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Review of Cellulose Smart Material: Biomass Conversion Process and Progress on Cellulose-Based Electroactive Paper
Get PDFCellulose is a renewable biomass material and natural polymer which is abundantly available on Earth, and includes agricultural wastes, forestry residues, and woody materials. The excellent and smart characteristics of cellulose materials, such as lightweight, biocompatibility, biodegradability, high mechanical strength/stiffness and low thermal expansibility, have made cellulose a high-potential material for various industry applications. Cellulose has recently been discovered as a smart material in the electroactive polymers family which carries the name of cellulose-based electroactive paper (EAPap). The shear piezoelectricity in cellulose polymers is able to induce large displacement output, low actuation voltage, and low power consumption in the application of biomimetic sensors/actuators and electromechanical system. The present study provides an overview of biomass pretreatment from various lignocellulosic cellulose (LC) resources and nanocellulose production via TEMPO-mediated oxidation reaction, followed by the production of different types of EAPap versus its performance, and lastly the applications of EAPap in different areas and industries. Specifically, LC biomass consists mainly of cellulose having a small content of hemicelluloses and lignins which form a defensive inner structure against the degradation of plant cell wall. Thus, selective approaches are discussed to ensure proper extraction of cellulosic fibers from complex biomass for further minimization to nano-dimensions. In addition, a comprehensive review of the development of cellulose-based EAPap as well as fabrication, characterization, performance enhancement and applications of EAPap devices are discussed herein
Carbon Nanotube/Cellulose Nanocrystal Hybrid Conducting Thin Films
Get PDFCellulose nanocrystals (CNCs) have a high ability to disperse single-walled carbon nanotubes (SWNTs) in aqueous media and to form hybrids. These hybrids are used to grow layer-by-layer thin films of controlled thickness. Thanks to the presence of SWNTs, these films are conducting. In this article, we describe the process by which the CNC/SWNT hybrids are obtained and discuss the electrical properties of the hybrid-based layer-by-layer films
Effect of Fiber Loadings and Treatment on Dynamic Mechanical, Thermal and Flammability Properties of Pineapple Leaf Fiber and Kenaf Phenolic Composites
No full textThis study deals with the analysis of dynamic mechanical, thermal and flammability properties of treated and untreated pineapple leaf fiber (PALF) and kenaf fiber (KF) phenolic composites. Results indicated that storage modulus was decreased for all composites with increases in temperature and pattern of slopes for all composites, having almost the same values of E' at glass transition temperature (Tg). The peak of the loss modulus of pure phenolic composites was shown to be much less. After the addition of kenaf/PALF, peaks were higher and shifted towards a high temperature. The Tan delta peak height was low for pure phenolic composites and maximum for 60% PALF phenolic composites. Cole-Cole analysis was carried out to understand the phase behavior of the composite samples. Thermogravimetric analysis (TGA) results indicated that pure phenolic composites have better thermal stability than PALF and kenaf phenolic composites. Vertical and horizontal UL-94 tests were conducted and showed pure phenolic resin is highly fire resistant. The overall results showed that treated KF composites enhanced the dynamic mechanical and thermal properties among all PALF/KF composites
Surfactant-Assisted Poly(lactic acid)/Cellulose Nanocrystal Bionanocomposite for Potential Application in Paper Coating
Get PDFThe current article addresses a new strategy for the preparation of polylactic acid/cellulose nanocrystal (PLA/CNCs) nanobiocomposite films with improved structural morphology, mechanical and barrier properties for food packaging applications. The addition of hexadecyltrimethylammonium bromide (CTAB) and sodium lauryl sulfate (SLS) as cationic and anionic surfactants respectively, was found to play a crucial role in preventing re-aggregation of the CNCs during drying and improving the dispersion of CNCs in the PLA. The coated paper was characterized using mechanical tests, water vapor permeability (WVP), X-ray diffraction (XRD), scanning electron microscopy (SEM) and air permeability. The results showed that the paper coated with PLA containing 7.5% CNCs and 0.15% CTAB based on weight of PLA, gives the highest measured paper properties, where an increase in tensile strength (+133%), Young's modulus (+309%), tear index (+183%), burst (+60.8) and a decrease in air permeability (–92%) was obtained
Biobased Aromatic-Aliphatic Polyols from Cardanol by Photochemical Thiol-ene Reaction
Get PDFBiobased aromatic-aliphatic polyols were previously synthesized from a thermal thiol-ene reaction of propoxylated cardanol with 2-mercaptoethanol (ME) in the presence of azobisisobutyronitrile (AIBN) as a radical initiator. Cardanol used for this purpose was obtained as a dark-brown liquid (Gardner Color Reference ∼18). The photochemical thiol-ene reaction can also be used to prepare aromatic-aliphatic polyols by employing cardanol. Via the photochemical thiol-ene reaction, 2-mercaptoethanol was added successfully to C=C double bond of cardanol, suggesting that phenolic group may not play an inhibitory role in the radical thiol-ene reaction. However, we preferred to alkoxylate the phenolic hydroxyl group of cardanol, which is much more reactive with isocyanates than phenolic hydroxyls, to generate a new aliphatic hydroxyl group. Furthermore, the functionality of polyols was also improved by two methods: 1) using 1-thio-glycerol instead of 2-mercaptoethanol and 2) using alkoxylated cardanol with glycidol (Cardanol-GLY) instead of propoxylated cardanol (Cardanol-PO). These polyols were then used in preparation of rigid polyurethane foams that can be useful in various applications such as insulation of freezers, pipes and storage tanks in food and chemical industries
Numerical Investigation of Convective Heat Transfer and Friction in Solar Air Heater with Thin Ribs
No full textThe three-dimensional numerical investigation of an incompressible flow through rib roughened solar air heater is carried out. A combination of thin transverse and truncated ribs is attached on the absorber plate to study its effect on the heat transfer and friction factor. The parameters in the form of Reynolds number (Re) of 4000-16000, relative roughness pitch (P/e) of 8-18 and relative roughness height (e/Dh) of 0.0366-0.055 is considered for the analysis. The CFD code ANSYS FLUENT is used to solve the governing equations of turbulent flow. The RNG k–ε turbulence model is used to solve the transport equations with enhanced wall treatment, keeping the Y+< 1. The maximum enhancement ratio of the Nusselt number and friction factor obtained is 1.91 and 3.61 respectively. The detailed investigation on average heat transfer, friction factor and flow structures have been discussed
Progressive Failure Evaluation of Composite Skin-Stiffener Joints Using Node to Surface Interactions and CZM
No full textT shaped skin-stiffener joint are one of the most commonly used structures in aerospace components. It has been proven in various studies that these joints are susceptible to failure when loaded in pull out conditions however, in specific applications these joints undergo pull loading. De-lamination/de-bond nucleation and its growth is one of the most common failure mechanisms in a fiber reinforced composite structure. Crack growth takes place due to the induced interlaminar normal and shear stresses between different structural constituents when a load is applied. In this study, Finite Element Analysis has been performed using cohesive contact interactions on a composite T-joint to simulate the pull out test conditions. A simplified shell based model coupled with CZM is proposed, which can evaluate the failure initiation and progression accurately with lesser computational efforts. The final failure occurred at a displacement of 4.71 mm at the computed failure load of 472.57 kgf for basic configuration. Computed Failure load for the padded configuration is 672.8 kgf and corresponding displacement is 4.6 mm. The results obtained by the proposed numerical model are validated by experimental results and it is observed that predicted failure displacements and failure load calculated were correlating reasonably well with the experiment
The Hemodynamic Comparative Study Between Pulsatile and Non-Pulsatile VA ECMO: A Primary Numerical Study
No full textAlthough pulsatile ECMO, as novel kinds of ECMO, has been attracted more and more attention, the differences of the hemodynamic effects of the pulsatile ECMO on the aorta, the cerebral perfusion, and left ventricular work were still under-investigated. The aim of this study was to clarify the hemodynamic differences of the cardiovascular system between the pulsatile and non-pulsatile VA ECMO. In this study, three ECMO support modes, named as “constant flow mode”, “co-pulse mode” and “counter pulse mode”, were designed. The computational fluid dynamics (CFD) study was carried out. The distribution of the oxygenated blood, the blood velocity vector, the oscillatory shear index (OSI), the relative residence time (RRT), the left ventricular external work (EW), the equivalent left ventricular afterload (EAL) and the energy loss of cardiovascular system (EL) were calculated to compare the hemodynamic differences. The simulation results demonstrate that the oxygenated blood under co-pulse mode was easier to perfuse into the three braches vessels than that under both other modes. In addition, the ECMO under counter pulse mode could also achieve lowest RRT (constant flow mode 220 vs. co-pulse mode 132 vs. counter pulse mode 93). Similarly, the ECMO under counter pulse mode could significantly reduce the left ventricular external work (co-pulse mode 1.51 w vs. constant flow mode 1.44 w and counter pulse mode 1.30 w), left ventricular afterload (constant flow mode 1.03 mmHg·s/ml vs. co-pulse mode 1.67 mmHg·s/ml vs. counter pulse mode 0.82 mmHg·s/ml) and energy loss of arterial system (constant flow mode 0.18 w vs. co-pulse mode 0.50 w vs. counter pulse mode 0.16 w). In short, the ECMO under counter pulse mode could have advantages to the left ventricular unloading. In contrast, the ECMO under co-pulse mode has more benefit to cerebral oxygen perfusion
Three-Dimensional Numerical Investigation of Convective Thermal Instabilities in the Sapphire Melt for Czochralski Growth Process
Get PDFIn this work we have performed a three-dimensional numerical investigation in order to find the optimal conditions for growing efficiently high quality sapphire crystals with good thermal properties. We have studied thermal instabilities near the melt-crystal interface and the convective heat transfer under the Czochralski (Cz) process. We performed 3-D CFD simulation in cylindrical coordinates and used the Fast Fourier Transform method to analyze the temperature fluctuations. We present a detailed investigation on the effects of the crystal rotation speed and the temperature distribution on thermal instabilities of sapphire melt under forced convection. Where the melt forced convection, the radiative heat transfer and the Marangoni convection, were conducted for Al2O3 melt in the Cz crucible. We have been able to determine the optimal rotation speed giving a planar crystal-melt interface where the symmetry of the flow in the crucible is conserved witch is found to be 13 rpm for the studied case. On the other hand we achieved a visualization of the temperature fluctuations just below the interface. These fluctuations give precious information about the melt -crystal interface, which plays an important role on the quality of the pulled crystal
On the Control of the Master Cylinder Hydraulic Pressure for Electro-Hydraulic Brake (EHB) Systems with the Sliding Mode Design Methodology
Get PDFThe brake-by-wire system requirement is promoted owing to the development of green energy vehicle, and the brake pressure control method is needed. A control method for the master cylinder hydraulic pressure based on the sliding mode control approach is proposed to provide the Electro-Hydraulic Brake system (EHB) of electric vehicles with superior system performances. An assessment is carried out about the complex nonlinear characteristics and sensitivity to the external environment of these systems, which include illustrating the working principle of the EHB system, establishing the dynamic models of the key components of the EHB system. The sliding mode control method is designed after introducing relevant dynamic models for the related key components. In particular, three kinds of wheel cylinder hydraulic response curves under different braking conditions (Normal braking conditions, Emergency braking conditions, and Failure safety protection braking conditions) are considered. The simulation results show that the sliding mode control method for the master cylinder under the EHB system has strong pressure-building capability, short response time and superior system performance Therefore, the sliding mode control method proposed in this paper is an ideal method for master cylinder hydraulic pressure control under the EHB system and has a wide range of engineering application for electric vehicles