جستجوی مقالات مرتبط با کلیدواژه « nanocomposites » در نشریات گروه « مواد و متالورژی »

In the present work we report the development of carbon nanotube reinforced copper-zinc alloy nanocomposites. The carbon nanotubes were used in both uncoated and nickel coated conditions to reinforce copper matrix. The nanocomposites with different carbon nanotubes (0.25 to 1.0) weight percentage were developed using a combination of ultrasonication, ball milling and sintering processes. The developed nanocomposites were subjected to microstructural characterization using scanning and transmission electron microscopes to observe the dispersion of carbon nanotubes. The effect of carbon nanotubes on friction and wear properties of copper nanocomposites were studied using pin on disc testing rig as per ASTM G99 standard. The coefficient of friction of both 1 wt% uncoated and nickel coated carbon nanotubes reinforced nanocomposites was found when compared to copper-zinc alloy. Similarly the wear rate of nanocomposites were found to decrease with the incoporation of carbon nanotubes. The low coefficient of friction and wear rate were attributed to uniform dispersion of carbon nanotubes and formation of carbonaceous layer on the surface of nanocomposites during dry sliding wear.

After the discovery of carbon nanotubes, observations showed that carbon nanotubes have multi-purpose properties and can be used as a reinforcing material for metal nanocomposites. In this research, multi-walled carbon nanotubes have been used as nanocomposite reinforcement with Cu-5Zn alloy base. Carbon nanotubes were added to the nanocomposite in percentages of 0.25-1. Ultrasonic waves were used for good dispersion of carbon nanotubes in the field. Pressing and sintering processes were used to make nanocomposite samples. The microstructure was studied using a scanning electron microscope. The effect of carbon nanotubes on mechanical properties such as microhardness and tensile strength of nanocomposite was investigated. The results showed that the mechanical properties are improved by adding carbon nanotubes. The proposed mechanism for increasing the strength in nanocomposites reinforced with carbon nanotubes is the bridging mechanism. The microhardness of nanocomposites increases linearly with the increase of carbon nanotubes up to 0.75%, and the increase in hardness of nanocomposite with carbon nanotube reinforcing phase is 36% more than copper-zinc base alloy. The tensile strength of copper nanocomposites is 289 MPa by increasing the amount of carbon nanotube reinforcement, which is a significant increase compared to the base copper-zinc alloy with a strength of 165 MPa.

Nanocomposites are widely used in dental restorative materials and medical equipment, among the most important of which, polymer-based nanocomposites can be mentioned. One of the most useful biocompatible polymers in this field is polymethylmethacrylate (PMMA). In the present study, the numerical analysis of the fatigue behavior of polymethyl methacrylate nanocomposite reinforced with hydroxyapatite nanoparticles has been investigated. For this purpose, standard samples of nanocomposite were made and their mechanical properties were investigated. To study the fatigue behavior and life cycle, a notched model was simulated in Abaqus and Fe-Safe software, and the data obtained from the tensile test were used as the mechanical properties of the material. By adding nanoparticles to the pure polymer, Young's modulus and tensile strength of the part, as well as the life cycle, were improved; However, it was observed that with the addition of more nanoparticles, the mechanical properties and the life cycle decreased slightly, which was caused by the accumulation of nanoparticles on the surface of the nanocomposite, which leads to a decrease in the strength of the samples.

In this research, the mechanical properties of polyamide 6/polyolefin elastomer (PA6/POE) blends reinforced with carbon nanotubes have been studied. Nanocomposites consisted of 10 and 20 wt% polyolefin elastomer, 0, 1, 2 and 3 wt% carbon nanotubes (MWCNT) and 5 and 10 wt% maleic anhydride (POE-gMA as compatiblizing agent) were made by an internal mixer based on the full factorial design of experiment. Tensile and impact tests were performed to extract mechanical properties including tensile strength, elastic modulus and impact strength. Scanning electron microscope (SEM) were used to observe the dispersion and distribution quality of MWCNT in the matrix. SEM images showed an acceptable distribution of carbon nanotubes up to 2 wt% in both polyamide matrices with 10 and 20 wt%, while adding 3 wt% of nanotubes in both matrices was associated with nanotubes accumulation. The test results showed that the addition of 2 wt% of carbon nanotubes improved the tensile strength and elastic modulus of the compounds by %21 and %23, respectively. the surfaces extracted from full factorial design method showed that there are no notable interaction between the input parameters in the case of mechanical properties. Finally, the R-squared above %92 for all mechanical properties showed that there is a good agreement between the experimental results and the extracted regression models.

In this article, the effect of adding nanoparticles into the matrix on improving the buckling strength of polymeric nanocomposite plates was investigated through finite element analysis. Two types of nanoparticles, including Carbon nanotubes (CNTs) and Nanoclays with different volume fractions (VF), were added randomly into the Epoxy matrix and mechanical properties of the reinforced matrix were estimated using simulation of a representative volume element (RVE). Moreover, a python script was generated to distribute CNT nanoparticles in aligned orientations and calculate the equivalent Young's modulus in horizontal and vertical directions. Afterwards, the critical buckling load of nanocomposite plates made of unidirectional glass fibers and nanoparticle reinforced Epoxy matrix were studied, using Eigenvalue analysis. Results were validated by previous studies and a very good agreement was obtained. In general, adding nanoparticles into the matrix led to increasing the critical buckling load with an increase of nano-additive’s VFs. When nanoparticles were dispersed aligned with fiber directions, which is the same as loading direction, a higher increase of critical buckling load was observed. For the case of reinforcing pure polymeric plates without fibers, when nanoparticles were aligned in the longitudinal direction, axial critical buckling load rose to 55.3%, whereas for the random distribution, it was increased by 14.2%. Finally, a parametric study was conducted to evaluate the effect of nanoparticle orientations, the aspect ratio of plates, transverse loading, type, and volume fraction of nano-additives on the critical buckling load of polymeric plates.

In this paper, the mechanical properties of nanocomposites based on a matrix of two phases of polyamide 6 polymer and ethylene propylene diene monomer (EPDM) reinforced with carbon nanotubes are investigated. The compounds include 0%, 1%, 2% and 3% by weight of carbon nanotubes as well as 5 and 10% by weight of EPDM-G-MA as compatible and 10 and 20% by weight of EPDM prepared by an internal mixer. Samples were prepared for mechanical tests by a hot press machine. Mechanical tests were performed to determine the impact and tensile strengths, modulus of elasticity and elongation at failure. It was observed that adding 1% by weight of carbon nanotubes increases the impact strength by 12%, tensile strength by 25% and elastic modulus by 43%, but decreases the failure length by 13%. Also, with the presence of 10% EPDM, impact strength increased by 27% and elongation at fracture by 34%, but the tensile strength of polyamide decreased by 5% and its elastic modulus by 19%. To improve the mentioned cases, by adding 5% EPDM-G-MA, the impact strength increased by 14%, the tensile strength by 5%, the elastic modulus by 20% and the elongation at break by 13%. Finally, by adding carbon nanotubes and combining EPDM and EPDM-G-MA, all the mechanical properties mentioned in polyamide 6 were improved

In this research, WS2 nanoparticles were synthesized using hydrothermal method and then added to aluminum matrix as reinforcement. Nanocomposites were fabricated by powder metallurgy processing followed by Spark Plasma Sintering (SPS) consolidation. Transmission electron microscopy (TEM) and XRD of synthesized powder showed WS2 nanoparticles were synthesized successfully. Microstructural properties of nanocomposites were investigated using optical microscopy (OM), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). Nanoparticles were well distributed in the aluminum matrix and have a good dispersion. The presence of nanoparticles in the matrix reduces the size of the grain less than 20 µm so that the size of the grain becomes smaller by increasing the amount of nanoparticles .The density of the sample showed that the nanocomposite had a very good compressibility and relative density reach to near 99% in 4wt. %WS2. Hardness and compressive strength of nanocomposites were evaluated. Mechanical evaluations indicated that, the increase in weight fraction of WS2 nanoparticles, resulted in improvement of hardness and compressive strength of aluminum. Concentration of tungsten disulfide nanoparticles has a direct effect on increasing the mechanical properties of nanocomposite. The compressive strength increased up to 120 MPa, about twice the base metal, and the hardness raised up to 30%.

Vinyl ester resins are widely used in structural composites because of their excellent mechanical properties. One of the main goals of adding nanofillers to polymer matrix is to enhance the Young’s modulus and strength of the original base polymers. Due to the rigid structure of carbon nanotube as well as their aspect ratios, they can effectively increase the elastic modulus and stiffness of the polymer matrix. The main practical target of the present study is to obtain the best distribution of the multi-walled carbon nanotubes (MWCNTs) with carboxylic group in order to simultaneously improve the elastic modulus, tensile strength and toughness of the resulted nanocomposite. In this regard, nanocomposites with six different weight fractions (wt%) of MWCNTs are made and the specimens are subjected to the tensile test. The results exhibit that addition of MWCNTs with low concentration leads to improvement in the mechanical properties of the vinyl ester polymer such that the optimum mechanical properties are obtained with 0.25wt% of MWCNTs. In this case, the fracture toughness, tensile strength and Young’s modulus are respectively enhanced by amount of 52%, 23%, and 14%. In order to validate the experimental results and investigation the role of MWCNTs on tensile behavior of vinyl ester resin, the scanning electron microscope (SEM) is used and the most important failure mechanisms are discussed and studied in details. Also, the experimental results are compared with existing theoretical models and a new correction factor based on Hirsch’s theory and experimental results is introduced for future industrial applications.

In recent years, methods based on sever plastic deformation have been considered to improve the structure and mechanical properties of various metals, especially aluminum. Among the different methods, accumulative roll boding process is appropriate to improve the structure of metals sheet. Using this method, nanostructured aluminum alloys and aluminum nanocomposites reinforced by particles can be manufactured and simultaneously improve mechanical properties such as tensile strength and hardness. In most researches, after applying of 6 to 8 cycle of accumulative roll boding process the average of grain size reduced to less than 500 nm and the tensile strength increased to more than 2 times of the strength of the annealed aluminum. Accumulative roll boding process can be applied to different sheets in different routes, which will have a different effect on structural modification and mechanical properties. In this paper, the effect of various methods of accumulative roll boding process on microstructure and mechanical properties of aluminum alloys and aluminum based composites has been investigated.