scholarly journals Influence of Carbon Nanotubes on the Mechanical Behavior and Porosity of Cement Pastes Prepared by A Dispersion on Cement Particles in Isopropanol Suspension

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3164 ◽  
Author(s):  
Vanessa Vilela Rocha ◽  
Péter Ludvig
Keyword(s):  
Carbon Nanotubes ◽  
Cement Hydration ◽  
Hydration Product ◽  
Image Correlation ◽  
Superior Performance ◽  
Cement Pastes ◽  
Three Point Bending ◽  
Flexural Tensile Strength ◽  
Nucleation Sites ◽  
Effective Dispersion

Cement composites prepared with nanoparticles have been widely studied in order to achieve superior performance structures. The incorporation of carbon nanotubes (CNTs) is an excellent alternative due to their mechanical, electrical, and thermal properties. However, effective dispersion is essential to ensure strength gains. In the present work, cement pastes were prepared incorporating CNTs in proportions up to 0.10% by weight of cement, dispersed on the surface of anhydrous cement particles in isopropanol suspension and using ultrasonic agitation. Digital image correlation was employed to obtain basic mechanical parameters of three-point bending tests. The results indicated a 34% gain in compressive strength and 12% in flexural tensile strength gains, respectively, as well as a 70% gain in fracture energy and 14% in fracture toughness in the presence of 0.05% CNTs were recorded. These results suggest that CNTs act as crack propagation controllers. Moreover, CNT presence contributes to pore volume reduction, increases the density of cement pastes, and suggests that CNTs additionally act as nucleation sites of the cement hydration products. Scanning electron microscopy images indicate effective dispersion as a result of the methodology adopted, plus strong bonding between CNTs and the cement hydration product. Therefore, CNTs can be used to obtain more resistant and durable cement-based composites.

New developments in understanding the chemistry of cement hydration

1983 ◽  
Vol 310 (1511) ◽  
pp. 53-66 ◽  
Keyword(s):  
Cement Hydration ◽  
Hydration Product ◽  
Solution Chemistry ◽  
Strength Development ◽  
Microstructural Development ◽  
Cement Pastes ◽  
Complex Process ◽  
Calcium Aluminates ◽  
Colloidal Gel ◽  
Reaction With Water

Portland cement is based on calcium silicates with lesser amounts.of calcium aluminates. Its reaction with water, which is responsible for strength development, is a complex process involving the precipitation of hydration products in colloidal gel and crystalline forms. This paper describes the microstructural development of the hydrates the structure of colloidal C—S—H gel, which is the main hydration product, the kinetics of hydration and the aqueous solution chemistry of cement pastes and pastes made with pure C 3 S. Theories relating to the mechanism of cement hydration are examined and these are discussed in terms of studies of the effect of accelerating and retarding admixtures for cement.

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

Surface modifications for the effective dispersion of carbon nanotubes in solvents and polymers

Carbon ◽  
2012 ◽  
Vol 50 (1) ◽  
pp. 3-33 ◽  
Author(s):  
Sang Won Kim ◽  
Taehoon Kim ◽  
Yern Seung Kim ◽  
Hong Soo Choi ◽  
Hyeong Jun Lim ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Surface Modifications ◽  
Effective Dispersion

scholarly journals Reinforcing Effect of Carbon Nanotubes/Surfactant Dispersions in Portland Cement Pastes

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Oscar A. Mendoza Reales ◽  
Caterin Ocampo ◽  
Yhan Paul Arias Jaramillo ◽  
Juan Carlos Ochoa Botero ◽  
Jorge Hernán Quintero ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Cement Matrix ◽  
Multiwalled Carbon ◽  
Element Analysis ◽  
Cement Pastes ◽  
Reinforcing Effect ◽  
Linear Elastic ◽  
Crack Propagation Process ◽  
Negative Effect ◽  
The Individual

Decoupling the individual effects of multiwalled carbon nanotubes (MWCNTs) and surfactants when used as reinforcement materials in cement-based composites is aimed in this study. Powder MWCNTs were dispersed in deionized water using different types of surfactants as chemical dispersing agents and an ultrasonic tip processor. Cement pastes with carbon nanotubes additions of 0.15% by mass of cement were produced in two steps: first, the MWCNT/surfactant dispersions were combined with the mixing water, and then, cement was added and mixed until a homogeneous paste was obtained. Mechanical properties of the pastes cured at 7 days were measured, and their fracture behavior was characterized using the linear elastic finite element analysis. It was found that the reinforcing effect of MWCNT was masked by the negative effect of surfactants in the cement matrix; nevertheless, nanotubes were capable of increasing both stress and strain capacity of the composite by controlling the crack propagation process at the tip of the crack.

Assessment of Hydration Degree of Cement in the Fly Ash-Cement Pastes Based on the Calcium Hydroxide Content

2014 ◽  
Vol 875-877 ◽  
pp. 177-182 ◽  
Author(s):  
Xiang Li ◽  
Hua Quan Yang ◽  
Ming Xia Li
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Cement Hydration ◽  
Ash Content ◽  
Content Increase ◽  
Hydration Degree ◽  
Equilibrium Calculation ◽  
Cement Pastes ◽  
Cement Ratio ◽  
Water Cement Ratio

The hydration degree of fly ash and the calcium hydroxide (CH) content were measured. Combined with the equilibrium calculation of cement hydration, a new method for assessment of the hydration degree of cement in the fly ash-cement (FC) pastes based on the CH content was developed. The results reveal that as the fly ash content increase, the hydration degree of fly ash and the CH content decrease gradually; at the same time, the hydration degree of cement increase. The hydration degree of cement in the FC pastes containing a high content of fly ash (more than 35%) at 360 days is as high as 80%, even some of which hydrates nearly completely. The effect of water-cement ratio to the hydration degree of cement in the FC pastes is far less distinct than that of the content of fly ash.

Metal Coated Functionalized Single-Walled Carbon Nanotubes for Composites Application

2007 ◽  
Vol 561-565 ◽  
pp. 655-658 ◽  
Author(s):  
Qiang Zeng ◽  
Jennifer Luna ◽  
Y. Bayazitoglu ◽  
Kenneth Wilson ◽  
M. Ashraf Imam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Single Walled Carbon Nanotubes ◽  
Metal Composite ◽  
X Ray ◽  
Single Walled Carbon ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Metal Composite Materials ◽  
Walled Carbon Nanotubes

This study is considered as a method for producing multifunctional metal composite materials by using Single-walled Carbon Nanotubes (SWNTs). In this research, various metals (Ni, Cu, Ag ) were successfully deposited onto the surface of SWNTs. It has been found that homogenous dispersion and dense nucleation sites are the necessary conditions to form uniform coating on SWNTs. Functionalization has been applied to achieve considerable improvement in the dispersion of purified single-walled carbon nanotubes. A three-step electroless plating approach was used and the coating mechanism is described in the paper. The samples were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). The application of coated SWNTs in Titanium will be discussed in this paper.

scholarly journals N-Dopant-Mediated Growth of Metal Oxide Nanoparticles on Carbon Nanotubes

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1882
Author(s):  
Jin Ah Lee ◽  
Won Jun Lee ◽  
Joonwon Lim ◽  
Sang Ouk Kim
Keyword(s):  
Carbon Nanotubes ◽  
Metal Oxide ◽  
Carbon Nanomaterials ◽  
Wide Spectrum ◽  
Metal Oxide Nanoparticles ◽  
Nucleation And Growth ◽  
Oxide Nanoparticles ◽  
Metal Oxide Nanoparticle ◽  
Nucleation Sites ◽  
Direct Growth

Metal oxide nanoparticles supported on heteroatom-doped graphitic surfaces have been pursued for several decades for a wide spectrum of applications. Despite extensive research on functional metal oxide nanoparticle/doped carbon nanomaterial hybrids, the role of the heteroatom dopant in the hybridization process of doped carbon nanomaterials has been overlooked. Here, the direct growth of MnOx and RuOx nanoparticles in nitrogen (N)-doped sites of carbon nanotubes (NCNTs) is presented. The quaternary nitrogen (NQ) sites of CNTs actively participate in the nucleation and growth of the metal nanoparticles. The evenly distributed NQ nucleation sites mediate the generation of uniformly dispersed <10 nm diameter MnOx and RuOx nanoparticles, directly decorated on NCNT surfaces. The electrochemical performance of the resultant hybridized materials was evaluated using cyclic voltammetry. This novel hybridization method using the dopant-mediated nucleation and growth of metal oxides suggests ways that heteroatom dopants can be utilized to optimize the structure, interface and corresponding properties of graphitic carbon-based hybrid materials.

scholarly journals The Effect of Water Acrylate Dispersion on the Properties of Polymer-Carbon Nanotube Composites / Wpływ Wodnej Dyspersji Akrylanowej Na Właściwości Kompozytów Polimer-Nanorurki Węglowe

2015 ◽  
Vol 60 (4) ◽  
pp. 2715-2720
Author(s):  
P. Zygoń ◽  
M. Gwoździk ◽  
J. Peszke ◽  
Z. Nitkiewicz
Keyword(s):  
Carbon Nanotubes ◽  
Roughness Parameter ◽  
Composition Analysis ◽  
Phase Imaging ◽  
X Ray ◽  
Three Point Bending ◽  
Force Microscopy ◽  
Mode Method ◽  
Nanotube Composites ◽  
Crystallite Sizes

The paper presents properties of polymer composites reinforced with carbon nanotubes (CNT) containing various mixtures of dispersion. Acrylates of different particle size and viscosity were used to produce composites. The mechanical strength of composites was determined by three-point bending tests. The roughness parameter of composites was determined with a profilometer and compared with the roughness parameter determined via atomic force microscopy (AFM). Also X-ray studies (phase composition analysis, crystallite sizes determination) were carried out on these composites. Measurements of the surface topography using the Tapping Mode method were performed, acquiring the data on the height and on the phase imaging. The change of intensity, crystallite size and half-value width of main reflections originating from carbon within the composites have been determined using the X-ray analysis. The density of each obtained composite was determined as well as the resistivity at room temperature. The density of composites is quite satisfactory and ranges from 0.27 to 0.35 g/cm3. Different composites vary not only in strength but also in density. Different properties were achieved by the use of various dispersions. Carbon nanotubes constituting the reinforcement for a polymer composite improve the mechanical properties and conductivity composite.

Modification of Multilayer Carbon Nanotubes for the Removal of Arsenate

2016 ◽  
Vol 16 (4) ◽  
pp. 3835-3840
Author(s):  
Libing Liao ◽  
Gin-Lung Liu ◽  
Jiin-Shuh Jean ◽  
Wei-Teh Jiang ◽  
Zhaohui Li
Keyword(s):  
Carbon Nanotubes ◽  
Contact Time ◽  
Carbon Adsorbent ◽  
Superior Performance ◽  
Solution Ph ◽  
Nano Composite ◽  
X Ray ◽  
Multilayer Carbon Nanotubes ◽  
Removal Of Arsenic ◽  
Composite Carbon

The aim of this study was to explore a new nano-composite carbon adsorbent material for the removal of arsenic from water. The multilayer carbon nanotubes (MCNTs) were treated with different acids and/or modified with iron to create more surface COOH sites or Fe-impregnated MCNTs for the enhanced uptake of As(V). Tests were conducted as a function of initial As(V) concentrations, contact time, and solution pH. The coverage of ferric hydroxides on MCNTs and the uptake of As on Fe-MCNTs were independently confirmed by field emission scanning electron microscope and energy dispersive X-ray spectroscopy analyses. With an As(V) uptake capacities of 27 mg/g on Fe-MCNTs and 14 mg/g on acid-MCNTs, the material showed superior performance for As(V) removal.

Selectively oxidized carbon nanocatalysts for the oxidation of cis-cyclooctene

2018 ◽  
Vol 42 (3) ◽  
pp. 2306-2319 ◽  
Author(s):  
Bruno Jarrais ◽  
Alexandra Guedes ◽  
Cristina Freire
Keyword(s):  
Carbon Nanotubes ◽  
Superior Performance ◽  
Graphene Flake ◽  
Graphene Flakes ◽  
Oxidized Carbon ◽  
Multi Walled Carbon Nanotubes ◽  
Cyclooctene Epoxidation ◽  
Walled Carbon Nanotubes

Selectively oxidized multi-walled carbon nanotubes and graphene flakes showed superior performance in cis-cyclooctene epoxidation: 47% conversion and 79% selectivity for the best in class oxidized MWCNT, and 57% coversion and 85% selectivity for the best graphene flake material.

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