Gui Fang Sun

Laser Surface Alloying of NiCr-Cr3C2 and C-B-W-Cr Powders on Nodular Cast Iron Rolls

The laser surface alloying(LSA) technique was firstly used to form wear resistant layers on nodular cast iron rolls with two different powders, A: NiCr-Cr3C2 and B: C-B-W-Cr. The microstructure, element distribution and phases of the layers were investigated. Results indicate that the alloying layers had pores and cracks, as well as a metallurgical bonding with the substrates. For layers with powder A, as the thickness of the pre-layers decreased, the numbers of pores and cracks of the LSA layers decreased but the thicknesses of them were close. Phases were barely influenced by the thickness of the pre-layer, while the content of them were affected. For layers with powder B, as the laser specific energy increased, the numbers of pores and cracks in the LSA layers decreased and the thicknesses of them increased. The microstructure in the layers with different powders was different.

Preparation and Magnetic Properties of BiFeO3 and NiCuZn Ferrite Multiferroic Composites

A series of xBiFeO3-(1-x) NiCuZn ferrite multiferroic composites have been prepared by solid state reaction method, in which x is 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. Composites are densified at 700 °C for 3 h. XRD results show that ferroelectric phase and ferromagnetic phase can be co-existed in the composites. The density of composites increases with an increase of BiFeO3 content. SEM results reveal that the bigger grains are BiFeO3 and the smaller grains are NiCuZn ferrite. Composites exhibits the typical magnetic hysteresis loops. Increasing x, the saturation magnetization of composites linearly decrease. The real part of permeability for composites decreases with increasing x. Meanwhile, the peak of imaginary part of permeability shifts toward higher frequency.

Preparation and Characterization of LaAlO3 via Sol-Gel Process

Lanthanum aluminate powders were synthesized by sol-gel process with metal nitrates as raw materials, 2-methoxyethanol/water as solvent and citric acid as chelating agent. The influence of this techniques (the amount of citric acid, pH value, calcination temperature and the ratio of 2-methoxyethanol/water) on the lanthanum aluminate powders were studied. The XRD shows pure LaAlO3 powders could be obtained after calcining at 600-900 °C. The SEM analysis indicates that the LaAlO3 particles are uniform and nanosized with a range of about 40-70 nm, which is slightly larger than the estimated particle size using Scherrer formula.

Study on Aging Strengthening of Mg-Zn-Cu Alloy Based on Component Optimization Design

In this study, we investigated the aging strengthening of Mg-Zn-Cu alloy based on component optimization design by FactSage software, optical microscope (OM), X-ray diffraction (XRD) and Vickers hardness tester. The results show that the precipitation rate of MgZn2 phase in Mg-6Zn-1Cu is significantly higher than that of the other alloys. When Mg-6Zn-1Cu alloy is subjected to aging at 160°C for different time, the phase consists of α-Mg, MgCu2 and MgZn2. The content of main strengthening phase MgZn2 is increasing with the prolonging of aging time. When Mg-6Zn-1Cu alloy aged at 160°C for 10h, the kinetics of precipitation is considerably accelerated. The results indicate that the hardening produced in the Cu-containing alloy is considerably higher than in the Mg-Zn alloy. Therefore, based on component optimization design to establish Mg-Zn-Cu alloy solidification database, and to predict the phase equilibrium and thermodynamic properties of the alloy, is an effective method for the development of new magnesium alloy.

Preparation and Characterization of Fe Doped Bi2Ga4O9 Ceramics

A series of Fe-doped Bi2(FexGa1-x)4O9 (x=0.1,0.2,0.3,0.4,0.5) ceramics were synthesized by solid-phase method with sintering process. The influences of Fe doping content on phase, morphology, dielectric properties are discussed. XRD results show that there is no second phase in Fe-doped Bi2(FexGa1-x)4O9 ceramics. The SEM analysis indicates the grain size of as-prepared doped samples are relatively uniform and estimated to be about 1–4μm. The permittivity of as-prepared doped samples increases and the dielectric loss decrease compared to pure Bi2Ga4O9 ceramics.

Preparation and Dielectric Properties of La Doped Bi2Al4O9

A series of (Bi1-xLax)2Al4O9 (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40) ceramics were prepared by sol-gel method with sintering process. Doping dependent investigations were carried out to show the influence of La atom on the structural stability. The products were characterized using X-ray diffraction, scanning electron microscopy. This showed that the second phase is increased gradually by La doping. When the value of La is 0.4, the main phase tends to become LaAlO3. Details on dielectric properties are reported. The permittivity of as-prepared doped samples increases slightly compared to pure Bi2Al4O9 and excellent frequency stability is exhibited.

Synthesis and Characterization of Bi2Al4O9 Powders

Bi2Al4O9 powders were prepared by sol-gel process. The precursors were heated at 500-800°C for 2h to obtain Bi2Al4O9 powder and X-ray diffraction (XRD), Differential thermal analysis (DTA), thermogravimetric analysis (TG), field emission scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) techniques were used to characterize precursor and derived oxide powders. XRD analysis show that the powder is still amorphous after calcined at 500°C. The peaks of Bi2Al4O9 become sharp after calcined at 575°C though still existing some amorphous phase. After calcining at 675-800°C, the powder has fully turned into pure Bi2Al4O9 phase. The crystallization process can also be confirmed by DTA-TG and IR. Calcining the precursor at 575°C, the absorption bands at 527 cm-1, 738 cm-1, 777 cm-1, and 919 cm-1are observed, which are assigned to Bi2Al4O9 and becoming stronger and sharper with the increase of temperature.

Preparation and Characterization of Bi-Doped LaAlO3 via Sol-Gel Process

A series of Bi-doped BixLa1-xAlO3 (x=0.0, 0.1, 0.2, 0.3, 0.4) powders have been prepared by sol-gel method at 800°C. The influences of Bi doping content on phase, morphology, particle size, surface area, infrared absorption spectrum are discussed. XRD results show that there is no second phase in powders when x≤0.3, however, there exist impure phases when x≥0.4. The SEM analysis indicates the particle size of powder is 50-150nm. The specific surface area is 5-13 m2/g.

Luminescent Properties of Zn2SiO4:Eu3+,Dy3+ Phosphors via Sol-Gel Process

Zn2SiO4:Eu3+, Dy3+ phosphors have been prepared through the sol-gel process. X-ray diffraction (XRD), thermogravimetric and ddifferential thermal analysis (TG-DTA), FT-IR spectra and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the phosphors crystallized completely at 1000oC. In Zn2SiO4:Eu3+,Dy3+ phosphors, the Eu3+ and Dy3+ show their characteristic red(613nm, 5D0-7F2), blue (481nm, 4F9/2–6H15/2) and yellow (577nm, 4F9/2–6H13/2) emissions.

Effect of Sc Doping on Ferroelectric and Dielectric Properties of Bi0.9La0.1FeO3 Thin Film by Sol-Gel Process

Pure Bi0.9La0.1Fe1-xScxO3 (x = 0, 0.05, 0.10, 0.15, 0.20) (BLFSO) thin films were deposited on conductive indium tin oxide (ITO)/glass substrates through a simple sol-gel process. The effect of Sc doping on the XRD, microstructure, dielectric and ferroelectric properties of BLFO films was studied. Compared to counterparts of Bi0.9La0.1FeO3 (BLFO) film, the grain refinement of all films is obvious. When the value of Sc is 0.15, the double remanent polarization 2Pr is effectively enhanced with the extreme value of 17.7µC/cm2. The dielectric constant exhibits a trends of increase firstly and then decrease with the increase amount of scandium level.