Aragonite Fraction Dating of Vermetids in the Context of Paleo Sea-Level Curves Reconstruction

Radiocarbon ◽  
2020 ◽  
Vol 62 (2) ◽  
pp. 335-348
Author(s):  
Vinicius N Moreira ◽  
Kita D Macario ◽  
Renato B Guimarães ◽  
Fábio F Dias ◽  
Julia C Araujo ◽  
...  
Keyword(s):  
Sea Level ◽  
Critical Factor ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Separation ◽  
Level Curves ◽  
Before And After ◽  
Ams Dating ◽  
Sodium Polytungstate

ABSTRACTIdentifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating.

scholarly journals Ostrich eggshell as calcium source for the synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc

Cerâmica ◽  
2016 ◽  
Vol 62 (364) ◽  
pp. 386-391 ◽  
Author(s):  
J. R. M. Ferreira ◽  
L. H. L. Louro ◽  
A. M. Costa ◽  
J. B. de Campos ◽  
M. H. Prado da Silva
Keyword(s):  
Xrd Analysis ◽  
Quantitative Chemical Analysis ◽  
X Ray Diffraction ◽  
Spectroscopy Technique ◽  
X Ray ◽  
Heat Treated ◽  
Before And After ◽  
Calcium Source ◽  
The Fourier Transform ◽  
Ostrich Eggshell

Abstract In the present study, hydroxyapatite and Zn-substituted hydroxyapatite powders were synthesized using ostrich eggshell as a calcium source. The samples were analyzed by scanning electron microscopy with field emission gun, and X-ray diffraction (XRD) to identify the present phases, and X-ray fluorescence spectroscopy for quantitative chemical analysis of the synthesized and heat treated powders. The Fourier transform infrared spectroscopy technique was used before and after heat treatments at 700, 900 and 1100 °C in order to identify the functional groups present, as an additional technique to the XRD analysis. The results presented in this study represent a promising method for synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc, since the results showed no undesirable phases or impurities in the produced powders. It was observed that Zn-substituted hydroxyapatite showed higher thermal stability, when compared to pure hydroxyapatite.

Large Size CH3NH3PbI3 Perovskite Microcrystalline with a Capsule-Free Cavity Box Structure Grown by Solvent Thermal Reaction

2021 ◽  
Vol 1032 ◽  
pp. 51-56
Author(s):  
Fei Han ◽  
Xi Ping Xi ◽  
Min Fan ◽  
Ling Ling Wang ◽  
Jin Ming Shi ◽  
...  
Keyword(s):  
Xrd Analysis ◽  
Thermal Reaction ◽  
Material Decomposition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Large Size ◽  
Composition And Structure ◽  
Before And After ◽  
Box Structure ◽  
Technical Guidance

In the paper, a novel perovskite microcrystalline with a capsule-free cavity box structure was creatively prepared through solvent thermal reaction, and the composition and structure of CH3NH3PbI3 perovskite microcrystalline were further characterized by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) element mapping. The SEM results show that the grain size of the prepared CH3NH3PbI3 perovskite microcrystalline is more than 100 μm. Furthermore, X-ray diffraction (XRD) analysis was used to characterize the material decomposition of perovskite microcrystals before and after 150 d of air aging. The XRD results indicate the prepared perovskite microcrystalline could be stably preserved in the air for 150 d without degradation. Our method provides technical guidance for further enriching the morphology of CH3NH3PbI3 perovskite microcrystalline.

Mineralogical Analysis of Portland Cement Pastes Rehydrated

2020 ◽  
Vol 46 (1) ◽  
pp. 15-23
Author(s):  
Tiago Assunção Santos ◽  
Guilherme Augusto de Oliveira e Silva ◽  
Daniel Véras Ribeiro
Keyword(s):  
Portland Cement ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
X Ray ◽  
Curing Period ◽  
Hydraulic Binder ◽  
Before And After ◽  
Hydrated Products ◽  
Rehydration Process

Hydrated products, such as (hydrated) cement pastes, decomposition through physical-chemical alterations when submitted to high temperatures. One of the main factors that lead to microstructural changes during calcination up to 800ºC, is the dehydration phases of hydrated Portland cement. The present study sought to characterize crystalline phases occurring before and after calcination to the produced pastes using X-ray diffraction (XRD) analysis. Cement pastes were produced using Portland cement CP V-ARI RS, similar to type II (ASTM C150-07), with water/cement ratio 0.5. After a 28-day curing period, the pastes were calcinated at 800°C for 60 minutes with a 10°C/min heating rate. Afterwards, the newly produced hydraulic binder was cooled abruptly and reactivated through a rehydration process, and underwent analyses on the 7 and 28 day. During this study it was observed that the originally hydrated products can be rehydrated.

scholarly journals Potential Peat Clay for Minerals Source Utilized as Adsorbent and Catalyst

2019 ◽  
Vol 280 ◽  
pp. 04003
Author(s):  
Agus Mirwan ◽  
Meilana Dharma Putra ◽  
Riani Ayu Lestari
Keyword(s):  
Xrd Analysis ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Huge Amount ◽  
Calcination Process ◽  
X Ray ◽  
Potential Source ◽  
Before And After ◽  
Flake Structure

The existence of peat clay is scattered in many parts of the world with the huge amount. The high compound of minerals in the peat clay can be potentially used as adsorbent and catalyst. This research aims to study the composition of peat clay and functional group of the compound in the peat clay. The characterization of x-ray fluorescence (XRF), fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and scanning electron microscope-energy dispersive x-ray (SEM- EDX) were assigned to compare the sample before and after calcination process at 700 oC 120 min. FTIR analysis showed the presence of quartz, kaolinite, hematite, illite in peat clay. The results of XRF analysis showed that chemical composition of peat clay was dominantly in the form of silica oxide (18%), aluminum oxide (7%), and iron oxide (15%). The amount of compounds was observed to increase to be 32%, 18% and 11%, respectively after calcinations. XRD analysis confirmed the presence of this mineral in the peat clay. SEM analysis showed flake structure of peat clay with EDX which indicated composition of the dominant element namely the presence of Al, Si, and Fe before and after calcination. This high amount of minerals in peat clay led to potential source to be utilized as adsorbent for removing the pollutant or as and catalyst for chemical process.

Comparison of Hydroxyapatite Synthesized under Different Conditions

2006 ◽  
Vol 510-511 ◽  
pp. 814-817 ◽  
Author(s):  
Li Rong Mo ◽  
Yu Bao Li ◽  
Guo Yu Lv ◽  
Ji Dong Li ◽  
Li Zhang
Keyword(s):  
Sodium Phosphate ◽  
Chemical Method ◽  
Calcium Nitrate ◽  
Reaction System ◽  
Xrd Analysis ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Before And After

In this paper, using sodium phosphate and calcium nitrate as reagents, nano-hydroxyapatite (n-HA) was synthesised under 8 conditions. The morphology and crystallinity of these prepared HA were investigated by Transmission Electron Microscope (TEM) and X-ray diffraction pattern (XRD). The Ca/P molar ratio of n-HA was tested by chemical method. In order to find a better way to obtain purer nano-hydroxyapatite, the phases transition and purification of these 8 samples before and after sintering at 1000°C were compared. The results indicated that all these samples showed similar, poorly crystallized apatite structures before sintering. The adding order between calcium and phosphate would affect the crystallinity, structure and Ca/P molar ratio of hydoxyapatite significantly. XRD analysis showed that adding sodium phosphate into calcium nitrate could gain more HA phase after sintering at 1000°C. The pH of reaction system had obvious effects on the structure of hydroxyapatite. Besides the pH of reactants also affected the structure of hydoxyapatite.

scholarly journals Improving heat aging and mechanical properties of fluoroelastomer using carbon nanotubes

2017 ◽  
Vol 19 (1) ◽  
pp. 132-142 ◽  
Author(s):  
Javad Heidarian ◽  
Aziz Hassan
Keyword(s):  
Crystal Size ◽  
Xrd Analysis ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Elongation At Break ◽  
X Ray ◽  
Before And After ◽  
The Degree Of Crystallinity ◽  
Stress Induced Crystallization ◽  
Induced Crystallization

Abstract Carbon nanotube (CNT)-, carbon black (CB)-filled fluoroelastomer (FE) and unfilled-FE compounds were prepared (CNT/FE, CB/FE and FE). The compounds were subjected to heat air aging and characterized by tensile test and X-Ray Diffraction (XRD) analysis. Results show that CNT improved tensile properties of FE before and after aging. All samples show stress induced crystallization (SIC) during tension. XRD results show that under all conditions, the crystals were in the form of γ-phase. For both aged and un-aged specimens, the degree of crystallinity (Xc) is low. After tensile stretching, Xc of un-aged specimens increases tremendously, with larger crystal size. Under the same conditions, the order of elongation at break (EL) was FE > CB/FE > CNT/FE. Normal modulus (NM) and tangent modulus (TM) at the same conditions was in the order of CNT/FE > CB/FE > FE. Tensile strength had the order of CNT/FE > CB/FE > FE.

Epitaxy in the Crystallization of Feldspar Gels and Glasses

1994 ◽  
Vol 346 ◽  
Author(s):  
Chunling Liu ◽  
Sridhar Komarneni ◽  
Rustum Roy
Keyword(s):  
Electron Microscope ◽  
Energy Dispersive Spectrometry ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Crystallization Product ◽  
X Ray ◽  
Seeding Effect ◽  
Before And After ◽  
Scanning Electron

ABSTRACTThe crystallization behaviors of stoichiometric feldspar gels and glasses before and after seeding have been compared, and the role of epitaxy in their crystallization upon seeding has been studied. The crystallization products were mainly determined by X-ray diffraction (XRD) analysis and epitaxy upon seeding was examined with a scanning electron microscope (SEM), and energy dispersive spectrometry (EDS). It was found that upon isostructural seeding, Na-and K-feldspars crystallized epitaxially from their gels and/or glasses. Little or no seeding effect was found in CaAl2Si2O8 and SrAl2Si2O8 gels and glasses. Isostructural seeding in BaAl2Si2O8 gels increased the formation of Ba-feldspar (monoclinic celsian) epitaxially, whereas without seeding hexacelsian was the crystallization product.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Identification of acid-insoluble filter-plugging compounds and optimal acid-washing procedures for tubular backpulse pressure filters

TAPPI Journal ◽  
2011 ◽  
Vol 10 (1) ◽  
pp. 17-23
Author(s):  
KEVIN TAYLOR ◽  
RICH ADDERLY ◽  
GAVIN BAXTER
Keyword(s):  
Calcium Sulfate ◽  
Membrane Filter ◽  
Sulfamic Acid ◽  
Xrd Analysis ◽  
Metal Sulfides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gypsum Formation ◽  
Acid Washing ◽  
Hydrolysis Of

Over time, performance of tubular backpulse pressure filters in kraft mills deteriorates, even with regular acid washing. Unscheduled filter replacement due to filter plugging results in significant costs and may result in mill downtime. We identified acid-insoluble filter-plugging materials by scanning electron microscope/energy-dispersion X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis in both polypropylene and Gore-Tex™ membrane filter socks. The major filter-plugging components were calcium sulfate (gypsum), calcium phosphate (hydroxylapatite), aluminosilicate clays, metal sulfides, and carbon. We carried out detailed sample analysis of both the standard acid-washing procedure and a modified procedure. Filter plugging by gypsum and metal sulfides appeared to occur because of the acid-washing procedure. Gypsum formation on the filter resulted from significant hydrolysis of sulfamic acid solution at temperatures greater than 130°F. Modification of the acid-washing procedure greatly reduced the amount of gypsum and addition of a surfactant to the acid reduced wash time and mobilized some of the carbon from the filter. With surfactant, acid washing was 95% complete after 40 min.

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