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.

Control of multiwall carbon nanotubes dispersion in polyamide6 matrix: An assessment through electrical conductivity

2006 ◽  
Vol 432 (4-6) ◽  
pp. 480-485 ◽  
Author(s):  
Pravin V. Kodgire ◽  
Arup R. Bhattacharyya ◽  
Suryasarathi Bose ◽  
Nitin Gupta ◽  
Ajit R. Kulkarni ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Multiwall Carbon Nanotubes ◽  
Multiwall Carbon

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.

Simultaneous enhancement in mechanical strength, electrical conductivity, and electromagnetic shielding properties in PVDF–ABS blends containing PMMA wrapped multiwall carbon nanotubes

2015 ◽  
Vol 17 (22) ◽  
pp. 14856-14865 ◽  
Author(s):  
Goutam Prasanna Kar ◽  
Sourav Biswas ◽  
Suryasarathi Bose
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Mechanical Strength ◽  
Multiwall Carbon Nanotubes ◽  
Electromagnetic Shielding ◽  
Unique Approach ◽  
Shielding Properties ◽  
Multiwall Carbon

A unique approach was adopted to drive the multiwall carbon nanotubes (MWNTs) to the interface of immiscible PVDF–ABS blends by wrapping the nanotubes with a mutually miscible homopolymer (PMMA).

scholarly journals Fabrication of Metal Alloy-Deposited Flexible MWCNT Buckypaper for Thermoelectric Applications

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Jih-Hsin Liu ◽  
Hsin-Yuan Miao ◽  
Saravanan Lakshmanan ◽  
Li-Chih Wang ◽  
Ren-Hui Tsai
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermal Evaporation ◽  
Multiwall Carbon Nanotubes ◽  
Metal Alloys ◽  
Thermal Evaporation Method ◽  
In Series ◽  
Multiwall Carbon ◽  
Temperature Resistivity

We report the fabrication of a flexible network of multiwall carbon nanotubes (MWCNTs) known as buckypaper (BP) for thermoelectric (TE) applications. A thermal evaporation method was used to deposit TE metal alloys onto the BP. The TE properties were improved primarily by increasing the Seebeck coefficient values (50 and 75 μV/K) and the electrical conductivity by approximately 10 000 S/m. High-temperature resistivity studies were performed to confirm the semiconductivity of buckypaper. Variations in resistivity were observed to be the result of the metal alloys coated on the BP surface. We also demonstrated that a substantial increase in the Seebeck coefficient values can be obtained by connecting 3 and 5 layers of metal-deposited BP in series, thereby enhancing the TE efficiency of MWCNT-based BP for application in thermoelectric devices.

scholarly journals Incorporation of Functionalized Multiwall Carbon Nanotubes into a Polyurethane Matrix

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Martin Michálek ◽  
Michael Bredol
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Percolation Threshold ◽  
Aqueous Suspension ◽  
Sodium Dodecyl ◽  
Multiwall Carbon Nanotubes ◽  
Glass Substrates ◽  
Functionalized Mwcnts ◽  
Multiwall Carbon

Functionalized and raw multiwall carbon nanotubes (MWCNTs) were investigated colloid-chemically in order to study the role of polar versus nonpolar interaction with a polyurethane (PU) matrix. Both kinds of MWCNTs were dispersed by ultrasonication in the presence of a surfactant (sodium dodecyl sulphate) in aqueous solution. Functional groups on the nanotube surface were characterized by infrared spectroscopy and by theζ-potential in aqueous suspension. Such suspensions were added to waterborne PU dispersions, drop-cast on glass substrates and cured. The percolation threshold for electrical conductivity with polar (functionalized) MWCNTs was reached at 0.24 wt.%, whereas at concentrations as high as 2 wt.%, PU films with nonpolar MWCNTs stayed below the percolation threshold. With an addition of 0.4 wt.% polar MWCNTs, the electrical conductivity increased to >10−6 S/cm in the cured coating layer. These results are interpreted with respect to the chemical nature of the PU matrix.

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