Basalt fiber was first treated in a mixture of formic acid (FA) and dichloromethane (DCM) to reduce its diameter down to one micrometer. Electrospinning process was utilized to produce treated basalt fiber (TBF)-reinforced nylon 6,6/epoxy (NY/EP) hybrid nanofibril composites. NY/EP polymers have been dissolved in 80:20 mixture of FA/DCM solvent to form a homogenous solution. TBFs with different weight ratios of 5, 10, 15, 20, and 25 wt% were added to NY/EP (ratio of 5:1). The morphology of the hybrid nanocomposites was investigated by scanning electron microscopy and their compositions were analyzed using energy-dispersive X-ray spectroscopy. The thermal properties were studied by differential scanning calorimetry and thermogravimetric analysis. The mechanical properties of the hybrid nanocomposites, including tensile strength and modulus, are improved with respect to NY/EP hybrid nanofibers. An increase of 76% and 87% in tensile strength and Young’s modulus was acquired, respectively, at 15 wt% of TBF. Also, the addition of TBF increased the thermal stability of nanofibril composites.
This study is an attempt to optimize the electrospinning process to produce minimum Nylon 6,6 nanofibers by using Taguchi statistical technique. Nylon 6,6 solutions were prepared in a mixture of formic acid (FA) and Dichloromethane (DCM). Design of experiment by using Taguchi statistical technique was applied to determine the most important processing parameters influence on average fiber diameter of Nylon 6,6 nanofiber produced by electrospinning process. The effects of solvent/nylon and FA/DCM ratio on average fiber diameter were investigated. Optimal electrospinning conditions were determined by using the signal-to-noise (S/N) ratio that was calculated from the electrospun Nylon 6,6 nanofibers diameters according to “the-smaller-the-better” approach. The optimum Nylon 6,6 concentration (NY%) and FA/DCM ratio were determined. The morphology of electrospun nanofibers is significantly altered by FA/DCM solvent ratio as well as Nylon 6,6 concentration. The smallest diameter and the narrowest diameter distribution of Nylon 6,6 nanofibers ([Formula: see text][Formula: see text]nm) were obtained for 10 wt% Nylon 6,6 solution in 80 wt% FA and 20 wt% DCM. An increase of 118%, 280% and 26% in tensile strength, modulus of elasticity and elongation at break over as-cast was obtained, respectively. Glass transition temperature of Nylon 6,6 nanofibers were determined by using differential scanning calorimeter (DSC). Analysis of variance ANOVA shows that NY% is the most influential parameter.
The present study is an attempt to fabricate composite nanofiber mats from polystyrene (PS) loaded with exfoliated graphite nanosheets (EGNS) by using electrospinning technique. EGNS with different weight ratios of 3, 6, and 9 wt.% were added to PS (20 wt.%). The fiber diameter and morphology of the composite nanofiber mats were investigated by scanning electron microscopy (SEM). Results revealed that as EGNS concentration was increased, the average diameter of EGNS/PS electrospun nanofibers decreased. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to investigate the thermal properties. The tensile strengths and Young’s modulus of the composites improve with the increasing EGNS concentrations compared to PS nanofiber, which indicates 84% and 88% augmentation, respectively at 6 wt.% of EGNS. Also, the addition of EGNS increased thermal stability of composite nanofiber mats.
The present work is an attempt to model the diameter of Poly Lactic-co-Glycolic Acid (PLGA) nanofibers by utilizing response surface methodology (RSM) and artificial neural networks (ANNs). Hence, determining the optimal electrospinning process conditions to produce a minimum fiber diameter. For modelling the average diameter of nanofibers, RSM approach based on four parameters (polymer concentration, high voltage and needle tip to collector distance and spinning angle) with five-level was compared to ANN technique. In the RSM approach, central composite design (CCD) was used to determine the individual and interaction impacts of the parameters on the average diameter of nanofibers. Several ANNs of single and double hidden layers with different number of cells for each were tried to obtain the best network structure. The experimental and predicted PLGA fiber diameters using an ANN showed a strong correlation, indicating that the network topology of 4-14-1 has good predictability for analyzing factors impacting PLGA fiber diameter. The average absolute relative error for predicting PLGA nanofibers’ diameter using ANN (2.24%) is slightly less than that obtained from RSM (2.59%). The high regression coefficient between the variables and the response (R2 = 0.9636) shows a good second-order polynomial regression model for evaluating experimental data. The R2 value was 0.945, indicating that the ANN model was good fitting with the experimental results. The optimum combinations (PLGA concentration of 26 wt.%, high voltage 22 kV, needle tip to collector distance 20 cm, and spinning angle 60o) were developed by RSM model for electrospinning PLGA nanofiber that can produce fine, consistent, and high-quality nanofibers.
This work is an attempt to fabricate aluminum (AA 5049) matrix composites (AMCs) reinforced with electrospun polyacrylonitrile (PAN) nanofibers and consisting of exfoliated graphite nanosheets (EGNS/PAN) by utilizing friction stir processing (FSP) to improve the mechanical characteristics of AA 5049. The electrospinning method was used for fabricating PAN and EGNS/PAN nanofibers. The average diameter of the electrospun PAN nanofibers is 195 ± 57 nm, and after EGNS incorporation is 180 ± 68 nm. Dynamic recrystallization was the main process in the microstructure evolution of the stir zone during the FSP with PAN and EGNS/PAN nanofibers. According to PAN and EGNS/PAN nanofibers were used in the FSP procedure, the grain size reduced as a result of the pinning effects. PAN and EGNS/PAN nanofiber reinforcement enhanced the hardness to 89 and 98 Hv, respectively. Also, the ultimate tensile strength was raised to 291 MPa and 344 MPa, respectively. Tensile strength and hardness of the stir zone increased during the FSP with PAN and EGNS/PAN nanofibers due to the higher density of the strengthening mechanisms of grain boundaries and dislocations. The mechanical characteristics of AA5049 can be enhanced by the procedure of incorporating nanofibers, making them an ideal choice for applications in the automotive and aerospace industries.
In this work, friction stir processing (FSP) was used to successfully embed boron carbide (B4C) particles into an aluminum matrix (AA6061-T6). Four specimens of aluminum 6061 composite reinforced with 4%, 6%, 8%, and 10% volume fraction of B4C were manufactured. The effects of B4C particles volume fraction on microstructure, mechanical and wear properties are investigated. The microstructural investigations demonstrated that a rise in the volume % of reinforcement greatly decreased the matrix grain size. The manufactured AA6061-T6 loaded with B4C surface composites demonstrated homogeneous B4C particle dispersion, with no significant particle clustering in the stir zone. In addition, it was established that increasing the volume fraction of B4C particles promoted grain refinement, increased hardness, and tensile strength. X-ray diffraction (XRD) was used to identify the reinforcement dispersion. For AA6061-T6 with 10% B4C particles, a maximum hardness value of 163 HV was obtained in the stir zone. Maximum yield strength of 165 MPa and ultimate tensile strength of 220 MPa were attained by AA6061-T6 with 10% B4C particles, which is an improvement of 21% over the specimen FSP without reinforcement. The strengthening of the grain refining was attributed for the increase in hardness and strength. The ductility was reduced by the incorporation of more B4C particles. Comparing the surface composite loaded with B4C to unreinforced friction stir processing and AA6061-T6 as received, it demonstrated superior wear resistance.
The present study is an attempt to optimize the electrospinning parameters to fabricate chitosan/polyethylene oxide hybrid nanofiber composite with minimum diameter and coefficient of variation (homogeneity) by using response surface methodology (RSM). Based on central composite design (CCD), four factors (the chitosan/PEO ratio, the applied voltage, the needle-to-collector distance, and the spinning angle) was applied to evaluate the individual and combined effects of the parameters on the average diameter of nanofibers. Chitosan (CH) was blended with Polyethylene oxide (PEO) at weight ratios of 1:1, 2:1, 3:1, 4:1, and 5:1. As the composition ratio of chitosan was reduced, the viscosity of the chitosan/PEO blend solution also dropped. The RSM model identified the following conditions as necessary to produce the desired and most uniform CS/PEO fiber diameter: a CS/PEO blend ratio of 2:1 (w/w), a voltage of 25 kV, a distance of 20 cm, and a spinning angle of 45°. The average nanofiber diameter and homogeneity under these conditions were calculated to be 73 nm and 20.5%, respectively, compared to the predicted values of 71 nm and 15.58%, respectively.
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