Keywords : composites

Hybrid Membrane based on Polymer-doped Phosposilicate and their Characterization

Uma Thanganathan

Advanced Materials Letters, 2021, Volume 12, Issue 8, Pages 1-6
DOI: 10.5185/amlett.2021.081652

A class of proton-conducting non-fluorinated hybrid composite membranes was produced based on poly(vinylpyrrolidone)-doped tetraethoxysilicate (TEOS) and triammoniumphosphate ((NH4)3PO4.3H2O) with and without phosphoricacid. The formation of hybrid composites was verified by various analyses, such as XRD and 1 H NMR, and the thermal degradation was determined by thermogravimetric analysis. The proton conductivity was measured using impedance spectroscopy and values of 3.4 × 10 ‒2 S/cm and 2.3 × 10 ‒2 S/cm were obtained at room temperature for the SiO2/P < sub>2O5/(NH4)3PO4/PVP (90/8/2 mol%/1g) and the SiO2/(NH4)3PO4/PVP (90/10 mol%/1g) hybrid composite membranes, respectively. The results were discussed based on the effects of P < sub>2O5 and (NH4)3PO4 on the hybrid composites.

Effects of Silica Modified NiFe2O4 on the Dielectric and Electrical Properties of NiFe2O4 filled Poly (methyl methacrylate) Composites

Srikanta Moharana; Anjali Kujur; Sudhir Minz; R. N. Mahaling; Banarji Behera

Advanced Materials Letters, 2020, Volume 11, Issue 2, Pages 57-62
DOI: 10.5185/amlett.2020.021480

Nickel ferrite [NiFe2O4 (NFO)] nanoparticles were synthesized using a simple precursor based chemical route and modified with tetraethoxysilane (TEOS) to form SiO2 layer adsorbed on the NFO particles (SiO2@NFO). Based on the nanoparticles, the SiO2@NFO-PMMA composite films were prepared embedded with SiO2@NFO nanoparticles in a poly (methylmethacrylate) (PMMA) matrix. The properties of the composites were characterized extensively using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, dielectric and electrical measurement. FTIR analysis showed that the SiO2 groups had been successfully introduced into the NFO nanoparticles. The SEM images of the SiO2 adsorbed NFO nanoparticles had better dispersion in the PMMA matrix than the unmodified one. The SiO2 modified NFO-PMMA composites had much higher dielectric constant and better suppressed dielectric loss than the other two phase composite systems. The maximum dielectric constant was up to ≈ 67 while the dielectric loss was controlled below 0.5. This study suggested that the SiO2 modified NFO-PMMA composite films with high dielectric constant and low loss might be promising candidates for application in microelectronic engineering.  

Natural Fibers as Viable Sources for the Development of Structural, Semi-Structural, and Technological Materials – A Review

Chioma E. Njoku; Kenneth K. Alaneme; Joseph A. Omotoyinbo; Michael O. Daramola

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 682-694
DOI: 10.5185/amlett.2019.9907

A systematic and critical review on the potentials and viability of naturally occurring fibers as suitable reinforcements for the development of composite systems for structural, semi-structural and technological materials is presented in this article. Globally, the movement towards greater protection of the environment and the use of cost-saving technologies has led to a surge in the consideration of natural (biodegradable) products for the development of technological materials. In this regard, natural fibers have been proven to be good substitutes to synthetic fibers for the development of composites - because they possess similar mechanical and physical characteristics, to the synthetic fibers. In addition, natural fibers are lighter non-toxic and biodegradable. It is on this premise that several studies on their use in a number of applications where composites are desirable have been reported. Therefore, this article discusses various types of natural fibers, their properties, and their applications in different technological domains. The documentation of this review is thought-provoking and provides challenges and future prospects in the development and application of natural fibers and their composites. Copyright © VBRI Press.

Staking lay-up effect on dynamic compression behaviour of e-glass/epoxy composite materials: experimental and numerical investigation

Mostapha Tarfaoui; Mourad Nachtane

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 816-822
DOI: 10.5185/amlett.2018.2060

Several industrial applications have exposed polymer matrix composite materials to a very high strain rate loading conditions, requiring an ability to understand and predict the material behaviour under these extreme conditions. Many composite aircraft structures such as fuselage, wing skins, engine nacelles and fan blades are situated such that impacts at high strain rates are a realistic threat. To investigate this threat, high velocity impact experiments and subsequent numerical analysis were performed in order to study the compressive loading of composite materials at high strain rates. Specimens are subjected with various orientations from low to high strain rates to determine the compressive material properties. Three fibre orientations such as: ±20°, ±60° and 90° of cubic geometry are tested in in-plane direction. The tests show a strong material sensitivity to dynamic loading and fibre direction. In the second part, the FEA results of the dynamic tests resulting in no damage appeared satisfactory. The FEA gives results which are in coherence with the experimental data. The improved understanding of these phenomena and the development of predictive tools is part of an ongoing effort to improve the long-term integrity of composite structures under dynamic loads.

Enhanced microwave absorption property of aluminum composites using fly ash derived cenosphere  

Rajeev Kuma; Saroj Kumari;S. Das; D.P. Mondal; Shyam Birla; Amit Vishwakarma; Anisha Chaudhary

Advanced Materials Letters, 2018, Volume 9, Issue 4, Pages 241-248
DOI: 10.5185/amlett.2018.1760

In the present investigation, influence of micronsize cenosphere particles derived from fly ash on the properties of aluminum composites was investigated. Aluminum-cenosphere (AC) composite was fabricated by modified stir casting technique. The mechanical and electromagnetic interference (EMI) shielding properties of AC composites were investigated. The obtained composites with cenosphere (+100 µm) loading demonstrate the excellent compressive strength of 251.3 MPa. This enhancement is due to the smaller size of cenosphere size provides the finer surface of the cenosphere. The addition of cenosphere in aluminum matrix improved dielectric and microwave absorption properties of composites in X band frequency region (8.2-12.4 GHz). The AC composites possess good EMI shielding effectiveness of -32.7 to -44.3 dB with 30% loading of cenosphere with various sizes (+212, +150 and +100 µm). The incorporation of lower size cenosphere (+100µm) in aluminum matrix significantly increases the interfacial polarization which leads to a higher absorption EMI shielding effectiveness (SE) of -31.1 dB at 2.0 mm thickness. This technique is very simple, economical and highly reproducible, which may facilitate the commercialization of such composite and it can be used as microwave absorbing materials in defense and aerospace applications.

Highly sensitive hydrogen gas sensor based on Al-doped SnO2/Polyaniline composite nanofibers

Hemlata J. Sharma; Bhaskar M. Bahirwar; Subhash B. Kondawar

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 182-187
DOI: 10.5185/amlett.2018.1591

Metal oxide nanofibers showed keen interest in chemical gas sensing due to their unique chemical and electrical properties at operating temperature more than 200 o C. Their sensitivity can be improved at low operating temperature closed to room temperature by using conducting polymers. In this paper, Al doped tin oxide/polyaniline composite nanofibers detected H2 molecules at room temperature. A simple versatile electrospinning technique is used for the fabrication of Aluminium (Al) doped (tin oxide) SnO2 nanofibers and polyaniline was encapsulated using chemical oxidative polymerization (COP) of aniline monomer using ammonium persulfate as redox initiator. The structure and morphology of Al-doped SnO2/PANI composite nanofibers were investigated by SEM-EDX, UV-VIS and XRD spectroscopy. Structural changes of SnO2/PANI crystal due to the incorporation of Al 3+ ions have been explained. Al-doped SnO2/PANI composite nanofiber is very much selective towards H2 gas molecules in terms of high sensitivity, rapid response and recovery around room temperature compared to that of Al-doped SnO2. The present sensing mechanism systematically explained the existence of PN junction which is formed by p-type and n-type semiconductors in Al-doped SnO2/PANI hybrid composite material.

Spinel NiCo2O4 and single walled carbon nanotube nanocomposites for high performance supercapacitor application  

Surjit Sahoo; Chandra Sekhar Rout

Advanced Materials Letters, 2017, Volume 8, Issue 8, Pages 847-851
DOI: 10.5185/amlett.2017.1539

In the present work, we report the hydrothermal synthesis of NiCo2O4/Single walled carbon nanotubes (SWNTs) nanocomposites for supercapacitor applications. The SWNTs provided the conductive network and favored the growth of NiCo2O4 nanoparticles on its surface to facilitate the collection and transportation of electrons during the electrochemical charge storage performance. Due to the improved conductivity and higher surface area of the NiCo2O4/SWNTs nanocomposites as compared to pure NiCo2O4 nanorods, it exhibited a specific capacitance of 1623 F/g and 1098 F/g at 1mV/s scan rate and 1A/g current density. Obtained energy density and power density of the NiCo2O4/SWNTs nanocomposites were 56.19 Wh/Kg and 9.824 kW/kg respectively. These results demonstrated that the nanocomposites could be a promising candidate for future high performance energy storage devices. 

Chitosan-mediated fabrication of metal nanocomposites for enhanced biomedical applications

Faruq Mohammad; Hamad A. Al-Lohedan; Hafiz N. Al-Haque

Advanced Materials Letters, 2017, Volume 8, Issue 2, Pages 89-100
DOI: 10.5185/amlett.2017.6925

Hybrid materials based on metals and natural polymers are a promising class of nanocomposites; there is an increasing interest in metal nanoparticles (NPs) due to some fascinating characteristics associated with their nanosizes such as optical, conducting, catalytic, mechanical, sensing and superparamagnetic properties. Despite these favorable properties, the natural tendency of NPs for aggregation, high reactivity due to surface charges, and high rate of toxicity are limiting their applicability in biomedical sector. Chitosan, a naturally available amino polysaccharide biopolymer obtained from the exoskeleton of crustaceans (crabs and shrimp) and cell walls of fungi, displays unique polycationic, porous, chelating, bioadhesive and film-forming properties. The in-built characteristics of chitosan biopolymer can be utilized to alter the negative shades of metal NPs, thereby enhancing the applications in many different areas. The incorporation of chitosan significantly affects the steric stabilization of metal colloids, creates extra functional groups for biomolecule conjugation, renders the NPs suitable for bio-markers, protects metal ions from further oxidation/reduction by means of polymer coordination and has a control over toxicity. Thus by taking advantage of the additional features offered by the combination of chitosan and metal NPs, this report is designed to provide an overview about the metal NPs type, synthesis and applications in bioengineering and biomedical sector. Starting with the influencing properties due to their combination, we further reviewed the literature related to chitosan and metal NPs applicable for medicine with a specific focus on cancer diagnosis and treatment, advanced drug delivery, tissue engineering and surgical aids, to mention some.

Structural, Dielectric, Magnetic And Magnetoelectric Characterization Of Co0.5Ni0.5Fe2O4 - Bi0.9La0.1FeO3 Composite

Manjusha and K. L. Yadav; Manjusha;K. L. Yadav

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 853-861
DOI: 10.5185/amlett.2015.5856

Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 ºC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 and rhombohedral perovskite Bi0.9La0.1FeO3 ceramics. FESEM micrographs show closely packed microstructure with grain size in the range 503 nm - 960 nm. Variation of dielectric constant and dielectric loss with temperature at two fixed frequencies (500 kHz and 1 MHz) was studied. The composite with composition x = 0.55/sintered at 850 ºC exhibits the largest coercitivity (Hc) of 883 Oe. The saturation magnetization (Ms) and magnetic moment (µB) increase with an increase of Co0.5Ni0.5Fe2O4 concentration in the composites. From ferroelectric hysteresis loop analysis the values of remnant polarization (Pr) and coercive field (Ec) was found to lie in the range of 0.018-0.745 µC/cm 2 and 3.89-6.06 kV/cm. The relative change of magnetocapacitance was found to be 6.6% at a magnetic field of 8 kOe for x = 0.55 composition. Impedance analysis suggests the presence of a temperature dependent electrical relaxation in the material having a typical negative temperature coefficient of the resistance (NTCR) behavior analogous to a semiconductor.

Aqueous Phase Photodegradation Of Rhodamine B And P-nitrophenol Desctruction Using Titania Based Nanocomposites

Suranjan Sikdar; Sayantan Pathak; Tanmay K Ghorai

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 867-873
DOI: 10.5185/amlett.2015.5858

Heterogeneous photocatalysts offer great potential for converting photon energy into chemical energy for decomposition and destruction of organic contaminants from organic molecules i.e. Rhodamine B (RhB) and p-nitophenol (p-NP) under UV light. The titania based novel MxNbxTi1-2xO2-x/2 (M = Cr, Fe; x = 0.01-0.2) was prepared by tetra and tri-podal amine type binder with iron or chromium support using sol–gel method followed by calcination at 150 o C in an auto generated pressure. The photodegradation performance of the optimized catalyst was compared with synthesized nano-compositions, P-25 titania with RhB and p-NP. The particle sizes, surface area, mesopore sizes of CrxNbxTi1-2xO2-x/2 (x = 0.01) (CNT1) and FexNbxTi1-2xO2-x/2 (x = 0.01) (FNT1) are 12±1 and 10±2 nm, SBET=162 and 145 m 2 g −1 , 4.9 and 4-5 nm, respectively. The energy band gap of CNT1, FNT1 and NT was found to be 1.85, 2.06 and 2.1 eV, respectively. The importance of CNT1 powders is that it shows good photocatalytic activity for the degradation of Rhodamine B (RhB) within only 180 min and the importance of FNT1 powders is that it reduces the p-NP to p-aminophenol using a little bit of NaBH4 (0.054 g) within 10 min as compared to pure anatase TiO2 and other compositions of MxNbxTi1-2xO2-x/2 (M = Cr, Fe).

Studies On The Chemical Resistance And Mechanical Properties Of Natural Polyalthia Cerasoides Woven Fabric/glass Hybridized Epoxy Composites  

J. Jayaramudu; S.C. Agwuncha; S.S. Ray; E. R. Sadiku; A. Varada Rajulu

Advanced Materials Letters, 2015, Volume 6, Issue 2, Pages 114-119
DOI: 10.5185/amlett.2015.5680

In the present work, natural Polyalthiacerasoide woven fabrics were extracted from the bark of the tree and using these woven fabrics/glass fibre as reinforcements and epoxy as matrix the hybrid composites were prepared by the hand lay-up technique, at room temperature. The effect of alkali treatment of Polyalthiacerasoide fabrics on the chemical structure and morphology was examined using Fourier transforms infrared spectroscopic (FT-IR) and scanning electron microscopic techniques respectively. FT-IR analyses indicated the lowering of hemi-cellulose and lignin contents by alkali treatment of the woven fabric. The scanning electron micrographs indicated the removal of hemicelluloses layer on the surface of the fabric by alkali treatment. The effect of alkali treatment of the natural fabric on the mechanical properties, chemical resistance, and interfacial bonding of the hybrid composites was examined.The mechanical properties of the woven fabric/glass fiber hybrid composites with surface modified natural fabric were found to be higher than those with untreated fabric. The fractographs indicated a better interfacial bonding between the woven fabric/glass fibres and the matrix, particularly when the alkali-treated natural fabrics were used in the hybrid composites. Furthermore, these hybrid composites showed resistance to acids, alkalis and various solvents and also possessed lower water absorption.The natural fabric/glass fibre hybrid composites have the properties which advise their relevance for application in the building and construction industries.

Thermal And Frequency Dependance Dielectric Properties Of Conducting Polymer/ Fly Ash Composites

Subhash B. Kondawar; A. D. Dahegaonkar; V. A. Tabhane; D. V. Nandanwar

Advanced Materials Letters, 2014, Volume 5, Issue 6, Pages 360-365
DOI: 10.5185/amlett.2014.amwc.1036

With more than 100 million tonnes of fly ash produced in India, use of fly ash for the preparation of polyaniline – fly ash composites will in no way help in its bulk utilization. Still the authors have made an effort towards the better utility of fly ash by synthesizing polyaniline –fly ash composites for electronic devices where the requirement of dielectric materials with good electrical conductivity. There is great challenge to use the waste of thermal power stations in the form of fly ash as reinforcement for the conducting polymers to be good dielectric materials. In this paper, we report the use of fly ash to prepare conducting polymer composite materials. In-situ polymerization of aniline was carried out in the presence of fly ash (FA) to synthesize conducting polyaniline–fly ash composites (PANI-FA) by chemical oxidation method.   The PANI-FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt %) of fly ash in conducting polymer matrix. The surface morphology of these composites was studied by scanning electron microscopy (SEM). These composites were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffractometry (XRD), Fourier Transform Infra-Red (FTIR) Spectroscopy to investigate surface morphology and structure of the composites. Thermal and frequency dependence dielectric properties of all the synthesized composites have been studied with the help of impedance analyzer. By incorporating fly ash into conducting polymers, dielectric constant of the composites was found to be improved as compared to that of pure conducting polymers. It was also noticed that the dielectric constant of all the composites found to be decreased with increasing frequency but increased with increasing temperature. The results obtained for these composites are of greater scientific and technological interest for good quality capacitors.

Mechanical Properties Of Multifunctional Epoxy  resin/glass Fiber Reinforced Composites Modified  with Poly(ether Imide)

Jagrati Kandpal; Samar B. Yadaw; Arun K. Nagpal

Advanced Materials Letters, 2013, Volume 4, Issue 3, Pages 241-249
DOI: 10.5185/amlett.2012.8403

In the present paper effect of thermoplastic on various mechanical and thermal properties of multifunctional epoxy resin have been studied. Epoxy phenol novolac resin has been cured with hardner diamino, diphenyl sulfone. Changes in mechanical and thermal properties of epoxy phenol novolac resin with engineering thermoplastic poly (ether imide) have been investigated. Specimens were prepared using different mixing orders for multifunctional epoxy resin with poly (ether imide). Effect on glass transition temperature (Tg) were observed by using DSC measurements. Variation in mechanical properties viz. Tensile strength, flexural strength, flexural modulus, interlaminar shear strength and impact strength have been observed. With the thermoplastic modification of thermoset matrix material, improvement in mechanical properties of epoxy-glass fiber reinforced composites have been expected. Changes in storage modulus and loss modulus of all specimens were also evaluated by dynamic mechanical analysis (DMA). Scanning electron microscopy (SEM) was used to investigate the relationship between the morphological study of the fractured epoxy resins and mechanical properties of the modified epoxy resins and glass fiber reinforced composites. If the polymer matrix is fairly brittle (unmodified epoxy), there may be a corresponding reduction in mechanical properties. Incorporation of engineering thermoplastic Poly (ether-imide) has resulted in improvement of above stated mechanical properties. All results indicated that thermoplastic modified multifunctional epoxy resin proved to be a good matrix material which enhances the mechanical properties of glass fiber reinforced composites.