Nano Hybrids and Composites
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Published By Trans Tech Publications

2297-3400

2021 ◽  
Vol 33 ◽  
pp. 47-60
Author(s):  
Syed Sajid Ali Shah ◽  
Habib Nasir ◽  
Shehla Honey

In this work, graphene was produced by liquid-phase exfoliation of graphite in different organic solvents with addition of picric acid. The graphene was easily produced by one step ultra-sonication of graphite powder in the organic solvents. The addition of picric acid has increased the graphene production yield in most of the solvents tested in this work. Picric acid serves as a “molecular wedge” to intercalate into the edge of graphite, which plays a key role during sonication and significantly improves the production yield of graphene. The products were analyzed by microscopic techniques, including atomic force microscopy (AFM) and scanning electron microscope (SEM). The AFM images indicate that the exfoliation efficiency and amount of graphene increased by addition of picric acid in organic solvents. Moreover, the AFM images also indicate presence of bilayer graphene. SEM analysis also shows that the addition of picric acid into the organic solvent favors the exfoliation process. The produced graphene was also analyzed by XRD, FTIR, Raman and UV-visible spectroscopy. The XRD results illustrate that exfoliation was best achieved in N-methyl-2-pyrrolidone (NMP) as a solvent. FTIR and Raman results indicate that addition of picric acid has slightly defected the produced graphene surface. The amount of graphene concentration was calculated by using Beer Lambert law, and it was observed that the graphene production yield was increased by using picric acid in most of the solvents. The maximum amount of graphene concentration (0.159 mg/ml) was achieved by adding 30 mg of picric acid in NMP.


2021 ◽  
Vol 33 ◽  
pp. 35-46
Author(s):  
Ankita Pandey ◽  
Abhishek Kumar Gupta ◽  
Shivani Gupta ◽  
Sarvesh Kumar Gupta ◽  
Rajesh Kumar Yadav

Polysaccharide biopolymer Agar-Agar extracted from red algae is a natural and biodegradable polymer. It is a combination of agarose (a neutral and linear polymer, with repeated units of agarobiose) and a heterogeneous mixture of agaropectin (a charged sulfated polymer). In this study, a comparative study of structural vibrational and electrochemical properties of agar-agar biopolymer with two different methods HF (Hartree-Fock) and DFT (Density Functional Theory) using a basis set 631+G (d, p) is performed. The comparative structural study of agar-agar biopolymer by HF and DFT method has been carried out to calculate the stability of the molecule. The thermionic properties and Mulliken charge distribution are analysed to deliver a quantitative study of partial atomic charge distribution. The overall vibrational analysis of primal modes of the biopolymer has been studied using FTIR analysis. Based on highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) composition and energies, various chemical parameters of the biopolymer have been evaluated. The Physico-chemical properties of this polysaccharide show a strong correlation with its optimized structure. Agar-agar has its application in the electrochemical, biotechnological, and pharmaceutical fields, as a stabilizer and gelling material.


2021 ◽  
Vol 33 ◽  
pp. 61-72
Author(s):  
Paolo Di Sia

Graphene has particularly interesting chemical and physical properties, including high chemical and mechanical resistance, excellent thermal and electric transport, high transparency. It combines the peculiarity of being an extremely light material with exceptional mechanical strength properties. Micro/nanoelectronics represents one of the key enabling technologies (KETs) of the future; it is the basis of innovation and competitiveness of almost all scientific and applicative sectors. Activities involving it are aimed at the development of new materials, processes, devices and technologies in a wide range of sectors, involving quantum information manipulation, multi-functional platforms, advanced materials, devices on flexible substrates. In the field of sensoristics, it is possible to create devices for applications in most sectors of global interest, such as punctual sensors, biosensors, specific transducers, multisensoristic systems, flexible sensoristic systems, multifunctional systems, advanced MEMS/MOEMS technologies for sensoristics, micro/nanoactuators, devices for energy convertion, gravimetric-electrochemical sensors. The paper provides an interesting overview of the possible applications of graphene in relation to its mechanical, thermal and optical properties, and relatively to the gas and biological sensoristic aspects, so as interesting informations for the increase in nanobio-devices performance by last efforts in theoretical nanophysics.


2021 ◽  
Vol 33 ◽  
pp. 83-92
Author(s):  
Hadj Mostefa Adda ◽  
Bouchafa Ali ◽  
Merdaci Slimane

This paper introduces the analytical solutions of complex behavior analysis utilizing high-order shear deformation plate theory of functionally graded FGM nano-plate content consisting of a mixture of metal and ceramics with porosity. To incorporate the small-scale effect, the non-local principle of elasticity is used. The impact of variance of material properties such as thickness-length ratio, aspect ratio, power-law exponent and porosity factor on natural frequencies of FG nano-plate is examined. Compared to those achieved from other researchers, the latest solutions are. Using the simulated displacements theory, equilibrium equations are obtained. Current solutions of the dimensionless frequency are compared with those of the finite element method. The effect of geometry, material variations of nonlocal FG nano-plates and the porosity factor on their natural frequencies are investigated in this review. The results are in good agreement with those of the literature.


2021 ◽  
Vol 33 ◽  
pp. 93-103
Author(s):  
Wasan R. Saleh ◽  
Salma M. Hassan ◽  
Samar Y. Al-Dabagh ◽  
Marwa A. Marwa

Infrared photoconductive detectors working in the far-infrared region and room temperature were fabricated. The detectors were fabricated using three types of carbon nanotubes (CNTs); MWCNTs, COOH-MWCNTs, and short-MWCNTs. The carbon nontubes suspension is deposited by dip coating and drop–casting techniques to prepare thin films of CNTs. These films were deposited on porous silicon (PSi) substrates of n-type Si. The I-V characteristics and the figures of merit of the fabricated detectors were measured at a forward bias voltage of 3 and 5 volts as well as at dark and under illumination by IR radiation from a CO2 laser of 10.6 μm wavelengths and power of 2.2 W. The responsivity and figures of merit of the photoconductive detector are improved by coating the MWCNTs films with a thin layer of a blend (polyaniline - polymethyl methacrylate) polymer with methylene blue dye. The coated MWCNTs films showed better performances, so this type of coating can be considered as a surface treatment of the detector film, which highly increased the responsivity and specific detectivity of the fabricated IR laser detector-based MWCNTs. The photocurrent response for the coated films was increased about 25 times than that for uncoated films. The results proved the role of the polymer in the enhancement of the performance of the IR photoconductive detectors. Keywords: Carbon nanotubes, Infrared detector, Polyaniline polymer, Polymethyl methacrylate polymer, Methyl Blue dye.


2021 ◽  
Vol 33 ◽  
pp. 73-81
Author(s):  
Amirouche Bouamer ◽  
Nasser Benrekaa ◽  
Abderrahmane Younes

In this work, we investigated the influence of physical aging on polylactic acid (PLA) films using thermal and optical techniques; Differential Scanning Calorimetry (DSC), Thermally Stimulated Depolarization Current (TSDC), and Attenuated Total Reflection Spectroscopy (ATR). The PLA films were aged for different periods: 60, 90, and 120 minutes at a temperature Ta = 43 °C. The result obtained by DSC showed that the effect of physical aging appeared as an endothermic peak, which increased with increasing aging time and evolved towards higher temperatures. TSDC results showed a thermal current peak located between 30 and 80 ° C, which represented the main relaxation mode (α relaxation) of the dielectric manifestation of the glass transition. The intensity of this peak decreased and was shifted to higher temperatures when aging time increased, this result can be explained by a decrease in the molecular mobility of macromolecular chains due to the decrease in the free volume. The effect of physical aging on the PLA by the ATR technique showed a gradual decrease in all absorption bands during the aging period. In particular, the wide absorption band between 3000 and 3700 cm-1 attributed to the hydroxyl group (OH), which disappeared after two hours of aging


2021 ◽  
Vol 33 ◽  
pp. 105-132
Author(s):  
Fateme Shayestenia ◽  
Mohadese Janmohammadi ◽  
Seyedabbas Sadatsakkak ◽  
Majid Ghadiri

Analysis of vibration stability of simply supported Euler-Bernoulli functionally graded (FG) nanobeam embedded in viscous elastic medium with thermal effect under external parametric excitation is presented in this work. An attempt has been made for the first time is investigating the effect of thermal load on dynamic behavior, amplitude response, instability region and bifurcation points of functionally graded nanobeam. Thermal loads are supposed to be uniform, linear or nonlinear distribution along the thickness direction. Nonlocal continuum theory and the principle of the minimum total potential energy are applied to derive the governing equations. The partial differential equations (PDE) are transported to the ordinary differential equations (ODE) by using the Petrov-Galerkin method and the multiple time scales method are manipulated to solve the motion equation. To study the effect of external parametric excitation and thermal effect, different temperature distributions along the thickness such as uniform, linear, and nonlinear distribution are considered. Moreover, stable and unstable regions and bifurcation points are determined. It is obtained that the thermal load can affect the amplitude response of FG nanobeam. Also, it is observed that the instability of the system is affected by the detuning parameter and the parametric excitation amplitude plays great role in the instability of system. Nanobeams are used in many devices like nanoresonators, nanosensors and nanoswitches. This paper is helpful for designing and manufacturing nanoscale structures specially nanoresonators under different thermal loads.


2021 ◽  
Vol 33 ◽  
pp. 13-34
Author(s):  
Alaa A. Mohammed ◽  
Jawad K. Oleiwi ◽  
Emad S. Al-Hassani

Polyetheretherketone (PEEK), as implants is broadly employed in orthopedic and dental uses owing to the brilliant chemical stability, biocompatibility and mechanical strength in addition to the modulus of elasticity alike the human bone. In the present work, the composite materials with PEEK as matrix and (n-HAp, n-TiO2) as the reinforced fillers loaded up to (1.5 wt%) were prepared by internal mixer and hot press. Following analysis by physical properties includes the thermal conductivity and the differential scanning calorimetry. Finite element analysis (FEA) was used to find the total deformation, Max. Von mises stress, elastic strain and safety factor. The results manifested that the thermal properties, total deformation and strain decreased with the increase of the reinforcement weight fraction, while, the stress and safety factor increased with the increased reinforcement weight fraction.


2021 ◽  
Vol 33 ◽  
pp. 1-11
Author(s):  
Md. Farhad Ali ◽  
Md. Sahadat Hossain ◽  
Samina Ahmed ◽  
A.M. Sarwaruddin Chowdhury

Now a days environment is getting polluted due to different types of manmade reasons than ever for extreme use of synthetic materials. Various kinds of waste materials from numerous industries are also enhancing this. So, Utilization of waste materials and reduction of synthetic materials will definitely subside the environmental pollution. In this research, waste jute fabric and leather waste (cow hides) were used as reinforcing agent and unsaturated polyester resin (UPR) as matrix to prepare environmental friendly composite materials. Hand-lay up method was conducted to fabricate composite materials. Different percentages of waste leather and used jute fabrics were used with the UPR. Improved mechanical properties, tensile strength (TS), tensile modulus (TM), and percentage elongation at break (EB) were observed with the certain percentage of waste materials. Composites were also characterised by the scanning electron microscope (SEM) and fourier transform infrared (FTIR).


2021 ◽  
Vol 32 ◽  
pp. 45-62
Author(s):  
Mohamed Khodjet Kesba ◽  
Noureddine El Meiche ◽  
A. Benkhedda

The influence of linear and non-linear temperature and moisture concentration distribution on the stress distribution was studied for metal/ceramic sandwich plate with transverse cracks. An interlaminar adhesive layer between two different layers is taken into account which transferring the normal stress and the interlaminar shear stress. The validation of the used model was done with the comparison of the stiffness reduction as a function of crack density and the experimental data. A comparison showed that a satisfactory qualitative and quantitative agreement was obtained. The temperature and moisture concentration variation are studied using the linear and non-linear distribution around the cracks to predict the stress distributions along the axis x. Finally, it observed through this study that the variations of the thermal and moisture concentration distribution largely impact the stress distribution for a sandwich plate with transverse cracks in the central layer and also with different mechanical properties of each layers.


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