scholarly journals Filling of Chrysotile Nanotubes with Metals

2002 ◽  
Vol 17 (5) ◽  
pp. 1129-1135 ◽  
Author(s):  
C. Métraux ◽  
B. Grobéty ◽  
P. Ulmer
Keyword(s):  
Surface Tension ◽  
High Surface ◽  
External Pressure ◽  
Limiting Factors ◽  
Infrared Spectrometry ◽  
Molten Metals ◽  
Stability Range ◽  
Transmission Electron ◽  
The Stability ◽  
Almost All

Nanowires were produced by injection of molten Hg and Pb into chrysotile nanotubes. The breakdown of chrysotile and the surface tension of the molten metals are the limiting factors for the filling procedure. The thermal stability of chrysotile nanotubes was investigated by infrared spectrometry, thermogravimetry, differential thermal analysis, and x-ray diffraction analyses. For short-term thermal annealing (30 min) the tube morphology remains stable up to 700 °C. The high surface tension of both molten Pb and Hg (γLV > 200 mN/m) requires external pressure for the melts to penetrate into the tubes. Filling of the tubes was achieved under high pressure and high temperature conditions compatible with the stability range for chrysotile determined in the annealing experiments. Transmission electron microscopy observations confirmed high filling yields for both metals. Almost all nanotubes were partially filled with lead. The length of continuous wires ranged from tens to hundreds of nanometers. Additional experiments with tin were not successful.

Enhanced Specific Heat of Silica Nanofluid

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Electron Microscopy ◽  
Specific Heat ◽  
Unit Volume ◽  
High Surface ◽  
High Surface Area ◽  
Lithium Carbonate ◽  
Sem Image ◽  
Surface Energies ◽  
Transmission Electron ◽  
The Stability

Silica nanoparticles (1% by weight) were dispersed in a eutectic of lithium carbonate and potassium carbonate (62:38 ratio) to obtain high temperature nanofluids. A differential scanning calorimeter instrument was used to measure the specific heat of the neat molten salt eutectic and after addition of nanoparticles. The specific heat of the nanofluid was enhanced by 19–24%. The measurement uncertainty for the specific heat values in the experiments is estimated to be in the range of 1–5%. These experimental data contradict earlier experimental results reported in the literature. (Notably, the stability of the nanofluid samples was not verified in these studies.) In the present study, the dispersion and stability of the nanoparticles were confirmed by using scanning electron microscopy (SEM). Percolation networks were observed in the SEM image of the nanofluid. Furthermore, no agglomeration of the nanoparticles was observed, as confirmed by transmission electron microscopy. The observed enhancements are suggested to be due to the high specific surface energies that are associated with the high surface area of the nanoparticles per unit volume (or per unit mass).

scholarly journals Design of magnetic spirals in layered perovskites: Extending the stability range far beyond room temperature

2018 ◽  
Vol 4 (10) ◽  
pp. eaau6386 ◽  
Author(s):  
Tian Shang ◽  
Emmanuel Canévet ◽  
Mickaël Morin ◽  
Denis Sheptyakov ◽  
María Teresa Fernández-Díaz ◽  
...  
Keyword(s):  
Room Temperature ◽  
Practical Interest ◽  
External Pressure ◽  
Magnetic Interactions ◽  
Stability Range ◽  
Chemical Disorder ◽  
Pressure Chemical ◽  
The Stability ◽  
Magnetic Spiral ◽  
Layered Perovskites

In insulating materials with ordered magnetic spiral phases, ferroelectricity can emerge owing to the breaking of inversion symmetry. This property is of both fundamental and practical interest, particularly with a view to exploiting it in low-power electronic devices. Advances toward technological applications have been hindered, however, by the relatively low ordering temperatures Tspiral of most magnetic spiral phases, which rarely exceed 100 K. We have recently established that the ordering temperature of a magnetic spiral can be increased up to 310 K by the introduction of chemical disorder. Here, we explore the design space opened up by this novel mechanism by combining it with a targeted lattice control of some magnetic interactions. In Cu-Fe layered perovskites, we obtain Tspiral values close to 400 K, comfortably far from room temperature and almost 100 K higher than using chemical disorder alone. Moreover, we reveal a linear relationship between the spiral’s wave vector and the onset temperature of the spiral phase. This linear law ends at a paramagnetic-collinear-spiral triple point, which defines the highest spiral ordering temperature that can be achieved in this class of materials. On the basis of these findings, we propose a general set of rules for designing magnetic spirals in layered perovskites using external pressure, chemical substitutions, and/or epitaxial strain, which should guide future efforts to engineer magnetic spiral phases with ordering temperatures suitable for technological applications.

Airway Closure: Occluding Liquid Bridges in Strongly Buckled Elastic Tubes

1999 ◽  
Vol 121 (5) ◽  
pp. 487-493 ◽  
Author(s):  
M. Heil
Keyword(s):  
Surface Tension ◽  
High Surface ◽  
Elastic Shell ◽  
External Pressure ◽  
Physiological Parameter ◽  
Liquid Bridges ◽  
Deformation Characteristics ◽  
Airway Closure ◽  
Elastic Tubes ◽  
Parameter Values

This paper is concerned with the airway closure problem and investigates the quasi-steady deformation characteristics of strongly collapsed (buckled) airways occluded by liquid bridges of high surface tension. The airway wall is modeled as a thin-walled elastic shell, which deforms in response to an external pressure and to the compression due to the surface tension of the liquid bridge. The governing equations are solved numerically using physiological parameter values. It is shown that axisymmetric configurations are statically unstable, as are buckled tubes whose opposite walls are not in contact. The quasi-steady deformation characteristics of strongly collapsed airways whose walls are in opposite wall contact show a pronounced hysteresis during the collapse/reopening cycle. Buckling is shown to occur over a short axial length with moderate circumferential wavenumbers. Finally, further implications of the results for the airway collapse/reopening problem are discussed.

The instability of streaming fluids in a porous medium

1982 ◽  
Vol 60 (10) ◽  
pp. 1391-1395 ◽  
Author(s):  
R. C. Sharma ◽  
T. J. T. Spanos
Keyword(s):  
Surface Tension ◽  
Porous Medium ◽  
Porous Media ◽  
Plane Interface ◽  
Helmholtz Instability ◽  
Stability Range ◽  
Wavenumber Range ◽  
Medium Porosity ◽  
The Stability

The instability of the plane interface between two uniform, superposed, and streaming fluids through porous media is considered. The configuration is taken to be bottom-heavy. In the absence of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by the presence of streaming if perturbation in the direction of streaming are ignored, whereas for perturbations in all other directions there exists instability for a certain wavenumber range. The surface tension is able to suppress this Kelvin–Helmholtz instability for small wavelength perturbations and the medium porosity reduces the stability range given in terms of a difference in streaming velocities. For the top-heavy configurations, the surface tension stabilizes a certain wavenumber range.

scholarly journals The surface adsorption, aggregate structure and antibacterial activity of Gemini quaternary ammonium surfactants with carboxylic counterions

2019 ◽  
Vol 6 (8) ◽  
pp. 190378 ◽  
Author(s):  
Xiqin Zhou ◽  
Siqi Hu ◽  
Yu Wang ◽  
Sana Ullah ◽  
Jun Hu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Antibacterial Activity ◽  
Quaternary Ammonium ◽  
Self Assembly ◽  
High Surface ◽  
Surfactant Molecule ◽  
Counterion Binding ◽  
High Antibacterial Activity ◽  
Transmission Electron ◽  
Quaternary Ammonium Surfactants

A group of Gemini quaternary ammonium surfactants with the formula C n H 2 n +1 CONH(CH 2 ) 2 N + (CH 3 ) 2 (CH 2 ) 2 N + (CH 3 ) 2 (CH 2 ) 2 NHCOC n H 2 n +1 · 2Y ( n = 11, 13 and 15, Y = HCOO − , CH 3 COO − and CH 3 CHOHCOO − ) have been synthesized by a counterion conversion process and characterized by Fourier transform infrared spectroscopy and mass spectroscopy. Their adsorption and self-aggregation properties are investigated by surface tension, conductivity, dynamic light scattering and transmission electron microscopy (TEM) measurements. The results show that these surfactants reduce the surface tension of water to a minimum value of 26.51 mN m −1 at a concentration of 5.72 × 10 −2 mmol l −1 . Furthermore, the increased alkyl chain length of the carboxylic counterions leads to the increased critical micelle concentration, the decreased degree of counterion binding ( β ) and the decreased self-assembly tendency, but the minimum area per surfactant molecule ( A min ) adsorbed at the air–aqueous solution are similar. TEM images reveal that these surfactants self-assemble spontaneously into aggregates with vesicle or bilayer structures. It is also found that they have superior antibacterial activity at a concentration of 0.1 g l −1 . The high surface activity and high antibacterial activity of the Gemini quaternary ammonium salt surfactants containing different carboxylic counterions bring more possibilities for the application in the field of biomedicine.

The Role of Surface Transport in the Stability and Breakdown of Foams

1952 ◽  
Vol 5 (4) ◽  
pp. 697 ◽  
Author(s):  
WE Ewers ◽  
KL Sutherland
Keyword(s):  
Surface Tension ◽  
Foam Stability ◽  
Surface Film ◽  
High Surface ◽  
Active Material ◽  
Dominant Factor ◽  
Surface Transport ◽  
The Stability ◽  
Surface Active Material

A new theory of foam stability is proposed which demonstrates that the transport of substrate. accompanying a movement of the surface of the bubble film, is a dominant factor in the stability of foams and in the action of foam breakers. The surface moves from a region of low surface tension (high surface pressure) to a region of high surface tension. The surface tension gradients arise from disturbances which may be caused by mechanical or thermal shocks, or by the addition to the surface of particles, droplets, or vapour of a surface-active material. When the surface tension is highest at the centre of disturbance the film mill be stable ; when the surface tension is lowest at this point the surface film and hence the substrate will be moved away from this point and the film will rupture.

Stability of single-wall carbon nanotubes under hydrothermal conditions

2002 ◽  
Vol 17 (4) ◽  
pp. 734-737 ◽  
Author(s):  
S. Srikanta Swamy ◽  
Jose Maria Calderon-Moreno ◽  
Masahiro Yoshimura
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Transmission Electron Microscopy ◽  
Single Wall Carbon Nanotubes ◽  
Hydrothermal Conditions ◽  
Short Term Treatment ◽  
Stability Range ◽  
Single Wall Carbon ◽  
Transmission Electron ◽  
The Stability

The stability of single-wall carbon nanotubes under hydrothermal conditions (100 MPa pressure, from 30 min to 48 h in the temperature range from 200 to 800 °C) has been investigated. The resultant products were characterized by Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. The stability range of single-wall carbon nanotubes (SWCNTs) under hydrothermal conditions suggests that they, similar to fullerenes, can only survive mild and short-term treatment in high-temperature, high-pressure water. SWCNTs gradually transform into multiwall carbon nanotubes (MWCNTs) and polyhedral graphitic nanoparticules. After 48 h at 750 °C only the Raman spectra characteristic of graphitic carbon were observed. Transmission electron microscopy revealed that after 800 °C and 48 h of treatment SWCNTs fully transformed into MWCNTs and polyhedral carbon nanoparticles.

TEM Analysis of Long-Period Polytypes in SiC—S

1976 ◽  
Vol 34 ◽  
pp. 630-631
Author(s):  
S. Shinozaki ◽  
J. W. Sprys
Keyword(s):  
Electron Diffraction ◽  
Isothermal Annealing ◽  
Tem Analysis ◽  
Long Period ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Structural Lattice ◽  
The Stability ◽  
Continuous Curves

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.

TEM characterization of Au/Polysilicon interactions

1990 ◽  
Vol 48 (4) ◽  
pp. 650-651
Author(s):  
N. David Theodore ◽  
Leslie H. Allen ◽  
C. Barry Carter ◽  
James W. Mayer
Keyword(s):  
Solid Phase ◽  
Single Crystal Silicon ◽  
Chemical Vapor ◽  
Electrical Contacts ◽  
Silicon Substrates ◽  
Crystal Silicon ◽  
Transmission Electron ◽  
Polysilicon Films ◽  
The Stability

Metal/polysilicon investigations contribute to an understanding of issues relevant to the stability of electrical contacts in semiconductor devices. These investigations also contribute to an understanding of Si lateral solid-phase epitactic growth. Metals such as Au, Al and Ag form eutectics with Si. reactions in these metal/polysilicon systems lead to the formation of large-grain silicon. Of these systems, the Al/polysilicon system has been most extensively studied. In this study, the behavior upon thermal annealing of Au/polysilicon bilayers is investigated using cross-section transmission electron microscopy (XTEM). The unique feature of this system is that silicon grain-growth occurs at particularly low temperatures ∽300°C).Gold/polysilicon bilayers were fabricated on thermally oxidized single-crystal silicon substrates. Lowpressure chemical vapor deposition (LPCVD) at 620°C was used to obtain 100 to 400 nm polysilicon films. The surface of the polysilicon was cleaned with a buffered hydrofluoric acid solution. Gold was then thermally evaporated onto the samples.

The size of extracellular vesicles secreted by different types of stem cells

2018 ◽  
pp. 38-42
Author(s):  
И.Б. Алчинова ◽  
М.В. Полякова ◽  
И.Н. Сабурина ◽  
М.Ю. Карганов
Keyword(s):  
Stem Cells ◽  
Extracellular Vesicles ◽  
Culture Media ◽  
Living Organism ◽  
Isolation And Characterization ◽  
Transmission Electron ◽  
Study Results ◽  
Multipotent Mesenchymal Stem Cells ◽  
Rat Adipose Tissue ◽  
Almost All

Механизм терапевтического действия мультипотентных мезенхимных стволовых клеток (ММСК) на облученный организм в последнее время вызывает повышенный интерес исследователей. В качестве активного участника паракринного механизма реализации этого эффекта предлагают рассматривать внеклеточные везикулы, секретируемые практически всеми клетками живого организма. Цель работы: выделить и охарактеризовать внеклеточные везикулы, продуцируемые стволовыми клетками различной природы. Материалы и методы. Суспензии внеклеточных везикул, выделенных по модифицированному протоколу дифференциального центрифугирования из культуральных жидкостей от культур ММСК костного мозга человека 2-го пассажа и ММСК жировой ткани крысы 4-го пассажа, были проанализированы методом просвечивающей электронной микроскопии и методом анализа траекторий наночастиц. Результаты. Исследование показало наличие в обоих образцах микрочастиц размерами до и около 100 нм, однако процентное содержание частиц разных размеров в суспензии различалось для двух анализируемых типов клеток. Заключение. Полученные результаты могут свидетельствовать о специфике секреции, обусловленной клеточным типом. A mechanism of the therapeutic effect of multipotent mesenchymal stem cells (MMSC) on irradiated body has recently arisen much interest of researchers. Extracellular vesicles (EVs) secreted by almost all cells of a living organism were suggested to actively contribute to the paracrine mechanism of this effect. The aim of the study was isolation and characterization of extracellular vesicles produced by various types of stem cells. Materials and methods. Suspensions of EVs were isolated from culture media of passage 2 human bone marrow-derived MMSC and passage 4 rat adipose tissue-derived MMSC using a modified protocol of differential centrifugation and then studied using transmission electron microscopy and nanoparticle tracking analysis. Results. The study showed the presence of microparticles with a size of >100 nm in the examined samples. However, the percent content of particles with different sizes in the suspension was different in two analyzed types of cell culture. Conclusion. The study results might reflect a specificity of secretion determined by the cell type.

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