Search results for "Grain Size"
showing 10 items of 131 documents
Control of grain size and morphologies of nanograined ferrites by adaptation of the synthesis route: mechanosynthesis and soft chemistry
2003
Abstract Nanocrystalline Fe-based spinels with composition Fe 2.5 Ti 0.5 O 4 can be synthesized using two different routes: soft chemistry and high-energy ball milling. This paper is focussed on the fact that each type of synthesis process can lead to powders with a crystallite size of about 15 nm but with significant differences in the grain size distribution and the agglomeration state. Whereas in the case of mechanosynthesis, the ball-milled powders consist of aggregates, those obtained by soft chemistry are very well dispersed. Moreover the chosen investigated nanopowders present a blocked/superparamagnetic transition depending on the grain size. The grain size morphologies obtained by …
Characteristics of LiFePO4 obtained through a one step continuous hydrothermal synthesis process working in supercritical water
2009
International audience; The olivine-like material LiFePO4 was prepared via a continuous hydrothermal synthesis process working from subcritical to supercritical water conditions. The influence of some processing parameters–temperature and reaction time–was investigated in terms of material purity, grain size and morphology. Supercritical conditions were found to be attractive to synthesize in one step a well-crystallized material without impurities. The primary particles size was in the nanometric range. They showed a natural tendency to form micron size agglomerates, which were supposed to be the cause of the limited capacity, as demonstrated through a cross study using laser particle size…
Mechanical, degradation and drug-release behavior of nano-grained Fe-Ag composites for biomedical applications.
2018
Abstract An original fabrication route of high-strength bulk Fe-5Ag and Fe-10Ag nanocomposites with enhanced degradation rate is reported. Near fully dense materials with fine nanostructures and uniform distribution of Ag nanoparticles were obtained employing high energy attrition milling of Fe-Ag2O powder blends followed by cold sintering – high pressure consolidation at ambient temperature that allowed the retention of the nanoscale structure. Annealing in hydrogen flow at 550 °C resulted in enhanced ductility without coarsening the nanostructure. The strength in compression of Fe5Ag and Fe10Ag nanocomposites was several-fold higher than the values reported for similar composites with mic…
Powder metallurgy processing and deformation characteristics of bulk multimodal nickel
2014
cited By 7; International audience; Spark plasma sintering was used to process bulk nickel samples from a blend of three powder types. The resulting multimodal microstructure was made of coarse (average size ∼ 135 μm) spherical microcrystalline entities (the core) surrounded by a fine-grained matrix (average grain size ∼ 1.5 μm) or a thick rim (the shell) distinguishable from the matrix. Tensile tests revealed yield strength of ∼ 470 MPa that was accompanied by limited ductility (∼ 2.8% plastic strain). Microstructure observation after testing showed debonding at interfaces between the matrix and the coarse entities, but in many instances, shallow dimples within the rim were observed indica…
The combined influence of grain size distribution and dislocation density on hardness of interstitial free steel
2020
Abstract Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties. The relationship between mean grain size and yield strength is established by the well-known Hall-Petch equation. But due to the complexity of the grain configuration within materials, considering only the mean value is unlikely to give a complete representation of the mechanical behavior. The classical Taylor equation is often used to account for the effect of dislocation density, but not thoroughly tested in combination with grain size influence. In the present study, systematic heat treatment routes and…
Deposition and characterization of cold sprayed nanocrystalline NiTi
2011
International audience; Binary 50Ni–50Ti mixture was prepared by mechanical alloying from elemental powders. After 48 h of milling, the nanocrystalline B2-NiTi powder was produced. Then, this as-milled powder was deposited by cold spraying in order to produce a target which can be used to create thin films by magnetron sputtering technique. The objective is to improve the electrical characterizations of the NiTi/SiO2/Si M.O.S structures. Themorphology evolution of the powder particles, the phase identification and the alloying evolution process as function of milling time were studied using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. In addition, th…
Deformation behavior of nanostructured ZnO films on glass
2012
Abstract Nanostructured ZnO films on glass substrate were studied by nanoindentation, scanning electron and atomic force microscopy. The films were obtained by a straightforward mechanoactivated oxidation method. The morphology of the obtained films was grained with a grain size in the range 50–100 nm and the thickness was approximately 2 μm. A detailed deformation behavior of ZnO films, critical parameters and indentation induced plastic deformation mechanisms were determined in correlation to bulk ZnO, Si single crystal and commercial ZnO films. In comparison to a single crystal ZnO, nanostructured films exhibit increased hardness (9 GPa); however, the Young's modulus is decreased (120 GP…
Studies and Researches on the Obtaining of Sintered Gradual Porous Structures by Irregular Nickel Powders Sedimentation
2012
The aim of this work is to obtain sintered porous membranes with graded structure for microfiltration by sedimentation and sintering of metallic powders. Our previous studies have demonstrated the possibility of obtaining sintered porous materials with graded structure by sedimentation. In this paper, irregular nickel particles were used having a grain size in the 2-90 µm range evaluated using scanning electron microscopy and laser scattering particle size analyzer. The powders were sedimented into a sintering die in a sedimentation medium consisting of water and dispersant agent. After drying, the samples were sintered at 1000°C for 10 minutes in vacuum (~1•10-3 Pa). The structures obtaine…
Improved Cu2O/AZO Heterojunction by Inserting a Thin ZnO Interlayer Grown by Pulsed Laser Deposition
2019
Cu2O/ZnO:Al (AZO) and Cu2O/ZnO/AZO heterojunctions have been deposited on glass substrates by a unique three-step pulsed laser deposition process. The structural, optical, and electrical properties of the oxide films were investigated before their implementation in the final device. X-ray diffraction analysis indicated that the materials were highly crystallized along the c-axis. All films were highly transparent in the visible region with enhanced electrical properties. Atomic force and scanning electron microscopies showed that the insertion of a ZnO layer between the Cu2O and AZO films in the heterojunction enhanced the average grain size and surface roughness. The heterojunctions exhibi…
Electrical and structural characterization of metal-oxide-semiconductor capacitors with silicon rich oxide
2001
Metal-oxide-semiconductor capacitors in which the gate oxide has been replaced with a silicon rich oxide (SRO) film sandwiched between two thin SiO2 layers are presented and investigated by transmission electron microscopy and electrical measurements. The grain size distribution and the amount of crystallized silicon remaining in SRO after annealing have been studied by transmission electron microscopy, whereas the charge trapping and the charge transport through the dots in the SRO layer have been extensively investigated by electrical measurements. Furthermore, a model, which explains the electrical behavior of such SRO capacitors, is presented and discussed. © 2001 American Institute of …