Reinforcing epoxy nanocomposites with functionalized carbon nanotubes via biotin–streptavidin interactions

We report on the preparation of nanocomposites consisting of biofunctionalized single-walled carbon nanotubes (BF-SWCNTs) reinforcing an ultraviolet curable epoxy polymer by means of biotin–streptavidin interactions. The as-produced laser ablation SWCNTs are biofunctionalized via acid oxidization based purification process and non-covalent functionalization using surfactant, followed by grafting the resulting nanotubes with biomolecules. The biotin-grafted nanotubes are capable of interacting with epoxy groups in presence of streptavidin molecules by which chemical bridges between BF-SWCNTs and epoxy matrix are formed. The biomolecules grafted to the nanotubes surface not only facilitate the load transfer, but also improve the nanotube dispersion into the epoxy matrix, as observed by optical imaging and scanning electron microscopy. Mechanical characterization on the nanocomposite microfibers demonstrates considerable enhancement in both strength (by 76%) and modulus (by 93%) with the addition of only 1 wt.% of BF-SWCNTs. The electrical measurements reveal a clear change in electrical conductivity of nanocomposite microfibers reinforced with 1 wt.% of BF-SWCNTs in comparison to the microfibers containing solely purified carbon nanotubes. These multifunctional nanocomposite materials could be used to fabricate macro and microstructures for a wide variety of applications such as high strength polymer nanocomposite and potential easily-manipulated biosensors

Direct-write fabrication of freestanding nanocomposite strain sensors

This paper deals with the design and microfabrication of two three-dimensional (3D) freestanding patterned strain sensors made of single-walled carbon nanotubes (SWCNTs) nanocomposites with the ultraviolet-assisted direct-write (UV-DW) technique. The first sensor consisted of three nanocomposite microfibers suspended between two rectangular epoxy pads. The flexibility of the UV-DW technique enables manufacturing the sensor and its housing in one monolithic structure. The second sensor was composed of a nanocomposite network consisting of four parallel microsprings, which demonstrates the high capability of the technique when compared to the conventional photolithographic technologies. The performances of the sensors were assessed under tension and compression, respectively. The sensors sensitivities were evaluated by correlating their measured resistivities to the applied displacements/strains. Electrical conductivity measurements revealed that the manufactured sensors are highly sensitive to small mechanical disturbances, especially for lower nanotube loadings when compared to traditional metallic or nanocomposite films. The present manufacturing method offers a new perspective for manufacturing highly sensitive 3D freestanding microstructured sensors

Structural Study of Asphaltenes from Iranian Heavy Crude Oil

In the present study, asphaltene precipitation from Iranian heavy crude oil (Persian Gulf off-shore) was performed using n-pentane (n-C5) and n-heptane (n-C7) as light alkane precipitants. Several analytical techniques, each following different principles, were then used to structurally characterize the precipitated asphaltenes. The yield of asphaltene obtained using n-pentane precipitant was higher than asphaltene precipitated with the use of n-heptane. The asphaltene removal affected the n-C5 and n-C7 maltene fractions at temperatures below 204°C, as shown by the data obtained through the simulated distillation technique. Viscosity of heavy oil is influenced by the asphaltene content and behavior. The viscosity dependence of the test heavy oil on the shear rate applied was determined and the flow was low at y. above 25 s-1 . The reconstituted heavy oil samples were prepared by adding different amounts of asphaltenes to the maltenes (deasphalted heavy oil) and asphaltene effects were more pronounced at the low temperature of 25°C as compared with those at the higher temperatures. According to the power law model used in this study the flowability of the test heavy oil exhibited a pseudoplastic character. Structural results obtained from Fourier Transform InfraRed (FTIR) spectroscopy showed the presence of the different functional groups in the precipitated asphaltenes. For instance, the presence of different hydrocarbons (aliphatic, aromatic and alicyclic) based on their characteristics in the FTIR spectra was confirmed. Resins are effective dispersants, and removal of this fraction from the crude oil is disturbing to the colloidal nature of heavy oil; asphaltene flocculation and precipitation eventually occur. Appearance of pores in the Scanning Electron Microscopy (SEM) images was used as an indicator of the resin detachment. With the use of 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy, two important structural parameters of the asphaltenes were determined. Namely, the aromaticity (fa) and the average number of carbon atoms per alkyl side chain (ncarbon), where fa for n-C5 asphaltenes was lower (0.39) than that obtained with n-C7 solvent (0.49). Additionally, the ncarbon parameter values were 7.7 and 5.7 for n-C5 and n-C7 asphaltenes, respectively. Structural recognition of the oil constituents is the prerequisite of different techniques usable for heavy oil upgrading

Structural Study of Asphaltenes from Iranian Heavy Crude Oil

In the present study, asphaltene precipitation from Iranian heavy crude oil (Persian Gulf off-shore) was performed using n-pentane (n-C5) and n-heptane (n-C7) as light alkane precipitants. Several analytical techniques, each following different principles, were then used to structurally characterize the precipitated asphaltenes. The yield of asphaltene obtained using n-pentane precipitant was higher than asphaltene precipitated with the use of n-heptane. The asphaltene removal affected the n-C5 and n-C7 maltene fractions at temperatures below 204°C, as shown by the data obtained through the simulated distillation technique. Viscosity of heavy oil is influenced by the asphaltene content and behavior. The viscosity dependence of the test heavy oil on the shear rate applied was determined and the flow was low at y. above 25 s-1 . The reconstituted heavy oil samples were prepared by adding different amounts of asphaltenes to the maltenes (deasphalted heavy oil) and asphaltene effects were more pronounced at the low temperature of 25°C as compared with those at the higher temperatures. According to the power law model used in this study the flowability of the test heavy oil exhibited a pseudoplastic character. Structural results obtained from Fourier Transform InfraRed (FTIR) spectroscopy showed the presence of the different functional groups in the precipitated asphaltenes. For instance, the presence of different hydrocarbons (aliphatic, aromatic and alicyclic) based on their characteristics in the FTIR spectra was confirmed. Resins are effective dispersants, and removal of this fraction from the crude oil is disturbing to the colloidal nature of heavy oil; asphaltene flocculation and precipitation eventually occur. Appearance of pores in the Scanning Electron Microscopy (SEM) images was used as an indicator of the resin detachment. With the use of 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy, two important structural parameters of the asphaltenes were determined. Namely, the aromaticity (fa) and the average number of carbon atoms per alkyl side chain (ncarbon), where fa for n-C5 asphaltenes was lower (0.39) than that obtained with n-C7 solvent (0.49). Additionally, the ncarbon parameter values were 7.7 and 5.7 for n-C5 and n-C7 asphaltenes, respectively. Structural recognition of the oil constituents is the prerequisite of different techniques usable for heavy oil upgrading