scholarly journals Chemical and Microstructural Properties of Designed Cohesive M-S-H Pastes

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 547
Author(s):  
Charlotte Dewitte ◽  
Alexandra Bertron ◽  
Mejdi Neji ◽  
Laurie Lacarrière ◽  
Alexandre Dauzères
Keyword(s):  
Silica Fume ◽  
Colloidal Silica ◽  
Magnesium Silicate ◽  
Cement Matrix ◽  
Thermal Curing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mesopore Size Distribution ◽  
Few Data ◽  
Highly Porous

Concretes can be exposed to a magnesium attack in several environments leading to the formation of magnesium silicate hydrates (M-S-H) and brucite (MH). The formation of M-S-H is likely to alter the properties of the cement matrix because it is linked to the decalcification of C-S-H. However, relatively few data on M-S-H exist in the literature. In order to characterize, physically and mechanically, the M-S-H phase, pure M-S-H cohesive pastes are needed. This work studies the formation of cohesive M-S-H pastes made with MgO-to-SiO2 atomic ratios of 0.78, 1 and 1.3, from two types of silica (silica fume or colloidal silica) and under 20 °C and 50 °C thermal curing. X-ray diffraction and thermogravimetric analyses confirmed that the consumption of brucite and the formation of M-S-H were quicker with a 50 °C curing. Energy-dispersive X-ray spectroscopy and microtomography showed that colloidal silica enabled a better distribution of the particles than silica fume. Microstructural characterizations were conducted under the protocol with colloidal silica and 50 °C thermal curing. Porosity investigations allowed to describe the M-S-H pastes as highly porous materials with a low content of micropores in comparison with mesopores. The type of mixing influenced the mesopore size distribution.

Chemical characteristics and leachability of organically contaminated heavy metal sludge solidified by silica fume and cement

2001 ◽  
Vol 44 (2-3) ◽  
pp. 399-407 ◽  
Author(s):  
K.-S. Jun ◽  
B.-W. Hwang ◽  
H.-S. Shin ◽  
Y.-S. Won
Keyword(s):  
Heavy Metal ◽  
Silica Fume ◽  
Industrial Wastewater ◽  
Cement Matrix ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ettringite Formation ◽  
Microstructural Studies ◽  
Cement Hydration Reaction

This paper discusses the development of mixtures with silica fume as a stabilization/solidification agent and binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (Unconfined Compressive Strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC and chromium decreased as more OPC was substituted with silica fume. When the mix had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76mg-Cr/g-Cr in acidic solution. Also, microstructural studies on the solidified wastes through the scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contribute to setting, but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and contaminant leachability.

Rapid Thermal Oxidation for Passivation of Porous Silicon

1994 ◽  
Vol 342 ◽  
Author(s):  
I. BÁrsony ◽  
J.G.E. Klappe ◽  
É. Vázsonyi ◽  
T. Lohner ◽  
M. Fried
Keyword(s):  
Porous Silicon ◽  
Mechanical Stability ◽  
Porous Substrate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Tetragonal Lattice ◽  
Optical Heating ◽  
Vertical Inhomogeneity ◽  
Highly Porous

ABSTRACTChemical and mechanical stability of porous silicon layers (PSL) is the prerequisite of any active (luminescent) or passive (e.g. porous substrate) integrated applications. In this work X-ray diffraction (XRD) was used to analyze quantitatively the strain distribution obtained in different morphology PSL that were prepared on (100) p and p+Si substrates. Tetragonal lattice constant distortion can be as high as 1.4% in highly porous “as-prepared” samples. Incoherent optical heating RTO is governed by the absorption in the oxidized specimen. PSL show vertical inhomogeneity according to interpretation of spectroscopic ellipsometry (SE) data. Oxygen incorporation during RTO is controlled by specific surface (in p+ proportional, in p inversely proportional with porosity), while the developing compressive stress depends on pore size, and decreases with porosity in both morphologies.

scholarly journals Features of the hydration process of the modified blended cement for fiber cement panels

2018 ◽  
Vol 170 ◽  
pp. 03030 ◽  
Author(s):  
Rustem Mukhametrakhimov ◽  
Liliya Lukmanova
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Blended Cement ◽  
Physical And Mechanical Properties ◽  
Hydration Process ◽  
Cement Matrix ◽  
X Ray Diffraction ◽  
Structure Form ◽  
Silicate Phase ◽  
X Ray

The paper studies features of the hydration process of the modified blended cement for fiber cement panels (FCP) using differential thermal analysis, X-ray diffraction analysis, electron microscopy and infrared spectroscopy. It is found that deeper hydration process in silicate phase, denser and finer crystalline structure form in fiber cement matrix based on the modified blended cement. Generalization of this result to the case of fiber cement panels makes it possible to achieve formation of a denser and homogeneous structure with increased physical and mechanical properties.

Research on Properties of Low Grade Cement-Based Composite Materials Modified by Silica Fume

2012 ◽  
Vol 174-177 ◽  
pp. 751-756
Author(s):  
Zi Fang Xu ◽  
Ming Xu Zhang ◽  
Jin Hua Li
Keyword(s):  
Silica Fume ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Cement Matrix ◽  
Hardened Cement ◽  
Low Grade ◽  
X Ray ◽  
Matrix Microstructure ◽  
Nano Powder ◽  
Strength And Durability

In order to notably improve the mechanical properties and durability of low-grade cement-based material, superfine silica fume was used to modify the cement-based composite based on special perfomance and effects of nano powder. The mechanical performance and durability were investigated.Then the phase compositions,microstructure and morphologies of as-received cement-based composite were studied by X-ray Diffractometer、TGA-DTA and SEM. The results show that： the best formula of raw materials is 1:1:0.025:0.015, and hydration can be accelerated and increasing of hydration products is observed after modification. In the hardened cement matrix, microstructure is very compacted and C-S-H gel forms densed structure, so the structure defect is notably reduced. This means that both strength and durability of cement-based composite are notably improved by the addition of superfine silica fume.

Influence of the Residue of Casting by Lost Wax in the Modulus of Elasticity and Porosity of Concretes

2014 ◽  
Vol 805 ◽  
pp. 343-349
Author(s):  
Carine F. Machado ◽  
Weber G. Moravia
Keyword(s):  
Construction Industry ◽  
Modulus Of Elasticity ◽  
Chemical Characterization ◽  
Microstructural Characterization ◽  
Cement Matrix ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardened State ◽  
Material Powder

This work evaluated the influence of additions of the ceramic shell residue (CSR), from the industries of Lost Wax Casting, in the modulus of elasticity and porosity of concrete. The CSR was ground and underwent a physical, chemical, and microstructural characterization. It was also analyzed, the environmental risk of the residue. In the physical characterization of the residue were analyzed, the surface area, and particle size distribution. In chemical characterization, the material powder was subjected to testing of X-ray fluorescence (XRF). Microstructural characterization was performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The residue was utilized like addition by substitution of cement in concrete in the percentages of 10% and 15% by weight of Portland cement. It was evaluated properties of concrete in the fresh and hardened state, such as compressive strength, modulus of elasticity, absorption of water by total immersion and by capillarity. The results showed that the residue can be used in cement matrix and improve some properties of concrete. Thus, the CSR may contribute to improved sustainability and benefit the construction industry.

Synthesis of Nanoporous Material from Lignin via Carbonization Assisted Acid Activation

2020 ◽  
Vol 990 ◽  
pp. 149-154
Author(s):  
Nutchaporn Ngamthanacom ◽  
Napat Kaewtrakulchai ◽  
Weerawut Chaiwat ◽  
Laemthong Chuenchom ◽  
Masayoshi Fuji ◽  
...  
Keyword(s):  
Pulp Mill ◽  
Total Pore Volume ◽  
Nanoporous Carbon ◽  
Carbonization Temperature ◽  
Acid Activation ◽  
High Porosity ◽  
Process Variables ◽  
X Ray Diffraction ◽  
X Ray ◽  
Highly Porous

Waste lignin (WL) from the pulp mill and paper was studied for its potential application to prepare the nanoporous carbon with high porosity via carbonization assisted acid activation. The effect of acid activation such as HNO3, HCl, H2SO4, and H3PO4 on lignin transformation to nanoporous carbon investigated. The physicochemical properties of nanoporous carbon were comprehensively characterized through N2 sorption, Scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), respectively. N2 sorption revealed that the condition using 5% vol of phosphoric acid activation at carbonization temperature of 700°C for 2 h exhibited the highly porous structure of carbon nanoparticles with a total pore volume of 0.035 cm3/g. With the properly selecting process variables of waste lignin development could be producing high porosity nanoporous carbon.

Photoluminescence of Chemically Etched Polycrystalline and Amorphous Si Thin Films

1993 ◽  
Vol 298 ◽  
Author(s):  
A. J. Steckl ◽  
J. Xu ◽  
H. C. Mogul
Keyword(s):  
Thin Films ◽  
Strong Relationship ◽  
Porous Si ◽  
X Ray Diffraction ◽  
X Ray ◽  
Amorphous Si ◽  
Si Films ◽  
Uv Excitation ◽  
Highly Porous ◽  
Stain Etching

AbstractSi thin films were deposited on quartz at temperatures ( TD ) ranging from 540 to 640°C. X-ray diffraction indicates that films deposited at TD < 580°C are amorphous, while those deposited above 600°C are poly-crystalline with a <220> texture. The Si films were made porous by stain-etching in HF:HNO3:H2O. Only Si films deposited at 590°C and above show photoluminescence (PL), centered at ∼650-670 nm under UV excitation. Films deposited at TD < 580°C do not luminesce even after very long etch times, which produce a highly porous structure. The PL intensity and the x-ray signal follow a very similar trend with TD. It appears that a minimum level of crystallinity is required for photoemission in porous Si and that a strong relationship exists between them.

scholarly journals RSM-BBD Optimization of Fenton-Like Degradation of 4-Nitrophenol Using Magnetite Impregnated Kaolin

2020 ◽  
Vol 13 ◽  
pp. 117862212093212
Author(s):  
Neway Belachew ◽  
Redeat Fekadu ◽  
Amare Ayalew Abebe
Keyword(s):  
Room Temperature ◽  
Low Cost ◽  
Quadratic Model ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
Box Behnken Design ◽  
X Ray ◽  
Sem Image ◽  
Pure Phases ◽  
Highly Porous

In this work, we have reported a low-cost and environmentally friendly Fe3O4-modified activated kaolin (AK-Fe3O4) composite for efficient Fenton-like degradation of 4-nitrophenol (4-NP) and optimization of the degradation variables. The AK-Fe3O4 composites were characterized by Fourier transform infrared spectroscopy, powder x-ray diffraction, scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). X-ray diffraction confirms the syntheses of pure phases of Fe3O4 and AK-Fe3O4. The SEM image of the AK-Fe3O4 composite reveals the formation of a highly porous surface. The room temperature VSM analysis describes the superparamagnetic nature of AK-Fe3O4 composites with 25 emu/g magnetization values. Response surface methodology coupled with Box-Behnken design was used to optimize the 4-NP degradation (%) variables such as contact time (10-90 minutes), 4-NP concentration (10-30 mg/L), and pH (3-8). The high regression value ( R² = 0.9964 and adjusted R² = 0.9917) and analysis of variance ( P < .0001) show that the quadratic model can sufficiently explain the 4-NP degradation (%). The optimum 4-NP degradation was found to be 96.01% ± 1.89% using 1 mg/mL of AK-Fe3O4, 20 mg/L of 4-NP, 97.9 mmol/L of H2O2, and pH of 3 at the end of 75 minutes of reaction time. Moreover, the catalyst shows good recyclability and stability after 5 successive degradations of 4-NP. In general, a low-cost and magnetically separable AK-Fe3O4 composite is an effective Fenton-like catalyst for the degradation of 4-NP.

Synthesis of Ca(OH)2 Nanoparticles Aqueous Suspensions and Interaction with Silica Fume

2012 ◽  
Vol 629 ◽  
pp. 482-487 ◽  
Author(s):  
V. Daniele ◽  
G. Taglieri ◽  
A. Gregori
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Silica Fume ◽  
Calcium Silicate Hydrate ◽  
Thermal Analyses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrate Phase ◽  
Work Interaction ◽  
Scanning Electron

In this work, interaction at ambient temperature between silica fume and artificially produced Ca(OH)2 nanoparticles by two different methods was analyzed. Initial products and formed hydrated phases were characterized by several investigations including X-ray diffraction, thermal analyses, transmission and scanning electron microscopy. Synthesized Ca(OH)2 nanoparticles appeared regularly shaped and hexagonally plated, with side dimensions from 200nm to less than 20nm. Characterization analyses showed that, by reducing particles dimensions, calcium silicate hydrate phase formation was evident already after 7 day of hydration and a nearly complete consuming of free Ca(OH)2 after 28 days was observed. Besides, formed hydrate phases showed a highly wrinkled layer with marked crumple and rough-edge surfaces.

The Weathering of Serpentinite by Lecanora Atra

1981 ◽  
Vol 13 (2) ◽  
pp. 167-176 ◽  
Author(s):  
M. J. Wilson ◽  
D. Jones ◽  
W. J. McHardy
Keyword(s):  
Electron Probe ◽  
Heavy Metal Ions ◽  
Magnesium Silicate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxalate Dihydrate ◽  
Lichen Thallus ◽  
Fibrous Morphology ◽  
Magnesium Silicates ◽  
Magnesium Oxalate

AbstractA study of the weathering phenomena brought about by the growth of Lecanora alra on a substrate of magnesium silicate minerals (serpentinite) has been carried out mainly by X-ray diffraction and scanning electron microscopy. The lichen thallus contains appreciable amounts of crystalline magnesium oxalate dihydrate, which occurs as an insoluble extra-cellular precipitate and derives from the decomposition of magnesium silicates (particularly chrysotile) by oxalic acid secreted by the mycobiont. In theory magnesium oxalate dihydrate should be capable of incorporating large amounts of heavy metal ions into its structure, as indeed the electron probe evidence indicates has happened, thus suggesting a mechanism for enabling some lichens to cope with environments that are high in these generally harmful ions. The only weathering product detected in the lichen weathering crust is an X-ray amorphous silica gel which often retains the fibrous morphology of the chrysotile from which it forms.

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