scholarly journals Microstructural Study of Hydration of C3S in the Presence of Calcium Nitrate Using Scanning Transmission X-Ray Microscopy (STXM)

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Qinfei Li ◽  
Yang Wang ◽  
Guoqing Geng ◽  
Heng Chen ◽  
Pengkun Hou ◽  
...  
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Calcium Silicate Hydrate ◽  
Calcium Nitrate ◽  
Early Age ◽  
Microstructural Study ◽  
X Ray ◽  
Scanning Transmission ◽  
X Ray Absorption ◽  
Scanning Electron

Calcium nitrate (CN) is used widely as an effectively inorganic setting accelerator and antifreeze admixture in concrete structures. In this paper, the multiscale investigation of CN on the hydration of C3S was studied by scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS), 29Si MAS NMR, calorimetry, scanning electron microscope, and N2 absorption. It was concluded that the calcium silicate hydrate (C-S-H) surrounds the unhydrated C3S at 1-day hydrated C3S in the presence of calcium nitrate, while portlandite is partly in transformation and is formed partly. Based on Ca L3,2-edge NEXAFS spectra for 1-day hydrated C3S particle, calcium nitrate does not change the structure of the asymmetrically 7-fold coordination of calcium in the C-S-H. Calcium nitrate can accelerate the hydration of C3S to some extent and polymerization of the silicate chains within C-S-H considerably at early age, resulting in the increasing specific surface area.

scholarly journals CaCl2-Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with29Si MAS NMR

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Qinfei Li ◽  
Yong Ge ◽  
Guoqing Geng ◽  
Sungchul Bae ◽  
Paulo J. M. Monteiro
Keyword(s):  
Fine Structure ◽  
Calcium Silicate Hydrate ◽  
Hydration Product ◽  
Tricalcium Silicate ◽  
Mas Nmr ◽  
Chemical Components ◽  
X Ray ◽  
Scanning Transmission ◽  
X Ray Absorption ◽  
Cp Mas Nmr

The effect of calcium chloride (CaCl2) on tricalcium silicate (C3S) hydration was investigated by scanning transmission X-ray microscopy (STXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and29Si MAS NMR. STXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system. The Ca L3,2-edge NEXAFS spectra obtained by examining C3S hydration in the presence of CaCl2showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C3S. Based on the Ca L3,2-edge spectra and chemical component mapping, we concluded that CaCl2prefers to coexist with unhydrated C3S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl2increases the degree of silicate polymerization of C-S-H in agreement with the29Si CP/MAS NMR results, which show that the presence of CaCl2in hydrated C3S considerably accelerates the formation of middle groups (Q2) and branch sites (Q3) in the silicate chains of C-S-H gel at 1-day hydration.

Exploring Hydrothermally Grown Potassium Titanate Fibers by STEM-in-SEM/EDX and XRD

2006 ◽  
Vol 12 (4) ◽  
pp. 322-326 ◽  
Author(s):  
Wilhelm Habicht ◽  
Nikolaos Boukis ◽  
Günter Franz ◽  
Olaf Walter ◽  
Eckhard Dinjus
Keyword(s):  
Thin Film ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Tubular Reactor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Potassium Titanate ◽  
Aqueous Solvent ◽  
Scanning Transmission ◽  
Scanning Electron

During lab-scale experiments on the reforming of methanol by means of water at supercritical conditions (T> 374°C,p> 22.1 MPa), a tubular reactor with a titanium liner was exposed to an aqueous solvent containing methanol (5 wt%) and KHCO3(0.3 wt%). At the end of the run, a fibrous precipitate was found at two positions in the reactor. The material was studied in a field emission scanning electron microscope equipped with an energy dispersive X-ray analysis unit (FESEM/EDX). A thin-film support technique using carbon-filmed TEM grids was applied to perform scanning transmission-type imaging (STEM-in-SEM operation) and transmission current measurements. The analysis of the hydrothermally grown fibers resulted in a potassium titanate species composed of approximately K2TiO3, which has been confirmed by X-ray diffraction (XRD).

Sorption Mechanisms of Zinc to Calcium Silicate Hydrate:  X-ray Absorption Fine Structure (XAFS) Investigation

2001 ◽  
Vol 35 (7) ◽  
pp. 1550-1555 ◽  
Author(s):  
Felix Ziegler ◽  
André M. Scheidegger ◽  
C. Annette Johnson ◽  
Rainer Dähn ◽  
Erich Wieland
Keyword(s):  
Fine Structure ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
X Ray ◽  
Absorption Fine ◽  
Sorption Mechanisms ◽  
X Ray Absorption

Multi-elemental scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy assessment of organo–mineral associations in soils from reduced environments

2015 ◽  
Vol 12 (1) ◽  
pp. 64 ◽  
Author(s):  
Chunmei Chen ◽  
Donald L. Sparks
Keyword(s):  
Fine Structure ◽  
X Ray ◽  
Fe Oxides ◽  
Absorption Fine ◽  
Nexafs Spectroscopy ◽  
Mineral Associations ◽  
Fundamental Process ◽  
Scanning Transmission ◽  
Mineral Components ◽  
X Ray Absorption

Environmental context Organo–mineral associations represent a fundamental process for stabilising organic carbon in soils. In this study, we employed scanning transmission X-ray microscopy–near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy at C, Al and Si K-edges as well as Ca and Fe L-edges to conduct submicrometre-level investigations of the associations of C with mineral components in soils from reduced environments. This study provides the first insights into organo–mineral associations in reduced environments and shows progress towards examining, at the submicrometre level, compositional chemistry and associative interactions between organic matter and soil mineral components. Abstract Organo–mineral associations represent a fundamental process for stabilising organic carbon (OC) in soils. However, direct investigation of organo–mineral associations has been hampered by a lack of methods that can simultaneously characterise organic matter (OM) and soil minerals, and most investigations have focussed only on well drained soils. In this study, we employed scanning transmission X-ray microscopy–near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy at C, Al and Si K-edges as well as Ca and Fe L-edges to conduct submicrometre-level investigations of the associations of C with mineral components in soils from reduced environments. Soils were collected from a forest footslope that is periodically poorly drained as well as a waterlogged wetland. OM was coated on mineral particles as thin films. Part of the mineral surface did not show detectable OM coverage with OC loadings of ≥1.3mg C m–2 determined for the clay fractions from these soils. C was not preferentially associated with Fe oxides in the footslope soil. A generally good C–Ca association was found in the anoxic wetland soil, which is free of Fe oxides. It was demonstrated for the first time that OM composition varied spatially at the submicrometre scale in the reduced soils free of Fe oxides. The composition of OM in the organo–mineral interface in the anoxic environments was highly complex and composed of aromatic, phenolic, aliphatic, carboxyl, carboxylamide and O-alkyl C functional groups. There was no consistent pattern for the association of certain types of organics with specific mineral components in both soils. The anoxic conditions resulted in the reduction of Fe in the aluminosilicates. This study provides the first insights into organo–mineral associations in reduced environments.

Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution

Nanoscale ◽  
2015 ◽  
Vol 7 (5) ◽  
pp. 1534-1548 ◽  
Author(s):  
Angela E. Goode ◽  
Alexandra E. Porter ◽  
Mary P. Ryan ◽  
David W. McComb
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Transmission Electron Microscope ◽  
High Spatial Resolution ◽  
Scanning Transmission Electron Microscope ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss ◽  
X Ray Absorption

Benefits and challenges of correlative spectroscopy: electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and X-ray absorption spectroscopy in the scanning transmission X-ray microscope (STXM-XAS).

Calculations of oxygen electron energy loss near edge structure

1987 ◽  
Vol 45 ◽  
pp. 128-129
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Nearest Neighbour ◽  
Edge Structure ◽  
X Ray ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Widespread Interest

Most analytical microscopes are equipped with energy loss spectrometers capable of giving spectra showing 1-2 eV resolution for inner shell edges. The relatively weak modulation starting 30-50 eV from threshold due to Extended X-ray Edge Energy Loss Fine Structure (EXELFS) which is analogous to EXAFS in X-ray absorption has been studied in some detail. Although the theory is, in principle, straightforward the technique using energy loss in the electron microscope to determine nearest neighbour distances has not attracted widespread interest. This is partly due to the long counting times involved. The near edge structure (NES) within 20-30 eV of threshold is characterized by a very strong modulation and is clearly visible even when small amounts of the element are present. Interpretation of the features is very much more difficult and except in those cases in which peaks can be clearly assigned to transitions to antibonding orbitals the main form of analysis has been limited to simple comparisons or fingerprinting.

Local Electronic Structure of Calcite Investigated Using X-ray Absorption Spectroscopy at Different Span of Time

2020 ◽  
Vol 20 (11) ◽  
pp. 6713-6717
Author(s):  
Varsha Singh ◽  
Jitendra Pal Singh ◽  
Cheol-Hwee Shim ◽  
Sangsul Lee ◽  
Keun Hwa Chae
Keyword(s):  
Electronic Structure ◽  
Fine Structure ◽  
Calcium Carbonate ◽  
Calcium Nitrate ◽  
Bond Distance ◽  
Spectral Features ◽  
X Ray ◽  
Absorption Fine ◽  
Local Electronic Structure ◽  
X Ray Absorption

For the present work, calcite nanoparticles was synthesized from calcium nitrate by annealing precursor at 300, 400, 500 and 600°C. Ca K-edge near edge X-ray absorption fine structure measurements revealed spectral features characteristics to the amorphous phase of calcium carbonate at 300 and 400°C. At 500 and 600°C, the spectra were analogues to the calcite phase of calcium carbonate. Simulation of extended X-ray absorption fine structure spectra envisaged that both coordination number and bond distance for Ca–O bonds decreased with annealing temperature. Both parameters attained values close to standard calcite when annealed at 600°C. The spectral features at Ca L-, O K- and C K-edge near edge X-ray absorption fine structure appeared at same positions for different ages, which envisaged the occurrence of almost same local electronic structure for different span of times.

SEM Examination of a Used Diamond Knife

1971 ◽  
Vol 29 ◽  
pp. 452-453
Author(s):  
J. Temple Black
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
High Magnification ◽  
Metallic Materials ◽  
Wide Spread ◽  
Thin Sections ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Scanning Electron ◽  
Diamond Knife

Since its introduction by Fernandez-Moran, the diamond knife has gained wide spread usage as a common material for cutting of thin sections of biological and metallic materials into thin films for examination in the transmission electron microscope. With the development of high voltage E.M. and scanning transmission E.M., microtomy applications will become increasingly important in the preparation of specimens. For those who can afford it, the diamond knife will thus continue to be an important tool to accomplish this effort until a cheaper but equally strong and sharp tool is found to replace the diamond, glass not withstanding.In Figs. 1 thru 3, a first attempt was made to examine the edge of a used (β=45°) diamond knife by means of the scanning electron microscope. Because diamond is conductive, first examination was tried without any coating of the diamond. However, the contamination at the edge caused severe charging during imaging. Next, a thin layer of carbon was deposited but charging was still extensive at high magnification - high voltage settings. Finally, the knife was given a light coating of gold-palladium which eliminated the charging and allowed high magnification micrographs to be made with reasonable resolution.

Sign in / Sign up

Export Citation Format

Share Document