Zhang Xianyou

Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

Abstract Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe 2 C 4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900 °C for 2 h has an average diameter of 60 ∼ 90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

XPS Study on Barium Lanthanum Magnesium Niobate

Abstract Relaxor-type ferroelectric perovskites attract a lot of attentions due to their excellent dielectric and electrostrictive properties. (Ba, La) (Mg, Nb)O3 (BLMN) ceramics were synthesized from oxides by sintering in airs using a conventional mixed oxide process. Thermogravimetry-differential analyzer (TG-DTA) analysis shows that the fired temperature of the Ba(Mg1/3, Nb2/3)O3 is above 1627.2 K. From the study of X-ray diffraction (XRD) patterns, it is founded that the amount of the perovskite phase increases with the increasing amount of La2O3. Furthermore, by the X-ray photoelectron spectroscopy (XPS) analysis, it is discovered that the amount of Nb4+ is increased as La2O3 dopant increases from 0 to 0.04.

Structure of BaLaxFe12-x O19/SiO2 Synthesized by Sol-Gel Method

Abstract M-type hexaferrites BaLa x Fe 12-x O 19 powders were synthesized by sol-gel method in the presence of SiO 2 nanoparticles. The X-ray diffraction patterns of BaLa x Fe 12-x O 19 /SiO 2 calcined at 1000 °C manifest that all the species have hexagonal crystal structure and no diffraction peaks of SiO 2 are found. The structure of BaLa x Fe 12-x O 19 seems uniform at different La doping dosage. Fourier transform infrared (FTIR) proves the co-existence of SiO 2 and ferrites in the products. The addition of SiO 2 nanoparticles promotes the formation of more homogeneous and finer ferrite crystal, as proved by scanning electron microscopy (SEM). Compared with BaLa 0.5 Fe 11.5 O 19 powders synthesized without SiO 2 nanoparticles, those synthesized in the presence of SiO 2 nanoparticles present in smaller powder size and similar structure.

Study on the properties of the wollastonite short fiber-PVC cable insulation composition

Surface-treated wollastonite powder is a kind of new inorganic filler for cable insulation applications. The elemental composition, properties and main uses of the wollastonite short fiber are described. The slenderness ratio, particle size, particle shape, content and ways of surface treatment of the wollastonite are discussed. Experiments show that the wollastonite short fiber is a kind of inorganic filler with good reinforcing and electrical insulation characteristics. By means of SEM and a rheogeniometer, the distribution and fluidity of the cable insulation compositions are observed. Balance experiments of the wollastonite powder and other inorganic fillers such as calcine clay and CaCO/sub 3/ are described.

Experimental Investigations on Yttrium Borate Phosphate Phosphors with Codoped Ce3+ and Tb3+ Ions

Abstract Green phosphor of Y(BO3, PO4): Ce, Tb was synthesized by means of sol-gel and conventional solid state methods. The thermal formation process was characterized by thermogravimetric analysis (TG) and differential thermal analysis (DTA). The effects of synthesis conditions on the crystalline and morphological structures were investigated using the X-ray diffraction (XRD) and Scanning Electronic Microsocpy (SEM). The results revealed that Y(BO3, PO4): Ce, Tb phosphors with the monocline structure and high purity were successfully prepared by the sol-gel method. Furthermore, the products synthesized by the sol-gel method showed a well developed crystal structure, small particle size, narrow size distribution, and high luminescent performance. The product synthesized at 1050 °C in 2 h had better emission intensity than the others.

Microwave-Induced Combustion Synthesis of Hexagonal Barium Ferrite Powders

A novel ceramic synthesis technique, microwave-assisted process was investigated for the production of Barium Hexagonal ferrite (BaFe^Oip) powders with improved physical properties. Compared to conventional synthetic route, 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 BaFe^Oy were further investigated by X-ray diffractometer (XRD), infrared spectroscopy (IR), 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.

Study of SO/sub 2/ removal using non-thermal plasma induced by corona discharge

Summary form only given. Application of plasma chemistry for gas cleaning is gaining prominence in recent years, mainly from the energy consideration point of view. Normally, the gas treatment is carried out at or above room temperature by the conventional dry-type corona reactor. However, this treatment is still inadequate for the removal of certain stable gases present in the flue gas mixture. In this paper, a new plasma reactor electrode configuration was used to remove SO2 from the flue gas. A high voltage needle electrode was submerged in the liquid phase while the plate ground electrode was placed in the gas above the liquid surface, resulting in a gas phase discharge in addition to the liquid phase discharge. The method of generating the radicals from H2O with positive DC corona discharge and the influence of the needle-plate electrode system on SO2 removal efficiency were experimentally studied. As a result, high amounts of hydrogen peroxide and dissolved ozone were found in the liquid. This new electrode configuration led to high SO2 removal efficiencies under several different operating conditions

Study on the positive and negative temperature coefficient effects of composite filler/PP composite

A crosslinked conductive material prepared by melt-mixing of CB (carbon black) and PE (polyethylene) was ground into fine power and screened, we get the composite filler. Then, a new conductive composite was prepared by melt-mixing of the composite filler and PP. A double-positive temperature coefficient (double-PTC) was observed in the composite. The phenomenon related to the large thermal expansion due to the consecutive melting of high-density polyethylene (HDPE) and polypropylene (PP) crystallites phase. At the same time, the negative temperature coefficient effect (NTC) was eliminated basically. This conclusion was confirmed by the morphology of SEM of the composite.