Addition Of Multi-walled Carbon Nanotubes Research Articles

Investigation of mechanical properties of phosphorus building gypsum modified by multi-walled carbon nanotubes

This study delves into the multifaceted effects of multi-walled carbon nanotubes (MWCNT) incorporation on phosphogypsum's properties. We investigated the phase composition and morphology of phosphogypsum and observed the influence of MWCNT on the setting time, flexural strength, compressive strength, water resistance, and hydration process. The results demonstrated that MWCNT significantly abbreviates the setting time of phosphogypsum, enhances its absolute dry flexural strength and compressive strength, and improves water resistance, with optimal effects occurring at a MWCNT content of around 1.00%. Nonetheless, these benefits diminish and can even be counterproductive if MWCNT content is excessively high. The enhanced properties of phosphogypsum upon MWCNT addition can be ascribed to the filling effect and mechanical interlocking facilitated by MWCNT. Additionally, MWCNT promoted the hydration of phosphogypsum, as evidenced by calorimetric measurements.

Thermo-mechanical characterization of electrospun polyurethane/carbon-nanotubes nanofibers: a comparative study

Creating ultrathin, mountable fibers from a wide range of polymeric functional materials has made electrospinning an adequate approach to producing highly flexible and elastic materials. In this paper, electrospinning was utilized to produce thermoplastic polyurethane (TPU) nanofibrous membranes for the purpose of studying their thermal and mechanical properties. Towards a study of the effects of fiber orientation and multi-walled carbon nanotubes (MWCNTs) as a filler on both mechanical and thermal characteristics of electrospun TPU mats, an experimental comparison was held between unidirectional and randomly aligned TPU and TPU/MWCNTs nanofibrous structures. The incorporation of MWCNTs into randomly oriented TPU nanofibers resulted in a significant increase in Young's modulus (E), from 3.9 to 7.5 MPa. On the other hand, for unidirectionally spun fibers, Young's modulus increased from 17.1 to 18.4 MPa upon the addition of MWCNTs. However, dynamic mechanical analysis revealed a different behavior. The randomly oriented specimens exhibited a storage modulus with a significant increase from 180 to 614 MPa for TPU and TPU/MWCNTs mats, respectively, and a slight increase from 119 to 143 MPa for unidirectional TPU and TPU/MWCNTs mats, respectively. Meanwhile, the loss modulus increased with the addition of MWCNTs from 15.7 to 58.9 MPa and from 6.4 to 12 MPa for the random and aligned fibers, respectively. The glass transition values for all the mats fell in the temperature range of – 60 to − 20 °C. The thermal degradation of the membranes was not significantly affected by the addition of MWCNTs, indicating that the mixing of the two constituents did not change the TPU’s polymer structure and that the TPU/MWCNTs nanocomposite exhibited stable thermal degradation properties.

An investigation of microstructural basis for corrosion behavior of Al-CNT composites fabricated by SPS

In this research effect of the addition of multi-wall carbon nanotubes (MWCNTs) as additive powder on microstructure and corrosion behavior of fabricated Al-CNT composites was studied. The aluminum powder and CNTs were mixed with high energy planetary ball-mill. It is observed that by increasing milling time, the uniformity of CNTs on aluminum matrix and consequently corrosion resistance of Al-CNT composite is increased. On the other hand, by increasing the volume percentage of CNTs, the uniformity of CNTs on aluminum matrix and corrosion resistance of fabricated Al-CNT composite is reduced. The value of polarization resistance, Rp, for fabricated composites with 2 % CNT is improved from 1.28 to 3.60 Ω/cm2 by increasing milling time. Also, the value of Rp for fabricated composites with 4 h milling time, is reduced from 3.60 to 2.76 Ω/cm2 by increasing the percentage of CNTs from 2 % up to 5 %. Moreover, Cyclic Polarization results showed that the pitting corrosion resistance improves by increasing milling time and deteriorates by increasing the percentage of CNTs. The electrochemical impedance spectroscopy (EIS) results showed that the corrosion mechanism of Al-CNT composites is a combination of uniform and pitting corrosion. Indeed, the CNTs act as preferred cathode regions and cause to formation of micro galvanic couples. The Al-2%CNT-4 h showed better uniformity and the highest corrosion resistance. The Al-5%CNT-2 h presented non-uniform distribution of CNTs and the lowest corrosion resistance.

Comparative analysis of the effect of single-walled and multi-walled carbon nanotube additives on the properties of hydrocarbon-based drilling fluids

The article presents the results of a comprehensive comparative analysis of the effect of single-walled and multi-walled carbon nanotubes on the main performance characteristics of mineral oil-based drilling emulsions. Such a systematic comparative study of hydrocarbon-based solutions has been performed for the first time. Weight concentration of single-walled nanotubes varied from 0.01 % to 0.1 %, and of multi-walled ones, from 0.1 % to 0.5 %. The formulation and preparation technique of stable drilling emulsions with single-walled and multi-walled nanotube additives were practiced. The effect of nanotube additives on rheology, filtration, and antifriction properties, as well as colloidal stability, and clay inhibition kinetics of hydrocarbon-based drilling fluids has been studied. As a result of the study, it has been successfully demonstrated that adding even very small amount of carbon nanotubes allows significantly controlling the main performance characteristics of drilling fluids. Thus, adding just 0.025 wt% of single-walled nanotubes increases effective viscosity of the drilling fluid by about 45 %, the yield stress – by 1.7 times, colloidal stability – by 36 %, reducing at the same time filtration loss by 55 %, and friction factor – by 20 %. At the same time, it has been shown that using single-walled nanotubes is several times more efficient compared to adding multi-walled nanotubes, and hundreds of times more efficient compared to using spherical metal oxide nanoparticles.

Three-dimensionally printed denture base resins modified by nanoglass particles and carbon nanotubes

Statement of problemThree-dimensionally (3D) printed denture base resins exhibit inferior mechanical properties compared with conventional and milled ones, a problem affecting their long-term clinical use. Improved 3D printed resins are required. PurposeThe purpose of this in vitro study was to determine whether a 3D printed denture base resin with nanoglass particles and multiwalled carbon nanotubes (MWCNTs) would exhibit enhanced mechanical properties. Material and methodsThe nanoglass particles and MWCNTs were silane coated and added to the resin to obtain the following groups: Control, resin modified with nanoglass particles with 2 percentages, 0.25 wt%, and 0.5 wt%; resin modified with MWCNTs with 2 percentages, 0.25 wt%, and 0.5 wt%; and a combination group with 0.25 wt% of each filler type. The printed specimens (N=330) were tested before and after thermocycling (600 cycles) for flexural strength (FS) and elastic modulus (n=22) by using a universal testing machine and for impact strength (IS) (n=22) by using a Charpy impact tester. The fractured impact specimens were then evaluated by using scanning electron microscopy (SEM). The surface roughness (Ra) (n=11) was assessed by using a profilometer. For data analysis, the 2-way ANOVA test was used for the analysis of FS, elastic modulus, and IS, and the 3-way ANOVA test was used for Ra with a subsequent Tukey post hoc test. Percentage change was compared among groups by using the Kruskal-Wallis test, followed by the Dunn post hoc test with Bonferroni correction (α=.05). ResultsThe filler content and thermocycling revealed a significant main interaction effect (P<.001) on FS, elastic modulus, and IS, with the 0.5% nanoglass group displaying the highest percentage decrease after thermocycling. The SEM images of fractured impact specimens revealed a brittle failure in the control and nanoglass groups. In contrast, the groups containing MWCNTs and the combination group displayed intermediate to ductile failure. Moreover, a significant inclusive interaction effect (P<.001) was found between the filler content, thermocycling, and polishing on surface roughness, with the 0.5% nanoglass group revealing the highest percentage increase in Ra of the polished surface after aging. ConclusionsThe addition of nanoglass and MWCNTs led to a significant improvement in the FS, elastic modulus, and IS of the 3D printed resin. The combination group displayed the least percentage change among all groups regarding the FS and IS, displaying intermediate to ductile failure. The control revealed the least percentage change in elastic modulus after thermocycling but with lower peak values compared with all other groups.

Development of nanomodified eco-friendly thermal energy storing cementitious composite using PCM microencapsulated in biosourced encapsulation shell

This study presents the development of a thermal energy storing cementitious composite that incorporates phase change material (PCM) microencapsulated in biosourced polymer shell (m-PCM). The biodegradability of the encapsulated PCM was assessed using Nuclear Magnetic Resonance (NMR), which confirmed the high biodegradability of the m-PCM shell under specific environmental conditions. To examine the thermophysical properties of the m-PCM, Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) were performed. The DSC results revealed exothermic enthalpies of 84.7 J/g and 140.2 J/g, with associated peak temperatures of − 3.2 °C and − 22.9 °C, respectively. Subsequently, the m-PCM was incorporated into cement-based mortar at proportions of 5%, 10%, and 15% by weight of binder. Uniaxial compression tests were conducted to evaluate the effect of the m-PCM on the mechanical properties of the mortar. The results indicated a significant decrease in mechanical strength upon incorporating the m-PCM. However, this reduction in strength was mitigated by the addition of silica fume (SF) and multiwalled carbon nanotubes (MWCNTs) in combination. Furthermore, a thermal cycling test was performed to examine the behavior of the nanomodified m-PCM incorporated mortar under varying ambient conditions. The results showed that the addition of MWCNTs improved both the mechanical performance and thermal performance of the composite.

The Effect of Multi-Wall Carbon Nanotubes Addition on the Shielding Properties Against Gamma Radiation

In this work, the effect of Multi-Wall Carbon Nanotubes (MWCNTs) addition on the materials shielding properties against Gamma radiation with an energy of 662 keV from a 137Cs source is investigated. The linear attenuation coefficient of MWCNTs-based materials (gelatin-water mixture) with MWCNTs concentrations of 0%, 5%, and 10% is measured. To isolate the contribution of the MWCNTs unique structure to the shielding capabilities, samples with the same concentrations of activated carbon were fabricated and their linear attenuation coefficients were obtained. Also, the linear and the mass attenuation coefficients are obtained theoretically for the same concentrations using the XCOM program and compared with measured values. It is found that the addition of MWCNTs by 5% or 10% has increased the linear attenuation coefficient by around 5% when compared to the same concentrations of activated carbon. This increase in the shielding apabilities against gamma radiation can be related to the interaction of gamma radiation with the extraordinary geometry and structure of MWCNTs.

Preparation and characterization of polyhydroxyamide composite fibers reinforced with carbon nanotubes—Experiment and computation collaborative approach

AbstractAn experiment‐computation collaborative approach is conducted to investigate and understand the mechanical reinforcement effect of carbon nanotubes (CNTs) on polyhydroxyamide (PHA) composite fibers. The experimental studies provide results of PHA composite fibers with enhanced mechanical properties based on well‐dispersed multi‐walled CNTs (MWCNTs) inside the PHA matrix, suggesting optimal conditions for the experiment‐computation collaborative approach in the polymer/CNT composite systems. For instance, adding MWCNTs up to 2.0 wt% results in an improvement of 48.0% in tensile strength, 36.7% in initial modulus, and 69.9% in breaking strain of the composite fibers. FE‐SEM images show that many MWCNTs are partially exposed or pulled out to the outside of the PHA matrix through the tensile fracture in a very homogeneous dispersion state. In addition, the molecular dynamics (MD) simulation study with a single‐walled CNT (SWCNT) exhibits that the overall displacements of PHA molecules near the CNT surface decrease gradually, which indicates that the PHA molecules form an effective interaction with the CNT. Therefore, it is clear that the excellent interaction between PHA and CNTs, obtained from the results of well‐dispersed CNTs (experiment) and the reduction of the overall displacement of PHA molecules near the CNT surface (computation), is a very important clue to support the improved mechanical characteristics of the PHA fibers reinforced with the CNTs. Moreover, we are confident that the combined experimental‐computational approach used this study will yield valuable insights into the design of composite systems.Highlights Experiment‐computation collaboration reveals enhanced mechanical properties of PHA composite fibers with well‐dispersed CNTs. Addition of MWCNTs up to 2.0 wt% improves tensile strength by 48.0%, initial modulus by 36.7%, and breaking strain by 69.9%. FE‐SEM images demonstrate homogeneous dispersion and partial exposure of MWCNTs in the fractured PHA matrix. MD simulation shows reduced displacements of PHA molecules near SWCNT surface, indicating effective interaction. Combined experimental‐computational approach offers valuable insights for designing composite systems.

Photocurable 3D printed anisotropic electrically conductive materials based on bio-renewable composites

The manufacturing industry is moving towards an environmentally friendlier and more sustainable economy by substituting fossil fuel-based materials for plant-based and related renewable resources obtained materials, such as soybean oil. The combination of these materials with electrically conductive fillers allows the fabrication of conductive tracks and sensors essential for the implementation of the internet of things (IoT) and Industry 4.0 concepts. Here, we've fine-tuned the combination of acrylated epoxidized soybean oil (AESO) and isobornyl methacrylate (IBOMA), considering factors like viscosity, photoreactivity, and physico-chemical properties, with the further addition of multiwalled carbon nanotubes (MWCNT) in varying amounts for selected formulations. The resulted materials obtained in films present gel times between 1 and 30 s, FTIR conversion between 75% and 50%, Tg in the range of 57–123 °C and crosslinking densities between 1.90 and 0.015 mmol/cm3. In addition, good MWCNT dispersion is achieved with conductivities as high as 1.4 × 10-4 S/m. The optimal formulation in terms of 3D printability was obtained for 0.6 wt% MWCNT content and AESO:IBOMA polymer matrix in a 50:50 ratio, showing a good fabrication precision for bulk and hollow structures (average dimensional differences between the model and printed objects of ± 100 mm). The 3D printed samples demonstrate anisotropic electrical conductivity ascribed to a MWCNT orientation that occurs during 3D printing process. The electrical conductivity values can vary in nearly 6 orders of magnitude depending on the orientation with respect to the printed pattern, − 6.6·10-3 S/m for parallel and 5.2·10-9 S/m for perpendicular - demonstrating the suitability for 3D printed electronic applications.

Buckling analysis of sandwich plates reinforced with various loading of multi-walled carbon nanotubes

The current investigation aims to examine the buckling behavior of sandwich structures reinforced with faces containing varying weight percentages (wt.%) of multi-walled carbon nanotubes (MWCNT), through the combined employment of experimental and numerical analysis techniques. In particular, the numerical analysis is executed through the implementation of the generalized differential quadrature method (GDQM). The study first determines the mechanical properties of the pure and reinforced samples via experimental tests. The buckling equations of the sandwich plate are then derived using the Frostig approach and a high-order shear deformation theory (SDT) for the flexible core. The continuity conditions between the faces and the core are considered to obtain the structural equations of the system, and Lagrange coefficients are introduced to enhance the accuracy of the governing equations. Subsequently, the study investigates the impact of various parameters, such as core thickness, aspect ratio, different boundary conditions (BC), and the addition of MWCNT nanoparticles on the critical buckling load of the system, utilizing the mechanical properties obtained for the composite faces. The present investigation reveals that the incorporation of MWCNT into the composite matrix brings about notable enhancements in the mechanical characteristics of sandwich structures. Specifically, the elastic modulus and ultimate strength of the faces are found to increase following the addition of MWCNT. Additionally, the critical buckling load of the sandwich plates is observed to rise with an increase in aspect ratio and length-to-thickness ratio, while a decrease in axial load yields similar results. The clamped boundary condition has higher critical buckling loads than the simply supported boundary condition. The addition of MWCNT nanoparticles decreases the dimensionless critical buckling force as the b/a ratio increases. Finally, the reported results of the current investigation present noteworthy findings about the advancement and improvement of sandwich composite structures to meet various application requirements.

Nanoadditives induced enhancement of thermal energy storage properties of molten salt: Insights from experiments and molecular dynamics simulations

Current concentrated solar power (CSP) plants use molten salts as heat storage and heat transfer medium. The thermal property enhancement of molten salts can increase the efficiency and lower the investment cost of CSP plants. In this study, the experiments and molecular dynamics (MD) simulations were employed to investigate the effect of doping Al2O3, SiO2 nanoparticles or multi-walled carbon nanotubes (MWCNTs) on the specific heat capacity (SHC) of ternary carbonate salt. The results show that the SHC of molten salt can be enhanced by adding nanoadditives. The addition of MWCNTs has the largest SHC enhancement in both solid and liquid states. Based on MD simulations, the radial distribution functions, number density distribution and vibrational density of states were further analyzed to reveal the effect of nanoadditive, base salt and interface thermal resistance between them on SHC at different temperatures. It is found that the nanoadditive agglomeration, the ion spacing of base salt, and the thermal resistance between base salt and nanoadditive is independent on temperature and cannot result in the enhanced SHC of liquid nanocomposites. Moreover, the thickness of interfacial layer changes with temperature. The thicker interfacial layer leads to the higher SHC of liquid nanocomposites. The interfacial layer also has a decisive influence on SHC of solid nanocomposites. The scanning electron microscopy images show that the layered, needle-like, and network-like interfacial layers are observed in Al2O3, SiO2 and MWCNT nanocomposites, respectively. The present findings are helpful to understand the mechanisms governing thermal energy storage, and provide guidelines for the performance optimization of molten salt based nanocomposites.

Ultrasonic-assisted of TiO2-MWCNT nanocomposite with advanced photocatalytic efficiency for elimination of dye pollutions

Nanocomposites of titanium dioxide (TiO2) and multi-wall carbon nanotubes (MWCNTs) were successfully synthesized (TiO2-MWCNTs) from MWCNTs and titanium tetrachloride (TiCl4) as starting precursors using ultrasonic-assisted technique. The impact of the different weight percentages of MWCNTs (1, 3, 5, and 7 wt%) on TiO2 optical, structural, and morphological properties were investigated. Subsequently, the photocatalytic activity was assessed by organic dyes degradation such as methylene Blue (MB) and rhodamine B (RhB) under ultraviolet (UV) light exposure. The characterization of synthesized materials demonstrated the anatase phase formation in both pure TiO2 and the TiO2-MWCNTs nanocomposite, according to X-ray diffraction analysis. The morphology analysis of TiO2-MWCNTs nanocomposites using FESEM and TEM confirmed the uniform dispersion of MWCNTs with an exterior diameter of 12–16 nm within the TiO2 matrix. The BET measurement of the sample's specific surface areas identified that the MWCNTs addition resulted in the increase of surface area from 76.34 to 194.35 m2 g−1 for pure TiO2 and TiO2/7 wt% MWCNTs, respectively. Furthermore, TiO2/7 wt% MWCNTs nanocomposite had lower optical bandgap energy and higher photocatalytic performance as compared to the pure TiO2. The photodegradation efficiency of TiO2/7 wt% MWCNTs nanocomposite increased from 63.63 % to 92.36 % for MB and 71.56 % to 94.13 % for RhB compared to pure TiO2, after 60 min UV light exposure.

Optical and Electrical Properties of Polystyrene/Poly‐methyl methacrylate Polymeric Blend Filled with Semiconductor and Insulator Nanofillers

The present study deals with the effect of adding different fillers (semiconductor and insulator) on a polystyrene (PS)/poly‐methyl methacrylate (PMMA) polymer blend using casting method. A constant content (1 wt%) of semiconductors [multiwalled carbon nanotubes (MWCNTs), polyaniline (PANI), zinc oxide nanoparticles (NPs), and titanium dioxide NPs] and insulator [silicon dioxide NPs] fillers is used. Transmission electron microscopy images for MWCNTs show that most nanotubes have an average diameter of 7–11 nm. Moreover, the average size of all metal nano‐oxides is almost 20 nm and confirmed by X‐ray diffraction. Fourier‐transform infrared spectroscopy confirms the formation and the interaction between PS/PMMA polymer blend and fillers. The structural, mechanical, optical, and dielectric properties of the prepared polymer nanocomposites are studied using different tools. Optical characteristics such as absorbance, reflection, bandgap energy (E g), and optical dielectric components (real and imaginary) are studied. These results reveal that pure 20PS/80PMMA film has E g(direct) = 4.46 eV, which drops as different fillers are incorporated into the blend. The addition of MWCNTs, PANI to the PS/PMMA blend improves the electrical conductivity due to the growth of conductive paths between the filler and the blending matrix.

Effects of MWCNTs on O2/N2 separation performance and morphology of sPEEK/PEI composite membranes: Experimental and molecular dynamics simulation studies

This study involved the development of blend membranes using sulfonated poly (ether ether ketone) (sPEEK) and poly (etherimide) (PEI) with varying amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 % by weight). The gas separation performance of these membranes was evaluated for the separation of O2 and N2 gases. In order to achieve a degree of sulfonation of 70 %, PEEK was sulfonated directly. The manufactured membranes were characterized using X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). Their operational evaluation was performed through permeability tests for pure gases of O2 and N2. The effect of sPEEK/PEI composition on membrane selectivity and gas permeability in the blend was studied. The selectivity and gas permeability values varied between those of individual polymers, fluctuating systematically with sPEEK/PEI content variation in the blends. The addition of MWCNTs to the blend improved the selectivity and permeability of O2 and N2 simultaneously. To further investigate the potential industrial application and stability of these membranes, experiments were conducted under different feed pressures (2 to 8 bar). The membrane containing 1 % of MWCNTs showed the best performance for O2 gas. Molecular dynamics simulations (MDS) were performed using the COMPASS force field to estimate the diffusivity of O2 and N2 gases through selected membrane systems. The simulated results agreed well with the available experimental data. With compared to the reported separating data, the prepared nanocomposite membrane was greatly efficient, which makes it promising platform to separate mixed gas flows and other related environmental processes.

Room temperature operated flexible La-ZnO/MWCNTs sensor for ppb level carbon monoxide detection

The advancement of gas sensors with ppb level concentration experiences profound challenges. In this research, Lanthanum (La)-Zinc Oxide (ZnO)/multi-walled carbon nanotubes (MWCNTs) composites were successfully fabricated and loaded on a flexible polyimide substrate where interdigitated electrodes (thickness: 300 µm and spacing: 300 µm) were prepared using a laser carbonation technique for room temperature (RT) carbon monoxide (CO) gas detection. The synthesized composites were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, UV–visible spectrophotometry, x-ray diffraction, and Fourier transform infrared spectroscopy. When compared to the La-ZnO composite, the addition of MWCNTs on the synthesized composite-based sensor exhibited ∼8 times higher response than La-ZnO to 100 ppm CO at 27 °C. The response of the La-ZnO/MWCNTs composite sensors to 20 ppm CO was tested at six different relative humidity (RH) levels ranging from 0% to 90% in the increments of 20% RH. These sensors exhibited humidity tolerant properties, as evidenced by their responses to different humidity levels. Even when exposed to 90% RH, the sensor only showed ∼13% reduction in response compared to 0% RH, indicating that it is a humidity tolerant sensor. Furthermore, the La-ZnO/MWCNTs sensor has excellent selectivity and can detect low CO concentrations of 100 ppb. As a result, the proposed high-performance flexible sensor has a lot of potential for use in wearable devices to sense CO gas at RT for trace level detection.

Addition of Multi‐walled Carbon Nanotubes to Fe‐ and Ru‐Metallopolymer Electrodes Enhances Response Time and Cycling Stability in Electrochromic Cells

AbstractMetallopolymers (MEPEs) show a strong absorption band attributed to a metal‐to‐ligand charge transfer (MLCT) transition. Fe‐MEPE and Ru‐MEPE thin films switch reversibly from blue‐purple (λmax=584 nm, Fe2+) to colorless (Fe3+) or orange (λmax=518 nm, Ru2+) to pale green (Ru3+). The addition of multi‐walled carbon nanotubes (MWCNTs) enhances the electrochromic (EC) properties of Fe‐ and Ru‐MEPE electrodes in several ways: (1) faster response for bleaching/coloring; (2) enhanced Coulombic efficiency; and (3) improved cycling stability, particularly for Ru‐MEPE. Moreover, the charge density of the thin film electrodes can be increased upon the addition of the MWCNTs. This performance improvement is demonstrated in electrochromic devices (ECDs) with titanium‐doped vanadium oxide (TiVOx) as the optically‐passive ion storage layer. The visible light transmittance τv values of the ECDs are improved by the addition of the MWCNTs from 20 %/56 % to 17 %/56 % and from 31 %/47 % and 34 %/55 % in the dark/bright state, for Fe‐MEPE and Ru‐MEPE, respectively. Thus, the addition of MWCNTs to Fe‐ or Ru‐MEPE is a very promising route for future fast‐switching EC applications, e. g., displays, sunroofs, and rear‐view mirrors.

Effects of multi-walled carbon nanotubes on the combustion, performance, and emission characteristics of a single-cylinder diesel engine fueled with palm-oil biodiesel-diesel blend

Multi-walled carbon nanotubes (MWCNTs) could be an effective fuel additive for 20 vol% palm-oil biodiesel in fossil diesel (B20) owing to its superior thermal conductivity. The effects of MWCNTs on the combustion, performance, and emission characteristics of B20 are investigated at various concentrations by a single-cylinder diesel engine under different engine speeds. The results show that B20 fuels with MWCNTs addition reduced the ignition-delay (ID), advanced the combustion phasing, and shortened the combustion duration by up to 17.6% (−2.6° CA), 12.9% (−1.8° CA), and 18.5% (−4.3° CA), respectively. The addition of MWCNTs in B20 also improved the brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) by up to 15.7% (−47.4 g/kW·h) and 16.3% (+4.6%), respectively. Compared with B20 fuel without MWCNTs, CO and UHCs emissions reduced by up to 34.7% (−8.2 g/kg-fuel) and 16.0% (−3.8 g/kg-fuel), respectively but NOx emissions increased by up to 43.5% (+7.6 g/kg-fuel). Overall, the results suggest that B20 with MWCNTs addition can enhance the combustion, performance, and emission characteristics of a light-duty diesel engine.

Influence of carbon nanotubes on the plasma electrolytic oxidation process of aluminum under “soft” sparking conditions

Plasma electrolytic oxidation of aluminum (PEO) was performed with dispersed multi-walled carbon nanotubes (MWCNTs) into the electrolyte. The effect of the carbon nanotubes concentration, as well as that of the electrical processing conditions, on the PEO process was investigated. From the point of view of the electrical response of the process, results show that the “soft” sparking regime appears earlier in presence of MWCNTs. The process time at which the transition to the “soft” regime occurs decreases linearly with the increase in the MWCNTs concentration. Over a concentration threshold, depending on the applied pulse bipolar current waveform, the PEO process is inhibited. The dispersion of MWCNTs in the electrolyte results in thicker but more porous alumina layers. More specifically, the proportion of the α-alumina phase relative to the γ-alumina phase decreases with the increase in the MWCNTs concentration. Results are explained by considering the increased coating growth kinetics and lower heat accumulation from MWCNTs addition. Finally, the present study gives new insights into the right management of the PEO process under “soft” sparking regime with dispersed carbon-based nanoparticles in the electrolyte.

Determination of optimum operating parameters of MWCNT-doped ethanol fueled HCCI engine for emission reduction

Carbon based metallic additives were widely researched to improve combustion charecteristics of spark ignition and compression ignition engines. It was proven that carbon nanotube additive shortens ignition delay period and improves combustion characteristics especially in diesel engines. HCCI is a lean burn combustion mode which provides high thermal efficiency and simultaneously low NOx and soot emission. However it has drawbacks such as misfire at leaner mixtures and knocking at high loads. Carbon nanotube could be used to improve combustion for HCCI engines as well. The aim of this study is to investigate the effects of multi-walled carbon nanotube addition to ethanol and n-heptane blends on HCCI engine performance, combustion and emission by experimentally and statistically. During the experiments, the mixed fuels formed with %25 ethanol, %75 n-heptane and 100, 150 and 200 ppm MWCNT additives were used. The experiment of these mixed fuels was carried out at different lambda and engine speed values. Response Surface Method was implemented to determine optimal additive amount and operation parameters of the engine. The variable parameter values to be used in the experiments were created with the central composite design, and a total of 20 experiments were performed. According to the obtained results, IMEP, ITE, BSFC, MPRR, COVimep, SOC, CA50, CO and HC response parameter values were obtained. Response parameter values were entered into the RSM environment and optimization studies were carried out depending on the response parameters targets. Among the optimum variable parameter values, the MWCNT ratio was determined as 102.16 ppm, lambda 2.7 and engine speed 1124.439 rpm. Response parameter values after optimization were determined as IMEP 4.988 bar, ITE 45.988 %, BSFC 227.846 g/kWh, MPRR 2.544 bar/CA, COVimep 1.722 %, SOC 4.445 CA, CA50 7 CA, CO 0.073 % and HC 476.452 ppm.

Biofilm Formation of Two Different Marine Bacteria on Modified PDMS Surfaces is Affected by Surface Roughness and Topography.

Different strategies were tested to reduce biofilm formation of the model marine bacteria Cobetia marina and Marinobacter hydrocarbonoclasticus on cross-linked polydimethylsiloxane (PDMS) coated aluminum and cellulose acetate surfaces modified by addition of multi-walled carbon nanotubes (MWCNT) or exposure of the surfaces to bromine vapors in the presence and absence of UV irradiation. The three surface modifications explored led to important reductions in biofilm formation for the two marine bacteria, up to 30% in the case of exposure to Br2(g). Biofouling reduction could be correlated to surface properties in all cases through the introduction of a quantitative theoretical model based on an effective roughness parameter, Raeff, that accounted for the different morphological changes observed. The model considers the possibility of bacterial inclusion into large surface wells, as observed by AFM in the case of Br2(g) + UV light treatment. In addition, a linear relationship was observed between biofouling reduction and the Raeff effective roughness parameter.