Papers by Keyword: MWNT

Abstract: Polyaniline (PAni) Nanocomposites Containinganiline (Ani) Monomer and Hexanoic Acid (HA) Dopant were Successfullysynthesized by Using Chemical Oxidation Method. Titanium Dioxide (TiO₂)and Different Dimension of Multiwall Carbon Nanotubes (MWNT) Have been Added Inorder to Improve the Dielectric Permeability and Magnetic Permittivityproperties of the Pani Nanocomposites. Fourier Transform Infrared (FTIR) Andultraviolet-Visible (UV-Vis) Spectra Confirmed the Chemical Structure of Paninanocomposites. Conductivity and Magnetization Behavior were Investigated Byresistivity Meter and Vibrating Sample Magnetometer (VSM). Microwave Absorptionstudies were Carried out by Microwave Vector Network Analyzer (MVNA) from 0.5to 18 Ghz. among all the Pani Nanocomposites, Pani Nanocomposites with MWNT (D = 10-2- Nm, l = 5-15 μm) Shows Agood Reflection Loss (RL = -58 Db) at 7 Ghz with a Sharp and Narrow Peak due Tohigher Values of Magnetization (0.074 Emu/g) Andmoderate Electrical Conductivity (1.11 x 10^-2 S/cm)

Abstract: Multi-walled carbon nanotube (MWNT) reinforced carbon foams were prepared by thermo-foaming of MWNT dispersions in molten sucrose followed by dehydration and carbonization. The rheological studies showed that the uniform dispersion of MWNT was achieved up to 1.5 wt.%. The carbon foams showed cellular structure. The density of the carbon foams increased with an increase in the MWNT concentration up to 0.25 wt.% and then remained more or less constant. The maximum compressive strength of 4.9 MPa was achieved at the MWNT concentration of 0.5 wt.%.

Abstract: 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%.

Abstract: Conductive polyacrylonitrile film reinforced by multiwall carbon nanotubes was prepared via ultrasonic dispersion and vacuum casting. The structure of MWNT/PAN composite film was characterized by WAXD and FT-IR. The LOI of the blend was enhanced from 18.1 % to 24.5 % and TGA show better thermal stability. MWNT composite at 10 wt% MWNT loading showed an electrical conductivity of 10^-2S/cm.

Abstract: Non-enzymatic biosensors employing multi-walled carbon nanotube (MWNT) with highly dispersed Pt-M (M = Ru, Sn, and Au) nanoparticles (Pt-M@MWNT catalysts) were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well-dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these non-enzymatic biosensors had larger currents (mA) than that of a bare glassy carbon (GC) electrode and one modified with MWNTs. The sensitivity (μA mM^-1), linear range (mM), and detection limit (mM) (S/N = 3) of the glucose biosensor with the Pt-Ru, Pt-Sn and Pt-Au catalysts in PBS electrolyte were determined, respectively. The experimental results show that such biosensors can be applied to glucose detection in food chemistry field.

Abstract: A series of novel conducting nanocomposite (NC) hydrogels, poly(N-isopropylacrylamide) /Clay/MWNT, were synthesized by in situ free-radical polymerization. The chemical structure of the gels was characterized by Fourier transform infrared spectroscopy (FTIR). The temperature responsive behaviors and mechanical properties were also investigated in detail. The prepared NC gels presented a rising volume phase transition temperature (VPTT) and enhanced mechanical properties. When the water content reached 700%, the conductivity increased from 0.46 to 1.09 ms•cm^-1 with the addition of MWNTs increasing from 0 to 1.19wt%. The improved mechanical strength and conductivity make the NC gels a potential material in the development of artificial muscles, biosensors, bioseparation and other advanced materials both academically and practically.

Abstract: Multi-walled carbon nanotubes (MWNT) were successfully chemically modified (MWNT-COOH) and reacted with polyethylene glycol (PEG) to prepare nanocomposites. As- prepared kinds of functionalized MWNT (MWNT-g-PEG) were characterized with FTIR, TGA and TEM. Nonisothermal crystallization kinetics of MWNT-g-PEG composites was investigated by differential scanning calorimeter (DSC). The kinetics was analyzed using the Ozawa and Avrami equation modified by Jeziorny. The results showed that the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the modified Avrami analysis could explain the behavior of MWNT-g-PEG nanocomposite only. It is observed that the presence of MWNT hindered the mobility of PEG chains and decreased the overall crystallization rate. It was found that the crystallization behavior of MWNT-g-PEG nanocomposite was strongly affected by the incorporation of MWNT. The data for the nonisothermal crystallization could be analyzed properly by the Avrami equation modified by Jeziorny. The results showed that the presence of MWNT decreased the overall nonisothermal crystallization rate of the PEG chains which were grafted onto the MWNT due to MWNT might act as physical hindrances retarding the mobility of PEG chains and decreased the crystallinity.

Abstract: The potential applications of carbon nanotubes are reviewed in this paper. With the development of modification and purification of carbon nanotubes, the scope of carbon nanotubes applications is expanded greatly. This paper pays attention to the modification and dispersion of multi-walled carbon nanotube (MWNTs). The results show that the acid treated MWNTs are highly pure and the surface of treated MWNTs is rough comparably. In addition, treated MWNTs are homogeneously dispersed without any surfactants present in organic solvents of acetone, toluene, and ethanol; the dispersive stability of carboxylic MWNTs dispersions is investigated over 2 weeks.

Abstract: Different opening and modifying methods of MWNTs are studied and compared in this paper. MWNTs are dipped in a refluxed HNO3 solution. The influence of temperature, concentration and holding time on the opening and modifying of MWNTs is studied. The compared process is that MWNTs are treated by O3. The solvent that can highly dissolve O3 and disperse MWNTs is crucial. In order to prompt the reaction, 1M CF3COOH is elected as reactant medium and catalysis. The opening of MWNTs is tested by BET and confirmed by TEM. The surface structure of MWNTs treated by different processes is analyzed by FT-IR. The optimum conditions of opening and modifying of MWNTs are discussed.

Abstract: In this article stable multi-walled carbon nanotubes (MWNTs) aqueous suspension with a 1.0 wt.% concentration was obtained with a very small quantity of dispersant. Precursor of ceramics were synthesized in the suspension and densely deposited on the surface of MWNTs successfully by a simple and effective in-situ precipitation method. The most important advantage for the in-situ composite method is to make MWNTs homogeneously distributed in the matrix. The fully dense compacts were obtained by spark-plasma-sintering (SPS) the in-situ precipitated composite powders at temperature 200 oC lower than that of composite powders made from the traditional mixing method. Furthermore, the microstructure and the mechanical property of the composites are much better than that of traditional method. The in-situ precipitation could be a promising method to fabricate CNTs composites of ceramics matrix especially those hard to sinter.