Self-Assembled Structures of Gas-Phase Prepared FePt Nanoparticles

2001 ◽  
Vol 705 ◽  
Author(s):  
Bernd Rellinghaus ◽  
Sonja Stappert ◽  
Mehmet Acet ◽  
Eberhard F. Wassermann
Keyword(s):  
Gas Phase ◽  
Elevated Temperatures ◽  
High Mobility ◽  
Carbon Layer ◽  
Carbon Films ◽  
Blocking Temperature ◽  
Fept Nanoparticles ◽  
Irregular Shapes ◽  
Transmission Electron ◽  
Self Assembled

AbstractWe report on a non-lithographic method for the preparation of self-assembled FePt nanoparticles via inert-gas condensation. Prior to deposition the particles can be sintered in flight at temperatures as high as TS = 1273 K. Whereas un-sintered particles have irregular shapes, particles sintered at elevated temperatures TS ≥ 793 K show a regular faceting. (High resolution) transmission electron microscopy ((HR)TEM) shows that these regularly faceted particles are of icosahedral structure. When being deposited onto amorphous carbon films, the gas-phase sintered particles are found to have a high mobility. In particular, for the high-temperature sintered FePt nanoparticles, we observe that this mobility leads to the formation of particle arrays with hexagonal close-packed arrangements. Within these ordered patches, the particles are separated from one another. Analytical investigations using energy filtered TEM (EFTEM) show that a carbon layer is formed between the particles. Magnetization analyses give results showing that the gas-phase sintered particles are superparamagnetic at room temperature with a blocking temperature of TB = 49K.

Self-Assembled Structures of Gas-Phase Prepared FePt Nanoparticles

2001 ◽  
Vol 707 ◽  
Author(s):  
Bernd Rellinghaus ◽  
Sonja Stappert ◽  
Mehmet Acet ◽  
Eberhard F. Wassermann
Keyword(s):  
Gas Phase ◽  
Elevated Temperatures ◽  
High Mobility ◽  
Carbon Layer ◽  
Carbon Films ◽  
Blocking Temperature ◽  
Fept Nanoparticles ◽  
Irregular Shapes ◽  
Transmission Electron ◽  
Self Assembled

ABSTRACTWe report on a non-lithographic method for the preparation of self-assembled FePt nanoparticles via inert-gas condensation. Prior to deposition the particles can be sintered in flight at temperatures as high as TS = 1273 K. Whereas un-sintered particles have irregular shapes, particles sintered at elevated temperatures TS ≤ 793 K show a regular faceting. (High resolution) transmission electron microscopy ((HR)TEM) shows that these regularly faceted particles are of icosahedral structure. When being deposited onto amorphous carbon films, the gas-phase sintered particles are found to have a high mobility. In particular, for the high-temperature sintered FePt nanoparticles, we observe that this mobility leads to the formation of particle arrays with hexagonal close-packed arrangements. Within these ordered patches, the particles are separated from one another. Analytical investigations using energy filtered TEM (EFTEM) show that a carbon layer is formed between the particles. Magnetization analyses give results showing that the gas-phase sintered particles are superparamagnetic at room temperature with a blocking temperature of TB = 49K.

Protonation state of core nitrogens in the meso-tetra(4-carboxyphenyl)porphyrin impacts the chemical and physical properties of nanostructures formed in acid solutions

2012 ◽  
Vol 16 (12) ◽  
pp. 1233-1243 ◽  
Author(s):  
Jeremy R. Eskelsen ◽  
Yingte Wang ◽  
Yun Qui ◽  
Monali Ray ◽  
Mzuri Handlin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Elevated Temperatures ◽  
Building Blocks ◽  
Acid Solutions ◽  
Protonation State ◽  
Preparation Temperature ◽  
Transmission Electron ◽  
Self Assembled

Organic self-assemblies of meso-tetra (4-carboxyphenyl)porphine (TCPP) prepared in trifluoroacetic acid (TFA) and hydrochloric acid solutions at pH < 1 were studied by X-ray photoelectron spectroscopy (XPS) in order to determine the protonation state of the porphyrin building blocks present in the solid self-assembled nanostructures. XPS measurements were conducted both at room and at elevated temperatures. Room temperature N 1s spectra showed two bands with a 3:1 intensity ratio consistent with three protonated and one unprotonated nitrogen in the structures prepared in both TFA and HCl solutions. We attribute this result to TCPP existing as a 50:50 mixture of the free-base and diacid forms of the porphyrin core in the self-assembled state. Upon heating to 150 °C the TCPP/TFA and TCPP/HCl nanomaterials exhibit loss of pyrrolic hydrogens and retain different amounts of their respective counter ions. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the nanostructures showed that these systems have different morphologies depending on the acid employed during fabrication and the post preparation temperature treatment. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) of the TCPP nanostructures indicate that those prepared in HCl are crystalline while the nanoassemblies made in TFA are polycrystalline or amorphous.

Multiply Twinned Structures in Gas-Phase Sintered Stoichiometric FePt Nanoparticles

2001 ◽  
Vol 704 ◽  
Author(s):  
Sonja Stappert ◽  
Bernd Rellinghaus ◽  
Mehmet Acet ◽  
Eberhard F. Wassermann
Keyword(s):  
Gas Phase ◽  
Intermetallic Phase ◽  
Structural Data ◽  
Building Blocks ◽  
High Resolution Electron Microscopy ◽  
Degree Of Crystallinity ◽  
Fept Nanoparticles ◽  
Irregular Shapes ◽  
Resolution Electron ◽  
Partial Formation

AbstractStoichiometric FePt nanoparticles with sizes in the range 3 – 6 nm were prepared in the gas-phase and thermally sintered prior to deposition. Whereas unsintered particles exhibit irregular shapes and a low degree of crystallinity, the majority of the sintered particles are multiply twinned and have predominantly icosahedral structure. There is no indication for the occurance of L10 ordering in the gas-phase sintered particles, although previous post-deposition annealing experiments of unsintered particles had shown the occurrence of partial formation of the L10 FePt intermetallic phase. On the other hand, analysis of the structural data obtained from (high resolution) electron microscopy shows that the relative amount of icosahedral particles increases with increasing sintering temperature. This result is discussed on the basis of a structure model of an irregular icosahedron, which is built up from distorted tetrahedral building blocks. The distortion in each tetrahedron is in accordance with the tetragonally compressed unit cell of the L10-phase.

scholarly journals Structure and Properties of Diamond-Like Carbon Films Deposited by PACVD Technique on Light Alloys

2016 ◽  
Vol 61 (3) ◽  
pp. 1321-1330 ◽  
Author(s):  
T. Tański ◽  
K. Labisz ◽  
M. Krupiński ◽  
K. Lukaszkowicz ◽  
Ł. Krzemiński
Keyword(s):  
Electron Microscopy ◽  
Corrosion Behaviour ◽  
Chemical Vapour ◽  
Electrochemical Corrosion ◽  
Carbon Layer ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Cast Magnesium

Abstract The investigations presented in this paper describe surface treatment performed on samples of heat-treated cast magnesium and aluminium alloy. The structure and chemical composition as well as the functional and mechanical properties of the obtained gradient/monolithic films were analysed by high resolution transmission electron microscopy and scanning electron microscopy, Raman spectroscopy, the ball-on-disk tribotester and scratch testing. Moreover, investigation of the electrochemical corrosion behaviour of the samples was carried out by means of potentiodynamic polarisation curves in 1-M NaCl solution. The coatings produced by chemical vapour deposition did not reveal any delamination or defects and they adhere closely to the substrate. The coating thickness was in a range of up to 2.5 microns. Investigations using Raman spectra of the DLC films confirmed a multiphase character of the diamond-like carbon layer, revealing the sp2 and sp3 electron hybridisation responsible for both the hardness and the friction coefficient. The best wear resistance test results were obtained for the magnesium alloy substrate - AZ61, for which the measured value of the friction path length was equal to 630 m.

Scanning Secondary Electron Microscopy of Myofibrils Using Transmission Techniques

1975 ◽  
Vol 33 ◽  
pp. 556-557
Author(s):  
M. K. Lamvik
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Carbon Films ◽  
Photographic Recording ◽  
Transmission Electron ◽  
Thin Carbon ◽  
The Common ◽  
Scanning Electron ◽  
Better Than ◽  
Cellular Organelles

When observing small objects such as cellular organelles by scanning electron microscopy, it is often valuable to use the techniques of transmission electron microscopy. The common practice of mounting and coating for SEM may not always be necessary. These possibilities are illustrated using vertebrate skeletal muscle myofibrils.Micrographs for this study were made using a Hitachi HFS-2 scanning electron microscope, with photographic recording usually done at 60 seconds per frame. The instrument was operated at 25 kV, with a specimen chamber vacuum usually better than 10-7 torr. Myofibrils were obtained from rabbit back muscle using the method of Zak et al. To show the component filaments of this contractile organelle, the myofibrils were partially disrupted by agitation in a relaxing medium. A brief centrifugation was done to clear the solution of most of the undisrupted myofibrils before a drop was placed on the grid. Standard 3 mm transmission electron microscope grids covered with thin carbon films were used in this study.

Carbon Film Deposition On Silicon Using Low Energy Ion Beams

1991 ◽  
Vol 223 ◽  
Author(s):  
Qin Fuguang ◽  
Yao Zhenyu ◽  
Ren Zhizhang ◽  
S.-T. Lee ◽  
I. Bello ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ion Beam ◽  
Carbon Film ◽  
Carbon Films ◽  
Film Deposition ◽  
Ion Energy ◽  
Transmission Electron ◽  
Higher Temperature ◽  
Post Implantation ◽  
Beam Deposition

ABSTRACTDirect ion beam deposition of carbon films on silicon in the ion energy range of 15–500eV and temperature range of 25–800°C has been studied using mass selected C+ ions under ultrahigh vacuum. The films were characterized with X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy and diffraction analysis. Films deposited at room temperature consist mainly of amorphous carbon. Deposition at a higher temperature, or post-implantation annealing leads to formation of microcrystalline graphite. A deposition temperature above 800°C favors the formation of microcrystalline graphite with a preferred orientation in the (0001) direction. No evidence of diamond formation was observed in these films.

scholarly journals In Situ Observation of Electron-Beam-Induced Formation of Nano-Structures in PbTe

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Iryna Zelenina ◽  
Igor Veremchuk ◽  
Yuri Grin ◽  
Paul Simon
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Atomic Scale ◽  
In Situ Observation ◽  
Nano Structures ◽  
Transmission Electron ◽  
Initial Crystal

Nano-scaled thermoelectric materials attract significant interest due to their improved physical properties as compared to bulk materials. Well-shaped nanoparticles such as nano-bars and nano-cubes were observed in the known thermoelectric material PbTe. Their extended two-dimensional nano-layer arrangements form directly in situ through electron-beam treatment in the transmission electron microscope. The experiments show the atomistic depletion mechanism of the initial crystal and the recrystallization of PbTe nanoparticles out of the microparticles due to the local atomic-scale transport via the gas phase beyond a threshold current density of the beam.

scholarly journals Synthesis and Characterization of a Bioconjugate Based on Oleic Acid and L-Cysteine

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1791
Author(s):  
Marco Vizcarra-Pacheco ◽  
María Ley-Flores ◽  
Ana Mizrahim Matrecitos-Burruel ◽  
Ricardo López-Esparza ◽  
Daniel Fernández-Quiroz ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Materials Science ◽  
Critical Micellar Concentration ◽  
Synthesis And Characterization ◽  
New Materials ◽  
Visible Spectroscopy ◽  
Amide Bonds ◽  
Transmission Electron ◽  
Self Assembled

One of the main challenges facing materials science today is the synthesis of new biodegradable and biocompatible materials capable of improving existing ones. This work focused on the synthesis of new biomaterials from the bioconjugation of oleic acid with L-cysteine using carbodiimide. The resulting reaction leads to amide bonds between the carboxylic acid of oleic acid and the primary amine of L-cysteine. The formation of the bioconjugate was corroborated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and nuclear magnetic resonance (NMR). In these techniques, the development of new materials with marked differences with the precursors was confirmed. Furthermore, NMR has elucidated a surfactant structure, with a hydrophilic part and a hydrophobic section. Ultraviolet-visible spectroscopy (UV-Vis) was used to determine the critical micellar concentration (CMC) of the bioconjugate. Subsequently, light diffraction (DLS) was used to analyze the size of the resulting self-assembled structures. Finally, transmission electron microscopy (TEM) was obtained, where the shape and size of the self-assembled structures were appreciated.

scholarly journals Thermal stability and diffusion characteristics of ultrathin amorphous carbon films grown on crystalline and nitrogenated silicon substrates by filtered cathodic vacuum arc deposition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shengxi Wang ◽  
Anurag Roy ◽  
Kyriakos Komvopoulos
Keyword(s):  
Thermal Stability ◽  
Amorphous Carbon ◽  
Silicon Substrate ◽  
Elevated Temperatures ◽  
Carbon Films ◽  
Vacuum Arc ◽  
Cross Sectional ◽  
Prolonged Heating ◽  
Filtered Cathodic Vacuum Arc ◽  
Thermal Stability Of

AbstractAmorphous carbon (a-C) films are widely used as protective overcoats in many technology sectors, principally due to their excellent thermophysical properties and chemical inertness. The growth and thermal stability of sub-5-nm-thick a-C films synthesized by filtered cathodic vacuum arc on pure (crystalline) and nitrogenated (amorphous) silicon substrate surfaces were investigated in this study. Samples of a-C/Si and a-C/SiNx/Si stacks were thermally annealed for various durations and subsequently characterized by high-resolution transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The TEM images confirmed the continuity and uniformity of the a-C films and the 5-nm-thick SiNx underlayer formed by silicon nitrogenation using radio-frequency sputtering. The EELS analysis of cross-sectional samples revealed the thermal stability of the a-C films and the efficacy of the SiNx underlayer to prevent carbon migration into the silicon substrate, even after prolonged heating. The obtained results provide insight into the important attributes of an underlayer in heated multilayered media for preventing elemental intermixing with the substrate, while preserving the structural stability of the a-C film at the stack surface. An important contribution of this investigation is the establishment of an experimental framework for accurately assessing the thermal stability and elemental diffusion in layered microstructures exposed to elevated temperatures.

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