Modulation in Electric Conduction of PVK and Ferrocene-Doped PVK Thin Films

In this article, the dielectric properties of poly (9-vinylcarbazole) (PVK) and ferrocene-doped PVK thin films are studied. The thin films were grown by the isothermal solution casting technique. Dielectric properties of grown films were studied as function of ferrocene concentration, frequency, and temperature. The relative permittivity (ε′) is increased with increasing ferrocene percentage (~1%) due to the free charge carriers. The relative permittivity decreases for higher ferrocene percentage (~2%). However, the relative permittivity of PVK and ferrocene-doped PVK samples remains almost constant for studied temperature range (313–413 K). The frequency dependence of tan δ for all samples is studied. The frequency dependence of dielectric parameter exhibits frequency dispersion behavior, which suggests all types of polarization present in the lower frequency range. The loss tangent (tanδ) values are larger at higher temperatures in the low frequency region. However, the tan δ values at different temperatures are almost similar in the high frequency region. It is observed that the relative permittivity is maximum, dielectric loss is minimum, and AC conductivity is minimum for 1% ferrocene doped PVK as compared to pure PVK and 2% ferrocene doped PVK samples.

Microstructure Evaluation on Micro and Nano Slag Particles Reinforced AA7075 Composites

The research work was focused on utilization of solid industrial waste. In order to investigate the properties of Fe-Cr slag particulates strengthened AA7075 composites. In this paper addition of ferrochrome slag particles as reinforcement in AA 7075 alloy processed through stir casting technique. By varying size of ferrochrome slag particles were added to evaluate the size effects in the given alloy matrix. Prepared composites were subjected to heat treatment and evaluated for microstructure analysis. The results show that there is a uniform distribution of particles in the matrix and that there is a strong bond between the matrix and the reinforcement. Grain refinement in the alloy matrix is observed by inducing slag particles. Further nanocomposites show lower grain size values.

Study About Some Mechanical Properties for Composites Reinforced with Corn Cob Powder

In this paper we have created some composites reinforced with corn cob powder and the matrix was made by a combination between Resoltech 1050 resin with its Resoltech 1058 hardener. For the composites manufacturing, we have used the manual casting technique. For the new manufactured composites, we have determined the mechanical properties from the tensile test according to ASTM D3039: Young modulus, breaking strength and elongation at break. We have also molded samples for the compression test according to ASTM D695-15 and we have determined the breaking strength. The tensile and compression tests were made on universal testing machines. In the end, we have determined also the dynamic mechanical properties for the studied material by clamping the samples at one edge and leaving the samples unconstrained at the other edge. At the unconstrained edge we have placed a Bruel&Kjaer accelerometer which recorded the samples free vibrations. From the free vibrations recording and Euler-Bernoulli theory, we have determined the next dynamic mechanical properties: damping factor per unit mass and length, eigenfrequency, dynamic modulus of elasticity, loss factor and dynamic rigidity. From the experimental results, we have obtained increased breaking strength values for the proposed material at compression compared to the tensile test. Compared to similar materials studied in the engineering literature, we have obtained increased compression breaking strength.

Effect of Different Preparation Conditions On The Properties of Bamboo Fiber-Based Bioactive Composite Membrane

A novel nano-hydroxyapatite/bamboo fiber (n-HA/BF) bioactive composite membrane was obtained by a simple casting technique. The membrane forming mechanism and the effects of different forming membrane methods, drying methods and n-HA amounts on the properties of n-HA/BF membrane were investigated by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester, in vitro soaking in simulated body fluid (SBF) and in vitro cell cultureexperiment. The results demonstrated that the n-HA dispersity in BF matix was not affected by the prepartion condition, however, the morphologies of membrane was determined by the different preparation conditions owing to different hydrogen bond shrinkage. Moreover, the hydrophilicity of the composite membrane was improved under the condition of the membrane formation in oven, freeze drying and high addition content of n-HA, and the mechanical properties of composite membrane depended on n-HA content. In vitro soaking behavior indicated that the degradability and bone-like apatite deposition could be controled by differentpreparation conditions. And the cell proliferation experiment showed that the n-HA/BF composite membranes obtained under different preparation conditions were all non-toxic. The above results indicated that the n-HA/BF composite membrane could be obtained by a simple casting technique, and the properties could be controlled by adopting different preparation conditions, which would have a great promising as guide bone tissue regeneration (GBR) membrane, and the study would provide a new application for BF in biomedical field.

Effect of Length of Cellulose Nanofibers on Mechanical Reinforcement of Polyvinyl Alcohol

Cellulose nanofibers (CNF), representing the nano-structured cellulose, have attained an extensive research attention due to their sustainability, biodegradability, nanoscale dimensions, large surface area, unique optical and mechanical performance, etc. Different lengths of CNF can lead to different extents of entanglements or network-like structures through van der Waals forces. In this study, a series of polyvinyl alcohol (PVA) composite films, reinforced with CNF of different lengths, were fabricated via conventional solvent casting technique. CNF were extracted from jute fibers by tuning the dosage of sodium hypochlorite during the TEMPO-mediated oxidation. The mechanical properties and thermal behavior were observed to be significantly improved, while the optical transparency decreased slightly (Tr. > 75%). Interestingly, the PVA/CNF20 nanocomposite films exhibited higher tensile strength of 34.22 MPa at 2 wt% filler loading than the PVA/CNF10 (32.55 MPa) while displayed higher elastic modulus of 482.75 MPa than the PVA/CNF20 films (405.80 MPa). Overall, the findings reported in this study provide a novel, simple and inexpensive approach for preparing the high-performance polymer nanocomposites with tunable mechanical properties, reinforced with an abundant and renewable material.

Experimental Studies on Mechanical Properties of Carbon Nanotube Reinforced Aluminum 7075 Composite Material

In the present work multiwalled carbon nanotubes were added as reinforcement to aluminum 7075 matrix at 0.5%, 0.75% and 1.25% by weight proportion through stir casting technique. The mechanical properties of the produced composite were studied. The composite has considerably good tensile and wear resistance properties and hence finds its best suited application in aircraft frame and wings structures. Microstructure analysis through SEM showed a uniform distribution of the reinforcement material in the matrix. XRD graphs were taken at selected points during microscopic studies to determine the chemical composition of the matrix alloy, the reinforcement and the composite. The experimental results showed that 1.25% reinforcement in the composite material exhibited a tensile strength of 560 N/mm2 and a compression strength of 649.6 N/mm2 as the highest among the compositions. Thus, the reinforcement addition at 1.25% improved the tensile and compression strength of the composite material.

Zein-Based Films Containing Monolaurin/Eugenol or Essential Oils with Potential for Bioactive Packaging Application

Zein is renewable plant protein with valuable film-forming properties that can be used as a packaging material. It is known that the addition of natural cross-linkers can enhance a film’s tensile properties. In this study, we aimed to prepare antimicrobial zein-based films enriched with monolaurin, eugenol, oregano, and thyme essential oil. Films were prepared using the solvent casting technique from ethanol solution. Their physicochemical properties were investigated using structural, morphological, and thermal techniques. Polar and dispersive components were analyzed using two models to evaluate the effects on the surface free energy values. The antimicrobial activity was proven using a disk diffusion method and the suppression of bacterial growth was confirmed via a growth kinetics study with the Gompertz function. The films’ morphological characteristics led to systems with uniform distribution of essential oils or eugenol droplets combined with a flat-plated structure of monolaurin. A unique combination of polyphenolic eugenol and amphiphilic monoglyceride provided highly stretchable films with enhanced barrier properties and efficiency against Gram-positive and Gram-negative bacteria, yeasts, and molds. The prepared zein-based films with tunable surface properties represent an alternative to non-renewable resources with a potential application as active packaging materials.

Comparison of Bond Strength in the Different Class of Resin Cements to Cast and CAD/CAM Co-Cr Alloys

Objectives. Despite the widespread use of resin cements in cementing dental restorations, their bond strength to CAD/CAM base metal alloys is not widely studied. This study aimed to evaluate the microshear bond strength (μSBS) between cobalt-chrome (Co-Cr) alloys fabricated using casting or CAD/CAM methods with three types of resin cements. Materials and Methods. Fifty Co-Cr blocks were prepared with CAD/CAM or casting technique. Specimens were divided using primer or not and bonded to three types of resin cements: Panavia F2, RelyX Unicem, and Duo-Link. The differences between the mean μSBS values were analyzed using the two-way ANOVA test and Tukey analysis (α = 0.05). The mode of failure was evaluated using a stereomicroscope. In addition, the specimens were examined by scanning electron microscopy (SEM) based on two received signals: backscattered electrons (SEB) and secondary electrons (SEs). One intact alloy specimen in each group was analyzed by energy-dispersive X-ray spectroscopy (EDX). Results. Most of the specimens in the no-primer group were prematurely debonded. Statistical analyses showed that the interaction between the alloy substrate and cement type was significant ( p = 0.001 ). The bond strength of Panavia F2 was significantly higher than Duo-Link in the CAD/CAM group ( p = 0.001 ). SEM evaluation confirmed the difference in grain structures, while EDX showed no remarkable difference in the chemical composition of the alloy substrates. Conclusion. Alloy fabrication technique may influence the bond strength of resin cements. In the CAD/CAM group, cement containing MDP molecules exhibited higher strength than the etch-and-rinse one.

Optimization of Aluminum Sand Casting process parameters on RSM and ANN methods

Sand casting is one of the best processes to produce a product to satisfy the customer requirements. The prime advantages of choosing the sand casting technique are perfect dimensional geometry, development of pattern is easy, production rate is high, and solidification time is low when compared to other casting techniques. The main purpose of sand casting is to produce a product with better quality in low cost. The properties of the green sand are based on the sand composition and the most important parameters in the preparation of moulding sand are green strength, moisture content and clay content. In this work, the silica oxide is blended in green sand with various compositions for cope box. The various compositions of sand parameters are experimentally investigated by using Response Surface Methodology (RSM). The results of sand parameters are compared with Artificial Neural Network (ANN) analysis. The blending of 9.2% SiO2 with green sand is very suitable for this casting process. The blending of 9.2% SiO2 with green sand is very suitable for this casting process. The effect of SiO2 blending with green sand, the initial raw material is reduced up to 25% of volume without casting defects. The hardness value increased up to 22% and the surface roughness decreased up to 12% by varying the percentage of SiO2 in green sand.

Influence Of Al203 Particle Mixed Dielectric Fluid on Machining Performance of Ti6Al4V

In this research work, an attempt was made to machine Ti6Al4V titanium alloy utilizing AA6061/10Gr composite tool. The composite tool was fabricated using stir casting technique and Al2O3 particles of size 5µm were incorporated in the dielectric fluid to enhance the machining performance. Experiments were conducted by varying Al203 concentration, pulse on time, current, and pulse off time, and the responses Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) were recorded. Experiments runs were planned using Taguchi orthogonal array. The results revealed that adding powder increases MRR and TWR owing to the excessive heat generation and bridging effect respectively. The best surface finish was attained due to the increase in spark gap and complete flushing of machined debris. Coating of materials over the machined specimen was observed when the parametric value of Ton was higher than 60s under PMEDM conditions. Pits, craters and cracks were observed on the machined topography which was eliminated when 5g/l of Al2O3 particles were added to dielectric fluid. MEIOT technique was utilized for optimization and it was observed that Ton 15µs, Toff 4µs and current 7A and powder concentration of 10g/l results in best machining performance.