material, it was a feasible way to reduce the damage to the environment and further to explore the ZnO phosphor technology and the application of light-emitting.
Authors: Li Min Dong, Yan Li Zhuang, Zhi Dong Han, Ze Wu, Xian You Zhang
Abstract: Green phosphor of La(BO3, PO4): Ce, Tb was synthesized by means of sol-gel method and conventional solid state method. The thermal formation process was characterized by thermogravimetric analysis (TG) and (DTA). The effects of synthesis method and conditions on the crystal and morphological structure were investigated by (XRD) and (SEM). The results revealed that La (BO3, PO4): Ce, Tb phosphors with monocline structure and high purity were successfully prepared by sol-gel method. Compared with solid state method, the products synthesized by sol-gel method presented well developed crystal structure, small particle size, narrow size distribution and high luminescent performances. The product synthesized at 1050°C for 2h had better emission intensity.
Authors: Xiao Qi Zhang, Li Min Dong, Xin Cheng Tang, Qin Li, Zhi Dong Han
Abstract: Ca2MgSi2O7: Eu3+, Ce3+, Tb3+, a single white Phosphor, was synthesized by the conventional solid-state reaction. The structure, surface morphology and luminescence properties of the prepared samples were investigated to evaluate its potentiality. XRD results confirm the orthorhombic phase of Ca2MgSi2O7: Eu3+, Ce3+, Tb3+ phosphors. The excitation spectra indicates the phosphor can be excited by 393 nm wavelength. The phosphor exhibits blue light at 467 nm, green light at 588 nm, red light at 618 nm. CIE chromaticity diagram indicates that Ca2MgSi2O7: Eu3+, Tb3+, Ce3+ exhibits white light. All properties show that the prepared phosphor is a single white phosphor suitable for near ultraviolet excitation which can be applied to new generation white LED lighting.
Authors: Lian Wei Shan, Wei Li, Ji Hua Wang, Zhong Li, Li Min Dong
Abstract: 0.7BaO·0.3SrO·0.3Nb2O5·0.7TiO2 (SBN/BST) composite ceramics werefabricated using a Powder-Sol (P-S) method with Nb2O5fine powder suspended in the barium strontium titanate (abbreviated as BST) solsolution. By X-ray diffraction (XRD) investigations, it is found that thetetragonal tungsten bronze (TTB) phase and perovskite phase were co-present incompositions. The average grain size of BST and SBN phase is 140 nm and 2.2 μm,respectively. The room temperature relative dielectric constant is 1445 forthis sample measured at 1 kHz and zero bias. In the room temperature, thepyroelectric coefficient of the 0.7BaO·0.3SrO·0.3Nb2O5·0.7TiO2is 39 nc/cm2·°C. The maximum value of FD is about 2.4×10-5 Pa-1/2at 45°C.
Authors: Jun Li Zhang, Ze Wu, Li Min Dong, Tao Jiang, Xian You Zhang
Abstract: Nanocrystalline M-type Co2+ substituted barium hexaferrites samples having generic formula barium Ba0.5Sr0.5Fe12-xCoxO19 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by chemical co-precipitation method. The sintered samples were characterized by XRD, SEM and VSM techniques. All the XRD patterns showed the single phase of the magnetoplumbite barium ferrite without other intermediate phase. The lattice parameters (a and c) obtained from XRD data decreases with increase in cobalt content x. The magnetic behavior of the samples was studied using vibrating sample magnetometer technique. The saturation magnetization (Ms) first increases reaching a maximum of 63.684 emu/g at x=0.4, and then decreases. The coercivity (Hc) decreases with increase in cobalt content x.
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