scholarly journals Effect of the thermal annealing on the phase transitions of biogenic CaCO3 nanostructures

2019 ◽  
Vol 63 (1) ◽  
Author(s):  
Candelario Ramón de los Santos ◽  
Angélica Silvestre López Rodríguez ◽  
Pio Sifuentes Gallardo ◽  
Miguel Angel Hernández Rivera ◽  
German Pérez-Hernández ◽  
...  
Keyword(s):  
Calcium Hydroxide ◽  
Thermal Annealing ◽  
Annealing Treatment ◽  
Orthorhombic Phase ◽  
Natural State ◽  
X Ray Diffraction ◽  
X Ray ◽  
Air Atmosphere ◽  
Thermal Annealing Treatment ◽  
Two Phases

The issue of the present research lays its foundation on the proposal of the Crassostrea virginica waste oyster shells (WOS) reuse to obtain calcium carbonate powder (CaCO3) and calcium hydroxide (Ca(OH)2) nanostructured, using thermal annealing treatments. The oysters shells were subjected to a previous physical grinding process to decrease their size (smaller sizes 0.074 mm). The parameter studied was the effect of annealing temperature (500, 700 and 900 °C in air atmosphere) on the structural properties and morphology of the powders by FTIR, XRD, SEM and HRTEM. The X-ray diffraction results indicate that the WOS in their natural state and thermally annealed at 500 °C  have two phases of CaCO3 the rhombohedral form for calcite with crystallite size around 24 nm and aragonite traces in orthorhombic phase. At 700 °C, the WOS powder is transformed into calcium hydroxide, also known as portlandite (Ca(OH)2), attributed to the absorption of water released during the thermal decomposition of CaCO3. This crystalline phase does not change when the temperature increases to 900 °C. The SEM and HRTEM analysis of WOS powders reveals that with a thermal annealing treatment it is possible to obtain   nanostructured CaCO3. FTIR analysis demonstrates the biogenic origin of CaCO3, due to amide groups. The nanostructured CaCO3 obtained by grinding and thermal annealing of WOS, can be used as drying agent, or as additive in ceramic and glass. The issue of the present research lays its foundation on the proposal of the Crassostrea virginica waste oyster shells (WOS) reuse to obtain calcium carbonate powder (CaCO3) and calcium hydroxide (Ca(OH)2) nanostructured, using thermal annealing treatments. The oysters shells were subjected to a previous physical grinding process to decrease their size (smaller sizes 0.074 mm). The parameter studied was the effect of annealing temperature (500, 700 and 900 °C in air atmosphere) on the structural properties and morphology of the powders by FTIR, XRD, SEM and HRTEM. The X-ray diffraction results indicate that the WOS in their natural state and thermally annealed at 500 °C  have two phases of CaCO3 the rhombohedral form for calcite with crystallite size around 24 nm and aragonite traces in orthorhombic phase. At 700 °C, the WOS powder is transformed into calcium hydroxide, also known as portlandite (Ca(OH)2), attributed to the absorption of water released during the thermal decomposition of CaCO3. This crystalline phase does not change when the temperature increases to 900 °C. The SEM and HRTEM analysis of WOS powders reveals that with a thermal annealing treatment it is possible to obtain   nanostructured CaCO3. FTIR analysis demonstrates the biogenic origin of CaCO3, due to amide groups. The nanostructured CaCO3 obtained by grinding and thermal annealing of WOS, can be used as drying agent, or as additive in ceramic and glass.

Improved Photovoltaic Efficiency of Polymer Photovoltaic Cells by Microwave Irradiation

2010 ◽  
Vol 663-665 ◽  
pp. 819-822
Author(s):  
Boeun Kim ◽  
Kyeong K. Lee ◽  
Sung Koo Lee ◽  
Eun Hee Lim
Keyword(s):  
Thermal Annealing ◽  
Acid Methyl Ester ◽  
Annealing Treatment ◽  
Polymer Chains ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Microwave Annealing ◽  
Photovoltaic Efficiency ◽  
Atomic Force ◽  
Thermal Annealing Treatment

In this study, microwave annealing treatment was introduced into poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61butyric acid methyl ester (PCBM) and poly(9,9‘-dioctylfluorene-cobithiophene (PFT2):PCBM systems instead of thermal annealing treatment. In both systems, microwave annealing showed photovoltaic performane comparable to that of conventional thermal annealing. Through the UV-vis absorption, atomic force microscopy (AFM) and X-ray diffraction (XRD) studies, we were able to confirm that the microwave annealing increases the crystallization of the P3HT polymer chains.

X-ray Diffraction and Modelling Studies of Multilayer SnO2 Thin Film Gas Sensors

1995 ◽  
Vol 403 ◽  
Author(s):  
L. E. Depero ◽  
C. Perego ◽  
L. Sangaletti ◽  
G. Sberveglieri
Keyword(s):  
Thin Film ◽  
Orthorhombic Phase ◽  
Sno2 Thin Film ◽  
X Ray Diffraction ◽  
X Ray ◽  
Modelling Studies ◽  
Cation Coordination ◽  
Diffraction Patterns ◽  
Two Phases ◽  
The Relationship

AbstractStructural studies have been carried out on SnO2 multilayer thin film grown by the Rheotaxial Growth and Thermal Oxidation method on A120 3 substrates. A preliminary analysis of the X-ray diffraction patterns shows that, in addition to the Sn0 2 cassiterite phase, a strong contribution from an orthorhombic Sn02 phase is present.In the case of the 3-layer film, the orthorhombic phase is structurally and microstructurally stable after an annealing up to 32 h at 400 'C. The cation coordination is similar to that found in cassiterite, but the chains of edge-sharing [SnO6]8- octahedra run in a zig-zag fashion along the [100] direction, each straight unit containing four octahedra. The relationship between the two phases is discussed on the basis of structural simulations including twinning planes in the crystal structure.

Growth of NdOHCO3 nanocrystals by chemical bath and its thermal annealing treatment in air atmosphere

Optik ◽  
2017 ◽  
Vol 130 ◽  
pp. 1045-1052 ◽  
Author(s):  
O. Portillo Moreno ◽  
R. Gutiérrez Pérez ◽  
R. Palomino Merino ◽  
G. Hernández Téllez ◽  
M. Chávez Portillo ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Annealing Treatment ◽  
Air Atmosphere ◽  
Thermal Annealing Treatment

Effect of Annealing Temperature on Structure and Optical Properties of Ta2O5 Thin Films Prepared by DC Magnetron Sputtering

2013 ◽  
Vol 770 ◽  
pp. 149-152 ◽  
Author(s):  
T. Plirdpring ◽  
M. Horprathum ◽  
C. Chananonnawathorn ◽  
P. Eiamchai ◽  
A. Harnwunggmoung ◽  
...  
Keyword(s):  
Optical Properties ◽  
Magnetron Sputtering ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Annealing Treatment ◽  
Orthorhombic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dc Reactive Magnetron Sputtering ◽  
Deposited Films

Tantalum oxide (Ta2O5) films at 400 nm thickness were prepared at room temperature by DC reactive magnetron sputtering. The effect of annealing temperature on film crystallinity, microstructure and optical properties were investigated. In order to indentify the crystalline structure and film morphology, X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) measurements were performance. The optical properties were determined by UV-Vis spectrophotometer and spectroscopic ellipsometry (SE). The result showed that, with the annealing treatment at high temperature (700-900°C), the as-deposited films were crystallized to orthorhombic phase of tantalum pentaoxide (β-Ta2O5). In addition, the transmittance spectrum percentage indicated 87%, which corresponded to the obtained optical characteristic. The refractive index varied at 550 nm from 2.17 to 2.21 with increased of the annealing temperature.

CeO2 nanoparticles growth by chemical bath and its thermal annealing treatment in air atmosphere

Optik ◽  
2017 ◽  
Vol 148 ◽  
pp. 142-150 ◽  
Author(s):  
O. Portillo Moreno ◽  
R. Gutiérrez Pérez ◽  
R. Palomino Merino ◽  
M. Chávez Portillo ◽  
G. Hernandez Tellez ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Annealing Treatment ◽  
Ceo2 Nanoparticles ◽  
Air Atmosphere ◽  
Thermal Annealing Treatment

Ferroelectric and proton conducting behavior of a new elpasolite-related vanadium oxyfluoride (NH4,K)3VO2F4

2010 ◽  
Vol 25 (7) ◽  
pp. 1251-1263 ◽  
Author(s):  
Sadequa J. Patwe ◽  
S. Nagabhusan Achary ◽  
Kalpathy Ganapathy Girija ◽  
C.G. Sivan Pillai ◽  
Avesh K. Tyagi
Keyword(s):  
Orthorhombic Phase ◽  
Impedance Analysis ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
First Order ◽  
Two Phases ◽  
Ferroelectric Hysteresis

A new elpasolite-type (NH4,K)3VO2F4 compound was prepared and characterized by x-ray diffraction, differential scanning calorimeter (DSC), impedance analysis, and electrical polarization measurements. It crystallizes in an orthorhombic lattice with unit-cell parameters: a = 8.9584(4), b = 18.6910(14), c = 6.2174(4) Å, V = 1041.04(11) Å3, Z = 6. NH4+, and K+ ions are distributed statistically over crystallographically four equivalent sites. There are two distinguishable vanadium atoms forming cis- and trans-VO2F4 octahedra present in the unit cell. High-temperature studies by DSC and in situ x-ray diffraction revealed a first-order structural transformation from orthorhombic to cubic lattice around 343 K. Impedance measurements show two different kinds of conductivity behaviors for the two phases. In orthorhombic phase a significant conductivity resulting from involvement of protonic species is observed. In the orthorhombic phase, a clear ferroelectric hysteresis loop is observed.

Sem and X-Ray Analysis of Renal and Biliary Calculi

1976 ◽  
Vol 34 ◽  
pp. 306-307
Author(s):  
R. J. Narconis ◽  
G. L. Johnson
Keyword(s):  
Chemical Constituents ◽  
Natural State ◽  
X Ray Diffraction ◽  
Chemical Methods ◽  
X Ray ◽  
Additional Dimension ◽  
Biliary Calculi ◽  
Calculus Formation ◽  
Scanning Electron

Analysis of the constituents of renal and biliary calculi may be of help in the management of patients with calculous disease. Several methods of analysis are available for identifying these constituents. Most common are chemical methods, optical crystallography, x-ray diffraction, and infrared spectroscopy. The application of a SEM with x-ray analysis capabilities should be considered as an additional alternative.A scanning electron microscope equipped with an x-ray “mapping” attachment offers an additional dimension in its ability to locate elemental constituents geographically, and thus, provide a clue in determination of possible metabolic etiology in calculus formation. The ability of this method to give an undisturbed view of adjacent layers of elements in their natural state is of advantage in determining the sequence of formation of subsequent layers of chemical constituents.

Defect structures of Nb1+αS2 sulfidation scales

1992 ◽  
Vol 50 (1) ◽  
pp. 38-39
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Stacking Faults ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Normal ◽  
Lower Case ◽  
Sulfur Layer ◽  
Two Phases

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.

Microdomains in BaFeO3-y (0.35 < y < 0.50)

1990 ◽  
Vol 48 (4) ◽  
pp. 780-781
Author(s):  
M. Vallet-Regí ◽  
M. Parras ◽  
J.M. González-Calbet ◽  
J.C. Grenier
Keyword(s):  
Electron Diffraction ◽  
Chemical Analysis ◽  
Monoclinic Phase ◽  
Orthorhombic Phase ◽  
Total Iron ◽  
Zone Axis ◽  
Electron Micrograph ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compositional Variations

BaFeO3-y compositions (0.35<y<0.50) have been investigated by means of electron diffraction and microscopy to resolve contradictory results from powder X-ray diffraction data.The samples were obtained by annealing BaFeO2.56 for 48 h. in the temperature range from 980°C to 1050°C . Total iron and barium in the samples were determined using chemical analysis and gravimetric methods, respectively.In the BaFeO3-y system, according to the electron diffraction and microscopy results, the nonstoichiometry is accommodated in different ways as a function of the composition (y):In the domain between BaFeO2.5+δBaFeO2.54, compositional variations are accommodated through the formation of microdomains. Fig. la shows the ED pattern of the BaFeO2.52 material along thezone axis. The corresponding electron micrograph is seen in Fig. 1b. Several domains corresponding to the monoclinic BaFeO2.50 phase, intergrow with domains of the orthorhombic phase. According to that, the ED pattern of Fig. 1a, can be interpreted as formed by the superposition of three types of diffraction maxima : Very strong spots corresponding to a cubic perovskite, a set of maxima due to the superposition of three domains of the monoclinic phase along [100]m and a series of maxima corresponding to three domains corresponding to the orthorhombic phase along the [100]o.

scholarly journals X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 84 ◽  
Author(s):  
Satoru Urakawa ◽  
Toru Inoue ◽  
Takanori Hattori ◽  
Asami Sano-Furukawa ◽  
Shinji Kohara ◽  
...  
Keyword(s):  
Oxide Glasses ◽  
Void Space ◽  
X Ray Diffraction ◽  
Amorphous Sio2 ◽  
Sio2 Glass ◽  
X Ray ◽  
X Ray Scattering ◽  
Medium Range ◽  
Two Phases ◽  
A Minor

The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra.

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