Research on the Surfactant-Assisted Synthesis of MnZn Ferrite Precursor Powders

MnZn ferrite precursor powders were prepared by the nano in situ composite method. Three surfactants, which include polyethylene glycol 400 (PEG-400), cetyltrimethyl ammonium bromide (CTAB), and sodium dodecyl sulfate (SDS), were usedM and the impact of the surfactants on the precursor sol solutions and precursor powders was studied. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM), a Zeta potential meter, a BET surface analyzer, and a vibrational sample magnetometer (VSM) were used to characterize the precursor sol solutions and the precursor powders. The results showed that these surfactants can improve the dispersion state and Zeta potentials of sol particles and increase the specific surface areas of the precursor powders. Moreover, the precursor powders were composed of MnZn ferrite, and some were amorphous. CTAB was the optimum surfactant and the zeta potential of the sol particles and the specific surface area of the precursor powders named P-0.1CTAB are 10.7 mV and 129.07 m2/g, respectively. In addition, the nano-particles that were made up of the P-0.1CTAB precursor powders had smaller sizes and more uniform particle distributions than the others. The magnetic properties’ improvement was attributed to the addition of surfactants, and CTAB is the optimal type. In addition, the novel nano in situ composite method will inspire fresh thinking and investigation into the research of ferrite

Effect of Vacuum Treatment and Ti Content on the Properties and Microstructure of Mo-0.1Zr Alloy

In order to reveal the effect of vacuum treatment and Ti content on the properties and microstructure of Mo-0.1Zr alloy, Mo-0.1Zr and Mo-0.1Zr-nTi (n=0.4, 0.55, 0.7 and 0.9) alloys were prepared via powder metallurgy processes and final vacuum treatment was adopted. The result shows that the mechanical properties of Mo-0.1Zr alloy were enhanced greatly by the vacuum treatment, especially the elongation of the alloy (25.6%), much higher than that of the forged Mo alloys. Simultaneously, obvious transgranular fracture was observed on the fracture surface after vacuum treatment instead of the intergranular fracture. It induces the generation of (Mo,Ti)(x)O(y) second-phase particles by adding element Ti into the Mo-0.1Zr alloy, which exists in the grain boundaries. With the increase of Ti content, the amount of second-phase particles increases and leads to the reduction of mechanical properties of the alloys

Effect of alloyed elements Ti, Zr on the property and microstructure of Mo alloy

Mo-Zr and Mo-Ti alloy were fabricated by powder metallurgy process, the effect of the adding forms and addition amount of Zr, Ti on the tensile property and microstructure of the alloy were studied. The results indicate that the addition of the alloyed element Zr, Ti obliviously enhances the mechanical property of molybdenum. The tensile strength of Mo-Zr alloy added pure Zr is higher than that of Mo-Zr alloy added ZrH(2) powder. The highest value of tensile strength is achieved when the addition amount of Zr is 0.1wt%. The minority of Zr solves in to the Mo matrix while the majority forms ZrO(2) particles with oxygen in the alloy. Mo-Ti alloy possesses higher tensile strength when the alloyed element Ti is added in the form of TiH(2) powder, which is of highest tensile strength when the addition amount of TiH(2) is 0.8wt%. One part of Ti solves into the Mo matrix and the others forms Mo(x)Ti(y)O(z) composite oxide particles with Mo and oxygen in the alloy

Effect of Rare Earth Y on Properties of Nanosized 90W-7Ni-3Fe Composite Powder Fabricated by Spray Drying-Hydrogen Reduction

(W,Ni,Fe) composite oxide powder synthesized by spray drying was reduced at 700∘C for 90 minutes in H2 atmosphere. The effect of rare earth Y on H2 reduction of (W,Ni,Fe) composite oxide powder was studied. Phase composition, crystalline size, and particle morphology of the reduced powder have been measured by X-ray diffraction and scanning electron microscope (SEM). Fsss particle size and special surface area of the reduced powder were also measured and analyzed. The result showed that new phase Y(Ni0.75W0.25)O3 appeared in the reduced powder and particle morphology was nearly spherical or polyhedron by Y additions. The higher the rare earth element content was, the bigger the influencing on particle morphology was. When the rare earth Y content was under 0.8%, with the increase of the rare earth element content, dBET, Fsss, and crystal sizes of the reduced powder decreased greatly

Influence of TiC Addition on Properties and Microstructure of Mo-Ti Alloy

Mo-Ti-TiC alloys were fabricated by powder metallurgy process through adding TiH2 powder and ultrafine TiC powder into Mo metal. The influence of the addition of nano-scale TIC particles on the microstructure and tensile properties of Mo-Ti alloy was studied. The results indicate that the tensile strength of Mo-Ti alloy was effectively increased by TiC particles addition. Mo-Ti with 0.05wt% TiC exhibited the highest tensile strength, which is 31.7% higher than that of Mo-Ti alloy. The addition of TiC protects Ti from oxidation, which is produced by decomposition and dehydrogenization of TiH2 particles. The second phase particles containing Mo, Ti, 0 and C in the alloy were formed with TiC addition. The grain size of the alloy decreased with the increase of the TIC content since the second phase particles can inhibit the grain growth

Effect of alloying elements Ti, Zr on the property and microstructure of molybdenum

Mo-Zr and Mo-Ti alloy were fabricated by adding alloying element Zr, Ti in molybdenum via powder metallurgy process. The effect of Zr, Ti alloying elements on the tensile strength and microstructure of molybdenum are investigated. Two types of alloying additives are used: one is elemental powder of Zr or Ti; the other is their respective hydride powders, TiH(2) or ZrH(2). The experimental results show that the formed Mo-Zr, Mo-Ti alloy possess much higher mechanical properties than pure sintered molybdenum. The tensile strength of Mo-Zr alloy is more affected by adding elemental Zr powder than ZrH(2) powder, the optimal tensile strength is obtained with addition of 0.1 wt% Zr, most of Zr forms Zr-oxide existed both inside the grain and at the grain boundaries, while very little Zr diffuses into the Mo matrix. Meanwhile, for Mo-Ti alloy, the tensile strength is more influenced by addition of TiH(2) powder than elemental Ti powder, the tensile strength is optimized at the content of 0.8 wt% TiH2, some Ti diffuses into molybdenum and forms Mo-Ti solid solution and some forms as Mo(x)Ti(y)O(z) oxide particles uniformly distributed at the grain boundaries. (C) 2008 Elsevier Ltd. All rights reserved

Effect of microelement Zr on the property and microstructure of Mo alloy

Mo-Zr alloy were fabricated by powder metallurgy process, the effect of the adding forms of Zr and its content on the tensile property and microstructure of the alloy were studied. The results indicate that the addition of alloying element Zr obliviously enhance the mechanical property of Mo alloy. Mo-Zr alloy added with element Zr powder exhibits higher tensile strength than that with ZrH. The highest tensile strength value is achieved at 0.1wt% of Zr. The minority of Zr solve into the Mo matrix while most of Zr form ZrO particles due to reaction with oxygen in the Mo powder

Hot Deformation Behavior and Simulation of Hot-Rolled Damage Process for Fine-Grained Pure Tungsten at Elevated Temperatures

Fine-grained pure tungsten fabricated by a sol drying reduction low-temperature sintering method and hot isothermal compression tests were performed by using the Gleeble 3800 thermo mechanical simulator at deformation temperatures from 1273 K to 1473 K and strain rates from 0.001 s−1 to 1 s−1. In addition, the constitutive equation was established by least square method combined with the Zerilli–Armstrong model, and the hot deformation behavior was discussed. Moreover, based on constitutive equation, the influence of the rolling process and its parameters on temperature, strain, density and rolling force in the hot rolling process was investigated at elevated temperature by the finite element model (FEM). Furthermore, the form of rolling damage and its formation mechanism were analyzed. Results showed the grains of pure tungsten are dense, irregular polyhedral spherical and very fine, and the average grain size is about 5.22 μm. At a high strain rate, the flow stress increases rapidly with the increase in strain, while the stress–strain curve shows a flattening trend in the tested strain rate range with increasing temperature, and no flow stress peak exists, showing obvious dynamic recovery characteristics. Furthermore, the FEM simulation showed that compared with the rolling temperature, the reduction has a greater influence on the temperature, stress–strain field and its distribution. There are three kinds of damage in the hot rolling process: transverse cracks, longitudinal cracks and side cracks, which are attributed to the competition between additional stress caused by uneven deformation and material strength. Moreover, the control method of hot rolling defects had been preliminarily proposed. These results should be of relevance for the optimum design of the hot rolling process of pure tungsten