scholarly journals Identification of Chemical Bonds and Microstructure of Hydrated Tricalcium Silicate (C3S) by a Coupled Micro-Raman/BSE-EDS Evaluation

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5144
Author(s):  
Zheyu Zhu ◽  
Zhongping Wang ◽  
Yue Zhou ◽  
Yuting Chen ◽  
Kai Wu
Keyword(s):  
Calcium Hydroxide ◽  
Phase Evolution ◽  
Cementitious Materials ◽  
Tricalcium Silicate ◽  
Chemical Bonds ◽  
Mixed Structure ◽  
Disassembly Process ◽  
Eds Analysis ◽  
Interface Transition Zone ◽  
Insight Into

Identifying the phase evolution and revealing the chemical bonds of hydrated cements accurately is crucial to regulate the performance of cementitious materials. In this paper, a coupled Raman/BSE-EDS analysis was proposed to determine the chemical bonds of tricalcium silicate hydrates and the interface transition zone (ITZ) between inner C-S-H and anhydrates. The results show that the Raman/BSE-EDS method can accurately identify the chemical bonds of inner C-S-H and inner ITZ regions, which confirms the mixed structure of inner C-S-H and nano calcium hydroxide (CH). The inner ITZ shows a lattice change region with a thickness of 700–1000 nm, which can be attributed to the pre-disassembly process of C3S crystal. The successful application of coupled Raman/BSE-EDS provides new insight into the hydration process and multi-structure features of traditional cementitious materials.

scholarly journals Coupled Preparation of Ferronickel and Cementitious Material from Laterite Nickel Ores

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4992
Author(s):  
Ruimeng Shi ◽  
Xiaoming Li ◽  
Yaru Cui ◽  
Junxue Zhao ◽  
Chong Zou ◽  
...  
Keyword(s):  
Direct Reduction ◽  
Cementitious Materials ◽  
Tricalcium Silicate ◽  
Cementitious Material ◽  
Raw Material ◽  
Tricalcium Aluminate ◽  
Thermodynamic Conditions ◽  
Nickel Ores ◽  
Main Components ◽  
Factsage Software

Nickel slags can be produced through ferronickel preparation by the pyrometallurgical processing of laterite nickel ores; however, such techniques are underutilized at present, and serious environmental problems arise from the stockpiling of such nickel ores. In this study, a modification to the process of ferronickel preparation by the direct reduction of carbon bases in laterite nickel ores is proposed. The gangue from the ore is used as a raw material to prepare a cementitious material, with the main components of tricalcium silicate and tricalcium aluminate. By using FactSage software, thermodynamic calculations are performed to analyze the reduction of nickel and iron and the effect of reduction on the formation of tricalcium silicate and tricalcium aluminate. The feasibility of a coupled process to prepare ferronickel and cementitious materials by the direct reduction of laterite nickel ore and gangue calcination, respectively, is discussed under varying thermodynamic conditions. Different warming strategies are applied to experimentally verify the coupled reactions. The coupled preparation of ferronickel and cementitious materials with calcium silicate and calcium aluminate as the main phases in the same experimental process is realized.

scholarly journals Passive ultrasonic irrigation in calcium hydroxide removal from root canals: a sem/eds analysis

2015 ◽  
Vol 3 (3) ◽  
pp. 668
Author(s):  
Fernanda Hoffmann Busanello ◽  
Angela Longo Do Nascimento ◽  
Lilian Tietz ◽  
Mirela Sangoi Barreto ◽  
Ricardo Abreu Da Rosa ◽  
...  
Keyword(s):  
Calcium Hydroxide ◽  
Root Canal ◽  
Control Group ◽  
Passive Ultrasonic Irrigation ◽  
Root Canals ◽  
Eds Analysis ◽  
Ultrasonic Irrigation ◽  
Calcium Hydroxide Removal ◽  
And Control ◽  
Elementary Chemical

AIM: The aim of this study was to evaluate the efficacy of different lengths of time of passive ultrasonic irrigation (PUI) in removing calcium hydroxide (CH) paste from root canal, using scanning electron microscopy and energy dispersive spectrometry (SEM/EDS). MATERIAL AND METHODS: Fifty-four human premolars were used. After coronal access, a size #15 K-file was used to obtain apical patency. Root canal preparation was performed using WaveOne 40.08 instruments. CH paste was placed into the root canal. Specimens were stored in a humid environment, and after seven days, they were divided into five groups (n=12) according to the irrigation protocols: Manual– a size #40 K-file; PUI/1– 1 min; PUI/2– 2 min; PUI/3– 3 min; and Control– without CH paste. An elementary chemical microanalysis (SEM/EDS) was performed to quantify the presence of calcium on the dentinal walls. RESULTS: The percentage of calcium was higher in all experimental groups when compared to the control group (P < 0.05); but no differences among them were found (P > 0.05). CONCLUSION: The amount of calcium hydroxide paste on the dentinal walls was not dependent on length of time of ultrasonic activation. SEM/EDS analysis seems to be a reliable method to assess CH paste removal from the root canals.

scholarly journals Computational Insight into the Rope-Skipping Isomerization of Diarylether Cyclophanes

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2127
Author(s):  
Thomas J. Summers ◽  
Hrishikesh Tupkar ◽  
Tyler M. Ozvat ◽  
Zoë Tregillus ◽  
Kenneth A. Miller ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Room Temperature ◽  
Chemical Bonds ◽  
Chiral Molecules ◽  
Free Energies ◽  
Design And Synthesis ◽  
The Impact ◽  
Rope Skipping ◽  
Temperature Factors ◽  
Insight Into

The restricted rotation of chemical bonds may lead to the formation of stable, conformationally chiral molecules. While the asymmetry in chiral molecules is generally observed in the presence of one or more stereocenters, asymmetry exhibited by conformational chirality in compounds lacking stereocenters, called atropisomerism, depends on structural and temperature factors that are still not fully understood. This atropisomerism is observed in natural diarylether heptanoids where the length of the intramolecular tether constrains the compounds to isolable enantiomers at room temperature. In this work, we examine the impact tether length has on the activation free energies to isomerization of a diarylether cyclophane substructure with a tether ranging from 6 to 14 carbons. Racemization activation energies are observed to decay from 48 kcal/mol for a 7-carbon tether to 9.2 kcal/mol for a 14-carbon tether. Synthetic efforts to experimentally test these constraints are also presented. This work will likely guide the design and synthesis of novel asymmetric cyclophanes that will be of interest in the catalysis community given the importance of atropisomeric ligands in the field of asymmetric catalysis.

Use of Algerian Natural Mineral Deposit as Supplementary Cementitious Materials

2018 ◽  
Vol 34 ◽  
pp. 48-58 ◽  
Author(s):  
Karima Arroudj ◽  
Saida Dorbani ◽  
Mohamed Nadjib Oudjit ◽  
Arezki Tagnit-Hamou
Keyword(s):  
Mechanical Strength ◽  
Calcium Hydroxide ◽  
Cement Paste ◽  
Cementitious Materials ◽  
Pozzolanic Reaction ◽  
Heat Of Hydration ◽  
Cement Industry ◽  
Supplementary Cementitious Materials ◽  
Natural Mineral ◽  
Different Ages

Much of the current research on concrete engineering has been focused on including siliceous additions as supplementary cementitious materials (SCMs). Silica reacts with Calcium hydroxide release during cement hydration, and produces more C-S-H. The latter contributes to increase compactness, mechanical strengths and sustainability of concrete. This paper explores the hydration characteristics of cement paste based on various natural mineral additions, that are very abundant in Algeria and present a high silica content (ground natural pozzolana “PZ” and ground dune sand “DS”). For this purpose, several analyses were carried out on modified cement pastes and mortars. TheseSCMswere introduced by replacement levels of 15, 20 and 25 by weight of cement. We first, studied the effect of these SCMs on the heat of hydration and mechanical strength of mortars at different ages. The evolution of hydration of modified paste was studied, by using Thermal analysis (TG/TDA) at different ages, to analyze the Calcium Hydroxide (CH) content of the modified pastes. It is shown that the CH content of the mixes including SCMs is lower than that of the plain cement paste, indicating that silica reacts with the cement paste through a pozzolanic reaction. Increased pozzolanic activity results in higher amounts of Calcium Silicate Hydrate in the paste, which in turn results in higher compressive strength for modified cement mortars. Due to its crystalline morphology, the ground DS particles present a partial pozzolanic effect, compared to PZ which is semi-crystalline. Modified mortars by 20% DS can be the optimal composition. It presents satisfactory results: good mechanical strength and low heat of hydration. It can lead to an economic and sustainable concrete. Ground DS is very abounded in Africa and free of any impurities and can be a good alternativeSCMsin cement industry.

Insight into adsorption mechanism of water on tricalcium silicate from first-principles calculations

2022 ◽  
Vol 152 ◽  
pp. 106684
Author(s):  
Yunjian Li ◽  
Haoqiang Ai ◽  
Kin Ho Lo ◽  
Youchao Kong ◽  
Hui Pan ◽  
...  
Keyword(s):  
First Principles ◽  
Adsorption Mechanism ◽  
Tricalcium Silicate ◽  
First Principles Calculations ◽  
Insight Into

Back Cover: Dynamic X-Ray Diffraction Computed Tomography Reveals Real-Time Insight into Catalyst Active Phase Evolution (Angew. Chem. Int. Ed. 43/2011)

2011 ◽  
Vol 50 (43) ◽  
pp. 10255-10255 ◽  
Author(s):  
Simon D. M. Jacques ◽  
Marco Di Michiel ◽  
Andrew M. Beale ◽  
Taha Sochi ◽  
Matthew G. O'Brien ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Real Time ◽  
Active Phase ◽  
Phase Evolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Back Cover ◽  
Insight Into

Development of Superfine Spherical Silica Grout as an Alternative Grouting Material for the Geological Disposal of Long-Lived Radioactive Waste

2010 ◽  
Author(s):  
Morimasa Naito ◽  
Hirokazu Kishi ◽  
Naomi Fukuoka ◽  
Tsutomu Yamada ◽  
Hideaki Ishida
Keyword(s):  
Radioactive Waste ◽  
Calcium Hydroxide ◽  
Cementitious Materials ◽  
Geological Disposal ◽  
Grouting Material ◽  
Spherical Silica ◽  
Geological Repository ◽  
Binder Ratio ◽  
Grouting Materials ◽  
Term Performance

As an alternative grouting material for the geological repository of long-lived radioactive waste, the “Superfine Spherical silica Grout” (SFSG) material is developed using a fine spherical silica and a fine calcium hydroxide. The developed SFSG material takes an advantage of its smaller particle size distribution (max. ∼1 micron or less) than those of the cementitious materials, and also provides a low alkaline environment so as to reduce unfavorable effects on the long-term performance of geological disposal system. The SFSG is a mixture of the “super fine silica powder”, the superfine calcium hydroxide and additives such as superplasticizer. Presently, the mixture being investigated for grouting materials is focused on water/binder ratio (W/B) of 1.2. Some preliminary laboratory experiments were carried out to characterize its fundamental properties from the viewpoint of practical use for geological disposal, which is required to be equivalent with the conventional cementitious materials in terms of penetrability, strength, pH performance and workability. From a series of experiments, it was concluded that SFSG is expected to become an alternative grouting material for a geological repository.

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