scholarly journals The Effect of Different Oxygen Surface Functionalization of Carbon Nanotubes on the Electrical Resistivity and Strain Sensing Function of Cement Pastes

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 807
Author(s):  
B. Del Moral ◽  
I. Martín Gullón ◽  
R. Navarro ◽  
O. Galao ◽  
F.J. Baeza ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Liquid Phase ◽  
Gas Phase ◽  
Functional Groups ◽  
Surface Oxidation ◽  
Cement Matrix ◽  
Strain Sensing ◽  
Cement Pastes ◽  
Functionalization Of Carbon Nanotubes

Different studies in the literature indicate the effectiveness of CNTs as reinforcing materials in cement–matrix composites due to their high mechanical strength. Nevertheless, their incorporation into cement presents some difficulties due to their tendency to agglomerate, yielding a non-homogeneous dispersion in the paste mix that results in a poor cement–CNTs interaction. This makes the surface modification of the CNTs by introducing functional groups on the surface necessary. In this study, three different treatments for incorporating polar oxygen functional groups onto the surface of carbon nanotubes have been carried out, with the objective of evaluating the influence of the type and oxidation degree on the mechanical and electrical properties and in strain-sensing function of cement pastes containing CNTs. One treatment is in liquid phase (surface oxidation with HNO3/H2SO4), the second is in gas phase (O3 treatment at 25 and 160 °C), and a third is a combination of gas-phase O3 treatment plus NaOH liquid phase. The electrical conductivity of cement pastes increased with O3- and O3-NaOH-treated CNTs with respect to non-treated ones. Furthermore, the oxygen functionalization treatments clearly improve the strain sensing performance of the CNT-cement pastes, particularly in terms of the accuracy of the linear correlation between the resistance and the stress, as well as the increase in the gage factor from 28 to 65. Additionally, the incorporation of either non-functionalized or functionalized CNTs did not produce any significant modification of the mechanical properties of CNTs. Therefore, the functionalization of CNTs favours the de-agglomeration of CNTs in the cement matrix and consequently, the electrical conductivity, without affecting the mechanical behaviour.

scholarly journals Chemical Functionalization of Carbon Nanotubes and its Effects on Electrical Conductivity

2014 ◽  
Vol 28 ◽  
pp. 51-61 ◽  
Author(s):  
José Encarnación Moreno Marcelino ◽  
Enrique Vigueras Santiago ◽  
Gustavo Lopez-Tellez ◽  
Susana Hernández López
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Electrical Conductivity ◽  
Functional Groups ◽  
Compression Technique ◽  
Chemical Functionalization ◽  
Mechanical Stirring ◽  
Chemically Modified ◽  
Functionalization Of Carbon Nanotubes ◽  
Microraman Spectroscopy

This work presents the study of the electrical conductivity in MWNT as a function of three different chemical functionalization conditions. Unmodified and chemically modified MWNT were characterized by microRaman spectroscopy, XPS and SEM whereas the electrical conductivity was determined by dust compression technique. MWNT were modified using three different oxidation conditions: (1) a mix of concentrated acids, H2SO4/HNO3 (3:1, v/v) sonicated for 2 h; (2) same mixture as (1) but using mechanical stirring for 6 h and (3) a reflux of an aqueous solution of HNO3 (20%, v/v) and mechanical stirring for 6 h. The characterization evidenced different functionalization degrees, based on the formation and detection of functional groups such as ether, carbonyl and carboxyl in different percentages. The unmodified CNT presented a conductivity of 510 S/m which decreased as the functionalization degree increased. For reactions (1) and (2) such conductivity was reduced by 8.8 and 15.5%, respectively, whereas for condition (3) it only decreased 0.98%.

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.

scholarly journals An Experimental Study on Static and Dynamic Strain Sensitivity of Smart Concrete Sensors Doped with Carbon Nanotubes for SHM of Large Structures

2018 ◽  
Author(s):  
Andrea Meoni ◽  
Antonella D'Alessandro ◽  
Austin Downey ◽  
Enrique García-Macías ◽  
Marco Rallini ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Reinforced Concrete ◽  
Experimental Testing ◽  
Dynamic Strain ◽  
Cement Matrix ◽  
Strain Sensitivity ◽  
Strain Sensing ◽  
Multi Walled Carbon Nanotubes ◽  
Material Fabrication ◽  
Smart Concrete

The availability of new self-sensing cement-based strain sensors allows the development of dense sensor networks for Structural Health Monitoring (SHM) of reinforced concrete structures. These sensors are fabricated by doping cement-matrix materials with conductive fillers, such as Multi Walled Carbon Nanotubes (MWCNTs), and can be embedded into structural elements made of reinforced concrete prior to casting. The strain sensing principle is based on the multifunctional composites outputting a measurable change in their electrical properties when subjected to a deformation. Previous work by the authors was devoted to material fabrication, modeling and applications in SHM. In this paper, we investigate the behavior of several sensors fabricated with and without aggregates and with different MWCNTs content. The strain sensitivity of the sensors, in terms of fractional change in electrical resistivity for unit strain, as well as their linearity are investigated through experimental testing under both static and dynamically varying compressive loadings. Moreover, the responses of the sensors when subjected to destructive compressive tests are evaluated. Overall, the presented results contribute to improving the scientific knowledge on the behavior of smart concrete sensors and to furthering their understanding for SHM applications.

scholarly journals Dispersion of Carbon Nanotubes with Different Types of Superplasticizer as a Dispersing Agent for Self-Sensing Cementitious Materials

2021 ◽  
Vol 11 (18) ◽  
pp. 8452
Author(s):  
Pedro de Almeida Carísio ◽  
Yasmim Gabriela dos Santos Mendonça ◽  
Carlos Fernando Teodósio Soares ◽  
Oscar Aurelio Mendoza Reales ◽  
Eduardo de Moraes Rego Fairbairn ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
Cement Pastes ◽  
Sensing Applications ◽  
Dispersing Agent ◽  
Vis Spectroscopy ◽  
Different Types ◽  
Conductive Fillers ◽  
Dispersing Agents

Due to their exceptional electrical properties, carbon nanotubes (CNTs) can be applied as conductive fillers to develop self-sensing cement-based matrices. In order to obtain an adequate self-sensing response, CNTs must be evenly dispersed through the cement matrix in a volume sufficient enough to create an electric percolation network. This is challenged by the difficulty of dispersing CNTs; therefore, there is a demand for an efficient dispersing agent that can be filled by superplasticiezers, which are products of known compatibility with cement and high availability. This research explores the use of four commercial superplasticizers available in Brazil, both naphthalene and ether polycarboxylate-based, as dispersing agents for CNTs in water. Ultrasonic energy was applied to aqueous solutions containing CNTs and superplasticizers. UV–Vis spectroscopy and ξ-potential measurements were used to investigate which superplasticizer was more effective to disperse the CNTs. Cement pastes were produced with the CNT dispersions and their electrical resistivity was measured. It was found that only superplasticizers without aliphatic groups in their structure were capable of dispersing CNTs in water. It was concluded that second-generation naphthalene-based superplasticizers were more efficient dispersing agents for CNTs than third-generation ether polycarboxylate-based ones for self-sensing applications.

Modification of Electrical and Mechanical Properties of Single Wall Carbon Nanotubes by Reaction with SOCl2

2003 ◽  
Vol 772 ◽  
Author(s):  
Urszula Dettlaff-Weglikowska ◽  
Viera Skakalova ◽  
Ralf Graupner ◽  
Lothar Ley ◽  
Siegmar Roth
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Functional Groups ◽  
Carboxyl Groups ◽  
Single Wall Carbon Nanotubes ◽  
Chemical Methods ◽  
Chemical Functionalization ◽  
Single Wall Carbon ◽  
Bucky Paper

AbstractAttaching chemical functional groups to single wall carbon nanotubes (SWNTs) has been achieved by chemical methods. Oxidized purified nanotubes have been treated by thionyl chloride in order to convert carboxyl groups into acylchloride groups. We observe by XPS and EDX that not only chlorine atoms but sulphur containing functional groups are covalently bound to the nanotubes. This chemical functionalization also causes significant changes in the electrical and mechanical properties of the nanotubes. The electrical conductivity measured on mats (bucky paper) increases from 500 S/cm in pristine tubes to 2500 S/cm in modified tubes. Similarly, the Young's modulus of bucky paper increases by about 100 %.

scholarly journals Infrared Spectroscopy of Ultraviolet-Irradiated Carbon Nanotubes

2020 ◽  
Vol 65 (4) ◽  
pp. 336
Author(s):  
I. Ovsiienko ◽  
T. Len ◽  
L. Matzui ◽  
O. Syvolozhskyi ◽  
D. Shpylka ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Infrared Spectroscopy ◽  
Functional Groups ◽  
Uv Irradiation ◽  
Relative Intensity ◽  
Multiwall Carbon Nanotubes ◽  
Short Term ◽  
Spectral Bands ◽  
Functionalization Of Carbon Nanotubes ◽  
Multiwall Carbon

The possibility of using the UV irradiation for a functionalization of carbon nanotubes with different degrees of structural perfection is considered. In investigations, the method of infrared spectroscopy is used. A change in the number of functional groups under the short-term UV irradiation of specimens with multiwall carbon nanotubes is estimated by a change in the relative intensity of the IR spectral bands corresponding to vibrations of the functional groups in comparison with the relative intensity of the band corresponding to vibrations of the carbon atoms in graphite.

scholarly journals Electrical Properties of Carbon Nanotubes Cement Composites for Monitoring Stress Conditions in Concrete Structures

2011 ◽  
Vol 82 ◽  
pp. 118-123 ◽  
Author(s):  
Luigi Coppola ◽  
Alessandra Buoso ◽  
Fabio Corazza
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Reinforced Concrete ◽  
Compressive Stress ◽  
Smart Materials ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Impact Loads ◽  
Pressure Sensitivity ◽  
Cement Pastes

Cement pastes reinforced with Multi-Walled carbon NanoTubes (MWNTs) are smart materials with piezoresistivity properties. Adding carbon nanotubes to the cement matrix, in fact, the electrical resistivity of cementitious composites changes with the stress conditions under static and dynamic loads. This particular behaviour can be used to evaluate the stress level in reinforced concrete structures, to monitor the traffic flow, to weigh vehicles. In this paper data on pressure-sensitive behaviour under compressive stress of cement pastes and mortars containing different percentages (from 0.0% to 1.0% vs. cement mass) of MWNTs are presented.In order to form a conductive network and enhancethe piezoresistive properties of cementitious mixtures, Carbon NanoTubes (CNTs) need to be efficiently dispersed in the cement matrix. Two different methods to disperse CNTsin the cement matrix were used. The first one uses a surfactant (Sodium Linear Alkyl Benzene Sulphonate - LAS): MWNTs were dispersed in a LAS aqueous solution,and thenmixed with cement and a defoamer (tributyl phosphate) to decrease the air bubble in MWNT filled cement-based composites. The second method consists in mixing CNTs with about 50% of the mixing water in a becker by means of a glass wand. Then, the solution is sonicated by an ultrasonic generator for 10 minutes. Finally, the sonicatedCNT-aqueous solution ismixed with cement (and sand for the mortars). The piezoresistivity properties of the cementitious mixtures manufactured with the two above mentioned CNTs dispersing methods will be compared.Experimental results show that the electrical resistance changes synchronously with the compressive stress levelsfor the specimens manufactured with both methods. Therefore, CNTs improve the pressure-sensitivity of cementitious composites. Moreover, the piezoresistive response is better for cementitious composites manufactured by using the surfactant agent to disperse CNTs. Data indicate that – thanks to the better dispersion of nanotubes promoted by the surfactant - the pressure-sensitivity properties of cement pastes can be achieved even by using a very low percentage of CNTS (0.1% vs. cement mass). These findings seem to indicate that self-sensing CNTs/cement composite can be produced. These smart materials have great potential and they could be used in the next future in concrete field for practical applications to monitor the stress level of reinforced concrete elements subjected to static, dynamic and impact loads. In particular, informations on actual stress existing under dynamic and impact loads could be improve design procedures in protective structures.

scholarly journals The Effect of Complex Modification on the Impedance of Cement Matrices

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 557
Author(s):  
Grigory Yakovlev ◽  
Černý Vít ◽  
Irina Polyanskikh ◽  
Anastasiya Gordina ◽  
Igor Pudov ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Negative Impact ◽  
Calcium Nitrate ◽  
Control Sample ◽  
Multiwall Carbon Nanotubes ◽  
Strength Loss ◽  
Cementitious Materials ◽  
Strength Properties ◽  
Cement Matrix

The research results presented in this article were obtained by joint scientific research on creatingcement materials with reduced impedance. It is known that functional additives added to impart electrically conductive properties have a negative impact on physical and mechanical characteristics of the material. This study suggests using the multiwall carbon nanotubes in the amount of 7% from binder mass as a functional additive. The results obtained prove that the addition of this amount of the modifier does not lead to a significant decrease of strength characteristics. Calcium nitrate in the amount of 1–7% was added in order to level the strength loss and to ensure the effective stable electrical conductivity. The multifunctionality of using this salt has been proven, which is manifested in the anti-frost and anticorrosive effects as well in enhancement of electrical conductivity. The optimal composition of the additive with 7% of carbon nanotubes and 3% of calcium nitrate ensures a reduced electrical impedance of cement matrix. The electrical conductivity was 2440 Ohm, while the decrease of strength properties was within 10% in comparison tothe control sample. The nature of changes in the microstructure were studied to determine the influence of complex modifications that showed significant changes in the morphology of the hydration products. The optimum electrical characteristics of cementitious materials are provided due to the uniform distribution of carbon nanotubes and the formation of a network of interconnected micropores filled with the solution of calcium nitrate that provides additional and stable electrical conductivity over time.

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