Natural and Treated Hectorites/Poly(Sodium Acrylate) Hybrids: Synthesis, Characterization, and Properties

2010 ◽  
Vol 63 (10) ◽  
pp. 1462
Author(s):  
Antonio E. Mucientes ◽  
Francisca Santiago ◽  
Ana Carrero ◽  
Carlos Rivera
Keyword(s):  
Bound Water ◽  
Free Water ◽  
Clay Content ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
Water Desorption ◽  
Transmission Electron ◽  
Electron Microscopy Analysis

Novel hybrids of poly(sodium acrylate) and natural and treated hectorites have been synthesized and characterized by X-ray diffraction, transmission electron microscopy analysis, and FTIR analysis. The thermal stability of these materials was studied. The swelling kinetics obey a Voigt-based equation. The experimental equilibrium water absorbency varies with the clay content and shows a minimum. All the hybrids showed excellent reswelling capability. Water desorption studies demonstrated the existence of ‘free water’ and ‘bound water’ within the polymeric matrix.

Superabsorbent hydrogels of poly(sodium acrylate) with crude and exfoliated vermiculites

2013 ◽  
Vol 33 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Antonio E. Mucientes ◽  
Francisca Santiago ◽  
Ana María Carrero ◽  
Beatriz Talavera
Keyword(s):  
Bound Water ◽  
Free Water ◽  
Clay Content ◽  
Absorption Capacity ◽  
Sodium Acrylate ◽  
Swelling Kinetics ◽  
Desorption Kinetics ◽  
Water Absorbency ◽  
Water Desorption ◽  
Superabsorbent Hydrogels

Abstract Novel superabsorbent hydrogels of poly(sodium acrylate) [poly(SA)] with crude vermiculite (CVMT) and exfoliated vermiculite (EVMT) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Both types of hybrids are more stable materials than poly(SA) and their thermal stability increases as the clay content increases. The equilibrium water absorbency for each hybrid type varies with the clay content, showing a maximum at 15 wt% and 20 wt% for EVMT and CVMT, respectively. The equilibrium water absorbency is higher for the hybrids than for poly(SA) at clay contents close to their maxima. The swelling kinetics obey a Voigt-based equation. The water desorption kinetics showed the existence of free water and bound water within the polymeric matrix. All of the superabsorbent materials investigated retained the water absorption capacity after repeating five wet-dry cycles.

High-Quality III-V Nitrides Grown by Metalorganic Chemical Vapor Deposition

1995 ◽  
Vol 395 ◽  
Author(s):  
R.D. Dupuis ◽  
A.L. Holmes ◽  
P.A Grudowski ◽  
K.G. Fertitta ◽  
F.A. Ponce
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
High Quality ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Metalorganic Chemical

ABSTRACTWe report the growth of high-quality III-V nitride heteroepitaxial films on (0001) sapphire substrates by low-pressure metalorganic chemical vapor deposition (MOCVD). These films have exhibited narrow X-ray diffraction rocking curves with full-width-at-half-maximum values as low as ΔΘ∼37 arc sec. Photoluminescence and transmission electron microscopy analysis further indicate the samples to be of high quality.

scholarly journals Effect of water/water vapor on microstructure and phase stability of (Y0.25Bi0.75)2O3 solid electrolytes

2003 ◽  
Vol 18 (11) ◽  
pp. 2624-2632 ◽  
Author(s):  
Chaur-Chi Huang ◽  
Kuan-Zong Fung
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Rhombohedral Phase ◽  
Stable Phase ◽  
Similar Reaction ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Humidified Air

Highly conductive cubic (Y0.25Bi0.75)2O3 tends to transform to rhombohedral (Y0.25Bi0.75)2O3 when annealed at 600°C for more than 200 h. Although the rhombohedral phase of (Y0.25Bi0.75)2O3 was known to be the stable phase at temperatures ≤600°C, it was found that the annealed (Y0.25Bi0.75)2O3 was not thermodynamically stable in the water-containing environment. From x-ray diffraction and transmission electron microscopy analysis, it was observed that the annealed (Y0.25Bi0.75)2O3 easily decomposed into monoclinic α-Bi2O3 and yttrium hydroxide at a temperature as low as 50°C. The monoclinic α-Bi2O3 further reacted with CO2 and formed Bi2O2CO3. Consequently, the annealed (Y0.25Bi0.75)2O3 degraded and became flaky powder. Scanning electron microscopy micrographs of water-reacted (Y0.25Bi0.75)2O3 also showed surface swelling and peeling. Such surface deterioration was caused by a large volume increase during the water reaction. Similar reaction was also observed when the annealed (Y0.25Bi0.75)2O3 was exposed in the humidified air at 300°C. As the temperature was raised to 500°C, little reaction was observed between water vapor and (Y0.25Bi0.75)2O3. The better stability of (Y0.25Bi0.75)2O3 at elevated temperature was observed.

Microstructures of Cu- and Y-rich YBa2Cu3O7−x thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 38-39
Author(s):  
A.F. Marshall
Keyword(s):  
Thin Films ◽  
Critical Currents ◽  
Electron Beam Evaporation ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Defect Microstructure

The defect microstructure of Cu- and Y-rich thin films of the high Tc superconductor YBa2Cu3O7−x (123) is of interest for several reasons. The highest Tc' reported for well-ordered stoichiometric films are typically 90-91 K. Post-annealed Cu- and Y-rich films may exhibit Tc's of 95-96 K. X-ray diffraction showed these non-stoichiometric films to be a highly faulted mixture of the 123 and 248 (Y2Ba4Cu8O16,Tc=80 K) phases. In situ films made by sputtering or electron beam evaporation typically show sharp but depressed Tc's (75-85 K); for our films these values approach 90 K when the films are Cu- and Y-rich. Both post annealed and in situ films exhibit high critical currents on and off stoichiometry; the pinning characteristics, which may be highly influenced by the defect microstructure, are superior for the in situ techniques.Transmission electron microscopy analysis shows that excess Cu and Y can be incorporated both as stacking fault (SF) defects and as second phase precipitates.

FORMATION OF TWO LAYERS IN Pr1-xCaxBa2Cu3O7-y(0≤x≤0.5) THIN FILMS DEPOSITED AT DIFFERENT TEMPERATURES

2000 ◽  
Vol 14 (16) ◽  
pp. 1651-1657
Author(s):  
J. A. DÍAZ ◽  
O. CONTRERAS ◽  
J. M. SIQUEIROS
Keyword(s):  
Thin Films ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Cell Parameters ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Different Temperatures ◽  
Microscopy Analysis

We have grown epitaxial Pr 1-x Ca x Ba 2 Cu 3 O 7-y(0≤x≤0.5) thin films on SrTiO 3 and Yttrium stabilized zirconia (YSZ) substrates by pulsed laser deposition at different temperatures. X-ray diffraction and transmission electron microscopy analysis revealed epitaxial growth on YSZ substrates for x=0 along the a and c axis directions for T=570° C , where first the film grows oriented along a-axis and afterward, it undergoes a shift in the orientation, growing in the c-axis direction from then on. The cell parameters were c=1.166 nm and a~b=0.386 nm .

Growth and Characterization of C-Axis Oriented YBa2Cu3O7-x/PrBa2Cu3O7-x Bilayers

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1005-1010 ◽  
Author(s):  
C. Beneduce ◽  
F. Bobba ◽  
M. Boffa ◽  
M. C. Cucolo ◽  
A. M. Cucolo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Resistivity Measurements ◽  
Transmission Electron ◽  
High Oxygen Pressure ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis

We report on the preparation and characterization of YBa 2 Cu 3 O 7-x/ PrBa 2 Cu 3 O 7-x bilayers onto (100) SrTiO 3 substrates. The samples have been prepared by sequential dc sputtering processes in high oxygen pressure from stoichiometric targets. The structural characterization of the YBa 2 Cu 3 O 7-x and PrBa 2 Cu 3 O 7-x films and of the bilayers has been performed by means of X-ray diffraction. The Scanning Electron Microscopy analysis has showed that the film surfaces are flat and free of precipitates. A detailed study of the interfaces has been performed by Transmission Electron Microscopy analysis. The electrical resistivity measurements showed for the YBa 2 Cu 3 O 7-x films sharp superconducting transitions at 91.5 K and critical current density of about 106 A/cm 2 at 77 K, while for the PrBa 2 Cu 3 O 7-x films a semiconductor-like behavior has been observed.

X-ray diffraction and transmission electron microscopy analysis of ordering and structure in Al1−xInxAs thin films

2000 ◽  
Vol 15 (1) ◽  
pp. 45-55 ◽  
Author(s):  
R. L. Forrest ◽  
J. Kulik ◽  
T. D. Golding ◽  
S. C. Moss
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Short Range ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Short Range Ordering ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis

This paper presents an x-ray diffraction and transmission electron microscopy analysis of Al1−xInxAs grown by molecular beam epitaxy. Two samples grown on (001) InP at temperatures of 370 and 400 °C are characterized. The first, which contains a high density of twin lamellae, exhibits triple-period short-range ordering with a rather short correlation range normal to the (111) planes. Within these (individual) planes, the concentration, however, is uniform over a considerably greater distance, leading to a highly anisotropic scattering. This is the first observation of triple-period short-range ordering in a sample that exhibits 2 × 1 surface reconstruction. The second sample exhibits CuPt-type short-range ordering with scattering that is significantly streaked, suggestive of lamellar-shaped ordered domains. Both samples contain high densities of stacking faults leading to additional sharp streaking along symmetry-allowed 〈111〉 directions.

SYNTHESIS OF MONODISPERSE Mn3O4 NANOCRYSTALS

2009 ◽  
Vol 08 (03) ◽  
pp. 281-283 ◽  
Author(s):  
MASOUD SALAVATI-NIASARI ◽  
FATEMEH DAVAR
Keyword(s):  
Photoelectron Spectroscopy ◽  
Average Diameter ◽  
Binding Energies ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis ◽  
20 Nm

Mn3O4 nanocrystals have been prepared using [bis(2-hydroxyacetophenato)manganese(II)] as precursor. Transmission electron microscopy analysis demonstrated nanocrystals Mn3O4 with an average diameter of about 20 nm. The structural study by X-ray diffraction indicates that these nanocrystals have pure tetragonal phase. The phase pure samples were characterized using X-ray Photoelectron Spectroscopy for Mn 2p level. The values of binding energies are consistent with the relative values reported in the literature.

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