Nanocrystalline Material Research Papers - Academia.edu (original) (raw)

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- Engineering, Materials Engineering, Mechanical Engineering, Microstructure
- by François Flory
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- Engineering, Physics, Remote Sensing, Applied Physics

Thermally-driven decomposition of various organosilicon derivatives under a neutral gas atmosphere constitutes a reliable way for the preparation of carbon/silicon carbide C/SiC composites (modified car-bon materials) in the nanosized range. The two-stage aerosol-assisted synthesis method appears to be especially well suited to fabricate such materials while offering spherical particle morphology with tai-lored particle size capability. In this method, in the first stage an aerosol mist is generated from a liquid precursor system and transported in a neutral gas stream to a pre-heated ceramic tube reactor where com-plex physical and chemical changes take place resulting in the formation of solid particles collected on an exit filter. The raw product is usually pyrolyzed in the second stage at appropriately high temperatures to complete the anticipated removal of residual oxygen if excess C is present via carbothermal reduction. In this study, preliminary results on the target C/SiC ...

- by Jerzy Janik
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- Nanocrystalline Material, Composite
- by Hoa Nguyen
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- Materials Engineering, Mechanical Engineering, Materials Science, Magnetic Materials
- by Pooja Kumari
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- Materials Engineering, Catalysis, Nanoparticle, Morphology
- by G. Strukova and +1
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- Engineering, Mechanical Engineering, Condensed Matter Physics, Materials Science
- by Iyyappan Raja
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- Engineering, Mechanical Engineering, Condensed Matter Physics, Technology
- by Thomas Klassen
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- Materials Engineering, Condensed Matter Physics, Catalysis, Kinetics
- by Y. Estrin
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- Materials Engineering, Mechanical Engineering, Nanocrystalline Material, Diffusion
- by Olivier Isnard and +1
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- Mechanical Engineering, Condensed Matter Physics, Nanocrystalline Material, Mechanical Alloying
- by Ionel Chicinas and +1
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- Mechanical Engineering, Condensed Matter Physics, Heat Treatment, Nanocrystalline Material
- by Enrique Lavernia and +1
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- Materials Engineering, Mechanical Engineering, Nanocrystalline Material, Grain size

In the electrodeposition system, adding saccharin alters the properties of the metal deposits by changing the electrode kinetics of the deposited surface. In this study, nanocrystalline cobalt-iron (CoFe) coating was synthesised using the electrodeposition technique with different saccharin concentrations. The results obtained showed that the coating thickness increased while the grain size decreased from 51 nm to 40 nm when the saccharin concentration increased from 0 to 2 g/L. The nanocrystalline CoFe coating produced with 2 g/L of saccharin concentration resulted in the smallest particle size of 71.22 nm and the highest microhardness of 251.86 HV. From the salt spray test (24 and 48 hours) it was found that the use of saccharin at higher concentration of 2 g/L improves the corrosion resistance of the nanocrystalline CoFe coating significantly due to the change of surface morphology as well as the decrease in grain size.

- by Aniq Aiman
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- Engineering, Mechanical Engineering, Nanomaterials, Corrosion Engineering
- by Abdelkader Kara
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- Engineering, Epitaxial Growth, Applied Physics, Density-functional theory

The mechanical behavior of nanocrystalline materials has been studied extensively for the past few years. Recent studies on artifact-free materials with nanosize grains less than 100 nm have been very fruitful. These nanograined metals have exhibited very high strengths with reasonably good ductility. While there have been a large number of studies on hardness and strength characteristics, studies on strain rate sensitivity (SRS) are very limited. We describe here some of our recent work in characterizing SRS as well as activation volumes of nanograined copper using different testing procedures. These tests have been carried out under iso-strain rate and iso-structural conditions.

- by Ronald Scattergood
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- Materials Engineering, Mechanical Engineering, Materials Science, Strain Rate
- by Zaoshi Yuan
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- Crack propagation, Nanocrystalline Material, Physical sciences, Grain Boundary
- by João Marcelo Cavalcante Albuquerque and +1
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- Materials Engineering, Materials, Finite element method, Nanocrystalline Material

Three dimensional (3D) nano-structured crystals have received extensive attention for their superior properties over zero dimensional (0D), one dimensional (1D), or two dimensional (2D) nanomaterials in many areas. This review is generalized for the group of chalcogenide nanoflowers (NFs) by the synthetic techniques, such as solvothermal, wet chemical, sol-gel, surface oxidation, microwave, coating, electrochemical, and several other methods. The formation mechanism was also described for the purpose of opening up new food for thoughts to bring up new functionality of materials by tuning the morphology of crystals. The pH value or the template plays fundamental role in forming the nano-flowered structure. Moreover, the correlations between the surface area (SA), contact angle (CA), and the NFs are also discussed within the context. Here, we also discussed some patents relevant to the topic.

Grain size has a profound effect on the mechanical response of metals. Molecular dynamics continues to expand its range from a handful of atoms to grain sizes up to 50 nm, albeit commonly at strain rates generally upwards of 10 6 s À 1. In this review we examine the most important theories of grain size dependent mechanical behavior pertaining to the nanocrystalline regime. For the sake of clarity, grain sizes d are commonly divided into three regimes: d4 1 μm, 1 μm od o100 nm; and d o100 nm. These different regimes are dominated by different mechanisms of plastic flow initiation. We focus here in the region d o 100 nm, aptly named the nanocrystalline region. An interesting and representative phenomenon at this reduced spatial scale is the inverse Hall–Petch effect observed experimentally and in MD simulations in FCC, BCC, and HCP metals. Significantly, we compare the results of molecular dynamics simulations with analytical models and mechanisms based on the contributions of Conrad and Narayan and Argon and Yip, who attribute the inverse Hall–Petch relationship to the increased contribution of grain-boundary shear as the grain size is reduced. The occurrence of twinning, more prevalent at the high strain rates enabled by shock compression, is evaluated.

In this paper, the state-of-the-art progress in research on novel mechanical properties of nanocrystalline materials and carbon nanotubes is reviewed. There is evidence that the relation between the strength of nanocrystalline materials and grain size does not observe the classic Hall-Petch plot. Lowtemperature and high-strain rate superplasticity have been found in some nanocrystalline materials. Theoretical prediction and experimental data indicate

- by Peter Liaw
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- Engineering, Materials Engineering, Mechanical Engineering, Carbon Nanotube
- by Prem P Vaishnava
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- Engineering, Applied Physics, Nanocrystalline Material, Mathematical Sciences
- by Rene Lopez
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- Engineering, Mechanical Engineering, Condensed Matter Physics, Applied Physics

Here we report our recent progress in the development, optimization, and application of a technique for the three-dimensional (3-D) high-resolution characterization of crystalline microstructures (3D EBSD; EBSD tomography). The technique is based on automated serial sectioning using a focused ion beam (FIB) and characterization of the sections by orientation microscopy based on electron backscatter diﬀraction (EBSD) in a combined FIB–scanning electron microscope (SEM). On our system, consisting of a Zeiss–Crossbeam FIB-SEM and an EDAX-TSL EBSD system, the technique currently reaches a spatial resolution of 100 100 100 nm3 as a standard, but a resolution of 50x50x50 nm^3 seems to be a realistic optimum. The maximum observable volume is on the order of 50x50x50um^3. The technique extends all the powerfulfeatures of two-dimensional (2-D) EBSD-based orientation microscopy into the third dimension of space. This allows new parameters of the microstructure to be obtained—for example, the full crystallographic characterization of all kinds of interfaces, including the morphology and the crystallographic indices of the interface planes. The technique is illustrated by four examples,including the characterization of pearlite colonies in a carbon steel, of twins in pseudo nano-crystalline NiCo thin ﬁlms, the description of deformation patterns formed under nanoindents in copper single crystals, and the characterization of fatigue cracks in an aluminum alloy. In view of these examples, we discuss the possibilities and limits of the technique. Furthermore, we give an extensive overview of parallel developments of 3-D orientation microscopy (with a focus on the EBSD-based techniques) in other groups.

- by C. Cerjan
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- Engineering, Magnetic Materials, Applied Physics, DISTRIBUTION
- by Fabio Piccinelli and +1
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- Materials Engineering, Electron Microscopy, Powder Diffraction, Heat Treatment
- by Galina Tsirlina
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- Nanocrystalline Material, Solid State Electrochemistry, Grain size, CO oxidation

Four different transition metals contained nanocrystalline glass ceramics are synthesized by melting and
quenching technique. The transition metal oxides play as former, modiﬁer or both the roles depending on
their oxidation states, ﬁeld strength and covalent characteristics. The optical band gaps are observed in
the range of 3.2–5.5 eV. The presence of nano-crystalline phases dominates the optical band gap. The
softening temperature (Ts) is mainly affected by the residual glass in glass ceramics. These glass ceramics
can be used as shielding materials for nuclear waste.

In this study, boron doped and undoped poly(vinyl) alcohol/zirconium-barium acetate (PVA/Zr-Ba) nanofibers were prepared using an electrospinning technique then calcinated at three different temperatures; 250 oC, 500 oC, 800 oC for 2 h. The
originality of this study is the addition of boron to metal acetates. The fibers were characterized by FT-IR, DSC, XRD and SEM. The addition of boron did not only increase the thermal stability of the fibers, but also increased their diameters, which gave stronger fibers. The FT-IR spectra of the fibers were in good accordance with literature data. The DSC results indicate that the glass transition (Tg) and melting temperatures (Tm) showed a change with the addition of boron. Also, boron doped fibers were observed to degrade at higher temperatures. XRD analyses showed that after further heat treatment at 800 oC, zirconia exists in two phases of tetragonal and monoclinic modifications. The systematic evolution of morphological features in the spun and the processed fibers were studied by scanning electron microscopy. The SEM appearance of the fibers showed
that the addition of boron resulted in the formation of cross linked bright surfaced fibers.

- by PD Sahare
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- Geology, Kinetics, Nanocrystalline Material, Radiation Measurements
- by Roberto Zysler
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- Field Theory, Nanocrystalline Material, Physical sciences, Magnetic Properties

Tb3+/Sm3+ ions co-doped Ca2La8(GeO4)6O2 (CLGO) phosphors are prepared by a pechini-type sol-gel technique. The nanocrystalline phosphors are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The photoluminescence emission and excitation spectra are measured for individually Tb3+, Sm3+ ions doped and Tb3+/Sm3+ ions co-doped phosphor samples. For the Tb3+/Sm3+ ions co-doped samples, we can observe emission covering the entire visible region with sharp peaks in green, orange, and red regions. As the Sm3+ ion concentration increases, the Commission International de I’Eclairage chromaticity coordinates shift towards warm white-light region due to the energy transfer from Tb3+ to Sm3+ ions. This energy transfer property is clearly visible in the emission spectra under 374 nm excitation.

- by Jeon Yong il and +1
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- Nanocrystalline Material, Energy Transfer, Luminescent Properties, White Light Emiting Phosphors
- by Zhanpeng Jin
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- Thermodynamics, Nanocrystalline Material, Phase equilibria, Thermodynamic Parameter
- by Fernando Rhen
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- Engineering, Applied Physics, Nanocrystalline Material, Mathematical Sciences
- by Rolf Hempelmann
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- Materials Engineering, Condensed Matter Physics, Time Use, Nanotechnology

Thermoluminescence (TL) of LiNaSO4:Eu phosphor, irradiated with 24 and 48MeV 7Li ions at different fluences in the range 5×109–1×1012ion/cm2, has been studied. The samples from the same batch were also exposed to γ-rays from a Cs137 source for comparative studies. The TL glow curves of the materials, irradiated with 7Li ions, have similar structures to that of γ-irradiated sample. They have a simple structure with a prominent peak at 412K along with small one at around 481K. The intensity ratios of 412–481K peaks have been observed to increase with fluence increasing, while that of γ-irradiated sample shows a reverse trend. This could be attributed to the changes in the recombination center populations due to 7Li ions, that have been implanted inside the matrix of LiNaSO4:Eu, during irradiation and might also act as a source for new trapping and luminescent centers. The implantation has been confirmed by TRIM calculations. The penetration depths (where the ion comes to rest) are fou...

- by PD Sahare
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- Chemical Engineering, Geochemistry, Radiation Physics, Comparative Study
- by Fabrizio Torricelli
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- Electronics, Numerical Analysis, Pyrolysis, Field effect transistors
- by Gerit Kulik
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- Engineering, Applied Physics, Nanowires, Nanocrystalline Material
- by Arcady Zhukov
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- Engineering, Kinetics, Applied Physics, Nanocrystalline Material

The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materiais processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by transmission electron microscopy (TEM), high-resolution X-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studi...

- by li w
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- Materials Engineering, Mechanical Engineering, Nanocrystalline Material, Activation Energy

A low-density nanocrystalline material was created by electroforming nanocrystalline Ni around a rapid prototyped acrylic photopolymer micro-truss. This new hybrid material combines the structural efficiency of micro-truss architectures with the ultra-high strength that can be achieved by grain size reduction to the nanometer scale. A range of strut thicknesses were electrodeposited and tested in uniaxial compression. Strut failure occurred by inelastic buckling in the core (compression) members and tensile fracture in the face-sheet (tension) members. Experimental knockdown factors were determined from the idealized compressive modulus and peak strength models and used to map the optimal strut geometry in terms of deposited Ni and the initial strut cross-section.

- by Lyle Gordon
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- Materials Engineering, Mechanical Engineering, Nanocrystalline Material, Grain size
- by Prof. HC Kuo
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- Engineering, Composites, Nanophotonics, Solar Cell