Robiul Islam Rubel; Md. Hasan Ali; Md. Abu Jafor; Sk. Suzauddin Yusuf
Abstract
The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The ...
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The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The CNT reinforced composite materials harvest the dual benefit of alloying metals with high mechanical properties of CNTs. Besides, the materials being innovated must have good forming or machining characteristics. However, no machining data or machining model are yet available for these newly developed composites. In this work, the mechanical machining of metal-matrix/CNTs composites has studied to review the available data and better understanding the material removal behaviour. The work also concludes on the suggestive machining techniques adopted that will not affect the structural deformation, mechanical, thermal, electrical properties as well as must not alter the mechanical characteristics of the machined surface. The present study will assist in optimizing the manufacturing composites with desirable mechanical properties in future CNT reinforced composite developments. Copyright © VBRI Press.
Romina P. Ollier*; Jimena S. Gonzalez;Vera A. Alvarez; Laura M. Sanchez
Abstract
Hydrogels are one of the most widely employed materials in biological, medical and technological areas. However, the use of hydrogels sometimes is restricted due to their specific properties. It is well-known that polymeric nanocomposites reinforced with clays show valuable improvements in their properties. ...
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Hydrogels are one of the most widely employed materials in biological, medical and technological areas. However, the use of hydrogels sometimes is restricted due to their specific properties. It is well-known that polymeric nanocomposites reinforced with clays show valuable improvements in their properties. In this work, eco-friendly composite hydrogels were prepared employing polyvinylalcohol (PVA) and bentonite (abundant and low cost smectite-type clay in Argentina) as raw materials through the previously optimized freezing-thawing (F-T) crosslinking method. Different nanocomposite hydrogels were obtained by varying the corresponding reactor feed. These materials have been recently chemically, morphologically and mechanically analysed in a recent work. Specifically, in the present work, thermal degradation behaviour of PVA-bentonite hydrogels was studied. Kinetic analytical models were applied to non-isothermal thermogravimetric (TGA) measurements trying to identify the possible mechanism for PVA degradation in the presence of bentonite.
R. K. Goyal; R. Sulakhe
Abstract
The preparation, electrical and thermal properties of nickel (Ni) particles filled poly(vinylidene fluoride) (PVDF) composites were discussed in this paper. The experimental density of the composites was close to that of theoretical density. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy ...
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The preparation, electrical and thermal properties of nickel (Ni) particles filled poly(vinylidene fluoride) (PVDF) composites were discussed in this paper. The experimental density of the composites was close to that of theoretical density. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that PVDF has primarily α-phase. The coefficient of thermal expansion of the composites decreased approximately 30 % compared to pure PVDF. The percolation threshold of the composite is about 5 vol% Ni, which is less than one-third of the value reported for metal filled polymer composites in the literature. The significantly lower percolation was attributed to the increased crystallinity and the better processing method which results in an easy formation of 3-dimensional network of Ni particles in the matrix, as confirmed by scanning electron microscopy (SEM). The electrical conductivity of these composites increased from 6.3×10 -13 S/cm to 2.6×10 -1 S/cm which is better and comparable than those of required for antistatic (10 -4 -10 -8 S/cm) and electromagnetic interference (EMI) shielding applications. The significant increase in electrical and thermal properties showed that these composites might be potential candidates for the EMI shielding and antistatic devices.
S. Kumari; A. Kumar; P. R. Sengupta; P. K. Dutta; R. B. Mathur
Abstract
Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for ...
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Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for structural, mechanical, electrical and thermal properties w.r.t. different mass fraction of MWCNT in C-Cu matrix. In comparison to C/Cu composite, addition of minute amount (0.25 wt%) of CNT in C-Cu substantially improved the mechanical, electrical and thermal properties of composites. These composites were mechanically stable and strong and exhibited high bending strength of 162 MPa, indicating a homogeneous dispersion of MWCNTs in the C-Cu matrix. Maximum thermal conductivity of 37.60 W/mK perpendicular to the pressing direction was obtained for 0.50 wt% CNT reinforced C-Cu composite exhibiting an improvement of 45% over pure C-Cu composite processed under identical conditions. High thermal conducting and mechanically strong composites can be used as heat sink for long time.
Abstract
In the present contribution, it has been reported about the effect of solvent, solvent concentration, flow rate and applied voltage on the fabrication of electrospun polycarbonate (PC) nanofibers. The morphology of fibers was studied by optical and scanning electron microscope. It is observed that morphology ...
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In the present contribution, it has been reported about the effect of solvent, solvent concentration, flow rate and applied voltage on the fabrication of electrospun polycarbonate (PC) nanofibers. The morphology of fibers was studied by optical and scanning electron microscope. It is observed that morphology of fibers depends upon the concentration of PC or viscosity of the solution, vapor pressure and diffusion coefficient of solvent. In fact, when viscosity of the solution is very low, beads or droplets are formed instead of fibers. The same problem arises when the viscosity of the solution is too high due to high surface tension. In this case, jet formation will not be observed and the solution will coagulate at the tip of needle. Tetrahydrofuran (THF) easily diffuses with polymer, at higher concentration of PC and at higher flow rate of solution; fibers of micron size are formed because of high vapor pressure of THF. On the other hand, in case of mixed solvents (DMF and THF), by controlling processing parameters one can get fiber diameter up to 200 nm. The study of Differential Scanning Calorimetry (DSC) indicates that less amount of heat energy is absorbed during endothermic reaction and there is a slight increase in glass transition temperature of nanofibers. Thermogravimetric analysis (TGA) shows an increase in thermal stability of PC nanofibers by 40ºC as compared to PC granules. This is due to the alignment of PC polymeric chains during stretching and whipping that occurs while electro spinning process.
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