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Showing 11 results for Cnt


Volume 9, Issue 4 (8-2020)
Abstract

Cellular energy allocation (CEA) test was performed in order to investigate the effects and costs of bare carbon nanotubes (CNTs) and CNTs in combination with titanium dioxide nanoparticles (CNTs/TiO2-NPs) on Glyphodes pyloalis Walker after 24, 48 and 72 hours of exposure to 100, 200, 300, 400 and 500 ppm of the treatments. Results showed the negative correlation between total lipid amounts and concentrations of treatments (i.e. CNTs and CNTs/TiO2-NPs) as well as exposure time. Contrary to CNTs treatments, carbohydrate contents were affected by both of CNTs/TiO2-NPs concentration and time of exposure. Results showed that the effect of bare CNTs in the enhancement of glycogen content appeared significantly faster than that of CNTs/TiO2-NPs. Increasing time of exposure to all concentrations of CNTs, except for 100 ppm, prevented enhancement of protein content. The effect of bare CNTs on the reduction of protein contents was faster and greater than that of CNTs/TiO2-NPs. The results indicated that G. pyloalis cannot regulate internal CNTs and CNTs/TiO2-NPs concentrations efficiently without considerable impact on the energy reserves (Ea). The comparison of energy consumed (Ec) in treated larvae showed that CNTs/TiO2-NPs reflected the higher energy demand of the stress response than CNTs. Generally, CEA was significantly decreased as the concentration of CNTs treatments increased. More reduction in CEA amount of all treatments by CNTs/TiO2-NPs than that of the control is also probably considered as a cost to deal with detoxification when the concentration increased and at all the tested time points. Therefore, CEA test might be considered as an early biochemical biomarker for assessing immediate response of organisms after acute exposure to stressors and thus could be applied to risk assessment of nanomaterials.

Volume 12, Issue 1 (3-2012)
Abstract

For extraordinary properties of carbon nanotube (CNT), a lot of research has been done about its application to reinforce different materials such as electronic and building materials, and good effects of CNT have been observed. Experimental approach for determining the properties of composites containing fibers, especially carbon nanotubes, needs using of complex experimental methods and expensive laboratorial equipments. Theoretical approach can lower the cost of predicting properties of these composites. So, in this paper, an analytical relation is presented by continuum mechanics method to predict the compressive strength of cement composite reinforced with carbon nanotube. For simplicity of computations, carbon nanotubes were assumed to be isotropicand firstly oriented unidirectionally and uniformly in the cement composite. Representative Elementary Volume(REV), as anindicatorelement of this nanocompositeis, was chosen and analyzed by continuum mechanics method. A fiber embedded in a cylinder of cement with certain radius is named REV. The strains under loads were calculated and the stresses were obtained by Hook’s law. Then, for prediction failure of composite, von Mises’ yield criterion was applied and by that, the compressive strength of cement composite reinforced with unidirectionally oriented carbon nanotubes was obtained. For real cases, the results of this analysis should be generalized to cement composites reinforced with random orientation of nanotubes, since there is no control on the distribution of fibers in the laboratory and they are oriented randomly in composites, although researchers are studying on production of CNT/cement composites with arbitrary orientation of fibers.To apply the random orientation effect, Cox’s method was used. For this purpose, the fibers' distribution function f ( ) was assumed and it was observed that the random orientation of fibers reduces the effect of fiber reinforcing with respect to unidirectional orientation. Therefore, an orientation factor  1 was used considering random orientation in comparison with unidirectional orientation. As a suggestion, this factor can be experimentally obtained too. Experimental method was used to determine the orientation factor of fibers incomposites and good results were obtained. Then the presented analytical relationship was compared with experimental data. Matches and differences between the analytical method and the experimental data were studied and the suggestions were presented to lower the differences between the analytical and experimental methods. The effect of some parameters such as compressive strength of cement and the amount of carbon nanotubes added on the compressive strength of CNT/cement composite were obtained too. Accordingly that an ideal nanocomposite with regard to economical considerations can be obtained.
Maryam Mehdizadeh, Mojgan Sheykhpour, Iman Salahshourifar, Seyed Davar Siadat, Parvaneh Saffarian,
Volume 12, Issue 2 (1-2022)
Abstract

Klebsiella pneumoniae is a gram-negative bacillus of the Enterobacteriaceae family. Despite being part of the natural human microflora, this is an opportunistic pathogen and a major cause of nosocomial infections. The increased emergence of multidrug resistance in Klebsiella pneumoniae has limited the treatment options for this bacterium. Carbon nanotubes (CNT), by improving the stability and solubulity of drugs, could increase the effectiveness of drugs for treatment. The aim of this study is to investigate the antibacterial effect of nanofluid containing functionalized multi-walled carbon nanotubes (f-CNT-NF) on Klebsiella pneumoniae isolated from clinical specimens. For the strain confirmation, biochemical ,API20E kit, and additional differential tests were performed, and antibiotic susceptibility test was performed by the disk diffusion method. The studied strain showed a resistance to all antibiotics such as cefepime.The minimum inhibitory concentration (MIC) was determined using the antibiotic micro dilution method. The MIC was determined in five effect modes including antibiotic (Ab), nanofluid containing functionalized multi-walled carbon nanotubes (f-CNT-NF) , nanofluid containing multi-walled carbon nanotubes (CNT-NF) ,Ab in combination with f-CNT-NF and Ab with CNT-NF. Nevertheless the individual effects of 10 µg mL-1 cefepime or 80 µg of nanofluid with f-CNT-NF did not inhibit the growth of the bacteria, but the co-administration of 10 µg mL-1 cefepime with 80 µg of the f-CNT-NF could inhibit the bacteria`s growth. It was concluded that f-CNT-NF could be more effective in drug delivery at lower concentrations than the free state, which could be used as a tool for optimal drug delivery.

Volume 13, Issue 3 (11-2013)
Abstract

A novel chemical solution deposition approach is reported for the deposition of nickel catalyst, which is a required step for the growth of carbon nanotubes (CNTs). In this work, after catalyst coating, vertically aligned CNTs have been grown on the silicon oxide and silicon surfaces. The results were studied using field emission scanning electron microscopy (SEM), Raman and X-ray diffraction. This technique has a high selectivity over the size of the catalyst nanoparticles, which results in the simple controlling of the average diameter of grown CNTs in the range of 30 to 150 nm. In addition, this approach leads to a more conformal coating on the surface of the sample in comparison with traditional vacuum-based deposition techniques, enabling the growth of CNTs on highly rough surfaces. The proposed catalyst deposition technique is a fast, inexpensive and simple Nickel catalyst deposition method that can significantly facilitate the growth process of CNTs

Volume 15, Issue 4 (12-2015)
Abstract

Mercury is a highly toxic and accumulative metal and its compounds, especially methyl mercury, are neurotoxins which cause blockage of the enzyme sites and interfere in protein synthesis. The fate of inorganic, mercury ions in nature is its turning into methyl mercury due to the aerobic action of microorganisms. Mercury is a toxic metal that causes the serious environmental problems. The main sources of mercury ions in aquatic ecosystems are divergent, chloralkali wastewater, oil refineries, power generation plants, paper and pulp manufacturing, rubber processing and fertilizers industries. Various methods have been used for removing heavy metals from aqueous environment such as reverse osmosis, chemical precipitation, ion exchange, coagulation and adsorption. Many carbon-based nanoparticles (CNTs) have been developed to remove heavy metals from aqueous media. They are promising material for numerous applications due to their unique electrical, mechanical, thermal, optical and chemical properties. In addition, CNTs are proven to be superior adsorbents for several divalent metal ions in water, because of their capability to establish (π–π) electrostatic interactions as well as for their large surface areas. Therefore, they have received considerable attention for usage in analytical chemistry and environmental remediation. Multi-walled carbon nanotubes (MWCNTs) were the first observed CNTs involving of up to several tens of graphite shells. The sorption capability of MWCNTs is related mainly to the functional groups attached on its surface. Generations of functional groups on the surface carbon nanotubes improves the reactivity and provides active sites for further chemical modifications. Many researchers have developed amino and thiol functionalization on carbon-based adsorbents and CNTs in order to increase the adsorption capacity, selectivity and removal efficiency of heavy metals and organic compounds. Among these functional groups, the thiols have an excellent binding ability to some metals such as silver, mercury, copper, nickel and zinc. In present study, multi-walled carbon nanotubes were functionalized in four stages to create thiolated multi-walled carbon nanotubes (MWCNTs-SH). The synthesized amino and thiolated MWCNTs were characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (CHNS) to ensur successfully entailing the functional groups on MWCNTs surface. The efficiency of all synthesized MWCNTs in mercury removal was investigated. MWCNTs-SH was more efficient rather than other synthetized adsorbents in mercury removal from aqueous solutions. Increasing in adsorbent dosage concluded an enhanced mercury removal. Solution pH has a more effect on mercury removal. When the pH increased from 2 to 8 the removal percentage ranged from 9.8 to 92%. The data fitted by Langmuir isotherm model (R2=0.966) better than Freundlich model (R2=0.935). The obtained maximum adsorption capacity (qm) by Langmuir model was 206.64 mg/g while its experimental value was 160.90 mg/g and was higher than that reported in other literatures. Thus the prepared synthetized adsorbent has high efficiency for mercury removal from aqueous solutions.

Volume 16, Issue 12 (2-2017)
Abstract

In this experimental study dynamic viscosity of hybrid engine oil (5w-50)-Cuo-MWCNT nanofluid for volume fractions of 0.05, 0.1, 0.25, 0.5, 0.75 and 1 percent of nanoparticles for temperatures of 5, 15, 25, 35, 45, 55 °C has been measured. This hybrid nanofluid has been prepared utilizing the two steps method. For viscosity measurement, the Brookfield viscometer has been used. The experimental measurments indicate that by increasing volume fraction of nanoparticles the viscosity increases; also by increasing the temperature the viscosity decreases. Based on the experimental results the maximum and minimum viscosity increases with volume fraction increase from 0.05 to 1 at a constant tempearture are 35.52 and 12.92 percent, respectively, relating to 55 and 15 °C. Measurement of the nanofluid viscosity with different volume fractions, shear rates and tempeartures indicate its Newtonian behavior. A new temperature and volume fraction dependent viscosity correlation, developed in this study to be used in numerical simulations, shows very good agreement with experimental results.

Volume 17, Issue 2 (3-2017)
Abstract

In, this research, the effects of adding silica and multiwall carbon nanotubes (MWCNT) nano particles on the low velocity impact response are experimentally studied. Vacuum assisted resin transfer molding (VARTM) method has been used to manufacture nano composite with 11 layers of plain weave carbon fibers 200 g⁄m^2 , resin R510 and hardener H515 with 66% fiber volume fraction. Samples made of nano silica and MWCNT particles have been dispersed with 1 wt. %. The prepared CARALL is made of two Aluminum 2024 facing sheets. Low velocity impact tests have been conducted using by drop weight device at the impact energy of 20, 40 and 60 j with velocity of 2.6, 3.68 and 4.5 m⁄s . The results of the low velocity impact experiments indicates that the MWCNT improves performance of fiber metal composite material and the effects of MWCNT in improving the impact properties of fiber metal laminate composite is better than of nano silica. Better adhering and dispersion of MWCNT and strong interfacial creation are some other effect factors of impact response sample reinforced with multiwall carbon nanotubes in comparison to nano silica.

Volume 17, Issue 8 (10-2017)
Abstract

One of the recent techniques which has attracted attention from researchers is the use of Nano particles to reinforce composites. While the technique does not make any changes in the weight of the structure, it improves its mechanical and physical properties. One form of Nano particles includes Carbonic Nano Tubes (CNT). Since its discovery, CNT has found wide application in industryIn this article, the response of aluminum hybrid panels and composites made from epoxy-Kevlar and aluminum hybrid panels and Nano-composites made from epoxy-Kevlar to ballistic impact was studied. Four groups of the panels were constructed using 0, 0.5, 1 and 1.5 percent of carbon nanotubes (CNT)s. The hybrid samples constructed and tried out in this experiment has been done using manual layer-making and heated press.The thickness of the panels constructed from two aluminum plates and ten Kevlar 29 plates was consistent. The ballistic impact test using gas gun was implementated by conical bullet 7.6 gr shooting in two avrege velocities (220 m/s and 275 m/s). input and output velocity with each sample was assessed using a laser speedometer. The amount of energy absorption and special energy absorption of passing of the rocket was determined as the criteria for the comparison of the efficiency of ballistic of different panels. The results indicated that among the four samples examined, the panel made up of 1 percent CNTs had the most amount of energy absorption and ballistic resistance.

Volume 17, Issue 12 (2-2018)
Abstract

In recent years, many attentions have been paid to decrease of the weight of components in automotive, transport and aeronautical industries, in respect of reduction of energy consumption and environmental pollution. Therefore, low-density aluminum alloys reinforced with nanoparticles especially CNT and Al2O3 have been broadly considered for application in such industries due to high strength/weight ratio. In current work, Al-CNT-Al2O3 nanocomposite was produced by accumulative roll bonding (ARB) after 6 passes. CNT-Al2O3 composite with 1wt% multi-wall carbon nanotube (MWCNT) and 2wt% nano-alumina was prepared by ball milling process. The effect of the ARB cycles on the microstructure and mechanical properties of nanocomposite were studied by field emission scanning electron microscopy images (FESEM), X-ray diffraction data, tensile and micro hardness results. FESEM images showed the uniform distribution and high quality bonding of carbon nanotubes in the matrix. X-ray diffraction analysis indicated the composite nanostructure formation with the crystal size of 53.3 nm after 6 cycles of ARB compared to 77 nm of Al after pass 11. The results obtained by the tensile and hardness tests showed that at the end of ARB process, ultimate strength was 5.9 times, and hardness was 3 times more than those of the annealed aluminum.

Volume 21, Issue 152 (9-2024)
Abstract

The purpose of this study was to compare the efficacy of citrus peel phenolic compounds extracted using carboxylated multi-walled carbon nanotubes (MWCNT–COOH) with common synthetic antioxidants [butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT)] in stabilizing sunflower oil (SO) during frying (180 ± 5 °C, 24 h). To evaluate the antioxidant activity of these compounds, total phenolic, and flavonoid contents, reducing power, ABTS scavenging activity, β-carotene bleaching ability, and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were measured. Extracts were combined at various concentrations (100-1000 ppm) with SO, and both synthetic antioxidants were standardized at 200 ppm. Thermal-oxidative stability was investigated by assessing the change in peroxide value (PV), color, free fatty acid (FFA) content, conjugated diene value (CDV), and thiobarbituric acid (TBA). Bitter orange peel extract (BPE) displayed a higher content of phenolic compounds and antioxidant activity. At 1000 ppm, it showed a lower FFA content, PV, TBA, and CDV. It can be used as an alternative to synthetic antioxidants. As a result, citrus peel phenolic compounds extracted with MWCNT–COOH can be used as preservatives in frying oils.
 

Volume 23, Issue 10 (10-2023)
Abstract

Composites reinforced with carbon fibers have various applications in different industries, due to their physical and mechanical properties. In this regard, multi-walled carbon nanotubes are used to strengthen the epoxy resin base, which is one of the emerging and important materials. Since machining is required to repair reinforced composite parts, in this research, the damages caused during the process should also be investigated and solutions should be provided. In this study, the delamination damage in the machining of composite parts of epoxy reinforced with carbon fibers and multi-walled carbon nanotubes has been discussed. In this regard, experiments have been conducted with a carbide end-mill at different cutting speeds and feed speeds. Then the delaminations created in these tests are studied. In the analysis of the results, by increasing the rotational speed from 500 to 2500, the amount of delamination increased by 25% and the force decreased by 87%. Also, solutions that include reducing the feed speed will have a significant effect on improving the final quality of the machined part.

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