Papers by Keyword: Powder

Abstract: In this paper, a fine pure Magnesium aluminate spinel powder was synesised by Gel solid reaction,using Al(NO₃)₃ 6H₂O and Mg(NO₃)₂6H₂O as raw materials under given condition. The precursor was formed by polymer gelling.The phase changed according to heating temperatures from 700°C to 900°C.The single phase of Magnesium aluminate spinel was obtained by calcining the precursor at temperatures higher than 900°C. The phase changing process and relationship among calcination parameters, phase composition and image of particle are studied to determine the optimal conditions for the synthesis of fine Magnesium aluminate spinel powder. The powder obtained was characterized by XRD,TEM etc. The results of analysis showed that the ultrafine powder is of spinel phase, high purity, good dispersion.This process for preparing fine Magnesium aluminate spinel powder was very simple and inexpensive.The results of analysis showed that the ultrafine powder was of mullite phase, high purity, good dispersion, and the particle were homogeneous.

Abstract: Nano-sized manganese-doped zinc aluminate spinel (Zn1−xMnxAl2O4; x = 0–6.0 mol%) powder phosphors were prepared by the sol–gel process. Zinc chloride, aluminum isopropoxide, and manganese chloride were employed as precursors. The influences of manganese concentration and heat treatment conditions on the crystallization and photoluminescence of the phosphors were investigated. The dried powders were amorphous to X-ray powder diffraction (XRD) and the single-phase ZnAl2O4 spinel crystallite started to form at temperatures as low as 600oC. The crystallization of powder did not significantly affected by various manganese concentrations. On heating at 1000oC, the resulting powder phosphors had the average crystallite and primary particle sizes of around 20–25 and 20–30 nm, respectively, depending on the dopant content and heating time. Photoluminescence spectra exhibited strong green emission bands centered at 512 nm under an excitation wavelength of 458 nm. The luminescence efficiency has been investigated as a function of dopant content, heating temperature, heating time, and specific surface area of the powders.

Abstract: The In₂Se₃/CuSe composite powders with the size in the range of 2-8µm for solar cell were successfully synthesized via using relatively simple solvothermal method at atmospheric pressure by the reaction between InCI₃.4H₂O, CuCI₂.2H₂O and Selenious acid and hydrazine hydrate in ethylene glycol.The influences of reaction temperature, reaction time, concentration of solution on the phase and morphology of In2Se3/CuSe composite powders were investigated. The phase and morphology of the products h_{Subscript text}ave been well studied by X-ray diffraction (XRD)and scanning electron microscope (S_{Subscript text}EM) techniques.The study revealed that under the conditions of solvothermal method at atmospheric pressure, relative pure In₂Se₃ and CuSe powder were synthesized at temperatures of 160°C and 100°C respectively. The In₂Se₃/CuSe of irregular flake composite powders with the average size of 2-8µm had been obtained.The morphology of the products can be controlled by adding different kinds of surfactants such as PVP (Polyvinylpyrrolidone), CTAB (Hexadecyl trimethyl ammonium Bromide) and so on.

Abstract: Submicron single-phase yttrium aluminum garnet (Y₃Al₅O₁₂, YAG) powders were fabricated by solid-state reactive heat-treating a mixture of pyrolysis product, heat-treating isopropyl aluminum at 500°C, and yttria (Y₂O₃) powders. The powders were mixed by ball milling for 2~3 h doped with 5wt% aluminium fluoride (AlF₃), and then heat-treated at 1200°C for 2~5 h. Characterized by XRD, mixing the powders by ball milling and doped with AlF₃ lowered the heat-treating temperature and made the forming of YAG phase be single.

Abstract: With the Aim of Preparing the Raw Powders Used for Soft Magnetic Compacts Production, Nanocrystalline Soft Magnetic Powders of Fe_84.3Si₄B₈P₃Cu_0.7 Were Successfully Fabricated Using Crystallization by Rapid Heat-Treatment and Mechanical Ball-Milling Methods. We Investigated the Relation of the Magnetic Properties, Crystallization Degree and Heat-Treatment Condition in Salt-Bath Process. In this Study, a Fine Nanocrystalline Structure with an Extremely Number of α-Fe Grains with the Similar Size of ~ 30 nm Was Obtained. This Led to Excellent Soft Magnetic Properties, i.e., 1.85 T (197.7 emu/g) and 10 A/m for Saturation Magnetization and Coercivity, Respectively. By Controlling the Milling Time, Different Particle Size of Powder Can Be Obtained.

Abstract: Due to outstanding properties of γ–TiAl intermetallic such as high resistance against fatigue, oxidation, corrosion, creep, dynamic vibration, high working temperature and also its application in aerospace, automotive industry and turbojet engines; in this paper, powder mixed electrical discharge machining (PMEDM) of γ–TiAl intermetallic by means of different additive powders including aluminum (Al), graphite (Gr), silicon carbide (SiC), chrome (Cr) and iron (Fe) is investigated to compare the output characteristic of surface quality and roughness. The results indicate that aluminum powder produces the best surface finish, followed by silicon carbide, graphite, chrome and iron respectively. The experimental results show that in the determined settings of input machining parameters, aluminum powder can improve the surface roughness of TiAl sample about 32%.

Abstract: Powder metallurgy is widely used to the production of AgNi and AgSnBi powders employed for electrical contacts. In the work AgNi and AgSnBi powders were consolidated by the cyclic extrusion compression (CEC) method enabling cyclic unlimited deformation. In the initial stage the AgNi powder contained the two phases Ag and Ni, recognized by the EDX technique using scanning electron microscopy (SEM). The investigations shown that the Ni phase is distributed in the form of small granules around larger Ag granules. In the AgSnBi powder phases Ag + Bi + Ag3Sn (ξ) were distributed uniformly. It was found that after the CEC consolidation phases were excellently joined without cavities and cracks. Detailed observations of microstructure have been performed by the transmission electron microscopy (TEM) and revealed inside the consolidated granules nanometric grains with the nanometric twins inside.

Abstract: Mechanical properties of Cu-based metallic glass matrix composites reinforced by ductile fugitive phases, synthesized by warm extrusion of gas atomized powders, has been investigated under the uniaxial compression condition at room temperature. The ductile fugitive phases are well distributed in the metallic glass matrix and enhanced macroscopic plasticity is observed due to the formation of multiple shear bands, initiated from the interface between ductile fugitive phase and metallic glass matrix, as well as their confinement between the reinforcements, stemming from the constrained plastic deformation of the reinforcing ductile phase.

Abstract: Electron beam melting (EBM) is a promising fabrication technique for directly producing metal products from powder as the starting material. Powders are provided as a thin layer (~100 μm) and melted layer by layer with an electron beam. In this study, the effects of the energy density of the incident beam on the mechanical properties of Ti–6 mass% Al–4 mass% V alloy products fabricated through EBM were examined. The products were fabricated using an electron beam at various energy densities depending on the electron beam current. The microstructures and crystallographic orientations were observed using optical microscopy and electron backscatter diffraction (EBSD), respectively. Compression tests were carried out in 2 loading directions using a mechanical testing machine equipped with strain gauges, one perpendicular (x–y direction) and the other parallel (z direction) to the stacking direction. In principle, the microstructure consisted of an acicular-shaped α phase (hcp lattice) and a small-volume β phase (bcc lattice). In addition, columnar grains elongated toward the z direction appeared during the repeated melting and solidification that occurred during the EBM process. An increase in the beam current of the incident beam enlarged the α grains and increased the relative density, resulting in the related Young’s modulus of the products. The energy density caused by the beam current also introduces anisotropy in the deformation behavior depending on the loading axis toward the stacking direction. This is closely related to the cast defect arranged along the stacking layers. It was concluded that the mechanical properties of the Ti–6 mass% Al–4 mass% V alloy products formed through EBM were very sensitive to the incident beam current and stacking direction, resulting in the exhibition of anisotropic deformation behavior within a limited range of energy density.

Abstract: The application of powder particle size measurement in engineering field are introduced, the major powder particle size research methods are also included. Furthermore we analyzed the characteristics of these methods. Based on these, we proposed a method, which makes full use of Matlab to process and analyze the SEM image of powders to get powder particle size and the distribution, and the method achieve a good effect. Finally, In order to verify the processing method, the authors performed an example of the approach. Based on the results, it can be confirmed, therefore, the method using MATLAB is convenient to analyze the powder particle size.