Vanadium Pentoxide Gels: Structural Development and Rheological Properties

1990 ◽  
Vol 180 ◽  
Author(s):  
J.K. Bailey ◽  
T. Nagase ◽  
G.A. Pozarnsky ◽  
M.L. Mecartney
Keyword(s):  
Vanadium Pentoxide ◽  
Structural Development ◽  
Small Particles ◽  
Rheological Characterization ◽  
Cryogenic Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Before And After ◽  
Constant Shear Stress ◽  
Steady Shearing ◽  
Rheological Experiments

ABSTRACTCryogenic transmission electron Microscopy (cryo-TEM) and rheological characterization were conducted in order to understand structural development of vanadium pentoxide gels during processing. Sols were prepared by ion exchange from sodium metavanadate solutions. Cryo-TEM revealed that fine threads about 1.5nm wide initially form and grow into ribbons approximately 25nm wide and at least 1000nm long. The threads appear to self assemble into the ribbons. During this structural development, the dynamic viscosity increased. Upon steady shearing of the sols, the system exhibited thixotropy, i.e. the viscosity decreased with time under constant shear stress and subsequently rheopexy, the viscosity increased with time. Comparison of the structure before and after shearing indicated that during the rheological experiments aggregation of small particles or fragments was occurring.

The Morphology of Carboxylated Composite Latex and Latex Film

1998 ◽  
Vol 4 (S2) ◽  
pp. 826-827
Author(s):  
O. L. Shaffer ◽  
M. W. Sandor ◽  
M. S. El-Aasser
Keyword(s):  
Uranyl Acetate ◽  
Latex Film ◽  
Second Phase ◽  
Small Particles ◽  
Latex Particles ◽  
Negative Stain ◽  
Transmission Electron ◽  
Cesium Hydroxide ◽  
Before And After ◽  
Core Phase

Carboxylated latex has become very important in the formation of polymer films. In order to study the film and its properties it is important to know the morphology of the latex that is forming the film. The latex for this study has been examined by transmission electron microscopy(TEM) using positive preferential stains such as ruthenium tetroxide (RuO4) and cesium hydroxide(CsOH); and uranyl acetate(UAc) as a negative stain.The polybutyl acrylate(PBA)/ polymethylmethacrylate(PMMA) composite latex particles consist of a soft core phase and a hard second phase with varying amounts of acrylic acid in the core, the shell and in both core and shell. The latexes were examined before and after cleaning. The cleaning was necessary in order to remove the surfactant and any small particles that might have formed during the emulsion polymerization. Prior to cleaning, the small particles adhered to the surfaces of the particles making it difficult to determine the final morphology of the latex particles.

The direct observation of structural development during vanadium pentoxide gelation

1992 ◽  
Vol 7 (9) ◽  
pp. 2530-2537 ◽  
Author(s):  
J.K. Bailey ◽  
G.A. Pozarnsky ◽  
M.L. Mecartney
Keyword(s):  
Vanadium Pentoxide ◽  
Colloidal Particles ◽  
Structural Evolution ◽  
Scanning Tunneling ◽  
Structural Development ◽  
Tunneling Microscopy ◽  
Homogeneous Solutions ◽  
Transmission Electron ◽  
Vanadic Acid ◽  
Rigid Mass

The sequence of structural evolution in the gelation of vanadic acid to form vanadium pentoxide gels was studied using cryogenic transmission electron microscopy (cryo-TEM) and scanning tunneling microscopy (STM). Small whiskers form from initially homogeneous solutions, and then grow into crystalline ribbon-like colloidal particles. It is proposed that the whiskers form from polymerization of dioxovanadium cations. The ribbons then grow by continued addition of dioxovanadium cations which are supplied by the decomposition of decavanadate ions. In solution, the ribbon-like particles have dimensions of approximately 25 nm × 3 nm × over 1 μm. These ribbons are flexible perpendicular to the plane of the ribbon. Upon drying, a flat rigid mass of ribbon-like particles is formed. The ribbons examined by STM showed striations 3 nm wide, a value that corresponds with the width of the unit cell proposed by J. Legendre and J. Livage [J. Colloid. and Interf. Sci. 94, 75 (1983)].

An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films

1973 ◽  
Vol 31 ◽  
pp. 32-33 ◽  
Author(s):  
T. C. Tisone ◽  
S. Lau
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Thermally Grown Oxide ◽  
Ion Milling ◽  
Compound Formation ◽  
Technology Application ◽  
Transmission Electron ◽  
Before And After ◽  
Au Thin Films

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.

Effect of MWCNT doping on the structural and optical properties of PVC/PVDF polymer blend

2017 ◽  
Vol 13 (2) ◽  
pp. 4640-4647
Author(s):  
A. M. Abdelghany ◽  
M.S. Meikhail ◽  
S.I. Badr ◽  
A. S. Momen
Keyword(s):  
Surface Damage ◽  
X Ray Diffraction ◽  
Dopant Content ◽  
Casting Technique ◽  
Transmission Electron ◽  
Dopant Level ◽  
Before And After ◽  
Carbon Nano Tubes ◽  
Small Band ◽  
Vibrational Bands

Thin film samples of pristine polyvinyl chloride (PVC), poly vinyldine fluoride (PVDF) in combination with their blend in addition to samples containing factorial mass fraction of multi wall carbon nano-tubes (MWCNTs) in the dopant level were prepared via routine casting technique using tetrahydrofurane (THF) as a common solvent. X-ray diffraction and transmission electron microscopy (TEM) depict the nano-scale (15-25 nm) of functionalized MWCNTs with no surface damage results from functionalization process.X-ray diffraction (XRD) shows a semi-crystalline nature of PVDF with evidence for more than one phase namely a and b phases. The fraction of b phase was calculated and correlated to the dopant content. FTIR optical absorption spectra revels a preservation of the main vibrational bands before and after addition of MWCNTs in the doping level with a presence of new small band 1151 cm-1 assigned for the interaction and complexation between constituents.

scholarly journals Probing the Na metal solid electrolyte interphase via cryo-transmission electron microscopy

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bing Han ◽  
Yucheng Zou ◽  
Zhen Zhang ◽  
Xuming Yang ◽  
Xiaobo Shi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solid Electrolyte ◽  
Solid Electrolyte Interphase ◽  
Metal Electrode ◽  
Liquid Electrolyte ◽  
Battery Materials ◽  
Cryogenic Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Fluoroethylene Carbonate

AbstractCryogenic transmission electron microscopy (cryo-TEM) is a valuable tool recently proposed to investigate battery electrodes. Despite being employed for Li-based battery materials, cryo-TEM measurements for Na-based electrochemical energy storage systems are not commonly reported. In particular, elucidating the chemical and morphological behavior of the Na-metal electrode in contact with a non-aqueous liquid electrolyte solution could provide useful insights that may lead to a better understanding of metal cells during operation. Here, using cryo-TEM, we investigate the effect of fluoroethylene carbonate (FEC) additive on the solid electrolyte interphase (SEI) structure of a Na-metal electrode. Without FEC, the NaPF6-containing carbonate-based electrolyte reacts with the metal electrode to produce an unstable SEI, rich in Na2CO3 and Na3PO4, which constantly consumes the sodium reservoir of the cell during cycling. When FEC is used, the Na-metal electrode forms a multilayer SEI structure comprising an outer NaF-rich amorphous phase and an inner Na3PO4 phase. This layered structure stabilizes the SEI and prevents further reactions between the electrolyte and the Na metal.

scholarly journals Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Przemysław Snopiński ◽  
Mariusz Król ◽  
Marek Pagáč ◽  
Jana Petrů ◽  
Jiří Hajnyš ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Equal Channel Angular Pressing ◽  
Heat Treatments ◽  
Electron Backscattered Diffraction ◽  
Angular Pressing ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Before And After ◽  
The Impact

AbstractThis study investigated the impact of the equal channel angular pressing (ECAP) combined with heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys fabricated via selective laser melting (SLM) and gravity casting. Special attention was directed towards determining the effect of post-fabrication heat treatments on the microstructural evolution of AlSi10Mg alloy fabricated using two different routes. Three initial alloy conditions were considered prior to ECAP deformation: (1) as-cast in solution treated (T4) condition, (2) SLM in T4 condition, (3) SLM subjected to low-temperature annealing. Light microscopy, transmission electron microscopy, X-ray diffraction line broadening analysis, and electron backscattered diffraction analysis were used to characterize the microstructures before and after ECAP. The results indicated that SLM followed by low-temperature annealing led to superior mechanical properties, relative to the two other conditions. Microscopic analyses revealed that the partial-cellular structure contributed to strong work hardening. This behavior enhanced the material’s strength because of the enhanced accumulation of geometrically necessary dislocations during ECAP deformation.

scholarly journals Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

Soft Matter ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. 3096-3104
Author(s):  
Valeria Castelletto ◽  
Jani Seitsonen ◽  
Janne Ruokolainen ◽  
Ian W. Hamley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Small Angle ◽  
Self Assembly ◽  
X Ray ◽  
Cryogenic Transmission Electron Microscopy ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ph Dependent ◽  
Ray Scattering

A designed surfactant-like peptide is shown, using a combination of cryogenic-transmission electron microscopy and small-angle X-ray scattering, to have remarkable pH-dependent self-assembly properties.

Microtexture of shock reaction products of niobium and silica mixtures

1999 ◽  
Vol 14 (7) ◽  
pp. 3169-3174 ◽  
Author(s):  
Reiko Murao ◽  
Masae Kikuchi ◽  
Kiyoto Fukuoka ◽  
Eiji Aoyagi ◽  
Toshiyuki Atou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Shock Compression ◽  
Pressure Range ◽  
Reaction Products ◽  
Small Particles ◽  
Powder Mixtures ◽  
X Ray ◽  
Transmission Electron

Shock compression experiments on powder mixtures of niobium metal and quartz were conducted for the pressure range of 30–40 GPa by a 25-mm single-stage propellant gun. Chemical reaction occurred above 35 GPa, and products were found to be mainly so-called “Cu3Au-type” Nb3Si, which contained a small amount of oxygen. Microtextures of the specimen were examined by scanning and transmission electron microscopy. A field-emission transmission electron microscope was used for energy-dispersive x-ray analysis of microtextures in small particles found in the SiO2 matrix, and various species with different Nb/Si ratio and oxygen content were shown to be produced through the nonequilibrium process of shock compression.

scholarly journals Evaluating biological activity of folic acid-modified and 10-hydroxycamptothecin-loaded mesoporous silica nanoparticles

2021 ◽  
Author(s):  
Mei-Xia Zhao ◽  
Di-Feng Chen ◽  
Xue-Jie Zhao ◽  
Lin-Song Li ◽  
Yong-Fang Liu
Keyword(s):  
Folic Acid ◽  
Mesoporous Silica ◽  
Silica Nanoparticles ◽  
Folate Receptor ◽  
Mesoporous Silica Nanoparticles ◽  
Drug Carriers ◽  
Transmission Electron ◽  
Before And After ◽  
Drug Efficiency

Targeted nanocarrier can selectively deliver anti-tumor drugs to cancer sites improving drug efficiency. Accordingly, a targeted nanocarrier (MSN-FA) was synthesized based on folic acid (FA) modified mesoporous silica nanoparticles (MSNs). These loaded with 10-hydroxycamptothecin (HCPT) to obtain the nano-drug MSN-FA@HCPT. These nanocarriers were characterized by transmission electron microscopy (TEM), zeta potential, ultraviolet-visible spectroscopy (UV-Vis), fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Notably, the nanocarriers were nearly spherical before and after loading HCPT and exhibited good dispersibility. Also, folate receptor (FR) over-expressing HeLa cells and FR deficient HepG2 cells were used to evaluate in vitro cellular uptake and cytotoxicity of MSN-FA@HCPT and MSN@HCPT. Interestingly, FA-modified nanocarriers enhanced the cytotoxicity of HCPT by improving drug targeting to tumor cells. Also, apoptotic and mitochondrial membrane potential (MMP) reducing effects of MSN-FA@HCPT were more prominent than the MSNs without FA modification. MSN-FA@HCPT can be excellent drug carriers with profound biomedical applications.

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